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WO2022108420A1 - Appareil et procédé permettant de commander une conversion de puissance de formation de réseau - Google Patents

Appareil et procédé permettant de commander une conversion de puissance de formation de réseau Download PDF

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Publication number
WO2022108420A1
WO2022108420A1 PCT/KR2021/017281 KR2021017281W WO2022108420A1 WO 2022108420 A1 WO2022108420 A1 WO 2022108420A1 KR 2021017281 W KR2021017281 W KR 2021017281W WO 2022108420 A1 WO2022108420 A1 WO 2022108420A1
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WIPO (PCT)
Prior art keywords
voltage
grid
power conversion
current
forming power
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/KR2021/017281
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English (en)
Korean (ko)
Inventor
강지성
허견
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Korea Grid Forming Co Ltd
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Korea Grid Forming Co Ltd
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Priority claimed from KR1020200158245A external-priority patent/KR102379169B1/ko
Priority claimed from KR1020200164432A external-priority patent/KR102390466B1/ko
Application filed by Korea Grid Forming Co Ltd filed Critical Korea Grid Forming Co Ltd
Publication of WO2022108420A1 publication Critical patent/WO2022108420A1/fr
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/70—Regulating power factor; Regulating reactive current or power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/12—Circuit arrangements for AC mains or AC distribution networks for adjusting voltage in AC networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for AC mains or AC distribution networks for adjusting voltage in AC networks by changing a characteristic of the network load by adjustment of reactive power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for AC mains or AC distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/36—Means for starting or stopping converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Definitions

  • the present invention relates to a grid-forming power conversion control apparatus, and more particularly, to a grid-forming power conversion control apparatus and method capable of stable operation based on system information connected with information of a power conversion apparatus to be connected.
  • New and renewable energy are defined slightly differently by each country. In Korea, it is defined as energy other than oil, coal, nuclear power, or natural gas, and it is defined as energy in eight fields (solar energy, biomass, wind power, small hydropower, geothermal energy). , marine energy, waste energy) and three fields (fuel cell, coal liquefaction and hydrogen energy) as new energy belong to this category.
  • Renewable energy can be classified into several types such as solar heat, photovoltaic power generation, wind power generation, small hydro power generation, waste incineration heat and power generation, biomass energy (biogas, gasification power generation, biofuel), geothermal energy, and marine energy, depending on the technology and type of final energy. can be divided into Since such renewable energy is to obtain clean energy using the natural energy sources of the sun (light, heat), wind, water, and the sea, which are the primary energy sources, the amount of resources is almost infinite.
  • a power converter is installed between the renewable energy generator and the grid power source, converts the power supplied from the renewable energy generator into a voltage suitable for supplying the grid power, and supplies power to the grid power.
  • the power converter charges the power supplied from the renewable energy generator or grid power, and when the power supply from the grid power is stopped due to an abnormality such as a power outage in the grid power, the power supply is pre-charged according to the command of the upper controller. It performs the function of supplying power to the load.
  • the grid-forming power converter is a device that independently generates power in the power system and performs a role similar to that of a generator.
  • the grid-forming power converter maintains independent voltage generation even in the event of an external system failure and is different from other power converters in that it is required to supply a fault current.
  • the present invention provides a grid-forming power conversion control device and method capable of stable operation by evaluating impedance adequacy based on system information connected with information of a power conversion device to be connected.
  • the present invention provides a grid-forming power conversion control apparatus and method capable of optimal operation voltage control in which the power conversion apparatus minimizes the intensity of overcurrent in consideration of both the failure current and the reverse current in the event of a failure.
  • the present invention calculates the impedance constraint that enables stable grid forming operation even in all failure situations and, when the impedance criterion is not met, through power conversion device design change, controller addition, transformer wiring change, external system grounding factor adjustment, etc.
  • a grid-forming power conversion control apparatus and method capable of alleviating restrictions are provided.
  • the present invention provides a grid-forming power conversion control device and method that can efficiently meet the demand for a grid-forming power conversion device according to the expansion of new and renewable power sources by determining whether stable operation is performed in the step of connecting the grid-forming power conversion device to provide.
  • the present invention provides a grid-forming power conversion control apparatus and method capable of controlling the frequency of the voltage output by the grid-forming power conversion device without controlling the direct current, and capable of operating at a high speed.
  • a grid-forming power conversion control device According to one aspect of the present invention, there is provided a grid-forming power conversion control device.
  • the grid-forming power conversion control device converts the power supplied from the renewable energy generator into a voltage for supplying the grid power to the grid-forming power conversion unit, the grid-forming power conversion unit for supplying power It is connected to calculate the fault current when a fault occurs and calculates the reverse current that occurs when the voltage is lowered in case of a fault and the recovery reverse current that occurs when the fault is removed according to the fault current supply characteristics required by the system.
  • Information on the optimum voltage control unit and power system to find the operating point where overcurrent is minimized and find the operating point that satisfies the requirements of the power system as much as possible within the range that does not exceed the limit of the current that the power converter can supply Impedance constraint evaluation control unit that collects parameters for impedance evaluation using may include
  • the fault current supply characteristic is controlled by calculating the fault current and the reverse current, and the parameter collection is performed using the information of the power system.
  • Step setting the reference MVA connection impedance input and GFM (Grid Forming Source) voltage in the input setting section, 3-phase short-circuit fault current, line-to-line short-circuit fault current, line-to-line short-circuit fault current and 1-line ground fault at fault current calculation section Calculating the fault current, storing the current GFM voltage, calculating the recovery reverse current, and judging whether the calculated recovery reverse current exceeds the set limit value and operating with the input impedance It may include the step of determining whether it is possible.
  • GFM Grid Forming Source
  • the grid-forming power conversion control apparatus and method according to the present invention as described above has the following effects.
  • the impedance criterion is not met by calculating the impedance constraint that enables stable grid forming operation even in all failure conditions, it is restricted through power conversion device design change, controller addition, transformer wiring change, external system grounding factor adjustment, etc. can alleviate
  • stable operation can be determined in the step of connecting the grid-forming power converter, so that the demand for the grid-forming power converter according to the expansion of new and renewable power sources can be efficiently met.
  • FIG. 1 is a model configuration diagram for the optimal voltage tracking control and impedance constraint evaluation of the grid-forming power conversion control device according to the present invention
  • FIG. 2 is a block diagram of a device for optimal voltage tracking control and impedance constraint evaluation of a grid-forming power conversion control device according to the present invention
  • FIG. 3 is a flowchart illustrating a method for optimal voltage tracking control and impedance constraint evaluation of a grid-forming power conversion control device according to the present invention
  • FIG. 4 is a block diagram of a failure model of a three-phase short circuit failure
  • FIG. 6 is a configuration diagram of a failure model of a one-line ground fault failure
  • FIG. 9 is a block diagram of a failure model of a short circuit between lines
  • FIG. 10 is a configuration diagram of a calculation model of HV Side Fault of line-to-line short circuit failure
  • 11 and 12 are Fault Current graphs in case of short circuit failure between HV side PCC points of GFM Source linked to AC system.
  • FIG. 13 is a flowchart illustrating an overview of an output frequency control method of a grid-forming power conversion control apparatus according to the present invention
  • FIG. 14 is a block diagram schematically showing an output frequency control unit of a grid-forming power conversion control device according to the present invention.
  • 15 is a droop plot illustrating that the power generation system and the grid-forming power converter divide and provide power to the load.
  • Figure 16 is a view showing the outline of the output frequency control method of the grid-forming power converter according to the prior art together with the droop diagram illustrated in Figure 15
  • 17 is an exemplary control diagram for controlling the matching control of the grid forming power conversion unit to control the output frequency according to the voltage
  • FIG. 18 is a view showing the outline of the output frequency control method of the grid-forming power conversion control apparatus according to the present invention together with the droop diagram illustrated in FIG.
  • VDC DC voltage
  • 21 is a view for explaining a fourth embodiment of the output frequency control method of the grid-forming power conversion control apparatus according to the present invention
  • FIG. 22 is a view for explaining a fifth embodiment of the output frequency control method of the grid-forming power conversion control apparatus according to the present invention
  • FIG. 23 is a view for explaining a sixth embodiment of the output frequency control method of the grid-forming power conversion control apparatus according to the present invention
  • 24 is a diagram illustrating a DC voltage and an output frequency provided to the grid-forming power converter when the grid-forming power converter is controlled in the first embodiment, the second embodiment, and the third embodiment, respectively;
  • Figure 25 (a) is a diagram showing the output frequency of the DC voltage provided to the grid-forming power converter according to the prior art and the first embodiment and the second embodiment
  • Figure 25 (b) is Figure 25 (a) A drawing showing an enlarged range of 225kV to 245KV of
  • 26 (a) and 26 (b) are diagrams showing the experimental results of the grid forming power conversion unit (solid line) and the power system (dotted line) controlled by the prior art
  • 27 (a) and 27 (b) are diagrams showing the experimental results of the grid forming power conversion unit (solid line) and the power system (dashed line) controlled in the first embodiment
  • 28 (a) and 28 (b) are diagrams showing experimental results of the grid forming power conversion unit (solid line) and the power system (dashed line) controlled in the second embodiment
  • 29 (a) and 29 (b) are diagrams showing the experimental results of the grid forming power conversion unit (solid line) and the power system (dashed line) controlled in the third embodiment
  • 30 (a) and 30 (b) are diagrams showing the experimental results of the grid forming power conversion unit (solid line) and the power system (dashed line) controlled in the fourth embodiment
  • Figure 31 (a) shows the experimental results of the grid forming power conversion unit (solid line) and the power system (dotted line) controlled in the fifth embodiment
  • Figure 31 (b) is from 1.2 seconds to 3.2 seconds in Figure 31 (a)
  • 32(a) and 32(b) are diagrams illustrating a case in which control is performed by droop control according to the prior art under the experimental conditions illustrated in FIG. 19;
  • 33 and 34 are diagrams showing experimental results of the grid forming power conversion unit (solid line) and the power system (dotted line) controlled in the sixth embodiment
  • FIG. 1 is a model configuration diagram for the optimal voltage tracking control and impedance constraint evaluation of the grid-forming power conversion control device according to the present invention.
  • Grid-forming power conversion control apparatus and method according to the present invention based on the information of the connected power conversion device and the system information connected to the power conversion device in the event of a failure in consideration of both the fault current and the reverse current optimal operation to minimize the overcurrent intensity Stable operation is possible by controlling voltage (optimal voltage) and evaluating impedance adequacy.
  • the present invention calculates the impedance constraint that enables stable grid forming operation even in all failure situations, and when the impedance criterion is not met, the power conversion device design change, the controller addition, the transformer wiring method change, the grounding factor adjustment of the external system It may include a configuration that can relieve the constraint through the
  • the present invention is a failure calculation method, and may include the steps of calculating the Thevenin equivalent impedance and calculating the abc phase ⁇ symmetrical coordinates ⁇ converting the abc phase back to the abc phase to calculate the unbalanced fault.
  • the magnitude of the voltage acts as a variable in the grid forming power source, and it is impossible to equalize it by adding it to the AC voltage source.
  • the superposition method which calculates each and then adds them to one another.
  • the power converter When the power converter is operated by grid forming, it is required to supply the fault current to the allowable limit. Considering this, the method of lowering the voltage by considering only the fault current in the case of a 3-phase short-circuit failure without considering the reverse current is the power It is judged that it can have a fatal effect on the converter.
  • the control in which the power converter finds the optimal voltage when an external power system failure occurs is the characteristic of the fault current and the reverse current, the characteristic that there is a limit of the current that the power converter can flow, and the power system is grid Consider all the requirements for the forming power converter.
  • the present invention calculates all failure types in consideration of the characteristics of the fault current and the reverse current, finds the operating point where the overcurrent is minimized even in the most severe fault among them, and does not exceed the limit of the current that the power conversion device can flow. It is to track the optimum voltage that satisfies the requirements of the power system as much as possible in the range.
  • impedance evaluation is to find the minimum impedance that does not exceed the limit range of the current that the power converter can flow based on the fault current and reverse current.
  • the present invention is particularly useful in the engineering phase of the power converter because it can determine the impedance of the power converter or determine whether the connection point of the system to be connected is appropriate by understanding the impedance constraint.
  • the present invention considers the following characteristics of the power conversion device.
  • a generator and a grid-forming power converter both have a voltage source in common.
  • a generator has no current limit, whereas a power converter has a low current limit value as a power electronic device.
  • the grid-forming power converter operates as a voltage source, but a method of controlling the current not to be exceeded by reducing the voltage in a situation such as a failure is required.
  • the current when the current is limited, it is considered that not only the fault current supplied by the power conversion device but also the reverse current and the recovery reverse current entering the power conversion device are limited.
  • V and E are voltage, I is current, and Z is impedance , F is the current flowing to the fault point.
  • GFM for converter
  • SM for external system power source
  • ext for external system excluding GFM
  • the symbol for equivalence Z th is the Thevenin equivalent impedance
  • I th is the current flowing through the Thevenin equivalent impedance, that is, the current generated in the GFM or the current generated in the SM.
  • SMdirection is the abbreviation of the current generated from GFM and directed to the external system, while SM and GFMdirection are the current generated from SM and directed to the GFM.
  • FIG. 2 is a block diagram of a grid-forming power conversion control apparatus according to the present invention.
  • the grid-forming power conversion control device is installed between the renewable energy generator and the grid power source, as shown in FIG. 3, and converts the power supplied from the renewable energy generator into a voltage for supplying the grid power,
  • the grid-forming power conversion unit 100 that supplies power to the power source, and the grid-forming power conversion unit 100 are connected to the calculation of the fault current when a fault occurs and the reverse current generated when the voltage is lowered in case of a fault.
  • the optimum voltage control unit 200 performs optimal voltage control to find an operating point that satisfies the requirements of the power system, and the parameters for impedance evaluation are collected using information on the power system, and the connection impedance and GFM voltage setting values are changed. and an impedance constraint evaluation control unit 300 to obtain a minimum impedance that does not exceed the limit of the current that the power conversion device can supply.
  • the optimum voltage control unit 200 includes an optimum voltage calculation unit 10 that calculates an optimum voltage as the FRT voltage command value of the optimum voltage control unit, and a limit voltage calculation unit ( 11), the minimum voltage calculation unit 12 that calculates the minimum voltage as the lower limit of safety measures in case of incomplete voltage control of the optimum voltage control unit, and the operating point where the overcurrent is minimized in consideration of the fault current supply characteristics required by the system and a fault current supply characteristic control unit 13 that performs optimal voltage control to find an operating point that satisfies the requirements of the power system as much as possible in a range that does not exceed the limit of the current that the converter can supply.
  • optimal voltage control lowers the voltage when the current exceeds, and solves the overcurrent by raising the voltage in a specific section where the reverse current is high. Therefore, it is not lowered below the limit voltage.
  • the impedance constraint evaluation control unit 300 includes a parameter collection unit 20 that collects parameters for impedance evaluation using information of the power system, and an input setting unit 21 that sets the reference MVA connection impedance input and GFM voltage and , a fault current calculation unit 22 that calculates a fault current to obtain the minimum impedance that does not exceed the limit of the current that the power converter can supply, and the current GFM by determining whether the power converter current exceeds the set limit value
  • the recovery reverse current calculation and determination unit 23 that stores the voltage, calculates the recovery reverse current, and determines whether the recovery reverse current exceeds the set limit value, and operates with the input impedance if the recovery reverse current does not exceed the set limit value It includes an impedance evaluation unit 24 that determines that it is possible.
  • the fault current calculation unit 22 calculates three-phase short-circuit fault current, line-to-line short-circuit fault current, line-to-line short-circuit fault current, and 1-line ground fault fault current.
  • FIG. 3 is a flowchart illustrating a method for optimal voltage tracking control and impedance constraint evaluation of a grid-forming power conversion control device according to the present invention.
  • fault current calculation and reverse current calculation are performed to control fault current supply characteristics, and parameters are collected using information from the power system (S301).
  • the input setting unit 21 sets the reference MVA connection impedance input and the GFM (Grid Forming Source) voltage. (S302)
  • GFM Grid Forming Source
  • SM Synchronous AC Machine Source
  • F Total Fault Current
  • G Grounding Voltage
  • 0,1,2 Zero Sequence, Positive Sequence, Negative Sequence
  • th Thevenin equivalent impedance
  • E Source Voltage
  • phase angle is -30° when connected with Yd1-connected 3-phase transformer, and may vary depending on the impedance angle of VI.
  • the important point is is a virtual power source and not an actual voltage.
  • the power that the GFM converter actually generates is a voltage less than or equal to this.
  • the equalized external AC system is indicated as The normal and reverse phase impedances are the same, but the image impedance is set as a variable depending on the level of grounding. put it as Since LV and HV of the GFM source are different points of failure, the transformer impedance is not expressed as equivalent. connect through
  • Transformer is connected wye on HV side and delta connection on LV side. When voltage and current vary depending on the measurement point, they are displayed separately as 'HV' and 'LV'.
  • Impedance of GFM consists of transformer and interfacing impedance. In order to keep the control characteristics of the converter constant regardless of the capacity, the impedance compared to the self-capacitance (DC MVA) is taken constant.
  • transformer impedance is the converter series impedance (including filter impedance).
  • Rotating equipment has different impedance for each sequence.
  • the AC source impedance is also classified.
  • the converter , of the transformer is a passive element, R, L, and C, so it can be expressed as the same value without distinction between 0, 1 and 2.
  • the failure model of 3-phase short circuit failure is as follows.
  • FIG. 4 is a block diagram of a three-phase short circuit failure model.
  • a 3-phase short circuit fault circuit as shown in Fig. 4 is written as a parallel circuit for each GFM and AC source, and the problem is analyzed by superposition.
  • HV Side Fault is calculated as follows.
  • GFM terminal voltage is controlled as follows.
  • FIG. 5 is a graph showing the current change of the converter according to different connection impedances in a 3-phase fault.
  • the conventional failure model of 1-wire ground fault is as follows.
  • FIG. 6 is a configuration diagram of a failure model of a one-line ground fault failure.
  • one-line ground fault circuit as shown in the figure above is written as a parallel circuit for each GFM and AC (SM) source, and the problem is analyzed by superposition.
  • Each Seq Circuit is a series structure, and the + side of the Pos Circuit is connected to the - side of the Neg Circuit. Neg Circuit + side is connected to Zero Circuit - side. And the + side of the Zero Circuit is connected to the - side of the Pos Circuit. If there is an impedance between the fault point and the ground, connect it to the + side of each Seq circuit.
  • HV Side Fault is calculated as follows.
  • FIG. 7 is a configuration diagram of a calculation model of HV Side Fault in 1-line ground fault failure.
  • the current generated from the Grid Forming Converter is calculated as follows.
  • the zero-phase current generated in the converter is defined as in Equation (6).
  • the current generated from the AC side SM Source is calculated as follows.
  • the Ry current on the HV side in case of a ground fault in HV 1 line is as follows.
  • HV is the current that finally flows to the high voltage side.
  • the external system current on the HV side is as follows.
  • the HV side voltage is as follows.
  • the converter current on the LV side is as follows.
  • the LV side voltage is as follows.
  • impedance Is as follows.
  • the healthy current cannot be zero in the case of a one-wire ground fault derived by superposition.
  • each sequence current component has a different value as the size changes. Accordingly, not only the a-phase current but also the b and c-phase currents are the voltage of the GFM. It is determined as a function according to As , the b and c phase currents increase.
  • each phase current can be either in the forward direction or in the reverse direction. If this formula is not satisfied, limiting fails, a distorted current waveform is output, and the FRT fails (unstable) because resynchronization is not performed even after the fault is removed. In this case, it is necessary to protect the IGBT by blocking the converter. In this case, the equipment can be protected, but the grid forming property is lost, so the stability in terms of system operation is deteriorated, and the correct operation of the protective relay cannot be induced because the fault current cannot be supplied. none.
  • FIG. 9 is a configuration diagram of a failure model of a line-to-line short circuit failure.
  • the line-to-line short circuit fault circuit as shown in FIG. 9 is written as a parallel circuit for each GFM and AC source, and the problem is analyzed by superposition.
  • Each Seq Circuit is a parallel structure, connecting the + sides and connecting the - sides.
  • the fault impedance connects 3Zf to the + side of Zero Seq.
  • HV Side Fault is calculated as follows.
  • FIG. 10 is a configuration diagram of a calculation model of HV Side Fault of line-to-line short circuit failure.
  • the LV side In the event of a short circuit between HV lines, the LV side has an open video circuit and no zero current flows.
  • the current generated from the AC side SM Source is calculated as follows.
  • the LV side In the event of a short circuit between HV lines, the LV side has an open video circuit and no zero current flows.
  • Equation 22 That is, it is defined as in Equation 22.
  • the Ry current on the HV side is defined as follows in case of a short circuit between HV lines.
  • the external system current on the HV side is as follows.
  • the voltage on the HV side is as follows.
  • the converter current on the LV side is as follows.
  • the image component is removed and it is simplified as follows.
  • the voltage on the LV side is as follows.
  • the healthy current does not become 0 in case of a short circuit between lines derived from Superposition.
  • each phase current can be either in the forward direction or in the reverse direction.
  • 11 and 12 are Fault Current graphs in case of a short circuit failure between the HV side PCC points of the GFM Source connected to the AC system.
  • the limit value of DC MVA which fails to limit in line-to-line short-circuit failure, is lower than that of line-to-line short circuit.
  • the optimum voltage, the limit voltage, and the minimum voltage to be used as the setting values of the voltage control unit based on the above-mentioned 1-line ground fault, line-to-line short circuit, and line short-circuit fault calculation are as follows.
  • the optimum voltage is the voltage at which the power converter is expected to produce the best FRT performance. At the optimum voltage, the power converter supplies the maximum fault current within the range that does not exceed the current limit.
  • the optimum voltage is obtained from the condition that the phase current of the line-to-line short circuit becomes equal to the limit value.
  • the formula is:
  • s is an abbreviated display of converter impedance
  • g is an abbreviated display of Thevenin equivalent impedance viewed from the converter
  • e is an abbreviated display of the Thevenin equivalent impedance viewed from an external system
  • b is an abbreviated display of external system impedance
  • L is an abbreviated display of current limit.
  • impedance constraint satisfaction takes precedence over control unit operation.
  • the success of current limit means that it is a sinusoidal three-phase AC waveform of the rated frequency, and the result is supplied so that the maximum wave height value among three phases does not exceed the limit.
  • the limit voltage is the voltage at the point where the magnitude of the fault current and the reverse current are equal. At the limit voltage, the power converter can no longer obtain the gain of lowering the voltage further. If the voltage is lowered than the limit voltage, the reverse current (RC) exceeds the fault current, so there is no real benefit of lowering the maximum current. Therefore, the voltage control unit performs control not to lower the voltage than the limit voltage.
  • the limit voltage is obtained from the condition that the two phase currents of the line-to-line short circuit fault are equal.
  • the formula is:
  • t is an abbreviation of the parallel composite impedance of the Thevenin equivalent impedance and the external system impedance viewed from the converter.
  • ⁇ k is set so that the phase angle of the right side becomes 0.
  • the limit voltage is always present regardless of whether the impedance constraint evaluation is satisfied. Therefore, if the limit current at the limit voltage does not exceed the current limit value, the impedance constraint is considered to be satisfied.
  • the minimum voltage is the lowest voltage the power converter can operate without leaving the range of a successful FRT.
  • the minimum voltage means both the voltage at the point where the reverse current exceeds the current limit when the voltage is lowered in a 1-line ground fault, and the voltage at the point where the recovery reverse current exceeds the limit regardless of the fault type. If the impedance limit is exceeded during operation due to an unexpected change in the system impedance, there is a risk that the voltage control unit will command the minimum voltage or less. As a safety measure, if the voltage command value is lower than the minimum voltage, anti-wind-up clamping is performed. Anti-wind-up clamping is a control that resets the voltage control unit integrator.
  • ⁇ k is set so that the phase angle of the right side becomes 0.
  • t0 and t2 are the zero-phase and inverse parts of the abbreviated impedance t
  • m is the abbreviated display of the sum of the zero-phase and inverse parts of the Thevenin equivalent impedance seen from the converter
  • the triangle is the abbreviated display of the loop impedance.
  • impedance constraint satisfaction takes precedence over control unit operation.
  • the output frequency control method of the grid-forming power conversion control apparatus includes: calculating a frequency corresponding to the DC voltage provided to the grid-forming power conversion unit 100 ( S1310 ) and the grid
  • the forming power conversion unit 100 includes a step (S1320) of outputting a frequency corresponding to the provided DC voltage, but outputting the calculated frequency does not control the DC current provided to the grid forming power conversion unit 100 is performed without
  • the output frequency control unit 400 of the grid-forming power conversion control apparatus includes an input unit 410 , an output unit 420 , a processor 450 , a memory 440 , and a database 430 .
  • the output frequency control unit 400 of FIG. 14 is according to an embodiment, and not all blocks shown in FIG. 14 are essential components, and in another embodiment, some blocks included in the output frequency control unit 400 are added or changed. Or it can be deleted.
  • the output frequency control unit 400 may be implemented as a computing device for controlling the grid forming power conversion unit 100, each component included in the output frequency control unit 400 is implemented as a separate software device, It may be implemented as a separate hardware device combined with software.
  • the output frequency control unit 400 calculates a frequency corresponding to the DC voltage provided to the grid forming power conversion unit 100, and controls the grid forming power conversion unit 100 to output a frequency corresponding to the provided DC voltage, The step of outputting the calculated frequency is performed without controlling the DC current provided to the grid-forming power conversion unit 100 .
  • the input unit 410 means a means for inputting or obtaining a signal or data for controlling the grid-forming power conversion unit 100 .
  • the input unit 410 may input various types of signals or data in association with the processor 450 , or may directly acquire data in association with an external device and transmit the data to the processor 450 .
  • the input unit 410 may be a device or a server for inputting or receiving an output voltage, an output frequency, a droop rate, set point information, etc. of the grid forming power conversion unit 100, but is not necessarily limited thereto.
  • the output unit 420 may display an output voltage, an output frequency, a droop rate, setpoint information, and the like of the grid forming power conversion unit 100 in conjunction with the processor 450 .
  • the output unit 420 preferably displays various information through a display (not shown), a speaker, etc. provided in the output frequency control unit 400 in order to output predetermined information, but is not necessarily limited thereto.
  • the processor 450 performs a function of executing at least one instruction or program included in the memory 440 .
  • the processor 450 calculates a frequency corresponding to the DC voltage provided to the grid forming power converter 100 based on the data obtained from the input unit 410 or the database 430, and the grid forming power An operation of controlling the converter 100 to output a frequency corresponding to the provided DC voltage is performed.
  • the memory 440 includes at least one instruction or program executable by the processor 450 .
  • the memory 440 may include instructions or programs for performing processing.
  • the memory 440 may store a program for calculating a frequency and the calculated frequency values.
  • the database 430 refers to a general data structure implemented in the storage space (hard disk or memory) of a computer system using a database management program (DBMS), and performs data search (extraction), deletion, editing, addition, etc.
  • DBMS database management program
  • Relational database management system such as Oracle, Infomix, Sybase, DB2, Gemston, Orion
  • OODBMS object-oriented database management system
  • XML Native Database such as Excelon, Tamino, Sekaiju, etc. It can be implemented according to the requirements, and has appropriate fields or elements to achieve its function.
  • the database 430 may store an algorithm for calculating the frequency of the grid forming power converter 100, and the like, and may provide the stored data. Meanwhile, although the database 140 is described as being implemented in the output frequency control unit 400, it is not necessarily limited thereto, and may be implemented as a separate data storage device.
  • 15 is a droop plot illustrating that the power generation system and the grid-forming power converter according to an embodiment of the present invention share and provide power to a load.
  • 15 illustrates a case in which the power generation system and the grid-forming power conversion unit supply power to the same load.
  • AC droop' is a plot showing the output frequency versus the power provided by the power generation system to the load
  • the GFM droop shows the output frequency versus the power provided by the grid forming power converter 100 to the load. It is a plot.
  • both the AC droop' diagram and the GFM droop diagram have a characteristic that the output frequency decreases as the power provided to the load increases.
  • an AC droop diagram can be formed, and a set point (Psp, set point), which is an intersection point with the GFM droop diagram, is formed.
  • the power generation system and the grid-forming power converter 100 have different ratios of sharing the power provided to the load based on the set point Psp.
  • the PGFM is 50 MW
  • the PAC is 10 MW
  • the grid forming power conversion unit 100 and the power generation system provide a total of 60 MW to the load. That is, the 50 MW grid-forming power conversion unit 100 provides power to the load, and the remaining 10 MW provides power to the load by the external AC power generation system.
  • the frequency output by the grid forming power converter 100 in the no-load state is the no-load frequency (fNLGFM), and as the power provided to the load increases, it decreases to the maximum load frequency (fFLGFM).
  • fNLGFM no-load frequency
  • fFLGFM maximum load frequency
  • the grid forming power converter 100 and the power generation system output a common frequency, and the frequency at that time is referred to as the set point frequency (fsp).
  • the grid forming power conversion unit 100 controls the power provided to the load by the grid forming power conversion unit 100 ) can be performed by controlling the GFM Droop.
  • the droop diagram (GFM Droop) of the grid-forming power converter 100 is a droop rate corresponding to the slope of the droop diagram (GFM droop) of the grid-forming power converter 100, a target set point , It can be made by adjusting the no-load frequency (fNLGFM) output by the grid-forming power converter 100 in a no-load state and the maximum load frequency (fFLGFM) output by the grid-forming power converter 100 in a maximum load state.
  • droop refers to the control principle for proportionally sharing the power load jointly supplied by generators running in parallel. This is called the droop rate. That is, the droop rate is defined as in Equation 41 below.
  • FIG. 16 is a diagram illustrating an overview of an output frequency control method of a grid forming power converter according to the prior art together with a droop diagram illustrated in FIG. 15 .
  • the droop diagram illustrated in FIG. 15 is shown in the first quadrant, and in the second quadrant, a function for the DC voltage (VDC) provided with the output frequency of the grid forming power converter 100 is shown.
  • VDC DC voltage
  • the grid forming power conversion unit 100 in the droop diagram changes the output frequency from the maximum load frequency fFLGFM to the no-load frequency fNLGFM It can be outputted and interlocked with the power generation system to provide power to the load.
  • the output frequency of the grid-forming power converter 100 When the grid-forming power conversion unit 100 is matched and controlled, the output frequency is controlled according to the provided DC voltage. That is, the output frequency of the grid-forming power converter 100 has the form of a linear function passing through the origin. Therefore, in order for the output frequency of the grid forming power conversion unit 100 to change from the maximum load frequency fFLGFM to the no-load output frequency fNLGFM, the voltage provided to the grid forming power conversion unit 100 must change within the range of ⁇ VDC. do.
  • the matching control of the grid forming power converter 100 is provided as illustrated in FIG. 17 in order to control the output frequency to correspond to the voltage (VDC), the rated DC voltage (VDC*) and the rating
  • the direct current (idc) formed from the power (P*) and the power loss (Ploss) is controlled and must be provided to the grid forming power converter 100 .
  • the DC current must be controlled so that the voltage provided to the grid forming power converter 100 exists within the range of ⁇ VDC, and accordingly, the output frequency changes from fFLGFM, which is the output frequency at maximum load, to fNLGFM, which is the output frequency at no load.
  • the kdc included in the control loop illustrated in FIG. 17 may be expressed as in Equation 42 below.
  • the denominator of kdc includes a droop rate (mp). That is, for the matching control, DC current control is required to implement the droop characteristic separately from the control unit that generates the AC frequency, and the droop rate, which is the power sharing ratio of the grid forming power conversion unit 100, is reflected during the DC current control. There is a difficulty in that it is necessary to implement a complex and sophisticated controller.
  • FIG. 18 is a diagram illustrating an outline of an output frequency control method of a grid-forming power conversion control apparatus according to the present invention together with the droop diagram illustrated in FIG. 15 .
  • the first quadrant is a droop diagram illustrated in FIG. 15, and the diagram shown in the second quadrant shows the output frequency of the grid-forming power conversion control device according to this embodiment as a function of the DC voltage (VDC) provided. .
  • VDC DC voltage
  • the output frequency shown by the thick solid line of the grid-forming power converter 100 may change according to a linear function with respect to the input DC voltage (VDC).
  • the first-order function may be a first-order function having a slope ⁇ ′ passing through the output frequency fFLGFM at maximum load.
  • the linear function can be expressed as Equation 43 below.
  • the linear function may be a linear function having a slope ⁇ ′ over the no-load output frequency fNLGFM.
  • the first-order function may be a first-order function passing through the no-load output frequency (fNLGFM) and the maximum-load output frequency (fFLGFM).
  • Equation 44 The slope ( ⁇ ′) of the linear function can be obtained from Equation 44 below.
  • the rated frequency is set to 60Hz in Korea and 50Hz or 60Hz in the case of overseas, and the rated DC voltage is a value determined according to the manufacturing specifications of the equipment.
  • the frequency control method of the grid-forming power conversion control apparatus is a grid-forming power conversion unit when the DC voltage (VDC) provided to the grid-forming power conversion unit 100 is 0, unlike the prior art illustrated in FIG. 17 . (100) outputs the output frequency (fFLGFM) at the maximum load, and as the DC voltage (VDC) provided to the grid forming power converter 100 increases, the output frequency (f) increases along the slope ⁇ '.
  • the grid forming power conversion control device outputs an output frequency fNLGFM at no load.
  • the method for controlling the output frequency of the grid-forming power conversion control apparatus controls the DC current provided to the grid-forming power conversion unit 100 to obtain an output frequency within a desired range, thereby controlling the grid-forming power conversion unit 100 ) was maintained within the desired range.
  • a controller for controlling a direct current has been required, but such a controller is complicated and uneconomical in terms of cost.
  • the output frequency can be formed from the DC voltage provided to the grid forming frequency without controlling the DC current. Accordingly, a controller for controlling a complicated current is unnecessary, and thus an advantage of economical efficiency is provided.
  • FIG. 19 is a diagram illustrating an output frequency for a DC voltage (VDC) provided to a grid-forming power converter according to a second embodiment of the present invention.
  • VDC DC voltage
  • the grid-forming power converter 100 changes exponentially when the input voltage VDC changes.
  • the rotational speed error (g) of the generator rotor is expressed in terms of the DC voltage (VDC) provided to the grid-forming generator, and Equation 1 and Assuming that it can be expressed in the form of an exponential function, the acceleration (g') obtained by differentiating it can be expressed by Equation (2).
  • Equation 45 the output frequency (f) of the grid forming frequency is expressed as the rotation speed (g) and the acceleration (g') as shown in Equation 46 below.
  • a coefficient a is related to a droop characteristic
  • b is related to an inertia characteristic
  • c corresponds to -Vd0 in which a minus sign is added to the DC voltage provided to the grid-forming power converter 100 when the grid-forming power converter 100 outputs the maximum load frequency.
  • Equation 48 the output frequency f of the grid forming frequency is expressed as Equation 48 below.
  • the DC voltage provided to the grid forming power converter 100 obtained by Equation 48 - the relationship between the output frequency is in the form of an exponential function convex downward as shown in FIG. 19 .
  • the grid-forming power converter 100 changes exponentially when the input voltage VDC changes.
  • the rotational speed error (g) of the generator rotor is expressed in terms of the DC voltage (VDC) provided to the grid-forming generator. Assuming that it can be expressed in the form of an exponential function as in Equation (1) of Equation 49 below, an acceleration (g') obtained by differentiating it can be expressed as Equation (2). In Equation 49, a minus sign is added to the coefficients a and b in Equation 6 described above.
  • Equation 48 the output frequency (f) of the grid forming frequency is expressed as the rotation speed (g) and the acceleration (g') as shown in Equation 50 below.
  • the coefficients a, b, c and d are design parameters. As exemplified by Equation 51 below, a coefficient a is related to a droop characteristic, and b is related to an inertia characteristic. c corresponds to -Vd0 by adding a minus sign to the DC voltage provided to the grid-forming power conversion unit 100 when the grid-forming power conversion unit 100 outputs the maximum load frequency.
  • Equation 52 the output frequency f of the grid forming frequency is expressed as in Equation 52 below.
  • the DC voltage provided to the grid forming power converter 100 obtained by Equation 52 - the relationship between the output frequency is in the form of an exponential function convex upward as shown in FIG. 20 .
  • Equation 54 the output frequency f of the grid forming frequency is expressed as in Equation 54 below.
  • the DC voltage provided to the grid-forming power converter 100 obtained by Equation 54-output frequency relationship is in the form of an exponential function convex upwards passing through the origin as shown in FIG. 21 . Even in the fourth embodiment, it is possible to form an output frequency with the voltage provided to the grid-forming power converter 100 without controlling the current formed in the grid-forming power converter 100 . Accordingly, there is provided an advantage that there is no need to introduce a separate and complicated current controller.
  • FIG. 22 (a) is a diagram illustrating a DC voltage versus frequency relationship according to the prior art and a voltage versus frequency according to the present embodiment
  • FIG. 22 (b) is an enlarged view of the operating point in FIG. 22 (a). It is a drawing.
  • reference numeral 221 denotes a frequency change according to the prior art
  • 222 denotes a case where the steady-state frequency fss is the maximum load frequency
  • 223 denotes the steady-state frequency fss.
  • ) represents the case of no-load frequency
  • (224) represents the case where the steady-state frequency (fss) is the rated frequency.
  • the rated frequency in Korea is 60 Hz
  • the rated frequency in foreign countries is 50 Hz or 60 Hz.
  • reference numeral 225 denotes a full load state output frequency
  • 226 denotes a steady state output frequency in a full load state
  • 227 denotes an output frequency in a no-load state
  • 228 denotes a no-load state. represents the steady-state output frequency.
  • Reference numeral 229 denotes the output frequency according to the prior art
  • 230 denotes the output frequency at the set point.
  • the frequency conversion equation was derived in a bottom-up manner by applying the boundary condition after reflecting the intended droop ratio and inertia property to each parameter of the equation in advance.
  • a top-down method of deriving an appropriate value of each parameter after first applying a boundary condition is adopted.
  • VDC DC voltage
  • the balanced rotational speed appears as a DC voltage, and is converted into a frequency through an exponential function. Therefore, if the DC voltage is the same as the rated voltage, it is regarded as a no-load state and the no-load frequency fFLGFM is output.
  • a droop control frequency fss corresponding to the load is output.
  • Equation 57 When the frequency converted for each voltage level is expressed as an equation, the relationship between parameters a and d is arranged as shown in Equation 57.
  • Equation 57 1, 2, 3 and 4 respectively, the DC voltage is rated, the voltage is dropped to an arbitrary value by the load supply, the voltage is the lowest by the full load supply, and the voltage is 0 corresponding to the state of being From this, it can be seen that the parameters of the fifth embodiment are not determined as constants, unlike the previous embodiment, but are determined as a function of VDC that changes according to the voltage level in order to match the measured voltage level and the target droop fss.
  • Equation 60 a may be expressed by Equation (1) of Equation 60.
  • b may be defined as in Equation 59.
  • a value selected based on the full load (refer to Equation 58) may be used.
  • Equation 61 (wc/(s+wc)) denotes a low-frequency bandpass filter. That is, the exponential term operates instantaneously and bar a and bar d operate with a delay, so that the inertia effect is expressed from the DC voltage in the transient section, and finally converges to the desired steady-state frequency fss.
  • VDC input DC voltage
  • the output frequency may be similar to the embodiment illustrated in FIG. 61, but in this embodiment, the final value of the output frequency is determined according to the frequency fss intended by the droop. It is different in that it draws a variety of different curves for the VDC.
  • FIG. 23 a sixth embodiment of the output frequency control method of the grid-forming power conversion control apparatus according to the present invention will be described with reference to FIG. 23 .
  • the description of elements that are the same as or similar to those of the above-described embodiments may be omitted.
  • the output frequency of the grid forming power converter 100 is linearly changed when the input voltage VDC is changed.
  • the operation of the sixth embodiment is as follows.
  • Equation 62 In order to achieve a desired load sharing from parallel operation of a plurality of generators, control according to the droop principle as shown in Equation 62 is common. All physical quantities are described according to the per unit unit method.
  • Controlling the GFM converter with droop converges to the steady-state frequency fss depending on interaction with other parallel operators, and if you want more load sharing, you can do this by lowering the droop m or increasing the setpoint PSP. If you want to reduce the load sharing, you can do it by increasing m or decreasing PSP. This is the output when the PSP system reaches f0, so the actual output may be higher or lower than the PSP depending on the fss.
  • An object of the present embodiment is to achieve control that achieves load sharing performance equivalent to droop by using a measurement value other than P.
  • the frequency fout can be controlled by having a proportional relationship with the DC voltage, so that the droop control can be replaced by controlling it according to Equation 63.
  • Equation 64 which is the fluctuation equation of the generator, it can be seen that P can also be indirectly grasped through VDC, paying attention to the matching principle that DC voltage means the rotation speed of the synchronous generator rotor.
  • K damping coefficient w
  • w’ rotor rotation angular velocity, angular acceleration
  • the output in the equilibrium state in which the rotor does not decelerate or accelerate any more, the output can be known from the rotational speed of the rotor. Also, since the rotation speed can be known from the DC voltage, the output can be known from the DC voltage as a result. Therefore, if 1 the relationship between DC voltage and output, 2 relationship between DC voltage and frequency, and 3 relationship between output and frequency, is accurately defined, then droop control can be replaced by DC voltage measurement.
  • VFL full-load voltage
  • VNL no-load voltage
  • Equation 65 Equation 65 2 in Equation 65 is p.u.
  • the existing matching principle of equalizing unit reference DC voltage and rotation speed is applied.
  • fNL No-load frequency
  • fFL Full-load frequency
  • Equation 67 The relationship between output and frequency means droop, and if Equation 62 is rewritten according to the relationship with DC voltage, Equation 67 is obtained.
  • Equation 67 can be expressed as Equation 68.
  • Equation 68 the same droop frequency as Equation 62 can be achieved in a steady state, and frequency control can be performed only by measuring the DC voltage without a separate control unit for controlling the DC current.
  • the purpose of the control parameter k is to reduce noise by increasing k when the high frequency component of the DC voltage is severe and to enable smooth tuning.
  • FIG. 24 is a diagram illustrating a DC voltage and an output frequency provided to the grid-forming power converter when the grid-forming power converter is controlled in the first embodiment, the second embodiment, and the third embodiment, respectively.
  • the grid-forming power converter 100 controlled by the first embodiment outputs a frequency that increases in a first-order function.
  • the grid forming power conversion unit 100 controlled by the second embodiment outputs a frequency increasing exponentially convex downwards
  • the grid forming power conversion unit 100 controlled by the third embodiment It can be seen that outputs an exponentially increasing frequency that is convex upwards.
  • FIG. 25 (a) is a diagram showing the output frequency versus the DC voltage provided to the grid-forming power converter according to the prior art and the first embodiment and the second embodiment.
  • FIG. 25(b) is an enlarged view of the range of 225kV to 245KV of FIG. 25(a).
  • the grid forming power conversion unit 100 controlled by the prior art is linear in the magnitude of the provided DC voltage.
  • this is performed by controlling the current provided to the grid forming power conversion unit 100 using a separate DC current controller.
  • the change width of the frequency is relatively small even when the first embodiment changes linearly with respect to the DC voltage and the second embodiment changes exponentially.
  • the range of change in frequency according to the embodiment and the second embodiment can be seen.
  • 26 to 30 show when the power system (dotted line) and the grid-forming power conversion unit 100 (solid line) supply power to the load, and when disturbance occurs at 2 seconds, 3 seconds, and 4 seconds, power according to time It is a figure which shows the fluctuation
  • 26(a) and 26(b) show experimental results of a grid-forming power conversion unit (solid line) and a power system (dotted line) controlled by the prior art.
  • the grid-forming power conversion unit 100 and the power system supply power to the load by 30Mw each from approximately 1.3 seconds.
  • a disturbance occurs in 2.0 seconds
  • both the power system and the grid-forming power conversion unit 100 vibrate, and the vibration is stabilized after approximately 2.5 seconds.
  • vibration occurs in the power supplied by the disturbance generated in 3 seconds, and the vibration is stabilized after 3.5 seconds.
  • the grid-forming power conversion unit 100 provides 60MW to the load.
  • FIG. 26(b) it can be seen that the output frequency fluctuates significantly whenever a disturbance occurs.
  • FIGS. 27 (a) and 27 (b) show the experimental results of the grid forming power conversion unit (solid line) and the power system (dotted line) controlled in the first embodiment
  • FIGS. 28 (a), 28 (b) ) shows the experimental results of the grid forming power conversion unit (solid line) and the power system (dotted line) controlled in the second embodiment
  • FIGS. 29 (a) and 29 (b) are the grids controlled by the third embodiment Showing the experimental results of the forming power conversion unit (solid line) and the power system (dotted line)
  • FIGS. 30 (a) and 30 (b) are grid forming power conversion unit 100 (solid line) controlled in the fourth embodiment and the experimental results of the power system (dotted line) are shown.
  • the grid-forming power conversion unit 100 and the power system supply power to the load by 30Mw, respectively, from about 1.3 seconds later.
  • a disturbance occurs at 2.0 seconds, it is confirmed that both the power system and the grid-forming power conversion unit 100 vibrate, and the vibration is stabilized after approximately 2.2 seconds. Also, in the case of a disturbance occurring in 3 seconds, the vibration is stabilized after 15.2 seconds. After 4 seconds, the grid-forming power conversion unit 100 provides 60MW to the load.
  • the grid-forming power conversion unit 100 controlled by the first to fourth embodiments can confirm that the vibration is stably stabilized faster than in the prior art even when a disturbance occurs, It can be seen that even when disturbance occurs, the range of variation of the frequency output by the grid-forming power conversion unit 100 is not large compared to the prior art.
  • Figure 31 (a) shows the experimental results of the grid forming power conversion unit (solid line) and the power system (dotted line) controlled in the fifth embodiment
  • Figure 31 (b) is from 1.2 seconds to 3.2 seconds in Figure 31 (a) It is an enlarged view of the second part.
  • the grid-forming power conversion unit 100 and the AC power generation system are connected in 1.5 seconds.
  • a disturbance occurs that increases the load, and the set-point of the grid forming converter decreases in 4.5 seconds, and the set-point of the AC power generation system is maintained.
  • the output frequency is the same as Figure 31 (c). It can be confirmed that smooth load sharing with the AC system is achieved by having different steady-state frequencies according to the load level.
  • the third guide line G3, the first guide line G1, and the second guide line G2 each show an output distribution according to an intended droop at the corresponding time point. Since the output of the grid forming power converter 100 shown by the red solid line converges on each guide line, it can be confirmed that the desired load sharing is performed.
  • FIG. 32(a) and 32(b) show a case in which control is performed by droop control according to the prior art in the experimental condition illustrated in FIG. 19 . It can be seen that the vibration is attenuated in about 0.35 seconds in the present embodiment illustrated in FIG. 31(b), but according to the prior art illustrated in FIG. 32(a), 0.6 seconds, which is approximately twice the time of this embodiment, is It can be seen that the vibration is attenuated over time. Furthermore, when the droop control according to the prior art is to be controlled at high speed as in the present embodiment, it can be confirmed that a large vibration occurs as shown in FIG. 32(b), and the droop control according to the prior art cannot be controlled at high speed. can confirm.
  • FIGS. 33 and 34 are diagrams showing experimental results of grid forming power conversion (solid line) and power system (dashed line) controlled in the sixth embodiment.
  • the grid-forming power conversion unit 100 and the power system supply power to the load by 30Mw each from about 1 second.
  • a disturbance occurs at 1.3 seconds
  • both the power system and the grid-forming power conversion unit 100 vibrate, and the vibration is stabilized after approximately 2.0 seconds.
  • the vibration is stabilized after approximately 0.3 seconds after the disturbance occurs.
  • the grid-forming power conversion unit 100 provides power to the load alone.
  • the grid forming power conversion unit 100 controlled according to the sixth embodiment can confirm that the vibration is stably stabilized faster than in the prior art even when a disturbance occurs, and the disturbance is Even if it occurs, it can be seen that the range of variation of the frequency output by the grid-forming power conversion unit 100 is not large compared to the prior art.
  • the present invention relates to a grid-forming power conversion control device, and since it can provide a stable operating environment based on system information connected with information of a power conversion device to be connected, there is potential for industrial application.

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Abstract

La présente invention se rapporte à un appareil permettant de commander une conversion de puissance de formation de réseau. L'appareil peut comprendre : une unité de conversion de puissance de formation de réseau qui convertit l'énergie fournie par un générateur d'énergie renouvelable en une tension pour l'alimentation d'une source d'alimentation de système, et qui fournit, de ce fait, de l'énergie à la source d'alimentation de système ; une unité de régulation de tension optimale qui est raccordée à l'unité de conversion de puissance de formation de réseau et qui, en calculant un courant de défaut lorsqu'un défaut se produit, et en calculant un courant inverse qui est généré lorsque la tension est abaissée lorsque le défaut se produit, et un courant inverse de récupération qui est généré lorsque le défaut est éliminé, qui effectue une régulation de tension optimale qui consiste à trouver un point de fonctionnement auquel une surintensité due aux caractéristiques d'alimentation en courant de défaut requises par le système est réduite à un minimum, et à trouver un point de fonctionnement qui satisfait aux exigences du système d'alimentation autant que possible dans une plage qui ne dépasse pas la limite du courant qu'un appareil de conversion de puissance peut fournir ; et une unité de commande d'évaluation de contrainte d'impédance qui collecte des paramètres pour une évaluation d'impédance à l'aide d'informations provenant du système d'alimentation, et qui définit une entrée d'impédance de connexion MVA de référence et une tension de source de formation de grille (GFM) de sorte à obtenir une impédance minimale qui ne dépasse pas la limite du courant que l'appareil de conversion de puissance peut fournir.
PCT/KR2021/017281 2020-11-23 2021-11-23 Appareil et procédé permettant de commander une conversion de puissance de formation de réseau Ceased WO2022108420A1 (fr)

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KR1020200164432A KR102390466B1 (ko) 2020-11-30 2020-11-30 그리드 포밍 컨버터 출력 주파수 제어 방법 및 그리드 포밍 컨버터의 제어 장치
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CN117081160B (zh) * 2023-10-17 2023-12-26 广州菲利斯太阳能科技有限公司 一种用于微电网的并离网切换系统
CN119130166A (zh) * 2024-07-30 2024-12-13 中国电力科学研究院有限公司 基于电流短路约束的构网型场站选址方案比选方法及系统

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