KR20140130319A - Multiple-Tuned Filter Design Method for HVDC system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for designing a multiple tuned filter (MTF) according to characteristics of a high voltage direct current (HVDC) system .
A method for designing a double-tuned filter (MTF) according to an exemplary embodiment of the present invention includes: setting an input parameter corresponding to the MTF; Setting a resonance frequency corresponding to the MTF; Setting a range of a resistance value corresponding to the MTF; Calculating a filter parameter corresponding to the MTF based on the input parameter and the resonance frequency; Calculating individual harmonic components or total harmonic distortion (THD) based on the calculated filter parameters; Determining whether the calculated individual harmonic component or total harmonic distortion factor satisfies an allowable level; Setting a resistance value within a predetermined resistance value range when the harmonic component or full harmonic distortion satisfies a predetermined allowable level; And connecting the load or the system based on the set resistance value.

Description

(Multiple-Tuned Filter Design Method for HVDC System)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for designing a multiple tuned filter (MTF) according to characteristics of a high voltage direct current (HVDC) system .

In the HVDC system, the harmonic filter suppresses the harmonics generated in the power conversion through the converter operation into the AC system, and also acts as a reactive power source due to the reactive power consumption. Since most current type HVDC systems operate with 12 pulses, they generate characteristic harmonics of 12n ㅁ 1 such as 11, 13, 23, 25 and so on. Especially, the 11th and 13th harmonics are large, 11th and 13th order filters are used.

In the current type HVDC system, the converter operates mostly with 12 pulses. The 80kV 60MW HVDC system currently installed in Jeju Island is also composed of 12 pulse converters using two 6 pulse group serial connection.

In the HVDC system, a single tuned filter (STF) or a double tuned filter (DTF) is widely used as a harmonic filter. Equations for the series-parallel impedance of the filter can be used to design such a filter.

There is a problem that the filter design is accurate, efficient, and does not have a formalized method or method, because the passive elements included in the filter are calculated by passive calculation based on design rating, gender, and the like.

In addition, there is a problem that stabilization is not taken into consideration when it is connected to the system.

It is an object of the present invention to provide an MTF and a damped-type MTF designing method and apparatus according to characteristics of a HVDC system.

A method for designing a double-tuned filter (MTF) according to an exemplary embodiment of the present invention includes: setting an input parameter corresponding to the MTF; Setting a resonance frequency corresponding to the MTF; Setting a range of a resistance value corresponding to the MTF; Calculating a filter parameter corresponding to the MTF based on the input parameter and the resonance frequency; Calculating individual hammer components or total harmonic distortion (THD) based on the calculated filter parameters; Determining whether the calculated individual harmonic component or total harmonic distortion factor satisfies an allowable level; Setting a resistance value within a predetermined resistance value range when the harmonic component or full harmonic distortion satisfies a predetermined allowable level; And connecting the load or the system based on the set resistance value.

The determination of whether or not the harmonic component or the total harmonic distortion factor satisfies the allowable level is performed by setting and storing the set input parameter in the MTF if the harmonic component or the total harmonic distortion factor is less than a predetermined allowable level, And resetting the predetermined resonance frequency and restricting the filter parameter when the predetermined resonance frequency is equal to or higher than the predetermined allowable level.

In addition, the resetting of the resonant frequency may be reset based on the filtering frequency that should be filtered in the MTF.

Further, the resonance frequency can be reset within the range of the frequency to be filtered.

Also, the MTF filter may be connected to an AC system of a HVDC (High Voltage Direct Current) system.

In addition, the resistance value is set within a range of predetermined minimum and maximum values, and a resistance value adjusted according to a load or a system connected to the MTF is set within a predetermined minimum and maximum value, and the MTF performance connected to the load or the system, Checking; And resetting the set resistance value according to the determined performance.

Further, the resistance value readjustment may adjust each of or a plurality of resistors included in the resonance tank required for the harmonic filtering at the same time.

Further, the filter parameter may be calculated based on the input parameter, the resonance frequency, and the resistance.

An MTF according to an embodiment of the present invention includes a high voltage capacitor bank; Low Voltage Air Core Reactor; And a plurality of resonance tanks connected in series so as to correspond to orders of the harmonics to be removed.

The plurality of resonance tanks may each have one capacitor, one resistor, and one inductor connected in parallel.

The resistors included in the plurality of resonance tanks may be adjusted and set independently or simultaneously in the increasing direction or the decreasing direction.

An MTF parameter setting apparatus according to an embodiment of the present invention includes an input unit for receiving input parameters and a resistance value; A storage unit for storing an input parameter and a resistance value input to the input unit and storing filter parameters calculated based on the input parameter and the resistance value; A resonance frequency corresponding to the MTF is set based on the inputted input parameter, a filter parameter corresponding to the MTF is calculated based on the input parameter and the resonance frequency, and the individual harmonic Component or a total harmonic distortion (THD), judges whether the calculated individual harmonic component or the total harmonic distortion satisfies an allowable level, and judges whether the harmonic component or the total harmonic distortion satisfies a predetermined allowable level And a controller for adjusting and setting a resistance value within a predetermined resistance value range.

In addition, the control unit may adjust the resistances respectively corresponding to the plurality of resonance tanks constituting the MTF.

According to the present invention, it is possible to have a stylized and efficient design method or design apparatus of the MTF.

In addition, according to the present invention, it is possible to secure safety against stabilization with the system connected to the MTF.

1 is a block diagram showing a general HVDC system.
2 is a diagram showing a harmonic equivalent model corresponding to a HVDC system in which a harmonic filter is inserted.
3 is an exemplary view showing a method of designing an MTF using an equivalent circuit method.
4 is an exemplary diagram illustrating an MTF design algorithm according to an embodiment of the present invention.
5 is a configuration diagram showing an MTF filter parameter setting apparatus to which an embodiment of the present invention is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 is a block diagram showing a general HVDC (High Voltage Direct Current) system.

Referring to FIG. 1, the HVDC system shown in FIG. 1 shows a general MTF (Multiple Tuned Filter) installed in an 80 kV class HVDC system. The 80 kV HVDC system has a typical anode system.

The 80-kV HVDC system is characterized by a 12-pulse converter with nine poles.

These HVDC converters can generate harmonic currents above a specified value. Hence, without filtering, harmonic currents can distort AC voltage and interfere with normal system operation.

Harmonic filters can be used to make harmonic currents flow by installing a parallel line with a small impedance so that distortion of the AC voltage can be accommodated within a range that can accommodate the AC voltage.

The 12-pulse converter has characteristic harmonics of 12n ㅁ primary. Therefore, the harmonic components required for the filter may be 11th, 13th, 23rd and 25th order components.

Higher order higher harmonic components can be attenuated by a high pass filter.

In an 80 kV HVDC system, an MTF filter that compensates for 17 Mvar of reactive power and a high-band filter that compensates for 17 Mvar of reactive power can be used.

The MTF may include one high voltage capacitor bank and a low voltage air core reactor in series and a low voltage capacitor bank and an air core reactor in parallel. The harmonic filter can serve to supply reactive power to the system at 60 Hz.

2 is a diagram showing a harmonic equivalent model corresponding to a HVDC system in which a harmonic filter is inserted.

Referring to FIG. 2, the current type HVDC converter can absorb reactive power from the AC system and supply the reactive power required by the converter through the harmonic filter.

This HVDC converter can be modeled as a constant current harmonic power supply in the AC stage and a constant voltage harmonic power supply in the DC stage. Since the harmonic filter suppresses the harmonic wave generated from the HVDC converter into the AC system, A harmonic equivalent model using a harmonic power source can be used.

Where In is the harmonic current generated from the HVDC converter, Ifn and Isn are the harmonic currents flowing into the filter and AC system, respectively. Zfn and Zsn represent the harmonic impedance of the AC system, respectively, and Vsn represents the harmonic voltage of the AC system.

The performance of the harmonic filter depends on the admittance value of the AC system. Since the admittance of such a system varies with the state of the actual power system, it is very difficult to know the correct admittance value at a given frequency. Therefore, it can be determined by fluttering the admittance according to a given frequency on a complex plane having the admittance angle as a boundary when designing a harmonic filter.

3 is an exemplary view showing a method of designing an MTF using an equivalent circuit method.

Referring to FIG. 3, there is a need to consider harmonic distortion, system reliability, cost, and the like when designing an AC filter (or a harmonic filter) in an HVDC system.

Since the harmonic filter has a cost corresponding to one bank, it is preferable to use two single tuned filters (hereinafter referred to as 'STF') to remove the two harmonics as shown in FIG. 3A (B) or (c), it is economically advantageous to utilize less space when removing the same number of harmonics by connecting one filter bank in parallel. This is because MTF has a merit that only one switchgear is required compared to STF.

Also, a damped-type MTF including a damping resistor R connected in parallel to the parallel LC resonance tank may be used as shown in FIG. 3 (C).

The equivalent circuit approach can be a relatively easy approach in designing an MFT.

In order to design the MTF, the amount of reactive power to be totally compensated is distributed equally to each STF, and then the parameter values of each STF can be selected.

In selecting the parameter value of the STF, it is necessary to first determine the magnitude of the voltage applied to the filter and the amount of reactive power to be compensated by the filter.

In this case, since the structure of the filter is a series connection of the capacitor and the inductor in the series LC filter, the reactance of the filter can be the difference between the reactance of the capacitor and the inductor.

On the other hand, at the harmonic of the h-th order to be removed, the impedance of the filter as a whole must be zero, so that the reactance of the capacitor is equal to the inductor's reactance times the square of h.

According to the general MTF designing method described above, the HVDC converter generates a harmonic current equal to or higher than a predetermined value, so that a harmonic filter is installed so that the harmonic current flows, thereby making the distortion of the AC voltage within a range that can accommodate the AC voltage.

The 12-pulse converter has a characteristic harmonic of 12n ㅁ 1. Therefore, the harmonic components needed for the filter are 11th, 13th, 23rd and 25th components, and higher order harmonic components can be attenuated by the high-pass filter.

The MTF can be a single high-voltage capacitor bank and a low-voltage air core reactor in series, and a low-voltage capacitor bank and an air core reactor in parallel. In addition, a plurality of parallel LC resonance tanks according to harmonics to be removed can be connected in series.

The harmonic filter serves to supply reactive power to the system at 60 Hz. Therefore, the terminals of the rectifier and the inverter absorb the reactive power in proportion to the active power exchanged between the converter and the AC system. The harmonic filter uses a capacitor, so it can supply the reactive power required by the converter. If the reactive power from the filter is not sufficiently compensated, the AC voltage at the terminal may not be large enough to allow the converter to operate normally.

On the other hand, the HVDC converter can be modeled as a constant-voltage harmonic power supply from a dc-stage and a constant-current harmonic power supply from an alternating-current stage. Since it is one of the role of the filter to prevent the harmonics generated from the HVDC converter from entering the system, modeling for harmonic analysis is required at the AC terminal.

Here, the filter and the power system (e.g., AC system) connected to the filter can be represented or modeled as an impedance.

Using the model of FIG. 2, it is possible to design the filter after determining the degree of harmonic current flowing in the converter and the harmonic characteristics of the resulting voltage.

Further, in order to increase stability of the relationship between the filter and the power system connected to the filter, it is possible to easily implement the filter by changing the resistance value of the filter.

The MTF design algorithm according to one embodiment disclosed herein will now be described in detail with reference to FIGS. 4 through 5. FIG.

4 is an exemplary diagram illustrating an MTF design algorithm according to an embodiment of the present invention.

Referring to FIG. 4, an MTF design algorithm according to an embodiment of the present invention may be performed as follows.

First, an input parameter corresponding to the MTF can be set (S402)

Specifically, the input parameter corresponding to the MTF should be set in the optimum filter parameter setting corresponding to the MTF.

The input parameter may be a parameter related to the rating or target performance of the MTF. The input parameter may also include at least one of a rated voltage of a load or a system connected to the MTF, a reactive power to be compensated for by the MTF, and a filtering frequency.

The load or system connected to the MTF may be a power system of the HVDC system (e.g., an AC system).

The filtering frequency may be a frequency that should be filtered by the MTF.

According to an exemplary embodiment, the filtering frequency may include a first filtering frequency and a second filtering frequency that is greater than the first filtering frequency.

For example, when the harmonic components to be filtered are the eleventh and thirteenth harmonic components described above, the first filtering frequency is a frequency corresponding to the eleventh harmonic component, and the second filtering frequency corresponds to the thirteenth harmonic component Lt; / RTI >

Next, the resonance frequency initial value can be set (S404)

According to one embodiment, the setting of the resonance frequency may be set based on a filtering frequency to be filtered by the double-tuned filter.

For example, the resonant frequency may be set to a frequency between the first filtering frequency and the second filtering frequency.

Specifically, the resonance frequency setting step may be an initial value of the resonance frequency, which is an initially inputted resonance frequency for setting a filter parameter.

For example, the resonance frequency may be set to the first filtering frequency as an initial value.

Next, the minimum and maximum values of the resistance value can be set (S406)

According to one embodiment, the resistance value can be set to the minimum value and the maximum value in consideration of the load connected to the MTF or the amount of reactive power required for stabilization with the system.

Next, a filter parameter corresponding to the MTF may be calculated based on the input parameter, the resonance frequency, and the resistance value (S408)

According to one embodiment, the filter parameter may mean a value corresponding to a passive element corresponding to the MTF.

For example, the MTF includes a first LC circuit portion having a first capacitor and a first inductor connected in series, a second LC circuit portion having a second capacitor and a second inductor connected in parallel, and a third LC circuit portion having a third capacitor and a third inductor connected in parallel The first LC circuit portion, the second LC circuit portion, and the third LC circuit portion may be connected in series.

In this case, the MTF parameter may include at least one of a capacitance value of the first capacitor, an inductance value of the first inductor, a capacitance value of the second capacitor, an inductance value of the second inductor, a capacitance value of the third capacitor, And may include at least one.

In this case, the resonance frequency may be a parallel resonance frequency corresponding to the second LC circuit part and the third LC circuit part.

Next, individual harmonic components or total harmonic distortion (THD) corresponding to the MTF can be calculated based on the filter parameters (S410)

According to one embodiment, the individual harmonic component may be a harmonic component corresponding to the harmonic current generated by the HVDC converter included in the HVDC system.

The total harmonic distortion may be a THD corresponding to the harmonic current.

Next, it is possible to determine whether the individual harmonic component or the total harmonic distortion factor is less than or equal to a reference value (S412)

The reference value may be determined based on performance, specifications, design specifications, and the like required for the MTF.

For example, the reference value may be determined based on the permission level of IEEE Std. 519.

For example, the reference value corresponding to the individual harmonic component may be 1.5% of the fundamental frequency component corresponding to the load or the system connected to the MTF, and the reference value corresponding to the total harmonic distortion may be 2.5%.

As a result of the determination, the individual harmonics section SEH can finally set (store) the calculated filter parameter as a parameter value of the MTF when the total harmonic distortion is smaller than the reference value (S414)

On the other hand, if it is determined that the individual harmonic component or the total harmonic distortion factor is larger than the reference value, the resonant frequency may be reset (S416)

Next, a resistance value according to the grid connection can be set (S418)

According to one embodiment, it may be set to any value within the range of the minimum and maximum values of the predetermined resistance value in order to ensure safety in connection with a load or a system. Next, the filter performance and the filter band pass can be confirmed by the set resistance value (S418)

According to one embodiment, the connection stability of the load or the system can be determined according to the resistance value adjusted through a predetermined program (algorithm) according to the adjusted and set resistance value. In addition, in consideration of cost and loss, it is judged whether or not the safety allowance level is satisfied according to the resampled resistance value (S422), and the resistance value can be readjusted (S424) and set (stored) (S426).

In the resistance value adjustment, the resistors (C1 and C2 in FIG. 3 (c)) included in each of the plurality of filter tanks constituting the MTF can be adjusted individually or simultaneously.

5 is a configuration diagram showing an MTF filter parameter setting apparatus to which an embodiment of the present invention is applied.

Referring to FIG. 5, the filter parameter setting apparatus 100 may include an input unit 110, a storage unit 120, and a control unit 130.

The input unit 110 may receive the input parameter and the resistance value corresponding to the MTF.

The input unit 110 may generate input data for controlling the operation of the filter parameter setting apparatus 100 by the user. The input unit 110 may include a keypad, a dome switch, a touch pad, a jog wheel, a jog switch, and the like.

The input unit 110 serves as an interface with all the external devices connected to the filter parameter setting apparatus 100.

The storage unit 120 may store a program for processing and controlling the control unit 130 and may temporarily store input / output data (input parameters, resistance values) and result data calculated and calculated by the control unit 130 And perform a function for storing final result data.

The controller 130 may control overall operation of the filter parameter setting apparatus 100 executed in the filter parameter setting apparatus 100. [

The controller 130 may be implemented as a microcontroller or a microprocessor. The controller 130 may set a resonance frequency corresponding to the MTF and a resistance value within a preset reference value. In addition, the controller 130 may set a parameter value corresponding to the MTF based on the input parameter, the resonance frequency, and the resistance value.

The control unit 130 can determine whether the individual harmonic component or the total harmonic distortion satisfies the reference level and can reset the resonance frequency according to the determination result.

The control unit 130 may set or reset the resistance value within a predetermined reference point according to securing of safety as the load or the system is connected to the MTF.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments.

The scope of protection of the present invention should be construed according to the following claims, and all technical ideas which are within the same range should be construed as being included in the scope of the present invention.

Claims (13)

In a double tuned filter (MTF) design method,
Setting an input parameter corresponding to the MTF;
Setting a resonance frequency corresponding to the MTF;
Setting a range of a resistance value corresponding to the MTF;
Calculating a filter parameter corresponding to the MTF based on the input parameter and the resonance frequency;
Calculating individual harmonic components or total harmonic distortion (THD) based on the calculated filter parameters;
Determining whether the calculated individual harmonic component or total harmonic distortion factor satisfies an allowable level;
Setting a resistance value within a predetermined resistance value range when the harmonic component or full harmonic distortion satisfies a predetermined allowable level;
And connecting a load or a system based on the set resistance value
MTF design method. The method according to claim 1,
The determination as to whether the harmonic component or the total harmonic distortion satisfies the allowable level
Setting and storing the set input parameter in the MTF if the harmonic component or the total harmonic distortion is less than a predetermined allowable level,
And resetting the predetermined resonance frequency when the harmonic component or the total harmonic distortion is equal to or higher than a predetermined allowable level and restoring the filter parameter
MTF design method. 3. The method of claim 2,
The resetting of the resonant frequency
And is reset based on the filtering frequency that should be filtered into the MTF
MTF design method. The method of claim 3,
The resonance frequency
Which is reset within the range of frequencies to be filtered
MTF design method. The method of claim 1, wherein
The MTF filter
Connected to the AC grid of the HVDC (High Voltage Direct Current) system
MTF design method. The method according to claim 1,
The resistance value
Confirming the performance of the MTF connected to the load or the system based on the set resistance value, the resistance value adjusted according to the load or the system connected to the MTF is set within a predetermined minimum and maximum value;
And resetting the set resistance value according to the identified performance
MTF design method. The method according to claim 6,
The resistance value readjustment
A plurality of resistors included in the resonance tank required for the harmonic filtering are individually or simultaneously adjusted
MTF design method. The method according to claim 1,
The filter parameter
Calculated based on the input parameter, the resonance frequency, and the resistance
MTF design method. MTF
High voltage capacitor bank;
Low Voltage Air Core Reactor;
And a plurality of resonance tanks connected in series so as to correspond to orders of harmonics to be removed
MTF. 10. The method of claim 9,
The plurality of resonance tanks
One capacitor, one resistor and one inductor are connected in parallel
MTF The method of claim 10, wherein
The resistors included in the plurality of resonance tanks
Independently or simultaneously adjusted and set in an increasing or decreasing direction
MTF. In the MTF parameter setting apparatus,
An input unit for receiving an input parameter and a resistance value;
A storage unit for storing an input parameter and a resistance value input to the input unit and storing filter parameters calculated based on the input parameter and the resistance value;
A resonance frequency corresponding to the MTF is set based on the inputted input parameter, a filter parameter corresponding to the MTF is calculated based on the input parameter and the resonance frequency, and the individual harmonic Component or a total harmonic distortion (THD), judges whether the calculated individual harmonic component or the total harmonic distortion satisfies the allowable level, and judges whether the harmonic component or the total harmonic distortion satisfies the predetermined allowable level And a controller for adjusting and setting a resistance value within a predetermined resistance value range;
MTF parameter setting device. 13. The method of claim 12,
The control unit
The resistors constituted by the number corresponding to the plurality of resonance tanks constituting the MTF are individually or simultaneously adjusted
MTF parameter setting device.

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