CN107834861A - Primary side capacitor voltage balance method and device based on primary side phase shift - Google Patents

Abstract

A primary side capacitor voltage balance method and device based on primary side phase shifting, the primary side capacitor voltage balancing method based on primary side phase shifting includes: detecting the voltage value of each primary capacitor; Obtaining a first phase shift angle of the first bridge arm and the second bridge arm of the primary side converter module of the first transformer according to the voltage value of the first primary side capacitor and the reference voltage at a preset reference voltage; Perform pulse width modulation control on the first transformer primary-side converter module according to the first phase-shift angle; wherein, the transformer primary-side converter module is a full-bridge converter module, and the first transformer primary-side converter module The current module is connected in parallel with the first primary capacitor, and the full-bridge converter module includes the first bridge arm and the second bridge arm. The primary capacitor voltage balance method and device based on the primary phase shift provided by the present invention can balance the voltage of the primary capacitor and improve the performance of the power electronic converter.

Description

Primary capacitor voltage balance method and device based on primary phase shift

technical field

The invention relates to the field of power electronic converters, in particular to a primary-side capacitor voltage balancing method and device based on primary-side phase shifting.

Background technique

The Dual Active Bridge (DAB for short) topology is a common series DC-DC converter structure. This topology can achieve functions such as energy bidirectional flow and wide-range soft switching, so it has attracted extensive attention from academia and industry.

As shown in Figure 1, in the DAB topology, the left side of the transformer is usually defined as the primary side, and the right side is the secondary side. The H-bridge converter modules on the primary side of the topology realize the function of high withstand voltage through series connection. The H-bridge converter modules generally adopt a modular design, and their circuits usually use exactly the same power devices and passive devices. At the same time, the transformer turn ratio corresponding to each H-bridge converter module is often designed to be consistent, that is, n _p1 /n _s =n _p2 /n _s =n. Therefore, the same driving signal can be used to control the H-bridge converter module on the primary side, that is, the driving signals of the switching tubes S ₁₁ , S ₁₂ , S ₁₃ , and S ₁₄ are the same as those of the switching tubes S ₂₁ , S ₂₂ , S ₂₃ , and S ₂₄ One-to-one correspondence is equal. For the control of the overall system, the primary and secondary side power devices are usually adopted, namely the switching tubes S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₂₂ , S ₂₃ , S ₂₄ and the switching tubes S ₃₁ , S ₃₂ , S ₃₃ , and S ₃₄ perform pulse width modulation (PulseWidth Modulation, PWM for short) control of the output voltage and current by means of phase shifting of control signals.

When performing the above voltage and current control, the specific relationship between input voltage, output power, output voltage and phase shift angle is

Among them, P1 is the power transmitted by an H-bridge on the primary side; d is the equivalent duty cycle of the power switching device, if the switching tubes S ₁₁ , S ₁₂ , S ₁₃ , S ₁₄ , S ₂₁ , S ₂₂ , S ₂₃ , The phase shift angle of the control signal between S ₂₄ and switch tubes S ₃₁ , S ₃₂ , S ₃₃ , and S ₃₄ is but Vo is the output voltage, L is the inductance value of L ₁ and L ₂ , fs is the switching frequency, and V _Ck is the voltage on the capacitor C _k . If the parameters of the electronic components are exactly the same, in this control scheme, the capacitor voltage on the primary side can be naturally balanced. However, in actual situations, there may be deviations in the parameters of each component, for example, the excitation inductance or leakage inductance of the transformer is not equal, and the inductance value of the energy storage inductance is not equal. Deviations in these parameters can cause capacitor voltage imbalance problems on the input side.

This voltage imbalance will lead to unequal voltages on the switching elements of the power electronic converter, causing damage to the switching elements, and even causing the power electronic converter to fail to work normally.

Contents of the invention

The purpose of the present invention is to propose a primary side capacitor voltage balancing method based on primary side phase shifting, so as to balance the primary side capacitor voltage and improve the performance of the power electronic converter.

For reaching this purpose, the present invention adopts following technical scheme:

A primary capacitor voltage balancing method based on primary phase shifting, suitable for a power electronic converter, the power electronic converter includes a transformer, a secondary converter module of the transformer, and at least two identical transformer primary terminals connected in series In the converter module, primary side capacitors are connected in parallel at both ends of each primary side converter module of the transformer, and the method includes: detecting the voltage value of each primary side capacitor; when the first primary side capacitor voltage is higher than a preset reference voltage, according to the voltage value of the first primary capacitor and the reference voltage to obtain the first phase shift angle of the first bridge arm and the second bridge arm of the primary side converter module of the first transformer; according to the first The phase shift angle performs pulse width modulation control on the first transformer primary-side converter module; wherein, the transformer primary-side converter module is a full-bridge converter module, and the first transformer primary-side converter module is connected to the The first primary capacitors are connected in parallel, and the full-bridge converter module includes the first bridge arm and the second bridge arm.

In the above solution, the obtaining the first phase shift angle between the first bridge arm and the second bridge arm according to the voltage value of the first primary capacitor and the reference voltage includes: using a proportional integral algorithm to obtain the first phase shift angle phase shift angle.

In the above solution, the performing pulse width modulation control on the primary side converter module of the transformer corresponding to the first primary side capacitance according to the first phase shift angle includes: controlling the primary side of the transformer corresponding to the first primary side capacitance The edge converter module performs pulse width modulation control with a duty cycle of 50%.

In the above solution, the method further includes: performing pulse width modulation control with a duty ratio of 50% on the secondary converter module of the transformer.

The present invention also provides a primary-side capacitor voltage balance control device based on primary-side phase shifting, which is suitable for a power electronic converter, and the power electronic converter includes a transformer, a secondary-side converter module of the converter, and at least Two identical transformer primary-side converter modules, the device includes: a primary-side voltage detection unit for obtaining the voltage value of the primary-side capacitor connected in parallel at both ends of the primary-side converter module; a phase-shift angle calculation unit for When the voltage of the first primary side capacitor is higher than the preset reference voltage, the first bridge arm and the second bridge arm of the primary side converter module of the first transformer are obtained according to the voltage value of the primary side capacitor and the reference voltage The first phase shift angle; the pulse drive unit is used to perform pulse width modulation control on the first transformer primary side converter module according to the first phase shift angle; wherein, the transformer primary side converter module is a full A bridge converter module, the first transformer primary side converter module is connected in parallel with the first primary side capacitor, and the full bridge converter module includes the first bridge arm and the second bridge arm.

In the above solution, the phase shift angle calculation unit is configured to use a PI integration algorithm to calculate the phase shift angle, and output the first phase shift angle.

In the above solution, the pulse driving unit is configured to perform pulse width modulation control with a duty ratio of 50% on the transformer primary-side converter module corresponding to the first primary-side capacitor.

In the above solution, the pulse driving unit is also used to perform pulse width modulation control with a duty ratio of 50% on the secondary converter module of the transformer.

Compared with the prior art, the primary capacitor voltage balancing method based on the primary phase shift provided by the present invention can balance the primary capacitor voltage and improve the performance of the power electronic converter.

Description of drawings

Fig. 1 is a schematic diagram of the circuit structure of a power electronic converter in the prior art;

Fig. 2 is the method flow chart of the primary capacitance voltage balancing method in the embodiment of the present invention;

Fig. 3 is the control block diagram that realizes the method for balancing the primary side capacitor voltage based on the primary side phase shift in the embodiment of the present invention;

Fig. 4 is a schematic diagram of the current flow of the primary side of the power electronic converter before the phase shift in the embodiment of the present invention;

Fig. 5 is a schematic diagram of current flow on the primary side of the power electronic converter after phase shifting in the embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention. In addition, it should be noted that, for the convenience of description, only some structures related to the present invention are shown in the drawings but not all structures.

Embodiment one

An embodiment of the present invention provides a primary side capacitor voltage balancing method based on primary side phase shifting, which is suitable for a power electronic converter. The power electronic converter includes a transformer, a secondary side converter module of the transformer, and at least two identical Transformer primary-side converter module, each transformer primary-side converter module has primary-side capacitors connected in parallel at both ends, as shown in Figure 2, the above method includes:

Step 210, detecting the voltage value of each primary capacitor.

Step 220, when the voltage of the first primary side capacitor is higher than the preset reference voltage, obtain the first bridge arm and the second bridge arm of the first transformer primary side converter module according to the voltage value of the first primary side capacitor and the reference voltage The first phase shift angle of .

Step 230, perform pulse width modulation control on the primary side converter module of the first transformer according to the first phase shift angle.

Wherein, the transformer primary-side converter module is a full-bridge converter module, the first transformer primary-side converter module is connected in parallel with the first primary-side capacitor, and the full-bridge converter module includes a first bridge arm and a second bridge arm.

In the embodiment of the present invention, as shown in FIG. 3 , the full-bridge converter module is controlled by pulse width modulation, and the control quantity of pulse width modulation is the phase angle.

Specifically, as shown in FIG. 1, the bridge arm where S _k1 and S _k2 are located is defined as the first bridge arm, and the bridge arm where S _k3 and S _k4 are located is the second bridge arm. In the embodiment of the present invention, by controlling the first bridge arm The phase shift angle of the power device driving signals of the first bridge arm and the second bridge arm is used to control the capacitor voltage balance.

For example, at the beginning, the voltage on capacitor _C1 is greater _than the voltage on capacitor C2, that is, capacitor voltage imbalance occurs. Assume that the working state at this moment is that power devices S _k1 and S _k4 are turned on, and S _k3 and S _k2 are turned off. off, the current flow direction of the primary side is shown by the dotted line with the arrow in Figure 4.

When performing capacitor voltage balance control, the core of controlling the capacitor voltage is to control the current flowing into the midpoint M of the two primary side capacitors. When the switching state is switched, the driving signal of the second bridge arm is delayed by a first phase shift angle θ _i relative to the first bridge arm, wherein i is a natural number greater than 1. When i=1, S ₁₁ is turned off immediately, and S ₁₂ is turned on immediately; but S ₁₄ is turned off after a period of time lagging behind S ₁₁ , and similarly, S ₁₃ is turned on after a period of time lagging behind S _12. At this time, the flow of current is shown in Figure 5 Shown by dashed line with arrow. It can be seen that a net inflow current is generated at point M, which makes the capacitor voltage of C ₂ rise and the capacitor voltage of C ₁ drop.

When obtaining the first phase shift angle between the first bridge arm and the second bridge arm in step 220, a proportional integral algorithm is used to obtain the first phase shift angle.

The proportional integral algorithm is the PI algorithm, and the mathematical expression is as follows:

u(t)＝K _p e(t)+k _l ∫e(t)dt

It can be seen that the PI algorithm performs proportional and integral operations on the error signal e(t), and weights and sums the results to obtain the output u(t) of the controller, which is the control value of the control object. The PI algorithm has become the most important control technology in the grid-connected inverter system due to its advantages of simple structure, good stability and reliable operation. In PI control, two control parameters, proportional coefficient (Kp) and integral coefficient (K _i ), need to be set.

In step 230, a pulse width modulation control with a duty ratio of 50% is performed on the primary side converter module of the transformer corresponding to the first primary side capacitor, and a pulse width modulation control with a duty ratio of 50% is performed on the secondary side converter module of the transformer .

In the embodiment of the present invention, the phase angle of the fixed secondary side is Modulating the phase angle θ _k of each module on the primary side can control the input voltage of each module, where k is a natural number greater than 1.

Using the primary side capacitor voltage balancing method based on primary side phase shift provided by the present invention, when the voltage of the first primary side capacitor is higher than the voltage of other primary side capacitors, the first primary side capacitor is calculated according to the voltage value of the first primary side capacitor Compared with the prior art, the phase shift angle of the first bridge arm and the second bridge arm of the primary side module of the transformer corresponding to the capacitor can balance the capacitor voltage of the primary side and improve the performance of the power electronic converter.

Embodiment two

An embodiment of the present invention provides a primary-side capacitor voltage balance control device based on primary-side phase shifting, which is suitable for a power electronic converter. The power electronic converter includes a transformer, a secondary-side converter module of the converter, and at least two The same transformer primary side converter module, the device includes:

The primary side voltage detection unit is used to obtain the voltage value of the primary side capacitor connected in parallel at both ends of the primary side converter module;

The phase-shift angle calculation unit is used to obtain the first bridge arm and the first bridge arm of the primary-side converter module of the first transformer according to the voltage value of the primary-side capacitor and the reference voltage when the voltage of the first primary-side capacitor is higher than the preset reference voltage. The first phase shift angle of the second bridge arm;

A pulse drive unit, configured to perform pulse width modulation control on the primary side converter module of the first transformer according to the first phase shift angle;

Wherein, the transformer primary-side converter module is a full-bridge converter module, the first transformer primary-side converter module is connected in parallel with the first primary-side capacitor, and the full-bridge converter module includes a first bridge arm and a second bridge arm.

As shown in Figure 3, the phase-shift pulse width modulation (PS-PWM) unit is the pulse drive unit, the PI unit is the phase-shift angle calculation unit, and V _C1 is the primary side voltage detection unit taken from both ends of the primary side converter module 2 of the transformer. The primary side voltage value is compared with the reference voltage V _{C_ref} to obtain the phase shift angle θ ₁ through PI calculation, and then the PS-PWM unit performs phase shift pulse width modulation control according to the phase shift angle θ ₁ . V _C2 is the primary side voltage value obtained by the primary side voltage detection unit from both ends of the primary side converter module 2 of the transformer. It is compared with the reference voltage V _{C_ref} and calculated by PI to obtain the phase shift angle θ ₂ , and then the PS-PWM unit again Phase-shift pulse width modulation control is performed according to the phase _- shift angle θ2.

The pulse drive unit is used to perform pulse width modulation control with a duty cycle of 50% on the transformer primary side converter module corresponding to the first primary side capacitor, and is also used to perform pulse width modulation control on the transformer secondary side converter module with a duty cycle of 50%. Pulse Width Modulation Control. In the embodiment of the present invention, the phase angle of the fixed secondary side is By modulating the phase angle θ _k of each module on the primary side, the input voltage of each module can be controlled.

Using the primary capacitor voltage balance device based on primary phase shift provided by the present invention, when the voltage of the first primary capacitor is higher than the voltage of other primary capacitors, the first primary capacitor is calculated according to the voltage value of the first primary capacitor Compared with the prior art, the phase shift angle of the first bridge arm and the second bridge arm of the primary side module of the transformer corresponding to the capacitor can balance the capacitor voltage of the primary side and improve the performance of the power electronic converter.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention.

Claims (8)

1. A primary capacitor voltage balance method based on primary phase shifting, suitable for a power electronic converter, the power electronic converter includes a transformer, a transformer secondary converter module and at least two identical transformers connected in series A primary-side converter module, each of the primary-side converter modules of the transformer is connected with a primary-side capacitor in parallel at both ends, and the method is characterized in that the method includes: Detect the voltage value of each primary capacitor; When the voltage of the first primary capacitor is higher than the preset reference voltage, the first bridge arm and the second bridge of the primary converter module of the first transformer are obtained according to the voltage value of the first primary capacitor and the reference voltage The first phase shift angle of the arm; performing pulse width modulation control on the primary side converter module of the first transformer according to the first phase shift angle; Wherein, the transformer primary-side converter module is a full-bridge converter module, the first transformer primary-side converter module is connected in parallel with the first primary-side capacitor, and the full-bridge converter module includes the first bridge arm and the second bridge arm. 2. The method according to claim 1, wherein said obtaining the first phase shift angle between the first bridge arm and the second bridge arm according to the voltage value of the first primary capacitor and the reference voltage includes : A proportional-integral algorithm is used to obtain the first phase shift angle. 3. The method according to claim 1, wherein the performing pulse width modulation control on the transformer primary side converter module corresponding to the first primary side capacitance according to the first phase shift angle comprises: A pulse width modulation control with a duty ratio of 50% is performed on the transformer primary-side converter module corresponding to the first primary-side capacitor. 4. The method according to any one of claims 1 to 3, characterized in that the method further comprises: The pulse width modulation control with a duty cycle of 50% is performed on the secondary converter module of the transformer. 5. A primary-side capacitor voltage balance control device based on primary-side phase shifting, suitable for a power electronic converter, the power electronic converter includes a transformer, a converter secondary-side converter module, and at least two connected in series The same transformer primary side converter module is characterized in that the device includes: a primary side voltage detection unit, configured to obtain the voltage value of the primary side capacitor connected in parallel at both ends of the primary side converter module; A phase-shift angle calculation unit, configured to obtain the first phase of the primary-side converter module of the first transformer according to the voltage value of the primary-side capacitor and the reference voltage when the voltage of the first primary-side capacitor is higher than a preset reference voltage. The first phase shift angle between the bridge arm and the second bridge arm; A pulse driving unit, configured to perform pulse width modulation control on the first transformer primary side converter module according to the first phase shift angle; Wherein, the transformer primary-side converter module is a full-bridge converter module, the first transformer primary-side converter module is connected in parallel with the first primary-side capacitor, and the full-bridge converter module includes the first bridge arm and the second bridge arm. 6. The device according to claim 5, wherein the phase-shift angle calculation unit is configured to use a PI integration algorithm to calculate the phase-shift angle and output the first phase-shift angle. 7. The device according to claim 5, wherein the pulse driving unit is configured to perform pulse width modulation with a duty ratio of 50% on the transformer primary-side converter module corresponding to the first primary-side capacitor control. 8 . The device according to any one of claims 5 to 7 , wherein the pulse driving unit is also used to perform pulse width modulation control with a duty ratio of 50% on the secondary converter module of the transformer.