A control method of three-phase SWISS rectifier based on instantaneous power theory

Abstract

The application discloses a three-phase SWISS rectifier control method based on instantaneous power theory, relates to the technical field of power electronic conversion, and comprises the following steps: acquiring three-phase grid voltage, three-phase input current, DC output voltage, DC output current and DC load current; solving the capacitor current required for maintaining the DC side capacitor voltage according to a rectifier voltage outer loop controller, and determining the given value of the DC side instantaneous output power according to the DC output voltage, the DC load current and the capacitor current; solving the d-axis component of the given value of the AC current corresponding to the given value of the instantaneous output power based on the instantaneous power theory; performing coordinate transformation on the d-axis component to obtain three-phase AC current given values, and sorting the instantaneous values of the three-phase AC current given values and three-phase grid voltage respectively; and determining the on-off state of a low-frequency switching tube and the duty cycle of a high-frequency switching tube according to the sorting result. The application has important significance for improving input current quality and output voltage stability.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, specifically to a three-phase SWISS rectifier control method based on instantaneous power theory. Background Technology

[0002] Three-phase SWISS rectifiers, with their advantages of high efficiency, high power density, and step-down rectification, have significant application value in industrial DC power supply and new energy fields.

[0003] Traditional control methods often employ a dual-PI dual-closed-loop architecture. However, when directly applied to three-phase Swiss rectifiers, this method has the following inherent drawbacks: First, the DC-side inductor current needs to be used as the feedback quantity for the inner current loop. However, high-frequency switching ripple in the inductor current affects the control effect of the inner current loop, leading to increased high-frequency ripple and harmonic content in the AC input current, severely impacting the input current quality. Second, while the outer voltage loop provides good control of the DC output voltage under steady-state conditions, when the load changes abruptly, the outer voltage loop PI regulator needs to use the DC output voltage as the feedback quantity. This inherent lag in control results in a slow response speed for the current setpoint, causing significant fluctuations in the DC output voltage. This makes it difficult to meet the application requirements for voltage regulation accuracy and dynamic response speed under dynamic load conditions.

[0004] Therefore, how to eliminate the impact of DC-side inductor current ripple on the quality of AC input current and improve the voltage regulation accuracy and dynamic response speed under dynamic load conditions are the technical problems that urgently need to be solved in the field of three-phase SWISS rectifier control. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, this application proposes the following technical solution: This application provides a three-phase SWISS rectifier control method based on instantaneous power theory, including: The three-phase grid voltage, three-phase input current, DC output voltage, DC output current, and DC load current are acquired within the same switching cycle. The capacitor current required to maintain the DC-side capacitor voltage stability is calculated based on the rectifier voltage outer loop controller, and the given value of the instantaneous DC-side output power is determined based on the DC output voltage, DC load current, and capacitor current. The d-axis component of the AC current given value corresponding to the given value of the instantaneous output power is solved based on the instantaneous power theory. The d-axis component of the given AC current is transformed to obtain the given three-phase AC current, and the instantaneous values ​​of the given three-phase AC current and the instantaneous values ​​of the three-phase grid voltage are sorted respectively. Based on the sorting results, the on / off states of the three-phase low-frequency switching transistors and the duty cycle of the high-frequency switching transistors are determined, and drive signals for the switching transistors are generated.

[0006] In one possible implementation, the capacitor current required to maintain a stable DC-side capacitor voltage is calculated based on the rectifier voltage outer loop controller, and a given value for the instantaneous DC-side output power is determined based on the DC output voltage, DC load current, and the capacitor current, including: A DC output voltage reference value is set, and the difference between the DC output voltage reference value and the DC output voltage is calculated to obtain a voltage deviation signal; The voltage deviation signal is input to the rectifier voltage outer loop controller, and after proportional-integral regulation, the capacitor current required to maintain the stability of the DC side capacitor voltage is generated. The instantaneous output power on the DC side is determined based on the capacitor current, DC output voltage, and DC load current, using the following formula: in, This is the given value for the instantaneous output power on the DC side. This is the DC output voltage. This is the DC load current. This represents the capacitor current.

[0007] In one possible implementation, the voltage deviation signal is input to the rectifier voltage outer loop controller, and after proportional-integral regulation, the formula for calculating the capacitor current required to maintain the stability of the DC-side capacitor voltage is as follows: in, This refers to the proportional gain of the rectifier voltage outer loop controller. The integral coefficient of the rectifier voltage outer loop controller is denoted as . This represents the unit step response in the time domain. This is the given value for the DC-side output voltage.

[0008] In one possible implementation, the calculation formula for solving the d-axis component of the given AC current corresponding to the given value of the instantaneous output power, based on instantaneous power theory, is as follows: in, The d-axis component of the given value of the alternating current. This is the given value for the DC-side output voltage. This is the DC load current. For capacitor current, This is the DC output voltage. The d-axis component is obtained by synchronous rotating coordinate transformation of the three-phase grid voltage.

[0009] In one possible implementation, the d-axis component of the AC current setpoint is transformed to obtain the three-phase AC current setpoint, and the instantaneous values ​​of the three-phase AC current setpoint and the instantaneous values ​​of the three-phase grid voltage are sorted, including: The d-axis component of the given AC current is used to calculate the given value of the three-phase AC current through the inverse Park and Clarke transformations. The instantaneous values ​​of the three-phase AC current setpoint and the instantaneous values ​​of the three-phase grid voltage are sorted respectively, and the phase with the largest instantaneous value of the three-phase grid voltage is defined as the phase with the largest grid voltage, and the phase with the largest instantaneous value of the three-phase AC current setpoint is defined as the phase with the largest current setpoint. The phase in the middle of the instantaneous values ​​of the three-phase grid voltage is defined as the middle phase of the grid voltage, and the phase in the middle of the instantaneous values ​​of the three-phase AC current setpoint is defined as the middle phase of the current setpoint. The phase with the smallest instantaneous voltage among the three-phase grid voltages is defined as the phase with the smallest grid voltage, and the phase with the smallest instantaneous current setpoint among the three-phase AC current setpoints is defined as the phase with the smallest current setpoint.

[0010] In one possible implementation, the on / off states of the three-phase low-frequency switching transistors and the duty cycle of the high-frequency switching transistors are determined based on the sorting results, and drive signals for the switching transistors are generated, including: The on / off states of the three-phase low-frequency switches are determined based on the phase with the highest grid voltage, the intermediate phase with the highest grid voltage, and the phase with the lowest grid voltage. Simultaneously, the duty cycle of the high-frequency switching transistor is determined based on the maximum phase of the current setpoint and the minimum phase of the current setpoint, and a drive signal for the switching transistor is generated.

[0011] In one possible implementation, the determination is based on the on / off states of the three-phase low-frequency switches for the phase with the highest grid voltage, the intermediate phase with the highest grid voltage, and the phase with the lowest grid voltage, including: like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; in, , , This is the three-phase grid voltage. The minimum phase of the grid voltage. The phase with the maximum grid voltage. It is the middle phase of the grid voltage. , , It is a three-phase low-frequency switching transistor.

[0012] In one possible implementation, the calculation formula for determining the duty cycle of the high-frequency switching transistor based on the phase with the maximum current setpoint and the phase with the minimum current setpoint is as follows: in, The duty cycle of the maximum phase high-frequency switch, For the minimum phase high-frequency switch duty cycle, This is the DC output current. For the phase with the maximum current setpoint, The phase with the minimum current setpoint.

[0013] Compared with the prior art, the beneficial effects of this application are as follows: The three-phase SWISS rectifier control method proposed in this application, based on instantaneous power theory, avoids introducing high-frequency ripple of DC-side inductor current into the control loop, significantly reducing high-frequency ripple of AC input current. Furthermore, by directly feeding the load power into the calculation of the AC input current setpoint based on instantaneous power theory, it can significantly reduce DC output voltage fluctuations caused by regulator hysteresis under dynamic load conditions. This method is of great significance for improving the input current quality, output voltage stability, and efficiency of SWISS rectifiers in practical applications. Attached Figure Description

[0014] Figure 1 A flowchart illustrating a three-phase SWISS rectifier control method based on instantaneous power theory, provided for an embodiment of this application; Figure 2 The main circuit diagram of the three-phase SWISS rectifier provided in the embodiments of this application; Figure 3 This is a core control block diagram of the instantaneous power theoretical control method provided in the embodiments of this application; Figure 4 This is a flowchart illustrating the implementation of low-frequency tube modulation in an embodiment of this application. Figure 5 Waveforms of the input current and input voltage for the conventional dual closed-loop control method provided in the embodiments of this application; Figure 6 The waveforms of the input current and input voltage in the method of the embodiments of this application are shown. Figure 7 DC output voltage waveform diagram of the conventional dual closed-loop control method provided in the embodiments of this application; Figure 8 This is a DC output voltage waveform diagram of the method in the embodiment of this application. Detailed Implementation

[0015] The present solution will now be described in conjunction with the accompanying drawings and specific embodiments.

[0016] Figure 1 A flowchart illustrating a three-phase SWISS rectifier control method based on instantaneous power theory, provided for an embodiment of this application, is shown below. Figure 1 This embodiment provides a three-phase SWISS rectifier control method based on instantaneous power theory, comprising: S101 acquires the three-phase grid voltage, three-phase input current, DC output voltage, DC output current and DC load current within the same switching cycle.

[0017] See Figure 2This is a main circuit diagram of a three-phase Swiss rectifier provided in an embodiment of this application. The main circuit topology of the three-phase Swiss rectifier includes: a three-phase power grid, an input filter inductor, a three-phase uncontrolled rectifier bridge, and low-frequency switching transistors on the positive and negative buses. , , Positive bus high-frequency switching transistor Sp, negative bus high-frequency switching transistor Sn, DC-side filter inductor, DC-side voltage regulator capacitor, DC load.

[0018] The a, b, and c phase outputs of the three-phase power grid serve as the AC inputs of the rectifier. Voltage sampling points are set at each phase input to detect the three-phase input voltage, and current sampling points are set on each phase line to detect the three-phase input current. Each phase output is connected in series with an input filter inductor before being connected to the subsequent power conversion circuit. The input filter inductor is used to suppress input current ripple. An input filter capacitor branch can also be connected in parallel after the input filter inductor to form an input-side filter network.

[0019] The filtered three-phase AC nodes are connected to the three AC input terminals of a three-phase uncontrolled rectifier bridge. The three-phase uncontrolled rectifier bridge consists of six diodes; the common terminal of the upper arm diodes forms the positive output terminal of the rectifier bridge, and the common terminal of the lower arm diodes forms the negative output terminal. The positive output terminal of the rectifier bridge is connected to the positive DC bus node P via a positive bus high-frequency switch, and the negative output terminal is connected to the negative DC bus node N via a negative bus high-frequency switch. The positive and negative bus high-frequency switches are located in the positive and negative bus branches, respectively, and are used for high-frequency chopping control of DC-side energy transmission.

[0020] Three-phase low-frequency switching transistor , , Each phase is connected to the corresponding AC node after the three-phase input filtering (a, b, and c). One end of the low-frequency switch branch of each phase is connected to the corresponding phase's AC node, and the other end is connected to the common commutation node. This common commutation node is then connected to the positive DC bus node (P) and the negative DC bus node (N) through a clamping diode branch. The switching is controlled by selecting the on / off state. , , The corresponding switches can introduce the corresponding phase voltage into the DC bus commutation branch, thereby cooperating with the high-frequency switching transistors to achieve input current shaping and power factor correction.

[0021] On the DC output side, the positive DC bus node (P) is connected in series with a DC-side filter inductor and then connected to the positive terminal of the DC output. The negative DC bus node (N) is connected in series with another DC-side filter inductor and then connected to the negative terminal of the DC output. A DC-side voltage regulator capacitor and a DC load are connected in parallel between the positive and negative terminals of the DC output. The voltage regulator capacitor is used to stabilize the DC bus voltage and reduce output voltage ripple, while the DC load receives the DC power output from the rectifier. A voltage sensor is also installed on the DC side to detect the DC bus voltage, and a current sensor is installed to detect the DC-side current or load current.

[0022] S102, based on the rectifier voltage outer loop controller, calculates the capacitor current required to maintain the DC side capacitor voltage stability, and determines the given value of the DC side instantaneous output power based on the DC output voltage, DC load current and capacitor current.

[0023] In this embodiment, a DC output voltage reference value is set using a host computer. Based on the DC output voltage obtained in the current switching cycle and the DC voltage reference value sent by the host computer, the capacitor current required to maintain the stability of the DC-side capacitor voltage is calculated through the rectifier's outer-loop PI controller. The core control logic is described in [link to core control logic]. Figure 3 .

[0024] First, the difference between the DC output voltage reference value and the DC output voltage is calculated to obtain the voltage deviation signal. This voltage deviation signal is then input to the rectifier voltage outer loop controller. After proportional-integral regulation, the capacitor current required to maintain the stability of the DC-side capacitor voltage is generated. The calculation formula is as follows: in, This refers to the proportional gain of the rectifier voltage outer loop controller. The integral coefficient of the rectifier voltage outer loop controller is denoted as . This represents the unit step response in the time domain. This is the given value for the DC-side output voltage.

[0025] The DC load current and the capacitor current output from the outer voltage loop are superimposed and combined with the real-time sampled DC output voltage. This is then used to generate the instantaneous DC output power setpoint required to maintain stable rectifier operation through AC / DC side instantaneous power balance calculation. The calculation formula is as follows: in, This is the given value for the instantaneous output power on the DC side. This is the DC output voltage. This is the DC load current. This represents the capacitor current.

[0026] S103, based on instantaneous power theory, solves for the d-axis component of the AC current given value corresponding to the given value of instantaneous output power.

[0027] In this embodiment, based on instantaneous power theory and the AC / DC side equal power conversion criterion, the d-axis component of the AC current given value corresponding to the instantaneous output power given value on the DC side is solved.

[0028] Based on the principle that the instantaneous input active power on the AC side is equal to the instantaneous output power on the DC side, the d-axis component of the AC current setpoint is calculated using the following formula: in, The d-axis component of the given value of the alternating current. This is the given value for the DC-side output voltage. This is the DC load current. For capacitor current, This is the DC output voltage. The d-axis component is obtained by synchronous rotating coordinate transformation of the three-phase grid voltage.

[0029] S104, perform coordinate transformation on the d-axis component of the AC current setpoint to obtain the three-phase AC current setpoint, and sort the instantaneous values ​​of the three-phase AC current setpoint and the instantaneous values ​​of the three-phase grid voltage respectively.

[0030] In this embodiment, the d-axis component of the AC current setpoint is calculated to obtain the setpoint value of the three-phase AC current through Park and Clarke inverse transforms. The instantaneous values ​​of the three-phase AC current setpoint and the instantaneous values ​​of the three-phase grid voltage are sorted by size. The phase with the largest instantaneous value of the three-phase grid voltage is defined as the phase with the largest grid voltage. The phase with the largest instantaneous value of the three-phase AC current setpoint is defined as the phase with the largest current setpoint. The phase with the middle instantaneous value of the three-phase grid voltage is defined as the middle phase of the grid voltage. The phase with the smallest instantaneous value of the three-phase AC current setpoint is defined as the phase with the smallest current setpoint.

[0031] S105 determines the on / off state of the three-phase low-frequency switching transistors and the duty cycle of the high-frequency switching transistors based on the sorting results, and generates the drive signal for the switching transistors.

[0032] See Figure 4 In this embodiment, the on / off state of the three-phase low-frequency switches is determined based on the phase with the highest grid voltage, the intermediate phase with the lowest grid voltage, and the phase with the lowest grid voltage. The principle for determining the on / off state of the low-frequency switches is that the low-frequency switch of the intermediate phase with the highest grid voltage is on, and the low-frequency switches of the other two phases are off, i.e., based on the ranking of the instantaneous grid voltage values. , , Three-phase low-frequency switching transistors were obtained , , The on / off state is determined by the following method: like and ,but , , ,So , , .

[0033] like and ,but , , ,So , , .

[0034] like and ,but , , ,So , , .

[0035] like and ,but , , ,So , , .

[0036] like and ,but , , ,So , , .

[0037] like and ,but , , ,So , , .

[0038] in, , , This is the three-phase grid voltage. The minimum phase of the grid voltage. The phase with the maximum grid voltage. It is the middle phase of the grid voltage. , , It is a three-phase low-frequency switching transistor.

[0039] Simultaneously, the duty cycle of the high-frequency switching transistor is determined based on the phase with the maximum current setpoint and the phase with the minimum current setpoint, and the driving signal for the switching transistor is generated. The calculation formula is as follows: in, The duty cycle of the maximum phase high-frequency switch, For the minimum phase high-frequency switch duty cycle, This is the DC output current. For the phase with the maximum current setpoint, The phase with the minimum current setpoint.

[0040] Figure 5 The graph shows the waveforms of the input current and input voltage in a traditional dual-loop control method. It can be seen from the graph that the input current exhibits significant distortion and ripple. Figure 6 The figure shows the waveforms of the input current and input voltage of the method proposed in this application. As can be seen from the figure, the sinusoidal characteristic is excellent, the waveform is smooth, and it is completely synchronized with the phase of the grid voltage, achieving steady-state operation with unity power factor. The total harmonic distortion (THD) of the input current of the traditional dual closed-loop control method is 9.12%, while the THD of the input current of the method proposed in this application is only 2.63%, reducing the current THD by 71.2%.

[0041] Figure 7 This is the DC output voltage waveform of the traditional dual-loop control method. In the simulation, the load is set to suddenly increase from 100% to 50% of the rated load in 0.25s. As can be seen from the graph, the DC output voltage of the traditional dual-loop control method experiences a drop of 23V. Figure 8 The waveform of the DC output voltage of the method proposed in this application shows a drop of only 2V.

[0042] In this embodiment, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, the simultaneous existence of A and B, or the existence of B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0043] The above description is merely a specific embodiment of this application. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. The protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A control method for a three-phase Swiss rectifier based on instantaneous power theory, characterized in that, include: The three-phase grid voltage, three-phase input current, DC output voltage, DC output current, and DC load current are acquired within the same switching cycle. The capacitor current required to maintain the DC-side capacitor voltage stability is calculated based on the rectifier voltage outer loop controller, and the given value of the instantaneous DC-side output power is determined based on the DC output voltage, DC load current, and capacitor current. The d-axis component of the AC current given value corresponding to the given value of the instantaneous output power is solved based on the instantaneous power theory. The d-axis component of the given AC current is transformed to obtain the given three-phase AC current, and the instantaneous values ​​of the given three-phase AC current and the instantaneous values ​​of the three-phase grid voltage are sorted respectively. Based on the sorting results, the on / off states of the three-phase low-frequency switching transistors and the duty cycle of the high-frequency switching transistors are determined, and drive signals for the switching transistors are generated.

2. The control method of three-phase SWISS rectifier based on instantaneous power theory according to claim 1, characterized in that, The calculation of the capacitor current required to maintain a stable DC-side capacitor voltage is performed based on the rectifier voltage outer loop controller, and the given value of the instantaneous DC-side output power is determined based on the DC output voltage, DC load current, and capacitor current, including: A DC output voltage reference value is set, and the difference between the DC output voltage reference value and the DC output voltage is calculated to obtain a voltage deviation signal; The voltage deviation signal is input to the rectifier voltage outer loop controller, and after proportional-integral regulation, the capacitor current required to maintain the stability of the DC side capacitor voltage is generated. The instantaneous output power on the DC side is determined based on the capacitor current, DC output voltage, and DC load current, using the following formula: wherein is a given value of the instantaneous output power at the DC side, is the DC output voltage, is the DC load current, is the capacitor current.

3. The control method of three-phase SWISS rectifier based on instantaneous power theory according to claim 2, characterized in that, The voltage deviation signal is input to the rectifier voltage outer loop controller, and after proportional-integral regulation, the formula for calculating the capacitor current required to maintain the stability of the DC-side capacitor voltage is as follows: in, This refers to the proportional gain of the rectifier voltage outer loop controller. The integral coefficient of the rectifier voltage outer loop controller is denoted as . This is the unit step response in the time domain. This is the given value for the DC-side output voltage.

4. The three-phase SWISS rectifier control method based on instantaneous power theory according to claim 1, characterized in that, The calculation formula for solving the d-axis component of the given AC current corresponding to the given value of the instantaneous output power based on instantaneous power theory is as follows: in, The d-axis component of the given value of the alternating current. This is the given value for the DC-side output voltage. This is the DC load current. For capacitor current, This is the DC output voltage. The d-axis component is obtained by synchronous rotating coordinate transformation of the three-phase grid voltage.

5. The three-phase SWISS rectifier control method based on instantaneous power theory according to claim 1, characterized in that, The d-axis component of the AC current setpoint is transformed to obtain the three-phase AC current setpoint, and the instantaneous values ​​of the three-phase AC current setpoint and the instantaneous values ​​of the three-phase grid voltage are sorted, including: The d-axis component of the given AC current is used to calculate the given value of the three-phase AC current through the inverse Park and Clarke transformations. The instantaneous values ​​of the three-phase AC current setpoint and the instantaneous values ​​of the three-phase grid voltage are sorted respectively, and the phase with the largest instantaneous value of the three-phase grid voltage is defined as the phase with the largest grid voltage, and the phase with the largest instantaneous value of the three-phase AC current setpoint is defined as the phase with the largest current setpoint. The phase in the middle of the instantaneous values ​​of the three-phase grid voltage is defined as the middle phase of the grid voltage, and the phase in the middle of the instantaneous values ​​of the three-phase AC current setpoint is defined as the middle phase of the current setpoint. The phase with the smallest instantaneous voltage among the three-phase grid voltages is defined as the phase with the smallest grid voltage, and the phase with the smallest instantaneous current setpoint among the three-phase AC current setpoints is defined as the phase with the smallest current setpoint.

6. The three-phase SWISS rectifier control method based on instantaneous power theory according to claim 1, characterized in that, Based on the sorting results, the on / off states of the three-phase low-frequency switching transistors and the duty cycle of the high-frequency switching transistors are determined, and drive signals for the switching transistors are generated, including: The on / off states of the three-phase low-frequency switches are determined based on the phase with the highest grid voltage, the intermediate phase with the highest grid voltage, and the phase with the lowest grid voltage. Simultaneously, the duty cycle of the high-frequency switching transistor is determined based on the maximum phase of the current setpoint and the minimum phase of the current setpoint, and a drive signal for the switching transistor is generated.

7. The three-phase SWISS rectifier control method based on instantaneous power theory according to claim 6, characterized in that, The determination is based on the on / off states of the three-phase low-frequency switches for the phase with the highest grid voltage, the intermediate phase with the highest grid voltage, and the phase with the lowest grid voltage, including: like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; like and ,but , , ,So , , ; in, , , This is the three-phase grid voltage. The minimum phase of the grid voltage. The phase with the maximum grid voltage. It is the middle phase of the grid voltage. , , It is a three-phase low-frequency switching transistor.

8. The three-phase SWISS rectifier control method based on instantaneous power theory according to claim 1, characterized in that, The calculation formula for determining the duty cycle of the high-frequency switching transistor based on the maximum phase and the minimum phase of the current setpoint is as follows: in, The duty cycle of the maximum phase high-frequency switch, For the minimum phase high-frequency switch duty cycle, This is the DC output current. For the phase with the maximum current setpoint, The phase with the minimum current setpoint.

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