Four-quadrant three-phase pwm rectifier circuit topology and control method thereof

Abstract

The present application relates to the technical field of rectifier, in particular to a four-quadrant three-phase PWM rectifier circuit topology and a control method thereof, the circuit topology comprises a first switching device group, a second switching device group and at least one supporting capacitor group, the first switching device group forms an A-phase control loop, the middle part of the A-phase control loop is connected to an A-phase AC incoming line, the two ends of the A-phase control loop are connected to DC positive and negative buses respectively, the second switching device group forms a B-phase control loop, the at least one supporting capacitor group is connected between the DC positive and negative buses, each supporting capacitor group comprises a first supporting capacitor and a second supporting capacitor, the first supporting capacitor is connected in series with the second supporting capacitor, and a C-phase AC incoming line is connected to the connecting point of the first supporting capacitor and the second supporting capacitor. The present application reduces the required devices of the PWM rectifier, and reduces the overall switching loss and electromagnetic noise of the equipment.

Description

Technical Field

[0001] This invention relates to the field of rectifier technology, specifically to a four-quadrant three-phase PWM rectifier circuit topology and its control method. Background Technology

[0002] A four-quadrant three-phase PWM rectifier (hereinafter referred to as "PWM rectifier") is a power electronic device that converts AC power signals into DC power signals. It can adjust the energy flow direction and flow rate between the AC and DC sides, and also adjust the power factor at the AC end. PWM rectifiers are based on pulse width modulation (PWM) technology. By controlling the on-time of the switching elements, the AC output voltage of the PWM rectifier is controlled, thereby controlling the DC voltage and AC current. There are many existing control strategies for PWM rectifiers, such as fixed-frequency voltage control, direct power control (DPC), space vector control, predictive control, amplitude and phase control, and current hysteresis. In practical applications, the numerous control strategies mentioned above can essentially be divided into two categories: Strategy 1, voltage-based control, which detects the three-phase voltage and phase on the AC side of the rectifier and controls the output amplitude and phase on the AC side of the PWM rectifier to control the output voltage on the DC side; Strategy 2, current-based control, which detects the three-phase voltage and phase on the AC side of the rectifier and decouples the three-phase current to a rotating Cartesian coordinate system of the grid phase (Clark transform + Park transform) to obtain the active current (I). sd ) and reactive current (I sq ), respectively for I sd and I sq Perform closed-loop control to obtain active voltage V sd and reactive voltage V sq The output control quantity, and then V sd and V sq The inverse transformation is performed to obtain the output three-phase voltage. During the current control process, due to I... sd and I sq All are DC components, and the control algorithm used is conventional PI control, V sd and V sq The inverse transformation process utilizes the grid phase mentioned above, which generally refers to the phase voltage angle (conventional control methods are typically based on phase voltage). Current-mode control strategies are widely used due to their good dynamic performance and high accuracy.

[0003] The aforementioned PWM rectifiers (including devices using both strategies) are characterized by stability, high efficiency, and controllability. They can quickly adjust the output voltage, regulate power flow in four quadrants, and adjust the AC power factor. However, PWM rectifiers also have some drawbacks: First, the switching devices used in PWM rectifiers are not ideal, resulting in switching losses and on-resistance losses, leading to higher system energy consumption and lower overall efficiency compared to technologies such as thyristor rectification. Second, the switching of power semiconductors during PWM rectifier operation generates high-frequency noise, which adversely affects the electrical operating environment.

[0004] In summary, there is an urgent need for a circuit topology of a PWM rectifier that can reduce switching losses and on-resistance losses to solve the problems existing in the prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a four-quadrant three-phase PWM rectifier circuit topology and its control method to solve the problem of high system energy consumption caused by switching losses and on-resistance losses in existing PWM rectifiers. The specific technical solution is as follows:

[0006] This invention provides a four-quadrant three-phase PWM rectifier circuit topology, including at least a first switching device group, a second switching device group, and at least one supporting capacitor group. The first switching device group forms an A-phase control loop, with the middle of the A-phase control loop connected to the A-phase AC input line and both ends of the A-phase control loop connected to the positive and negative DC buses, respectively. The second switching device group forms a B-phase control loop, with the middle of the B-phase control loop connected to the B-phase AC input line and both ends of the B-phase control loop connected to the positive and negative DC buses, respectively. At least one supporting capacitor group is connected between the positive and negative DC buses. Each supporting capacitor group includes a first supporting capacitor and a second supporting capacitor, which are connected in series. The C-phase AC input line is connected to the connection point of the first and second supporting capacitors.

[0007] A further improvement to the four-quadrant three-phase PWM rectifier circuit topology of the present invention is that the first switching device group includes a first switching device and a second switching device, which are connected in series, and the A-phase AC input line is connected to the connection point of the first switching device and the second switching device; the second switching device group includes a third switching device and a fourth switching device, which are connected in series, and the B-phase AC input line is connected to the connection point of the third switching device and the fourth switching device.

[0008] A further improvement of the four-quadrant three-phase PWM rectifier circuit topology of the present invention is that the first switching device group includes a first switching device, a second switching device, a third switching device, and a fourth switching device connected in series, and the A-phase AC input line is connected to the connection point of the second switching device and the third switching device; the second switching device group includes a fifth switching device, a sixth switching device, a seventh switching device, and an eighth switching device connected in series, and the B-phase AC input line is connected to the connection point of the sixth switching device and the seventh switching device; the O point of the three-level topology is connected to the connection point of the first supporting capacitor and the second supporting capacitor.

[0009] The present invention also provides a control method for the four-quadrant three-phase PWM rectifier circuit topology described above, comprising the following steps:

[0010] S1. Using voltage sampling and PLL technology, the grid angle is tracked and the grid line voltage is detected to obtain θ;

[0011] S2. Sample the three-phase current of the power grid to obtain the current i a i b i c ;

[0012] S3, i a i b i c The current i in the αβ coordinate system is obtained by Clarke transformation. α_act i β_act ;

[0013] S4, i α_act i β_act The current i in the dq coordinate system is obtained by performing a Park transformation with θ as the reference. sq_act and i sd_act ;

[0014] S5. Calculate the given DC voltage U dc_ref+ and actual DC voltage U dc_act The error between them is used to obtain the output control current i by the PI controller. sd_ref ;

[0015] S6, Calculate i sd_ref i sq_ref with i sq_act i sd_act The error is input into the PI controller and the resonant regulator to obtain the output control voltage V. d V q In the closed-loop control of active and reactive current, the negative sequence component generated by the three-phase current imbalance and the DC component of active and reactive current are adjusted.

[0016] S7, Vd and V q The vector length V is obtained through the inverse Park transform and the inverse Clarke transform. length And the vector angle θ', the vector angle θ' is then transformed to obtain θ”;

[0017] S8, change the vector length V length The vector angle θ” is input to the SPWM module for natural modulation, and the drive signal of the rectifier power component is obtained through angle compensation;

[0018] S9. Control the rectifier drive component according to the drive signal, and after filtering, modulate the traditional phase voltage into line voltage modulation so that the two-phase modulated output and the unmodulated output are at a fixed angle.

[0019] S10. Repeat the above steps.

[0020] A further improvement of the four-quadrant three-phase PWM rectifier circuit topology control method of the present invention is that the three-phase voltages A / B / C are distributed in positive order, with phase A leading phase B by 120°, phase B leading phase C by 120°, the AC line voltage forming a 30° angle with the A phase voltage, and the BC line voltage forming a 60° angle with the AC line voltage. S7 further includes converting the vector angle θ' according to the vector image to obtain the AC line voltage angle and the BC line voltage angle, specifically:

[0021] S701, Deflect the A-phase vector angle by 30°;

[0022] S702. The phase of the B-phase modulation voltage is obtained by deflecting the AC line voltage by 60°.

[0023] A further improvement of the four-quadrant three-phase PWM rectifier circuit topology control method of the present invention lies in the following expression for the resonant control principle of the resonant regulator:

[0024] s1=s'1+(2×kr×wi×err-s2-2×wi×s1)×Ts

[0025] s2=s'2+wn×wn×s1×Ts

[0026] Where wn is the center frequency, wi is the sideband of the resonant controller, s'1 represents the value of s1 in the previous cycle, s'2 represents the value of s2 in the previous cycle, kr represents the proportional coefficient of the controller, err represents the error, and Ts represents the control period.

[0027] A further improvement of the four-quadrant three-phase PWM rectifier circuit topology control method of the present invention is that, when adjusting the negative sequence component generated by the three-phase current imbalance and adjusting the DC components of active and reactive current, the negative sequence component generated by the three-phase imbalance is specifically adjusted by a resonant regulator, and the DC components of active and reactive current are adjusted to match the expected values ​​by a PI controller.

[0028] The application of the technical solution of the present invention has the following beneficial effects:

[0029] This invention presents a four-quadrant three-phase PWM rectifier circuit topology, eliminating one phase control loop. This reduces the number of components required for the PWM rectifier, lowers overall switching losses and electromagnetic noise, and solves the problem of high system energy consumption caused by switching losses and on-resistance losses in existing PWM rectifiers. Furthermore, it optimizes the closed-loop strategy and modulation output strategy of the current-type control algorithm, allowing the circuit to operate normally with one less control dimension. This reduces the number of PWM control channels in the PWM rectifier and the required number of control system channels. This invention is applicable not only to two-level circuits and NPC-type three-level circuits but also to other types of three-phase rectifier circuits. For NPC three-level PWM rectifier circuits, since the three-phase circuit itself includes bus support capacitors C1 and C2, the modification is simpler; only one phase AC input line needs to be connected to point O of the three-level topology. Because the PO and ON voltages are formed by rectifying the AC line voltage, the PO and ON voltages are naturally balanced, requiring no additional balancing algorithm for control, making it more economical and practical.

[0030] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0031] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a schematic diagram of a two-level PWM rectifier circuit in the prior art;

[0033] Figure 2 This is a schematic diagram of a two-level PWM rectifier circuit with a four-quadrant three-phase PWM rectifier circuit topology according to the present invention.

[0034] Figure 3 This is a schematic diagram of a three-level NPC structure PWM rectifier circuit in the prior art;

[0035] Figure 4This is a schematic diagram of a three-level NPC structure PWM rectifier circuit with a four-quadrant three-phase PWM rectifier circuit topology according to the present invention.

[0036] Figure 5 This is a schematic diagram of the two-phase PWM rectifier optimization control algorithm of the four-quadrant three-phase PWM rectifier circuit topology of the present invention;

[0037] Figure 6 This is a vector diagram of the two-phase PWM rectifier optimization control algorithm for the four-quadrant three-phase PWM rectifier circuit topology of this invention;

[0038] Figure 7 The current waveform diagram of the two-phase PWM rectifier circuit topology of the present invention after removing one phase modulation output without optimizing the algorithm is shown.

[0039] Figure 8 The diagram shows the current waveform of a two-phase PWM rectifier with a four-quadrant three-phase PWM rectifier circuit topology of this invention after removing one phase modulation output and optimizing the algorithm.

[0040] Among them, IGBT1 is the first switching device; IGBT2 is the second switching device; IGBT3 is the third switching device; IGBT4 is the fourth switching device; IGBT5 is the fifth switching device; IGBT6 is the sixth switching device; IGBT7 is the seventh switching device; IGBT8 is the eighth switching device; IGBT9 is the ninth switching device; IGBT10 is the tenth switching device; IGBT11 is the eleventh switching device; and IGBT12 is the twelfth switching device. Detailed Implementation

[0041] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0042] See Figures 1 to 8 As shown, a four-quadrant three-phase PWM rectifier circuit topology includes a first switching device group, a second switching device group, and at least one supporting capacitor group. The first switching device group forms an A-phase control loop, with the middle of the A-phase control loop connected to the A-phase AC input line and the two ends of the A-phase control loop connected to the DC positive and negative buses, respectively. The second switching device group forms a B-phase control loop, with the middle of the B-phase control loop connected to the B-phase AC input line and the two ends of the B-phase control loop connected to the DC positive and negative buses, respectively. At least one supporting capacitor group is connected between the DC positive and negative buses. Each supporting capacitor group includes a first supporting capacitor and a second supporting capacitor, which are connected in series. The C-phase AC input line is connected to the connection point of the first supporting capacitor and the second supporting capacitor.

[0043] This invention discloses a four-quadrant three-phase PWM rectifier circuit topology and its control method. Compared with traditional four-quadrant three-phase PWM rectifiers, under the premise of the same power devices (power devices mainly refer to IGBTs (Insulated-Gate Bipolar Transistors), different IGBTs will cause changes in the loss characteristics of the device) and the same control conditions (such as input voltage, carrier, etc.), this structure requires fewer bridge arms and control channels, and has lower switching losses and noise. It is particularly suitable for rectifier topologies with three-level or multi-level architectures and is mainly used in the rectifier front end of frequency converters, welding machines, power systems, and distributed energy systems.

[0044] Example 1: The first switching device group includes a first switching device IGBT1 and a second switching device IGBT2, which are connected in series. The A-phase AC input line is connected to the connection point of the first switching device IGBT1 and the second switching device IGBT2. The second switching device group includes a third switching device IGBT3 and a fourth switching device IGBT4, which are connected in series. The B-phase AC input line is connected to the connection point of the third switching device IGBT3 and the fourth switching device IGBT4.

[0045] Figure 1 The diagram shows a traditional two-level PWM rectifier circuit topology, which includes six high-speed switching devices (IGBT1 to IGBT6). The first switching device IGBT1 and the second switching device IGBT2 form the A-phase control loop. Similarly, the other IGBTs form the B-phase and C-phase control loops. The phase control loops are connected to the DC positive and negative buses (DC+ / DC-), and a supporting capacitor C is connected between the positive and negative buses. When the rectifier is working, each IGBT module is controlled by an algorithm to perform high-speed switching, thereby regulating the DC-side output voltage and output current.

[0046] This invention relates to Figure 1 The PWM rectifier circuit structure has been improved. The improved two-phase two-level PWM rectifier structure is as follows: Figure 2 As shown, compared to Figure 1 The traditional rectifier circuit has removed the C-phase control loop (the A-phase or B-phase control loop can also be removed, and the control algorithm will be slightly different). The bus support capacitor has been replaced with the first support capacitor C1 and the second support capacitor C2. The first support capacitor C1 and the second support capacitor C2 are two capacitors with equal capacitance values. At the same time, the C-phase AC input line is connected to the connection point of the first support capacitor C1 and the second support capacitor C2.

[0047] Example 2: The first switching device group includes IGBT1, IGBT2, IGBT3, and IGBT4 connected in series. The A-phase AC input line is connected to the connection point of IGBT2 and IGBT3. The second switching device group includes IGBT5, IGBT6, IGBT7, and IGBT8 connected in series. The B-phase AC input line is connected to the connection point of IGBT6 and IGBT7. The O point of the three-level topology is connected to the connection point of the first supporting capacitor and the second supporting capacitor.

[0048] Figure 3 This is a traditional NPC three-level topology, similar to the two-level topology. For the three-phase AC input of A, B, and C, each phase has the same IGBT switching device control circuit. The difference is that the O point of the three-level topology is connected to the diode clamping point of the three-phase control circuit. The first supporting capacitor C1 is connected between the positive bus and the O point, and the second supporting capacitor C2 is connected between the O point and the negative bus. Figure 3 The C-phase control circuit is equipped with a ninth switching device IGBT9, a tenth switching device IGBT10, an eleventh switching device IGBT11, and a twelfth switching device IGBT12. Figure 3 In the diagram, D1-D6 represent diodes, respectively.

[0049] This invention relates to Figure 3 Improvements to the traditional NPC three-level topology. Figure 4 It is an improved two-phase three-level PWM rectifier structure, compared to Figure 3 The traditional rectifier circuit also eliminates the C-phase control loop (A-phase and B-phase can also be used), and connects the C-phase AC input to the midpoint of the DC bus.

[0050] Figure 2 and Figure 4 Both simplified the PWM rectifier circuit, but due to the reduction of one control dimension, the original control algorithm cannot... Figure 2 and Figure 4 The circuit is operating normally, but the algorithm needs to be optimized.

[0051] Given the above issues, such as Figure 5 As shown, the present invention also provides a control method for the four-quadrant three-phase PWM rectifier circuit topology described above, comprising the following steps:

[0052] S1. Use voltage sampling and PLL technology to track the grid angle and obtain θ;

[0053] S2. Sample the three-phase current of the power grid to obtain the current i ai b i c ;

[0054] S3, i a i b i c The current i in the αβ coordinate system is obtained by Clarke transformation. α_act i β_act ;

[0055] S4, i α_act i β_act Using θ as a reference, the Park transformation (a coordinate transformation technique) is performed to obtain the current i in the dq coordinate system. sq_act and i sd_act ;

[0056] S5. Calculate the given DC voltage U dc_ref+ and actual DC voltage U dc_act The error between them is used to obtain the output control current i through a PI controller (a type of linear controller). sd_ref ;

[0057] S6, Calculate i sd_ref i sq_ref with i sq_act i sd_act The error is input into the PI controller and the resonant regulator to obtain the output control voltage V. d V q In the closed-loop control of active and reactive current, the negative sequence component generated by the three-phase current imbalance and the DC component of active and reactive current are adjusted. Specifically, the negative sequence component generated by the three-phase imbalance is suppressed by a parallel PR regulator (resonant regulator), and the DC component of active and reactive current is adjusted to match the expected state (the expected state refers to the state before the structure was modified) by a PI controller (proportional-integral controller).

[0058] S7, V d and V q The vector length V is obtained through the inverse Park transform and the inverse Clarke transform. length And the vector angle θ', the vector angle θ' is transformed according to the vector image to obtain the AC line voltage angle and the BC line voltage angle, and the vector angle θ' is then transformed to obtain θ”;

[0059] S8, change the vector length V length The vector angle θ is input to the SPWM module (Sinusoidal Pulse Width Modulation) for natural modulation, and the drive signal of the rectifier power component is obtained through angle compensation.

[0060] S9. Control the rectifier drive component according to the drive signal, and after filtering, modulate the phase voltage into line voltage modulation so that the two-phase modulated output and the unmodulated output are at a fixed angle.

[0061] S10. Repeat the above steps.

[0062] PLL (Phase-Locked Loop) technology is an electronic circuit that uses a feedback mechanism to lock the frequency and phase of the input signal, achieving synchronization between the output and input signals. The inverse Park transform is the reverse process of the Park transform, used to convert a rotating d,q coordinate system back to a stationary α,β coordinate system. The inverse Clarke transform is the process of converting electrical quantities in a two-phase orthogonal stationary coordinate system (αβ coordinate system) back to a three-phase system (abc coordinate system).

[0063] The improvements of this invention are mainly aimed at changing the phase voltage modulation to line voltage modulation, so that the two-phase modulated output and the unmodulated output are at a fixed angle; and connecting a resonant regulator (PR regulator) in parallel in the active current and reactive current closed-loop control links, with the PR controller having a center frequency of 100Hz, to suppress the three-phase current imbalance phenomenon (i.e., the three-phase negative sequence component).

[0064] Figure 5 The meanings of each parameter in U are as follows: dc_ref+ Given a DC voltage, U dc_act i is the actual DC voltage. sd_ref i is the reference current calculated by the voltage outer loop PI controller. sq_ref Given an electrical current, i sq_act and i sd_act Let i be the actual current in the rotating coordinate system (called the dq coordinate system) obtained after the Park transformation. α_act i β_act V represents the actual current in the stationary coordinate system (called the αβ coordinate system) obtained after Clarke transformation. d V q The output voltage, i, is calculated by the lsq closed-loop PI controller and the lsq resonant controller. a i b i c These are the currents in the three-phase circuit of the power grid, V. lengthθ is the vector length after Park transformation, θ is the vector angle obtained from the grid voltage detection, θ' is the vector angle after Park transformation, θ” is the vector angle after angle transformation, Vabc is the voltage of the three-phase circuit in the grid, DC+ is the positive terminal of the DC input power supply, DC- is the negative terminal of the DC output power supply, and the PI voltage outer loop refers to the external closed-loop control link used in power electronic control systems to stabilize the output voltage at a set or reference value. Here, PI refers to the proportional-integral (PI) controller, which is a commonly used linear controller that reduces system error by adjusting the proportional and integral gains. Isq setpoint represents the reactive current setting. PI Isd closed loop represents an active current closed-loop control method that combines proportional and integral control strategies, and Isd resonant control represents 100Hz component suppression for active current. These two modules constitute the active current regulator. Isq closed-loop represents a reactive current closed-loop control method combining proportional and integral control strategies. Isq resonant control represents the suppression of the 100Hz component of reactive current. These two modules constitute a reactive current regulator. Idq represents the current component in the rotating coordinate system. Iαβ represents the two-phase current component in the stationary coordinate system. Iabc represents the three-phase current component in the stationary coordinate system. Vdq represents the voltage component in the rotating coordinate system. V length / θ It represents the voltage length and angle components. SPWM stands for Sinusoidal Pulse Width Modulation, which refers to the technique of modulating a series of pulses of varying widths to create an equivalent sine wave.

[0065] Typical power grid vector diagrams, such as Figure 6 As shown, the three-phase voltages A / B / C are distributed in positive sequence, with phase A leading phase B by 120° and phase B leading phase C by 120°. Conventional PWM rectifiers use three-phase modulation. The phase of the three-phase output voltage (fundamental phase, i.e., 50Hz phase) on the AC side of the rectifier is basically close to the phase voltage of the power grid, and a third harmonic needs to be injected during the modulation process to meet the requirements of bus utilization. However, the circuit structure of this invention eliminates one phase of modulation output and connects one phase of the three-phase input to the midpoint of the bus capacitor. This topology change has two effects: First, if the phase voltage phase matching control strategy is still used, the DC output of the PWM rectifier cannot be stabilized due to the lack of one phase control, and the DC output will fluctuate by tens of volts. No means can suppress the unstable state in the current control strategy. Second, if the third harmonic is still injected in the two-phase control mode, since the third harmonic is not injected into the uncontrolled voltage of one phase, the line voltage synthesized by the voltage of this phase and the voltage of the other two phases will generate a huge third low-frequency contamination (three times that of 50Hz, about 150Hz). Not only will stable control not be achieved, but the power grid will also be seriously polluted.

[0066] To achieve the same or even better technical results in a two-phase control circuit, this invention improves the modulation strategy. The following explanation uses a circuit with the C-phase capacitor removed (the same derivation can be made for circuits with the A-phase or B-phase capacitor removed). Figure 6 As shown, in a three-phase AC circuit, the line voltage and phase voltage vectors have a certain angular relationship. The AC line voltage forms a 30° angle with the A-phase voltage, and the BC line voltage forms a 60° angle with the AC line voltage. In the two-phase PWM rectifier control, phases A and C need to work together to output a voltage close to the phase of the line voltage AC, and phases B and C need to work together to output a voltage close to the phase of the line voltage BC. Therefore, the A-phase vector angle needs to be deflected, and the deflection angle is the same as the angle between the A-phase vector and the AC-phase vector, i.e., S101, deflect the A-phase vector angle by 30°; at the same time, the phase of the B-phase modulated voltage is no longer obtained by rotating the A-phase phase by 120°, i.e., S102, deflect the AC line voltage by 60° to obtain the phase of the B-phase modulated voltage.

[0067] In addition, since phase C is connected to the midpoint of the bus capacitor, the DC bus voltage is no longer approximately three-phase diode rectified voltage when the PWM rectifier is in diode rectification mode. Instead, it is equivalent to the series connection of two diode rectified voltages. Since the bus voltage is increased and there is only two-phase output, the modulation output of phases A and B does not need to be injected with the third harmonic, so it can match the input AC voltage.

[0068] In addition to adjusting the modulation strategy, this invention improves the control strategies for reactive and active currents. Compared to a three-phase symmetrical circuit, the two-phase PWM rectifier circuit introduces asymmetry, leading to an imbalance in the three-phase current during rectifier loading, such as... Figure 7 As shown. In classical circuit theory, three-phase load imbalance is generally caused by negative sequence components, which is specifically reflected in the rotating coordinate system as a 100Hz oscillating component in the reactive and active currents (for positive sequence systems, the active and reactive currents are DC). The 100Hz oscillation cannot be eliminated by adjusting the PI control parameters, and other control methods need to be introduced.

[0069] like Figure 5 As shown, this invention solves the three-phase imbalance problem by introducing a resonant control component into the current control inner loop. Specifically, a resonant control component is introduced into the current control inner loop, and the resonant control principle expression of the resonant regulator is as follows:

[0070] s1=s'1+(2×kr×wi×err-s2-2×wi×s1)×Ts

[0071] s2=s'2+wn×wn×s1×Ts

[0072] Where wn is the center frequency, usually set to 100, used to suppress oscillations caused by negative sequence components; wi is the sideband of the resonant controller, adding a certain fault tolerance range to the resonant control strategy. s'1 represents the value of s1 in the previous cycle, s'2 represents the value of s2 in the previous cycle, kr represents the proportional coefficient of the controller, err represents the error, and Ts represents the control period.

[0073] Figure 8 Compare the loaded current waveform after adding the resonant controller. Figure 7 and Figure 8 It can be seen that the three-phase current imbalance was suppressed after the addition of the resonant controller, which reduced the impact on the power grid, and the rectifier could also work normally.

[0074] This invention presents a four-quadrant three-phase PWM rectifier circuit topology that eliminates one phase control loop, thereby reducing the number of components required for the PWM rectifier, lowering overall switching losses and electromagnetic noise, and solving the problem of high system energy consumption caused by switching losses and on-resistance losses in existing PWM rectifiers. Furthermore, it optimizes the closed-loop strategy and modulation output strategy of the current-type control algorithm, enabling the circuit to operate normally with one less control dimension, thus reducing the number of PWM control channels in the PWM rectifier and the required number of control system channels. This invention is applicable not only to two-level circuits and NPC-type three-level circuits, but also to other types of three-phase rectifier circuits.

[0075] For NPC three-level PWM rectifier circuits, such as Figure 3 and Figure 4 As shown, since the three-phase circuit itself includes bus support capacitors C1 and C2, the modification is simpler. It is only necessary to connect one phase AC input line to point O of the three-level topology. Since the PO and ON voltages are formed by rectifying the AC line voltage, the PO and ON voltages are naturally balanced, and no additional balancing algorithm is needed for control, making it more economical and practical.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a four-quadrant three-phase PWM rectifier circuit topology, characterized in that, Includes the following steps: S1. Using voltage sampling and PLL technology, the grid angle is tracked and the grid line voltage is detected to obtain θ; S2. Sample the three-phase currents of the power grid to obtain the currents ia, ib, and ic; S3. Obtain the current iα in the αβ coordinate system by performing Clarke transformation on ia, ib, and ic. act iβ act ; S4, iα act iβ act The current isq in the dq coordinate system is obtained by performing a Park transformation with θ as the reference. act and isd act ; S5. Calculate the given DC voltage Udc ref + and actual DC voltage Udc act The error between them is used to obtain the output control current isd by the PI controller. ref Isq is given according to reactive current demand. ref The value; S6, Calculate isd ref isq ref with isq act isd act The error is input into the PI controller and the resonant regulator to obtain the output control voltages Vd and Vq. In the closed-loop control of active and reactive current, the negative sequence component generated by the three-phase current imbalance and the DC component of active and reactive current are adjusted. S7. Obtain the vector length Vlength and vector angle θ' from Vd and Vq through inverse Park transform and inverse Clarke transform, and then obtain θ” from the vector angle θ' through angle transformation. S8. Input the vector length Vlength and vector angle θ” into the SPWM module for natural modulation, and obtain the drive signal of the rectifier power component through angle compensation; S9. Control the rectifier drive component according to the drive signal, and after filtering, modulate the phase voltage into line voltage modulation so that the two-phase modulated output and the unmodulated output are at a fixed angle. S10. Repeat the above steps. The three-phase voltages A / B / C are distributed in positive sequence, with phase A leading phase B by 120° and phase B leading phase C by 120°. The AC line voltage forms a 30° angle with the A phase voltage, and the BC line voltage forms a 60° angle with the AC line voltage. S7 also includes transforming the vector angle θ' according to the vector image to obtain the AC line voltage angle and the BC line voltage angle, specifically: S701, Deflect the A-phase vector angle by 30°; S702. The phase of the B-phase modulation voltage is obtained by deflecting the AC line voltage by 60°. The expression for the resonance control principle of the resonance regulator is as follows: s1=s'1+(2×kr×wi×err-s'2-2×wi×s'1)×Ts s2=s'2+wn×wn×s1×Ts Where s1 is the output of the resonant controller, s2 is the internal integral state during the calculation process, wn is the center frequency, wi is the sideband of the resonant controller, s'1 represents the value of s1 in the previous cycle, s'2 represents the value of s2 in the previous cycle, kr represents the proportional coefficient of the controller, err represents the error, and Ts represents the control period. When adjusting the negative sequence component generated by the three-phase current imbalance and adjusting the DC components of active and reactive current, the negative sequence component generated by the three-phase imbalance is adjusted by the resonant regulator, and the DC components of active and reactive current are adjusted by the PI controller to match the expected values.

Images