A current stress control method in single-phase mode of three-phase four-wire PFC

Abstract

The application discloses a current stress control method of three-phase four-wire PFC in single-phase mode, which is based on split capacitor three-phase four-wire PFC circuit topology structure, and A phase and B phase in the topology are staggered and connected in parallel as an input port, C phase and N line are staggered and connected in parallel as another input port, voltage mode control is adopted for A phase and B phase to adjust grid-side alternating current and bus DC voltage, current mode control is adopted for C phase to adjust C phase current, current distribution coefficient is set to distribute the current of C phase and N line, three-phase control signals are obtained, comparison with high-frequency carrier is carried out to generate PWM driving signals, and the current stress control of three-phase four-wire PFC in single-phase mode is realized. The application can realize power factor correction and bus DC voltage stabilization, can distribute the current of C phase and N line, and can use power devices with low current level to realize higher power level.

Description

Technical Field

[0001] This invention belongs to the field of control of three-phase four-wire PFC systems, specifically relating to a current stress control method in single-phase mode of three-phase four-wire PFC. Background Technology

[0002] With the increasing popularity of electric vehicles, the development of on-board chargers (OBCs) is crucial for meeting battery charging requirements. As a key component of the OBC, the demand for power factor correction (PFC) rectifiers with higher rated power and higher power density has become increasingly apparent in recent years. Initially, single-phase PFC rectifiers were developed to meet the charging needs of homes or offices, with power levels typically below 3.7kW. With the increase in electric vehicle battery capacity and the demand for fast charging, the rated power of OBCs has gradually increased to the typical levels of national power grids, namely 6.6kW, 7.4kW, 11kW, and 22kW. When the rated power of the OBC exceeds 7.4kW, three-phase input is required, necessitating a corresponding three-phase PFC. To improve charging feasibility, PFC rectifiers above 7.4kW need to be compatible with both three-phase and single-phase power grids. In higher power applications, three-phase power is often used to charge electric vehicles; however, considering the prevalence of single-phase power in my country, it is necessary to conduct in-depth research on electric vehicle compatibility with single-phase 220V power grids.

[0003] To address this issue, academic papers and invention patent analyses have proposed solutions. For example, the paper "Analysis, Design, and Performance Evaluation of SiC Active Soft-Switching Cell for 1-ph / 3-ph Universal Voltage Input PFC for On-Board Charger Applications" by T. Sadilek, L. Huber, Y. Jang, P. Barbosa and I. Husain, published in IEEE Transactions on Power Electronics, vol.38, no.1, pp.1204-1217, Jan.2023, proposes interleaved parallel totem pole control for split-capacitor three-phase four-wire PFC compatible with single-phase power grids, but does not consider the C-phase current overcurrent problem at higher power levels. Another example is "Modified Deadbeat Predictive Current Control Method for Single-Phase AC–DC PFC". The paper, "An Improved Deadbeat Predictive Current Control Method for Single-Phase AC-DC PFC Converters in Electric Vehicle Charging Systems," by Yuxuan Bi, Chao Wu, Tong Zhao, Houji Li, Junzhong Xu, Guohua Shu, and Yong Wang, published in IEEE Transactions on Industrial Electronics, vol.70, no.1, pp.286-297, Jan.2023, proposes an interleaved parallel boost control method for single-phase AC-DC PFC converters compatible with split capacitor three-phase four-wire PFC grids. However, it does not consider the overcurrent problem of phase C when the power level is high.

[0004] In summary, there are relatively few existing control methods for single-phase input in a split capacitor three-phase four-wire PFC system. The proposed control methods do not consider the overcurrent of the C-phase current or how to distribute the C-phase current. Summary of the Invention

[0005] To overcome the limitations of the above-mentioned technical solutions, this invention proposes a current stress control method for single-phase mode of three-phase four-wire PFC based on split capacitor type, in order to enable electric vehicles to be compatible with single-phase power grids for charging, making the charging methods of electric vehicles more diversified, and at the same time, it can realize current distribution to avoid overcurrent, thereby enabling the use of lower current-rated power devices and line cables to achieve higher power levels.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The present invention provides a current stress control method for a three-phase four-wire PFC system in single-phase mode, characterized by the following steps:

[0008] Step 1: Based on the topology of the split capacitor three-phase four-wire PFC circuit, the A phase and B phase in the topology are connected in parallel in an alternating manner as one input port, and the C phase and N line are connected in parallel in an alternating manner as another input port to form a single-phase input;

[0009] Step 2: Use voltage mode control for the bridge arms of phase A and phase B to adjust the AC current on the grid side to be in phase with the grid voltage and stabilize the bus voltage to the target value.

[0010] The bridge arm of phase C is controlled in current mode to adjust the magnitude of the phase C current;

[0011] By setting different current distribution coefficients, the current magnitudes of the C-phase and N-line are distributed, thereby obtaining the three-phase control signal;

[0012] Step 3: Perform logical operations on the three-phase modulation control signal and the high-frequency carrier to generate the PWM drive signal for the control switch, so as to realize the current stress control of the three-phase four-wire PFC in single-phase mode.

[0013] The current stress control method for a three-phase four-wire PFC in single-phase mode described in this invention is also characterized in that step 2 includes:

[0014] Step 2.1: Collect the AC current of phases A, B, and C of the AC filter inductor L using a current sensor. The grid-side AC voltage u is collected by a voltage sensor. g DC voltage of the busbar u bulk The voltage u of the two bus split capacitors C1 u C2 ;

[0015] Step 2.2: Assess the grid-side voltage u g Perform SOGI-type phase-locked loop operation to obtain the grid-side AC voltage u.g phase angle θ g Then, regarding the phase angle θ g Perform trigonometric sin operations to obtain the normalized phase sinθ of the grid-side AC voltage. g ;

[0016] Step 2.3: Obtain the first voltage regulation difference using equation (1)

[0017]

[0018] In equation (1), u bulk_ref This represents the set target value of the DC bus voltage, where s is the Laplace operator, and G... DVC This indicates an outer-loop PI controller for voltage, and in, The adjustment coefficient for the voltage outer loop ratio P. The adjustment coefficient for the voltage outer loop integral I;

[0019] Step 2.4: Obtain the second voltage regulation difference using equation (2).

[0020]

[0021] In equation (2), G VBC It is an average voltage loop PI controller, and in, The adjustment coefficient for the average voltage loop proportional gain P. The adjustment coefficient for the average voltage loop integral I;

[0022] Step 2.5: Use equations (3) and (4) to obtain the control signals for phase A and phase B respectively.

[0023]

[0024]

[0025] In equations (3) and (4), G ACC Indicates the current inner loop PR controller; in, This is the adjustment coefficient for the current inner loop proportional gain P. ω is the adjustment coefficient of the inner current loop resonance R. g The rated angular frequency of the grid voltage;

[0026] Step 2.6: Obtain the C-phase control signal using equation (5)

[0027]

[0028] In equation (5), k is a given current distribution coefficient.

[0029] The control parameters of the voltage outer loop PI controller and the current inner loop PR controller are based on the PFC system parameters and rated capacity S. n Settings.

[0030] The present invention provides an electronic device, comprising a memory and a processor, wherein the memory is used to store a program supporting the processor to execute any one of the single-phase control methods of claims 1-3, and the processor is configured to execute the program stored in the memory.

[0031] The present invention discloses a computer-readable storage medium on which a computer program is stored, wherein the computer program, when executed by a processor, performs the steps of the current stress control method in single-phase mode.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. This invention addresses the single-phase control problem of split capacitor three-phase four-wire PFC. Unlike existing interleaved parallel totem pole control and interleaved parallel Boost control, it adopts a hybrid control mode of voltage mode and current mode, which can achieve power factor correction and DC side bus voltage stability. It is suitable for bidirectional on-board chargers operating in G2V and V2V modes.

[0034] 2. The control method proposed in this invention can flexibly allocate the magnitude of the C-phase current and N-phase current by setting the corresponding current distribution coefficient, so that the split capacitor can act as the fourth bridge arm. Compared with the corresponding three-phase four-bridge PFC, the split capacitor three-phase four-wire PFC has a lower cost advantage, so that lower current level and lower cost power devices and line cables can be used to achieve a higher power level. Attached Figure Description

[0035] Figure 1 This is a topology diagram of a three-phase four-wire PFC used in the implementation of this invention;

[0036] Figure 2 This is a structural block diagram of the three-phase four-wire PFC control system used in the implementation of this invention;

[0037] Figure 3 To employ the control method of this invention, a three-phase four-wire PFC at power level S n Voltage and current waveforms when the power is 6.6 kW and k = 1 / 2.

[0038] Figure 4To employ the control method of this invention, a three-phase four-wire PFC at power level S n =6.6kW, k=1 / 3 voltage and current waveforms. Detailed Implementation

[0039] The specific embodiments and working principles of the present invention will be further described in detail below with reference to the accompanying drawings.

[0040] In this embodiment, a current stress control method for a three-phase four-wire PFC in single-phase mode is proposed. Considering the widespread use of single-phase electricity in my country, the on-board charger (OBC) with a split capacitor three-phase four-wire PFC at the front end can not only be compatible with a three-phase 380V power grid to charge electric vehicles, but also with a single-phase 220V power grid to charge electric vehicles, while also taking into account the current distribution problem.

[0041] The topology used in this embodiment is as follows: Figure 1 As shown. This topology includes a three-phase full-bridge PFC rectifier, an AC-side inductor L, and an AC-side filter capacitor C. In this embodiment, L = 300uH and C = 10uF.

[0042] This describes a current stress control method for a three-phase four-wire PFC system in single-phase mode, such as... Figure 2 As shown, the procedure is as follows:

[0043] Step 1: Based on the topology of the split capacitor three-phase four-wire PFC circuit, the A phase and B phase in the topology are connected in parallel in an alternating manner as one input port, and the C phase and N line are connected in parallel in an alternating manner as another input port to form a single-phase input;

[0044] Step 2: Use voltage mode control for the bridge arms of phases A and B to adjust the AC current on the grid side to be in phase with the grid voltage and stabilize the bus voltage to the target value; and use current mode control for the bridge arm of phase C to adjust the magnitude of the phase C current; by setting different current distribution coefficients, the current magnitude of phase C and the N line is distributed to obtain the three-phase control signal.

[0045] Step 2.1: Collect the AC current of phases A, B, and C of the AC filter inductor L using a current sensor. The grid-side AC voltage u is collected by a voltage sensor. g DC voltage of the busbar u bulk The voltage u of the two bus split capacitors C1 u C2 In this embodiment

[0046] Step 2.2: Assess the grid-side voltage u gPerform SOGI-type phase-locked loop operation to obtain the grid-side AC voltage u. g phase angle θ g Then, regarding the phase angle θ g Perform trigonometric sin operations to obtain the normalized phase sinθ of the grid-side AC voltage. g ;

[0047] Step 2.3: Based on the set target value u of the bus DC voltage bulk_ref The DC voltage u of the busbar bulk The target value of DC voltage u of the bus bulk_ref Perform a difference operation, and then perform proportional-integral control operation on the result to obtain the first voltage regulation difference, which is expressed by equation (1):

[0048] In equation (1), s is the Laplace operator, and G DVC This indicates an outer-loop PI controller for voltage, and in, The adjustment coefficient for the voltage outer loop ratio P. This is the adjustment coefficient for the voltage outer loop integral I; in this embodiment, u bulk_ref =800V,

[0049] Step 2.4: Voltage u of the bus split capacitor C1 u C2 Perform a difference operation, and then perform proportional-integral control operation on the result to obtain the second voltage regulation difference, which is expressed by equation (2):

[0050]

[0051] In equation (2), G VBC It is an average voltage loop PI controller, and in, The adjustment coefficient for the average voltage loop proportional gain P. This is the adjustment coefficient for the average voltage loop integral I; in this embodiment,

[0052] Step 2.5: Multiply the first voltage regulation difference obtained in Step 2.3 by 1 / 2 and then compare it with the phase sinθ of the grid-side voltage obtained in Step 2.2. g Perform a multiplication operation, and add the result to the second voltage adjustment difference obtained in step 2.3 to obtain the AC currents of phases A and B, respectively. Inner ring reference value The obtained inner loop reference values ​​of phase A and phase B currents AC current of phases A and B of AC filter inductor L The difference operation is performed, and the result is then used for proportional resonance control to obtain the control signals for phases A and B. Using equations (3) and (4):

[0053]

[0054]

[0055] In equations (3) and (4), G ACC Indicates the current inner loop PR controller; in, This is the adjustment coefficient for the current inner loop proportional gain P. ω is the adjustment coefficient of the inner current loop resonance R. g The rated angular frequency of the grid voltage; in this embodiment, ω g = 314 rad / s.

[0056] Step 2.6: Measure the current in phases A and B of the AC filter inductor L. Add them together and then invert them to get the product. Multiply by the given current distribution coefficient k to obtain the C-phase AC current. Inner ring reference value The obtained C-phase current inner loop reference value AC current of phase C with AC filter inductor L The difference operation is performed, and the result is then used for proportional resonance control to obtain the C-phase control signal. Using equation (5):

[0057]

[0058] In equation (5), k is a given current distribution coefficient. In this embodiment, the reference values ​​for the inner loop of the AC current in phases A and B are... Since the currents in phases A and B are the same, to balance the currents in phases C and N, we take k = 1 / 2, so that the inner loop reference value of the AC current in phase C is... The current is half of the total current. Let half of the total current (phase A current or phase B current) flow through phase C, and the remaining half of the current will automatically flow through phase N.

[0059] In practice, the control parameters of the voltage outer-loop PI controller and the current inner-loop PR controller are based on the PFC system parameters and rated capacity S. n The settings. In this embodiment, S n =6.6kw.

[0060] In practice, the control parameters of the average voltage loop PI controller, the outer voltage loop PI controller, and the inner current loop PR controller are based on the PFC system parameters and rated capacity S. n The settings. In this embodiment, S n =6.6kw.

[0061] Step 3: Perform logical operations on the three-phase modulation control signal and the high-frequency carrier to generate the PWM drive signal for the control switch, so as to realize the current stress control of the three-phase four-wire PFC in single-phase mode.

[0062] To verify the effectiveness of the control method of this invention, a hardware circuit was built, and the experimental results are as follows: Figure 3 , Figure 4 As shown.

[0063] Figure 3 To employ the control method of this invention, a three-phase four-wire PFC at power level S n =6.6kW, grid-side AC voltage u when current distribution factor k = 1 / 2 g , grid-side AC current i g DC voltage of the busbar u bulk C-phase current i C N-line current i N The waveform diagram. (From...) Figure 3 As shown: Using the control method of this invention, the grid-side AC voltage u g , grid-side AC current i g In phase, bus DC voltage u bulk With target voltage u bulk_ref =800V consistent, C-phase current i C N-line current i N It can achieve flow sharing control, i C =i N ≈15A, which complies with the national standard "GB / T40432-2021 Conductive On-board Charger for Electric Vehicles". Moreover, compared with interleaved parallel totem pole control and interleaved parallel Boost control, the C-phase bridge arm can use power devices and line cables with lower current ratings to achieve higher power ratings.

[0064] To further verify the universality of the control method of the present invention, consider the current distribution coefficient k = 1 / 3, i.e., i N =2i C The situation at that time.

[0065] Figure 4 To employ the control method of this invention, a three-phase four-wire PFC at power level S n =6.6kW, grid-side AC voltage u when k=1 / 3 g , grid-side AC current ig DC voltage of the busbar u bulk C-phase current i C N-line current i N .Depend on Figure 4 It can be observed that: if the control strategy of this invention is adopted, the grid-side AC voltage u g , grid-side AC current i g In phase, bus DC voltage u bulk With target voltage u bulk_ref =800V consistent, N-line current i N It is the C-phase current i C Twice as much.

[0066] In this embodiment, an electronic device includes a memory and a processor. The memory stores a program that supports the processor in executing the single-phase control method described above, and the processor is configured to execute the program stored in the memory.

[0067] In this embodiment, a computer-readable storage medium stores a computer program, which is executed by a processor to perform the steps of the single-phase control method described above.

[0068] In summary, the above control method can not only achieve power factor correction and DC bus voltage stability, but also flexibly distribute the C-phase and N-line currents by setting the current distribution coefficient, avoiding overcurrent, thereby enabling the use of power devices and line cables with lower current ratings to achieve higher power ratings.

Claims

1. A current stress control method in single-phase mode of a three-phase four-wire PFC, characterized in that, Follow these steps: Step 1: Based on the topology of the split capacitor three-phase four-wire PFC circuit, the A phase and B phase in the topology are connected in parallel in an alternating manner as one input port, and the C phase and N line are connected in parallel in an alternating manner as another input port to form a single-phase input; Step 2: Use voltage mode control for the bridge arms of phase A and phase B to adjust the AC current on the grid side to be in phase with the grid voltage and stabilize the bus voltage to the target value. The bridge arm of phase C is controlled in current mode to adjust the magnitude of the phase C current; By setting different current distribution coefficients, the current magnitudes of the C-phase and N-line are distributed, thereby obtaining the three-phase control signal; Step 2.1: Acquire AC filter inductance using a current sensor AC current of phases A, B, and C , , The AC voltage on the grid side is collected by a voltage sensor. DC voltage of the bus The voltage of the two bus split capacitors ; Step 2.2: Check the grid-side voltage Perform SOGI-type phase-locked loop operation to obtain the AC voltage on the grid side. phase angle Then adjust the phase angle Perform trigonometric sin operations to obtain the phase of the normalized AC voltage on the grid side. ; Step 2.3: Obtain the first voltage regulation difference using equation (1) : (1) In equation (1), This indicates the set target value for the DC voltage of the bus. For the Laplace operator, This indicates an outer-loop PI controller for voltage, and ,in, The adjustment coefficient for the voltage outer loop ratio P. The adjustment coefficient for the voltage outer loop integral I; Step 2.4: Obtain the second voltage regulation difference using equation (2). : (2) In equation (2), It is an average voltage loop PI controller, and ,in, The adjustment coefficient for the average voltage loop proportional gain P. The adjustment coefficient for the average voltage loop integral I; Step 2.5: Use equations (3) and (4) to obtain the control signals for phase A and phase B respectively. , : (3) (4) In equations (3) and (4), Indicates the current inner loop PR controller; ,in, This is the adjustment coefficient for the current inner loop proportional gain P. This is the adjustment coefficient of the current inner loop resonance R. The rated angular frequency of the grid voltage; Step 2.6: Obtain the C-phase control signal using equation (5) : (5) In equation (5), Given the current distribution coefficient; Step 3: Perform logical operations on the three-phase modulation control signal and the high-frequency carrier to generate the PWM drive signal for the control switch, so as to realize the current stress control of the three-phase four-wire PFC in single-phase mode.

2. The current stress control method for a three-phase four-wire PFC in single-phase mode according to claim 1, characterized in that, The control parameters of the voltage outer loop PI controller and the current inner loop PR controller are based on the PFC system parameters and rated capacity. Settings.

3. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports the processor in executing the current stress control method in any of the single-phase modes according to claims 1-2, and the processor is configured to execute the program stored in the memory.

4. A computer-readable storage medium storing a computer program thereon, characterized in that, When the computer program is run by the processor, it executes the steps of the current stress control method in any of the single-phase modes described in claims 1-2.

Images