A single-phase control method for three-phase four-wire PFC

Abstract

The application discloses a single-phase control method of three-phase four-wire PFC, and is a topological structure of split capacitor three-phase four-wire PFC, A phase and B phase are staggered and connected in parallel, C phase and N phase are staggered and connected in parallel to form a single-phase input, in the process of adopting DC voltage outer ring and AC current inner ring control on A phase, B phase and C phase, the current distribution coefficient is set as the distribution current of C phase and N phase to adjust the DC side bus voltage and current, and after three-phase control signals are obtained, the three-phase control signals are input into a pulse width modulator to generate PWM switching signals for controlling the turn-on and turn-off of power devices in the PFC, so that the single-phase control on the PFC is realized. The application not only can realize power factor correction and DC side bus voltage stabilization, but also can flexibly distribute the current of C phase and N phase to avoid overcurrent, so that power devices with lower current level and line cables can be used to realize higher power level.

Description

Technical Field

[0001] This invention belongs to the field of control of three-phase four-wire PFC systems, and specifically relates to a single-phase control method for three-phase four-wire PFC systems. Background Technology

[0002] Currently, with the rapid integration and development of power electronics technology and new energy vehicles, more and more electric vehicles are equipped with corresponding on-board chargers (OBCs). These chargers primarily draw power from the grid to charge electric vehicles when there are no dedicated charging stations available, thus meeting users' electricity needs. Most current on-board chargers (OBCs) on the electric vehicle market have unidirectional charging functionality (G2V), meaning they are compatible with single-phase 220V or three-phase 380V grid charging. In higher-power applications, three-phase power is often used for charging electric vehicles. However, considering the prevalence of single-phase power in my country, it is necessary to conduct in-depth research on electric vehicles' compatibility with single-phase 220V grid charging.

[0003] To address this issue, academic papers and patent analyses have proposed solutions, such as the article "Design and Control of the Centerline Bridge Arm of a Hybrid Switching Bidirectional Vehicle Charger for SiC-MOSFET and Si-IGBT," published in the Proceedings of the Chinese Society for Electrical Engineering, Vol. 40, No. 19, 2020, and "Common-Mode-Free Bidirectional Three-Phase PFC-Rectifier for Non-Isolated EV Charger," by B. Strothmann and F. Schafmeister, J. The 2021 IEEE Applied Power Electronics Conference and Exposition (APEC), 2021, pp. 2783-2790, "Common-Mode-Free Bidirectional Three-Phase PFC Rectifier for Non-Isolated Electric Vehicle Chargers," 2021 IEEE Applied Power Electronics Conference and Exposition, pp. 2783-2790, both proposed control strategies for three-phase four-wire PFC connected to a three-phase power grid in G2V mode, but did not propose control strategies for three-phase four-wire PFC connected to a single-phase power grid. This fails to meet the requirement of electric vehicles being compatible with single-phase power grids for charging, resulting in a relatively limited charging method for electric vehicles and reducing charging efficiency. 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, IEEE Transactions on Power Electronics, vol.38, no.1, pp.1204-1217, Jan.2023, (“Analysis, design and performance evaluation of SiC active soft-switching battery for single-phase / three-phase universal voltage input PFC for on-board charger applications”, IEEE Transactions on Power Electronics, Vol.38, No.1, January 2023) proposed interleaved parallel totem pole control for split capacitor three-phase four-wire PFC compatible with single-phase grids, but did not consider the C-phase current overcurrent problem at higher power levels.

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

[0005] To overcome the limitations of the above-mentioned technical solutions, this invention proposes a single-phase control method for a three-phase four-wire PFC based on a split capacitor type. The aim is to enable electric vehicles to be compatible with single-phase power grids for charging, making the charging methods of electric vehicles more diversified. 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 single-phase control method of a three-phase four-wire PFC of the present invention is characterized by the following: the topology of the split capacitor three-phase four-wire PFC is to form a single-phase input by interleaving the A and B phases and interleaving the C and N phases in parallel. During the process of controlling the A, B, and C phases using the DC voltage outer loop and the AC current inner loop, the DC bus voltage and current are adjusted by setting the current distribution coefficient to distribute the current between the C and N phases. After obtaining the three-phase control signal, it is input to the pulse width modulator to generate PWM switching signals for controlling the power devices in the PFC to turn on and off, so as to realize the single-phase control of the PFC.

[0008] The single-phase control method of a three-phase four-wire PFC described in this invention is also characterized in that the control process of the DC voltage outer loop and the AC current inner loop is as follows:

[0009] Step 1: Collect the AC current of phases A, B, and C of the AC side inductor L. AC input voltage u in DC bus voltage u bulk ;

[0010] Step 2: Based on the bus voltage reference value u bulk_ref For the DC side bus voltage u bulk After performing proportional-integral control, the output control result is multiplied by 1 / 2 to obtain the final output result.

[0011] The output result is related to the AC side input voltage u. in phase u in / |u in The products are then used as the alternating currents for phases A and B, respectively. Inner ring reference value

[0012] The AC input voltage u in phase u in / |u in |Invert the product to get -u in / |u in The current is obtained by multiplying the output result by the given current distribution coefficient k, which is then used to obtain the C-phase AC current. Inner ring reference value

[0013] Step 3: Based on the alternating currents of phases A, B, and C Inner ring reference value AC currents in phases A, B, and C of the AC side inductor L Proportional resonance control is performed, thereby obtaining the A, B, and C phase control signals of the PFC using equations (1), (2), and (3).

[0014]

[0015]

[0016]

[0017] In equations (1), (2), and (3), s is the Laplace operator. It is a voltage outer loop PI controller. The adjustment coefficient for the voltage outer loop ratio P is... The adjustment coefficient for the voltage outer loop integral I; It is a current inner loop PR controller. 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 This is the rated angular frequency of the grid voltage.

[0018] 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.

[0019] The present invention provides an electronic device, including a memory and a processor, wherein the memory is used to store a program supporting any of the single-phase control methods executed by the processor, and the processor is configured to execute the program stored in the memory.

[0020] The present invention discloses a computer-readable storage medium on which a computer program is stored, wherein the computer program is executed by a processor to perform any step of the single-phase control method.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention addresses the single-phase control problem of split capacitor three-phase four-wire PFC. Unlike the existing interleaved parallel totem pole control, it adopts three-phase independent DC voltage outer loop and AC current inner loop control, 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.

[0023] 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 arm 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

[0024] Figure 1 This is a topology diagram of a three-phase four-wire PFC used in the implementation of this invention;

[0025] Figure 2 This is a structural block diagram of the three-phase four-wire PFC control system used in the implementation of this invention;

[0026] 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.

[0027] Figure 4 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. Detailed Implementation

[0028] The specific embodiments and working principles of the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] In this embodiment, a single-phase control method for a three-phase four-wire PFC 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 sharing problem.

[0030] 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.

[0031] like Figure 2As shown, the single-phase control method of this three-phase four-wire PFC is based on the topology of a split-capacitor three-phase four-wire PFC. Phases A and B are connected in parallel alternately, and phases C and N are connected in parallel alternately to form a single-phase input. During the process of controlling phases A, B, and C using a DC voltage outer loop and an AC current inner loop, the current is distributed to phases C and N by setting an appropriate current distribution coefficient to adjust the DC bus voltage and current. After obtaining the three-phase control signal, it is input to the pulse width modulator to generate PWM switching signals for controlling the power devices in the PFC to turn on and off, thereby realizing the single-phase control of the PFC.

[0032] In practice, the control process for the DC voltage outer loop and the AC current inner loop is as follows:

[0033] Step 1: Collect the AC current of phases A, B, and C of the AC side inductor L. AC input voltage u in DC bus voltage u bulk In this embodiment, ω g = 314 rad / s.

[0034] Step 2: Based on the bus voltage reference value u bulk_ref For the DC side bus voltage u bulk After performing proportional-integral control, the output control result is multiplied by 1 / 2 to obtain the final output. In this embodiment, u bulk_ref =800V.

[0035] Output result and AC side input voltage u in phase u in / |u in The multiplication results in reference values ​​for the inner loop of AC current in phases A and B, respectively.

[0036] Because the C-phase current is 180° out of phase with respect to the A-phase and B-phase currents, the inner loop reference value of the C-phase AC current is... Relative to the inner loop reference values ​​of phase A and phase B AC current The phase difference is 180°, therefore the AC side input voltage u in phase u in / |u in |Invert the product to get -u in / |u in The value is obtained by multiplying the output result by the given current distribution coefficient k, and then multiplying by the value of the inner loop of the C-phase AC current. In this embodiment, the inner loop reference values ​​of the AC current for 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, so that the inner loop reference value of the AC current in phase C is... Allow half of the total current (phase A or phase B) to flow through phase C, and the remaining half of the current will automatically flow through phase N.

[0037] Step 3: Based on the inner loop reference values ​​of the AC current for phases A, B, and C. Currents in phases A, B, and C of the AC-side inductor L Proportional resonance control is performed, thereby obtaining the A, B, and C phase control signals of the PFC using equations (1), (2), and (3).

[0038]

[0039]

[0040]

[0041] In equations (1), (2), and (3), s is the Laplace operator. It is a voltage outer loop PI controller. The adjustment coefficient for the voltage outer loop ratio P is... The adjustment coefficient for the voltage outer loop integral I; It is a current inner loop PR controller. 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 This is the rated angular frequency of the grid voltage. In this embodiment,

[0042] 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.

[0043] To verify the effectiveness of the control method of this invention, a corresponding simulation model was built using the power electronics simulation software PLECS, and the simulation results are as follows. Figure 3 , Figure 4 As shown.

[0044] Figure 3 To employ the control method of this invention, a three-phase four-wire PFC at power level S n =6.6kW, AC input voltage u when current distribution coefficient k=1 in AC input current i in DC bus voltage u bulk C-phase current i C N-phase current iN Waveform diagram. (From...) Figure 3 As shown: Using the control method of this invention, the AC side input voltage u in AC input current i in In phase, DC side bus voltage u bulk With target voltage u bulk_ref =800V consistent, C-phase current i C N-phase current i N It can achieve flow sharing control, i C =i N It has an output of approximately 15A, which complies with the national standard GB / T40432-2021 Conductive On-board Charger for Electric Vehicles. Moreover, compared to the interleaved parallel totem pole control, the C-phase bridge arm can use power devices and cables with lower current ratings to achieve a higher power rating.

[0045] To further verify the universality of the control method of the present invention, consider the current distribution coefficient k = 1 / 2, i.e., i N =3i C The situation at that time.

[0046] Figure 4 To employ the control method of this invention, a three-phase four-wire PFC at power level S n =6.6kW, AC input voltage u when k=1 / 2 in AC input current u in DC bus voltage u bulk C-phase current i C N-phase current i N .Depend on Figure 4 It can be observed that: if the control strategy of this invention is adopted, the AC side input voltage u in AC input current i in In phase, DC side bus voltage u bulk With target voltage u bulk_ref =800V consistent, N-phase current i N It is the C-phase current i C Three times that.

[0047] 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.

[0048] 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.

[0049] In summary, the above control method can not only achieve power factor correction and DC bus voltage stability, but also flexibly allocate the C-phase and N-phase current 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 single-phase control method for a three-phase four-wire PFC, characterized in that: The topology of a split-capacitor three-phase four-wire PFC involves alternating parallel connections of phases A and B, and alternating parallel connections of phases C and N to form a single-phase input. During the control process of phases A, B, and C using a DC voltage outer loop and an AC current inner loop, the DC bus voltage and current are adjusted by setting a current distribution coefficient to distribute current between phases C and N. The resulting three-phase control signal is then input to a pulse width modulator (PWM) to generate PWM switching signals for controlling the on / off switching of power devices in the PFC, thus achieving single-phase control of the PFC. The control process of the DC voltage outer loop and AC current inner loop is as follows: Step 1: Collect AC side inductance The alternating current of phase A, phase B, and phase C , , AC input voltage DC bus voltage ; Step 2: Based on the bus voltage reference value For the DC side bus voltage After performing proportional-integral control, the output control result is multiplied by 1 / 2 to obtain the final output result. The output result is related to the AC side input voltage. phase After multiplication, they are respectively used as alternating currents for phases A and B. , Inner ring reference value , ; AC side input voltage phase Invert the product to get the product. Multiply the result by the given output and then multiply by the given current distribution coefficient. As the C-phase alternating current Inner ring reference value ; Step 3: Based on the alternating currents of phases A, B, and C , , Inner ring reference value , , For AC side inductance A, B, and C phase AC current , , Proportional resonance control is performed, thereby obtaining the A, B, and C phase control signals of the PFC using equations (1), (2), and (3). , , : (1) (2) (3) In equations (1), (2), and (3), For the Laplace operator, It is a voltage outer loop PI controller. The adjustment coefficient for the voltage outer loop ratio P. The adjustment coefficient for the voltage outer loop integral I; It is a current inner loop PR controller. 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; 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.

2. 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 single-phase control method of claim 1, and the processor is configured to execute the program stored in the memory.

3. A computer-readable storage medium storing a computer program, characterized in that, The computer program is executed by the processor to perform the steps of the single-phase control method of claim 1.

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