Single-phase control method of three-phase four-wire inverter

Abstract

The application discloses a single-phase control method of a three-phase four-wire inverter, and is a topological structure of a split capacitor three-phase four-wire inverter, wherein A phase and B phase are connected in parallel alternately, C phase and N phase are connected in parallel alternately to form a single-phase output, AC voltage loop control is adopted for A phase and B phase, AC voltage is adjusted, AC current loop control is adopted for C phase, C phase current is adjusted, three-phase control signals are obtained, and then are input into a pulse width modulator, so that PWM switching signals for controlling the turn-on and turn-off of power devices in the inverter are generated, and single-phase control of the inverter is realized. The application not only can realize AC voltage stability, but also can flexibly distribute C phase and N phase currents, avoids overcurrent, and thus can use power devices with low current levels and line cables to realize higher power levels.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of control of three-phase four-wire inverter systems, and particularly relates to a single-phase control method of a three-phase four-wire inverter. BACKGROUND

[0002] At present, with the rapid integration of power electronics technology and new energy vehicles, more and more electric vehicles are equipped with corresponding on-board chargers (OBCs). In the absence of electric vehicle charging piles, the on-board chargers (OBCs) are used to charge electric vehicles from the power grid to meet the power demand of users. However, most of the on-board chargers (OBCs) in the current electric vehicle market only have one-way charging function (G2V), that is, they can only be compatible with single-phase 220V or three-phase 380V power grid charging. With the continuous improvement of consumers' demand for electric vehicles, more and more consumers hope that electric vehicles have discharging function and can act as 220V mobile power supply in outdoor, have V2V (electric vehicle to electric vehicle), V2L (electric vehicle to load), V2H (electric vehicle to residence) function, and can also be used as distributed energy storage station. Therefore, it is necessary to conduct in-depth research on the discharging function of electric vehicles.

[0003] To solve this problem, academic papers and invention patents have proposed solutions. For example, the article "SiC-MOSFET and Si-IGBT hybrid switching vehicle bidirectional charger middle bridge arm design and control" in the 40th volume, 19th issue of the China Electrical Engineering Journal in 2020 proposes a control strategy for a three-phase four-wire inverter working in three-phase independent output mode in V2L (V2H, V2V) mode, but does not propose a control strategy for a three-phase four-wire inverter working in single-phase output mode. The article "Design, and Control of a SiC Isolated Bidirectional Power Converter for V2L Applications to both DC and AC Load" by X. Wang et al. in 2019 IEEE 7th Workshop on Wide Bandgap Power Devices and Applications (WiPDA), 2019, pp. 143-150 proposes a control strategy for a three-phase four-wire inverter working in single-phase output mode in V2L (V2H, V2V) mode, but does not consider the current overcurrent problem when the power level is high. The article "A 25kW SiC Universal Power Converter Building Block for G2V, V2G, and V2L Applications" by X. Wang et al. in 2018 IEEE International Power Electronics and Application Conference and Exposition (PEAC), 2018, pp. 1-6 proposes a control strategy for a three-phase four-wire inverter working in three-phase output mode in V2L (V2H, V2V) mode, and considers controlling the current to some extent to avoid overcurrent problems, but this control strategy is not suitable for a three-phase four-wire inverter working in single-phase output mode.

[0004] In summary, there are few existing control methods for split capacitor three-phase four-wire inverters in single-phase output mode, and the relevant control methods proposed do not comprehensively consider output voltage stability and current overcurrent problems. SUMMARY

[0005] In order to overcome the limitations of the above technical solutions, the present invention proposes a single-phase control method for a three-phase four-wire inverter based on a split-capacitor three-phase four-wire inverter, in order to realize the V2V, V2L, and V2H functions of electric vehicles, and at the same time realize current distribution to avoid overcurrent, so that power devices and line cables with lower current levels can be used to achieve higher power levels.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The single-phase control method of a three-phase four-wire inverter of the present invention is characterized in that: the topology of the split-capacitor three-phase four-wire inverter interlaces and connects the A phase and the B phase in parallel, and interlaces and connects the C phase and the N phase in parallel to form a single-phase output; AC voltage loop control is adopted for the A phase and the B phase to adjust the AC voltage; AC current loop control is adopted for the C phase to adjust the C phase current; and after obtaining the three-phase control signal, it is input into a pulse width modulator to generate a PWM switching signal for controlling the opening and closing of power devices in the inverter, thereby realizing single-phase control of the inverter.

[0008] The single-phase control method of a three-phase four-wire inverter described in the present invention is also characterized in that the control process of the AC voltage loop is as follows:

[0009] Step 1: Collect the A-phase and B-phase voltages of the AC side filter capacitor C

[0010] Step 2: The voltage of the AC side filter capacitor C Perform RMS calculation to obtain the A-phase and B-phase voltages of the AC side filter capacitor C. The effective value of

[0011] According to the effective reference value of the target voltage of phase A and phase B Phase A and phase B voltage of AC side filter capacitor C The effective value of Perform proportional-integral control to obtain the control output result;

[0012] The control output result is compared with the real-time reference value of the target voltage of phase A and phase B respectively After multiplication, we get the voltage of phase A and phase B Inner loop reference value According to the voltage of phase A and phase B Inner loop reference value The A-phase and B-phase voltages of the AC side filter capacitor C are respectively Perform proportional control, and then use equations (1) and (2) to obtain the inverter A phase and B phase control signals

[0013]

[0014]

[0015] In formula (1) and formula (2), s is a Laplace operator, is a voltage outer loop PI controller, is a voltage outer loop proportional P adjustment coefficient, is a voltage outer loop integral I adjustment coefficient; is a voltage inner loop P controller, is a voltage inner loop proportional P adjustment coefficient.

[0016] The control process of the alternating current loop is as follows:

[0017] Step 1: Collecting A-phase, B-phase and C-phase inductor currents of the inverter side inductance L

[0018] Step 2: Adding A-phase and B-phase inductor currents after taking the negative, multiplying by the current distribution coefficient k, and obtaining the result as the reference value of the C-phase inductor current According to the reference value of the C-phase inductor current

[0019] , proportional resonance control is performed on the C-phase inductor current , so that the inverter C-phase control signal is obtained by using formula (3)

[0020]

[0021] In formula (3), s is a Laplace operator, is a current loop PR controller, is a current loop proportional P adjustment coefficient, is a current loop resonance R adjustment coefficient, and ω g is a rated angular frequency of the grid voltage.

[0022] The control parameters of the alternating voltage loop PI controller, the P controller and the alternating current loop PR controller are set according to the system parameters and the rated capacity S n of the inverter.

[0023] The electronic device comprises a memory and a processor, characterized in that the memory is used for storing a program supporting the processor to execute any single-phase control method, and the processor is configured to execute the program stored in the memory.

[0024] ​The computer readable storage medium stores a computer program, and when the computer program is run by a processor, steps of any single-phase control method are executed.

[0025] Compared with the prior art, the application has the beneficial effects that:

[0026] 1. The single-phase control method of the split capacitor three-phase four-wire inverter is different from the existing pure voltage loop control, and adopts alternating voltage loop control and alternating current loop control, so that output voltage stability and current sharing can be realized, and the method is suitable for bidirectional vehicle-mounted chargers working in V2V, V2L and V2H modes.

[0027] 2. The control method can flexibly distribute the sizes of C-phase current and N-phase current by setting a corresponding current distribution coefficient, so that the split capacitor plays the role of the fourth bridge arm, and compared with the corresponding three-phase four-bridge-arm inverter, the split capacitor three-phase four-wire inverter has the advantage of lower cost, so that power devices and line cables with lower current level and lower cost can be used, and a higher power level is realized. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The three-phase four-wire inverter topology structure used in the implementation of the application is shown in the figure.

[0029] Figure 2 The structure block diagram of the three-phase four-wire inverter control used in the implementation of the application is shown in the figure.

[0030] Figure 3 The voltage and current waveform diagram of the three-phase four-wire inverter when the power level S n = 6.6kw, k = 1 / 2 is shown in the figure.

[0031] Figure 4 The voltage and current waveform diagram of the three-phase four-wire inverter when the power level S n = 6.6kw, k = 1 / 3 is shown in the figure. DETAILED DESCRIPTION

[0032] The specific embodiments and working principles of the application will be further described in detail below with reference to the accompanying drawings.

[0033] In this embodiment, the single-phase control method of the three-phase four-wire inverter is considered for bidirectional vehicle-mounted chargers working in V2V, V2L and V2H modes, and the vehicle-mounted charger (OBC) of the split capacitor three-phase four-wire inverter in the front stage not only can supply power to the load as a three-phase 380V power grid, but also can supply power to the load as a single-phase 220V power grid, while considering the current sharing problem.

[0034] The topology used in this embodiment is shown in Figure 1 The topology includes a three-phase full-bridge inverter, an AC side inductor L, and an AC side filter capacitor C. In this embodiment, L = 300 uH and C = 10 uF.

[0035] As shown in Figure 2 The single-phase control method of the three-phase four-wire inverter is as follows. The topology of the split capacitor three-phase four-wire inverter has A phase and B phase connected in parallel in an interleaved manner, and C phase and N phase connected in parallel in an interleaved manner to form a single-phase output. AC voltage loop control is used for A phase and B phase to regulate the AC voltage, and AC current loop control is used for C phase to regulate the C phase current. After obtaining the three-phase control signals, the control signals are input to a pulse width modulator to generate PWM switching signals for controlling the turn-on and turn-off of power devices in the inverter, thereby achieving single-phase control of the inverter.

[0036] In a specific implementation, the control process of the AC voltage loop is as follows:

[0037] Step 1: Collect the A phase and B phase voltages of the AC side filter capacitor C

[0038] Step 2: Calculate the effective value RMS of the A phase and B phase voltages of the AC side filter capacitor C to obtain the A phase and B phase voltage effective values of the AC side filter capacitor C According to the effective value reference value of the A phase and B phase target voltages

[0039] Perform proportional-integral control on the A phase and B phase voltage effective values of the AC side filter capacitor C to obtain the control output results. In this embodiment,

[0040] Multiply the control output results by the real-time reference values of the A phase and B phase target voltages to obtain the inner loop reference values of the A phase and B phase voltages According to the voltage inner loop reference values Perform proportional control on the voltages of the AC side filter capacitor C to obtain the inverter A phase and B phase control signals using equations (1) and (2)

[0041]

[0042]

[0043] where s is the Laplace operator, is the voltage outer loop PI controller,​​​​ is the adjustment coefficient of the voltage outer loop ratio P, is the I regulation coefficient of the voltage outer loop integration; is the voltage inner loop P controller, is the voltage inner loop ratio P adjustment coefficient. In this embodiment,

[0044] In specific implementation, the control process of the AC current loop is as follows:

[0045] Step 1: Collect the A-phase, B-phase, and C-phase inductor currents of the inverter-side inductor L

[0046] Step 2: Calculate the inductor current of phase A and phase B Add and invert, and multiply by the current distribution coefficient k, the result is the C phase inductor current Reference value In this embodiment, phase A and phase B are controlled by the same AC voltage loop, so the voltage and current of phase A and phase B are the same. In order to balance the current of phase C and phase N, k=1 / 2, so that the reference value of the inner loop of the AC current of phase C is half of the total current, and half of the total current (phase A current or phase B current) flows through phase C, and the remaining half of the current automatically flows through phase N.

[0047] According to the C phase inductor current Reference value For the C phase inductor current Proportional resonance control is performed, and the inverter C phase control signal is obtained using formula (3):

[0048]

[0049] Where s is the Laplace operator, is the current loop PR controller, is the adjustment coefficient of the current loop ratio P, is the adjustment coefficient of the current ring resonance R, ω g is the rated angular frequency of the grid voltage. In this embodiment,

[0050] In the specific implementation, the control parameters of the AC voltage loop PI controller, P controller and AC current loop PR controller are based on the system parameters of the inverter and the rated capacity S n In this embodiment, S n =6.6kw.

[0051] In order to verify the effectiveness of the control method of the present invention, a corresponding simulation model was built using the power electronics simulation software Plecs, and the simulation results were as follows:Figure 3 、 Figure 4 as shown.

[0052] Figure 3 For the control method of the application, the output voltage of the three-phase four-wire inverter at the power level S n = 6.6kw, the current distribution coefficient k = 1 / 2 C-phase current i A , N-phase current i N waveform diagram. As shown in Figure 3 : using the control method of the application, the output voltage is consistent with the target voltage , the C-phase current i C , the N-phase current i N can realize current sharing control, i C = i N ≈ 15A, which meets the national standard “GB / T 40432-2021 Electric Vehicle Conductive On-Board Charger”, so that the C-phase bridge arm can use power devices with lower current level and line cable, realizing higher power level.

[0053] In order to further verify the universality of the control method of the application, the case where the current distribution coefficient k = 1 / 3, i N = 3i C is considered.

[0054] Figure 4 For the control method of the application, the output voltage of the three-phase four-wire inverter at the power level S n = 6.6kw, the current distribution coefficient k = 1 / 3 C-phase current i A , N-phase current i N waveform diagram. As shown in Figure 4 : using the control method of the application, the output voltage is consistent with the target voltage , the N-phase current i N is three times the C-phase current i C .

[0055] In this embodiment, an electronic device includes a memory for storing a program supporting a processor to execute the above-mentioned single-phase control method, and a processor configured to execute the program stored in the memory.

[0056] In this embodiment, a computer readable storage medium has a computer program stored thereon, and the computer program is executed by a processor to perform the steps of the above-mentioned single-phase control method.

[0057] In summary, the control method can not only realize output voltage stability, but also can flexibly distribute C-phase and N-phase currents by setting the current distribution coefficient, thereby avoiding overcurrent, and thus can use power devices with lower current levels and line cables to realize higher power levels.

Claims

1. A single-phase control method of a three-phase four-wire inverter, characterized by: The topology of the split capacitor three-phase four-wire inverter is that the A phase and the B phase are connected in parallel alternately, and the C phase and the N phase are connected in parallel alternately to form a single-phase output. The AC voltage loop control is adopted for the A phase and the B phase to adjust the AC voltage. The AC current loop control is adopted for the C phase to adjust the C phase current. After the three-phase control signals are obtained, the three-phase control signals are input into a pulse width modulation (PWM) modulator to generate PWM switching signals for controlling the turn-on and turn-off of power devices in the inverter, so as to realize the single-phase control of the inverter. The control process of the AC voltage loop is as follows: Step 1: Collecting AC side filter capacitor A phase, B phase voltage , ; Step 2: RMS value calculation is performed on the voltage of the AC side filter capacitor C to obtain the RMS value of the A-phase and B-phase voltage of the AC side filter capacitor C , , , ;​​ According to the effective value reference value of the A-phase and B-phase target voltage , , the effective value of the A-phase and B-phase voltage of the AC side filter capacitor C , , , , proportional integral control is carried out to obtain the control output result; The control output results are multiplied with real-time reference values of the A-phase and B-phase target voltages respectively to obtain inner loop reference values of the A-phase and B-phase voltages , , The control output results are multiplied with real-time reference values of the A-phase and B-phase target voltages respectively to obtain inner loop reference values of the A-phase and B-phase voltages , , The control output results are multiplied with real-time reference values of the A-phase and B-phase target voltages respectively to obtain inner loop reference values of the A-phase and B-phase voltages , , The control output results are multiplied with real-time reference values of the A-phase and B-phase target voltages respectively to obtain inner loop reference values of the A-phase and B-phase voltages , , The control output results are multiplied with real-time reference values of the A-phase and B-phase target voltages respectively to obtain inner loop reference values of the A-phase and B-phase voltages , , The control output results are multiplied with real-time reference values of the A-phase and B-phase target voltages respectively to obtain inner loop reference values of the A-phase and B-phase voltages , , The control output results are multiplied with real-time reference values of the A-phase and B-phase target voltages respectively to obtain inner loop reference values of the A-phase and B-phase voltages , : (1) (2) In formula (1) and formula (2), is a Laplacian operator, is a voltage outer loop PI controller, is a voltage outer loop proportional P regulation coefficient, is a voltage outer loop integral I regulation coefficient; is a voltage inner loop P controller, is a voltage inner loop proportional P regulation coefficient; The control process of the AC current loop is as follows: Step 1: Collecting inverter side inductance A-phase, B-phase, C-phase inductance current 、 、 ; Step 2: add the A-phase and B-phase inductor currents , , multiply the result by the current distribution coefficient , and the result is taken as the reference value of the C-phase inductor current . ; According to the reference value of the C-phase inductor current The proportional-resonant control is performed on the C-phase inductor current , so that the inverter C-phase control signal is obtained by using formula (3) :​ (3) In formula (3), is the Laplace operator, is the current loop PR controller, is the current loop proportional P tuning coefficient, is the current loop resonant R tuning coefficient, is the grid voltage nominal angular frequency.

2. The single-phase control method of a three-phase four-wire inverter according to claim 1, characterized by, The control parameters of the AC voltage loop PI controller, P controller and AC current loop PR controller are determined according to the system parameters and rated capacity of the inverter are set.

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

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: The computer program, when executed by the processor, performs the steps of the single-phase control method according to any one of claims 1-2.

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