Control method of power conversion module and charging and discharging system

Abstract

The application provides a control method of a power conversion module and a charging and discharging system, and relates to the technical field of power electronics. The method comprises the following steps: obtaining a port voltage and a port current output by an output port of a target phase in a power conversion module; determining active voltage, active current, active power, reactive voltage, reactive current and reactive power corresponding to the target phase according to the port voltage and the port current; determining a reactive voltage adjustment value according to the reactive power corresponding to the target phase, and determining a given voltage corresponding to the target phase according to the reactive voltage adjustment value, the active current, the reactive current, the active voltage and the reactive voltage; obtaining an instantaneous given current corresponding to the target phase based on the given voltage corresponding to the target phase and a predetermined phase; and determining a switching control signal of the target phase according to a direct-current bus voltage of the power conversion module, the instantaneous given current corresponding to the target phase, the port voltage, the port current and an inductance current, so as to realize accurate management of single-phase active / reactive power.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and more specifically, to a control method and charging / discharging system for a power conversion module. Background Technology

[0002] With the accelerated construction of new power systems, a high proportion of distributed renewable energy sources, such as photovoltaics and wind power, are being integrated into the distribution network, placing higher demands on the active support capabilities of grid-connected converters. Among these technologies, Virtual Synchronous Generator (VSG) technology, due to its ability to simulate the inertial response, frequency / voltage support, and fault ride-through characteristics of synchronous machines, has become the core control paradigm for grid-forming (GFM) inverters and is widely used in microgrids, islanded systems, and weak grid scenarios.

[0003] Currently, the control architecture of VSG grid-type inverters generally adopts three-phase symmetrical sampling and control, which is based on the cascaded design of the overall power loop-virtual impedance-rotor motion equations in the symmetrical component method or abc coordinate system to achieve coordinated regulation of active and reactive power. This type of solution has advantages such as simple structure, mature parameter tuning, and coordinated dynamic response under ideal three-phase balanced operating conditions, and is suitable for the operation scenarios of three-phase symmetrical power grids.

[0004] However, the existing three-phase symmetrical VSG architecture cannot meet the needs of asymmetric operation scenarios. Summary of the Invention

[0005] The purpose of this application is to provide a control method and charging / discharging system for a power conversion module to address the shortcomings of the prior art and solve the technical problems existing in the prior art.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows: In a first aspect, embodiments of this application provide a control method for a power conversion module, which is applied to a power conversion module including: a three-phase output port and a switching unit; Obtain the port voltage and port current output from the output port of the target phase in the power conversion module, and determine the active voltage, active current, active power, reactive voltage, reactive current, and reactive power corresponding to the target based on the port voltage and port current. Based on the reactive power corresponding to the target, determine the reactive voltage adjustment value, and based on the reactive voltage adjustment value, the active current, the reactive current, the active voltage, and the reactive voltage, determine the given voltage corresponding to the target; Based on the given voltage corresponding to the target and the predetermined phase, the instantaneous given current corresponding to the target is obtained; Based on the DC bus voltage of the power conversion module, the instantaneous given current, port voltage, port current, and inductor current corresponding to the target, the switching control signal of the target phase is determined, and the switching control signal is used to control the switching unit of the switching unit of the target phase.

[0007] Optionally, determining the active voltage, active current, active power, reactive voltage, reactive current, and reactive power corresponding to the target based on the port voltage and the port current includes: The port voltage is decomposed into active and reactive power to obtain the active and reactive voltages corresponding to the target; and the current is decomposed into active and reactive power to obtain the active and reactive currents corresponding to the target. Based on the active voltage, active current, reactive voltage, and reactive current corresponding to the target, the active power and reactive power corresponding to the target are obtained.

[0008] Optionally, determining the given voltage corresponding to the target based on the reactive voltage adjustment value, the active current, the reactive current, the active voltage, and the reactive voltage includes: The reactive voltage adjustment value corresponding to the target is superimposed with the preset voltage reference value to obtain the actual reactive voltage value corresponding to the target; Based on the actual value of the reactive voltage corresponding to the target, the active current, the reactive current, the active voltage, and the reactive voltage, the given voltage corresponding to the target is obtained.

[0009] Optionally, obtaining the given voltage corresponding to the target based on the actual value of the reactive voltage corresponding to the target, the active current, the reactive current, the active voltage, and the reactive voltage includes: Based on the reactive current and virtual inductive reactance corresponding to the target, a first intermediate voltage value is obtained, and based on the active current and virtual resistance corresponding to the target, a second intermediate voltage value is obtained. Determine the first difference between the second intermediate voltage value and the first intermediate voltage value, and determine the second difference between the actual reactive voltage value corresponding to the target and the first difference. Based on the second difference, the reactive voltage and active voltage corresponding to the target, obtain the given reactive voltage corresponding to the target. The third intermediate voltage value is obtained based on the active current corresponding to the target and the virtual inductive reactance, and the fourth intermediate voltage value is obtained based on the reactive current corresponding to the target and the virtual resistance. The first summation result of the third intermediate voltage value and the fourth intermediate voltage value is determined, and the first summation result is filtered and limited to obtain the limiting result. Based on the limiting result, the reactive voltage and active voltage corresponding to the target, the given active voltage corresponding to the target is obtained.

[0010] Optionally, determining the reactive voltage regulation value based on the reactive power corresponding to the target includes: Based on the reactive power corresponding to the target and the preset reactive power reference value, the reactive power adjustment amount corresponding to the target is obtained; A second summation result is determined between the reactive power adjustment amount corresponding to the target and the reactive power reference value, and a third difference is determined between the second summation result and the reactive power corresponding to the target. Based on the third difference and a preset droop coefficient, the reactive voltage adjustment value corresponding to the target is obtained.

[0011] Optionally, the process of determining the phase corresponding to the target includes: Obtain all corresponding active power in the power conversion module, and determine the total active power of the power conversion module based on all corresponding active power; The basic phase of the power conversion module is determined based on the total active power, the preset total rated active power, and the preset rated frequency. The adjustment phase value corresponding to the target is determined based on the active power corresponding to the target, the rated active power corresponding to the target, the preset equivalent damping coefficient, and the equivalent filter constant. The phase corresponding to the target is obtained based on the adjustment phase value corresponding to the target and the base phase.

[0012] Optionally, using phase A as a reference phase, obtaining the phase corresponding to the target based on the adjusted phase value corresponding to the target and the base phase includes: If the target phase is phase A, then the adjustment phase value corresponding to phase A is superimposed on the base phase to obtain the phase corresponding to phase A; If the target phase is phase B, then based on the base phase and the preset phase, the base phase corresponding to B is determined, and the base phase corresponding to B is superimposed with the adjustment phase value corresponding to B to obtain the phase corresponding to B; If the target phase is phase C, then based on the base phase and the preset phase, the base phase corresponding to phase C is determined, and the base phase corresponding to phase C is superimposed with the adjustment phase value corresponding to phase C to obtain the phase corresponding to phase C.

[0013] Optionally, obtaining the instantaneous given current corresponding to the target based on the given voltage corresponding to the target and a predetermined phase includes: A matrix transformation is performed based on the phase corresponding to the target, the given active voltage corresponding to the target, and the given reactive voltage to obtain the instantaneous given current corresponding to the target.

[0014] Optionally, determining the switching control signal of the target phase based on the DC bus voltage of the power conversion module, the instantaneous given current, port voltage, port current, and inductor current corresponding to the target phase includes: The product of the port current of the target phase and a preset coefficient is determined, and based on the product, the instantaneous given current corresponding to the target, the inductor current corresponding to the target, the port voltage corresponding to the target, and the DC bus voltage, the corresponding switch control signal is obtained.

[0015] Secondly, embodiments of this application also provide a charging and discharging system, the system comprising: at least one power conversion module, the power conversion module comprising: a controller; The input terminal of the controller is connected to the DC bus port and the output port of the power conversion module, respectively, and the output terminal of the controller is connected to the control terminal of the switching unit of each phase in the power conversion module. The controller is used to execute the control method of the power conversion module described above.

[0016] The beneficial effects of this application are: This application provides a control method and charging / discharging system for a power conversion module. In this application, a VSG network control architecture is used, with single-phase as the basic control unit and three-phase coordination as the constraint. Specifically, the port voltage and port current of the target phase's output port are obtained. Based on the port voltage and port current, the corresponding active voltage, active current, active power, reactive voltage, reactive current, and reactive power are obtained, realizing online decoupling calculation of active / reactive components under unbalanced power grids. Based on the target's corresponding reactive power, the reactive voltage adjustment value is determined. Based on the reactive voltage adjustment value, active current, reactive current, active voltage, and reactive voltage, the target's corresponding setpoint voltage is determined. Based on the target's corresponding setpoint voltage and a predetermined phase, the target's corresponding instantaneous voltage is obtained. The system uses a given current to determine the reactive voltage regulation by introducing the instantaneous reactive power of the target phase. This avoids the phase error and delay caused by the traditional reactive power compensation relying on grid voltage phase estimation, and achieves active, precise, and rapid closed-loop control of reactive power. Finally, based on the DC bus voltage of the power conversion module, the instantaneous given current, port voltage, port current, and inductor current corresponding to the target, a switching control signal for the target phase is generated to control the switching unit corresponding to the target to turn on and off, achieving independent regulation of a single phase. This enables precise management of single-phase active / reactive power under grid connection, while maintaining adjustable three-phase voltage amplitude and approximately symmetrical phase under off-grid conditions. It also supports seamless switching between grid-connected and grid-connected modes, meeting the needs of asymmetrical operation scenarios faced by three-phase four-wire energy storage grids.

[0017] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The main power circuit diagram for a three-phase four-wire topology grid-connected inverter; Figure 2 This is a schematic diagram of a charging and discharging system provided in an embodiment of this application; Figure 3 A flowchart illustrating a control method for a power conversion module provided in an embodiment of this application; Figure 4 A flowchart illustrating another control method for a power conversion module provided in an embodiment of this application; Figure 5 A schematic diagram illustrating the decomposition of single-phase voltage and current dq and the calculation of active and reactive power provided in the embodiments of this application; Figure 6 A flowchart illustrating another control method for a power conversion module provided in an embodiment of this application; Figure 7 A flowchart illustrating another control method for a power conversion module provided in an embodiment of this application; Figure 8 A schematic diagram of a single-phase dq voltage loop and reactive-voltage control loop provided in the embodiments of this application. Figure 1 ; Figure 9 A flowchart illustrating another control method for a power conversion module provided in an embodiment of this application; Figure 10 A schematic diagram of a single-phase dq voltage loop and reactive-voltage control loop provided in the embodiments of this application. Figure 2 ; Figure 11 A flowchart illustrating another control method for a power conversion module provided in an embodiment of this application; Figure 12 The loop structure based on total active frequency (VSG) control provided in the embodiments of this application; Figure 13 The loop structure for A-phase droop adjustment provided in this application embodiment; Figure 14 A flowchart illustrating another control method for a power conversion module provided in an embodiment of this application; Figure 15 The loop structure for B-phase droop adjustment provided in this application embodiment; Figure 16 The loop structure for C-phase droop adjustment provided in the embodiments of this application; Figure 17 A schematic diagram of a single-phase dq voltage loop and reactive-voltage control loop provided in the embodiments of this application. Figure 3 ; Figure 18 A schematic diagram of a single-phase instantaneous current loop provided for embodiments of this application. Figure 4 . Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] First, the background technology involved in this application will be introduced.

[0024] Currently, the control architecture of VSG grid-connected inverters generally adopts three-phase symmetrical sampling and control, which is based on the cascaded design of the overall power loop-virtual impedance-rotor motion equations in the symmetrical component method or abc coordinate system to achieve coordinated regulation of active and reactive power. Under ideal three-phase balanced operating conditions (i.e., symmetrical three-phase currents when connected to the grid and symmetrical three-phase voltage and current when disconnected from the grid), this type of scheme has advantages such as simple structure, mature parameter tuning, and coordinated dynamic response, and is suitable for the operation of three-phase symmetrical power grids.

[0025] However, the existing three-phase symmetrical VSG architecture cannot meet the needs of asymmetrical operation scenarios with unbalanced three-phase impedance or unbalanced load.

[0026] Therefore, to address the above problems, this application proposes a control method for a power conversion module, which uses a VSG grid control architecture with single-phase as the basic control unit and three-phase coordination as the constraint condition. This architecture can achieve precise management of single-phase active / reactive power or unified regulation of three phases under grid connection, and can also maintain independent adjustable amplitude of three phases and arbitrary and unrestricted magnitude and direction of load current under off-grid conditions. At the same time, it supports seamless switching between grid connection and grid connection modes.

[0027] Optionally, refer to Figure 1 The diagram shown is the main power circuit diagram of a three-phase four-wire topology grid inverter. Figure 1 As shown, the power conversion module 1 provided in this embodiment can convert the DC voltage Vdc output from the energy storage battery into three-phase AC voltages Va, Vb, and Vc, with R1, R2, and R3 serving as external loads. When the power conversion module 1 operates in grid-connected mode, R1, R2, and R3 are powered by Va, Vb, and Vc output from the power conversion module 1, while the power conversion module 1 simultaneously charges or discharges the entire power grid.

[0028] It is worth noting that, see Figure 1The power conversion module 1 consists of capacitors Cdc1~Cdc2, N-type metal oxide semiconductor transistors Q1~Q6, inductors L1~L3, and an electromagnetic compatibility module (EMC). The gates of the N-type metal oxide semiconductor transistors Q1~Q6 are connected to the controller in the power conversion module 1, and N is the neutral line.

[0029] When the power conversion module 1 is operating in off-grid mode, only the port voltages Va, Vb, and Vc output by the power conversion module 1 supply power to the loads R1, R2, and R3. At this time, the phase switching units S1, S2, and S3 are all open, and the external public power grid does not need to provide grid voltage. When the controller in the power conversion module 1 receives the off-grid to grid-connected command from the host computer, the port voltages Va, Vb, and Vc output by the power conversion module 1 are clamped by the grid voltages Ua, Ub, and Uc provided by the external public power grid, so that when entering the grid-connected operation mode, the power conversion module 1 operates in constant current or constant power mode and provides stable operating power to the loads R1, R2, and R3. At this time, the phase switching units S1, S2, and S3 are all closed.

[0030] When switching is required, such as from off-grid to grid-connected, to ensure a seamless switch, the off-grid circuit generally needs to be adjusted to be completely consistent with the grid waveform (amplitude, frequency, and phase). If the three phases are different, each phase is adjusted independently. When they are completely consistent, synchronization is considered complete, and the three-phase switching unit can be closed, resulting in a smaller inrush current. Then, the power conversion module 1 starts the grid-connected mode.

[0031] In order to take full advantage of the more flexible and reliable single-phase topology with N-line, the original three-phase symmetrical detection and loop VSG architecture based on three-phase current balance or three-phase voltage balance is no longer applicable. Although the symmetrical loop control has added features such as three-phase voltage imbalance negative sequence detection control, it is only a patchwork and cannot achieve the goal of free adjustment of single phase.

[0032] Therefore, this application proposes a single-phase VSG network system that is compatible with off-grid three-phase phase symmetrical mode. When connected to the grid, the single-phase active and reactive power can be independently adjusted, and when off-grid, the three-phase load current can be arbitrarily adjusted.

[0033] Optionally, refer to Figure 2 The diagram shown is a structural schematic of a charging and discharging system provided in this application. The system includes at least one power conversion module 1, and the power conversion module includes a controller 2. The input terminal of controller 2 is connected to the DC bus port and the output port of the power conversion module, respectively, and the output terminal of controller is connected to the control terminal of the switching unit of each phase in the power conversion module. The controller is used to execute the control method of the power conversion module provided in the following embodiments to meet the requirement of independent adjustment of single-phase voltage in a three-phase four-wire energy storage grid system.

[0034] The following embodiments will be used to explain in detail the specific implementation process and beneficial effects of the control method for the power conversion module proposed in this application.

[0035] Optionally, refer to Figure 3 The diagram shown is a flowchart illustrating a control method for a power conversion module provided in this application, applied to the above-mentioned... Figure 2 The power conversion module shown includes: a three-phase output port and a switching unit; as shown Figure 3 As shown, the method includes: S101. Obtain the port voltage and port current output from the output port of the target phase in the power conversion module, and determine the corresponding active voltage, active current, active power, reactive voltage, reactive current and reactive power based on the port voltage and port current.

[0036] For example, the target phase is phase A. The port voltage Va and port current Ia of phase A are obtained, and active and reactive power decomposition is performed on the port voltage Va and port current Ia respectively to obtain the reactive voltage Vd_a, active voltage Vq_a, reactive current Id_a, and active current Iq_a corresponding to A. Based on the reactive voltage Vd_a, active voltage Vq_a, reactive current Id_a, and active current Iq_a, the active power Pa and reactive power Qa corresponding to A are calculated, realizing the online decoupling calculation of active / reactive components under unbalanced power grid.

[0037] S102. Determine the reactive voltage adjustment value based on the reactive power corresponding to the target, and determine the given voltage corresponding to the target based on the reactive voltage adjustment value, active current, reactive current, active voltage, and reactive voltage.

[0038] The given voltages include: given reactive voltage Vq_ref and given active voltage Vd_ref.

[0039] In one feasible approach, the reactive voltage regulation value can be determined based on the reactive power corresponding to phase A. Based on the reactive voltage regulation value, active current, reactive current, active voltage, and reactive voltage, the given voltage corresponding to phase A can be determined. That is, the instantaneous reactive power of the target phase is introduced to back-calculate the reactive voltage regulation amount. This avoids the phase error and delay caused by the traditional reactive power compensation relying on grid voltage phase estimation, and realizes active, accurate, and fast closed-loop control of reactive power.

[0040] S103. Based on the given voltage corresponding to the target and the predetermined phase, obtain the instantaneous given current corresponding to the target.

[0041] The phase corresponding to the target can be obtained using traditional methods. Specifically, the total active power is calculated based on the corresponding active power, and the basic phase θa0 is obtained based on the total active power and the given active power, P_ref. Taking phase A as a reference, the phase corresponding to A is the basic phase. Then, the phases corresponding to phases B and C are obtained by adding or subtracting 120 degrees (2π / 3) from the basic phase. The addition or subtraction is based on the positive or negative sequence (positive sequence: subtract 120 degrees from phase B, add 120 degrees to phase C, and vice versa for negative sequence). The positive or negative sequence determination will not be explained further.

[0042] In one feasible approach, the given voltage corresponding to A and the predetermined phase θa can be input into the inverse rotational transform, i.e., the dq / abc transform, to generate the instantaneous given current corresponding to A. Therefore, in this embodiment, by adding a voltage loop and reactive power regulation before the original instantaneous current loop, active, precise, and rapid closed-loop control of reactive power is achieved.

[0043] S104. Determine the switching control signal of the target phase based on the DC bus voltage of the power conversion module, the instantaneous given current, port voltage, port current and inductor current corresponding to the target.

[0044] Among them, the switch control signal is used to control the switch unit of the target phase.

[0045] In one feasible approach, a PWM signal (i.e., a switching control signal) for the upper and lower switching units Q1 / Q2 connected to inductor L1 corresponding to phase A can be generated based on the DC bus voltage, the instantaneous given current corresponding to the target, the port voltage, the port current, and the inductor current. This switching control signal for phase A is then input to the control terminals of Q1 / Q2 to control the on / off state of the switching units Q1 / Q2, achieving independent regulation of phase A. Therefore, in this embodiment, multiple source state variables such as DC bus voltage, port voltage, port current, and inductor current are uniformly incorporated into the switching signal generation model, improving the robustness of the power conversion module operation.

[0046] Therefore, in this application, the control logic of each phase is decoupled from each other and the parameters are independently settable. Without relying on the three-phase coupling model or global coordinate transformation, the requirements of the asymmetric operation scenario faced by the three-phase four-wire energy storage network can be met. In the grid-connected operation state, each phase independently performs closed-loop regulation of reactive power Q to manage the three-phase imbalance. In the off-grid operation state, the three-phase voltage can be independently adjusted, which has a power balancing effect on the three-phase impedance asymmetry.

[0047] In summary, this application provides a control method for a power conversion module. This application uses a VSG network control architecture with single-phase as the basic control unit and three-phase coordination as the constraint. Specifically, it acquires the port voltage and port current output from the target phase's output port, and based on the port voltage and port current, obtains the corresponding active voltage, active current, active power, reactive voltage, reactive current, and reactive power, achieving online decoupling calculation of active / reactive components under unbalanced power grid conditions. Based on the reactive power corresponding to the target, it determines the reactive voltage adjustment value, and based on the reactive voltage adjustment value, active current, reactive current, active voltage, and reactive voltage, it determines the corresponding setpoint voltage for the target. Based on the corresponding setpoint voltage and pre-setpoint voltage... First, the phase is determined, and the instantaneous given current corresponding to the target is obtained. That is, by introducing the instantaneous reactive power of the target phase, the reactive voltage regulation amount is determined, realizing active, precise, and rapid closed-loop control of reactive power. Finally, based on the DC bus voltage of the power conversion module, the instantaneous given current corresponding to the target, the port voltage, the port current, and the inductor current, the switching control signal of the target phase is generated to control the switching unit corresponding to the target to turn on and off, realizing independent regulation of a single phase. In this way, it is possible to achieve precise management of single-phase active / reactive power under grid connection, and to maintain adjustable three-phase voltage amplitude and approximately symmetrical phase under off-grid conditions. At the same time, it supports seamless switching between grid-connected and grid-connected modes, meeting the needs of asymmetrical operation scenarios faced by three-phase four-wire energy storage grids.

[0048] Optionally, refer to Figure 4 As shown, in step S101 above, determining the corresponding active voltage, active current, active power, reactive voltage, reactive current, and reactive power of the target based on the port voltage and port current includes: S201. Perform active and reactive decomposition on the port voltage to obtain the active and reactive voltages corresponding to the target; and perform active and reactive decomposition on the current to obtain the active and reactive currents corresponding to the target.

[0049] In one feasible approach, refer to Figure 5 As shown, a generalized integrator (SOGI) phase-locked loop and dq transform structure can be used to decompose the active and reactive power of the phase A port voltage Va, obtaining the corresponding reactive voltage Vd_a and active voltage Vq_a. Specifically, the phase A port voltage Va is input to the SOGI phase-locked loop to obtain the grid frequency ω_pll and the phase θga of phase A; the AC side frequency ω, the phase A port voltage Va, and the phase θa are then input to the single-phase active and reactive power decomposition module to decompose the phase A port voltage Va into active and reactive power, obtaining the reactive voltage Vd_a and active voltage Vq_a. This achieves decoupling of the active and reactive components, providing a theoretical basis for subsequent single-phase independent regulation and imbalance management.

[0050] Among them, the active voltage Vq_a represents the active component that is in phase with the voltage, and Vd represents the orthogonal reactive component.

[0051] Similarly, a generalized integrator (SOGI) phase-locked loop and dq transform structure can be used to decompose the active and reactive currents of phase A's port current Ia into active and reactive currents Iq_a and Id_a corresponding to phase A.

[0052] S202. Based on the active voltage, active current, reactive voltage, and reactive current corresponding to the target, obtain the active power and reactive power corresponding to the target.

[0053] Optionally, continue to refer to Figure 5 As shown, the reactive voltage Vd_a, active voltage Vq_a, reactive current Id_a, and active current Iq_a corresponding to A can also be input into the power calculation module to obtain the active power Pa and reactive power Qa corresponding to A. Where P = 0.5(Vq*Iq + Vd*Id), Q = 0.5(Vq*Id - Vd*Iq).

[0054] Optionally, refer to Figure 6 As shown, in step S102 above, determining the given voltage corresponding to the target based on the reactive voltage adjustment value, the active current, the reactive current, the active voltage, and the reactive voltage includes: S301. The reactive voltage adjustment value corresponding to the target is superimposed with the preset voltage reference value to obtain the actual reactive voltage value corresponding to the target.

[0055] S302. Based on the actual value of reactive voltage, active current, reactive current, active voltage and reactive voltage corresponding to the target, obtain the given voltage corresponding to the target.

[0056] In one feasible approach, the reactive voltage adjustment value corresponding to A is superimposed with a preset voltage reference value Va_ref to obtain the actual reactive voltage value corresponding to A. Based on the actual reactive voltage value corresponding to A, reactive current Id_a, active current Iq_a, reactive voltage Vd_a, and active voltage Vq_a, the given voltage corresponding to A output by the dq voltage loop is obtained. The given voltage includes the reactive given voltage Vda_ref and the active given voltage Vqa_ref.

[0057] Therefore, in this embodiment, the reactive voltage regulation value is treated as an independent controllable variable and directly injected into the dq voltage loop to achieve regulation of the given voltage value.

[0058] Optionally, refer to Figure 7 As shown, step S302 above includes: S401. Based on the reactive current and virtual inductive reactance corresponding to the target, obtain the first intermediate voltage value, and based on the active current and virtual resistance corresponding to the target, obtain the second intermediate voltage value.

[0059] S402. Determine the first difference between the second intermediate voltage value and the first intermediate voltage value, and determine the second difference between the actual value of the reactive voltage corresponding to the target and the first difference. Based on the second difference, the reactive voltage and active voltage corresponding to the target, obtain the given reactive voltage corresponding to the target.

[0060] Optionally, refer to Figure 8 As shown, to improve the accuracy of the given voltage corresponding to the target, capacitive impedance decoupling and superposition are introduced. Specifically, the product of the reactive current Id_a corresponding to A and the virtual inductive reactance ωLa can be used as the first intermediate voltage value, and the active current Iq_a corresponding to A and the virtual resistance R can be used as the second intermediate voltage value. The difference between the second intermediate voltage value and the first intermediate voltage value is used to obtain the first difference value. The difference between the actual value of the reactive voltage corresponding to A and the first difference value is used to obtain the second difference value. Then, the second difference value is subjected to low-pass filtering and limiting processing to obtain the limiting result of the second difference value. The limiting result of the second difference value, the active voltage Vq_a corresponding to A, and the reactive voltage Vd_a are input to the q-axis voltage loop to obtain the given reactive voltage Vda_ref corresponding to A.

[0061] S403. Based on the active current and virtual inductive reactance corresponding to the target, obtain the third intermediate voltage value, and based on the reactive current and virtual resistance corresponding to the target, obtain the fourth intermediate voltage value.

[0062] S404. Determine the first summation result of the third intermediate voltage value and the fourth intermediate voltage value, and perform filtering and limiting processing on the first summation result to obtain the limiting result. Based on the limiting result, the reactive voltage and active voltage corresponding to the target, obtain the given active voltage corresponding to the target.

[0063] Optionally, continue to refer to Figure 8 As shown, the product between the reactive current Id_a corresponding to A and the virtual inductive reactance ωLa can be used as the third intermediate voltage value. Based on the reactive current Id_a corresponding to A and the virtual resistance R, the fourth intermediate voltage value can be obtained. Then, the third intermediate voltage value and the fourth intermediate voltage value are superimposed to obtain the first summation result. The first summation result is subjected to low-pass filtering and limiting processing to obtain the limiting result. The limiting result is then input to the d-axis voltage loop to obtain the given active voltage Vqa_ref corresponding to A.

[0064] The reverse multiplication of the q-axis voltage loop output by -1 is obtained according to the relevant reference direction definition and is no longer constrained. The q-axis voltage loop output is the given active voltage, and the d-axis voltage loop output is the given reactive voltage. Cross-control is based on the inductive impedance characteristics and is not mandatory.

[0065] Optionally, refer to Figure 9 As shown, in step S102 above, determining the reactive voltage adjustment value based on the reactive power corresponding to the target includes: S501. Based on the reactive power corresponding to the target and the preset reactive power reference value, obtain the reactive power adjustment amount corresponding to the target.

[0066] Optionally, refer to Figure 10 As shown, a constant reactive power PI control loop is added externally, that is, a static error compensation, i.e., reactive power regulation, is superimposed on the original droop QV loop. The compensation range of the reactive power regulation is limited by amplitude limiting to avoid over-limit runaway. Specifically, the reactive power Qa corresponding to A is subtracted from the preset reactive power reference value Qa_ref, and the difference result is subjected to PI control and amplitude limiting to obtain the reactive power regulation ΔQa_ref.

[0067] It should be noted that when using the existing VSG control, the reactive power regulation ΔQa_ref is forced to 0. If constant reactive power control is required under grid connection, this loop can perform static error superposition compensation, which is flexible in switching but has a limited compensation range. Even when switching from grid connection to islanded mode, the loop PI saturation output is fixed, and the output voltage waveform is still a sinusoidal controllable waveform with good reliability. Compared with the QV direct PI control, it is more flexible and adaptable to energy.

[0068] S502. Determine the second summation result between the reactive power adjustment amount corresponding to the target and the reactive power reference value, and determine the third difference between the second summation result and the reactive power corresponding to the target. Based on the third difference and the preset droop coefficient, obtain the reactive voltage adjustment value corresponding to the target.

[0069] In one feasible way, continue to refer to Figure 10 As shown, the reactive power regulation value ΔQa_ref corresponding to A and the reactive power reference value Qa_ref are input into the reactive power-voltage (QV) droop loop to calculate the second summation result, i.e., ΔQa_ref + Qa_ref. At the same time, the second summation result is subtracted from the reactive power Qa corresponding to A to obtain the third difference value, i.e., ΔQa_ref + Qa_ref - Qa. Then, the third difference value is multiplied by the droop coefficient Kv to obtain the reactive voltage regulation value corresponding to A, thus realizing the autonomous adjustment of the output voltage amplitude.

[0070] Optionally, refer to Figure 11 As shown, the process of determining the phase corresponding to the target includes: S601. Obtain all corresponding active power in the power conversion module, and determine the total active power of the power conversion module based on all corresponding active power.

[0071] S602. Determine the basic phase of the power conversion module based on the total active power.

[0072] It is important to note that the total active power reference value must be equal to the sum of the phase active power reference values, i.e., P_ref = Pa_ref + Pb_ref ​​+ Pc_ref, to avoid target conflicts.

[0073] Optionally, refer to Figure 12 As shown, in order to obtain the phase of each phase separately, it is proposed that the total active power of the power conversion module can be calculated based on all the corresponding active power in the power conversion module, namely, the active power Pa corresponding to A, the active power Pb corresponding to B, and the active power Pc corresponding to C, i.e., Pa+Pb+Pc. Then, the total active power Pa+Pb+Pc, the preset total rated active power P_ref, and the preset rated frequency ω0 are input to the active-frequency (Pf) droop adjustment loop to obtain the basic phase θa0 of the power conversion module output by the active-frequency (Pf) droop adjustment loop.

[0074] S603. Determine the corresponding adjustment phase value based on the target's corresponding active power and rated active power.

[0075] In another possible approach, refer to Figure 13 As shown, taking phase A as an example, we can utilize... Figure 13 The constant active power control loop and the active-frequency (Pf) droop adjustment loop corresponding to A are shown. The active power Pa and the rated active power Pa_ref corresponding to A are processed to obtain the adjustment phase value Δθa corresponding to A.

[0076] S604. Based on the adjustment phase value corresponding to the target and the basic phase, obtain the phase corresponding to the target.

[0077] Optionally, taking phase A as the reference phase, the adjustment phase value corresponding to phase A can be directly superimposed with the basic phase to obtain the phase θa corresponding to phase A, i.e., θa = Δθa + θa0.

[0078] Therefore, based on the unified regulation of the three-phase total active power, the active power is differentiated by the independent regulation of each phase, so as to achieve the goal of phase-by-phase active power management under grid connection.

[0079] Optionally, refer to Figure 14As shown, with phase A as the reference phase, step S604 above includes: S701. If the target phase is phase A, then the adjustment phase value corresponding to A is superimposed with the basic phase to obtain the phase corresponding to A.

[0080] The calculation process of the phase corresponding to A has been described in detail in the above embodiments, and will not be repeated here.

[0081] S702. If the target phase is phase B, then based on the basic phase and the preset phase, determine the basic phase corresponding to B, and superimpose the basic phase corresponding to B with the adjustment phase value corresponding to B to obtain the phase corresponding to B.

[0082] Optionally, refer to Figure 15 As shown, taking phase A as a reference and the positive sequence as an example, the explanation is as follows. Specifically, after subtracting 120 degrees (2π / 3) from the basic phase, the basic phase of phase B is obtained, namely θa0-2π / 3. Then, the phase difference is superimposed with the corresponding adjustment phase value of B to obtain the phase corresponding to B, namely θb=Δθb+(θa0-2π / 3).

[0083] Optionally, addition or subtraction can be performed based on the positive or negative order (subtract 120 degrees from B for positive order, add 120 degrees to C for negative order, and vice versa). The positive or negative order determination will not be explained further.

[0084] S703. If the target phase is phase C, then based on the basic phase and the preset phase, determine the basic phase corresponding to C, and superimpose the basic phase corresponding to C with the adjustment phase value corresponding to C to obtain the phase corresponding to C.

[0085] Optionally, refer to Figure 16 As shown, we will continue to explain using the positive sequence as an example. Specifically, after adding 120 degrees (2π / 3) to the basic phase, we obtain the basic phase of phase C, i.e., θa0 + 2π / 3. Then, we superimpose the basic phase of phase C with the corresponding adjustment phase value of C to obtain the phase corresponding to C, i.e., θc = Δθc + (θa0 + 2π / 3).

[0086] Optionally, step S103 above includes: The instantaneous given current corresponding to the target is obtained by performing matrix transformation based on the phase corresponding to the target, the given active voltage corresponding to the target, and the given reactive voltage.

[0087] In one feasible approach, refer to Figure 17 As shown, the phase θa corresponding to A, the given reactive voltage Vda_ref corresponding to A, and the given active voltage Vqa_ref are input to the dq / abc conversion module. The dq / abc conversion module performs matrix transformation to generate the instantaneous given current corresponding to the target.

[0088] Optionally, step S104 above includes: The product of the target phase port current and the preset coefficient is determined, and based on the product, the target corresponding instantaneous given current, the target corresponding inductor current, the target corresponding port voltage, and the DC bus voltage, the target corresponding switch control signal is obtained.

[0089] In one feasible approach, considering the slightly slower response of single-phase dq decomposition, instantaneous current inner-loop control is still used for single-phase control based on speed considerations. To improve the voltage loop response speed, a port current (also known as load current) feedforward Ia multiplied by a coefficient k is introduced. Considering grid-connected or off-grid online integration, a proportional feedforward of the instantaneous grid voltage is introduced (this can be added before dq transformation or a fixed voltage feedforward). The proportional coefficient is less than 1, and 0.5Udc represents the DC half-bus. Simultaneously, the AC component of the actual half-bus is sampled and decomposed and introduced into the feedforward. Therefore, refer to... Figure 18 As shown, the DC bus voltage Udc, the instantaneous given current Ila_ref corresponding to A, the port voltage Va, the port current Ia, and the inductor current ILa can be input into the instantaneous inner loop of the inductor current. The output results are then passed through a limiting module and a pulse width modulation (PWM) circuit to generate PWM signals for the upper and lower switching units Q1 / Q2 connected to the inductor L1 corresponding to A, i.e., switching control signals. Based on the switching control signals, the switching units Q1 / Q2 are controlled to turn on and off, thereby achieving independent adjustment of phase A.

[0090] It should be noted that off-grid systems generally incorporate load current feedforward to improve dynamics, while grid-connected systems incorporate grid feedforward or fixed feedforward to facilitate startup stability or suppress grid fluctuations. Load current feedforward and voltage feedforward can also be introduced simultaneously, as long as the feedforward coefficient k does not cause stability issues.

[0091] Therefore, this application proposes a control method for a power conversion module in a three-phase four-wire topology. Based on the port voltage and port current of a single phase, the corresponding active power and reactive power are obtained. Then, through a phase-by-phase reactive-voltage droop loop, the reactive-voltage amplitude of each phase responds independently, and through a phase-by-phase active-frequency droop loop, the active-frequency response of each phase is mapped independently. This enables the three phases to autonomously adjust their phase angles and given voltage amplitudes in the network configuration mode, significantly suppressing interphase active circulating currents and voltage distortions caused by line parameter asymmetry, load imbalance, or neutral line impedance.

[0092] It is worth noting that the control architecture proposed in this application has strong topology adaptability, is compatible with both two-level / three-level inverter structures, and supports flexible configuration of N-line connection mode to achieve phase power decoupling. Thus, without increasing hardware costs, it can fully adapt to typical three-phase four-wire application scenarios such as rural distribution networks, microgrid terminals, and marine DC networks.

[0093] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0094] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A control method for a power conversion module, characterized in that, The power conversion module is used in a power conversion module, which includes a three-phase output port and a switching unit. Obtain the port voltage and port current output from the output port of the target phase in the power conversion module, and determine the active voltage, active current, active power, reactive voltage, reactive current, and reactive power corresponding to the target based on the port voltage and port current. Based on the reactive power corresponding to the target, determine the reactive voltage adjustment value, and based on the reactive voltage adjustment value, the active current, the reactive current, the active voltage, and the reactive voltage, determine the given voltage corresponding to the target; Based on the given voltage corresponding to the target and the predetermined phase, the instantaneous given current corresponding to the target is obtained; Based on the DC bus voltage of the power conversion module, the instantaneous given current, port voltage, port current, and inductor current corresponding to the target, the switching control signal of the target phase is determined, and the switching control signal is used to control the switching unit of the switching unit of the target phase.

2. The method according to claim 1, characterized in that, The step of determining the active voltage, active current, active power, reactive voltage, reactive current, and reactive power corresponding to the target based on the port voltage and the port current includes: The port voltage is decomposed into active and reactive power to obtain the active and reactive voltages corresponding to the target; and the current is decomposed into active and reactive power to obtain the active and reactive currents corresponding to the target. Based on the active voltage, active current, reactive voltage, and reactive current corresponding to the target, the active power and reactive power corresponding to the target are obtained.

3. The method according to claim 2, characterized in that, The step of determining the given voltage corresponding to the target based on the reactive voltage adjustment value, the active current, the reactive current, the active voltage, and the reactive voltage includes: The reactive voltage adjustment value corresponding to the target is superimposed with the preset voltage reference value to obtain the actual reactive voltage value corresponding to the target; Based on the actual value of the reactive voltage corresponding to the target, the active current, the reactive current, the active voltage, and the reactive voltage, the given voltage corresponding to the target is obtained.

4. The method according to claim 3, characterized in that, The step of obtaining the given voltage corresponding to the target based on the actual value of the reactive voltage corresponding to the target, the active current, the reactive current, the active voltage, and the reactive voltage includes: Based on the reactive current and virtual inductive reactance corresponding to the target, a first intermediate voltage value is obtained, and based on the active current and virtual resistance corresponding to the target, a second intermediate voltage value is obtained. Determine the first difference between the second intermediate voltage value and the first intermediate voltage value, and determine the second difference between the actual reactive voltage value corresponding to the target and the first difference. Based on the second difference, the reactive voltage and active voltage corresponding to the target, obtain the given reactive voltage corresponding to the target. Based on the active current corresponding to the target and the virtual inductive reactance, a third intermediate voltage value is obtained, and based on the reactive current corresponding to the target and the virtual resistance, a fourth intermediate voltage value is obtained. The first summation result of the third intermediate voltage value and the fourth intermediate voltage value is determined, and the first summation result is filtered and limited to obtain the limiting result. Based on the limiting result, the reactive voltage and active voltage corresponding to the target, the given active voltage corresponding to the target is obtained.

5. The method according to claim 1, characterized in that, The step of determining the reactive voltage adjustment value based on the reactive power corresponding to the target includes: Based on the reactive power corresponding to the target and the preset reactive power reference value, the reactive power adjustment amount corresponding to the target is obtained; A second summation result is determined between the reactive power adjustment amount corresponding to the target and the reactive power reference value, and a third difference is determined between the second summation result and the reactive power corresponding to the target. Based on the third difference and a preset droop coefficient, the reactive voltage adjustment value corresponding to the target is obtained.

6. The method according to claim 1, characterized in that, The process of determining the phase corresponding to the target includes: Obtain all corresponding active power in the power conversion module, and determine the total active power of the power conversion module based on all corresponding active power; The basic phase of the power conversion module is determined based on the total active power. The adjustment phase value corresponding to the target is determined based on the active power corresponding to the target, the rated active power corresponding to the target, the preset equivalent damping coefficient, and the equivalent filter constant. The phase corresponding to the target is obtained based on the adjustment phase value corresponding to the target and the base phase.

7. The method according to claim 6, characterized in that, Using phase A as a reference phase, the step of obtaining the phase corresponding to the target based on the adjusted phase value corresponding to the target and the base phase includes: If the target phase is phase A, then the adjustment phase value corresponding to phase A is superimposed on the base phase to obtain the phase corresponding to phase A; If the target phase is phase B, then based on the base phase and the preset phase, the base phase corresponding to B is determined, and the base phase corresponding to B is superimposed with the adjustment phase value corresponding to B to obtain the phase corresponding to B; If the target phase is phase C, then based on the base phase and the preset phase, the base phase corresponding to phase C is determined, and the base phase corresponding to phase C is superimposed with the adjustment phase value corresponding to phase C to obtain the phase corresponding to phase C.

8. The method according to claim 1, characterized in that, The step of obtaining the instantaneous given current corresponding to the target based on the given voltage and a predetermined phase includes: A matrix transformation is performed based on the phase corresponding to the target, the given active voltage corresponding to the target, and the given reactive voltage to obtain the instantaneous given current corresponding to the target.

9. The method according to claim 1, characterized in that, The step of determining the switching control signal of the target phase based on the DC bus voltage of the power conversion module, the instantaneous given current, port voltage, port current, and inductor current corresponding to the target phase includes: The product of the port current of the target phase and a preset coefficient is determined, and based on the product, the instantaneous given current corresponding to the target, the inductor current corresponding to the target, the port voltage corresponding to the target, and the DC bus voltage, the corresponding switch control signal is obtained.

10. A charging and discharging system, characterized in that, The system includes: at least one power conversion module, the power conversion module including: a controller; The input terminal of the controller is connected to the DC bus port and the output port of the power conversion module, respectively, and the output terminal of the controller is connected to the control terminal of the switching unit of each phase in the power conversion module. The controller is used to execute the control method of the power conversion module according to any one of claims 1-9.

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