Split-phase networking control method for three-phase four-leg energy storage PCS

Abstract

The invention belongs to the technical field of converters / inverters, and particularly relates to a split-phase networking control method of a three-phase four-leg energy storage PCS. The method comprises the following steps: collecting grid-side three-phase voltage and current of a three-phase four-leg energy storage PCS, positive and negative DC bus voltage of an energy storage side and a battery SOC; calculating split-phase / shaft voltage and current components according to the three-phase voltage and current, and then carrying out phase locking; calculating instantaneous power based on the split-phase / shaft voltage and current components; carrying out dynamic amplitude limiting on the instantaneous power according to the SOC of the battery to obtain actual power; performing split-phase droop control on each phase, and calculating a power reference value; based on the actual power and the power reference value, split-phase VSG control is carried out, and an instantaneous voltage reference value is obtained through calculation; based on the instantaneous voltage reference value, split-phase double-loop PR control is carried out, and original modulation voltage is obtained through calculation; and modulating the four-bridge-arm voltage based on the original modulation voltage to realize network construction power supply and charge and discharge.

Description

Technical Field

[0001] This invention belongs to the field of converter / inverter technology, specifically relating to a phase-by-phase grid control method for a three-phase four-arm energy storage PCS. Background Technology

[0002] With the rapid development of distributed energy storage and microgrid technologies, the role of power storage converters (PCS) in microgrid systems has undergone a fundamental transformation, evolving from a simple "energy conversion unit" to the "microgrid regulation core." Under this new role, energy storage PCS is no longer solely responsible for energy conversion; it also needs to possess multiple key capabilities. On one hand, it must be able to simulate a synchronous generator to support the grid, enabling grid-connected power supply and providing stable voltage and frequency support for the microgrid. On the other hand, it must be able to respond to energy storage dispatch commands, performing bidirectional charging and discharging operations to flexibly adjust energy storage and release. Furthermore, it must possess the ability to adapt to unbalanced operating conditions to address various problems arising from differences in three-phase loads. However, existing three-phase energy storage PCS face numerous challenges in achieving these functions.

[0003] Currently, existing three-phase energy storage PCS (Power Control System) suffers from significant technical challenges. In terms of control methods, most employ a uniform three-phase control strategy. When faced with unbalanced three-phase loads or grid conditions, this control approach easily leads to voltage distortion and uneven power distribution, resulting in degraded output power quality and failing to meet the high power quality requirements of grid construction. From a control coordination perspective, there is a disconnect between grid construction control (such as droop control and virtual synchronous generator (VSG) control) and energy storage charging and discharging management. Power surges during charging and discharging can easily trigger grid-side frequency and voltage fluctuations, potentially leading to grid instability and affecting the stable operation of the microgrid. Furthermore, for energy storage PCS using a three-phase four-arm topology, the coordination between bus voltage equalization, zero-sequence control, and DC-side energy storage management is poor, making it difficult to simultaneously meet the bus fluctuation requirements of the energy storage side and the grid construction needs.

[0004] In addition, while traditional PR controllers can achieve zero steady-state error tracking, they are not optimized for the "DC-AC bidirectional conversion" characteristics of energy storage PCS. When the energy storage PCS switches between charging and discharging modes, traditional PR controllers are prone to current surges, which not only affect the operational stability of the energy storage PCS itself but also adversely impact the overall performance of the microgrid, severely restricting the application of energy storage PCS in microgrid construction. Therefore, a new control method is urgently needed to address the problems of poor imbalance adaptation, weak charging / discharging and grid coordination, and large bus voltage fluctuations in existing three-phase four-arm energy storage PCS grid construction, in order to achieve stable operation and efficient bidirectional energy conversion of energy storage PCS in grid construction scenarios. Summary of the Invention

[0005] To overcome the problems in the prior art, this invention proposes a phase-by-phase grid control method for a three-phase four-arm energy storage PCS.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a phase-by-phase grid control method for a three-phase four-arm energy storage PCS, comprising the following steps: Step 100: Collect the grid-side three-phase voltage and current, the positive and negative DC bus voltages on the energy storage side, and the battery SOC of the three-phase four-arm energy storage PCS; and calculate the phase-by-phase data based on the three-phase voltage and current. / The shaft voltage and current components are then phase-locked; Step 200: Based on phase splitting / Calculate the instantaneous power based on the shaft voltage and current components; and dynamically limit the instantaneous power according to the battery SOC to obtain the actual power; Step 300: Perform phase-by-phase droop control for each phase and calculate the power reference value; Step 400: Based on the actual power and power reference value, perform phase-by-phase VSG control and calculate the instantaneous voltage reference value; Step 500: Based on the instantaneous voltage reference value, perform phase-separated dual-loop PR control to calculate the original modulation voltage; Step 600: Modulate the voltage of the four bridge arms based on the original modulation voltage.

[0007] Further, step 100 includes: For each phase voltage and current, the voltage of each phase is obtained by using a double second-order generalized integrator. α Axis components, voltage β Axial components, current α Axis components, current β Axial components; Based on the voltage of each phase α The square of the axial component and the voltage per phase β Calculate the voltage amplitude of each phase by taking the square root of the sum of the squares of the axial components; Based on the voltage of each phase α Axial components, β Shaft components, calculate each phase d Axis voltage components, q Axis voltage components: Each phase q The axial voltage component is used as a PI input, and after being superimposed with the fundamental angular frequency and integrated, the phase of each phase is obtained to achieve phase locking.

[0008] Further, step 300 includes: calculating the active power reference value through active power-frequency droop. Set the rated frequency range ,in, Indicates the lower limit of the rated frequency range. Indicates the upper limit of the rated frequency range; Calculate the active power slope within the set rated frequency range. m : ; In the above formula, This indicates the rated active power of the energy storage PCS; Based on the active power slope, calculate the active power reference value: ; In the above formula, Indicates the first x The active power setpoint of the phase; Indicates the active power reference value; Indicates the first x The actual measured frequency of the phase; Indicates the rated frequency.

[0009] Further, step 300 includes: calculating the reactive power reference value through reactive power-voltage droop. Set the rated voltage range ,in, This indicates the lower limit of the rated voltage range, and this indicates the upper limit of the rated voltage range. Calculate the reactive power slope within the set rated voltage range. n : ; In the above formula, This indicates the rated reactive power of the energy storage PCS; Calculate the reactive power reference value based on the reactive power slope and voltage amplitude: ; In the above formula, Indicates the first x The reactive power setting value of the phase; Indicates the reactive power reference value; Indicates the first x The actual voltage of the phase.

[0010] Further, step 400 includes: calculating the phase through active-frequency control, specifically including: Based on the actual active power and the active power reference value, the active power deviation is calculated and converted into torque deviation: Based on torque deviation and VSG mechanical equations, the inertia is calculated and integrated to obtain the phase frequency, and then the phase is obtained by integration.

[0011] Further, step 400 includes: calculating an instantaneous voltage reference through reactive power-voltage control, specifically including: Calculate the reactive power deviation based on the actual reactive power and the reactive power reference value; Based on the reactive power deviation, the voltage amplitude is adjusted integrally to obtain a reference value for the voltage amplitude adjusted integrally. The instantaneous voltage reference is calculated based on the reference values ​​of phase and integral-regulated voltage amplitude.

[0012] Furthermore, step 500 includes voltage outer loop control, specifically including: The voltage deviation is calculated based on the acquired phase voltage and instantaneous voltage reference. Based on the voltage deviation, after passing through the PR controller of the outer voltage loop, the grid-side current feedforward is superimposed to obtain the inner loop current reference.

[0013] Furthermore, step 500 includes current inner loop control, specifically including: The current deviation is calculated based on the collected phase current and inner loop current reference. Based on the current deviation, after passing through the PR controller in the inner current loop, the original modulation voltage is obtained by superimposing the AC current feedforward.

[0014] Further, step 600 includes: Based on the original modulation voltage, calculate the maximum and minimum values ​​of the modulation voltage; The zero-sequence component is calculated based on the maximum and minimum values ​​of the modulation voltage; Based on the modulation voltage and the zero-sequence component, the modulation voltage of the three-phase bridge arm after injection is calculated, and the modulation voltage of the N-phase bridge arm is equal to the zero-sequence component. The modulation voltage of the three-phase bridge arm after injection is converted into the conduction time of the four bridge arms, and the SPWM drive signal is output.

[0015] Furthermore, the modulation voltage of the injected three-phase bridge arm is converted into the conduction time of the four bridge arms, and an SPWM drive signal is output, including: When the modulation voltage of the three-phase bridge arm is injected hour, ; In the above formula, This indicates the conduction time of the first IGBT in the upper bridge arm; This indicates the conduction time of the second IGBT in the upper bridge arm; When the modulation voltage of the three-phase bridge arm is injected hour, ; In the above formula, This indicates the conduction time of the first IGBT in the upper bridge arm; This indicates the conduction time of the second IGBT in the upper bridge arm; This refers to the DC bus voltage on the energy storage side. T This represents the switching cycle of the IGBT.

[0016] Compared with the prior art, the present invention has the following technical effects: (1) The phase-by-phase grid control method proposed in this invention can adapt to the differences in three-phase loads by independently controlling and adjusting each phase. For example, in phase-by-phase droop control and phase-by-phase VSG control, the power reference value is calculated and the frequency and voltage are adjusted according to the actual situation of each phase, which effectively avoids various problems caused by three-phase imbalance, significantly improves the adaptability of energy storage PCS under unbalanced conditions, and provides more stable and high-quality power for microgrids.

[0017] (2) The instantaneous power is dynamically limited based on the battery SOC to obtain the actual power, fully considering the state of the energy storage system. In the subsequent phase droop control, VSG control, and dual-loop PR control, the actual power is used as the basis for adjustment, so that the charging and discharging process is closely coordinated with the grid construction control. In this way, the grid-side frequency and voltage stability can be better maintained during charging and discharging, avoiding the adverse effects of power surges, greatly enhancing the coordination between charging and discharging and grid construction, and ensuring the stable operation of the microgrid.

[0018] (3) When modulating the voltage of the four bridge arms, this invention calculates the maximum and minimum values ​​of the modulation voltage to obtain the zero-sequence component, and adjusts the modulation voltage of each bridge arm based on the zero-sequence component. This control method optimizes the control of the bus voltage, enabling better coordination between the bus fluctuations on the energy storage side and the grid-side network requirements. At the same time, the phase-separated dual-loop PR control is optimized for the "DC-AC bidirectional conversion" characteristics of the energy storage PCS, reducing the current impact during charging and discharging mode switching, further improving the stability of the system, and realizing the stable operation of the energy storage PCS and efficient bidirectional energy conversion in the grid construction scenario. Attached Figure Description

[0019] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a schematic diagram of the phase-locked loop structure for fundamental wave extraction. Figure 3 This is a schematic diagram of the active-frequency section in a phase-splitting SVG control system. Figure 4 This is a schematic diagram of the reactive power-voltage section in a phase-splitting SVG control system. Figure 5 This is a schematic diagram of a phase-separated dual-loop PR control structure. Detailed Implementation

[0021] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the specific implementation methods, structures, features, and effects of the technical solutions proposed according to the present invention are described in detail below with reference to the accompanying drawings and preferred embodiments. Specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] The three-phase four-arm topology consists of three phase arms (A, B, and C phases) and one neutral point arm (N phase). The topology of this invention adopts an NPC structure, with each arm divided into an upper arm and a lower arm, each containing two IGBTs (Insulated Gate Bipolar Transistors).

[0023] The A, B, and C phase bridge arms are primarily responsible for exchanging three-phase AC power with the power grid. By controlling the switching state of the IGBTs, DC power can be converted into three-phase AC power that meets the grid requirements, thus achieving grid-connected power generation. Conversely, it can also convert the grid's three-phase AC power into DC power to charge the energy storage batteries.

[0024] The main function of the neutral point arm is to provide a neutral point connection and handle zero-sequence current under three-phase unbalanced load or fault conditions. It can effectively suppress the negative impact of three-phase imbalance, improve the stability and reliability of the system, and ensure stable power conversion under various operating conditions.

[0025] In this embodiment, refer to Figures 1-5 A phase-by-phase grid control method for a three-phase four-arm energy storage PCS is provided, comprising the following steps: Step 100: Collect the grid-side three-phase voltage and current, positive and negative DC bus voltages on the energy storage side, and battery SOC of the three-phase four-bridge arm energy storage PCS; Calculate the voltage amplitude of each phase based on the three-phase voltage and current, and calculate the phase-by-phase voltage. / The shaft voltage and current components are then phase-locked; Step 200: Based on phase splitting / Calculate the instantaneous power based on the shaft voltage and current components; and dynamically limit the instantaneous power according to the battery SOC to obtain the actual power; Step 300: Perform phase-by-phase droop control for each phase and calculate the power reference value; Step 400: Based on the actual power and power reference value, perform phase-by-phase VSG control and calculate the instantaneous voltage reference value; Step 500: Based on the instantaneous voltage reference value, perform phase-separated dual-loop PR control and calculate the original modulation voltage; Step 600: Modulate the voltage of the four bridge arms based on the original modulation voltage.

[0026] The following is a detailed explanation of each of the above steps: Step 100: Collect the grid-side three-phase voltage and current of the three-phase four-arm energy storage PCS, as well as the positive and negative DC bus voltages and battery SOC on the energy storage side; calculate the voltage amplitude of each phase based on the three-phase voltage and current, and calculate the phase-by-phase voltage. / The shaft voltage and current components are then phase-locked.

[0027] Collect grid-side three-phase (A / B / C) voltages of a three-phase four-arm energy storage PCS. Current ( x =A,B,C), and the positive and negative DC bus voltages on the energy storage side. U dc + / U dc Battery current i bat Battery SOC.

[0028] For each phase voltage and current Inputting into an independent DSOGI (Dual Second-Order Generalized Integrator) module yields the voltage of each phase. α Axial components voltage β Axial components , current α Axial components , current β Axial components By processing the voltage and current of each phase using an independent DSOGI module, phase-specific fundamental frequency extraction is achieved.

[0029] Based on the voltage of each phase α Axial components , β Axis voltage components Calculate the voltage amplitude of each phase. : : Based on the voltage of each phase α Axial components , β Axial components Calculate each phase d Axis voltage components, q Axis voltage components: ; ; In the above formula, Indicates each phase d Axis voltage components; Indicates phase; express q Axis voltage component.

[0030] Each phase q Axis voltage components As a PI input, the fundamental angular frequency is superimposed. After integration, the phase of each phase is obtained. Phase-locked loop (PLL) is implemented to achieve synchronization with the power grid, ensuring that the frequency and phase of the AC power output by the PCS are consistent with those of the power grid, thus achieving stable grid-connected operation.

[0031] In subsequent steps, the calculation variables used in phases A / B / C / N will all be represented by subscripts. Replacement, such as , wait.

[0032] Specifically, taking phase A as an example, regarding the voltage of phase A... Current Inputting each phase into an independent DSOGI module yields the output voltage of phase A. α Axial components , β Axial components Current α Axial components β-axis components ; Based on the output voltage of phase A α Axial components , β Axial components Calculate the voltage amplitude of phase A. : : Based on the output voltage of phase A α Axial components , β Axial components Calculate phase A d Axis voltage components,q Axis voltage components: ; ; In the above formula, Indicates phase A d Axis voltage components; Indicates phase A; Indicates phase A q Axis voltage component.

[0033] The q-axis voltage component of phase A As a PI input, the fundamental angular frequency is superimposed. After integration, the phase of phase A is obtained. Phase-locked loop (PLL) is achieved. This closed-loop control method enables... It can accurately track the actual phase of the A-phase voltage and achieve phase-locked loop function.

[0034] Step 200: Based on phase splitting / The instantaneous power is calculated from the axis voltage and current components, including instantaneous active power and instantaneous reactive power; the instantaneous power is dynamically limited according to the battery SOC to obtain the actual active power and actual reactive power.

[0035] Based on phase separation / Axis components, calculate instantaneous power: ; In the above formula, express x Mutually( x The instantaneous active power of (A, B, C) is expressed in kW. The power unit is converted from watt (W) to kilowatt (kW) by dividing the calculation result by 1000. express x Mutually( x The instantaneous reactive power of (A, B, C) is expressed in kVar. Similarly, dividing by 1000 is to convert the unit from reactive volt-amperes (Var) to kiloreactive volt-amperes (kVar).

[0036] The power symbol is determined based on the charge and discharge state of the energy storage PCS. When the energy storage system discharges, the instantaneous active power... A positive value indicates the active power delivered to the grid or load; when the energy storage system is charging, the instantaneous active power... Taking a negative value indicates that active power is absorbed from the power grid and stored.

[0037] Instantaneous active power based on battery state of charge (SOC) Dynamic power limiting is implemented. When the battery's State of Charge (SOC) is less than or equal to a first threshold, charging power is limited to prevent over-discharge; when the battery's SOC is greater than or equal to a second threshold, discharging power is limited. Specifically, the SOC threshold recommended by the battery manufacturer is set. For example, for ternary lithium batteries, the recommended upper limit is 80% and the lower limit is 20%. That is, when the battery's SOC is less than or equal to 20%, charging power is limited to prevent over-discharge; when the battery's SOC is greater than or equal to 80%, discharging power is limited to prevent overcharging. In this way, the actual active power adapted to the energy storage operating conditions can be obtained. and actual reactive power This ensures that the energy storage system operates under safe and reasonable conditions.

[0038] ; In the above formula, The permissible charge and discharge power range (kW) for the PCS; Rated power (kW) for energy storage PCS; This is the lower limit threshold of SOC; This is the upper limit threshold of SOC; This triggers forced charging at the SOC critical lower limit. This represents the critical upper limit of SOC.

[0039] Active power is subject to SOC (State of Charge) limitations, while reactive power is not subject to SOC limitations and can be output normally. ; In the above formula, This represents the actual reactive power.

[0040] Step 300: Perform phase-by-phase droop control for each phase and calculate the active power reference value and reactive power reference value.

[0041] Phase-by-phase droop control includes active-frequency droop and reactive-voltage droop.

[0042] (1) Calculate the active power reference value by means of active power-frequency droop: Set the rated frequency range ,in, Indicates the lower limit of the rated frequency range. Indicates the upper limit of the rated frequency range; Calculate the active power slope within the set rated frequency range. m : ; In the above formula, This indicates the rated active power of the energy storage PCS.

[0043] Based on the active power slope, calculate the active power reference value: ; In the above formula, Indicates the first x The active power setpoint of the phase; Indicates the active power reference value; Indicates the first x The actual measured frequency of the phase; Indicates the rated frequency.

[0044] (2) Calculate the reactive power reference value by means of reactive power-voltage droop: Set the rated voltage range ,in, Indicates the lower limit of the rated voltage range. Indicates the upper limit of the rated voltage range; Calculate the reactive power slope within the set rated voltage range. n : ; In the above formula, This indicates the rated reactive power of the energy storage PCS.

[0045] Calculate the reactive power reference based on the reactive power slope and voltage amplitude: ; In the above formula, Indicates the first x The reactive power setting value of the phase; Indicates the reactive power reference value; Indicates the first x The actual voltage of the phase.

[0046] Step 400: Based on the actual active power, actual reactive power, active reference value, and reactive reference value, perform phase-by-phase VSG control and calculate the instantaneous voltage reference value.

[0047] Phase-separated VSG (virtual synchronous generator) control includes active-frequency control and reactive-voltage control.

[0048] (1) Based on the actual active power and active power reference value, the phase is calculated through active power-frequency control: Calculate the active power deviation based on the actual active power and the active power reference value. : ; Convert active power deviation into torque deviation : ; The VSG mechanical equations are given below: ; In the above formula, J represents the virtual moment of inertia; D is the damping coefficient. Calculate inertia based on VSG mechanical equations The phase frequency is obtained by integration. Then integrate to obtain the phase. .

[0049] VSG is designed to simulate the inertial response of virtual synchronization. When the grid phase fluctuates, the PCS follows the grid phase fluctuation due to the preceding phase-locked loop. However, due to the grid construction characteristics of the PCS, an inertial response occurs, which plays the role of active frequency regulation. After the grid frequency stabilizes, the phase also stabilizes.

[0050] (2) Based on the actual reactive power and reactive power reference value, the instantaneous voltage reference value is calculated through reactive power-voltage control: Calculate the reactive power deviation based on the actual reactive power and the reactive power reference value. : ; Based on reactive power deviation, integral adjustment of voltage amplitude: ; In the above formula, This represents a reference value indicating the amplitude of the integral-regulated voltage. This indicates the voltage amplitude setting value; Represents the integral gain constant; This indicates the IGBT switching cycle.

[0051] Calculate the instantaneous voltage reference value based on the reference values ​​of phase and integral-regulated voltage amplitude: ; In the above formula, This indicates the instantaneous voltage reference value.

[0052] Step 500: Based on the instantaneous voltage reference value, the original modulation voltage is calculated using phase-separated dual-loop PR (proportional-resonant) control. The dual loop consists of an outer voltage loop and an inner current loop.

[0053] (1) Voltage outer loop: Based on the acquired phase voltage values ​​and instantaneous voltage reference values, the voltage deviation is calculated. : ; Based on the voltage deviation, the PR controller outputs: ; In the above formula, This indicates the output value of the PR controller; This indicates the output value of the PR integral controller; This represents the proportional gain of the PR controller; PR controller output value superimposed with grid-side current feedforward The inner loop current reference is obtained: ; In the above formula, This indicates the inner loop current reference.

[0054] (2) Inner current loop: Based on the acquired phase current and inner loop current reference, the current deviation is calculated: ; Based on the current deviation, the PR controller outputs: ; In the above formula, This indicates the output value of the PR controller; This indicates the integral output value of the PR controller; This represents the proportional gain of the PR controller; PR controller output value superimposed with AC current feedforward The original modulation voltage is obtained: ; In the above formula, This represents the original modulation voltage, used to control the output voltage of each phase bridge arm to achieve functions such as tracking the grid voltage and power regulation.

[0055] The PR control is calculated as follows: ; In the above formula, For the first k The control deviation at each sampling time, i.e., the difference between the reference value and the actual feedback value, corresponds to the voltage outer loop deviation in (1). Current inner loop deviation in (2) . The intermediate output of the resonant circuit of the PR controller at the k-th sampling time is the core output of the PR controller for tracking the fundamental (or harmonic) component. Finally, after superimposing the proportional term, it forms the voltage loop control output in (1). The current inner loop control output in (2) . The value of the integral state variable of the controller resonant circuit at the k-th sampling time corresponds to the integral term output of the resonant circuit in the continuous system, which is used to achieve zero steady-state error tracking of the fundamental frequency signal. Let the value of the damped state variable of the controller resonant circuit at the k-th sampling time be obtained from the current integral state. and resonant output The calculated value is used for iterative calculations fed back to the next sampling time to maintain the dynamic stability of the resonant circuit. The angular frequency of the target tracking frequency. For resonant gain, T This refers to the IGBT switching cycle.

[0056] Step 600: Modulate the voltage of the four bridge arms based on the original modulation voltage, drive the four bridge arm IGBTs, and realize grid power supply and charging / discharging.

[0057] This invention adopts an NPC topology, with each bridge arm divided into upper and lower arms, and each upper and lower arm containing 2 IGBTs.

[0058] Based on the original modulation voltage, calculate the maximum and minimum values ​​of the modulation voltage: ; ; Calculate the zero-sequence component based on the maximum and minimum values ​​of the modulation voltage: ; In the above formula, This represents the zero-sequence component. The purpose of injecting the zero-sequence component is to optimize the modulation effect of the three-phase four-arm bridge system, improve the DC voltage utilization rate, make the modulation wave closer to a sine wave, and reduce the harmonic content.

[0059] Based on the modulation voltage and zero-sequence component, the modulation voltage of the A / B / C phase bridge arms after injection is calculated: ; In the above formula, This represents the modulation voltage of phases A, B, and C after injection. After zero-sequence component injection, the modulation voltage of each phase is adjusted to meet the control requirements of the three-phase four-arm system.

[0060] The modulation voltage of the N-phase bridge arm is equal to the zero-sequence component: In a three-phase four-arm system, the modulation voltage of the N-phase arm is coordinated and controlled with the other three phases in this way.

[0061] The modulation voltage injected into the A / B / C phase bridge arms This is converted to the conduction time of the four bridge arms, and the SPWM drive signal is output. The SPWM modulation is shown in the following formula: When the modulation voltage of the A / B / C phase bridge arms is injected hour, ; In the above formula, This indicates the conduction time of the first IGBT in the upper bridge arm; This indicates the conduction time of the second IGBT in the upper bridge arm; When the modulation voltage of the A / B / C phase bridge arms is injected hour, ; In the above formula, This indicates the conduction time of the first IGBT in the upper bridge arm; This indicates the conduction time of the second IGBT in the upper bridge arm; This refers to the DC bus voltage on the energy storage side. T This represents the switching cycle of the IGBT.

[0062] By calculating the conduction time of the two IGBTs in the upper arm using different formulas based on the positive and negative values ​​of the injected modulation voltage, and then obtaining the on / off time of the lower arm based on the complementary relationship, the switching state of the IGBTs is controlled to achieve voltage tracking and power regulation of the grid, complete the charging and discharging operations of the phase-separated grid, and ensure the stable and efficient operation of the power electronic system.

[0063] In a bridge arm, the IGBT switching states of the upper and lower arms are mutually exclusive. That is, when an IGBT in the upper arm is turned on, the corresponding IGBT in the lower arm must be turned off, and vice versa. Assume the turn-on time of the first IGBT in the upper arm is... The conduction time of the second IGBT in the upper bridge arm is The switching period of the IGBT is T. For the lower arm, taking the first lower arm IGBT as an example, its conduction time... It can be calculated by subtracting the time of the corresponding state of the upper bridge arm from the switching cycle T.

[0064] In practical implementation, parameter configuration includes: Energy storage PCS parameters: Rated active power of energy storage PCS For 125kW, the first x Phase reactive power setpoint 125kVar, DC bus rated voltage 750V, rated frequency The frequency is 18kHz, and the IGBT period is T = 1 / 18000s; Control parameters: DSOGI damping k =0.707, PLL PI parameters (K_p=0.05), (K_i=8×T), VSG parameters J=40, D=200, PR parameters are set according to step 500; In the parameters of energy storage batteries, the rated capacity P n It has a capacity of 100kWh and a SOC adjustment range of 20%-80%.

[0065] During initialization, variables such as DSOGI input / output, PR state variable, and VSG integral variable are set to zero, and the initial frequency is set to 50Hz, phase to 0, and SOC initial value to 50%.

[0066] The control method of this invention can be integrated into the main control unit of a three-phase four-arm energy storage PCS and implemented through software algorithms, without additional hardware costs. It is compatible with energy storage systems ranging from 100kWh to 1MWh and can be applied to scenarios such as isolated microgrids (e.g., power supply to remote areas), distributed energy storage grid connection (e.g., energy storage in industrial parks), and emergency power supply systems. It can meet the grid construction support requirements of microgrids and efficiently manage the charging and discharging of energy storage, thus possessing significant industrial promotion value.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A phase-by-phase grid control method for a three-phase four-arm energy storage PCS, characterized in that, Includes the following steps: Step 100: Collect the grid-side three-phase voltage and current, the positive and negative DC bus voltages on the energy storage side, and the battery SOC of the three-phase four-arm energy storage PCS; and calculate the phase-by-phase data based on the three-phase voltage and current. / The shaft voltage and current components are then phase-locked; Step 200: Based on phase splitting / Calculate the instantaneous power based on the shaft voltage and current components; and dynamically limit the instantaneous power according to the battery SOC to obtain the actual power; Step 300: Perform phase-by-phase droop control for each phase and calculate the power reference value; Step 400: Based on the actual power and power reference value, perform phase-by-phase VSG control and calculate the instantaneous voltage reference value; Step 500: Based on the instantaneous voltage reference value, perform phase-separated dual-loop PR control to calculate the original modulation voltage; Step 600: Modulate the voltage of the four bridge arms based on the original modulation voltage.

2. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 1, characterized in that, Step 100 includes: For each phase voltage and current, the voltage of each phase is obtained by using a double second-order generalized integrator. α Axis components, voltage β Axial components, current α Axis components, current β Axial components; Based on the voltage of each phase α The square of the axial component and the voltage per phase β Calculate the voltage amplitude of each phase by taking the square root of the sum of the squares of the axial components; Based on the voltage of each phase α Axial components, β Shaft components, calculate each phase d Axis voltage components, q Axis voltage components: Each phase q The axial voltage component is used as a PI input, and after being superimposed with the fundamental angular frequency and integrated, the phase of each phase is obtained to achieve phase locking.

3. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 1, characterized in that, Step 300 includes: calculating the active power reference value through active power-frequency droop. Set the rated frequency range ,in, Indicates the lower limit of the rated frequency range. Indicates the upper limit of the rated frequency range; Calculate the active power slope within the set rated frequency range. m : ； In the above formula, This indicates the rated active power of the energy storage PCS; Based on the active power slope, calculate the active power reference value: ； In the above formula, Indicates the first x The active power setpoint of the phase; Indicates the active power reference value; Indicates the first x The actual measured frequency of the phase; Indicates the rated frequency.

4. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 3, characterized in that, Step 300 includes: calculating the reactive power reference value based on reactive power-voltage droop. Set the rated voltage range ,in, This indicates the lower limit of the rated voltage range, and this indicates the upper limit of the rated voltage range. Calculate the reactive power slope within the set rated voltage range. n : ； In the above formula, This indicates the rated reactive power of the energy storage PCS; Calculate the reactive power reference value based on the reactive power slope and voltage amplitude: ； In the above formula, Indicates the first x The reactive power setting value of the phase; Indicates the reactive power reference value; Indicates the first x The actual voltage of the phase.

5. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 1, characterized in that, Step 400 includes: calculating the phase through active-frequency control, specifically including: Based on the actual active power and the active power reference value, the active power deviation is calculated and converted into torque deviation: Based on torque deviation and VSG mechanical equations, the inertia is calculated and integrated to obtain the phase frequency, and then the phase is obtained by integration.

6. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 5, characterized in that, Step 400 includes: calculating the instantaneous voltage reference through reactive power-voltage control, specifically including: Calculate the reactive power deviation based on the actual reactive power and the reactive power reference value; Based on the reactive power deviation, the voltage amplitude is adjusted integrally to obtain a reference value for the voltage amplitude adjusted integrally. The instantaneous voltage reference is calculated based on the reference values ​​of phase and integral-regulated voltage amplitude.

7. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 1, characterized in that, Step 500 includes voltage outer loop control, specifically including: The voltage deviation is calculated based on the acquired phase voltage and instantaneous voltage reference. Based on the voltage deviation, after passing through the PR controller of the outer voltage loop, the grid-side current feedforward is superimposed to obtain the inner loop current reference.

8. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 7, characterized in that, Step 500 includes current inner loop control, specifically including: The current deviation is calculated based on the collected phase current and inner loop current reference. Based on the current deviation, after passing through the PR controller in the inner current loop, the original modulation voltage is obtained by superimposing the AC current feedforward.

9. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 1, characterized in that, Step 600 includes: Based on the original modulation voltage, calculate the maximum and minimum values ​​of the modulation voltage; The zero-sequence component is calculated based on the maximum and minimum values ​​of the modulation voltage; Based on the modulation voltage and the zero-sequence component, the modulation voltage of the three-phase bridge arm after injection is calculated, and the modulation voltage of the N-phase bridge arm is equal to the zero-sequence component. The modulation voltage of the three-phase bridge arm after injection is converted into the conduction time of the four bridge arms, and the SPWM drive signal is output.

10. The phase-by-phase grid control method for a three-phase four-arm energy storage PCS according to claim 9, characterized in that, The injected modulation voltage of the three-phase bridge arm is converted into the conduction time of the four-phase bridge arm, and the SPWM drive signal is output, including: When the modulation voltage of the three-phase bridge arm is injected hour, ； In the above formula, This indicates the conduction time of the first IGBT in the upper bridge arm; This indicates the conduction time of the second IGBT in the upper bridge arm; When the modulation voltage of the three-phase bridge arm is injected hour, ； In the above formula, This indicates the conduction time of the first IGBT in the upper bridge arm; This indicates the conduction time of the second IGBT in the upper bridge arm; This refers to the DC bus voltage on the energy storage side. T This represents the switching cycle of the IGBT.

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