An active power distribution network power closed-loop dynamic simulation system and an application method thereof

Abstract

The application discloses a kind of active power distribution network power closed-loop type dynamic model simulation system and its application method, the simulation system of the application includes analog power grid unit, photovoltaic physical platform, controller platform and be used to simulate the circuit breaker of one secondary deep fusion circuit breaker of active power distribution network, analog power grid unit includes simulator and power amplifier, photovoltaic physical platform includes photovoltaic inverter, photovoltaic cell, energy storage inverter, energy storage battery and low-voltage bus, photovoltaic cell is connected with low-voltage bus by photovoltaic inverter, energy storage battery is connected with low-voltage bus by energy storage inverter, controller platform is connected with the control end of photovoltaic inverter, energy storage inverter respectively.The application adopts semi-physical simulation to overcome the limitation of offline simulation and pure digital real-time simulation, and the simulation result is closer to actual situation, in the research of high-power device of power system, semi-physical simulation not only improves reliability, and can shorten development cycle, reduce development cost.

Description

Technical Field

[0001] The present invention relates to an active distribution network dynamic simulation technology of an electric power system, and in particular to an active distribution network power closed-loop dynamic simulation system and an application method thereof. Background Art

[0002] With the introduction of high-proportion photovoltaic (PV) integration, high-penetration new power electronic devices, and advanced strategies such as multi-source coordinated control, the characteristics of distribution networks have shifted from passive to active, and from single-source to multi-source, posing significant challenges to the regulation and safety management capabilities of traditional power systems. Furthermore, distributed PV integration transforms distribution networks from traditional radial to active networks, altering operational and fault characteristics. Existing protection systems cannot meet system safety requirements, necessitating timely adjustments to protection configurations and setting settings. Inverter control strategies vary across different active distribution network modes, such as predictive control, low-voltage ride-through optimization control, and neural network control, making it difficult to centrally compare and verify their effectiveness and cost-effectiveness. Current simulation research on power electronics and power systems primarily utilizes offline simulation software, such as Maltab / Simulink and PSCAD, which is susceptible to limitations in computer performance, simulation scale, and simulation step size. When the scale of the simulation model is large, the actual time taken for simulation will be much longer than the simulation time, and even no simulation results may be obtained, making it impossible to simulate large-scale systems. In addition, in the process from simulation model to physical development, due to errors in manually written algorithm code and incorrect configuration of digital signal processors, it is easy for simulation and physical development to be disconnected. Real-time simulation is difficult to reproduce the operating scenarios of the entire distribution network, and for fault scenarios, physical simulation is even more difficult to reproduce.

[0003] The existing technologies for the test methods of dynamic simulation of active distribution networks include: Reference [1]: Huang Xin, Yi Yingping, Fan Lijun. Modeling and simulation of RTDS of large-power photovoltaic grid-connected power generation system [J]. Automation of Electric Power Systems, 2014, 38(22): 32-37. Reference [1] uses the small step size model and large step size model of RTDS to build a 100kW photovoltaic grid-connected power generation system simulation test platform, including photovoltaic converters, controllers and external power systems. Then, the working principle of the current controller and the RTDS modeling method are introduced in detail, and the steady-state and transient simulation experiments to verify the control performance of the current controller are designed and completed based on the platform; at the same time, the same field test is carried out on an actual large-power photovoltaic grid-connected inverter for comparative analysis. Reference [2]: Zheng Fei, Zhang Junjun, Ding Mingchang. Modeling and control strategy of low voltage ride-through of photovoltaic power generation system based on RTDS [J]. Automation of Electric Power Systems, 2012, 36(22): 19-24. Reference [2] built a complete LVRT simulation platform through the large step size model and small step size model of RTDS, including voltage drop generator, photovoltaic array, isolation transformer and photovoltaic grid-connected inverter, and designed the LVRT control strategy of photovoltaic grid-connected inverter under two operating conditions: normal and symmetrical voltage drop of three-phase grid. Reference [3]: Zhang Xiaolin, Wu Zongguang, Wang Weixing, Qin Xiaodi. Research on semi-physical simulation platform of high-power grid-connected inverter [J]. Power Electronics Technology, 2018, 52(09): 104-106+111. Reference [3] established a simulation model for the photovoltaic converter grid-connected system, and applied the system simulation model to the real-time semi-physical simulation system with the help of RT-LAB simulation platform, and established a semi-physical simulation platform for high-power photovoltaic grid-connected inverter. The semi-physical simulation platform completed the semi-physical simulation low voltage ride-through test of photovoltaic converter. Reference [4]: ​​Ge Xinglai, Feng Xiaoyun, Huang Jin. SVPWM control of three-level inverter based on FPGA and dSPACE [J]. Power Electronics Technology, 2009, 43(12): 10-11+27. Reference [4] analyzes the principle and implementation strategy of the three-level inverter using constant switching frequency asynchronous modulation at low speed and multi-pulse synchronous modulation at high speed, theoretically analyzes the switch multi-pulse combination mode suitable for high-speed EMU variable frequency speed control, and derives the corresponding implementation algorithm. Using FPGA controller and dSPACE semi-physical simulation platform, simulation experiments of various modulation modes mentioned above were completed, and the results confirmed the effectiveness of this control strategy. However, the above existing technologies are all based on semi-physical simulation at the controller level, and do not integrate the interaction between RTDS and real primary equipment, and the physical characteristics of primary equipment are difficult to fully simulate at the simulation level. Summary of the Invention

[0004] The present invention aims to solve the following technical problems: In response to the above-mentioned problems in the prior art, an active power distribution network closed-loop dynamic simulation system and its application method are provided. The present invention uses semi-physical simulation to overcome the limitations of offline simulation and pure digital real-time simulation, and its simulation results are closer to the actual situation. In the research of high-power devices in power systems, semi-physical simulation not only improves reliability, but also shortens the development cycle and reduces development costs.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A power closed-loop dynamic simulation system for an active distribution network comprises a simulated grid unit, a photovoltaic physical platform, a controller platform, and a circuit breaker for simulating a primary-secondary deep-fusion circuit breaker of an active distribution network. The simulated grid unit comprises a simulator and a power amplifier for simulating a main loop model of the active distribution network. The photovoltaic physical platform comprises a photovoltaic converter, a photovoltaic cell, an energy storage converter, an energy storage battery, and a low-voltage bus. The photovoltaic cell is connected to the low-voltage bus via the photovoltaic converter, and the energy storage battery is connected to the low-voltage bus via the energy storage converter. The output end of the controller platform is respectively connected to the control ends of the photovoltaic converter and the energy storage converter, and the voltage and current signal output ends of the photovoltaic converter and the energy storage converter are connected to the input end of the simulator. The analog signal output end of the simulator is respectively connected to the primary interfaces of the photovoltaic converter and the energy storage converter via the power amplifier. The simulator is respectively connected to the controller platform and the circuit breaker.

[0007] Optionally, the simulator is an RTDS simulator for running RTDS simulation software, and the feedback quantities of the photovoltaic converter, energy storage converter and circuit breaker pass through the digital channel of the interface card of the RTDS simulator, and the digital signals are transmitted to the RTDS simulation software and controller platform in the RTDS simulator to complete closed-loop control.

[0008] Optionally, the controller platform includes an FPGA small-step real-time simulator and a DSP control board, the FPGA small-step real-time simulator and the DSP control board are respectively connected to the RTDS simulator, the output end of the FPGA small-step real-time simulator is connected to the control end of the photovoltaic converter for controlling the photovoltaic converter, and the output end of the DSP control board is connected to the control end of the energy storage converter for controlling the energy storage converter.

[0009] Optionally, the power amplifier is a four-quadrant simulated power amplifier.

[0010] Optionally, the photovoltaic physical platform further includes an adjustable load for adjusting three-phase imbalance, and the adjustable load is connected to the low-voltage bus.

[0011] Optionally, the photovoltaic physical platform further includes a charging pile, which is connected to a low-voltage busbar.

[0012] The present invention further provides an application method of the above-mentioned active power distribution network power closed-loop dynamic simulation system, comprising:

[0013] S1: Build the main circuit model of the active distribution network based on the RTDS simulation software in the RTDS simulator; write the control strategies of the photovoltaic converter and energy storage converter into the controller platform respectively;

[0014] S2 generates node voltages, currents, and signals of primary and secondary fusion circuit breakers through the main loop model of the active distribution network. The node voltages and currents are transmitted to the power amplifier through the analog channel of the interface card of the RTDS simulator. After power amplification by the power amplifier, they are connected to the primary interfaces of the photovoltaic converter and the energy storage converter respectively. The signals of the primary and secondary fusion circuit breaker are transmitted to the circuit breaker through the digital channel of the interface card of the RTDS simulator.

[0015] S3, collects the voltage and current signals of the photovoltaic physical platform under the control of the photovoltaic converter and energy storage converter through the digital channel of the interface card of the RTDS simulator.

[0016] Optionally, building a main loop model of the active distribution network in step S1 refers to building a main loop model of a photovoltaic power generation system, and includes: defining battery components in the photovoltaic power generation system, setting the number of parallel and series connections of the battery components in the main loop model of the photovoltaic power generation system, thereby forming the battery components into a photovoltaic array; selecting the Boost circuit and full-bridge inverter circuit of the grid-connected inverter from the built-in devices in the RTDS simulation software, building a controller of the grid-connected inverter and selecting a control strategy, and connecting the photovoltaic array and the grid-connected inverter to obtain the main loop model of the photovoltaic power generation system.

[0017] Optionally, in step S1, writing the control strategies of the photovoltaic converter and the energy storage converter into the controller platform respectively includes writing the control strategy of the photovoltaic converter into the FPGA small-step real-time simulator to control the photovoltaic converter, and writing the control strategy of the energy storage converter into the DSP control board to control the energy storage converter.

[0018] Optionally, when writing the control strategy of the energy storage converter into the DSP control board, it includes judging the operating mode of the active distribution network. If the operating mode of the active distribution network is grid-connected operation, the preset grid-connected control strategy of the energy storage converter is written into the DSP control board; otherwise, the preset island control strategy of the energy storage converter is written into the DSP control board.

[0019] Compared with the prior art, the present invention mainly has the following advantages:

[0020] 1. The present invention adopts semi-physical simulation to overcome the limitations of offline simulation and pure digital real-time simulation. Its simulation results are closer to the actual situation. In the research of high-power devices in power systems, semi-physical real-time simulation not only improves reliability, but also shortens the R&D cycle and reduces R&D costs.

[0021] 2. The active power distribution network power closed-loop dynamic simulation system of the present invention can not only conduct theoretical algorithm research and verification, but also detect and analyze the primary equipment of the active power distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the system according to an embodiment of the present invention.

[0023] Figure 2 Schematic diagram of an example structure of a system according to an embodiment of the present invention.

[0024] Figure 3 Schematic diagram of a power amplifier in an embodiment of the present invention.

[0025] Figure 4 Schematic diagram of the control strategy of the photovoltaic converter in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] like Figure 1 As shown, the active distribution network power closed-loop dynamic simulation system of this embodiment includes a simulated grid unit 1, a photovoltaic physical platform 2, a controller platform 3 and a circuit breaker 4 for simulating a primary and secondary deep fusion circuit breaker of the active distribution network. The simulated grid unit 1 includes a simulator and a power amplifier for simulating the main loop model of the active distribution network. The photovoltaic physical platform 2 includes a photovoltaic converter, a photovoltaic cell, an energy storage converter, an energy storage battery and a low-voltage bus. The photovoltaic cell is connected to the low-voltage bus through the photovoltaic converter, and the energy storage battery is connected to the low-voltage bus through the energy storage converter. The output end of the controller platform 3 is respectively connected to the control end of the photovoltaic converter and the energy storage converter, and the voltage and current signal output ends of the photovoltaic converter and the energy storage converter are connected to the input end of the simulator. The analog signal output end of the simulator is respectively connected to the primary interface of the photovoltaic converter and the energy storage converter through the power amplifier. The simulator is respectively connected to the controller platform 3 and the circuit breaker 4.

[0027] See also Figure 1The simulator is an RTDS simulator for running RTDS simulation software. The feedback quantities of the photovoltaic converter, energy storage converter and circuit breaker 4 are transmitted through the digital channel of the interface card of the RTDS simulator, and the digital signals are transmitted to the RTDS simulation software and controller platform 3 in the RTDS simulator to complete closed-loop control. The RTDS simulator realizes signal interaction with the outside through the interface card. The interface card includes analog channels and digital channels. The analog channel can input and output analog signals, and the digital channel can input and output digital signals (open input and open output). The analog channel of the interface card is used to transmit the analog quantity of the RTDS simulation software to the power amplifier. The analog quantity amplified by the power amplifier is connected to the photovoltaic converter and the primary and secondary fusion circuit breaker (circuit breaker 4). The feedback quantities of the photovoltaic converter and the primary and secondary fusion circuit breaker are transmitted through the digital channel of the interface card, and the digital signals are transmitted to the RTDS simulation software and controller platform 3 to complete closed-loop control.

[0028] See also Figure 1 The controller platform 3 includes an FPGA small-step real-time simulator and a DSP control board. The FPGA small-step real-time simulator and the DSP control board are respectively connected to the RTDS simulator. The output end of the FPGA small-step real-time simulator is connected to the control end of the photovoltaic converter (the control end of the switching devices such as IGBT and thyristor) for controlling the photovoltaic converter. The output end of the DSP control board is connected to the control end of the energy storage converter (the control end of the switching devices such as IGBT and thyristor) for controlling the energy storage converter.

[0029] In this embodiment, the power amplifier is a four-quadrant simulation power amplifier. Figure 2 As shown, the power amplifier specifically adopts the PAV5000 four-quadrant linear power amplifier, which uses the input three-phase 380V power supply as the power supply. Based on digital optical fiber and analog simulation signal input, the power supply is converted into voltage through the PAV5000 main power supply unit to power the PAV5000 four-quadrant linear power amplifier. The three PAV5000 four-quadrant linear power amplifiers output the analog voltage signals Ua, Ub and Uc of the three phases a, b, and c respectively, and jointly output the zero-phase voltage Un (output performance is 0-279Vrms, 5KVA). At the same time, the PAV5000 four-quadrant linear power amplifier is also connected to a system monitoring unit, which is used to monitor the analog voltage signals Ua, Ub and Uc of the three phases a, b, and c and the common output zero-phase voltage Un and output the monitoring results to the RTDS simulator through the RJ45 interface or USB interface.

[0030] like Figure 3As shown, the photovoltaic physical platform 2 in this embodiment also includes an adjustable load for adjusting the three-phase imbalance. The adjustable load is connected to the low-voltage bus. The adjustable load includes a regulating switch corresponding to each phase. The regulating switch includes multiple loads of different sizes and a multiple-selection switch. The multiple loads of different sizes are each arranged in series with a selection branch of the multiple-selection switch to be used to select a load through the multiple-selection switch to connect to the corresponding phase line, so that the load size of different phases can be adjusted as needed to achieve the purpose of adjusting the three-phase imbalance.

[0031] It should be noted that three-phase imbalance refers to an existing indicator of the degree of three-phase imbalance in a three-phase power system. It can generally be expressed as a percentage of the root mean square value of the negative-sequence fundamental component or zero-sequence fundamental component of voltage and current to the positive-sequence fundamental component. Since this indicator is an existing indicator, its specific calculation details are omitted here and will not be elaborated.

[0032] like Figure 3 As shown, the photovoltaic physical platform 2 in this embodiment also includes a charging pile, which is connected to the low-voltage bus. As an optional embodiment, the charging pile in this embodiment is specifically connected to the low-voltage bus (named "low-voltage I bus" in the figure, specifically a 380V bus) through a branch box, a line impedance simulation panel, and a circuit breaker. The branch box is used to converge the lines to enable multiple devices to access the low-voltage bus. The line impedance simulation panel contains resistors connected in series to each phase line to simulate the line impedance. The circuit breaker is used to control the connection between the entire branch box line and the low-voltage bus.

[0033] See also Figure 3 In this embodiment, the photovoltaic cells of Photovoltaic Platform 2 are distributed rooftop photovoltaics. The figure shows various types, including 20kW, 30kW, 78kW, and 120kW rooftop photovoltaics. Each is connected to the low-voltage busbar via its own photovoltaic converter. Some of these rooftop photovoltaics are also connected to the low-voltage busbar (designated "Low-Voltage I Bus" in the figure, specifically a 380V busbar) via branch boxes, line impedance simulation panels, and circuit breakers.

[0034] See also Figure 3 As an optional implementation, the energy storage battery in this embodiment specifically adopts a 30Kw / 30kW multifunctional power quality management energy storage device to prevent overcharging and over-discharging of the energy storage battery. Since overcharging, over-discharging, large charging, large discharging, etc. cause great damage to the battery, the battery's charge and discharge current, terminal voltage, and battery remaining capacity SOC are detected, and the SOC is set within a certain range. In addition, the energy storage battery can also directly adopt an ordinary energy storage battery, such as a battery, a supercapacitor, etc. As an optional implementation, the simulator in this embodiment is also connected to a portable digital / analog universal recording device.

[0035] In summary, the active distribution network power closed-loop dynamic simulation system of this embodiment includes RTDS simulation software, a four-quadrant simulation power amplifier, an FPGA small-step real-time simulator, a DSP control board, and a tested photovoltaic converter. The active distribution network power closed-loop dynamic simulation system of this embodiment is suitable for rapid strategy verification, wherein the active distribution network main loop model is built in the RTDS simulation software, and then the analog channel of the RTDS interface card is used to transmit the analog value of the simulation software to the power amplifier. The amplified analog value output by the power amplifier is connected to the photovoltaic converter and the primary and secondary fusion circuit breaker. The feedback value of the photovoltaic converter and the primary and secondary fusion circuit breaker is transmitted to the RTDS simulation software and the FPGA small-step real-time simulator through the digital channel of the interface card to complete the closed-loop control. The active power distribution network closed-loop dynamic simulation system of this embodiment can firstly verify the performance of inverters under different power grid environments; secondly, it can simulate distribution networks under complex fault conditions, allowing complex faults that occur in actual power grids to be replicated in the laboratory, providing a feasible basis for engineering practice; and thirdly, it can quickly verify different control strategies through power closed-loop experimental methods, shortening the overall development cycle. This active power distribution network closed-loop dynamic simulation system of this embodiment can be used for both theoretical algorithm research and verification, as well as detection and analysis of active distribution network primary equipment.

[0036] This embodiment further provides an application method of the aforementioned active power distribution network power closed-loop dynamic simulation system, including:

[0037] S1, build the main loop model of the active distribution network based on the RTDS simulation software in the RTDS simulator; write the control strategies of the photovoltaic converter and energy storage converter in the controller platform 3 respectively;

[0038] S2, generates node voltage, current and primary / secondary fusion circuit breaker signals through the main loop model of the active power distribution network, transmits the node voltage and current to the power amplifier through the analog channel of the interface card of the RTDS simulator, performs power amplification through the power amplifier (the amplification ratio of the power amplifier can be pre-set within the amplification ratio operating range of the power amplifier as needed), and then connects to the primary interface of the photovoltaic converter and the energy storage converter respectively, and transmits the primary / secondary fusion circuit breaker signal to the circuit breaker 4 through the digital channel of the interface card of the RTDS simulator;

[0039] S3. The voltage and current signals of PV Platform 2 are collected through the digital channels of the RTDS simulator's interface card under the control strategies of the PV converter and energy storage converter. Based on the voltage and current signals of PV Platform 2 under the control strategies of the PV converter and energy storage converter, test results corresponding to the control strategies of the PV converter and energy storage converter can be obtained. For example, the energy storage charging and discharging characteristics of the energy storage converter's control strategy can be verified.

[0040] The main loop model of the active distribution network can be built in the RTDS simulation software to reproduce the scene according to the actual park-level distribution network topology diagram as needed. As an optional implementation method, the main loop model of the active distribution network built in step S1 of this embodiment refers to building the main loop model of the photovoltaic power generation system, and includes: defining the battery components in the photovoltaic power generation system, setting the parallel number Np and series number Ns of the battery components in the main loop model of the photovoltaic power generation system, thereby forming a photovoltaic array with the parallel number Np and series number Ns battery components; selecting the Boost circuit and full-bridge inverter circuit of the grid-connected inverter from the built-in devices in the RTDS simulation software, building the controller of the grid-connected inverter and selecting the control strategy, connecting the photovoltaic array and the grid-connected inverter to obtain the main loop model of the photovoltaic power generation system, which can be used to simulate and verify that the main loop model of the active distribution network is the component characteristics adopted. As an optional implementation method, the control strategy selected by the controller of the grid-connected inverter in this embodiment is the MPPT (Maximum Power Point Tracking) control strategy. It should be noted that the MPPT control strategy is an existing inverter control strategy. This embodiment only involves the application of the MPPT control strategy and does not involve the improvement of the MPPT control strategy. Therefore, the specific implementation details of the MPPT control strategy will not be described in detail here. The photovoltaic array power generation output system depends on factors such as sunlight intensity (sunshine), environment, temperature, solar cell parameters and / or array configuration, and each of these factors cannot be controlled. Therefore, extracting the maximum power operating conditions under a specific given set becomes very important for the overall economic efficiency of photovoltaics. The maximum power point tracking control strategy (MPPT) can achieve effective tracking. Its principle is based on the incremental conductance method algorithm, which is efficient and does not generate excessive computational burden.

[0041] It should be noted that when building the main circuit model of the active distribution network based on the RTDS simulation software in the RTDS simulator, it is possible to build a main circuit model of the active distribution network under normal working conditions, or to build a main circuit model of the active distribution network under fault working conditions as needed, and it can be configured as needed. According to the system parameters in the active distribution network, the RTDS simulation software can be used to build an RTDS simulation model of the active distribution network (the main circuit model of the active distribution network). The rooftop photovoltaic and energy storage batteries of the photovoltaic physical platform 2 are connected to the power grid at a voltage level of 380V / 220V. The power grid RTDS simulation model is suitable for simulating normal working conditions or fault conditions of the active distribution network.

[0042] As an optional implementation, in this embodiment, when the main loop model of the active distribution network is built based on the RTDS simulation software in the RTDS simulator, the main loop model of the active distribution network built also includes lithium iron phosphate batteries and energy storage converters (PCS), and the RTDS lithium iron phosphate battery model adopts a curve fitting method. The modeling focus of the main loop model of the active distribution network is the voltage-current characteristics, and the battery life modeling and thermal characteristics are not considered. According to the system parameters in the active distribution network, the RTDS simulation software is used to build an RTDS simulation model of the active distribution network. The above-mentioned photovoltaic and energy storage are connected to the power grid at a voltage level of 380V / 220V. The power grid RTDS simulation model is suitable for simulating normal operating conditions or fault conditions of the active distribution network. The RTDS's GTAO and GTDO interfaces then output the active distribution network's node voltages, currents, and signals from the primary and secondary integrated circuit breakers. After power amplification via a four-quadrant power amplifier, the signals are connected to the primary interface of the converter under test. The four-quadrant linear power amplifier unit consists of digital and analog simulation signal processing circuits, a four-quadrant linear simulation power amplifier module, a power monitoring unit, and an output voltage and current measurement unit. The system monitoring unit, primarily comprised of an ARM digital control system, DA conversion, switches, and I / O control circuits, controls the power amplifier system's output voltage, measures output voltage and current, protects the amplifier from overheating, overload, and short-circuit overload, and simulates the system's three-phase manual control output.

[0043] In this embodiment, writing the control strategies for the photovoltaic converter and the energy storage converter into the controller platform 3 in step S1 includes writing the photovoltaic converter control strategy into the FPGA small-step real-time simulator to control the photovoltaic converter, and writing the energy storage converter control strategy into the DSP control board to control the energy storage converter. This allows for rapid verification of the effectiveness of different control strategies. The photovoltaic converter control strategy and the energy storage converter control strategy are the tested objects. For example, the photovoltaic converter control strategy may adopt a constant DC voltage control strategy or a dual closed-loop control strategy with a voltage outer loop and a current inner loop (the voltage outer loop is used to stabilize the DC side voltage, and the current inner loop is used to achieve power decoupling control). This embodiment uses RTDS to build a system model by combining large step size and small step size. The simulation model can achieve a relatively close simulation with the on-site environment. Moreover, the simulation model is simpler than changing the operating environment on-site, and it is safe and reliable. The construction of this model is relatively difficult. This embodiment can perform rapid strategy verification. Because in actual work, it is relatively difficult to change the control strategy of the photovoltaic inverter or energy storage PCS, but it is easier to achieve in simulation. Therefore, this embodiment uses FPGA small step size real-time simulator for control. The FPGA small step size real-time simulator can be simulated using Matlab, and then the simulated algorithm is downloaded to the simulator in real time to apply the new strategy.

[0044] The FPGA small step real-time simulator can be based on the offline simulation verification of Simulink / Starsim, automatically download the control strategy to the controller to generate the control signal and send it to the converter. The control strategy of the photovoltaic converter in this embodiment adopts the principle of dual-loop control. Figure 3 , the control strategy steps of the photovoltaic converter include:

[0045] S101, set the DC side voltage reference value V dc.：ref (obtained through the maximum power tracking control strategy MPPT or a fixed value), the DC side voltage V dc Actual voltage comparison, after passing through the PI controller, the d-axis reference current i is obtained d·.ref ;

[0046] S102, the d-axis reference current i d·.ref , d-axis current i d The difference is obtained by PI controller to obtain the d-axis voltage component, and then the d-axis voltage component and the d-axis electromotive force e of the photovoltaic converter are converted into sd , intermediate variable i q The sum of ωL is used to obtain the d-axis voltage command v d , where the intermediate variable i q ωL is determined by the q-axis current i of the photovoltaic converter. q , current angular frequency ω, and inductance L are multiplied to obtain; the q-axis reference current i q·.ref (value is 0), q-axis current i q The difference is obtained by PI controller to obtain the q-axis voltage component, and then the q-axis voltage component and the q-axis electromotive force e of the photovoltaic converter are converted into sq , intermediate variable i d The q-axis voltage command v is obtained by summing ωL q , where the intermediate variable i d ωL is determined by the d-axis current i of the photovoltaic converter d , current angular frequency ω, and inductance L are multiplied to obtain; among them, the d-axis electromotive force e of the photovoltaic converter sd , q-axis electromotive force e sq is the three-phase electromotive force e of the primary port (AC side) of the photovoltaic converter a 、e b 、e c The d-axis current i is obtained by dq / abc axis coordinate transformation; d , q-axis current i q is the three-phase current i at the primary port (AC side) of the photovoltaic converter a 、i b 、i c Obtained through dq / abc axis coordinate transformation;

[0047] S103, the d-axis voltage command v d , q-axis voltage command v q The three-phase voltage instructions a, b, and c are obtained through dq / abc axis coordinate transformation, and the three-phase switching signal S is generated through SPWM modulation. a 、S b 、S c To control the switching state of the IGBT / thyristor of each phase of the photovoltaic converter.

[0048] In this embodiment, when writing the control strategy of the energy storage converter into the DSP control board, the operating mode of the active distribution network is determined. If the active distribution network is in grid-connected operation, the preset grid-connected control strategy of the energy storage converter is written into the DSP control board. Otherwise, the preset island control strategy of the energy storage converter is written into the DSP control board. For example, the preset grid-connected control strategy uses a PQ dual-loop control strategy to regulate grid-connected power, while the preset island control strategy uses V / F control to stabilize grid voltage. When the microgrid system is grid-connected, the preset grid-connected control strategy is used to optimize the utilization of the various power sources in the photovoltaic platform 2. When the microgrid is in islanded operation, the preset island control strategy ensures that the photovoltaic platform 2 operates stably under various operating conditions to meet load requirements. By changing the different operating conditions of the RTDS, the support role of photovoltaic and energy storage for the grid can be tested.

[0049] In summary, this embodiment uses RTDS to simulate the inverter simulation signal of the output characteristics of the distributed photovoltaic platform. After passing through the power amplifier, it is connected to the energy storage PCS and the photovoltaic converter. At the same time, it uses the FPGA small step real-time simulator and the DSP control board to control it and connect it to the simulated power grid, forming a closed-loop simulation of the power type closed-loop active distribution network. The method of using RTDS equipment, high-speed IO interface, four-quadrant simulation power amplifier and power electronic device controller to build a closed-loop test platform for testing can more fully and comprehensively evaluate the dynamic performance of the controller. This embodiment uses semi-physical simulation to overcome the limitations of offline simulation and pure digital real-time simulation. Its simulation results are closer to the actual situation. In the research of high-power devices in the power system, semi-physical simulation not only improves reliability, but also shortens the R&D cycle and reduces R&D costs.

[0050] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An active power distribution network closed-loop dynamic simulation system, characterized in that: The invention comprises a simulated grid unit (1), a photovoltaic physical platform (2), a controller platform (3) and a circuit breaker (4) for simulating a primary and secondary deep fusion circuit breaker of an active distribution network, wherein the simulated grid unit (1) comprises a simulator and a power amplifier for simulating a main loop model of an active distribution network, the photovoltaic physical platform (2) comprises a photovoltaic converter, a photovoltaic cell, an energy storage converter, an energy storage battery and a low-voltage bus, the photovoltaic cell is connected to the low-voltage bus through the photovoltaic converter, the energy storage battery is connected to the low-voltage bus through the energy storage converter, the output end of the controller platform (3) is respectively connected to the control end of the photovoltaic converter and the energy storage converter, and the voltage and current signal output ends of the photovoltaic converter and the energy storage converter are connected to the input end of the simulator, and the analog signal output end of the simulator is respectively connected to the primary connection end of the photovoltaic converter and the energy storage converter through the power amplifier. The simulator is connected to the controller platform (3) and the circuit breaker (4) respectively. The simulator is an RTDS simulator for running RTDS simulation software. The feedback of the photovoltaic converter, the energy storage converter and the circuit breaker (4) is transmitted through the digital channel of the interface card of the RTDS simulator, and the digital signal is transmitted to the RTDS simulation software and the controller platform (3) in the RTDS simulator to complete closed-loop control. The controller platform (3) includes an FPGA small-step real-time simulator and a DSP control board. The FPGA small-step real-time simulator and the DSP control board are connected to the RTDS simulator respectively. The output end of the FPGA small-step real-time simulator is connected to the control end of the photovoltaic converter for controlling the photovoltaic converter. The output end of the DSP control board is connected to the control end of the energy storage converter for controlling the energy storage converter.

2. The active power distribution network power closed-loop dynamic simulation system according to claim 1, characterized in that: The power amplifier is a four-quadrant simulated power amplifier.

3. The active power distribution network power closed-loop dynamic simulation system according to claim 2, characterized in that: The photovoltaic physical platform (2) further comprises an adjustable load for adjusting the three-phase imbalance, and the adjustable load is connected to the low-voltage bus.

4. The active power distribution network power closed-loop dynamic simulation system according to claim 3, characterized in that: The photovoltaic physical platform (2) further comprises a charging pile, which is connected to a low-voltage busbar.

5. An application method of the active power distribution network power closed-loop dynamic simulation system according to any one of claims 1 to 4, characterized in that: include: S1, build the main circuit model of the active distribution network based on the RTDS simulation software in the RTDS simulator; Writing the control strategies of the photovoltaic converter and the energy storage converter into the controller platform (3) respectively; S2, generates node voltage, current and primary and secondary fusion circuit breaker signals through the main loop model of the active distribution network, transmits the node voltage and current to the power amplifier through the analog channel of the interface card of the RTDS simulator, amplifies the power through the power amplifier and then connects to the primary interface of the photovoltaic converter and the energy storage converter respectively, and transmits the primary and secondary fusion circuit breaker signals to the circuit breaker through the digital channel of the interface card of the RTDS simulator (4); S3, collects voltage and current signals of the photovoltaic physical platform (2) under the control of the photovoltaic converter and energy storage converter control strategy through the digital channel of the interface card of the RTDS simulator.

6. The application method of the active power distribution network power closed-loop dynamic simulation system according to claim 5, characterized in that: Building the main loop model of the active power distribution network in step S1 refers to building the main loop model of the photovoltaic power generation system, and includes: defining the battery components in the photovoltaic power generation system, setting the parallel number and series number of battery components in the main loop model of the photovoltaic power generation system, thereby forming the battery components into a photovoltaic array; selecting the boost circuit and full-bridge inverter circuit of the grid-connected inverter from the built-in devices in the RTDS simulation software, building the controller of the grid-connected inverter and selecting the control strategy, and connecting the photovoltaic array and the grid-connected inverter to obtain the main loop model of the photovoltaic power generation system.

7. The application method of the active power distribution network power closed-loop dynamic simulation system according to claim 6, characterized in that: In step S1, when the control strategies of the photovoltaic converter and the energy storage converter are written into the controller platform (3), the control strategies of the photovoltaic converter are written into the FPGA small-step real-time simulator to control the photovoltaic converter, and the control strategies of the energy storage converter are written into the DSP control board to control the energy storage converter.

8. The application method of the active power distribution network power closed-loop dynamic simulation system according to claim 7, characterized in that: When writing the control strategy of the energy storage converter into the DSP control board, it includes judging the operation mode of the active distribution network. If the operation mode of the active distribution network is grid-connected operation, the preset grid-connected control strategy of the energy storage converter is written into the DSP control board; otherwise, the preset island control strategy of the energy storage converter is written into the DSP control board.

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