A power electronic grid-connected equipment multi-working condition simulation platform and a control method thereof

Abstract

The application discloses a kind of power electronic grid-connected equipment multi-working condition simulation platform and its control method, the topological structure of platform includes the accompanying measurement system and the system to be measured between parallel in direct current bus and alternating current bus;Accompanying measurement system provides different simulation working condition for the operation of system to be measured, it is composed of several accompanying measurement sub-modules, system to be measured is composed of several measured sub-modules, isolation DC-DC converter includes measured DC-AC converter and isolation DC-DC converter, isolation DC-DC converter protects measured DC-AC converter, isolation, provides direct current voltage for it, by setting control principle, realize master-slave mode, droop mode and hybrid mode multiple control mode.The application provides different running scenarios for the DC-AC converter to be measured, i.e.grid-connected inverter, facilitate to measure its performance index, evaluate its operation reliability and stability;It can pry with small power loss to drive high-power working condition simulation, greatly reduce power loss while reducing the power demand of simulation platform power supply.

Description

Technical Field

[0001] This invention relates to the field of power electronics and electric drive technology, specifically to a multi-condition simulation platform for power electronic grid-connected equipment and its control method. Background Technology

[0002] Currently, actively developing new energy sources, represented by wind and solar power, and accelerating the green and low-carbon transformation of the energy system is a consistent choice for countries worldwide to address climate change and strengthen energy security. With increasing research into renewable energy utilization, the proportion of renewable energy power generation in total electricity generation is rising year by year, including biomass power generation, solar power generation, and tidal power. In recent years, the power output of new energy power generation has gradually increased, but new energy power plants are generally built in areas with low economic development and low electricity demand, resulting in significant energy waste. Therefore, new energy power generation and long-distance power transmission have become the main pathways for new energy consumption, providing significant impetus for the development of power electronic grid-connected conversion equipment.

[0003] The field of power electronic grid-connected conversion equipment is developing rapidly, but the operation of the power grid itself is not stable, with certain randomness and seasonality, and there are harmonic interference, short circuits, open circuits and other situations, which pose a great challenge to the reliability and stability of power electronic grid-connected conversion equipment.

[0004] Currently, there is a lack of reliable and comprehensive testing platforms for the reliability and stability of power electronic grid-connected equipment. These platforms cannot simulate various complex grid operating conditions, and consequently cannot accurately simulate the grid-connected characteristics of various new energy power generation systems. Consequently, the experimental evaluation of the reliability and stability of power electronic grid-connected converters remains incomplete and inaccurate. Furthermore, traditional multi-condition simulation platforms for power electronic grid-connected converters have high power requirements, making it impossible to conduct efficient and high-precision experimental evaluations of high-power power electronic grid-connected equipment.

[0005] Therefore, in order to reduce the power demand of the power supply, simulate the multi-condition operation of power electronic grid-connected equipment, and realize the practical evaluation of the reliability and stability of power electronic grid-connected equipment, it is urgent to propose a multi-condition simulation and testing evaluation platform for power electronic grid-connected conversion equipment. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a multi-condition simulation platform and control method for grid-connected power electronic equipment, offering different operating scenarios for the DC-AC converter under test, i.e., the grid-connected inverter, facilitating the measurement of its performance indicators and the evaluation of its operational reliability and stability. The technical solution is as follows:

[0007] A multi-condition simulation platform for grid-connected power electronic equipment, the topology of which includes a test system and a system under test connected in parallel between a DC bus and an AC bus;

[0008] The accompanying test system provides different simulated operating conditions for the system under test. It consists of several accompanying test sub-modules, and the DC port and AC port of each accompanying test sub-module are connected in parallel to the DC bus and AC bus, respectively.

[0009] The accompanying test submodule includes a first DC filter, a bidirectional isolation DC-DC converter, a second DC filter, a DC-AC converter, an AC filter, and a line impedance connected in series between the DC port and the AC port.

[0010] The system under test (SUT) consists of multiple sub-modules, each including a series-connected DC-AC converter under test and its associated isolation DC-DC converter. The isolation DC-DC converter protects and isolates the DC-AC converter under test and provides it with DC voltage. The DC and AC ports of each sub-module under test are connected in parallel to the DC bus and the AC bus, respectively.

[0011] A control method for a multi-condition simulation platform for grid-connected power electronic equipment, including control principles and control modes;

[0012] The control principles include:

[0013] Principle 1: Define the reference direction of power flow for all submodules, including the submodule under test and the submodule being tested, as follows: DC port power inflow is positive, outflow is negative; AC port power outflow is positive, inflow is negative; the AC port output power of the i-th submodule is denoted as P. i The line loss of the i-th submodule is denoted as p. i Then the DC port input power of the i-th submodule is P. i +p i ;

[0014] Principle 2: For the output power of the AC port, ∑P always holds. i =0, meaning there is no power output at the AC port; for the DC port power, there is always an input ∑(P) i +p i )=∑p i >0, meaning the DC port is the power source, inputting power to the platform;

[0015] Principle 3: For every submodule, p always holds. i <<P i That is, the line loss of the submodule is much smaller than the output power; due to ∑P i =0, then there exist at least two submodules a and b with output power P a With P b The opposite sign of the output power allows it to circulate and be reused between submodules, rather than being dissipated as a loss; therefore, the platform achieves this with minimal line loss ∑p iAt the cost of leveraging high-power P i A circulating flow is formed between sub-modules;

[0016] Principle 4: Use constant current control, constant voltage control, constant power control, or droop control to control the AC ports of all submodules, including the test submodule and the submodule under test; since the AC ports of the submodules are connected in parallel, at most one submodule is allowed to control the voltage of the AC port at the same time.

[0017] The control modes include:

[0018] Master-slave mode: The accompanying test system consists of only one accompanying test sub-module, and the accompanying test sub-module adopts AC constant voltage control; the system under test consists of several sub-modules under test, and the sub-modules under test adopt constant current control, constant power control or droop control;

[0019] Drooping mode: Both the test system and the test system consist of several sub-modules, and both the test sub-module and the test sub-module are controlled by drooping control.

[0020] Hybrid mode: The test system consists of no fewer than two test sub-modules, and the control methods of the test sub-modules are no fewer than two of the four control methods: constant current control, constant voltage control, constant power control, and droop control; the system under test consists of several test sub-modules, and the control methods of the test sub-modules are any one of the four control methods: constant current control, constant voltage control, constant power control, and droop control.

[0021] The master-slave mode is used to simulate arbitrary external voltage characteristics, as well as three-phase asymmetrical operating conditions and impedance simulation; droop control is used to control the droop coefficient and simulate different droop characteristics; the hybrid mode is used to simulate real systems with different control modes to measure the capacity ratio of inverters under different control modes.

[0022] The beneficial effects of this invention are: this invention provides different operating scenarios for the DC-AC converter under test, i.e., the grid-connected inverter, which facilitates the measurement of its performance indicators and the evaluation of its operational reliability and stability; it can leverage high-power operating condition simulation with low power loss, which greatly reduces power loss and reduces the power demand of the simulation platform power supply. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the topology of the multi-condition simulation platform for the power electronic grid-connected conversion equipment of the present invention.

[0024] Figure 2 This is a schematic diagram of the topology of the test module.

[0025] Figure 3 This is a schematic diagram of the topology of the submodule under test.

[0026] Figure 4 This is a schematic diagram of the power flow direction of the platform.

[0027] Figure 5 Platform design based on master-slave model.

[0028] Figure 6 The platform is designed for a drooping mode.

[0029] Figure 7 Platform design for hybrid mode.

[0030] Figure 8 The schematic diagram of the master-slave mode design for a multi-condition simulation platform for power electronic grid-connected conversion equipment.

[0031] Figure 9 The voltage and AC current diagrams for the DC and AC ports are shown to simulate the AC port voltage spurt.

[0032] Figure 10 The voltage and AC current diagrams for the DC and AC ports are shown to simulate the AC port voltage dip. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] The topology of the multi-condition simulation platform for the power electronic grid-connected converter equipment of the present invention is as follows: Figure 1 As shown, its structure is as follows:

[0035] The multi-condition simulation platform of this invention consists of a test system and a system under test (SUT), with their DC and AC ports connected in parallel to the DC and AC buses, respectively. The test system is composed of several test sub-modules with their DC and AC ports connected in parallel, while the SUT is composed of several test sub-modules with their DC and AC ports connected in parallel. In other words, the only difference between the two systems is the different sub-modules that constitute them; the connection method of each sub-module is identical, being parallel.

[0036] The test system and the system under test (SUT) are distinguished based on their functions. The function of the test system is to provide different simulated operating conditions for the SUT; the function of the SUT is to act as the device under test on this platform, while the isolated DC-DC converter within it protects and isolates the DC-AC converter under test and provides it with DC voltage.

[0037] The testing support system consists of several testing support sub-modules, and the topology of the testing support sub-modules is as follows: Figure 2 As shown, it consists of a first DC filter, a bidirectional isolated DC-DC converter, a second DC filter, a DC-AC converter, an AC filter, and line impedance connected in series.

[0038] The system under test consists of several sub-modules under test, and the topology of the sub-modules under test is as follows: Figure 3 As shown, it consists of a bidirectional isolated DC-DC converter connected in series with the DC-AC converter under test.

[0039] The multi-condition simulation platform of this invention must comply with several control principles, as follows:

[0040] Principle 1: Define the power of the submodule (without distinguishing between the submodule under test and the submodule to be tested), such as... Figure 4 As shown, the reference flow direction of submodule power is from the DC port to the AC port. Therefore, power inflow into the DC port is defined as positive, and power outflow as negative; power outflow into the AC port is defined as positive, and power inflow as negative. The AC port output power of the i-th submodule is denoted as P. i The line loss of the i-th submodule is denoted as p. i Then the DC port input power of the i-th submodule is P. i +p i .

[0041] Principle 2: For the output power of the AC port, ∑P always holds. i =0, meaning there is no power output at the AC port; for the DC port power, there is always an input ∑(P) i +p i )=∑p i >0, meaning the DC port is the power source, inputting power to the platform.

[0042] Principle 3: For every submodule, p always holds. i <<P i This means that the line loss of the submodule is much smaller than the output power. Furthermore, according to control principle 2, ∑P... i =0, indicating that there exist at least two submodules a and b, where P a With P b The sign is reversed, meaning that large output power forms a circulating current between submodules and is recycled rather than dissipated as losses. The cost of maintaining this platform's operation is low line losses ∑p. i Therefore, this platform can achieve a small line loss ∑p i At the cost of leveraging high-power P i A circulating current is formed between the sub-modules. Based on this, this platform not only simulates the high-power impact during the actual grid connection process, but also greatly reduces the power loss during the simulation process compared with traditional grid connection simulation methods, while reducing the power requirements of the simulation platform's power supply.

[0043] Principle 4: Control the AC ports of submodules (regardless of whether they are under test or not) using constant current control, constant voltage control, constant power control, or droop control. The AC ports of submodules on this platform are connected in parallel, and at most one submodule is allowed to control the voltage of its AC port at any given time.

[0044] The multi-condition simulation platform of this invention can simulate various operating conditions under the following control modes. The characteristics of the control modes and the simulation conditions are as follows:

[0045] Master-slave mode: such as Figure 5 As shown, the test system consists of only one test submodule, and the test submodule adopts AC constant voltage control; the test system consists of several test submodules, and the test submodules can be any control method other than AC constant voltage control in control principle 4.

[0046] Drooping pattern: such as Figure 6 As shown, both the test system and the test system consist of several sub-modules, and both the test sub-module and the test sub-module are controlled by droop control.

[0047] Hybrid mode: such as Figure 7 As shown, the test system consists of several test sub-modules (no less than two), and the control methods of the test sub-modules are no less than two of those mentioned in control principle 4; the test system consists of several test sub-modules, and the control methods of the test sub-modules can be any control method in control principle 4, provided that they comply with control principle 4.

[0048] All of the above modes can provide various operating condition simulations for the DC-AC converter under test. The master-slave mode can simulate arbitrary external voltage characteristics and is used for three-phase asymmetrical operating condition simulation and impedance simulation, etc.; droop control can control the droop coefficient to simulate different droop characteristics; the hybrid mode can simulate real systems with different control modes, which is convenient for measuring the capacity ratio of inverters under different control modes.

[0049] Example 1:

[0050] like Figure 8 As shown, the platform adopts a master-slave mode. The test system consists of a test submodule controlled by a certain voltage, while the system under test consists of a test submodule controlled by a certain current. This platform can simulate the operating condition of AC port voltage spurs. The voltages of the DC and AC ports and the AC current measurement are as follows: Figure 9 As shown.

[0051] Example 2:

[0052] like Figure 8As shown, the platform adopts a master-slave mode. The test system consists of a test submodule controlled by a certain voltage, while the system under test consists of a test submodule controlled by a certain current. This platform can simulate the operating condition of AC port voltage dips. The voltages of the DC and AC ports and the AC current measurement are as follows: Figure 10 As shown.

Claims

1. A control method for a multi-condition simulation platform of power electronic grid-connected equipment, characterized in that, The platform's topology includes a test system and a system under test connected in parallel between a DC bus and an AC bus; The accompanying test system provides different simulated operating conditions for the system under test. It consists of several accompanying test sub-modules, and the DC port and AC port of each accompanying test sub-module are connected in parallel to the DC bus and AC bus, respectively. The accompanying test submodule includes a first DC filter, a bidirectional isolation DC-DC converter, a second DC filter, a DC-AC converter, an AC filter, and a line impedance connected in series between the DC port and the AC port. The system under test (SUT) consists of multiple sub-modules under test. Each sub-module includes a DC-AC converter under test connected in series and an isolated DC-DC converter. The isolated DC-DC converter protects and isolates the DC-AC converter under test and provides it with DC voltage. The DC port and AC port of each sub-module under test are connected in parallel to the DC bus and the AC bus, respectively. The control method includes control principles and control modes; The control principles include: Principle 1: Define the reference power flow direction for all submodules, including the submodule under test and the submodule being tested, as follows: DC port power inflow is positive, outflow is negative; AC port power outflow is positive, inflow is negative; The AC port output power of each submodule is denoted as... , No. The line loss of each submodule is denoted as Then the first The DC port input power of each submodule is ; Principle 2: For AC port output power, always... That is, there is no power output at the AC port; for the DC port, there is always power input. That is, the DC port is the power source, inputting power to the platform; Principle 3: For every submodule, there is always That is, the line loss of the submodule is much smaller than the output power; because Then there are at least two submodules. Output power and The opposite sign of the sign makes this output power circulate between sub-modules and be recycled, rather than being dissipated as a loss. Principle 4: Use constant current control, constant voltage control, constant power control, or droop control to control the AC ports of all submodules, including the test submodule and the submodule under test; since the AC ports of the submodules are connected in parallel, at most one submodule is allowed to control the voltage of the AC port at the same time. The control modes include: Master-slave mode: The accompanying test system consists of only one accompanying test sub-module, and the accompanying test sub-module adopts AC constant voltage control; the system under test consists of several sub-modules under test, and the sub-modules under test adopt constant current control, constant power control or droop control; Drooping mode: Both the test system and the test system consist of several sub-modules, and both the test sub-modules and the test sub-modules are controlled by drooping control. Hybrid mode: The test system consists of no fewer than two test sub-modules, and the control methods of the test sub-modules are no fewer than two of the four control methods: constant current control, constant voltage control, constant power control, and droop control; the system under test consists of several test sub-modules, and the control methods of the test sub-modules are any one of the four control methods: constant current control, constant voltage control, constant power control, and droop control. The master-slave mode is used to simulate arbitrary external voltage characteristics, as well as three-phase asymmetrical operating conditions and impedance simulation; droop control is used to control the droop coefficient and simulate different droop characteristics; the hybrid mode is used to simulate real systems with different control modes to measure the capacity ratio of inverters under different control modes.

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