Virtual-impedance-based inverter parallel running method

Abstract

The invention provides a virtual-impedance-based inverter parallel running method, which is characterized by comprising the following steps of: for each inverter, introducing a virtual generator which is connected to a point with the inverter by virtual impedance; performing droop control on the virtual generators, regulating the frequency and voltage amplitude of each virtual generator by utilizing the active power and reactive power of the corresponding inverters respectively, and further calculating voltage directive values of the virtual generators; and based on the voltage directive values, further calculating output voltage directive values of the inverters, and controlling the inverters to output voltages to track the directive values, thereby realizing control over the voltages of the virtual generators and finally realizing the decoupling regulation of the active power and the reactive power. In the method, a control policy for the wireless parallel running of the inverters is realized by utilizing the virtual impedance; and compared with the conventional control methods, the invention is not required to remarkably increase hardware investment, and betters the using effects of droop characteristics to make applicable the droop characteristics to resistive environments.

Description

technical field [0001] The invention relates to a control method for parallel operation of inverters, in particular to a control method for realizing wireless parallel operation of inverters by using virtual impedance. Background technique [0002] With the deepening of the energy crisis and the prominence of environmental problems, distributed generation (DG), which mainly utilizes renewable energy, is developing rapidly. Microgrids control many DGs as an organism and have broad prospects. Since most DGs are inverter-type, it is necessary to study the parallel operation technology of inverters. In addition, parallel operation of inverters is also involved in uninterruptible power supply UPS. The parallel operation technology of inverters based on droop characteristics does not require communication, has good robustness, and is widely used. [0003] The droop characteristic control principle is indirectly as follows: For such as figure 1 In the system shown, the line impe...

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Problems solved by technology

[0024] Adding an isolation transformer between the inverter and the line can make the line inductive, but greatly increases the cost

The article "Current Sharing Control of Uninterruptible Power Supply Parallel System Based on Virtual Impedance" (Proceedings of the Chinese Society for Electrical Engineering, 2009, 29(24): 32-39) published by Yu Wei et al. The circulating current of inverters in parallel operation, but did not study the power (especially reactive power) coordination of inverters in detail; "Multi-loop feedback control strategy of DG inverter in microgrid" published by Wang Chengshan et al. The output impedance of the control converter disclosed in the article of Chinese Journal of Electrotechnical Society, 2009, 24(2): 100-107 is inductive, but the virtual impedance of this method is limited by the control parameters

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