Inverter parallel-connection loop current restraining system based on PR control and dual-carrier modulation

Abstract

The invention discloses an inverter parallel-connection loop current restraining system based on PR control and dual-carrier modulation. By means of the inverter parallel-connection mode, the power capacity of an inverter system is increased. Meanwhile, a proportion resonance control device is adopted in an inverter, and therefore low-frequency zero-sequence loop currents can be effectively restrained; the dual-carrier modulation method is used, a zero vector is replaced by a non-zero vector so that the high-frequency zero-sequence loop currents can be restrained. The restraining system has the advantages of being high in direct-current voltage utilization rate and small in zero-sequence loop current.

Description

technical field [0001] The invention belongs to the technical field of inverters, and more specifically relates to an inverter parallel circulation suppression system based on PR control and dual-carrier modulation. Background technique [0002] As the power capacity of the system increases, a single inverter can no longer meet the actual needs. At present, an effective solution is to run the inverters in parallel. However, due to the difference in the output voltage of the inverters, the zero-sequence circulating current problem is introduced between the parallel inverters, which will cause distortion of the inverter output current, unbalanced load current distribution, and in severe cases, it will cause overcurrent in the inverter. Failure, or even damage to power devices. [0003] In order to suppress the zero-sequence circulating current between parallel inverters, scholars at home and abroad have done a lot of research work in this area and proposed many methods. [0...

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Problems solved by technology

However, when it is used for zero-sequence current control, its hysteresis bandwidth is not easy to determine, and the controller design is inconvenient

Moreover, when the carrier frequency is low, the zero-sequence current ripple of the system is large

[0008] There are usually two types of zero-sequence circulating current control based on the PWM modulation algorithm: one is to use the SPWM modulation algorithm, and its principle itself does not generate zero-sequence voltage. This is an open-loop control method, but its DC voltage utilization rate is low; two. It is a SVPWM single-carrier modulation algorithm using PI control. The sensor detects the zero-sequence circulating current of the parallel system and uses the PI controller to suppress the zero-sequence circulating current. It is a closed-loop control method that can effectively suppress the zero-sequence circulating current. However, due to The main components of zero-sequence circulation are the 3rd and 9th fundamental frequency components, and PI control cannot achieve static error-free tracking

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