Control method of virtual synchronous motor based on virtual impedance voltage source converter

Abstract

The invention discloses a virtual impedance voltage converter-based control method of a virtual synchronous motor. Output voltage and current of a voltage converter is controlled to have the characteristic of a synchronous motor through electric and mechanical main parts of the virtual synchronous motor, wherein the electric part comprises a novel virtual impedance simulation algorithm, a conventional converter current inner ring and a modulation strategy and the mechanical part comprises a power calculating module, a rotor mechanical equation and a virtual damping module. The virtual impedance voltage converter-based control method of the virtual synchronous motor can be used for simulating winding impedance without introducing a differential term of current output by the converter, so that the influence on impedance simulation by an extra low pass filter is overcome, and the current inner ring control of a parallel converter is not sacrificed, and therefore, alternating current is controlled, and the converter has the capacity of preventing current fluctuation, overcurrent and even impact without quick current inner ring control. A silent pole motor and a non-salient pole motor can be simultaneously simulated.

Description

Technical field: [0001] The patent of the present invention belongs to the field of virtual synchronous motor control, and specifically relates to a virtual synchronous motor control method based on a virtual impedance voltage type converter. Background technique: [0002] Most of the distributed new energy generation units are connected to the distribution network and are close to the load. As the proportion of distributed new energy access increases, the distribution network develops from a traditional vertical structure to a grid structure. The most typical feature of the grid structure distribution network is that the power generation units are no longer the traditional few large-capacity units, but the majority of small-capacity units. In addition, most distributed generation units are connected to the grid through power electronic converters, so their grid-connected characteristics are determined by the control method of the converter. Usually, when distributed new e...

AI Technical Summary

Problems solved by technology

These make the distribution network face some new problems: First, the distribution network has a greater impact on the reliability, stability and security of the entire power grid system. The power imbalance in the transient process of the system; the second is that the intermittent characteristics of new energy have brought serious voltage fluctuations to the high-impedance distribution network; the third is that the power flow of the distribution network has changed from a simple one-way to a complex two-way, It affects the voltage control, relay protection, network loss and power quality of the distribution network

Among them, the electromagnetic characteristics adopt the impedance simulation method, and they are all based on the simulated stator winding, including voltage type and current type schemes, but each scheme has its inherent disadvantages: all voltage type impedance simulation methods, because the calculated voltage commands are all The bridge wall voltage is directly controlled through PWM modulation. The current loop control mode of the traditional converter is sacrificed, and the AC current is not directly controlled, which will cause fluctuations, overcurrent or even impact on the AC current, especially at the grid voltage at the grid-connected point. When the amplitude or phase changes suddenly, it will seriously affect the normal operation of the converter; while the current-type impedance simulation method completely replicates and simulates the impedance characteristics of the synchronous machine, there is already an obvious lag in the impedance simulation link. In order to ensure the overall control If the delay of the current control loop is within a certain range, the response speed of the current control loop must be very high.

However, none of the existing current loop control strategies can meet such high requirements, resulting in a large delay in the control method, insufficient current regulation, and poor control effect.

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