A control method for grid-connected cut-in of virtual synchronous machines

Abstract

The invention relates to the field of electrical control, and aims to provide a control method for grid-connected switching-in of a virtual synchronous machine. The method comprises the steps of switching on a direct-current circuit breaker and an alternating-current circuit breaker in sequence, and sampling a direct-current capacitor voltage and an alternating-current capacitor voltage after switching-on; if a direct-current voltage sampling value is larger than a rated direct-current voltage by 0.9 times, and the sum of absolute values of phase voltage sampling values of three phases of an alternating current is larger than a rated phase voltage amplitude of the alternating current, the direct-current circuit breaker and the alternating-current circuit breaker are considered to be switched on; a phase-locked loop is started to work stably, an angle difference between a rotor phase of the virtual synchronous machine and a power grid voltage phase obtained by the phase-locked loop is detected, and comparison is carried out; and if the angle difference is within 0.1 rad, the virtual synchronous machine is switched on for control, otherwise, the operation is not executed. The methodis based on a common three-phase inverter grid-connected topological structure, so that any hardware cost is not increased, and a control algorithm is simple to use; and the sampling accuracy of a control system can be improved, so that smooth grid connection of a VSG is realized.

Description

technical field [0001] The invention belongs to the field of electrical control, and in particular relates to a control method for virtual synchronous machine grid-connected cut-in. Background technique [0002] With the crisis of fossil energy, distributed energy represented by photovoltaics, wind energy, and tidal energy has shown strong advantages, including economy, environmental protection, and sustainability. As one of the powerful countries in developing countries, our country consumes a lot of energy. In the case of increasing shortage of traditional energy sources, we must seek diversified development of energy sources. The country has also promulgated various policies and measures to promote the promotion of distributed energy sources. [0003] Distributed energy is controlled by power electronic equipment such as inverters and integrated into the grid. The size of the power flow is limited by the type of energy connected to the source of the inverter. For example,...

AI Technical Summary

Problems solved by technology

However, during the dynamic adjustment process, if the VSG starts to cut into the power grid, the output frequency of the VSG is not necessarily consistent with the power grid frequency, and there is even a large phase angle difference. Smoothly connected to the grid, even causing adverse effects on the grid

[0006] In addition, in actual control, factors such as temperature changes in the control system are often encountered, resulting in the drift of the sampling offset value, which further affects the control accuracy.

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