Novel voltage source control method of LCL type grid-connected converter

Abstract

The invention provides a novel voltage source control method of an LCL type grid-connected converter, which takes the DC side voltage and output reactive power of the converter as control targets, and adopts a three-ring control structure of a reactive power outer ring, an AC voltage middle ring and a grid-connected current inner ring. The ratio of the direct current side voltage to the reference value is multiplied by the rated angular frequency of the power grid voltage and then passes through an integrator, and the output of the integrator serves as the phase of conversion from the three-phase alternating current voltage and current to the two-phase voltage and current; the reactive power control outer ring controls the adjustment of reactive power and active power output by the grid-connected converter, the output of the filter capacitor voltage control ring is used as a reference value of the current inner ring, and the output of the current ring is used as a trigger pulse of the grid-connected converter after rotation transformation and modulation. According to the grid-connected control method, the converter shows external characteristics of a voltage source, autonomous synchronization of the converter to the power grid can be dynamically realized according to the direct-current capacitance, and the method has an amplitude limiting function on the alternating-current side current of the converter.

Description

technical field [0001] The invention relates to the technical field of electrical control of new energy grid-connected converters, in particular to a novel voltage source control method of an LCL-type grid-connected converter with the functions of autonomously synchronizing the grid and limiting output current. Background technique [0002] The conventional control strategy of the converter adopts a phase-locked loop (PLL) to synchronize with the power grid, direct it, and realize power regulation in the form of current injection, reflecting the characteristics of a current source. This control strategy can be called current source control. Current source control belongs to grid following control, lacks active inertia support capability, and is suitable for grid environment dominated by synchronous generators. The voltage source control directly controls the amplitude and phase of the output voltage of the converter by simulating the synchronous generator equation. It has th...

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Problems solved by technology

However figure 1 The control architecture of the grid-side converter is relatively simple. The phase θ output by the DC voltage control loop and the voltage amplitude output by the reactive power control directly generate a modulation voltage. This control architecture lacks a current control loop and cannot limit the output current of the converter. piece

When abnormal conditions such as sudden voltage changes occur in the power grid, the converter is prone to overcurrent, which will damage the converter

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