Asymmetric direct power control method of grid-connected three-phase voltage source converter

Abstract

The invention discloses an asymmetric direct power control method of grid-connected three-phase Voltage Source Converter (VSC). Instantaneous active and reactive powers of VSC inputted from electricity grid are calculated by collecting three-phase network voltage and input current signals of the VSC, and the error signal between the instantaneous active and reactive powers and given active and reactive powers is adjusted by using a proportional resonance adjuster; the output signal of the adjuster obtains the VSC output reference voltage signal of synchronous rotary coordinate system after feedback compensation decoupling, and a switch signal controlling VSC operation condition is produced after spatial vector pulse-with modulation. The method in the invention can eliminate double frequency wave motion of direct-current busbar voltage and instantaneous reactive power due to asymmetric electricity grid voltage without decomposition of positive-negative sequence component, thereby avoiding incoming decomposition delay and error, and thus being capable of improving dynamic response and stable operation ability of VSC in the condition of asymmetric electricity grid failure.

Description

technical field [0001] The invention relates to a control method of a voltage source converter, in particular to an asymmetric direct power control method of a grid-connected three-phase voltage source converter. Background technique [0002] The three-phase voltage source converter (VSC) has been widely used in industrial production due to its advantages of bidirectional flow of power, high current sine degree, adjustable power factor and DC bus voltage, especially in distributed energy grid-connected , high-voltage direct current transmission, servo motor drive and other fields are widely used. At present, most of the control of VSC stays under ideal grid conditions, but because various symmetrical and asymmetrical faults often occur in the actual grid, and some advantages of VSC are difficult to realize under grid faults, it is necessary to carry out operation under grid faults Control research and propose corresponding control technology. Compared with symmetrical grid...

AI Technical Summary

Problems solved by technology

figure 1 In the traditional control method shown, the separation of positive and negative sequences generally adopts 2ω s Frequency notch filter 16 (or low-pass filter, 1 / 4 grid voltage fundamental wave period delay and other methods), in addition to introducing delay in the separation, the control system bandwidth will be affected, which will cause dynamic tracking error and dynamic control effect not ideal

What's more, this method cannot distinguish whether the grid voltage is symmetrical. If the VSC operates in a strictly balanced grid voltage state, the control system will still use the notch filter to separate the voltage and current signals, which will bring unnecessary damage to the normal control of the system. The delay seriously affects the dynamic control performance of the system

In addition, since the traditional VSC control method only has four controllable quantities of the positive sequence d and q axis components and the negative sequence d and q axis components of the current, it can only control the average value of the VSC input active and reactive power. Selectively control the double-frequency oscillation in active or reactive power, but cannot control the double-frequency oscillation in active and reactive power at the same time, and it is even more difficult to eliminate the double-frequency fluctuation in the DC bus voltage

Images