A control method and system for an h-bridge three-level active power filter

Abstract

The present invention discloses a control method of an H-bridge three-level active power filter and a system. When DC bus voltage phase to phase balance is carried out, through detecting the deviation between each phase DC bus voltage and DC bus average bus, the given amount of fundamental negative sequence current is determined, the system is a dual-closed-loop structure, thus the system robustness is high. Compared with a traditional method based on negative sequence voltage injection, the performance of a current loop is not affected. Compared with a traditional method based on zero sequence voltage injection, the ability of phase to phase balance control is strong. When the load current harmonic detection is carried out, a fundamental positive sequence component and a fundamental negative sequence component are detected respectively in a dual-dq-axis coordinate system, and thus the precision of the harmonic detection is high. Since the fundamental negative sequence component is detected in a negative sequence dq-axis coordinate system, a fundamental negative sequence current component does not appear in a harmonic command, and thus the adverse effects to the DC bus voltage phase to phase balance control brought by the fundamental negative sequence current component is eliminated.

Description

technical field [0001] The invention belongs to the technical field of power quality control, and more specifically relates to a control method and system for an H-bridge three-level active power filter. Background technique [0002] With the development of power electronic devices, a series of non-linear loads such as switching power supplies and rectifier loads are increasingly connected to the power grid, which brings a large number of harmonic problems to the power grid. While increasing line losses, it also threatens To the safe and stable operation of the power grid. Active power filter is one of the best ways to solve such power quality problems. It can compensate harmonics at full frequency points, and has high compensation accuracy and fast response speed. Most traditional active power filters use two-level inverters, which have problems such as high DC bus voltage, large du / dt, high rated voltage of selected power devices, and low quality of output voltage wavefor...

AI Technical Summary

Problems solved by technology

However, since the inverter control of this topology has three DC buses, its control complexity is relatively high, especially how to keep the voltage of the three DC buses consistent is a difficult problem

The document "Zero-sequence and negative-sequence voltage injection cascaded grid-connected inverter DC side voltage balance control" gives the method of zero-sequence voltage injection and negative-sequence voltage injection to solve the problem of this type of topology inverter. DC bus voltage imbalance problem, but this method requires the inverter to output a certain fundamental current, while the current output by the active power filter is mostly harmonic current

In addition, the traditional load current harmonic detection method only extracts the fundamental positive sequence component of the load current by extracting the DC component of the dq axis, but does not take into account the negative sequence fundamental current component in the dq axis coordinate system. Due to the existence of frequency multiplier components, the obtained harmonic detection results are not accurate. At the same time, the existence of negative sequence components has a negative impact on the phase-to-phase balance of the DC bus voltage, reducing the harmonic compensation accuracy of the active power filter.

Images