A Hybrid Unified Power Quality Conditioner with Short Circuit Current Limiting Function

Abstract

The invention discloses a hybrid unified power quality regulator with the function of short-circuit current limiting. The current unified power quality conditioner, regardless of the three-phase three-wire system or the three-phase four-wire system, cannot achieve individual control of a certain phase. The present invention includes a parallel converter, three single-phase H-bridge inverters with short-circuit current limiting function and three-phase series transformer; the three single-phase H-bridge inverters with short-circuit current limiting function DC The side is connected in parallel to the DC bus of the parallel converter, and the AC side is respectively connected to the secondary side of the three-phase series transformer; the single-phase H-bridge inverter with short-circuit current limiting function is composed of the H-bridge inverter and the H-bridge The AC side of the type current limiter is connected in series, and its DC side contains a short-circuit current release circuit. The regulator of the invention can realize independent control of the three phases at the series side and can output zero-sequence components. Additionally, in the event of a single-phase or two-phase short-circuit fault, the non-faulted phases can continue to operate without requiring the entire regulator to drop out.

Description

technical field [0001] The invention belongs to the field of power quality control devices, in particular to a hybrid unified power quality regulator with short-circuit current limiting function. Background technique [0002] Unified power quality conditioner (unified power quality conditioner, UPQC) combines the functions of active power filter (APF) and dynamic voltage restorer (dynamic voltage restorers, DVR), it combines series compensation function and parallel compensation function Combined, it can solve the problems of voltage mutation, voltage fluctuation and flicker, short-term voltage interruption, and improve voltage unbalance and harmonic level. It is a power quality control device with better comprehensive performance. [0003] At present, the research on UPQC is mainly focused on the three-phase three-wire system. Since there is no zero-sequence path, the zero-sequence component cannot be output, which limits its application in the fields of voltage unbalance c...

AI Technical Summary

Problems solved by technology

[0003] At present, the research on UPQC is mainly focused on the three-phase three-wire system. Since there is no zero-sequence path, the zero-sequence component cannot be output, which limits its application in the fields of voltage unbalance compensation and harmonic compensation.

In order to solve this problem, a three-phase four-wire UPQC with a three-arm structure at the midpoint of the DC side appeared, but its control strategy is more complicated, and the three-phase cannot be completely decoupled

Moreover, regardless of the three-phase three-wire UPQC or the three-phase four-wire UPQC, individual control of a certain phase cannot be realized; in addition, when a single-phase short-circuit fault occurs on the AC side, the other two phases cannot continue to work, causing the entire UPQC device to exit operation

[0004] More importantly, like other series-type flexible AC transmission systems (FACTS), since they are connected in series in the line, once a short circuit occurs on the load side, the short-circuit current of the system will all flow through the series part of the device. It is fatal for power electronic devices with low overload capacity, and will inevitably cause damage to UPQC series converters, which also limits the application of UPQC and even all series FACTS devices in power systems

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