APF (Active Power Filter)parallel system and control method thereof

Abstract

The invention discloses an APF (Active Power Filter) parallel system. The APF parallel system comprises a plurality of APFs connected with a power grid, and a detection control unit. High-voltage ends of direct current support capacitors of all the APFs are commonly connected, and low-voltage ends of the direct current support capacitors of all the APFs are commonly connected. The parallel system provided by the invention only needs a set of detection control equipment to control the plurality of APFs, thus, less hardware resource is occupied. Simultaneously, the invention further discloses a control method of the APF parallel system. The control method comprises the following steps of: (1) obtaining state information of the power grid, the loads and the parallel system; (2) extracting a current instruction from the load current; (3) calculating a current error signal; (4) performing repetitive control and PI (proportional integral) regulation on the current error signal to obtain a modulation signal; (5) forming a PWM (Pulse-Width Modulation) signal. The method provided by the invention has higher reactive compensation precision and harmonic suppression capability, and can effectively suppress system circulating current.

Description

technical field [0001] The invention belongs to the technical field of reactive power compensation, and in particular relates to an APF parallel system and a control method thereof. Background technique [0002] The power quality problem is attracting more and more attention. Compared with traditional passive filters and reactive power compensation devices, active power filters (Active Power Filter, APF) can better eliminate harmonics, reactive power and unbalanced currents generated by nonlinear loads, and improve grid power quality , can realize dynamic tracking and compensation of load reactive power and harmonics. [0003] The structure of the active power filter is as figure 1 As shown, it is composed of a converter and a filter device. The grid side of the converter is connected to the three-phase grid through the filter device, and the DC side is connected in parallel with a DC support capacitor C dc ; In addition, the active power filter also needs a detection and...

AI Technical Summary

Problems solved by technology

There are three problems in large-capacity active power filters: (1) As the compensation current increases, the switching frequency of the power switching device should be appropriately reduced to meet the heat dissipation requirements; this will increase the control delay on the one hand, and on the other hand On the one hand, the lower frequency switching ripple brings difficulty to filtering, which will seriously affect the performance of APF; (2) The large-capacity converter will bring more severe tests to the heat dissipation of power switching devices, and there will be more serious (3) When excessive compensation current passes through the filter device, due to the high frequency of the current, passive components such as the filter device will generate higher heat, and heat dissipation needs to be considered

Wanjun Lei et al. proposed an APF in an article titled Development of 100kVA active filter with digital controlled multiple parallel power converters (Power Electronics Specialists Conference, PESC 04.2004IEEE 35th Annual.2004.p.1121-1126Vol.2.) Parallel technology, which detects the output compensation of each APF for control, and uses carrier phase shifting technology to realize multiple parallel connections; but its disadvantage is that multiple sets of detection and control equipment are required, which takes up too much hardware resources, and carrier phase shifting at the same time Technology will intensify the circulation and require more control resources, so it needs dual DSP to meet normal work, which brings difficulties to system design

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