Abstract
<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Load harmonic currents and load unbalances reduce power quality (PQ) supplied by electrical networks. Shunt active power filters (SAPFs) are a well-known solution that can be employed to enhance electrical PQ by injecting a compensation current at the point of common coupling (PCC) of the SAPF, the load, and the electrical grid. Hence, SAPF controllers must determine the instantaneous values of the compensation reference current, including nondesirable components of the load current. A family of SAPF controllers, which evaluates the compensation reference current using synchronous rotating frames (SRFs), employs a structure based on Park transformations: direct transform, low-pass filtering (LPF), and inverse transform. The cutoff frequency and the filter order of the LPF stage must be designed properly in order to obtain an accurate reference current and a fast dynamic response of these SAPF controllers. This paper proposes a recursive implementation of the direct Park transformation that avoids the filtering stage and allows accurate SRF controllers to be designed. Moreover, the proposed implementation is not dependent on PCC conditions. The proposed implementation is evaluated using a three-phase, three-wire SAPF and compared with LPF-based controllers by simulation and experiment. </para>
Highlights
Shunt active power f ltering is a well-known technique employed to compensate load harmonic currents, load unbalance or load reactive power at the point of common coupling (PCC) of the Shunt Active Power Filters (SAPFs), the electrical grid and the distorting load [1] [2]
This paper focuses on single synchronous rotating frames (SRFs) based methods for harmonic currents compensation, where the compensation reference current i∗αβ(k) can be evaluated by subtracting the target source currentiαβ(k) from the load current iαβ(k)
It is considered that only harmonic compensation is required
Summary
Shunt active power f ltering is a well-known technique employed to compensate load harmonic currents, load unbalance or load reactive power at the PCC of the SAPF, the electrical grid and the distorting load [1] [2]. 1.b, consists of direct DQ and inverse DQ−1 Park Transformations, which allow the evaluation of a specif c harmonic component of the input signal iαβ(k), and a low-pass f ltering stage LP F. Is the number of samples which should be considered at the fundamental grid frequency, synchronized with the fundamental component of the grid voltage These signals can be applied to iαβ(k) through the direct Park Transformation (DQ) in order to obtain a frequency shifting effect of the harmonic components of the load current. This paper presents a recursive implementation of the DQ transform, DQr, which avoids the low-pass f ltering stage in SRF based structures This implementation allows an accurate evaluation of specif c harmonic components independent of PCC conditions. The mathematical analysis, simulation and experimental results obtained on a three-phase three-wire SAPF are given
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