Recursive Least Squares and Sliding Mode Control for Voltage Compensation of Three-Phase Loads
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Recursive Least Squares and Sliding Mode Control for Voltage Compensation of Three-Phase Loads Alfeu J. Sguarezi Filho1 · Darlan A. Fernandes2 · José H. Suárez3 · Fabiano F. Costa3 · José A. T. Altuna1 Received: 30 October 2017 / Revised: 18 March 2018 / Accepted: 8 August 2018 © Brazilian Society for Automatics–SBA 2018
Abstract This paper proposes a sliding mode control method to be used in the dynamic voltage restorer (DVR) system for regulating voltages of three-phase loads. The voltages produced by the DVR’s inverter are provided by three sliding mode controllers. Each of them operates on a error resulting from the difference between the phase reference and the measured single-phase load voltage. The reference synchronization is carried out by a recursive least-square (RLS) algorithm. Moreover, a flag procedure is applied to assure that the DVR operates only on periods of time where system is in steady state. This is suitable for saving energy. The technique has been evaluated in Simulink for different sag conditions. Finally, an experimental setup of a DVR has been used to evaluate the method, and the results show the effectiveness of it. Keywords Dynamic voltage restorer · Recursive least squares · Sliding mode control · Voltage compensation
List of symbols Variables v Voltage i Current vl Measured load voltage Reference for each phase vl∗ Proportional gain for a PI controller KP Integral gain for a PI controller KI Voltage applied by the inverter vinv eval Evaluation function Sliding surface sn Amplitude VGm αm Phase of the sinusoid Sinusoid frequency mω0 t Sample period φn Vector of regressors Subscripts i Inverter f Leakage
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José A. T. Altuna [email protected]
1
Universidade Federal do ABC, São Paulo, Brazil
2
Universidade Federal da Paraiba, João Pessoa, Brazil
3
Universidade Federal da Bahia, Salvador, Brazil
l c
Load Capacitor
Superscripts Estimated value ∗ Reference value
1 Introduction Voltage sags are common disorders that contaminate electric power system. Investigations indicate that at 92% interruptions in industrial plants can occur due to voltage sags (Chen et al. 2012). The economic impact of industry and public services is serious due to equipment damage and lost production (Tan and Ramachandaramurthy 2012). Two approaches can be considered to eliminate this problem. In the first case, the electric utility can invest in frameworks, such as repowering, construction of redundant lines, renewal of transformers, as well as the improvement of such systems to reduce the occurrence of sags in the electrical grid (Mora and Milanovic 2012). Unfortunately, these solutions are complex and costly. The another type of approach, in general, starting the users of the power system is economically viable for the protection of certain critical loads. An example of this approach is the use of dynamic voltage restorers.
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Journal of Control, Automation and Electrical Systems
The DVR is one of the most popular devices to compensation voltage sag or surge. It has been attracting inc
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