Design and Experimental Realization of Robust and Adaptive Control Schemes for Hybrid Series Active Power Filter

Abstract

The degradation in power quality causes adverse economical impact on the utilities and customers. Harmonics in current and voltage are one of the most commonly known power quality issues and are solved by employing passive power filter. But these filters are designed to provide a low impedance path for harmonics and maintaining good power quality with an simplest design and low cost. However PPFs have some drawbacks such as its performance is not better for transient condition of load. So for high-quality power requirements, numerous topologies of active filters i.e. APF connected in series or in parallel (series active filters and shunt active filters) to the non-linear loads with the aim of improving voltage or current distortion. These filters are the most widely used solution, as they efficiently eliminate current distortion and the reactive power produced by non-linear loads. But they are generally expensive and have high operating losses. Henceforth to overcome these drawbacks and to improve the compensation performance with reduced cost of the APFs, a novel HSAPF is introduced by Peng et al., in which APF is connected in series with the source as well as non-linear load and PPF connected in parallel with the load, which behave as power factor correction capacitor. This topology attracted much more attention to endure high load currents and work as a harmonic isolator between source and non-linear load.

Selection of an appropriate reference voltage extraction approach plays an impor- tant role in HSAPF performance. This thesis analyzes three time-domain approaches namely p-q, dual-p-q and HSRF schemes along with one switching pattern technique based on CBPWM method. The objective is to bring down the THD of source current below 5%, to fulfill the condition of IEEE-519 standard recommendations on harmonic limits. The comparative investigation proves that, HSRF is the best reference gener- ation approach in HSAPF irrespective of various grid perturbation conditions. The efficacy of the proposed HSRF-CBPWM based HSAPF are validated through simula-tion as well as experimentation.

Subsequently, Two voltage control techniques namely, CSVPWM and DSVPWM are proposed in HSAPF system along with a fast reference generation approach based on the proposed HSRF method. This CSVPWM and DSVPWM based HSAPF system is employed for compensation of both harmonic voltage as well as current simultane- ously. The efficacy of the proposed HSRF-CSVPWM and HSRF-DSVPWM based HSAPF system has been verified through MATLAB/Simulink power system block en- vironment and also validated by experimentation through dSPACE 1103 controller board. Moreover, to study the performance of DSVPWM over CSVPWM, a com- parative analysis has been performed using both steady state as well as transient conditions. It is observed from the result that the HSRF-DSVPWM based HSAPF is more efficient than HSRF-CBPWM and HSRF-CSVPWM based HSAPF in terms of harmonic compensation and relative power compensation under different operating condition of load.

Subsequently, one robust control approach namely sliding mode control-2 (SMC2) is proposed in HSAPF along with one adaptive DC-link voltage control (ADCV) scheme and one improved reference generation approach based on HSRF. The con- trol scheme is designed with the purpose to achieve gain stability, perfect tracking and distortion free current and load voltage. From the simulation results, it is observed that they are not only adaptive and robust against parametric variation condition of load, but also gives satisfactory THD as well as HCR factor in HSAPF. An experimen-tal laboratory prototype has been developed with dSPACE 1103 controlling platform to verify their adaptivity and robustness. It is observed from the simulation and ex- perimentation that the proposed HSRF-SMC2-ADCV based HSAPF system is found to be more adaptive, robust as compared to the HSRF-SMC2 based HSAPF system. Therefore, the superiority of proposed HSRF-SMC2-ADCV is proved among all the proposed control approaches of HSAPF system.