To reduce the harmonics injected by non-linear loads, power quality improvement devices like shunt active power filters (SAPFs) are commonly employed. This study presents a digital signal processor (DSP) TMS320LF2407A based hardware implementation of current error space phasor-based hysteresis controller for SAPF. The proposed controller-based SAPF allows precise compensation of harmonic currents. Design considerations for practical implementation of the proposed space phasor-based current error hysteresis controller for SAPF are explained here. Performance analysis of space phasorbased current error hysteresis controller for SAPF is explained in the study. The controller's self-adaptive nature is studied for different logics of necessary sector changes. Here, the versatile nature of the controller is proved by analysing its performance for different reference compensating current generation methods. The proposed controller works on the principle of switching voltage vectors adjacent to the desired output voltage vector of SAPF (voltage vector at the point of common coupling). This strategy helps in restricting the current error within the desired hexagonal boundary. A comparative study of DSP-based implementation for two different schemes of reference compensating currents generation is presented in this study. Instantaneous reactive power theory and Fryze current computation methods are chosen for this comparative study. Experimental results of reference compensating currents generated by different strategies using DSP are presented in this study.

This paper investigates different types of Flexible AC transmission System (FACTS) controllers with focus on various operational and control aspects of static synchronous compensators (STATCOM) to different performance characteristics like power transfer capability, voltage regulation, reactive power management, stability limits, power factor improvement etc. In addition, various features related to STATCOM like converter topologies, reference compensating signal generation schemes, controllers, and generation of switching signals are reviewed.

Shunt Active Power Filters (SAPF) are commonly employed to reduce current harmonics, which are injected in the utility by nonlinear loads. This paper presents performance of current error space phasor based hysteresis controller for threelevel Neutral Point Clamped (NPC) and Flying Capacitor (FC) converters used in SAPF. Operation of two-level converter based SAPF is also demonstrated in this paper with the proposed controller. The proposed controller is self-adaptive in nature and does not require any particular calculation of Point of Common Coupling (PCC) voltage vector (E) because of proper sector change detection logic used. The proposed current controller overcomes inherent problem of random voltage vector switching encountered in conventional hysteresis current controller based SAPFs. It allows switching of only adjacent voltage vectors for position of PCC voltage vector in a given sector of voltage space phasor of SAPF. Region detection logic causes switching of SAPF voltage vector which keeps the current error well within the prescribed hexagonal boundary. The SAPF based on the proposed controller provides adequate compensation for removal of harmonics produced by nonlinear loads. Detailed theoretical analysis and simulation studies are presented in the paper and the claimed performance of the proposed controller is evident from the simulation results provided in the paper. This paper addresses issues like dc-link capacitor voltage unbalance for NPC and clamping capacitor voltage unbalance for Flying Capacitor based SAPF and also provides solution. The proposed controller can be easily extended for any multi-level converter topology used for SAPFs.

This paper provides an insight on various random pulse width modulation techniques and their effect on spreading the harmonic spectrum for various applications like drives, hybrid electric vehicles and renewable energy sources, for two level as well as three level inverter. Acoustic noise reduction, electromagnetic interference conducted and torque ripple are obvious advantages of random pulse width modulation (PWM). PWM converters with multilevel topology can meet with global quality standards for power supplies. The random PWM technique provides additional advantages. Among others, it may be implemented to achieve switching loss equalization in power switches for cascaded H-Bridge multilevel inverters. This paper provides in depth understanding for different random PWM techniques and their applications.

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