An improved selective harmonic elimination-pulse width modulation (SHE-PWM) scheme has been proposed for a three-phase seven-level cascaded H-bridge (CHB) inverter that enhances the power utilisation capability of the inverter by sharing the desired amount of power among the H-bridge cells and also eliminates both 5th-and 7th-order harmonic components from the inverter output voltage maintaining the desired fundamental voltage component for a wide range of modulation index. Compared to conventional SHE-PWM, this scheme introduces two additional switching in the first cell, while the second and the third cells are switched at advanced switching angles. The differential search algorithm (DSA) technique has been applied to solve the proposed SHE-PWM scheme, and it exhibited comparatively better performance than the algorithm based on genetic algorithm, BEE algorithm and particle swarm optimisation. The effectiveness of the proposed scheme has been verified by both simulation and experimental study on a seven-level CHB inverter. Finally, the proposed scheme has been applied to the closed-loop constant V/f control of the induction motor drive application. It has been established that the proposed scheme is independent of the load power factor angle, and it improved the power conversion efficiency of the conventional SHE-PWM scheme. * reference rotor speed, rpm N r actual rotor speed, rpm T e electromagnetic torque, N-m V ab output line voltage, V i a , i b , i c output phase currents, A IET Power Electron.

This study proposes a selective harmonic minimisation-pulse amplitude modulation (SHM-PAM) technique utilising least number of switching based on optimised waveform pattern for five-level cascaded H-bridge (CHB) inverter to satisfy the NRS 048-2:2003 grid code standard. Here, particle swarm optimisation method is used to evaluate the solution of the optimised switching angles and variable DC-link voltages. A comparison between the proposed SHM-PAM and conventional selective harmonic elimination-pulse width modulation (SHE-PWM) techniques has been carried out by harmonic performance analysis (total harmonic distortion (THD), weighted current THD and harmonic loss factor) and loss analysis (conduction, switching and their cumulative losses) of the switches of five-level CHB inverter under different load power factor angles for medium-voltage application. The performances of the conventional SHE-PWM and proposed SHM-PAM techniques are examined through experimentation using a three-phase five-level CHB inverter. Finally, the proposed technique based 5-level CHB inverter is applied to shunt active power filter using tuned proportional plus parallel resonant current controller for improvement in power quality under non-ideal grid conditions.

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This paper proposes an improved space vector pulse width modulation (SVPWM) based DC link voltage balancing control of a three-phase three-level neutral point clamped (NPC) centralised inverter supplying the generated power from photo voltaic (PV) array to a three-phase utility grid. Two possible schemes have been developed based on the power conversion stage between PV array and the utility grid namely, two-stage (three-level boost converter three-phase three-level NPC inverter) and single-stage (three-phase three-level NPC inverter alone). The comparison between these two schemes has been thoroughly discussed in terms of the control strategies employed, power loss analysis and efficiency. The performance of the centralised inverter under different modes of operation has been investigated by developing the required control strategies for smooth operation. Using the proposed control strategy, the centralised inverter can be operated as a static synchronous compensator (STATCOM) during night time, if needed. The power loss incurred in the power-electronic converters has been analysed for constant and also for variable ambient temperature. The effectiveness of the centralised inverter as an active filter (AF) has also been verified when a three-phase non-linear load is considered in the system.

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The present work describes a control methodology for a hybrid energy storage system (HESS) to improve its transient performance under dynamic load conditions. The proposed coordination control enhanced life cycle performance by segregating the power between battery energy storage systems (BESS) and a supercapacitor (SC). The BESS and SC are connected parallel to each other, and two individual DC–DC bidirectional converters connect them to a common DC bus. The coordination control is established between the controllers of BESS and the SC of HESS, which helps to utilise the usable energy capacity of the HESS. The charging/discharging current of the BESS is controlled within the allowable safety range based on the slope and magnitude of the BESS current. The high-frequency power component is handled by the SC, which helps to reduce the extra exhaustion on the BESS during operation with a higher current. The proposed coordination control of HESS is validated through simulation and the results show the effectiveness of the proposed controller.