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Pulse width modulation controlled inverters produce common-mode voltage, which has been reported to cause many system drawbacks. This voltage along with high dv/dt raises leakage currents which can result in serious problems such as motor damage and electromagnetic interference to the surrounding equipment. Also common-mode voltage is responsible for bearing failure and overvoltage stress to the winding insulation of an AC motor. Therefore knowledge of reducing common-mode voltage is essential to provide a correct insight into the design of the drive system. Previous methods for common-mode voltage reduction cause extra harmonic in output currents, since they are based on voltage control. This study proposes new modulation strategies based on predictive current control (PCC) for three-phase pulse width modulation inverters-fed AC motor drive systems which mitigate the common-mode voltage and moreover, decrease the harmonic contents of output currents. As PCC can be employed in low voltage and medium voltage drive applications, the proposed strategies have been implemented on two-level and three-level neutral-point clamped inverter. A comparative study of proposed techniques with traditional ones has been carried out from the output current total harmonic distortion point of view. Simulation results and mathematical analyses, along with experimental tests for two-level inverter using Texas Instrument DSP model TMS320F28335, confirm that the new strategies improve behavior of drive systems in comparison with previous methods.

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Summary This paper proposes a new control strategy to consider the doubly fed induction generator (DFIG) wind generation contribution in frequency control and regulation of multi‐area interconnected power system when the wind power is the main generation of one area. Based on frequency requirements and system conditions, the proposed control approach determines whether to switch the wind generation into the maximum power tracking mode or the frequency regulation mode. In the frequency regulation mode, the output power of the wind power plant is controlled through a PID controller. At this mode of operation, the input signal of the PID controller is the system frequency. Finally, the PID performance is optimized by tuning its parameters through fuzzy and Zigler–Nicholes methods. The proposed control strategy is applied to a multi‐area control system including thermal and wind power generations. The simulation results indicate that the proposed control scheme works desirably and thereby wind generation can effectively participate in load frequency control (LFC). Copyright © 2014 John Wiley & Sons, Ltd.

Hysteresis Current Control (HCC) is widely used due to its simplicity in implementation, fast and accurate response. However, the main issue is its variable switching frequency which leads to extraswitching losses and injecting high-frequency harmonics into the system current. To solve this problem, adaptive hysteresis current control (AHCC) has been introduced which produces hysteresis bandwidth which instantaneously results in smoother and constant switching frequency. In this paper the instantaneous power theory is used to extract the harmonic components of system current. Then fixed-band hysteresis current control is explained. Because of fixed-band variable frequency disadvantages, the adaptive hysteresis current control is explained that leads to fixing the switching frequency and reducing the high-frequency components in source current waveform. Due to these advantages of AHCC, the switching frequency and switching losses will be diminished appropriately. Some simulations are done in MATLAB/Simulink. The Fourier Transform and THD results of source and load currents and the instantaneous switching frequency diagram are discussed to prove the efficiency of this method. The Fourier Transform and THD results of source and load currents are discussed to prove the validity of this method.

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