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This paper proposes a novel 12-pulse hybrid-mode thyristor rectifier (HMTR) that can operate in either parallel mode or series mode with the help of a switch. No matter in which mode it operates, the proposed 12-pulse HMTR keeps the same pulses in the load current. It is designed to operate in parallel mode when low output voltage is required and in series mode when high output voltage is required. This way, the firing angle of the thyristor is reduced and thereby the total harmonic distortion (THD) in the input current is improved. The predictive current control strategy is also proposed to achieve the hybrid-mode operation. Fast current response is achieved both in parallel and series modes as well as in transitions between parallel and series modes. The concept of the proposed predictive current control scheme is quite simple and understandable, and easy to be implemented by a microprocessor. This paper includes analysis, simulation, experiment, and a comparison of the proposed control method with the conventional PI controller. Results from both simulation and experiment demonstrate the validity of the proposed 12-pulse HMTR and the effectiveness of the predictive current control algorithm.

This paper proposes a new structure of serial hybrid active power filter which can reduce the power rating of the active power filter dramatically, and has good performance for harmonic suppression. The principle and designing rules are analyzed. The proposed structure is rational and feasible for high kVA applications. Simulation results are presented too.

This paper discusses the robust H ∞ control problem for discrete-time switched interval system. The multiple Lyapunov function method is combined with the Finsler's Lemma to generate several new results which provide extra degree of freedom for stability analysis and control synthesis. A new sufficient condition is obtained for the unforced discrete-time switched interval system, then, based on the above discussion, the robust H ∞ control synthesis via state feedback is studied for the closed-loop switched interval system. Finally, two simulation examples are given to illustrate the validity of the results.

Position sensorless PM brushless DC motor generates pilsating current in the course of nature commutation, which causes torque ripple. In order to reduce the torque ripple, the current during commutation is controlled by certain methods which need current sensors usually. This paper proposed a novel and low cost method which can reduce torque ripple by changing the duty cycle during comutation. Experimental results show that this method is easily used to reduce the pulsating current and torque ripple during comutation without current sensors.

Usually, the deadbeat control strategy is applied to three-phase voltage source PWM rectifiers. Often, deadbeat control uses a forward predictive algorithm of the reference current to compensate the control delay. Because of the uncertainty of reference variations, single predictive algorithm may cause large current overshoot or phase delay in different reference changes. The paper obtained the relationship among the prediction parameter, the current overshoot, and the phase delay after comparing and analyzing three commonly used predictive algorithms. Based on it, a new predictive algorithm was introduced using fuzzy control method. This algorithm chose appropriate prediction parameter according to different reference current changes, which was a tradeoff between current overshoot and phase delay. As a result, the maximum value of current overshoot was limited and the phase delay was optimized. Finally, an experimental prototype of a three-phase voltage source PWM rectifier controlled by a TMS320F2812 DSP was built and tested. The experimental results verified the validity of the proposed control approach.

This paper presents a comprehensive analysis on torque ripples of brushless dc motor drives in conduction region and commutation region. A novel method for reducing the torque ripple in brushless dc motors with a single current sensor has been proposed by adding BUCK converter in the front of 3-phase inverter. In such drives, torque ripple suppression technique is theoretically effective in commutation region as well as conduction region. Effectiveness and feasibility of the proposed control method is verified through experiments.

Using adjustable speed scheme in high power motor drive can not only save energy greatly but also improve the dynamic performance of the motor. Recently, medium-voltage inverter becomes the most popular scheme for high-power motor drive, but in some especial fields multi-phase motor drives have more advantages. In this paper a vector control method of six-phase synchronous motor (SM) based on three-level inverter is studied and some key techniques are analyzed in detail such as air gap flux-oriented vector control of six-phase SM, space vector pulse-width modulation (SVPWM) of six-phase three-level inverter and its neutral-point control. Then a 690 V/200 kW three-level inverter of six-phase SM is developed, and experimental results verify the techniques presented in the paper

This paper deals with a 3KW power factor correction (PFC) circuit based on the isolated full-bridge (FB) converter. The operation principle of the very converter is simply analyzed. Digital design consideration based on the small-signal dynamic modeling of the isolated PFC converter is specified in this paper. Implementation strategy and cost effectiveness of digital control for the single-stage PFC converter are studied. A transformer is used to provide galvanic isolation enables a wide range of output voltages, either lower or higher than the input voltage, allowing multi-output solutions. The adopted digital control strategy features fast dynamic response and excellent steady regulation characteristic without multiplying the input feedforward. High power factor and high efficiency are both achieved by combining FB main circuit and digital control. That flexibility is greatly increased can further contribute to system integration research on distributed power system[1]. Without multiplying the input feedforward, fast dynamic can be achieved due to the flexibility of digital control strategy. The above excellent performances are verified by an experimental prototype, whose output power is 3KW and PFC operating frequency is 110K.

A new method of neutral-point balance based on hysteresis-band control for NPC three-level inverters is proposed in this paper. The neutral-point is balanced by PWM control according to the direction of neutral-point current and the state of neutral-point voltage. The neutral-point current direction is got by output current of each phase and PWM group. The state of neutral point voltage is decided by hysteresis-band control. PWM group is regrouped when it goes against the neutral point potential balance. Being independent of PWM mode, this scheme can be used in any PWM mode for neutral-point balance control. The amplitude of neutral point voltage ripple and the switch times of IGBT can be adjusted by regulating the width of hysteresis-band. The method is verified by simulation and experiment of three-level converter with SHEPWM control scheme.

The paper presents a novel commutation torque ripple suppression scheme in BLDCM. In the proposed method based on the DC current sensing, smooth commutation is realized by combining two effective measures with together. The two methods are commutation current prediction method and the negative DC current elimination scheme. The theoretical and mathematical analyses are given in detail. The experimental results are demonstrated to verify the validity of the proposed method

This paper focuses on the relationship of three-level and two-level pulse width modulation (PWM) methods. A scheme of three-level space-vector PWM (SVPWM) based on one chip DSP is proposed depends on two groups of three-phase traditional PWM cell integrated in DSP. Neutral-point balance is achieved by adjusting the output voltage vectors based on the neutral-point current judging. This method simplified the digital control of three-level inverters, and improved the reliability of system. 660 V three-level converter with full digital control is proposed to verify the scheme.

This paper proposes a new structure of serial hybrid active power filter which can reduce the power rating of the active power filter dramatically, and has good performance for harmonic suppression. The principle and designing rules are analyzed. The proposed structure is rational and feasible for high kVA applications. Simulation results are presented too.

Some important factors of a series hybrid active power filter are presented in this paper for the case when the load is varied in a wide range and/or the source voltage is seriously distorted. Special designs of passive filters, adaptive control of parameter and multi variant control are discussed in detail. The filter is stable, has good performance, and causes small, capacitive reactive current. The simulation and experimental results accorded with the theoretical analysis results.