PERFORMANCE EVALUATION OF NEUTRAL POINT CLAMPED ACTIVE RECTIFIER

Abstract

The AC-DC converters, also known as rectifiers, are developed using diodes and thyristors to provide uncontrolled and controlled, unidirectional and bidirectional dc power. However, these rectifiers can pollute AC supply with significant levels of low frequency harmonics, pulsating input current (electromagnetic interference (EMI)), and excessive VAR. with tough regulations and severe economic restraints, the design of Active rectifier which draws nearly sinusoidal current with unity power factor is very important from the point of view of energy saving and also to satisfy harmonic standards such as IEEE 1000-3-2. In response to these problems, a significant amount of research has been devoted to the area of switch-mode rectifiers (SMRs), power-factor correctors (PFCs), pulse width-modulation (PWM) rectifiers and multilevel rectifiers. Current research has been focusing recently on decreasing the number of power switches to simplify the circuit, complexity of control circuit and increase its reliability. In the present work, a four switch Single-phase neutral-point diode-clamped active rectifier (reduced switch topology) is considered. Detailed power circuit analysis for the undertaken topology is presented. Two high performance control strategies (two level PWM and three level PWM) are discussed and verified through simulations. These control schemes for single-phase diode-clamped active rectifier is proposed to achieve a unity power factor, balanced neutral-point voltage and constant DC-bus voltage. The application of considered active rectifier topology is to improvement of power quality is investigated. The considered rectifier can also be used for harmonic current filtering. Finally experimental prototype of the considered four switch single-phase diode-clamped rectifier is developed and tested. Theoretical and practical results of the system show that the developed system can eliminate the harmonics and achieve unity power factor with minimum complexity