Showing papers by "Fang Zheng Peng published in 1998"

Application issues of active power filters

Abstract: In this article, common nonlinear loads have been characterized into two types of harmonic sources, current-source type of harmonic source and voltage-source type of harmonic source. Compensation characteristics of both parallel active filters and series active filters have been discussed analytically and experimentally for these two types of harmonic sources. The corresponding required operation conditions, features, application issues, and adaptive harmonic sources of both filters have been presented. The fact that the traditional active filter, the parallel active filter, is not a panacea to harmonic compensation, and that one cannot use it blindly, has been clearly addressed. The parallel active filter will increase harmonic current and may cause overcurrent of the load when the load is a harmonic voltage source. Instead, it has been verified that the series active filter is better suited for compensation of a harmonic voltage source such as a diode rectifier with smoothing DC capacitor. The conclusions of this article also imply that when a parallel active filter is installed in a power system network such as at a point of common coupling, the network impedance and main harmonic sources downstream from the installation point should be investigated in order to get good performance and to minimize influence to the loads downstream. In some cases, a combined system of parallel active filter and series active filter may be necessary by utilizing the harmonic isolation function of the series active filters. No doubt active filters are superior to passive filters if used in their niche applications.

Harmonic and reactive power compensation based on the generalized instantaneous reactive power theory for three-phase four-wire systems

Abstract: This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal and balanced or unbalanced three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic-distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented.

Multilevel converters for large electric drives

Abstract: Traditional two-level high-frequency pulse width modulation (PWM) inverters for motor drives have several problems associated with their high frequency switching which produces common-mode voltage and high voltage change (dV/dt) rates to the motor windings. Multilevel inverters solve these problems because their devices can switch at a much lower frequency. Two different multilevel topologies are identified for use as a power converter for electric drives: a cascade inverter with separate DC sources; and a back-to-back diode clamped converter. The cascade inverter is a natural fit for large automotive all-electric drives because of the high VA ratings possible and because it uses several levels of DC voltage sources which would be available from batteries or fuel cells. The back-to-back diode clamped converter is ideal where a source of AC voltage is available such as a hybrid electric vehicle. Simulation and experimental results show the superiority of these two power converters over PWM-based drives.

Multilevel inverters for electric vehicle applications

Abstract: This paper presents multilevel inverters as an application for all-electric vehicle (EV) and hybrid-electric vehicle (HEV) motor drives. Diode-clamped inverters and cascaded H-bridge inverters: (1) can generate near-sinusoidal voltages with only fundamental frequency switching; (2) have almost no electromagnetic interference (EMI) and common-mode voltage; and (3) make an EV more accessible/safer and open wiring possible for most of an EV's power system. This paper explores the benefits and discusses control schemes of the cascade inverter for use as an EV motor drive or a parallel HEV drive and the diode-clamped inverter as a series HEV motor drive. Analytical, simulated, and experimental results show the superiority of these multilevel inverters for this new niche.