22-05-2012, 12:21 PM
a novel active power filter for harmonic suppression
a novel active power filter for harmonic suppression.doc (Size: 238 KB / Downloads: 46)
INTRODUCTION
The power electronic related facilities may generate a large amount of harmonic current due to the nonlinear input characteristic. The harmonic current may pollute the power system causing problems such as transformer overheating, rotary machine vibration, voltage quality degradation, destruction of electric power components, and alfunctining of medical facilities .In order to solve the problem of harmonic pollution effectively, many harmonic limitation standards.
SYSTEM CONFIGURATION AND OPERATION PRINCIPLE
It consists of a series connected inductor and capacitor set, a power converter and a high frequency ripple filter. The voltage-mode control is used to control the power converter. The power converter generates a compensating voltage that is converted into a compensating current flowing through the series connected inductor and capacitor set, and the compensating current flows into the power feeder in order to filter harmonic currents generated by nonlinear loads. The configuration of the proposed active power filter is similar to that of the hybrid power filter in the first view. However, the function and dimension of the passive elements (L-C) are not the same. In the proposed method, the inductor of the series connected inductor and capacitor set is very small, and it is used to filter the switching ripple of the power converter.
CONTROL THEORY
Conventionally, the active power filter was controlled by the current-mode. However, it is hard to be implemented under low filter inductance due to the high switching ripple, and it may generate multiple crossing during a carrier period of pulse-width modulator. The phenomenon of multiple crossing will result in more than one switching operation during a carrier period. In the proposed active power filter, the voltage-mode control is used.
EXPERIMENTAL RESULTS
For demonstrating the performance of the proposed active power filter, a three-phase 100KVA prototype is developed. The major parameters of the prototype are shown in Table I.
The utility power is supplied by a three-phase three-wire utility system with 380 V and 60 Hz. A comparison of the proposed active power filter and the conventional parallel active power filter is shown in Table II. Since the inductance of series connected inductor and capacitor set is only 58 H, a ferrite core can be used to reduce the power