Enhancement of Power Quality by MC-UPQC Using PI & ANN Technique

Abstract

Power quality (PQ) of power operating device is one of today’s most discussed topic but also it is a most problematic subject in recent years. The increasing application of power operating device can cause PQ disturbances. Avoiding the PQ disturbance and enhancing the PQ are the difficult tasks. More power electronics devices are used to overcome the PQ disturbances. Multi converter -Unified power quality conditioner (MC-UPQC) is one of the new power electronics devices that are used for enhancing the PQ. This

paper presents a new unified power-quality conditioning system (MC-UPQC), capable of simultaneous  compensation for voltage and current in multibus/multifeeder systems. In this configuration, one shunt voltagesource converter (shunt VSC) and two or more series VSCs exist.

The system can be applied to adjacent feeders to compensate for supply-voltage and load current imperfections on the main feeder and full compensation of supply voltage imperfections on the other feeders. In the proposed configuration, all converters are connected back to back on the dc side and share a common dc-link capacitor. sharing with one DC link capacitor. The discharging time of DC link capacitor is very high, and so it is the main problem in MC- UPQC device. To eliminate this problem, an enhanced ANN based MC-UPQC is proposed in this paper. Initially, the error voltage and change of error voltage of a nonlinear load is determined. Then the voltage variation is applied separately to ANN-based controller. In order to regulate the dc-link capacitor voltage, conventionally, a proportional controller (PI) is used to maintain the dc-link voltage at the reference value. The transient response of the PI dc-link voltage controller is slow. So, a fast acting dc-link voltage controller based on the energy of a dc-link capacitor is proposed. The transient response of this controller is very fast when compared to that of the conventional dc-link voltage controller. By using fuzzy logic controller instead of the PI controller the transient response is improved. The DC capacitor charging output voltage is increased and the response is fast when compared with PI by using the ANN controller and hence, the PQ of the system is enhanced.

The proposed controller is tested and the results of tested system and their performances are evaluated. Therefore, power can be transferred from one feeder to adjacent feeders to compensate for sag/swell and interruption. The performance of the proposed configuration has been verified through simulation studies using MATLAB/SIMULATION on a two-bus/two-feeder system show the effectiveness of the proposed configuration.