Abstract

This paper presents a new technique for the voltage regulation of a radial medium voltage (MV) distribution grid in presence of distributed generation (DG) units. The proposed technique consists of the coordinated action of on-load tap changer (OLTC) of transformer and hybrid power compensation by D-GUPFC. Managing the system voltage using the action of OLTC is one of the most common ways for voltage regulation of MV systems. However, OLTC cannot be used for voltage regulation of long radial distribution feeders as it changes the sending point voltage of the feeder. In this study, the problem of using OLTC for the voltage regulation of a radial distribution feeder will be solved by using reactive power compensation at the DG connected bus. Simulation results reveal that the proposed control method is capable of maintaining the system voltage within the permitted range in the worst scenarios of the test system.

I. INTRODUCTION

The proportion of renewable energies in power generation has increased significantly in recent years according to the political aims. Thus, the distribution networks have to meet hitherto unfamiliar technical challenges. A temporary reversal of the power flow can cause overvoltage problems. Traditional voltage regulation strategies cannot solve this problem. Consequently, regenerative sources need to be turned off temporarily or on the long term the network infrastructure has to be extended by the network operator. In some areas, the installed generation power is significantly higher than the consumption. Distributed generation (DG) causes altered power flow patterns. Thus, the power flow may even become bidirectional. The temporary reversal of the power flow can provoke voltage rises away from the substation, especially at remote feeder ends. If the voltage exceeds the tolerance of usually 10 % above nominal voltage, other devices and equipment might be damaged [1].

V. CONCLUSION

A new idea was presented in this paper for the voltage regulation of multiple feeders radial distribution systems with Distributed Generation connected at the systems bus. The proposed method was principally based on the combination of the two different control methods which are static compensator and OLTC action. The idea was to use (based on the permitted range of voltage) the OLTC action in the predefined range and allow the D-GUPFC to manage the rest of the voltage violations. Simulation results revealed that proposed idea enables us to control the voltage problem of a radial medium voltage distribution system with multiple feeders in the worst working conditions. Moreover, as the DGUPFC is used in the extreme voltage conditions ( when OLTC cannot work anymore ), it doesn’t considerably increase network losses. In the future research, the cost of implementation and a practical evaluation of the proposed method will be investigated.