With more and more distributed photovoltaic (PV) plants access to the distribution system, whose structure is changing and becoming an active network. The traditional methods of voltage regulation may hardly adapt to this new situation. To address this problem, this paper presents a coordinated control method of distributed energy storage systems (DESSs) for voltage regulation in a distribution network. The influence of the voltage caused by the PV plant is analyzed in a simple distribution feeder at first. The voltage regulation areas corresponding to DESSs are divided by calculating and comparing the voltage sensitivity matrix. Then, a coordinated voltage control strategy is proposed for the DESSs. Finally, the simulation results of the IEEE 33-bus radial distribution network verify the effectiveness of the proposed coordinated control method.

Introduction

In the past decade, the development of wind power and PV generation is very fast because of their technical and environmental advantages. They also bring several new challenges to power system. With the improvement of permeability of PV generation in the distribution network, the traditional distribution network becomes an active network, whose voltage bus connected PV generation is higher than other bus [1]. The traditional distribution network has multiple voltage regulation methods, such as on-load tap changer (OLTC) [2], reactive power regulator [3]. However, these methods cannot always regulate the voltage flexibly and effectively, because the voltage is different from the network without PV. The voltage of one node is regulated to the normal range, the others maybe exceed caused by the action of regulator. Moreover, the frequent transformation of the power grid will be very uneconomical. There are usually two ways to adjust voltage using a distributed generation (DG). One is to increase the reserve capacity of the distributed power supply, which obviously cannot maximize the utilization rate of renewable energy. The other is to apply inverter to generate reactive power to regulate voltage, which will increase inverter efficiency. In [4], the authors proposed a voltage regulation method by adjusting the inverter DG injected active power. In [5], the voltage regulation criterion of DG connected to the distribution network is proposed, and the capacity and position of reactive power compensation are determined accordingly. In [6, 7], it is found that DG should reduce the active output according to the actual voltage of the grid. Obviously, this method is not conducive to the full play of DG. In [8], a coordinated control method based on DGs and OLTC voltage regulation is proposed, which divides the DGs and OLTC adjustment area and controls its processing order to reduce the operation times of the on-load tap changer. The DESS is usually installed with distributed PV plant. Expect for the normal operation, DESS can be used to regulate the voltage. It can not only improve the utilization of PV power, but also improve the voltage quality of power system [9, 10]. Distribution network contains a number of DESSs, if they are in a chaotic state, it cannot play the role in voltage regulation. Therefore, the main challenge using DESSs to regulate voltage is how to coordinate DESSs reasonably and determine the output power [11, 12]. In [13], the authors propose a coordinated control method of DESSs, which includes distributed and localized controls. The consensus algorithm is used to regulate the feeder voltage, while the localized control regulates the state of charge (SoC) of each ESS within the desired SoC range. In [14], the former one is voltage regulation in terms of their installed capacity and the latter one modifies the BESs performance according to their SoC. These papers mainly focus on the voltage regulation of low voltage distribution network that the area is small. They are not suitable for large area medium voltage distribution network.