Grid Code for PV Integration in Distribution Circuits Considering Overvoltage and Voltage Variation Pisitpol Chirapongsananurak and Naebboon Hoonchareon Department of Electrical Engineering Faculty of Engineering Chulalongkorn University Bangkok, Thailand E-mail: pisitpol.c@chula.ac.th and naebboon.h@chula.ac.th Abstract—This paper proposes a grid code for photovoltaic (PV) integration to mitigate overvoltage and voltage variation problems caused by a large amount of PV generation in distribution circuits. According to the simulation results, PV generation causes overvoltage and voltage variation problems in distribution circuits. To mitigate the overvoltage and voltage variation problems due to the high penetration of PV generation, the proposed grid code employs the inverter of PV to absorb reactive power using a fixed power factor control approach. This control approach instructs the inverter of each PV to absorb reactive power so that the PV power factor is fixed at the desired value determined by the reactance to resistance ratio of the equivalent impedance at the PV location. The results show that the proposed grid code is effective in reducing the voltage variation of the test feeder and mitigating the overvoltage condition due to PV generation. Keywords—Distributed power generation; Photovoltaic systems; Voltage regulation I. INTRODUCTION The rapid increase in the power generation from renewable energy sources such as photovoltaic (PV) systems may cause power quality problems in distribution feeders. One of the most concerned problems caused by a large amount of PV generation in distribution circuits is the overvoltage [1-4] and voltage variation [3-5] problems. Because PV produces power to distribution circuits, the voltages along the distribution feeders are raised. As a result, the voltages may rise beyond 1.05 pu and an overvoltage condition might occur. Note that according to ANSI standard [6], the overvoltage condition occurs when the voltage rises above 1.05 pu. In addition to the voltage rise, PV can cause the fluctuation of feeder voltages due to the rapid variation of the solar irradiance, given that there is no inertia in PV systems [4]. Traditional voltage control devices, e.g., capacitor banks and on-load tap-changing (OLTC) transformers, cannot mitigate the overvoltage and voltage variation problems due to PV generation. Note that capacitor banks cannot absorb reactive power to reduce the feeder voltages, and the operation of OLTC transformers is not fast enough to compensate for the rapid voltage variations due to the sudden change of PV generation. Moreover, the increase in the number of OLTC operations will reduce the lifetime of the OLTC [4]. Due to the lack of suitable voltage control approaches, the amount of PV generation which can be integrated into a distribution circuit is usually limited by the voltage concerns. At present, distributed energy resource technologies such as PV inverters are able to provide a fast reactive power generation or absorption for regulating feeder voltages. Therefore, the grid code proposed in this paper employs each PV inverter to consume reactive power to regulate the voltage at its location. Since the largest size of PV that can be installed in a distribution feeder is usually limited by the overvoltage criterion [7-11], the proposed grid code can help reduce the feeder voltages and therefore increase the PV hosting capacity of a distribution circuit. The objective of this paper is to develop a grid code for PV integration in distribution circuits to mitigate the adverse impacts of PV systems on overvoltage and voltage variation by using the inverter of each PV system to consume reactive power to regulate the voltage at its location. This paper is organized as follows: Section II presents the overvoltage and voltage regulation problems caused by PV generation and the fixed power factor control approach for the proposed grid code. Section III explains the test distribution circuit used to demonstrate the effectiveness of the proposed grid code. Section IV describes the results and discussions of the simulation of the test circuit, followed by the conclusion in Section V. II. VOLTAGE PROBLEMS AND FIXED POWER FACTOR CONTROL APPROACH A. Overvoltage and Voltage Regulation Problems For the sake of simplicity in analyzing the PV impacts on the voltages of distribution circuits, the distribution system upstream from the PV location is represented by a Thevenin equivalent model as shown in Fig. 1. Note that the Thevenin equivalent circuit consists of an equivalent voltage source behind an equivalent impedance. As presented in Fig. 1, the real and reactive power of PV (P PV and Q PV ) are positive when PV generates real and reactive power and injects into the distribution feeder. However, P PV and Q PV are negative when PV consumes real and reactive power. This research is supported by the Grants for Development of New Faculty Staff, Ratchadaphiseksomphot Endowment Fund, Chulalongkorn University.