Long-term Evaluation of DRES Penetration in LV Networks using Droop Control Techniques Eleftherios O. Kontis, Georgios C. Kryonidis, Andreas I. Chrysochos, Charis S. Demoulias, Grigoris K. Papagiannis * School of Electrical and Computer Engineering Aristotle University of Thessaloniki Thessaloniki, Greece * corresponding author’s email: grigoris@eng.auth.gr Abstract—The main objective of this paper is to investigate the maximum penetration level of distributed renewable energy sources (DRESs) in a real radial low-voltage network. For this purpose, the business as usual (BAU) scenario, where no control scheme is applied to the installed DRESs, is compared with two conventional droop control techniques, namely the active power curtailment and the uniform power curtailment. Appropriate key performance indicators are introduced to evaluate the long- term performance of the examined control strategies. Simulation results show that, compared to the BAU scenario, a higher penetration level can be attained by exploiting the above- mentioned droop control schemes. Index Terms--Active power curtailment, distributed generation, droop control, key performance indicators, overvoltage mitigation. I. INTRODUCTION Over the last decade, environmental concerns, regarding the reduction of carbon emissions as well as the market deregulation, have increased the penetration of distributed renewable energy sources (DRESs), which are mainly connected to the distribution network by means of electronic power inverters [1]. This advent has changed the conventional operation of the distribution network from a downstream unidirectional power flow to a bidirectional one, posing a series of technical challenges, which must be addressed by the distribution system operators (DSOs) [2]. One of the most substantial problems in low-voltage (LV) distribution networks is the overvoltages that occur due to the active power injection of the DRESs. Therefore, voltage rise is considered as an important limiting factor, concerning the further penetration of DRESs in the existing distribution networks [3]. Although classical approaches, such as the grid reinforcement and the use of transformer on-load tap changers, are the most straightforward solutions, they are not commonly preferred by the DSOs due to the high investment costs. On the other hand, techniques based on active power curtailment are the most promising methods for efficient voltage regulation [4]. The P(V) droop characteristic is considered as the most typical decentralized active power curtailment (APC) method and is preferred over conventional centralized techniques, since no communication infrastructure is required [6]-[7]. The principal objective of the APC method is to mitigate overvoltages by curtailing part of the total injected active power of the installed DRESs. However, a significant drawback of the APC strategy is the non-uniform power curtailment among the DRESs [8]. To alleviate this problem, a number of coordinated APC techniques, known as fair power sharing (FPS) algorithms, has been proposed that reallocate the curtailed power among the DRESs [9]-[12] in a more uniform way. In this paper, the conventional APC method and the most common FPS control scheme are thoroughly investigated to evaluate the maximum penetration level of DRESs in a radial LV network. Time-series simulations are performed for both short- and long-term periods and appropriate key performance indicators (KPIs) are proposed so as to quantify the performance of the examined methods, compared to the business as usual (BAU) scenario, where no DRES control scheme is considered. The paper is organized as follows: In Section II, the examined control schemes are briefly described and appropriate KPIs are proposed. The system under study is discussed in Section III, while in Section IV the corresponding simulation results and the evaluation of the control schemes are presented. Finally, in Section V the conclusions are drawn and plans for future work are proposed. II. DESCRIPTION AND EVALUATION OF THE PROPOSED CONTROLS The most common approaches, regarding the voltage regulation in LV networks, are briefly presented and discussed. Furthermore, appropriate KPIs are introduced to assess the effectiveness of each approach. A. Active Power Curtailment Method One of the most promising and effective solutions to the overvoltage problems in LV networks is the APC method This work is supported by the EC-FP7 project “INCREASE” with Grant agreement: 608998. Website: http://www.project-increase.eu/. The work of G. C. Kryonidis is supported by the Research Committee of Aristotle University of Thessaloniki via a merit scholarship between 2016 and 2017. 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republising this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Citation Information: DOI: 10.1109/ISGTEurope.2016.7856244