IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, VOL. 8,NO. 1, JANUARY 2017 13 Distribution Voltage Regulation Through Active Power Curtailment With PV Inverters and Solar Generation Forecasts Shibani Ghosh, Student Member, IEEE, Saifur Rahman, Life Fellow, IEEE, and Manisa Pipattanasomporn, Senior Member, IEEE Abstract—Distribution voltage profiles are subjected to over- voltage limit violations from high penetration of grid-connected photovoltaic (PV) systems. Such voltage rises seen at the point of PV interconnection can be mitigated by adaptively changing the active and/or reactive power injection from the PV inverter. This work proposes a local voltage regulation technique that utilizes very short-term (15 s) PV power forecasts to circumvent imminent upper voltage limit violation or an overvoltage scenario. To provide these PV generation forecasts, a hybrid forecasting method is for- mulated based on Kalman filter theory, which applies physical PV generation modeling using high-resolution (15 s) data from on-site measurements. The proposed algorithm employs an active power curtailment based on these PV power forecasts, when the reactive power estimate given by a droop-based method cannot provide the desired voltage regulation within predefined power factor limits. The curtailment threshold values are calculated in such a way that this voltage regulation technique can reduce possible voltage limit violations. The effectiveness of the proposed method is demon- strated with case studies developed on a standard test feeder with realistic load and PV generation profiles. Index Terms—Active power curtailment, distribution voltage regulation, high photovoltaic (PV) penetration, Kalman filter (KF), overvoltage prevention, solar forecasting. I. INTRODUCTION S OLAR photovoltaic (PV) energy deployment is accelerat- ing at a rapid pace throughout the world. On a global scale, more PV capacity was added into the generation mix since 2010 than in the previous four decades [1]. As the number of PV sys- tems interconnected to the distribution grid grows, the grid faces several opportunities as well as challenges. One of the major concerns from network operation standpoint is the overvoltage or violation of voltage limit (for example, ±5% of nominal volt- age as given by service voltage limits of ANSI C84.1 [2]) in a distribution network due to high PV penetration. To address this issue of variable voltage rise, advanced PV inverters are being considered as a viable source of reactive power, which was not allowed under existing standards. But rapid growth of renewable Manuscript received November 5, 2015; revised April 22, 2016; accepted June 1, 2016. Date of publication June 7, 2016; date of current version December 14, 2016. Paper no. TSTE-00919-2015.R2. The authors are with the Bradley Department of Electrical and Computer Engineering, Advanced Research Institute,Virginia Polytechnic Institute and State University, Arlington, VA 22203 USA (e-mail: shibani@vt.edu; srah- man@vt.edu; mpipatta@vt.edu). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TSTE.2016.2577559 sources has led to the revision of existing standards so that dis- tributed resources, in general, can actively participate in feeder voltage regulation when necessary [2]. Besides alleviating volt- age rise, inverters can also mitigate sudden voltage drops or undervoltage scenario by capacitive VAR compensation. A lo- cal voltage regulation technique was presented by the authors in [3], which combined an inverter reactive power injection algo- rithm and real or active power curtailment (APC) technique to keep the voltage profile within a predefined upper threshold. In the literature, several methods are discussed to implement volt- age regulation by controlling the reactive injection from the PV inverter [4]–[6]. Centralized control schemes use network-wide optimization to derive optimal real/reactive input set-points for inverter(s) [7]–[9]. However, emerging techniques like positive semidefinite optimal power flow using sparsity-promoting reg- ularization approaches are being discussed in literature which can reduce computational burden when the voltage regulation needs to be managed on a real-time basis [8], [10]. On the other hand, decentralized or local voltage control methods can re- spond faster as they only involve local voltage and/or PV power production measurements [11]–[13], and thus can be deployed as an online application. The reactive power capability of a PV inverter is limited by the instantaneous real power generation and its apparent power rating [4]. Consequently, the reactive power control strategies alone cannot yield sufficient voltage regulations when PV power output is high. So APC is regarded as another lucrative option with reactive power control to prevent distribution overvoltage [3], [14]–[15]. Besides, curtailing real power can yield in better voltage regulation given that the distribution network is resistive in nature (high R/X ratio). Inverter-based voltage regulation applications can be further augmented by using PV generation forecasts. Solar forecast- ing is being used as a support tool to manage the intermittent nature of solar energy production which can lead to potential reliability concerns regarding network operation like voltage and frequency regulation [16]. Dispatching regulation reserves require short-term PV output forecasts for real-time market ap- plications. For example, California Independent System Oper- ator (CAISO) provides forecasts 105 minutes before the op- erating hour for its participating intermittent resource program [17]. The time horizon for short-term solar forecasting is widely considered to be within few hours, whereas minutes timescale falls within very short-term category [18]–[20]. In the litera- ture, researchers have approached the offline short-term solar 1949-3029 © 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information.