Article Transactions of the Institute of Measurement and Control 1–11 Ó The Author(s) 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0142331218790314 journals.sagepub.com/home/tim Photovoltaic tied unified power quality conditioner topology based on a novel notch filter utilized control algorithm for power quality improvement Santanu Kumar Dash and Pravat Kumar Ray Abstract Nonlinear loads and grid side disturbances in the power distribution network cause harmonic rich currents and voltage perturbations such as voltage harmonics, voltage sags and voltage swells. The unified power quality conditioner (UPQC) with shunt inverter and series inverter are usually employed for elimination of current and voltage related power quality issues. However, elimination of voltage and current quality issues in a grid connected Photovoltaic (PV) system is essential. Therefore, PV integrated UPQC topology is proposed in this paper with a novel controller for power quality improvement. The control algorithm based on notch filter Phase Locked Loop (PLL) is utilized for proper phase detection and elimination of voltage and current disturbances. PV tied UPQC controller based on notch filter PLL has the capability to avoid multiple zero crossing during highly distorted grid voltage condition. Conventional control algorithms such as synchronous reference frame theory, unit vector controller based on traditional PLL are also analyzed for the control of PV tied UPQC. The proposed system is developed in Matlab/Simulink and the results obtained are evaluated to measure the performance. A real-time hardware prototype is developed using dSPACE processor. The obtained experimental results validate the effi- ciency of the proposed controller for PV tied UPQC. Keywords Phase locked loop, PV-UPQC, current harmonics, voltage sags, voltage swells Introduction Power quality disturbances in power system have increased the difficulties of the consumer by affecting to the sensitive loads. Issues related to power quality such as voltage and cur- rent quality issues have been focused on by Subjak and Mcquilkin (1990), Salmeron and Litran (2010) and Tey et al. (2005). In addition to this, non-conventional energy sources such as solar power and wind generated electrical power have shown their effectiveness over conventional energy sources. Thereby, solar as well as wind energy sources have been adopted at the distribution level for clean energy generation. However, there is requirement of power electronic converters/ inverters for the grid penetration of renewable energy system (Hamid et al., 2014; Mishra and Ray, 2016; Tuyen and Fujita, 2015). The literature survey report about the presence of voltage and current quality issues in the grid connected systems. The power quality issues are desired to be eliminated for the regu- lation of power quality at the consumer end. Sensitive loads at various levels of distribution system behave abnormally in presence of voltage and current distortions. For the mitiga- tion of power quality based issues power electronics based conditioners have been installed at various levels of distribu- tion system. These power conditioners are allowed to operate in a controlled manner for elimination of voltage and current power quality issues. Power conditioners development in vari- ous categories such as shunt active power filter, series active power filter and hybrid active power filters have been widely studied and implemented in the literature (Corasaniti VF et al., 2009; Dash and Ray, 2017a; Fallah et al., 2017; Garnayak and Panda, 2016, 2018; Panda et al., 2013) to prove the effectiveness. The aforementioned power conditioners have been used specifically for various nature of power qual- ity means used separately for voltage and current quality issues. Estimation of parameters before elimination of power quality issues have been also widely investigated in literature, which play a significant role (Subudhi et al., 2008, 2009) The combination of series active power filter and shunt active power filter of Photovoltaic (PV) tied Unified Power Quality Conditioner (UPQC) are connected back to back through dc- link capacitor and have been reported for simultaneous miti- gation of both current related and voltage based power qual- ity issues. The combine operation of series and shunt inverter Department of Electrical Engineering, National Institute of Technology, Rourkela, India Corresponding author: Pravat Kumar Ray, Department of Electrical Engineering, National Institute of Technology, Rourkela, 769008, India. Email: rayp@nitrkl.ac.in