Performance Enhancement of Photovoltaic Integrated Unified Power Quality Conditioner for Power Quality Improvement

Abstract

A drastic improvement in the conventional grid towards an efficient and advanced grid solutions are noticed after rise in demand in power quality by the domestic and commercial consumers. In the mean time, shortage of conventional sources of electricity and high demand for electricity including transmission and distribution losses are reported by many countries. Therefore researchers are finding efficient solutions for integration of renewable energy sources to the present grid. Among the various type of renewable energy sources, photovoltaic (PV) systems are more reliable for the proper grid integration due to its low installation costs. However, proliferations in the distribution systems are present because of voltage disturbances in the grid and various non linear loads connected to the grid. Aforementioned perturbations gives rise to power quality issues related to voltage and current such as voltage sags, voltage swells, voltage unbalance and current harmonics etc. Therefore power conditioners and various custom power devices are developed in order to compensate the power quality issues and improve the power quality. Previously distribution static compensators are widely used for grid connected PV systems for the elimination of current quality issues by neglecting the situations of grid voltage disturbances. For the compensation of voltage and current quality issues in a grid integrated PV system, unified power quality conditioners (UPQC) are developed and controlled sophisticatedly in this thesis to achieve the desired power quality standard.
Integration of PV system to single phase grid through UPQC has been developed for its performance analysis and improvement of power quality. Presence of grid disturbances and harmonic rich currents due to nonlinear loads in a single phase grid connected PV systems are compensated effectively. A notch filter based control algorithm is developed and implemented for the PV-UPQC system. A detail stability analysis has been discussed of the controller with the system. The performance of the proposed controller is compared with SRF and UVT controller, both in simulation and experimentally to validate its efficiency.
The design and development of three phase PV tied UPQC is presented to achieve the required power quality standard. The analysis on the performance of proposed system has been carried out in comparison with simple SRF controller and UVTG controller. Development of resonant controller for PV tied UPQC for making the system robustagainst grid disturbances has been discussed and experimentally validated with dSPACE1103 processor.
Generation of accurate compensating signal for the inverters of PV-UPQC is highly important as various type of disturbances arise unexpectedly in the distribution system. Therefore utilization of conventional PI controllers by the controller of the system may not reach the expected solution. Therefore an advanced optimization algorithm is proposed by overcoming the demerits of conventional optimizations. The proposed JAYA (means victory) optimization algorithm is utilized to find the best controller gains. As the shunt and series inverter of PV-UPQC are employed for different control purpose, two different objective functions are designed for the algorithm. Performance of the system is analyzed for the proposed controller with JAYA optimization in comparison with conventional teaching learning based algorithm (TLBO), Particle swarm optimization algorithm. The proposed JAYA based controllers along with other conventional optimization methods are implemented in real-time for PV-UPQC system to validate the efficiency.
A new PV tied UPQC topology with an improved LCL filter at shunt inverter part is proposed, which provides better compensation to current quality issues. This chapter also proposes a novel model reference tracker (MRT) control law to improve power quality and elimination of current harmonics, voltage sag/swells and unbalance. It has feature to regulate tracking error between model reference signal and actual measured signal. Therefore, proposed model reference approach provides robustness and flexibility for various operating conditions. In addition, integral plus sliding mode controller (SMCi) has been used for better control of DC-Link voltage to deal with severe change in power system conditions. Performance and efficiency of present topology with novel controller is analyzed along with conventional controllers through laboratory developed prototype, controlled by DS1103 dsp processor.
A new topology for Photovoltaic fed open unified power quality conditioner has been proposed focusing on the requirement of voltage sensitive loads. It has incorporated the advantages of open UPQC and grid connected PV systems by providing a possible solution towards the demand of different power quality levels at end user. Adaptive notch filter based instantaneous symmetric components (ANF-ISC) controller scheme has been utilized for the control of series compensator. An adaptive logarithmic absolute algorithm has been implemented for shunt part of proposed system. The proposed controllers are verified on a developed prototype of proposed system in the laboratory. The system performance is found satisfactory under various grid conditions.