Improved Current Sensorless Maximum Power Point Tracking for Flyback converter based PV system

  • P. Sarath Samrat

Student thesis: Master's Thesis

Abstract

The maximum power point tracking (MPPT) for any photovoltaic (PV) application has been vital and a key performance indicator for the PV power system. Generally, the MPPT techniques proposed in literature are classified based on the complexity of the algorithm, number of sensors used in the control, the speed of tracking, and ease of implementation. In literature, efficiencies of close to 98% have been reported in the power conditioner stage of the PV power system. However, efforts are being made to increase this efficiency and to also reduce the size and cost of the power electronic interface between the PV array and load. In line with this philosophy, many Current Sensorless Maximum Power Point Tracking (CSLMPPT) techniques which eliminate the use of an expensive DC current sensor (hall-effect transducer) have been proposed. The approach of CSLMPPT has manifold advantages which can be listed as reduction in cost of MPPT control implementation, reliability of measurements due to elimination of measurement noise, and reduction in losses due to eliminating the use of shunt resistors. Moreover, at the module integrated converter (MIC) level, which is gaining popularity due to its resilience to problems like partial-shading and module-mismatch, the concept of CSLMPPT is more advantageous. This is due to the fact that multiple PV modules in the modular level are connected in parallel to increase the power rating of the system, and the elimination of the expensive DC current sensor would have significant cost benefits associated with it. This thesis conducts a review on the existing main CSLMPPT techniques reported in literature. The CSLMPPT based control for the Flyback converter based PV system, is chosen as the benchmark technique due to advantages in the topology such as lowered component count, electrical isolation between the DC/AC side and single stage power conversion and its implementation at the MIC level. A new control scheme is proposed, that combines the existing benchmark CSLMPPT with an additional inner voltage control loop for the Flyback Module Integrated Converter (FMIC) to achieve an improved CSLMPPT performance. This new control scheme for the FMIC has been verified using detailed simulation studies in the MATLAB/Simulink environment. Additionally, the experimental investigation is carried out to prove its viability under practical conditions. The simulation and experimental results are presented to demonstrate the effectiveness and superiority of the proposed technique. Furthermore, an evaluation of the proposed scheme versus the benchmark CSLMPPT using key parameters such as energy yield and speed of tracking as the indices for comparison is also conducted.
Date of Award2014
Original languageAmerican English
SupervisorMichael Weidong Xiao (Supervisor)

Keywords

  • Maximum Power Point Tracking (MPPT); Photovoltaic (PV); Flyback Module Integrated Converter (FMIC).

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