Grey Wolf Optimization Algorithm Based Maximum Power Point Tracking, and Voltage Control of Stand-alone PV System with Storage Device: Application to Multi-Service Access Node

Abstract

Current energy sources that show the most promise are renewable sources. Among the more encouraging forms of renewable energy sources is solar energy. The weather (temperature and radiation) has a significant impact on how well a PV module or array operates. Therefore, maximum power point tracking (MPPT) techniques are necessary to guarantee that the PV array generates the highest power feasible at all times and independent of the external conditions. The PV system's produced energy needs to be stored in order to be used during night time and cloudy days. To store PV generated energy, it is necessary to control the storage device with appropriate controller. In this thesis work a PV system of three modules of series connection is designed to supply a constant voltage for telecommunication multiservice access node. The storage battery and PV are both connected to a DC-bus via boost converter and bidirectional non- isolated converter respectively. The load terminal (multi-service access node) is connected to DC-bus via a buck converter. The maximum power of the designed PV system is tracked by grey wolf optimization based MPPT method. The Grey Wolf MPPT algorithm determines the point at which maximum power is present by using PV voltage and current as inputs. Then the algorithm generates duty cycle for operation of boost converter. The proposed MPPT technique was tested against 600W PV system under three various shading scenarios. The efficiency of the technique to track a maximum power under standard test condition is found to be 99.98%. Under shading condition of irradiation 1000W/m2, 900W/m2 and 700W/m2 and constant temperature of 25°C, is found to be 99.83% and under shading condition of irradiation 1000W/m2, 400W/m2 and 600W/m2 and temperature of 20°C, 18°C and 19°C is found to be 99.8%. The bidirectional converter determines the charge/discharge of the battery such that to keep DC-bus voltage at 72V. The converter is controlled by double loop optimal PI controller. If PV can generate a voltage more than 72V the converter will act in buck-mode to charge the battery by keeping DC-bus voltage at 72V. It will act in boost to discharge the battery mode if PV generate voltage less than 72V. The buck-converter takes DC- bus voltage as an input and produce a constant voltage of 48V for the load. The buck converter’s voltage output is controlled by an optimal PID controller. Parameters of the controllers are optimized by PSO. The overall system supplies a constant voltage of fast response time and less oscillation for the load with buck converter’s rise time and settling time being 0.78 and 1.98 second respectively.