Coordination between the central control unit and local control function of a photovoltaic system under the uncertainties of sunlight and three-phase unbalanced loads

At present, high penetration of photovoltaic (PV) systems on low voltage (LV) distribution systems is increasing worldwide because of several favourable conditions, such as government policies, decreasing cost of PV technologies, and environmental awareness. However, varying sunlight and three-phase unbalanced load conditions can result in voltage violation, especially an overvoltage problem, and voltage unbalanced conditions that deteriorate the power quality. Therefore, disconnection of PV systems, especially on the downstream node, can occur due to the overvoltage protection of the PV system, which results in PV owners losing revenue from selling electricity. Moreover, some electrical appliances can be damaged from voltage unbalanced conditions. To support a high PV penetration and prevent these adverse impacts, this study applies a control strategy involving coordination between the Central Control Unit (CCU) and Local Control Functions (LCFs) of PV systems. The CCU applies the Adaptive Tabu Search (ATS) technique to search for the optimal LCF parameter setting of PV systems and adjusted this weekly. The optimization problem is the maximization of real power generation from all PV systems under varying (uncertain) sunlight and three-phase unbalanced loads. MATLAB programming is used for the Newton-Raphson power flow simulation on a modified 19-node distribution system.