Abstract
Voltage violation is the main challenge in distribution networks (DN) with connected single-phase distributed photovoltaic (PV) sources. The main concern of this paper is to suppress the overvoltage (OV), undervoltage, and voltage unbalance (VU) in DN to achieve the EN50160 standard. Two control levels are proposed; the first controller is an H-infinity (H-infinity) controller for adjusting battery systems in distributed PV sources to alleviate VU. The second controller is a fuzzy logic controller (FLC) for selecting the appropriate taps of the distribution transformer's on-load tap changer (OLTC). Two challenges should be avoided; excessive batteries currents and extreme taps of OLTC. Therefore, the parameter of the H-infinity controller is instantaneously adjusted by a FLC to determine the optimal batteries currents required. The OLTC controller operates in case of extremely either high OV or under-voltage (UV) values. The simulation results verify the proposed control based on two power flow scenarios in DN. The first scenario represents power flow during the night when there are no PV generation powers with high loads consumption. On the contrary, the other scenario represents power flow during daylight in the presence of high PV powers with low loads' power. The model of DN with controllers is implemented using MATLAB/script.The main contribution of this paper can be summarized as follows:1. Proposing a two-layer control scheme to mitigate the over/under voltage and voltage imbalance and avoid excessive both batteries' currents and OLTC tapping steps.2. Designing a self-tuning H-infinity controller using FLC for dynamic adjusting of the controller weighted parameters.3. Mitigating the voltage violations using the primary control level by optimizing the batteries' currents.4. Performing a secondary control level based OLTC optimal tapping selection for voltage regulation in the extreme over and under voltage events.2