No abstract

Study the impacts of lightning-induced transient overvoltage on a hybrid PV-Wind system has been addressed in this work. Overvoltage that is generated due to lightning stroke travels along the system where it can be very harmful to the expensive equipment of the system such as PV models, inverters, charge controllers, batteries, transformers, and generator etc. The simulation model of a system has been completed by using PSCAD/EMTDC software. The system comprises of 2 MW PV farm, battery system, 2.1 MW wind farm and loads which are all connected to the common AC bus and then to the utility grid through an interfacing transformer. Lightning current is generated by using the double exponential function, from the simulation results, when the lightning current is injected to the AC and DC sides of PV system, the transient current and voltage have appeared at different points of the hybrid system. The results were obtained for 8/20 μs and 10/350 μs standards lightning waveforms with current magnitude of 100 kA.

Geomagnetic induced current (GIC) occurs as a direct consequence of abnormal space weather which starts from the sun and may flow into a power system network through neutral grounding connections. The flow of GIC through grounded neutral power transformer has been a major concern to researchers since it can potentially affect power system equipment. Most of the previous research was focused on high and mid latitude countries only. However, it has been proven that the GIC is not only limited to high and mid latitudes, but also extends to power systems at lower geographic latitudes. This paper aims to investigate the impacts of GIC on selected 275 kV subpower system networks in Peninsular Malaysia, which is among the low latitude countries. Its impact in terms of magnitude and duration is also assessed together with the use of neutral earthing resistor (NER) as a potential blocking component to reduce the impact of GIC on the Malaysian power system network. Results demonstrated that when GIC exists in the power system, power transformers undergo half-cycle saturation that may lead to a reactive power loss and power system voltage instability. In this case, the power transformer can only withstand a maximum GIC value of 7 A, and beyond this value, if prolonged, may lead to voltage instability. It turned out that GIC magnitude had more impact compared to duration. However, long duration with high magnitude of GIC is the most hazardous to power transformers and could potentially cause major faults in the power system network. As part of mitigation, NER with a value of 315.10 Ω can be used to limit the GIC current flow and thus provide protection to the power system network. Clearly, the issue of GIC undoubtedly affects the reliability, security and sustainability of power system operation, especially networks with highly critical load and capacity and, therefore, thorough studies are required to assess and mitigate this issue.

Lightning strike causes large transient current injection into hybrid systems at the point of contact. The generated transient overvoltage due to lightning current is a high concern on various expensive electrical equipment of the hybrid system and is meant to be studied in depth to reduce damages caused by this overvoltage. Analysis of lightning transient effects on a hybrid PV-wind system has been carried out in this study. The complete model of the system has been simulated by PSCAD /EMTDC software. The system consists of 2 MW PV farm, 2.1 MW wind farm, energy storage system and load. The entire system is integrated with the utility grid. Lightning current is generated by Heidler function with the help of same software. In this work, two points are selected from hybrid system to inject lightning current. The first point is the DC side of the PV modules whereas the other is the wind turbine tower. In the second case, the partial lightning current is assumed to be injected into the electrical part in the form of arcing. Transient overvoltage has been observed at different locations of the hybrid system by injecting lightning currents; the simulation results are obtained for 50% waveform of negative first stroke and negative subsequent stroke.