Proposed mitigation techniques for non-compliance challenges of a grid-connected photovoltaic plant

Abstract

South Africa has a need for renewable energy generation as the utility struggles to maintain base load requirements for the country, leaving most of the customers without electricity for hours a day. Detailed information regarding the requirements for connecting a solar photovoltaic plant (SPP) to the South African (SA) utility grid, including legal aspects and boundaries will be presented in a legislative context for grid code compliance (GCC). A network model will be created in DIgSILENT PowerFactory, which includes the utility grid and the connection of a grid-connected SPP. The values of the equipment will be obtained from industry standards and the software program PowerFactory, which the model will be implemented to determine whether there are non-compliance factors during steady-state conditions. A primary objective of this dissertation will be to test the performance of a static inverter model within a designed network for possible non-compliance factors for a Category B SPP with a capacity of 9 MW, located close to an existing Eskom 22 kV network. In addition to providing insight into possible mitigation techniques that can be used by independent power producers (IPPs) to overcome non-compliance with a proposed SPP. The following compliance factor was investigated: 1. Reactive power compliance, 2. Voltage capability requirements, and 3. Power quality. The investigation could provide valuable insight into what methods could be implemented to avoid violations in the GCC. A description of the main electrical equipment for a grid-connected SPP installation is provided, along with a list of the components applicable to a grid-connected SPP installation. Control strategies play a crucial role in assisting SPP inverters in performing according to the grid code to avoid the mitigation of non-compliance factors, which is why the dissertation also provides an understanding on different types of control measures. The simulation requirements for the South African renewable energy grid code (SAREGC) simulations will be discussed and analysed. This is to provide a comprehensive set of simulation requirements that may be defined for grid-connected SPPs in steady-state environments. An analysis of the SPP network model will indicate the necessary steps to conduct reactive compliance simulations at the point of connection (POC) and how the study can be completed by means of adding additional inverters to increase the generation capacity. As part of the steady-state performance simulations, the voltage capability requirements and compliance issues will also be scrutinized for possible issues related to non-compliance. Studies will also focus on fault level inverter contributions and their effect on the utility grid when the utility grid is subjected to maximum and minimum fault level conditions. The power quality requirements will be done for the SPP at the POC with the modelling done in terms of steady-state requirements for the SAREGC. There are several power quality issues challenges that can result in the SPPs producing a non-compliance issue, such as harmonic distortion and can be mitigated by installing a harmonic filter in the SPP network. In the area of grid codes, observational studies are now being used to develop methods of mitigation for violations or non-compliances to be encountered when violations or non-compliances are observed. The impact of proposing the mitigation techniques will result in the following: 1. Achieving grid code compliance, 2. Optimizing plant performance, and 3. Increasing the lifespan of electrical equipment. Consequently, it is possible to gain a deeper understanding of the main challenges associated with grid code compliance. A comparison of the mitigation techniques implemented and their impact on achieving compliance will be carried out during the studies.