Improving the integration of photovoltaic generation on distribution networks via advanced control of inverters

The number of new rooftop photovoltaic (PV) installations has been unprecedented in recent years and utility distribution networks are beginning to experience negative impacts caused by large amounts of distributed PV generation. In particular, distribution lines experience voltage fluctuations caused by reverse power flows and poor coordination between PV systems and existing voltage regulation. These violations limit the amount of PV that can be installed on a network since utilities must approve each new PV interconnection under the presumption that it will not adversely impact the distribution network. The first goal of the research presented in this dissertation is to investigate whether a PV installation size may be limited by any adverse effect it may have on distribution network protection. The research concludes that protection issues caused by PV can be readily detected or prevented in most cases. The focus of the research is then shifted to the study of advanced inverter functions that will aid in mitigating the impact of more common network problems caused by PV generation. Several local inverter control strategies are simulated in the quasi-static time-series (QSTS) domain on real-world distribution networks. A parametric study is performed on each inverter control strategy’s settings to determine the range of effectiveness of these advanced control functions. Lastly, several control strategies are selected to study the simultaneous control of many PV distributed throughout a distribution network to mitigate network over-voltages. Trade-offs are explored between the effectiveness, cost, and fairness of the local inverter controls and centralized control strategies that necessitate a communication infrastructure.Ph.D

A Self-Organizing Strategy For Power Flow Control Of Photovoltaic Generators In A Distribution Network

The focus of this paper is to develop a distributed control algorithm that will regulate the power output of multiple photovoltaic generators (PVs) in a distribution network. To this end, the cooperative control methodology from network control theory is used to make a group of PV generators converge and operate at certain (or the same) ratio of available power, which is determined by the status of the distribution network and the PV generators. The proposed control only requires asynchronous information intermittently from neighboring PV generators, making a communication network among the PV units both simple and necessary. The minimum requirement on communication topologies is also prescribed for the proposed control. It is shown that the proposed analysis and design methodology has the advantages that the corresponding communication networks are local, their topology can be time varying, and their bandwidth may be limited. These features enable PV generators to have both self-organizing and adaptive coordination properties even under adverse conditions. The proposed method is simulated using the IEEE standard 34-bus distribution network. © 2011 IEEE