Distributed Voltage Control in Distribution Networks with Electric Vehicle Charging Stations and Photovoltaic Generators

The developments of distributed generators (DGs) and electric vehicles (EVs) are dramatical due to the rapid increase of friendly environment desire. While on another hand, the proliferation of distributed generators (DGs) and electric vehicle charging stations (EVCSs) has brought voltage regulation challenges to distribution systems due to their high generations and heavy loads. In this thesis, a distributed control strategy is proposed which mainly consisted by a reactive compensation algorithm to dispatch surplus reactive power from DGs and EVCSs for proper voltage regulation without violating their converters’ capacity limits or stressing conventional voltage control devices, i.e., on-load tap changers (OLTCs), and an active power curtailment algorithm for DGs to properly integrate OLTC in voltage regulation when the reactive power compensation is deficient. The proposed control algorithms rely on consensus theory and sensitivity analysis, thus, minimizing the active and reactive powers needed for voltage support, and decreasing the net cost of voltage regulation. In the proposed control strategy, three distributed voltage regulation algorithms, as well as a distributed control method for OLTC, are developed and coordinated to realize adequate voltage maintaining effects. Simulation results of a typical distribution system confirm the effectiveness and robustness of the proposed distributed control strategy in continuously maintaining proper voltage regulation for the whole distribution system with minimum power demands from DGs and EVCSs, and reduced tap operation for OLTC, within every 24 hours

Synchrophasors-based Distributed Secondary Voltage/VAR Control via Cellular Network

The impact of the increasing connection of distributed generation to medium voltage (MV) feeders, with particular reference to photovoltaic (PV) units, justifies the investigation on secondary voltage/VAR control (VVC) schemes able to improve the utilization of available control resources and to reduce reactive power flows. The paper deals with a secondary VVC scheme based on a distributed multi-agent approach that requires only the estimation of the reactive power flows between the buses where the PV units with reactive power control capability are connected. Phasor Measurement Units (PMUs) are used to get the relevant information. In general, distributed control approaches are expected to work adequately even by using communication infrastructures with lower performances than those required by centralized approaches. The paper addresses such an issue by the analysis of the distributed VVC performance when a shared cellular network is used for the cooperative adjustment of PV inverters reactive power outputs and of tap positions of transformers equipped with on-load tap changers. The analysis is carried out by using a specifically developed ICT (Information and Communications Technology)- power co-simulation platform. It is shown that the VVC scheme has adequate performances also in the presence of significant levels of background traffic and data loss

Peer-to-peer energy trading in electrical distribution networks

In response to the challenges posed by the increasing penetration of distributed generation from renewable energy sources and the increasing electricity retail prices with decreasing Feed-In Tariff rates, a new energy trading arrangement, “peer-to-peer (P2P) energy trading” has been proposed. It refers to the direct energy trading among consumers and prosumers in distribution networks, which is developed based on the “P2P economy” concept (also known as sharing economy). A hierarchical system architecture model has been proposed in order to identify and categorise the key elements and technologies involved in P2P energy trading. A P2P energy trading platform called “Elecbay” is designed. The P2P bidding is simulated using game theory. Test results in a grid-connected LV Microgrid with distributed generators and flexible demands show that P2P energy trading is able to improve the local balance of energy generation and consumption, and the enhanced variety of peers is able to further facilitate the balance. Two necessary control systems are proposed for the Microgrid with “Elecbay”. A voltage control system which combines droop control and on-load-tap-changer (OLTC) control is designed and simulated. Simulation results show that the proposed voltage control system is sufficient for supporting the P2P energy trading in the Microgrid. The total number of operation times of the OLTC is reduced with P2P energy trading compared to the reference scenario. The information and communication technology (ICT) infrastructures for the P2P bidding platform and the voltage control system are investigated. The information exchange among peers and other parties (Elecbay, distribution system operators, etc.) is designed based on TCP/IP protocol. Existing and private communication networks with different communication medium, bandwidths, etc., are modelled. Simulation results show that the existing ICT infrastructures are sufficient for supporting both the P2P energy trading platform and the voltage control system. Therefore, no large amount of additional investments are required