Mahmud, Nasif (2017) High penetration of solar photovoltaics into low-voltage distribution networks: developing novel feeder voltage control strategies. PhD thesis, James Cook University.

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Abstract

Integration of renewable energy sources (RES) into traditional power system is one of the most viable technologies to meet the ever-increasing energy demand efficiently. Penetrating renewable distributed generators (DGs) such as solar panels, wind turbines into low-voltage distribution network is being a popular tradition nowadays. Increased interconnection of renewable DGs such as solar PVs arise several crucial issues that actually impose limitations on the amount of solar PV penetration. The most significant issue that arises due to large-scale PV interconnection with low-voltage power distribution system is voltage regulation issue. Due to high power generation during midday by solar PVs, the excess power, after satisfying the load demand, reverses back to distribution grid, which causes voltage rise through the feeder. On the other hand, during evening, there is increased load demand and there is no PV generation. As a result, evening peak load consumes high power from distribution grid, which causes voltage sag. These phenomena cause the feeder voltage to exceed the allowable voltage zone and trip the power supply. To interconnect solar PVs into distribution grid spontaneously, intelligent and robust voltage control strategies should be designed and implemented to regulate the feeder voltage within allowable limit.

Firstly, this thesis attempts to present a detailed overview of voltage control strategies that are being utilized to mitigate voltage regulation challenges when increased amount of renewable DGs are penetrated. The impact of high PV penetration on single bus and multi-bus low-voltage distribution systems have been analysed with mathematical representations. A comprehensive qualitative analysis has been performed for different voltage control approaches with comparisons among them. In addition, recent status of ongoing research on distribution system voltage control strategies has been briefly analysed.

This thesis has proposed novel mitigation strategies for the adverse impacts of high penetration of solar PVs on feeder voltages.

A novel intelligent, adaptive and robust control strategy has been proposed for PV interfacing 3-phase inverters where the control parameters of proportional-integral-derivative control scheme is dynamically auto-tuned in real time by adaptive neuro-fuzzy inference system (ANFIS) to provide robust response during any nonlinear and fluctuating operating conditions. This ANFIS-based PID (ANFISPID) is capable of handling fluctuating operating conditions and damping system oscillations, which ensures power system stability and reliability. ANFISPID controls the injection/ absorption of appropriate reactive power by 3-phase PV interfacing inverter and regulates the voltage at point of common coupling (PCC). A novel intelligent supervisory energy management system (EMS) based on ANFIS has been proposed to control the charge/ discharge of battery energy storage system (BESS) to provide voltage support at PCC. The performance of the cooperative operation of these two novel voltage control strategies has been analysed and evaluated in realistic low-voltage distribution system model and their performance has been compared with classic PID control scheme and classic EMS in different worst-case scenarios.

Then, the impact of high PV penetration has been evaluated on large-distribution system with multiple buses and a novel distributed cooperative voltage control strategy has been proposed to regulate the bus voltages through the feeder in a coordinated fashion. A discrete event-triggered communication-based distributed cooperative control strategy has been proposed to control BESSs and PV interfacing inverters for feeder voltage regulation that requires minimal communication. The distributed cooperative voltage control strategy has been separated into two different control layers (distributed control layer and cooperative control layer). Discrete event-triggered communication mechanism has been implemented among neighbour agents in each layer and appropriate triggering conditions have been designed that dramatically reduces the amount of communication and relax the real-time information exchange requirement among agents. A realistic radial distribution feeder has been designed in MATLAB/ Simulink environment to show that the proposed discrete event-triggered distributed cooperative voltage control strategy requires lower communication rates while preserving the desired voltage control performance.

Finally, the impact of high penetration of solar PVs on feeder bus voltages has been evaluated on a partly cloudy day. The performance of the discrete event-triggered communication based distributed cooperative control has been evaluated in the occurrences of random communication link failures. An algorithm has been designed and implemented to provide robustness against random communication link failures while implementing distributed voltage control through the feeder.

Overall, in this thesis, the impacts of large-scale solar PV penetration into low-voltage distribution network on the PCC and across the feeder have been analysed. Novel control strategies have been designed and implemented to regulate the voltage and their performances have been evaluated in realistic low-voltage distribution system model in MATLAB/ Simulink environment.

Item ID:	53041
Item Type:	Thesis (PhD)
Keywords:	ANFIS, distributed generation, distribution feeders, distribution networks, renewable energy, solar photovoltaic, voltage control, voltage regulation
Related URLs:	https://researchonline.jcu.edu.au/46090/
Additional Information:	Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 2: Mahmud, Nasif, and Zahedi, A. (2016) Review of control strategies for voltage regulation of the smart distribution network with high penetration of renewable distributed generation. Renewable & Sustainable Energy Reviews, 64. pp. 582-595.
Date Deposited:	05 Apr 2018 01:17
FoR Codes:	09 ENGINEERING > 0906 Electrical and Electronic Engineering > 090602 Control Systems, Robotics and Automation @ 100%
SEO Codes:	85 ENERGY > 8505 Renewable Energy > 850504 Solar-Photovoltaic Energy @ 100%
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