Browsing by Author "De Wet, Werner"

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    Inverter control for voltage unbalance mitigation on low voltage electricity networks
    (Stellenbosch : Stellenbosch University, 2024-03) De Wet, Werner; Beukes, Johan; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The use of single-phase power lines to electrify low consumption areas in South Africa leads to undesired levels of voltage unbalance at certain point on the distribution network. The increased use of inverter-based generation in the distribution network provides the opportunity for the utitlisation of these inverters to be increased by providing an ancillary service such as voltage regulation and voltage unbalance mitigation. This thesis provides a detailed design of a positive and negative sequence dq domain control system that can be implemented in grid-connected inverters to perform voltage regulation and voltage unbalance mitigation. This control system allows the inverter to perform voltage regulation by means of reactive power compensation and mitigate voltage unbalance by transferring active and reactive power between the three phases. The inverter system is experimentally tested by adapting an existing three-phase 80 kVA inverter and connecting it to the electricity grid. Resistive loads are connected to the inverter-grid system to generate undesired levels of voltage unbalance. The control system implemented in the inverter consists of an inner dual current controller which is supplied current references from an outer control loop than consists of the DC voltage controller, positive sequence voltage controller and a negative sequence voltage controller.