A Bidirectional Three-Phase Smart Inverter with Frequency and Voltage Regulation under an Unbalanced System

  • 黃 文堯

Student thesis: Master's Thesis


In recent years the use of renewable energy (RE) in distributed power generation has been increasing because the demand for electrical power has grown and communities have emphasized environmental awareness However a key drawback of RE is unstable power output that causes systemic effects Moreover with the increasing penetration of RE in three-phase distribution systems the problem of unbalanced three-phase systems becomes increasingly challenging Therefore the use of power electronics control technology for rapid regulation of system frequency and voltage in microgrids is discussed broadly This thesis proposes a novel control strategy for a grid-connected three-phase four-wire smart inverter By using positive and negative sequence decoupling controls and the proposed power control strategy the smart inverter can provide not only frequency regulation but also voltage compensation to maintain a balanced and stable system Furthermore the proposed power control strategy can be divided into two stages In the first stage power command from a remote control center is divided into three phases according to the status of the three-phase system If an inverter exists without the precondition of overcurrent the second stage is used to provide ancillary services such as frequency and voltage regulation through the integration of conventional droop control To verify the feasibility of the proposed method a grid-connected inverter was simulated using PSIM Furthermore a 2 kW grid-connected three-phase four-wire prototype inverter was implemented which was connected to a three-phase AC source for analysis The simulation and experimental results indicate that the proposed control strategy is a feasible scheme System frequency regulation and phase voltage compensation can be achieved to support the system under an unbalanced or unstable condition
Date of Award2018 Jul 27
Original languageEnglish
SupervisorHong-Tzer Yang (Supervisor)

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