Abstract
In this paper, a coordinated harmonic compensation and voltage support scheme is presented for distributed generations’ (DGs’) interface inverters in a resistive grid-connected microgrid. Voltage support is performed by reactive power compensation which can mitigate the over/under voltage problem; furthermore, the active power curtailment is proposed in order to mitigate the overvoltage problem when the reactive power compensation is not sufficient. Harmonic compensation is achieved by using virtual admittances in selected harmonic frequencies. Reactive power and harmonic compensation currents are injected with regards to the limited capacity of the interface inverter. If necessary, the reference powers of the grid-tied inverters are changed. Voltage support and harmonic compensation can be achieved based on local or central (communication-based) measurement schemes. The effect of communication delay is also investigated in this study. Experimental and simulation results are obtained in order to demonstrate the effectiveness of the proposed method.
Highlights
Voltage Source Inverters (VSIs) are widely used for interfacing Distributed Generation (DG) systems to the grid [1]
In [2] and [3], the voltage rise problem caused by high penetration of DGs in an LV distribution system has been studied and a droop-based reactive power control is proposed for Current Controlled Mode (CCM) of VSIs
The parameters of power and control systems of the case study are listed in Tables1 and 2, respectively. As it can be found in Table.1, the lines impedances of DG1 and DG2 are considered different in order to evaluate the proposed algorithm better; it is assumed that the capacities of the inverters are 10% more than their available maximum powers which can be delivered in order to provide some rooms for reactive power and harmonics compensation
Summary
Voltage Source Inverters (VSIs) are widely used for interfacing Distributed Generation (DG) systems to the grid [1]. A coordinated harmonic compensation and voltage support method are proposed for CCM VSIs in a grid-tied MG. The voltage support algorithm can mitigate under/over voltage problems of the grid-tied MG by using reactive power control with considering the limited capacity of the inverters; a power curtailment algorithm is proposed in order to mitigate voltage rise problem when the reactive power compensation is not sufficient. A harmonic mitigation method is proposed based on the virtual admittance which has the flexibility for changing from central measurement to local measurement when the communication system failure happens or the delay of the communication system is too high The fundamental and harmonic transmitted data are fed to each DG local controller for voltage support and harmonic compensation, respectively
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