Abstract
In microgrid, the grid-connected inverter current with the LCL (inductor-capacitor-inductor) output filter is amplified at certain frequencies. Using virtual resistor damping method can help suppress the amplification. By choosing an appropriate virtual resistor value, the model of the inverter current control loop is simplified as a 2nd-order lowpass filter. Based on such simplified model, this paper proposes a design method of reference current compensation controller, which does not require decomposition of harmonic components. With the reference compensation, the inverter output current control precision is improved obviously. The simulation and experimental results verify the accuracy of the inverter simplified model and effectiveness of the reference compensation design method.
Highlights
With the increasing concerns of traditional energy shortage, greenhouse gas emissions, environmental pollution problem and so on, applications of microgrid become popular [1,2].The typical microgrid system contains traditional power grid and DG (Distributed Generation) system [3,4,5]
A lot of research results show that the DG inverter has the power quality control ability [8,9], such as being used to compensate load harmonic current [10,11]
Because the potential resonance problem [17,18,19,20], precise current control of inverter with LCL filter is difficult in practical application
Summary
With the increasing concerns of traditional energy shortage, greenhouse gas emissions, environmental pollution problem and so on, applications of microgrid become popular [1,2]. In [23,24], the feeding back capacitor current is used to generate an additional current reference This is equivalent to adding a resistor to the mathematical model. In [30], dead-beat control is used as current controller and the capacitor harmonic voltage is introduced into the current control loop through a proportional controller, suppressing resonance effectively. In [31], based on NORTON’s equivalence circuit, the effect of effect on the output harmonic current control is not analyzed. Thecurrent outputamplitude harmonic equivalence circuit, of virtual the inverter output harmonic current phase is compensated by closed-loop control of filter capacitor harmoniccontrol voltageofphase. The output harmonic current is controlled, the out and the capacitor of each harmonics are extracted separately.
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