Abstract
This paper presents an improved control strategy to cancel the double grid frequency oscillations in the active power, reactive power, and DC-link voltage of a three-phase grid-connected photovoltaic (PV) system under unbalanced grid condition. To achieve these goals, an enhanced positive–negative-sequence control (PNSC) to remove oscillations of active power and an instantaneous active–reactive control (IARC) to mitigate the fluctuations of active and reactive power, simultaneously, are suggested. These methods are also effective to reduce the oscillations of the DC-link voltage. To track the desired unbalanced or harmonic reference currents, improved proportional resonant (PR) current controllers have been designed using the Bode frequency analysis. Simulation studies are carried out via Matlab/Simulink® software to verify the effectiveness of the suggested control strategies.
Highlights
Despite numerous benefits provided by large power plants, economic, technical, and environmental advantages have led to the gradual development of small-scale renewable energy resources (RERs) into the power system [1,2,3,4,5]
There has been increasing interest in power quality in grid-connected PV inverters under grid faults, as the non-sinusoidal current is injected into the power system under such conditions, and the active/reactive power includes double frequency contents [9]
The simulation results include a comparison between three tests under two types of voltage sag: (1) the conventional current control strategy, (2) the positive–negative-sequence control (PNSC) method performance using the type II
Summary
Despite numerous benefits provided by large power plants, economic, technical, and environmental advantages have led to the gradual development of small-scale renewable energy resources (RERs) into the power system [1,2,3,4,5]. Among different types of RERs, solar photovoltaic (PV) is a suitable choice owing to the possibility of direct conversion of sunlight into electricity using power electronic devices [6,7] This system can operate in two main operation modes, including grid-connected and stand-alone [8]. There has been increasing interest in power quality in grid-connected PV inverters under grid faults, as the non-sinusoidal current is injected into the power system under such conditions, and the active/reactive power includes double frequency contents [9]. These oscillations in the active/reactive power can lead to undesired variation in the DC-link voltage. Oscillations occur due to the poor performance of both current control strategies of the PV system and the grid synchronization system
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