Abstract
This paper proposed an improved control method for grid-connected voltage source converter (VSC), when the grid voltage consisted of the integer harmonics and inter-harmonics. Control object of the proposed control can be alternated to achieve the sinusoidal current or smooth output power, which enhances the operation adaption of VSC under the harmonically distorted grid. On the basis of a PI regulator in the fundamental current control loop, the novel control strategy was proposed with a supplementary controller which consisted of a prepositive high-pass filter and a modified proportional-derivative controller. In the proposed control, the inter-harmonics could be suppressed without detecting frequency, while the traditional resonator was effective in the premise of knowing the harmonics frequency. Also, the influence of control gain on the steady performance and the stability of VSC was analyzed, and the influences on the fundamental control caused by the proposed controller were also analyzed to verify the practicability of the proposed control strategy. Finally, the effectiveness of the proposed strategy was verified by the experiments.
Highlights
Grid-connected voltage source converters (VSC) have been applied widely in renewable power generation systems and electric power transmission, due to the advantages of the controllable power factor and sinusoidal current output [1,2,3]
When VSC operates on the distorted grid voltage, the non-sinusoidal currents including harmonic components will be generated, which results in the output power ripples and deteriorates the power quality outputted into the grid
In order to achieve the alternative control targets, i.e., sinusoidal output current or smooth active/reactive power output, the control control targets, i.e., sinusoidal output current or smooth active/reactive power output, the control strategy based on a high-pass filter and a modified proportional-derivative controller (H-MPD) was strategy based on a high-pass filter and a modified proportional-derivative controller (H-MPD) was proposed in this paper, which can be shown in Figure 2 and consists of the following three parts
Summary
Grid-connected voltage source converters (VSC) have been applied widely in renewable power generation systems and electric power transmission, due to the advantages of the controllable power factor and sinusoidal current output [1,2,3]. When VSC operates on the distorted grid voltage, the non-sinusoidal currents including harmonic components will be generated, which results in the output power ripples and deteriorates the power quality outputted into the grid. In order to suppress the current distortions within the whole high frequency range with the consideration of integer and inter-harmonic components, a high-pass filter and a modified differential controller was employed to improve the control gain within the high frequency range in the proposed control strategy, so that the harmonics frequency identification could be avoided. The derivations ofi=Equations (5) and (6) indicates the output power of VSC under a distorted grid consist of the DC components. QhPh, Qh. the power analysis in the existing researches about the operation of VSC under 6n±1th harmonically distorted grid were the.
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