对各种电网阻抗下并联电网变频器稳定性的前馈控制研究

OPAL-RT

A Study of Feedforward Control on Stability of Grid-parallel Inverter with Various Grid Impedance
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对各种电网阻抗下并联电网变频器稳定性的前馈控制研究
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1 `, P/ B( @2 [! IThe Current Controlled Voltage Source Inverter (CCVSI) has attracted substantial research due to its common application for the integration of renewable energy resources into the main grid. The single loop current controller is commonly used in industry for CCVSI due to its simplicity, desirable stability margins and dynamic performance. For the single loop controller, the point of common coupling (PCC) voltage feed forward control is used to improve the transient and disturbance rejection performance. However, this solution exhibits one drawback that has not yet been adequately discussed in the literature: the poor stability caused by the feed forward control itself. It is proved that the feedforward voltage results in a "positive feedback control" which essentially degrades the stability of the system and its control performance. Since the gain of the "positive feedback control" depends on the grid impedance, it is necessary to study how the stability and control performance of the grid parallel inverter is affected by the feed forward control under various grid impedances. The system without feed forward control is also investigated due the fact that the grid impedance generally affects the system stability. The analytical study shows that two cases have similar performance under stiff grid, while the case without feedforward has superior stability and control performance under weak grid impedance. The simulation and experimental results also validate the outcome of the analytical study
/ B! z* z4 U: E- x" q5 i由于将可再生能源并入主电网这一过程中电流控制电压源逆变器（Current Controlled Voltage Source Inverter：CCVSI）被广泛应用，大量研究针对它展开。单环电流控制器因其简易性、令人满意的稳定性和动态性能在行业中被广泛用于CCVSI。对于单环电流控制器来说，公共连接点（PCC）电压前馈控制被用来改善暂态和干扰抑制性能。然而，这种解决方法存在一种尚未在文献资料中得到充分讨论的缺点：前馈控制自身的不稳定性。事实证明前馈电压会造成“正反馈控制”，从而降低系统稳定性及其控制性能。由于“正反馈控制”的增益取决于电网阻抗，在不同电网阻抗下研究前馈控制是怎样影响并联电网变频器的稳定性和控制性能变得十分必要。由于电网阻抗会影响几乎所有系统稳定性，因此对没有前馈控制的系统也作了研究。这项分析研究表明在刚性电网中两种情况性能相似，而在弱电网阻抗情况下，没有前馈的系统有更高的稳定性和控制性能。仿真和实验结果也证实了该分析研究的正确性。

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