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为了提高并网逆变器在电网电压不平衡及谐波状态下的适应能力，使其能够输出高质量的并网电流，需对传统并网逆变器控制策略进行改进。以卵坐标系下LCL型并网逆变器模型为研究对象，提出一种基于准比例谐振（QPR）和电网电压前馈的控制策略。首先，分析了并网电流与其给定值和电网电压之间的关系，得出稳态误差及扰动分量产生的原因。然后，通过QPR控制策略来实现并网电流的无静差控制，引入电网电压前馈控制来抑制电网扰动对并网电流的直接影响。同时，为了提高传统锁相环在电网电压非理想情况下锁相精度及谐波抑制能力，对传统锁相环做进一步改进，以提高锁相环抗扰能力。最后，在Matlab／Simulink中进行仿真验证，仿真结果表明该控制策略能够在电网电压不平衡及谐波状态下得到高质量的并网电流，使逆变器能高效稳定运行，验证了该控制方法的有效性和正确性。

The anchoring property of the substrate surface of liquid crystal cells plays an important role in display and nondisplay fields. This property directly affects the deformation of liquid crystal ... molecules to change the phase difference through liquid crystal cells. In this paper, a test method based on the alternating-current bridge is proposed to determine the capacitance of liquid crystal cells and thus measure the anchoring energy of the substrate surface. The anchoring energy can be obtained by comparing the capacitance-voltage curves of twisted nematic liquid crystal cells with different anchoring properties in experimental and theoretical results simulated on the basis of Frank elastic theory. Compared with the other methods to determine the anchoring energy, our proposed method requires a simple treatment of liquid crystal cells and allows easy and high-accuracy measurements, thereby expanding the test ideas on the performance parameters of liquid crystal devices. more