柔性直流输电换流阀型式实验平台谐波注入方法

Harmonic Wave Injection Method for Type Test Platform of VSC-HVDC Converter Valve

柔性直流输电系统已广泛应用于我国电力系统,其核心设备柔直换流阀的可靠性直接影响电网的安全稳定运行。随着国内外柔直系统谐波振荡等现象的出现,换流阀在型式实验阶段除了满足IEC标准规定的实验项目外,还需要考核换流阀的谐波耐受能力。基于柔直换流阀对拖实验平台,提出了谐波电流注入控制方法,建立了阀段实验系统电流控制回路等效模型,与常规基于比例-谐振(PR)调节器的电流控制策略进行对比,证明了所提出的基于二阶低通滤波环节的谐波电流控制方法能够明显改善电流控制回路的幅频特性,消除注入谐波的稳态波动。最后,采用PSCAD软件对所提出的电流控制方法进行仿真验证,对比常规PR调节器和二阶低通滤波环节下稳态谐波电流的控制性能,表明所提出电流控制方法的有效性,并进一步在换流阀对拖实验平台进行实验验证,稳态时谐波电流跟踪给定值,满足换流阀谐波电流应力的工程验证需要。

The VSC-HVDC transmission system has been widely used in power system of China.The reliability of its core equipment,the converter valve,directly affects the safe and stable operation of the power grid.With the emergence of harmonic oscillations in VSC-HVDC projects around the world,in the type test,in addition to meeting the experimental items specified in the IEC standard,the harmonic tolerance capability of the converter valve also needs to be assessed.For this reason,a harmonic current injection control method is proposed based on the converter valve type test platform.An equivalent model of the current control circuit is established,which is compared with the conventional current control strategy based on a proportional-resonance(PR)regulator.By comparison,it proves that the proposed harmonic current control method based on the second-order low-pass filter can significantly improve the amplitude-frequency characteristics of the current control loop and eliminate the steady-state fluctuations of injected harmonics.Finally,the PSCAD software is used to simulate and verify the proposed current control method,and the control performance of the steady-state harmonic current based on the conventional PR regulator and the second-order low-pass filter is compared,which shows the effectiveness of the proposed current control method.Further,test verification is carried out on the converter valve type test platform.In the steady state,the harmonic current tracks the given value,which can meet the engineering verification needs of the converter valve harmonic current stress.