高海拔地区气压较低,在这种低气压下,会使得换流阀设备内部保护层的空间减小,降低电流传输能力,因此需要在极短的时间内完成开关动作,以实现交流电和直流电之间的转换,但会导致其在运行过程中电压和电流变化速度较快,从而产生多种频率的谐波,进而影响谐波检测的准确性。这些谐波的频率通常分布在较高的频段,提取其序列难度极大。为此,研究一种高海拔环境下绝缘架空地线输电直流侧换流阀负荷高频谐波检测方法。捕捉换流阀产生负荷时高频谐波电流随时间变化数值,采用功率流理论确定负荷信号在高频范围内的传递函数,提取换流阀负荷高频谐波序列。根据 LAPC(low arm passive clamp)运行原理,确定换流阀负荷的瞬时电压,控制桥臂投入的总数为固定值,实现对绝缘架空地线输电直流侧逼近调制,修正高频谐波内瞬时频率所带来的挤压干扰。设置一个窗函数来抑制高频谐波的衰减产生的频谱泄露,将主瓣宽度转换为其他谐波高频频率,最终实现对高频谐波的全检测。 搭建谐波检测环境后,通过对高频谐波的全检测可知,所设计的谐波检测方法产生的幅值误差最小,检测性能最佳。
英文摘要:
The low air pressure at high altitude will reduce the space of the protective layer inside the converter valve equipment and reduce the current transmission capacity, so it is necessary to complete the switching action in a very short time to achieve the conversion between alternating current and direct current, while it will lead to the voltage and current change faster during operation, resulting in a variety of frequencies of harmonics. Then, the accuracy of harmonic detection is affected. The frequencies of these harmonics are usually distributed in higher frequency bands, and it is very difficult to extract their sequence. Therefore, a high frequency harmonic detection method of direct current side converter valve load in insulated overhead ground wires transmission in high-altitude environment is studied. The frequency harmonic current changes with time when the converter valve is loaded, and the transfer function of the load signal in the high frequency range is determined by the power flow theory to extract the frequency harmonic sequence of the converter valve load. According to the operating principle of low arm passive clamp, the instantaneous voltage of the converter valve load is determined, and the total number of bridge arm inputs is controlled to be a fixed value, achieving approximate modulation of the direct current side of insulated overhead ground wire transmission and correcting the squeezing interference caused by the instantaneous frequency of high-frequency harmonics. A window function is set to suppress the spectral leakage caused by the attenuation of high-frequency harmonics, convert the main lobe width to other high-frequency harmonics, and ultimately achieve full detection of high-frequency harmonics. After setting up a harmonic detection environment, it can be concluded through full detection of high-frequency harmonics that the designed harmonic detection method produces the smallest amplitude error and the best detection performance.