基于光伏逆变器的电网谐波阻抗测量新技术

New Technology of Grid Harmonic Impedance Measurement Based on Photovoltaic Inverter

针对新型电力系统背景下电网谐波阻抗的测量需求,提出了一种基于光伏逆变器的新型电网谐波阻抗测量方法。所提方法不会对电网产生扰动,无需安装额外的测量设备,并且还能在阻抗测量过程中治理电网谐波。该方法在基波下控制光伏逆变器实现正常发电功能,在谐波下控制其等效为虚拟电阻。通过改变逆变器的等效虚拟谐波电阻值,测量并网点谐波电压的幅值,并结合最小二乘法来估算系统的谐波阻抗幅值。利用硬件在环实时仿真试验平台进行阻抗测量试验,测量结果与设定值相符,系统5次谐波阻抗的测量精度达99%,7次谐波阻抗的测量精度达97%,验证了所提方法不仅可测量系统多次谐波阻抗幅值,且能保证较高的测量精度。

In response to the demand for grid harmonic impedance measurement in the context of new power systems,a novel grid harmonic impedance measurement method based on photovoltaic inverter is proposed.The proposed method does not disturb the power grid,does not require the installation of additional measurement equipment,and can also control grid harmonics during the impedance measurement.The method controls the photovoltaic inverter to function as a normal power generator under fundamental waves and controls it to be equivalent to a virtual resistor under harmonics.By changing the equivalent virtual harmonic resistance value of the inverter,the amplitude of the harmonic voltage at the grid connection point is measured,and combined with the least squares method to estimate the harmonic impedance amplitude of the system.The impedance measurement experiment is conducted using the hardware-inloop real-time simulation experimental platform,and the measurement results are consistent with the set values.The measurement accuracy of the 5th harmonic impedance of the system reaches 99%,and the measurement accuracy of the 7th harmonic impedance reaches 97%,which verifies that the proposed method can not only measure the amplitude of the system’s multiple harmonic impedance,but also ensure high measurement accuracy.