基于Sobol拟随机脉宽调制的电网阻抗测量方法

利用并网逆变器获取的实时电网阻抗信息可用于电网状态监测、故障诊断、并网设备稳定控制等领域,提高并网设备和电网调控的智能化水平。由于注入的扰动信号常施加于逆变器电流控制环路,阻抗测量频段受限于控制器带宽。为了提高高频阻抗测量的准确性,文中利用随机脉宽调制的频谱搬移和Sobol拟随机序列的均匀性,提出了一种基于Sobol拟随机脉宽调制(SQRPWM)的电网阻抗测量方法,并根据系统带宽和稳定性约束等条件优化设计了SQRPWM频率边界。在Starsim的实验平台上验证了所提出的SQRPWM阻抗测量方案以及单脉冲+SQRPWM混合阻抗测量方案的可行性,结果表明所提阻抗测量方案具有扰动小、高频段测量精度高的优点,并可与基于电流扰动的阻抗测量方案联合,扩展电网阻抗测量的频段,获取宽频阻抗信息。

Power Grid Impedance Measurement Method Based on Sobol Quasi-random Pulse Width Modulation

The real-time power grid impedance information obtained by grid-connected inverters can be used in power grid status monitoring, fault diagnosis, and grid-connected equipment stability control, to improve the intelligent level of grid-connected equipment and power grid regulation. Since the injected disturbance signal is often applied to the current control loop of the inverter, the impedance measurement frequency band is limited by the bandwidth of the controller. In order to improve the accuracy of high-frequency impedance measurement, this paper proposes a power grid impedance measurement method based on Sobol quasi-random pulse width modulation (SQRPWM) by taking advantages of the characteristic of the frequency spectrum shift of random pulse width modulation and the uniformity of Sobol quasi-random sequences. The frequency boundary of SQRPWM is optimized and designed according to the system bandwidth and stability constraints. The feasibility of the proposed impedance measurement scheme based on SQRPWM and the mixed impedance measurement scheme combined with the single pulse and SQRPWM is verified on the experimental platform of Starsim. The results show that the proposed impedance measurement scheme has the advantages of small disturbance and high measurement accuracy in a high frequency band. Moreover, if the proposed method is combined with the current-disturbance based impedance measurement method, the frequency band of the power grid impedance measurement can be further expanded and the broadband impedance information can be obtained.