Inversion Algorithm for Surface Charge Distribution on Insulator in Shift-Invariant System Based on Constrained Least Square Filter

Surface flashover on an insulator caused by the charge accumulation at the gas-solid interface is one of the main reasons limiting the development of gas insulated equipment in high voltage direct current (HVDC) condition. Therefore, it is helpful to clarify the mechanism of surface flashover and surface charge behavior by measuring charge distribution with high accuracy. In this article, a surface charge inversion algorithm based on constrained least square filter (CLSF) is proposed for surface charge measurement in a shift-invariant system. By taking the image restoration technology as an analogy, the algorithm transfers matrix equation into frequency domain by 2-D Fourier transform, which significantly simplifies the computational process. Then the CLSF is used to suppress the noise signal and actualize the conduction from surface potential distribution to surface charge density distribution. The calculation process and accuracy of the algorithm are discussed in detail with the simulated examples, and the inversion performance of CLSF is compared with Wiener filter. At last, the effectiveness of the algorithm is verified by performing surface charge measurement and dust figure. This methodology gives an innovative idea of potential-charge transformation process with higher accuracy and stability, which benefits the development of surface charge measurement technology.