Research On Modeling And Compensation Method For Time Delay Of Wide Area Measurement Signals

Inter-area low frequency oscillation problem is a big threat to the security and stability of power system in interconnected power grid. The wide area measurement system (WAMS) is based on synchronized phasor measurement technology, can provide real-time, accurate synchronous signals of many nodes in power system, which can be used for designing wide area network controller to solve the inter-area low frequency oscillation problem. But the information delay of WAMS is a non-negligible factor during controller design, modeling and compensation method of WAMS’s latency is of great importance for solving the time delay issues.In this paper, the components of time delay are introduced based on the structure of WAMS. A method based on probabilistic model to describe the delay in WAMS is proposed according to the characteristics of randomness of delay. Under the actual operation condition of WAMS of Zhejiang power grid, the information delay of WAMS is measured, and the statistical characteristics of the delay are analyzed. A model of time delay is built based on the probabilistic model and the large amount of actual operation data measured in the WAMS of Zhejiang power grid. The result indicates that Rice distribution can effectively show the probability distribution characteristics of communication delay in WAMS during different period of time and in different PMU sub-stations. As for compensation method for time delay, this paper tackles the time delay problem by integrating a compensator for time delay with typical wide area networked control system (WNCS). Based on the well learned fact that signals as input for wide area controller of power systems, such as angular velocity and power angle of generator, can be approximated by linear combination of attenuation trigonometric functions, an improved prony algorithm is proposed and a validity index for assessing effectiveness of compensation method is provided. The proposed method solves noise problem with Butterworth filter and eliminates the introduced phase shifting of the filter by modifying compensator parameters. The proposed method is presented in detail and its effectiveness is verified, with application to time series signals extracted from transient simulation of standard IEEE four-machine two-area system and PMU measured data in Zhejiang power grid. Also, a closed-loop system, which includes RTDS, power amplifier, and wide area damping controller, is used to test the compensation effect, the result shows that this algorithm can be used in real-time compensation for time delay, and can improve the control performance of the controller.