Deterministic Characteristics Analy-sis Of Nonlinear Dynamic Load And De-sign Of Dynamic Current Control Unit

The existence of the nonlinear dynamic load in the smart grid will cause the impact power, harmonic current, voltage deviation and three-phase imbalance. The influence of dynamic load characteristics on the measurement of electric energy meter and the measurement error of electric energy meter has attracted the attention of relevant researchers.Firstly, this paper introduced the development and research status of nonlinear dynamic load characteristic analysis and dynamic characteristic test of energy meter, and the importance of dynamic load deterministic characteristics analysis and dynamic current control unit are elaborated.Secondly, this paper point out that the distributed photovoltaic power,arc furnace, electric railway and rolling mill are typical nonlinear dynamic load, and acquired the instantaneous voltage and current signal when the load were working. This paper proposed the deterministic characteristic quantities of typical nonlinear dynamic loads by combining the indexes of load power quality and power characteristic. According to the definition and mathematical description of deterministic characteristic parameters, analyzed the data of distributed PV power supply, arc furnace,electrified railway and rolling mill applying piecewise FFT cosine window interpolation FFT and other methods. Then drew the conclusion of nonlinear dynamic load characteristic analysis, confirmed the main characteristic parameters and secondary characteristic parameters.Thirdly, the dynamic current control unit based on SCR was designed, realized the generation of dynamic current with changing amplitude by SCR. The dynamic current which maximum effective value up to 20A, was outputted to tested electric energy meter, to test and understand the dynamic characteristics of the measured energy meter adequately. The control signal of SCR is square wave signal whose on-off ratio is adjustable, so that the dynamic current has three mode, transient mode, short-time mode and long-time mode.Finally, a testing system is set upped with dynamic current control unit and several electric energy meter. The test result shows that the wave form of the dynamic current is complete and has small turn-on delay time,so the dynamic current control unit can be used for the dynamic characteristic test of the electric energy meter.