Study On Non-contact Synchronized Measurement Method For Alternate Electrical Power System With Renewable Energy Sources

With the proportion of renewable energy sources continuously increasing,the closed-loop control methods driven by both model and data are gradually replacing those model-driven methods,which presents a new requirement for panoramic synchronized real-time monitoring in the area with high penetration of renewables.However,there is no PT/CT at many key monitoring nodes in the area with high penetration of renewables due to the manufacturing and installation costs,which limits synchronous measurement.Non-contact sensing technology has the advantage of flexible,safe,and cost-effective,which provides a practical foundation for large-scale deployment of synchronous measurement devices.Non-contact voltage and current sensing-based synchronized phasor measurement method are presented in this thesis,the main innovations are as follows:Aiming at the issue of non-contact voltage sensing for insulated wire,the wire electric field model is established and a concentric cylindrical capacitors-based voltage probe is proposed.The function between probe’s gain and the wire radius is derived,and an inverse voltage calculation method is proposed,which builds measurement equations by changing the thickness of capacitor dielectric.Experimental data indicate that the sampling circuit extracts a weak current from the probe,which changes the probe output voltage phase and causes voltage calculation errors.Aiming at the issue of probe voltage phase deviation,the equivalent circuit diagram and transfer function are derived,and a double probes-based voltage phasor inverse calculation method is proposed.Simulation and experimental results show that the proposed method can figure out the wire voltage phasor without damaging wire sheath.For steady-state voltage,the amplitude measurement error is less than 2%,the phase measurement error is less than 0.2°.Aiming at the issue of non-contact current sensing,the magnetic field model of a long straight current-carrying wire is established in Cartesian coordinate system.The equation among the magnetic sensor’s position,sensitive direction and output magnetic field intensity is derived.A magnetic sensor array-based current sensor design and the corresponding current inverse calculation method are proposed,the current can be figure out by using 4 magnetic sensors with same sensitive direction.A current sensor prototype is developed by using tunneling magnetoresistance(TMR)chip.Experimental results show that,the prototype has an amplitude measurement error of less than 1%and a phase measurement error of less than 0.1° for steady-state current.Aiming at the issue of non-contact voltage and current phasor measurement,the electrical signal characteristic in the area with high penetration of renewables is analyzed.The transfer characteristic of the proposed non-contact voltage probe and TMR chip are analyzed.The problem and reason of multicomponent signal distortion caused by non-contact sensor are revealed.Time-domain fitting-based non-contact voltage and current phasor measurement algorithms are proposed.Simulation and experiment results show that the algorithms combined with the proposed non-contact sensors can achieve non-contact phasor measurement.The voltage amplitude measurement errors are less than 5%,the voltage phase measurement errors are less than 2°,and the current amplitude measurement errors are less than 1.2%,the current phase errors are less than 0.25°.