Reserch On Dynamic Voltage Regulating Device Of Distribution Network

To meet the requirements of voltage quality of distribution networks for China’s industrial structure upgrade and to ensure that high-tech equipment and other sensitive load can keep running safely and efficiently.Improving voltage quality of distribution network has become the focus and aim of the work of the power supply sector.With high operating efficiency,good dynamic performance and strong real-time compensation ability,Dynamic voltage regulating device has become a research hotspot on the aspect of solving the problem of low voltage quality of distribution networks.The working principle and topology of DVR are analysed in this thesis,and the advantages and limitations of different types of device structure are compared and analysed.According to analysis,the DC energy storage unit,inverter structure and the network connectivity method of DVR device are determined.The cascade multi-level structure is used as the inverter unit of DVR,and the corresponding modulation methods are studied and the simulations are built respectively.It is proved that the technology of carrier phase-shifted modulation can improve the harmonic characteristics of the output voltage.The control strategy of PWM rectifier unit is designed,and the triangular carrier comparison control method is used,and P combined with feedforward controller and PI controller are used as current loop and voltage loop respectively.Then,the tracking effect of current loop is simulated and analysed.The applicable scope and limitations of the conventional voltage detection methods and traditional three-phase dqO transformation method are introduced and analysed,and the single-phase dqO transformation methods are researched in depth,single-phase dqO transformation method and dqO derivative detection method,single-phase αβ-dq transformation method and ap-dq derivation method are simulated and compared with their real-time performance.In order to make up for the shortcomings of the derivative detection method in practical application,a single-phase voltage three-point detection method is presented and simulated in this thesis.Three voltage compensation strategies are studied and compared with their applicable scope and compensation effect.The main circuit topologies of 10kV/800kVA and 0.4kV/20kVA DVR devices are given and the component parameters are calculated.The stability of feedforward control strategy and composite control strategy are analysed.The simulation model of 10kV and 0.4kV voltage regulator are built using simulation software PSIM,and the common voltage quality problems of distribution network are simulated and analysed respectively.Based on the results of the previous analysis,The hardware design and software design of control system of a 380V DVR experimental prototype are completed.The experimental prototype is realized.The DVR prototype is tested by experiments which simulate the common voltage quality problems of the distribution network.The experimental result verifies the DVR prototype has the ability to compensate for voltage and good voltage tracking performance.