The Voltage Regulation Technology Research Of Distribution Network Based On Controllable Series Devices

Distribution network is in the grid distribution power network,which is in the power system directly to the load power supply.At present,the frame structure of the vast distribution network is weak,running situation complex,which frequently leads to the phenomenon of supply voltage droping,unqualified to load voltage and so on.Since the science and technology progress and the development of industrialization,all kinds of modern electric equipment is more and more high to the requirement of power quality.Once the power is out of order,it will interfere with the normal operation of sensitive equipment,causing huge economic losses as well as influencing the development of social economic construction.So,the research of power compensation equipment is more and more attention.Regarding the common voltage quality in distribution network power quality as the research object,we designed a Series Voltage Quality Controller(SVQC).The series voltage quality controller is a way to solve a variety of voltage quality problems which is a new power electronic devices.It is connected between sensitive load and the power grid by the transformer detecting the power grid voltage quality(such as voltage up and down,harmonic,etc)in real-time,which is to produce the required compensation voltage according to the appropriate control strategy to ensure the quality of power supply of sensitive load.SVQC can realize dynamic and steady-state voltage compensation at the same time,reducing the adverse impact of the load duo to the supply voltage distortion,managing comprehensively the user side voltage,which is a flexible and effective device to control the quality of power grid voltage.The innovation of the paper mainly focused on the control strategy of the device and proposed a new control scheme-variable hyteresis width but constant frequency switched control.We used the theory of lyapunov quadratic stability and convex combination,constructing the common lyapunov function of each subsystem and dividing the movement of each subsystem into new areas,which can make the system always run in the derivative minimum lyapunov function subsystem so as to realise the stability control.It is the case that it will appear frequent switching problem near the switched equilibrium in the process of switched control,so we introduced a variable width but fixed frequency hysteresis control inthe switching laws,which is helpful for the selection of the output filter parameters,greatly alleviating the problem of frequent switching,lowering the switching frequency,reducing the noise of the converter as well as prolonging the service life of the switcher.The source of energy of SVQC is different when making the different compensation function,when the compensation for dynamic voltage which is the dc power supply while the static compensation its using the energy storage power from the rectifier device.In this paper we studied both the dynamic and steady state compensation research respectively and among the steady-state we divided it into two ways-voltage regulator and voltage stabilizer.So-called voltage regulator is that no matter how to change(up/down)grid voltage,the load voltage is always higher than the grid voltage a percentage.So-called voltage stabilizer is that no matter how to change(up/down)grid voltage,the load voltage always maintains the preset value.We introduced the voltage detection method and the compensation way of SVQC in detail,having comparatively studied the difference between voltage regulator and voltage stabilizer about the structure and performance and calculated the respective voltage compensation scope.Finally,through the dynamic and steady-state voltage compensation waveform simulation,we verified the feasibility and effectiveness of the variable hyteresis width but constant frequency switched control strategy.