Research And Design Of Reactive Power Compensation Device For Intelligent Distribution Network

Smart distribution network,as an important part of knowledge network,is closely related to the needs of users.It has the characteristics of distributed production,nonlinear load and power electronics.So that we can make full use of renewable energy,power efficiency has been significantly improved.But it also makes the power quality seriously reduced.Static var generator(SVG),as a kind of contemporary reactive power compensation device,has become the mainstream of reactive power compensation market due to its fast response,low loss,small volume of energy storage element and low harmonic content of output current.Among them,cascaded H-bridge SVG has the characteristics of modularization and high compensation accuracy,Widely used in high pressure and large capacity facilities.Taking a 10 k V system with 1000 kvar compensation capacity as an example,this paper applies cascaded H-bridge SVG to control the DC side voltage under balanced and unbalanced conditions,and studies its control strategy.Firstly,a SVG mathematical model based on dq coordinate system and H bridge function is established.The CPS-SPWM voltage is modulated by technology Then,the SVG system is designed to measure the reactive current based on the instantaneous reactance theory under balanced condition,Based on instantaneous symmetrical component method,reactive current can be tracked effectively under unbalanced condition.Due to the complexity of SVG design and the modular control strategy of SVG under balanced and unbalanced conditions,In this paper,the step control system of DC bus voltage is adopted,that is,the step control system of DC bus voltage.The inner current loop is used to track and compensate the working loss,The external voltage is environmentally friendly and provides constant active balance,which provides a useful reference for the internal current loop.Due to the difference of phase loss,the voltage of each phase of capacitor is unbalanced,However,it may inject additional reverse sequence current into the system,The problem of zero sequence input voltage is solved;Aiming at the problem of positive and negative error segmentation sequence in the system,a segmentation method with high dynamic characteristics is proposed Moreover,it has high precision,which not only ensures the accurate series separation of asymmetric network,but also ensures the accurate closing of voltage;The voltage fluctuation caused by input current and output current leads to static error,Based on the original phase balance control strategy,an improvement is made.Finally,the compensation effect and dynamic response of the SVG simulation system are tested.The validity of the control method and the accuracy of parameter design are verified.The SVG system is verified by application program.