Mathematieal Modeling And Simulation For Voltage Source Converter Based HVDC System

With the development and the progress of electric power technology, the highvoltage direct current transmission based on voltage source (VSC-HVDC) technologyis increasingly mature and widely used in transmission areas. It has been adopted in thecontrol systems as the grid interconnection of wind power station, a lonely island, andweak power supply and power supply project of the city.However, the traditional PIDcontrol algorithm for the VSC-HVDC is difficult to achieve satisfactory controlperformance in nonlinear, strong coupling, multivariable system.This study uses the Park transform and Clark transform, under the three-phasestatic ABC coordinate and the dq coordinates system witch suitable for control systemdesign, set up the mathematical model of the VSC-HVDC system at both end in bystudying the system structure. On the basis of the mathematical model, the PID controlalgorithm and ADRC control algorithm is applied to the control of VSC-HVDCconverter station system. From the simulation curve,we can see that the controller basedon PI and ADRC implemente the decoupled of the inner ring, and can completelyindependent control of active power and reactive power, and the system has goodtraceability, stability and rapidity.Applying the same disturbance and make the system of load change at the sametime respectively in the two different systems, through the analysis and comparison, wecan draw a conclusion that the two systems of dc voltage and reactive power, activepower and other parameters will have corresponding change when there is interferencesystem or the system load changes, but the whole system can still maintain the powerbalance of system, to realize independent control of active power and reactive power,the real value of its parameter can also be a good tracking parameter value.But compared to the PI,the converter station based on the ADRC has higher steadyprecision, stronger anti-interference ability, and it can make control parameters toachieve stable value more quickly, and the converter station based on the ADRCimproves the disadcantage the PID controller that based on the operating conditionschange constantly adjust the control parameters.So, the ADRC is suitable to the controlsystem of VSC-HVDC converter station.In addition,when the VSC-HVDC occursing system failure, it can cause damageto equipment or interrupt transmission and so on.In view of this characteristic,the studyfocus on the running condition of the both system under the eight kinds offault.Through the analysis of the simulation curve, the conclusion is that when thesystem occurses failure, the dc side and ac side is easy to appear the phenomenon ofover current, over voltage, and the failure will affect the size of transmission power.Andthis effectively provides a theoretical basis for the research of the failure protection inthe future.