Research On HVDC Physical Simulation Experimental System Design

There is a reverse distribution between the energy resources and the power demands,Our Country has to implement west-to-east power transmission and power exchange nationwide interconnection. Compared to AC transmission, HVDC has lots of advantages in long distance and large capacity transmission, HVDC is widely used in long distance and large capacity transmission and power grid interconnection..This paper aimed at develop the experimental platform of HVDC system in the dynamic simulation experimental center, the main work of this paper is to design the parameter of converter transformer and smoothing reactor,and to establish the control strategy of HVDC system. the main tasks of the paper are organized as follows:(1)Parameters design of converter transformer and smoothing reactor is investigated. According to the valve surge current, together with three-phase AC short-circuit capacity,rated parameter of HVDC system, the minimal short-circuit impedance of the converter transformer is obtained. The other parameter of converter transformer are obtained based on the impedance of converter transformer. To consider some constraints of smoothing reactor design, an comprehensive expression is obtained to ascertain the reactance of the smoothing reactor. converter transformer and smoothing reactor Parameters of6kilowatt,400volt monopole DC transmission system are designed.(2)Equidistant firing pulse phase control of HVDC converter can effectively eliminate non-characteristics harmonic, this type of pulse control method became most used control mode. Equidistant firing pulse phase control need the phase information of AC system,which can obtained through synchronization phase lock loop(PLL). In this paper, the fundamental theory, the basic composition and mathematic phase model of PLL are established, Aiming at unbalanced and distorted voltage in AC system, parameters of PLL is designed.(3)According to the parameters of Dynamic simulation Experimental Center obtained through three-phase AC short-circuit test, monopole6kilowatt,400volt DC power transmission system is established based on the first CIGRE HVDC benchmark test system. Extinction angle measurement, firing pulse generator, synchronization phase lock loop module are founded using user-defined module, based on user-defined modules,the DC power transmission system is founded,the simulation results of the developed model are given together with the CIGRE benchmark system, the simulation results indicate that the developed model is reasonable and can be used in the following research.In the simulation system of DC transmission system,control output delay time is considered and random disturbance are added into the sampled signal. Finally, this paper analyzes the commutation failure caused by single-phase grounding short circuit and missing firing pulses fault, The work of this paper lays a good foundation for the following testing of equipment.