Design And Development Of Experimental Platform For Hybrid HVDC System

Hybrid high voltage direct current(HVDC)system structure,which is constructed by Line Commutated Converter(LCC)and Voltage Sourced Converter(VSC),has won the attention of academics because it has advantages of both LCC and VSC.Nowadays,researches about hybrid HVDC system are mostly about theories and simulations.To further study the characteristics of hybrid HVDC system and make the results match the actual projects,practical experiments are necessary.Meanwhile,hybrid HVDC system has a number of different structures.As a result,the experiment platform should be designed with the capacity of constructing different structures of hybrid HVDC system to improve the expansibility of the platform,and make it more convenient to conduct experiments under different hybrid HVDC system structures.Based on the requirements mentioned above,this paper designed and developed an experimental platform composed of LCC and VSC modules for researching characteristics of hybrid HVDC systems with different structures.By flexibly combining different modules,various hybrid HVDC structures can be constructed,and its control system framework can meet the requirements of the system control for various hybrid HVDC topologies.To start with,the paper determined the overall design of the experimental platform for hybrid HVDC system,and finishes the design of the parameters and circuits of the experiment platform.Then,the control structure of the experimental platform was designed and a general control framework composed of systematical and converter-based controllers was constructed.Then,the communication protocol was established and the core control algorithm was programmed for the overall system.After the work of designing and developing the experiment platform,experiments were conducted under different hybrid HVDC system structures.First,this paper conducted the DC current and voltage step-change experiments based on the hybrid HVDC structure,which adopted LCC as rectifier and VSC as inverter.The experiment results had proved the adaptability of the overall design of the experiment platform and its benign features under stable conditions,Then,the series hybrid HVDC system was constructed on the experiment platform.Experiments focused on the control strategy and DC fault blocking were conducted and the experiment results tested the rationality of the control strategy and the capability of DC fault blocking along with the results of theoretical analysis.