Research On Equivalent Test Method For Fault Ride-through Of Flexible DC Converter Valves Modules Which Integrated Energy Dissipation Function

The integrated energy-consuming MMC(IEC-MMC)converter valve can effectively dissipate the surplus power generated during the low-voltage ride-through of the offshore wind system to achieve low-voltage fault ride-through.At the same time,the converter valve is the core equipment of the converter station and a complete type test is an important means of ensuring the normal operation of the converter valve and achieving fault crossing.However,existing studies have only carried out theoretical analysis and simulation verification of the energy dissipation process of the integrated energy consuming MMC converter valve,without studying the equivalence of the stress changes inside the converter valve,and lacking research on the equivalent test of the integrated energy consuming MMC converter valve modules fault ridethrough.Therefore,this paper proposes an equivalent assessment index covering the fault ride-through process,taking the integrated energy-consuming MMC valve as the research object,and solves the problem of the lack of assessment index for the fault ride-through equivalent test;An equivalent test circuit with integrated energy dissipation and a corresponding equivalent test method are proposed to provide a feasible solution for reproducing the stress changes during valve fault ride-thro ugh.At the same time,it also provides an important reference value for the type test of the converter valve.Firstly,this paper introduces the existing mainstream MMC topologies and their corresponding operating modes and states.On this basis,the sub-module topology and three-phase topology of the integrated energy-consuming MMC converter valve are introduced in detail,and the operating principle is analysed to reveal the operating mechanism of the integrated energy-consuming MMC converter valve.The control logic of the converter valve with integrated energy consumption during fault ridethrough is presented in relation to the existing MMC control logic,and the function of the converter valve with integrated energy consumption to dissipate the surplus power is verified by simulation.Secondly,the stress changes of the integrated energy-consuming MMC converter valve during operation and fault ride-through are analysed in detail.Based on the selection of key indicators,equivalent assessment indicators covering the whole process of operation and fault ride-through are proposed,providing a technical reference standard for fault ride-through equivalence tests.Then,the equivalent test circuit with integrated energy consumption and the corresponding equivalent test method for fault ride-through are proposed according to the equivalent assessment index.The correctness of the proposed test circuit and the test method is verified by simulation.Finally,a 100kW equivalent test rig was built and the parameters for the selection of the test rig were matched,and work related to the construction of the water cooling system,the selection of the measurement equipment and the coding of the FPGA hardware program was carried out.Equivalent tests of fault ride-through at low voltage levels were then carried out using an equivalent test platform to further validate the effectiveness and feasibility of the integrated energy dissipating MMC converter valve and the correctness of the research work in this paper.