Parallel converter system controller and control method

Abstract

The invention discloses a parallel converter system controller and a control method. The controller comprises a common direct current instruction generation unit and independent control units of all converters. The direct current instruction generation unit generates a direct current reference value and sends the direct current reference value to the control unit of each converter in the constantactive power control mode through communication to serve as a converter control signal; and the converters are controlled to correct the bridge arm control reference voltage value of the modular multilevel converter in real time according to the received control signal and the acquired direct current flowing through the converters, thereby realizing common control of the direct current power by the parallel converter system. The method and the system are high in reliability, have the capability of distributing power among the parallel converters, can effectively ensure the synchronization of the plurality of converters, avoid direct current oscillation among the converters, and improve the stability of the system.

Description

technical field [0001] The invention belongs to the field of direct current transmission, and in particular relates to a parallel converter system controller and a control method. Background technique [0002] In recent years, integrated LCC-HVDC has low cost, low loss, mature operation technology and MMC-HVDC can realize decoupling control of active power and reactive power, can supply power to passive network, compact structure, small footprint, and no inverter The hybrid DC transmission technology for the problem of commutation failure on the rectifier side has been developed rapidly and has good engineering application prospects. By using LCC-HVDC on the rectifier side and MMC-HVDC on the inverter side, the commutation failure on the inverter side can be reduced or avoided. problems, and at the same time guarantee the advantages of project cost to a certain extent. Therefore, the hybrid HVDC system combining conventional HVDC and flexible HVDC will have good engineering...

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Problems solved by technology

However, these methods have great disadvantages: the first two methods not only greatly increase the hardware cost and system volume and additional hardware power loss, but also cannot completely suppress the DC side resonance phenomenon, and the newly added LC components may stimulate new The resonant frequency point of the third method; the essential idea of ​​the third method is to suppress the peak of the impedance frequency response characteristic of the DC network through the idea of ​​loop shaping to suppress the resonance. However, it can only suppress the resonance of a specific frequency, and it may increase The possibility of resonance excitation at other frequency points is large. In addition, since the frequency response of the DC network in actual engineering is difficult to estimate and the natural frequency cannot be determined, the feasibility of implementation is not high, and it is difficult to promote in a large area

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