A parallel converter system controller and control method

Abstract

The invention discloses a parallel converter system controller and control method, comprising a common DC command generation unit and an independent control unit for each converter, the DC command generation unit generates a DC current reference value and sends it to each inverter through communication The control unit of the converter in the constant active power control mode is used as the converter control signal, and according to the received control signal and the collected DC current flowing through the converter, it controls the converter to correct the modular multi-level in real time. The bridge arm of the converter controls the reference voltage value to realize the joint control of the DC power by the parallel converter system. The method and system have high reliability, and at the same time have the power distribution capability between parallel converters, can effectively ensure the synchronization of multiple converters, avoid DC oscillation among the converters, and improve the stability of the system.

Description

technical field [0001] The invention belongs to the field of direct current power transmission, and particularly relates to a parallel converter system controller and a control method. Background technique [0002] In recent years, the comprehensive LCC-HVDC has low cost, low loss, mature operating technology, and MMC-HVDC can realize active power and reactive power decoupling control, can supply power to passive networks, compact structure, small footprint, and no inverter. The hybrid DC transmission technology with side commutation failure 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. At the same time, to a certain extent, the advantages of the project cost are guaranteed. Therefore, the hybrid DC transmission system combining conventional DC transmission and flexible DC transmission will have good ...

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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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