The Key Technology Research Of A Multi-level Reinjection Current Source Converter

The multi-level reinjection current source converter (Multi-level Current Reinjection-Current Source Converter, MLCR-CSC) which is researched in this paper is based on the traditional12-pulse rectifier circuit with injection unit in DC side, through switching the equivalent load of two sets of parallel three-phase bridge periodically, thus transforming the current of the DC side from the constant DC current into two groups DC current with zero zone periodic step changes which are distributed to two groups of three-phase main bridge. Injection circuit not only reduces the switching losses and current change rate of the main bridge, but also overcomes disadvantages of installing large capacity filter device on the AC side of the current source converter. In summary, this new topological structure is combined with multi level, harmonic injection, soft switch and a number of power electronic technologies, can apply to a variety of high voltage and high power applications, having a very broad application prospects.This paper uses the dSPACE real-time simulator researching the key technology of this new multi-level reinjection current source converter, mainly work will be stated in the following:1. Analyzed the topology of a three level reinjection current source converter, to satisfy the requirement of the low distortion of the line current, five level reinjection topology is studied, then proposing the pulse width modulation of the injection circuit, which easier to implementation, can ensure branch current sharing, quickly response to the changes of the main bridge pulses, laying the foundation of the following study.2. Based this topology three parts key technical problem is studied:the critical impedance value design, optimization of the current-sharing element, active power and reactive power decoupling control, and then through off-line simulation verified the correctness of the parameters design.3. Design hardware circuits of control system, which can satisfy the requirement of the AD sampling, data communication, power decoupling, voltage synchronous, pulses producing. Writing switch pulses of the system main bridge and the injected bridge based on Quartus Ⅱ. The shape of experimental wave is observed by high performance storage oscilloscope, providing the reliable trigger pulse which is synchronized with the grid voltage. 4. Configuration the hardware and software system, building MLCR-CSC real time simulation platform based on the dSPACE. The input-output description method is adopted to build the hardware in loop real-time simulation modeling of the MLCR-CSC system. The experiment results show the feasibility of pulse modulation and correctness of the parameter design, laying the foundation of the verification of the experimental platform.