一种适用于风电直接经直流大规模远距离外送的新型换流器

This project proposed an innovative type of converter (denoted as VSC PLUS) that is constituted by series connecting line commutated converter (LCC) and voltage source converter (VSC). VSC PLUS overcomes challenges that LCC cannot be directly connected to wind farms and the defects of VSC that are characterized by high cost, high power loss and the high possibility of tripping wind power generators during DC line faults. VSC PLUS combines the advantages of self-converting, blacking start ability that are associated with VSC and the high power, high voltage rating, low loss, relatively low investment and the DC fault current control ability of LCC. The VSC in VSC PLUS is used to establish the AC voltage of the wind farm so that the VSC PLUS can be connected to AC system such as wind farms which has no stiff supporting AC voltages. During DC line fault, the LCC is used to control the DC fault current, meanwhile the VSC still maintains the AC voltage at the wind farm so that wind power generators do not need to be tripped. The research will be carried out through the three aspects of modeling, control, system analysis. We will establish an integral set of models for analysis of VSC PLUS. Controllers such as black start controller, power flow controller, power flow reverse controller and fault ride through controller will be designed. Detailed design of VSC PLUS will be studied. The feasibility and effective ness will be verified by digital simulation and prototype experiments. The results of this project will provide an innovative economic and applicable technology for inland wind power transmission over long distance.

提出了一种由电压源型换流器(VSC)和电流源型相控换流器(LCC)串联而成的新型换流器VSC PLUS，解决了LCC不能直接联接风电场，VSC高成本、高损耗、直流故障时风电机组容易脱网的问题。VSC PLUS兼具VSC自换相和黑启动能力以及LCC高压大功率、低损耗、更低成本、能控制直流故障电流的优点。VSC PLUS中VSC用于建立风电场的交流电压从而使得VSC PLUS可以直接联接于风电场。当直流输电线路发生故障时，LCC用于控制故障直流电流，而VSC仍维持风电场交流电压，从而保证风电机组不脱网。将从建模、控制和系统分析三个层面开展研究。建立VSC PLUS的各种分析模型，提出黑启动控制、潮流控制、潮流反转控制和故障穿越控制等有效控制策略，给出VSC PLUS的具体设计方法，通过数字仿真和动模实验，验证VSC PLUS的可行性和有效性，为内陆大规模风电远距离外送提供一种经济实用的新技术。

针对相控换流器(LCC)无法直接联接新能源发电，需要火力发电等传统发电系统为相控换流器提供换相电压，电压源型换流器(VSC)可以直接联接新能源发电并网，但成本、损耗高的缺陷，提出了一种由电压源型换流器(VSC)和电流源型相控换流器(LCC)串联而成的新型换流器 VSC PLUS，研究了VSC PLUS的建模、控制、系统分析、设计及实验。所提出的VSC PLUS兼具了VSC自换相和黑启动能力以及LCC高压大功率、低损耗、更低成本、能控制直流故障电流的优点，并克服了VSC以及LCC各自的缺点。所提出的VSC PLUS成本相比于VSC降低了15%，损耗相比于VSC降低了22%。提出了VSC PLUS的黑启动控制、潮流控制、潮流反转控制和故障穿越控制等有效控制策略，给出了VSC PLUS的具体设计方法，通过数字仿真和动模实验，验证了VSC PLUS的可行性和有效性，为内陆大规模风电远距离外送提供了一种经济实用的新技术，为通过多换流器的组合从而产生新的换流器拓扑提供了新的科学方法。