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提出具备阻断直流故障电流的两端口直流–直流自耦变压器。共提出两种方案，分别为将直流自耦变的第一、第三换流器改造为具备阻断直流故障电流能力的换流器，以及在直流自耦变直流高低压直流端口间安装直流断路器。论述了两种方案的拓扑结构，推导了两种方案下所使用的换流器总容量随变比的关系，分析结果表明，安装直流断路器的方案所使用的换流器总容量少于改造换流器的方案。仿真验证了加装直流断路器方案的有效性，结果表明，在变比为1~2.5 的范围内，两种方案下，具备阻断直流故障电流的直流–直流自耦变压器所使用的换流器总容量始终小于1.3 倍互联功率，且所使用换流器总容量随变比降低而降低；而常规的直流–交流–直流变换技术无论变比如何变化，所使用的换流器总容量始终为2 倍的互联功率。在PSCAD/EMTDC 下仿真验证了所提出的保护方案的正确性。“,”This paper proposes a DC-DC autotransformer that is able to block the propagation of DC fault current. Two schemes are presented. Scheme1 is to employ self-blocking MMC that is able to block DC fault current for VSC1 and VSC3 in the DC auto. Scheme2 is to install semiconductor based DC circuit breaker between the high and low DC voltage terminals of the DC-DC autotransformer. The relationship of the total used converters versus the changes of the voltage stepping ratio is deduced. Methodologies of dimensioning the voltage and power ratings of the self-blocking MMC and the DC circuit breaker are proposed. It is found that DC circuit breaker scheme requires lower total used converters than the self-blocking MMC scheme. With the voltage stepping ratio varies from 1~2.5, the total required converter is always below 1.3 times the rated transferred power for both the schemes. The total required converter reduces with the reduction of the turn ratio while for the conventional DC-AC-DC technology; rating of the total used converters is always two times the rated transferred power. Simulations on PSCAD/EMTDC verified Scheme of installing DC circuit breakers.