Matching method of electric turbo compound for two-stroke low-speed marine diesel engine

•Advantage of electric turbo compound (ETC) on fuel economy in low-speed marine engine is proved.•Turbine/compressor efficiency is the root for influences of ETC matching on engine performance.•Peak engine nominal efficiency appears at EMG power which achieves peak turbocharger efficiency.•A matching guideline of ETC for two-stroke low speed engine is obtained.•2–3% improvement of fuel economy in a marine engine is achieved based on matching guideline.