Variable Speed Diesel Electric Generators: Technologies, Benefits, Limitations, Impact on Greenhouse Gases Emissions and Fuel Efficiency

Abstract

A substantial share of the electric energy is generated with synchronous generators that provide sustained alternating current (AC) voltage and frequency energy to regional and national power systems, which subsequently transport and distribute it to diverse users. In an attempt to reduce environmental effects, electric energy markets have recently become more open, resulting in more flexible distributed electric power systems. In such distributed systems, stability, quick and efficient delivery, and control of electric power require some degree of power electronics control to allow for lower power in the electric generators to tap the primary fuel energy potential better and increase efficiency and stability. This is how variable-speed electric generators (VSEG) recently came into play, up to the 400-megavolt ampere (MVA)/ unit size, and which have been at work since 1996. This paper provides coverage of variable-speed electric diesel generators (VSDEG) in distributed generation and their impacts on fuel efficiency and greenhouse gases (GHG). It discusses permanent-magnet-(PM) synchronous generators, solutions based on power electronics such as diesel-driven wound-rotor-induction generator, doubly-fed-induction generator (DFIG), rotating stator generator, and the application of continuously variable transmission to a VSEG. The benefits and limitations of the selected technologies are also presented. The list of references given at the end of the paper should offer aids for students and researchers working in this field.

Experimental Underperformance Detection of a Fixed-Speed Diesel–Electric Generator Based on Exhaust Gas Emissions

“…Conversely, an engine may be operating at low RPMs without necessarily underperforming. This could be intentional during a time of load transition, for example, onboard ships or in rail transport, when the diesel-electric generators operate under low load (≤30%) but for a determined time (less than 30 min) [6][7][8][9]. According to the Caterpillar manufacturer, underperformance occurs when the diesel generator operates under low load (≤30%) for an extended period (over 30 min) and frequently.…”

Modeling and design optimization of a hybrid power generator for full-electric naval propulsion

“…In this way, the limit of working at the fixed frequency of the AC grid is overcome allowing to optimize the engine operating point according to the required load by adjusting its speed [6,7]. It results in different considerable advantages over Fixed Speed DEGs (FSDEGs): fuel saving (around 20% on average depending on the load profile [8]); pollutant and noise emissions reduction [9,10]; maintenance costs reduction and engine life extension (increased time between overhauls by up to 20 percent [11]); and finally higher power density with less installation space.…”