Design of the control circuit used in variable speed diesel generator set
The advanced circuit design of boost and inverter has created much interest in generator of variable speed diesel generating sets. The boost circuit and the topological structure of the three-phase half-bridge inverter were analyzed. The control strategy of Sinusoidal PWM (SPWM) was implemented. To reduce the noise in the control feedback, a low pass filter was in used. At the end of this paper, the authors performed a series of experiments to confirm the stability of the generator set. The experiment results verified that the boost circuit and the inverter designed in this paper are reasonable and can satisfy all the requirements of the diesel generator set.
Variable speed genset with full rated power converter using readily available industrial products
Although a classic diesel genset may reach 35% efficiency at nominal load, it has very poor efficiency at low load conditions. Still, these conditions often occur in real world applications when combining gensets with variable autonomous loads. Previously, the authors built a hybrid genset prototype achieving fuel consumption reductions of over 30%. As an alternative to this hybrid genset, this paper reports on a variable speed genset prototype. To demonstrate a higher fuel efficiency, a prototype 50 kVA variable speed genset has been built using readily available industrial products. A diesel internal combustion engine supplies power to a PM synchronous generator to produce variable voltage, variable frequency AC. Using a four-quadrant variable-frequency drive and transformer this electrical energy is converted to produce an autonomous 4-wire 50 Hz 3×400 V grid. Operation principle, prototype implementation, first load tests (speed response and power quality) and possible improvements are discussed in this paper.
Biodiesel combustion in an optical HSDI diesel engine under low load premixed combustion conditions
An optically accessible single-cylinder high-speed direct-injection (HSDI) diesel engine was used to investigate the spray and combustion processes for biodiesel blends under different injection strategies. The experimental results indicated that the heat release rate was dominated by a premixed combustion pattern and the heat release rate peak became smaller with injection timing retardation. The ignition and heat release rate peak occurred later with increasing biodiesel content. Fuel impingement on the wall was observed for all test conditions. The liquid penetration became longer and the fuel impingement was stronger with the increase of biodiesel content. Early and late injection timings result in lower flame luminosity due to improved mixing with longer ignition delay. For all the injection timings, lower soot luminosity was seen for biodiesel blends than pure diesel fuel. Furthermore, NOx emissions were dramatically reduced for premixed combustion mode with retarded post-TDC injection strategies.