Advanced Control of a Compensator Motor Driving a Variable Speed Diesel Generator with Rotating Stator

Abstract

Variable speed generators can improve overall genset performance by allowing the diesel engine to reduce its speed at lower loads. In this project, a variable speed diesel generator (VSDG) uses a rotating stator driven by a compensator motor. At lower loads, the stator turns in the opposite direction of the rotor, a process that can be used for purposes like maintaining a fixed relative speed between the two components of a generator. This allows the diesel engine to turn at a lower speed (same as the rotor) and to increase its efficiency. The present research addresses the control of the compensator motor driving the generator’s stator using a variable-frequency drive that adapts the speed to its optimal value according to the load. The performance of the proposed control strategy was tested using a Freescale microcontroller card programmed in C-code to determine the appropriate voltage for the variable-frequency drive. The control algorithm uses a real-time application implemented on an FDRM-KL25Z signal processor board. The control performance of a 2 kW asynchronous motor (LabVolt EMS 8503-00/208 V/3 ϕ/60(50) Hz) was demonstrated experimentally at different operating conditions.

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

“…This is because the power generator reaches synchronous speed by turning the stator in the opposite direction to the rotor. This feature allows the DE to operate within its optimum speed range while there is a considerable change in electrical load [65].…”

“…Power converters are used to control the Genset-Synchro compensator motor. As this motor has a power equal to a small fraction of the permanent magnet synchronous generator (PMSG), the costs with the power electronics are less, as are the negative impacts of the power converters on the system, such as the presence of harmonics due to the switching thyristors [65]. Figure 11 shows a diagram representation of this control system.…”

“…The main advantage is that this solution can be applied in isolated locations in the existing generator without modifying the diesel engine block. Studies [1,3,[64][65][66] show that the Genset-Synchro system saves up to 15% when the applied load is below 40% of the rated power and an average reduction of 7% of pollutant emissions. The disadvantage of this technology is the presence of brushes in the synchronous generator that require higher maintenance frequency.…”

“…The disadvantage of this technology is the presence of brushes in the synchronous generator that require higher maintenance frequency. In addition, its maximum power is limited to 85% due to the compensation motor that drives the stator [1,3,[64][65][66].…”

A grid frequency control on small scale power system by introduction of variable speed diesel‐driven power plant

“…As regards studies on diesel power generation assuming variable speed control, there are examples of analysis of generator main circuit and its control system response using simulations and mini-model experimental systems, or methods of high-efficiency operation based on characteristics of generators and diesel engines, [4][5][6][7] but few, if any, reports deal with a comprehensive analysis involving demand-and-supply balance and grid frequency fluctuations in a power system.…”