Control and optimal coordination on multiple power sources for improving power efficiency

Due to the shortage of energy in the world, renewable energy, such as wind, solar, biomass, bio-diesel, nuclear, fuel cell, etc, becomes more and more promising for our future life. In order to fully make use of these possible renewable energy sources, combinations of two or more energy sources for one application have to be considered. The switch and/or control between the renewable energy sources and traditional energy also become an issue in the applications.;In this thesis, in order to achieve a successful control on the multi-energy mode, the power distribution of two sources buck converter controlled by Pusle Width Modual (PWM) has been studied by simulation using the software SIMULINK running in MATLAB environment. Firstly two DC power sources were included into the buck converter, then one of the DC power was replaced by a Proton Exchange Membrane (PEM) fuel cell source. To validate the method, converters with either one DC source or one fuel cell source was firstly simulated. The multi-power mode requires the two power 88 sources not work at the same time. A time delay was added to one of the power supplies.;It is found that, for the open-loop Buck Converter, (i) time delay can be put on any one of the two DC power supplies; (ii) the two DC source converter consumes more power than single DC source converter; (iii) when duty cycle ratio is >75%, higher power efficiency can be obtained. For the closed-loop Buck Converter, (i) the two DC source closed-loop converter consumes less power than one DC buck converter when duty cycle ratio is >60%; (ii) when duty cycle ratio is <60%, higher power efficiency (85%) can be obtained; (iii) the DC1 power supply provide fewer and fewer contribution when the duty cycle ratio keep increasing, and when the duty cycle ratio is 90%, the DC source without the time delay stops providing any power.;For the hybrid source power with one PEM fuel cell in the converter, it is found that similar to the situation of two DC power buck converter, but (i) when the duty cycle ratio is higher enough (>50% for RL=2O), the DC power source will not provide any power, fuel cell source will provide the full power for the converter; (ii) when the duty cycle ratio is small (<50% for RL=2O), the power provided by the DC source will decrease with the increase of the duty cycle ratio; (iii) time delay on different sources will cause different performance. When duty cycle ratio is <50%, time delay on DC source causes higher power efficiency; however, when duty cycle ratio is >50%, time delay on FC source will cause higher efficiency. All these simulations indicate that, multi-power mode control for one application can be achieved.