Patent Application
20070166576
The present invention relates to a fuel cell power generation control methodology and the applications thereof, particularly to a fuel cell power generation control methodology, wherein a current value of an input side of a DC converter is controlled by the DC converter to keep it within a constant current limit, so that the fuel cell operates below or at maximum power output or optimum efficiency output, and can supply electricity at energy-saving status together with other electric power output devices.
Conventional DC converters, for example, conventional DC converters for use in secondary batteries, generally only need to consider the stability design of constant voltage output, and their output current can change with the load, and need not concern the effects of the voltage of electric power generated by secondary batteries on conventional DC converters. In addition, as secondary batteries are energy capacitors for storing energy after recharging, so that when using it, energy is released because of electricity discharge, and if the electric current is sufficient when secondary batteries are discharging electricity, the output current of secondary batteries can be kept at a constant current. Therefore, under sufficient electricity, secondary batteries can be considered constant voltage elements. However, fuel cells are energy converters, and do not store energy in advance. Therefore, if fuel cells are used together with conventional DC converters, and because the current value of the electricity generated by fuel cells will be subjected to great changes due to external load, conventional DC converters still convert energy based on the input current after fuel cells have been changed. Although conventional DC converts can still supply the power required by the load, the fuel cells do not necessarily operate at optimum power output.
In addition, an electronic system that uses fuel cells generally also uses other electric power output devices, for example, rechargeable secondary lithium batteries. Especially in a portable electronic system, it is not possible to know when the electricity of secondary batteries can be supplied, and the life of secondary batteries will be shortened due to frequency recharges. However, the fuel of fuel cells can be refilled at any time. Therefore, it is necessary to lower the electric power output of secondary batteries as far as possible, and electric power output supply achieves energy conservation of secondary batteries, primarily based on fuel cells.
In view of the foregoing weakness of conventional DC converters in providing the operational model for the optimum power output status of the fuel cell, the present inventor has come up with an improved fuel cell power generation control methodology, so that fuel cells continue to operate at optimum power output, and this control methodology is then applied in a multi-energy supply system that combines fuel cells and other electric power output devices.
It is a primary objective of this invention to provide a fuel cell power generation control methodology and the applications thereof, so that DC converters keep output current at a constant current, and fuel cells continue to operate at optimum power output.
To achieve the above objective, the present invention provides a fuel cell power generation control methodology and the applications thereof, comprising the following steps: providing DC converters and fuel cells, and electrically connecting an input side of DC converters to an output side of fuel cells; converting the output electricity of fuel cells into a constant voltage output by means of DC converters; so that DC converters keep the input side of DC converters within the planned limit of a constant current. In other words, even if the output current of fuel cells are kept within a planned limit of a constant current, a current limit value is set for the planned limit of the constant current according to the quantity of membrane electrode assembly (MEAs) of the fuel cell and the current limit generated at optimum power interval of MEA, wherein the optimum power interval refers to any status of maximum electric power output and maximum power output of MEA that can be generated by the MEA at unit fuel consumption.
The present invention can also be applied in fuel cells, and together with other electric power output devices, provide multi-energy output.
The above objects and advantages of the present invention will become more apparent with reference to the appended drawings wherein:
The fuel cell output side (11) of the fuel cell (1) is electrically connected to a DC converter input side (31) of the DC converter (3) and the secondary battery output side (21) of the secondary battery (2) is electrically connected to another DC converter input side (31) of the DC converter (3), so that electricity generated by the fuel cell (1) and the secondary battery (2) is transmitted to the DC converter (3). In addition, the DC converter output side (32) of the DC converter (3) is electrically connected to the load (4) to transmit electricity at a specific voltage to the load (4).
The fuel cell (1) is a fuel cell made by the manufacturing process of a printed circuit board.
The step (103) is to convert the output electricity of the DC converter (3) by the fuel cell (1) into a constant voltage output. The DC converter (3) converts the electricity generated by the fuel cell (1) through buck logic or boost logic, by circuit into constant voltage output, which is then outputted by the DC converter output side (32) for the load (4.) Of course, the constant voltage output of the DC converter (3) is not limited to the output of a constant voltage, and based on the actual needs of the load, the DC converter (3) can also be converted into a different constant voltage output.
The Step (105) is a process in which the DC converter (3) keeps the DC converter input side (31) within the planned limit of a constant current. In other words, the fuel cell output side (11) is kept within the planned limit of the constant current, wherein the planned limit of the constant current is determined by the quantity of MEAs in the fuel cell (1) and the Imax below the maximum power interval generated by the MEA.
According to the above-mentioned steps, the DC converter (3) decides if the magnitude of the current or power required by the load (4) is greater than the Imax or the Pmax corresponding to the fuel cell (1). If the magnitude of the current or power required by the load (4) is smaller than or equal to the Imax or the Pmax corresponding to the fuel cell (1), the electricity outputted by the fuel cell (1) is sufficient to supply the required load (4); if the magnitude of the current or power required by the load (4) is greater than the Imax or the Pmax corresponding to the fuel cell (1), then the electricity outputted by the fuel cell (1) is not sufficient to supply the required load (4).
According to the above-mentioned steps, when the current value outputted by the fuel cell (1) is kept below or equal to Imax, and the electricity outputted by the fuel cell (1) is sufficient to supply the required load (4), the DC converter (3) selects to terminate the status of electricity supplied by the secondary battery (2). In addition, the DC converter (3) will convert the electricity outputted by the fuel cell (1) into a stable voltage and current, which are then supplied to the electricity required by the load (4) through the DC converter output side (32).
According to the above-mentioned steps, when the current value output by the fuel cell (1) is kept below or equal to Imax, and the electricity outputted by the fuel cell (1) is not sufficient to supply the required load (4), the DC converter (3) selects to terminate the status of electricity [0] supplied by the secondary battery (2). In addition, the DC converter (3) will convert the electricity outputted by the fuel cell (1) and the secondary battery (2) into a stable voltage and current, which are then supplied to the electricity required by the load (4) through the DC converter output side (32).
In addition, according to the above-mentioned steps, the power value outputted by the fuel cell (1) can be used to decide if the secondary battery (2) supplies electricity or not. In other words, when the power value outputted by the fuel cell (1) is kept smaller or equal to Pmax, and the electricity outputted by the fuel cell (1) is sufficient to supply the required load (4), the DC converter (3) selects to terminate the status of electricity supplied by the secondary battery (2). In addition, the DC converter (3) will convert electricity outputted by the fuel cell (1) into a stable voltage and current, which are then supplied to the electricity required by the load (4) through the DC converter output side (32). Furthermore, when the power value output by the fuel cell (1) is kept smaller or equal to Pmax, and the electricity outputted by the fuel cell (1) is not sufficient to supply the required load (4), the DC converter (3) selects the status of electricity supplied by parallel connection of the secondary battery (2) and the fuel cell (1). In addition, the DC converter (3) will convert electricity outputted by the fuel cell (1) and the secondary battery (2) into a stable voltage and current, which are then supplied to the electricity required by the load (4) through the DC converter output side (32).
According to the above-mentioned steps, when the fuel cell (1) is sufficient to independently supply electricity required by load (4), the DC converter (3) can select to terminate the electricity supplied by the secondary battery (2) to the load (4), and select electricity supply of the fuel cell (1) to the secondary battery (2) for recharging the secondary battery (2).
According to the above-mentioned steps, the DC converter (3) keeps the DC converter input side (31) within the planned limit of a constant current. In other words, the fuel cell output side (11) is kept within the planned limit of a constant current, wherein the planned limit of the constant current limits the planned limit of the constant current, based on the quantity of MEAs of the fuel cell (1) and the power output of the optimum operating efficiency generated by a MEA, wherein the power output of the optimum operating efficiency generated by the MEA refers to the status of maximum electric power output generated by the MEA at unit fuel consumption.
It is to be understood that the foregoing description of the present invention should not be based to restrict the invention, and that all equivalent modifications and variations made without departing from the intent and import of the foregoing description should be included in the following claim.
