Co-generated power supply system
In a co-generated power supply system for performing dispersed power supply to a load, a wind turbine generator, a solar cell and a fuel cell whose rated voltages are made equal to a rated voltage of a storage battery are used as DC power sources. These DC power sources, a commercial AC power source and the load are connected to each other via a bi-directional electronic transformer. Thus, the co-generated power supply system, in which the electric power of a natural energy system having many fluctuation factors is combined with stable electric power such as a load leveling battery or a fuel cell, allows the stable electric power to be supplied to the load via the electronic transformer commonly, thereby reducing the cost and enhancing the performance of the entire system.
This application is a divisional application of application Ser. No. 10/630,692, filed Jul. 31, 2003.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a novel co-generated power supply system, which is useful for co-generated power supply of a combination of natural energy and stable energy such as a fuel cell and power storage energy during the nighttime and midnight, and especially, which can efficiently supply electric power to a load by connecting a plurality of AC and DC energy sources to each other via an electronic transformer, a diode and an OR circuit.
2. Description of the Related Art
As a typical example of clean energy, the solar cell has been prevalant. Furthermore, the wind turbine generator has been introduced in local regions. Since in these types of natural energy, the duration of sunshine, the operation rate of a windmill or generated electric power fluctuates at all times due to variations in weather or meteorological situations, it is difficult to stably supply electric power. Therefore, natural energy is used as an auxiliary energy source while commercial electric power is mainly used in many cases under current circumstances.
However, an electric power supply system in the 21st century in which global warming is suppressed has been studied in a global scope, and thus, various types of efficient electric power supply means by co-generated power supply in closer touch with a consumption region have been studied in addition to conventional concentrated power generation by nuclear energy, thermal energy or hydraulic energy.
Moreover, in order to perform loadleveling, it is necessary to store surplus energy from a commercial AC line in a battery during nighttime and release this energy for use during daytime so as to efficiently actuate a power generation and distribution system even in the above-described conventional concentrated power distribution systems.
In the meantime, in the field of power electronics, there has been developed an electronic transformer compatible with both AC and DC, which could not achieved by a conventional copper-iron type transformer, and therefore, the electric power can be converted irrespective of the AC and the DC of the energy source. Consequently, the AC power, such as from a commercial power source or wind turbine generation, is combined with the DC power, such as from a solar cell, a fuel cell or a battery, for storing midnight electric power via the electronic transformer, and then, the AC power and the DC power can be used at home, in an office or the like as an uninterruptible power supply for allowing instantaneous power interruption within a half cycle by switching over the energy sources.
Examples of household electric appliances which are currently prevalent in Japan and can be securely used for both of AC and DC include a light bulb, an inverter type fluorescent lamp and an electric tool, and further, there can be used, in principle, inverter types of an air-conditioner, a refrigerator, a microwave oven, a vacuum cleaner, a personal computer and a facsimile except for some types in which a voltage doubler rectifying circuit or an AC protective circuit is incorporated. In contrast, a dimmer, a space heating appliance and an automatic rice cooker of a thyristor phase control system cannot be used with DC under present circumstances. As a consequence, there has arisen an immediate inconvenience that the appliance only for AC and the household electric appliance for both of AC and DC must be used with separate indoor wiring systems (i.e., receptacles) independent of each other.
However, the DC power generation energy always is reversely converted into the commercial AC through an inverter in the conventional system, and then, is converted into the DC again within an actual load, and further, is converted into a high frequency inverter or a variable frequency AC power, so as to drive an electric motor or a compressor, thereby increasing a conversion loss.
If control equipment such as an inverter is provided for each electric power of the energy generating source of a low operating rate in the above-described manner, the cost of the entire system is increased, thereby leading to one factor of inhibition of popular use.
SUMMARY OF THE INVENTIONIn view of the foregoing, it is the main object of the present invention to provide a novel co-generated power supply system, in which electric power of a natural energy system having many fluctuation factors is combined with stable electric power such as a battery storing midnight electric power or a fuel cell, so that the stable electric power is supplied to a load via an electronic transformer commonly used at a usage rate of almost 100%, thus reducing the cost and enhancing the performance of the entire system, so as to spread and make more prevalent the co-generated power supply and save the energy.
According to the novel co-generated power supply system of the present invention, in the case where the electric power is supplied directly to the load from both AC and DC sources as illustrated in
The foregoing and other objects, features and advantages of the present invention will be apparent from the following more particular description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings, in which:
In the co-generated power supply system in the embodiment illustrated in
The storage battery B is electrically charged normally by the wind turbine generator WTB and the solar cell PV. In the case of insufficient generated electric power, the storage battery B is electrically charged by the fuel cell FC during the daytime; in contrast, the storage battery B is electrically charged via a charger CHG1 during the nighttime and midnight, that is, in a time zone in which an electric charge (tariff) is lower than that during the daytime.
When the storage battery B has been fully charged, a switch SW is opened in response to a command from a control circuit, and an AC relay RL is restored to switch the AC power source to the DC power source, thereby sequentially supplying the DC power to the load Lac/dc for both AC and DC.
As the storage battery B approaches the terminal period of electric discharging, the switch SW is closed in response to a command from the control circuit, and the AC power is supplied again by the commercial AC power source Utility.
Second EmbodimentThe co-generated power supply system in the embodiment illustrated in
The two-winding electronic transformer 2 is used for both AC and DC and has two bidirectional input/output terminals 2a and 2b. One bidirectional input/output terminal 2a is connected to an output side of a DC power source; in contrast, the other bidirectional input/output terminal 2b is connected in a T-shaped manner between a commercial AC power source Utility and a load Lac/dc for both AC and DC.
With this circuit configuration, AC power from the commercial AC power source Utility is supplied to the load Lac/dc for both AC and DC not via the two-winding electronic transformer 2 until a storage battery B is fully charged by DC power sources WTG, PV and FC; DC power from the DC power sources WTG, PV and FC and the storage battery B is supplied to the load Lac/dc for both AC and DC via the two-winding electronic transformer 2 when the storage battery B has been fully charged or the commercial AC power source Utility fails; the electric power is replenished from the fuel cell FC when the storage battery B is being discharged; the AC power is supplied to the load Lac/dc for both AC and DC from the commercial AC power source Utility in a time zone of the nighttime and midnight electric power supply; and further, the storage battery B is electrically charged by the bidirectional function of the two-winding electronic transformer 2 and the AC/DC converting function.
As for fluctuations in voltage of the storage battery B accompanied by the electric charging or discharging, the fluctuations in voltage of the storage battery B are adjusted for by the voltage adjusting function of the bidirectional DC-DC converter Conv irrespective of the electric charging or discharging time, such that the voltage can be stably supplied to the load Lac/dc for both AC and DC.
Furthermore, the two-winding electronic transformer 2 can transmit bidirectional energy forward and backward by the bidirectional function and the AC/DC converting function, so that it can function as a charger (i.e., corresponding to the charger CHG illustrated in
The co-generated power supply system in the embodiment illustrated in
With this circuit configuration, AC power from the commercial AC power source Utility is supplied to the load Lac/dc for both of the AC and the DC via the three-winding electronic transformer 3 until the storage battery B is fully charged by the DC power sources WTG, PV and FC; DC power from the DC power sources WTG, PV and FC and the storage battery B is supplied to the load Lac/dc for both AC and DC via the three-winding electronic transformer 3 when the storage battery B has been fully charged or the commercial AC power source Utility fails; the electric power is replenished from the fuel cell FC when the storage battery B is being discharged; the AC power from the commercial AC power source Utility is supplied to the load Lac/dc for both of the AC and the DC in a time zone of the nighttime and midnight electric power supply; and further, the storage battery B is charged by the bidirectional function of the three-winding electronic transformer 3 and the AC/DC converting function.
Here, as for fluctuations in voltage of the commercial AC power source Utility, the voltage can be adjusted by a pulse width modulation (PWM) control or a pulse phase modulation (PPM) control of the modulation/demodulation semiconductor switches SW1 and SW2, thereby stably supplying a load voltage with respect to the fluctuations in the commercial AC power source Utility and the DC power sources WTG, PV and FC, and simultaneously, charging can be achieved by the nighttime and midnight electric power via the modulation/demodulation semiconductor switches SW1 and SW3.
In the above-described co-generated power supply systems in the embodiments illustrated in
In the present embodiments, first, AC power from a commercial AC power source Utility is supplied to a load Lac only for AC via neither the bidirectional DC-DC converter Conv nor a two-winding electronic transformer 4 in
Here, a specific description will be given of a drive system of the bidirectional DC-DC converter Conv in the embodiment illustrated in
In
In the case where the modulation/demodulation semiconductor switch SW3 on the side of the storage battery is constituted of the two unidirectional semiconductor switches S5 and S6, a DC output voltage 6 of a two-phase half-wave is generated (see
In the meantime, as illustrated in
Furthermore, in the same manner, the system consisting of the commercial AC power source Utility, the load Lac only for the AC and storage battery B is completely insulated by the use of the three-winding electronic transformer 5 illustrated in
Incidentally, although all of the three DC power sources WTB, PV and FC are combined with each other in the above-described embodiments, it is to be understood that the present invention can be applied to the case where only one of the DC power sources is used or arbitrary two of the DC power sources are combined with each other, thus implementing the excellent co-generated power supply system in the same manner.
EXAMPLES Example 1First of all, reference character TM designates a timer for AC/DC power supply and nighttime and midnight electric power charging, and it is controlled by a control circuit CONT-2. Reference character CONT-1 denotes a control circuit for a wind turbine generator WTG. The control circuit CONT-1 is a generally known control circuit for performing rectification in the case where the wind turbine generator WTG is operated by AC, like in a generator for an automobile while for performing voltage adjustment as it is in the case where the wind turbine generator WTG is operated by DC. Reference characters S3 and S4 designate bidirectional semiconductor switches, in which two unidirectional semiconductor switches are connected back to back (i.e., Back to Back Connection) for switching AC and DC, as enlarged in
In the example illustrated in
Although the above description has been given of the case of a long failure time of the commercial AC power source Utility, a switch SW is turned off by the timer TM in response to a command from the control circuit CONT-2 in the case where the storage battery B has been fully charged even without any failure, so that the AC power supply is switched to the DC power supply, thus achieving a co-generated power supply by natural energy and the fuel cell.
Example 2Next, when the commercial AC power source Utility fails or the storage battery B has been fully charged, a high frequency rectangular wave signal is generated by a push-pull type inverter circuit with the coils N3 and N4 and semiconductor switches S5 and S6 in the high frequency transformer HFT. At this time, a rectangular wave voltage generated in the coil N2 by the switches S3 and S4 becomes a DC having a double voltage value by the voltage-doubler circuit, and thus, DC power is supplied to a load Lac/dc for both AC and DC. That is to say, the electronic transformer operated by the high frequency modulation/demodulation can convert the voltage irrespective of the AC and the DC.
Incidentally, if compressed fuel Fuel (containing mainly hydrogen) for a fuel cell FC is produced as a part of the load by a compressor COMP at a light load, and then, is reserved, the capacity of the storage battery can be reduced and the fluctuation in load can be leveled or environmental improvement prepared for a clean engine age can be achieved for use in self-generation of electricity, a motor-driven vehicle and the like.
Example 3A great difference from the cases illustrated in
In order to implement the above-described operation, the drive pulse phase of switches S1 to S6 in the three-winding electronic transformer 5 is alternately reversed for a positive half cycle and a negative half cycle of the commercial AC power source Utility, as illustrated in, for example,
The two-winding electronic transformer 4 illustrated in
At any rate, a great difference from a commercial power transformer resides in that the bidirectional transmission of the electric energy can be achieved at both the DC and several hundreds Hz of the AC between input/output terminals in the two or three pairs of two-winding electronic transformers 4 and three-winding electronic transformers 5. This point is a basic feature of the system configuration according to the present invention.
Moreover, another feature resides in that a reverse flow of the current can be achieved from the side of the storage battery onto the side of the commercial AC power source through the two-winding electronic transformer 4 and the three-winding electronic transformer 5 unless the commercial AC power source Utility fails. Incidentally, in this case, it is understood that an oscillator for an inverter operation at the time of a failure should be built in the system.
As the detailed descriptions have been given above, according to the present invention, there can be provided the novel co-generated power supply system, in which the electric power of the natural energy system having many fluctuation factors is combined with the stable electric power such as the midnight electric power or the fuel cell, so that the stable electric power is supplied to the load via the electronic transformer commonly used at a usage rate of almost 100%, thus reducing the cost and enhancing the performance of the entire system, so as to spread and make prevalent the co-generated power supply and save the energy.
Of course, the present invention is not restricted to the particular embodiments and examples given above, and that various aspects can be realized in detail without departing from the scope of the present invention.
Claims
1-4. (canceled)
5. A power supply system for selectively supplying power to a load that operates with both AC power and DC power, the power supply system comprising:
- a storage battery that stores DC power;
- a plurality of DC power sources including a wind turbine generator, a solar cell and a fuel cell, each having a rated voltage made equal to a rated voltage of the storage battery, and an output of each being connected to the storage battery;
- a switching device connected in series between a utility AC power source and the load, and connected in series between the storage battery and the load, the switching device switching between supplying power from the utility AC power source to the load and supplying power from the storage battery to the load;
- a bidirectional converter;
- a two-winding electronic transformer having a first bidirectional terminal, a second bidirectional terminal, a high frequency transformer that matches and insulates a voltage on a battery side of the two-winding electronic transformer and a voltage on a load side of the two-winding electronic transformer, a first modulation/demodulation semiconductor switch connected to a winding at the storage battery side, and a second modulation/demodulation semiconductor switch connected to a winding at the load side; and
- a controller that controls operation of the two-winding electronic transformer by controlling operation of the switching device, wherein
- the two-winding electronic transformer has a bidirectional function and an AD/DC converting function,
- the first bidirectional terminal of the two-winding electronic transformer is connected via the bidirectional converter and the storage battery to the DC power sources,
- the second bidirectional terminal of the two-winding electronic transformer is connected in a T-shaped manner between the utility AC power source and the load,
- the controller controls the operation of the two-winding electronic transformer to (1) during a first time period, (i) supply AC power from the utility AC power source to the load not via the two-winding electronic transformer while the storage battery is being charged by at least one of the DC power sources until the storage battery is fully charged and (ii) supply DC power from the storage battery to the load once the storage battery has been fully charged or if the utility AC power source fails, and (2) during a second time period, (i) supply the AC power from the utility AC power source to the load and (ii) convert the AC power from the utility AC power source into DC power and supply the converted DC power to the storage battery to charge the storage battery by the bidirectional function and the AC/DC converting function of the two-winding electronic transformer, and
- the fuel cell charges the storage battery while the storage battery is being charged.
6. A power supply system for selectively supplying power to a load that operates with only AC power, the power supply system comprising:
- a storage battery that stores DC power;
- a plurality of DC power sources including a wind turbine generator, a solar cell and a fuel cell, each having a rated voltage made equal to a rated voltage of the storage battery, and an output of each being connected to the storage battery;
- a switching device connected in series between a utility AC power source and the load;
- a bidirectional converter;
- a two-winding electronic transformer having a first bidirectional terminal, a second bidirectional terminal, a high frequency transformer that matches and insulates a voltage on a battery side of the two-winding electronic transformer and a voltage on a load side of the two-winding electronic transformer, a first modulation/demodulation semiconductor switch connected to a winding at the storage battery side, and a second modulation/demodulation semiconductor switch connected to a winding at the load side; and
- a controller that controls operation of the two-winding electronic transformer by controlling operation of the switching device, wherein
- the two-winding electronic transformer has a bidirectional function and an AC/DC converting function,
- the first bidirectional terminal of the two-winding electronic transformer is connected via the bidirectional converter and the storage battery to the DC power sources,
- the second bidirectional terminal of the two-winding electronic transformer is connected in a T-shaped manner between the utility AC power source and the load,
- the first modulation/demodulation semiconductor switch includes two unidirectional switches or two pairs of unidirectional switches,
- the controller controls the operation of the two-winding electronic transformer to (1) during a first time period, (i) supply AC power from the utility AC power source to the load not via the two-winding electronic transformer while the storage battery is being charged by at least one of the DC power sources until the storage battery is fully charged and (ii) supply AC power from the DC power stored in the storage battery to the load once the storage battery has been fully charged or if the utility AC power source fails by modulating the DC power into single-phase full-wave form per half cycle by the bidirectional converter, alternately reversing a high frequency modulation phase of the two unidirectional switches or the two pairs of unidirectional switches of the first modulation/demodulation semiconductor switch per half cycle of a utility AC power frequency and then demodulating into sinusoidal wave AC output by the second modulation/demodulation semiconductor switch, and (2) during a second time period, (1) supply the AC power from the utility AC power source to the load and (ii) convert the AC power from the utility AC power source into DC power and supply the DC power to the bidirectional converter to perform a boost type rectifying operation at a high power factor to charge the storage battery by the bidirectional function and the AC/DC converting function of the two-winding electronic transformer,
- the two-winding electronic transformer converts the DC power from the storage battery into AC power when the storage battery has been substantially fully charged at a load in an off-peak period for electric power supply and the utility AC power source has not failed on a side of the two-winding electronic transformer of the utility AC power source to achieve a reverse flow of AC current, and
- the fuel cell charges the storage battery while the storage battery is being charged.
Type: Application
Filed: Sep 15, 2008
Publication Date: Apr 2, 2009
Inventors: Yasunobu Suzuki (Tokyo), Toru Teshima (Kanagawa)
Application Number: 12/232,308
International Classification: H02J 3/32 (20060101);