Patent Application
20120236439
The present application is directed toward power generation systems, and more particularly toward a power generation system using an electrical accumulator unit.
Electrical accumulator units are bi-directional systems for transferring power between power sources. Aircraft power generator systems oftentimes employ electrical accumulator units as part of the power generation system. An on-board generator converts mechanical energy provided by the engine to electrical energy for supply to various electrical loads. During normal operations, electrical accumulator units transfer excess power provided on the bus (either excess power provided by the generator due to a demand to be charged by the power storage components or regenerative power provided by the one or more active loads) to a power storage device for storage. The power storage device may be a battery, super-capacitor, or some other device capable of storing the excess energy. In response to a spike in power required by the load, the electrical accumulator units provide energy stored by the power storage device onto the bus for supply to the one or more loads.
An electrical accumulator unit includes a power storage device, a first switch, a power converter, a controller, and a dissipation circuit for dissipating residual energy in the power converter when the electrical accumulator unit is turned Off. The first switch is connected between the power storage device and the power converter. The power converter is connected via the first switch to the power storage device, the power converter including at least a second switch that is selectively turned On and Off to regulate the transfer of power between an output of the electrical accumulator unit and the power storage device. The dissipation circuit is connected to the power converter. The controller controls the state of the first switch and the second switch, wherein the controller turns the electrical accumulator Off by turning Off the first switch to disconnect the power storage device from the power converter, and turns the second switch On to connect the dissipation circuit to the power converter in a recirculating circuit path that dissipates energy stored in the power converter.
Electrical accumulator unit 22 includes a power storage device (e.g., battery, super-capacitor, etc.) for storing energy. Electrical accumulator unit 22 provides for bi-directional power transfer between DC bus 18 and the power storage device. In instances in which excess power is available on DC bus 18, electrical accumulator unit 22 transfers power from DC bus 18 to the power storage device. This may be in response to three phase generator 12 generating excess power due to a demand to be charged by the energy storage device or in response to load 20 providing regenerative power back onto DC bus 18. Conversely, when power on DC bus 18 is insufficient, electrical accumulator unit 22 transfers power from the power storage device to DC bus 18 to augment the power provided by three-phase generator 12 and AC/DC rectifier 16.
In applications in which the voltage supplied by power storage device 26 is less than the voltage provided on DC bus 18, electrical accumulator unit 22 includes a boost converter to increase or step-up the magnitude of the voltage supplied by power storage device 26 to DC bus 18. In the embodiment shown in
Controller 34 controls the operation of switch Q1, as well as the operation of bi-directional switch 28, which includes switches Q2 and Q3, and diodes D2 and D3. To transfer power from power storage device 26 to DC bus 18, controller 34 turns On switch Q3, and controls switch Q1 to be On and Off as required to provide the desired boost voltage onto DC bus 18. In one embodiment, controller 34 turns switch Q1 On and Off using pulse width modulation (PWM techniques). For the sake of simplicity, only the boost converter is shown in the circuit illustrated in
Electrical accumulator unit 22 is turned Off following operation of the power converter 30 to transfer power from power storage device 26 to DC bus 18, or to transfer power from DC bus 18 to power storage device 26. Traditionally, power converter 30 is turned Off by turning Off switch Q1 and/or bi-directional switch 28. However, this method of turn-off results in residual energy stored in inductor L1 at the time of turn-off being discharged onto DC bus 18, potentially with undesirable effects.
To mitigate the effects of remnant energy at turn-off of electrical accumulator unit 22, dissipation circuit 36 is connected to power converter 30. Assuming operation in the boost mode, in which power is being transferred from power storage device 26 to DC bus 18, when the operation is complete controller disconnects power storage device 26 from DC bus 18 by opening bi-directional switch 28 (e.g., turning Off switch Q3). Excess power stored in inductor L1 is dissipated by closing (or maintaining in a closed state) switch Q1 to create a recirculation circuit path that includes inductor L1, switch Q1, and dissipation circuit 36 (including resistor R1 and diode D4, which is forward biased or conducting in the recirculation circuit path). In this way, excess energy stored in inductor L1 is prevented from being discharged onto DC bus 18 when bi-directional switch 28 is turned Off.
Controller 34 may maintain switch Q1 in an On state for a defined period of time known to be of sufficient duration to dissipate excess energy, or may monitor the power dissipated by dissipation circuit 36 to determine when it is safe to switch Q1 Off. In some embodiments, depending on the amount of energy to be dissipated, free-wheeling diode D4 may be sufficiently capable of dissipating energy stored in inductor L1. In this embodiment, energy-dissipating resistor R1 would not be required as part of dissipation circuit 36.
In the embodiment shown in
In the embodiment shown in
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the present invention has been described with respect to a particular DC-DC circuit topology. However, it will be understood by those of skill in the art that other well-known DC-DC circuit topologies finding applicability to electrical accumulator units may be employed without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. For example, depending on the circuit topology employed, the location of certain circuit elements, such as inductive and switching elements within a converter, may change, without departing from the essential scope of the present invention. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
