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 Electrical power system for multi-use power conditioning and engine startUSPTO Application #: 20060232249Title: Electrical power system for multi-use power conditioning and engine start Abstract: A synchronous and bi-directional power conversion module (140) for use in a variable frequency power conversion system (100) comprises a first input/output side (142) for AC power input/output and DC power source input; a second input/output side (144) for DC link connection; and an active power switching arrangement (Q1-Q6), which is controlled by a gating pattern to perform multi-mode power conversion. The active power switching arrangement (Q1-Q6) is controlled to convert DC link voltage from the DC link connection (144) to an AC load supply voltage during a forward power mode; convert AC input power from the first input/output side (142) to a regulated DC link voltage during an AC source input, reverse power mode; and convert DC input power from the first input/output to a regulated DC link voltage during a DC source input, reverse power mode. (end of abstract)
Agent: Honeywell International Inc. - Morristown, NJ, US Inventor: Hassan A. Kojori USPTO Applicaton #: 20060232249 - Class: 322029000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060232249. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to electrical power systems, and more particularly to an electrical power conversion system that achieves multi-purpose power conditioning for generator power flow and starter power flow operating modes. BACKGROUND OF THE INVENTION [0002] As an alternative to conventional fixed frequency power generation systems, recent aerospace applications have utilized variable frequency generators that typically deliver electrical power at frequencies between 320 and 800 Hz. In one such application, a synchronous machine (e.g., a brushless synchronous machine) operates in a first mode as a generator to convert mechanical energy from a prime mover, such as a gas turbine engine, into variable frequency AC power and operates in a second mode as a main or auxiliary power unit starter to convert electrical power into mechanical power, which is supplied to the prime mover until it reaches a self-sustaining speed. [0003] Traditionally, an auxiliary power unit (APU) start power system architecture has two main subsystems: a start power unit (SPU); and a start converter unit (SCU). FIG. 1 illustrates a conventional aircraft power system 10, which includes: a synchronous machine 20; an SCU 30; and an SPU 40. The SCU 20 includes a first inverter 32, which supplies multi-phase AC power to the synchronous machine 20 during a starter mode. The SCU 30 includes a second inverter 34 to provide the exciter power supply field for the synchronous machine 20. [0004] The SPU 40 includes an AC to DC converter 42 and a DC to DC converter 44. When connected to an AC input power source during the starter mode, the AC-DC converter 42 converts AC power from the AC input power source (e.g., supplying 115 VAC) to a DC bus/link voltage, typically around 270 VDC or higher. In FIG. 1, the AC input power source is illustrated as an aircraft start ground panel 64. When connected to an on-board DC power source (battery) 62 or a ground-based DC power source (aircraft start ground panel 64) during the starter mode, the DC-DC converter 44 converts input DC power to the DC bus voltage. The DC input power is typically 28 VDC. During starter mode, the first inverter 32 converts DC power from the SPU 40 to a three-phase voltage for the stator windings of the synchronous machine 20. Furthermore, the second inverter 34 converts the DC power from the SPU 40 to an Exciter Power Supply (EXPS) voltage. The first inverter 32, the second inverter 34, the AC-DC converter 42, and the DC-DC converter 44 are typically provided as discrete units ("boxes"), thereby each requiring a separate DC link. Although not shown, the first inverter 32, the second inverter 34, and the DC-DC converter 44 include individual controllers in this conventional arrangement. In this arrangement, DC bus regulation is performed by a generator control unit (GCU, not shown), through a point of regulation either at the input three-phase AC power or at the DC bus. [0005] During generator mode, the AC-DC converter 42 of the SPU 40 converts multi-phase AC power from the synchronous machine 20 into a DC bus voltage. The AC-DC converter 42 performs passive rectification and is comprised of a three-phase diode bridge in this conventional arrangement. The first inverter 32 of the SCU 30 converts the DC bus voltage to variable voltage (VV), fixed frequency (FF) or variable frequency (VF) power to supply aircraft load(s). [0006] As illustrated, power flow in the conventional arrangement of FIG. 1 is not bi-directional and is managed using at least the following electrical contactors: a first contactor 50-1 between the synchronous machine 20 and the AC side of the first inverter 32; a second contactor 50-2 between the synchronous machine 20 and the AC side of the AC-DC converter 42; a third contactor 50-3 between the first inverter 32 and aircraft load(s); a fourth contactor 50-4 between external DC power source 64 and the DC-DC converter 44; a fifth contactor 50-5 between the external AC power source 64 and the AC side of the AC-DC converter 42; and a sixth contactor 50-6 between aircraft battery 62 and the DC-DC converter 44. Opened/closed states for these various electrical contactors to achieve different operating modes are shown below in Table 1, wherein "C" represents a closed contactor state and "O" represents an opened contactor state. TABLE-US-00001 TABLE 1 Different Modes of Operation Starter/Gen. Modes 50-1 50-2 50-3 50-4 50-5 50-6 SM Start Ground DC C O O C O O SM Start Aircraft DC C O O O O C SM Start Ground AC C O O O C O SM Generate O C C O O O [0007] This particular arrangement of electrical contactors is required in part due to uni-directional power flow requirements. Furthermore, thermal management and DC linking for the SCU 30 and the SPU 40 are fragmented. This is illustrated in FIG. 1 as separate heat sinks and DC links for SCU and SPU components (heat flow being represented as cross-hatched arrows). Separate connectors (power and discrete input/output) are typically required. Thus, overall system weight, volume, and cost are increased and reliability is reduced due to increased part count. SUMMARY OF THE INVENTION [0008] In one aspect, the present invention relates to a synchronous and bi-directional power conversion module for use in a variable frequency power conversion system. In one embodiment of the present invention, the power conversion module comprises: a first input/output side for AC power input/output and DC power source input; a second input/output side for DC link connection; and an active power switching arrangement, which is controlled by a gating pattern to perform multi-mode power conversion. The active power switching arrangement is controlled to: convert DC link voltage from the DC link connection to an AC load supply voltage during a forward power mode; convert AC input power from the first input/output side to a regulated DC link voltage during an AC source input, reverse power mode; and convert DC input power from the first input/output side to a regulated DC link voltage during a DC source input, reverse power mode. [0009] Another aspect of the present invention relates to a multi-mode power conversion system in which a synchronous machine operates as a generator during a forward power mode and a starter during a reverse power mode. The system comprises: a first multi-mode power conversion module, having an AC input/output connected to the synchronous machine, a DC input/output connected to a DC link, and an active power switching arrangement for converting multi-phase AC power from the synchronous machine to regulated DC link voltage during the forward power mode and converting DC link voltage to multi-phase AC power for supply to the synchronous machine during the reverse power mode; and a second multi-mode power conversion module, having a first input/output side for AC power input/output, a second input/output side for DC link connection, and an active power switching arrangement, wherein the active power switching arrangement is controlled to convert DC link voltage from the DC link connection to an AC load supply voltage during the forward power mode and convert AC input power from the first input/output side to a regulated DC link voltage during a reverse power mode, wherein the multi-mode power conversion system includes an electrical contactor between the first multi-mode power conversion module and the synchronous machine that is closed during both the forward power mode and the reverse power mode and does not include an electrical connection or electrical contactor between the first input/output side of the second multi-mode power conversion module and the synchronous machine. [0010] The multi-mode conversion system according to another embodiment comprises: a first multi-mode power conversion module, having an AC input/output connected to the synchronous machine, a DC input/output connected to a DC link, and an active power switching arrangement for converting multi-phase AC power from the synchronous machine to regulated DC link voltage during the forward power mode and converting DC link voltage to multi-phase AC power for supply to the synchronous machine during the reverse power mode; and a second multi-mode power conversion module, having a first input/output side for AC power input/output and DC power source input, a second input/output side for DC link connection, and an active power switching arrangement. The active power switching arrangement of the second multi-mode power conversion module is controlled to: convert DC link voltage from the DC link connection to an AC load supply voltage during the forward power mode; convert AC input power from the first input/output side to a regulated DC link voltage during an AC source input, reverse power mode; and convert DC input power from the first input/output side to a regulated DC link voltage during a DC source input, reverse power mode. BRIEF DESCRIPTION OF THE DRAWINGS [0011] Further aspects of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which: [0012] FIG. 1 illustrates a conventional aircraft power system utilizing a synchronous machine as both a generator and a starter; [0013] FIG. 2A illustrates an electrical power system utilizing a synchronous machine as both a generator and a starter in accordance with an embodiment of the present invention; [0014] FIG. 2B illustrates a bi-directional voltage source inverter, which is used for multi-mode power conditioning according to an implementation of the present invention; [0015] FIG. 3 illustrates an electrical power system utilizing a synchronous machine as both a generator and a starter in accordance with another embodiment of the present invention; [0016] FIG. 4 illustrates a bi-directional voltage source inverter for either AC-DC, DC-AC, or DC-DC power conversion in accordance with an embodiment of the present invention; [0017] FIG. 5A illustrates one leg of a voltage source inverter for realizing a boost converter function in accordance with an embodiment of the present invention; and [0018] FIG. 5B illustrates one leg of a voltage source inverter for realizing a buck converter function in accordance with an embodiment of the present invention. DETAILED DESCRIPTION [0019] Embodiments of the present invention are described below with reference to the appended Figures. Although these embodiments are described in the context of aerospace applications, and are applicable to "more electric aircraft" platforms, it should be recognized that principles of the present invention may be applied to other technical environments. Continue reading... Full patent description for Electrical power system for multi-use power conditioning and engine start Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electrical power system for multi-use power conditioning and engine start patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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