Patent Description:
Existing portable power generator sets ("gensets"), such as for radar and launcher applications, typically require the ability to connect in parallel to a utility grid, with the ability to switch the load's power source between the genset and grid. However, a utility grid typically operates at a different frequency and different voltage level than is required by the load. As a result, large and heavy power transformers are often used to achieve grid matching. For these applications, the size and weight of the required transformers are prohibitive to mobility. In addition, energy storage is required to maintain power to the loads during the genset to grid, or grid to genset switch transition periods, which may be minutes in duration.

<CIT> relates to an uninterruptable power supply (UPS) system for providing power to a load coupled to a utility power source. The UPS system includes a doubly-fed induction generator (DFIG), a rechargeable energy storage system, a first inverter, and a controller in communication with the DFIG and the first inverter. The DFIG generates an auxiliary power output.

<CIT> relates to a double-stator AC/DC generator motor system applied to an energy storage power station. The double-stator AC/DC generator motor system comprises a double-stator AC-DC generator motor, a prime mover, an AC doubly-fed frequency conversion device and an AC/DC frequency conversion device. The double-stator AC/DC generator motor comprises an outer stator, an inner stator and a rotor. The outer stator winding is directly connected with a power grid through a step-up transformer. The inner stator winding is connected with the DC power grid through the AC/DC frequency conversion device.

<CIT> relates to a hybrid energy storage system configured to control pulsed power. A first dynamo-electric machine is coupled to an inertial energy storage device and has multiple input stator windings configured to accept input power from a source.

This disclosure relates to a mobile hybrid electric power system. The present disclosure provides a system according to claims <NUM> and <NUM>.

In a first embodiment, a system includes a prime mover configured to rotate a shaft. The system also includes a wound rotor induction generator (WRIG). The WRIG includes a rotor coupled to the shaft of the prime mover and configured to rotate when the shaft rotates, where the rotor includes a polyphase rotor winding. The WRIG also includes a polyphase stator winding electrically connected to a utility source and a load. When the stator winding receives first power from the utility source, the WRIG is configured to transform at least one of a voltage and a frequency of the first power before outputting at least a portion of the first power to the load. When the stator winding does not receive the first power from the utility source, the WRIG is configured to generate second power due to kinetic energy of the rotor, and output at least a portion of the second power to the load. The system also includes an energy storage bank, which receives and stores a second portion of the first or second powers, for use to power the load during transitions between the first and second power sources.

In a second embodiment, a system includes a prime mover configured to rotate a shaft. The system also includes a WRIG. The WRIG includes a rotor coupled to the shaft of the prime mover and configured to rotate when the shaft rotates, where the rotor includes a polyphase rotor winding. The WRIG also includes a first polyphase stator winding electrically connected to a utility source and a load. The WRIG further includes a second stator winding electrically connected to an energy storage bank. When the first stator winding receives first power from the utility source, the WRIG is configured to transform at least one of a voltage and a frequency of the first power before outputting at least a portion of the first power to the load. When the first stator winding does not receive an adequate amount of the first power from the utility source, the WRIG is configured to generate second power due to kinetic energy of the rotor and output at least a portion of the second power to the load. This second power may be combined with a contribution of power from the utility source if the two sources are of the same frequency.

<FIG>, described below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any type of suitably arranged device or system.

As noted above, existing portable power generator sets ("gensets"), such as for radar and launcher applications, typically require the ability to connect onto a utility grid. However, a utility grid may operate at a different frequency and different voltage level than is required by the load. As a result, large and heavy power transformers are often used to solve the grid matching problem. For these applications, the size and weight of the required transformers are prohibitive to mobility. In addition, energy storage is required to maintain power to the loads during the genset to grid, or grid to genset switch transitions.

To address these or other issues, this disclosure provides various mobile hybrid electric power systems that allow efficient and compact frequency and voltage transformation with inputs from either a utility source or a local prime mover generator (such as a diesel engine). Circuitry forming part of each power system obviates the need for traditional power transformers, resulting in high overall power density and greater mobility. The disclosed power systems can also transition from a utility source to a local prime mover in a manner that is transparent to one or more loads, and in so doing can accomplish a transition from one power source to a second source within one electrical cycle. In addition, the disclosed power systems facilitate variable frequency output, which accommodates the needs of different types of loads.

<FIG> illustrates an example mobile hybrid electric power system <NUM> according to this disclosure. As described below, the system <NUM> enables significant energy storage and provides a seamless transfer between portable power and utility power without the need for large power transformers to transform voltage levels. The system <NUM> is compact and lightweight and allows output frequency conversion to suit an associated load with single stage conversion.

As shown in <FIG>, the system <NUM> includes a prime mover <NUM>. The prime mover <NUM> is configured to generate rotational power that is used to drive rotational kinetic energy in a wound rotor induction generator (WRIG) <NUM>, which is connected to the prime mover <NUM> by a shaft <NUM>. The stator of the WRIG <NUM> is normally a polyphase stator, but in special circumstances the stator can be a single-phase stator to accommodate single phase utility feeds. In some embodiments, the prime mover <NUM> operates to rotate the shaft <NUM> at a speed of approximately <NUM>,<NUM> to approximately <NUM>,<NUM> rotations per minute (RPMs), although other rotational speeds are possible and within the scope of this disclosure. The prime mover <NUM> includes any suitable structure that can generate rotational power, such as a motor with or without a gear mechanism on the output shaft. In some embodiments, the prime mover <NUM> represents or includes a diesel engine.

The WRIG <NUM> is configured to operate and output power in either of two modes: "utility mode" or "island mode. " "Utility mode" refers to a mode in which the WRIG <NUM> receives power from a utility source <NUM> (such as a utility grid source) or another external power source and provides power to at least one load <NUM>. "Island mode" refers to a mode in which the WRIG <NUM> operates off the prime mover <NUM> instead of the utility source <NUM> and thereby generates power that is provided to the load(s) <NUM>. The WRIG <NUM> is configured to quickly and seamlessly transfer between utility mode and island mode as described in greater detail below.

In this example, the WRIG <NUM> includes a rotor <NUM> coupled to the shaft <NUM> of the prime mover <NUM>, a stator winding <NUM>, and a rotor winding <NUM>. The WRIG <NUM> is configured to generate alternating current (AC) power when the rotor <NUM> is rotated by the shaft <NUM>. In island mode, through the connection to the prime mover <NUM>, the WRIG <NUM> can operate as a generator for portable power generation. An advantage of the WRIG <NUM> is that rotor excitation can be commanded to be a variable frequency to provide for constant output frequency when the rotor speed deviates from normal synchronous speed. In utility mode, the system <NUM> is powered by the utility source <NUM>, through a switch <NUM> which is connected to the WRIG stator windings, yet the WRIG <NUM> does not operate as a generator. In utility mode, when the shaft <NUM> is not turning and the rotor <NUM> is stationary, the WRIG <NUM> operates as a voltage transformer through the voltage taps on the stator winding <NUM>.

In utility mode, the WRIG <NUM> allows input-to-output voltage transformation within machine windings, thereby negating the need for transformers or phase shifters. For example, the stator winding <NUM> of the WRIG <NUM> may be tapped to transform the input line voltage received from the utility source <NUM> to a different output voltage level consistent with the voltage level of the load(s) <NUM>. In some embodiments, the stator winding <NUM> may be tapped at one of <NUM>%, <NUM>%, <NUM>%, or <NUM>%. In general, the WRIG <NUM> can include one or multiple taps at one or multiple voltage levels. In some embodiments, the WRIG <NUM> can be wound for multiple voltage outputs. When combined with a controlled rectifier <NUM> and a DC-to-AC inverter <NUM>, the different voltage outputs of the WRIG <NUM> enable the system <NUM> to generate power at different voltages and different frequencies.

The AC output power of the WRIG <NUM> can be converted through the rectifier <NUM> to direct current (DC) power, which feeds both an energy storage bank <NUM> and a DC input to the inverter <NUM>. The inverter <NUM> operates as the main frequency converter before power is sent to the load(s) <NUM>. The net result here is seamless and rapid power source transfer from the portable power of the prime mover <NUM> to the utility source <NUM> and vice versa. The output power of the WRIG <NUM> feeds the rectifier <NUM>, the energy storage bank <NUM> on a DC bus <NUM>, and the inverter <NUM>. The output of the WRIG <NUM> may have a number of phases greater than the utility source. For example, the WRIG <NUM> may have <NUM>-phase output whereas the utility may be a <NUM>-phase source. This arrangement yields a lower harmonic content for the DC output of the rectifier and minimizes the amount of filtering required in the DC bus <NUM>.

Use of the WRIG <NUM> (instead of a conventional DC field synchronous generator) allows use of newer, variable-speed, high-efficiency versions of the prime mover <NUM>. For example, in some embodiments, the WRIG <NUM> can be configured to operate with a high-speed prime mover <NUM> exceeding <NUM>,<NUM> RPMs, which enables lightweight, efficient power generation. For example at a <NUM> RPM shaft speed representative of a compact prime mover and with a <NUM> pole WRIG, if the rotor frequency is controlled to be <NUM>, the stator output can be maintained at <NUM>, which is of interest to many applications. In island mode, the WRIG <NUM> can maintain constant, high-frequency output power, even with wide speed variations in the shaft <NUM> connecting the WRIG <NUM> to the prime mover <NUM>. By having variable frequency excitation to the rotor circuit of the WRIG <NUM>, the prime mover <NUM> can operate over a wide range of operating speeds and not be bound by fixed speed operation as in conventional systems. Thus, even without a standard solid-state frequency converter, the WRIG <NUM> can output full power to the load(s) <NUM> at one or more specified frequencies, such as <NUM> or <NUM>, with no change in circuitry. The system <NUM> is also "transformer-less" (meaning it lacks transformers), which greatly enhances power density.

The output frequency of the WRIG <NUM> represents a summation of the synchronous shaft field frequency and the injected rotor frequency. For example, if the speed of the shaft <NUM> is <NUM>,<NUM> RPMs on a <NUM>-pole machine (which yields <NUM> for a synchronous machine) and the injected rotor frequency is <NUM>, the output frequency at the stator winding <NUM> would equal <NUM> (<NUM> + <NUM>). The voltage transformation ratio in the WRIG <NUM> may be step-up or step-down due to the specific design of the stator winding <NUM>. In some embodiments, the WRIG <NUM> provides a <NUM>% voltage step-down (such as 416V to 208V), which is advantageous in some applications. Of course, this is merely one example, and other voltage transformation ratios are possible and within the scope of this disclosure.

The WRIG <NUM> can be configured in different ways depending on the application. For example, in some embodiments, the WRIG <NUM> can be configured as a three-phase, six-phase, or twelve-phase transformer. Other configurations are possible, as well. Also, in some embodiments, the stator winding <NUM> of the WRIG <NUM> includes a six-phase stator winding with wye and delta output windings at a <NUM>° phase shift to allow the use of a twelve-pulse rectifier <NUM> with low harmonics. In particular embodiments, the stator winding <NUM> can be configured for dual wye-delta outputs (e.g., a <NUM>-phase <NUM>-pulse system) to suit high-order rectifier systems with very low harmonic content. In such configurations, external power filters are minimized.

The switch <NUM>, typically a contactor, operates to disconnect the system <NUM> from the utility source <NUM> when the utility source <NUM> becomes unavailable and to connect the system <NUM> to the utility source <NUM> when the utility source <NUM> is available. The switch <NUM> may also take the form of a solid-state transfer switch utilizing thyristor, IGBT, or high power MOSFET switches. If the utility source <NUM> is initially available, becomes unavailable, and then becomes available again, the switch <NUM> operates to switch the utility source <NUM> back into the system <NUM>, and the prime mover <NUM> can stop and thereby stop rotation in the WRIG <NUM>.

Before a transition from utility mode to island mode, the WRIG <NUM> can be stationary. The transition from utility mode to island mode may become necessary when power from the utility source <NUM> is unavailable or is not reliable, including when there is a loss of a phase input or low voltage. At the start of island mode, to initiate movement of the rotor <NUM> after being disconnected from the utility source <NUM>, the WRIG <NUM> is first excited by a DC-to-AC rotor exciter <NUM>, which is a DC-to-AC inverter connected to the rotor winding <NUM> and configured to supply power to the rotor circuit of the WRIG <NUM>. The DC-to-AC rotor exciter <NUM> receives suitable power, such as from a capacitor source <NUM> or an engine battery <NUM>, and uses the received power to start the WRIG <NUM>. The capacitor source <NUM> represents any suitable source of capacitor power and may include the energy storage bank <NUM> or may represent another energy source, such as an external capacitive energy storage bank. The engine battery <NUM> represents any suitable battery source. In some embodiments, the engine battery <NUM> is a <NUM> VDC battery and may include a battery of the prime mover <NUM>.

In island mode, once the WRIG <NUM> is operating at a specified speed (such as a <NUM>% speed or greater), the WRIG <NUM> builds up excitation to the preferred voltage level to charge the energy storage bank <NUM>. Steady-state operation of the WRIG <NUM> uses DC power received from the energy storage bank <NUM> as a source of excitation energy, such as at <NUM>% of main output rating. Thus, the power amplification would be <NUM>:<NUM> in this example, although other ratios are also possible.

Power that is output from the WRIG <NUM> in either island mode or utility mode is input to the rectifier <NUM>. The rectifier <NUM> is a controlled AC-DC rectifier that receives the AC power output from the WRIG <NUM> and rectifies the power to DC power, which allows the DC power to be stored in the energy storage bank <NUM>. The rectifier <NUM> includes any suitable structure for AC-DC power rectification.

The energy storage bank <NUM> operates as the central energy storage element of the system <NUM> when in utility mode and the WRIG <NUM> is stationary. In island mode, when the WRIG <NUM> is operating from the prime mover <NUM>, there is combined energy storage of the energy storage bank <NUM> and engine flywheel inertia that is part of the WRIG <NUM>. Thus, in island mode, the energy storage bank <NUM> may operate as the primary energy storage, while the inertial energy of the engine flywheel may represent the secondary energy storage.

During a transition from utility mode to island mode, the energy storage bank <NUM> facilitates the rapid switching between the utility source <NUM> and the prime mover <NUM>. When the WRIG <NUM> has not yet started spinning at the start of island mode and is not yet generating power, the energy storage bank <NUM> can temporarily provide power to the load(s) <NUM> while the WRIG <NUM> spins up. Likewise, the energy storage bank <NUM> maintains bus voltage and provides power to the load <NUM> during a transition from island mode to utility mode. A charging circuit <NUM> connects the energy storage bank <NUM> to the DC bus <NUM>, and controls the charging and discharging of the energy storage bank <NUM>.

The inverter <NUM> is a frequency converter that receives power on the DC bus (from the WRIG <NUM>, the energy storage bank <NUM>, or both) and converts the DC power to controlled AC power for output to the load(s) <NUM>. The inverter <NUM> can convert the power to any suitable frequency, such as <NUM>, <NUM>, or the like. This allows different loads <NUM> at different voltages and frequencies to be connected to the system <NUM>. Frequency conversion by the inverter <NUM> further obviates the need for a separate, heavy power transformer to yield the correct output voltage. A three-pole double-throw (3PDT) switch <NUM> is disposed in front of the load(s) <NUM> and allows switching between power from the inverter <NUM> and an alternate power path directly from the WRIG <NUM>. The switch <NUM> may be an electromechanical device or a solid-state transfer switch.

The transition between using the utility source <NUM> as a source (utility mode) and using the prime mover <NUM> as a source (island mode) is seamless and transparent to the load(s) <NUM>, due to the energy available from the energy storage bank <NUM>. It is noted that use of the switch <NUM> for switching the utility source <NUM> can, in some cases, create voltage spikes at the time of a switch. Such spikes may be harmful to downstream components, such as the load(s) <NUM>. To alleviate this issue, the system <NUM> uses the rectifier <NUM> and the inverter <NUM> to electrically isolate the load(s) <NUM> from the prime mover <NUM> or the utility source <NUM>. Thus, switching the system <NUM> from utility mode to island mode (or vice versa) is seamless and fast, since all energy from the WRIG <NUM> passes through the rectifier <NUM>, the DC bus <NUM>, and the inverter <NUM> under typical operating conditions.

Use of the WRIG <NUM> as a step-up or step-down transformer (when the prime mover <NUM> is off) obviates the need for a separate and heavy input transformer. Such transformers typically add substantial weight and size to a power system and generate a substantial amount of heat in the power system. Thus, compared to conventional power systems, the system <NUM> is capable of improved kW/kg overall power density. In some embodiments, without a transformer, the entire system <NUM> can be <NUM>,<NUM> or less and can be portable enough (both in size and weight) to be placed on a trailer, pallet, or other platform, that can fit in an aircraft or land or sea cargo vehicle. Of course, these values are merely examples, and other weights are within the scope of this disclosure.

Although <FIG> illustrates one example of a mobile hybrid electric power system <NUM>, various changes may be made to <FIG>. For example, the components shown in <FIG> may be removed or arranged in other configurations, and additional components may be added. As a particular example, it is practical to insert a step-up gearbox between the prime mover <NUM> and the WRIG <NUM> so that the generator operates at a speed substantially higher than the prime mover <NUM>. In general, power systems come in a wide variety of configurations, and <FIG> does not limit this disclosure to any particular configuration of power system. Also, while <FIG> illustrates one example operational environment in which a mobile hybrid electric power system can be used, this functionality may be used in any other suitable system.

<FIG> illustrates another example mobile hybrid electric power system <NUM> according to this disclosure. As shown in <FIG>, the system <NUM> includes multiple components that may be the same as or similar to corresponding components of the system <NUM> of <FIG>. For example, the system includes a WRIG <NUM> that is coupled to a prime mover <NUM> and electrically connected to a utility source <NUM>, and the WRIG <NUM> is configured to provide power to at least one load <NUM>. These components may be the same as or similar to the WRIG <NUM>, the prime mover <NUM>, the utility source <NUM>, and the load(s) <NUM> of <FIG>.

Like the WRIG <NUM>, the WRIG <NUM> is configured to operate in utility mode or island mode. In utility mode, the WRIG <NUM> receives power from the utility source <NUM> via an AC-to-AC frequency converter <NUM>, which converts the voltage (V1) and frequency (f1) from the utility source <NUM> to an input voltage (V2) and frequency (f2) for the WRIG <NUM>. When power from the utility source <NUM> becomes unavailable or unreliable, the WRIG <NUM> switches to island mode.

At the start of island mode, to initiate movement of a rotor <NUM> after being disconnected from the utility source <NUM>, the WRIG <NUM> is first excited by a DC-to-AC rotor exciter <NUM> or an AC-to-AC rotor exciter <NUM>. In some embodiments, the DC-to-AC rotor exciter <NUM> may receive power from an engine battery <NUM>, while the AC-to-AC rotor exciter <NUM> may receive power from the utility source <NUM>. The DC-to-AC exciter <NUM> and the engine battery <NUM> may be the same as or similar to the DC-to-AC rotor exciter <NUM> and the engine battery <NUM> of <FIG>.

The WRIG <NUM> includes the rotor <NUM> and a corresponding polyphase rotor winding <NUM>, which may be the same as or similar to the rotor <NUM> and rotor winding <NUM> of <FIG>. The WRIG <NUM> also includes multiple stator windings 212a-212b, which are advantageous to enhance system operational flexibility. In utility mode, the stator winding 212a receives the (V2) power originating at the utility source <NUM> and transforms the power to a different voltage (V2/k<NUM>), where k<NUM> is a transformation coefficient determined by the configuration of the stator winding 212a. Some example configurations of stator windings are described in greater detail below in conjunction with <FIG>, <FIG>, and <FIG>. The stator winding 212b provides power to be stored in an ultra-capacitor storage <NUM>. The stator winding 212b can be a delta configuration, whereas the stator winding 212a is a wye configuration; additionally the output of the stator winding 212b can be a higher phase number (e.g., <NUM>, <NUM> or <NUM>) than the utility source, which reduces harmonic content on the rectified output. The ultra-capacitor storage <NUM> is charged by the WRIG <NUM> during island mode when the prime mover <NUM> moves. During charging, power from the stator winding 212b is output to the ultra-capacitor storage <NUM> via a AC-DC rectifier <NUM>. The AC-DC rectifier <NUM> also provides for a discharge of the capacitor bank, which is necessary for a transport mode or if the voltage rises beyond safe levels.

The ultra-capacitor storage <NUM> may be the same as or similar to the energy storage bank <NUM> of <FIG>. Power from the ultra-capacitor storage <NUM> can be supplied to the load(s) <NUM> when the utility source <NUM> is unavailable. The DC power from the ultra-capacitor storage <NUM> is converted to AC by a DC-to-AC converter <NUM> and filtered by a Pi-type L-C filter <NUM> before being supplied to the load(s) <NUM>. The DC-to-AC converter <NUM> also generates the frequency of the power to be suitable for the load(s) <NUM>, similar to the inverter <NUM> of <FIG>. In some embodiments, the DC-to-AC converter <NUM> is bidirectional in power and current flow and is configured to allow load energy to charge the ultra-capacitor storage <NUM>.

Unlike the system <NUM> of <FIG>, the ultra-capacitor storage <NUM> is not used as an energy source when the system <NUM> is running off the utility source <NUM>. When the utility source <NUM> becomes unavailable, the system <NUM> switches to power received from the ultra-capacitor storage <NUM>. A solid-state transfer switch <NUM> is configured to switch between power from the utility source <NUM> and power from the ultra-capacitor storage <NUM>.

Although <FIG> illustrates another example of a mobile hybrid electric power system <NUM>, various changes may be made to <FIG>. For example, the stator winding 212a may also be an input to the AC-DC rectifier <NUM>, in addition to the stator winding 212b input forming a higher pulse system with lower harmonic levels. The components shown in <FIG> may be removed or arranged in other configurations, and additional components may be added. In general, power systems come in a wide variety of configurations, and <FIG> does not limit this disclosure to any particular configuration of power system. Also, while <FIG> illustrates another example operational environment in which a mobile hybrid electric power system can be used, this functionality may be used in any other suitable system.

<FIG> and <FIG> illustrate schematic layouts of example stator and rotor windings <NUM> and <NUM> for use in a mobile hybrid electric power system according to this disclosure. In particular, <FIG> shows a stator winding <NUM>, and <FIG> shows a rotor winding <NUM>. The rotor winding <NUM> is fed by a slip-ring and brush subsystem typical of standard wound rotor AC machines. Together, the stator winding <NUM> and the rotor winding <NUM> form a power generator that is applicable to any shaft speed. For ease of explanation, the stator winding <NUM> and the rotor winding <NUM> are described as forming part of the WRIG <NUM> of <FIG> or the WRIG <NUM> of <FIG>. However, the stator winding <NUM> and the rotor winding <NUM> shown in <FIG> and <FIG> may be used in any other suitable electrical or electronic component.

As shown in <FIG>, the stator winding <NUM> has an "auto-transformer" connection and includes forty-eight coils or slots <NUM> and four poles <NUM>, which are numbered as shown in <FIG>. In some embodiments, the stator winding <NUM> is a <NUM>% voltage-tapped polyphase stator winding with three taps T1, T2, and T3. In the embodiment shown in <FIG>, the slots <NUM> and poles <NUM> are arranged in a three-phase wye configuration. In some embodiments, the stator winding <NUM> can represent the stator winding <NUM> of <FIG>.

As shown in <FIG>, the rotor winding <NUM> includes twenty-four slots <NUM> and four poles <NUM>, which are numbered as shown in <FIG>. The slots <NUM> and poles <NUM> are arranged in a three-phase delta configuration. In some embodiments, the rotor winding <NUM> can represent the rotor winding <NUM> of <FIG>.

Although <FIG> and <FIG> illustrate schematic layouts of examples of the stator winding <NUM> and the rotor winding <NUM> for use in a mobile hybrid electric power system, various changes may be made to <FIG> and <FIG>. For example, the stator winding <NUM> and the rotor winding <NUM> may each include any suitable number of slots and any suitable number of poles, which can be arranged in suitable configurations that have multiples of four poles.

<FIG> illustrate schematic layouts of other example stator and rotor windings <NUM>, <NUM>, <NUM> for use in a mobile hybrid electric power system according to this disclosure. In particular, <FIG> and <FIG> show two electrically independent stator windings <NUM> and <NUM> that can be used together, and <FIG> shows a rotor winding <NUM> that can be used with the stator windings <NUM> and <NUM>. Together, the stator windings <NUM> and <NUM> and the rotor winding <NUM> form a power generator that is applicable to any shaft speed. For ease of explanation, the stator windings <NUM> and <NUM> and the rotor winding <NUM> are described as forming part of the WRIG <NUM> of <FIG>. However, the stator windings <NUM> and <NUM> and the rotor winding <NUM> shown in <FIG> may be used in any other suitable electrical or electronic component.

As shown in <FIG>, the stator winding <NUM> includes forty-eight double-layer coils arranged in forty-eight slots <NUM>, which are numbered as shown in <FIG>, and eight poles. In some embodiments, the stator winding <NUM> is a <NUM>% voltage-tapped polyphase stator winding with three taps T1, T2, and T3. In the embodiment shown in <FIG>, the slots <NUM> are arranged in a three-phase wye configuration. In some embodiments, the stator winding <NUM> can represent the stator winding 212a of <FIG>.

As shown in <FIG>, the stator winding <NUM> includes forty-eight coils arranged in forty-eight slots <NUM>, which are numbered as shown in <FIG>, and eight poles. In the embodiment shown in <FIG>, the slots <NUM> are arranged in a three-phase delta configuration. In some embodiments, the stator winding <NUM> can represent the stator winding 212b of <FIG>. The stator winding <NUM> here shadows the main stator winding <NUM> in consequent slots. In some embodiments, there is a <NUM>° phase shift between the outputs of the stator winding <NUM> and the stator winding <NUM>.

As shown in <FIG>, the rotor winding <NUM> includes twenty-four slots <NUM> and eight poles <NUM>, which are numbered as shown in <FIG>. The slots <NUM> and poles <NUM> are arranged in a three-phase, lap-wound delta, double-layer configuration. In some embodiments, the rotor winding <NUM> can represent the rotor winding <NUM> of <FIG>. In operation, variable frequency can be applied to the rotor winding <NUM> to yield a wide range of output frequencies. The applied rotor current may be positive sequence or negative sequence.

Together, the stator windings <NUM> and <NUM> and the rotor winding <NUM> form a wye-delta, six-phase, eight-pole, <NUM>% tapped power generator in ninety-six slots. Similar embodiments can include other numbers of tapped windings for higher pole numbers, such as <NUM>-pole, <NUM>-pole, <NUM>-pole, <NUM>-pole, and the like. The stator windings <NUM> and <NUM> have two slots/pole/phase and the rotor winding <NUM> has one slot/pole/phase.

Although <FIG> illustrate schematic layouts of other examples of the stator windings <NUM> and <NUM> and the rotor winding <NUM> for use in a mobile hybrid electric power system, various changes may be made to <FIG>. For example, the stator windings <NUM> and <NUM> and the rotor winding <NUM> may each include any suitable number of slots and any suitable number of poles, which can be arranged in many suitable configurations.

<FIG> illustrates another example mobile hybrid electric power system <NUM> according to this disclosure. As shown in <FIG>, the system <NUM> includes multiple components that may be the same as or similar to corresponding components of the system <NUM> of <FIG>. For example, the system <NUM> includes a WRIG <NUM> that is coupled to a prime mover <NUM>, and the WRIG <NUM> is configured to provide power to at least one load <NUM>. These components may be the same as or similar to the WRIG <NUM>, the prime mover <NUM>, and the load(s) <NUM> of <FIG>.

As shown in <FIG>, the WRIG <NUM> can receive power from two independent utility sources 530a and 530b at different voltage levels Va & Vb respectively. The WRIG <NUM> has two independent stator input windings 512a and 512b, which are matched in frequency, winding pitch, and poles, but have different airgap flux levels to accommodate different input voltages and power Pa and Pb derived from two different sources. The stator winding 512a is tapped to allow for a direct AC output at a voltage different from the source voltage Va and also allows for charging the DC capacitor storage bank <NUM> at an optimum voltage level without use of conventional power transformers.

The power ratings of the two sources 530a and 530b or input windings need not be matched; however the design of the WRIG <NUM> allows the inputs from the two sources 530a and 530b to be combined into a common output power as Pt = Pa + Pb, which then undergoes voltage transformation to a third voltage level V4 for an output port on a third stator winding 512c used to charge the capacitive energy storage bank <NUM> after full wave rectification. The sources 530a and 530b can be utilized simultaneously or one at a time.

The system <NUM> has two paths to charge the DC energy storage capacitor bank <NUM>-one from the tapped stator winding 512a and one from the stator winding 512c. The AC output from the stator winding 512a is at utility source frequency, which is usually a lower frequency (<NUM> or <NUM>). When the utility source is disconnected or inactive, the AC output from the stator winding 512c can be at significantly higher frequency f4 than the utility source, such as <NUM>, which makes for a more efficient and compact rectifier subsystem. The higher frequency output at the stator winding 512c is due to the excitation of the rotor circuit <NUM> at a frequency f3 which when numerically combined with the actual rotor speed produces a higher frequency f4 in the stator winding 512c. In one embodiment, the rotor frequency f3 can be progressively increased as the rotor drops in speed due to extracting energy from the rotor inertia, and in so doing, the output frequency f4 remains nearly constant over a wide speed range.

The system <NUM> uses a polyphase rotor winding <NUM> for overall machine excitation at excitation frequency f3. The system <NUM> can be extended to have greater than two independent input or utility sources, and the WRIG <NUM> can be designed to have greater than three stator windings.

Although <FIG> illustrates another example of a mobile hybrid electric power system <NUM>, various changes may be made to <FIG>. For example, the components shown in <FIG> may be removed or arranged in other configurations, and additional components may be added. In general, power systems come in a wide variety of configurations, and <FIG> does not limit this disclosure to any particular configuration of power system. Also, while <FIG> illustrates another example operational environment in which a mobile hybrid electric power system can be used, this functionality may be used in any other suitable system.

Table <NUM> shows a specific <NUM> kW example of a wound-rotor <NUM>-pole multi-port induction machine design for the system <NUM>, whereby there are two independent power sources at a low frequency and the machine polyphase output is at a higher frequency. This machine includes a tapped stator winding so output can be derived directly from the source at source frequency but a voltage different from source without use of discrete transformers.

As shown in <FIG>, the WRIG <NUM> can receive power from two independent utility sources 630a and 630b at different voltage levels Va & Vb respectively and at different frequencies fa and fb. The system <NUM> includes two AC to AC frequency converters 633a and 633b (one for each source 630a and 630b), which convert both input frequencies to a common frequency f2 for input to the WRIG <NUM>. The WRIG <NUM> has two independent stator input windings 612a and 612b, which are matched in frequency, winding pitch, and poles, but may have different airgap flux levels to accommodate different input voltages and power Pa and Pb derived from two different sources. The stator winding 612a is tapped to allow for a direct AC output at a voltage different from the source voltage Va when in the "utility" mode.

The output of the WRIG <NUM> from a third stator winding 612c in the "island" mode is the only means for charging the DC capacitor storage bank <NUM> at an optimum voltage level without use of conventional power transformers.

The power ratings of the two sources 630a and 630b or input windings need not be matched; however the design of the WRIG <NUM> allows the inputs from the two sources 630a and 630b to be combined into a common output power as Pt = Pa + Pb, which then undergoes voltage transformation to a third voltage level V3 as an output port on the third stator winding 612c subsequently used to charge the capacitive energy storage bank <NUM> after full wave rectification. The stator may have a total of <NUM> phases or alternately <NUM> phases total for a higher phase output for the stator winding 612c to allow more efficient rectification.

The system <NUM> in "island" mode allows the WRIG <NUM> to operate at high rotational speeds exceeding <NUM> rpm by use of a step-up gearbox, and when combined with excitation of the rotor at a high frequency produces a high frequency output (<NUM>-<NUM>) f3 at the stator winding 612c, which is advantageous for compact rectification. For example if the shaft speed is <NUM> rpm on a <NUM>-pole WRIG, and rotor frequency is <NUM>, the output frequency f3 can be <NUM>.

The system <NUM> can be extended to have greater than two independent input or utility sources, greater than two frequency converters, and the WRIG <NUM> can be designed to have greater than three stator windings.

The system <NUM> utilizes stored kinetic energy of the electrical machine- flywheel inertia to provide a seamless transfer of power from the utility source to the load when the energy storage capacitor is discharged or not of sufficient charge to fully support the load. The system <NUM> also provides a continuous stream of power from the two sources 630a and 630b through the electrical machine to the rectifiers, energy storage bank, and DC-AC converter and hence to the load, independent of machine speed and irrespective of stored energy in the flywheel.

The electrical machine provides a voltage transformation from its two input sources after frequency converters 633a and 633b and can be at different or same input voltages V2 and V6 to the WRIG <NUM>, hence to its common output terminal of voltage V3. Voltage transformation occurs since the WRIG <NUM> may have a different number of turns per phase, different distribution factors and different chording factors for its three stator windings 612a-612c. The system <NUM> does not permit the utility source to directly charge the energy storage bank <NUM>; rather the energy storage bank <NUM> is exclusively charged by the stator winding 612c acting as the singular supply through an AC-DC rectifier system <NUM>. The stator winding 612c can be single phase or polyphase. The energy storage bank output has one output DC to AC converter <NUM> and one output power filter <NUM>. The DC to AC converter may have either single phase or polyphase output. The energy storage bank <NUM> may be an ultra-capacitor, electrochemical storage battery, or auxiliary kinetic energy device.

<FIG> illustrates another example mobile hybrid electric power system <NUM> according to this disclosure. As shown in <FIG>, the system <NUM> includes multiple components that may be the same as or similar to corresponding components of the system <NUM> of <FIG>. For example, the system <NUM> includes a WRIG <NUM> that is coupled to a prime mover <NUM>. These components may be the same as or similar to the WRIG <NUM> and the prime mover <NUM> of <FIG>.

As shown in <FIG>, the system <NUM> includes multiple independent energy storage banks 740a and 740b and dual AC outputs 760a and 760b. The outputs 760a and 760b can be at different frequencies f5 and f7 as well at different voltage levels V5 and V7. The WRIG <NUM> has one input stator winding 712a and two independent output stator windings 712b and 712c. In an embodiment, all stator windings are double-layer lap-wound <NUM>-phase or higher phase number windings. Also, the stator windings can have separate and distinct voltage levels and are electrically isolated. In an embodiment, the combined apparent power rating of the stator windings 712b and 712c should be equal to or close to the apparent power rating of the stator winding 712a. The WRIG <NUM> has attached to the shaft directly or through a gearbox, a flywheel able to provide inertial storage energy to the WRIG <NUM> and hence to the two outputs 760a and 760b when the power from the utility source <NUM> to the stator winding 712a is not available. The system <NUM> also includes a tapped winding on the stator winding 712a so that without the WRIG <NUM> having inertial energy input or rotation, the load at the output 760a may access the utility power directly at the utility frequency fa albeit at a voltage different from the source voltage according to the tap percentage of the machine winding.

A further advantage of the dual output system <NUM> is that the two loads can be of totally different characteristics in terms of duty cycle, peak power, pulse repetition rate or time constants. For example the load at the output 760a may be a steady-state load such as a compressor, and the load at the output 760b can be a pulsed load such as a radar, which creates significant current and power transients. With the included energy storage banks and rectifiers, the electrical interaction between these two outputs 760a and 760b is minimized at the machine level by having the output windings S2 and S3 in separate stator slots or electrically-isolated winding segments, and thus there is little or no interference of one output to the other. The WRIG <NUM> is shown with three stator ports by example; the concept can be extended to any number of stator ports. The WRIG <NUM> is shown with one rotor AC port by example; the concept can be extended to a wound rotor electrical machine with multiple rotor polyphase ports.

As described above, the disclosed embodiments provide mobile hybrid electric power systems that can seamlessly switch between grid and generator prime power sources. This is advantageous for many applications that require or prefer a system that includes both, such as ground-based mobile radar systems, missile defense systems, and marine-based platforms. The disclosed power systems are beneficial, as power capabilities increase for sensors and support equipment, while demands to reduce overall system weight and size also grow. The disclosed power systems can also advantageously supply various loads with power at variable power frequencies and voltage levels from a universal platform while maintaining mobility and portability.

Claim 1:
A system (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
a prime mover (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured to rotate a shaft (<NUM>); and
a wound rotor induction generator, WRIG, (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
a rotor (<NUM>, <NUM>) coupled to the shaft (<NUM>) of the prime mover (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and configured to rotate when the shaft (<NUM>) rotates, the rotor (<NUM>, <NUM>) comprising a rotor winding (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
a stator winding (<NUM>, 212a-212b, <NUM>, <NUM>, <NUM>, 512a-512c, 612a-612c, 712a-712c) electrically connected to a utility source (<NUM>, <NUM>, 530a-530b, 630a-630b, <NUM>) and a load (<NUM>, <NUM>, <NUM>, <NUM>);
wherein:
when the stator winding (<NUM>, 212a-212b, <NUM>, <NUM>, <NUM>, 512a-512c, 612a-612c, 712a-712c) does not receive first power from the utility source (<NUM>, <NUM>, 530a-530b, 630a-630b, <NUM>), the WRIG (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is configured to generate second power due to kinetic energy of the rotor (<NUM>, <NUM>), and output at least a portion of the second power to the load (<NUM>, <NUM>, <NUM>, <NUM>),
characterized in that
when the stator winding (<NUM>, 212a-212b, <NUM>, <NUM>, <NUM>, 512a-512c, 612a-612c, 712a-712c) receives the first power from the utility source (<NUM>, <NUM>, 530a-530b, 630a-630b, <NUM>), the WRIG (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is configured to transform at least one of a voltage and a frequency of the first power before outputting at least a portion of the first power to the load (<NUM>, <NUM>, <NUM>, <NUM>).