Patent Description:
Typically, cold chain distribution systems are used to transport and distribute cargo, or more specifically perishable goods and environmentally sensitive goods (herein referred to as perishable goods) that may be susceptible to temperature, humidity, and other environmental factors. Perishable goods may include but are not limited to fruits, vegetables, grains, beans, nuts, eggs, dairy, seed, flowers, meat, poultry, fish, ice, and pharmaceuticals. Advantageously, cold chain distribution systems allow perishable goods to be effectively transported and distributed without damage or other undesirable effects.

Refrigerated vehicles and trailers are commonly used to transport perishable goods in a cold chain distribution system. A transport refrigeration system is mounted to the vehicles or to the trailer in operative association with a cargo space defined within the vehicles or trailer for maintaining a controlled temperature environment within the cargo space.

Conventionally, transport refrigeration systems used in connection with refrigerated vehicles and refrigerated trailers include a transportation refrigeration unit having a refrigerant compressor, a condenser with one or more associated condenser fans, an expansion device, and an evaporator with one or more associated evaporator fans, which are connected via appropriate refrigerant lines in a closed refrigerant flow circuit. Air or an air/ gas mixture is drawn from the interior volume of the cargo space by means of the evaporator fan(s) associated with the evaporator, passed through the airside of the evaporator in heat exchange relationship with refrigerant whereby the refrigerant absorbs heat from the air, thereby cooling the air. The cooled air is then supplied back to the cargo space.

On commercially available transport refrigeration systems used in connection with refrigerated vehicles and refrigerated trailers, the compressor, and typically other components of the transportation refrigeration unit, must be powered during transit by a prime mover. In mechanically driven transport refrigeration systems the compressor is driven by the prime mover, either through a direct mechanical coupling or a belt drive, and other components, such as the condenser and evaporator fans are belt driven.

Transport refrigeration systems may also be electrically driven. In an electrically driven transport refrigeration system, components of the transportation refrigeration unit (such as a compressor) can be powered by an electric current supplied by a battery during a "road mode" and an electric current supplied by a power grid during a "standby mode. " A "road mode" refers to a mode of operation in which the transport refrigeration system is unconnected to a power grid, such as when a refrigerated vehicle is in transit. Conventionally, when in road mode, the transportation refrigeration system has one source (e.g., a battery) and one load (e.g., the compressor motor), which requires the use of two power bridges and a DC link to convert the electrical characteristics (e.g., amplitude, phase, frequency) of the power between them. A "standby mode" refers to a mode of operation in which the transport refrigeration system is connected to a power grid, such as when a refrigerated vehicle is parked and plugged in to a charging station. Conventionally, when in standby mode, the transportation refrigeration system has an additional source (e.g., the power grid), which requires the use of a third power bridge and an additional DC link. Each power bridge includes a converter or inverter, which is typically an expensive component. Therefore it is desirable to provide the functionalities of a conventional road mode and standby mode using less power bridges. <CIT> teaches a power supply device for a vehicle which inputs voltage from a generator into a DC boost circuit through a circuit switching device. The boost voltage is converted into AC by the inverter, and supplied to a compressor device. At the same time, the voltage is applied to the storage battery device through a circuit switching device to be charged. When the engine is stopped, and the power generation is stopped, the circuit switching devices are switched to a fixed contact side, the charged voltage of the storage battery device is inputted to the DC boost circuit. The boost voltage is inputted into the inverter to be supplied to the compressor device. <CIT> discloses a further transport refrigeration system of the prior art.

According to a first aspect of the invention, a transport refrigeration system is provided. The transportation refrigeration system includes: a transportation refrigeration unit including a motor; a power conversion unit configured to convert an amplitude, a frequency and a phase of an input electrical power signal, wherein the power conversion unit includes a first power bridge, a DC link and a second power bridge; an energy storage device configured to supply electrical power to the motor via the power conversion unit during a road mode; a first switch configured to selectively connect the first power bridge to the energy storage device or the motor; and a second switch configured to selectively connect the second power bridge to the motor or a power grid; wherein during the road mode, the first switch is positioned to connect the first power bridge to the energy storage device and the second switch is positioned to connect the second power bridge to the motor, wherein during a standby mode, the second switch is positioned to connect the second power bridge to the power grid, wherein during a first time share phase of the standby mode, the first switch is positioned to connect the first power bridge to the energy storage device, and wherein during a second time share phase of the standby mode, the first switch is positioned to connect the first power bridge to the motor.

Optionally, the transport refrigeration system may include a controller configured to control the positions of the first switch and second switch during the road mode and the standby mode.

Optionally, the controller is configured to determine a duration of the first time share phase and a duration of the second time share phase and change the position of the first switch at an expiration of the first time share phase and at an expiration of the second time share phase.

Optionally, the controller is configured to continuously cycle between the first time share phase and the second time share phase until the road mode is initiated.

Optionally, the controller is configured to determine the duration of the first time share phase and the duration of the second time share phase based on a measurement of a charge of the energy storage device.

Optionally, the controller is configured to reduce the duration of the first time share phase in response to determining that the charge of the energy storage device exceeds a threshold charge level.

Optionally, the controller is configured to determine the duration of the first time share phase and the duration of the second time share phase based on a measurement of a temperature of a cargo space of the transport refrigeration system.

Optionally, the controller is configured to increase the duration of the second time share phase in response to determining that the temperature of the cargo space is below a threshold temperature level.

According to a second aspect of the invention, a method of operating a transport refrigeration system including a vehicle integrally connected to a transport container is provided. The method includes: during a road mode of operation of the transport refrigeration system, placing a first switch and a second switch in a first configuration, wherein the first configuration includes positioning the first switch to connect a first power bridge of a power conversion unit of the transport refrigeration system to an energy storage device and positioning the second switch to connect a second power bridge of the power conversion unit of the transport refrigeration system to a motor of a transportation refrigeration unit of the transport refrigeration system; during a standby mode of operation of the transportation refrigeration unit, repeatedly cycling between a second configuration of the first switch and the second switch and a third configuration of the first switch and the second switch, wherein the second configuration includes positioning the first switch to connect the first power bridge to the energy storage device and positioning the second switch to connect the second power bridge to a power grid; wherein the third configuration includes positioning the first switch to connect the first power bridge to the motor and positioning the second switch to connect the second power bridge to the power grid.

Optionally, the method of operating a transport refrigeration system may include that during the first configuration, the motor is supplied with power from the energy storage device via the power conversion unit.

Optionally, the method of operating a transport refrigeration system may include that during the second configuration, the energy storage device is charged with power from the power grid via the power conversion unit.

Optionally, the method of operating a transport refrigeration system may include that during the third configuration, the motor is supplied with power from the power grid via the power conversion unit.

Optionally, the method of operating a transport refrigeration system may include determining, by a controller, a duration of the second configuration and a duration of the third configuration of a cycle.

Optionally, the method of operating a transport refrigeration system may include that the controller determines the duration of the second configuration based on a measured charge of the energy storage device.

Optionally, the method of operating a transport refrigeration system may include that the controller determines the duration of the third configuration based on a measured temperature of a cargo space of the transport refrigeration system. Optionally, the method may comprise using the invention as described herein with reference to the first aspect of the invention.

According to a third aspect of the invention, a transport refrigeration system is provided. The transportation refrigeration system including: a transportation refrigeration unit including a motor; a power conversion unit configured to convert an amplitude, a frequency and a phase of an input electrical power signal, wherein the power conversion unit includes a first power bridge, a DC link and a second power bridge; an energy storage device configured to supply electrical power to the motor via the power conversion unit during a road mode; a first switch configured to selectively connect the first power bridge to the energy storage device or a power grid; and a second switch configured to selectively connect the second power bridge to the motor or the power grid; wherein during the road mode, the first switch is positioned to connect the first power bridge to the energy storage device and the second switch is positioned to connect the second power bridge to the motor, wherein during a first time share phase of a standby mode, the first switch is positioned to connect the first power bridge to the energy storage device and the second switch is positioned to connect the second power bridge to the power grid, and wherein during a second time share phase of the standby mode, the first switch is positioned to connect the first power bridge to the power grid and the second switch is positioned to connect the second power bridge to the motor.

Optionally, the controller is configured to determine a duration of the first time share phase and a duration of the second time share phase and change the positions of the first switch and the second switch at an expiration of the first time share phase and at an expiration of the second time share phase.

Optionally, the controller is configured to determine the duration of the first time share phase and the duration of the second time share phase based on a measurement of a charge of the energy storage device. Optionally, the system of the third aspect may comprise features of the invention as described herein with reference to the first aspect of the invention. The system of the first aspect of the invention and/or the system of the third aspect of the invention may be configured to perform the method according to the second aspect of the invention. The method of the second aspect of the invention may comprise using the invention as described herein with reference to the third aspect of the invention.

Technical effects of embodiments of the present disclosure include providing the conventional functionalities of a transport refrigeration system in both road mode and standby mode using only two power bridges and one DC link.

It should be understood, however, that the following description and drawings are included by way of example only and are intended to be illustrative and explanatory in nature and non-limiting.

Referring to <FIG>, <FIG>and <FIG>, various embodiments of the present disclosure are illustrated. <FIG> shows a schematic illustration of a transport refrigeration system <NUM>, according to an embodiment of the present disclosure. <FIG> shows a block diagram of a conventional transport refrigeration system operating in road mode, whereas <FIG> shows a block diagram of a transport refrigeration system <NUM> of <FIG> operating in road mode according to an embodiment of the present disclosure. <FIG> shows a block diagram of a conventional transport refrigeration system operating in standby mode, whereas <FIG> shows a block diagram of a transport refrigeration system <NUM> of <FIG> operating in standby mode according to an embodiment of the present disclosure. <FIG> show block diagrams of an alternate embodiment of a transport refrigeration system <NUM> of <FIG> operating in road mode (<FIG>) and standby mode (<FIG>).

The transport refrigeration system <NUM> is being illustrated as a trailer system <NUM>, as seen in <FIG>. The trailer system <NUM> includes a vehicle <NUM> integrally connected to a transport container <NUM>. The vehicle <NUM> includes an operator's compartment or cab <NUM> and a propulsion motor <NUM> which acts as the drive system of the trailer system <NUM>. The propulsion motor <NUM> is configured to power the vehicle <NUM>. The energy source that powers the propulsion motor <NUM> may be at least one of compressed natural gas, liquefied natural gas, gasoline, electricity, diesel, or a combination thereof. The propulsion motor <NUM> may be an electric motor or a hybrid motor (e.g., a combustion engine and an electric motor). The transport container <NUM> is coupled to the vehicle <NUM>. The transport container <NUM> may be removably coupled to the vehicle <NUM>. The transport container <NUM> is a refrigerated trailer and includes a top wall <NUM>, a directly opposed bottom wall <NUM>, opposed side walls <NUM>, and a front wall <NUM>, with the front wall <NUM> being closest to the vehicle <NUM>. The transport container <NUM> further includes a door or doors <NUM> at a rear wall <NUM>, opposite the front wall <NUM>. The walls of the transport container <NUM> define a refrigerated cargo space <NUM>. According to some embodiments, the refrigerated cargo space <NUM> may include a temperature sensor that can measure the temperature of the refrigerated cargo space <NUM> and provide the measurement to a controller for use in determining the durations of time share phases, as described in greater detail below. It is appreciated by those of skill in the art that embodiments described herein may be applied to a tractor-trailer refrigerated system or non-trailer refrigeration such as, for example a rigid truck, a truck having refrigerated compartment.

Typically, transport refrigeration systems <NUM> are used to transport and distribute perishable goods and environmentally sensitive goods (herein referred to as perishable goods <NUM>). The perishable goods <NUM> may include but are not limited to fruits, vegetables, grains, beans, nuts, eggs, dairy, seed, flowers, meat, poultry, fish, ice, blood, pharmaceuticals, or any other suitable cargo requiring temperature controlled transport. The transport refrigeration system <NUM> includes a transportation refrigeration unit <NUM>, an energy storage device <NUM> and a power conversion unit <NUM>. The transportation refrigeration unit <NUM> includes a refrigerant compression device for providing a heat transfer functionality and an electric motor <NUM> for driving the refrigerant compression device. The transportation refrigeration unit <NUM> is in operative association with the refrigerated cargo space <NUM> and is configured to provide conditioned air to the transport container <NUM>. The transportation refrigeration unit <NUM> functions, under the control of a controller (not shown), to establish and regulate a desired environmental parameters, such as, for example temperature, pressure, humidity, carbon dioxide, ethylene, ozone, light exposure, vibration exposure, and other conditions in the cargo space <NUM>, as known to one of ordinary skill in the art. In an embodiment, the transportation refrigeration unit <NUM> is capable of providing a desired temperature and humidity range. According to some embodiments, the controller can include a processor and an associated memory comprising computer-executable instructions that, when executed by the processor, cause the processor to perform various operations. The processor may be but is not limited to a single-processor or multi-processor system of any of a wide array of possible architectures, including field programmable gate array (FPGA), central processing unit (CPU), application specific integrated circuits (ASIC), digital signal processor (DSP) or graphics processing unit (GPU) hardware arranged homogenously or heterogeneously. The memory may be a storage device such as, for example, a random access memory (RAM), read only memory (ROM), or other electronic, optical, magnetic or any other computer readable medium.

Airflow is circulated into and through the refrigerated cargo space <NUM> of the transport container <NUM> by means of the transportation refrigeration unit <NUM>. According to some embodiments, the transportation refrigeration unit <NUM> can include a refrigerant compression device (which includes motor <NUM>), a refrigerant heat rejection heat exchanger, an expansion device, and a refrigerant heat absorption heat exchanger connected in refrigerant flow communication in a close loop refrigerant circuit and arranged in a conventional refrigeration cycle. The refrigerant compression device may be a single-stage or multiple-stage compressor such as, for example, a reciprocating compressor or a scroll compressor. The transportation refrigeration unit <NUM> can also include one or more fans associated with the refrigerant heat rejection heat exchanger and can be driven by fan motor(s) and one or more fans associated with the refrigerant heat absorption heat exchanger and driven by fan motor(s). The transportation refrigeration unit <NUM> may also include a heater associated with the refrigerant heat absorption heat exchanger. It is to be understood that other components may be incorporated into the refrigerant circuit as desired, including for example, but not limited to, a suction modulation valve, a receiver, a filter/dryer, an economizer circuit. Those of skill in the art will understand the conventional components and functionality provided by the refrigeration unit <NUM> to circuit airflow into the refrigerated cargo space <NUM> and as such they will not be shown or described in detail herein. It will be understood that motor <NUM> shown in <FIG> can be a component of a refrigeration unit <NUM> and in particular, motor <NUM> can be a motor that powers a compressor of the refrigeration unit <NUM>.

The transportation refrigeration unit <NUM> can be powered by the energy storage device <NUM> (which may for simplicity be referred to as battery <NUM>), which provides electrical power to the transportation refrigeration unit <NUM> during operation of the transport refrigeration system in road mode. Examples of the energy storage device <NUM> may include a battery system (e.g., a battery or bank of batteries), fuel cells, flow battery, and others devices capable of storing and outputting electric energy that may be direct current (DC). The energy storage device <NUM> may include a battery system, which may employ multiple batteries organized into battery banks. According to some embodiments, the energy storage device <NUM> may include a sensor that is configured to determine the charge of the energy storage device <NUM> and provide that information to the controller for use in determining the durations of time share phases, as described in greater detail below.

The battery <NUM> may be charged by a stationary charging station such as, for example a wall 48V power outlet, or some other outlet connected to a power grid <NUM>. The charging station may provide single phase (e.g., level <NUM> charging capability) or three phase AC power to the power conversion unit <NUM>, which may then supplied converted power to the energy storage device <NUM> and/or transportation refrigeration unit <NUM>. It is understood that the charging station may have any phase charging and embodiments disclosed herein are not limited to single phase or three phase AC power. In an embodiment, the single phase AC power may be a high voltage DC power, such as, for example, 500VDC.

In one embodiment, the energy storage device <NUM> is located outside of the transportation refrigeration unit <NUM>, as shown in <FIG>. In another embodiment, the energy storage device <NUM> is located within the transportation refrigeration unit <NUM>. The transportation refrigeration unit <NUM> can have a plurality of electrical power demand loads on the energy storage device <NUM>, including, but not limited to, a motor for compressor <NUM>, a drive motor for a fan associated with a refrigerant heat rejection heat exchanger, a drive motor for a fan associated with a refrigerant heat absorption heat exchanger, or any other such aspects of the transportation refrigeration unit <NUM> that may require electrical power.

The motor <NUM> used to power the refrigerant compression device is typically an alternating current (AC) motor, whereas the power supplied by the battery <NUM> is a DC voltage, therefore a power conversion unit <NUM> is electrically connected between the battery <NUM> and the refrigerant compression device to convert power supplied from the battery <NUM> to the refrigerant compression device from DC to AC. The power conversion unit <NUM> of a transportation refrigeration unit <NUM> can also connect a power grid <NUM> to either or both of the battery <NUM> and motor <NUM>. As will be appreciated by those of skill in the art, the power conversion unit <NUM> can be configured to change one or more electrical characteristics of an input power signal and output a modified signal having modified characteristics in order to regulate the power between supplies (e.g., battery <NUM>, power grid <NUM>) and loads (e.g., motor <NUM>). For example, the power conversion unit <NUM> can modify one or more of amplitude, frequency and/or phase of a signal, so that for example, a power signal output by the battery <NUM> may be changed to have electrical characteristics that are suitable for powering the compressor <NUM>.

As shown in <FIG>, a conventional power conversion unit <NUM> of a transportation refrigeration unit <NUM> includes a first power bridge <NUM>, a first DC link <NUM> and a second power bridge <NUM> connected in series between the battery <NUM> and the motor <NUM>, for converting power supplied from the battery <NUM> to the motor <NUM>. According to some embodiments, a power bridge can include semiconductor devices that perform one or more of the following functions: AC to DC conversion, DC to AC conversion, AC to AC conversion, and DC to DC conversion. In some embodiments, a DC link can be an array of capacitors. Due to the additional source of the power grid <NUM>, a conventional power conversion unit <NUM> also includes additional circuitry <NUM> that includes a second DC link <NUM> and a third power bridge <NUM> that are connected to the first DC link <NUM> and are connectable to the power grid <NUM> (e.g., via plugging in a power cable from the vehicle <NUM> to a charging station). As will be appreciated by those of skill in the art, this additional circuitry <NUM> is typically expensive and thus would be desirable to eliminate.

<FIG> depicts a conventional power conversion unit <NUM> of a transport refrigeration system <NUM> operating in road mode. As shown in <FIG>, when in road mode, a conventional power conversion unit <NUM> supplies power from the battery <NUM> to the motor <NUM>. As will be appreciated by those of skill in the art, the power conversion unit <NUM> can, for example, convert a DC power signal supplied by the battery <NUM> to an AC power signal appropriate for use by the motor <NUM>. During road mode, the power grid <NUM> is not connected to the transportation refrigeration system <NUM> and therefore the additional circuitry <NUM> of the second DC link <NUM> and the third power bridge <NUM> is not used and presents a waste of resources.

<FIG> depicts a conventional power conversion unit <NUM> of a transport refrigeration system <NUM> operating in standby mode. As shown in <FIG>, when in standby mode, a conventional power conversion unit <NUM> supplies power from the power grid <NUM> to the battery <NUM> and the motor <NUM> via the power conversion unit <NUM>. In this case, all three power bridges <NUM>, <NUM>, <NUM> and both DC links <NUM>, <NUM> are required convert the power output by the power grid <NUM> and convert it to power that is suitable for use to both charge the battery <NUM> and power the motor <NUM>.

<FIG> depicts a power conversion unit <NUM> of a transport refrigeration system <NUM> operating in road mode according to an embodiment of the present disclosure. As shown in this embodiment, the power conversion unit <NUM> includes a first switch <NUM> and a second switch <NUM>. The first switch <NUM> can selectively connect the first power bridge <NUM> to the battery <NUM> or the motor <NUM>. The second switch <NUM> can selectively connect the second power bridge <NUM> to the motor <NUM> or the power grid <NUM>. According to some embodiments, these switches can be controlled by a controller (not shown) that positions the switches based on which mode the transport refrigeration system <NUM> is operating in. During road mode, the switches are positioned in a first configuration in which the first switch <NUM> connects the first power bridge <NUM> to the battery <NUM> and the second switch is positioned to connect the second power bridge <NUM> to the motor <NUM>. As shown, the disclosed power conversion unit <NUM> eliminates the additional circuitry <NUM> of the second DC link <NUM> and the third power bridge <NUM> of the conventional design, which was not needed during road mode.

<FIG> depicts a power conversion unit <NUM> of a transport refrigeration system <NUM> operating in standby mode according to an embodiment of the present disclosure. As shown in <FIG>, during the standby mode, the second switch <NUM> is positioned to connect the second power bridge <NUM> to the power grid <NUM>, whereas the first switch <NUM> cycles back and forth between connecting the first power bridge <NUM> to the battery <NUM> and connecting the first power bridge <NUM> to the motor <NUM>. In this way, the power conversion unit <NUM> effectuates a time share of the grid power between the battery <NUM> and the motor <NUM> by providing limited durations of power to each in a repeated cycle. Each half of a cycle can referred to as a time share phase. Thus, in a first time share phase of a cycle, the battery <NUM> can be charged using the grid power and in a second time share phase of the cycle the motor <NUM> can be powered using the grid power. In this way, the battery <NUM> may charge over time and the motor <NUM> may continue to be powered in order to provide cool air to the cargo space <NUM>. Both of these ends can be achieved while eliminating the additional circuitry <NUM> of the second DC link <NUM> and the third power bridge <NUM> of the conventional design by utilizing this time sharing method. A controller (not shown) can determine the duration of each time share phase and can varying the phases over time. In some embodiments, the controller may increase or decrease the duration of the time share phase in which the battery <NUM> is charged using grid power based on a measured charge of the battery <NUM>. For example, if the battery <NUM> is approaching being fully charged, the controller may decrease the duration of the time share phase in which the battery <NUM> is charged. Similarly, based on a measured temperature of the cargo space, the controller may increase or decrease the duration of the time share phase in which the motor <NUM> is supplied with power from the power grid <NUM>. Thus, in some embodiments, if the temperature of the cargo space drops below a threshold temperature, the controller may increase the duration of the share phase in which the motor <NUM> is supplied with power from the power grid <NUM>. According to some embodiments, the controller may determine the duration of a time share phase based on a combination of the measured temperature of the cargo space and the measured charge of the battery <NUM>.

As will be appreciated by those of skill in the art, the operation of the power conversion unit <NUM> may differ based on the time share phase the power conversion unit <NUM> is in. For example, when powering the battery <NUM> using grid power, the second power bridge <NUM> can be operable to convert an AC power supplied by the power grid to a DC power and the first power bridge <NUM> can be operable to change the voltage level of the DC power received from the first power bridge <NUM> to a new DC level that is appropriate for charging the battery <NUM>. When powering the motor <NUM> using grid power, the second power bridge <NUM> may operate in an active rectifier mode to convert an AC power supplied by the power grid <NUM> to a DC power and reduce grid harmonic distortion and the first power bridge <NUM> can provide a controlled AC power with a specified amplitude and frequency that is appropriate for operation and control of the motor <NUM>.

<FIG> depicts another embodiment of a power conversion unit <NUM> of a transport refrigeration system <NUM> operating in road mode according to an alternate embodiment of the present disclosure. As shown in <FIG>, the structure of the power conversion unit <NUM> is different from that shown in <FIG> in that the first switch <NUM> is configured to selectively connect the first power bridge <NUM> to the battery <NUM> or the power grid <NUM> (instead of the motor <NUM>). However, as shown in <FIG>, during road mode, the power conversion unit <NUM> will operate identically to that shown in <FIG> by providing power supplied by the battery <NUM> to the motor <NUM>. As will be described below, during standby mode, both the first switch <NUM> and the second switch <NUM> will cycle between different configurations.

<FIG> depicts the power conversion unit <NUM> of <FIG> now operating in standby mode during a first stage of a time share according to an alternate embodiment of the present disclosure. As shown, during the first stage of the time share, the first switch <NUM> is positioned to connect the first power bridge <NUM> to the battery <NUM> and the second switch is positioned to connect the power grid <NUM> to the second power bridge <NUM>. During this stage of the time share, the power grid <NUM> is used to charge the battery <NUM>.

<FIG> depicts a power conversion unit <NUM> of <FIG> now operating in standby mode during a second stage of a time share according to an alternate embodiment of the present disclosure. As shown, during this second stage of the time share, the first switch <NUM> is positioned to connect the power grid <NUM> to the first power bridge <NUM> and the second switch is positioned to connect the second power bridge <NUM> to the motor <NUM>. During this stage of the time share, the power grid <NUM> is used to provide power to the motor <NUM>.

Referring now to <FIG>, with continued reference to <FIG> and <FIG>. <FIG> shows a flow process illustrating a method <NUM> of operating a transport refrigeration system <NUM> comprising a vehicle <NUM> integrally connected to a transport container <NUM>, according to an embodiment of the present disclosure.

At block <NUM>, during a road mode of operation of the transport refrigeration system <NUM>, the method includes placing a first switch <NUM> and a second switch <NUM> in a first configuration. The first configuration comprises positioning the first switch <NUM> to connect a first power bridge <NUM> of a power conversion unit <NUM> of the transport refrigeration system <NUM> to an energy storage device <NUM> and positioning the second switch <NUM> to connect a second power bridge <NUM> of the power conversion unit <NUM> of the transport refrigeration system <NUM> to a motor <NUM> of a transportation refrigeration unit of the transport refrigeration system <NUM>. During the first configuration, the motor <NUM> is supplied with power from the energy storage device <NUM> via the power conversion unit <NUM>.

At block <NUM>, during a standby mode of operation of the transportation refrigeration unit, the method <NUM> includes repeatedly cycling between a second configuration of the first switch <NUM> and the second switch <NUM> and a third configuration of the first switch <NUM> and the second switch <NUM>. The second configuration includes positioning the first switch <NUM> to connect the first power bridge <NUM> to the energy storage device <NUM> and positioning the second switch <NUM> to connect the second power bridge <NUM> to a power grid <NUM>. During this second configuration, the energy storage device <NUM> will be charged with power from the power grid <NUM> via the power conversion unit <NUM>. The third configuration includes positioning the first switch <NUM> to connect the first power bridge <NUM> to the motor <NUM> and positioning the second switch <NUM> to connect the second power bridge <NUM> to the power grid <NUM>. During this third configuration, the motor <NUM> is supplied with power from the power grid <NUM> via the power conversion unit <NUM>.

According to some embodiments, the method further includes determining a duration of the second configuration and a duration of the third configuration of a cycle. For example, in some embodiments, the controller can determine the duration of the second configuration based on a measured charge of the energy storage device <NUM>. Thus, for example, the controller may increase the duration of the second configuration if the charge of the energy storage device <NUM> is low to allow it more time to charge. In some embodiments, the controller can determine the duration of the third configuration based on a measured temperature of a cargo space <NUM> of the transport refrigeration system <NUM>. Thus, for example, if the cargo space is below a threshold level of coldness, the controller may determine that more time needs to be spent powering the motor <NUM> to provide an increased amount of cold air to the cargo space <NUM>. As will be appreciated by those of skill in the art, various different algorithms can be used by the controller to determine the appropriate durations of the time share between the second and third configurations to maximize values such as the charge of the battery <NUM> or the temperature of the cargo space <NUM>.

As described above, embodiments can be in the form of processor-implemented processes and devices for practicing those processes, such as processor. Embodiments can also be in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes a device for practicing the embodiments. Embodiments can also be in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into an executed by a computer, the computer becomes an device for practicing the exemplary embodiments.

Claim 1:
A transport refrigeration system comprising:
a transportation refrigeration unit (<NUM>) comprising a motor (<NUM>);
a power conversion unit (<NUM>) configured to convert an amplitude, a frequency and a phase of an input electrical power signal,
an energy storage device (<NUM>) configured to supply electrical power to the motor (<NUM>) via the power conversion unit (<NUM>) during a road mode; characterised in that
the power conversion unit (<NUM>) comprises a first power bridge (<NUM>), a DC link (<NUM>) and a second power bridge (<NUM>); and in that the transport refrigeration system comprises:
a first switch (<NUM>) configured to selectively connect the first power bridge (<NUM>) to the energy storage device (<NUM>) or the motor (<NUM>); and
a second switch (<NUM>) configured to selectively connect the second power bridge (<NUM>) to the motor (<NUM>) or a power grid (<NUM>);
wherein during the road mode, the first switch (<NUM>) is positioned to connect the first power bridge (<NUM>) to the energy storage device (<NUM>) and the second switch (<NUM>) is positioned to connect the second power bridge (<NUM>) to the motor (<NUM>),
wherein during a standby mode, the second switch (<NUM>) is positioned to connect the second power bridge (<NUM>) to the power grid (<NUM>),
wherein during a first time share phase of the standby mode, the first switch (<NUM>) is positioned to connect the first power bridge (<NUM>) to the energy storage device (<NUM>), and
wherein during a second time share phase of the standby mode, the first switch (<NUM>) is positioned to connect the first power bridge (<NUM>) to the motor (<NUM>).