Time-sharing control of transport refrigeration systems

Abstract

The subject matter of the present invention is "Time-Sharing Control of a Transport Refrigeration System." A transport refrigeration system includes: a transport refrigeration unit including a motor; a power conversion unit configured to convert the amplitude, frequency, and phase of an input electric 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 electric power to the motor via the power conversion unit during 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 the first switch and the second switch are positioned to connect the first power bridge and the second power bridge to a specified source and output during each of road mode and standby mode.

Description

Technical Field

[0001] Embodiments herein relate generally to transport refrigeration systems, and more particularly to energy management of such transport refrigeration systems. Background Art

[0002] Typically, cold chain distribution systems are used to transport and deliver goods, or more specifically, perishable and environmentally sensitive items (referred to herein as perishables) that are susceptible to temperature, humidity, and other environmental factors. Perishables may include, but are not limited to, fruits, vegetables, grains, legumes, nuts, eggs, dairy products, seeds, flowers, meat, poultry, fish, ice, and pharmaceuticals. Advantageously, cold chain distribution systems allow for the efficient transportation and delivery of perishables without damage or other undesirable effects.

[0003] Refrigerated vehicles and trailers are commonly used to transport perishable goods in cold chain distribution systems. A transport refrigeration system is mounted to the vehicle or trailer in operative association with a cargo space defined within the vehicle or trailer for maintaining a controlled temperature environment within the cargo space.

[0004] Conventionally, transport refrigeration systems used in conjunction with refrigerated vehicles and refrigerated trailers include a transport 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, all connected via suitable 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 over the air side of the evaporator in heat exchange relationship with the refrigerant, whereby the refrigerant absorbs heat from the air, thereby cooling the air. The cooled air is then supplied back to the cargo space.

[0005] On commercially available transport refrigeration systems used in conjunction with refrigerated vehicles and refrigerated trailers, the compressor, and typically other components of the transport refrigeration unit, must be powered by a prime mover during transport. In mechanically driven transport refrigeration systems, the compressor is driven by the prime mover through direct mechanical coupling or belt drive, and other components, such as the condenser and evaporator fans, are belt driven.

[0006] Transport refrigeration systems can also be electrically powered. In electrically powered transport refrigeration systems, components of the transport refrigeration unit (such as the compressor) can be powered by current supplied by the battery during "road mode" and by current supplied by the grid during "standby mode." "Road mode" refers to an operating mode in which the transport refrigeration system is not connected to the grid, such as when the refrigerated vehicle is in transit. Conventionally, when in road mode, a transport refrigeration system has one source (e.g., battery) and one load (e.g., compressor motor), requiring the use of two power bridges and a DC link to convert the electrical characteristics of the power (e.g., amplitude, phase, frequency) between them. "Standby mode" refers to an operating mode in which the transport refrigeration system is connected to the grid, such as when the refrigerated vehicle is parked and plugged into a charging station. Conventionally, when in standby mode, the transport refrigeration system has an additional source (e.g., the grid), requiring 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 functionality of both conventional road mode and standby mode using fewer power bridges. Summary of the Invention

[0007] According to one embodiment, a transport refrigeration system is provided. The transport refrigeration system includes: a transport refrigeration unit including a motor; a power conversion unit configured to convert the amplitude, frequency, and 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-sharing 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-sharing phase of the standby mode, the first switch is positioned to connect the first power bridge to the motor.

[0008] In addition to or as an alternative to one or more of the features described above, further embodiments of the transport refrigeration system may include a controller configured to control the positions of the first and second switches during the road mode and the standby mode.

[0009] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to determine a duration of the first time-sharing phase and a duration of the second time-sharing phase, and to change the position of the first switch upon expiration of the first time-sharing phase and upon expiration of the second time-sharing phase.

[0010] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to continuously cycle between the first time-sharing phase and the second time-sharing phase until the road mode is initiated.

[0011] In addition to or as an alternative to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to determine the duration of the first time-sharing phase and the duration of the second time-sharing phase based on a measurement of the charge of the energy storage device.

[0012] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to reduce the duration of the first time-sharing phase in response to determining that the charge of the energy storage device exceeds a threshold charge level.

[0013] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to determine the duration of the first time-sharing phase and the duration of the second time-sharing phase based on a measurement of a temperature of a cargo space of the transport refrigeration system.

[0014] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to increase the duration of the second time-sharing phase in response to determining that the temperature of the cargo space is below a threshold temperature level.

[0015] According to another embodiment, a method of operating a transport refrigeration system including a vehicle integrally connected to a transport container is provided. The method includes: during road mode 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 transport refrigeration unit of the transport refrigeration system; during standby mode operation of the transport 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 an electrical grid; and 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 electrical grid.

[0016] In addition to or as an alternative to one or more of the features described above, further embodiments of methods of operating a transport refrigeration system may include supplying power from the energy storage device to the motor via the power conversion unit during the first configuration.

[0017] In addition to or as an alternative to one or more of the features described above, further embodiments of methods of operating a transport refrigeration system may include, during the second configuration, charging the energy storage device with power from the grid via the power conversion unit.

[0018] In addition to or as an alternative to one or more of the features described above, further embodiments of methods of operating a transport refrigeration system may include supplying the motor with power from the grid via the power conversion unit during the third configuration.

[0019] In addition to or as an alternative to one or more of the features described above, further embodiments of methods 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 the cycle.

[0020] In addition to or as an alternative to one or more of the features described above, further embodiments of methods of operating a transport refrigeration system may include the controller determining the duration of the second configuration based on a measured charge of the energy storage device.

[0021] Additionally or alternatively to one or more of the features described above, further embodiments of methods of operating a transport refrigeration system may include the controller determining the duration of the third configuration based on a measured temperature of a cargo space of the transport refrigeration system.

[0022] According to another embodiment, a transport refrigeration system is provided. The transport refrigeration system includes: a transport refrigeration unit including a motor; a power conversion unit configured to convert the amplitude, frequency, and 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-sharing phase of the 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-sharing 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.

[0023] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include a controller configured to control the positions of the first and second switches during the road mode and the standby mode.

[0024] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to determine a duration of the first time-sharing phase and a duration of the second time-sharing phase, and to change the positions of the first switch and the second switch upon expiration of the first time-sharing phase and upon expiration of the second time-sharing phase.

[0025] In addition to or alternatively to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to continuously cycle between the first time-sharing phase and the second time-sharing phase until the road mode is initiated.

[0026] In addition to or as an alternative to one or more of the features described above, further embodiments of the transport refrigeration system may include the controller being configured to determine the duration of the first time-sharing phase and the duration of the second time-sharing phase based on a measurement of the charge of the energy storage device.

[0027] Technical effects of embodiments of the present disclosure include providing conventional functionality of a transport refrigeration system in both road mode and standby mode using only two power bridges and one DC link.

[0028] The foregoing features and elements may be combined in various combinations without exclusivity, unless otherwise expressly indicated. These features and elements and their operation will become more apparent in view of the following description and accompanying drawings. However, it should be understood that the following description and drawings are intended to be illustrative and explanatory in nature and are non-restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following description should not be considered limiting in any way. Referring to the drawings, similar elements are numbered similarly:

[0030] Figure 1 is a schematic illustration of a transport refrigeration system according to an embodiment of the present disclosure;

[0031] Figure 2A is a block diagram of a conventional transport refrigeration system operating in road mode;

[0032] Figure 2B is a block diagram of a conventional transport refrigeration system operating in standby mode;

[0033] Figure 3A is a block diagram of a transport refrigeration system operating in road mode according to an embodiment of the present disclosure;

[0034] Figure 3B is a block diagram of a transport refrigeration system operating in a standby mode according to an embodiment of the present disclosure;

[0035] Figure 4A is a block diagram of a transport refrigeration system operating in road mode according to an embodiment of the present disclosure;

[0036] Figure 4B is a block diagram of a transport refrigeration system operating in a standby mode during a first period of time sharing according to an embodiment of the present disclosure;

[0037] Figure 4C is a block diagram of a transport refrigeration system operating in a standby mode during a second period of time sharing according to an embodiment of the present disclosure; and

[0038] Figure 5 is a diagram illustrating the operation of an embodiment according to the present disclosure Figure 3A and3B A method flow diagram of a transport refrigeration system. DETAILED DESCRIPTION

[0039] A detailed description of one or more embodiments of the disclosed apparatus and methods is presented herein by way of illustration and not limitation with reference to the accompanying figures.

[0040] refer to Figure 1 、 3A -3B and 4A-4C, illustrate various embodiments of the present disclosure. Figure 1 A schematic illustration of a transport refrigeration system 200 is shown in accordance with an embodiment of the present disclosure. Figure 2A A block diagram showing a conventional transport refrigeration system operating in road mode is shown. Figure 3A FIG. 1 shows an embodiment of the present disclosure operating in road mode. Figure 1 A block diagram of a transport refrigeration system 200 is shown. Figure 2B A block diagram showing a conventional transport refrigeration system operating in standby mode is shown. Figure 3B FIG. 1 shows an embodiment of the present disclosure operating in standby mode. Figure 1 A block diagram of a transport refrigeration system 200 is shown. Figures 4A-4C Shown in road mode ( Figure 4A ) and standby mode ( Figures 4B-4C ) operation Figure 1 A block diagram of an alternative embodiment of a transport refrigeration system 200 is shown.

[0041] The transport refrigeration system 200 is shown as a trailer system 100, as in Figure 1As seen in [1], trailer system 100 includes a vehicle 102 integrally connected to a shipping container 106. Vehicle 102 includes an operator cabin or operator compartment 104 and a propulsion motor 120 serving as the drive system for trailer system 100. Propulsion motor 120 is configured to power vehicle 102. The energy source powering propulsion motor 120 may be at least one of compressed natural gas, liquefied natural gas, gasoline, electricity, diesel, or a combination thereof. Propulsion motor 120 may be an electric motor or a hybrid motor (e.g., an internal combustion engine and an electric motor). Transport container 106 is coupled to vehicle 102. Transport container 106 can be removably coupled to vehicle 102. Transport container 106 is a refrigerated trailer and includes a top wall 108, a diametrically opposed bottom wall 110, opposing side walls 112, and a front wall 114, with front wall 114 being closest to vehicle 102. Transport container 106 further includes one or more doors 117 located on a rear wall 116 opposite front wall 114. The walls of the transport container 106 define a refrigerated cargo space 119. According to some embodiments, the refrigerated cargo space 119 can include a temperature sensor that can measure the temperature of the refrigerated cargo space 119 and provide the measurement to a controller for use in determining the duration of the time-sharing phase, as described in more detail below. Those skilled in the art will appreciate that the embodiments described herein can be applied to tractor-trailer refrigeration systems or non-trailer refrigeration, such as, for example, trucks with refrigerated compartments, rigid trucks.

[0042] Generally, transport refrigeration system 200 is used for transporting and distributing perishable and environmentally sensitive items (referred to herein as perishables 118). Perishables 118 may include, but are not limited to, fruits, vegetables, grains, legumes, nuts, eggs, dairy products, seeds, flowers, meat, poultry, fish, ice, blood, pharmaceuticals, or any other suitable cargo requiring temperature-controlled transportation. Transport refrigeration system 200 includes a transport refrigeration unit 22, an energy storage device 24, and a power conversion unit 26. Transport refrigeration unit 22 includes a refrigerant compression device for providing heat transfer functionality and a motor 32 for driving the refrigerant compression device. Transport refrigeration unit 22 is operatively associated with refrigerated cargo space 119 and configured to provide conditioned air to transport container 106. Transport refrigeration unit 22 functions under the control of a controller (not shown) to establish and manage desired environmental parameters within cargo space 119, such as temperature, pressure, humidity, carbon dioxide, ethylene, ozone, light exposure, vibration exposure, and other conditions, as known to those skilled in the art. In an embodiment, transport refrigeration unit 22 is capable of providing a desired temperature and humidity range. According to some embodiments, the controller may include a processor and associated memory, the associated memory including 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 a multi-processor system of any of a wide range of possible architectures, including, but not limited to, field programmable gate arrays (FPGAs), central processing units (CPUs), application-specific integrated circuits (ASICs), digital signal processors (DSPs), or graphics processing units (GPUs) hardware in homogeneous or heterogeneous arrangements. The memory may be a storage device such as, for example, random access memory (RAM), read-only memory (ROM), or other electronic, optical, magnetic, or any other computer-readable medium.

[0043] Airflow is circulated into and through the refrigerated cargo space 119 of the transport container 106 by means of a transport refrigeration unit 22. According to some embodiments, the transport refrigeration unit 22 may include a refrigerant compression device (including a motor 32), a refrigerant heat rejection heat exchanger, an expansion device, and a refrigerant heat absorption heat exchanger, connected in refrigerant flow communication in a closed-loop refrigerant circuit and arranged in a conventional refrigeration cycle. The refrigerant compression device may be a single-stage or multi-stage compressor, such as a reciprocating compressor or a turbo compressor. The transport refrigeration unit 22 may also include one or more fans associated with the refrigerant heat rejection heat exchanger and driven by one or more fan motors, as well as one or more fans associated with the refrigerant heat absorption heat exchanger and driven by one or more fan motors. The transport refrigeration unit 22 may also include a heater associated with the refrigerant heat absorption heat exchanger. It will be appreciated 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, and an economizer circuit. Those skilled in the art will appreciate the conventional components and functionality provided by the refrigeration unit 22 for circulating airflow into the refrigerated cargo space 119, and as such they will not be shown or described in detail herein. Figures 2A-4C The motor 32 shown in FIG. 2 may be a component of the refrigeration unit 22 , and in particular, the motor 32 may be a motor that powers a compressor of the refrigeration unit 22 .

[0044] The transport refrigeration unit 22 may be powered by an energy storage device 24 (which may be referred to as a battery 24 for simplicity), which provides electrical power to the transport refrigeration unit 22 during operation of the transport refrigeration system in road mode. Examples of the energy storage device 24 may include a battery system (e.g., a battery or battery pack), a fuel cell, a flow battery, and other devices capable of storing and outputting electrical energy, which may be direct current (DC). The energy storage device 24 may include a battery system that may employ a plurality of batteries organized into battery packs. According to some embodiments, the energy storage device 24 may include a sensor configured to determine the charge of the energy storage device 24 and provide this information to the controller for use in determining the duration of the time-sharing phase, as described in more detail below.

[0045] The battery 24 can be charged by a fixed charging station (such as, for example, a 48V wall outlet, or some other outlet connected to the power grid 30). The charging station can provide single-phase (e.g., Level 2 charging capability) or three-phase AC power to the power conversion unit 26, which can then supply converted power to the energy storage device 24 and / or the transport refrigeration unit 22. It is understood that the charging station can have any phase charging and the embodiments disclosed herein are not limited to single-phase or three-phase AC power. In embodiments, the single-phase AC power can be high-voltage DC power, such as, for example, 500 VDC.

[0046] In one embodiment, the energy storage device 24 is located external to the transport refrigeration unit 22, such as in Figure 1 In another embodiment, the energy storage device 24 is located within the transport refrigeration unit 22. The transport refrigeration unit 22 may have multiple electric power demanding loads on the energy storage device 24, including, but not limited to, the motor 32 for the compressor, the drive motor for the fan associated with the refrigerant heat rejection heat exchanger, the drive motor for the fan associated with the refrigerant heat absorption heat exchanger, or any other such aspect of the transport refrigeration unit 22 that may require electric power.

[0047] The motor 32 used to power the refrigerant compression device is typically an alternating current (AC) motor, while the power supplied by the battery 24 is a DC voltage. Therefore, a power conversion unit 26 is electrically connected between the battery 24 and the refrigerant compression device to convert the power supplied from the battery 24 to the refrigerant compression device from DC to AC. The power conversion unit 26 of the transport refrigeration unit 22 also allows the grid 30 to be connected to either or both of the battery 24 and the motor 32. As will be appreciated by those skilled in the art, the power conversion unit 26 can be configured to modify one or more electrical characteristics of an input power signal and output a modified signal having the modified characteristics in order to regulate power between a source (e.g., the battery 24, the grid 30) and a load (e.g., the motor 32). For example, the power conversion unit 26 can modify one or more of the signal's amplitude, frequency, and / or phase, so that, for example, the power signal output by the battery 24 is altered to have electrical characteristics suitable for powering the compressor 32.

[0048] As in Figures 2A-2BAs shown in FIG, the conventional power conversion unit 26 of the transport refrigeration unit 22 includes a first power bridge 262, a first DC link 264, and a second power bridge 266 connected in series between the battery 24 and the motor 32 for converting power supplied from the battery 24 to the motor 32. According to some embodiments, the power bridge may 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, the DC link may be a capacitor array. Due to the additional source of the grid 30, the conventional power conversion unit 26 also includes additional circuitry 270, including a second DC link 272 and a third power bridge 274, connected to the first DC link 264 and connectable to the grid 30 (e.g., via a power cable inserted from the vehicle 102 to the charging station). As will be appreciated by those skilled in the art, this additional circuitry 270 is typically expensive and therefore would be desirable to eliminate.

[0049] Figure 2A A conventional power conversion unit 26 of a transport refrigeration system 200 is depicted operating in road mode. Figure 2A , when in road mode, a conventional power conversion unit 26 supplies power from the battery 24 to the motor 32. As will be appreciated by those skilled in the art, the power conversion unit 26 may, for example, convert a DC power signal supplied by the battery 24 into an AC power signal suitable for use by the motor 32. During road mode, the grid 30 is not connected to the transport refrigeration system 200 and therefore the additional circuitry 270 of the second DC link 272 and the third power bridge 274 are not used and represent a waste of resources.

[0050] Figure 2B A conventional power conversion unit 26 of a transport refrigeration system 200 is depicted operating in a standby mode. Figure 2B , when in standby mode, the conventional power conversion unit 26 supplies power from the grid 30 to the battery 24 and the motor 32 via the power conversion unit 26. In this case, all three power bridges 262, 266, 274 and two DC links 264, 272 are required to convert the power output by the grid 30 and convert it into power suitable for both charging the battery 24 and powering the motor 32.

[0051] Figure 3AThe power conversion unit 26 of the transport refrigeration system 200 is depicted operating in road mode, according to an embodiment of the present disclosure. As shown in this embodiment, the power conversion unit 26 includes a first switch 302 and a second switch 304. The first switch 302 selectively connects the first power bridge 262 to the battery 24 or the motor 32. The second switch 304 selectively connects the second power bridge 266 to the motor 32 or the grid 30. According to some embodiments, these switches may be controlled by a controller (not shown) that positions the switches based on the mode in which the transport refrigeration system 200 is operating. During road mode, the switches are positioned in a first configuration, in which the first switch 302 connects the first power bridge 262 to the battery 24 and the second switch connects the second power bridge 266 to the motor 32. As shown, the disclosed power conversion unit 26 eliminates the additional circuitry 270 of the conventional second DC link 272 and third power bridge 274, which is not required during road mode.

[0052] Figure 3B The power conversion unit 26 of the transport refrigeration system 200 is depicted operating in standby mode according to an embodiment of the present disclosure. Figure 3BAs shown in FIG, during standby mode, second switch 304 is positioned to connect second power bridge 266 to grid 30, while first switch 302 cycles back and forth between connecting first power bridge 262 to battery 24 and connecting first power bridge 262 to motor 32. In this manner, power conversion unit 26 time-shares grid power between battery 24 and motor 32 by providing power to each of these for a limited duration in repeated cycles. Each half-cycle can be referred to as a time-share phase. Thus, during the first time-share phase of the cycle, grid power can be used to charge battery 24, and during the second time-share phase of the cycle, grid power can be used to power motor 32. In this way, battery 24 can be charged over time while motor 32 can continue to be powered to provide cool air to cargo space 119. By utilizing this time-share approach, both objectives can be achieved while eliminating the additional circuitry 270 of second DC link 272 and third power bridge 274 of conventional designs. A controller (not shown) can determine the duration of each time-share phase and can vary the phase over time. In some embodiments, the controller can increase or decrease the duration of the time-sharing phase during which battery 24 is charged using grid power based on the measured charge of battery 24. For example, if battery 24 is nearly fully charged, the controller can decrease the duration of the time-sharing phase during which battery 24 is charged. Similarly, based on the measured temperature of the cargo space, the controller can increase or decrease the duration of the time-sharing phase during which motor 32 is supplied with power from grid 30. Thus, in some embodiments, if the temperature of the cargo space drops below a threshold temperature, the controller can increase the duration of the time-sharing phase during which motor 32 is supplied with power from grid 30. According to some embodiments, the controller can determine the duration of the time-sharing phase based on a combination of the measured temperature of the cargo space and the measured charge of battery 24.

[0053] As will be appreciated by those skilled in the art, the operation of the power conversion unit 26 may differ based on the time-sharing phase that the power conversion unit 26 is in. For example, when grid power is used to power the battery 24, the second power bridge 266 may be operable to convert AC power supplied by the grid to DC power and the first power bridge 262 may be operable to change the voltage level of the DC power received from the first power bridge 266 to a new DC level suitable for charging the battery 24. When grid power is used to power the motor 32, the second power bridge 266 may operate in an active rectifier mode to convert AC power supplied by the grid 30 to DC power and reduce grid harmonic distortion, and the first power bridge 262 may provide controlled AC power having a prescribed amplitude and frequency suitable for operation and control of the motor 32.

[0054] Figure 4AAnother embodiment of a power conversion unit 26 of a transport refrigeration system 200 operating in road mode according to an alternative embodiment of the present disclosure is depicted. Figure 4A As shown in FIG, the structure of the power conversion unit 26 is similar to Figure 3A The difference shown in FIG is that the first switch 302 is configured to selectively connect the first power bridge 262 to the battery 24 or the grid 30 (rather than the motor 32). However, as in Figure 4A As shown in FIG, during road mode, the power conversion unit 26 will be Figure 3A 2 and 3. The first and second switches 302 and 304 operate identically as shown in FIG by providing power supplied by the battery 24 to the motor 32. As will be described below, during the standby mode, both the first and second switches 302 and 304 will cycle between different configurations.

[0055] Figure 4B Depicts an alternative embodiment of the present disclosure now operating in standby mode during the first period of time sharing. Figure 4A As shown, during a first period of time-sharing, the first switch 302 is positioned to connect the first power bridge 262 to the battery 24 and the second switch is positioned to connect the grid 30 to the second power bridge 266. During this period of time-sharing, the grid 30 is used to charge the battery 24.

[0056] Figure 4C Depicts an alternative embodiment of the present disclosure now operating in standby mode during the second period of time sharing. Figure 4B As shown, during this second period of time-sharing, the first switch 302 is positioned to connect the grid 30 to the first power bridge 262 and the second switch is positioned to connect the second power bridge 266 to the motor 32. During this period of time-sharing, the grid 30 is used to provide power to the motor 32.

[0057] Now refer to Figure 5 , continue to refer to Figure 3A and 3B . Figure 5 A flow chart illustrating a method 500 of operating a transport refrigeration system 200 including a vehicle 102 integrally connected to a transport container 106 according to an embodiment of the present disclosure is shown.

[0058] At block 502, during road mode operation of the transport refrigeration system 200, the method includes placing the first switch 302 and the second switch 304 in a first configuration. The first configuration includes positioning the first switch 302 to connect the first power bridge 262 of the power conversion unit 26 of the transport refrigeration system 200 to the energy storage device 24 and positioning the second switch 304 to connect the second power bridge 266 of the power conversion unit 26 of the transport refrigeration system 200 to the motor 32 of the transport refrigeration unit of the transport refrigeration system 200. During the first configuration, the motor 32 is supplied with power from the energy storage device 24 via the power conversion unit 26.

[0059] At block 504, during standby mode operation of the transport refrigeration unit, method 400 includes repeatedly cycling between a second configuration of first switch 302 and second switch 304 and a third configuration of first switch 302 and second switch 304. The second configuration includes positioning first switch 302 to connect first power bridge 262 to energy storage device 24 and positioning second switch 304 to connect second power bridge 266 to grid 30. During this second configuration, energy storage device 24 is charged with power from grid 30 via power conversion unit 26. The third configuration includes positioning first switch 302 to connect first power bridge 262 to motor 32 and positioning second switch 304 to connect second power bridge 266 to grid 30. During this third configuration, motor 32 is supplied with power from grid 30 via power conversion unit 26.

[0060] According to some embodiments, the method further includes determining a duration for the second configuration of the cycle and a duration for the third configuration. For example, in some embodiments, the controller may determine the duration of the second configuration based on the measured charge of the energy storage device 24. Thus, for example, if the charge of the energy storage device 24 is low enough to allow it more time to charge, the controller may increase the duration of the second configuration. In some embodiments, the controller may determine the duration of the third configuration based on the measured temperature of the cargo space 119 of the transport refrigeration system 200. Thus, for example, if the cargo space is below a threshold level of coldness, the controller may determine that more time is needed to power the motor 32 to provide an increased amount of cool air to the cargo space 119. As will be appreciated by those skilled in the art, the controller may use a variety of different algorithms to determine the appropriate duration for the time-sharing between the second and third configurations to maximize values ​​such as the charge of the battery 24 or the temperature of the cargo space 119.

[0061] Although the above description has been described in a specific order Figure 5 The present invention provides a flow diagram of the present invention, but it should be appreciated that the order of the steps may be changed unless otherwise explicitly required in the appended claims.

[0062] As described above, embodiments may take the form of processor-implemented processes and apparatus for practicing those processes (such as a processor). Embodiments may also take the form of computer program code comprising instructions embodied in a tangible medium, such as a floppy disk, CD ROM, hard drive, or any other computer-readable storage medium, wherein when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the embodiments. Embodiments may also take 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 (such as by electrical wiring or cable, by optical fiber, or via electromagnetic radiation), wherein when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the exemplary embodiments. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits.

[0063] The term "about" is intended to include the degree of error associated with measuring a particular quantity based on the equipment available at the time the application was filed. For example, "about" may include a range of ±8%, 5%, or 2% of the specified value.

[0064] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and "comprising," when used in this specification, specify the presence of recited features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0065] Although the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its essential scope. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out the present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.

Claims

1. A transport refrigeration system comprising: a transport refrigeration unit, the transport refrigeration unit comprising a motor; a power conversion unit configured to convert the amplitude, frequency and phase of an input electric power signal, wherein the power conversion unit comprises a first power bridge, a DC link and a second power bridge; an energy storage device configured to supply electric 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; as well as a second switch configured to selectively connect the second power bridge to the motor or a 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 standby mode, the second switch is positioned such that the second power bridge is connected to the grid, wherein during a first time-sharing 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-sharing phase of the standby mode, the first switch is positioned to connect the first power bridge to the motor.

2. The transport refrigeration system of claim 1, further comprising a controller configured to control positions of the first switch and the second switch during the road mode and the standby mode.

3. The transport refrigeration system of claim 2, wherein the controller is configured to determine a duration of the first time-sharing phase and a duration of the second time-sharing phase and to change the position of the first switch upon expiration of the first time-sharing phase and upon expiration of the second time-sharing phase.

4. The transport refrigeration system of claim 3, wherein the controller is configured to continuously cycle between the first time-sharing phase and the second time-sharing phase until the road mode is initiated.

5. The transport refrigeration system of claim 3, wherein the controller is configured to determine the duration of the first time-sharing phase and the duration of the second time-sharing phase based on a measurement of the charge of the energy storage device.

6. The transport refrigeration system of claim 5, wherein the controller is configured to reduce the duration of the first time-sharing phase in response to determining that the charge of the energy storage device exceeds a threshold charge level.

7. The transport refrigeration system of claim 3, wherein the controller is configured to determine the duration of the first time-sharing phase and the duration of the second time-sharing phase based on a measurement of a temperature of a cargo space of the transport refrigeration system.

8. The transport refrigeration system of claim 7, wherein the controller is configured to increase the duration of the second time-sharing phase in response to determining that the temperature of the cargo space is below a threshold temperature level.

9. A method of operating a transport refrigeration system comprising a vehicle integrally connected to a transport container, the method comprising: during road mode 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 transport refrigeration unit of the transport refrigeration system; 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 during standby mode operation of the transport refrigeration unit, 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 the 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 grid.

10. The method of claim 9, wherein during the first configuration, the motor is supplied with power from the energy storage device via the power conversion unit.

11. The method of claim 9, wherein during the second configuration, the energy storage device is charged with power from the grid via the power conversion unit.

12. The method of claim 9, wherein during the third configuration, the motor is supplied with power from the grid via the power conversion unit.

13. The method of claim 9, further comprising: A duration of the second configuration and a duration of the third configuration of the cycle are determined by a controller.

14. The method of claim 13, wherein the controller determines the duration of the second configuration based on a measured charge of the energy storage device.

15. The method of claim 13, wherein the controller determines the duration of the third configuration based on a measured temperature of a cargo space of the transport refrigeration system.

16. A transport refrigeration system comprising: a transport refrigeration unit, the transport refrigeration unit comprising a motor; a power conversion unit configured to convert the amplitude, frequency and phase of an input electric power signal, wherein the power conversion unit comprises a first power bridge, a DC link and a second power bridge; an energy storage device configured to supply electric 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 grid; as well as a second switch configured to selectively connect the second power bridge to the motor or the 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-sharing phase of the 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 grid, and Wherein during a second time-sharing phase of the standby mode, the first switch is positioned to connect the first power bridge to the grid and the second switch is positioned to connect the second power bridge to the motor.

17. The transport refrigeration system of claim 16, further comprising a controller configured to control positions of the first switch and the second switch during the road mode and the standby mode.

18. The transport refrigeration system of claim 17, wherein the controller is configured to determine a duration of the first time-sharing phase and a duration of the second time-sharing phase and to change the positions of the first switch and the second switch upon expiration of the first time-sharing phase and upon expiration of the second time-sharing phase.

19. The transport refrigeration system of claim 18, wherein the controller is configured to continuously cycle between the first time-sharing phase and the second time-sharing phase until the road mode is initiated.

20. The transport refrigeration system of claim 18, wherein the controller is configured to determine the duration of the first time-sharing phase and the duration of the second time-sharing phase based on a measurement of the charge of the energy storage device.

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