Patent Description:
Existing transport refrigeration systems use batteries to power components of the transport refrigeration system. Batteries can suffer damage in extreme temperatures which can impact the performance and/or life of the battery during its lifetime. The extreme heat and/or cold temperatures effect the chemical reaction of the batteries that produces power. For example, in colder weather the battery may produce less current which can cause unreliable or insufficient power for a connected device.

<CIT> discloses a transportation refrigeration unit comprising: a compressor configured to compress a refrigerant; a compressor motor configured to drive the compressor, the compressor motor being powered by an energy storage device; an evaporator heat exchanger operatively coupled to the compressor; a controller to control operation of the transportation refrigeration unit; an ambient air temperature sensor in electronic communication with the controller, the ambient air temperature sensor detects ambient air temperature outside of the transportation refrigeration unit, wherein the controller adjusts operation of a temperature control system for the energy storage device in response to the ambient air temperature, the temperature control system adjusts a temperature of the energy storage device.

According to a first aspect of the present invention, a transport refrigeration system according to claim <NUM> is provided.

According to a second aspect of the present invention, a method for controlling temperature of a battery according to claim <NUM> is provided.

Technical effects of embodiments of the present invention include using power electronics to control temperature of a battery in a transport refrigeration system.

<FIG> is a block diagram of a transport refrigeration system <NUM>. The transport refrigeration system <NUM> may be configured to condition air in a refrigerated container, a refrigerated trailer, refrigerated truck, etc. The transport refrigeration system <NUM> includes a variable speed motor <NUM> that is coupled to a compressor <NUM>. The compressor <NUM> includes an impeller/rotor that rotates and compresses liquid refrigerant to a superheated refrigerant vapor for delivery to a condenser <NUM>. In the condenser <NUM>, the refrigerant vapor is liquefied at high pressure and rejects heat (e.g., to the outside air via a condenser fan in an air-cooled application). The liquid refrigerant exiting the condenser <NUM> is delivered to an evaporator <NUM> through an expansion valve <NUM>. The refrigerant passes through the expansion valve <NUM> where a pressure drop causes the high-pressure liquid refrigerant to achieve a lower pressure combination of liquid and vapor. As fluid passes the evaporator <NUM>, the low-pressure liquid refrigerant evaporates, absorbing heat from the fluid, thereby cooling the fluid and evaporating the refrigerant. The low-pressure refrigerant is again delivered to the compressor <NUM> where it is compressed to a high-pressure, high temperature gas, and delivered to the condenser <NUM> to start the refrigeration cycle again. It is to be appreciated that while a specific transport refrigeration system is shown in <FIG>, the present teachings may be applicable to any transport refrigeration system.

As shown in <FIG>, the compressor <NUM> driven by a variable speed motor <NUM> from power supplied from power electronics <NUM>. The power electronics are connected to a battery <NUM>. The battery <NUM> may be a comprise a single battery, several batteries and/or a battery pack having a plurality of cells. The power electronics <NUM> may include an inverter that converts the DC voltage from the battery <NUM> into a multiphase, AC output voltage, at a desired frequency and/or magnitude in order to drive the multiphase motor <NUM>.

In electronic transport refrigeration unit (eTRU) applications, such as that in <FIG>, the battery <NUM> is a primary source of power and must provide reliable and predictable service for operation. Battery performance is directly impacted by environmental temperature of the battery <NUM>. For a typical Li-ion battery, a low ambient temperature would significantly reduce the capacity of the battery <NUM>, and therefore, impact operation of the transport refrigeration system <NUM>.

<FIG> depicts a system <NUM> for controlling temperature of the battery <NUM>. The system <NUM> may be implemented in various vehicles such as transport refrigeration trucks, trailers, or containers having a power electronics unit <NUM> and a battery <NUM> that may be housed in the same compartment or within proximity of one another. <FIG> depicts fans <NUM> which directed cooled air over the evaporator <NUM> to cool air in a refrigerated container, a refrigerated trailer, refrigerated truck, etc..

In a non-limiting example, the power electronics <NUM> and the battery <NUM> can be co-located in the same compartment <NUM>. The heat generated by the power electronics <NUM> can be used to increase the temperature in the compartment <NUM> housing the battery <NUM>. A cooling unit <NUM> provides cooling to the power electronics <NUM>. The cooling unit <NUM> may use fan(s) <NUM> to air cool the power electronics <NUM> or pump(s) <NUM> to circulate a cooling fluid to a heat exchanger in the power electronics <NUM>.

A controller <NUM> may be located in the power electronics unit <NUM> or may be located external to the power electronics unit <NUM>. The controller <NUM> may configured to send control signals to the power electronics unit <NUM> to control the operation of one or more components within the power electronics unit <NUM>. The controller <NUM> may be implemented using a general-purpose microprocessor executing a computer program stored on a storage medium to perform the operations described herein. Alternatively, the controller <NUM> may be implemented in hardware (e.g., ASIC, FPGA) or in a combination of hardware/software. The controller <NUM> may also be part of a control system of the transport refrigeration system <NUM>.

The controller <NUM> communicates with one or more sensors. The controller <NUM> may be in communication with the sensors via a wired or wireless connection. A power electronics temperature sensor <NUM> monitors a temperature of the power electronics <NUM>. An air temperature sensor <NUM> monitors temperature of ambient air in the compartment <NUM>.

The cooling unit <NUM> may operate at different cooling rates, such as low, medium, and high, to help regulate temperature of the power electronics <NUM>. The speed of the fans(s) <NUM> and/or pump(s) <NUM> is controlled to achieve the desired cooling rate. Other speed or flow rate settings can be used and is not intended to be limited by the examples discussed herein. The controller <NUM> can be configured to obtain the current cooling rate of the cooling unit <NUM> and the controller <NUM> can be further configured to modify operation of the cooling unit <NUM> to increase or decrease the cooling rate.

<FIG> is a flowchart of method for battery temperature control. The operations in <FIG> may be implemented by controller <NUM>. The method begins at block <NUM> where the controller <NUM> detects, via air temperature sensor <NUM>, the ambient temperature of the compartment <NUM>. At decision block <NUM>, the controller <NUM> determines if the ambient temperature is low by comparing the ambient temperature to a temperature threshold. If the ambient temperature is less than the temperature threshold, the ambient temperature is considered low. In a non-limiting example, the temperature threshold can be configured to -<NUM>, -<NUM>, <NUM> degrees Fahrenheit (approx. -<NUM>, -<NUM>, -<NUM> degrees Celsius). It can be appreciated that the temperature threshold can be set to any other value and is not limited to the examples discussed herein. If the controller <NUM> determines, based on comparing the current ambient temperature reading to the temperature threshold, the ambient temperature is not low, the controller <NUM> continues to monitor the ambient temperature of the ambient temperature at <NUM>.

If at <NUM> the controller <NUM> determines the ambient temperature is low, one or more temperature control schemes can be implemented to increase the low ambient temperature. At block <NUM>, the controller <NUM> detects if the cooling rate of the cooling unit <NUM> is greater than zero. This indicates that the fans(s) <NUM> and/or pump(s) <NUM> of the cooling unit <NUM> are operating.

If at <NUM> the controller <NUM> determines the cooling unit <NUM> is operating, the controller <NUM> can decrease the cooling rate of the cooling unit <NUM> at <NUM>. At <NUM>, the controller <NUM> commands the cooling unit <NUM> to reduce the cooling rate by reducing the fan <NUM> speed and/or pump <NUM> coolant flow rate to allow the heat to increase in the power electronics <NUM>. In some non-limiting embodiments, the fan <NUM> speed and/or the pump <NUM> coolant flow rate can be completely powered off thus, ceasing cooling of the power electronics <NUM>.

At <NUM>, the controller <NUM> determines if a temperature of the power electronics <NUM>, sensed by power electronics temperature sensor <NUM>, exceeds a limit. If the temperature of the power electronics <NUM> exceeds the limit, the controller <NUM> determines at <NUM> that operating conditions of the power electronics <NUM> are not to be changed. In one or more embodiments, should the temperature of the power electronics <NUM> exceed a second limit greater than the limit, the cooling rate of the cooling unit <NUM> may be increased to avoid damage or shut down of the power electronics <NUM>.

At block <NUM>, the controller <NUM> checks the ambient temperature of compartment <NUM> via air temperature sensor <NUM>. If the ambient temperature is low (e.g., below the temperature threshold), flows returns to block <NUM> to determine whether the cooling rate of the cooling unit <NUM> should be further reduced or stopped. Otherwise, the method <NUM> can return to block <NUM> to continue to monitor the ambient temperature of the battery.

Referring to block <NUM>, if the cooling rate of the cooling unit <NUM> is not greater than zero (e.g., cooling unit <NUM> off), flow proceeds to block <NUM>, where the controller <NUM> can increase a switching frequency of the power electronics unit <NUM> to increase the amount of heat generated by the power electronics <NUM>. The power electronics include a plurality of switches (IGBTs and/or MOSFETs). The switches are turned on and off in response to a control signal (e.g., from controller <NUM>) having a switching frequency. As the switching frequency increases, the amount of heat produced by the power electronics <NUM> increases and causes the temperature of the compartment <NUM> to increase.

At block <NUM>, the controller <NUM> checks the ambient temperature via the air temperature sensor <NUM>. If the ambient temperature is low (e.g., below the temperature threshold), flows returns to block <NUM> to again increase a switching frequency of the power electronics unit <NUM> to increase the amount of heat generated by the power electronics <NUM>. Otherwise, the method returns to block <NUM> to continue to monitor the ambient temperature the compartment <NUM>.

A detailed description of one or more embodiments of the present invention are presented herein by way of exemplification and not limitation with reference to the Figures.

Claim 1:
A transport refrigeration system (<NUM>), comprising:
a compressor (<NUM>), a condenser (<NUM>) and an evaporator (<NUM>) configured to circulate a refrigerant;
a motor (<NUM>) configured to drive the compressor (<NUM>);
a battery (<NUM>) and power electronics (<NUM>) configured to power the motor (<NUM>);
an ambient air temperature sensor (<NUM>) configured to monitor ambient air at the battery (<NUM>);
a cooling unit (<NUM>) configured to cool the power electronics (<NUM>);
a controller (<NUM>), wherein the controller (<NUM>) is configured to:
receive an ambient air temperature of a compartment (<NUM>) housing the battery (<NUM>);
compare the ambient air temperature to a temperature threshold; and
based at least in part on comparing the ambient air temperature to the temperature threshold, performing at least one of (i) modifying a cooling rate of the cooling unit (<NUM>) and (ii) modifying an operating parameter of the power electronics (<NUM>);
wherein modifying the operating parameter of the power electronics (<NUM>) includes increasing heat generated by the power electronics (<NUM>).