METHOD FOR CONTROLLING A COMPRESSOR OF A THERMAL STORAGE HEAT PUMP SYSTEM

A method of controlling a compressor of a thermal storage heat pump system of a vehicle is provided. The system may operate in one of a heating mode and a cooling mode, as determined by at least one system controller based on at least one parameter. The at least one parameter may be ambient air temperature. The compressor has a compressor motor and a motor controller configured to selectively operate the compressor in an unmodified state or a modified state based on the operating mode of the system. The compressor motor is operated in the unmodified state when the system is in the cooling mode, and in the modified state when the system is in the heating mode. Operating the compressor motor in the modified state may include decreasing its coefficient of performance (COP).

DETAILED DESCRIPTION

The following description and figures refer to example embodiments and are merely illustrative in nature and not intended to limit the invention, its application, or uses. Throughout the figures, some components are illustrated with standardized or basic symbols. These symbols are representative and illustrative only, and are in no way limiting to any specific configuration shown, to combinations between the different configurations shown, or to the claims. All descriptions of componentry are open-ended and any examples of components are non-exhaustive.

Referring to the drawings, wherein like reference numbers correspond to like or similar components wherever possible throughout the several figures, a thermal storage heat pump system100for use in a vehicle101, including, but not limited to, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or the like, is shown inFIG. 1. The vehicle101may selectively operate in a range extending mode, a hybrid, or charge-sustaining, mode, and an electric vehicle (EV), or charge-depleting, drive mode. In range extending mode, an internal combustion engine (ICE)128, described hereinafter, operates as the sole propulsion system for the vehicle101. In hybrid mode, the vehicle101operates using both electric power from an electric motor (not shown) and power from the ICE128. In EV drive mode, the vehicle101operates solely on electricity.

The thermal storage heat pump system100generally includes a refrigeration circuit103in thermal communication with a first coolant circuit104and a second coolant circuit105via a first heat exchanger106and a second heat exchanger107, respectively. The refrigeration circuit103, the first coolant circuit104, and the second coolant circuit105are configured to circulate a refrigerant, a first coolant, and a second coolant, respectively. The first heat exchanger106may be a refrigerant-to-liquid chiller heat exchanger that may function as a heat pump evaporator to dissipate heat from the first coolant in the first coolant circuit104to the refrigerant in the refrigeration circuit103. The second heat exchanger107may also be a refrigerant-to-liquid heat exchanger that may function as a heat pump condenser to dissipate heat from the refrigerant in the refrigeration circuit103to the second coolant in the second coolant circuit105.

The refrigeration circuit103includes a compressor108located downstream of the first heat exchanger106and upstream of the second heat exchanger107. The compressor108may be configured to compress the refrigerant. The compressor108is driven by a compressor motor109, which may be a brushless direct current (DC) electric motor, as depicted in the schematic diagram inFIG. 2.

Referring now toFIG. 2, the compressor motor109generally receives a DC power input signal from a power source110. An inverter111converts the DC signal into an alternating current (AC) signal to drive the compressor motor109. The compressor motor109generally is a three-phase system, and as such, has three motor windings112around a rotor113to receive the AC signal. While the motor windings112are shown in a wye (Y) configuration, it should be appreciated that they may be in a delta (Δ) configuration as well. In an unmodified state of the compressor motor109, in which the compressor motor109is most efficient, each phase is offset by a set angle equivalent to one third of a period, or 120 degrees. In addition, each phase runs at a defined frequency. As explained in method200hereinafter, these and other characteristics of the compressor motor109may be modified to reduce its coefficient of performance (COP), i.e., make it less efficient.

The compressor motor109further includes a motor controller114configured to control the operation of the compressor motor109, including, but not limited to, the speed and position of the rotor113of the compressor motor109, the frequency and offset of the three phases, commutation, and the like.

Referring back toFIG. 1, the refrigeration circuit103also includes a first thermal expansion device115, a second thermal expansion device116, and a third heat exchanger117. The third heat exchanger117may be an ambient-to-refrigerant heat exchanger that may function as a cabin evaporator. It may be configured to absorb heat from the air flowing across it to cool and dehumidify the passenger compartment102, and to transfer the heat to the refrigerant flowing through it. The refrigerant may then be distributed to the compressor108and subsequently to the second heat exchanger107, where the heat in the refrigerant may be absorbed by the second coolant, as explained above.

The first thermal expansion device115and the second thermal expansion device116may be located downstream of the second heat exchanger107, and may be configured to cool and expand the refrigerant to be distributed to the first heat exchanger106and to the third heat exchanger117, respectively. The first thermal expansion device115and the second thermal expansion device116may be thermostatic or thermal expansion valves, and may be either electronically or mechanically actuated.

The refrigeration circuit103may also include a fourth heat exchanger118. The fourth heat exchanger118may be a refrigerant-to-ambient heat exchanger, and may function as a condenser for an air conditioning (A/C) system (not shown) in the vehicle101.

The refrigeration circuit103may further include a plurality of flow control valves119,120,121, and122. The flow control valves119,120,121, and122may be configured to control the flow to the various components in the refrigeration circuit103. It should be appreciated that the flow control valves119,120,121, and122may be any valve capable of restricting the flow of refrigerant in a particular line, and may be, but are not limited to, two-position, open/closed valves, or alternatively, modulating valves.

The first coolant circuit104includes a thermal storage device123and a first coolant pump124. The thermal storage device123may be any medium, device, machine, or the like, capable of generating and storing thermal energy. For example, the thermal storage device123may be an energy storage system (ESS) that includes at least one battery or battery pack.

The first coolant pump124, which may be variable speed, may be configured to circulate the first coolant through the thermal storage device123such that the first coolant may absorb heat generated by the thermal storage device123, or deposit heat within the thermal storage device123. The first coolant pump124further may be configured to circulate the first coolant through the first heat exchanger106such that heat may be transferred from the first coolant to the refrigerant, as explained above. While the first coolant pump124is shown downstream of the thermal storage device123, it should be appreciated that it may be located upstream of the thermal storage device123.

The first coolant circuit104also may include a heater125. The heater125may be configured to heat the first coolant in the first coolant circuit104, which flows to the thermal storage device123where the heat may be deposited and stored. The heater125may be, but is not limited to, a resistive heater.

The second coolant circuit105includes a heater core126and a second coolant pump127. The second coolant pump127, which may be variable speed, may be configured to circulate the second coolant through the heater core126. The heater core126, in turn, may be configured to receive the second coolant to heat air flowing across it and into the passenger compartment102. As explained above, the second coolant may receive heat from the thermal storage device123via the first heat exchanger106, and/or from the ambient air via the third heat exchanger117. While the second coolant pump127is shown downstream of the heater core126, it should be appreciated that it may be located upstream of the heater core126.

The second coolant circuit105also may include the ICE128, mentioned above. The ICE128may have heat within it from having been in operation. The heat may be deposited in the second coolant as it flows through the ICE128, thereby cooling the ICE128.

The second coolant circuit105further may include a bypass valve129and a bypass line130. The bypass valve129is configured to selectively direct the second coolant to the ICE128to cool it when the vehicle101is in range extending mode or hybrid mode, or to the bypass line130when the vehicle101is in EV drive mode. While the bypass valve129is shown inFIG. 1as a two-position three-way valve, it should be appreciated that the bypass valve129may be any three-way valve configured to selectively direct the flow to the ICE128and/or to the bypass line129. In an alternative embodiment not shown, in lieu of a three-way valve, there may be two separate flow control valves, one each on the bypass line130and the second coolant circuit105downstream of the takeoff for the bypass line130.

The thermal storage heat pump system100may also include at least one system controller131that may be electrically connected to the thermal storage heat pump system100to control its operation. In particular, the system controller131may communicate with and control the operation of various devices of the thermal storage heat pump system100, including the motor controller114, based on at least one parameter, including, but not limited to, ambient air temperature, as described in method200hereinafter.

The system controller131also may be configured to communicate with and receive information from other ancillary devices, including, but not limited to, a temperature sensor132and an input module133, describer hereinafter. The system controller131may process the information received from these ancillary devices to determine the operating mode in which the thermal storage heat pump system100is to operate, and to operate the devices accordingly. As explained hereinafter, the thermal storage heat pump system100may operate in a heating mode or in a cooling mode. The system controller131may further be configured to control any other devices in the thermal storage heat pump system100, as well as any other subsystems in the vehicle101.

The temperature sensor132generally is any device configured to measure the ambient air temperature. The temperature sensor132may be configured to transmit data, such as the ambient air temperature measurement, to the system controller131to be stored and/or processed. The temperature sensor132may be external to the system controller131, as depicted inFIG. 1, and may transmit the data through a wired or wireless connection. In another embodiment not shown, the temperature sensor may be internal to the system controller131. In yet another embodiment not shown, the system controller131may be configured to obtain such data as the ambient air temperature from a remote source (not shown) via the internet or other communications network.

The input module133may be any device configured to receive an input, such as a desired temperature or heat supply for the passenger compartment102, or other data from a user of the thermal storage heat pump system100. The input module133further may be configured to transmit such data to the controller131. The input module133may be, but is not limited to, an onboard computer in the vehicle101.

As mentioned above, the thermal storage heat pump system100may operate in a heating mode or a cooling mode. In the heating mode, the refrigerant in the refrigeration circuit103may be used to transfer heat to the second coolant in the second coolant circuit105via the second heat exchanger107to heat the passenger compartment102via the heater core126, as explained above. Conversely, in the cooling mode, the refrigerant may be used to absorb heat from the ambient air via the third heat exchanger117to cool the passenger compartment102. The thermal storage heat pump system100may selectively switch between the two modes based on a parameter, such as ambient air temperature.

In either mode, the refrigerant in the refrigeration circuit103is utilized to transfer heat, and as such, the compressor108and compressor motor109operate to compress the refrigerant. The compressor motor109requires a certain amount of electrical power received from the power source110to operate. In compressing the refrigerant, the compressor motor109converts the electrical power into electrical heat, which then may be transferred to the refrigerant.

In the heating mode, the electrical power necessary for the compressor motor109, and thus the electrical heat produced by the compressor motor109, is equal to the total thermal load required to heat the passenger compartment102divided by the COP of the compressor motor109. The total thermal load required may be determined by the system controller131based on a desired temperature or heat supply for the passenger compartment102as received from the input module133. The remaining thermal load not provided by the electrical heat produced from the compressor motor109may be provided from the thermal storage device123.

Referring now toFIGS. 5 and 6, the effect of modifying the COP, represented by the y-axis302inFIG. 5, on the electrical heat produced, represented by the y-axis312inFIG. 6, when switching between the heating and cooling modes, represented by sections308and310, respectively, inFIGS. 5 and 6, is shown. The x-axis304inFIGS. 5 and 6represents the ambient air temperature. As explained above, the compressor motor109may be made less efficient by modifying its characteristics to reduce its COP. Generally, the compressor motor109is in its unmodified state in the cooling mode. However, by reducing the COP in the heating mode, the electrical heat produced increases with a fixed total thermal load required. As such, the amount of thermal load to be drawn from the thermal storage device123may decrease. This in turn may decrease the need to operate the heater125to provide the heat stored in the thermal storage device123.

Referring now toFIG. 3, a method200for controlling the thermal storage heat pump system100, particularly the compressor108and the compressor motor109, is shown.

Method200begins at step202in which the system controller131receives a measurement of at least one parameter. The at least one parameter may be, but is not limited to, ambient air temperature. As explained above, the ambient air temperature measurement may be taken and transmitted to the system controller131by the temperature sensor132.

After step202, method200proceeds to step204. At step204, the system controller131determines the operating mode of the thermal storage heat pump system100based on the measurement of the at least one parameter. As explained above, the thermal storage heat pump system100may operate in either a heating mode or a cooling mode.

When the measurement of the at least one parameter meets a certain condition, the thermal storage heat pump system100will operate in the particular mode associated with that condition. For example, as seen in the graphs ofFIGS. 5 and 6, when the ambient air temperature (x-axis304) is at or below a switchover temperature306, the thermal storage heat pump system100may operate in the heating mode (section308). Conversely, when the ambient air temperature is above the switchover temperature306, the thermal storage heat pump system100may operate in the cooling mode (section310). The switchover temperature may be stored in the system controller131, and may be adjustable.

After step204, method200proceeds to step206. At step206, the compressor controller114operates the compressor motor109in either an unmodified state or a modified state, depending on the mode of operation. As explained above, when the thermal storage heat pump system is in the cooling mode, the compressor controller114operates the compressor motor109in the unmodified, or most efficient, state. When the thermal storage heat pump system100is in the heating mode, the compressor controller114operates the compressor motor109in the modified state in which its COP is decreased. This may include several sub-steps, as depicted inFIG. 4.

Referring toFIG. 4, at sub-step206a,the compressor controller114may offset from the set angle at least one of the three phases of the compressor motor109. For example, the compressor controller114may offset one of the phases by 30 degrees. At sub-step206b,the compressor controller114may alter the defined frequency of at least one of the three phases. As explained above, each phase operates at a defined frequency. Altering at least one of them may reduce the COP. It should be appreciated that step204may include any one of sub-steps206aand206b,which may be performed in any order. It should further be appreciated that step206may include more sub-steps in which the compressor motor109may be altered in other ways, such as internal motor restriction, mechanical losses internal to the compressor motor109(or frictional losses), mechanical braking, and the like, to reduce the COP.