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EP-4738694-A1 - OPTIMAL BUS VOLTAGE AND SWITCHING FREQUENCY STRATEGY

EP4738694A1EP 4738694 A1EP4738694 A1EP 4738694A1EP-4738694-A1

Abstract

A transportation refrigeration system (101) is provided and includes a trailer refrigeration unit (TRU) (110), a battery (120) to provide electricity for the TRU (110), an electrical system (140) and a controller (160). The electrical system (140) includes a direct current (DC) bus (141) electrically interposed between the battery (120) and the TRU (110). The electrical system (140) further includes an inverter (142) and a boost converter (143) disposed on the DC bus (141). The controller (160) includes a memory unit (202) storing first, second and third efficiency tables (181, 182, 183) for the TRU (110), the inverter (142) and the boost converter (143), respectively, and a processor (201. The processor (201) sets an operational target for the TRU (110) and achieves the operational target by controlling the inverter (142) and the boost converter (143) according to a voltage of the battery (120), the first, second and third efficiency tables (181, 182, 183) and real-time operating conditions.

Inventors

  • SHIN, Jaegue
  • AGIRMAN, ISMAIL
  • ARNEDO, Luis
  • GINSBERG, DAVID
  • LIAO, XUQIANG

Assignees

  • Carrier Corporation

Dates

Publication Date
20260506
Application Date
20251104

Claims (15)

  1. A transportation refrigeration system (101), comprising: a trailer refrigeration unit, TRU (110); a battery (120) to provide electricity for the TRU (110); an electrical system (140) comprising a direct current, DC, bus (141) electrically interposed between the battery (120) and the TRU (110) and further comprising an inverter (142) and a boost converter (143) disposed on the DC bus (141); and a controller (160) comprising: a memory unit (202) storing first, second and third efficiency tables (181, 182, 183) for the TRU (110), the inverter (142) and the boost converter (143), respectively; and a processor (201) to set an operational target for the TRU (110) and to achieve the operational target by controlling the inverter (142) and the boost converter (143) according to a voltage of the battery (120), the first, second and third efficiency tables (181, 182, 183) and real-time operating conditions.
  2. The transportation refrigeration system (101) according to claim 1, wherein the controller (160) is distributed between the inverter (142) and the boost converter (143).
  3. The transportation refrigeration system (101) according to either of claims 1 or 2, wherein the controller (160) controls the inverter (142) and the boost converter (143) by issuing first and second signals to the inverter (142) and the boost converter (143), respectively; optionally wherein the first and second signals comprise pulse width modulation, PWM, signals.
  4. The transportation refrigeration system (101) according to any of claims 1-3, wherein the first, second and third efficiency tables (181, 182, 183) are based on historical data and are updateable.
  5. The transportation refrigeration system (101) according to any of claims 1-4, wherein the operational target comprises a compressor speed.
  6. The transportation refrigeration system (101) according to claim 5, wherein the real-time operating conditions comprise at least one or more of ambient temperature and pressure characteristics around the TRU (110), temperature and pressure characteristics of a container to be conditioned by the TRU (110), pressure and flow rate characteristics of the TRU (110) and additional electrical characteristics of the electrical system (140).
  7. The transportation refrigeration system according to claim 5 or 6, wherein the processor (201) is configured to: determine a maximally efficient voltage requirement for the compressor speed and a voltage difference between the voltage of the battery (120) and the voltage requirement, modulate switching frequencies of the boost converter (143) to compensate for the voltage difference with maximum efficiency, and modulate switching frequencies of the inverter (142) to build a sinusoidal voltage output from boost converter output with maximum efficiency.
  8. A transportation refrigeration system (401), comprising: trailer refrigeration units, TRUs (410); loads (415); a battery (420) to provide electricity for the TRUs (410) and the loads (415); an electrical system (440) comprising a direct current, DC, bus (441) electrically interposed between the battery (420) and the TRUs (410) and the loads (415) and further comprising inverters (442) for each TRU (410) and each load (415) and boost converters (443) for some inverters (442) disposed on the DC bus (441); and a controller (460) comprising: a memory unit (502) storing first, second and third efficiency tables (481, 482, 483) for the TRUs (410) and the loads (415), the inverters (442) and the boost converters (443), respectively; and a processor (501) to set operational targets for the TRUs (410) and the loads (415) and to achieve the operational targets by controlling the inverters (442) and the boost converters (443) according to a voltage of the battery (420) the first, second and third efficiency tables (481, 482, 483) and real-time operating conditions.
  9. The transportation refrigeration system (401) according to claim 8, wherein the first, second and third efficiency tables (481, 482, 483) are based on historical data and are updateable.
  10. The transportation refrigeration system (401) according to either of claims 8 or 9, wherein operational targets for the TRUs (410) comprise compressor speeds; optionally wherein the real-time operating conditions comprise at least one or more of ambient temperature and pressure characteristics around the TRUs (410) and the loads (415), temperature and pressure characteristics of containers to be conditioned by the TRUs (410) and the loads (415), pressure and flow rate characteristics of the TRUs (410) and the loads (415) and additional electrical characteristics of the electrical system (440).
  11. The transportation refrigeration system (401) according to claim 10, wherein the processor (501) is configured to: determine maximally efficient voltage requirements for the compressor speeds and voltage differences between the voltage of the battery (420) and the voltage requirements, modulate switching frequencies of the boost converters (443) to compensate for the voltage differences with maximum efficiency, and modulate switching frequencies of the inverters (442) to build sinusoidal voltage outputs from boost converter outputs with maximum efficiency.
  12. A method (600) of operating a transportation refrigeration system (101; 401) comprising a trailer refrigeration unit, TRU (110; 410), and a battery (120; 420) to provide electricity for the TRU (110; 410), the method comprising: setting a compressor speed of the TRU (110; 410) for a target temperature of a container; referring to an efficiency table (181; 481) of the TRU (110; 410) to determine a voltage requirement of the compressor speed; determining a voltage difference between a voltage of the battery (120; 420) and the voltage requirement; and compensating for the voltage difference to achieve the target temperature by controlling an inverter (142; 442) and a boost converter (143; 443) disposed on a direct current, DC, bus (141; 441) of an electrical system (140; 440) electrically interposed between the battery (120; 420) and the TRU (110; 410) in accordance with efficiency tables (182, 183; 482, 483) of the inverter (142; 442) and the boost converter (143; 443) and real-time operating conditions.
  13. The method (600) according to claim 12, wherein the controlling of the inverter (142; 442) and the boost converter (143; 443) comprises issuing pulse width modulation, PWM, signals to the inverter and the boost converter.
  14. The method (600) according to claim 13, wherein the method further comprises modulating the PWM signals to the inverter (142; 442) and the boost converter (143; 443); optionally wherein at least one of: the modulating of the PWM signals to the inverter changes a duty cycle of the inverter to build a sinusoidal voltage output from boost converter output; the modulating of the PWM signals to the boost converter changes a duty cycle of the boost converter to obtain a desired output voltage.
  15. The method (600) according to any of claims 12-14, wherein the method further comprises generating the efficiency tables (181, 182, 183; 481, 482, 483) of the TRU (110; 410), the inverter (141; 441) and the boost converter (142; 442) based on historical data and updating the efficiency tables of the TRU, the inverter and the boost converter; and/or wherein the real-time operating conditions comprise at least one or more of ambient temperature and pressure characteristics around the TRU, temperature and pressure characteristics of a container to be conditioned by the TRU, pressure and flow rate characteristics of the TRU and additional electrical characteristics of the electrical system (140; 440).

Description

BACKGROUND The present invention relates to compressor systems and, more particularly, to an optimal direct current (DC) bus voltage and switching frequency strategy for a compressor system. Refrigerated vehicles transport perishable or temperature-sensitive goods within logistics networks. Refrigerated vehicles typically include a trailer refrigeration unit (TRU) that regulates the environment within a storage area of the vehicle, such as a container or trailer, within which the goods are stored during transit. The TRU includes a refrigeration system or the like, which is powered by an energy source. Traditionally, in the case of a tractor-trailer system where the storage area is within the trailer, the trailer has been provided with an internal combustion engine to power the TRU. The internal combustion engine of the TRU is separate from the internal combustion engine of the tractor providing motive force. In recent years, electrical power sources have been used to power the TRU, rather than internal combustion engines. Such electrical power sources may include batteries that are charged using electrical energy from an electrical grid and/or a generator coupled to a wheel axle of the trailer. This increases the fuel consumption of the internal combustion engine of the tractor, but permits the use of a smaller battery. BRIEF DESCRIPTION According to an aspect of the disclosure, a transportation refrigeration system is provided and includes a trailer refrigeration unit (TRU), a battery to provide electricity for the TRU, an electrical system and a controller. The electrical system includes a direct current (DC) bus electrically interposed between the battery and the TRU. The electrical system further includes an inverter and a boost converter disposed on the DC bus. The controller includes a memory unit storing first, second and third efficiency tables for the TRU, the inverter and the boost converter, respectively, and a processor. The processor sets an operational target for the TRU and achieves the operational target by controlling the inverter and the boost converter according to a voltage of the battery, the first, second and third efficiency tables and real-time operating conditions. The controller may be distributed between the inverter and the boost converter. The controller may control the inverter and the boost converter by issuing first and second signals to the inverter and the boost converter, respectively. The first and second signals may include pulse width modulation (PWM) signals. The first, second and third efficiency tables may be based on historical data and are updateable. The operational target may include a compressor speed. The real-time operating conditions may include at least one or more of ambient temperature and pressure characteristics around the TRU, temperature and pressure characteristics of a container to be conditioned by the TRU, pressure and flow rate characteristics of the TRU and additional electrical characteristics of the electrical system. The processor may be configured to determine a maximally efficient voltage requirement for the compressor speed and a voltage difference between the voltage of the battery and the voltage requirement, modulate switching frequencies of the boost converter to compensate for the voltage difference with maximum efficiency and modulate switching frequencies of the inverter to build a sinusoidal voltage output from boost converter output with maximum efficiency. According to an aspect of the disclosure, a transportation refrigeration system is provided and includes trailer refrigeration units (TRUs), loads, a battery to provide electricity for the TRUs and the loads, an electrical system and a controller. The electrical system includes a direct current (DC) bus electrically interposed between the battery and the TRUs and the loads. The electrical system further includes inverters for each TRU and each load and boost converters for some inverters disposed on the DC bus. The controller includes a memory unit storing first, second and third efficiency tables for the TRUs and the loads, the inverters and the boost converters, respectively, and a processor. The processor sets operational targets for the TRUs and the loads and achieves the operational targets by controlling the inverters and the boost converters according to a voltage of the battery the first, second and third efficiency tables and real-time operating conditions. The first, second and third efficiency tables may be based on historical data and are updateable. The operational targets for the TRUs may include compressor speeds. The real-time operating conditions may include at least one or more of ambient temperature and pressure characteristics around the TRUs and the loads, temperature and pressure characteristics of containers to be conditioned by the TRUs and the loads, pressure and flow rate characteristics of the TRUs and the loads and additional electrical characteristic