System controller for variable speed hvac system

Abstract

A control system for a heating, ventilation, and air conditioning (HVAC) system is provided. The system controller includes a processor configured to receive an indoor temperature measurement or estimate and an indoor temperature setpoint, and to control a speed of at least one of an indoor blower motor and an outdoor blower motor based on the indoor temperature measurement during operation of a compressor motor in a line-run mode or a drive-run mode to converge an indoor temperature to the indoor temperature setpoint.

Description

Technical Field

[0001] The field of this disclosure generally relates to system controllers, and more specifically to system controllers for variable capacity air conditioning or heat pump systems. Background Technology

[0002] Heating, ventilation, and air conditioning (HVAC) systems typically include electric motors that power the system's compressors or fans. At least some known induction motors are fixed-speed motors, which are most efficient when operating on line-frequency power. Such motors exhibit uncontrolled acceleration during startup. Furthermore, they operate less efficiently under low-load conditions. Alternatively, some induction motors can be driven by variable-speed motor controllers to adapt the motor speed to the load level. Such configurations can be limited by power factor, electromagnetic interference, and electrical losses.

[0003] Drive circuits for certain motors enable efficient operation under both high and low load conditions. For example, a motor driving a compressor in an HVAC system can experience high load conditions during peak temperatures and low load conditions during milder temperature periods. The drive circuit operates the motor using an inverter under low load conditions and uses mains power under high load conditions. Summary of the Invention

[0004] In one aspect, a control system for an HVAC system is provided. The control system includes a processor configured to receive a measured or estimated indoor temperature value and an indoor temperature setpoint, and, during operation of a compressor motor in either a line operation mode (power frequency operation mode) or a drive operation mode (variable frequency drive operation mode), control the speed of at least one of an indoor fan motor and an outdoor fan motor based on the measured indoor temperature value to bring the indoor temperature to the indoor temperature setpoint.

[0005] In another aspect, a method for controlling an HVAC system is provided. The method includes receiving a measured or estimated indoor temperature value and an indoor temperature setpoint, and, while operating a compressor motor in a line-operated mode or a drive-operated mode, controlling the speed of at least one of an indoor fan motor and an outdoor fan motor based on the measured indoor temperature value to bring the indoor temperature to the indoor temperature setpoint.

[0006] In another aspect, an HVAC system is provided. The HVAC system includes a compressor motor, an indoor fan motor, an outdoor fan motor, and a control system communicatively connected to the compressor motor, the indoor fan motor, and the outdoor fan motor. The control system includes a processor configured to receive a measured or estimated indoor temperature value and an indoor temperature setpoint, and, during operation of the compressor motor in a line-operated mode or a drive-operated mode, control the rotational speed of at least one of the indoor fan motor and the outdoor fan motor based on the measured indoor temperature value to bring the indoor temperature to the indoor temperature setpoint. Attached Figure Description

[0007] Figure 1A This is a block diagram of an HVAC system based on this disclosure;

[0008] Figure 1B This is a block diagram of another HVAC system according to this disclosure;

[0009] Figure 2 It is a graph showing the indoor and outdoor temperatures during the first example period;

[0010] Figure 3 It is shown in Figure 2 The graph shows the motor speed and airflow during the first example period;

[0011] Figure 4 This is a graph showing the indoor and outdoor temperatures during the transition period in the second example;

[0012] Figure 5 It is shown in Figure 4 The graph shown illustrates the motor speed and airflow during the second example period;

[0013] Figure 6 This is a flowchart illustrating an example method for controlling an HVAC system. Detailed Implementation

[0014] HVAC systems typically include a compressor, indoor fans (e.g., blowers or evaporator fans), and outdoor fans (e.g., condenser fans), each powered by a corresponding electric motor. In some cases, the compressor motor employs a hybrid drive, with the motor powered by an inverter under low load conditions and by mains power under high load conditions. While this configuration allows the compressor speed to vary based on demand, in some situations, the compressor can only operate at certain discrete speed values ​​and / or reach certain speed thresholds. In situations where cooling demand (e.g., based on outdoor temperature) varies gradually over time, requiring cooling capacity to vary gradually to maintain a constant indoor temperature, the compressor motor cannot operate within certain speed ranges, potentially limiting the HVAC system's ability to accurately match system capacity to current cooling demands.

[0015] The embodiments described herein include a control system for an HVAC system. The controller system may include, for example, a system controller, one or more local controllers (e.g., motor controllers or fan controllers), a thermostat, or any combination thereof. In an example embodiment, the control system is configured to communicate with and control the motors of the HVAC system, including compressor motors, indoor fan motors, and outdoor fan motors. The control system is configured to receive measured or estimated indoor temperature values ​​and an indoor temperature setpoint. For example, the indoor temperature setpoint may be received as a thermostat command.

[0016] In an example embodiment, the compressor motor operates in one or more discrete operating modes. For example, the compressor motor may be a hybrid drive motor configured to operate at a fixed speed in line operation mode and at a variable speed in drive operation mode. During operation of the compressor motor in either line or drive operation mode, the control system controls the speed of at least one of the indoor fan motors and the outdoor fan motor based on the measured or estimated indoor temperature value to bring the indoor temperature to the setpoint. Therefore, the system controller can vary the system capacity of the HVAC system to meet cooling demands at specific times without adjusting the compressor motor speed. This is advantageous when the compressor motor operates at a fixed speed in line operation mode. During operation of the compressor motor in drive operation mode, the compressor motor speed can also be varied to achieve the desired indoor temperature.

[0017] While the systems and methods described herein are generally intended for use in HVAC systems, it should be understood that they can also be applied to other types of climate control, heating, and / or cooling systems, including compressor motors and at least one fan motor.

[0018] Figure 1A and Figure 1B This is a block diagram illustrating an example embodiment of an HVAC system 100. In the example embodiment, the HVAC system 100 includes a control system 102, a compressor motor 104, an indoor fan motor 106, an outdoor fan motor 108, a sensor 110, and a thermostat 112. In various example implementations, the control system 102 may include a system controller; local motor controllers for the compressor motor 104, the indoor fan motor 106, and / or the outdoor fan motor 108; the thermostat 112, and / or some combination thereof. The control system 102 includes at least one processor and at least one memory device configured to store instructions that, when executed by the at least one processor, cause the at least one processor to perform the functions of the control system 102 described herein. The control system 102 is communicatively coupled to the compressor motor 104, the indoor fan motor 106, the outdoor fan motor 108, and the thermostat 112. In some embodiments, such as Figure 1A As shown, the control system 102 is also communicatively connected to the sensor 110. Alternatively, such as... Figure 1B As shown, sensor 110 can be communicatively connected to temperature controller 112. In some cases, temperature controller 112 can provide data received from sensor 110 to control system 102.

[0019] In an exemplary embodiment, compressor motor 104 is coupled to compressor and configured to operate at multiple speed values. For example, in some embodiments, compressor motor 104 is configured to operate in one of two different operating modes, namely a line operating mode and a drive operating mode. In the line operating mode, the windings of compressor motor 104 are directly powered by a line source (power frequency) at a line frequency (power frequency / grid frequency) (e.g., 60 Hz), and compressor motor 104 operates at a fixed speed, typically the maximum speed of compressor motor 104. In the drive operating mode, the windings are powered by an inverter at a variable frequency, enabling compressor motor 104 to operate at a variable speed. In some implementations, when operating in the drive operating mode, the speed of compressor motor 104 varies between multiple predefined frequency values. Therefore, the compressor motor can operate at multiple different speed settings (e.g., one speed setting in line operating mode and one or more speed settings in drive operating mode).

[0020] Indoor fan motor 106 is connected to an indoor fan, such as an evaporator fan and / or a blower fan. Outdoor fan motor 108 is connected to an outdoor fan, such as a condenser fan. In some embodiments, indoor fan motor 106 and / or outdoor fan motor 108 are configured to operate at variable speeds. Indoor fan motor 106 and / or outdoor fan motor 108 can be controlled based on various types of setpoints—such as speed, torque, or (particularly in the case of indoor fan motor 106) airflow.

[0021] The control system 102 is configured to receive measured or estimated indoor temperature values. For example, sensor 110 may include at least one indoor temperature sensor located within the interior space of the structure, and in some cases may include additional sensors (e.g., an outdoor temperature sensor located outside the structure), and the control system 102 may receive data from these sensors 110. The control system may further receive indoor temperature setpoints. For example, the control system 102 may receive thermostat commands from thermostat 112, based on which the system controller determines the required indoor temperature.

[0022] The control system 102 is also configured to periodically calculate one or more motor speed values ​​(e.g., the speeds of compressor motor 104, indoor fan motor 106, and / or outdoor fan motor 108) based on the measured or estimated indoor temperature value, said one or more motor speed values ​​achieving a system capability sufficient to meet the indoor temperature requirement. The control system 102 is also configured to control the speeds of indoor fan motor 106 and / or outdoor fan motor 108 based on the measured or estimated indoor temperature value during operation of compressor motor 104 in line operation mode or drive operation mode, so that the indoor temperature converges to the indoor temperature setpoint. In some embodiments, a characterization process is used to determine specific setpoints or combinations of setpoints for indoor fan motor 106 and / or outdoor fan motor 108, such as speed, torque, airflow, and / or other motor settings, said specific setpoints or combinations of setpoints achieving a certain system capability or the ability to achieve a specific temperature requirement based on the current measurement results. The characterization results are stored in the memory of the control system 102, for example, in the form of a formula (e.g., linear regression or multinomial regression) or a lookup table. The control system 102 can then recall these data based on the required indoor temperature to determine the appropriate setpoints for the indoor fan motor 106 and / or the outdoor fan motor 108.

[0023] By controlling and changing the speed of the indoor fan motor 106 and / or the outdoor fan motor 108 when the compressor motor 104 is operating at a constant speed setpoint (e.g., during line operation mode), the control system 102 can change the system capacity of the HVAC system 100 without adjusting the speed of the compressor motor 104. This capability is particularly advantageous during line operation mode, in which the compressor motor 104 operates at a fixed (i.e., power line / grid) frequency. Furthermore, controlling and changing the speed of the indoor fan motor 106 and / or the outdoor fan motor 108 allows for the control system capacity to be controlled during transitions between various modes or speed settings of the compressor motor 104. For example, the control system 102 can control the indoor fan motor 106 and / or the outdoor fan motor 108 to maintain a constant system capacity or ramp up the system capacity at a predefined rate.

[0024] In some embodiments, the control system 102 is configured to select a mode and / or speed setting for operating the compressor motor based on sensor data received from sensor 110. The sensor data may include, for example, measured or estimated indoor or outdoor temperature, compressor power consumption, compressor input current, expected inverter phase current, expected inverter thermal margin, indoor temperature change rate (slope), outdoor temperature change rate, system pressure, or cumulative (e.g., historical) operating time under various operating modes or speed settings. Furthermore, or alternatively, in some embodiments, the control system 102 selects to control the compressor motor 104 to operate in a line-operated mode or a drive-operated mode based on at least one of the compressor motor 104, indoor fan motor 106, and outdoor fan motor 108 meeting a predefined threshold (e.g., meeting or exceeding a threshold speed) or experiencing another threshold event (e.g., exceeding a temperature threshold or a threshold difference between the measured or estimated indoor temperature and the temperature setpoint).

[0025] Figure 2 Figure 200 shows the indoor and outdoor temperatures during a first example transition of the compressor motor 104 from operating in line mode to operating in drive mode due to reduced cooling demand. Figure 3 Figure 300 shows the rotational speeds of the compressor motor 104 and the outdoor fan motor 108, as well as the indoor airflow generated by the indoor fan motor 106, during this transition.

[0026] See Figure 2 Chart 200 includes: a horizontal axis 202 representing time in minutes over a first time period; a first vertical axis 204 representing dry-bulb temperature in Fahrenheit; and a second vertical axis 206 representing wet-bulb temperature in Fahrenheit. Chart 200 also includes an outdoor temperature curve 208 representing outdoor dry-bulb temperature; an indoor dry-bulb temperature curve 210 representing indoor dry-bulb temperature; and an indoor wet-bulb temperature curve 212 representing indoor wet-bulb temperature.

[0027] See Figure 3Chart 300 includes: a horizontal axis 302 representing time in minutes, the time being consistent with the first time period shown by the horizontal axis 302 in Chart 200; a first vertical axis 304 representing motor speed in revolutions per minute; and a second vertical axis 306 representing airflow in standard cubic feet per minute. Chart 300 also includes a compressor motor speed curve 308 representing the speed of compressor motor 104; an outdoor fan speed curve 310 representing the speed of outdoor fan motor 108; and an indoor airflow curve 312 representing the airflow generated by indoor fan motor 106 (e.g., through a blower or other predefined point within HVAC system 100).

[0028] See you again Figure 2 The outdoor temperature (indicated by outdoor temperature profile 208) decreases from approximately 95 degrees Fahrenheit to approximately 85 degrees Fahrenheit during the first time period. During this temperature change, it is desirable to maintain a constant indoor dry-bulb temperature (indicated by indoor dry-bulb temperature profile 210) at 80 degrees Fahrenheit in this example, and a constant indoor wet-bulb temperature (indicated by indoor wet-bulb temperature profile 212) at 67 degrees Fahrenheit in this example. To maintain a constant indoor temperature while the outdoor temperature gradually changes, the system capacity needs to be gradually adjusted. In other words, although the outdoor temperature of the residence may vary, the HVAC system adjusts its capacity to keep the indoor temperature substantially the same.

[0029] See you again Figure 3 The control system 102 controls the compressor motor 104, the indoor fan motor 106, and the outdoor fan motor 108 to achieve the specific system capability required to maintain the indoor air temperature. As indicated by the compressor motor speed curve 308, the compressor motor 104 operates at a first discrete value when operating in the line operation mode and at a second discrete value when operating in the drive operation mode. Therefore, in this example, simply switching the compressor motor 104 from line operation mode to drive operation mode does not provide a gradual change in the system capability required to maintain a constant temperature. To provide a gradual change in system capability, as indicated by the outdoor fan speed curve 310 and the indoor airflow curve 312, the speed of the outdoor fan motor 108 and the airflow provided by the indoor fan motor 106 are also varied to provide the required system capability at a given time.

[0030] Figure 4 Figure 400 shows the indoor and outdoor temperatures during a second example transition when the compressor motor 104 is operating in drive mode and is capable of operating at a variable frequency. Figure 5Figure 500 shows the rotational speeds of the compressor motor 104 and the outdoor fan motor 108, as well as the indoor airflow generated by the indoor fan motor 106, during this transition.

[0031] See Figure 4 Chart 400 includes: a horizontal axis 402 representing time in minutes over a second time period; a first vertical axis 404 representing dry-bulb temperature in Fahrenheit; and a second vertical axis 406 representing wet-bulb temperature in Fahrenheit. Chart 400 also includes an outdoor temperature curve 408 representing outdoor dry-bulb temperature; an indoor dry-bulb temperature curve 410 representing indoor dry-bulb temperature; and an indoor wet-bulb temperature curve 412 representing indoor wet-bulb temperature.

[0032] See Figure 5 Chart 500 includes: a horizontal axis 502 representing time in minutes, the time being consistent with the second time period shown by the horizontal axis 502 in Chart 500; a first vertical axis 504 representing motor speed in revolutions per minute; and a second vertical axis 506 representing airflow in standard cubic feet per minute. Chart 500 also includes a compressor speed curve 508 representing the speed of compressor motor 104; an outdoor fan speed curve 510 representing the speed of outdoor fan motor 108; and an indoor airflow curve 512 representing the airflow generated by indoor fan motor 106 (e.g., through a blower or other predefined point within HVAC system 100).

[0033] See you again Figure 4 The outdoor temperature (indicated by outdoor temperature profile 408) decreases from approximately 85 degrees Fahrenheit to approximately 67 degrees Fahrenheit during the second time period. During this temperature change, it is desirable to maintain a constant indoor dry-bulb temperature (indicated by indoor dry-bulb temperature profile 410) at 80 degrees Fahrenheit in this example, and a constant indoor wet-bulb temperature (indicated by indoor wet-bulb temperature profile 412) at 67 degrees Fahrenheit in this example. To maintain a constant indoor temperature while the outdoor temperature gradually changes, the system capacity needs to be gradually adjusted. In other words, although the outdoor temperature of the residence may vary, the HVAC system adjusts its capacity to keep the indoor temperature substantially the same.

[0034] See you again Figure 5The control system 102 controls the compressor motor 104, the indoor fan motor 106, and the outdoor fan motor 108 to achieve the specific system capability required to maintain the indoor air temperature. As indicated by the compressor motor speed curve 508, when in the drive operation mode, the compressor motor 104 operates at a controlled variable speed to achieve the required system capability. To help provide or provide further degrees of control freedom to achieve gradual changes in system capability, as indicated by the indoor airflow curve 512, the airflow provided by the indoor fan motor 106 is also varied to provide the required system capability at a given time. Although the speed of the outdoor fan motor 108 does not change in this example, as shown in the outdoor fan speed curve 510, the speed of the outdoor fan motor 108 may also be varied in some example implementations.

[0035] Figure 6 This is a flowchart illustrating an example method 600 for controlling an HVAC system 100. The control system 102 receives an indoor temperature measurement (e.g., from sensor 110) or an estimated value, and an indoor temperature setpoint (e.g., from thermostat 112). During operation of the compressor motor 104 in either line-operated or drive-operated mode, the control system 102 controls the rotational speed of at least one of the indoor fan motor 106 and the outdoor fan motor 108 based on the indoor temperature measurement or estimated value, so that the indoor temperature converges to the indoor temperature setpoint.

[0036] In some embodiments, during operation in the drive mode, the control system 102 controls the rotational speed of the compressor motor 104 within a predefined range to bring the indoor temperature to the indoor temperature setpoint.

[0037] In some embodiments, during operation in the line operation mode, the control system 102 operates the compressor motor 104 at a constant speed.

[0038] In some embodiments, the control system 102 controls the compressor motor 104 to operate in the line operation mode or the drive operation mode based on at least one of the compressor motor 104, the indoor fan motor 106 and the outdoor fan motor 108 meeting a predefined threshold (e.g., threshold speed).

[0039] In some embodiments, during the transition of the compressor motor 104 between a line operation mode and a drive operation mode, the control system 102 changes the speed of at least one of the indoor fan motor 106 and the outdoor fan motor 108 to bring the indoor temperature to the indoor temperature setpoint.

[0040] In some embodiments, the control system 102 controls the compressor motor 104 to operate in the line operation mode or the drive operation mode based on sensor data.

[0041] In some such embodiments, the sensor data includes one or more of the following: outdoor temperature measurement, compressor power consumption, compressor input current, inverter expected phase current, inverter expected thermal margin, indoor temperature change rate, outdoor temperature change rate, system pressure, and cumulative operating time in various operating modes.

[0042] In some embodiments, the control system 102 determines the indoor temperature setpoint based on thermostat commands.

[0043] In some embodiments, the control system 102 controls the rotational speed of the indoor fan motor 106 based on the target airflow to bring the indoor temperature to the set indoor temperature value.

[0044] In some embodiments, the control system 102 controls at least one of the indoor fan motor 106 and the outdoor fan motor 108 to operate at a variable speed while the compressor motor operates at a constant speed.

[0045] In some embodiments, the control system 102 controls the speed of at least one of the indoor fan motor and the outdoor fan motor based on the indoor temperature measurement value to minimize disturbances to the system capability of the HVAC system.

[0046] The exemplary technical effects of the methods, systems, and apparatuses described herein include at least one of the following: (a) by changing the rotational speed of one or more fan motors of the HVAC system, the system capability of the HVAC system can be varied to achieve a target system capability during operation of the compressor motor of the HVAC system in a discrete or fixed speed operating mode; and (b) by changing the rotational speed of the compressor motor and one or more fan motors of the HVAC system, the system capability of the HVAC system can be varied to achieve a target system capability during operation of the compressor motor of the HVAC system in a variable speed operating mode.

[0047] Some embodiments involve the use of one or more electronic or computing devices (e.g., for controlling the operation of drive circuitry and / or its individual components). Such devices typically include processors, processing devices, or controllers, such as general-purpose central processing units (CPUs), graphics processing units (GPUs), microcontrollers, reduced instruction set computer (RISC) processors, application-specific integrated circuits (ASICs), programmable logic circuits (PLCs), field-programmable gate arrays (FPGAs), digital signal processing (DSP) devices, and / or any other circuitry or processing device capable of performing the functions described herein. The methods described herein may be encoded as executable instructions embodied in a computer-readable medium, including but not limited to storage devices and / or memory devices. When executed by a processing device, such instructions cause the processing device to perform at least a portion of the methods described herein. The examples above are merely exemplary and are therefore not intended to limit the definitions and / or meanings of the following terms: processor, processing device, and controller.

[0048] In the embodiments described herein, the memory may include, but is not limited to, computer-readable media, such as random access memory (RAM) and computer-readable non-volatile media, such as flash memory. Alternatively, floppy disks, optical disc read-only memory (CD-ROM), magneto-optical disk (MOD), and / or digital versatile optical disk (DVD) may also be used. Furthermore, in the embodiments described herein, additional input channels may include, but are not limited to, computer peripherals associated with the operator interface, such as a mouse and keyboard. Alternatively, other computer peripherals may be used, such as, but not limited to, scanners. Additionally, in the example embodiments, additional output channels may include, but are not limited to, operator interface monitors.

[0049] As used herein, the terms “software” and “firmware” are used interchangeably and include any computer program executed by a processor and stored in memory, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The memory types described above are merely exemplary and therefore do not limit the types of memory that can be used to store computer programs.

[0050] As used herein, an element or step in the singular form preceded by the words "a" or "an" should be understood as not excluding plural elements or steps, unless such exclusion is explicitly stated. Furthermore, references to "exemplary implementations" or "an implementation" in this disclosure are not intended to be construed as excluding the existence of additional implementations that also incorporate the described features.

[0051] The systems and methods described herein are not limited to the specific embodiments described herein, but rather, components of the system and / or steps of the method may be utilized independently of other components and / or steps described herein.

[0052] This written specification uses examples to provide details about this disclosure, including best practices, and also enables any person skilled in the art to implement this disclosure, including making and using any apparatus or system and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims and may include other examples that would occur to a person skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that differ from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A control system for a heating, ventilation, and air conditioning (HVAC) system, the control system comprising a processor configured to: Receives indoor temperature measurements or estimates, as well as indoor temperature setpoints; and During operation of the compressor motor in line operation mode or drive operation mode, the speed of at least one of the indoor fan motor and the outdoor fan motor is controlled based on the measured or estimated indoor temperature value to bring the indoor temperature to the indoor temperature setpoint.

2. The control system according to claim 1, wherein, The processor is further configured to control the rotational speed of the compressor motor within a predefined range during operation in the drive mode, so that the indoor temperature converges to the indoor temperature setpoint.

3. The control system according to claim 1, wherein, The processor is further configured to operate the compressor motor at a constant speed during operation in the line operation mode.

4. The control system according to claim 1, wherein, The processor is further configured to control the compressor motor to operate in the line operation mode or the drive operation mode based on at least one of the compressor motor, the indoor fan motor and the outdoor fan motor meeting a predefined threshold.

5. The control system according to claim 1, wherein, The processor is further configured to change the speed of at least one of the indoor fan motor and the outdoor fan motor during the transition between the compressor motor in line operation mode and drive operation mode, so as to bring the indoor temperature to the indoor temperature setpoint.

6. The control system according to claim 1, wherein, The processor is further configured to control the compressor motor to operate in the line operation mode or the drive operation mode based on sensor data.

7. The control system according to claim 6, wherein, The sensor data includes one or more of the following: outdoor temperature measurement, compressor power consumption, compressor input current, inverter expected phase current, inverter expected thermal margin, indoor temperature change rate, outdoor temperature change rate, system pressure, and cumulative operating time in each operating mode.

8. The control system according to claim 1, wherein, The processor is further configured to determine the indoor temperature setpoint based on thermostat commands.

9. The control system according to claim 1, wherein, The processor is further configured to control the speed of the indoor fan motor based on the target airflow, so that the indoor temperature converges to the indoor temperature setpoint.

10. The control system according to claim 1, wherein, The processor is further configured to control at least one of the indoor fan motor and the outdoor fan motor to operate at a variable speed while the compressor motor is running at a constant speed.

11. The control system according to claim 1, wherein, The processor is further configured to control the speed of at least one of the indoor fan motor and the outdoor fan motor based on the indoor temperature measurement, so as to minimize disturbances to the system capability of the HVAC system.

12. A method for controlling a heating, ventilation, and air conditioning (HVAC) system, the method comprising: Receives indoor temperature measurements or estimates, as well as indoor temperature settings; as well as During operation of the compressor motor in line operation mode or drive operation mode, the speed of at least one of the indoor fan motor and the outdoor fan motor is controlled based on the measured or estimated indoor temperature value to bring the indoor temperature to the indoor temperature setpoint.

13. The method of claim 12, further comprising controlling the rotational speed of the compressor motor within a predefined range during operation in the drive mode, so that the indoor temperature converges to the indoor temperature setpoint.

14. The method of claim 12, further comprising operating the compressor motor at a constant speed during operation in the line operation mode.

15. The method of claim 12, further comprising controlling the compressor motor to operate in the line operation mode or the drive operation mode based on at least one of the compressor motor, the indoor fan motor and the outdoor fan motor satisfying a predefined threshold.

16. The method of claim 12, further comprising, during the transition of the compressor motor between a line operation mode and a drive operation mode, changing the rotational speed of at least one of the indoor fan motor and the outdoor fan motor to bring the indoor temperature to the indoor temperature setpoint.

17. The method of claim 12, further comprising controlling the compressor motor to operate in the line operation mode or the drive operation mode based on sensor data.

18. The method of claim 12, further comprising determining the indoor temperature setpoint based on a thermostat command.

19. The method of claim 12, further comprising controlling at least one of the indoor fan motor and the outdoor fan motor to operate at a variable speed while the compressor motor is operating at a constant speed.

20. A heating, ventilation, and air conditioning (HVAC) system, comprising: Compressor motor; Indoor fan motor; Outdoor fan motor; as well as A control system communicatively connected to the compressor motor, the indoor fan motor, and the outdoor fan motor, the control system including a processor configured to: Receives indoor temperature measurements or estimates, as well as indoor temperature settings; as well as During operation of the compressor motor in the line operation mode or the drive operation mode, the speed of at least one of the indoor fan motor and the outdoor fan motor is controlled based on the indoor temperature measurement or estimate, so that the indoor temperature converges to the indoor temperature setpoint.

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