Air conditioner

Abstract

The application relates to the technical field of household appliances, in particular to an air conditioner which comprises a refrigerant circulation loop, a PFC circuit and a controller. The controller first determines the output duty cycle and the inductance current of the PFC circuit; then determines the target carrier frequency corresponding to the PFC circuit according to the output duty cycle and the inductance current, and updates the frequency of the carrier signal of the PFC circuit according to the target carrier frequency; finally, generates a driving control signal according to the output duty cycle and the updated carrier signal, and controls the on-off state of the power tube in the PFC circuit according to the driving control signal; that is, the PFC carrier frequency is automatically adjusted in real time according to the PFC duty cycle and the inductance current, the fixed carrier frequency is changed into the real-time changing carrier frequency, the EMI energy is dispersed, the energy density of each frequency point is greatly reduced, the nonlinear characteristic that the inductance inductance changes with the current is considered, the reliability problem of inductance attenuation under the condition of large current is avoided, different input voltages and load conditions are adapted, and the reliability of PFC control is ensured.

Description

Technical Field

[0001] This invention relates to the field of home appliance technology, and in particular to an air conditioner. Background Technology

[0002] Air conditioners often use PFC (Power Factor Correction Circuit) circuits to improve the input current waveform, optimize power quality, improve the power factor, and reduce harmonic pollution.

[0003] The existing PFC circuit uses a fixed carrier frequency to adjust the duty cycle to achieve a fixed output voltage. This control method is easy to implement and has the best control stability, but it will generate concentrated EMI (Electromagnetic Interference) energy in a specific frequency range, making it difficult to pass EMC (Electromagnetic Compatibility) tests. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0005] Therefore, the purpose of this invention is to provide an air conditioner that can automatically adjust the PFC carrier frequency in real time according to the PFC duty cycle, transforming the fixed carrier frequency into a real-time changing carrier frequency, thereby dispersing EMI energy, significantly reducing the energy density at each frequency point, avoiding peak interference at a single frequency point, and thus adapting to different input voltages and load conditions, ensuring the reliability of PFC control.

[0006] This invention provides an air conditioner comprising: a refrigerant circulation loop, wherein the refrigerant circulates in a loop consisting of a compressor, a four-way valve, a condenser, an expansion valve, and an evaporator, wherein one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger; a power factor correction (PFC) circuit; and a controller configured to: determine the output duty cycle and inductor current of the PFC circuit; determine a target carrier frequency corresponding to the PFC circuit based on the output duty cycle and the inductor current; update the frequency of the carrier signal of the PFC circuit based on the target carrier frequency; generate a drive control signal based on the output duty cycle and the updated carrier signal; and control the on / off state of the power transistor in the PFC circuit based on the drive control signal.

[0007] The above technical solution has the following advantages or beneficial effects: The air conditioner provided by the embodiment of the present invention includes a refrigerant circulation loop, a PFC circuit, and a controller. The controller first determines the output duty cycle and inductor current of the PFC circuit; then, it determines the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and inductor current, and updates the frequency of the carrier signal of the PFC circuit according to the target carrier frequency; finally, it generates a drive control signal based on the output duty cycle and the updated carrier signal, and controls the on / off state of the power transistor in the PFC circuit according to the drive control signal; that is, it automatically adjusts the PFC carrier frequency in real time according to the PFC duty cycle and inductor current, not only transforming the fixed carrier frequency into a real-time changing carrier frequency, thereby dispersing EMI energy and significantly reducing the energy density at each frequency point, avoiding peak interference at a single frequency point, but also considering the nonlinear characteristics of the inductance changing with the current, avoiding reliability problems caused by inductor attenuation under high current conditions. In this way, it can adapt to different input voltages and load conditions, thereby comprehensively ensuring the reliability of PFC control.

[0008] In addition, the air conditioner according to embodiments of the present invention may also have the following additional technical features:

[0009] Furthermore, when determining the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and the inductor current, the controller is configured to: calculate the target carrier frequency based on a preset target carrier frequency algorithm, wherein the preset target carrier frequency algorithm includes the operational relationship between the target carrier frequency and the output duty cycle, the inductor current, the inductor value of the PFC circuit, and the inductor current ripple value, wherein the inductor value is a value that changes with the inductor current, and the inductor current ripple value is calculated based on the inductor value, the input voltage, the output duty cycle, and the switching cycle of the PFC circuit.

[0010] The above technical solution has the following advantages or beneficial effects: According to the air conditioner provided in the embodiment of the present invention, the controller calculates the target carrier frequency based on the preset target carrier frequency algorithm, so as to determine the target carrier frequency corresponding to the PFC circuit according to the output duty cycle and inductor current, which facilitates the real-time automatic adjustment of the PFC carrier frequency according to the PFC duty cycle and inductor current.

[0011] Furthermore, the target carrier frequency and the output duty cycle are configured to have a linear relationship.

[0012] The above technical solution has the following advantages or beneficial effects: In the air conditioner provided by the embodiment of the present invention, the target carrier frequency and the output duty cycle are configured to have a linear relationship, which simplifies the calculation process of the carrier frequency and facilitates the real-time automatic adjustment of the PFC carrier frequency according to the PFC duty cycle.

[0013] Furthermore, when determining the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and the inductor current, the controller is configured to: determine that the target carrier frequency is positively correlated with the output duty cycle when the output duty cycle does not exceed a preset duty cycle threshold; or, determine that the target carrier frequency is negatively correlated with the output duty cycle when the output duty cycle exceeds the preset duty cycle threshold; or, determine that the corresponding target carrier frequency is maximum when the output duty cycle is equal to the preset duty cycle threshold.

[0014] The above technical solution has the following advantages or beneficial effects: According to the air conditioner provided in the embodiment of the present invention, when the output duty cycle does not exceed the preset duty cycle threshold, the controller determines that the target carrier frequency is positively correlated with the output duty cycle; when the output duty cycle exceeds the preset duty cycle threshold, the controller determines that the target carrier frequency is negatively correlated with the output duty cycle; when the output duty cycle is equal to the preset duty cycle threshold, the controller determines that the corresponding target carrier frequency is maximum; thereby, the target carrier frequency can be calculated quickly, which facilitates real-time automatic adjustment of the PFC carrier frequency based on the PFC duty cycle and inductor current.

[0015] Furthermore, when determining the output duty cycle of the PFC circuit, the controller is configured to: acquire the target DC bus voltage and the actual DC bus voltage, calculate the difference between the two, and output a control signal through a voltage controller; multiply the control signal by the absolute value of the AC input voltage to obtain a target current signal; calculate the difference between the target current signal and the actual current, and output a target duty cycle through a current controller, using the target duty cycle as the output duty cycle.

[0016] The above technical solution has the following advantages or beneficial effects: According to the air conditioner provided in the embodiment of the present invention, the controller first obtains the target DC bus voltage and the actual DC bus voltage, calculates the difference between the two, and outputs a control signal through the voltage controller; then, the control signal is multiplied by the absolute value of the AC input voltage to obtain the target current signal; finally, the difference between the target current signal and the actual current is calculated, and the target duty cycle is output through the current controller. The target duty cycle is used as the output duty cycle, thereby determining the output duty cycle of the PFC circuit, which facilitates real-time automatic adjustment of the PFC carrier frequency based on the PFC duty cycle and the inductor current.

[0017] Furthermore, when determining the output duty cycle of the PFC circuit, the controller is also configured to: after the current controller outputs the target duty cycle, compensate the target duty cycle to obtain an optimized duty cycle, and use the optimized duty cycle as the output duty cycle.

[0018] The above technical solution has the following advantages or beneficial effects: According to the air conditioner provided by the embodiment of the present invention, after the controller outputs the target duty cycle through the current controller, it compensates the target duty cycle to obtain an optimized duty cycle, and uses the optimized duty cycle as the output duty cycle. In this way, the output duty cycle of the PFC circuit can be determined more accurately, which facilitates the real-time automatic adjustment of the PFC carrier frequency based on the PFC duty cycle and the inductor current.

[0019] Furthermore, when compensating for the target duty cycle to obtain an optimized duty cycle, the controller is configured to: multiply the absolute value of the AC input voltage by a preset coefficient to obtain a compensation value; and compensate for the target duty cycle according to the compensation value to obtain the optimized duty cycle.

[0020] The above technical solution has the following advantages or beneficial effects: According to the air conditioner provided in the embodiment of the present invention, the controller uses the absolute value of the AC input voltage multiplied by a preset coefficient to obtain a compensation value; the target duty cycle is compensated according to the compensation value to obtain an optimized duty cycle, thereby more accurately determining the output duty cycle of the PFC circuit, and facilitating real-time automatic adjustment of the PFC carrier frequency according to the PFC duty cycle and inductor current.

[0021] Furthermore, the current controller and / or the voltage controller are configured as PI controllers.

[0022] The above technical solution has the following advantages or beneficial effects: In the air conditioner provided according to the embodiments of the present invention, the current controller and / or voltage controller is configured as a PI controller, which facilitates the calculation and output of signals.

[0023] Furthermore, when generating the drive control signal, the controller is also configured to: determine the target current and the maximum current ripple limit; determine the upper limit and the lower limit of hysteresis control based on the target current and the maximum current ripple limit; and generate an optimized drive control signal based on the comparison result between the actual current and the upper limit and the lower limit of hysteresis control to control the actual current of the PFC circuit.

[0024] The above technical solution has the following advantages or beneficial effects: According to the air conditioner provided in the embodiment of the present invention, the controller first determines the target current and the maximum current ripple limit; then, it determines the upper limit and lower limit of hysteresis control based on the target current and the maximum current ripple limit; finally, it generates an optimized drive control signal based on the comparison result between the actual current and the upper and lower limits of hysteresis control to control the actual current of the PFC circuit; that is, it adopts a control method that combines average current control and current hysteresis control. Based on the maximum current ripple limit, the upper limit and lower limit of hysteresis control current are set. When the current reaches the limit of hysteresis control, the PWM signal is executed according to the hysteresis control output. When the current is within the hysteresis control range, the PWM signal is executed according to the average current control + variable carrier frequency control output. This ensures that the current ripple is within a controllable range under any abnormal conditions.

[0025] Furthermore, when generating an optimized drive control signal to control the actual current of the PFC circuit based on the comparison results between the actual current and the upper and lower limits of the hysteresis control, the controller is configured to: generate a first signal to control the actual current of the PFC circuit to decrease when the actual current is greater than the upper limit of the hysteresis control; or, generate a second signal to control the actual current of the PFC circuit to increase when the actual current is less than the lower limit of the hysteresis control; or, generate a third signal to control the actual current of the PFC circuit to remain unchanged when the actual current is greater than or equal to the lower limit of the hysteresis control and less than or equal to the lower limit of the hysteresis control.

[0026] The above technical solution has the following advantages or beneficial effects: According to the air conditioner provided in the embodiment of the present invention, when the actual current is greater than the upper limit of the hysteresis control, the controller generates a first signal to control the actual current of the PFC circuit to decrease; when the actual current is less than the lower limit of the hysteresis control, the controller generates a second signal to control the actual current of the PFC circuit to increase; when the actual current is greater than or equal to the lower limit of the hysteresis control and less than or equal to the lower limit of the hysteresis control, the controller generates a third signal to control the actual current of the PFC circuit to remain unchanged; thereby realizing current hysteresis control and ensuring that the current ripple is within a controllable range.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0029] Figure 1This is a schematic diagram of the refrigeration cycle system of an air conditioner according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the controller according to an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram illustrating the relationship between the carrier frequency and input voltage in a traditional PFC system.

[0032] Figure 4 This is the control principle diagram of a traditional PFC;

[0033] Figure 5 This is a schematic diagram of the energy distribution between a fixed carrier frequency and a dithered frequency.

[0034] Figure 6 This is a schematic diagram of the structure of an air conditioner according to an embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of the PFC control principle according to an embodiment of the present invention;

[0036] Figure 8 This is a nonlinear characteristic curve of the inductance as a function of current according to an embodiment of the present invention;

[0037] Figure 9 This is a schematic diagram of the PFC carrier frequency variation control law according to an embodiment of the present invention;

[0038] Figure 10 This is a schematic diagram of the PFC control principle according to another embodiment of the present invention;

[0039] Figure 11 This is a schematic diagram of the integration of average current control and hysteresis control PWM signals according to an embodiment of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0042] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0043] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0044] Figure 1 This is a schematic diagram of the refrigeration cycle system of an air conditioner according to an embodiment of the present invention, as shown below. Figure 1 As shown, one of the indoor heat exchangers and the other of the outdoor heat exchanger is a condenser, and the other is an evaporator. In this invention, the air conditioner performs a refrigeration cycle by using a compressor, a condenser, an expansion valve, an evaporator, and a four-way valve. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation, and supplies refrigerant to the conditioned and heat-exchanged air.

[0045] The compressor compresses the refrigerant gas, which is in a high-temperature, high-pressure state and enters through the return pipe, and then discharges the compressed refrigerant gas through the exhaust pipe. The discharged refrigerant gas flows into the condenser through the condenser inlet pipe. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0046] The indoor and outdoor heat exchangers function as either condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air conditioner functions as a heater in heating mode; when the indoor heat exchanger is used as an evaporator, the air conditioner functions as a cooler in cooling mode.

[0047] The expansion valve expands the high-temperature, high-pressure liquid refrigerant, which condenses in the condenser and is discharged through the condenser outlet pipe, into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the expansion valve and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves a cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cycle, the air conditioner regulates the temperature of the indoor space.

[0048] In the embodiments shown in this application, the air conditioner also includes a controller 71. The controller 71 is a device that can generate operation control signals according to instruction operation codes and timing signals to instruct the air conditioner to execute control commands. For example, in response to a power-on or power-off command issued by a user, the controller 71 can perform an operation related to the object selected by the power-on or power-off command.

[0049] This application embodiment also provides a hardware structure diagram of the controller 71, such as... Figure 2 As shown, the controller 71 includes a processor 83, and optionally, a memory 82 and a communication interface 84 connected to the processor 83. The processor 83, memory 82, and communication interface 84 are connected via a bus 81.

[0050] Processor 83 can be a central processing unit (CPU), a general-purpose processor (NP), a network processor (NP), a digital signal processor (DSP), a microprocessor (Microcontroller), a programmable logic device (PLD), or any combination thereof. Processor 83 can also be any other device with processing capabilities, such as a circuit, device, or software module. Processor 83 can also include multiple CPUs, and processor 83 can be a single-core processor 83 or a multi-core processor 83. Here, processor 83 can refer to one or more devices, circuits, or processing cores used for processing data (e.g., computer program instructions).

[0051] The memory 82 can be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, a random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CDROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer. This application embodiment does not impose any limitations on this. The memory 82 can exist independently or be integrated with the processor 83. The memory 82 may contain computer program code. The processor 83 is used to execute the computer program code stored in the memory 82, thereby implementing the air conditioner control method provided in this application embodiment.

[0052] The communication interface 84 can be used to communicate with other devices or communication networks (such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc.). The communication interface 84 can be a module, circuit, transceiver, or any device capable of communication.

[0053] Bus 81 can be a peripheral component interconnect (PCI) bus 81 or an extended industry standard architecture (EISA) bus 81, etc. Bus 81 can be divided into address bus 81, data bus 81, control bus 81, etc.

[0054] The following is combined with Figures 3-11 An air conditioner according to an embodiment of the present invention is described.

[0055] Figure 3 This is a schematic diagram illustrating the relationship between the carrier frequency and input voltage in traditional PFC, such as... Figure 3As shown, current PFC circuits in the industry use a fixed carrier frequency and adjusted duty cycle to achieve a fixed voltage value, resulting in the concentration of harmonic energy at specific frequency points (such as the switching frequency and its harmonics). This energy manifests as sharp peaks in the spectrum, easily exceeding EMI regulations and failing EMC tests, requiring designers to continuously adjust the carrier frequency to achieve optimal performance.

[0056] Figure 4 This is a control principle diagram of a traditional PFC, such as... Figure 4 As shown, traditional PFC control originally uses an average current control method, which generates the output duty cycle through voltage loop and current loop control, and finally synchronizes it with the carrier wave (…). Figure 4 The triangular wave is compared to form a PWM (Pulse Width Modulation) output signal. Specifically, this includes the following steps:

[0057] (1) Obtain the target DC bus voltage V dc * and actual DC bus voltage V dc The difference between the two is used to output a control signal U1 through a voltage controller (usually a PI controller);

[0058] (2) The absolute value of the control signal U1 and the AC input voltage |V ac Multiplying these two signals yields the target current signal I. ac *;

[0059] (3) Target current signal I ac *With actual current I ac The difference between the two is used to output the duty cycle d1 through a current controller (usually a PI controller);

[0060] (4) Absolute value of AC input voltage |V ac | Multiply by coefficient K c The duty cycle d1 in step (3) is compensated to form the final output duty cycle d;

[0061] (5) Duty cycle d and carrier signal ( Figure 4 The signal is compared with a triangular wave to form a PWM signal, which controls the on / off state of the IGBT (Insulated Gate Bipolar Transistor), thereby realizing the V of PFC. dc I ac Control functions.

[0062] It can be seen that the fixed carrier frequency of traditional control methods will cause EMI energy to concentrate at specific frequency points (such as the carrier frequency and its harmonics). This energy is manifested as sharp peaks in the spectrum, which can easily exceed the limits of EMI regulations and make it difficult to pass EMC tests. Designers need to constantly adjust the carrier frequency to achieve the optimal state.

[0063] Figure 5 This is a schematic diagram of the energy distribution between a fixed carrier frequency and a dithered frequency, such as... Figure 5 As shown, frequency dithering introduces frequency changes, causing these peak energies to be transferred to frequency bands with larger EMI margins. Although the total energy remains unchanged, the energy density at each frequency point is significantly reduced, thereby avoiding peak interference at a single frequency point and achieving the effect of EMI suppression.

[0064] Conventional frequency dithering techniques can disperse EMI energy by periodically changing the switching frequency, but they have the following drawbacks: periodically adjusting the carrier frequency according to the input voltage phase cannot adapt to different input voltages and load conditions. In particular, when the input voltage is distorted, the reliability of traditional methods is significantly affected.

[0065] In other words, the traditional method periodically adjusts the carrier frequency based on the input voltage phase, meaning the PFC carrier frequency is fixed for a given voltage phase. However, under different input voltages, different load currents, or voltage distortion conditions, the voltage and current corresponding to the same voltage phase are different, resulting in different output duty cycles. As discussed later, the inductor current ripple varies with the duty cycle. Therefore, the traditional method may experience a mismatch between the carrier frequency and the duty cycle, leading to excessive inductor current ripple and reliability issues such as inductor heating and false triggering of current protection.

[0066] To address the above problems, the present invention provides an air conditioner 10:

[0067] Figure 6 This is a schematic diagram of the structure of an air conditioner according to an embodiment of the present invention, as shown below. Figure 6 As shown, an air conditioner 10 includes: a refrigerant circulation loop, in which the refrigerant circulates in a loop consisting of a compressor, a four-way valve, a condenser, an expansion valve, and an evaporator, wherein one of the condenser and the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger; a PFC circuit; and a controller 71 configured to: determine the output duty cycle and inductor current of the PFC circuit; determine the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and inductor current; update the frequency of the carrier signal of the PFC circuit based on the target carrier frequency; generate a drive control signal based on the output duty cycle and the updated carrier signal; and control the on / off state of the power transistor in the PFC circuit based on the drive control signal.

[0068] In a specific embodiment, the PFC circuit in the air conditioner 10 improves power utilization, reduces energy loss, and minimizes interference with the power grid. Its working principle involves dynamically adjusting voltage and current to ensure that the input current changes synchronously with the mains voltage, thereby optimizing energy efficiency. Specifically, the PFC circuit employs a boost topology, converting unstable voltage into a stable DC voltage through primary regulation, while simultaneously ensuring that the input current follows the sinusoidal waveform of the mains voltage, thus reducing grid pollution. In inverter air conditioners, the PFC circuit works in conjunction with the IGBT module to ensure efficient energy conversion.

[0069] Figure 7 This is a schematic diagram of the PFC control principle according to an embodiment of the present invention, as shown below. Figure 7 As shown, in a specific embodiment, the controller 71 first determines the output duty cycle and inductor current of the PFC circuit; then, based on the output duty cycle and inductor current, it determines the target carrier frequency corresponding to the PFC circuit, and updates the frequency of the carrier signal of the PFC circuit according to the target carrier frequency; finally, based on the output duty cycle and the updated carrier signal, it generates a drive control signal, and controls the on / off state of the power transistor in the PFC circuit according to the drive control signal. Specifically, the controller 71 is based on... Figure 7 The PFC circuit shown is used for control. The target carrier frequency corresponding to the PFC circuit is determined according to the output duty cycle and inductor current. The fixed carrier frequency is transformed into a real-time changing carrier frequency, thereby dispersing EMI energy and significantly reducing the energy density at each frequency point. This avoids peak interference at a single frequency point and suppresses EMI. At the same time, the nonlinear characteristics of the inductance changing with the current are considered to avoid the reliability risk caused by inductor attenuation under high current conditions. The output duty cycle and inductor current can be determined based on the PFC circuit. The target carrier frequency can be calculated based on a preset target carrier frequency algorithm. The target carrier frequency and the output duty cycle are configured to have a linear relationship.

[0070] Figure 8 This is a nonlinear characteristic curve of the inductance as a function of current according to an embodiment of the present invention, such as... Figure 8 As shown in the specific embodiment, since the inductance of the inductance exhibits nonlinear characteristics with the change of current, in order to avoid the reliability risk caused by inductor attenuation under high current conditions, the present invention determines the target carrier frequency corresponding to the PFC circuit based on the inductor current.

[0071] Figure 9 This is a schematic diagram of the PFC carrier frequency variation control law according to an embodiment of the present invention, as shown below. Figure 9 As shown, in a specific embodiment, the controller 71 may be based on Figure 9When determining the target carrier frequency for the PFC circuit based on the output duty cycle and inductor current, the controller 71 can first determine the duty cycle corresponding to the maximum inductor current ripple value under the current inductor current. At this time, since the inductor current ripple is the maximum, the required PFC carrier frequency is also the highest. Under other duty cycle conditions, the inductor current ripple decreases with the change of duty cycle.

[0072] Specifically, the air conditioner 10 provided according to the embodiments of the present invention includes a refrigerant circulation loop, a PFC circuit, and a controller 71. The controller 71 first determines the output duty cycle and inductor current of the PFC circuit; then, it determines the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and inductor current, and updates the frequency of the carrier signal of the PFC circuit according to the target carrier frequency; finally, it generates a drive control signal based on the output duty cycle and the updated carrier signal, and controls the on / off state of the power transistor in the PFC circuit according to the drive control signal. That is, the PFC carrier frequency is automatically adjusted in real time according to the PFC duty cycle and inductor current, which not only transforms the fixed carrier frequency into a real-time changing carrier frequency, thereby dispersing EMI energy and significantly reducing the energy density at each frequency point, avoiding peak interference at a single frequency point, but also considers the nonlinear characteristics of the inductance changing with the current, avoiding reliability problems caused by inductor attenuation under high current conditions. In this way, it can adapt to different input voltages and load conditions, thereby comprehensively ensuring the reliability of PFC control.

[0073] In one embodiment of the present invention, when determining the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and inductor current, the controller 71 is configured to: calculate the target carrier frequency based on a preset target carrier frequency algorithm, wherein the preset target carrier frequency algorithm includes the operational relationship between the target carrier frequency and the output duty cycle, inductor current, inductor value of the PFC circuit and inductor current ripple value, wherein the inductor value is a value that changes with the inductor current, and the inductor current ripple value is calculated based on the inductor value, input voltage, output duty cycle and switching cycle of the PFC circuit.

[0074] In a specific embodiment, the controller 71 calculates the target carrier frequency based on a preset target carrier frequency algorithm. Specifically, the preset target carrier frequency algorithm includes the operational relationship between the target carrier frequency and the output duty cycle, inductor current, inductance value of the PFC circuit, and inductor current ripple value. The inductance value is a value that varies with the inductor current, and the inductor current ripple value is calculated based on the inductance value, input voltage, output duty cycle, and switching cycle of the PFC circuit.

[0075] In a specific embodiment, a method is provided for determining the target carrier frequency corresponding to the PFC circuit based on the output duty cycle:

[0076] like Figure 7 As shown, the differential equation for the inductor current when the IGBT is turned on is:

[0077] According to equation (1), the inductor current ripple is: (2) In the formula, D is the duty cycle of PFC, Ts is the switching period of PFC, which is the reciprocal of the PFC carrier frequency. We can get Ts = 1 / f, where f is the PFC carrier frequency, Vin is the PFC input voltage, the duty cycle D and the input voltage Vin both change in real time with time, and L(i) represents the inductance as a function of current. Its typical curve is shown in the figure. Figure 8 As shown;

[0078] According to equation (2) and Figure 8 It can be seen that the magnitude of the inductor current ripple Δi is related to the duty cycle D and the current i. The duty cycle corresponding to the maximum inductor current ripple under different current conditions can be calculated and denoted as D_Δi_max. At this point, because the inductor current ripple is at its maximum, the required PFC carrier frequency is also the highest. Under other duty cycle conditions, the inductor current ripple Δi decreases with the change of the duty cycle D. Simultaneously, from... Figure 8 It can be seen that the inductance decreases as the current increases, therefore the PFC carrier frequency also needs to increase as the current i increases;

[0079] PFC stands for Boost (Boost Chopper) circuit, and its input voltage Vin (i.e., the absolute value of the AC input voltage |V_in|) is used to calculate the input voltage. ac |), Output voltage (i.e., DC bus voltage V) dc The relationship between duty cycle D and duty cycle D is as follows:

[0080] Substituting equation (3) into equation (2), we can obtain the relationship between the inductor current ripple and the duty cycle as follows:

[0081] V can generally be considered dc Assuming a constant value, the inductor current ripple is related to the duty cycle D and the inductance L. The current ripple exhibits a parabolic relationship with the duty cycle D, thus possessing a maximum value. The current ripple is inversely proportional to the inductance; that is, the smaller the inductance, the larger the current ripple. Conversely, the inductance varies with the current; the larger the current, the smaller the inductance. Figure 8 As shown, it can be assumed that the inductor current ripple increases with the increase of current. Therefore, the larger the current, the higher the required PFC carrier frequency.

[0082] First, keep the current constant, at which point the inductance is constant. Taking the partial derivative of equation (4) with respect to the duty cycle, we can obtain...

[0083] Let the partial differential of equation (5) be 0, which is the maximum value of the inductor current ripple. At this time, the corresponding duty cycle is D = 50%. It can be seen that the inductor current ripple is the maximum when the duty cycle is 50%, so the required PFC carrier frequency is the highest at this time.

[0084] Based on the above analysis, it can be concluded that adjusting the PFC carrier frequency according to the duty cycle can avoid the problem of excessive inductor current ripple caused by the mismatch between the carrier frequency and the duty cycle.

[0085] Keeping the inductor current ripple Δi constant, the relationship between the carrier frequency and the duty cycle can be obtained from equation (5) as follows:

[0086] The target carrier frequency corresponding to the PFC circuit can be determined according to equation (6);

[0087] Furthermore, taking into account the factor of inductance changing with current, equation (6) assumes that the current remains constant. In this case, the inductance is a constant value, which is the curve of the carrier frequency versus duty cycle under a specific current. In practical applications, as shown in Figure 8, the inductance changes with the current. Therefore, each current value corresponds to a curve of the carrier frequency versus duty cycle. Based on this, a three-dimensional surface showing the carrier frequency changing with duty cycle and current can be obtained, such as... Figure 9 As shown.

[0088] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, the controller 71 calculates the target carrier frequency based on a preset target carrier frequency algorithm, so as to determine the target carrier frequency corresponding to the PFC circuit according to the output duty cycle and inductor current, which facilitates the real-time automatic adjustment of the PFC carrier frequency according to the PFC duty cycle and inductor current.

[0089] In one embodiment of the invention, the target carrier frequency and the output duty cycle are configured to have a linear relationship.

[0090] In a specific embodiment, the target carrier frequency and the output duty cycle are configured to have a linear relationship. Specifically, although the target carrier frequency corresponding to the PFC circuit can be determined according to equation (6), in practical applications, to simplify the calculation process of the carrier frequency, a minimum carrier frequency is limited, such as... Figure 9 As shown, the carrier frequency and duty cycle are approximately treated as having a linear relationship.

[0091] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, the target carrier frequency and the output duty cycle are configured to have a linear relationship, thereby simplifying the calculation process of the carrier frequency and facilitating the real-time automatic adjustment of the PFC carrier frequency based on the PFC duty cycle and inductor current.

[0092] In one embodiment of the present invention, when determining the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and the inductor current, the controller 71 is configured to: determine that the target carrier frequency is positively correlated with the output duty cycle when the output duty cycle does not exceed a preset duty cycle threshold; or, determine that the target carrier frequency is negatively correlated with the output duty cycle when the output duty cycle exceeds the preset duty cycle threshold; or, determine that the corresponding target carrier frequency is maximum when the output duty cycle is equal to the preset duty cycle threshold.

[0093] In a specific embodiment, when the output duty cycle does not exceed a preset duty cycle threshold, the controller 71 determines that the target carrier frequency and the output duty cycle are positively correlated; when the output duty cycle exceeds the preset duty cycle threshold, the controller 71 determines that the target carrier frequency and the output duty cycle are negatively correlated; when the output duty cycle is equal to the preset duty cycle threshold, the controller 71 determines that the corresponding target carrier frequency is maximum. Specifically, as shown... Figure 9 As shown, the preset duty cycle threshold is, for example, 50%. A 50% duty cycle corresponds to the maximum carrier frequency, while 0 and 100% duty cycles correspond to the minimum carrier frequency. Between these values, the carrier frequency changes linearly with the duty cycle.

[0094] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, when the output duty cycle does not exceed the preset duty cycle threshold, the controller 71 determines that the target carrier frequency is positively correlated with the output duty cycle; when the output duty cycle exceeds the preset duty cycle threshold, the controller 71 determines that the target carrier frequency is negatively correlated with the output duty cycle; when the output duty cycle is equal to the preset duty cycle threshold, the controller 71 determines that the corresponding target carrier frequency is maximum; thereby, the target carrier frequency can be quickly calculated, which facilitates real-time automatic adjustment of the PFC carrier frequency based on the PFC duty cycle and inductor current.

[0095] In one embodiment of the present invention, when determining the output duty cycle of the PFC circuit, the controller 71 is configured to: acquire the target DC bus voltage and the actual DC bus voltage, calculate the difference between the two, and output a control signal through the voltage controller; multiply the control signal by the absolute value of the AC input voltage to obtain the target current signal; calculate the difference between the target current signal and the actual current, and output the target duty cycle through the current controller, and use the target duty cycle as the output duty cycle.

[0096] In a specific embodiment, the controller 71 first acquires the target DC bus voltage and the actual DC bus voltage, calculates the difference between them, and outputs a control signal through the voltage controller; then, it multiplies the control signal by the absolute value of the AC input voltage to obtain the target current signal; finally, it calculates the difference between the target current signal and the actual current, outputs the target duty cycle through the current controller, and uses the target duty cycle as the output duty cycle. Specifically, as shown... Figure 7 As shown, the target DC bus voltage V is obtained. dc * and actual DC bus voltage V dcThe difference between the two is used to output a control signal U1 via a voltage controller; the absolute value of the control signal U1 and the AC input voltage |V ac Multiplying these two signals yields the target current signal I. ac *; Target current signal I ac *With actual current I ac The difference between the two is used to calculate the duty cycle d1 output by the current controller, which is then used as the target duty cycle.

[0097] In a specific embodiment, the voltage controller and / or current controller is configured as a PI controller to facilitate signal calculation and output.

[0098] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, the controller 71 first obtains the target DC bus voltage and the actual DC bus voltage, calculates the difference between the two, and outputs a control signal through the voltage controller; then, the control signal is multiplied by the absolute value of the AC input voltage to obtain the target current signal; finally, the difference between the target current signal and the actual current is calculated, and the target duty cycle is output through the current controller. The target duty cycle is used as the output duty cycle, thereby determining the output duty cycle of the PFC circuit, which facilitates real-time automatic adjustment of the PFC carrier frequency based on the PFC duty cycle and the inductor current.

[0099] In one embodiment of the present invention, when determining the output duty cycle of the PFC circuit, the controller 71 is further configured to: after the current controller outputs the target duty cycle, compensate the target duty cycle to obtain an optimized duty cycle, and use the optimized duty cycle as the output duty cycle.

[0100] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, after the current controller outputs the target duty cycle, the controller 71 compensates for the target duty cycle to obtain an optimized duty cycle, and uses the optimized duty cycle as the output duty cycle. In this way, the output duty cycle of the PFC circuit can be determined more accurately, which facilitates the real-time automatic adjustment of the PFC carrier frequency based on the PFC duty cycle and the inductor current.

[0101] In one embodiment of the present invention, when compensating for the target duty cycle to obtain an optimized duty cycle, the controller 71 is configured to: multiply the absolute value of the AC input voltage by a preset coefficient to obtain a compensation value; and compensate the target duty cycle according to the compensation value to obtain an optimized duty cycle.

[0102] In a specific embodiment, the controller 71 multiplies the absolute value of the AC input voltage by a preset coefficient to obtain a compensation value; based on the compensation value, it compensates for the target duty cycle to obtain an optimized duty cycle. Specifically, as shown... Figure 7 As shown, the absolute value of the AC input voltage |V ac | Multiply by coefficient K cThe duty cycle d1 is compensated to form the final output duty cycle d as the optimized duty cycle.

[0103] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, the controller 71 uses the absolute value of the AC input voltage multiplied by a preset coefficient to obtain a compensation value; the target duty cycle is compensated according to the compensation value to obtain an optimized duty cycle, thereby more accurately determining the output duty cycle of the PFC circuit, and facilitating real-time automatic adjustment of the PFC carrier frequency according to the PFC duty cycle and inductor current.

[0104] In one embodiment of the present invention, when generating the drive control signal, the controller 71 is further configured to: determine a target current and a maximum current ripple limit; determine an upper limit and a lower limit of hysteresis control based on the target current and the maximum current ripple limit; and generate an optimized drive control signal to control the actual current of the PFC circuit based on a comparison result between the actual current and the upper and lower limits of hysteresis control.

[0105] Figure 10 This is a schematic diagram of the PFC control principle according to another embodiment of the present invention, such as... Figure 10 As shown, in a specific embodiment, since the inductor current ripple cannot be guaranteed to remain within a reasonable range during frequency jittering, the reliability of the system is reduced. Although the PFC carrier frequency variation control method described above can adapt to different input voltages and load conditions, it is an open-loop control method for inductor current ripple. When inductor attenuation, core saturation, abnormal interference, etc. occur, the above method alone cannot effectively limit the inductor current ripple. Therefore, in this embodiment, the controller 71 first determines the target current and the maximum current ripple limit; then, based on the target current and the maximum current ripple limit, it determines the upper limit and lower limit of the hysteresis control. The limit is then set; finally, based on the comparison between the actual current and the upper and lower limits of the hysteresis control, an optimized drive control signal is generated to control the actual current of the PFC circuit; that is, a control method combining average current control and current hysteresis control is adopted. According to the maximum current ripple limit, the upper and lower limits of the hysteresis control current are set. When the current reaches the limit of the hysteresis control, the PWM signal is executed according to the hysteresis control output. When the current is within the hysteresis control range, the PWM signal is executed according to the average current control + variable carrier frequency control output. This ensures that the current ripple is within a controllable range under any abnormal conditions.

[0106] like Figure 10 As shown, in a specific embodiment, hysteresis control uses the target current signal i ac Using * as a benchmark, and based on the maximum current ripple limit △i_max, the upper limit i of the hysteresis control can be obtained. max With lower limit i min They are respectively

[0107] Figure 11 This is a schematic diagram of the integration of average current control and hysteresis control PWM signals according to an embodiment of the present invention, as shown below. Figure 11 As shown, in a specific embodiment, the PWM signal integration principle of average current control and hysteresis control includes: (1) detecting changes in the switching actions of both outputs, i.e., PWM signal edge detection (rising edge, falling edge); (2) when the switching action of a certain control method changes, the final output is based on the output of that control method; (3) as Figure 11 This allows for PFC variable carrier frequency control while ensuring that the inductor current ripple never exceeds the maximum current ripple limit △i_max.

[0108] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, the controller 71 first determines the target current and the maximum current ripple limit; then, it determines the upper limit and lower limit of hysteresis control based on the target current and the maximum current ripple limit; finally, it generates an optimized drive control signal based on the comparison result between the actual current and the upper and lower limits of hysteresis control to control the actual current of the PFC circuit; that is, it adopts a control method combining average current control and current hysteresis control. Based on the maximum current ripple limit, the upper limit and lower limit of hysteresis control current are set. When the current reaches the limit of hysteresis control, the PWM signal is executed according to the hysteresis control output. When the current is within the hysteresis control range, the PWM signal is executed according to the average current control + variable carrier frequency control output. This ensures that the current ripple is within a controllable range under any abnormal conditions.

[0109] In one embodiment of the present invention, when generating an optimized drive control signal to control the actual current of the PFC circuit based on a comparison between the actual current and the upper and lower limits of the hysteresis control, the controller 71 is configured to: generate a first signal to control the actual current of the PFC circuit to decrease when the actual current is greater than the upper limit of the hysteresis control; or generate a second signal to control the actual current of the PFC circuit to increase when the actual current is less than the lower limit of the hysteresis control; or generate a third signal to control the actual current of the PFC circuit to remain unchanged when the actual current is greater than or equal to the lower limit of the hysteresis control and less than or equal to the lower limit of the hysteresis control.

[0110] In a specific embodiment, when the actual current is greater than the upper limit of the hysteresis control, the controller 71 generates a first signal to control the actual current of the PFC circuit to decrease; when the actual current is less than the lower limit of the hysteresis control, the controller 71 generates a second signal to control the actual current of the PFC circuit to increase; when the actual current is greater than or equal to the lower limit of the hysteresis control and less than or equal to the lower limit of the hysteresis control, the controller 71 generates a third signal to control the actual current of the PFC circuit to remain unchanged. Specifically, the first signal is, for example, a turn-off signal, the second signal is, for example, a turn-on signal, and the third signal is, for example, a hold signal.

[0111] like Figure 11 As shown, in a specific embodiment, the basic principle of hysteresis control is: (1) when the actual current i ac >i max When, output a turn-off signal, causing i ac (2) When the actual current i decreases; ac min When, output an on signal, making i ac (3) When the actual current i rises; ac In [i min i max Within the specified interval, the switching signal remains unchanged. According to the principle of hysteresis control, hysteresis control can make the actual current i... ac Always in [i min i max Within the range, thus ensuring that the current ripple does not exceed the maximum current ripple limit △i_max.

[0112] Specifically, according to the air conditioner 10 provided in the embodiment of the present invention, when the actual current is greater than the upper limit of the hysteresis control, the controller 71 generates a first signal to control the actual current of the PFC circuit to decrease; when the actual current is less than the lower limit of the hysteresis control, the controller 71 generates a second signal to control the actual current of the PFC circuit to increase; when the actual current is greater than or equal to the lower limit of the hysteresis control and less than or equal to the lower limit of the hysteresis control, the controller 71 generates a third signal to control the actual current of the PFC circuit to remain unchanged; thereby realizing current hysteresis control and ensuring that the current ripple is within a controllable range.

[0113] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0114] ​Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An air conditioner, characterized in that, include: The refrigerant circulation loop allows the refrigerant to circulate in a loop consisting of a compressor, a four-way valve, a condenser, an expansion valve, and an evaporator. One of the condensers and the other of the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger. PFC circuit; The controller is configured to: Determine the output duty cycle and inductor current of the PFC circuit; The target carrier frequency is calculated based on a preset target carrier frequency algorithm, and the frequency of the carrier signal of the PFC circuit is updated according to the target carrier frequency. The preset target carrier frequency algorithm includes the operational relationship between the target carrier frequency and the output duty cycle, the inductor current, the inductance value of the PFC circuit, and the inductor current ripple value. The inductance value is a value that changes with the inductor current, and the inductor current ripple value is calculated based on the inductance value, the input voltage, the duty cycle, and the switching cycle of the PFC circuit. Based on the output duty cycle and the updated carrier signal, a drive control signal is generated, and the on / off state of the power transistor in the PFC circuit is controlled according to the drive control signal.

2. The air conditioner according to claim 1, characterized in that, The target carrier frequency and the output duty cycle are configured to have a linear relationship.

3. The air conditioner according to claim 2, characterized in that, When determining the target carrier frequency corresponding to the PFC circuit based on the output duty cycle and the inductor current, the controller is configured to: When the output duty cycle does not exceed a preset duty cycle threshold, it is determined that the target carrier frequency and the output duty cycle are positively correlated. or, When the output duty cycle exceeds a preset duty cycle threshold, it is determined that the target carrier frequency and the output duty cycle are negatively correlated. or, When the output duty cycle is equal to a preset duty cycle threshold, the corresponding target carrier frequency is determined to be at its maximum.

4. The air conditioner according to claim 1, characterized in that, When determining the output duty cycle of the PFC circuit, the controller is configured to: The target DC bus voltage and the actual DC bus voltage are obtained, the difference between the two is calculated, and the control signal is output through the voltage controller. The control signal is multiplied by the absolute value of the AC input voltage to obtain the target current signal; The difference between the target current signal and the actual current is calculated, and the target duty cycle is output by the current controller. The target duty cycle is then used as the output duty cycle.

5. The air conditioner according to claim 4, characterized in that, When determining the output duty cycle of the PFC circuit, the controller is also configured to: After the current controller outputs the target duty cycle, the target duty cycle is compensated to obtain an optimized duty cycle, which is then used as the output duty cycle.

6. The air conditioner according to claim 5, characterized in that, When compensating for the target duty cycle to obtain an optimized duty cycle, the controller is configured as follows: The compensation value is obtained by multiplying the absolute value of the AC input voltage by a preset coefficient. The target duty cycle is compensated based on the compensation value to obtain the optimized duty cycle.

7. The air conditioner according to claim 4, characterized in that, The current controller and / or the voltage controller are configured as PI controllers.

8. The air conditioner according to claim 1, characterized in that, When generating drive control signals, the controller is also configured to: Determine the target current and maximum current ripple limit; The upper limit and lower limit of hysteresis control are determined based on the target current and the maximum current ripple limit. Based on the comparison results between the actual current and the upper and lower limits of the hysteresis control, an optimized drive control signal is generated to control the actual current of the PFC circuit.

9. The air conditioner according to claim 8, characterized in that, When generating an optimized drive control signal to control the actual current of the PFC circuit based on a comparison between the actual current and the upper and lower limits of the hysteresis control, the controller is configured to: When the actual current exceeds the upper limit of the hysteresis control, a first signal is generated to control the actual current of the PFC circuit to decrease. or, When the actual current is less than the lower limit of the hysteresis control, a second signal is generated to control the actual current of the PFC circuit to rise. or, When the actual current is greater than or equal to the lower limit of the hysteresis control and less than or equal to the lower limit of the hysteresis control, a third signal is generated to control the actual current of the PFC circuit to remain unchanged.

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