Variable frequency drive control circuit and variable frequency drive control method

Abstract

The application relates to a variable frequency drive control circuit and a variable frequency drive control method, wherein the method comprises the following steps: acquiring a cold quantity demand signal output by an air conditioner master control unit and operation state signals of a first compressor and a second compressor; determining on-off combination states of a first switch, a second switch and a third switch and determining a bridge arm combination to be put into operation according to the cold quantity demand signal and the operation state signals; and controlling corresponding bridge arms to output drive signals by using a preset modulation algorithm to drive corresponding compressors to operate according to the determined on-off combination states and the bridge arm combination. By the application, the problem that when a compressor needs to be overhauled, a standby air conditioner unit needs to be started to cause multiple air conditioner units to be arranged to guarantee reliability, thereby leading to high air conditioner operation cost is solved.

Description

Technical Field

[0001] This application relates to the field of air conditioning technology, and in particular to a variable frequency drive control circuit and a variable frequency drive control method. Background Technology

[0002] Currently, in DC data center power supply scenarios with extremely high environmental control requirements, very high reliability demands are placed on air conditioning. Furthermore, if a compressor needs maintenance, the existing solution is to activate a backup air conditioning unit, requiring additional units on-site to ensure reliability, which is costly. Existing inverter air conditioners use a 3-arm inverter system, such as... Figure 1 As shown, existing technology uses a single three-arm unit to drive the compressor. When the air conditioning system is used in a high-reliability environment, to ensure the stability of the environmental control system in case of compressor failure, a backup air conditioner is needed to achieve stable operation control. If two compressors are used on a common bus, two three-arm systems are required, resulting in a large number of Insulated-Gate Bipolar Transistors (IGBTs), high cost, and an architecture as shown... Figure 2 As shown. Summary of the Invention

[0003] This application provides a variable frequency drive control circuit and a variable frequency drive control method to solve the problem in the prior art that when the compressor needs to be repaired, a backup air conditioning unit needs to be activated, or even more air conditioning units need to be installed to ensure reliability, resulting in high air conditioning operating costs.

[0004] In a first aspect, this application provides a variable frequency drive control circuit for driving a first compressor and a second compressor. The variable frequency drive control circuit includes: a DC bus, a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm, a fifth bridge arm, a sixth bridge arm, a first switch, a second switch, and a third switch. The first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm are all connected across the positive and negative terminals of the DC bus, and each of the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm has a midpoint for outputting a drive signal. The midpoints of the first bridge arm, the second bridge arm, and the third bridge arm are respectively connected to the three-phase winding of the first compressor via the first switch; The midpoints of the third bridge arm, the fourth bridge arm, and the fifth bridge arm are respectively connected to the three-phase winding of the second compressor via the second switch; The midpoint of the sixth bridge arm is connected via the third switch to one phase of the three-phase winding of the first compressor, or to one phase of the three-phase winding of the second compressor.

[0005] Optionally, the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm are all composed of an upper bridge arm power switch and a lower bridge arm power switch connected in series. The first end of the upper bridge arm power switch is connected to the positive terminal of the DC bus, the second end of the upper bridge arm power switch is connected to the first end of the lower bridge arm power switch and forms the midpoint, and the second end of the lower bridge arm power switch is connected to the negative terminal of the DC bus.

[0006] Optionally, when the first switch is closed, the second switch is open, and the third switch is open, the first bridge arm, the second bridge arm, and the third bridge arm constitute a three-phase inverter bridge arm group for driving the first compressor.

[0007] Optionally, when the second switch is closed, the first switch is open, and the third switch is open, the third bridge arm, the fourth bridge arm, and the fifth bridge arm constitute a three-phase inverter bridge arm group for driving the second compressor.

[0008] Optionally, when the first switch is closed, the second switch is closed, and the third switch is open, the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm constitute a five-bridge-arm inverter bridge arm group for driving the first compressor and the second compressor.

[0009] Secondly, this application provides a variable frequency drive control method based on the variable frequency drive control circuit described in the first aspect, comprising: Acquire the cooling demand signal output by the air conditioning main control unit and the operating status signals of the first compressor and the second compressor; Based on the cooling demand signal and the operating status signal, determine the on / off combination status of the first switch, the second switch and the third switch, and determine the bridge arm combination to be put into operation; Based on the determined on / off combination state and the bridge arm combination, the corresponding bridge arm is controlled to output a drive signal using a preset modulation algorithm to drive the corresponding compressor to run.

[0010] Optionally, determining the on / off combination state of the first switch, the second switch, and the third switch, and determining the bridge arm combination to be put into operation, based on the cooling demand signal and the operating status signal, includes: When the cooling demand signal is less than a first preset threshold and the first compressor is in normal operation, it is determined that the first switch is closed, the second switch is open, and the third switch is open, and the bridge arm combination put into operation is determined to be the first bridge arm, the second bridge arm, and the third bridge arm; When the first compressor is in a fault or maintenance state, it is determined that the second switch is closed, the first switch is open, and the third switch is open, and the bridge arm combination put into operation is determined to be the third bridge arm, the fourth bridge arm, and the fifth bridge arm; When the cooling demand signal is greater than or equal to a first preset threshold and less than a second preset threshold, and both the first compressor and the second compressor are in normal operating condition, it is determined that the first switch is closed, the second switch is closed, and the third switch is open, and the bridge arm combination put into operation is determined to be the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm.

[0011] Optionally, the corresponding bridge arm is controlled to output a drive signal using a preset modulation algorithm, including: When the cooling demand signal is less than a first preset threshold and the first compressor is in normal operation, the first bridge arm, the second bridge arm and the third bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor to run. When the first compressor is in a fault or maintenance state, the third, fourth and fifth bridge arms are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the second compressor to run; When the cooling demand signal is greater than or equal to a first preset threshold and less than a second preset threshold, and both the first compressor and the second compressor are in normal operating condition, the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm and the fifth bridge arm are controlled to output drive signals using a five-bridge arm half-cycle modulation algorithm, and drive the first compressor and the second compressor to run.

[0012] Optionally, based on the determined on / off combination state and the bridge arm combination, controlling the corresponding bridge arm to output a drive signal using a preset modulation algorithm to drive the corresponding compressor to operate includes: When the cooling demand signal is greater than or equal to the second preset threshold, the first switch is controlled to close, the second switch is controlled to open, and the third switch is controlled to open. The first bridge arm, the second bridge arm, and the third bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor to run at the maximum frequency. After the operating frequency of the first compressor reaches a preset frequency threshold, an updated cooling demand signal is obtained. When the updated cooling demand signal is less than the second preset threshold, the first switch is closed, the second switch is closed, and the third switch is opened. The first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm are controlled to output drive signals using a five-bridge arm half-cycle modulation algorithm to drive the first compressor and the second compressor to run.

[0013] Optionally, based on the determined on / off combination state and the bridge arm combination, controlling the corresponding bridge arm to output a drive signal using a preset modulation algorithm to drive the corresponding compressor to operate includes: When the cooling demand signal is greater than or equal to the second preset threshold, the first switch is controlled to close, the second switch is controlled to open, and the third switch is controlled to open. The first bridge arm, the second bridge arm, and the third bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor to run at the maximum frequency. After the operating frequency of the first compressor reaches a preset frequency threshold, an updated cooling demand signal is obtained. When the updated cooling demand signal is greater than or equal to the second preset threshold, the first switch is closed, the second switch is opened, and the third switch is closed. The first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor and the second compressor to operate.

[0014] Compared with the prior art, the above-mentioned technical solution provided in this application has the following advantages: Based on the variable frequency drive control circuit in this application, after obtaining the cooling demand signal output by the air conditioning main control unit and the operating status signals of the first compressor and the second compressor, the on / off combination state of the first switch, the second switch and the third switch are determined according to the cooling demand signal and the operating status signal, and the combination of bridge arms to be put into operation is determined. Then, according to the determined on / off combination state and the combination of bridge arms, the corresponding bridge arms are controlled to output drive signals using a preset modulation algorithm to drive the corresponding compressor to run. As can be seen, in this embodiment, the software control logic, in conjunction with the aforementioned hardware topology, achieves automated control of multi-mode operation, enabling the system to adaptively switch operating modes based on cooling demand and compressor status without manual intervention. Furthermore, by adapting different modulation algorithms to different bridge arm combinations (three / six bridge arms with SVPWM, five bridge arms with half-cycle modulation), optimal utilization of hardware resources and minimization of system energy consumption are achieved while ensuring drive capability. Moreover, by incorporating compressor operating status signals into the decision-making process, automatic fault-tolerant switching under fault conditions is achieved. When one compressor fails, drive resources can be switched to another compressor without shutdown, eliminating the need to configure and activate backup air conditioning units to ensure reliability. This not only improves system reliability and availability but also reduces air conditioning operating costs. In other words, system reliability is improved through the control of metal-oxide-semiconductor field-effect transistors (bridge arms) and switching transistors. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a schematic diagram of the air conditioning drive architecture in the prior art; Figure 2 This is a schematic diagram of the common bus in the existing air conditioning drive architecture; Figure 3A schematic diagram of a frequency converter drive control circuit based on a five-bridge arm provided for an embodiment of this application; Figure 4 This is a flowchart of a variable frequency drive control method provided in an embodiment of this application; Figure 5 A flowchart of a frequency converter drive control method with compressor fault tolerance and multi-mode operation provided in an embodiment of this application; Figure 6 This is a schematic diagram of the structure of the air conditioner control device provided in the embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0021] To address the problem in existing technologies where compressor maintenance necessitates the activation of backup air conditioning units, or even additional units, to ensure reliability, leading to higher air conditioning operating costs, this application provides a variable frequency drive control circuit. This circuit drives both a first compressor and a second compressor. Figure 3 As shown, the frequency converter drive control circuit includes: a DC bus, a first bridge arm S1, a second bridge arm S2, a third bridge arm S3, a fourth bridge arm S4, a fifth bridge arm S5, a sixth bridge arm S6, a first switch K1, a second switch K2, and a third switch K3. The first bridge arm S1, the second bridge arm S2, the third bridge arm S3, the fourth bridge arm S4, the fifth bridge arm S5, and the sixth bridge arm S6 are all connected across the positive and negative terminals of the DC bus, and each of the first bridge arm S1, the second bridge arm S2, the third bridge arm S3, the fourth bridge arm S4, the fifth bridge arm S5, and the sixth bridge arm S6 has a midpoint for outputting the drive signal. The midpoints of the first bridge arm S1, the second bridge arm S2, and the third bridge arm S3 are respectively connected to the three-phase winding of the first compressor PMSM1 via the first switch K1. The midpoints of the third bridge arm S3, the fourth bridge arm S4, and the fifth bridge arm S5 are respectively connected to the three-phase windings of the second compressor PMSM2 via the second switch K2. The midpoint of the sixth bridge arm S6 is connected via the third switch K3 to one phase of the three-phase winding of the first compressor PMSM1, or to one phase of the three-phase winding of the second compressor PMSM2.

[0022] It should be noted that each bridge arm consists of two power switches connected in series, including an upper bridge arm power switch and a lower bridge arm power switch. The first terminal of the upper bridge arm power switch (e.g., the drain of a MOSFET or the collector of an IGBT) is connected to the positive terminal of the DC bus, and the second terminal of the upper bridge arm power switch is connected to the first terminal of the lower bridge arm power switch. This connection point serves as the output midpoint of the bridge arm. The second terminal of the lower bridge arm power switch (e.g., the source of a MOSFET or the emitter of an IGBT) is connected to the negative terminal of the DC bus. By controlling the alternating on and off of the upper and lower bridge arm power switches, a pulse width modulation signal can be output at the midpoint of the bridge arm to drive the compressor's motor windings.

[0023] This application comprises six bridge arms, designated as bridge arm S1, bridge arm S2, bridge arm S3, bridge arm S4, bridge arm S5, and bridge arm S6. Each bridge arm is connected between the positive and negative terminals of the DC bus. Specifically, the first terminal of the upper bridge arm power switch of each bridge arm is connected to the positive terminal of the DC bus, and the second terminal of the lower bridge arm power switch of each bridge arm is connected to the negative terminal of the DC bus, thereby obtaining the DC power required to drive the compressor motor. Each bridge arm provides one phase drive signal, and three bridge arms combined constitute a standard three-phase inverter bridge arm group, realizing the drive control of a three-phase AC compressor. The configuration of six bridge arms provides the hardware foundation for subsequent multi-mode switching and bridge arm multiplexing.

[0024] Furthermore, the three-phase AC compressor in this embodiment includes three-phase stator windings, namely phase A, phase B, and phase C windings. These three-phase windings are spatially spaced with a 120° electrical angle difference. When a symmetrical three-phase AC current is applied to the three-phase windings, a rotating magnetic field is generated inside the motor, driving the compressor rotor to rotate. The midpoint of each bridge arm, i.e., the series connection point between the upper and lower bridge arm power switches, is the port where the bridge arm outputs the drive signal. When the inverter drives the motor, the midpoint of each bridge arm is connected to one phase winding of the motor, and the corresponding phase winding is driven by the pulse-width modulated voltage signal output from the bridge arm. Through the corresponding connection between the bridge arm midpoints and the three-phase windings of the compressor, the function of converting the DC bus voltage into the three-phase AC voltage required to drive the compressor is realized.

[0025] Furthermore, this application includes a first switch K1 between the midpoints of the first bridge arm S1, the second bridge arm S2, and the third bridge arm S3 and the three-phase windings of the first compressor. Specifically, the midpoint of the first bridge arm S1 is connected to the A-phase winding of the first compressor via one path of the first switch; the midpoint of the second bridge arm S2 is connected to the B-phase winding of the first compressor via one path of the first switch K1; and the midpoint of the third bridge arm S3 is connected to the C-phase winding of the first compressor via one path of the first switch K1. The first switch K1 is a three-way interlocking switch. When it is closed, the midpoints of the first bridge arm S1, the second bridge arm S2, and the third bridge arm S3 are electrically connected to the three-phase windings of the first compressor; when it is open, the above electrical connections are broken.

[0026] Furthermore, this application includes a second switch K2 between the midpoints of the third bridge arm S3, the fourth bridge arm S4, and the fifth bridge arm S5 and the three-phase windings of the second compressor. Specifically, the midpoint of the third bridge arm S3 is connected to the A-phase winding of the second compressor via one path of the second switch K2; the midpoint of the fourth bridge arm S4 is connected to the B-phase winding of the second compressor via one path of the second switch K2; and the midpoint of the fifth bridge arm S5 is connected to the C-phase winding of the second compressor via one path of the second switch K2. The second switch K2 is a three-way interlocking switch. When it is closed, the midpoints of the third bridge arm S3, the fourth bridge arm S4, and the fifth bridge arm S5 are electrically connected to the three-phase windings of the second compressor; when it is open, the above electrical connections are broken.

[0027] This application includes a third switch K3 between the midpoint of the sixth bridge arm S6 and the windings of either the first or second compressor. The midpoint of the sixth bridge arm S6 is selectively connected via the third switch K3 to any one phase of the three-phase windings of the first compressor, or to any one phase of the three-phase windings of the second compressor. The function of the third switch K3 is to activate the sixth bridge arm S6 in a specific operating mode to expand the system's drive capability.

[0028] It should be noted that the first switch K1, the second switch K2, and the third switch K3 mentioned above can all be implemented using switching devices with on / off control functions, such as relays, contactors, or circuit breakers.

[0029] By combining the on / off states of the first switch K1, the second switch K2, and the third switch K3, dynamic allocation and reuse of bridge arm resources among different compressors are achieved. This allows a limited number of bridge arms to flexibly adapt to various operating conditions, such as single-compressor operation, simultaneous operation of two compressors, and fault-tolerant operation. The specific modes are as follows: 1) When the first switch is closed, the second switch is open, and the third switch is open, the first, second, and third bridge arms form a three-phase inverter bridge arm group to drive the first compressor. That is, when the air conditioning system only needs to operate the first compressor, the first switch K1 is closed, the second switch K2 is open, and the third switch K3 is open. At this time, the midpoints of the first bridge arm S1, the second bridge arm S2, and the third bridge arm S3 are electrically connected to the three-phase windings of the first compressor via the closed first switch K1, forming a complete three-phase inverter bridge arm group to drive the first compressor. Because the second switch K2 is open, the electrical connection between the second compressor and each bridge arm is cut off, and the second compressor is in a stopped state. Because the third switch K3 is open, the sixth bridge arm S6 is not connected to any load.

[0030] 2) When the second switch is closed, the first switch is open, and the third switch is open, the third, fourth, and fifth bridge arms form a three-phase inverter bridge arm group to drive the second compressor. That is, when the first compressor malfunctions and needs to be shut down for maintenance, the second switch K2 is closed, the first switch K1 is open, and the third switch K3 is open. At this time, the midpoints of the third bridge arm S3, the fourth bridge arm S4, and the fifth bridge arm S5 are electrically connected to the three-phase windings of the second compressor via the closed second switch K2, forming a complete three-phase inverter bridge arm group to drive the second compressor. This example shows that when the first switch K1 is closed, the third bridge arm S3 serves the first compressor (as the C-phase drive bridge arm of the first compressor), and when the second switch K2 is closed, it switches to serve the second compressor (as the C-phase drive bridge arm of the second compressor), thus achieving bridge arm multiplexing.

[0031] It should be noted that in both modes described above, the third bridge arm S3 remains operational, but the object it serves changes depending on the on / off state of the first switch K1 and the second switch K2. Specifically, when the first switch K1 is closed, the midpoint of the third bridge arm S3 is connected to the C-phase winding of the first compressor; when the second switch K2 is closed, the midpoint of the third bridge arm S3 is connected to the C-phase winding of the second compressor. This reuse of the third bridge arm S3 in different modes allows six bridge arms to achieve the drive and fault-tolerant functions that would require more bridge arms in existing solutions.

[0032] 3) When the first switch is closed, the second switch is closed, and the third switch is open, the first, second, third, fourth, and fifth bridge arms form a five-bridge inverter bridge arm group to drive the first and second compressors. That is, when the air conditioning system needs to operate two compressors simultaneously to meet higher cooling capacity requirements, the first switch K1 is closed, the second switch K2 is closed, and the third switch K3 is open. At this time, the midpoints of the first and second bridge arms S1 and S2 are connected to the A and B phase windings of the first compressor via the first switch K1. The midpoint of the third bridge arm S3 is simultaneously connected to the C phase winding of the first compressor via the first switch K1 and to the C phase winding of the second compressor via the second switch K2 (the third bridge arm is shared by both compressors). The midpoints of the fourth and fifth bridge arms S4 and S5 are connected to the A and B phase windings of the second compressor via the second switch K2. Therefore, five inverter arms—the first arm S1, the second arm S2, the third arm S3, the fourth arm S4, and the fifth arm S5—are simultaneously put into operation, forming a five-arm inverter arm group to simultaneously drive the first compressor and the second compressor. In this mode, the third arm S3, as a shared arm, needs to distribute drive capacity between the two compressors in a time-sharing manner.

[0033] The configuration of the sixth bridge arm S6 and its selective connection via the third switch provide the hardware foundation for expanding the drive capability of this application. When both compressors are operating simultaneously and the cooling capacity demand is high, the sixth bridge arm S6 can be activated by closing the third switch K3, forming a six-bridge-arm drive topology together with the first to fifth bridge arms, providing more sufficient drive capability for both compressors. Whether the sixth bridge arm S6 is specifically connected to the first or second compressor, and to which phase winding, depends on the specific control strategy and operating conditions. The selective connection characteristic of the third switch K3 allows for flexible configuration of this connection relationship according to actual needs. The introduction of the sixth bridge arm S6 enables the system to further expand its drive capability based on the five-bridge-arm topology, ensuring stable and efficient operation of both compressors in high cooling capacity demand scenarios, overcoming the shortcomings of the traditional five-bridge-arm topology, which has limited voltage utilization and cannot meet high cooling capacity demands when both compressors are operating simultaneously.

[0034] Through the aforementioned switch switching control, this application achieves flexible drive control of two compressors using a topology structure with six bridge arms and three switches. It can provide standard three-phase inverter drive capability (100% voltage utilization) when a single machine is running, and can also achieve dual-machine joint control through a five-bridge-arm topology when both machines are running simultaneously. Furthermore, it can achieve fault-tolerant switching without shutdown through bridge arm redistribution when one compressor fails, significantly improving the system's reliability and hardware resource utilization.

[0035] Therefore, the variable frequency drive control circuit described above achieves drive control of two compressors with a relatively small number of power devices (six bridge arms). Compared to the existing scheme that uses two sets of three-bridge arm units (a total of six bridge arms) to drive two compressors respectively, the number of bridge arms in this application is not increased. However, the reuse and flexible configuration of bridge arms are achieved through switching, and fault-tolerant operation capability is obtained under the premise of basically the same hardware cost. Moreover, through the combination control of the on and off of the first, second, and third switches, multiple operating modes such as single compressor operation, dual compressor simultaneous operation, and fault-tolerant switching are realized. This allows the system to adaptively switch operating modes according to the cooling demand signal of the air conditioning main control unit and the operating status signal of the compressor, realizing the fine control of the system. In addition, when one compressor fails, the drive bridge arm can be redistributed to another compressor through switching, ensuring the continuous and stable operation of the environmental control system without the need for additional backup air conditioning units, significantly reducing the air conditioning power cost and equipment investment cost of the data center.

[0036] The variable frequency drive control method in this application will be further explained below in conjunction with the aforementioned variable frequency drive control circuit, such as... Figure 4 As shown, the steps of this method include: Step 401: Obtain the cooling demand signal output by the air conditioning main control unit and the operating status signals of the first compressor and the second compressor; In this embodiment, the cooling demand signal is output by the air conditioning main control unit. Based on temperature parameters detected by ambient temperature sensors, return air temperature sensors, evaporator temperature sensors, etc., and combined with a preset temperature control target (e.g., the set temperature of a data center server room), the air conditioning main control unit calculates the cooling capacity required by the current system using a built-in control algorithm (e.g., a PID control algorithm), and outputs it to the variable frequency drive controller in the form of a cooling demand signal. The cooling demand signal can typically be represented as an analog signal (e.g., a 0~10V voltage signal or a 4~20mA current signal) or a digital signal (e.g., a numerical signal transmitted via a communication bus). Its amplitude or value reflects the urgency of the current system's cooling demand; that is, the larger the signal value, the higher the required cooling capacity.

[0037] In addition, the compressor's operating status signals include the operating status of both the first and second compressors. These operating status signals may include, but are not limited to, the following information: whether the compressor is currently running, whether it is in a fault state, whether it is in a maintenance lockout state, the current operating frequency, winding temperature, and current value. These signals can be acquired through various sensors installed on the compressor (such as temperature sensors, current sensors, Hall effect sensors, etc.), or through the internal status monitoring module of the compressor driver.

[0038] In a specific implementation, the variable frequency drive controller can read the analog value of the cooling demand signal through an analog-to-digital conversion interface, and read the compressor's operating status data through a communication interface (such as a CAN bus, RS485 bus, or internal chip-to-chip communication). The above signal acquisition operations can be executed periodically according to a preset control cycle (e.g., every 100 microseconds or every 1 millisecond) to ensure that the control system can respond promptly to changes in cooling demand and compressor status.

[0039] As can be seen, in this embodiment of the application, by acquiring the cooling demand signal and the compressor operating status signal, an accurate and timely decision basis is provided for subsequent mode determination and on / off control, enabling the system to dynamically adjust the working mode according to the actual working conditions and achieve refined control.

[0040] Step 402: Based on the cooling demand signal and the operating status signal, determine the on / off combination status of the first switch, the second switch and the third switch, and determine the bridge arm combination to be put into operation. In response, the system determines whether a fault or maintenance requirement exists based on the compressor's operating status signal. If the first compressor is detected to be in a faulty state (e.g., overcurrent protection triggered, overheat protection triggered, winding short circuit, etc.) or in a maintenance-locked state (e.g., manually set to maintenance mode), the control system should prioritize fault-tolerant operation and switch the drive resources to the second compressor. In this case, regardless of the magnitude of the cooling demand signal, the second switch is closed, the first switch is open, and the third switch is open, with the bridge arm combination in operation being the third, fourth, and fifth bridge arms.

[0041] Assuming all compressors are operating normally, the operating mode is determined based on the magnitude of the cooling demand signal. The control system compares the cooling demand signal with a preset first threshold and a second threshold, where the first preset threshold is less than the second preset threshold, and then determines the operating mode based on the comparison result.

[0042] Step 403: Based on the determined on / off combination state and bridge arm combination, control the corresponding bridge arm to output a drive signal using a preset modulation algorithm to drive the corresponding compressor to run.

[0043] As can be seen, in this embodiment of the application, based on the above-mentioned variable frequency drive control circuit, after acquiring the cooling demand signal output by the air conditioning main control unit and the operating status signals of the first compressor and the second compressor, the on / off combination state of the first switch, the second switch and the third switch are determined according to the cooling demand signal and the operating status signal, and the combination of bridge arms to be put into operation is determined. Then, according to the determined on / off combination state and the combination of bridge arms, the corresponding bridge arms are controlled to output drive signals using a preset modulation algorithm to drive the corresponding compressor to run. As can be seen, in this embodiment, the software control logic, in conjunction with the aforementioned hardware topology, achieves automated control of multi-mode operation, enabling the system to adaptively switch operating modes according to cooling demand and compressor status without manual intervention. Furthermore, by adapting different modulation algorithms to different bridge arm combinations (three-bridge / six-bridge with SVPWM, five-bridge with half-cycle modulation), optimal utilization of hardware resources and minimization of system energy consumption are achieved while ensuring drive capability. Moreover, by incorporating compressor operating status signals into the decision-making process, automatic fault-tolerant switching under fault conditions is realized. When one compressor fails, drive resources can be switched to another compressor without shutdown, eliminating the need to configure and activate backup air conditioning units to ensure reliability. This not only improves system reliability and availability but also reduces air conditioning operating costs.

[0044] In an optional embodiment of this application, the method of determining the on / off combination state of the first switch, the second switch, and the third switch based on the cooling demand signal and the operating status signal, and determining the bridge arm combination to be put into operation in step 402 above, may further include: Step 11: When the cooling demand signal is less than the first preset threshold and the first compressor is in normal operation, determine that the first switch is closed, the second switch is open, and the third switch is open, and determine that the bridge arm combination put into operation is the first bridge arm, the second bridge arm, and the third bridge arm. In this case, the first bridge arm, the second bridge arm, and the third bridge arm are further controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor to run; Therefore, when the cooling demand signal is less than the first preset threshold, it indicates that the current system's cooling demand is low, and only one compressor needs to be running to meet the cooling requirements. At this time, the first switch closes, electrically connecting the midpoints of the first, second, and third bridge arms to the three-phase windings of the first compressor; the second switch opens, disconnecting the connection between the three-phase windings of the second compressor and each bridge arm, ensuring the second compressor is completely disconnected from the circuit and does not generate any electromagnetic interference or circulating current; the third switch opens, leaving the sixth bridge arm unconnected to any load and in an idle standby state. Thus, the first, second, and third bridge arms constitute a complete three-phase inverter bridge arm group, electrically connected to the three-phase windings of the first compressor, forming a standard single-compressor inverter drive circuit. In this scenario, the control system only drives the first compressor, while the second compressor is completely stopped. This mode is the default operating mode for the air conditioning system under low load conditions and is also the most energy-efficient operating mode because only three bridge arms are engaged, minimizing switching and conduction losses.

[0045] Step 12: If the first compressor is in a fault or maintenance state, determine that the second switch is closed, the first switch is open, and the third switch is open, and determine that the bridge arm combination put into operation is the third bridge arm, the fourth bridge arm, and the fifth bridge arm. In this case, the third, fourth, and fifth bridge arms are further controlled to output drive signals using a space vector pulse width modulation algorithm to drive the second compressor to run; Therefore, if the first compressor is detected to be in a faulty state (e.g., overcurrent protection triggered, overheat protection triggered, winding short circuit, etc.) or in a maintenance-locked state (e.g., manually set to maintenance mode), the control system should prioritize ensuring the fault-tolerant operation of the system and switch the drive resources to the second compressor. Specifically, the first switch being open disconnects the electrical connection between the first compressor and each bridge arm, ensuring physical isolation between the faulty compressor and the drive circuit, complying with electrical safety regulations, and avoiding possible feedback interference from the faulty compressor to the drive circuit; the second switch being closed connects the midpoints of the third, fourth, and fifth bridge arms to the three-phase windings of the second compressor; the third switch being open disconnects the sixth bridge arm from any load. Thus, the third, fourth, and fifth bridge arms constitute a complete three-phase inverter bridge arm group, which is electrically connected to the three-phase windings of the second compressor, forming an alternative single-compressor inverter drive circuit.

[0046] In this scenario, the third bridge arm is reused. When the cooling demand signal is less than a first preset threshold, the third bridge arm is used as the C-phase drive bridge arm of the first compressor. In a fault scenario, the third bridge arm is switched to be used as the C-phase drive bridge arm of the second compressor. Through the interlocking control of the first and second switches (i.e., they do not open or close simultaneously; in a fault scenario, the first switch opens while the second switch closes), the service target of the third bridge arm switches from the first compressor to the second compressor, realizing the dynamic reallocation of bridge arm resources. In other words, when a compressor fails and needs to be shut down for maintenance, the drive resources can be automatically switched to another compressor, achieving fault-tolerant operation without shutdown. Compared with the existing solution that requires an additional complete backup air conditioning unit, this application significantly reduces equipment redundancy costs.

[0047] Step 13: When the cooling demand signal is greater than or equal to the first preset threshold and less than the second preset threshold, and both the first compressor and the second compressor are in normal operation, determine that the first switch is closed, the second switch is closed, and the third switch is open, and determine that the bridge arm combination put into operation is the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm.

[0048] In this case, the first, second, third, fourth, and fifth bridge arms are further controlled to output drive signals using a five-bridge-arm half-cycle modulation algorithm, and drive the first and second compressors to operate.

[0049] Therefore, when the cooling demand signal is greater than or equal to the first preset threshold and less than the second preset threshold, it indicates that the current system's cooling demand is at a moderate level. A single compressor cannot meet the requirement, but running both compressors at full speed may result in energy waste. Specifically, closing the first switch connects the midpoints of the first, second, and third bridge arms to the three-phase windings of the first compressor; closing the second switch connects the midpoints of the third, fourth, and fifth bridge arms to the three-phase windings of the second compressor. At this time, the third bridge arm is simultaneously connected to the C-phase winding of the first compressor via the first switch and to the C-phase winding of the second compressor via the second switch, making the third bridge arm a common bridge arm shared by both compressors. The fourth and fifth bridge arms are connected to the A-phase and B-phase windings of the second compressor via the second switch. Thus, all five bridge arms—the first, second, third, fourth, and fifth bridge arms—are simultaneously in operation, forming a five-bridge-arm inverter bridge arm group. This five-arm inverter arm assembly drives the common five-phase windings of two compressors (three phases A, B, and C of the first compressor, and two phases A and B of the second compressor) through five arms, achieving synchronous drive of the two compressors. The five arms drive the five-phase windings, with the third arm serving as a common arm that is time-shared by the two compressors. Because there is no independent sixth arm to supply power to the C phase of the second compressor, the two compressors cannot simultaneously obtain 100% drive voltage, thus limiting their operating frequency. However, in scenarios with medium cooling capacity requirements, the compressors can meet the cooling requirements by operating at low to medium frequencies, so this limitation does not constitute a practical defect.

[0050] As can be seen, the three switch combinations in the three scenarios of steps 11 to 13 above correspond to three different circuit topology reconfiguration schemes: the first allocates the first to third bridge arms to the first compressor, the second allocates the third to fifth bridge arms to the second compressor, and the third allocates the first to fifth bridge arms to both compressors simultaneously. The difference in these switch combinations directly determines the electrical connection between the bridge arms and the compressors, and thus, at the physical level, the driving capability of the system. Furthermore, the first and second scenarios both use the space vector pulse width modulation algorithm, while the third scenario uses a five-bridge-arm half-cycle modulation algorithm. Although the first two scenarios use different bridge arm numbers, their topology is essentially a standard three-phase inverter composed of three independent bridge arms; therefore, using the same modulation algorithm is reasonable and necessary. The third scenario, due to the presence of a common bridge arm, fundamentally changes its topology; therefore, a five-bridge-arm half-cycle modulation algorithm is used.

[0051] Furthermore, the SVPWM algorithm in the first scenario (step 11) and the second scenario (step 12) of steps 11 to 13 above can achieve 100% DC bus voltage utilization, which means that the compressor can operate at the highest frequency and output the maximum cooling capacity. The five-arm half-cycle modulation algorithm in the third scenario (step 13) can only achieve about 50%~60% voltage utilization, and the compressor operating frequency is limited to the low to medium frequency range. This difference determines the applicable scope of the three scenarios. The first two scenarios are suitable for high-requirement situations that require the compressor to run at full speed (rapid response at low cooling capacity or full protection in case of failure), while the third scenario is suitable for maintaining medium cooling capacity in steady state. It can be seen that in the first scenario, achieving efficient full-frequency drive of a single compressor with the least hardware investment (three arms) and the lowest loss is the system's default most energy-efficient operating mode. In the second scenario, when one compressor fails, the combination of bridge arm multiplexing and the SVPWM algorithm enables the replacement compressor to obtain the same full-frequency drive capability as the failed compressor, achieving a seamless transition in cooling capacity before and after the failure and ensuring high system reliability. In the third scenario, simultaneous drive of two compressors is achieved at the cost of five bridge arms. Although voltage utilization is limited, this precisely meets the low-to-medium frequency operation requirements of medium-capacity cooling scenarios, achieving a smooth expansion of system cooling capacity supply at a relatively low cost.

[0052] Furthermore, the control combinations in the three scenarios do not exist in isolation, but together constitute a complete, closed-loop, adaptive multi-mode drive control system. During operation, the system can dynamically switch between these three combinations based on real-time changes in cooling demand signals and compressor status signals, thereby responding to system demands with optimal hardware and algorithm configurations at different operating stages. This dynamic adaptive capability enables the air conditioning system to maintain efficient, stable, and reliable operation across the entire operating range, making it particularly suitable for data center applications with extremely high requirements for reliability and energy efficiency.

[0053] Furthermore, in this embodiment, when the bridge arm combination in operation is three bridge arms (e.g., the first, second, and third bridge arms, or the third, fourth, and fifth bridge arms), the three bridge arms constitute a standard three-phase inverter bridge arm group, each driving the three-phase windings of a compressor. In this mode, the control system uses a space vector pulse width modulation algorithm to output the drive signal. Space vector pulse width modulation (SVPWM) is an advanced pulse width modulation technology. Specifically, it uses the ideal magnetic flux circle of an AC motor under a three-phase symmetrical sinusoidal voltage supply as a reference, and utilizes different combinations of the inverter's bridge arm switching control signals to make the actual magnetic flux trajectory formed by the vector action of the inverter's output working voltage approximate the reference circular magnetic flux trajectory. SVPWM technology can significantly reduce the harmonic components of the inverter output current and the harmonic losses of the motor, reduce pulsating torque, and its digital implementation is convenient, with high DC bus voltage utilization. In a standard three-phase inverter topology with three bridge arms, SVPWM can achieve 100% DC bus voltage utilization. This means the compressor can obtain maximum voltage output capability, enabling stable operation over a wide frequency range (including high-frequency bands) and outputting a large cooling capacity. Therefore, in scenarios where the system requires a single compressor to run at full speed for rapid cooling (such as during startup or high cooling capacity demand), using the SVPWM algorithm is the preferred choice.

[0054] Furthermore, in this embodiment, when the bridge arm combination in operation consists of five bridge arms (e.g., the first, second, third, fourth, and fifth bridge arms), these five bridge arms need to simultaneously drive the common five-phase windings of two compressors (phases A, B, and C of the first compressor, and phases A and B of the second compressor), with the third bridge arm serving as a common bridge arm shared by both compressors. In this mode, due to the presence of a common bridge arm, the standard SVPWM algorithm cannot be directly used; instead, a modulation strategy specifically designed for the five-bridge-arm topology is required. In the five-bridge-arm mode of this application, a five-bridge-arm half-cycle modulation algorithm is employed. Specifically, within one PWM carrier cycle, time is divided into two half-cycles. In the first half-cycle, the control system allocates the common arm (third arm) to the first compressor, which, together with the other two arms (first arm and second arm), forms the three-phase drive arm group for the first compressor, enabling drive control of the first compressor. In the second half-cycle, the control system switches the common arm (third arm) to the second compressor, which, together with the other two arms (fourth arm and fifth arm), forms the three-phase drive arm group for the second compressor, enabling drive control of the second compressor. Through this time-division multiplexing method, the five-arm inverter arm group can provide three-phase drive capability to two compressors respectively in different time periods.

[0055] The five-bridge-arm half-cycle modulation algorithm enables independent control of the two motors. This means that each motor receives drive voltage for only half the time within a control cycle, resulting in low DC bus voltage utilization. Specifically, the voltage utilization of the five-bridge-arm half-cycle modulation algorithm is typically only about 50% to 60% of that of standard SVPWM. This implies that the two compressors cannot operate at very high frequencies, but can only operate stably at medium to low frequencies. However, this limitation happens to match the application scenario of the five-bridge-arm mode. As mentioned earlier, the five-bridge-arm mode is activated when the cooling demand is at a medium level. At this time, the system does not need the compressors to operate at the highest frequency; medium to low frequency operation is sufficient to meet the cooling requirements. Therefore, although the five-bridge-arm half-cycle modulation algorithm sacrifices some voltage utilization, it can achieve simultaneous operation of both units in medium cooling demand scenarios, ensuring cooling performance while avoiding the waste of additional hardware resources.

[0056] Furthermore, when the cooling demand signal is greater than or equal to the second preset threshold, it indicates that the current system has a high demand for cooling and needs to provide stronger driving capability to the system. At this time, the control system can adopt different control strategies. For example, during the startup phase, the first compressor can be driven to run at full speed in three-arm mode. After the system stabilizes, it can be switched to five-arm or six-arm mode according to actual needs (by closing the third switch to put the sixth arm into operation).

[0057] Based on this, the method in step 403 above, which involves controlling the corresponding bridge arm to output a drive signal using a preset modulation algorithm based on the determined on / off combination state and bridge arm combination, in order to drive the corresponding compressor to operate, may further include: Step 21: When the cooling demand signal is greater than or equal to the second preset threshold, control the first switch to close, the second switch to open, and the third switch to open, and control the first bridge arm, the second bridge arm and the third bridge arm to output drive signals using the space vector pulse width modulation algorithm to drive the first compressor to run at the maximum frequency; When the system detects a cooling demand signal greater than or equal to a second preset threshold, it indicates that the current ambient temperature is significantly higher than the set temperature, and the system needs to quickly establish cooling capacity to lower the ambient temperature. Under this high cooling demand condition, the control system first closes the first switch, electrically connecting the midpoints of the first, second, and third bridge arms to the three-phase windings of the first compressor; simultaneously, it opens the second and third switches to ensure that the second compressor and the sixth bridge arm are not connected to the circuit. Thus, the first, second, and third bridge arms constitute a standard three-phase inverter bridge arm group, driving only the first compressor. The control system uses a space vector pulse width modulation algorithm to drive the first compressor and controls it to operate at its maximum frequency to establish the required cooling capacity in the shortest possible time, meeting the rapid response requirements under high cooling demand startup scenarios.

[0058] Step 22: After the operating frequency of the first compressor reaches the preset frequency threshold, obtain the updated cooling demand signal. Step 23: When the updated cooling demand signal is less than the second preset threshold, control the first switch to close, the second switch to close, and the third switch to open. Control the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm to output drive signals using a five-bridge arm half-cycle modulation algorithm to drive the first compressor and the second compressor to run.

[0059] It should be noted that the updated cooling demand signal refers to the cooling demand signal that the control system re-acquires from the air conditioning main control unit after the first compressor operating frequency reaches the preset frequency threshold. The term "updated" emphasizes that after acquiring the initial cooling demand signal during the startup phase, the control system acquires the cooling demand signal again after a certain period (i.e., the time required for the compressor to accelerate from zero frequency to the preset frequency threshold) to reflect the system's current actual cooling demand.

[0060] It is evident that once the system stabilizes and the cooling demand drops from high to moderate, continuing to operate a single compressor at full speed would lead to higher motor temperatures and increased mechanical wear due to prolonged operation near the maximum frequency. Furthermore, the energy efficiency of a single compressor operating at full speed might not be as economical as two compressors operating at low to medium frequencies. Therefore, the system switches from a single-unit full-speed mode to a dual-unit low-to-medium frequency mode, where two compressors share the moderate cooling demand. Each compressor operates in the low to medium frequency range, satisfying the cooling requirements while reducing the operating load and energy consumption of a single compressor. Although the five-bridge half-cycle modulation algorithm has lower voltage utilization, limiting the upper limit of the compressor's operating frequency, low to medium frequency operation is sufficient for moderate cooling demand scenarios, eliminating the need for the compressor to operate at its highest frequency.

[0061] Furthermore, the method described in step 403 above, which involves controlling the corresponding bridge arm to output a drive signal using a preset modulation algorithm based on the determined on / off combination state and bridge arm combination, in order to drive the corresponding compressor to operate, may further include: Step 31: When the cooling demand signal is greater than or equal to the second preset threshold, control the first switch to close, the second switch to open, and the third switch to open, and control the first bridge arm, the second bridge arm and the third bridge arm to output drive signals using the space vector pulse width modulation algorithm to drive the first compressor to run at the maximum frequency; Step 32: After the operating frequency of the first compressor reaches the preset frequency threshold, obtain the updated cooling demand signal. Step 33: When the updated cooling demand signal is greater than or equal to the second preset threshold, control the first switch to close, the second switch to open, and the third switch to close, and control the first bridge arm, second bridge arm, third bridge arm, fourth bridge arm, fifth bridge arm, and sixth bridge arm to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor and the second compressor to run.

[0062] It is evident that when the cooling demand remains high even after the system stabilizes, it indicates that the cooling capacity generated by a single compressor operating at full speed during startup is insufficient to lower the ambient temperature to near the target value, or that the ambient heat load remains consistently high. In this case, the system requires both compressors to operate at full speed to meet the cooling demand. By closing the third switch to activate the sixth bridge arm, the six bridge arms drive all six-phase windings of the two compressors (three phases for each compressor). The constraint of a common bridge arm is eliminated, allowing for independent SVPWM algorithm control of each compressor. This ensures both compressors achieve 100% voltage utilization and can operate across the entire frequency range, outputting their respective maximum cooling capacity. The introduction of the sixth bridge arm extends the system from limited operation of a five-bridge-arm dual-machine configuration to full-speed operation of a six-bridge-arm dual-machine configuration, effectively overcoming the inherent limitation of voltage utilization in traditional five-bridge-arm topologies when both compressors operate simultaneously.

[0063] Therefore, in steps 21 and 31 above, driving the first compressor to operate at its maximum frequency means that the fundamental frequency of the drive voltage output by the variable frequency drive controller for the first, second, and third bridge arms is equal to the highest operating frequency at which the compressor can stably operate under rated voltage, rated current, and rated load conditions. The value of this maximum frequency depends on the compressor's motor design parameters (including the number of pole pairs, rated speed, rated power, etc.), and different types and specifications of compressors have different maximum frequency values. In a specific implementation, the variable frequency drive controller internally stores a table of rated parameters for each compressor and can automatically obtain the corresponding maximum frequency value as the control target based on the currently driven compressor model.

[0064] Furthermore, the preset frequency threshold is a frequency parameter pre-stored in the variable frequency drive controller. Its value is usually set as a certain percentage of the maximum frequency (e.g., 80% or 90% of the maximum frequency), but it can also be calibrated according to the actual operating characteristics of the air conditioning system. When the first compressor accelerates from zero frequency during the startup phase and its operating frequency rises to or exceeds the preset frequency threshold, it indicates that the system has completed the startup acceleration process, the compressor has entered a stable operating range, and the air conditioning system has initially established sufficient cooling capacity. At this point, the control system can safely make mode switching decisions. The purpose of setting the preset frequency threshold is to avoid switching the operating mode prematurely before the compressor has completed startup acceleration, and to prevent the compressor from losing synchronization or the system from oscillating due to voltage and current surges during the switching process.

[0065] It should be noted that steps 21 to 23 and steps 31 to 33 above collectively describe a special operation control strategy, namely a dynamic timing control scheme that first starts a single unit at high speed and then adaptively switches based on steady-state cooling demand. This control scheme is specifically designed for application scenarios where the cooling demand is high during the air conditioning system startup phase (i.e., the cooling demand signal is greater than or equal to the second preset threshold). It first establishes cooling capacity quickly by running a single compressor at full speed. After the system stabilizes, the subsequent operating mode is determined based on the updated cooling demand signal. This time-sharing switching control approach complements the static mode selection scheme protected in steps 11 to 13 above. Steps 11 to 13 focus on directly selecting the most suitable static operating mode under a given operating condition; while steps 21 to 23 and steps 31 to 33 focus on phased control during the special dynamic process of system startup, prioritizing rapid response and then adapting to steady-state demand.

[0066] Furthermore, steps 21 to 23 and steps 31 to 33 are completely identical in the initial stage. The difference lies in the changing trend of cooling demand after the system stabilizes. Steps 21 to 23 describe a control scheme where the cooling demand is high during startup and then drops to a moderate level after stabilization; while steps 31 to 33 describe a control scheme where the cooling demand is high during startup and remains at a relatively high level after stabilization. These two schemes respectively cover the two most common dynamic operating conditions of air conditioning systems in actual operation, together forming a complete branching solution for high cooling demand startup scenarios.

[0067] Therefore, through steps 21 to 23 above, when the cooling demand drops after system startup, switching to the five-arm half-cycle modulation mode achieves a smooth transition from high-speed response of a single unit to low-frequency maintenance of both units. This reduces energy consumption and single-unit load while ensuring cooling effect, demonstrating the system's energy-saving advantages under partial load conditions. Through steps 31 to 33 above, when the cooling demand remains high after system startup, closing the third switch puts the sixth arm into operation, forming a six-arm full SVPWM drive topology. This allows both compressors to run at full speed, meeting continuous high cooling demand and overcoming the technical bottleneck of limited voltage utilization in traditional five-arm topology dual-unit drive, demonstrating the system's performance guarantee capability under full load conditions.

[0068] Furthermore, steps 21 to 23 and steps 31 to 33 together constitute a complete control over the dynamic process of high-capacity startup and stable operation of the air conditioning system. Although the two branches have different directions, they share the same startup phase control strategy, respectively covering two operating conditions that may occur in actual operation: a decline in cooling demand after steady state and a sustained high cooling demand after steady state. In practical application scenarios, the air conditioning system may experience multiple start-ups and shutdowns or multiple load fluctuations every day. The dynamic switching logic protected by steps 21 to 23 and steps 31 to 33 can be repeatedly invoked during each startup process and each load change, ensuring that the system can achieve the comprehensive control goals of rapid response, stable operation, and energy efficiency under various operating conditions. Especially in application scenarios such as data centers that are extremely sensitive to temperature fluctuations, rapid cooling during startup and precise temperature control after steady state are equally important. Steps 21 to 23 and steps 31 to 33 together ensure optimized control of the system throughout the entire operating timeline.

[0069] The following detailed description, in conjunction with specific embodiments of this application, further explains and illustrates this application. These specific embodiments provide a frequency converter drive control method with compressor fault tolerance and multi-mode operation. Figure 3 The method steps in this specific implementation are as follows: Figure 5 As shown, it includes: Step 501: Obtain the system cooling demand status; Step 502: Determine if the system is running normally. If not, proceed to step 503; if yes, proceed to step 504. Step 503, execute Mode2; Step 504: Determine whether the cooling demand is greater than the second preset threshold. If yes, proceed to step 505; otherwise, proceed to step 508. Step 505: Determine whether the cooling demand is continuously greater than the second preset threshold. If yes, proceed to step 506; otherwise, proceed to step 507. Step 506: Execute Mode1 first, then execute Mode3; Step 507: Execute Mode1 first, then execute Mode2; Step 508: Determine whether the cooling demand is less than the first preset threshold. If yes, proceed to step 509; otherwise, proceed to step 510. Step 509, execute Mode1; Step 510: Execute Mode1 and Mode2.

[0070] The following provides further explanation of each mode; Mode 1: When the main controller detects that the cooling demand is low, the system only needs to turn on one compressor. When the main controller's start command is received, K1 closes, K2 and K3 open, S1-S3 bridge arms work, and S4-S6 bridge arms close. The SVPWM modulation algorithm is used to run compressor PMSM1 to drive the motor. At this time, the system can meet the requirements. Mode 2: When the main controller detects that the cooling demand is low, and if the compressor PMSM1 is damaged and needs maintenance during operation, K1 is disconnected, K2 is closed, K3 is disconnected, S3-S5 bridge arms are working, and S1, S2, and S6 bridge arms are closed. The SVPWM modulation algorithm is used to run the compressor PMSM2 to achieve stable system operation and ensure the normal operation of the system during maintenance and repair of motor 1.

[0071] Mode1 and Mode2 are used together: When the main controller has a moderate demand for cooling capacity, K1 is closed, K2 is closed, K3 is open, S1-S5 bridge arms are working, and S6 bridge arm is closed. The five-bridge arm half-cycle modulation algorithm is used to realize the simultaneous start of two compressors. However, due to the limitation of voltage utilization of the half-cycle algorithm, the motor runs at a low to medium frequency point.

[0072] Start Mode 1 first, then Mode 2: If the initial detection indicates a high demand for cooling capacity from the main controller, compressor 1 is already running, K1 is closed, K2 is open, K3 is open, S1-S3 bridge arms are working, and S4-S6 bridge arms are closed. Under these conditions, the compressor runs at its maximum frequency. Once the system stabilizes, the frequency requirement is not too high. When switching to Mode 1 and Mode 2, K1 is closed, K2 is closed, K3 is open, S1-S5 bridge arms are working, and S6 bridge arm is closed. This mode is suitable for situations where the initial cooling capacity demand is high, and the cooling capacity demand is moderate after stabilization.

[0073] Start with Mode 1, then switch to Mode 3: If the initial detection indicates a high cooling demand from the main controller, compressor 1 is already running, K1 is closed, K2 and K3 are open, S1-S3 bridge arms are engaged, and S4-S6 bridge arms are closed. Under these conditions, the compressor operates at its maximum frequency. After the system stabilizes, if the cooling demand remains high, switch to Mode 1 and Mode 3, with K1 closed, K2 open, K3 closed, and S1-S6 bridge arms engaged. This mode is suitable for situations where the initial cooling demand is high, and the demand remains high even after stabilization.

[0074] like Figure 6 As shown in the figure, this application provides an air conditioner control device, including a processor 611, a communication interface 612, a memory 613, and a communication bus 614, wherein the processor 611, the communication interface 612, and the memory 613 communicate with each other through the communication bus 614. Memory 613 is used to store computer programs; In one embodiment of this application, when the processor 611 executes the program stored in the memory 613, it implements the frequency conversion drive control method provided in any of the aforementioned method embodiments, and its function is similar, so it will not be described again here.

[0075] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the variable frequency drive control method provided in any of the foregoing method embodiments.

[0076] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0077] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented using software plus a general-purpose hardware platform, or of course, using hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0078] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0079] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A variable frequency drive control circuit, characterized in that, The variable frequency drive control circuit is used to drive the first compressor and the second compressor. The variable frequency drive control circuit includes: a DC bus, a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm, a fifth bridge arm, a sixth bridge arm, a first switch, a second switch, and a third switch. The first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm are all connected across the positive and negative terminals of the DC bus, and each of the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm has a midpoint for outputting a drive signal. The midpoints of the first bridge arm, the second bridge arm, and the third bridge arm are respectively connected to the three-phase winding of the first compressor via the first switch; The midpoints of the third bridge arm, the fourth bridge arm, and the fifth bridge arm are respectively connected to the three-phase winding of the second compressor via the second switch; The midpoint of the sixth bridge arm is connected via the third switch to one phase of the three-phase winding of the first compressor, or to one phase of the three-phase winding of the second compressor.

2. The variable frequency drive control circuit according to claim 1, characterized in that, The first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm are all composed of an upper bridge arm power switch and a lower bridge arm power switch connected in series. The first end of the upper bridge arm power switch is connected to the positive terminal of the DC bus, the second end of the upper bridge arm power switch is connected to the first end of the lower bridge arm power switch and forms the midpoint, and the second end of the lower bridge arm power switch is connected to the negative terminal of the DC bus.

3. The variable frequency drive control circuit according to claim 1, characterized in that, When the first switch is closed, the second switch is open, and the third switch is open, the first bridge arm, the second bridge arm, and the third bridge arm constitute a three-phase inverter bridge arm group for driving the first compressor.

4. The variable frequency drive control circuit according to claim 1, characterized in that, When the second switch is closed, the first switch is open, and the third switch is open, the third bridge arm, the fourth bridge arm, and the fifth bridge arm constitute a three-phase inverter bridge arm group for driving the second compressor.

5. The variable frequency drive control circuit according to claim 1, characterized in that, When the first switch is closed, the second switch is closed, and the third switch is open, the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm constitute a five-bridge-arm inverter bridge arm group for driving the first compressor and the second compressor.

6. A variable frequency drive control method based on the variable frequency drive control circuit of any one of claims 1 to 5, characterized in that, include: Acquire the cooling demand signal output by the air conditioning main control unit and the operating status signals of the first compressor and the second compressor; Based on the cooling demand signal and the operating status signal, determine the on / off combination status of the first switch, the second switch and the third switch, and determine the bridge arm combination to be put into operation; Based on the determined on / off combination state and the bridge arm combination, the corresponding bridge arm is controlled to output a drive signal using a preset modulation algorithm to drive the corresponding compressor to run.

7. The method according to claim 6, characterized in that, Based on the cooling demand signal and the operating status signal, the on / off combination status of the first switch, the second switch, and the third switch is determined, and the bridge arm combination to be put into operation is determined, including: When the cooling demand signal is less than a first preset threshold and the first compressor is in normal operation, it is determined that the first switch is closed, the second switch is open, and the third switch is open, and the bridge arm combination put into operation is determined to be the first bridge arm, the second bridge arm, and the third bridge arm; When the first compressor is in a fault or maintenance state, it is determined that the second switch is closed, the first switch is open, and the third switch is open, and the bridge arm combination put into operation is determined to be the third bridge arm, the fourth bridge arm, and the fifth bridge arm; When the cooling demand signal is greater than or equal to a first preset threshold and less than a second preset threshold, and both the first compressor and the second compressor are in normal operating condition, it is determined that the first switch is closed, the second switch is closed, and the third switch is open, and the bridge arm combination put into operation is determined to be the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm.

8. The method according to claim 7, characterized in that, The corresponding bridge arm is controlled to output a drive signal using a preset modulation algorithm, including: When the cooling demand signal is less than a first preset threshold and the first compressor is in normal operation, the first bridge arm, the second bridge arm and the third bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor to run. When the first compressor is in a fault or maintenance state, the third, fourth and fifth bridge arms are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the second compressor to run; When the cooling demand signal is greater than or equal to a first preset threshold and less than a second preset threshold, and both the first compressor and the second compressor are in normal operating condition, the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm and the fifth bridge arm are controlled to output drive signals using a five-bridge arm half-cycle modulation algorithm, and drive the first compressor and the second compressor to run.

9. The method according to claim 6, characterized in that, Based on the determined on / off combination state and the bridge arm combination, controlling the corresponding bridge arm to output a drive signal using a preset modulation algorithm to drive the corresponding compressor to operate includes: When the cooling demand signal is greater than or equal to the second preset threshold, the first switch is controlled to close, the second switch is controlled to open, and the third switch is controlled to open. The first bridge arm, the second bridge arm, and the third bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor to run at the maximum frequency. After the operating frequency of the first compressor reaches a preset frequency threshold, an updated cooling demand signal is obtained. When the updated cooling demand signal is less than the second preset threshold, the first switch is closed, the second switch is closed, and the third switch is opened. The first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, and the fifth bridge arm are controlled to output drive signals using a five-bridge arm half-cycle modulation algorithm to drive the first compressor and the second compressor to run.

10. The method according to claim 6, characterized in that, Based on the determined on / off combination state and the bridge arm combination, controlling the corresponding bridge arm to output a drive signal using a preset modulation algorithm to drive the corresponding compressor to operate includes: When the cooling demand signal is greater than or equal to the second preset threshold, the first switch is controlled to close, the second switch is controlled to open, and the third switch is controlled to open. The first bridge arm, the second bridge arm, and the third bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor to run at the maximum frequency. After the operating frequency of the first compressor reaches a preset frequency threshold, an updated cooling demand signal is obtained. When the updated cooling demand signal is greater than or equal to the second preset threshold, the first switch is closed, the second switch is opened, and the third switch is closed. The first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm, the fifth bridge arm, and the sixth bridge arm are controlled to output drive signals using a space vector pulse width modulation algorithm to drive the first compressor and the second compressor to operate.

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