Inverter compressor input voltage compensation method and device

Abstract

The invention provides an inverter compressor input voltage compensation method and device. The method comprises the following steps: acquiring a rear-end line voltage of an electric reactor, a phase voltage of a compressor, a phase current of the compressor and an angular speed of a motor in real time; analyzing the phase voltage and the phase current by adopting fast Fourier transform to obtain a power factor of the compressor side; calculating characteristic parameters for voltage compensation calculation based on the rear-end line voltage, the phase voltage, the phase current, the power factor and the motor angular velocity; according to the phase voltage and the phase current, indexing a characteristic coefficient in a predefined current-voltage partition coefficient table; and calculating a compensation voltage based on the characteristic parameter, the characteristic coefficient and the back-end line voltage. According to the invention, the influence of a compressor side power factor on voltage compensation is eliminated by adopting a mode of fast Fourier transform and a power conservation model, a current sensor at the rear end of an electric reactor is omitted, and compensation is realized only by utilizing an existing sampling circuit of a driver.

Description

Technical Field

[0001] This application relates to the field of compressor power supply control, and in particular to a method and apparatus for compensating the input voltage of a variable frequency compressor. Background Technology

[0002] In industrial variable frequency compressor drive systems, voltage sampling circuits are typically used to monitor the input power supply status to ensure stable system operation. Traditional solutions generally sample the input line voltage directly at the input reactor and use this sampled value to implement overvoltage, undervoltage, and phase loss protection for the system.

[0003] However, this traditional approach has the following technical limitations:

[0004] There is a systematic bias in voltage measurement: due to the non-negligible impedance characteristics of the input reactor (for example, the resistance R and inductance L of a typical 13A30mH reactor will introduce voltage drop), the voltage sampled at the back end of the reactor cannot accurately reflect the actual grid voltage at the front end. This bias is particularly significant when the load changes, which seriously affects the authenticity of the voltage sampling results.

[0005] The system's protection function carries a risk of misjudgment: overvoltage and undervoltage protection mechanisms should be based on the actual voltage at the reactor's upstream end. Traditional solutions directly use the voltage sampled from the reactor's downstream end as the basis for judgment. When the system load is heavy, the sampled voltage may be lower than the actual voltage due to the reactor's voltage drop. This can cause the system to falsely trigger undervoltage protection when the actual undervoltage condition has not been met, affecting the continuous operation of the equipment.

[0006] Insufficient adaptability to multiple compressors: When a single variable frequency drive drives multiple compressors of different models, the output power factor of each compressor is different. The traditional voltage compensation model with fixed parameters is difficult to adapt to such dynamic changes, resulting in a decrease in compensation effect and affecting the overall performance and energy efficiency of the system.

[0007] Currently, conventional solutions to the above problems also have obvious shortcomings:

[0008] Adding a front-end voltage sensor: Although it can obtain the actual voltage, it increases the system cost and is subject to installation space limitations;

[0009] Traditional compensation formulas that rely on input phase current: In practical systems, only a single input line voltage is often configured for sampling, and there is no available input phase current signal, making this type of compensation method impossible to implement;

[0010] Fixed parameter compensation model: cannot adapt to power factor changes caused by inductance differences under different compressor loads, and has poor versatility and adaptability.

[0011] Therefore, there is an urgent need for a voltage sampling and compensation method that can accurately reflect the real power grid status and adapt to the operating conditions of multiple compressors without increasing hardware costs, so as to improve the control accuracy and operational reliability of variable frequency compressor systems. Summary of the Invention

[0012] The purpose of this application is to provide a method and apparatus for compensating the input voltage of a variable frequency compressor, which can solve one or more of the above-mentioned problems.

[0013] To achieve the above and other related objectives, a first aspect of this application provides a method for compensating the input voltage of a variable frequency compressor. The method includes: real-time acquisition of the line voltage at the rear end of the reactor, the phase voltage of the compressor, the phase current of the compressor, and the angular velocity of the motor;

[0014] The phase voltage and phase current are analyzed using Fast Fourier Transform to obtain the power factor on the compressor side;

[0015] The characteristic parameters used for voltage compensation calculation are calculated based on the back-end line voltage, the phase voltage, the phase current, the power factor, and the motor angular velocity.

[0016] Based on the phase voltage and the phase current, index the characteristic coefficients in a predefined current-voltage partition coefficient table;

[0017] The reconstructed voltage after voltage compensation is calculated based on the characteristic parameters, the characteristic coefficients, and the back-end line voltage.

[0018] In some embodiments of the first aspect of this application, the condition for determining that the input voltage is too high includes the following characteristic parameters: power-voltage ratio, angular frequency coupling term, and nonlinear compensation term. The characteristic parameters for voltage compensation are calculated based on the back-end line voltage, the phase voltage, the phase current, the power factor, and the motor angular velocity using the following formula:

[0019] The formula for calculating the power-voltage ratio is:

[0020]

[0021] The formula for calculating the angular frequency coupling term is:

[0022]

[0023] The formula for calculating the nonlinear compensation term is:

[0024]

[0025] in, Indicates phase voltage. Indicates phase current, Indicates the power factor. Indicates the angular velocity of the motor. This indicates the line voltage at the back end.

[0026] In some embodiments of the first aspect of this application, a fast Fourier transform is used to analyze the phase voltage and the phase current to obtain the power factor on the compressor side, including:

[0027] Fast Fourier transform is performed on the phase voltage and the phase current respectively, and the fundamental voltage component corresponding to the phase voltage and the fundamental current component corresponding to the phase current are extracted.

[0028] The fundamental phase of the voltage and the fundamental phase of the current are calculated based on the fundamental voltage component and the fundamental current component, and the phase difference between the fundamental voltage phase and the fundamental current phase in the radian domain is calculated.

[0029] The power factor is obtained based on the phase difference.

[0030] In some embodiments of the first aspect of this application, characteristic coefficients are indexed in a predefined current-voltage partitioning coefficient table based on the phase voltage and the phase current, including:

[0031] Traverse the predefined current-voltage partitioning coefficient table to find the matching row corresponding to the phase current and the matching column corresponding to the phase voltage, respectively;

[0032] The corresponding feature coefficients are obtained based on the intersection of the matching row and the matching column.

[0033] In some embodiments of the first aspect of this application, obtaining the predefined current-voltage partitioning coefficient table includes:

[0034] During the initialization of the variable frequency compressor, an m×n test grid is established within a predefined current and voltage range, where m and n are integers greater than 1;

[0035] Five-tuple sample data are collected synchronously at each grid operating point. The five-tuple sample data includes: the back-end line voltage, the phase voltage, the phase current, the motor angular velocity, and the DC bus voltage.

[0036] Calculate the feature parameters of each sample based on the quintuple sample data;

[0037] Construct a least-squares matrix equation based on the aforementioned feature parameters;

[0038] The least squares matrix equation is solved by the determinant method to obtain the optimal eigenvalues.

[0039] The optimal characteristic coefficients are stored according to the current-voltage partition coefficient table.

[0040] In some embodiments of the first aspect of this application, an m×n test grid is established within a predefined current and voltage range, including:

[0041] The predefined current range is divided into m-1 intervals to obtain m current test points;

[0042] The predefined voltage range is divided into n-1 intervals to obtain n voltage test points;

[0043] The m×n test grid includes all combinations of current test points and voltage test points.

[0044] In some embodiments of the first aspect of this application, the formula for calculating the reconstruction voltage is:

[0045]

[0046] in, Indicates the power-voltage ratio. Indicates angular frequency coupling terms. Represents the nonlinear compensation term. , , For characteristic coefficients, This indicates the line voltage at the back end.

[0047] In some embodiments of the first aspect of this application, the method further includes:

[0048] Determine whether the compensation voltage exceeds the overvoltage threshold; if so, trigger overvoltage protection.

[0049] In some embodiments of the first aspect of this application, the method further includes:

[0050] The DC bus voltage is monitored in real time when the variable frequency compressor is in standby mode.

[0051] If the DC bus voltage continues to exceed the fault voltage threshold within a preset period, then the driver of the variable frequency compressor has a phase loss fault.

[0052] The signal output of the driver is cut off based on the phase loss fault, and the phase loss fault is saved to the log.

[0053] To achieve the above and other related objectives, a second aspect of this application provides a variable frequency compressor input voltage compensation device, applicable to the variable frequency compressor input voltage compensation method described in any of the first aspects of this application. The variable frequency compressor input voltage compensation device includes: a data acquisition module for real-time acquisition of the reactor's downstream line voltage, the compressor's phase voltage, the compressor's phase current, and the motor's angular velocity;

[0054] The power factor calculation module is used to analyze the phase voltage and the phase current using fast Fourier transform to obtain the power factor on the compressor side.

[0055] The feature parameter calculation module is used to calculate feature parameters for voltage compensation calculation based on the back-end line voltage, the phase voltage, the phase current, the power factor, and the motor angular velocity.

[0056] The characteristic coefficient acquisition module is used to index the characteristic coefficients in a predefined current-voltage partition coefficient table based on the phase voltage and the phase current;

[0057] The voltage compensation module is used to calculate the reconstructed voltage after voltage compensation based on the characteristic parameters, the characteristic coefficients, and the back-end line voltage.

[0058] As described above, the variable frequency compressor input voltage compensation method and apparatus of this application have the following beneficial effects:

[0059] Significantly reduced hardware costs: No additional current sampling circuit is required at the back end of the reactor. High-precision voltage reconstruction and compensation can be achieved by simply reusing the existing output current, output voltage and back-end line voltage sampling resources in the driver. While maintaining system performance, the number of components is effectively reduced, and hardware complexity and manufacturing costs are lowered.

[0060] The compensation accuracy is significantly improved: the compensation algorithm is built based on the power conservation model and fast Fourier transform, which effectively eliminates the model error caused by the power factor fluctuation of the compressor; the parameters are identified and fitted for different current and voltage ranges, so that the compensation model has excellent adaptability to operating conditions; by measuring the power factor in real time and dynamically correcting the compensation parameters, the problem of inductance difference when multiple compressors are running in parallel is effectively addressed.

[0061] Enhanced multi-compressor compatibility: By constructing a current-voltage partition coefficient table, independent optimization of parameters in different current-voltage ranges is achieved, improving the control consistency of the system under various load conditions; combined with real-time power factor feedback, compensation accuracy is maintained under different motor types and load conditions, improving the overall system compatibility.

[0062] Improved system protection reliability: The proposed compensation method accurately restores the reactor front-end voltage, providing a reliable basis for overvoltage, undervoltage, and phase loss protection functions; the detection logic based on reconstructed voltage effectively avoids false protection actions caused by sampling deviations, enhancing the continuity and safety of system operation. Attached Figure Description

[0063] Figure 1 The diagram shown is a structural schematic of the industrial variable frequency compressor drive system described in an embodiment of this application.

[0064] Figure 2 The diagram shown is a flowchart illustrating the inverter compressor input voltage compensation method described in an embodiment of this application.

[0065] Figure 3 The diagram shows a flowchart illustrating the calculation of the fundamental voltage and fundamental current components using Fast Fourier Transform as described in an embodiment of this application.

[0066] Figure 4 The diagram shows a flowchart illustrating the calculation of the power factor on the compressor side according to an embodiment of this application.

[0067] Figure 5 The diagram shows a flowchart of the index characteristic coefficients in the predefined current-voltage partition coefficient table described in this application embodiment.

[0068] Figure 6 The diagram shows a flowchart of obtaining a predefined current-voltage partition coefficient table as described in an embodiment of this application.

[0069] Figure 7 The diagram shown is a structural schematic of the inverter compressor input voltage compensation device described in an embodiment of this application.

[0070] Label Explanation

[0071] 70 Variable frequency compressor input voltage compensation device 71 Filtering module 72 PTC precharge circuit module 73 rectifier module 74 PFC circuit module 75 Capacitor energy storage module S21~S27 step Detailed Implementation

[0072] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0073] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0074] like Figure 1 As shown, this is an industrial variable frequency compressor drive system. The system mainly consists of an AC power input unit, an inductor filter unit, a variable frequency drive unit, and a compressor load unit, forming a complete electromechanical energy conversion chain.

[0075] The mains input unit is a three-phase 230V mains power supply, which is a standard industrial power supply configuration.

[0076] The core component of the reactor filter unit is the reactor. The reactor suppresses harmonic currents on the grid side, improves the system power factor, limits the inrush current, and protects downstream power devices.

[0077] The variable frequency drive unit includes a signal acquisition unit, a control unit, and a protection unit. The signal acquisition unit is equipped with multiple high-precision ADC synchronous sampling channels to sample the reactor's downstream line voltage, compressor phase voltage, and compressor phase current. The sampling point for the reactor's downstream line voltage is located between the reactor's output terminal and the inverter's input terminal. The sampling point for the compressor phase voltage is located between the inverter's output and the compressor windings. The sampling point for the compressor phase current is located in the motor's phase line circuit. The control unit is used to implement V / F control or vector control algorithms and generate PWM drive signals. The protection unit implements overvoltage / undervoltage protection, phase loss detection, and fault response based on the reactor's downstream line voltage.

[0078] The following will describe in detail the principle and implementation of the inverter compressor input voltage compensation method and device according to the embodiments of this application, with reference to the accompanying drawings, so that those skilled in the art can understand the inverter compressor input voltage compensation method and device of this embodiment without creative effort.

[0079] To facilitate understanding of the embodiments of this application, the appendix will be consulted first. Figure 2 Detailed explanation, such as Figure 2 As shown, the inverter compressor input voltage compensation method of this application embodiment includes the following steps S21 to S25.

[0080] Step S21: Real-time acquisition of the reactor's back-end line voltage, compressor's phase voltage, compressor's phase current, and motor angular velocity.

[0081] In this embodiment, by Figure 1The signal acquisition unit shown is configured with multiple high-precision ADC synchronous sampling channels to sample the back-end line voltage of the reactor, the phase voltage of the compressor, and the phase current of the compressor. The sampling point for the back-end line voltage is located between the output terminal of the reactor and the input terminal of the frequency converter, the sampling point for the phase voltage is located between the output of the frequency converter and the compressor winding, and the sampling point for the phase current is located in the motor phase line circuit.

[0082] In this embodiment, the motor angular velocity is obtained in real time in the motor control algorithm based on the control unit.

[0083] Step S22: Use Fast Fourier Transform to analyze the phase voltage and phase current to obtain the power factor on the compressor side.

[0084] In this embodiment, fast Fourier transform is performed on the phase voltage and phase current respectively, and the fundamental voltage component corresponding to the phase voltage and the fundamental current component corresponding to the phase current are extracted.

[0085] The fundamental phases of the voltage and current are calculated based on the fundamental voltage and current components, respectively. The phase difference between the fundamental voltage and current phases in the radian domain is then calculated, and the power factor is obtained based on the phase difference.

[0086] Specifically, such as Figure 3 As shown, the phase voltage and phase current are processed using Fast Fourier Transform (FFT) to obtain the corresponding fundamental voltage and fundamental current components:

[0087] Before performing the calculation, the input data is first reversed and rearranged.

[0088] The FFT is set to 5 processing levels, with each level containing 4 butterfly operation stages, and the FFT has 32 points.

[0089] In order Figure 3 The process shown is used to calculate and extract the fundamental components of the phase voltage and phase current, respectively. The fundamental components include phase and amplitude.

[0090] Furthermore, such as Figure 4 As shown, after the phase voltage and phase current are detected and the fast Fourier transform is completed, the difference between the obtained voltage fundamental component and current fundamental component is calculated to obtain the phase difference. Then, the power factor on the compressor side is calculated using the basic formula of power factor.

[0091] Step S23: Calculate the characteristic parameters used for voltage compensation calculation based on the back-end line voltage, phase voltage, phase current, power factor, and motor angular velocity.

[0092] In this embodiment, the characteristic parameters include: power-voltage ratio, angular frequency coupling term, and nonlinear compensation term. The characteristic parameters used for voltage compensation, calculated based on the back-end line voltage, phase voltage, phase current, power factor, and motor angular velocity, include the following formula:

[0093] The formula for calculating the power-voltage ratio is:

[0094]

[0095] The formula for calculating the angular frequency coupling term is:

[0096]

[0097] The formula for calculating the nonlinear compensation term is:

[0098]

[0099] in, Indicates phase voltage. Indicates phase current, Indicates the power factor. Indicates the angular velocity of the motor. This indicates the line voltage at the back end.

[0100] Step S24: Index the characteristic coefficients in the predefined current-voltage partition coefficient table based on the phase voltage and phase current.

[0101] In this embodiment, as Figure 5 As shown, based on the acquired phase voltage and phase current, the voltage range and current range are traversed respectively, indexed to the column corresponding to the phase voltage and the row corresponding to the phase current, and the corresponding side parameter coefficients are extracted according to the intersection of the row and column.

[0102] The process of obtaining the predefined current-voltage partitioning coefficient table includes:

[0103] During the initialization of the variable frequency compressor, an m×n test grid is established within a predefined current and voltage range, where m and n are integers greater than 1;

[0104] Five-tuple sample data are collected synchronously at each grid operating point. The five-tuple sample data includes: back-end line voltage, phase voltage, phase current, motor angular velocity, and DC bus voltage.

[0105] Calculate the feature parameters of each sample based on the quintuple sample data;

[0106] Constructing least-squares matrix equations based on feature parameters;

[0107] The optimal eigenvalues ​​are obtained by solving the least squares matrix equation using the determinant method.

[0108] The optimal characteristic coefficients are stored in the current-voltage partition coefficient table.

[0109] Specifically, such as Figure 6 As shown, a data structure is defined to store data such as compensation values, parameter coefficients, and errors. This data structure is prepared for subsequent burning to the DSP Flash memory.

[0110] The predefined current range and predefined voltage range are divided into multiple segments for subsequent segment parameter coefficient calculations. Specifically, the predefined current range is divided into m-1 intervals to obtain m current test points; the predefined voltage range is divided into n-1 intervals to obtain n voltage test points; the m×n test grid contains all combinations of current test points and voltage test points.

[0111] Create a three-dimensional array to store the calculated parameter coefficients. Optional, the three-dimensional array is represented as [current segment, voltage segment, parameter coefficients];

[0112] Under each current segment, each voltage segment is processed cyclically, and the current-voltage combination is checked to see if it is within the effective measurement or calculation range.

[0113] Based on the current-voltage combination, the solution function is invoked within the effective measurement or calculation range to calculate the parameter coefficients. , , Preferably, the calculation is performed using the least squares method;

[0114] In calculating parameter coefficients , , During the process, the determinant of the parameter coefficient matrix is ​​checked to see if it is 0. If it is 0, it means that the current-voltage combination has no unique solution, so the parameter coefficients are set to 0. Otherwise, Cramer's rule is used to solve the linear equation system to obtain the result. , , ;

[0115] The calculated parameter coefficients are stored in the corresponding positions in the data structure;

[0116] Iterate through all current-voltage combinations, solve for the corresponding parameter coefficients, store them in the corresponding positions in the data structure, and output them as a current-voltage partition coefficient table.

[0117] Step S25: Calculate the reconstructed voltage after voltage compensation based on characteristic parameters, characteristic coefficients and back-end line voltage.

[0118] In this embodiment, the formula for calculating the reconfiguration voltage is:

[0119]

[0120] in, Indicates the power-voltage ratio. Indicates angular frequency coupling terms. Represents the nonlinear compensation term. , , For characteristic coefficients, This indicates the line voltage at the back end.

[0121] The derivation process of the above formula for calculating the reconstructed voltage is provided below.

[0122] The input current is calculated based on the principle of power conservation and energy conversion relationships. :

[0123] Output power is :

[0124]

[0125] Input power is :

[0126]

[0127] in, Indicates phase voltage. Indicates phase current, Indicates the power factor. Indicates system efficiency. This indicates the line voltage at the back end of the reactor. Indicates the input phase current. This represents the input-side power factor.

[0128] Based on the above formulas for calculating input power and output power, the input current can be obtained. :

[0129]

[0130] The acquired input current By incorporating the physical compensation model, the measurable parameter, the line voltage at the reactor's downstream end, is extracted. :

[0131]

[0132] Further simplification yields:

[0133]

[0134] Among them, the line voltage at the back end of the reactor This is the reconfiguration voltage.

[0135] In some implementations, the input voltage compensation method for variable frequency compressors also includes:

[0136] Step S26: Determine whether the reconstructed voltage exceeds the overvoltage threshold. If so, trigger overvoltage protection.

[0137] Step S27: When the inverter compressor is in standby mode, the DC bus voltage is monitored in real time; if the DC bus voltage continues to exceed the fault voltage threshold within a preset period, the inverter compressor driver has a phase loss fault; based on the phase loss fault, the driver signal output is cut off and the phase loss fault is saved to the log.

[0138] In this embodiment, considering the bus rise margin caused by a 30% phase loss, the fault voltage threshold is set to 1.3 × 1.414 × If the DC bus voltage exceeds the fault voltage threshold for 10 control cycles, it is determined to be an input phase loss fault. All PWM signal inputs are immediately cut off, and the fault status is recorded in the log.

[0139] The scope of protection of the variable frequency compressor input voltage compensation method in this application is not limited to the execution order of the steps listed in this embodiment. Any solution implemented by adding, subtracting, or replacing steps in the prior art based on the principles of this application is included within the scope of protection of this application.

[0140] This application also provides a variable frequency compressor input voltage compensation device. The variable frequency compressor input voltage compensation device can implement the variable frequency compressor input voltage compensation method of this application. However, the implementation device of the variable frequency compressor input voltage compensation method of this application includes, but is not limited to, the structure of the variable frequency compressor input voltage compensation device listed in this embodiment. All structural modifications and substitutions of the prior art made according to the principle of this application are included within the protection scope of this application.

[0141] It should be understood that the module division in the embodiments of this application is illustrative and only represents a logical functional division. In actual implementation, there may be other division methods. Furthermore, the functional modules in the various embodiments of this application can be integrated into a single processor, exist as separate physical entities, or be integrated into a single module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0142] Please see Figure 7 The image shows a variable frequency compressor input voltage compensation device provided in this application embodiment. The variable frequency compressor input voltage compensation device 70 includes:

[0143] The acquisition module 71 is used to acquire the line voltage at the back end of the reactor, the phase voltage of the compressor, the phase current of the compressor, and the angular velocity of the motor in real time.

[0144] The power factor calculation module 72 is used to analyze the phase voltage and phase current using fast Fourier transform to obtain the power factor on the compressor side.

[0145] The characteristic parameter calculation module 73 is used to calculate the characteristic parameters for voltage compensation calculation based on the back-end line voltage, phase voltage, phase current, power factor and motor angular velocity.

[0146] The characteristic coefficient acquisition module 74 is used to index the characteristic coefficients in a predefined current-voltage partition coefficient table based on the phase voltage and phase current;

[0147] Voltage compensation module 75 is used to calculate compensation voltage based on characteristic parameters, characteristic coefficients and back-end line voltage.

[0148] Since the specific implementation of this embodiment corresponds to the aforementioned method embodiment, the same details will not be repeated here. Those skilled in the art should also understand that the division of each module in the embodiment of Figure x is only a logical functional division. In actual implementation, all or part of them can be integrated into one or more physical entities. These modules can all be implemented in software through processing element calls, or all of them can be implemented in hardware. Alternatively, some modules can be implemented in software through processing element calls, and some modules can be implemented in hardware.

[0149] It should be noted that the above division of modules is merely a logical functional division. In actual implementation, they can be fully or partially integrated into a single physical entity, or they can be physically separated. Furthermore, these modules can be implemented entirely in software via processing element calls; they can be fully implemented in hardware; or some modules can be implemented by processing element calls to software, while others are implemented in hardware. For example, module x can be a separate processing element, or it can be integrated into a chip in the aforementioned device. Alternatively, it can be stored as program code in the memory of the aforementioned device, and its function can be called and executed by a processing element of the device. The implementation of other modules is similar. Moreover, these modules can be fully or partially integrated together, or they can be implemented independently. The processing element here can be an integrated circuit with signal processing capabilities. In the implementation process, the steps of the above method or the various modules can be completed through integrated logic circuits in the hardware of the processor element or through software instructions.

[0150] It should be noted that, in the embodiments of this application, the words "exemplary" or "for example" indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0151] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, or methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules / units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or units may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the shown or discussed mutual couplings or direct couplings or communication connections may be through some interfaces, or indirect couplings or communication connections between devices, modules, or units, and may be electrical, mechanical, or other forms. Modules / units described as separate components may or may not be physically separate. Components shown as modules / units may or may not be physical modules, i.e., they may be located in one place or distributed across multiple network units. Some or all of the modules / units can be selected to achieve the purpose of the embodiments of this application according to actual needs. For example, the functional modules / units in the various embodiments of this application may be integrated into one processing module, or each module / unit may exist physically separately, or two or more modules / units may be integrated into one module / unit.

[0152] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0153] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0154] The descriptions of the processes or structures corresponding to the above figures each have their own emphasis. For parts of a process or structure that are not described in detail, please refer to the relevant descriptions of other processes or structures.

[0155] In summary, this application provides a method and apparatus for compensating the input voltage of a variable frequency compressor. This invention significantly reduces hardware costs. Based on a power conservation model and fast Fourier transform, a compensation algorithm is constructed to dynamically correct compensation parameters, thereby improving compensation accuracy. By constructing a current-voltage partitioned coefficient table, independent optimization of parameters in different current-voltage ranges is achieved, enhancing the control consistency of the system under various load conditions. Combined with real-time power factor feedback, compensation accuracy is maintained under different motor types and load conditions, improving the overall system compatibility. Therefore, this application effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0156] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A method of input voltage compensation for a variable frequency compressor, the method comprising: The method comprises: collecting a back-end line voltage of the reactor, a phase voltage of the compressor, a phase current of the compressor and an angular velocity of the motor in real time; analyzing the phase voltage and the phase current by using fast Fourier transform to obtain a power factor on the compressor side; calculating a characteristic parameter for voltage compensation calculation based on the back-end line voltage, the phase voltage, the phase current, the power factor and the angular velocity of the motor; indexing a characteristic coefficient in a predefined current-voltage partition coefficient table according to the phase voltage and the phase current; calculating a reconstructed voltage after voltage compensation based on the characteristic parameter, the characteristic coefficient and the back-end line voltage.

2. The input voltage compensation method of a variable frequency compressor according to claim 1, characterized in that, The characteristic parameter comprises a power-voltage ratio, an angular frequency coupling term and a nonlinear compensation term, and the calculation of the characteristic parameter for voltage compensation based on the back-end line voltage, the phase voltage, the phase current, the power factor and the angular velocity of the motor comprises using the following formula: The calculation formula of the power-voltage ratio is: ； The calculation formula of the angular frequency coupling term is: ； The calculation formula of the nonlinear compensation term is: ； wherein, denotes the phase voltage, denotes the phase current, denotes the power factor, denotes the motor angular velocity, denotes the back-end line voltage.

3. The input voltage compensation method of a variable frequency compressor according to claim 1, characterized in that, The analysis of the phase voltage and the phase current by using fast Fourier transform to obtain a power factor on the compressor side comprises: respectively performing fast Fourier transform on the phase voltage and the phase current, and extracting a voltage fundamental component corresponding to the phase voltage and a current fundamental component corresponding to the phase current; calculating a voltage fundamental phase and a current fundamental phase based on the voltage fundamental component and the current fundamental component, and calculating a phase difference value of the voltage fundamental phase and the current fundamental phase in the radian domain; obtaining the power factor according to the phase difference value.

4. The input voltage compensation method of a variable frequency compressor according to claim 1, characterized in that, The indexing of the characteristic coefficient in the predefined current-voltage partition coefficient table according to the phase voltage and the phase current comprises: traversing the predefined current-voltage partition coefficient table to find a matching row corresponding to the phase current and a matching column corresponding to the phase voltage respectively; obtaining a corresponding characteristic coefficient based on the intersection of the matching row and the matching column.

5. The input voltage compensation method of a variable frequency compressor according to claim 1, characterized in that, The obtaining of the predefined current-voltage partition coefficient table comprises: At the initialization of the variable frequency compressor, a test grid is established within a predefined current range and voltage range where m and n are integers greater than 1; synchronously collecting five-tuple sample data at each grid operating point, the five-tuple sample data comprising the back-end line voltage, the phase voltage, the phase current, the angular velocity of the motor and a DC bus voltage; calculating characteristic parameters of each sample based on the five-tuple sample data; constructing a least square matrix equation based on the characteristic parameters; solving the least square matrix equation by a determinant method to obtain optimal characteristic coefficients; storing the optimal characteristic coefficients in a current-voltage partition coefficient table.

6. The input voltage compensation method of a variable frequency compressor according to claim 5, characterized in that, Establish within the predefined current and voltage ranges The test grid includes: equally divide the predefined current range into m intervals to obtain m current test points; Divide the predefined voltage range into equal parts. Given n intervals, n voltage test points are obtained; The The test grid of the combination of all current test points and voltage test points.

7. The variable frequency compressor input voltage compensation method of claim 1, wherein, The calculation formula of the reconstructed voltage is: ； wherein represents the power-voltage ratio, represents the angular frequency coupling term, represents the non-linear compensation term, , , are characteristic coefficients, represents the back-end line voltage.

8. The variable frequency compressor input voltage compensation method of claim 1, wherein, The method further comprises: judging whether the reconstructed voltage exceeds an overvoltage threshold, and if so, triggering an overvoltage protection.

9. The variable frequency compressor input voltage compensation method of claim 1, wherein, The method further comprises: detecting a DC bus voltage in real time when the variable frequency compressor is in a standby state; if the DC bus voltage continuously exceeds a fault voltage threshold in a preset period, there is an open-phase fault of a driver of the variable frequency compressor; based on the open-phase fault, cutting off a signal output of the driver and saving the open-phase fault into a log.

10. A variable frequency compressor input voltage compensation device, characterized by, The device comprises: The collection module is configured to collect the back-end line voltage of the reactor, the phase voltage of the compressor, the phase current of the compressor, and the angular velocity of the motor in real time. The power factor calculation module is configured to analyze the phase voltage and the phase current by using fast Fourier transform to obtain the power factor on the compressor side. The characteristic parameter calculation module is configured to calculate characteristic parameters for voltage compensation calculation based on the back-end line voltage, the phase voltage, the phase current, the power factor, and the angular velocity of the motor. The characteristic coefficient acquisition module is configured to index a characteristic coefficient in a pre-defined current-voltage partition coefficient table according to the phase voltage and the phase current. The voltage compensation module is configured to calculate a reconstructed voltage after voltage compensation based on the characteristic parameters, the characteristic coefficient, and the back-end line voltage.

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