Calculation method and device for input voltage of three-phase AC inverter

Abstract

The present application provides a method and device for calculating the input voltage of a three-phase AC inverter, which is applied to the field of inverter technology. The method includes: obtaining a first parameter and a second parameter of the three-phase AC inverter; determining a target compensation coefficient corresponding to the target current effective value based on the target current effective value; wherein the target compensation coefficient is used to compensate for the error of current harmonics under different loads; determining the effective value of the voltage drop of the inductor based on the target compensation coefficient and the first parameter; determining the effective value of the input voltage based on the effective value of the voltage drop and the effective value of the phase voltage. The method can obtain the input voltage of the three-phase AC inverter without increasing the hardware cost.

Description

Technical Field

[0001] The present application relates to the technical field of frequency converters, and more specifically, to a method and device for calculating the input voltage of a three-phase AC frequency converter in the technical field of frequency converters. Background Art

[0002] The three-phase AC inverter is a typical drive structure, which consists of a rectifier, a DC side reactor, a DC bus capacitor and an inverter. The input quantity of the three-phase AC inverter mainly includes the three-phase input voltage V ac , three-phase input current I ac And input power factor PF. In order to limit the voltage frequency, current frequency, overvoltage, undervoltage and overcurrent protection on the input side, it is usually necessary to obtain the input quantity.

[0003] In the related art, a voltage sampling circuit is used to obtain the input voltage V of the three-phase AC inverter. ac , but this approach will result in excessively high hardware costs.

[0004] So, how to obtain the input voltage V of the AC inverter without increasing the hardware cost? ac It has become an urgent problem to be solved. Summary of the invention

[0005] The present application provides a method and device for calculating the input voltage of a three-phase AC inverter. The method can obtain the input voltage of the three-phase AC inverter without increasing the hardware cost.

[0006] In a first aspect, a method for calculating an input voltage of a three-phase AC inverter is provided, the method comprising:

[0007] Acquire a first parameter and a second parameter of the three-phase AC inverter; wherein the first parameter includes a target current effective value of an input current of the three-phase AC inverter, a fundamental angular frequency of the input current, and an inductance of an inductor in the three-phase AC inverter; and the second parameter is an effective value of a phase voltage at the rear end of the inductor;

[0008] Based on the target current effective value, determining a target compensation coefficient corresponding to the target current effective value; wherein the target compensation coefficient is used to compensate for errors of current harmonics under different loads;

[0009] Determining an effective value of a voltage drop of the inductor based on the target compensation coefficient and the first parameter;

[0010] The effective value of the input voltage is determined based on the voltage drop effective value and the phase voltage effective value.

[0011] In an embodiment of the present application, a first parameter and a second parameter of a three-phase AC inverter are obtained; based on the target current effective value, a target compensation coefficient corresponding to the target current effective value is determined; based on the target compensation coefficient and the first parameter, the effective value of the voltage drop of the inductor is determined; based on the effective value of the voltage drop and the effective value of the phase voltage, the effective value of the input voltage is determined; in the above scheme, since the corresponding compensation coefficient can be determined by obtaining the effective value of the input current of the three-phase AC inverter, a more accurate effective value of the voltage drop can be calculated based on the compensation coefficient and the effective value of the current of the input current, the fundamental angular frequency and the inductance of the inductor. Combined with the more accurate effective value of the voltage drop and the obtained effective value of the phase voltage at the rear end of the inductor, a more accurate effective value of the input voltage can be obtained, so there is no need to add a sampling circuit on the input side of the three-phase AC inverter. It only needs to calibrate the compensation coefficient in advance to calculate a more accurate input voltage; therefore, the above scheme can obtain the input voltage of the three-phase AC inverter without increasing the hardware cost.

[0012] In combination with the first aspect, in some possible implementations, determining a target compensation coefficient corresponding to the target current effective value based on the target current effective value includes:

[0013] Based on the target current effective value and the fitting function, a target compensation coefficient is calculated; wherein the fitting function is used to indicate the relationship between the current effective value and the compensation coefficient.

[0014] In the embodiment of the present application, the target compensation coefficient corresponding to the current target current effective value can be calculated by the fitting function, so that the error of the current harmonic under the current load can be compensated by the target compensation coefficient.

[0015] In combination with the first aspect and the above implementation manner, in some possible implementation manners, obtaining the first parameter of the three-phase AC inverter includes:

[0016] Obtaining the bus voltage and input power of the three-phase AC inverter;

[0017] The target current effective value is determined based on the bus voltage and the input power.

[0018] In the embodiment of the present application, the target current effective value can be determined by the acquired bus voltage and input power, so as to facilitate the subsequent selection of a suitable compensation coefficient for compensation based on the target current effective value.

[0019] In combination with the first aspect and the above implementation manner, in some possible implementation manners, obtaining the first parameter and the second parameter of the three-phase AC inverter includes:

[0020] Obtaining the bus voltage of the three-phase AC inverter;

[0021] Based on the bus voltage, the phase voltage effective value is determined.

[0022] In the embodiment of the present application, since the effective value of the phase voltage can be determined by obtaining the bus voltage, it is convenient to subsequently calculate the effective value of the input voltage based on the effective value of the phase voltage.

[0023] In combination with the first aspect and the above implementation manner, in some possible implementation manners, determining the effective value of the phase voltage based on the bus voltage includes:

[0024] Based on the bus voltage, an average value of the effective value of the line voltage at the rear end of the inductor is obtained; wherein the average value of the effective value of the line voltage is the average value of the sum of the squares of the line voltage at the rear end of each capacitor in the three-phase AC inverter;

[0025] The phase voltage effective value is determined based on the average value of the line voltage effective values.

[0026] In the embodiment of the present application, since the average value of the effective value of the line voltage at the rear end of the inductor can be obtained based on the bus voltage, the accurate effective value of the phase voltage can be obtained based on the average value of the effective value of the line voltage.

[0027] In combination with the first aspect and the above implementation manner, in some possible implementation manners, obtaining the average value of the effective value of the line voltage at the rear end of the inductor based on the bus voltage includes:

[0028] Based on the relationship between the area enclosed by the line voltage at the rear end of each capacitor and the area enclosed by the bus voltage, a target association relationship is obtained; wherein the target association relationship is used to indicate the relationship between the bus voltage and the average value of the effective value of the line voltage;

[0029] Based on the bus voltage and the target association relationship, an average value of the effective value of the line voltage is obtained.

[0030] In an embodiment of the present application, since a target association relationship can be obtained based on the relationship between the area enclosed by the line voltage at the rear end of each capacitor and the area enclosed by the bus voltage, when the bus voltage is obtained, the average value of the effective value of the line voltage can be accurately calculated based on the bus voltage and the target association relationship.

[0031] In combination with the first aspect and the foregoing implementation manner, in some possible implementation manners, determining the effective value of the voltage drop of the inductor based on the target compensation coefficient and the first parameter includes:

[0032] The effective value of the pressure drop is determined based on the following formula:

[0033] V Lin= Kω1L I ac ;

[0034] Among them, V Lin represents the effective value of the inductor voltage drop, K represents the target compensation coefficient, ω1 represents the fundamental angular frequency, L represents the inductance, I ac Indicates the target current effective value.

[0035] In an embodiment of the present application, after the target compensation coefficient and the first parameter are obtained, the target current effective value can be accurately calculated based on a specific calculation formula, thereby facilitating the subsequent calculation of an accurate input voltage.

[0036] In a second aspect, a device for calculating input voltage of a three-phase AC inverter is provided, the device comprising:

[0037] A first acquisition module, used to acquire a first parameter and a second parameter of the three-phase AC inverter; wherein the first parameter includes a target current effective value of an input current of the three-phase AC inverter, a fundamental angular frequency of the input current, and an inductance of an inductor in the three-phase AC inverter; and the second parameter is an effective value of a phase voltage at a rear end of the inductor;

[0038] A first determination module, configured to determine a target compensation coefficient corresponding to the target current effective value based on the target current effective value; wherein the target compensation coefficient is used to compensate for errors of current harmonics under different loads;

[0039] A second determination module, configured to determine an effective value of a voltage drop of the inductor based on the target compensation coefficient and the first parameter;

[0040] The third determination module is used to determine the effective value of the input voltage based on the effective value of the voltage drop and the effective value of the phase voltage.

[0041] In a third aspect, an air conditioner is provided, comprising a processor, a memory, a three-phase AC inverter, and a load; the processor is communicatively connected to the memory; the three-phase AC inverter is coupled to the processor and connected to the load;

[0042] The processor controls the rotation speed of the load through the three-phase AC inverter;

[0043] The memory stores computer-executable instructions;

[0044] The processor executes the computer-executable instructions stored in the memory to implement the method as described in the first aspect or any possible implementation manner of the first aspect.

[0045] In a fourth aspect, a computer program product is provided, comprising: a computer program code, which, when executed on a computer, enables the computer to execute the method in the first aspect or any possible implementation of the first aspect.

[0046] In a fifth aspect, a computer-readable storage medium is provided, which stores a computer program code. When the computer program code runs on a computer, the computer executes the method in the above-mentioned first aspect or any possible implementation manner of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural schematic diagram of a three-phase AC inverter provided in an embodiment of the present application;

[0048] Figure 2 It is a flowchart of a method for calculating the input voltage of a three-phase AC inverter provided in an embodiment of the present application;

[0049] Figure 3 It is a schematic diagram of the relationship between the line voltage at the rear end of the inductor and the bus voltage of a three-phase AC inverter under heavy load provided by an embodiment of the present application;

[0050] Figure 4 This is a schematic diagram of the relationship between the line voltage behind the inductor and the bus voltage of a three-phase AC inverter under light load provided by an embodiment of the present application;

[0051] Figure 5 It is a phase relationship diagram of the phase voltage at the rear end of the inductor and the input current of the phase when the three-phase AC inverter is lightly loaded, provided in an embodiment of the present application;

[0052] Figure 6 It is a phase relationship diagram of the phase voltage at the rear end of the inductor and the input current of the phase when the three-phase AC inverter provided by the embodiment of the present application is under medium load;

[0053] Figure 7 It is a phase relationship diagram of the phase voltage at the rear end of the inductor and the input current of the phase when the three-phase AC inverter is overloaded, provided in an embodiment of the present application;

[0054] Figure 8 It is a schematic diagram of the relationship between the inductor voltage drop, the inductor rear end voltage and the input voltage of a three-phase AC inverter under light load provided by an embodiment of the present application;

[0055] Fig. 9 It is a schematic diagram of the relationship between the inductor voltage drop, the inductor rear end voltage and the input voltage of a three-phase AC inverter under heavy load provided by an embodiment of the present application;

[0056] Fig.10It is a flowchart of another method for calculating the input voltage of a three-phase AC inverter provided in an embodiment of the present application;

[0057] Fig.11 It is a structural schematic diagram of a device for calculating the input voltage of a three-phase AC inverter provided in an embodiment of the present application;

[0058] Fig.12 It is a structural schematic diagram of an air conditioner provided in an embodiment of the present application. DETAILED DESCRIPTION

[0059] The technical solution in the present application will be described clearly and in detail below in conjunction with the accompanying drawings. In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "multiple" means two or more than two.

[0060] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as suggesting or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features.

[0061] Figure 1 A schematic diagram of the structure of a three-phase AC inverter provided in an embodiment of the present application.

[0062] like Figure 1 As shown, the three-phase AC inverter includes an AC power module 110, a reactance module 120, a rectifier module 130, a DC bus capacitor C, and an inverter module 140. Among them, the first end of the rectifier module 130 is connected to the AC power module 110 through the reactance module 120, the second end of the rectifier module 130 is connected to the first end of the DC bus capacitor C and the first end of the inverter module 140, and the third end of the rectifier module can be connected to the second end of the DC bus capacitor and the second end of the inverter module 140. The third end of the inverter module 140 can be connected to a load (such as a motor).

[0063] Exemplarily, the rectifier module 130, i.e., the rectifier, is used to convert the three-phase AC power into DC power; the DC link usually includes a large-capacity electrolytic capacitor (such as Figure 1 The capacitor C in the inverter module 140 is used to smooth the rectified DC voltage; the inverter module 140, that is, the inverter, is used to convert the DC power into a three-phase AC power with adjustable frequency and voltage.

[0064] Optionally, the three-phase AC inverter further includes a filter inductor, which is installed at the output end of the inverter and is used to filter out high-frequency harmonics in the inverter output, reduce fluctuations in the output current, and improve the quality of the current.

[0065] It should be noted that the above Figure 1 The description is made by taking a three-phase AC power supply as an example, and the present application does not limit the specific structure of the AC inverter.

[0066] Above Figure 1 The three-phase AC inverter shown can control the output voltage of the AC power supply. Figure 1 The speed of the motor in.

[0067] The following will describe in detail the method for calculating the input voltage of the three-phase AC inverter provided in the embodiment of the present application in conjunction with the above-mentioned drawings.

[0068] Figure 2 It is a flow chart of a method for calculating the input voltage of a three-phase AC inverter provided in an embodiment of the present application.

[0069] For example, Figure 2 The calculation method of the input voltage of the three-phase AC inverter shown in FIG. Figure 1 The three-phase AC inverter shown in the figure may be used for execution; or it may be used by an electronic device having a processing function, such as an air conditioner for execution.

[0070] like Figure 2 As shown, the method may include S201 to S204, and S201 to S204 are described in detail below.

[0071] S201, obtaining a first parameter and a second parameter of a three-phase AC inverter.

[0072] The first parameter includes the target current effective value of the input current of the three-phase AC inverter, the fundamental angular frequency of the input current and the inductance of the inductor in the three-phase AC inverter; the second parameter is the effective value of the phase voltage at the rear end of the inductor.

[0073] It should be noted that phase voltage refers to the voltage between any phase (live wire) and the neutral wire, such as Figure 1 The phase voltages at the rear end of the inductor in the reactance module 120 are V L1-inv 、V L2-inv and V L3-inv .

[0074] Optionally, the sine waveform of the AC power supply, that is, the fundamental wave, can be obtained through an oscilloscope, that is, the frequency f of the fundamental wave can be obtained, and the fundamental wave angular frequency can be obtained through the formula ω1=2πf.

[0075] Optionally, the inductance depends on the number of turns of the inductor coil, the winding method, the presence or absence of a magnetic core, and the material of the magnetic core. Figure 1 The three inductors shown are identical, ie, have the same inductance.

[0076] In one implementation, the step of obtaining the first parameter and the second parameter of the three-phase AC inverter may specifically include:

[0077] Obtain the bus voltage of the three-phase AC inverter; based on the bus voltage, determine the effective value of the phase voltage.

[0078] In the embodiment of the present application, the effective value of the phase voltage can be determined by the acquired bus voltage, so it is convenient to calculate the effective value of the input voltage based on the effective value of the phase voltage. The method of determining the effective value of the phase voltage based on the bus voltage is described in detail below.

[0079] Optionally, in an implementation manner, the step of determining the effective value of the phase voltage based on the bus voltage may specifically include the following steps (1) and (2):

[0080] (1) Based on the bus voltage, the average value of the effective value of the line voltage at the rear end of the inductor is obtained.

[0081] The average value of the effective value of the line voltage is the average value of the sum of the squares of the line voltages at the rear end of each capacitor in the three-phase AC inverter.

[0082] It should be noted that the line voltage refers to the voltage between two live wires (usually marked as L1, L2, and L3 in a three-phase system); Figure 1 As shown, it is assumed that the phase voltages at the rear end of the inductor in the reactance module 120 are V L1-inv 、V L2-inv and V L3-inv , then the line voltages at the rear end of the inductor are V L12-inv 、V L23-inv and V L31-inv .

[0083] Further, in one implementation, the step of obtaining the average value of the effective value of the line voltage at the rear end of the inductor based on the bus voltage may specifically include:

[0084] Based on the relationship between the area enclosed by the line voltage at the rear end of the inductor and the area enclosed by the bus voltage, a target association relationship is obtained.

[0085] The target association relationship is used to indicate the relationship between the bus voltage and the average value of the effective value of the line voltage.

[0086] Based on the bus voltage and the target association relationship, the average value of the line voltage effective value is obtained.

[0087] It should be understood that the relationship between the area enclosed by the line voltage at the rear end of the inductor and the area enclosed by the bus voltage can be understood as that the area enclosed by the line voltage at the rear end of the inductor is equal to twice the area enclosed by the bus voltage.

[0088] Optionally, based on the relationship between the area enclosed by the line voltage at the rear end of the inductor and the area enclosed by the bus voltage, a target association relationship is obtained. It can be understood that based on the relationship between the area enclosed by the line voltage at the rear end of the inductor and the area enclosed by the bus voltage, a relationship between the line voltage at the rear end of the inductor and the bus voltage is obtained, and then based on the relationship between the line voltage at the rear end of the inductor and the bus voltage, a relationship between the bus voltage and the average value of the effective value of the line voltage is obtained, that is, the target association relationship.

[0089] Combined with the above Figure 1 The structural schematic diagram of the three-phase AC inverter shown; Figure 3 1 is a schematic diagram of the relationship between the line voltage at the rear end of the inductor and the bus voltage of a three-phase AC inverter under heavy load provided by an embodiment of the present application. Figure 3 As shown, the horizontal axis is time (t), and the vertical axis is line voltage. When the AC inductor is overloaded, the line voltage V L12-inv 、V L23-inv and V L31-inv It will become a standard three-level step wave, V L12-inv 、V L23-inv 、V L31-inv The area formed by the enclosure is exactly equal to the bus voltage V dc Twice the area.

[0090] It should be noted that the standard three-level step wave is a voltage waveform generated by a modulation strategy used in power electronic converters, especially in three-level inverters. This waveform generates three levels of voltage at the output end through a switch combination: positive maximum value, zero voltage, and negative maximum value, forming a waveform similar to a step. The three-level step wave can provide a higher quality output voltage, reduce harmonic distortion, improve efficiency, and is more friendly to loads such as motors.

[0091] Combined with the above Figure 1 The structural schematic diagram of the three-phase AC inverter shown; Figure 4 1 is a schematic diagram of the relationship between the line voltage behind the inductor and the bus voltage of a three-phase AC inverter under light load provided by an embodiment of the present application. Figure 4 As shown, the horizontal axis is time (t), and the vertical axis is line voltage. When the load is light, the line voltage V L12-inv 、V L23-inv and V L31-inv Although it is not a standard step wave, V L12-inv 、V L23-inv 、V L31-invThe area formed by the enclosure is still exactly equal to the bus voltage V dc Twice the area.

[0092] It should be noted that Figure 3 and Figure 4 This is an example of the changing trend of line voltage and bus voltage; it is only used to illustrate V L12-inv 、V L23-inv 、V L31-inv The area formed by the enclosure is exactly equal to the bus voltage V dc Twice the area; this application does not impose any limitation on this.

[0093] Because under light load or heavy load, V L12-inv 、V L23-inv 、V L31-inv The area formed by the enclosure is exactly equal to the bus voltage V dc The area is twice that of the inductor, and the area is represented by the square of the effective value of the line voltage. Therefore, the effective value of the line voltage at the rear end of the inductor has the following relationship with the bus voltage:

[0094] V L12-inv 2 + V L23-inv 2 + V L31-inv 2 =2V dc 2

[0095] Based on the above formula, the target association relationship can be obtained, which can be expressed by the following formula (1):

[0096] V inv-avg = V dc (1)

[0097] Among them, V inv-avg Represents the average value of the effective value of the line voltage, V dc Indicates the bus voltage.

[0098] In this way, after the bus voltage is obtained, the average value of the effective value of the line voltage can be calculated using the above formula.

[0099] In an embodiment of the present application, since a target association relationship can be obtained based on the relationship between the area enclosed by the line voltage at the rear end of each capacitor and the area enclosed by the bus voltage, when the bus voltage is obtained, the average value of the effective value of the line voltage can be accurately calculated based on the bus voltage and the target association relationship.

[0100] (2) Determine the effective value of the phase voltage based on the average value of the line voltage effective value.

[0101] Alternatively, since the line voltage is the phase voltage multiplied by (i.e. 1.732), the effective value of the phase voltage can be calculated based on the following formula (2):

[0102] V LN-inv = V inv-avg = V dc (2)

[0103] Among them, V LN-inv Represents the effective value of the phase voltage at the rear end of the inductor, V inv-avg Represents the average value of the effective value of the line voltage; V dc Indicates the bus voltage.

[0104] It should be noted that in a three-phase system, the phase voltage refers to the voltage from any phase to the neutral point (or virtual neutral point), while the line voltage is the voltage between any two phases. For a three-phase circuit connected in star (Y shape), there is a corresponding relationship between the phase voltage and the line voltage: the line voltage is the phase voltage. times; the line voltage is the phase voltage multiplied by (i.e. 1.732) is the value obtained. For a three-phase circuit connected in a triangle (Δ shape): the phase voltage and the line voltage are the same; i.e. V LN-inv =V inv-avg The calculation methods of other steps refer to the above description; they will not be repeated here.

[0105] In the embodiment of the present application, since the average value of the effective value of the line voltage at the rear end of the inductor can be obtained based on the bus voltage, the accurate effective value of the phase voltage can be obtained based on the average value of the effective value of the line voltage.

[0106] In one implementation, when the first parameter includes a target current effective value of an input current of the three-phase AC inverter, the step of obtaining the first parameter of the three-phase AC inverter may specifically include:

[0107] Obtain bus voltage and input power of three-phase AC inverter;

[0108] The target current effective value is determined based on the bus voltage and input power.

[0109] Optionally, the bus voltage is the voltage across a DC bus capacitor in a three-phase AC inverter; the bus voltage can be obtained by sampling a voltage divider circuit.

[0110] Optionally, the load power connected to the three-phase AC inverter can be obtained first, for example, the motor power can be obtained first. Figure 1 The power of the motor shown is obtained, and then the circuit loss power in the three-phase AC inverter is obtained, and the sum of the circuit loss power and the load power is determined as the input power.

[0111] Optionally, the above-mentioned determination of the target current effective value based on the bus voltage and the input power may specifically include:

[0112] The target current effective value is calculated based on the following formula (3):

[0113] I ac = P / ( V dc )(3)

[0114] Among them, I ac represents the effective value of the target current, P represents the input power, V dc Indicates the bus voltage.

[0115] In this way, after obtaining the bus voltage and input power, the target current effective value can be obtained by substituting them into the above formula (3).

[0116] It should be noted that the phase voltage at the rear end of the capacitor in the above three-phase AC inverter is completely consistent with the phase of the input current of the phase, that is, the phase power factor between the two is equal to 1.

[0117] Combined with the above Figure 1 The structural schematic diagram of the three-phase AC inverter shown; Figure 5 1 is a phase relationship diagram of the phase voltage at the rear end of the inductor and the input current of the phase when the three-phase AC inverter is lightly loaded, provided in an embodiment of the present application. Figure 5 As shown, the abscissa of the first figure is time (t), and the ordinate is phase voltage; the abscissa of the second figure is time (t), and the ordinate is current I L1 , the phase voltage V at the rear end of the inductor L1-inv The input current I L1 The phases are completely consistent.

[0118] Combined with the above Figure 1 The structural schematic diagram of the three-phase AC inverter shown; Figure 6 1 is a phase relationship diagram of the phase voltage at the rear end of the inductor and the input current of the phase when the three-phase AC inverter is under medium load provided by the embodiment of the present application. Figure 6 As shown, the abscissa of the first figure is time (t), and the ordinate is phase voltage; the abscissa of the second figure is time (t), and the ordinate is current I L1 , the phase voltage V at the rear end of the inductor L1-inv The input current I L1 The phases are completely consistent.

[0119] Combined with the above Figure 1 The structural schematic diagram of the three-phase AC inverter shown; Figure 71 is a phase relationship diagram of the phase voltage at the rear end of the inductor and the input current of the phase when the three-phase AC inverter is overloaded, provided in an embodiment of the present application. Figure 7 As shown, the abscissa of the first figure is time (t), and the ordinate is phase voltage; the abscissa of the second figure is time (t), and the ordinate is current I L1 , the phase voltage V at the rear end of the inductor L1-inv The input current I L1 The phases are completely consistent.

[0120] Through the above Figures 5 to 7 It can be found that when the three-phase AC inverter is lightly loaded, medium loaded and heavily loaded, the phase of the phase voltage at the rear end of the inductor is completely consistent with the phase of the input current; further, the phase voltage at the rear end of the capacitor is a standard four-level step wave when it is heavily loaded. The heavier the load of the three-phase AC inverter, the lower the harmonic content of the input current, that is, the closer it is to a sine wave.

[0121] Based on the above characteristics that the phase voltage at the rear end of the light-load, medium-load and heavy-load inductor is completely consistent with the phase of the input current of the phase, that is, the phase power factor between the two is equal to 1, the relationship between the effective value of the current and the effective value of the phase voltage can be obtained, which can be expressed by the following formula (4):

[0122] I ac = P / (3 V LN-inv )(4)

[0123] Among them, I ac represents the effective value of current, P represents the input power, V LN-inv Indicates the effective value of the phase voltage at the end of the inductor.

[0124] It should be noted that in an AC circuit, the phase relationship between voltage and current reflects the way energy is exchanged. When the two are in phase, it indicates that there is only energy consumption in the circuit (such as heating of resistors), and there is no process of energy conversion between electric and magnetic fields, that is, there is no reactive power exchange. When the phase of the phase voltage at the rear end of the inductor is exactly the same as the phase of the input current, the phase power factor between the two is equal to 1, indicating that all the power provided by the power supply is consumed by the load in the form of active power, and there is no reactive power loss, which means that the power system operates efficiently and energy is fully utilized.

[0125] It should be understood that since the line voltage is the phase voltage multiplied by The value obtained by (i.e. 1.732) is based on the relationship between the average values ​​of the bus voltage and the line voltage effective values. That is, the above formulas (1) and (2) can be substituted into the above formula (4) to obtain the above formula (3).

[0126] In the embodiment of the present application, the target current effective value can be determined by the acquired bus voltage and input power, so as to facilitate the subsequent selection of a suitable compensation coefficient for compensation based on the target current effective value.

[0127] S202: Determine a target compensation coefficient corresponding to the target current effective value based on the target current effective value.

[0128] The target compensation coefficient is used to compensate for the error of current harmonics under different loads.

[0129] It should be noted that the above compensation coefficient is only related to the effective value of the target current and has nothing to do with the input voltage. When the effective value of the target current is larger, the compensation coefficient is greater than 1, that is, the heavier the load, the lower the harmonic content of the input current, and the closer it is to a sine wave, that is, the error caused by the current harmonics is close to zero.

[0130] In one implementation, the target compensation coefficient corresponding to the target current effective value is determined based on the target current effective value, including:

[0131] Based on the target current effective value and the fitting function, the target compensation coefficient is calculated.

[0132] The fitting function is used to indicate the relationship between the effective value of the current and the compensation coefficient.

[0133] Optionally, calibration data may be pre-tested, the calibration data including the effective current value I ac and compensation coefficient K; the calibration data is fitted with a program tool (such as a function generation function of a spreadsheet software) to obtain a fitting curve, and a fitting function expression of the fitting curve is obtained, which can be expressed by the following formula (5):

[0134] (5)

[0135] Among them, a, b, and c are constants.

[0136] In this way, when the target current effective value is obtained When the target current effective value is substituted into the above formula (5), the target compensation coefficient can be obtained.

[0137] In the embodiment of the present application, the target compensation coefficient corresponding to the current target current effective value can be calculated by the fitting function, so that the error of the current harmonic under the current load can be compensated by the target compensation coefficient.

[0138] S203: Determine an effective value of a voltage drop of the inductor based on the target compensation coefficient and the first parameter.

[0139] In one implementation, the determining of the effective value of the voltage drop of the inductor based on the target compensation coefficient and the first parameter may specifically include:

[0140] The effective value of the pressure drop is determined based on the following formula (6):

[0141] V Lin = Kω1LI ac (6)

[0142] Among them, V Lin represents the effective value of the inductor voltage drop, K represents the target compensation coefficient, ω1 represents the fundamental angular frequency, L represents the inductance, I ac Indicates the effective value of the target current.

[0143] In an embodiment of the present application, after the target compensation coefficient and the first parameter are obtained, the target current effective value can be accurately calculated based on a specific calculation formula, thereby facilitating the subsequent calculation of an accurate input voltage.

[0144] S204, determining the effective value of the input voltage based on the effective value of the voltage drop and the effective value of the phase voltage.

[0145] Combined with the above Figure 1 The structural schematic diagram of the three-phase AC inverter shown; Figure 8 1 is a schematic diagram of the relationship between the inductor voltage drop, the inductor rear end voltage and the input voltage of a three-phase AC inverter under light load provided by an embodiment of the present application; Figure 8 As shown, the horizontal axis is time (t) and the vertical axis is voltage; including the inductor voltage drop V Lin1 、Inductor back-end voltage V L1-inv With input voltage V L1 .

[0146] It should be noted that inductance voltage drop is a type of voltage, which refers to the voltage drop caused by the resistance of inductance to current change in an AC circuit.

[0147] Combined with the above Figure 1 The structural schematic diagram of the three-phase AC inverter shown; Fig. 9 1 is a schematic diagram of the relationship between the inductor voltage drop, the inductor rear end voltage and the input voltage of a three-phase AC inverter under heavy load provided by an embodiment of the present application; Fig. 9 As shown, the horizontal axis is time (t) and the vertical axis is voltage; including the inductor voltage drop V Lin1 、Inductor back-end voltage V L1-inv With input voltage V L1 .

[0148] like Figure 8 and Fig. 9 As shown, the inductor voltage drop V Lin1The area formed by the enclosure and the voltage V at the rear end of the inductor L1-inv The sum of the areas enclosed is equal to the input voltage V L1 The area enclosed.

[0149] Since the sum of the instantaneous value of the voltage at both ends of the inductor and the instantaneous value of the voltage at the rear end of the inductor is equal to the input voltage; and because when the three-phase AC inverter is under light load and heavy load, the sum of the area surrounded by the voltage drop at both ends of the inductor and the area surrounded by the voltage at the rear end of the inductor is equal to the area surrounded by the input voltage, the effective value of the voltage drop, the effective value of the phase voltage, and the effective value of the input voltage have the following relationship:

[0150] V Lin 2 + V LN-inv 2 =V ac 2

[0151] Among them, V Lin Indicates the effective value of the inductor voltage drop, V LN-inv Represents the effective value of the phase voltage at the rear end of the inductor, V ac Indicates the effective value of the input voltage.

[0152] Furthermore, the effective value of the input voltage is determined based on the effective value of the inductor voltage drop and the effective value of the phase voltage at the rear end of the inductor, which can be specifically calculated by the following formula (7):

[0153] V ac = (7)

[0154] In this way, after obtaining the effective value of the voltage drop and the effective value of the phase voltage, the effective value of the input voltage can be obtained by substituting them into the above formula (7).

[0155] It should be understood that the V involved in the above formula Lin is the inductor voltage drop V Lin1 The effective value, V ac is the input voltage V L1 Valid values.

[0156] In an embodiment of the present application, since the corresponding compensation coefficient can be determined by obtaining the effective current value of the input current of the three-phase AC inverter, a relatively accurate voltage drop effective value can be calculated based on the compensation coefficient and the effective current value of the input current, the fundamental angular frequency and the inductance of the inductor. By combining the relatively accurate voltage drop effective value and the obtained effective value of the phase voltage at the rear end of the inductor, a relatively accurate input voltage effective value can be obtained, thereby eliminating the need to add a sampling circuit on the input side of the three-phase AC inverter. It is only necessary to calibrate the compensation coefficient in advance to calculate the accurate input voltage. Therefore, the above scheme can obtain the input voltage of the three-phase AC inverter without increasing the hardware cost.

[0157] Based on the calculation method of the three-phase AC inverter input voltage in the above embodiment, the following is a verification result of the effect that can be achieved by the calculation method of the three-phase AC inverter input voltage provided by the present application, taking a three-phase small multi-split air conditioner system as an example. The verification process tests the input voltage V of the three-phase AC inverter when the compressor (the aforementioned load) runs at different frequencies under different voltages. ac The calculated value and input current I ac The calculated value and the input voltage V ac The calculated value is compared with the actual input voltage, and the input current I ac The calculated value and the actual current I a、 I b and I c The actual average value I ac For comparison, the test results are shown in Tables 1 to 3 below.

[0158] The following table 1 shows the calculated input voltage V of the three-phase AC inverter at different compressor frequencies when the actual input voltage of the three-phase AC inverter is 220V. ac .

[0159] Table 1

[0160]

[0161] The following table 2 shows the calculated input voltage V of the three-phase AC inverter at different compressor frequencies when the actual input voltage of the three-phase AC inverter is 187V. ac .

[0162] Table 2

[0163]

[0164] The following table 3 shows the calculated input voltage V of the three-phase AC inverter at different compressor frequencies when the actual input voltage of the three-phase AC inverter is 254V. ac .

[0165] Table 3

[0166]

[0167] From the above test results, we can see that the input voltage V calculated under various voltages and loads is ac The deviation from the actual value of the input voltage is within 3V, and is fixedly 2-3V smaller, because the filter circuit at the front end of the rectifier will produce a certain voltage drop. The test results confirm the effectiveness and practical application value of the present invention.

[0168] In an embodiment of the present application, since the corresponding compensation coefficient can be determined by obtaining the effective current value of the input current of the three-phase AC inverter, a relatively accurate voltage drop effective value can be calculated based on the compensation coefficient and the effective current value of the input current, the fundamental angular frequency and the inductance of the inductor. By combining the relatively accurate voltage drop effective value and the obtained effective value of the phase voltage at the rear end of the inductor, a relatively accurate input voltage effective value can be obtained, thereby eliminating the need to add a sampling circuit on the input side of the three-phase AC inverter. It is only necessary to calibrate the compensation coefficient in advance to calculate the accurate input voltage. Therefore, the above scheme can obtain the input voltage of the three-phase AC inverter without increasing the hardware cost.

[0169] Fig.10 is a flow chart of another method for calculating the input voltage of a three-phase AC inverter provided in an embodiment of the present application, which can be used in the above-mentioned embodiment. Figure 1 The three-phase AC inverter shown in the figure or the air conditioner or other electronic equipment equipped with the three-phase AC inverter.

[0170] For example, Fig.10 As shown, the method includes the following implementation process:

[0171] S301, obtaining a bus voltage, input power, fundamental angular frequency of input current of a three-phase AC inverter, and inductance of an inductor in the three-phase AC inverter.

[0172] Optionally, the bus voltage is also the voltage across the capacitor in the three-phase AC inverter; the bus voltage can be acquired based on a corresponding voltage-dividing sampling circuit.

[0173] Optionally, the inductance of the inductor depends on the number of turns of the inductor coil, the winding method, the presence or absence of a magnetic core, and the material of the magnetic core, etc. It can be obtained based on a calculation method in the relevant technology, and the embodiments of the present application will not be described in detail.

[0174] S302, determining a target current effective value based on the bus voltage and the input power.

[0175] Optionally, the input power may be understood as the sum of the load power connected to the three-phase AC inverter and the circuit loss power.

[0176] Optionally, the above target current effective value may be understood as the effective value of the input current.

[0177] S303: Calculate a target compensation coefficient based on the target current effective value and the fitting function.

[0178] The fitting function is used to indicate the relationship between the effective value of the current and the compensation coefficient.

[0179] Optionally, the above fitting function is pre-fitted based on calibration data. The calibration data includes the effective value of the current I ac And compensation coefficient K.

[0180] S304, determining the effective value of the voltage drop of the inductor based on the target compensation coefficient, the fundamental angular frequency, the inductance, and the target effective value of the current.

[0181] Optionally, a calculation formula for the effective value of the voltage drop may be obtained in advance, and then the target compensation coefficient, fundamental angular frequency and inductance, and the target current effective value are substituted into the calculation formula to obtain the effective value of the voltage drop.

[0182] It should be understood that the heavier the load, the lower the harmonic content of the input current and the closer it is to a sine wave. Therefore, a compensation coefficient is introduced to compensate for the error caused by current harmonics under different loads, and the calculation formula for the effective value of the voltage drop is derived based only on the current fundamental wave.

[0183] S305, based on the bus voltage, obtaining an average value of the effective value of the line voltage at the rear end of the inductor.

[0184] S306, determining the phase voltage effective value based on the average value of the line voltage effective value.

[0185] S307, determining the effective value of the input voltage based on the effective value of the voltage drop and the effective value of the phase voltage.

[0186] Optionally, for the above S301 to 307, reference may be made to the detailed description of S201 to S204 in the above embodiment, and the embodiments of the present application will not be repeated here.

[0187] In the application embodiment, since the corresponding compensation coefficient can be determined by obtaining the effective current value of the input current of the three-phase AC inverter, a relatively accurate voltage drop effective value can be calculated based on the compensation coefficient and the effective current value of the input current, the fundamental angular frequency and the inductance of the inductor. By combining the relatively accurate voltage drop effective value and the obtained effective value of the phase voltage at the rear end of the inductor, a relatively accurate input voltage effective value can be obtained. Therefore, there is no need to add a sampling circuit on the input side of the three-phase AC inverter. It is only necessary to calibrate the compensation coefficient in advance to calculate the accurate input voltage, thereby greatly saving hardware costs.

[0188] Combination of the above Figures 1 to 10 The calculation method of the input voltage of the three-phase AC inverter provided in the embodiment of the present application is described in detail; Fig.11 and Fig.12 The device embodiments of the present application are described in detail. It should be understood that the device in the embodiments of the present application can execute the various methods of the aforementioned embodiments of the present application, that is, the specific working processes of the following various products can refer to the corresponding processes in the aforementioned method embodiments.

[0189] Fig.11 It is a structural schematic diagram of a three-phase AC inverter input voltage calculation device provided in an embodiment of the present application.

[0190] For example, Fig.11 As shown, the computing device 400 includes:

[0191] The first acquisition module 401 is used to acquire the first parameter and the second parameter of the three-phase AC inverter; wherein the first parameter includes the target current effective value of the input current of the three-phase AC inverter, the fundamental angular frequency of the input current and the inductance of the inductor in the three-phase AC inverter; the second parameter is the effective value of the phase voltage at the rear end of the inductor;

[0192] A first determination module 402 is used to determine a target compensation coefficient corresponding to the target current effective value based on the target current effective value; wherein the target compensation coefficient is used to compensate for errors of current harmonics under different loads;

[0193] A second determination module 403, configured to determine an effective value of a voltage drop of the inductor based on the target compensation coefficient and the first parameter;

[0194] The third determination module 404 is configured to determine the effective value of the input voltage based on the effective value of the voltage drop and the effective value of the phase voltage.

[0195] In a possible implementation, the first determination module 402 is specifically used to: calculate a target compensation coefficient based on the target current effective value and a fitting function; wherein the fitting function is used to indicate a relationship between the current effective value and the compensation coefficient.

[0196] In a possible implementation, the first acquisition module 401 is specifically used to: acquire the bus voltage and input power of the three-phase AC inverter; and determine the target current effective value based on the bus voltage and the input power.

[0197] In a possible implementation, the first acquisition module 401 is specifically used to: acquire the bus voltage of the three-phase AC inverter; and determine the effective value of the phase voltage based on the bus voltage.

[0198] In one possible implementation, the first acquisition module 401 is specifically used to: obtain the average value of the effective value of the line voltage at the rear end of the inductor based on the bus voltage; wherein the average value of the effective value of the line voltage is the average value of the sum of the squares of the line voltage at the rear end of each capacitor in the three-phase AC inverter; and determine the effective value of the phase voltage based on the average value of the effective value of the line voltage.

[0199] In one possible implementation, the first acquisition module 401 is specifically used to: obtain a target association relationship based on the relationship between the area enclosed by the line voltage at the rear end of each capacitor and the area enclosed by the bus voltage; wherein the target association relationship is used to indicate the relationship between the bus voltage and the average value of the effective value of the line voltage; based on the bus voltage and the target association relationship, obtain the average value of the effective value of the line voltage.

[0200] In a possible implementation, the second determining module 403 is specifically configured to determine the effective value of the voltage drop based on the following formula:

[0201] V Lin = Kω1L I ac ;

[0202] Among them, V Lin represents the effective value of the inductor voltage drop, K represents the target compensation coefficient, ω1 represents the fundamental angular frequency, L represents the inductance, I ac Indicates the target current effective value.

[0203] Fig.12 It is a structural schematic diagram of an air conditioner provided in an embodiment of the present application.

[0204] For example, Fig.12As shown, the air conditioner 500 includes: a memory 501 and a processor 502, wherein the memory 501 stores an executable program code 5011, and the processor 502 is used to call and execute the executable program code 5011 to perform a method for calculating the input voltage of a three-phase AC inverter.

[0205] In addition, an embodiment of the present application also protects a device, which may include a memory and a processor, wherein the memory stores an executable program code, and the processor is used to call and execute the executable program code to execute a method for calculating the input voltage of a three-phase AC inverter provided in an embodiment of the present application.

[0206] In this embodiment, the functional modules of the device can be divided according to the above method example. For example, each functional module can be corresponded, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware. It should be noted that the division of modules in this embodiment is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0207] In the case of dividing each functional module according to each function, the device may also include a first acquisition module, a first determination module, a second determination module, and a third determination module, etc. It should be noted that all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module, which will not be repeated here.

[0208] It should be understood that the device provided in this embodiment is used to execute the above-mentioned method for calculating the input voltage of a three-phase AC inverter, and thus can achieve the same effect as the above-mentioned implementation method.

[0209] In the case of an integrated unit, the device may include a processing module and a storage module. When the device is applied to an air conditioner, the processing module may be used to control and manage the air conditioner. The storage module may be used to support the air conditioner to execute related program codes, etc.

[0210] The processing module may be a processor or a controller, which may implement or execute various exemplary logic blocks, modules and circuits shown in combination with the contents disclosed in this application. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of digital signal processing (DSP) and a microprocessor, etc. The storage module may be a memory.

[0211] In addition, the device provided in the embodiments of the present application may specifically be a chip, a component or a module, and the chip may include a connected processor and a memory; wherein the memory is used to store instructions, and when the processor calls and executes the instructions, the chip can execute a method for calculating the input voltage of a three-phase AC inverter provided in the above embodiment.

[0212] This embodiment also provides a computer-readable storage medium, in which a computer program code is stored. When the computer program code is executed on a computer, the computer executes the above-mentioned related method steps to implement a method for calculating the input voltage of a three-phase AC inverter provided in the above embodiment.

[0213] This embodiment further provides a computer program product. When the computer program product is run on a computer, the computer is caused to execute the above-mentioned related steps to implement a method for calculating the input voltage of a three-phase AC inverter provided in the above embodiment.

[0214] Among them, the device, computer-readable storage medium, computer program product or chip provided in this embodiment is used to execute the corresponding method provided above. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects in the corresponding method provided above, and will not be repeated here.

[0215] Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0216] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0217] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for calculating the input voltage of a three-phase AC inverter, characterized in that: The method comprises: Acquire a first parameter and a second parameter of a three-phase AC inverter; wherein the first parameter includes a target current effective value of an input current of the three-phase AC inverter, a fundamental angular frequency of the input current, and an inductance of an inductor in the three-phase AC inverter; and the second parameter is an effective value of a phase voltage at the rear end of the inductor; Based on the target current effective value, determining a target compensation coefficient corresponding to the target current effective value; wherein the target compensation coefficient is used to compensate for errors of current harmonics under different loads; Based on the target compensation coefficient and the first parameter, the effective value of the voltage drop of the inductor is determined; based on the effective value of the voltage drop and the effective value of the phase voltage, the effective value of the input voltage is determined.

2. The method according to claim 1, characterized in that The determining, based on the target current effective value, a target compensation coefficient corresponding to the target current effective value comprises: Based on the target current effective value and the fitting function, a target compensation coefficient is calculated; wherein the fitting function is used to indicate the relationship between the current effective value and the compensation coefficient.

3. The method according to claim 1, characterized in that The obtaining of the first parameter of the three-phase AC inverter comprises: Obtaining the bus voltage and input power of the three-phase AC inverter; The target current effective value is determined based on the bus voltage and the input power.

4. The method according to claim 1, characterized in that: The obtaining of the first parameter and the second parameter of the three-phase AC inverter comprises: Obtaining the bus voltage of the three-phase AC inverter; Based on the bus voltage, the phase voltage effective value is determined.

5. The method according to claim 4, characterized in that The determining the effective value of the phase voltage based on the bus voltage includes: Based on the bus voltage, an average value of the effective value of the line voltage at the rear end of the inductor is obtained; wherein the average value of the effective value of the line voltage is the average value of the sum of the squares of the line voltage at the rear end of each capacitor in the three-phase AC inverter; The phase voltage effective value is determined based on the average value of the line voltage effective values.

6. The method according to claim 5, characterized in that The step of obtaining an average value of the effective value of the line voltage at the rear end of the inductor based on the bus voltage includes: Based on the relationship between the area enclosed by the line voltage at the rear end of each capacitor and the area enclosed by the bus voltage, a target association relationship is obtained; wherein the target association relationship is used to indicate the relationship between the bus voltage and the average value of the effective value of the line voltage; Based on the bus voltage and the target association relationship, an average value of the effective value of the line voltage is obtained.

7. The method according to claim 1, characterized in that The determining, based on the target compensation coefficient and the first parameter, the effective value of the voltage drop of the inductor includes: The effective value of the pressure drop is determined based on the following formula: V Lin = K ω1 LI ac ; Among them, V Lin represents the effective value of the voltage drop, K represents the target compensation coefficient, ω1 represents the fundamental angular frequency, L represents the inductance, I ac Indicates the target current effective value.

8. A device for calculating input voltage of a three-phase AC inverter, characterized in that: The device comprises: A first acquisition module is used to acquire a first parameter and a second parameter of a three-phase AC inverter; wherein the first parameter includes a target current effective value of an input current of the three-phase AC inverter, a fundamental angular frequency of the input current, and an inductance of an inductor in the three-phase AC inverter; and the second parameter is an effective value of a phase voltage at a rear end of the inductor; A first determination module, configured to determine a target compensation coefficient corresponding to the target current effective value based on the target current effective value; wherein the target compensation coefficient is used to compensate for errors of current harmonics under different loads; A second determination module, configured to determine an effective value of a voltage drop of the inductor based on the target compensation coefficient and the first parameter; The third determination module is used to determine the effective value of the input voltage based on the effective value of the voltage drop and the effective value of the phase voltage.

9. An air conditioner, characterized in that: include: A processor, a memory, a three-phase AC inverter, and a load; the processor is communicatively connected with the memory; A three-phase AC inverter is coupled to the processor and connected to the load; The processor controls the rotation speed of the load through the three-phase AC inverter; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method for calculating the input voltage of a three-phase AC inverter according to any one of claims 1 to 7.

11. A computer program product, characterized in that The invention comprises a computer program, which, when executed by a processor, implements the method for calculating the input voltage of a three-phase AC inverter as claimed in any one of claims 1 to 7.

Images