A method and device for controlling output voltage of a motor inverter and an inverter

Abstract

The present invention discloses a method, device and inverter for controlling the output voltage of a motor frequency converter, which belongs to the field of frequency converter control. After obtaining the motor operating frequency and the spatial vector phase of the frequency converter output voltage, the actual output voltage vector amplitude of the frequency converter is controlled according to the operating frequency and the spatial vector phase. During the operation of one cycle, the present application scheme controls the actual output voltage vector amplitude according to the operating frequency and the spatial vector phase, and reduces the effective value of the frequency converter output voltage while ensuring the normal operation of the motor, thereby achieving the effect of reducing the motor operating current. While ensuring the load capacity of the frequency converter, the operating current is reduced, and the application scheme has the advantages of low temperature rise and low hardware cost.

Description

Technical Field

[0001] The present invention relates to the field of frequency converter control, and in particular, to a method and device for controlling output voltage of a motor frequency converter and a frequency converter. Background Art

[0002] As market competition becomes increasingly fierce, the current inverter solution for air-conditioning compressor drive is developing towards high power density, low loss and low cost. The working principle of the inverter is to first convert the AC power with frequency into DC power without frequency, and then convert the DC power into AC power with a preset frequency through the inverter.

[0003] like Figure 1 As shown, the sectors of the regular hexagon are the limit ranges that can be modulated by the eight voltage vectors in the inverter when SVPWM modulation is adopted, and the radius of the inscribed circle of the regular hexagon represents the amplitude of the maximum spatial voltage vector that can be modulated without overmodulation. In this application, this amplitude is used as the maximum basic amplitude.

[0004] When the voltage vector reaches the maximum basic amplitude, the existing control method further increases the speed by increasing the current to offset or reduce the effect of the back electromotive force. However, when the motor current increases, the temperature rise also increases. At the same time, the higher the current level, the higher the hardware cost. Summary of the invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a motor inverter output voltage control method, device and inverter to solve the problem that when the operating current of the existing motor increases, the temperature rise also increases, and at the same time, the higher the current level, the higher the hardware cost.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] First,

[0008] A method for controlling the output voltage of a motor inverter comprises the following steps:

[0009] Obtaining the operating frequency of the motor and the space vector phase of the output voltage of the inverter;

[0010] The actual output voltage vector amplitude of the inverter is controlled according to the operating frequency and the space vector phase.

[0011] Further, the controlling the voltage vector amplitude of the inverter according to the operating frequency and the space vector phase includes:

[0012] Determine an interval in which the operating frequency is located, the interval includes a first interval, a second interval and a third interval, any frequency in the first interval is less than any frequency in the second interval; any frequency in the second interval is less than any frequency in the third interval;

[0013] In the determined interval, the voltage vector amplitude of the frequency converter is controlled according to the space vector phase.

[0014] Further, controlling the voltage vector amplitude of the inverter according to the space vector phase within the determined interval includes: when the operating frequency is in the first interval:

[0015] If the space vector phase reaches the basic vector position, the actual output voltage vector amplitude at the basic vector position is reduced to a first preset value;

[0016] If the space vector phase reaches a preset phase, the actual output voltage vector amplitude at the preset phase is reduced to a second preset value; the preset phases include 30°, 90°, 150°, 210°, 270° and 330°, and the first preset value is greater than the second preset value.

[0017] Furthermore, the first preset value is 90% of the actual voltage vector amplitude to be output, and the second preset value is 85% of the actual voltage vector amplitude to be output.

[0018] Further, controlling the voltage vector amplitude of the inverter according to the space vector phase within the determined interval includes:

[0019] When the operating frequency is in the second interval, if the space vector phase reaches the basic vector position, the actual output voltage vector amplitude at the basic vector position is reduced to a third preset value.

[0020] Furthermore, the third preset value is 90% of the actual output voltage vector amplitude.

[0021] Further, controlling the voltage vector amplitude of the inverter according to the space vector phase within the determined interval includes:

[0022] When the operating frequency is in the third interval, the actual output voltage vector amplitude is kept unchanged.

[0023] Furthermore, the first interval is less than 30 Hz, the second interval is not less than 30 Hz and not more than 60 Hz, and the third interval is more than 60 Hz.

[0024] Second,

[0025] A motor inverter output voltage control device, comprising:

[0026] A parameter acquisition module, used to acquire the operating frequency of the motor and the space vector phase of the output voltage of the inverter;

[0027] The amplitude control module is used to control the actual output voltage vector amplitude of the inverter according to the operating frequency and the space vector phase.

[0028] Thirdly,

[0029] A frequency converter, comprising:

[0030] processor;

[0031] a memory for storing instructions executable by the processor;

[0032] The processor is configured to execute the method described in any one of the technical solutions of the first aspect.

[0033] Beneficial effects:

[0034] The technical solution of the present application provides a method, device and inverter for controlling the output voltage of a motor inverter; after obtaining the motor operating frequency and the spatial vector phase of the inverter output voltage, the actual output voltage vector amplitude of the inverter is controlled according to the operating frequency and the spatial vector phase. During the operation of one cycle, the present application scheme controls the actual output voltage vector amplitude according to the operating frequency and the spatial vector phase, reduces the effective value of the inverter output voltage while ensuring the normal operation of the motor, and achieves the effect of reducing the motor operating current. While ensuring the load capacity of the inverter, the operating current is reduced, and has the advantages of low temperature rise and low hardware cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 is a schematic diagram of a voltage space vector within a sector provided by an embodiment of the present invention;

[0037] Figure 2 It is a flow chart of a method for controlling output voltage of a motor frequency converter provided by an embodiment of the present invention;

[0038] Figure 3 is a flow chart of a specific motor inverter output voltage control method provided by an embodiment of the present invention;

[0039] Figure 4 The present invention is a schematic diagram of the structure of a motor inverter output voltage control device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other implementation methods obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0041] Reference Figure 2 The embodiment of the present invention provides a method for controlling the output voltage of a motor inverter, comprising the following steps:

[0042] Obtain the operating frequency of the motor and the space vector phase of the output voltage of the inverter;

[0043] The actual output voltage vector amplitude of the inverter is controlled according to the operating frequency and space vector phase.

[0044] The embodiment of the present invention provides a method, device and inverter for controlling the output voltage of a motor inverter; after obtaining the motor operating frequency and the spatial vector phase of the inverter output voltage, the actual output voltage vector amplitude of the inverter is controlled according to the operating frequency and the spatial vector phase. During the operation of one cycle, the present application scheme controls the actual output voltage vector amplitude according to the operating frequency and the spatial vector phase, and reduces the effective value of the inverter output voltage while ensuring the normal operation of the motor, thereby achieving the effect of reducing the motor operating current. While ensuring the load capacity of the inverter, the operating current is reduced, and the temperature rise is low and the hardware cost is low.

[0045] In order to further illustrate the above embodiment, the embodiment of the present invention provides a specific implementation method. The solution is based on FOC space vector control. On the basis of SVPWM modulation, the voltage vector is appropriately reduced in part of the space of each sector to reduce the output voltage. Since the variable frequency compressor is an inductive load, reducing the voltage will reduce the motor running current. The control method is as follows Figure 3 As shown, the following steps are included:

[0046] Obtain the operating frequency of the motor and the space vector phase of the output voltage of the inverter;

[0047] Determine the operating frequency range.

[0048] When the motor is running, when the operating frequency is below 30Hz, due to the low system load and the inertial load of the motor during operation, the sector judgment is performed through the SVPWM modulation process. When the sector judgment logic confirms that the voltage space vector phase reaches the basic vector position, the voltage vector amplitude is reduced to 90% of the actual output voltage vector. Among them, the basic vector position is 60°, 120°, 180°, 240°, 300°, and 360°.

[0049] When the sector judgment logic confirms that the voltage space vector phase reaches 30°, 90°, 150°, 210°, 270°, or 330°, the voltage vector amplitude is reduced to 85% of the actual output voltage vector.

[0050] When the operating frequency is between 30 Hz and 60 Hz, the voltage vector amplitude is reduced to 90% of the actual output voltage vector only when the voltage space vector phase reaches the basic vector position.

[0051] When the motor operating frequency reaches above 60 Hz, the restored voltage vector is the voltage vector amplitude actually calculated by SVPWM modulation.

[0052] It should be noted that the reduction ratios in the embodiment of the present invention are 90% and 85%, but in the actual control process, they can be set as needed.

[0053] The specific control method provided by the embodiment of the present invention reduces the voltage vector amplitude every 30° electrical angle during the operation of each electrical cycle, and maintains correct phase control on this basis. Due to the inertia of the motor operation, the motor can still maintain normal operation, but the effective value of the output voltage of the inverter is reduced, thereby achieving the effect of reducing the motor operating current.

[0054] It should be noted that in the above-mentioned embodiment of the invention, the operating frequency is divided into three intervals with 30 Hz and 60 Hz as the boundaries, but in the actual process, it is not limited to 30 Hz and 60 Hz as the boundaries; the three intervals can be divided according to the actual situation to better control the voltage output of the inverter.

[0055] In one embodiment, the present invention further provides a motor inverter output voltage control device, such as Figure 4 As shown, including:

[0056] The parameter acquisition module 41 is used to acquire the operating frequency of the motor and the space vector phase of the output voltage of the inverter.

[0057] The amplitude control module 42 is used to control the actual output voltage vector amplitude of the inverter according to the operating frequency and the space vector phase. Specifically, the amplitude control module 42 determines the interval where the operating frequency is located, and the interval includes a first interval, a second interval, and a third interval. Any frequency in the first interval is less than any frequency in the second interval; any frequency in the second interval is less than any frequency in the third interval; within the determined interval, the actual output voltage vector amplitude of the inverter is controlled according to the space vector phase. Among them, the first interval is less than 30Hz, the second interval is not less than 30Hz and not more than 60Hz, and the third interval is greater than 60Hz.

[0058] Furthermore, within the determined interval, the actual output voltage vector amplitude of the inverter is controlled according to the space vector phase, including:

[0059] When the operating frequency is in the first interval: if the space vector phase reaches the basic vector position, the actual output voltage vector amplitude at the basic vector position is reduced to a first preset value; if the space vector phase reaches the preset phase, the actual output voltage vector amplitude at the preset phase is reduced to a second preset value; the preset phases include 30°, 90°, 150°210°, 270° and 330°, and the first preset value is greater than the second preset value. The first preset value is 90% of the actual output voltage vector amplitude, and the second preset value is 85% of the actual output voltage vector amplitude.

[0060] When the operating frequency is in the second interval, if the space vector phase reaches the basic vector position, the actual output voltage vector amplitude at the basic vector position is reduced to a third preset value, which is 90% of the actual output voltage vector amplitude.

[0061] When the operating frequency is in the third interval, the actual output voltage vector amplitude is kept unchanged.

[0062] The device provided by the embodiment of the present invention reduces the voltage vector amplitude every 30° electrical angle during the operation of each electrical cycle, and maintains correct phase control on this basis. Due to the inertia of the motor operation, the motor can still maintain normal operation, but the effective value of the output voltage of the inverter is reduced, thereby achieving the effect of reducing the motor operating current.

[0063] In one embodiment, the present invention further provides a frequency converter, comprising:

[0064] processor;

[0065] a memory for storing processor-executable instructions;

[0066] The processor is configured to execute the method provided in any of the above embodiments.

[0067] The inverter provided by the embodiment of the present invention stores executable instructions through a memory; when the processor executes the executable instructions, the voltage vector amplitude is reduced every 30° electrical angle during the operation of each electrical cycle, and correct phase control is maintained on this basis. Due to the inertia of the motor operation, the motor can still maintain normal operation, but the effective value of the inverter's output voltage is reduced, thereby achieving the effect of reducing the motor operating current.

[0068] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0069] It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0070] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0071] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0072] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0073] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0074] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0076] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for controlling the output voltage of a motor inverter, characterized in that: The following steps are involved: Obtaining the operating frequency of the motor and the space vector phase of the output voltage of the inverter; Controlling the actual output voltage vector amplitude of the inverter according to the operating frequency and the space vector phase includes: Determine an interval in which the operating frequency is located, the interval includes a first interval, a second interval and a third interval, any frequency in the first interval is less than any frequency in the second interval; any frequency in the second interval is less than any frequency in the third interval; Within the determined interval, the actual output voltage vector amplitude of the inverter is controlled according to the space vector phase, including: when the operating frequency is in the second interval, if the space vector phase reaches the basic vector position, the actual output voltage vector amplitude at the basic vector position is reduced to a third preset value.

2. The method according to claim 1, characterized in that: The step of controlling the actual output voltage vector amplitude of the inverter according to the space vector phase within the determined interval includes: when the operating frequency is in the first interval: If the space vector phase reaches the basic vector position, the actual output voltage vector amplitude at the basic vector position is reduced to a first preset value; If the space vector phase reaches a preset phase, the actual output voltage vector amplitude at the preset phase is reduced to a second preset value; the preset phases include 30°, 90°, 150°, 210°, 270° and 330°, and the first preset value is greater than the second preset value.

3. The method according to claim 2, characterized in that: The first preset value is 90% of the actual output voltage vector amplitude, and the second preset value is 85% of the actual output voltage vector amplitude.

4. The method according to claim 1, characterized in that: The third preset value is 90% of the actual output voltage vector amplitude.

5. The method according to claim 1, characterized in that: The step of controlling the actual output voltage vector amplitude of the inverter according to the space vector phase within the determined interval includes: When the operating frequency is in the third interval, the actual output voltage vector amplitude is kept unchanged.

6. The method according to claim 1, characterized in that: The first interval is less than 30 Hz, the second interval is not less than 30 Hz and not more than 60 Hz, and the third interval is more than 60 Hz.

7. A motor inverter output voltage control device, characterized in that: include: A parameter acquisition module, used to acquire the operating frequency of the motor and the space vector phase of the output voltage of the inverter; an amplitude control module, for controlling the actual output voltage vector amplitude of the inverter according to the operating frequency and the space vector phase; specifically for determining the interval in which the operating frequency is located, the interval comprising a first interval, a second interval and a third interval, any frequency in the first interval being less than any frequency in the second interval; any frequency in the second interval being less than any frequency in the third interval; when the operating frequency is in the second interval, if the space vector phase reaches a basic vector position, the actual output voltage vector amplitude at the basic vector position is reduced to a third preset value.

8. A frequency converter, characterized in that: include: processor; a memory for storing instructions executable by the processor; The processor is configured to execute the method according to any one of claims 1 to 6.

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