Magnetic suspension frequency conversion unit, control method and device thereof and storage medium

Abstract

The invention discloses a control method and device of a magnetic suspension frequency conversion unit, the magnetic suspension frequency conversion unit, a storage medium and a computer program product, the magnetic suspension frequency conversion unit comprises a frequency converter, and the frequency converter comprises a rectification unit and an inversion unit; the method comprises the following steps: determining whether to adjust the carrier frequency of a frequency converter according to the operation frequency of the unit when the magnetic suspension frequency converter unit operates; and if the carrier frequency of the frequency converter is determined to be adjusted, controlling the carrier frequency of the rectification unit and the carrier frequency of the inversion unit according to the input current and the output current of the frequency converter and a preset model. According to the scheme, the rectification carrier frequency and the inversion carrier frequency of the frequency converter are flexibly controlled, so that current harmonics at the input side and the output side of the frequency converter are effectively reduced, the working loss of internal devices of the frequency converter is reduced, and the reliability of the frequency converter and the operation stability of a unit are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic suspension frequency conversion units, and specifically relates to a control method and device for a magnetic suspension frequency conversion unit, a magnetic suspension frequency conversion unit, a storage medium and a computer program product. Background Art

[0002] The inverter is a DC signal through IGBT full-controlled rectification or uncontrolled rectification, and then converted into AC power to supply the load through the fully controlled IGBT. In the application system of the inverter, such as central air conditioning, air compression system, etc., the inverter is the connection point between the entire system and the power grid. The non-sinusoidal current generated by the non-linear load and the power grid system will inject a large amount of harmonics into the inverter, seriously polluting the power supply quality, causing the inverter input and output current and voltage to be distorted, affecting the normal operation of the inverter's internal components and component losses.

[0003] The core component of magnetic levitation frequency conversion central air conditioner, the frequency converter, selects a reactor and carrier to match a certain power level frequency converter to meet the harmonic requirements, and fails to consider the harmonic requirements of magnetic levitation frequency conversion central air conditioner under different operating conditions, power and frequency. The operating power and frequency are limited based on a certain operating state, which causes abnormal phenomena such as excessive harmonic content at the input and output ends of the magnetic levitation frequency conversion central air conditioner frequency converter and severe heating of internal components. Such abnormal phenomena directly affect the working stability and life of the frequency converter, and reduce the safety and reliability of the magnetic levitation frequency conversion central air conditioner and the frequency converter.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0005] The object of the present invention is to provide a control method and device for a magnetic levitation frequency conversion unit, a magnetic levitation frequency conversion unit, a storage medium and a computer program product to solve the problems in related schemes such as excessive harmonic content at the input and output ends of the frequency converter in the magnetic levitation frequency conversion unit, severe heating of internal components, and reduced stability and service life of the frequency converter, so as to achieve the effect of effectively reducing the current harmonics on the input and output sides of the frequency converter and reducing the working loss of the internal components of the frequency converter by flexibly controlling the rectifier carrier frequency and the inverter carrier frequency of the frequency converter, thereby improving the reliability of the frequency converter and the operating stability of the unit.

[0006] The present invention provides a control method for a magnetic levitation frequency conversion unit, wherein the magnetic levitation frequency conversion unit comprises a frequency converter; the frequency converter comprises a rectifier unit and an inverter unit; the method comprises: during the operation of the magnetic levitation frequency conversion unit, obtaining the input current and output current of the frequency converter and the operating power of the magnetic levitation frequency conversion unit; determining whether to adjust the carrier frequency of the frequency converter according to the operating frequency; the carrier frequency of the frequency converter comprises the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit; if it is determined to adjust the carrier frequency of the frequency converter, controlling the carrier frequency of the frequency converter according to the input current, the output current and a preset model.

[0007] In some embodiments, determining whether to adjust the carrier frequency of the inverter according to the operating frequency includes: judging whether the continuous operation time of the magnetic levitation frequency conversion unit at the operating frequency is greater than or equal to a preset time; if the continuous operation time of the magnetic levitation frequency conversion unit at the operating frequency is greater than or equal to the preset time, determining whether to adjust the carrier frequency of the inverter according to the operating frequency and a preset target frequency; if the continuous operation time of the magnetic levitation frequency conversion unit at the operating frequency is less than the preset time, determining not to adjust the carrier frequency of the inverter.

[0008] In some embodiments, determining whether to adjust the carrier frequency of the frequency converter is based on the operating frequency and the preset target frequency, including: judging the size relationship between the operating frequency and the preset target frequency; if the operating frequency is greater than or equal to the preset target frequency, determining not to adjust the carrier frequency of the frequency converter; if the operating frequency is less than the preset target frequency, determining to adjust the carrier frequency of the frequency converter.

[0009] In some embodiments, the preset model is a Markov chain prediction model; the carrier frequency of the inverter is controlled according to the input current, the output current, and the preset model, including: subjecting the input current to the preset Markov chain prediction model to obtain the target carrier frequency of the rectifier unit; compensating the target carrier frequency of the rectifier unit according to a preset first carrier frequency compensation value to obtain the compensated target carrier frequency of the rectifier unit; controlling the carrier frequency of the rectifier unit to be the compensated target carrier frequency of the rectifier unit.

[0010] In some embodiments, the preset model is a Markov chain prediction model; the carrier frequency of the inverter is controlled according to the input current, the output current, and the preset model, and also includes: bringing the output current into the preset Markov chain prediction model to obtain the target carrier frequency of the inverter unit; compensating the target carrier frequency of the inverter unit according to a preset second carrier frequency compensation value to obtain the compensated target carrier frequency of the inverter unit; controlling the carrier frequency of the inverter unit to be the compensated target carrier frequency of the inverter unit.

[0011] Matching the above method, the present invention provides a control device for a magnetic levitation frequency conversion unit on the other hand, wherein the magnetic levitation frequency conversion unit includes a frequency converter; the frequency converter includes a rectifier unit and an inverter unit; the device includes: an acquisition module, configured to acquire the input current and output current of the frequency converter and the operating power of the magnetic levitation frequency conversion unit during the operation of the magnetic levitation frequency conversion unit; a control module, configured to determine whether to adjust the carrier frequency of the frequency converter according to the operating frequency; the carrier frequency of the frequency converter includes the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit; the control module is also configured to control the carrier frequency of the frequency converter according to the input current, the output current and a preset model if it is determined to adjust the carrier frequency of the frequency converter.

[0012] In some embodiments, the control module determines whether to adjust the carrier frequency of the inverter according to the operating frequency, including: judging whether the continuous operation time of the magnetic levitation frequency conversion unit at the operating frequency is greater than or equal to a preset time; if the continuous operation time of the magnetic levitation frequency conversion unit at the operating frequency is greater than or equal to the preset time, determining whether to adjust the carrier frequency of the inverter according to the operating frequency and a preset target frequency; if the continuous operation time of the magnetic levitation frequency conversion unit at the operating frequency is less than the preset time, determining not to adjust the carrier frequency of the inverter.

[0013] In some embodiments, the control module determines whether to adjust the carrier frequency of the frequency converter according to the operating frequency and the preset target frequency, including: judging the size relationship between the operating frequency and the preset target frequency; if the operating frequency is greater than or equal to the preset target frequency, determining not to adjust the carrier frequency of the frequency converter; if the operating frequency is less than the preset target frequency, determining to adjust the carrier frequency of the frequency converter.

[0014] In some embodiments, the preset model is a Markov chain prediction model; the control module controls the carrier frequency of the inverter according to the input current, the output current, and the preset model, including: subjecting the input current to the preset Markov chain prediction model to obtain the target carrier frequency of the rectifier unit; compensating the target carrier frequency of the rectifier unit according to a preset first carrier frequency compensation value to obtain the compensated target carrier frequency of the rectifier unit; controlling the carrier frequency of the rectifier unit to be the compensated target carrier frequency of the rectifier unit.

[0015] In some embodiments, the preset model is a Markov chain prediction model; the control module controls the carrier frequency of the inverter according to the input current, the output current, and the preset model, and also includes: bringing the output current into the preset Markov chain prediction model to obtain the target carrier frequency of the inverter unit; compensating the target carrier frequency of the inverter unit according to a preset second carrier frequency compensation value to obtain the compensated target carrier frequency of the inverter unit; controlling the carrier frequency of the inverter unit to be the compensated target carrier frequency of the inverter unit.

[0016] Matching the above device, the present invention provides a magnetic levitation frequency conversion unit on another aspect, including: the control device of the magnetic levitation frequency conversion unit mentioned above.

[0017] Matching the above method, the present invention provides a storage medium on another aspect, wherein the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the control method of the magnetic levitation variable frequency unit described above.

[0018] Matching the above method, the present invention provides a computer program product on another aspect, wherein the computer program product includes a computer program, and when the computer program product is processed and executed, the steps of the control method of the above magnetic levitation variable frequency unit are implemented.

[0019] The solution of the present invention determines whether to adjust the carrier frequency of the frequency converter according to the operating frequency of the unit when the magnetic suspension frequency conversion unit is running; if it is determined to adjust the carrier frequency of the frequency converter, the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit are controlled according to the input current and output current of the frequency converter and the preset model. Thus, by flexibly controlling the rectifier carrier frequency and the inverter carrier frequency of the frequency converter, the current harmonics on the input and output sides of the frequency converter are effectively reduced, the working loss of the internal components of the frequency converter is reduced, and the reliability of the frequency converter and the operating stability of the unit are improved.

[0020] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic flow chart of an embodiment of a control method for a magnetic suspension frequency conversion unit of the present invention;

[0023] Figure 2 It is a structural schematic diagram of an embodiment of a control device for a magnetic suspension frequency conversion unit of the present invention;

[0024] Figure 3 It is the system topology diagram of the magnetic suspension frequency conversion unit of the present invention;

[0025] Figure 4 It is a structural diagram of the control principle of the main control unit of the magnetic suspension frequency conversion unit of the present invention;

[0026] Figure 5 The figure is a flow chart of a method for controlling the carrier frequency of a frequency converter of the present invention.

[0027] In conjunction with the accompanying drawings, the reference numerals in the embodiments of the present invention are as follows:

[0028] 1-inverter input side; 2-three-phase circuit breaker; 3-reactor; 4-bus capacitor; 5-inverter output side; 102-acquisition module; 104-control module. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] According to an embodiment of the present invention, a control method for a magnetic levitation variable frequency machine set is provided, wherein the magnetic levitation variable frequency machine set comprises a frequency converter; the frequency converter comprises a rectifier unit and an inverter unit. The system topology of the magnetic levitation variable frequency machine set is as follows: Figure 3As shown, at the input side 1 of the frequency converter, three-phase electricity flows into the frequency converter through the three-phase circuit breaker 2 for rectification and inversion. At the output side 5 of the frequency converter, the frequency converter provides AC power to the motor in the unit. The frequency converter includes: a rectifier unit and an inverter rectifier unit. The rectifier unit is divided into a controllable type and an uncontrollable type. A reactor 3 and a bus capacitor 4 are arranged on the two busbars between the rectifier unit and the inverter rectifier unit. The reactor 3 is an inductor. When the frequency of the bus current is high, the inductive reactance of the inductor is large, and the high frequency is blocked, thereby filtering out the high-frequency harmonics. When the frequency of the bus current is low, the capacitive reactance of the bus capacitor 4 is large, and the low frequency is blocked, thereby filtering out the low-frequency harmonics. When the unit is running, the main control unit will send PWM waves to the rectifier unit and the inverter unit respectively to control the IGBT switch tube.

[0031] like Figure 1 The control method of the magnetic suspension variable frequency machine set may include: step S110 to step S130.

[0032] In step S110, during the operation of the magnetic levitation frequency conversion unit, the input current and output current of the inverter and the operating power of the magnetic levitation frequency conversion unit are obtained.

[0033] The magnetic levitation frequency conversion unit is also equipped with a sampling unit for collecting the current on the input side of the frequency converter and the current on the output side of the frequency converter. The input current is the current of the three-phase power of the power grid, and the current on the output side is the current transmitted to the motor after rectification and inversion by the frequency converter. The operating power of the magnetic levitation frequency conversion unit is the operating power of the motor in the unit.

[0034] Optionally, the input voltage and output voltage of the inverter may also be obtained, and subsequent judgment and control may be performed based on the input voltage and the output voltage.

[0035] In step S120, it is determined whether to adjust the carrier frequency of the frequency converter according to the operating frequency; the carrier frequency of the frequency converter includes the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit.

[0036] In order to ensure the stability of the unit when reducing the current harmonic content and to effectively reduce the current harmonics, it is necessary to determine whether the current state is appropriate to control the carrier frequency of the inverter based on the operating frequency of the unit.

[0037] In some implementations, in step S120, the specific process of determining whether to adjust the carrier frequency of the inverter according to the operating frequency includes: steps S210 to S230.

[0038] Step S210, determining whether the continuous operation time of the magnetic suspension variable frequency unit at the operating frequency is greater than or equal to a preset time.

[0039] Step S220: If the continuous operation time of the magnetic suspension variable frequency unit at the operating frequency is greater than or equal to a preset time, determine whether to adjust the carrier frequency of the inverter according to the operating frequency and a preset target frequency.

[0040] Step S230: If the continuous operation time of the magnetic suspension variable frequency machine set at the operating frequency is less than a preset time, it is determined not to adjust the carrier frequency of the inverter.

[0041] When the operating frequency or power of the unit is in an unstable state, the operating parameters of the unit are constantly changing, and it is impossible to accurately predict the target carrier frequency of the inverter based on the input current and output current of the inverter, and thus it is impossible to effectively suppress harmonics. Therefore, when the continuous operation time of the unit at a certain operating frequency is less than the preset time, the carrier frequency of the inverter is not adjusted; when the continuous operation time of the unit at a certain operating frequency exceeds the preset time, the unit is considered to be in a stable state, and then further judge whether it is suitable for adjustment at the current operating frequency.

[0042] In some embodiments, in step S230, the specific process of determining whether to adjust the carrier frequency of the frequency converter according to the operating frequency and the preset target frequency includes: judging the size relationship between the operating frequency and the preset target frequency; if the operating frequency is greater than or equal to the preset target frequency, determining not to adjust the carrier frequency of the frequency converter; if the operating frequency is less than the preset target frequency, determining to adjust the carrier frequency of the frequency converter.

[0043] The target frequency is determined by the main control unit according to the terminal demand of the unit before the unit is started. If the operating frequency of the unit is ≥ the target frequency, the unit will automatically reduce the operating frequency. At this time, the operating parameters of the unit are constantly changing, and harmonics cannot be effectively suppressed, so the carrier frequency of the inverter is not adjusted. If the operating frequency of the unit is less than the target frequency, the carrier frequency of the inverter is controlled to reduce the current harmonic content on the input and output sides of the inverter.

[0044] At step S130, if it is determined to adjust the carrier frequency of the inverter, the carrier frequency of the inverter is controlled according to the input current, the output current, and a preset model to reduce the current harmonic content of the inverter. The preset model is a Markov chain prediction model.

[0045] The Markov chain can predict the future state based on the past state of the unit. For example, different carrier frequencies, different input currents, different output currents and their corresponding current harmonic contents are used as states in the Markov chain. By predicting the possibility and size of harmonics generated by the unit under different carrier frequencies based on the transition probability between these states in historical data, the optimal carrier frequency can be selected to reduce harmonics.

[0046] Specifically, firstly, the relevant parameters of the inverter when it is running at different carrier frequencies are collected, including input current, output current, harmonic content, load characteristics of the unit, etc., and the operating status of the inverter is classified and defined according to the collected data. For example, the carrier frequency can be divided into different intervals, each of which corresponds to a state; at the same time, the harmonic content is also divided into different levels as another state description. In addition, it is also possible to consider discretizing factors such as load size and ambient temperature as state variables in the Markov chain to more comprehensively describe the state of the unit.

[0047] Then, a transition probability matrix is ​​constructed. According to the collected data, the number of transitions between different states is counted, and the transition probability between states is calculated based on the number of transitions, thereby constructing a multidimensional transition probability matrix.

[0048] When the unit is running, the state that the unit may be in at the next moment or the next few moments is predicted based on the current operating state of the inverter and the constructed transfer probability matrix. At the same time, combined with the prediction of the harmonic content, the carrier frequency that can minimize the harmonic content is selected as the target carrier frequency. For example, when it is predicted that when the carrier frequency is adjusted from the current state to another state, the harmonic content has a high probability of being reduced to a lower level, the carrier frequency in the other state is determined as the target carrier frequency.

[0049] This solution flexibly controls the carrier frequency of the inverter's rectifier unit and inverter unit according to the different operating states of the unit to match the actual operating frequency requirements, thereby effectively reducing the current harmonic content on the input and output sides of the inverter, reducing the working loss of the inverter's internal components, balancing the relationship between harmonics and losses, and further improving the operating stability of the magnetic levitation variable frequency central air conditioner and the reliability of the inverter.

[0050] In some embodiments, in step S130, the specific process of controlling the carrier frequency of the inverter according to the input current, the output current, and a preset model includes: subjecting the input current to a preset Markov chain prediction model to obtain a target carrier frequency of the rectifier unit; compensating the target carrier frequency of the rectifier unit according to a preset first carrier frequency compensation value to obtain the compensated target carrier frequency of the rectifier unit; and controlling the carrier frequency of the rectifier unit to be the compensated target carrier frequency of the rectifier unit.

[0051] The principle of the main control unit controlling the carrier frequency of the inverter is as follows Figure 4 As shown, a carrier frequency PWM wave generator is provided in the unit, which is used to send PWM waves to the rectifier unit and the inverter unit to control the switching frequency of the IGBT switch tube. First, the main control unit determines whether to adjust according to the target frequency f and the current operating frequency f1. If it is determined to adjust, the operating parameters of the motor and the input current and output current of the inverter are collected. The operating parameters of the motor include the operating frequency and power. After that, the main control unit calculates the target carrier frequencies of the rectifier unit and the inverter unit according to the input current and the output current, compensates the target frequency, and sends the compensated target carrier frequency to the carrier frequency PWM wave generator. In each cycle, the carrier frequency PWM wave generator generates multiple carrier frequencies of random sizes, and selects the carrier frequency that is equal to or closest to the target frequency, and sends them to the rectifier unit and the inverter unit of the inverter respectively.

[0052] For the rectifier unit, the main control unit predicts the target carrier frequency of the rectifier unit with the minimum harmonics under the premise of meeting the input harmonic content requirements based on the input current of the inverter and the Markov chain prediction model, and calibrates the target carrier frequency according to the operating parameters of the unit to obtain the target switching frequency of the IGBT switch tube in the rectifier unit. In this way, while meeting the input harmonic content requirements, the loss of the unit is greatly reduced, the life of the internal components of the inverter is avoided, and the stability of the unit and the reliability of the inverter are improved.

[0053] In some embodiments, in step S130, the specific process of controlling the carrier frequency of the inverter according to the input current, the output current, and a preset model also includes: subjecting the output current to a preset Markov chain prediction model to obtain a target carrier frequency of the inverter unit; compensating the target carrier frequency of the inverter unit according to a preset second carrier frequency compensation value to obtain the compensated target carrier frequency of the inverter unit; and controlling the carrier frequency of the inverter unit to be the compensated target carrier frequency of the inverter unit.

[0054] For the inverter unit, the main control unit predicts the target carrier frequency of the inverter unit with the minimum harmonics under the premise of meeting the input harmonic content requirements based on the output current of the inverter and the Markov chain prediction model, and calibrates the target carrier frequency according to the operating parameters of the unit to obtain the target switching frequency of the IGBT switch tube in the inverter unit. In this way, while meeting the output harmonic content requirements, the loss of the unit is greatly reduced, the life of the internal components of the inverter is avoided, and the stability of the unit and the reliability of the inverter are improved.

[0055] Figure 5 FIG. 1 is a flow chart of a method for controlling the carrier frequency of a frequency converter of the present invention, as shown in FIG. Figure 5 As shown, including:

[0056] Step 1: After the inverter is powered on, the main control unit determines the target frequency f of the unit according to the terminal demand of the unit. After the unit is stable, the operating frequency f1 of the unit is calculated according to the current and voltage signals on the input and output sides of the unit, and the main control unit starts to lock the operating frequency f1 at this time.

[0057] Step 2, determine whether the operating frequency f1 ≥ the maximum value of the target frequency f. If the operating frequency f1 ≥ the maximum value of the target frequency f, the inverter automatically reduces the operating frequency without adjusting the carrier cycle. If the operating frequency f1 < the maximum value of the target frequency f, for the rectifier unit of the inverter, the main control unit calculates the target carrier frequency f2 of the rectifier unit based on the Markov chain model through the input current and voltage signals obtained by the acquisition unit, and then compensates the target carrier frequency f2 by the given compensation value δ, and finally the carrier frequency PWM wave generator sends the PWM wave of the target carrier frequency f2 to the IGBT switch tube of the rectifier unit; for the inverter unit of the inverter, the main control unit calculates the target carrier frequency f3 of the inverter unit based on the Markov chain model through the output current and voltage signals obtained by the acquisition unit, and then compensates the target carrier frequency f3 by the given compensation value δ, and finally the carrier frequency PWM wave generator sends the PWM wave of the target carrier frequency f3 to the IGBT switch tube of the inverter unit.

[0058] By adopting the technical solution of this embodiment, when the magnetic suspension frequency conversion unit is running, it is determined whether to adjust the carrier frequency of the frequency converter according to the operating frequency of the unit; if it is determined to adjust the carrier frequency of the frequency converter, the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit are controlled according to the input current and output current of the frequency converter and the preset model. Thus, by flexibly controlling the rectifier carrier frequency and the inverter carrier frequency of the frequency converter, the current harmonics on the input and output sides of the frequency converter are effectively reduced, the working loss of the internal components of the frequency converter is reduced, and the reliability of the frequency converter and the operating stability of the unit are improved.

[0059] According to an embodiment of the present invention, a control device for a magnetic levitation variable frequency machine set corresponding to the control method of the magnetic levitation variable frequency machine set is also provided. The magnetic levitation variable frequency machine set includes a frequency converter; the frequency converter includes a rectifier unit and an inverter unit. The system topology of the magnetic levitation variable frequency machine set is as follows: Figure 3 As shown, at the input side 1 of the frequency converter, three-phase electricity flows into the frequency converter through the three-phase circuit breaker 2 for rectification and inversion. At the output side 5 of the frequency converter, the frequency converter provides AC power to the motor in the unit. The frequency converter includes: a rectifier unit and an inverter rectifier unit. The rectifier unit is divided into a controllable type and an uncontrollable type. A reactor 3 and a bus capacitor 4 are arranged on the two busbars between the rectifier unit and the inverter rectifier unit. The reactor 3 is an inductor. When the frequency of the bus current is high, the inductive reactance of the inductor is large, and the high frequency is blocked, thereby filtering out the high-frequency harmonics. When the frequency of the bus current is low, the capacitive reactance of the bus capacitor 4 is large, and the low frequency is blocked, thereby filtering out the low-frequency harmonics. When the unit is running, the main control unit will send PWM waves to the rectifier unit and the inverter unit respectively to control the IGBT switch tube.

[0060] See also Figure 2 The control device of the magnetic suspension variable frequency machine set may include: an acquisition module 102 and a control module 104 .

[0061] The acquisition module 102 is configured to acquire the input current and output current of the inverter and the operating power of the magnetic levitation frequency conversion unit during the operation of the magnetic levitation frequency conversion unit.

[0062] The magnetic levitation frequency conversion unit is also equipped with a sampling unit for collecting the current on the input side of the frequency converter and the current on the output side of the frequency converter. The input current is the current of the three-phase power of the power grid, and the current on the output side is the current transmitted to the motor after rectification and inversion by the frequency converter. The operating power of the magnetic levitation frequency conversion unit is the operating power of the motor in the unit.

[0063] Optionally, the input voltage and output voltage of the inverter may also be obtained, and subsequent judgment and control may be performed based on the input voltage and the output voltage.

[0064] The control module 104 is configured to determine whether to adjust the carrier frequency of the frequency converter according to the operating frequency; the carrier frequency of the frequency converter includes the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit.

[0065] In order to ensure the stability of the unit when reducing the current harmonic content and to effectively reduce the current harmonics, it is necessary to determine whether the current state is appropriate to control the carrier frequency of the inverter based on the operating frequency of the unit.

[0066] In some implementations, the control module 104 determines whether to adjust the carrier frequency of the frequency converter according to the operating frequency, including:

[0067] The control module 104 is further specifically configured to determine whether the continuous operation time of the magnetic levitation variable frequency unit at the operating frequency is greater than or equal to a preset time.

[0068] The control module 104 is further specifically configured to determine whether to adjust the carrier frequency of the inverter according to the operating frequency and a preset target frequency if the continuous operating time of the magnetic levitation variable frequency unit at the operating frequency is greater than or equal to a preset time.

[0069] The control module 104 is further specifically configured to determine not to adjust the carrier frequency of the inverter if the continuous operation time of the magnetic levitation variable frequency machine set at the operating frequency is less than a preset time.

[0070] When the operating frequency or power of the unit is in an unstable state, the operating parameters of the unit are constantly changing, and it is impossible to accurately predict the target carrier frequency of the inverter based on the input current and output current of the inverter, and thus it is impossible to effectively suppress harmonics. Therefore, when the continuous operation time of the unit at a certain operating frequency is less than the preset time, the carrier frequency of the inverter is not adjusted; when the continuous operation time of the unit at a certain operating frequency exceeds the preset time, the unit is considered to be in a stable state, and then further judge whether it is suitable for adjustment at the current operating frequency.

[0071] In some embodiments, the control module 104 determines whether to adjust the carrier frequency of the frequency converter according to the operating frequency and the preset target frequency, including: judging the size relationship between the operating frequency and the preset target frequency; if the operating frequency is greater than or equal to the preset target frequency, determining not to adjust the carrier frequency of the frequency converter; if the operating frequency is less than the preset target frequency, determining to adjust the carrier frequency of the frequency converter.

[0072] The target frequency is determined by the main control unit according to the terminal demand of the unit before the unit is started. If the operating frequency of the unit is ≥ the target frequency, the unit will automatically reduce the operating frequency. At this time, the operating parameters of the unit are constantly changing, and harmonics cannot be effectively suppressed, so the carrier frequency of the inverter is not adjusted. If the operating frequency of the unit is less than the target frequency, the carrier frequency of the inverter is controlled to reduce the current harmonic content on the input and output sides of the inverter.

[0073] The control module 104 is further configured to control the carrier frequency of the inverter according to the input current, the output current and a preset model to reduce the current harmonic content of the inverter if it is determined to adjust the carrier frequency of the inverter. The preset model is a Markov chain prediction model.

[0074] The Markov chain can predict the future state based on the past state of the unit. For example, different carrier frequencies, different input currents, different output currents and their corresponding current harmonic contents are used as states in the Markov chain. By predicting the possibility and size of harmonics generated by the unit under different carrier frequencies based on the transition probability between these states in historical data, the optimal carrier frequency can be selected to reduce harmonics.

[0075] Specifically, firstly, the relevant parameters of the inverter when it is running at different carrier frequencies are collected, including input current, output current, harmonic content, load characteristics of the unit, etc., and the operating status of the inverter is classified and defined according to the collected data. For example, the carrier frequency can be divided into different intervals, each of which corresponds to a state; at the same time, the harmonic content is also divided into different levels as another state description. In addition, it is also possible to consider discretizing factors such as load size and ambient temperature as state variables in the Markov chain to more comprehensively describe the state of the unit.

[0076] Then, a transition probability matrix is ​​constructed. According to the collected data, the number of transitions between different states is counted, and the transition probability between states is calculated based on the number of transitions, thereby constructing a multidimensional transition probability matrix.

[0077] When the unit is running, the state that the unit may be in at the next moment or the next few moments is predicted based on the current operating state of the inverter and the constructed transfer probability matrix. At the same time, combined with the prediction of the harmonic content, the carrier frequency that can minimize the harmonic content is selected as the target carrier frequency. For example, when it is predicted that when the carrier frequency is adjusted from the current state to another state, the harmonic content has a high probability of being reduced to a lower level, the carrier frequency in the other state is determined as the target carrier frequency.

[0078] This solution flexibly controls the carrier frequency of the inverter's rectifier unit and inverter unit according to the different operating states of the unit to match the actual operating frequency requirements, thereby effectively reducing the current harmonic content on the input and output sides of the inverter, reducing the working loss of the inverter's internal components, balancing the relationship between harmonics and losses, and further improving the operating stability of the magnetic levitation variable frequency central air conditioner and the reliability of the inverter.

[0079] In some embodiments, the control module 104 controls the carrier frequency of the inverter according to the input current, the output current, and a preset model, including: subjecting the input current to a preset Markov chain prediction model to obtain a target carrier frequency of the rectifier unit; compensating the target carrier frequency of the rectifier unit according to a preset first carrier frequency compensation value to obtain the compensated target carrier frequency of the rectifier unit; and controlling the carrier frequency of the rectifier unit to be the compensated target carrier frequency of the rectifier unit.

[0080] The principle of the main control unit controlling the carrier frequency of the inverter is as follows Figure 4 As shown, a carrier frequency PWM wave generator is provided in the unit, which is used to send PWM waves to the rectifier unit and the inverter unit to control the switching frequency of the IGBT switch tube. First, the main control unit determines whether to adjust according to the target frequency f and the current operating frequency f1. If it is determined to adjust, the operating parameters of the motor and the input current and output current of the inverter are collected. The operating parameters of the motor include the operating frequency and power. After that, the main control unit calculates the target carrier frequencies of the rectifier unit and the inverter unit according to the input current and the output current, compensates the target frequency, and sends the compensated target carrier frequency to the carrier frequency PWM wave generator. In each cycle, the carrier frequency PWM wave generator generates multiple carrier frequencies of random sizes, and selects the carrier frequency that is equal to or closest to the target frequency, and sends them to the rectifier unit and the inverter unit of the inverter respectively.

[0081] For the rectifier unit, the main control unit predicts the target carrier frequency of the rectifier unit with the minimum harmonics under the premise of meeting the input harmonic content requirements based on the input current of the inverter and the Markov chain prediction model, and calibrates the target carrier frequency according to the operating parameters of the unit to obtain the target switching frequency of the IGBT switch tube in the rectifier unit. In this way, while meeting the input harmonic content requirements, the loss of the unit is greatly reduced, the life of the internal components of the inverter is avoided, and the stability of the unit and the reliability of the inverter are improved.

[0082] In some implementations, the control module 104 controls the carrier frequency of the inverter according to the input current, the output current, and a preset model, and further includes:

[0083] The output current is brought into a preset Markov chain prediction model to obtain the target carrier frequency of the inverter unit; the target carrier frequency of the inverter unit is compensated according to a preset second carrier frequency compensation value to obtain the compensated target carrier frequency of the inverter unit; and the carrier frequency of the inverter unit is controlled to be the compensated target carrier frequency of the inverter unit.

[0084] For the inverter unit, the main control unit predicts the target carrier frequency of the inverter unit with the minimum harmonics under the premise of meeting the input harmonic content requirements based on the output current of the inverter and the Markov chain prediction model, and calibrates the target carrier frequency according to the operating parameters of the unit to obtain the target switching frequency of the IGBT switch tube in the inverter unit. In this way, while meeting the output harmonic content requirements, the loss of the unit is greatly reduced, the life of the internal components of the inverter is avoided, and the stability of the unit and the reliability of the inverter are improved.

[0085] Figure 5 FIG. 1 is a flow chart of a method for controlling the carrier frequency of a frequency converter of the present invention, as shown in FIG. Figure 5 As shown, including:

[0086] Step 1: After the inverter is powered on, the main control unit determines the target frequency f of the unit according to the terminal demand of the unit. After the unit is stable, the operating frequency f1 of the unit is calculated according to the current and voltage signals on the input and output sides of the unit, and the main control unit starts to lock the operating frequency f1 at this time.

[0087] Step 2, determine whether the operating frequency f1 ≥ the maximum value of the target frequency f. If the operating frequency f1 ≥ the maximum value of the target frequency f, the inverter automatically reduces the operating frequency without adjusting the carrier cycle. If the operating frequency f1 < the maximum value of the target frequency f, for the rectifier unit of the inverter, the main control unit calculates the target carrier frequency f2 of the rectifier unit based on the Markov chain model through the input current and voltage signals obtained by the acquisition unit, and then compensates the target carrier frequency f2 by the given compensation value δ, and finally the carrier frequency PWM wave generator sends the PWM wave of the target carrier frequency f2 to the IGBT switch tube of the rectifier unit; for the inverter unit of the inverter, the main control unit calculates the target carrier frequency f3 of the inverter unit based on the Markov chain model through the output current and voltage signals obtained by the acquisition unit, and then compensates the target carrier frequency f3 by the given compensation value δ, and finally the carrier frequency PWM wave generator sends the PWM wave of the target carrier frequency f3 to the IGBT switch tube of the inverter unit.

[0088] Since the processing and functions implemented by the device of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0089] By adopting the technical solution of the present invention, when the magnetic suspension frequency conversion unit is running, it is determined whether to adjust the carrier frequency of the frequency converter according to the operating frequency of the unit; if it is determined to adjust the carrier frequency of the frequency converter, the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit are controlled according to the input current and output current of the frequency converter and the preset model. Thus, by flexibly controlling the rectifier carrier frequency and the inverter carrier frequency of the frequency converter, the current harmonics on the input and output sides of the frequency converter are effectively reduced, the working loss of the internal components of the frequency converter is reduced, and the reliability of the frequency converter and the operating stability of the unit are improved.

[0090] According to an embodiment of the present invention, a magnetic suspension variable frequency machine set corresponding to the control device of the magnetic suspension variable frequency machine set is also provided. The magnetic suspension variable frequency machine set may include: the control device of the magnetic suspension variable frequency machine set described above.

[0091] Since the processing and functions implemented by the magnetic levitation frequency conversion unit of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned device, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0092] By adopting the technical solution of the present invention, when the magnetic suspension frequency conversion unit is running, it is determined whether to adjust the carrier frequency of the frequency converter according to the operating frequency of the unit; if it is determined to adjust the carrier frequency of the frequency converter, the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit are controlled according to the input current and output current of the frequency converter and the preset model. Thus, by flexibly controlling the rectifier carrier frequency and the inverter carrier frequency of the frequency converter, the current harmonics on the input and output sides of the frequency converter are effectively reduced, the working loss of the internal components of the frequency converter is reduced, and the reliability of the frequency converter and the operating stability of the unit are improved.

[0093] According to an embodiment of the present invention, a storage medium corresponding to a control method for a magnetic levitation variable frequency unit is also provided, wherein the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the control method for the magnetic levitation variable frequency unit described above.

[0094] Since the processing and functions implemented by the storage medium of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0095] By adopting the technical solution of the present invention, when the magnetic suspension frequency conversion unit is running, it is determined whether to adjust the carrier frequency of the frequency converter according to the operating frequency of the unit; if it is determined to adjust the carrier frequency of the frequency converter, the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit are controlled according to the input current and output current of the frequency converter and the preset model. Thus, by flexibly controlling the rectifier carrier frequency and the inverter carrier frequency of the frequency converter, the current harmonics on the input and output sides of the frequency converter are effectively reduced, the working loss of the internal components of the frequency converter is reduced, and the reliability of the frequency converter and the operating stability of the unit are improved.

[0096] According to an embodiment of the present invention, a computer program product corresponding to the control method of the magnetic levitation variable frequency machine set is also provided, and the computer program product includes a computer program, and when the computer program product is processed and executed, the steps of the control method of the magnetic levitation variable frequency machine set are implemented.

[0097] Since the processing and functions implemented by the computer program product of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0098] By adopting the technical solution of the present invention, when the magnetic suspension frequency conversion unit is running, it is determined whether to adjust the carrier frequency of the frequency converter according to the operating frequency of the unit; if it is determined to adjust the carrier frequency of the frequency converter, the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit are controlled according to the input current and output current of the frequency converter and the preset model. Thus, by flexibly controlling the rectifier carrier frequency and the inverter carrier frequency of the frequency converter, the current harmonics on the input and output sides of the frequency converter are effectively reduced, the working loss of the internal components of the frequency converter is reduced, and the reliability of the frequency converter and the operating stability of the unit are improved.

[0099] In summary, it is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0100] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A control method for a magnetic suspension variable frequency unit, characterized in that: The magnetic suspension frequency conversion unit includes a frequency converter; the frequency converter includes a rectifier unit and an inverter unit; The method comprises: During the operation of the magnetic suspension frequency conversion unit, obtaining the input current and output current of the frequency converter and the operating power of the magnetic suspension frequency conversion unit; Determining whether to adjust the carrier frequency of the frequency converter according to the operating frequency; the carrier frequency of the frequency converter includes the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit; If it is determined to adjust the carrier frequency of the frequency converter, the carrier frequency of the frequency converter is controlled according to the input current, the output current, and a preset model.

2. The control method of the magnetic suspension frequency conversion unit according to claim 1 is characterized in that: Determining whether to adjust the carrier frequency of the frequency converter according to the operating frequency includes: Determine whether the continuous operation time of the magnetic suspension variable frequency unit at the operating frequency is greater than or equal to a preset time; If the continuous operation time of the magnetic suspension variable frequency unit at the operating frequency is greater than or equal to the preset time, determining whether to adjust the carrier frequency of the inverter according to the operating frequency and the preset target frequency; If the continuous operation time of the magnetic suspension variable frequency machine set at the operating frequency is less than a preset time, it is determined not to adjust the carrier frequency of the inverter.

3. The control method of the magnetic suspension frequency conversion unit according to claim 2 is characterized in that: Determining whether to adjust the carrier frequency of the frequency converter according to the operating frequency and the preset target frequency includes: Determining the magnitude relationship between the operating frequency and a preset target frequency; If the operating frequency is greater than or equal to the preset target frequency, determining not to adjust the carrier frequency of the frequency converter; If the operating frequency is less than the preset target frequency, it is determined to adjust the carrier frequency of the frequency converter.

4. The control method of the magnetic suspension frequency conversion unit according to any one of claims 1 to 3, characterized in that: The default model is the Markov chain prediction model; Controlling the carrier frequency of the frequency converter according to the input current, the output current, and a preset model includes: Submitting the input current into a preset Markov chain prediction model to obtain a target carrier frequency of the rectifier unit; Compensating the target carrier frequency of the rectifier unit according to a preset first carrier frequency compensation value to obtain the compensated target carrier frequency of the rectifier unit; The carrier frequency of the rectifier unit is controlled to be the target carrier frequency of the rectifier unit after compensation.

5. The control method of the magnetic suspension frequency conversion unit according to any one of claims 1 to 3, characterized in that: The default model is the Markov chain prediction model; According to the input current, the output current, and a preset model, the carrier frequency of the frequency converter is controlled, and further comprising: Substituting the output current into a preset Markov chain prediction model to obtain a target carrier frequency of the inverter unit; Compensating the target carrier frequency of the inverter unit according to a preset second carrier frequency compensation value to obtain the compensated target carrier frequency of the inverter unit; The carrier frequency of the inverter unit is controlled to be the target carrier frequency of the inverter unit after compensation.

6. A control device for a magnetic suspension variable frequency unit, characterized in that: The magnetic suspension frequency conversion unit includes a frequency converter; the frequency converter includes a rectifier unit and an inverter unit; The device comprises: An acquisition module is configured to acquire the input current and output current of the inverter and the operating power of the magnetic levitation frequency conversion unit during the operation of the magnetic levitation frequency conversion unit; A control module, configured to determine whether to adjust the carrier frequency of the frequency converter according to the operating frequency; the carrier frequency of the frequency converter includes the carrier frequency of the rectifier unit and the carrier frequency of the inverter unit; The control module is further configured to control the carrier frequency of the inverter according to the input current, the output current, and a preset model if it is determined to adjust the carrier frequency of the inverter.

7. The control device of the magnetic suspension frequency conversion unit according to claim 6 is characterized in that: The control module determines whether to adjust the carrier frequency of the inverter according to the operating frequency, including: Determine whether the continuous operation time of the magnetic suspension variable frequency unit at the operating frequency is greater than or equal to a preset time; If the continuous operation time of the magnetic suspension variable frequency unit at the operating frequency is greater than or equal to the preset time, determining whether to adjust the carrier frequency of the inverter according to the operating frequency and the preset target frequency; If the continuous operation time of the magnetic suspension variable frequency machine set at the operating frequency is less than a preset time, it is determined not to adjust the carrier frequency of the inverter.

8. A magnetic suspension variable frequency unit, characterized in that: include: A control device for a magnetic levitation frequency conversion unit as claimed in claim 6 or 7.

9. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the control method of the magnetic levitation variable frequency machine set according to any one of claims 1 to 5.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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