Vector frequency conversion control method and system from motor rotor side

Abstract

The invention relates to the field of application frequency conversion technology and microelectronic technology, and discloses a vector frequency conversion control method and system from a motor rotor side, and the method comprises the steps: obtaining control parameters, inputting the control parameters into a motor stator flux linkage orientation model, calculating a first current component and a second current component, and inputting the first current component and the second current component into a motor vector control model, calculating to obtain a corresponding voltage component, and converting the corresponding voltage component into a rotor three-phase voltage through inverse transformation to control the rotor side of the motor; and judging the running state of the rotor side of the motor by using a stability augmentation device, adjusting the input control parameters according to the judgment result, inputting the adjusted control parameters into the stator flux linkage orientation model of the motor again, starting the motor, closing the high-voltage circuit breaker and matching the voltage of a synchronizing device, and starting the high-voltage circuit breaker. Obtaining a motor in a normal operation state; fault processing is carried out on the motor in the normal operation state, the normal operation state of the motor is achieved, and high reliability, speed regulation technical indexes and performance are achieved when the motor is applied to a high-voltage motor.

Description

Technical Field

[0001] The present invention relates to the fields of applied frequency conversion technology and microelectronics technology, and in particular to a method and system for performing vector frequency conversion control from the rotor side of an electric motor. Background Art

[0002] A variable-frequency drive (VFD) is a power control device that applies variable-frequency and microelectronics technology to control AC motors by varying the motor's operating power supply frequency. A VFD primarily consists of a rectifier (AC to DC), filter, inverter (DC to AC), brake unit, drive unit, detection unit, and microprocessor. Vector control, also known as field-oriented control (FOC), is a technique for controlling three-phase AC motors using a variable-frequency drive (VFD). The motor's output is controlled by adjusting the VFD's output frequency, voltage, and angle. Its characteristic is the ability to independently control the motor's magnetic field and torque, achieving characteristics similar to those of a separately excited DC motor. Because the three-phase output current and voltage are represented as vectors during processing, it is called vector control.

[0003] Traditional inverters currently utilize a series arrangement of a power supply, inverter, and motor. 100% of the motor's required power (P) must be converted from the power supply to the motor through the inverter. Therefore, controlling a motor with a rated power of PN using a conventional inverter requires an inverter capacity greater than PN. High-voltage motors are typically high-power, ranging from several hundred kilowatts to tens of thousands of kilowatts. This results in bulky systems, complex systems, numerous failure factors, and reduced reliability. In the medium- and high-voltage inverter sector, manufacturing high-power, high-voltage-resistant power electronic devices presents difficulties in withstanding the 6kV and 10kV voltages. Consequently, current high- and medium-voltage inverter technologies often employ transformers to reduce the voltage in multiple steps, connecting multiple power units (converter units) in series to address this high-voltage tolerance. The complexities of voltage balancing and other associated issues associated with series-connected power units complicate the inverter circuitry, increase the number of failure factors, and compromise reliability. Summary of the Invention

[0004] In view of the above existing problems, the present invention is proposed.

[0005] Therefore, the present invention provides a method and system for vector frequency conversion control from the rotor side of the motor to solve the problem that traditional frequency converters use a power supply, frequency converter, and motor in series, requiring full power conversion, resulting in a large, complex device and low reliability when controlling high-voltage and high-power motors; due to the voltage resistance limitations of power electronic devices in the medium and high voltage frequency conversion fields, transformer step-down and multiple power unit series connection technology are often used, but this technology makes the circuit complex and increases the number of failure factors.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a method for performing vector frequency conversion control from the rotor side of a motor, comprising:

[0008] Acquiring control parameters, inputting the control parameters into a stator flux orientation model of the motor, and calculating a first current component and a second current component;

[0009] Inputting the first current component and the second current component into a motor vector control model to calculate corresponding voltage components, and converting the voltage components into rotor three-phase voltages through inverse transformation to control the rotor side of the motor;

[0010] The stabilization device is used to judge the operating state of the motor rotor side, and according to the judgment result, the input control parameters are adjusted, the adjusted control parameters are input into the motor stator flux orientation model again, and the motor is started;

[0011] The started motor is subjected to high-voltage circuit breaker closing and voltage matching of the synchronization device to obtain the motor in normal operating state;

[0012] Fault processing is performed on the motor in the normal operating state to achieve the normal operating state of the motor.

[0013] As a preferred solution of the method for performing vector frequency conversion control from the motor rotor side of the present invention, the first current component includes:

[0014] The first calculation formula is obtained by subtracting the square of the stator voltage from the product of twice the motor electrical angular velocity, stator resistance, and motor torque, plus the square root of the difference between the fourth power of the stator voltage and four times the motor electrical angular velocity multiplied by the stator resistance multiplied by the motor torque multiplied by the square of the stator voltage, and four times the square of the stator resistance multiplied by the square of the motor torque divided by the square of the stator inductance.

[0015] The second calculation formula is twice the square of the stator resistance plus the square of the motor's electrical angular velocity multiplied by the square of the stator inductance;

[0016] The first current component is obtained by dividing the first calculation formula by the square root of the quotient of the second calculation formula.

[0017] As a preferred solution of the method for performing vector frequency conversion control from the motor rotor side of the present invention, the second current component is:

[0018] The third calculation formula is the square root of the difference between the square of the stator voltage minus the product of twice the motor electrical angular velocity, stator resistance, and motor torque, minus the fourth power of the stator voltage, four times the motor electrical angular velocity multiplied by the stator resistance multiplied by the motor torque multiplied by the square of the stator voltage, and four times the square of the stator resistance multiplied by the square of the motor torque divided by the square of the stator inductance.

[0019] Twice the square of the stator resistance is the fourth calculation formula;

[0020] The second current component is obtained by dividing the third calculation formula by the square root of the quotient of the fourth calculation formula.

[0021] As a preferred solution of the method for performing vector frequency conversion control from the motor rotor side of the present invention, wherein: using the stabilization device to judge the operating state of the motor rotor side includes:

[0022] The operating state of the motor rotor side is judged by detecting the frequency and voltage of the high-voltage grid and measuring the amplitude and phase angle difference of the voltage and current on the stator side by CT;

[0023] When the first current component is equal to 0, the motor is in a critical stable state;

[0024] When the first current component is less than 0, the motor is in an understable state;

[0025] When the first current component is greater than 0, the motor is in an overstable state.

[0026] As a preferred solution of the method for performing vector frequency conversion control from the motor rotor side of the present invention, adjusting the input control parameters includes:

[0027] When the motor is in a critical stable state, the input signal speed command and torque command are not interfered with;

[0028] When the motor is in an understable state, increase the torque command. When the torque command reaches the maximum, the motor is still in an understable state, reduce the speed command until the motor is critically stable.

[0029] When the motor is in an overstable state, the input signal speed command and torque command are not intervened or the torque command is reduced until the motor is critically stable.

[0030] As a preferred solution of the method for performing vector frequency conversion control from the motor rotor side of the present invention, the steps of closing the high-voltage circuit breaker and performing voltage matching of the synchronization device on the started motor include:

[0031] The high-voltage circuit breaker of the started motor is closed, the stator winding is energized, and a no-load excitation current is generated;

[0032] The rotor side is open circuit, generating no-load voltage;

[0033] The initial phase angle is adjusted by the synchronization device to match the rotor three-phase voltage output by the inverter device with the no-load voltage on the rotor side in terms of amplitude, frequency and phase;

[0034] Once the matching is completed, the contactor closes, the inverter outputs electrical energy to the rotor side, and the motor enters normal operation.

[0035] In a second aspect, the present invention provides a vector frequency conversion control system from the motor rotor side, comprising:

[0036] a calculation module, configured to obtain control parameters, input the control parameters into a stator flux orientation model of the motor, and calculate a first current component and a second current component;

[0037] a control module, configured to input the first current component and the second current component into a motor vector control model, calculate corresponding voltage components, and convert the voltage components into rotor three-phase voltages through inverse transformation to control the rotor side of the motor;

[0038] an adjustment module, configured to determine the operating state of the motor rotor side using the stabilization device, adjust the input control parameters according to the determination result, input the adjusted control parameters into the motor stator flux orientation model again, and start the motor;

[0039] A matching module is used to close the high-voltage circuit breaker and match the voltage of the synchronization device of the started motor to obtain the motor in normal operating state;

[0040] The fault processing module is used to perform fault processing on the motor in the normal operating state to achieve the normal operating state of the motor.

[0041] As a preferred solution of the present invention for performing a vector frequency conversion control system from the motor rotor side, the vector frequency conversion control system from the motor rotor side includes:

[0042] A wound-rotor three-phase asynchronous motor is used, which is directly connected to the industrial frequency high and medium voltage power busbars through a circuit breaker. The rotor winding is directly connected to the low-voltage inverter VF through carbon brushes and slip rings. The low-voltage inverter VF is connected to the AC400V AC power grid.

[0043] In a third aspect, the present invention provides a computing device, comprising:

[0044] memory and processor;

[0045] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the vector frequency conversion control method from the motor rotor side are implemented.

[0046] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for performing vector frequency conversion control from the rotor side of the motor.

[0047] Compared with existing technologies, the present invention offers the following advantages: The variable-frequency vector control method and system implemented from the motor rotor side achieves high reliability, speed regulation technical indicators, and performance in high-voltage motor applications. Furthermore, compared with high-voltage variable-frequency technology, the present invention offers significant advantages in terms of speed regulation modification investment, power savings, resource consumption, environmental requirements, operating and maintenance costs, installation size, and cost-effectiveness. Therefore, the technology should be vigorously promoted. Its industrial development will bring significant benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 This is a logic diagram of the overall process of a method for performing vector frequency conversion control from the rotor side of a motor according to an embodiment of the present invention;

[0050] Figure 2 This is a framework diagram of a method for performing vector frequency conversion control from the rotor side of a motor according to an embodiment of the present invention;

[0051] Figure 3 This is an equivalent circuit diagram of the DQ (MT) coordinate axis of an asynchronous motor according to a method for performing vector frequency conversion control from the motor rotor side according to an embodiment of the present invention;

[0052] Figure 4 This is an equivalent circuit diagram of an asynchronous motor based on stator flux orientation MT, in which a vector frequency conversion control method is performed from the rotor side of the motor according to an embodiment of the present invention;

[0053] Figure 5 The stator side voltage and current of the vector frequency conversion control method from the motor rotor side according to one embodiment of the present invention are based on the stator flux orientation MT coordinate diagram;

[0054] Figure 6A schematic diagram of motor system stability according to a method for performing vector frequency conversion control from the motor rotor side according to an embodiment of the present invention;

[0055] Figure 7 The rotor side M-axis current I of the method for performing vector frequency conversion control from the motor rotor side according to one embodiment of the present invention is rm MT equivalent circuit diagram of ≠0;

[0056] Figure 8 The rotor side M-axis current I of the method for performing vector frequency conversion control from the motor rotor side according to one embodiment of the present invention is rm MT coordinate diagram ≠0;

[0057] Figure 9 This is a flow chart of a stabilization system for a method of performing vector frequency conversion control from the rotor side of a motor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0058] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0059] Example 1, reference Figure 1-9 , which is an embodiment of the present invention, provides a method for performing vector frequency conversion control from the motor rotor side, comprising:

[0060] S100: Acquire control parameters, input the control parameters into a motor stator flux orientation model, and calculate a first current component and a second current component;

[0061] S200: Inputting the first current component and the second current component into a motor vector control model, calculating corresponding voltage components, and converting the voltage components into rotor three-phase voltages through inverse transformation to control the rotor side of the motor;

[0062] Specifically, the first current component is the motor stator current component on the M coordinate axis, the second current component is the motor stator current component on the T coordinate axis, and the rotor side MT coordinate axis voltage U rm 、U rt :

[0063]

[0064] Where s is the slip rate, ω is the motor electrical angular velocity, L s is the stator inductance in the MT coordinate equivalent circuit, L ris the rotor inductance in the MT coordinate equivalent circuit, L m is the mutual inductance of the stator and rotor in the MT coordinate equivalent circuit, I rt is the component of the motor stator current on the M coordinate axis, I st is the component of the motor stator current on the T axis, R r is the rotor resistance in the MT coordinate equivalent circuit;

[0065] Will U rm 、U rt Through Park inverse transform and Clark inverse transform U a 、U b 、U c The signal is output to the inverter, and the inverter outputs the electrical energy to the motor rotor side;

[0066] The Park inverse transform includes the rotor side MT coordinate axis U rm 、U rt After input, the DC voltage is converted into AC voltage according to the input phase angle. The Park inverse transform and Clark inverse transform are no different from the Park inverse transform and Clark inverse transform of the traditional inverter.

[0067] It should be noted that by precisely controlling the rotor side voltage, efficient motor control can be achieved, energy loss can be reduced, and system efficiency can be improved.

[0068] S300: Using the stabilization device to determine the operating state of the motor rotor side, adjusting the input control parameters based on the determination result, re-inputting the adjusted control parameters into the motor stator flux orientation model, and starting the motor;

[0069] S400: Closing the high-voltage circuit breaker and performing voltage matching of the synchronization device on the started motor to obtain a normal operating state of the motor;

[0070] S500: Perform fault processing on the motor in a normal operating state to achieve normal operating state of the motor.

[0071] Specifically, such as Figure 2 As shown, in normal operation, the circuit breaker QF is closed, the contactor KM1 is closed, and the inverter operates normally;

[0072] When the inverter fails, the inverter stops working; contactor KM2 closes, contactor KM1 opens, and the inverter is completely offline; contactor KM2 drives the starting current limiting resistor R to work;

[0073] Finally, contactor KM3 is closed and KM2 is opened, and the motor will switch to the power frequency mode.

[0074] It should be noted that the present invention compares traditional inverters in fault scenarios. Traditional high-voltage inverters use semiconductor modules in series. If a single module fails, even if a bypass is activated to remove the faulty module, the inverter will not be able to output full voltage and power. Variable frequency vector control is implemented from the motor rotor side. The closer the motor is to full power output, the lighter the inverter load. The inverter modules are used in parallel. If a faulty module needs to be removed, it will only affect the motor's output torque at low frequencies. When the application scenario has a lower frequency operating limit, the impact of module failure will be minimized.

[0075] It should be noted that the traditional inverter outputs the same amount of power as the motor requires; in the present invention, only a portion of the power will be returned to the grid through the inverter, and the rest will be directly output to the load by the motor. The closer the motor is to the rated speed, the smaller the power diverted by the inverter, and the greater the power directly output by the motor; traditional high-voltage inverters use semiconductor modules in series. When a single module fails, even if the faulty module is bypassed and removed, the inverter cannot output full voltage and full power. In the present invention, the closer the motor is to full power output, the lighter the inverter load is. The inverter modules are used in parallel. If the faulty module needs to be removed, it will only affect the output torque of the motor when running at low frequency. When the application scenario has a lower limit for frequency operation, the impact of module failure being removed will be smaller.

[0076] In the embodiment of the present application, the above step S100 includes the following sub-steps A1-A3;

[0077] In A1: The first calculation formula is the square root of the difference between the square of the stator voltage minus the product of twice the motor electrical angular velocity, the stator resistance, and the motor torque, plus the fourth power of the stator voltage, four times the motor electrical angular velocity multiplied by the stator resistance multiplied by the motor torque multiplied by the square of the stator voltage, and four times the square of the stator resistance multiplied by the square of the motor torque divided by the square of the stator inductance.

[0078] In A2: twice the square of the stator resistance plus the square of the motor electrical angular velocity multiplied by the square of the stator inductance is the second calculation formula;

[0079] In A3: the first calculation formula is divided by the square root of the quotient of the second calculation formula to obtain the first current component.

[0080] In A4: The third calculation formula is the square root of the difference between the stator voltage to the fourth power and the product of four times the motor electrical angular velocity multiplied by the stator resistance multiplied by the motor torque multiplied by the square of the stator voltage and four times the square of the stator resistance multiplied by the square of the motor torque divided by the square of the stator inductance, which is subtracted from the square of the stator voltage.

[0081] In A5: twice the square of the stator resistance is the fourth calculation formula;

[0082] In A6: the third calculation formula is divided by the square root of the quotient of the fourth calculation formula to obtain the second current component.

[0083] Specifically, the frequency and voltage of the high-voltage grid are detected in real time, and the output is the frequency f and the voltage √(3 / 2)U, where U is the phase voltage peak of the high-voltage grid;

[0084] like Figure 3 As shown, according to the MT coordinate equivalent circuit diagram of the asynchronous motor, the equation of the MT coordinate equivalent circuit is expressed as:

[0085]

[0086] From the rotor side of the motor, vector control based on stator flux orientation is implemented. The total stator flux ψs vector of the motor is oriented along the d-axis of the internal coordinate system. This coordinate axis is called the M-axis. Correspondingly, the axis perpendicular to the M-axis is called the T-axis, which is used to control the electromagnetic torque and is expressed as:

[0087]

[0088] Control rotor side input voltage U rm =sω(L r I rt +L m I st ), so that the rotor side current I rm =0;

[0089] like Figure 4 As shown in the figure, the MT coordinate equivalent circuit equation of the asynchronous motor is simplified to:

[0090]

[0091] like Figure 5 As shown in the figure, by measuring the stator-side voltage and current amplitudes and phase angle difference θ using PTs and CTs, the coordinate T-axis position based on the stator flux orientation can be directly calculated. The amplitude of voltage U is line segment AO in the figure; the amplitude of current I multiplied by the stator resistance Rs is line segment BO in the figure; the voltage and current phase angle difference θ is angle ∠AOB in the figure. Once the coordinate T-axis position is determined, the coordinate M-axis position can also be determined.

[0092] After the coordinates M and T axes are determined, I sm R s , I st R s 、-ωL s I sm Mark the line segments AC, DO, and CD on the coordinate axis; observe Figure 4It can be seen that: since the amplitude of the stator voltage U can be considered fixed, as the load current changes, the range of I changes is [0,I n ]; the range of ∠AOC and α angle is [0,β]; the ∠ADC of triangle △ACD is fixed value β and the size of triangle △ACD is I sm multiples of .

[0093] according to Figure 5 The following equation can be listed for △ADO:

[0094]

[0095] The equation simplifies to:

[0096]

[0097] The torque equation of the motor is:

[0098]

[0099] Ignoring the number of motor pole pairs P, the motor torque is normalized and I is set rm =0; Combining the above two equations, we get:

[0100]

[0101] Solve Equation I st <0,I sm >0 we get:

[0102]

[0103] Without considering the number of motor pole pairs P, the motor torque can be normalized to obtain:

[0104]

[0105] Combine Figure 5 Middle I sm R s , I st R s The line segments AC and DO are respectively, and the equations are:

[0106]

[0107] Taking the derivative of the above function T with respect to angle α, we can get:

[0108]

[0109] T ′ =0, we can find the maximum value of torque T is 2α=β, where the maximum value of torque T is:

[0110]

[0111] Since the torque T reaches the maximum, continue to increase I st / I rt , the torque T will decrease instead, so I st / I rt The value range is [0,I MAX ], in [0,I MAX ] The value range is |I sm |>|I st |, discard the solution I s ′ m , I s ′ t , retain the solution of equation I sm , I st That is, the first current component and the second current component are:

[0112]

[0113] When T reaches its maximum value T MAX Sometimes:

[0114]

[0115] Among them, U is the stator voltage, I is the stator current, ω is the motor electrical angular velocity, T is the motor torque, U sm , I sm is the component of the motor stator voltage and current on the M coordinate axis, U st , I st is the motor stator voltage and current component on the T coordinate axis, U rt , I rt is the voltage and current component of the motor rotor on the T axis, R s is the stator resistance in the MT coordinate equivalent circuit, L s is the stator inductance in the MT coordinate equivalent circuit, L m is the mutual inductance of the stator and rotor in the MT coordinate equivalent circuit, R r is the rotor resistance in the MT coordinate equivalent circuit, L r is the rotor inductance in the MT coordinate equivalent circuit, and s is the slip rate.

[0116] In summary, by inputting U, ω (stator side frequency), and T (torque) into the above function, the output I can be directly solved. sm , I st , and because the I of the T axis st =-L m I rt / L s, when controlling the T-axis current I on the rotor side rt Within [0, I MAX , the motor torque T can be directly controlled within [0, T MAX ;

[0117] It should be noted that through an accurate mathematical model and calculation method, the current components of the motor can be directly calculated, thereby achieving precise control of the motor torque. By using the vector control method, the complex motor control problem is transformed into a simple current control problem, simplifying the control process.

[0118] In the embodiment of the present application, the above step S300 includes the following sub-steps B1 - B4;

[0119] In B1: The operating state of the motor rotor side is judged by detecting the frequency and voltage of the high-voltage power grid, and measuring the amplitude and phase angle difference of the stator side voltage and current by CT;

[0120] In B2: When the first current component is equal to 0, the motor is in a critically stable state;

[0121] In B3: When the first current component is less than 0, the motor is in an under-stable state;

[0122] In B4: When the first current component is greater than 0, the motor is in an over-stable state;

[0123] Specifically, the stability enhancement device includes that the motor output torque T is balanced with the load torque T1: T = T1 + (J / p)dω / dt; if the torque T is not balanced with the load torque T1, the rotor will accelerate / decelerate;

[0124] As Figure 6 shown, the motor has an under-stable state, a critically stable state, and an over-stable state. When oriented based on the stator flux linkage, when I rm on the rotor M-axis = 0, the magnetomotive force of the rotor is completely perpendicular to the stator flux linkage, and the motor is in a critically stable state; when I rm on the rotor M-axis > 0, the torque T > T1, the motor rotor accelerates, and the magnetomotive force of the rotor and the stator flux linkage present an acute angle, and the motor is in an over-stable state; when I rm on the rotor M-axis < 0, the torque T < T1, the motor rotor decelerates, and the magnetomotive force of the rotor and the stator flux linkage present an obtuse angle, and the motor is in an under-stable state. The motor can continue to operate in both the critically stable state and the over-stable state, but once it enters the under-stable state, the obtuse angle between the magnetomotive force of the rotor and the stator flux linkage will increase. The larger the obtuse angle, the smaller the output torque T, and the motor enters an oscillating state, and the rotor will eventually stop. This oscillation of the asynchronous motor is similar to that of the synchronous motor. To prevent the frequency converter and the asynchronous motor from entering the under-stable / oscillating state, a stability enhancement device needs to be added.

[0125] like Figure 7 As shown, I rm When ≠0, the equivalent circuit equation of the asynchronous motor is:

[0126]

[0127] like Figure 8 As shown, by displaying the various terms ①③ of the above equation on the MT coordinate axis, it can be seen that the stator-side voltage and current amplitudes and phase angle difference θ are measured by the high-voltage grid frequency voltage detection module and CT, and the coordinate T-axis position based on the stator flux orientation is calculated. The amplitude of the voltage U is the line segment AO in the figure; the amplitude of the current I*Rs is the line segment BO in the figure; ∠AOB is the voltage and current phase angle difference θ; line segment AB is parallel to the T-axis of the MT coordinate. After obtaining the coordinate T-axis position, the coordinate M-axis position can also be determined.

[0128] like Figure 9 As shown, the I of the rotor M axis rm = 0, the motor is in a critical stable state and meets the following conditions:

[0129]

[0130]

[0131] I of rotor M axis rm When <0, the motor is in an understable state and meets the following conditions:

[0132]

[0133] I of rotor M axis rm When >0, the motor is in an overstable state and meets the following conditions:

[0134]

[0135] In the embodiment of the present application, after completing steps B1-B4 in the above step S300, the following steps B5-B7 are further included;

[0136] In B5: when the motor is in a critical stable state, the input signal speed command and torque command are not intervened;

[0137] In B6: When the motor is in an understable state, increase the torque command. When the torque command reaches the maximum, the motor is still in an understable state, and reduce the speed command until the motor is critically stable.

[0138] In B7: When the motor is in an over-stable state, the input signal speed command and torque command are not intervened or the torque command is reduced until the motor is critically stable.

[0139] Specifically, when the stabilization device determines that the motor is in critical stability, it does not interfere with the input signal speed command n and torque command T; when the stabilization device determines that the motor is overstable, it does not interfere with the input signal speed command n and torque command T or reduces the torque command T until the motor is critically stable; when the stabilization device determines that the motor is understable, it first increases the torque command T. When the torque command T reaches the maximum and the motor is still understable, the speed command n is reduced until the motor is critically stable.

[0140] It should be noted that traditional inverters output power based on the motor's required power. With this design, only a portion of the power is returned to the grid through the inverter, with the remainder being directly delivered to the load by the motor. As the motor approaches rated speed, the power diverted by the inverter decreases, and the motor's direct output power increases. The rotor circuit of a high-voltage motor is a low-voltage circuit. The open-circuit voltage (E2E) of a high-voltage wound-rotor motor rotor typically ranges from several hundred volts to 1.5 kV. When the rotor circuit is closed and operating via a speed control device, the actual operating voltage is multiplied by a slip factor of less than 1, resulting in an operating voltage generally ranging from several hundred volts to around 1 kV. This voltage is within the tolerances of a single semiconductor power electronic device. Consequently, the converter is very simple, with fewer potential failures and significantly improved reliability.

[0141] Due to the limited voltage resistance of semiconductors in traditional high-voltage inverters, semiconductors must be connected in series. Each semiconductor module needs to be connected to a set of low-voltage side windings of a Yanbian transformer. The series use of semiconductors and the addition of a transformer complicates the system and leads to a higher failure rate. Because the rotor circuit of the present invention is a low-voltage circuit, only low-voltage semiconductor devices are required. Although the rotor-side windings are low-voltage and high-current, compared to the complex and low-reliability series connection with high voltage resistance, parallel semiconductors can be used in low-voltage and high-current scenarios. Furthermore, implementing variable-frequency vector control from the motor rotor side eliminates the need for a transformer, significantly reducing the size and weight of the device.

[0142] In the embodiment of the present application, the above step S400 includes the following sub-steps D1-D4;

[0143] In D1: the high-voltage circuit breaker of the started motor is closed, the stator winding is energized, and a no-load excitation current is generated;

[0144] In D2: the rotor side is open, generating no-load voltage;

[0145] In D3: The initial phase angle is adjusted by the synchronization device to match the rotor three-phase voltage output by the inverter device with the no-load voltage on the rotor side in terms of amplitude, frequency and phase;

[0146] In D4: When the matching is completed, the contactor closes, the inverter outputs electrical energy to the rotor side, and the motor enters normal operation.

[0147] Specifically, the synchronization device includes: after the system receives the start command, the high-voltage circuit breaker QF is closed, and KM1, KM2, and KM3 do not operate. At this time, the stator winding of the motor is energized, and there is a no-load excitation current in the stator winding. However, the rotor side is open, and the motor is equivalent to a no-load transformer, and there is a no-load voltage on the rotor side of the motor. Since the position of the motor rotor is random, when the high-voltage circuit breaker QF is closed, the position of the stator A phase does not necessarily correspond to the rotor a phase. Therefore, the synchronization device needs to adjust the value of the initial phase angle so that the inverter output rotor three-phase voltage matches the no-load voltage on the motor rotor side. When the amplitude, frequency, and phase of the two are the same, the synchronization device controls the KM1 contactor to close;

[0148] After closing the circuit, the position between the motor rotor and the air gap flux is relatively fixed. The relationship between the high-voltage grid frequency f and the motor speed n is expressed as:

[0149]

[0150] Among them, s is the slip rate of the motor, p is the number of pole pairs of the motor, sω is the slip angular velocity of the alternating current transmitted to the motor rotor by the inverter transposition, the slip angular velocity is integrated over time and then added to the initial phase angle to obtain the phase angle, which is then input into the Park inverse transform and Clark inverse transform to generate a signal to drive the inverter to work, which is expressed as:

[0151] φ=∫sωdt+φ0

[0152] Among them, φ0 is the initial phase angle, φ is the phase angle;

[0153] It should be noted that traditional frequency conversion technology requires converting the full power of the high-voltage motor, resulting in high power consumption. Depending on the inverter's power conversion technology, this power consumption ranges from 3% to 6% of the motor's power. The efficiency ranges from 97% to 94%. Furthermore, as high-power motors, this 3% to 6% of power conversion losses converts into a significant amount of heat, necessitating the installation of a considerable amount of cooling and air conditioning in the inverter room to dissipate the heat. The power consumption of these air conditioners is approximately 1% to 2% of the motor's power. Therefore, the efficiency of traditional high-voltage inverters should be between 93% and 95.5%.

[0154] The present invention only converts the slip power of 14.815% (pump and fan load) of the motor power in the low frequency range. Therefore, the power consumption of the cascade speed regulation device is only about 15% of the power consumption of the frequency conversion device, and its own power consumption is less than 1% of the rated power of the motor. Due to the low power consumption, the device generates very little heat and does not require air conditioning for cooling and heat dissipation at normal factory temperatures. Therefore, the device utilization efficiency is greater than 99%, which is 4 to 6 percentage points higher than the power saving rate of frequency conversion.

[0155] The above is a schematic diagram of the method for performing vector frequency conversion control from the motor rotor side according to this embodiment. It should be noted that the technical solution for performing vector frequency conversion control from the motor rotor side and the technical solution for performing vector frequency conversion control from the motor rotor side described above share the same concept. For details not described in detail in the technical solution for performing vector frequency conversion control from the motor rotor side according to this embodiment, please refer to the description of the technical solution for performing vector frequency conversion control from the motor rotor side described above.

[0156] In this embodiment, a vector frequency conversion control system is implemented from the motor rotor side, including:

[0157] a calculation module, configured to obtain control parameters, input the control parameters into a stator flux orientation model of the motor, and calculate a first current component and a second current component;

[0158] a control module, configured to input the first current component and the second current component into a motor vector control model, calculate corresponding voltage components, and convert the voltage components into rotor three-phase voltages through inverse transformation to control the rotor side of the motor;

[0159] an adjustment module, configured to determine the operating state of the motor rotor side using the stabilization device, adjust the input control parameters according to the determination result, input the adjusted control parameters into the motor stator flux orientation model again, and start the motor;

[0160] A matching module is used to close the high-voltage circuit breaker and match the voltage of the synchronization device of the started motor to obtain the motor in normal operating state;

[0161] The fault processing module is used to perform fault processing on the motor in the normal operating state to achieve the normal operating state of the motor.

[0162] Specifically, a wound-rotor three-phase asynchronous motor is directly connected to the industrial high- and medium-voltage power busbars via a circuit breaker. The rotor winding is directly connected to a low-voltage inverter (VF) via carbon brushes and slip rings. The low-voltage inverter (VF) is connected to the 400V AC power grid. The low-voltage inverter (VF) allows bidirectional power flow, both outputting and absorbing power. QF is a high-voltage circuit breaker, and KM1, KM2, and KM3 are 400V AC low-voltage contactors. R is a three-phase starting resistor.

[0163] This embodiment further provides a computing device suitable for performing vector frequency conversion control from the rotor side of a motor, comprising:

[0164] Memory and processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement the vector frequency conversion control method from the motor rotor side as proposed in the above embodiment.

[0165] This embodiment further provides a storage medium storing a computer program, which, when executed by a processor, implements the vector frequency conversion control method from the rotor side of the motor as proposed in the above embodiment.

[0166] The storage medium proposed in this embodiment and the method for implementing vector frequency conversion control from the motor rotor side proposed in the above embodiment belong to the same inventive concept. Technical details not fully described in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0167] Through the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented with the help of software and necessary general hardware, and of course can also be implemented by hardware. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods of various embodiments of the present invention.

Claims

1. A vector frequency conversion control method from the motor rotor side is characterized in that: include: Acquiring control parameters, inputting the control parameters into a stator flux orientation model of the motor, and calculating a first current component and a second current component; Inputting the first current component and the second current component into a motor vector control model to calculate corresponding voltage components, and converting the voltage components into rotor three-phase voltages through inverse transformation to control the rotor side of the motor; The stabilization device is used to judge the operating state of the motor rotor side, and according to the judgment result, the input control parameters are adjusted, the adjusted control parameters are input into the motor stator flux orientation model again, and the motor is started; The started motor is subjected to high-voltage circuit breaker closing and voltage matching of the synchronization device to obtain the motor in normal operating state; Fault processing is performed on the motor in the normal operating state to achieve the normal operating state of the motor.

2. The method for performing vector frequency conversion control from the motor rotor side according to claim 1, characterized in that: The first current component includes: The first calculation formula is obtained by subtracting the square of the stator voltage from the product of twice the motor electrical angular velocity, stator resistance, and motor torque, plus the square root of the difference between the fourth power of the stator voltage and four times the motor electrical angular velocity multiplied by the stator resistance multiplied by the motor torque multiplied by the square of the stator voltage, and four times the square of the stator resistance multiplied by the square of the motor torque divided by the square of the stator inductance. The second calculation formula is twice the square of the stator resistance plus the square of the motor's electrical angular velocity multiplied by the square of the stator inductance; The first current component is obtained by dividing the first calculation formula by the square root of the quotient of the second calculation formula.

3. The method for performing vector frequency conversion control from the motor rotor side according to claim 2, wherein: The second current component is: The third calculation formula is the square root of the difference between the square of the stator voltage minus the product of twice the motor electrical angular velocity, stator resistance, and motor torque, minus the fourth power of the stator voltage, four times the motor electrical angular velocity multiplied by the stator resistance multiplied by the motor torque multiplied by the square of the stator voltage, and four times the square of the stator resistance multiplied by the square of the motor torque divided by the square of the stator inductance. Twice the square of the stator resistance is the fourth calculation formula; The second current component is obtained by dividing the third calculation formula by the square root of the quotient of the fourth calculation formula.

4. The method for performing vector frequency conversion control from the motor rotor side according to claim 2 or 3, characterized in that: Determining the operating state of the motor rotor side by using the stabilization device includes: The operating state of the motor rotor side is judged by detecting the frequency and voltage of the high-voltage grid and measuring the amplitude and phase angle difference of the voltage and current on the stator side by CT; When the first current component is equal to 0, the motor is in a critical stable state; When the first current component is less than 0, the motor is in an understable state; When the first current component is greater than 0, the motor is in an overstable state.

5. The method for performing vector frequency conversion control from the motor rotor side according to claim 4, characterized in that: Adjustments to the input control parameters include: When the motor is in a critical stable state, the input signal speed command and torque command are not interfered with; When the motor is in an understable state, increase the torque command. When the torque command reaches the maximum, the motor is still in an understable state, reduce the speed command until the motor is critically stable. When the motor is in an overstable state, the input signal speed command and torque command are not intervened or the torque command is reduced until the motor is critically stable.

6. The method for performing vector frequency conversion control from the motor rotor side according to claim 5, characterized in that: The voltage matching of high-voltage circuit breaker closing and synchronization device for the started motor includes: The high-voltage circuit breaker of the started motor is closed, the stator winding is energized, and a no-load excitation current is generated; The rotor side is open circuit, generating no-load voltage; The initial phase angle is adjusted by the synchronization device to match the rotor three-phase voltage output by the inverter device with the no-load voltage on the rotor side in terms of amplitude, frequency and phase; Once the matching is completed, the contactor closes, the inverter outputs electrical energy to the rotor side, and the motor enters normal operation.

7. A vector frequency conversion control system is implemented from the motor rotor side, using the method according to any one of claims 1 to 6, characterized in that: a calculation module, configured to obtain control parameters, input the control parameters into a stator flux orientation model of the motor, and calculate a first current component and a second current component; a control module, configured to input the first current component and the second current component into a motor vector control model, calculate corresponding voltage components, and convert the voltage components into rotor three-phase voltages through inverse transformation to control the rotor side of the motor; an adjustment module, configured to determine the operating state of the motor rotor side using the stabilization device, adjust the input control parameters according to the determination result, input the adjusted control parameters into the motor stator flux orientation model again, and start the motor; A matching module is used to close the high-voltage circuit breaker and match the voltage of the synchronization device of the started motor to obtain the motor in normal operating state; The fault processing module is used to perform fault processing on the motor in the normal operating state to achieve the normal operating state of the motor.

8. The vector frequency conversion control system from the motor rotor side according to claim 7, characterized in that: The vector frequency conversion control system from the motor rotor side includes: A wound-rotor three-phase asynchronous motor is used, which is directly connected to the industrial frequency high and medium voltage power busbars through a circuit breaker. The rotor winding is directly connected to the low-voltage inverter VF through carbon brushes and slip rings. The low-voltage inverter VF is connected to the AC400V AC power grid.

9. An electronic device comprising: memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing computer-executable instructions, wherein the computer-executable instructions, when executed by a processor, implement the steps of the method according to any one of claims 1 to 7.

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