Method and system for applying vector control to generalized frequency conversion system

Abstract

The invention discloses a method and system for applying vector control to a generalized frequency conversion system. The method comprises the steps that stator flux linkage orientation parameters and torque control parameters are generated according to high-voltage power grid operation parameters collected in real time and an obtained torque instruction; the target slip rate of the motor is dynamically determined through a slip rate limiting module so as to ensure that the inverter works in a power output or absorption safety interval; according to the target slip ratio and the torque control parameter, a rotor side voltage waveform is generated through an inverter, vector control is carried out on a motor rotor, and the torque and the rotating speed of the motor are adjusted; the stability of the system is monitored in real time through the stability augmentation device, the critical stable, over-stable or under-stable state is compensated, and the control parameters or the power grid frequency are adjusted to maintain stable operation of the system. According to the method, the variable-frequency variable-torque control precision and the response speed which are equivalent to those of a traditional high-voltage frequency converter system are achieved, and an efficient, economical and reliable speed regulation solution is provided for a power plant auxiliary engine system.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a method and system for applying vector control to a generalized frequency conversion system. Background Art

[0002] In thermal power plants, steam generated by boilers drives turbines, which in turn drive generators. This process consumes significant amounts of electricity for numerous rotating auxiliary machines, such as pumps and fans. Currently, power plants typically extract a portion of the electricity from the generator output via a plant transformer to supply these auxiliary machines. However, during the engineering design phase, auxiliary machine capacity is typically selected based on maximum demand with a certain margin, resulting in significant capacity overages in actual operation. When auxiliary machines operating at a fixed speed are not fully loaded (especially at low loads), their efficiency decreases significantly, resulting in significant energy waste. Variable frequency speed regulation (VVVSR) technology can effectively address this issue. By adjusting the auxiliary machine speed to maintain a constant operating point in the high-efficiency range, it significantly reduces throttling losses caused by dampers or valves. According to the principles of fluid mechanics, the shaft power of centrifugal equipment is proportional to the cube of the speed, so variable speed regulation can significantly save energy.

[0003] Currently, there are two main technical routes for speed regulation of auxiliary equipment in power plants: one is the traditional solution based on power electronic inverters, and the other is a generalized variable frequency power supply system. Traditional power electronic inverters have obvious technical limitations: first, they adopt a series structure of power supply-inverter-motor. The power required by the motor must all be converted by the inverter, resulting in the inverter capacity must be greater than the rated power of the motor. For high-voltage and high-power motors (usually hundreds of kilowatts to tens of thousands of kilowatts), this will result in a large device, complex system and reduced reliability. Secondly, in medium and high voltage application scenarios, due to the voltage resistance level of power electronic devices, it is usually necessary to adopt multi-power unit series technology, which further increases the complexity of the system and the risk of failure.

[0004] The generalized variable frequency power supply system proposed in existing technology uses a small steam turbine to drive a variable frequency generator to directly generate variable frequency AC power, eliminating the need for a traditional frequency converter. This system uses a feedwater pump steam turbine to drive a variable frequency generator set, which supplies power to auxiliary equipment such as induced draft fans and forced draft fans via a 10kV variable frequency bus. While this solution addresses some of the inherent shortcomings of traditional frequency converters, the following issues remain: 1) The system can only adjust the operating frequency of auxiliary equipment and cannot actively control torque and output power; 2) When multiple auxiliary equipment are operated in parallel, dampers or valves are required to throttle the output of individual equipment, making precise independent control impossible; 3) Due to motor slip, speed control accuracy is insufficient; and 4) the inrush current is high when starting a single auxiliary equipment.

[0005] Vector control (also known as field-oriented control) offers a potential solution to these problems. By independently controlling the motor's magnetic field and torque components, this technology can achieve speed regulation similar to that of a DC motor. However, existing research has yet to effectively address the key challenges of integrating vector control into generalized variable-frequency systems, particularly in the areas of parallel operation of multiple auxiliary machines, precise torque control, and starting current suppression. Summary of the Invention

[0006] In view of the above existing problems, the present invention is proposed.

[0007] Therefore, the present invention provides a method and system for applying vector control to a generalized frequency conversion system to solve the defects of traditional power electronic frequency converters, such as bulky devices and low reliability. The generalized frequency conversion system cannot achieve precise control of torque and power, has difficulty in independent adjustment of multiple auxiliary machines, has insufficient speed control accuracy, and has a large starting current impact.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a method for applying vector control to a generalized frequency conversion system, comprising: generating stator flux orientation parameters and torque control parameters based on real-time collected high-voltage grid operating parameters and obtained torque instructions; dynamically determining the target slip rate of the motor through a slip limiting module based on the stator flux orientation parameters and torque control parameters to ensure that the inverter operates within a safe range of power output or absorption; generating a rotor-side voltage waveform through the inverter based on the target slip rate and torque control parameters, implementing vector control on the motor rotor, and adjusting the torque and speed of the motor; monitoring the system stability in real time through a stabilization device, compensating for critical stability, overstability or understability, and adjusting the control parameters or grid frequency to maintain stable operation of the system.

[0010] As a preferred solution of the method of applying vector control to a generalized frequency conversion system described in the present invention, the system connection of the inverter includes: a wound three-phase asynchronous motor is directly connected to a high-voltage frequency conversion busbar through a circuit breaker, and a rotor winding is directly connected to a low-voltage frequency converter VF through carbon brushes and slip rings, and the low-voltage frequency converter VF is connected to an AC400V AC power grid.

[0011] As a preferred solution of the method of applying vector control to a generalized frequency conversion system according to the present invention, the generating of stator flux orientation parameters and torque control parameters includes:

[0012] The real-time collected voltage, stator side frequency and torque command are input into the motor stator flux orientation module to obtain the stator current flux component I sm and torque component I st, the flux component and torque component of the stator current are input into the motor vector control module, and the rotor side MT coordinate axis voltage U is calculated and output. rm 、U rt ;

[0013] By directly measuring the motor stator voltage, stator current, phase angle difference and high-voltage grid angular velocity, the rotor side MT shaft current I is calculated. rt and I rm ;

[0014] The initial phase angle setting module adjusts the rotor side measured current according to the given phase angle The rotor side MT shaft current I is converted into the actual rotor MT shaft current and then the rotor side MT shaft current I is converted into the actual rotor MT shaft current I rt and I rm Convert the measured rotor MT shaft current and output the signal to adjust the initial phase angle

[0015] Setting the phase angle Register and initial phase angle Register, the timer interrupts once every 2π / (256*sω) and executes the phase angle Register plus one operation, phase angle The initial value of the register is from the initial phase angle Register assignment; by multiplying the slip angular velocity by the time and adding the initial phase angle Get the phase angle

[0016] As a preferred solution of the method of applying vector control to a generalized frequency conversion system according to the present invention, the method of dynamically determining the target slip rate of the motor by using the slip rate limiting module includes:

[0017] When the unidirectional inverter performs vector control and the motor operates in the motor rotor short-circuit mode, the real-time measured slip rate is directly output and the inverter 0 power line is calculated;

[0018] A slip rate s matching the torque command is searched within the positive power output region of the inverter, and the slip rate s is sent to the inverter.

[0019] As a preferred solution of the method of applying vector control to a generalized frequency conversion system according to the present invention, the method of dynamically determining the target slip rate of the motor by the slip rate limiting module further comprises:

[0020] When the bidirectional inverter performs vector control, when the motor works in the motor rotor short-circuit mode, it directly outputs the real-time measured slip rate s and outputs the power capacity P of the inverter. + And the power capacity P absorbed by the inverter -Calculate the inverter's 0 power line and the inverter's maximum negative power line;

[0021] In the inverter's positive power output region, the system allows the motor to output 100% of its rated torque. The inverter should operate in this region as much as possible, handing over the frequency conversion task to the high-voltage frequency conversion bus of the generalized frequency conversion system. When the system needs to fine-tune the motor frequency while the frequency conversion bus frequency remains unchanged, the inverter can be operated in the inverter's negative power output region.

[0022] When the inverter starts to generate output, the slip limiting module controls the slip of the output within the positive power output region of the inverter and the negative power output region of the inverter.

[0023] As a preferred solution of the method of applying vector control to a generalized frequency conversion system described in the present invention, wherein: during normal operation, the circuit breaker QF is closed, the low-voltage contactor KM1 is closed, and the inverter operates normally; when the inverter fails, the inverter stops working, the low-voltage contactor KM2 is closed, the low-voltage contactor KM1 is opened, and the inverter is completely offline; the low-voltage contactor KM2 drives the starting current limiting resistor R to operate; the low-voltage contactor KM3 is closed, the low-voltage contactor KM2 is opened, and the motor will switch to the motor rotor short-circuit mode.

[0024] As a preferred solution of the method of applying vector control to a generalized frequency conversion system described in the present invention, the inverter power is selected according to the torque-speed curve of the load, motor parameters, and the slip rate s range required by the frequency conversion system.

[0025] In the second aspect, the present invention provides a system for applying vector control to a generalized frequency conversion system, including: a parameter generation unit, for generating stator flux orientation parameters and torque control parameters based on real-time collected high-voltage grid operating parameters and the obtained torque instructions; a dynamic control unit, for dynamically determining the target slip rate of the motor through a slip limiting module based on the stator flux orientation parameters and torque control parameters, so as to ensure that the inverter operates within a safe range of power output or absorption; a modulation execution unit, for generating a rotor-side voltage waveform through the inverter according to the target slip rate and torque control parameters, implementing vector control on the motor rotor, and adjusting the torque and speed of the motor; a monitoring and compensation unit, for real-time monitoring of system stability through a stabilization device, compensating for critical stability, overstability or understability, and adjusting control parameters or grid frequency to maintain stable operation of the system.

[0026] In a third aspect, the present invention provides an electronic device, comprising:

[0027] memory and processor;

[0028] 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 of applying vector control to a generalized frequency conversion system are implemented.

[0029] 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 of applying vector control to a generalized variable frequency system.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method and system for applying vector control to a generalized frequency conversion system. By combining the generalized frequency conversion system with the vector control on the motor rotor side, the division of labor and cooperation between frequency regulation and torque regulation is achieved, which not only ensures precise control but also improves system efficiency. The method of the present invention only requires the addition of a low-voltage frequency converter (one-way or two-way) with a capacity of only about 10% of the motor capacity on the basis of the generalized frequency conversion system, which greatly reduces the cost of transformation, and the more auxiliary machines there are, the more economical it is. The system has high reliability and can switch to the generalized frequency conversion frequency modulation mode when the inverter fails. It can also switch to the industrial frequency backup power supply when the generalized frequency conversion system fails to ensure continuous and stable operation. In addition, the method of the present invention achieves frequency conversion and torque conversion control accuracy and response speed comparable to those of traditional high-voltage frequency converter systems, providing an efficient, economical and reliable speed regulation solution for the auxiliary system of a power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 This is a framework diagram of a vector control (unidirectional inverter) system for stator flux positioning according to a method according to an embodiment of the present invention;

[0033] Figure 2 This is a flowchart of the stabilization system module of the method according to an embodiment of the present invention;

[0034] Figure 3 This is a system framework diagram of the initial phase angle setting device of the method according to an embodiment of the present invention;

[0035] Figure 4 A schematic diagram illustrating the working area of an inverter according to the method of an embodiment of the present invention;

[0036] Figure 5 This is a system framework diagram of a slip rate s limiter (unidirectional inverter) according to the method of an embodiment of the present invention;

[0037] Figure 6 This is a framework diagram of a vector control (bidirectional inverter) system for stator flux positioning according to a method according to an embodiment of the present invention;

[0038] Figure 7 This is a system framework diagram of a slip rate s limiter (bidirectional inverter) according to the method of an embodiment of the present invention;

[0039] Figure 8 A schematic diagram comparing the variable frequency vector control implemented from the motor rotor side in the method according to an embodiment of the present invention and a traditional frequency converter;

[0040] Figure 9 This is an equivalent circuit diagram of the DQ (MT) coordinate axis of the asynchronous motor according to the method of the embodiment of the present invention;

[0041] Figure 10 The stator side voltage and current of the method according to the embodiment of the present invention are based on the stator flux orientation MT coordinate diagram (I rm =0);

[0042] Figure 11 The MT equivalent circuit diagram of the asynchronous motor based on the stator flux orientation according to the method of the embodiment of the present invention;

[0043] Figure 12 The rotor side M-axis current I rm MT coordinate diagram ≠0;

[0044] Figure 13 The rotor side M-axis current I rm MT equivalent circuit diagram of ≠0;

[0045] Figure 14 A schematic diagram of the stability of a motor system according to the method of an embodiment of the present invention;

[0046] Figure 15 This is a Ts diagram of a motor vector-controlled from the motor rotor side according to the method of an embodiment of the present invention;

[0047] Figure 16 This is a Ts diagram of a motor (maximum value description) controlled by vector control from the motor rotor side according to the method of an embodiment of the present invention;

[0048] Figure 17 A schematic diagram of a three-dimensional inverter power function according to the method of an embodiment of the present invention;

[0049] Figure 18 This is a comparison diagram of a generalized frequency conversion system using vector control and a traditional frequency conversion system according to the method described in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] 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.

[0051] Example 1, with reference to Figure 1-Figure 7 As one embodiment of the present invention, a method for applying vector control to a generalized frequency conversion system is provided. To achieve this, two technical solutions are used: the first solution is to apply a vector control solution (unidirectional inverter) with stator flux linkage positioning in a generalized frequency conversion system; the second solution is to apply a vector control solution (bidirectional inverter) with stator flux linkage positioning in a generalized frequency conversion system. Specifically, the following are included:

[0052] In the embodiment of the present application, the steps of applying the vector control scheme (unidirectional inverter) of stator flux positioning in the generalized frequency conversion system are as follows:

[0053] The specific hardware structure of the unidirectional inverter solution is as follows: Figure 1 As shown in the framework diagram of the stator flux positioning vector control (unidirectional inverter) system, the wound three-phase asynchronous motor is directly connected to the high-voltage frequency conversion bus through a circuit breaker. The rotor winding is directly connected to the low-voltage frequency converter VF through carbon brushes and slip rings. The low-voltage frequency converter VF is connected to the AC400V AC power grid. The low-voltage frequency converter VF can only output power to the motor. Among them, QF is the high-voltage circuit breaker, KM1, KM2, and KM3 are AC400V low-voltage contactors, and R is the three-phase starting resistor.

[0054] like Figure 1 As shown in the figure, the "high-voltage grid frequency and voltage detection module" detects the high-voltage grid frequency and voltage in real time, and its output is frequency f and voltage U=U3, where U3 is the effective value of the line voltage of the high-voltage variable frequency bus; the "motor stator flux orientation model" module ① inputs U, ω (stator side frequency), T (torque) according to the following function, and outputs the stator current flux component I sm and torque component I st :

[0055]

[0056] The stator current flux component I sm and torque component I st Input the "Motor Vector Control Model" module ② and output the rotor side MT coordinate axis voltage U according to the following equation: rm 、U rt :

[0057]

[0058] like Figure 2 As shown in the flowchart, the "stability augmentation device" module ③ uses the high-voltage grid frequency and voltage detection module and the CT to measure the stator-side voltage, current amplitude, and phase angle difference θ to determine whether the motor is in a critically stable, overstable, or understable state, and then compensates the input accordingly to stabilize the system.

[0059] After the motor starts, the high-voltage circuit breaker QF is closed, and the asynchronous motor is started by connecting a current-limiting resistor in series with the rotor. After the contactor KM3 is closed, the motor enters the rotor short-circuit and load operation state. When the frequency conversion system receives the start-up inverter, it closes the low-voltage side contactor KM1 and turns on the lower tubes Q8, Q10, and Q12 inside the inverter. Then, the low-voltage side contactor KM3 is disconnected. By directly measuring the motor stator voltage U, stator current I, phase angle difference θ, and high-voltage grid angular velocity ω, the following formula is input to directly calculate the rotor side MT shaft current I rt and I rm :

[0060]

[0061] Specifically, such as Figure 3 The "initial phase angle setting device" module ④ shown in the figure contains Park and Chark conversion modules, which are responsible for converting the rotor side measured current ia, ib, ic according to the given phase angle Converted into the measured rotor MT shaft current I rt and I rm The comparator module in the “initial phase angle setting device” module ④ is responsible for comparing and converting the rotor side MT shaft current I rt , I rm and the measured rotor MT shaft current I rt , I rm , and output signal to adjust the initial phase angle Until the converted current I rt , I rm and the measured current I rt , I rm consistent;

[0062] Set with phase angle Register and initial phase angle The registers are all 8 bits, and the timer interrupts every 2π / (256*sω) to execute the phase angle Register plus one operation, phase angle The initial value of the register is from the initial phase angle Register assignment. Slip angular velocity sω multiplied by time t and then added to the initial phase angle Get the phase angle Afterwards, Input the "Park inverse transform module" and "Park transform module", and the calculation formula is expressed as:

[0063] φ=sωt+φ0

[0064] Furthermore, when the motor operates in the motor rotor short-circuit mode, the real-time measured slip rate s is directly output. The inverter 0 power line (red line) is calculated according to the following formula, as follows: Figure 4 The inverter working area is shown as follows:

[0065]

[0066] It should be noted that the area to the left of the red line (red shaded area) is the inverter's positive power output region. The system allows the motor to output 100% of its rated torque. The inverter is primarily responsible for torque conversion, leaving the frequency conversion task to the high-voltage frequency conversion bus of the generalized frequency conversion system. The motor speed command (slip command) of the unidirectional inverter system is automatically generated by the "slip rate s limiting module" ⑤. Figure 5 As shown in the system framework diagram of the slip rate s limiter (unidirectional inverter), the "slip rate s limit module" is based on the torque command T. Figure 4 Find the slip rate s that matches the instruction T in the red shaded area and send it to the inverter; Figure 4 The red line in the figure will be adjusted in real time as the U and ω of the high-voltage variable frequency bus change.

[0067] During normal operation, circuit breaker QF is closed, KM1 is closed, and the inverter operates normally. When the inverter fails, the inverter stops working, KM2 is closed, KM1 is opened, and the inverter is completely offline. KM2 drives the starting current limiting resistor R to work. Finally, KM3 is closed, KM2 is opened, and the motor will switch to the motor rotor short-circuit mode.

[0068] A unidirectional inverter can only deliver active power to the motor rotor. Based on the load's torque-speed curve, motor parameters, and the slip rate (s) range required by the frequency conversion system, substitute the following formula to select the appropriate inverter power:

[0069]

[0070] In order to eliminate DC bus overvoltage, the "inverter module" ⑥ has a braking resistor R cd , automatically switched on when the DC bus is over-voltage.

[0071] In the embodiment of the present application, the steps of applying the vector control scheme (bidirectional inverter) of stator flux positioning in the generalized frequency conversion system are as follows:

[0072] The specific hardware structure of the bidirectional inverter solution is as follows: Figure 6As shown in the framework diagram of the stator flux positioning vector control (bidirectional inverter) system, the wound three-phase asynchronous motor is directly connected to the high-voltage frequency conversion bus through a circuit breaker. The rotor winding is directly connected to the low-voltage frequency converter VF through carbon brushes and slip rings. The low-voltage frequency converter VF is connected to the AC400V AC power grid. The low-voltage frequency converter VF can only output power to the motor. Among them, QF is the high-voltage circuit breaker, KM1, KM2, and KM3 are AC400V low-voltage contactors, and R is the three-phase starting resistor.

[0073] like Figure 6 As shown in the figure, the "high-voltage grid frequency and voltage detection module" detects the high-voltage grid frequency and voltage in real time, and its output is frequency f and voltage U=U3, where U3 is the effective value of the line voltage of the high-voltage variable frequency bus; the "motor stator flux orientation model" module ① inputs U, ω (stator side frequency), T (torque) according to the following function, and outputs the stator current flux component I sm and torque component I st ;

[0074] The stator current flux component I sm and torque component I st Input the "Motor Vector Control Model" module ② and output the rotor side MT coordinate axis voltage U according to the following equation: rm 、U rt ;

[0075] like Figure 2 As shown in the flowchart, the "stability augmentation device" module ③ uses the high-voltage grid frequency and voltage detection module and the CT to measure the stator-side voltage, current amplitude, and phase angle difference θ to determine whether the motor is in a critically stable, overstable, or understable state, and then compensates the input accordingly to stabilize the system.

[0076] After the motor starts, the high-voltage circuit breaker QF is closed, and the asynchronous motor is started by connecting a current-limiting resistor in series with the rotor. After the contactor KM3 is closed, the motor enters the rotor short-circuit and load operation state. When the frequency conversion system receives the start-up inverter, it closes the low-voltage side contactor KM1 and turns on the lower tubes Q8, Q10, and Q12 inside the inverter. Then, the low-voltage side contactor KM3 is disconnected. By directly measuring the motor stator voltage U, stator current I, phase angle difference θ, and high-voltage grid angular velocity ω, the following formula is input to directly calculate the rotor side MT shaft current I rt and I rm :

[0077]

[0078] Specifically, such as Figure 3 The "initial phase angle setting device" module ④ shown in the figure contains Park and Chark conversion modules, which are responsible for converting the rotor side measured current ia, ib, ic according to the given phase angle Converted into the measured rotor MT shaft current I rt and I rm The comparator module in the “initial phase angle setting device” module ④ is responsible for comparing and converting the rotor side MT shaft current I rt , I rm and the measured rotor MT shaft current I rt , I rm , and output signal to adjust the initial phase angle Until the converted current I rt , I rm and the measured current I rt , I rm consistent;

[0079] Set with phase angle Register and initial phase angle The registers are all 8 bits, and the timer interrupts every 2π / (256*sω) to execute the phase angle Register plus one operation, phase angle The initial value of the register is from the initial phase angle Register assignment. Slip angular velocity sω multiplied by time t and then added to the initial phase angle Get the phase angle Afterwards, Input the "Park inverse transform module" and "Park transform module", and the calculation formula is expressed as:

[0080] φ=sωt+φ0

[0081] Furthermore, when the motor operates in the motor rotor short-circuit mode, the real-time measured slip rate s is directly output. + And the power capacity P absorbed by the inverter - , calculate the inverter 0 power line (red line) and the inverter maximum negative power line (blue line) according to the following formula, such as Figure 4 The inverter working area is shown as follows:

[0082]

[0083] It should be noted that the left side of the above red line (red shaded area) is the positive power output area of the inverter. The system can allow the motor to output 100% rated torque. The inverter should try to work in this area, and the frequency conversion task will be handed over to the high-voltage frequency conversion bus of the generalized frequency conversion system. The blue shaded area between the red line and the blue line is the negative power output area of the inverter. The blue line represents the maximum power that the inverter can absorb. When the system needs to fine-tune the motor frequency and the frequency conversion bus frequency does not change, the inverter can be allowed to enter the blue shaded area to work. When the inverter starts to generate output, the "slip rate s limiting module" ⑦ will allow the output slip rate s to be within Figure 4In the red shaded area or the blue shaded area. Figure 4 The red and blue lines in the figure will adjust in real time as the U and ω of the high-voltage variable frequency bus change. The specific principle of the "slip rate s limiting module" ⑦ is as follows Figure 7 shown.

[0084] During normal operation, circuit breaker QF is closed, KM1 is closed, and the inverter operates normally. When the inverter fails, the inverter stops working, KM2 is closed, KM1 is opened, and the inverter is completely offline. KM2 drives the starting current limiting resistor R to work. Finally, KM3 is closed, KM2 is opened, and the motor will switch to the motor rotor short-circuit mode.

[0085] A bidirectional inverter can generate and absorb active power. Based on the load's torque-speed curve, motor parameters, and the slip rate (s) range required by the frequency conversion system, substitute the following formula to select the appropriate inverter power:

[0086]

[0087] As can be seen from the above two technical solutions, the present invention realizes the division of labor and cooperation between frequency regulation and torque regulation by combining the generalized frequency conversion system with the motor rotor side vector control, which not only ensures precise control but also improves system efficiency. The method of the present invention only requires adding a low-voltage frequency converter (one-way or two-way) with a capacity of only about 10% of the motor capacity on the basis of the generalized frequency conversion system, which greatly reduces the cost of transformation, and the more auxiliary machines there are, the more economical it is. The system has high reliability and can switch to the generalized frequency conversion frequency modulation mode when the inverter fails. When the generalized frequency conversion system fails, it can also switch to the industrial frequency backup power supply to ensure continuous and stable operation.

[0088] Example 2, reference Figures 1 to 18 Based on the previous embodiment, this embodiment provides a specific implementation method of a method for applying vector control to a generalized frequency conversion system. To provide a detailed description of the technical solution of this method, the method specifically includes:

[0089] like Figure 9 The figure shows the MT coordinate equivalent circuit diagram of the asynchronous motor. Figure 10 The equivalent circuit of MT coordinates can be listed as follows:

[0090]

[0091] The above equation must also satisfy the following two conditions:

[0092] 1. Implement vector control based on stator flux orientation from the motor rotor side. Orient the motor's total stator flux vector ψs along the d-axis of the internal coordinate system, which 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. The following equation is obtained:

[0093]

[0094] 2. Control the rotor side input voltage U rm =sω(L r I rt +L m I st ), so that the rotor side current I rm =0.

[0095] The MT coordinate equivalent circuit equation of the asynchronous motor is simplified to:

[0096]

[0097] According to the above equation, we can get: Figure 11 The figure shows the MT equivalent circuit diagram of an asynchronous motor based on stator flux orientation and rotor M axis current is 0. According to the above equations and Figure 11 Plotting the various voltage and current quantities on the MT coordinate graph yields: Figure 10 The stator side voltage and current are based on the stator flux orientation MT coordinate diagram. Figure 10 The following four conclusions can be drawn:

[0098] 1. By measuring the amplitude and phase angle difference θ of the stator side voltage and current through PT and CT, the coordinate T-axis position based on the stator flux orientation can be directly calculated. The amplitude of the voltage U is the line segment AO in the figure; the amplitude of the current I is multiplied by the stator resistance R s This is the line segment BO in the figure; the phase angle difference θ between voltage and current is the angle ∠AOB in the figure; after obtaining the coordinate T-axis position, the coordinate M-axis position can also be determined;

[0099] 2. After the coordinates M and T axes are determined, I sm R s , I st R s 、-ωL s I sm Mark them on the coordinate axis as line segments AC, DO, and CD. Figure 10 It 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

[0100] 3. According to Figure 10 The following equation can be listed for △ADO:

[0101]

[0102] The equation simplifies to:

[0103]

[0104] The torque equation of the motor is:

[0105]

[0106] Ignoring the number of motor pole pairs P, the motor torque is normalized and I is set rm =0;

[0107] Combining the above two equations, we can get the equation:

[0108]

[0109] Solve this 4th degree equation (I st <0,I sm >0) we can get:

[0110]

[0111] 4. Without considering the number of motor pole pairs P, the motor torque can be normalized to obtain:

[0112]

[0113] Combine Figure 10 Middle I sm R s , I st R s The line segments AC and DO are respectively, and the equations are:

[0114]

[0115] Derivative the above T function with respect to angle α, we get:

[0116]

[0117] When T'=0, we can find the maximum value of torque T at 2α=β, where the maximum value of torque T is:

[0118]

[0119] Since the torque T reaches the maximum value, if Ist / Irt continues to increase, the torque T will decrease instead. st / I rt The value range is [0,I MAX ], in [0,I MAX ] The value range is |Ism |>|I st |. Discard the equation and solve I' sm 、I' st , retain the solution of equation I sm , I st :

[0120]

[0121] When T reaches its maximum value T MAX Sometimes:

[0122] In summary, Figure 1 、 Figure 6 In the system framework diagram, the "Motor Stator Flux Orientation Model" module ① can directly calculate the output I by inputting U, ω (stator side frequency), and T (torque) according to the above function. sm , I st ; and because of the I of the T axis st =-L m I rt / L s , when controlling the rotor side T axis current I rt In [0,I max ] interval, the motor torque T can be directly controlled in the range [0,T MAX ] interval.

[0123] Furthermore, the "Motor Stator Flux Orientation Model" module ① outputs I sm , I st Go to the "Motor Vector Control Model" module ②. The "Motor Vector Control Model" module ② calculates the rotor side MT coordinate axis voltage U according to the following equation rm 、U rt Output to the "Park Inverse Transform Module":

[0124]

[0125] The “Park inverse transformation module” obtains the rotor side MT coordinate axis voltage U rm 、U rt After input, it is responsible for converting the DC voltage U rm 、U rt According to the input phase angle Converts the voltage into an AC voltage. The Park inverse conversion module here is no different from the Park inverse conversion in a traditional inverter. The Clark inverse conversion module is no different from the Clark inverse conversion in a traditional inverter.

[0126] Further, in Figure 1 、 Figure 6 Introduction to the "initial phase angle setting device" module ④ in the system framework diagram:

[0127] After the system receives the start command, the asynchronous motor starts by connecting a current-limiting resistor in series with the rotor. Low-voltage contactor KM2 closes, followed by high-voltage circuit breaker QF. Low-voltage contactors KM1 and KM3 remain inoperative. After a delay, low-voltage contactor KM3 closes, followed by KM2 tripping, while KM1 remains inoperative. The asynchronous motor is now started and enters the rotor short-circuit mode, operating under load.

[0128] After the motor starts, the rotor current measured by the rotor side CT does not exceed the inverter capacity, and a signal is issued to allow the inverter to start. When the frequency conversion system receives the signal to start the inverter, the low-voltage side KM1 contactor is closed, and the lower tubes Q8, Q10, and Q12 inside the inverter are turned on. Then the low-voltage side contactor KM3 is disconnected. At this time, it is equivalent to a short circuit in the motor rotor winding, and the motor is in a motor rotor short-circuit and load operation state. Since the position of the motor rotor is random, when the motor starts, the angle between the motor air gap magnetic field and the rotor phase a is also random, so the "initial phase angle adjustment device" module ④ needs to adjust the initial phase angle. The value of the phase angle is correct Enter the "Inverse Park Transform Module".

[0129] Specifically, such as Figure 10 Rotor side M axis current I rm As shown in the MT coordinate diagram, when the motor rotor winding is short-circuited and the motor is in the state of running with load due to the motor rotor short-circuit, U rm =0, U rt =0, and I rm ≠0, I rt ≠0. Due to the positioning of the stator flux, AO in △ABO is the stator voltage U, and BO is the stator current I*R s , ∠AOB is the voltage and current phase angle difference θ, and AB must be parallel to the T axis. Because:

[0130] It is on the T axis, AB=-ω(L s I sm +L m I rm )So AB is parallel to the T axis.

[0131] Applying the cosine formula to ∠AOB=θ in △ABO gives:

[0132]

[0133] thereby:

[0134]

[0135] Applying the cosine formula to ∠ABO=π-θ-α in △ABO gives:

[0136]

[0137] Specifically solve the above I rm as follows:

[0138]

[0139] Therefore, Figure 3 Modules ④-① in the initial phase angle setting device system framework are responsible for calculating the input stator voltage U, stator current I, phase angle difference θ, and high-voltage grid angular velocity ω and outputting the converted rotor side MT shaft current I rt and I rm , the specific function is as follows:

[0140]

[0141] exist Figure 3 In the system framework diagram of the initial phase angle setting device, modules ④-② and ④-③ are Park and Chark conversion modules, which are responsible for converting the rotor side measured current i a 、i b ,i c According to the given phase angle Converted into the measured rotor MT shaft current I rt and I rm , Figure 3 Comparator module ④ in the initial phase angle setting device system framework diagram

[0142] ④ Responsible for comparing and converting the rotor side MT shaft current I rt , I rm and the measured rotor MT shaft current I rt , I rm , and output signal to adjust the initial phase angle Until the converted current I rt , I rm and the measured current I rt , I rm consistent.

[0143] Furthermore, after the inverter is started, the position between the motor rotor and the air gap flux is relatively fixed; Figure 1 、 Figure 6 In the system framework diagram, the high-voltage grid frequency f and the motor speed n have the following relationship:

[0144]

[0145] Where s is the slip rate of the motor, p is the number of pole pairs of the motor, and sω is the slip angular velocity of the alternating current delivered to the motor rotor by the inverter. The slip angular velocity sω is multiplied by the time t and then added to the initial phase angle Get the phase angle Afterwards, The input "Park inverse transformation module" and "Clark inverse transformation module" generate signals to drive the inverter to work. At the same time, it will be sent Figure 3 The "Park transformation module" in the system framework diagram of the initial phase angle setting device.

[0146] φ=sωt+φ0

[0147] Furthermore, the "Timer Module" and "Phase Angle "Module includes: set with phase angle Register and initial phase angle The registers are all 8 bits, so the phase angle The resolution is 2π / 2 8 =2π / 256; the timer interrupts once every 2π / (256*sω) and executes the phase angle Register plus one operation, phase angle The initial value of the register is from the initial phase angle Register assignment. Phase angle The register value range is [0, 255], and the corresponding phase angle value range is [0, (255 / 256)*2π]. Similarly, the phase angle Register and initial phase angle Registers can be set to 16 or 32 bits, with correspondingly higher resolutions, and so on.

[0148] Initial phase angle After the adjustment is completed, the "Park inverse transform" module can be used to calculate the value of the U rt 、U rm 、 The input generates a corresponding output to the "Clark Inverse Transformation Module", which ultimately starts the inverter and puts it into operation. The following discusses how much inverter output power is required when the motor needs to output torque T and the operating speed is n, and whether the inverter output power is positive or negative:

[0149] from Figure 11 The asynchronous motor is based on the stator flux orientation MT equivalent circuit diagram and knows:

[0150] 1. Under steady state, control U rm Make I rm =0, so the inverter output of the rotor M axis circuit is P' inv =U rm *I rm=0; 2. Since in steady state, the inverter output power is fully reflected in the rotor T-axis circuit, so P inv =I rt *U rt ; 3. When P inv =I rt *U rt >0, the inverter outputs power to the motor; P inv =I rt *U rt <0, the inverter absorbs power; 4, and P inv =I rt *U rt = 0, the inverter output active power is 0. At this moment, the inverter works on the dividing line between positive output and negative output. Although the active power P inv is 0, but U rm ≠0, I rm =0, U rt =0,I rt ≠0, the reactive power of the inverter is not 0; 5. Using the motor torque T and the motor slip rate s (when the high-voltage bus frequency remains unchanged, the slip rate can represent the motor speed) as independent variables, solve the inverter power P inv , and draw P inv -Ts three-dimensional function curve. It is the key to reasonably design the positive and negative output capacity of the inverter and thus apply vector control to the generalized frequency conversion system. Figure 11 The rotor T-axis circuit of the asynchronous motor based on the stator flux orientation MT equivalent circuit diagram is obtained as follows:

[0151]

[0152] observe Figure 10 The stator side voltage and current are based on the stator flux orientation MT coordinate diagram (Irm = 0), in which the line segment DO = U (cosα - sinα cotβ) and the line segment CD = U sinα cotβ. Therefore, the above formula P inv = 0 to find the function of T with respect to s (Ts function):

[0153]

[0154] Solving the above equation yields: Substitute the solution of this equation into

[0155]

[0156] We will get the function of T with respect to s:

[0157]

[0158] The above function is drawn on the torque T-slip rate s coordinate to get P inv = 0. Select a U N =6kV,P N =2MW typical motor parameters are shown in the following table:

[0159] U Rs Rr Ls Lm ω 6000 2.99 0.3 1.99 1.93 314.1592654

[0160] Substitute the above parameters into the above function and draw the Ts curve of this motor as shown below Figure 15 As shown in the motor Ts diagram of vector control from the motor rotor side, Figure 15 It is similar to the Ts diagram of asynchronous motor, but not the same. The Ts diagram of asynchronous motor is under the condition of short circuit on the rotor side, U rm =0,I rm ≠0, U rt =0,I rt ≠0, and Figure 15 The condition is U rm ≠0, I rm =0, U rt =0,I rt ≠0. Therefore, the principles of these two curves are similar but their essences are different. st |The maximum value is |I st |If the maximum value is exceeded, the motor torque will decrease. Figure 16 The motor Ts diagram (maximum value description) of the motor vector control from the motor rotor side is shown. In order to limit the inverter output power and IGBT current, The working condition is abandoned, that is, the inverter will not work in interval.

[0161] The output of the "Motor Stator Flux Orientation Model" module ① is I st Substitution get:

[0162]

[0163] The above formula is the inverter power P inv As a function of the motor torque T and slip rate s, plot the above P on the coordinates. inv -Ts three-dimensional function curve, such as Figure 4 Inverter operating area and Figure 17 The three-dimensional inverter power function is shown.

[0164] The following 4 points are Figure 4 Description and correction of the inverter working area Figure 17 Introduction to three-dimensional inverter power function:

[0165] 1. The red shaded area indicates the inverter's output active power. Generally speaking, the red shaded area has low requirements for the inverter's output power and is easier to meet. The blue shaded area and the dark blue area in the upper right corner indicate the inverter's absorption of active power. The darker the blue, the higher the power absorbed by the inverter. The larger s and the larger the output T, the higher the power required to be absorbed by the inverter.

[0166] 2. The dividing line between the red shaded area and the blue shaded area is the following function. The dividing line is Figure 15 、 Figure 16 The curve in the motor Ts diagram of the vector controlled motor from the motor rotor side is discarded. The function expression of this curve is as follows:

[0167]

[0168] 3. Introduction to the stator flux positioning vector control (unidirectional inverter) system: Since we require that the power input from the stator to the motor should not flow out from the motor rotor side, or the inverter we use is a unidirectional inverter (can only input active power to the motor), the T (torque command) and s (speed command) of the frequency conversion system should fall within Figure 4 The red shaded area in the middle indicates that the inverter can only adjust the frequency within a very narrow range and is mainly responsible for torque conversion, while the frequency conversion task will be handed over to the frequency conversion bus (generalized frequency conversion system). For this reason, a vector control (unidirectional inverter) system with stator flux positioning is designed. It is hereinafter referred to as the unidirectional inverter system. The framework diagram of the unidirectional inverter system is shown in the figure below. Figure 1 The framework diagram of the stator flux positioning vector control (unidirectional inverter) system (PDF) is shown. According to calculations, only one inverter with an output of 185kW is needed to control a 2MW motor. The motor speed command (slip command) of the unidirectional inverter system is given by Figure 1 The "slip rate s limiting module" module ⑤ in the stator flux positioning vector control (unidirectional inverter) system framework diagram (PDF) is automatically generated, such as Figure 5 As shown in the system framework diagram of the slip rate s limiter (unidirectional inverter), the "slip rate s limit module" is based on the torque command T. Figure 4 Find the slip rate s that matches the instruction T in the red shaded area and send it to the inverter. If the slip rate measured in real time is not Figure 4 In the red shaded area in the figure, the "slip rate s limiting module" is Figure 4 The value closest to the measured slip rate is found in the red shaded area and sent to the inverter.

[0169] 4. Introduction to the vector control (bidirectional inverter) system for stator flux positioning: If the inverter used is a bidirectional inverter (which can input or absorb active power to the motor), the inverter can work in Figure 4 The red shaded area or the blue shaded area. Since we require that the power that has been input into the motor from the stator should not flow out from the rotor side of the motor, the inverter should try to work in the red shaded area, and the frequency conversion task will be handed over to the frequency conversion bus (generalized frequency conversion system). When the system needs to fine-tune the motor frequency, and the frequency conversion bus frequency cannot be changed, the inverter can be allowed to work in the blue shaded area. At this time, the inverter absorbs power. At this time, the right boundary of the blue shaded area should be delineated according to the inverter's ability to absorb power. The stronger the inverter's ability to absorb power, the larger the blue shaded area. Figure 4 In the figure, the blue color in the upper right corner gradually becomes darker, indicating that the power that the inverter needs to absorb gradually increases. To this end, a vector control (bidirectional inverter) system with stator flux positioning is designed. It is hereinafter referred to as the bidirectional inverter system. The framework diagram of the bidirectional inverter system is shown in the figure below. Figure 6 The framework diagram of the stator flux positioning vector control (bidirectional inverter) system (PDF) is shown. According to calculations, to control a 2MW motor, only an inverter with an output of 185kW is needed. The higher the power that the inverter can absorb, the stronger its ability to fine-tune the motor operating frequency. For example, if the power absorption capacity of the inverter that controls the 2MW motor mentioned above also reaches 185kW, and the high-voltage variable frequency bus operates at 50Hz, the system can provide a maximum of 8.6% of the rated torque when the rotor is stopped; a maximum of 18% of the rated torque when the rotor is running at 50% of the synchronous speed; and a maximum of 38% of the rated torque when the rotor is running at 75% of the synchronous speed. The closer the motor rotor speed is to the synchronous speed, the higher the torque that can be output. If the motor operates at Figure 4 In the red shaded area, the rated torque can be output 100%. Therefore, the inverter should be operated as much as possible in Figure 4 In the red shaded area, the frequency conversion task is handed over to the frequency conversion bus (generalized frequency conversion system). The inverter is responsible for the torque conversion function and leaves only when it is necessary to fine-tune the motor speed. Figure 4 The red shaded area in the middle enters the power absorption state.

[0170] Further, in Figure 1 、 Figure 6 Introduction to the "stabilization device" module ③ in the system framework diagram: As mentioned above: after closing the circuit, the position between the motor rotor and the air gap flux is relatively fixed, the premise is that the motor output torque T and the load torque T l Balance: T = T l +(J / p)dω / dt. If the torque T and the load torque T l If the rotor is unbalanced, it will accelerate / decelerate. Figure 14As shown in the diagram of motor system stability, the motor has under-stable state, critical stable state and over-stable state. rm = 0, the rotor's magnetomotive force is completely perpendicular to the stator flux, and the motor is in a critical stable state; the rotor M axis I rm >0, torque T>T l , the motor rotor accelerates, the rotor's magnetomotive force and the stator flux present an acute angle, and the motor is in an overstable state; the rotor M axis I rm <0, torque T <T l The motor rotor slows down, and the rotor's magnetomotive force (MMF) and stator flux form an obtuse angle, putting the motor in an understable state. The motor can continue to operate in both critically stable and overstable states. However, once it enters understable conditions, the obtuse angle between the rotor's MMF and stator flux increases. The larger the obtuse angle, the smaller the output torque T, causing the motor to oscillate and eventually stop. This type of oscillation in an asynchronous motor is similar to that in a synchronous motor. To prevent the inverter and asynchronous motor from entering understable / oscillating states, a "stabilization device" module (3) is required.

[0171] like Figure 13 As shown in the MT equivalent circuit diagram when the rotor side M-axis current Irm≠0, the equivalent circuit equation of the asynchronous motor when Irm≠0 is:

[0172]

[0173] Figure 12 Rotor side M axis current I rm ≠0 MT coordinate diagram Plot the terms of formula ①③ above on the MT coordinate axis. Figure 12 Rotor side M axis current I rm The following four conclusions can be drawn from the MT coordinate diagram ≠0:

[0174] 1. The "stabilization device" module ③ measures the amplitude and phase angle difference θ of the stator side voltage and current through the high-voltage grid frequency voltage detection module and CT, and can directly calculate the coordinate T-axis position based on the stator flux orientation. Figure 12 The MT coordinate diagram of the rotor side M-axis current Irm≠0, the amplitude of the voltage U is the line segment AO in the diagram; the current I*R s The amplitude is the line segment BO in the figure; ∠AOB is the phase angle difference θ between voltage and current; 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.

[0175] 2. From equations ① and ③ of the above-mentioned asynchronous motor equivalent circuit equation, it can be obtained that when Irm of the rotor M axis is 0, the motor is in a critical stable state and satisfies the following conditions:

[0176]

[0177] I of rotor M axis rm When <0, the motor is in an under-stable state, which is determined by the following conditions:

[0178]

[0179] I of rotor M axis rm When >0, the motor is in an overstable state, which is determined by the following conditions:

[0180]

[0181] 3. When Figure 1 In the system framework diagram, module ③ of the "Stability Augmentation Device" determines that the motor is in critical stability and does not intervene in the torque command T. If the "Stability Augmentation Device" determines that the motor is in overstability, it does not intervene in the torque command T or reduces it until the motor reaches critical stability. If the "Stability Augmentation Device" determines that the motor is in understability, it first increases the torque command T. When the torque command T reaches its maximum and the motor is still understability, it sends a command to the generalized frequency conversion system to reduce the high-voltage grid frequency until the motor reaches critical stability. If the motor is still understability after a certain delay, a motor trip command is issued, and an "understability trip" alarm is issued.

[0182] 4. When Figure 6 In the system framework diagram, the "Stability Augmentation Device" module ③ does not intervene in the input speed command n and torque command T when the motor is determined to be critically stable. If the "Stability Augmentation Device" determines that the motor is overstable, it does not intervene in the input speed command n and torque command T, or it reduces torque command T until the motor reaches critical stability. If the "Stability Augmentation Device" determines that the motor is understable, it first increases torque command T. When torque command T reaches its maximum and the motor is still understable, it reduces speed command n until the motor reaches critical stability. If the motor is still understable after a certain delay, a motor trip command is issued, and an "understable trip" alarm is issued.

[0183] Example 3, reference Figure 8 Based on the previous embodiment, this embodiment provides a verification example of a method of applying vector control to a generalized frequency conversion system and compares it with the prior art, in order to verify and illustrate the technical effect of the method of the present invention.

[0184] like Figure 8The figure shows a comparison diagram between a generalized variable frequency drive system using vector control and a traditional variable frequency drive. The most obvious difference is that a traditional variable frequency drive outputs power based on the motor's power requirements. In a generalized variable frequency drive system using vector control, only a portion of the power is returned to the grid through the inverter, while the rest is directly delivered to the load by the motor. As the motor approaches synchronous speed (which is determined by the ω of the high-voltage variable frequency grid), the power diverted by the inverter decreases, and the direct motor output power increases.

[0185] The rotor circuit of the high-voltage motor is a low-voltage circuit. The open-circuit voltage E of the high-voltage winding motor rotor is 2E Typically, the voltage ranges from several hundred volts to 1.5 kV. However, when the rotor circuit is closed and operating via the speed control device, the actual circuit operating voltage is multiplied by a slip factor of less than 1, so the operating voltage generally ranges from several hundred volts to around 1 kV. This voltage is withstandable by a single semiconductor power electronic device. As a result, the converter is very simple, with fewer potential failures and significantly improved reliability.

[0186] Traditional high-voltage inverters require semiconductors to be connected in series due to their limited voltage resistance. Each semiconductor module needs to be connected to a set of low-voltage windings on the Yanbian transformer. The combination of series semiconductors and a transformer complicates the system and leads to a higher failure rate. A generalized inverter system using vector control implements vector control from the motor rotor side. Since the rotor circuit is a low-voltage circuit, only low-voltage semiconductor devices are required. Although the rotor-side windings are low-voltage and high-current, parallel semiconductors are suitable for low-voltage, high-current scenarios, compared to the complex and less reliable high-voltage series windings. 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 equipment.

[0187] Traditional high-voltage inverters use semiconductor modules in series. If a single module fails, even if bypassing the faulty module removes it, the inverter will not be able to output full voltage and power. A generalized frequency conversion system using vector control implements variable frequency vector control from the motor rotor side. The closer the motor approaches full power output, the lighter the inverter load. The inverter modules are used in parallel, and if a faulty module needs to be removed, it only affects the motor's output torque at low frequencies. When the application scenario has a lower frequency operating limit, the impact of module failure is minimized. If a serious inverter fault occurs, it can be directly shut down. Even if the torque regulation function is lost due to the shutdown of all semiconductor devices, the generalized frequency conversion system can still be used for frequency regulation. This provides extremely high reliability.

[0188] The present invention utilizes a generalized frequency conversion system with vector control, fully and rationally utilizing modern semiconductor power electronics technology. The generalized frequency conversion system regulates frequency, while the vector control system on the motor rotor side regulates torque. These two systems work together in a coordinated manner. This system enables active and precise control of the speed, torque, and output power of auxiliary machines, allowing for individual fine-tuning of the speed of specific auxiliary machines. Its performance and functionality are identical to those of traditional full-power high-voltage inverters, while surpassing those of pure generalized frequency conversion systems. Furthermore, it offers advantages in terms of scale and cost over traditional full-power high-voltage inverters.

[0189] Embodiment 4: This embodiment provides a system for applying vector control to a generalized frequency conversion system, including:

[0190] A parameter generation unit, configured to generate stator flux orientation parameters and torque control parameters based on real-time collected high-voltage grid operating parameters and acquired torque instructions;

[0191] A dynamic control unit is used to dynamically determine the target slip rate of the motor through the slip rate limiting module based on the stator flux orientation parameters and torque control parameters to ensure that the inverter operates within the safe range of power output or absorption;

[0192] The modulation execution unit is used to generate a rotor-side voltage waveform through the inverter according to the target slip rate and torque control parameters, implement vector control on the motor rotor, and adjust the torque and speed of the motor;

[0193] The monitoring and compensation unit is used to monitor the system stability in real time through the stabilization device, compensate for critical stability, overstability or understability, and adjust the control parameters or grid frequency to maintain stable system operation.

[0194] This embodiment also provides an electronic device, which includes a processor, a memory, a communication interface, a display screen, and an input device connected via a system bus. When the computer program is executed by the processor, a method for applying vector control to a generalized variable frequency system is implemented.

[0195] This embodiment further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the method proposed in the above embodiment is implemented.

[0196] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for applying vector control to a generalized frequency conversion system, characterized in that: include: Generate stator flux orientation parameters and torque control parameters based on real-time collected high-voltage grid operating parameters and obtained torque instructions; Based on the stator flux orientation parameters and the torque control parameters, a slip limiting module dynamically determines a target slip of the motor to ensure that the inverter operates within a safe range of power output or absorption; According to the target slip rate and torque control parameters, a rotor-side voltage waveform is generated through an inverter, and vector control is performed on the motor rotor to adjust the torque and speed of the motor; The system stability is monitored in real time through the stabilization device, critical stability, overstability or understability are compensated, and the control parameters or grid frequency are adjusted to maintain stable system operation.

2. The method for applying vector control to a generalized frequency conversion system according to claim 1, wherein: The system connection of the inverter includes: the wound three-phase asynchronous motor is directly connected to the high-voltage frequency conversion bus through a circuit breaker, the rotor winding is directly connected to the low-voltage frequency converter VF through carbon brushes and slip rings, and the low-voltage frequency converter VF is connected to the AC400V AC power grid.

3. The method for applying vector control to a generalized frequency conversion system according to claim 2, wherein: The generating of stator flux orientation parameters and torque control parameters includes: The real-time collected voltage, stator side frequency and torque command are input into the motor stator flux orientation module to obtain the stator current flux component I sm and torque component I st , the flux component and torque component of the stator current are input into the motor vector control module, and the rotor side MT coordinate axis voltage U is calculated and output. rm 、U rt ; By directly measuring the motor stator voltage, stator current, phase angle difference and high-voltage grid angular velocity, the rotor side MT shaft current I is calculated. rt and I rm ; The initial phase angle setting module converts the rotor side measured current into the measured rotor MT axis current according to the given phase angle φ, and then uses the comparator to compare the rotor side MT axis current I rt and I rm It is converted to the actual rotor MT shaft current and the output signal is used to adjust the initial phase angle φ0; A phase angle φ register and an initial phase angle φ0 register are set. The timer is interrupted once every 2π / (256*sω) and performs an operation of adding one to the phase angle φ register. The initial value of the phase angle φ register is assigned from the initial phase angle φ0 register. The phase angle φ is obtained by multiplying the slip angular velocity by the time and adding the initial phase angle φ0.

4. The method for applying vector control to a generalized frequency conversion system according to claim 3, wherein: The dynamically determining the target slip rate of the motor by the slip rate limiting module includes: When the unidirectional inverter performs vector control and the motor operates in the motor rotor short-circuit mode, the real-time measured slip rate is directly output and the inverter 0 power line is calculated; A slip rate s matching the torque command is searched within the positive power output region of the inverter, and the slip rate s is sent to the inverter.

5. The method for applying vector control to a generalized frequency conversion system according to claim 4, wherein: The dynamically determining the target slip rate of the motor by the slip rate limiting module further includes: When the bidirectional inverter performs vector control, when the motor works in the motor rotor short-circuit mode, it directly outputs the real-time measured slip rate s and outputs the power capacity P of the inverter. + And the power capacity P absorbed by the inverter - Calculate the inverter's 0 power line and the inverter's maximum negative power line; In the inverter's positive power output region, the system allows the motor to output 100% of its rated torque. The inverter should operate in this region as much as possible, handing over the frequency conversion task to the high-voltage frequency conversion bus of the generalized frequency conversion system. When the system needs to fine-tune the motor frequency while the frequency conversion bus frequency remains unchanged, the inverter can be operated in the inverter's negative power output region. When the inverter starts to generate output, the slip limiting module controls the slip of the output within the positive power output region of the inverter and the negative power output region of the inverter.

6. The method for applying vector control to a generalized frequency conversion system according to claim 5, wherein: During normal operation, the circuit breaker QF is closed, the low-voltage contactor KM1 is closed, and the inverter operates normally; when the inverter fails, the inverter stops working, the low-voltage contactor KM2 is closed, the low-voltage contactor KM1 is opened, and the inverter is completely offline; the low-voltage contactor KM2 drives the starting current limiting resistor R to work; the low-voltage contactor KM3 is closed, the low-voltage contactor KM2 is opened, and the motor will switch to the motor rotor short-circuit mode.

7. The method for applying vector control to a generalized frequency conversion system according to claim 6, wherein: Select the inverter power based on the load's torque-speed curve, motor parameters, and the slip rate s range required by the frequency conversion system.

8. A system for applying vector control to a generalized frequency conversion system, applying the method according to any one of claims 1 to 7, characterized in that: include: A parameter generation unit, configured to generate stator flux orientation parameters and torque control parameters based on real-time collected high-voltage grid operating parameters and acquired torque instructions; a dynamic control unit, configured to dynamically determine a target slip rate of the motor through a slip rate limiting module based on the stator flux orientation parameter and the torque control parameter, so as to ensure that the inverter operates within a safe range of power output or absorption; a modulation execution unit, configured to generate a rotor-side voltage waveform through an inverter according to the target slip rate and torque control parameters, implement vector control on the motor rotor, and adjust the torque and speed of the motor; The monitoring and compensation unit is used to monitor the system stability in real time through the stabilization device, compensate for critical stability, overstability or understability, and adjust the control parameters or grid frequency to maintain stable system operation.

9. An electronic device comprising a memory and a processor, characterized in that: 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 having computer-executable instructions stored thereon, characterized in that: When the computer executable instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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