Alternating current excitation system self-starting control method and system

Abstract

The invention discloses an AC excitation system self-starting control method and system, and the method comprises the steps: obtaining a rotor current rotation frequency and an actual rotor rotation frequency, and generating a slip frequency; the slip frequency is compared with a preset dynamic threshold value, and the rotating speed given value is dynamically adjusted; inquiring a preset multi-stage sectional type current control curve according to the actual rotor rotation frequency, and outputting a d-axis current given value; pI adjustment is carried out based on the slip frequency to generate a q-axis current given value, and corresponding preset current threshold limit is applied according to the frequency band where the actual rotor rotation frequency is located; performing independent parameter configuration on the magnetic flux current control loop and the torque current control loop by adopting a non-coupling parameter setting algorithm; and in the unit starting process, under the condition that the stable starting constraint condition is met, an optimal starting parameter combination is generated. According to the invention, by dynamically adjusting the rotating speed given value and controlling the current in a segmented manner, the stable self-starting of the alternating current excitation system is realized, and the reliability and efficiency of the starting process are improved.

Description

Technical Field

[0001] The present invention relates to the field of power system control, and in particular to a self-starting control method and method for an AC excitation system. Background Art

[0002] An AC excitation system is a device that provides AC excitation power to the rotor of devices such as synchronous motors and doubly-fed induction motors. Its core function is to inject AC current with adjustable frequency, amplitude, and phase into the rotor windings through a power electronic converter (such as a fully controlled converter based on IGBTs), enabling flexible control of motor speed, reactive power, and energy flow. Leveraging algorithms such as vector control and direct torque control, this system enables wide-range variable-speed operation, four-quadrant energy conversion (electrical energy can flow bidirectionally into and out of the rotor), and dynamic reactive power compensation. It is widely used in wind power generation (such as doubly-fed wind turbines that achieve variable-speed constant-frequency power generation through rotor excitation), variable-speed pumped hydro storage, and flywheel energy storage. In particular, it can optimize power quality and enhance grid stability by regulating rotor current in renewable energy grid integration. It boasts advantages such as zero mechanical contact losses, high control precision, and adaptability to renewable energy volatility, making it a key technology for modern smart grids and efficient drive systems.

[0003] The existing self-starting control method of the AC excitation system still has some technical problems: First, during the self-starting process, when the slip is too large, it is easy to cause the magnetic flux to break, affecting the stability of the system; second, under the principle of weak magnetic control, if the magnetic field decays too early, the motor's initial torque is insufficient and it cannot start effectively; if it decays too late, it will be difficult to increase the speed later, affecting the starting efficiency; third, under the constant power control strategy, there is a coupling relationship between the torque current and the flux current, and parameter matching is difficult, which can easily cause oscillation shutdown and affect the reliability of the system.

[0004] Furthermore, existing control methods typically use fixed control parameters, lacking the ability to dynamically adjust based on actual operating conditions and adapting to startup requirements under varying load conditions. Furthermore, existing control methods often employ a unified parameter configuration for both d-axis and q-axis currents, failing to fully account for the distinct characteristics of the two control loops and resulting in insufficient control accuracy.

[0005] Therefore, there is an urgent need for a self-starting control method for an AC excitation system that can remove current coupling, simplify parameter setting, and optimize the control curve to improve the starting performance and operating stability of the system. Summary of the Invention

[0006] In order to overcome the technical problems existing in the self-starting process of the AC exciter, such as excessive slip leading to magnetic flux breakage, improper attenuation timing under the weak magnetic control principle leading to insufficient torque or difficulty in speed increase, and oscillation shutdown caused by current coupling under the constant power control strategy, the present invention provides a self-starting control method and system for an AC excitation system.

[0007] In order to solve the above problems, the present invention is implemented according to the following technical solutions:

[0008] In the first aspect, the present invention provides a self-starting control method for an AC excitation system, comprising the following steps: obtaining the rotor current rotation frequency and the actual rotor rotation frequency, and generating the slip frequency through a slip calculation module; comparing the slip frequency with a preset dynamic threshold, and dynamically adjusting the speed set value according to the comparison result; querying a preset multi-stage segmented current control curve according to the actual rotor rotation frequency, and outputting a d-axis current set value and a change slope parameter set; performing PI adjustment based on the slip frequency to generate a q-axis current set value, and applying a corresponding preset current threshold limit to the q-axis current set value according to the frequency band in which the actual rotor rotation frequency is located; using a non-coupled parameter tuning algorithm to independently configure the parameters of the flux current control loop based on the d-axis current set value and the torque current control loop based on the q-axis current set value; during the unit startup process, generating an optimal startup parameter combination while satisfying the unit's stable startup constraint conditions.

[0009] In combination with the first aspect, the present invention provides a first specific implementation of the first aspect. Specifically, the slip frequency is compared with a preset dynamic threshold, and the speed set value is dynamically adjusted according to the comparison result, specifically including: when the slip frequency is not less than the preset dynamic threshold, maintaining the current speed set value; when the slip frequency is less than the preset dynamic threshold and the slip frequency is greater than 0, incrementally adjusting the speed set value; when the slip frequency is less than 0, forcing the speed set value to track the actual rotor rotation frequency to form a closed-loop frequency correction mechanism.

[0010] In combination with the first aspect, the present invention provides a second specific implementation of the first aspect. Specifically, the calculation formula for incrementally adjusting the speed given value is: N' reset =N reset +T S ·K reset ; Among them, N reset is the speed given value, N' reset is the adjusted speed given value, T S is the system interrupt frequency, K reset is the growth coefficient of the given speed.

[0011] In combination with the first aspect, the present invention provides a third specific implementation of the first aspect. Specifically, the preset multi-level segmented current control curve is as follows: different d-axis current setting values ​​are set in sequence in multiple continuous speed ranges; the multiple continuous speed ranges include a first speed range, a second speed range, a third speed range and a fourth speed range; wherein, an initial d-axis current setting value is set in the first speed range, a first d-axis current setting value is set in the second speed range, a second d-axis current setting value is set in the third speed range, and a third d-axis current setting value is set in the fourth speed range; the initial d-axis current setting value is dynamically corrected according to the inertia characteristics of the mechanical system.

[0012] In combination with the first aspect, the present invention provides a fourth specific implementation of the first aspect. Specifically, the PI adjustment based on the slip frequency is used to generate a q-axis current set value, and a corresponding preset current threshold limit is applied to the q-axis current set value according to the frequency band in which the actual rotor rotation frequency is located. Specifically, it includes: performing PI adjustment based on the slip frequency to generate a q-axis current set value; applying a preset maximum current threshold limit to the q-axis current set value according to different speed bands in which the actual rotor rotation frequency of the motor is located; wherein the different speed bands include at least three consecutive frequency bands, and different maximum current threshold limits are applied respectively in the at least three consecutive frequency bands.

[0013] In combination with the first aspect, the present invention provides a fifth specific implementation of the first aspect. Specifically, in the weak magnetic control state, the initial d-axis current setting value, the first d-axis current setting value, the second d-axis current setting value and the third d-axis current setting value decrease in sequence.

[0014] In a second aspect, the present invention also provides an AC excitation system self-starting control system, comprising: a signal acquisition module for acquiring the rotor current rotation frequency and the actual rotor rotation frequency; a slip calculation module, the slip calculation module being connected to the signal acquisition module for calculating the slip frequency; a dynamic adjustment module, the dynamic adjustment module being connected to the slip calculation module for comparing the slip frequency with a preset dynamic threshold and dynamically adjusting the speed set value according to the comparison result; a segmented control module for querying a preset multi-stage segmented current control curve according to the actual rotor rotation frequency, and outputting a d-axis current set value and a change slope parameter set; a q-axis limiting module for performing PI adjustment based on the slip frequency to generate a q-axis current set value, and applying a corresponding preset current threshold limit to the q-axis current set value according to the frequency band in which the actual rotor rotation frequency is located; a decoupling tuning module for using a non-coupling parameter tuning algorithm to independently configure parameters of a flux current control loop based on the d-axis current set value and a torque current control loop based on the q-axis current set value; and an optimization engine module for generating an optimal starting parameter combination during the unit startup process while satisfying the unit's stable startup constraints.

[0015] In combination with the second aspect, the present invention provides a first specific implementation of the second aspect. Specifically, the dynamic adjustment module dynamically adjusts the speed set value based on the comparison result of the slip signal and the preset dynamic threshold, specifically including: when the slip frequency is not less than the preset dynamic threshold, maintaining the current speed set value; when the slip frequency is less than the preset dynamic threshold and the slip frequency is greater than 0, performing incremental adjustment on the speed set value; when the slip frequency is less than 0, forcing the speed set value to track the actual rotor speed signal to form a closed-loop frequency correction mechanism.

[0016] In combination with the second aspect, the present invention provides a second specific implementation of the second aspect, specifically, the segmented control module executes a preset multi-level segmented current control curve, specifically: different d-axis current setting values ​​are set in sequence in multiple continuous speed ranges; the multiple continuous speed ranges include a first speed range, a second speed range, a third speed range and a fourth speed range; wherein, an initial d-axis current setting value is set in the first speed range, a first d-axis current setting value is set in the second speed range, a second d-axis current setting value is set in the third speed range, and a third d-axis current setting value is set in the fourth speed range; the initial d-axis current setting value is dynamically corrected according to the inertia characteristics of the mechanical system; in the weak magnetic control state, the initial d-axis current setting value, the first d-axis current setting value, the second d-axis current setting value and the third d-axis current setting value decrease in sequence.

[0017] In combination with the second aspect, the present invention provides a third specific implementation of the second aspect. Specifically, the q-axis limiting module performs PI adjustment based on the slip frequency to generate a q-axis current set value, and applies a corresponding preset current threshold limit to the q-axis current set value according to the frequency band in which the actual rotor rotation frequency is located. Specifically, it includes: performing PI adjustment based on the slip frequency to generate a q-axis current set value; applying a preset maximum current threshold limit to the q-axis current set value according to different speed bands in which the actual rotor rotation frequency of the motor is located; wherein the different speed bands include at least three consecutive frequency bands, and different maximum current threshold limits are applied respectively in the at least three consecutive frequency bands.

[0018] Compared with the existing technology, the present invention has the following advantages: improved system stability through optimized speed control strategy; segmented control of flux current and torque current based on frequency optimizes the current control curve, resulting in different current slopes at different stages to match actual motor characteristics; decoupling of torque current and flux current simplifies parameter configuration; and rapid adjustment of startup parameters while ensuring stable unit startup, optimizing startup speed. This avoids the problem of flux fracture caused by excessive q-axis current during the field weakening phase. Compared with the existing technology, the present invention effectively solves the technical difficulties encountered in the traditional AC exciter self-starting process through a segmented current control curve and an uncoupled parameter tuning algorithm, achieving more stable and efficient self-starting control. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0020] Figure 1 The present invention is a flowchart of a self-starting control method for an AC excitation system. DETAILED DESCRIPTION

[0021] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0022] like Figure 1 As shown, the present invention provides an AC excitation system self-starting control method and system.

[0023] Example 1

[0024] A self-starting control method for an AC excitation system comprises the following steps:

[0025] S100: Obtain the rotor current rotation frequency and the actual rotor rotation frequency, and generate a slip frequency through a slip calculation module;

[0026] S200: Compare the slip frequency with a preset dynamic threshold value and dynamically adjust the speed setting value according to the comparison result;

[0027] S300: querying a preset multi-stage segmented current control curve according to the actual rotor rotation frequency, and outputting a d-axis current set value and a change slope parameter set;

[0028] S400: performing PI regulation based on the slip frequency to generate a q-axis current set value, and applying a corresponding preset current threshold limit to the q-axis current set value according to the frequency band of the actual rotor rotation frequency;

[0029] S500: Uses a non-coupled parameter tuning algorithm to independently configure the parameters of the flux current control loop based on the d-axis current given value and the torque current control loop based on the q-axis current given value;

[0030] S600: During the unit startup process, the optimal startup parameter combination is generated while satisfying the unit's stable startup constraint conditions.

[0031] In a preferred embodiment, the rotor current rotation frequency and the actual rotor rotation frequency are obtained, and the slip frequency is generated by the slip calculation module. The slip frequency calculation formula is ΔNr=Nr ram -Nr; where ΔNr is the corner frequency, Nr ram is the rotor current rotation frequency, and Nr is the actual rotor rotation frequency.

[0032] Specifically, in an AC excitation system, a current sensor collects the three-phase rotor current. This three-phase current is transformed through the Clark transform, Park transform, and their inverse transforms to obtain the rotor current rotational frequency. The actual rotor rotational frequency is directly measured and obtained using a speed sensor (such as a photoelectric encoder or resolver). The photoelectric encoder outputs a pulse signal corresponding to the actual rotor speed. The actual rotor rotational frequency is calculated by counting the number of pulses per unit time. The slip calculation module receives these two frequency signals and calculates the slip frequency, which is the difference between the rotor current rotational frequency and the actual rotor rotational frequency.

[0033] Specifically, the given values ​​of the three-phase AC excitation current are obtained from the motor control system and are denoted as i a 、i b 、i c ; Convert the given value of the AC excitation current in the three-phase stationary coordinate system (abc) to the two-phase stationary coordinate system (αβ). The conversion formula is: Convert the current given value in the two-phase stationary coordinate system (αβ) to the two-phase rotating coordinate system (dq). The conversion formula is as follows: Where θ is the rotor position angle, which can be obtained by position sensor or position sensorless estimation method. After the above transformation, the obtained ip_ref That is the given value of the d-axis current, i q_ref is the given value of q-axis current.

[0034] In a preferred embodiment, the slip frequency is compared with a preset dynamic threshold, and the speed set value is dynamically adjusted according to the comparison result; when the slip frequency is not less than the preset dynamic threshold, the system maintains the current speed set value unchanged; when the slip frequency is less than the preset dynamic threshold and greater than 0, the system incrementally adjusts the speed set value; when the slip frequency is less than 0, the system forces the speed set value to track the actual rotor rotation frequency, forming a closed-loop frequency correction mechanism.

[0035] Specifically, a dynamic threshold Nr is set according to the motor's operating conditions, load characteristics, and control requirements. deltaSet , whose value range is [0,10]Hz (the specific unit can be determined according to the actual motor parameters and frequency conversion). In the initial stage, the dynamic threshold is preset to 1Hz as a benchmark for judging whether the slip is reasonable. During the operation of the motor, the calculated slip is compared with the preset dynamic threshold Nr in real time. deltaSet A comparison is performed and different speed setting value adjustment states are triggered according to the comparison results.

[0036] State 1: ΔNr ≥ Nr deltaSet , indicating that the motor rotor has a large slip, and may be in a light load or under load state, and its speed is too high. At this time, the speed setting value N reset Maintain the original state of operation and wait for the rotor frequency to increase due to load changes or motor self-regulation, thereby reducing the slip. During the maintenance period, the slip frequency is continuously monitored. Once the slip frequency decreases and falls below the threshold, consider entering another state to adjust the speed setpoint.

[0037] State 2: 0<ΔNr <Nr deltaSet , indicating that the motor is operating normally, but there is still room for increasing the speed to better adapt to possible load requirements or improve operating efficiency. At this time, according to the formula N' reset =N reset +T S ·K reset Incremental adjustment of the speed setting value, where N reset is the speed given value, N' reset is the adjusted speed given value, T S is the system interrupt frequency, K reset is the given speed growth coefficient. S is the system interruption frequency, that is, the periodic interval at which the system updates the speed given value, K resetThe speed increase factor is a given value and can be pre-set and adjusted based on the motor's dynamic response characteristics and control requirements. This allows the speed setpoint to increase steadily, gradually increasing the motor speed to optimize its operating performance.

[0038] State 3: When ΔNr<0, it means that the actual rotor rotation frequency is higher than the rotor current rotation frequency. This may happen when the motor is in a braking state or the load is suddenly reduced. In this case, in order to quickly adapt to this change and avoid the motor from running in an unstable state, the speed reference value N is directly increased. reset Set the speed value corresponding to the actual rotor rotation frequency collected in this cycle. This will immediately match the motor speed setting with the actual speed, ensuring the stability and safety of the motor operation.

[0039] In a preferred embodiment, the system queries a preset multi-stage segmented current control curve based on the actual rotor rotation frequency and outputs a corresponding d-axis current set value and a set of change slope parameters. The preset multi-stage segmented current control curve is specifically as follows: different d-axis current set values ​​are sequentially set in multiple continuous speed ranges; the multiple continuous speed ranges include a first speed range, a second speed range, a third speed range, and a fourth speed range; wherein an initial d-axis current set value is set in the first speed range, a first d-axis current set value is set in the second speed range, a second d-axis current set value is set in the third speed range, and a third d-axis current set value is set in the fourth speed range; the initial d-axis current set value is dynamically corrected according to the inertia characteristics of the mechanical system.

[0040] Specifically, the specific segmented control is as follows: the first speed interval is within the speed range of 0 to 30 Hz, and the system sets an initial d-axis current setting value. The second speed interval is within the speed range of 30 to 40 Hz, and the system sets a first d-axis current setting value. The third speed interval is within the speed range of 40 to 45 Hz, and the system sets a second d-axis current setting value. The fourth speed interval is within the speed range of 45 to 50 Hz, and the system sets a third d-axis current setting value, wherein the initial d-axis current setting value is dynamically corrected by the adaptive adjustment module according to the inertia characteristics of the mechanical system so that the d-axis current rise rate matches the mechanical characteristics of the load; the initial d-axis current setting value, the first d-axis current setting value, the second d-axis current setting value, and the third d-axis current setting value decrease in sequence to achieve weak magnetic control.

[0041] According to the actual rotor rotation frequency (Nr) converted to the corresponding frequency value (f = Nr / 60, unit: Hz), the frequency of 50Hz is divided into four frequency ranges: 0-30Hz, 30-40Hz, 40-45Hz, and 45-50Hz, which correspond to the initial d-axis current setting value Ird_set30, the first d-axis current setting value Ird_set40, the second d-axis current setting value Ird_set45, and the third d-axis current setting value Ird_set50, respectively. The value range of each level of d-axis setting value is 0 to the rated excitation current value (the rated excitation current value is based on the specific parameters and rated operating conditions of the motor). In the initial stage, the setting values ​​of each level can be set to a smaller initial value and then adjusted according to the tuning requirements.

[0042] To tune the initial d-axis current setpoint Ird_set30, start with a low initial value. Then gradually increase the value of Ird_set30 in regular increments. After each adjustment, start the motor and observe its initial ramp-up speed, startup stability, and system current. Determine the initial ramp-up speed and startup stability by measuring the motor speed ramp-up time and speed fluctuations during startup. Record the time it takes for the motor to accelerate from a standstill to a certain speed; a shorter time indicates a faster initial ramp-up speed. Also, observe the smoothness of the speed curve during startup. Minimal speed fluctuations and no significant oscillation indicate good startup stability. Monitor the motor's current, speed, and other signals in real time. If the current or speed exhibits significant periodic fluctuations with increasing amplitude during startup, this indicates system oscillation. If oscillation occurs, stop increasing Ird_set30 and appropriately reduce its value. Install a current monitoring device to monitor the motor's phase current or total current in real time. If the current exceeds the motor's rated current or the maximum current allowed by the control system, the system is deemed to be overcurrent. At this point, you should stop increasing Ird_set30 and return it to the set value that does not cause overcurrent. After gradually increasing and adjusting, when Ird_set30 reaches a certain value that meets the requirements of a high initial ramp speed and good startup stability without causing system oscillation and overcurrent, the corresponding Ird_set30 value is the final determined d-axis current setpoint for this frequency range.

[0043] Field-weakening control aims to maintain the motor's air-gap flux constant or near the rated value by appropriately reducing the excitation current (i.e., the d-axis current) when the motor is operating at higher frequencies (near the rated frequency or above). This prevents problems such as increased iron losses, reduced efficiency, and deteriorated motor performance due to magnetic circuit oversaturation. Therefore, as the frequency increases, the d-axis setpoints must be gradually decreased according to a specific pattern. Based on the determination of Ird_set30, the first d-axis current setpoint Ird_set40, the second d-axis current setpoint Ird_set45, and the third d-axis current setpoint Ird_set50 are initially set according to the general principles of field-weakening control. After each adjustment of the setpoints, a motor self-start test is performed, recording the startup time from standstill to the rated speed of 50 Hz, as well as the current and speed changes during startup. Observe whether the motor starts smoothly and reaches the rated speed, and whether there are any abnormalities such as oscillation or overcurrent during startup. With the goal of reducing the self-start time, the setpoints for each level were repeatedly adjusted and optimized, ensuring that the system did not oscillate, did not overcurrent, and could self-start to the rated 50Hz. If the self-start time was found to be long under the current settings, but within the specified limits, the values ​​of Ird_set40, Ird_set45, and Ird_set50 could be appropriately increased to speed up the motor's initial acceleration. Conversely, if oscillation or overcurrent occurred, the corresponding setpoints should be reduced. Through repeated testing and adjustments, a set of four d-axis current settings was ultimately determined that achieved fast self-start while ensuring system stability and safety. The determined values ​​of Ird_set30, Ird_set40, Ird_set45, and Ird_set50 were plotted on a d-axis current vs. frequency graph according to the corresponding frequency ranges, forming a segmented d-axis current control curve. At the same time, a corresponding slope parameter is determined for each setpoint. This slope parameter can be set based on the motor's dynamic response requirements and system stability. A gentler slope can be set in lower frequency ranges to ensure a smooth startup process; in higher frequency ranges, the slope can be increased to accelerate current adjustment, allowing the motor to quickly adapt to high-frequency operating conditions. During motor operation, the actual rotor rotation frequency (Nr) is acquired in real time and converted to a corresponding frequency value (f = Nr / 60). Based on this frequency value, the corresponding d-axis current setpoint and slope parameter set are queried from the preset multi-stage segmented current control curve. When f = 35 Hz, the corresponding d-axis current setpoint is Ird_set40, and the slope parameter is the pre-set k40_slope. When f = 48 Hz, the corresponding d-axis current setpoint is Ird_set50, and the slope parameter is k50_slope.The queried d-axis current set value and change slope parameter set are output to the motor control system for real-time control and adjustment of the d-axis current to achieve optimal operating performance of the motor at different speeds.

[0044] In a preferred embodiment, a q-axis current setpoint is generated by performing PI regulation based on the slip frequency, and a preset current threshold limit is applied to the q-axis current setpoint based on the frequency band of the actual rotor rotation frequency. Specifically, this is achieved by performing PI regulation based on the slip frequency to generate the q-axis current setpoint; and applying a preset maximum current threshold limit to the q-axis current setpoint based on the different speed bands within which the actual rotor rotation frequency of the motor resides. The different speed bands include at least three consecutive frequency bands, and different maximum current threshold limits are applied to each of the at least three consecutive frequency bands.

[0045] Specifically, based on the actual motor rotor rotation frequency, preset maximum current thresholds are applied to the q-axis current setpoint: a first maximum current threshold is applied within the 0-40 Hz speed range; a second maximum current threshold is applied within the 40-45 Hz speed range; and a third maximum current threshold is applied within the 45-50 Hz speed range. These three maximum current thresholds are theoretically in an increasing relationship to ensure that the q-axis current can be increased as the d-axis current decreases, allowing continued speed increase in a near-constant power mode. In particular, if the calculated q-axis current is excessive during the actual motor startup process, causing the unit to oscillate, this increasing relationship may not be followed. When the actual speed is within a certain frequency band, the system limits the q-axis current setpoint to no more than the maximum current threshold corresponding to that frequency band.

[0046] Perform PI operation on the slip frequency ΔNr to obtain the q-axis current given value i q_ref The PI calculation formula is: q_ref =K p_q· ΔNr+K i_q ∫ΔNr·dt, where K p_q is the proportional gain, K i_q is the integral gain. Adjust the PI parameter K p_q and K i_q , with the goal of reducing the motor's self-starting time while ensuring that the system does not oscillate and does not overcurrent. Appropriately increase K p_q It can speed up the system response and make the speed track the given value faster, thus shortening the self-starting time; increasing K i It helps to eliminate the speed steady-state error and further improve the starting accuracy. p_q If it is too large, the system may oscillate easily. Therefore, K should be reduced. p_q ; If the integral effect is too strong (K i_q Too large) will also cause oscillation, and K needs to be adjusted i_qMonitor the motor current in real time and if there is an overcurrent tendency, reduce K appropriately. p_q and K i_q , limiting the growth rate of the q-axis current given value.

[0047] According to the actual rotor rotation frequency Nr, it is converted to the corresponding frequency value f=Nr / 60, and 0-50Hz is divided into three frequency intervals: 0-40Hz corresponds to the first maximum current threshold I rq_max40 , 40~45Hz corresponds to the second maximum current threshold I rq_max45 , 45~50Hz corresponds to the third maximum current threshold I rq_max50 The threshold value range of each level is 0 to the rated excitation current value. When the motor is running, the actual rotor rotation frequency Nr is obtained in real time, converted into the frequency value f, and the frequency range to which it belongs is determined. The q-axis current given value i q_ref Apply corresponding threshold limits:

[0048] If f∈[0Hz,40Hz], then i q_limited =min(i q_ref , I rq_max40 );

[0049] If f∈(40Hz,45Hz], then i q_limited =min(i q_ref , I rq_max45 );

[0050] If f∈(45Hz,50Hz], then i q_limited =min(i q_ref , I rq_max50 );

[0051] In the range of 0-40Hz, the system drives the rotor frequency to rise steadily at a relatively fast speed. rq_max40 The threshold value allows a larger q-axis current setting value, so that the motor can output a larger torque, speed up the rotor acceleration process, and shorten the starting time. In the 40-50Hz range (weakening magnetic stage), as the frequency increases and enters the weakening magnetic stage, if the magnetic flux is stable, the threshold value (I rq_max45 and I rq_max50 ) can be increased step by step so that the motor continues to run at approximately constant power. If the magnetic flux is broken due to the decrease of d-axis current and the increase of q-axis current, the threshold (I rq_max45 and I rq_max50 ), continue to increase the speed at a lower power. In this way, under the premise of ensuring system stability, the q-axis current is reasonably limited to ensure the stability of the magnetic flux and make the motor run smoothly to the rated 50Hz. The q-axis current after the threshold limit is given by i q_limitedThe output is sent to the motor control system and works together with the D-axis current set value to control the motor operation. During the actual operation of the motor, the PI parameters and the three-level threshold are further optimized according to the startup time and stability performance: if the startup time is too long, K can be appropriately increased. p_q and K i_q At the same time, check for overcurrent or oscillation. If the flux is unstable during the field weakening stage, reduce I rq_max45 and I rq_max50 .

[0052] In a preferred embodiment, the system uses a decoupled parameter tuning algorithm to independently configure the parameters of the flux current control loop (based on the d-axis current reference) and the torque current control loop (based on the q-axis current reference). Based on the motor's mathematical model, the decoupled parameter tuning algorithm decouples the d-axis and q-axis control loops, allowing them to be adjusted independently.

[0053] The purpose of the non-coupling parameter tuning algorithm is to decouple the dq axis current control loop so that the two loops can be independently configured and optimized. Its core idea is to eliminate the mutual coupling between the dq axes through reasonable control law design based on the mathematical model of the motor, thereby achieving accurate and independent control of the flux current (d axis current) and torque current (q axis current). The d axis current control model is established based on the voltage equation of the motor. In the dq rotating coordinate system, the d axis voltage equation is: d =R s ·i d +L d ·(d(i d ) / dt)-ω e ·L q ·i q +dΨ / dt; where u d is the d-axis voltage, R s is the stator resistance, L d is the d-axis inductance, i d is the d-axis current, ω e is the motor electrical angular velocity, L q is the q-axis inductance, i q is the q-axis current, Ψ is the magnetic flux. In the steady state, ignoring the magnetic flux change rate dψ / dt, the simplified equation is: d ≈R s ·i d +L d ·(d(i d ) / dt)-ω e ·L q ·i q .

[0054] The PI controller is used to adjust the d-axis current, and the controller output is the d-axis voltage given value ud_ref The expression of PI controller is: d_ref =K p_d ·(i rd_ref -i rd )+K i_d ·∫(i rd_ref -i rd )dt; where i rd_ref is the given value of d-axis current, i rd is the actual d-axis current feedback value, K p_d is the d-axis current loop proportional gain, K i_d is the d-axis current loop proportional gain.

[0055] Establish the q-axis current control model, also based on the motor voltage equation. In the dq rotating coordinate system, the q-axis voltage equation is: q =R s ·i q +L q ·(d(i q ) / dt)-ω e ·L d ·i d +dΨ / dt; where u q is the q-axis voltage, i q is the q-axis current, and the other parameters have the same meaning as the d-axis voltage equation. In steady state, the simplified equation is: q ≈R s ·i q +L q ·(d(i q ) / dt)-ω e ·L d ·i d ; The PI controller is also used to adjust the q-axis current, and the controller output is the q-axis voltage given value u q_ref The expression of PI controller is: q_ref =K p_q ·(i rq_ref -i rq )+K i_q ·∫(i rq_ref -i rq )dt; where i rq_ref is the given value of q-axis current, i rq is the actual q-axis current feedback value, K p_q is the q-axis current loop proportional gain, K i_q is the q-axis current loop proportional gain.

[0056] In order to eliminate the mutual coupling between the dq axis, a decoupling control law is designed. According to the voltage equation of the motor, the decoupling control law can be expressed as: d_ref =Kp_d ·(i rd_ref -i rd )+K i_d ·∫(i rd_ref -i rd )dt+ω e ·L q ·i q ;u q_ref =K p_q ·(i rq_ref -i rq )+K i_q ·∫(i rq_ref -i rq )dt+ω e ·L d ·i d ; Among them, the first two items are the outputs of the dq axis current loop PI controller, and the last two items are decoupling compensation items, which are used to eliminate the coupling effect between the dq axes.

[0057] By obtaining the electrical angular velocity ω of the motor in real time e , actual d-axis current feedback value i rd and the actual q-axis current feedback value i rq . Calculate the d-axis and q-axis voltage given values ​​u according to the decoupling control law d_ref and u q_ref The calculated u d_ref and u q_ref The voltage reference value u is converted to the two-phase stationary coordinate system through Park inverse transformation α_ref and u β_ref Finally, a three-phase PWM signal is generated through SVPWM (space vector pulse width modulation) or other PWM techniques to control the switching action of the inverter, thereby achieving precise control of the motor.

[0058] In a preferred embodiment, during the generator startup process, the system generates an optimal combination of startup parameters while meeting the generator's stable startup constraints. Based on the generator's characteristics and load, the system dynamically adjusts startup parameters, including the d-axis current rise rate, q-axis current limit, and speed setpoint increase factor, to achieve optimal startup performance.

[0059] Specifically, the system monitors key parameters during startup, such as rotor current, stator current, slip frequency, and speed change rate, to determine whether the startup state is stable. If instability is detected, the system automatically adjusts the startup parameters to ensure a stable startup of the unit. The optimal startup parameter combination is generated using a multi-objective optimization algorithm, taking into account factors such as startup time, peak startup current, and energy consumption. Based on historical startup data and current unit status, the system predicts the optimal parameter combination and makes fine-tuning adjustments during startup based on actual responses.

[0060] Example 2

[0061] An AC excitation system self-starting control system, comprising:

[0062] A signal acquisition module is used to obtain the rotor current rotation frequency and the actual rotor rotation frequency;

[0063] a slip calculation module, connected to the signal acquisition module, and configured to calculate a slip frequency;

[0064] a dynamic adjustment module, connected to the slip calculation module, configured to compare the slip frequency with a preset dynamic threshold and dynamically adjust a speed setting value according to the comparison result;

[0065] The segmented control module is used to query the preset multi-stage segmented current control curve according to the actual rotor rotation frequency and output the D-axis current set value and change slope parameter set;

[0066] The q-axis limiting module is used to generate a q-axis current set value by performing PI regulation based on the slip frequency, and to impose a corresponding preset current threshold limit on the q-axis current set value according to the frequency band of the actual rotor rotation frequency;

[0067] Decoupling tuning module, used to use non-coupled parameter tuning algorithm to independently configure parameters of the flux current control loop based on the d-axis current given value and the torque current control loop based on the q-axis current given value;

[0068] The optimization engine module is used to generate the optimal startup parameter combination while meeting the unit's stable startup constraints during the unit startup process.

[0069] In a preferred embodiment, the signal acquisition module includes a current sensor and a speed sensor. The current sensor collects the rotor's three-phase current signal, processes it through a signal conditioning circuit and an analog-to-digital converter, and outputs a digitized current signal. The speed sensor collects the rotor's actual rotational speed signal, which is also conditioned and digitized before output. The signal acquisition module also includes a filtering unit to remove noise and interference from the signal, improving signal quality.

[0070] In a preferred embodiment, the slip calculation module receives the rotor current rotational frequency and the actual rotor rotational frequency signal from the signal acquisition module and calculates the difference between the two, namely the slip frequency. The slip calculation module includes a frequency extraction unit and a difference calculation unit. The frequency extraction unit extracts the rotational frequency from the rotor current signal, and the difference calculation unit calculates the slip frequency.

[0071] In a preferred embodiment, the dynamic adjustment module dynamically adjusts the speed setpoint based on a comparison of the slip signal with a preset dynamic threshold. The dynamic adjustment module includes a comparison unit and an adjustment unit. The comparison unit compares the slip frequency with the preset dynamic threshold, and the adjustment unit adjusts the speed setpoint based on the comparison result.

[0072] In a preferred embodiment, when the slip frequency is not less than a preset dynamic threshold, the dynamic adjustment module maintains the current speed set value; when the slip frequency is less than the preset dynamic threshold and greater than 0, the dynamic adjustment module incrementally adjusts the speed set value; when the slip frequency is less than 0, the dynamic adjustment module forces the speed set value to track the actual rotor speed signal, forming a closed-loop frequency correction mechanism.

[0073] In a preferred embodiment, the segmented control module queries a preset multi-stage segmented current control curve based on the actual rotor rotational frequency and outputs a set of d-axis current setpoints and slope parameters. The segmented control module includes a frequency detection unit, a table lookup unit, and an output unit. The frequency detection unit detects the actual rotor rotational frequency, the table lookup unit queries the corresponding d-axis current setpoint based on the frequency, and the output unit generates the d-axis current setpoint and slope parameters.

[0074] In a preferred embodiment, the segmented control module executes a preset multi-level segmented current control curve, specifically: different d-axis current setting values ​​are set in sequence in multiple continuous speed ranges; the multiple continuous speed ranges include a first speed range, a second speed range, a third speed range and a fourth speed range; wherein, an initial d-axis current setting value is set in the first speed range, a first d-axis current setting value is set in the second speed range, a second d-axis current setting value is set in the third speed range, and a third d-axis current setting value is set in the fourth speed range; the initial d-axis current setting value is dynamically corrected according to the inertia characteristics of the mechanical system; in the weak magnetic control state, the initial d-axis current setting value, the first d-axis current setting value, the second d-axis current setting value and the third d-axis current setting value decrease in sequence.

[0075] Specifically, an initial d-axis current set value is set within the first speed range of 0 to 30 Hz; a first d-axis current set value is set within the second speed range of 30 to 40 Hz; a second d-axis current set value is set within the third speed range of 40 to 45 Hz; and a third d-axis current set value is set within the fourth speed range of 45 to 50 Hz. The initial d-axis current set value is dynamically modified by the adaptive adjustment module based on the inertia characteristics of the mechanical system to ensure that the d-axis current rise rate matches the load's mechanical characteristics. The initial d-axis current set value is adjusted based on the inertia characteristics to ensure that the d-axis current rise rate matches the load's mechanical characteristics. For systems with high inertia, the inertia adaptive unit increases the initial d-axis current set value; for systems with low inertia, it decreases the initial d-axis current set value. In the field-weakening control state, the initial d-axis current set value, the first d-axis current set value, the second d-axis current set value, and the third d-axis current set value decrease in sequence.

[0076] In a preferred embodiment, the q-axis limiting module performs PI regulation based on the slip frequency to generate a q-axis current setpoint value and applies a preset current threshold limit to the q-axis current setpoint value based on the frequency band of the actual rotor rotational frequency. The q-axis limiting module includes a PI regulation unit, a frequency band determination unit, and a limiting unit. The PI regulation unit generates an initial q-axis current setpoint value based on the slip frequency, the frequency band determination unit determines the frequency band of the current speed, and the limiting unit applies a current threshold limit based on the frequency band.

[0077] In a preferred embodiment, the q-axis limiting module performs PI adjustment based on the slip frequency to generate a q-axis current set value, and applies a corresponding preset current threshold limit to the q-axis current set value according to the frequency band in which the actual rotor rotation frequency is located. Specifically, the following steps are performed: performing PI adjustment based on the slip frequency to generate the q-axis current set value; applying a preset maximum current threshold limit to the q-axis current set value according to different speed bands in which the actual rotor rotation frequency of the motor is located; wherein the different speed bands include at least three consecutive frequency bands, and different maximum current threshold limits are respectively applied within the at least three consecutive frequency bands.

[0078] Specifically, PI adjustment is performed based on the slip frequency to generate a q-axis current set value; a preset maximum current threshold limit is applied to the q-axis current set value according to the actual rotor rotation frequency of the motor, and a first maximum current threshold is applied in the speed range of 0 to 40 Hz; a second maximum current threshold is applied in the speed range of 40 to 45 Hz; and a third maximum current threshold is applied in the speed range of 45 to 50 Hz; when the actual speed is in a certain frequency band, the q-axis current set value is limited not to exceed the maximum current threshold corresponding to the frequency band.

[0079] In a preferred embodiment, the decoupling tuning module uses a non-coupled parameter tuning algorithm to independently configure the parameters of the flux current control loop based on the d-axis current setpoint and the torque current control loop based on the q-axis current setpoint. The decoupling tuning module includes a model calculation unit, a parameter optimization unit, and a controller configuration unit. The model calculation unit establishes a mathematical model based on the motor parameters, the parameter optimization unit calculates the optimal control parameters, and the controller configuration unit applies the parameters to the control loops.

[0080] In a preferred embodiment, the optimization engine module generates an optimal startup parameter combination during the unit startup process, while satisfying the unit's stable startup constraints. The optimization engine module includes a state monitoring unit, a parameter prediction unit, and a parameter adjustment unit. The state monitoring unit monitors key parameters during the startup process, the parameter prediction unit predicts the optimal parameter combination, and the parameter adjustment unit adjusts the parameters based on the actual response.

[0081] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Therefore, any modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A self-starting control method for an AC excitation system, characterized in that: The following steps are involved: Obtain the rotor current rotation frequency and the actual rotor rotation frequency, and generate the slip frequency through the slip calculation module; Comparing the slip frequency with a preset dynamic threshold, and dynamically adjusting the speed setpoint according to the comparison result; Query the preset multi-stage segmented current control curve according to the actual rotor rotation frequency, and output the D-axis current set value and change slope parameter set; Performing PI regulation based on the slip frequency to generate a q-axis current set value, and applying a corresponding preset current threshold limit to the q-axis current set value according to the frequency band of the actual rotor rotation frequency; Using a non-coupled parameter tuning algorithm, independently configuring parameters of a flux current control loop based on the d-axis current given value and a torque current control loop based on the q-axis current given value; During the unit startup process, the optimal startup parameter combination is generated while satisfying the unit's stable startup constraints.

2. The AC excitation system self-starting control method according to claim 1, characterized in that: Comparing the slip frequency with a preset dynamic threshold and dynamically adjusting the speed setting value according to the comparison result specifically includes: When the slip frequency is not less than the preset dynamic threshold, the current speed setting value is maintained; When the slip frequency is less than a preset dynamic threshold and the slip frequency is greater than 0, the speed setting value is incrementally adjusted; When the slip frequency is less than 0, the speed setpoint is forced to track the actual rotor rotation frequency, forming a closed-loop frequency correction mechanism.

3. The AC excitation system self-starting control method according to claim 2, characterized in that: The calculation formula for incrementally adjusting the speed set value is: N′ reset =N reset +T S ·K reset ; Among them, N reset is the speed given value, N′ reset is the adjusted speed given value, T S is the system interrupt frequency, K reset is the growth coefficient of the given speed.

4. The AC excitation system self-starting control method according to claim 1, characterized in that: The preset multi-stage segmented current control curve is specifically: Sequentially setting different d-axis current setting values ​​in a plurality of continuous speed intervals; The plurality of continuous speed intervals include a first speed interval, a second speed interval, a third speed interval and a fourth speed interval; wherein an initial d-axis current setting value is set in the first speed range, a first d-axis current setting value is set in the second speed range, a second d-axis current setting value is set in the third speed range, and a third d-axis current setting value is set in the fourth speed range; The initial d-axis current setting value is dynamically modified according to the inertia characteristics of the mechanical system.

5. The AC excitation system self-starting control method according to claim 1, characterized in that: The step of performing PI regulation based on the slip frequency to generate a q-axis current given value, and applying a corresponding preset current threshold limit to the q-axis current given value according to the frequency band of the actual rotor rotation frequency, specifically includes: Performing PI regulation based on the slip frequency to generate a q-axis current given value; According to different speed frequency bands of the actual rotor rotation frequency of the motor, a preset maximum current threshold limit is imposed on the q-axis current given value; The different speed frequency bands include at least three continuous frequency bands, and different maximum current threshold limits are applied to the at least three continuous frequency bands respectively.

6. The AC excitation system self-starting control method according to claim 4, characterized in that: In the field weakening control state, the initial d-axis current setting value, the first d-axis current setting value, the second d-axis current setting value and the third d-axis current setting value decrease in sequence.

7. An AC excitation system self-starting control system, characterized in that: include: A signal acquisition module is used to obtain the rotor current rotation frequency and the actual rotor rotation frequency; a slip calculation module, connected to the signal acquisition module, and configured to calculate a slip frequency; a dynamic adjustment module, connected to the slip calculation module, configured to compare the slip frequency with a preset dynamic threshold and dynamically adjust a speed setting value according to the comparison result; The segmented control module is used to query the preset multi-stage segmented current control curve according to the actual rotor rotation frequency and output the D-axis current set value and change slope parameter set; A q-axis limiting module is used to generate a q-axis current set value by performing PI regulation based on the slip frequency, and to impose a corresponding preset current threshold limit on the q-axis current set value according to the frequency band of the actual rotor rotation frequency; a decoupling tuning module, configured to independently configure parameters of a flux current control loop based on the d-axis current given value and a torque current control loop based on the q-axis current given value using a non-coupling parameter tuning algorithm; The optimization engine module is used to generate the optimal startup parameter combination while meeting the unit's stable startup constraints during the unit startup process.

8. The AC excitation system self-starting control system according to claim 7, characterized in that: The dynamic adjustment module dynamically adjusts the speed setting value according to the comparison result of the slip frequency and the preset dynamic threshold, specifically including: When the slip frequency is not less than the preset dynamic threshold, the current speed setting value is maintained; When the slip frequency is less than a preset dynamic threshold and the slip frequency is greater than 0, the speed setting value is incrementally adjusted; When the slip frequency is less than 0, the speed set value is forced to track the actual rotor speed signal, forming a closed-loop frequency correction mechanism.

9. The AC excitation system self-starting control system according to claim 7, characterized in that: The segmented control module executes a preset multi-stage segmented current control curve, specifically: Sequentially setting different d-axis current setting values ​​in a plurality of continuous speed intervals; The plurality of continuous speed intervals include a first speed interval, a second speed interval, a third speed interval and a fourth speed interval; wherein an initial d-axis current setting value is set in the first speed range, a first d-axis current setting value is set in the second speed range, a second d-axis current setting value is set in the third speed range, and a third d-axis current setting value is set in the fourth speed range; The initial d-axis current setting value is dynamically corrected according to the inertia characteristics of the mechanical system; In the field weakening control state, the initial d-axis current setting value, the first d-axis current setting value, the second d-axis current setting value and the third d-axis current setting value decrease in sequence.

10. The AC excitation system self-starting control system according to claim 7, characterized in that: The q-axis limiting module performs PI regulation based on the slip frequency to generate a q-axis current set value, and applies a corresponding preset current threshold limit to the q-axis current set value according to the frequency band of the actual rotor rotation frequency, specifically including: Performing PI regulation based on the slip frequency to generate a q-axis current given value; According to different speed frequency bands of the actual rotor rotation frequency of the motor, a preset maximum current threshold limit is imposed on the q-axis current given value; The different speed frequency bands include at least three continuous frequency bands, and different maximum current threshold limits are applied to the at least three continuous frequency bands respectively.

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