A method and device for cooperative control of transformer step voltage regulation and inter-step fine tuning

Abstract

The application discloses a transformer hierarchical voltage regulation and inter-stage fine adjustment cooperative control method and device, and relates to the technical field of transformer voltage regulation control. The application first collects the actual voltage of the transformer, adopts a smooth tracking differentiator to obtain a smooth target voltage and a voltage change rate, adopts an extended state observer to obtain an actual voltage tracking value, a voltage change rate estimation value and a total disturbance estimation value, and determines a total control amount through a nonlinear state error feedback control law; determines a hierarchical instruction or a fine adjustment instruction according to the total control amount and a preset hierarchical threshold value, controls a load tap changer and a thyristor respectively, and performs closed-loop regulation by using the actual voltage after voltage regulation. The application can improve the coordination of hierarchical voltage regulation and inter-stage fine adjustment, and reduce the influence of instantaneous voltage fluctuation on voltage regulation control.

Description

Technical Field

[0001] This invention relates to the field of transformer voltage regulation control technology, and in particular to a method and apparatus for coordinated control of transformer graded voltage regulation and inter-grade fine adjustment. Background Technology

[0002] Industrial rectifier units used in processes such as copper electrolysis and electroplating typically require adjustment of the transformer output voltage based on load conditions and power supply requirements. The stability of the output voltage directly impacts the rectifier unit's operating status and the technological process. Existing transformer voltage regulation methods mainly include on-load tap changer regulation and thyristor phase-controlled regulation. On-load tap changers alter the transformer winding tap position to change the turns ratio, enabling a wide range of output voltage regulation with low operating losses. However, the regulation process exhibits distinct tap characteristics, with a large single-stage voltage regulation range, and the mechanical switching process is limited by operating time and switch lifespan.

[0003] Thyristor phase-controlled voltage regulation continuously adjusts the output voltage of the rectifier unit by changing the thyristor control angle. It features high adjustment accuracy and fast response speed, making it suitable for fine-tuning the voltage between adjacent voltage levels. However, the usable range of the thyristor control angle is limited by the output waveform and device losses. If the control angle is too small, waveform distortion is likely to occur; if the control angle is increased, conduction losses will increase accordingly. Therefore, it is difficult to simultaneously meet the requirements of wide voltage regulation range and low loss operation by using thyristor phase-controlled voltage regulation alone.

[0004] To balance voltage regulation range and accuracy, existing technologies employ a combined voltage regulation approach, using on-load tap changers for graded voltage regulation and thyristors for fine-tuning between stages. For example, CN102851703A discloses an intelligent automatic voltage regulation optimization control method for an electrolytic aluminum power supply system. This method divides the fine-tuning voltage regulation range into an ascending segment, a free segment, and a descending segment. When the voltage value enters the ascending segment, the on-load tap changer is controlled to ascend; when it enters the descending segment, the on-load tap changer is controlled to descend; and no segment switching is performed in the free segment. Simultaneously, a delay time is set to reduce frequent segment adjustments caused by short-term operating condition changes. This control method reflects the development trend of industrial rectifier unit voltage regulation control from a single voltage regulating element to a combination of graded voltage regulation and continuous fine-tuning.

[0005] Existing coarse and fine voltage regulation control typically determines the timing of on-load tap changer operation based on pre-set voltage regulation ranges and delay times. When grid voltage fluctuates or load conditions change, the control system needs to wait a set delay before deciding whether to perform a tap change. Fixed delay times are difficult to adapt to changes in disturbance amplitude and duration, and fixed segment thresholds are difficult to adjust in real-time according to the rectifier unit's operating status. The division of labor between on-load tap changers and thyristors mainly relies on preset rules, lacking real-time observation and compensation for external disturbances during control, which can easily affect the coordination between staged voltage regulation and inter-stage fine regulation.

[0006] Active disturbance rejection control (ADRC) can estimate the state of the controlled object and the total disturbance using an extended state observer, thus it can be used in voltage regulation control processes with external disturbances. Traditional ADRC tracking differentiators are typically constructed using the fastest control synthesis function. In traditional schemes, the fastest control synthesis function includes a sign function and piecewise operations, resulting in a certain phase delay when implemented in a digital controller, and a coupling relationship exists between filtering performance and tracking speed. Existing techniques using hyperbolic tangent or inverse hyperbolic sine functions to construct smooth tracking differentiators are mainly geared towards filtering and differential extraction of general signals, and have not yet established corresponding coordinated voltage regulation relationships for the control processes of transformer staged voltage regulation and inter-stage fine-tuning. Therefore, how to improve inter-stage adjustment accuracy while maintaining a large voltage regulation range and reducing unnecessary stage switching caused by instantaneous disturbances remains a problem to be solved in the voltage regulation control of existing industrial rectifier transformers. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for coordinated control of transformer graded voltage regulation and inter-stage fine adjustment. This method can solve the problems of insufficient coordination between graded voltage regulation and inter-stage fine adjustment caused by the reliance on fixed judgment methods and the difficulty of participating in voltage regulation control under existing coarse and fine adjustment control. It can achieve closed-loop coordination of graded voltage regulation and inter-stage fine adjustment based on actual voltage state and total disturbance estimation.

[0008] To achieve the above objectives, the present invention provides the following solution: A coordinated control method for transformer staged voltage regulation and inter-stage fine-tuning includes: Collect the actual voltage of the transformer; A smooth tracking differentiator based on the hyperbolic tangent function is used to smoothly track the preset target voltage, thereby obtaining the smooth target voltage and the rate of voltage change. An extended state observer is used to observe the actual voltage, and the actual voltage tracking value, voltage change rate estimate, and total disturbance estimate are obtained. Based on the error between the actual voltage tracking value and the smoothed target voltage, the error between the estimated voltage change rate and the voltage change rate, and the estimated total disturbance, a nonlinear state error feedback control law is used to determine the total control quantity. When the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper limit of the gear position nor the lower limit of the gear position, the grading instruction is determined according to the total control quantity; when the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer has reached the upper limit of the gear position or the lower limit of the gear position, the total control quantity is determined as a fine adjustment instruction. The on-load tap changer is switched according to the graded instructions, or the fine-tuning instructions are converted into thyristor control angles according to the mapping relationship, and the thyristor is adjusted according to the thyristor control angles. The actual voltage after voltage regulation is collected and used as the input of the extended state observer in the next control cycle.

[0009] Preferably, a smooth tracking differentiator based on the hyperbolic tangent function to construct an acceleration function is used to smoothly track a preset target voltage, obtaining a smooth target voltage and voltage change rate, including: The rate of change of voltage is defined as the rate of change of the smoothed target voltage. The product of the slope factor and the deviation between the smoothed target voltage and the preset target voltage, divided by the velocity factor, is used as the independent variable of the first hyperbolic tangent function; the product of the slope factor and the rate of change of voltage, divided by the velocity factor, is used as the independent variable of the second hyperbolic tangent function. The rate of change of voltage is determined by the negative of the sum of the product of the square of the velocity factor and the function value of the first hyperbolic tangent function and the function value of the velocity factor and the function value of the second hyperbolic tangent function. The target voltage and the rate of change of voltage are iteratively updated based on the rate of change of the target voltage and the rate of change of the voltage change.

[0010] Preferably, an extended state observer is used to observe the actual voltage to obtain the actual voltage tracking value, the voltage change rate estimate, and the total disturbance estimate, including: The observation error is determined based on the difference between the actual voltage tracking value and the actual voltage. The rate of change of the actual voltage tracking value is determined by the difference between the estimated voltage change rate and the product of the first observation gain and the observation error. The observation error is processed using a nonlinear function fal with a first exponential parameter and a threshold parameter. The rate of change of the voltage change rate estimate is determined based on the difference between the total disturbance estimate and the product of the second observation gain and the processed observation error. The observation error is processed using a nonlinear function fal with a second exponential parameter and a threshold parameter. The rate of change of the total disturbance estimate is determined based on the negative value of the product of the third observation gain and the processed observation error.

[0011] Preferably, based on the error between the actual voltage tracking value and the smoothed target voltage, the error between the estimated voltage change rate and the voltage change rate, and the estimated total disturbance, a nonlinear state error feedback control law is used to determine the total control quantity, including: The difference between the actual voltage tracking value and the smoothed target voltage is defined as the voltage tracking error, and the difference between the estimated voltage change rate and the voltage change rate is defined as the voltage change rate error. The voltage tracking error is handled by a nonlinear function fal with a third exponential parameter and a threshold parameter, and the voltage change rate error is handled by a nonlinear function fal with a fourth exponential parameter and a threshold parameter. The basic control quantity is determined based on the two processing results and the corresponding feedback gain. The total control quantity is obtained by subtracting the ratio of the total disturbance estimate to the control gain coefficient from the basic control quantity.

[0012] Preferably, the preset grading threshold is the product of the grading threshold coefficient, the voltage regulation amplitude of each stage of the on-load tap changer, and the preset target voltage, the voltage regulation amplitude of each stage is the voltage regulation ratio between adjacent taps of the on-load tap changer, and the grading threshold coefficient is 0.5 to 0.8.

[0013] Preferably, when the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper limit of the gear position nor the lower limit, a grading instruction is determined based on the total control quantity; when the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer has reached the upper limit of the gear position or the lower limit of the gear position, the total control quantity is determined as a fine-tuning instruction, including: When the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper limit of the gear position nor the lower limit of the gear position, the grading instruction is determined according to the positive or negative sign of the total control quantity, and the fine adjustment instruction is set to zero. When the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer reaches the upper or lower limit of the gear position, the grading instruction is set to zero, and the total control quantity is used as the fine-tuning instruction.

[0014] Preferably, the fine-tuning command is converted into a thyristor control angle according to the mapping relationship, and the thyristor is adjusted according to the thyristor control angle, including: Set the mapping relationship to a linear mapping relationship; Using 15° as the reference value for the thyristor control angle, the product of the fine-tuning command and the mapping coefficient is superimposed onto the reference value to obtain the thyristor control angle; Adjust the thyristor according to the thyristor control angle.

[0015] Preferably, during the process of converting the fine-tuning command into a thyristor control angle according to the mapping relationship and adjusting the thyristor according to the thyristor control angle, when the thyristor control angle reaches 5° or 25° and the absolute value of the total control quantity is greater than zero, the graded command is determined according to the positive or negative sign of the total control quantity, the on-load tap changer is switched according to the graded command, and the thyristor control angle is restored to 15° after the switch is completed.

[0016] Preferably, switching the on-load tap changer position according to the graded instruction includes: After determining the grading instruction, the fine-tuning instruction is locked to zero, and the on-load tap changer is driven to switch gears according to the grading instruction. After gear shifting, continuously read the gear position feedback of the on-load tap changer. When the gear position feedback read three times in a row is consistent, it is confirmed that the on-load tap changer has completed gear shifting. After confirming that the on-load tap changer has completed the gear switching, the lock on the fine-tuning command is released after a preset delay time.

[0017] A coordinated control device for transformer graded voltage regulation and inter-stage fine adjustment includes a controller module, a detection module, an on-load switch execution module, and a thyristor triggering module. The detection module is connected to the controller module and is used to collect the actual voltage of the transformer and transmit the actual voltage to the controller module. The on-load tap changer execution module includes an on-load tap changer and a drive circuit. The drive circuit is connected to the controller module, and the tap position feedback interface of the on-load tap changer is connected to the controller module. The thyristor trigger module is connected to the controller module and is connected to the thyristor gate via a pulse transformer; The controller module is used to smoothly track a preset target voltage using a smooth tracking differentiator based on the hyperbolic tangent function to construct an acceleration function, obtaining the smoothed target voltage and voltage change rate; it uses an extended state observer to observe the actual voltage, obtaining the actual voltage tracking value, voltage change rate estimate, and total disturbance estimate; based on the error between the actual voltage tracking value and the smoothed target voltage, the error between the voltage change rate estimate and the voltage change rate, and the total disturbance estimate, a nonlinear state error feedback control law is used to determine the total control quantity; when the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper or lower limit of the tap position, a grading instruction is determined based on the total control quantity; when the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer has reached the upper or lower limit of the tap position, the total control quantity is determined as a fine-tuning instruction, and the fine-tuning instruction is converted into a thyristor control angle according to the mapping relationship; The on-load tap changer execution module is used to drive the on-load tap changer to switch positions according to the graded instructions. The thyristor triggering module is used to generate trigger pulses based on the thyristor control angle, and transmits the trigger pulses to the thyristor gate via a pulse transformer.

[0018] The present invention discloses the following beneficial effects: (1) The present invention uses a smooth tracking differentiator based on the hyperbolic tangent function to construct an acceleration function to smoothly track the preset target voltage, thereby obtaining a smooth target voltage and voltage change rate. This allows the target voltage to undergo continuous and smooth state processing before participating in voltage regulation control, reducing the impact of short-term voltage changes on subsequent control quantity calculations, and thus reducing the possibility of instantaneous fluctuations causing graded voltage regulation actions.

[0019] (2) The present invention observes the actual voltage through an extended state observer to obtain the actual voltage tracking value, the voltage change rate estimate and the total disturbance estimate. Combined with the smoothed target voltage and voltage change rate, the total control quantity is determined by the nonlinear state error feedback control law, so that the actual voltage state and disturbance change participate in the voltage regulation control together, reducing the influence of simply relying on delay judgment to wait for the disturbance to subside on the voltage regulation response.

[0020] (3) This invention compares the absolute value of the total control quantity with the preset grading threshold and determines the grading instruction or fine adjustment instruction by combining the position status of the on-load tap changer. The voltage regulation demand that meets the grading conditions is switched by the on-load tap changer, and the voltage regulation demand that does not meet the grading conditions is adjusted by the thyristor control angle. This realizes the coordination between grading voltage regulation and inter-stage fine adjustment, and reduces the frequent operation of the on-load tap changer caused by small voltage deviations.

[0021] (4) This invention converts the fine-tuning command into the thyristor control angle according to the mapping relationship, and re-acquires the actual voltage after voltage regulation. The actual voltage after voltage regulation is used for the expansion state observation of the next control cycle, so that the control state and total control quantity can be re-determined according to the actual voltage after voltage regulation in each control cycle, forming a continuous closed-loop voltage regulation process, improving the recovery ability and regulation stability of the output voltage after being subjected to external disturbances. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The flowchart illustrates the transformer graded voltage regulation and inter-stage fine-tuning coordinated control method provided in this embodiment of the invention.

[0024] Figure 2 This is a structural block diagram of the collaborative control device provided in an embodiment of the present invention.

[0025] Figure 3 A comparison diagram of the hyperbolic tangent acceleration function and the fhan function provided in the embodiments of the present invention.

[0026] Figure 4 A comparison chart of the tracking effects of the smooth tracking differentiator and the Fhan tracking differentiator provided in the embodiments of the present invention.

[0027] Figure 5 This is a magnified comparison image of the steady-state region provided in an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram illustrating the structure and operational relationships of the improved active disturbance rejection control algorithm provided in an embodiment of the present invention.

[0029] Figure 7 The overall control flowchart of the collaborative control method provided in the embodiment of the present invention is shown. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Figure 1 The method flowchart provided in the embodiments of the present invention is as follows: Figure 1 As shown, this embodiment provides a coordinated control method for transformer staged voltage regulation and inter-stage fine-tuning, including: Step 100: Collect the actual voltage of the transformer; Step 200: Use a smooth tracking differentiator based on the hyperbolic tangent function to construct an acceleration function to smoothly track the preset target voltage, and obtain the smooth target voltage and voltage change rate; Step 300: Use an extended state observer to observe the actual voltage and obtain the actual voltage tracking value, the voltage change rate estimate, and the total disturbance estimate; Step 400: Based on the error between the actual voltage tracking value and the smoothed target voltage, the error between the voltage change rate estimate and the voltage change rate, and the total disturbance estimate, the total control quantity is determined using a nonlinear state error feedback control law; Step 500: When the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper limit of the gear position nor the lower limit of the gear position, the grading instruction is determined according to the total control quantity; when the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer has reached the upper limit of the gear position or the lower limit of the gear position, the total control quantity is determined as a fine adjustment instruction. Step 600: Switch the on-load tap changer position according to the graded instruction, or convert the fine-tuning instruction into the thyristor control angle according to the mapping relationship, and adjust the thyristor according to the thyristor control angle; Step 700: Acquire the actual voltage after voltage regulation and use the actual voltage after voltage regulation as the input of the extended state observer in the next control cycle.

[0033] Before executing step 100, control parameters can be initialized based on the unit's rated voltage and on-load tap changer configuration. The initialization includes setting a preset target voltage. Number of on-load tap changers Voltage regulation amplitude at each level Preset grading threshold thyristor control angle range, slope factor of smooth tracking differentiator And other parameters of the improved active disturbance rejection control algorithm. During the initial commissioning of the device, the thyristor control angle... The default value is set to 15°, and the controller will automatically adjust it after the improved active disturbance rejection control algorithm is run.

[0034] The collaborative control method of this embodiment can be applied to industrial rectifier units, including electrolytic copper supporting rectifier units and electroplating supporting rectifier units. To implement the above voltage regulation process, a collaborative control device can be used to complete actual voltage acquisition, control calculation, gear switching, thyristor triggering, status feedback, and parameter setting. The collaborative control device includes a controller module, a detection module, an on-load switching execution module, a thyristor triggering module, a human-machine interface module, a communication module, and a power supply module.

[0035] This embodiment employs an on-load tap changer for graded voltage regulation and thyristors for fine-tuning between stages. The on-load tap changer alters the transformer winding taps to change the turns ratio, with a typical voltage regulation range of ±15% to ±20%. Each stage's voltage regulation amplitude is typically no less than 1%, and the mechanical response time is approximately 50 to 150 ms. The typical design life is approximately 1 million mechanical cycles and 500,000 electrical cycles; therefore, it is necessary to minimize unnecessary tap switching caused by instantaneous disturbances. The thyristor achieves continuous regulation by changing the control angle, achieving a voltage regulation accuracy within 0.1% and a response time no greater than 20 ms. However, waveform distortion worsens when the control angle is less than 5°, and conduction losses increase significantly when the control angle is greater than 25°, accounting for 15% to 20% of the overall system losses. Based on these device characteristics, this embodiment limits the commonly used fine-tuning range of the thyristor control angle to 5° to 25°, and through automatic decomposition of graded and fine-tuning commands, ensures that the two types of actuators operate within their respective voltage regulation ranges.

[0036] The controller module can use the TMS320F28335 DSP chip. Figure 2 The controller shown has a main frequency of 150MHz. The DSP chip's ADC module has 16 channels and 12-bit resolution, the ePWM module has 6 groups, the GPIO interface is used to send gear shifting commands and receive gear feedback, and the SCI or SPI interface is used for human-machine interaction and communication. The controller module runs an improved active disturbance rejection control algorithm, which includes a smooth tracking differentiator, an extended state observer, and a nonlinear state error feedback control law.

[0037] The detection module includes a voltage detection branch, a current detection branch, and a pulse detection branch. For 10kV units, the voltage transformer can be JDZ-10 with a transformation ratio of 10000V / 100V and an accuracy class of 0.2; for 35kV units, the voltage transformer can be JDZ-35 with a transformation ratio of 35000V / 100V and an accuracy class of 0.2. The 0-100V AC signal on the secondary side of the voltage transformer is converted into a 0-3V signal by a voltage divider network with R1=97kΩ and R2=3kΩ, with a voltage division ratio of 3 / 100. The voltage signal after voltage division is sent to the ADCINA0 pin of the DSP through an LM358 voltage follower and an RC low-pass filter. The RC low-pass filter has R=1kΩ, C=0.1μF, and a cutoff frequency of 1.59kHz. The quantization step size corresponding to the 12-bit ADC is 0.732mV. After calculation based on the aforementioned voltage divider ratio and voltage transformer ratio, the primary voltage resolution is approximately 0.01kV.

[0038] In the current detection branch, the 8MVA unit can use an LZZBJ9-10 current transformer with a transformation ratio of 400A / 5A and an accuracy class of 0.5; the 15MVA unit can use an LZZBJ9-35 current transformer with a transformation ratio of 800A / 5A and an accuracy class of 0.5. The 0-5A signal from the secondary side of the current transformer is converted to voltage by a 0.6Ω precision resistor, forming a 0-3V voltage signal, which is then fed into the ADCINA1 pin of the DSP after passing through a voltage follower and an RC low-pass filter. The pulse detection branch uses a 6N137 high-speed optocoupler to acquire the thyristor trigger pulse. Figure 2 The delay of the 6N137 high-speed optocoupler shown is 75ns. The isolated trigger pulse is sent to the eCAP pin of the DSP. The controller calculates the thyristor control angle based on the timestamp of the captured pulse edge, and the control angle detection accuracy is no greater than 0.5°.

[0039] The on-load tap changer execution module includes an on-load tap changer, a drive circuit, and a stepper motor. For 10kV units with a capacity not exceeding 8MVA, the Huaguang Electric ZYD-10 vacuum-type on-load tap changer can be used, with 17 stages, each stage having a voltage regulation range of 2%, and a single-stage switching time not exceeding 80ms. For 35kV units with a capacity not less than 10MVA, the ABM0C200 oil-immersed on-load tap changer can be used, with 33 stages, each stage having a voltage regulation range of 1.25%, and a single-stage switching time not exceeding 60ms. The on-load tap changer is equipped with an RS485 feedback interface and a parallel BCD code feedback interface. The drive circuit uses an L298N driver chip and a 57HS22 stepper motor with a torque of 2.2N·m and a step angle of 1.8°, driving the on-load tap changer to complete the stage switching via a 1:50 reduction gear mechanism.

[0040] The thyristor triggering module can use the TC787 trigger chip. Fine-tuning commands generated by the controller are converted into 0-5V analog control signals by a TLV5616 digital-to-analog converter (12-bit resolution). The analog control signal is sent to the phase-shift control terminal of the TC787. The trigger pulse generated by the TC787 is isolated by a pulse transformer with a 1:1 turns ratio and an isolation voltage of not less than 5kV before being sent to the thyristor gate. For 8MVA units, the thyristor valve group can use KP-200A / 1600V; for 15MVA units, the thyristor valve group can use KP-500A / 2600V. During normal fine-tuning, the thyristor control angle is limited to 5° to 25°.

[0041] The human-machine interface module can use a 7-inch industrial touchscreen MCGSTPC7062Ti, connected to the controller module via an RS485 interface. The communication protocol is Modbus-RTU with a communication rate of 9600bps, used for setting preset target voltages, control parameters, and displaying operating status. The communication module includes one ESP8266 wireless module and one RS485 wired module. The power supply module uses an AC-DC switching power supply, converting 220VAC to 5VDC / 5A and 12VDC / 3A to power the controller module, detection module, on-load switching execution module, thyristor triggering module, human-machine interface module, and communication module.

[0042] Figure 2 This is a structural block diagram of the collaborative control device provided in an embodiment of the present invention. Figure 2 Centered on the TMS320F28335 DSP controller module, the module is labeled with a 150MHz main frequency, a 12-bit ADC, and a built-in improved ADRC algorithm. On the left side of the controller module are voltage transformers, current transformers, and a pulse detection module: the voltage transformers correspond to JDZ-10 or JDZ-35, with an accuracy class of 0.2, a transformation ratio of 10000V / 100V for 10kV units, and 35000V / 100V for 35kV units; the current transformers correspond to LZZBJ9-10 or LZZBJ9-35, with an accuracy class of 0.5, a transformation ratio of 400A / 5A for 8MVA units, and 800A / 5A for 15MVA units; the pulse detection module uses a 6N137 high-speed optocoupler, with a delay of 75ns as indicated in the diagram. All the above detection signals are sent to the controller module in the direction of the arrows.

[0043] Figure 2The right side of the controller module houses the on-load tap changer execution module, thyristor triggering module, and communication module. The on-load tap changer execution module includes an L298N driver chip, a 57HS22 stepper motor, and a ZYD-10 or ABM0C200 on-load tap changer, corresponding to 17 or 33 tap positions; the single-tap switching time for 10kV units is no more than 80ms, and for 35kV units, it is no more than 60ms. The thyristor triggering module receives fine-tuning commands from the controller module, generates phase-shift trigger signals via a TLV5616 digital-to-analog converter and a TC787 trigger chip, and then sends these signals to the thyristor gate via a pulse transformer. The communication module includes an ESP8266 wireless module and an RS485 wired module. Below the controller module is an MCGSTPC7062Ti human-machine interface module, which enables parameter setting and status display via bidirectional connection. The controller module also receives the actual tap position information of the on-load tap changer through a tap position feedback interface, thereby confirming the execution status of the graded commands.

[0044] To describe the voltage regulation control process, the transformer voltage regulation control object of the industrial rectifier unit can be represented as a first-order integral series system: In the formula, This represents the actual output voltage, corresponding to the actual voltage acquired in step 100. Indicates external disturbance; Indicates control input; This represents the control gain. The model is used to illustrate the relationship between external disturbances, control input, and actual voltage changes. The actual control operations are performed using the following smooth tracking differentiator, extended state observer, and nonlinear state error feedback control law.

[0045] In step 100, the controller acquires the actual transformer voltage at a detection period of no more than 10ms, and simultaneously acquires the actual thyristor control angle. The actual voltage is obtained by a voltage detection branch consisting of a voltage transformer, a voltage divider network, a voltage follower, and an RC low-pass filter; the actual thyristor control angle is calculated based on the timestamp of the trigger pulse edge captured by the pulse detection branch. The current detection branch synchronously acquires the unit current signal, which can be used for operational status monitoring. When the device is first put into operation, the thyristor control angle is set to a default intermediate value of 15°. After the improved active disturbance rejection control algorithm starts running, the controller adjusts the thyristor control angle according to fine-tuning instructions.

[0046] In step 200, a preset target voltage is used as the tracking input of the smooth tracking differentiator. The smooth tracking differentiator uses a hyperbolic tangent function to form a smooth acceleration characteristic. The acceleration function used by the smooth tracking differentiator can be expressed as: In its single-variable form, the acceleration function can be expressed as: In the formula, This represents the saturation amplitude, which can be taken as 0.25 in this embodiment; This represents the slope factor, which can be set to 5 in this embodiment; This represents the velocity factor, which can be set to 1.5 in this embodiment. (Function) It is an odd function that satisfies .when When it approaches 0, Approximately The slope of the small deviation region is ;when When it approaches infinity, tending to This results in bounded saturation characteristics. The hyperbolic tangent function is... A continuous function ensures that there are no piecewise function switching points during the acceleration process.

[0047] With preset target voltage As input The first state quantity of the smooth tracking differentiator Corresponding smooth target voltage Second state quantity Corresponding voltage change rate A continuous smooth tracking differentiator can be represented as: velocity factor Used to control the overall response bandwidth. The value of should be matched with the amplitude of the input signal. When the input signal amplitude is in the range of 10kV, a value of 100 to 500 can be used; when the input signal amplitude is in the range of 0 to 0.2V, a value of 100 to 500 can be used. The gain is proportionally reduced to 0.5–5 to decrease the possibility of system divergence caused by excessive gain. This embodiment uses a signal amplitude of 0–0.2V. Slope factor Controlling the response steepness in the small deviation region, As the value increases, the small signal tracking speed increases accordingly. In this embodiment, we take... When the deviation is small: Accordingly: The equivalent gain is The velocity factor and slope factor together determine the response speed in the small deviation region.

[0048] Discretization of the continuous smooth tracking differentiator is performed using the forward Euler method, with an integration step size of [missing information]. Discrete iterative relations preserve the state variables and sign directions of the continuous system equations and can be expressed as: Updated As a smoothing target voltage The updated As the rate of change of voltage It is used for calculating state errors by extended state observers and nonlinear state error feedback control laws.

[0049] To illustrate the stability of a continuous smooth tracking differentiator, assuming the target voltage remains constant during the stability analysis period, the Lyapunov function can be defined: The hyperbolic tangent function is an odd function, and... When satisfied: therefore, It is a positive definite function. Differentiating along the system trajectory yields: Depend on and The positive definite level set is bounded, and the convergence of the system trajectory can be determined by the LaSalle invariant set principle. The largest invariant set. (By...) achievable Substituting this into the continuous state equation, we can obtain... That is, smoothing the target voltage Converging to the preset target voltage .

[0050] Traditional FHAN tracking differentiators include a sign function and piecewise logic, which can introduce a phase delay of 1 to 2 sampling periods in DSP digital implementations. Furthermore, there is a strong coupling between filtering effectiveness and tracking speed, and parameter tuning relies heavily on trial and error. This embodiment uses a continuous and smooth hyperbolic tangent function to form the tracking differentiating process, reducing local abrupt changes caused by piecewise switching.

[0051] Figure 3 This is a comparison graph of the hyperbolic tangent acceleration function and the fhan function provided in an embodiment of the present invention. The horizontal axis represents a dimensionless variable. The graph shows a range of approximately -8 to 8; the vertical axis represents the function response. The solid line in the graph represents a smooth, continuous hyperbolic tangent response, while the dashed line represents the piecewise linear response corresponding to fhan. The hyperbolic tangent curve transitions continuously near zero and enters the upper and lower saturation regions as the absolute value of the input increases; the fhan curve exhibits piecewise linear changes within the illustrated range. Figure 3It is used to visually represent the differences between smooth functions and piecewise functions in terms of continuity, slope variation, and saturation characteristics near zero.

[0052] Figure 4 This is a comparison chart of the tracking performance of the smooth tracking differentiator and the FHAN tracking differentiator provided in this embodiment of the invention. The horizontal axis represents time, ranging from 0 to 3 seconds, and the vertical axis represents voltage, in kV. The chart includes the noisy target curve, the lc-TD smooth tracking curve, and the FHAN-TD tracking curve. The noisy target changes from approximately 0.1 kV to approximately 0.2 kV around 0.5 seconds, and then decreases again to approximately 0.15 kV around 1.8 seconds, with random fluctuations superimposed. The lc-TD curve shows a continuous and smooth change, while the FHAN-TD curve follows the target change faster, but retains more obvious local fluctuations near the noisy target. Figure 4 This is used to display the tracking differences between two types of tracking differentiators when both step changes and noise are present.

[0053] Figure 5 This is a magnified comparison diagram of the steady-state region provided in an embodiment of the present invention. The horizontal axis represents time, ranging from 1.0 to 1.6 seconds, and the vertical axis represents voltage, in kV. The diagram also includes a noisy target, an lc-TD smooth tracking curve, and a fhan-TD tracking curve. The noisy target fluctuates randomly around approximately 0.2 kV. The fhan-TD curve still exhibits local fluctuations corresponding to the noise in the steady-state region, while the lc-TD curve maintains a continuous and smooth change. Figure 4 and Figure 5 Together they are used to illustrate the continuity of the curve when the smooth tracking differentiator smoothly tracks changes in the target.

[0054] In step 300, the extended state observer uses the actual voltage acquired in step 100. As input. Let the actual voltage tracking value be... The estimated voltage change rate is The total disturbance estimate is The observation error is The extended state observer can then be expressed as: nonlinear functions Represented as: In the formula, , and These represent the first observation gain, the second observation gain, and the third observation gain of the extended state observer, respectively. and This represents the exponential parameter corresponding to the nonlinear function; This represents the threshold parameter. The observation gain can be expressed according to the characteristic polynomial. Theoretical configuration: For 10kV units, this embodiment can be adopted. , , For 35kV units, the following can be adopted: , , .

[0055] Threshold parameter The quantization error can be determined by combining the quantization error of the voltage detection link. The 12-bit ADC quantization step size of the TMS320F28335 is 0.732mV. After being back-calculated to the secondary side of the voltage transformer through a 3 / 100 voltage divider network, it is approximately 24.4mV. Then, based on a turns ratio of 100, it is back-calculated to the primary side, which is approximately 2.44V, or about 0.00244kV. Considering noise sources such as circuit thermal noise and common-mode interference, the noise in industrial environments can reach 2 to 5 times the quantization noise. In this embodiment, we take... It is approximately four times the quantization noise value.

[0056] In step 400, based on the actual voltage tracking value obtained in step 300... and voltage change rate estimate and the smoothed target voltage obtained in step 200 and voltage change rate Determine two state errors: The basic control quantity is calculated using a nonlinear state error feedback control law: Combined with the total disturbance estimate Determine the total control quantity: In the formula, and Indicates feedback gain; and This represents the exponential parameter corresponding to the nonlinear function; Indicates control gain. Total control quantity. The dimension is kV.

[0057] Control gain Theoretical estimation can be performed first based on the thyristor voltage regulation relationship. For a 10kV unit, it can be expressed as: In the formula, This is the voltage corresponding to the regulating side of the thyristor; in this embodiment, it is taken as approximately 0.6kV. The reference control angle is set at 15°. To fine-tune the proportional parameter between the command and control angle, a value of 20° / kV can be used. In practical applications, adjustments can also be made under steady-state conditions with the transformer unloaded and the thyristor control angle at 15°. Calibration is performed. Known small-step fine-tuning commands are applied via the human-computer interaction module. For example, 0.05kV, record the steady-state change of the output voltage. The control gain is determined according to the following formula: The calibration was repeated three times, and the average value was taken. The three calibration results for the 10kV prototype were 0.49, 0.51, and 0.50, respectively, with a maximum deviation of ±2%. In this embodiment, the average value was taken as... The difference between the theoretical value and the rated value can be caused by actual factors such as transformer leakage reactance and thyristor voltage drop. The rated value should be used for specific control.

[0058] Figure 6 This is a schematic diagram illustrating the structure and operational relationships of the improved active disturbance rejection control algorithm provided in an embodiment of the present invention. Figure 6 The signal transmission direction is sequentially configured with four parts: LCTD, ESO, NLSEF, and automatic command decomposition. The LCTD section uses a preset target voltage. As input, to smooth the target voltage and voltage change rate The results are shown, and the aforementioned discretization iterative relationships and the velocity and slope factors corresponding to the hyperbolic tangent acceleration function are indicated. The ESO section uses actual voltage. As input, the actual voltage tracking value Estimated voltage change rate Total disturbance estimate As a result, the observation error is indicated in the figure. Three state observation equations and nonlinear functions ; This represents the total disturbance estimate after incorporating the effects of grid fluctuations, load changes, etc. The NLSEF part uses voltage tracking error as the basis for estimation. Voltage change rate error Total disturbance estimate As input, the total control quantity is formed according to the basic control quantity and the disturbance compensation relationship. The dimension of the total control quantity is kV.

[0059] Figure 6 Total control quantity Further into the automatic instruction decomposition section. The automatic instruction decomposition section... and preset grading thresholds The comparison results and the on-load tap changer position status are used as judgment conditions; when the classification conditions are met, a classification command is generated and the fine-tuning command is set to zero; when the classification conditions are not met, the classification command is set to zero and a fine-tuning command is generated. (The diagram is composed of...) , To NLSEF, by , , To NLSEF, and then from the total control quantity The arrows pointing to the automatic decomposition of commands indicate the order of operations between the target state, observation state, disturbance estimation, and voltage regulation commands.

[0060] In step 500, the voltage regulation amplitude of each stage of the on-load tap changer is determined. Preset target voltage and grading threshold coefficient Determine the preset grading threshold : In the formula, The value range is 0.5 to 0.8, and 0.8 is preferred in this embodiment; The voltage regulation ratio corresponding to adjacent tap positions is used. Taking a 10kV on-load tap changer with 17 levels and a voltage regulation range of 2% per level as an example, ,when hour, .

[0061] The controller compares the absolute value of the total control quantity with a preset grading threshold. In the gear coding used in this embodiment, the grading instruction... This indicates a gear shift. This indicates downshifting; since the aforementioned error definition uses the actual state minus the target state, the total control quantity is negative when the actual voltage is lower than the target voltage. Therefore, the direction code of the gear position command has the opposite sign to the total control quantity. Furthermore, when the on-load tap changer has not reached the upper limit of its tap position and has not reached the lower limit of its tap position, the grading instruction and fine-tuning instruction are satisfied as follows: When the absolute value of the total control quantity is not greater than the preset grading threshold, or when the on-load tap changer has reached the upper or lower limit of the tap position, the grading instruction and fine-tuning instruction satisfy the following: Therefore, larger voltage regulation demands are addressed through on-load tap changer tiered adjustment, while smaller demands that do not meet the tiered adjustment criteria are addressed through thyristor-based fine-tuning. When the tap position is at the upper or lower limit, the controller will no longer generate tiered actions that exceed the available tap range.

[0062] In step 600, when the hierarchical instruction... When the value is not zero, the on-load tap changer execution module drives the on-load tap changer to switch positions according to the graded instructions, and sends the fine-tuning instructions. Locked to zero. After gear shifting, the controller continuously reads the gear position feedback from the on-load tap changer; three consecutive consistent readings confirm the gear shift is complete, with each reading interval being 10ms. After confirming the gear shift is complete, a 50ms delay is added to release the lock on fine-tuning commands. When the gear reaches its upper or lower limit, the controller ignores gear shifting commands that continue beyond the corresponding boundary.

[0063] When the grading command is zero and the fine-tuning command is not zero, the controller determines the thyristor control angle based on the fine-tuning command. For a three-phase fully controlled thyristor bridge, the DC side voltage can be expressed as: In this embodiment, within the operating range, the fine-tuning command and the thyristor control angle are linearly mapped: Mapping coefficients The dimension is ° / kV. The theoretical value of the mapping coefficient can be obtained according to the following formula: For 10kV units, the calculation is obtained according to the above relationship. In practice, a voltage of 20° / kV can be used for control; for 35kV units, theoretical calculations yield... The actual control angle is taken as 15° / kV. The normal adjustment range of the thyristor control angle is 5° to 25°. When the control angle reaches the 5° or 25° boundary and At that time, the controller follows Generate hierarchical instructions; as agreed in this embodiment To upgrade, To downshift, the total control quantity is negative, which corresponds to upshifting, and the total control quantity is positive, which corresponds to downshifting. After the on-load tap changer is switched to the adjacent position, the thyristor control angle is restored to 15° before entering the subsequent closed-loop regulation.

[0064] In step 700, the controller re-acquires the actual voltage after voltage regulation, uses this regulated voltage as the input to the extended state observer for the next control cycle, and continues to execute target voltage smoothing, actual state observation, total control quantity calculation, instruction decomposition, and voltage regulation execution. The control process can continue until: During closed-loop operation, the priority of abnormal operating conditions and interlocking strategies are set according to the current operating status, triggering conditions and controller response. The specific relationship is shown in Table 1.

[0065] Table 1. Priority of Abnormal Operating Conditions and Interlocking Strategies Table 1 lists the operation protection relationships according to four items: current status, triggering conditions, controller response, and priority. During normal operation, if the total control quantity does not reach the classification condition, fine-tuning of the thyristor is performed; if the classification condition is reached, the on-load tap changer classification is initiated and fine-tuning is locked. When the control angle reaches the boundary, the tap position feedback jitter occurs, continuous switching still exceeds the tolerance, or the detection signal is abnormal, classification, locking, alarm, or shutdown processing is performed according to the corresponding priority in the table.

[0066] Abnormal detection signals can be determined according to the following conditions: when the actual voltage... And after three consecutive sampling cycles, the voltage transformer signal is determined to be abnormal; when the detected thyristor control angle is... or When this occurs, the pulse detection is deemed abnormal.

[0067] Figure 7 The overall control flowchart of the collaborative control method provided in the embodiment of the present invention is shown. Figure 7 The top layer first initializes parameters, including LCTD and ADRC parameters. Then, real-time monitoring is initiated, acquiring voltage, current, and thyristor control angles. After the real-time monitoring results enter the cyclic control region, the LCTD first smooths the preset target voltage, forming a smoothed target voltage and voltage change rate. Then, the ESO observes the disturbance, and the NLSEF calculates the total control quantity. The total control quantity enters the automatic instruction decomposition stage, determining whether to trigger a tiered control based on the tiered conditions.

[0068] Figure 7 When the "whether to trigger tiered adjustment" condition is "yes", the system enters the on-load tap changer tiered voltage regulation branch and receives the on-load tap changer tap position feedback signal; when the condition is "no", the system enters the thyristor inter-stage fine-tuning branch and generates the thyristor control angle signal. After execution, both branches merge into the closed-loop feedback loop. The closed-loop feedback is judged based on the deviation between the actual voltage and the preset target voltage; if the deviation does not reach the termination condition, it continues to the next detection and control cycle. Figure 7 The system is configured at the bottom for fault detection and judgment. If no fault is detected, it returns to the loop control area; if a fault is detected, it enters the fault handling branch of "trigger alarm and lock command". After fault handling, the connection to return to the detection link is maintained so that the operating status can be reassessed after the fault condition is cleared or the safety process is completed. Figure 7 This represents the complete timing relationship between parameter initialization, real-time detection, target state smoothing, disturbance observation, total control quantity calculation, instruction decomposition, graded voltage regulation or inter-stage fine-tuning, closed-loop feedback, and fault protection.

[0069] The following describes the specific implementation of this invention using the test process of a 10kV / 8MVA industrial electroplating rectifier unit. The controller uses a TMS320F28335, the voltage transformer uses a JDZ-10, the current transformer uses an LZZBJ9-10, and the on-load tap changer uses a Huaguang Electric ZYD-10, with 17 levels, each level representing 2%. The drive section uses L298N and 57HS22 stepper motors. The thyristor valve group uses six KP-200A / 1600V thyristors. The pulse transformer has a 1:1 turns ratio and an isolation voltage of not less than 5kV. The human-machine interface module uses an MCGSTPC7062Ti touchscreen.

[0070] In this embodiment, a preset target voltage is used. Number of on-load tap changers Voltage regulation amplitude at each level Preset grading threshold The thyristor control angle range is 5° to 25°, and the mapping coefficient is... Smooth tracking differentiator , ; Extended state observer takes , , ;Nonlinear state error feedback control law is taken , , ; Nonlinear function parameter selection , , , , When the device is first put into operation, the thyristor control angle is set to 15°.

[0071] Initially, the on-load tap changer is in position 8, and the actual voltage is... thyristor control angle The improved active disturbance rejection control algorithm calculates the total control quantity. ,at this time It meets the classification criteria. According to... Set the hierarchical instruction to +1, and fine-tune the instruction. The on-load tap changer switches from position 8 to position 9, with a single switching time of 80ms. Further calculations yield... If the grading conditions are still met, the controller continues to generate grading instructions in the corresponding direction, and the on-load tap changer switches from 9 to 10 positions.

[0072] After completing two gear shifts, the calculation is obtained. ,at this time The hierarchical instruction sets the value to zero, and the fine-tuning instruction... .according to Calculations show that adjusting the thyristor control angle from 15° to 12.6° results in an actual voltage increase to 9.83kV, with a single fine-tuning time of 20ms. During the second fine-tuning, the fine-tuning command... The thyristor control angle was further reduced by 0.6° from 12.6° to 12.0° after the first fine-tuning, and the actual voltage rose to 9.95kV. The second fine-tuning took 20ms. After completing the above two fine-tunings, the actual voltage reached 9.95kV, and the deviation from the preset target voltage of 10kV was 0.05kV, which met the judgment condition that the deviation should not exceed 0.1kV. Therefore, it was recorded as stable operation. If the control process adopts the aforementioned... As a closed-loop termination condition, the corresponding termination deviation for the 10kV unit is 0.01kV. After reaching the 9.95kV state, the controller continues to execute step 700 and subsequent control cycles until the termination condition is met. Two fine-tuning adjustments total 40ms, and two on-load tap changer switching adjustments total 160ms, for a total adjustment time of 200ms.

[0073] During disturbance rejection testing on the 10kV / 8MVA unit, the grid voltage momentarily dropped to 9.5kV, a drop of -4.2%, lasting for 100ms. The preset target voltage remained constant, and the smooth tracking differentiator maintained a smooth target voltage and voltage change rate; the extended state observer obtained the total disturbance estimate. The total control quantity did not trigger the on-load tap changer to operate in stages. The controller performed fine-tuning compensation of the thyristor, adjusting the thyristor control angle to 13.4°. During the test, the on-load tap changer did not operate.

[0074] The 10kV / 8MVA prototype completed three rounds of preliminary verification, each lasting 500 hours, for a total of 1500 hours. Long-term statistical results are as follows: voltage control accuracy is ±0.08kV, on-load tap changer operation count is 42 times / 500h, number of maloperations is 0, dynamic response time is no more than 50ms, and thyristor loss accounts for 3.2%. The long-term industrial field verification target is 5000 hours.

[0075] Furthermore, the aforementioned coordinated control method was applied to a 35kV / 15MVA electrolytic copper rectifier unit. The on-load tap changer was an ABM0C200, with 33 stages, each stage at 1.25%, and a single-stage switching time not exceeding 60ms; the thyristor valve group was a KP-500A / 2600V. The preset target voltage... Preset grading threshold Mapping coefficients Smooth tracking differentiator , ; Extended state observer takes , , ;Nonlinear state error feedback control law is taken , , The measured results are: voltage control accuracy ±0.05kV, on-load tap changer operation 38 times / 500h, 0 false trips, dynamic response time no more than 40ms, and thyristor loss ratio of 4.1%.

[0076] To illustrate the control performance, two PID delay schemes and a traditional fhan-ADRC scheme, operating alternately within the same 10kV / 8MVA unit and cycle, were used as comparison benchmarks. The prototype has completed three rounds of preliminary verification, each lasting 500 hours, for a total of 1500 hours. The long-term industrial field verification target is 5000 hours. The control performance comparison results are shown in Table 2.

[0077] Table 2 Comparison of Control Performance of 10kV / 8MVA Test Prototypes Table 2 lists the voltage control accuracy, number of on-load switch malfunctions, dynamic response time, thyristor loss ratio, and DSP single-step calculation time. Compared to the two PID delay schemes, the voltage control accuracy is improved by approximately 73%, and the dynamic response time is shortened by approximately 58%; compared to the traditional fhan-ADRC scheme, the DSP single-step calculation time is reduced by approximately 66%.

[0078] Compared with the 20s to 100s voltage regulation process described in CN102851703A, the dynamic response speed of this embodiment is no more than 60ms; in the early verification, the number of on-load tap changer operations was reduced by more than 40%.

[0079] In the embodiment of the device, the coordinated control device for transformer graded voltage regulation and inter-grade fine adjustment consists of a controller module, a detection module, an on-load tap changer execution module, and a thyristor triggering module. Each module is configured according to the aforementioned connection relationship. The detection module collects the actual transformer voltage and transmits it to the controller module; the on-load tap changer execution module is configured with a tap position feedback interface, and the tap position feedback is returned to the controller module; the thyristor triggering module is connected to the controller module and connected to the thyristor gate via a pulse transformer. The controller module performs smooth tracking differentiation, extended state observation, nonlinear state error feedback, total control quantity decomposition, and thyristor control angle mapping; the on-load tap changer execution module completes tap position switching according to the graded instructions; the thyristor triggering module generates trigger pulses based on the thyristor control angle and applies them to the thyristor gate. The hardware configuration, detection link parameters, control parameters, interlocking conditions, and operating data of the aforementioned 10kV / 8MVA and 35kV / 15MVA units can all serve as specific implementation forms of this coordinated control device.

[0080] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0081] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A coordinated control method for staged voltage regulation and inter-stage fine-tuning of a transformer, characterized in that, include: Collect the actual voltage of the transformer; A smooth tracking differentiator based on the hyperbolic tangent function is used to smoothly track the preset target voltage, thereby obtaining the smooth target voltage and the rate of voltage change. An extended state observer is used to observe the actual voltage to obtain the actual voltage tracking value, the voltage change rate estimate, and the total disturbance estimate; Based on the error between the actual voltage tracking value and the smoothed target voltage, the error between the estimated voltage change rate and the estimated voltage change rate, and the estimated total disturbance, a nonlinear state error feedback control law is used to determine the total control quantity. When the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper limit of the gear position nor the lower limit of the gear position, a grading instruction is determined based on the total control quantity; when the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer has reached the upper limit of the gear position or the lower limit of the gear position, the total control quantity is determined as a fine-tuning instruction. The on-load tap changer is switched according to the graded instruction, or the fine-tuning instruction is converted into a thyristor control angle according to the mapping relationship, and the thyristor is adjusted according to the thyristor control angle. The actual voltage after voltage regulation is acquired, and the actual voltage after voltage regulation is used as the input of the expansion state observer in the next control cycle.

2. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, A smooth tracking differentiator based on the hyperbolic tangent function is used to smoothly track a preset target voltage, obtaining the smoothed target voltage and voltage change rate, including: The rate of change of voltage is determined as the rate of change of the smoothed target voltage; The product of the slope factor and the deviation between the smoothed target voltage and the preset target voltage, divided by the velocity factor, is used as the independent variable of the first hyperbolic tangent function; the product of the slope factor and the rate of change of voltage, divided by the velocity factor, is used as the independent variable of the second hyperbolic tangent function. The rate of change of the voltage change is determined by the negative value of the sum of the product of the square of the velocity factor and the function value of the first hyperbolic tangent function and the function value of the second hyperbolic tangent function. The smoothed target voltage and the voltage change rate are iteratively updated based on the rate of change of the smoothed target voltage and the rate of change of the voltage change rate.

3. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, An extended state observer is used to observe the actual voltage, obtaining the actual voltage tracking value, the voltage change rate estimate, and the total disturbance estimate, including: The observation error is determined based on the difference between the actual voltage tracking value and the actual voltage. The rate of change of the actual voltage tracking value is determined based on the difference between the estimated voltage change rate and the product of the first observation gain and the observation error. The observation error is processed using a nonlinear function fal with a first exponential parameter and a threshold parameter. The rate of change of the voltage change rate estimate is determined based on the difference between the total disturbance estimate and the product of the second observation gain and the processed observation error. The observation error is processed using a nonlinear function fal with a second exponential parameter and the threshold parameter. The rate of change of the total disturbance estimate is determined based on the negative value of the product of the third observation gain and the processed observation error.

4. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, Based on the error between the actual voltage tracking value and the smoothed target voltage, the error between the estimated voltage change rate and the estimated voltage change rate, and the estimated total disturbance, a nonlinear state error feedback control law is used to determine the total control quantity, including: The difference between the actual voltage tracking value and the smoothed target voltage is defined as the voltage tracking error, and the difference between the estimated voltage change rate and the voltage change rate is defined as the voltage change rate error. The voltage tracking error is processed by a nonlinear function fal with a third exponential parameter and a threshold parameter, and the voltage change rate error is processed by a nonlinear function fal with a fourth exponential parameter and the threshold parameter. The basic control quantity is determined based on the two processing results and the corresponding feedback gain. The total control quantity is obtained by subtracting the ratio of the total disturbance estimate to the control gain coefficient from the basic control quantity.

5. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, The preset grading threshold is the product of the grading threshold coefficient, the voltage regulation amplitude of each stage of the on-load tap changer, and the preset target voltage. The voltage regulation amplitude of each stage is the voltage regulation ratio between adjacent taps of the on-load tap changer. The grading threshold coefficient is 0.5 to 0.

8.

6. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, When the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper limit of the gear position nor the lower limit, a grading instruction is determined based on the total control quantity; when the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer has reached the upper limit of the gear position or the lower limit of the gear position, the total control quantity is determined as a fine-tuning instruction, including: When the absolute value of the total control quantity is greater than the preset grading threshold and the on-load tap changer has not reached the upper limit of the gear position and has not reached the lower limit of the gear position, the grading instruction is determined according to the positive or negative sign of the total control quantity, and the fine-tuning instruction is set to zero. When the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer reaches the upper or lower limit of the gear position, the grading instruction is set to zero, and the total control quantity is used as the fine-tuning instruction.

7. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, The fine-tuning command is converted into a thyristor control angle according to the mapping relationship, and the thyristor is adjusted according to the thyristor control angle, including: Set the mapping relationship to a linear mapping relationship; Using 15° as the reference value for the thyristor control angle, the product of the fine-tuning command and the mapping coefficient is superimposed onto the reference value to obtain the thyristor control angle; The thyristor is adjusted according to the thyristor control angle.

8. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, During the process of converting the fine-tuning command into a thyristor control angle according to the mapping relationship, and adjusting the thyristor according to the thyristor control angle, when the thyristor control angle reaches 5° or 25° and the absolute value of the total control quantity is greater than zero, the graded command is determined according to the positive or negative sign of the total control quantity, the on-load tap changer is switched according to the graded command, and the thyristor control angle is restored to 15° after the switch is completed.

9. The coordinated control method for transformer graded voltage regulation and inter-stage fine adjustment according to claim 1, characterized in that, Switching the on-load tap changer according to the graded instructions includes: After determining the grading instruction, the fine-tuning instruction is locked to zero, and the on-load tap changer is driven to switch gears according to the grading instruction. After gear switching, the gear feedback of the on-load tap changer is continuously read. When the gear feedback read three times in a row is consistent, it is confirmed that the on-load tap changer has completed gear switching. After confirming that the on-load tap changer has completed the gear switching, the lock on the fine-tuning command is released after a preset delay time.

10. A coordinated control device for graded voltage regulation and fine-tuning between stages of a transformer, characterized in that, It includes a controller module, a detection module, an on-load switch execution module, and a thyristor triggering module; The detection module is connected to the controller module and is used to collect the actual voltage of the transformer and transmit the actual voltage to the controller module. The on-load tap changer execution module includes an on-load tap changer and a drive circuit. The drive circuit is connected to the controller module, and the tap position feedback interface of the on-load tap changer is connected to the controller module. The thyristor triggering module is connected to the controller module and is connected to the thyristor gate via a pulse transformer; The controller module is used to smoothly track a preset target voltage using a smooth tracking differentiator based on the hyperbolic tangent function to construct an acceleration function, thereby obtaining the smooth target voltage and the rate of voltage change. An extended state observer is used to observe the actual voltage to obtain the actual voltage tracking value, the voltage change rate estimate, and the total disturbance estimate; Based on the error between the actual voltage tracking value and the smoothed target voltage, the error between the estimated voltage change rate and the estimated voltage change rate, and the estimated total disturbance, a nonlinear state error feedback control law is used to determine the total control quantity. When the absolute value of the total control quantity is greater than a preset grading threshold and the on-load tap changer has not reached the upper limit of its gear position nor the lower limit, a grading instruction is determined based on the total control quantity. When the absolute value of the total control quantity is not greater than the preset grading threshold or the on-load tap changer has reached the upper limit or the lower limit of its gear position, the total control quantity is determined as a fine-tuning instruction, and the fine-tuning instruction is converted into a thyristor control angle according to a mapping relationship. The on-load switch execution module is used to drive the on-load tap changer to switch gears according to the graded instruction. The thyristor triggering module is used to generate a trigger pulse according to the thyristor control angle, and transmit the trigger pulse to the thyristor gate through the pulse transformer.

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