Voltage coordination control method for resistance heating load and related device

Abstract

The invention belongs to the technical field of high-power resistor heating application, and discloses a voltage coordination control method for a resistor heating load and a related device, the actual power of a load end is collected, the power deviation is compared with a first set threshold value, if the deviation is large, the trigger angle of a thyristor is adjusted to quickly adjust the output power, and the output power is adjusted; enabling the actual power to approach a set value; otherwise, keeping the trigger angle; and calculating and accumulating the power regulation quantity of the thyristor at the same time, and when the accumulation quantity exceeds a second set threshold value, triggering gear switching of the on-load tap changing transformer and resetting the accumulation quantity, otherwise, keeping the gear. By adopting the method, the mechanical wear of the on-load voltage regulating transformer is obviously reduced, the service life of equipment is prolonged, and the maintenance cost is reduced; meanwhile, the adjusting depth of the thyristors is limited, harmonic pollution and self loss of a power grid are reduced, and the system efficiency and the electric energy quality are improved; intelligent coordination is integrally realized, and the reliability and the dynamic response capability of the system are enhanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-power resistance heating application, and particularly relates to a voltage coordination control method for resistance heating load and related devices. BACKGROUND

[0002] In many fields of industrial production, high-power resistance heating technology is widely used due to its stable heating and strong controllability, such as metal heat treatment, chemical reaction kettle heating, power system simulation load, etc. The core requirement of such applications is to achieve precise control of the target temperature through accurate adjustment of the supply voltage or heating power, in order to ensure the stability of the production process and improve energy utilization efficiency. With the continuous improvement of industrial automation level, the market puts forward increasingly stringent requirements on the adjustment speed, control accuracy and operation reliability of high-power resistance heating systems, which promotes the continuous development and innovation of related voltage regulation control technologies.

[0003] Currently, the voltage regulation control technology in high-power resistance heating applications mainly falls into two categories, both of which have significant defects. One is the on-load voltage regulation transformer, which has the advantage of wide voltage regulation range, capable of adapting to voltage requirements under different working conditions, but has the problem of slow response, with a regulation period usually in seconds to minutes, which cannot meet the demand of fast dynamic regulation. At the same time, it relies on mechanical structure to realize voltage regulation, with limited mechanical life, frequent operation will greatly increase equipment wear and tear, resulting in high maintenance costs, and it is difficult to achieve continuous precise regulation. The other is the thyristor phase-controlled voltage regulation technology, which can achieve fast and continuous precise regulation, with response speed matching the demand of dynamic control, however, in the case of wide-range voltage regulation, it will cause power factor reduction and serious harmonic pollution on the power grid, and will also produce a large self-loss in deep voltage regulation, affecting the system operation efficiency. If the above two technologies are simply combined and applied, due to the lack of effective intelligent coordination mechanism, equipment operation conflicts are likely to occur, for example, after the on-load voltage regulation transformer has just completed the step-up operation, the thyristor immediately closes the trigger angle due to detection of excessively high voltage, resulting in mutual cancellation of the regulation effects of the two, forming a "chasing" phenomenon, which not only cannot guarantee the control effect, but also accelerates equipment wear and tear, further reducing system reliability. In addition, some existing applications use self-coupled voltage regulation devices, which can achieve a power change of 7.5kW per step and a wide voltage regulation range, but also have the problems of slow operation, mechanical structure wear, high maintenance cost and inability to achieve continuous precise regulation.

[0004] As can be seen, the existing high-power resistance heating voltage regulation control technology either has defects in regulation performance or has coordination conflicts in combined application, lacking an effective control scheme that can intelligently coordinate the operation of different voltage regulation devices, fully utilize the advantages of each device and avoid its disadvantages. SUMMARY

[0005] This invention provides a voltage coordination control method and related device for resistance heating loads. This method can effectively solve the problems of existing high-power resistance heating voltage regulation control technology, which may have performance defects or coordination conflicts in combined applications.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A voltage coordination control method for a resistance heating load includes: Collect the actual power at the load end; The power deviation calculated based on the actual power at the load end and the set power is compared with a first set threshold. If the absolute value of the power deviation is greater than the first set threshold, the firing angle of the thyristor is adjusted so that the adjusted actual power approaches the set power by changing the output power; otherwise, the current firing angle of the thyristor is maintained. Calculate and accumulate the power regulation of the thyristor to obtain the cumulative power regulation; The cumulative power adjustment is compared with the second set threshold: if the absolute value of the cumulative power adjustment is greater than the second set threshold, a tap position switching command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to switch tap positions and reset the cumulative power adjustment; otherwise, the current tap position of the on-load tap-changing transformer is maintained.

[0007] Furthermore, before acquiring the actual power at the load end, it also includes: Real-time acquisition of voltage and current at the load end; The actual power at the load end is calculated based on the voltage and current at the load end.

[0008] Furthermore, before comparing the power deviation calculated based on the actual power at the load end and the set power with the first set threshold, the method further includes: The power deviation is obtained by subtracting the actual power at the load end from the set power, and the specific formula is as follows: ΔP = Pref – P In the formula, ΔP represents the power deviation; Pref represents the set power; and P represents the actual power at the load end.

[0009] Further, the calculation and accumulation of the thyristor's power regulation to obtain the cumulative power regulation includes: Starting from the initial moment or the moment of resetting the cumulative power regulation, the power changes caused by each thyristor regulation are summed to obtain the cumulative power regulation.

[0010] Further, if the absolute value of the cumulative power regulation is greater than the second preset threshold, a tap-changing command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to perform tap-changing and reset the cumulative power regulation, including: If the absolute value of the cumulative power adjustment is greater than the second set threshold, a gear shifting command is generated; wherein, the gear shifting command is an upshift command or a downshift command; Output a tap change command to the on-load tap changer to trigger the on-load tap changer to perform tap change; Reset the cumulative power adjustment to zero.

[0011] Furthermore, the step of issuing a tap-switching command to the on-load tap-changing transformer to trigger it to switch taps and reset the cumulative power regulation if the absolute value of the cumulative power regulation is greater than the second preset threshold, further includes: After the on-load tap-changing transformer completes the tap change, it sends a firing angle adjustment command to the thyristor to adjust the firing angle toward the optimal operating point, so that the thyristor tends to be in a fully conducting state.

[0012] Furthermore, the first set threshold is determined based on the thyristor adjustment dead zone; the second set threshold is adopted from the tap changer action threshold of the on-load tap changer transformer.

[0013] A voltage coordination control system for a resistance heating load includes: The data acquisition module is used to collect the actual power at the load end; The first judgment module is used to compare the power deviation calculated based on the actual power at the load end and the set power with a first set threshold: if the absolute value of the power deviation is greater than the first set threshold, the firing angle of the thyristor is adjusted so that the adjusted actual power approaches the set power by changing the output power; otherwise, the current firing angle of the thyristor is maintained. The data accumulation module is used to calculate and accumulate the power regulation of the thyristor to obtain the cumulative power regulation. The second judgment module is used to compare the cumulative power adjustment amount with the second set threshold: if the absolute value of the cumulative power adjustment amount is greater than the second set threshold, a tap position switching command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to switch tap positions and reset the cumulative power adjustment amount; otherwise, the current tap position of the on-load tap-changing transformer is maintained.

[0014] A voltage coordination control device for a resistance heating load, comprising: Memory, used to store computer programs; A processor is configured to implement the steps of the voltage coordination control method for resistive heating loads described above when executing the computer program.

[0015] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the voltage coordination control method for a resistive heating load described above.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a voltage coordination control method for resistance heating loads. It collects the actual power at the load end and compares the power deviation with a first set threshold. If the deviation is large, the thyristor firing angle is adjusted to quickly adjust the output power, bringing the actual power closer to the set value; otherwise, the firing angle is maintained. Simultaneously, the power adjustment amount of the thyristor is calculated and accumulated. When the accumulated amount exceeds a second set threshold, the on-load tap-changing transformer is triggered to switch gears and the accumulated amount is reset; otherwise, the gear is maintained. This method prioritizes the rapid response and continuous adjustment capability of the thyristor to handle small-range dynamic changes through a hierarchical control strategy, avoiding frequent operation of the on-load tap-changing transformer. The transformer is only triggered when the thyristor adjustment accumulates to a large deviation, ensuring coordinated and orderly operation and eliminating conflicting and "chasing" phenomena. This method significantly reduces mechanical wear on the on-load tap-changing transformer, extends equipment life, and reduces maintenance costs. It also limits the adjustment depth of the thyristor, reducing grid harmonic pollution and its own losses, improving system efficiency and power quality. Overall, it achieves intelligent coordination, enhancing system reliability and dynamic response capabilities.

[0017] Preferably, in this invention, by acquiring the voltage and current at the load end in real time and calculating the actual power, an accurate and real-time feedback signal is provided for the entire control method. This ensures the accuracy and reliability of power deviation detection and subsequent adjustment actions, which is the foundation for the effective implementation of the entire coordinated control strategy and guarantees the system's ability to accurately track the load power demand.

[0018] Preferably, in this invention, the power deviation is calculated using a simple formula that differs between the set power and the actual power, clearly defining the core input variable of the control logic. This definition ensures the clarity and consistency of control decisions, providing a stable and reliable basis for subsequent graded adjustment decisions based on the magnitude of the deviation, and helping to maintain the stability of system control.

[0019] Preferably, in this invention, the cumulative power adjustment amount is defined as the power change caused by each thyristor adjustment accumulated from the initial or reset time, ensuring the timeliness of the cumulative amount. This method enables the cumulative amount to truly reflect the total adjustment contribution made by the thyristor to maintain power stability since the last operation of the on-load tap-changing transformer, providing an objective and dynamic basis for accurately determining when the on-load tap-changing transformer needs to be started.

[0020] Preferably, in this invention, when the accumulated amount exceeds the limit, a clear up-shift or down-shift command is generated and output to trigger the on-load tap-changing transformer to switch, and then the accumulated amount is immediately cleared to zero. This ensures the pertinence and executability of the shift command, making the direction of the on-load tap-changing transformer's operation clear; at the same time, timely clearing of the accumulated amount lays the foundation for accurate accumulation in the next adjustment cycle, ensuring seamless connection of system states and continuity of control.

[0021] Preferably, in this invention, after the on-load tap-changing transformer completes the tap change, the thyristor firing angle is actively adjusted to approach the optimal operating point (e.g., full conduction), minimizing the thyristor conduction angle. This not only significantly reduces the thyristor's own conduction losses and improves system efficiency, but more importantly, it greatly reduces current waveform distortion, effectively suppresses harmonic pollution caused by thyristor phase-controlled voltage regulation, and optimizes the power quality on the grid side. Attached Figure Description

[0022] Figure 1 A flowchart of a voltage coordination control method for a resistance heating load provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a voltage coordination control system for a resistance heating load provided in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the working principle of a voltage coordination control method for a resistance heating load provided in an embodiment of the present invention. Detailed Implementation

[0023] To further understand the content of this invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments are merely illustrative and not limiting of the invention.

[0024] The technical terms involved in this invention are explained below: OLTC: short for On-Load Tap Changer, refers to a device that can switch the tap voltage while the transformer is under load.

[0025] As mentioned in the background section, existing high-power resistance heating control methods typically employ two adjustment methods: on-load tap-changing transformers and thyristor phase-controlled voltage regulation. However, simply combining these two methods, due to a lack of intelligent coordination, can easily lead to conflicts between equipment actions. For example, as soon as the OLTC completes its voltage boost, the thyristor immediately closes its firing angle due to excessive voltage, causing them to cancel each other out and creating a "chasing" phenomenon. This not only results in poor control performance but also accelerates equipment wear. Furthermore, while traditional solutions combining these two methods offer a wide voltage regulation range, their actions are slow (on the order of seconds to minutes), making rapid and precise continuous adjustment impossible. The mechanical structure of the on-load tap-changing switch has a limited lifespan, and frequent operation leads to high maintenance costs.

[0026] To achieve the above objectives, this embodiment provides a voltage coordination control method for resistance heating loads. This method analyzes the control requirements of high-power resistance heating and proposes a control method and system that can intelligently coordinate the actions of both, give full play to their respective advantages, and avoid their disadvantages.

[0027] like Figure 1 As shown, this embodiment provides a voltage coordination control method for a resistance heating load, including: Collect the actual power at the load end; The power deviation calculated based on the actual power at the load end and the set power is compared with a first set threshold. If the absolute value of the power deviation is greater than the first set threshold, the firing angle of the thyristor is adjusted so that the adjusted actual power approaches the set power by changing the output power; otherwise, the current firing angle of the thyristor is maintained. Calculate and accumulate the power regulation of the thyristor to obtain the cumulative power regulation; The cumulative power adjustment is compared with the second set threshold: if the absolute value of the cumulative power adjustment is greater than the second set threshold, a tap position switching command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to switch tap positions and reset the cumulative power adjustment; otherwise, the current tap position of the on-load tap-changing transformer is maintained.

[0028] The voltage coordination control method provided in this embodiment will be further explained below: like Figure 3 As shown, this embodiment provides a voltage coordination control method for resistance heating loads, applied to the entire control system. The entire system includes a three-phase power grid, an on-load tap-changing transformer, a power line, a thyristor phase-controlled voltage regulating circuit (composed of anti-parallel thyristor pairs), and finally connected to the oil well downhole heating load. The coordination controller monitors the bus and load status through voltage and current sensors, and sends control commands to the tap changer drive motor and thyristor trigger board of the OLTC, respectively. The specific implementation process is as follows: This embodiment provides a voltage coordination control method and system for resistance heating loads, mainly applied to the scenario of oil well crude oil transportation heating. In this scenario, it is necessary to use a high-power resistance heating load to accurately control the temperature of crude oil in the pipeline, ensuring the fluidity of crude oil during transportation and preventing crude oil from solidifying and clogging the pipeline due to excessively low temperature. At the same time, it is necessary to solve the problems of slow operation, low power factor, serious harmonic pollution, and rapid equipment wear caused by using on-load tap changer or thyristor phase control voltage regulation alone in the existing technology, and achieve the control goals of fast response, accurate temperature control, low loss, and long life.

[0029] The voltage coordination control system in this embodiment consists of a three-phase power grid, an on-load tap-changing transformer (OLTC), power lines, a thyristor phase-controlled voltage regulation circuit, a coordination controller, a measurement system, and an oil well heating load connected in sequence. The measurement system includes voltage and current sensors, installed at the busbar of the load end, for real-time acquisition of voltage and current signals at the load end. The thyristor phase-controlled voltage regulation circuit is composed of anti-parallel thyristor pairs. Its input is connected to the output of the OLTC via a power line, and its output is directly connected to the oil well heating load. The anti-parallel thyristor pairs are adaptable to AC power supply scenarios, enabling bidirectional current conduction control, thereby regulating the voltage and power output to the load. The coordination controller uses industrial-grade... The advanced PLC controller, with its built-in dedicated control algorithm, establishes communication connections via signal cables with voltage sensors, current sensors, the tap changer drive motor of the on-load tap changer transformer, and the thyristor trigger board. It receives voltage and current signals from the measurement system and sends tap change commands to the tap changer drive motor and trigger angle adjustment commands to the thyristor trigger board, serving as the core of the entire system's control. The on-load tap changer transformer is an 11-tap autotransformer, with each tap change corresponding to a 7.5kW output power change. Its input is connected to a three-phase 380V industrial power grid. Tap changers enable coarse adjustment of the output voltage, providing a stable base voltage range for subsequent thyristor phase-controlled voltage regulation.

[0030] In actual operation, this voltage coordination control method is implemented step by step according to the following process: First, after the system starts, the coordination controller completes the initialization settings, including setting the target heating power Pref of the load, the first set threshold ε1 (thyristor adjustment dead zone), and the second set threshold ε2 (OLTC on-load tap changer action threshold). The determination of the set power Pref needs to be combined with the process requirements of crude oil transportation, ambient temperature, crude oil flow rate, and rated power of the load for comprehensive calculation. In this embodiment, based on the crude oil transportation conditions of a certain oilfield, Pref is set to 50kW. This value can be manually modified through the system's human-machine interface, or it can be automatically and dynamically adjusted by the coordination controller according to the real-time collected crude oil temperature and flow rate data to ensure that the temperature control requirements under different operating conditions are met. The first set threshold ε1 is determined based on the minimum adjustment accuracy of the thyristor and the allowable power fluctuation range of the load. Since the thyristor used in this embodiment... The minimum adjustment step of the trigger board corresponds to a power change of 0.3kW, and the allowable power fluctuation range for crude oil transportation temperature control is ±1kW. Therefore, ε1 is set to 1kW. When the absolute value of the power deviation does not exceed this threshold, there is no need to adjust the thyristor firing angle, thus avoiding system instability caused by frequent fine-tuning. The second threshold ε2 is set in combination with the power change corresponding to each tap of the on-load tap changer and the optimal operating range of the thyristor. Considering that each tap switching of the OLTC in this embodiment can bring a power change of 7.5kW, and that when the firing angle α≤10° (close to full conduction state), the power factor on the grid side can be maintained above 0.95, the harmonic distortion rate is less than 5%, and the loss is small, ε2 is set to 7.5kW. This ensures that when the cumulative power adjustment of the thyristor reaches this threshold, the thyristor can quickly return to the optimal operating range through OLTC tap switching, avoiding the adverse effects of deep adjustment.

[0031] After initialization, the voltage and current sensors in the measurement system begin to acquire the three-phase voltage and three-phase current signals at the load end in real time. The acquisition frequency is set to 100Hz, that is, a set of data is acquired every 10ms. This acquisition frequency can ensure the real-time performance of the data and avoid excessive computational load on the coordinating controller due to excessive acquisition frequency. The voltage and current signals collected by the sensors are analog signals, which are transmitted to the analog input module of the coordinating controller through shielded cables. The coordinating controller filters the received analog signals using a moving average filtering algorithm, averaging 10 consecutive sets of collected data to remove high-frequency noise caused by power grid fluctuations and line interference, ensuring the accuracy of voltage and current data. For example, if the voltage of phase A at the load end collected at a certain moment is 378V, 382V, 380V, 379V, 381V, 383V, 377V, 380V, 382V, and 379V respectively, the average value of phase A voltage after moving average filtering is 380V. Similarly, the average values ​​of phase B and phase C voltages and the average values ​​of three-phase currents A, B, and C can be calculated.

[0032] The coordinating controller calculates the actual power P at the load end based on the filtered three-phase voltage and current data. Since the oil well heating load is a symmetrical three-phase resistive load, the three-phase power calculation formula is used: P = √3 × U × I × cosφ, where U is the average three-phase line voltage, I is the average three-phase line current, and cosφ is the power factor. For a purely resistive load, cosφ = 1. Therefore, in this embodiment, the power calculation can be simplified to P = √3 × U × I. For example, if the average three-phase line voltage after filtering is U = 380V and the average three-phase line current is I = 76.2A, substituting into the formula, the actual power P = √3 × 380V × 76.2A ≈ 50kW, which is consistent with the set power Pref. In this case, no power adjustment is required. If at a certain moment the average line voltage after filtering is U = 370V and the average line current is I = 74.1A, the calculated actual power P = √3 × 370V × 74.1A ≈ 47kW, which deviates from the set power Pref = 50kW.

[0033] Next, the coordinating controller calculates the power deviation ΔP based on the actual power P and the set power Pref. The calculation formula strictly follows ΔP = Pref – P, where a positive ΔP indicates that the actual power is less than the set power, requiring an increase in output power; a negative ΔP indicates that the actual power is greater than the set power, requiring a decrease in output power. When P = 47kW, ΔP = 50kW – 47kW = 3kW. At this point, the coordinating controller determines whether the absolute value of the power deviation |ΔP| = 3kW is greater than the first set threshold ε1 = 1kW. Obviously, 3kW > 1kW, therefore the thyristor firing angle α needs to be adjusted to change the output power. The thyristor phase-controlled voltage regulation circuit adopts an anti-parallel thyristor pair structure. Each phase circuit consists of two anti-parallel thyristors, which control the conduction of the positive and negative half-cycles of the AC voltage, respectively. The firing angle α refers to the electrical angle corresponding to the time from the voltage zero-crossing point to the issuance of the trigger signal. The magnitude of the firing angle α directly determines the conduction time of the thyristor, thus affecting the effective value of the output voltage: when α = 0°, the thyristor conducts immediately at the voltage zero-crossing point, with the longest conduction time and the largest effective value of the output voltage, close to the input voltage; as α increases, the conduction time shortens, the effective value of the output voltage decreases, and the output power also decreases accordingly; when α = 180°, the thyristor is completely cut off, the output voltage is zero, and the power is zero. In this embodiment, a PID control algorithm is used to perform closed-loop control of the firing angle α. The firing angle is dynamically adjusted according to the magnitude and direction of the power deviation ΔP. The proportional coefficient Kp of the PID algorithm is set to 0.5° / kW, the integral coefficient Ki is set to 0.1° / (kW·s), and the derivative coefficient Kd is set to 0.05° / (kW·s). -1 The PID controller rapidly responds to deviations through a proportional element, eliminates static errors through an integral element, and suppresses overshoot through a derivative element. When ΔP = 3kW, the PID algorithm determines that the trigger angle α needs to be reduced from the initial 20° to 12°. The controller then sends a trigger angle adjustment command to the thyristor trigger board. Upon receiving the command, the trigger board generates a corresponding trigger pulse signal through an opto-isolation circuit, precisely controlling the thyristor's conduction time. This increases the effective output voltage from 370V to 378V, thereby increasing the actual power from 47kW to 49.2kW.

[0034] After each thyristor firing angle adjustment, the coordinating controller calculates the power change ΔP_adjustment resulting from this adjustment and adds it to the cumulative power adjustment ΣΔP. The calculation of the cumulative power adjustment ΣΔP follows the algebraic summation rule, starting from the completion of system initialization or the last ΣΔP reset. If the power change after each adjustment is positive (power increases), a positive value is taken; if it is negative (power decreases), a negative value is taken. For example, the power before the first adjustment was 47kW, and after the adjustment it was 49.2kW. The power change ΔPadjustment1 = 49.2kW – 47kW = 2.2kW, and ΣΔP = 2.2kW. After running for 30 seconds, due to a slight increase in the ambient temperature downhole, the load resistance slightly increased, and the actual power dropped to 48.5kW. ΔP = 50kW – 48.5kW = 1.5kW > 1kW. The coordinating controller then adjusted the trigger angle α again from 12° to 10°, increasing the output power to 49.8kW. The power change ΔPadjustment2 = 49.8kW – 48.5kW = 1.3kW, and ΣΔP was updated to 2.2kW + 1.3kW = 3.5kW. After another 2 minutes of operation, the original... The oil flow rate increased slightly, carrying away more heat, and the actual power dropped to 48.2kW. Since ΔP = 1.8kW > 1kW, the trigger angle α was adjusted from 10° to 8°, and the power increased to 49.9kW. This adjustment of ΔP by 3 = 1.7kW resulted in ΣΔP = 3.5kW + 1.7kW = 5.2kW. Subsequently, with subtle changes in the operating conditions, the thyristor underwent several small adjustments, with each adjustment resulting in a power change between 0.5kW and 1.2kW. After accumulating 15 minutes of operation, ΣΔP accumulated to 7.6kW. At this point, the coordinating controller determined whether the absolute value of the accumulated power adjustment, |ΣΔP| = 7.6kW, was greater than the second set threshold ε2 = 7.5kW. If the condition was met, a gear switching command was immediately generated. Since ΣΔP is a positive value, it indicates that all adjustments are positive adjustments to increase power. The thyristor firing angle has decreased from the initial 20° to 6°, and it is close to the full conduction state. It still needs to continuously compensate for power. Therefore, the gear switching command is set to the gear up command, that is, to control the on-load tap-changing transformer to go from the current 5th gear to the 6th gear.

[0035] The coordination controller sends an upshift command to the tap changer drive motor of the on-load tap-changing transformer via the relay output module. Upon receiving the command, the tap changer drive motor activates the mechanical transmission mechanism to switch the taps. This switching process is a second-level operation; in this embodiment, the OLTC completes one tap change in approximately 3 seconds. During the switching process, the output voltage of the on-load tap-changing transformer gradually increases from 380V to 395V. At this time, the coordination controller pauses the adjustment of the thyristor firing angle and only continuously monitors the load power change to avoid excessive power fluctuations caused by dual adjustments during OLTC switching. Once the tap changer drive motor sends a signal indicating that the tap change is complete, the coordination controller confirms that the OLTC has stabilized at tap 6 and immediately resets the accumulated power adjustment ΣΔP to 0, starting a new accumulation cycle.

[0036] After the OLTC completes the gear shift, the actual power at the load end increases due to the increased output voltage. At this time, the average line voltage collected by the measurement system rises to 395V, and the average line current rises to 80.5A. The calculated actual power is P = √3 × 395V × 80.5A ≈ 55kW, ΔP = 50kW – 55kW = -5kW. To bring the thyristor back to its optimal operating point (firing angle α approaching full conduction), and to adjust the actual power to the set value, the controller sends a trigger signal to the thyristor trigger board. The firing angle adjustment command increases the firing angle α from 6° to 15° through a PID algorithm. At this time, the effective value of the output voltage drops to 381V, the actual power stabilizes at 50.3kW, and ΔP=-0.3kW. Its absolute value is less than the first set threshold ε1=1kW, which meets the control accuracy requirements. The thyristor is now operating in a near-full conduction state with α=15°. The grid-side power factor is detected to be 0.96, and the harmonic distortion rate is 3.2%, which is far better than the performance indicators under deep adjustment state, effectively reducing power loss and grid pollution.

[0037] During stable system operation, the coordinating controller continuously repeats the above-mentioned acquisition, calculation, judgment, and adjustment process to respond in real time to power fluctuations caused by changes in operating conditions. For example, when the ambient temperature drops by 5°C, the oil cools down faster, and the actual power at the load end drops to 48.9kW. Since ΔP = 1.1kW > 1kW, the coordinating controller adjusts the firing angle α from 15° to 13°, increasing the power to 49.8kW. ΔP = 0.2kW, which meets the requirements. The power change in this instance is 0.9kW, and ΣΔP = 0.9kW. When the oil flow suddenly increases by 10%, the load cooling power increases, and the actual power drops to 48.3kW. Since ΔP = 1.7kW > 1kW, the firing angle α is adjusted to 11°, increasing the power to 50.1kW. ΔP = 0.1kW, and the power change in this instance is 1.8kW. ΣΔP = 0.9kW + 1.8kW = 2.7kW. After several similar small adjustments, the cumulative power adjustment gradually increases. When ΣΔP reaches 7.5kW again, the OLTC performs another upshift, and the thyristor returns to near full conduction, forming a virtuous cycle.

[0038] To ensure the reliability and safety of the system operation, this embodiment also includes multiple protection mechanisms: When the voltage signal collected by the measurement system exceeds 420V or falls below 340V, or the current signal exceeds 100A, it is determined to be an overvoltage, undervoltage, or overcurrent fault. The coordinating controller immediately cuts off the thyristor trigger signal, stops the OLTC gear switching action, and sends an alarm signal to the remote monitoring center through the communication module. At the same time, the backup cooling system is activated to cool down the thyristor and OLTC to prevent equipment damage due to abnormal operating conditions. When the OLTC gear switching process is stuck and fails to complete the switching within 5 seconds, the coordinating controller determines it to be a gear switching fault, immediately issues an alarm, and keeps the current thyristor trigger angle unchanged until maintenance personnel troubleshoot the fault before resuming normal adjustment. When the communication between the coordinating controller and the sensor or actuator is interrupted, the system automatically switches to manual control mode. The operator can manually adjust the OLTC gear and thyristor trigger angle through the on-site control panel to ensure that the crude oil heating process is not interrupted.

[0039] Therefore, this embodiment achieves intelligent linkage between the on-load tap-changing transformer and the thyristor phase-controlled voltage regulation through a coordination controller. It not only solves the problem of slow operation of existing OLTCs by utilizing the millisecond-level response speed of thyristor phase-controlled voltage regulation, ensuring that power deviations can be quickly corrected to meet the precise temperature control requirements of crude oil transportation, but also avoids the thyristor from working in a deep adjustment state for a long time by triggering the OLTC range switching through the cumulative power adjustment amount. This effectively improves the power factor on the grid side, reduces harmonic pollution and thyristor losses, and at the same time reduces the frequency of OLTC operation, extends the service life of its mechanical structure, and reduces maintenance costs. Actual operating condition tests show that after adopting the control method and system of this embodiment, the temperature fluctuation range of crude oil transportation is controlled within ±0.5℃, which is far superior to the ±2℃ control accuracy of existing methods; the system response time is shortened to within 50ms, which is more than 20 times faster than using OLTC alone; the power factor on the grid side is stabilized above 0.95, which is 15% higher than when using thyristor phase control voltage regulation alone; the operation frequency of OLTC is reduced from 3-5 times per hour to once every 8-10 hours, the equipment maintenance cycle is extended by 3 times, and the maintenance cost is reduced by more than 60%. It fully meets the precise, efficient, and stable control requirements of high-power resistance heating loads and has broad application prospects in similar high-power resistance heating scenarios such as oil well heating and industrial resistance furnace heating.

[0040] like Figure 2 As shown, this embodiment also provides a voltage coordination control system for a resistance heating load, including: a data acquisition module for acquiring the actual power at the load end; a first judgment module for comparing the power deviation calculated based on the actual power at the load end and a set power with a first set threshold: if the absolute value of the power deviation is greater than the first set threshold, the firing angle of the thyristor is adjusted to change the output power so that the adjusted actual power approaches the set power; otherwise, the current firing angle of the thyristor is maintained; a data accumulation module for calculating and accumulating the power adjustment amount of the thyristor to obtain the accumulated power adjustment amount; and a second judgment module for comparing the accumulated power adjustment amount with a second set threshold: if the absolute value of the accumulated power adjustment amount is greater than the second set threshold, a tap-changing command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to perform tap-changing and reset the accumulated power adjustment amount; otherwise, the current tap of the on-load tap-changing transformer is maintained.

[0041] The present invention also provides a voltage coordination control device for a resistance heating load, comprising: a memory for storing a computer program; and a processor for executing the computer program to implement the steps of the voltage coordination control method for the resistance heating load.

[0042] The present invention also provides a computer program product, including a computer program / instructions that, when executed by a processor, implement the steps of the voltage coordination control method for a resistive heating load.

[0043] When the processor executes the computer program, it implements the above-mentioned steps for voltage coordination control of the resistance heating load, for example: acquiring the actual power at the load end; comparing the power deviation calculated based on the actual power at the load end and the set power with a first set threshold; if the absolute value of the power deviation is greater than the first set threshold, adjusting the firing angle of the thyristor to make the adjusted actual power approach the set power by changing the output power; otherwise, maintaining the current firing angle of the thyristor; calculating and accumulating the power adjustment amount of the thyristor to obtain the accumulated power adjustment amount; comparing the accumulated power adjustment amount with a second set threshold; if the absolute value of the accumulated power adjustment amount is greater than the second set threshold, issuing a tap-changing command to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to perform tap-changing and reset the accumulated power adjustment amount; otherwise, maintaining the current tap of the on-load tap-changing transformer.

[0044] Exemplarily, the computer program may be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing preset functions, the instruction segments describing the execution process of the computer program in the voltage coordination control device for resistive heating loads. For example, the computer program can be divided into a data acquisition module, a first judgment module, a data accumulation module, and a second judgment module, with the following specific functions: The data acquisition module is used to acquire the actual power at the load end; the first judgment module is used to compare the power deviation calculated based on the actual power at the load end and the set power with a first set threshold: if the absolute value of the power deviation is greater than the first set threshold, the firing angle of the thyristor is adjusted so that the adjusted actual power approaches the set power by changing the output power; otherwise, the current firing angle of the thyristor is maintained; the data accumulation module is used to calculate and accumulate the power adjustment amount of the thyristor to obtain the accumulated power adjustment amount; the second judgment module is used to compare the accumulated power adjustment amount with a second set threshold: if the absolute value of the accumulated power adjustment amount is greater than the second set threshold, a tap-changing command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to perform tap-changing and reset the accumulated power adjustment amount; otherwise, the current tap of the on-load tap-changing transformer is maintained.

[0045] The voltage coordination control device for the resistance heating load can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The voltage coordination control device for the resistance heating load may include, but is not limited to, a processor and memory. Those skilled in the art will understand that the above are examples of a voltage coordination control device for a resistance heating load and do not constitute a limitation on the voltage coordination control device for the resistance heating load. It may include more components than described above, or combine certain components, or different components. For example, the voltage coordination control device for the resistance heating load may also include input / output devices, network access devices, buses, etc.

[0046] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or any conventional processor. This processor is the control center for voltage coordination control of the resistive heating load, connecting various parts of the voltage coordination control device for the resistive heating load through various interfaces and lines.

[0047] The memory can be used to store the computer program and / or modules. The processor implements various functions of the voltage coordination control device for resistance heating load by running or executing the computer program and / or modules stored in the memory and calling the data stored in the memory.

[0048] The memory may primarily include a program storage area and a data storage area. The program storage area may store the operating system and at least one application program required for a function (such as sound playback, image playback, etc.). The data storage area may store data created based on the use of the mobile phone (such as audio data, phonebook, etc.). Furthermore, the memory may include high-speed random access memory and non-volatile memory, such as hard disks, RAM, plug-in hard disks, smart media cards (SMC), secure digital cards (SD cards), flash cards, at least one disk storage device, flash memory device, or other volatile solid-state storage devices.

[0049] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the voltage coordination control method for a resistive heating load.

[0050] If the integrated module / unit of the voltage coordination control system for resistance heating load is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium.

[0051] Based on this understanding, the present invention can implement all or part of the processes in the voltage coordination control method for resistive heating loads described above, or it can be accomplished by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the voltage coordination control method for resistive heating loads described above. The computer program includes computer program code, which can be in the form of source code, object code, executable file, or a preset intermediate form, etc.

[0052] The computer-readable storage medium may include: any entity or device capable of carrying the computer program code, recording media, USB flash drive, portable hard drive, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0053] It should be noted that the content contained in the computer-readable storage medium may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electrical carrier signals and telecommunication signals.

[0054] In summary, this invention provides a voltage coordination control method and related apparatus for resistance heating loads, which has the following advantages compared to existing control methods: This invention analyzes the control requirements of high-power resistance heating and proposes a control method that can intelligently coordinate the actions of on-load tap changers and thyristor phase-controlled voltage regulation. This method can give full play to the advantages of each and avoid the disadvantages of existing control methods, thereby reducing equipment wear and greatly improving the accuracy and response time of system temperature regulation.

[0055] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A voltage coordination control method for a resistance heating load, characterized in that, include: Collect the actual power at the load end; The power deviation calculated based on the actual power at the load end and the set power is compared with the first set threshold. If the absolute value of the power deviation is greater than the first set threshold, the firing angle of the thyristor is adjusted so that the adjusted actual power approaches the set power by changing the output power. Otherwise, maintain the current firing angle of the thyristor; Calculate and accumulate the power regulation of the thyristor to obtain the cumulative power regulation; The cumulative power adjustment is compared with the second set threshold: if the absolute value of the cumulative power adjustment is greater than the second set threshold, a tap position switching command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to switch tap positions and reset the cumulative power adjustment; otherwise, the current tap position of the on-load tap-changing transformer is maintained.

2. The voltage coordination control method for a resistance heating load according to claim 1, characterized in that, Before collecting the actual power at the load end, it also includes: Real-time acquisition of voltage and current at the load end; The actual power at the load end is calculated based on the voltage and current at the load end.

3. The voltage coordination control method for a resistance heating load according to claim 1, characterized in that, Before comparing the power deviation calculated based on the actual power at the load end and the set power with the first set threshold, the method further includes: The power deviation is obtained by subtracting the actual power at the load end from the set power, and the specific formula is as follows: ΔP = Pref – P In the formula, ΔP represents the power deviation; Pref represents the set power; and P represents the actual power at the load end.

4. The voltage coordination control method for a resistance heating load according to claim 1, characterized in that, The calculation and accumulation of the thyristor power regulation to obtain the cumulative power regulation includes: Starting from the initial moment or the moment of resetting the cumulative power regulation, the power changes caused by each thyristor regulation are summed to obtain the cumulative power regulation.

5. The voltage coordination control method for a resistance heating load according to claim 1, characterized in that, If the absolute value of the cumulative power regulation is greater than the second preset threshold, a tap-changing command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to switch taps and reset the cumulative power regulation, including: If the absolute value of the cumulative power adjustment is greater than the second set threshold, a gear shifting command is generated; wherein, the gear shifting command is an upshift command or a downshift command; Output a tap change command to the on-load tap changer to trigger the on-load tap changer to perform tap change; Reset the cumulative power adjustment to zero.

6. The voltage coordination control method for a resistance heating load according to claim 1, characterized in that, If the absolute value of the cumulative power regulation is greater than the second preset threshold, a tap-changing command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to perform tap-changing. After resetting the cumulative power regulation, the method further includes: After the on-load tap-changing transformer completes the tap change, it sends a firing angle adjustment command to the thyristor to adjust the firing angle toward the optimal operating point, so that the thyristor tends to be in a fully conducting state.

7. The voltage coordination control method for a resistance heating load according to claim 1, characterized in that, The first set threshold is determined based on the thyristor adjustment dead zone; the second set threshold is adopted from the tap changer action threshold of the on-load tap changer transformer.

8. A voltage coordination control system for a resistance heating load, characterized in that, include: The data acquisition module is used to collect the actual power at the load end; The first judgment module is used to compare the power deviation calculated based on the actual power at the load end and the set power with the first set threshold. If the absolute value of the power deviation is greater than the first set threshold, the firing angle of the thyristor is adjusted so that the adjusted actual power approaches the set power by changing the output power. Otherwise, maintain the current firing angle of the thyristor; The data accumulation module is used to calculate and accumulate the power regulation of the thyristor to obtain the cumulative power regulation. The second judgment module is used to compare the cumulative power adjustment amount with the second set threshold: if the absolute value of the cumulative power adjustment amount is greater than the second set threshold, a tap position switching command is sent to the on-load tap-changing transformer to trigger the on-load tap-changing transformer to switch tap positions and reset the cumulative power adjustment amount; otherwise, the current tap position of the on-load tap-changing transformer is maintained.

9. A voltage coordination control device for a resistance heating load, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program, implement the steps of the voltage coordination control method for a resistive heating load as described in any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it is used to implement the steps of the voltage coordination control method for a resistance heating load as described in any one of claims 1-7.

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