A controller and method for a series compensation device

Abstract

The application discloses a controller and method of series compensation device, and belongs to the technical field of power electronics. The method firstly extracts the deviation of real-time active power and expected active power of a power transmission line, and obtains basic target equivalent impedance through closed-loop adjustment. Secondly, the trigger delay time difference of thyristors is obtained to determine the equivalent current flow weight of forward and reverse thyristors, and the junction temperature observation values of the two are independently recursively calculated. Then, the absolute junction temperature difference of the forward and reverse thyristors is extracted to generate a thermal-electric cross-coupling asymmetric penalty factor, and the basic impedance is nonlinearly corrected to obtain a corrected target equivalent impedance. Finally, the real-time evolution rate of the valve group is extracted as a feedforward intervention variable to generate a pre-compensation phase angle, which is combined with the basic trigger angle, and the final trigger angle is output after physical limiting. The application effectively overcomes the unilateral thermal fatigue problem caused by asymmetric current flow in the traditional control, realizes thermal-electric deep coupling and early anti-disturbance intervention, and greatly improves the operation safety and stability of the device.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and particularly relates to a controller and method for a series compensation device. Background Technology

[0002] Series compensation devices (such as controllable series compensators) are widely used in modern power systems to flexibly adjust the equivalent impedance of transmission lines, control power flow distribution, and improve the transient stability of the system. The core actuator of a series compensation device is the thyristor valve group. In traditional control strategies, the control system typically assumes that the forward and reverse half-wave triggering of the thyristor is perfectly symmetrical and ideal, and the control loop often uses a single electrical parameter (such as power, current, or impedance) as the feedback variable.

[0003] However, in actual engineering operation, due to time delay differences in hardware drive circuits, grid harmonic interference, or truncation errors in control algorithms, thyristors often generate positive and negative half-wave trigger delay time differences. This asymmetrical trigger pulse leads to inconsistencies in the current integral carried by the forward and reverse thyristors, resulting in uneven thermal stress on the power devices in both directions and significant junction temperature deviations. Traditional system thermal protection typically uses a single static temperature threshold for passive limiting or cutoff, failing to feed back this thermal deviation caused by electrical asymmetry to the upstream impedance control loop in real time. Furthermore, passive static thermal protection often lags behind the transient deterioration rate of junction temperature, easily causing thyristor commutation failure or thermal breakdown during short circuits or sudden heavy load changes.

[0004] Therefore, there is an urgent need for a series compensation control method that can deeply cross-couple thermal parameters with electrical parameters and has the ability to intervene in transient thermal feedforward. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a controller and method for a series compensation device, thus solving the aforementioned problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a control method for a series compensation device, comprising:

[0007] S10. Extract the deviation between the real-time active power and the expected active power of the transmission line in the current discrete sampling period, and obtain the basic target equivalent impedance required by the series compensation device through the closed-loop adjustment model.

[0008] S20. Obtain the trigger delay time difference between the positive and negative half-waves of the thyristor. Based on the asymmetric current conduction characteristics characterized by the trigger delay time difference, determine the equivalent current conduction weights of the forward thyristor and the reverse thyristor respectively, and independently recursively obtain the observed junction temperature values ​​of the forward thyristor and the reverse thyristor in the current cycle.

[0009] S30. Extract the absolute junction temperature difference between the observed junction temperature of the forward thyristor and the observed junction temperature of the reverse thyristor as a thermodynamic feedback quantity, generate the thermo-electric cross-coupling asymmetric penalty factor, and use the thermo-electric cross-coupling asymmetric penalty factor to perform nonlinear correction on the basic target equivalent impedance to obtain the corrected target equivalent impedance.

[0010] S40. Extract the real-time evolution rate of the highest junction temperature of the thyristor valve group as the thermal inertia feedforward intervention variable. Combine the real-time evolution rate with the corrected target equivalent impedance to generate the feedforward pre-compensation phase angle. Combine the feedforward pre-compensation phase angle with the basic trigger angle generated based on the corrected target equivalent impedance mapping. After physical boundary limiting, output the final target trigger angle and trigger the execution unit to execute.

[0011] Based on the above technical solutions, the present invention also provides the following optional technical solutions:

[0012] A further technical solution: When calculating the basic target equivalent impedance in S10, the basic target equivalent impedance is a linear superposition of the initial reference static impedance, the power deviation proportional adjustment term, and the power deviation integral adjustment term.

[0013] The power deviation proportional adjustment term is directly proportional to the proportional adjustment coefficient and the deviation between the real-time active power and the expected active power in the current sampling period; the power deviation integral adjustment term is directly proportional to the integral adjustment coefficient, the discrete sampling period, and the cumulative amount of active power deviation from the past to the current sampling period.

[0014] Further technical solution: The method for determining the equivalent current weights of the forward and reverse thyristors in S20 is as follows:

[0015] The equivalent current-carrying coefficient of the forward thyristor and the equivalent current-carrying coefficient of the reverse thyristor are both based on the reference half-wave conduction weight.

[0016] The equivalent current-carrying coefficient of the forward thyristor is the reference half-wave conduction weight minus the asymmetric offset, and the equivalent current-carrying coefficient of the reverse thyristor is the reference half-wave conduction weight plus the asymmetric offset.

[0017] The asymmetric offset is positively correlated with the ratio of the thyristor's positive and negative half-wave trigger delay time difference to the fundamental period of the system's AC current.

[0018] A further technical solution: The method for independently recursively obtaining the observed values ​​of the forward and reverse thyristor junction temperatures for the current cycle in S20 is as follows:

[0019] The current period's forward thyristor junction temperature observation value is obtained by superimposing the previous period's forward thyristor junction temperature observation value with the heat source temperature rise increment during the current sampling period, and subtracting the environmental heat dissipation temperature drop decrease during the current sampling period.

[0020] The temperature rise increment of the heat source is positively correlated with the product of the equivalent current coefficient of the forward thyristor and the square of the effective current of the thyristor branch, and is directly proportional to the equivalent on-resistance of the thyristor and inversely proportional to the equivalent heat capacity.

[0021] The reduction in ambient heat dissipation temperature drop is positively correlated with the temperature difference between the observed value of the forward thyristor junction temperature in the previous cycle and the external ambient temperature, and is inversely proportional to the equivalent thermal resistance and equivalent heat capacity.

[0022] The junction temperature observation value of the reverse thyristor is obtained synchronously and recursively in the same way as that of the forward thyristor, combined with the equivalent current coefficient of the reverse thyristor.

[0023] A further technical solution: The mechanism for generating the thermo-electric cross-coupling asymmetric penalty factor in S30 is as follows:

[0024] The thermo-electric cross-coupling asymmetric penalty factor is obtained by adding the baseline physical asymmetric gain to the thermo-electric coupling dynamic increment;

[0025] The thermoelectric coupling dynamic increment is the product of the absolute junction temperature difference between the forward and reverse thyristors and the thermoelectric coupling sensitivity coefficient, which is used to characterize the negative feedback depth of asymmetric thermal stress on the control system.

[0026] A further technical solution: The method for calculating the corrected target equivalent impedance in S30 is as follows:

[0027] The modified target equivalent impedance is the product of the base target equivalent impedance and the asymmetric amplification factor;

[0028] The asymmetric amplification factor is an amplification function with a base of 1, and its super-base increment is positively correlated with the thermal-electric cross-coupling asymmetric penalty factor, and is positively proportional to the square of the ratio of the thyristor positive and negative half-wave trigger delay time difference to the fundamental period.

[0029] Further technical solution: In step S40, the mechanism for calculating the real-time evolution rate and the basic trigger angle includes:

[0030] The real-time evolution rate is equal to the ratio of the highest temperature value in the current cycle of the bidirectional thyristor minus the highest temperature value in the previous cycle to the discrete sampling cycle.

[0031] The basic firing angle is obtained by nonlinear quadratic polynomial mapping of the corrected target equivalent impedance, which includes a constant bias term, a linear term based on the corrected target equivalent impedance, and a quadratic parabolic term.

[0032] Further technical solution: The control logic in S40 for generating the feedforward pre-compensation phase angle and synthesizing the final target firing angle is as follows:

[0033] When the real-time evolution rate is less than or equal to zero, the thermal inertia feedforward pre-compensation angle is zero.

[0034] When the real-time evolution rate is greater than zero, the thermal inertia feedforward pre-compensation angle is activated, and its magnitude is equal to the product of the real-time evolution rate, the thermal inertia feedforward coefficient, and the impedance state margin ratio; the impedance state margin ratio is the ratio of the corrected target equivalent impedance to the maximum reference static impedance.

[0035] The final target trigger angle is the sum of the base trigger angle and the thermal inertia feedforward pre-compensation angle. When the sum is less than the minimum allowable trigger angle, the final target trigger angle is hard-bounded and truncated at the minimum allowable trigger angle.

[0036] A controller for a series compensation device employs the control method described above for the series compensation device.

[0037] This invention provides a controller and method for a series compensation device, which has the following advantages compared with the prior art:

[0038] 1. This invention innovatively generates a thermoelectric cross-coupling asymmetry penalty factor by extracting the absolute junction temperature difference between forward and reverse thyristors as a thermodynamic feedback quantity. This factor is directly used to nonlinearly correct the equivalent impedance of the basic target, so that the control system can actively adopt a yielding or compensation strategy when facing electrical triggering asymmetry, fundamentally balancing the thermal stress of bidirectional power devices and avoiding unilateral thermal fatigue.

[0039] 2. This invention breaks through the limitations of traditional static threshold protection by extracting the real-time evolution rate of the highest junction temperature of the thyristor valve group as a thermal inertia feedforward intervention variable. When the temperature rises sharply but has not yet reached the danger boundary, the system can generate a pre-compensated phase angle in advance, which greatly improves the safety margin and anti-disturbance capability of the device during power grid faults or load changes.

[0040] 3. This invention no longer uses a coarse overall thermal model, but instead uses the trigger delay time difference to quantify the asymmetric current characteristics and determine the equivalent current weights of the forward and reverse thyristors respectively. In this way, the junction temperature observation values ​​of the forward and reverse directions can be obtained independently and recursively, which significantly improves the evaluation accuracy of the transient thermodynamic state of semiconductor devices.

[0041] 4. In the final output stage, this invention integrates the feedforward pre-compensation phase angle with the basic trigger angle of the polynomial mapping and performs strict physical boundary limiting processing. This not only reduces the computational complexity of the underlying hardware, but also ensures that the output instructions are within a safe and controllable execution range under any extreme conditions. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the process of the present invention.

[0043] Figure 2 This is a block diagram of the logical architecture of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0046] Please see Figure 1 as well as Figure 2 A control method for a series compensation device, provided in one embodiment of the present invention, includes:

[0047] S10. Extract the deviation between the real-time active power and the expected active power of the transmission line in the current discrete sampling period, and obtain the basic target equivalent impedance required by the series compensation device through the closed-loop adjustment model.

[0048] S20. Obtain the trigger delay time difference between the positive and negative half-waves of the thyristor. Based on the asymmetric current conduction characteristics characterized by the trigger delay time difference, determine the equivalent current conduction weights of the forward thyristor and the reverse thyristor respectively, and independently recursively obtain the observed junction temperature values ​​of the forward thyristor and the reverse thyristor in the current cycle.

[0049] S30. Extract the absolute junction temperature difference between the observed junction temperature of the forward thyristor and the observed junction temperature of the reverse thyristor as a thermodynamic feedback quantity, generate the thermo-electric cross-coupling asymmetric penalty factor, and use the thermo-electric cross-coupling asymmetric penalty factor to perform nonlinear correction on the basic target equivalent impedance to obtain the corrected target equivalent impedance.

[0050] S40. Extract the real-time evolution rate of the highest junction temperature of the thyristor valve group as the thermal inertia feedforward intervention variable. Combine the real-time evolution rate with the corrected target equivalent impedance to generate the feedforward pre-compensation phase angle. Combine the feedforward pre-compensation phase angle with the basic trigger angle generated based on the corrected target equivalent impedance mapping. After physical boundary limiting, output the final target trigger angle and trigger the execution unit to execute.

[0051] Traditional control methods typically assume that the positive and negative half-wave triggering of the thyristor is perfectly symmetrical and primarily use a single electrical parameter as the feedback variable. For example, in heavy-load events, traditional methods may adjust the impedance only based on the power deviation, ignoring the potential thermal stress unevenness that may occur inside the thyristor. This embodiment, however, obtains the time difference between the positive and negative half-wave triggering of the thyristor in S20 and independently recursively obtains the observed junction temperatures of the forward and reverse thyristors, achieving precise perception of the thermal asymmetry inside the thyristor—something traditional methods cannot achieve.

[0052] Furthermore, traditional methods for thermal protection often employ a single static temperature threshold for passive limiting or cutoff, which frequently lags behind the transient deterioration rate of junction temperature. In heavy-load events, relying solely on the static temperature threshold may result in measures being taken only after the junction temperature reaches a dangerous level, increasing the risk of thyristor commutation failure or thermal breakdown. In contrast, this embodiment, in S30, uses the absolute junction temperature difference between the forward and reverse thyristors as a thermodynamic feedback quantity to generate a thermo-electrical cross-coupling asymmetry penalty factor, which is then used to nonlinearly correct the basic target equivalent impedance. This mechanism directly feeds back thermal asymmetry to the adjustment of electrical control parameters, achieving deep thermo-electrical cross-coupling, enabling the control system to actively suppress electrical asymmetry caused by thermal imbalance, rather than responding passively.

[0053] Furthermore, in S40 of this embodiment, the real-time evolution rate of the highest junction temperature of the thyristor valve group is extracted as a thermal inertia feedforward intervention variable, and combined with the corrected target equivalent impedance to generate a feedforward pre-compensation phase angle, which is then synthesized and output as the final target firing angle. This feedforward control strategy enables the system to predict the transient deterioration trend of the junction temperature and actively adjust the firing angle before thermal breakdown occurs, thereby significantly improving the thermal stability and operational reliability of the system under heavy load or sudden change conditions. Compared with the passive static thermal protection of traditional methods, the active feedforward intervention mechanism of this embodiment can more effectively avoid transient thermal failure of the thyristor.

[0054] In summary, this embodiment achieves a shift from single electrical control to electrothermal coordinated control by constructing a closed-loop control architecture with thermo-electric cross-coupling and introducing thermal inertia feedforward intervention. This method not only solves the problem of thermal stress imbalance caused by thyristor trigger asymmetry, but also effectively addresses the risks brought about by transient junction temperature deterioration through the feedforward mechanism, significantly improving the operational reliability and safety of the series compensation device.

[0055] Preferably, when calculating the basic target equivalent impedance in S10, the basic target equivalent impedance is a linear superposition of the initial reference static impedance, the power deviation proportional adjustment term, and the power deviation integral adjustment term;

[0056] The power deviation proportional adjustment term is directly proportional to the proportional adjustment coefficient and the deviation between the real-time active power and the expected active power in the current sampling period; the power deviation integral adjustment term is directly proportional to the integral adjustment coefficient, the discrete sampling period, and the cumulative amount of active power deviation from the past to the current sampling period.

[0057] Specifically, the closed-loop regulation model uses a discretized power-impedance proportional-integral regulation model to calculate the basic target equivalent impedance, as follows:

[0058]

[0059] in, Indicates the first The basic target equivalent impedance (in ohms) for each sampling period. This represents the initial reference static impedance (in ohms). This represents the proportional adjustment factor (unit: ohms per watt). This represents the expected active power of a transmission line (in watts). and The real-time active power (in watts) represents the sampling period. This represents the integral adjustment factor (in ohms per watt-second). This represents the discrete sampling period (in seconds). This is the power deviation proportional adjustment term. This is the power deviation integral adjustment term.

[0060] The aforementioned closed-loop control model can be implemented in various forms. For example, in addition to the proportional-integral (PI) control model, it can also employ a proportional-integral-derivative (PID) control model, a fuzzy logic control model, or a neural network-based adaptive control model. In this application, the model specifically refers to a discretized power-impedance proportional-integral control model. Its core lies in using a feedback mechanism to take the deviation between the real-time active power of the transmission line and the desired active power as input. After proportional and integral calculations, the output is a control quantity used to adjust the equivalent impedance of the series compensation device.

[0061] Discretized power-impedance proportional-integral control (PIC) is a classic control algorithm. Its discretization allows for easy implementation in digital controllers. This model generates an error signal by periodically sampling the real-time active power of the transmission line and comparing it with the desired active power. (Proportional term) Adjustments are made based on the instantaneous magnitude of the current error to provide a rapid response capability, quickly reducing the current power deviation. Integral term. The historical errors are accumulated to eliminate steady-state errors that may occur during long-term operation of the system, ensuring that the final output basic target equivalent impedance can accurately enable the active power of the transmission line to track the expected value.

[0062] Basic target equivalent impedance The series compensation device is in the first The equivalent impedance value required for each sampling period is intended to make the active power of the transmission line as close as possible to the desired active power by adjusting the output of the series compensation device. The calculation result will serve as the reference input for subsequent thermal-electric cross-coupling correction. Therefore, its accuracy and stability are crucial to the performance of the entire control method.

[0063] Initial reference static impedance It is a reference impedance value set during the design or commissioning of the system. It represents the static compensation amount that the series compensation device should provide under ideal or specific operating conditions. This value can be preset according to the physical parameters of the transmission line and the system operating requirements, or obtained through offline optimization calculation.

[0064] Proportional adjustment coefficient and integral adjustment coefficient These are key parameters in the proportional-integral control model, which determine the controller's response characteristics to power deviations. The larger the value, the faster the controller responds to the current deviation, but too large a value can cause system oscillation. The larger the coefficient, the stronger the ability to eliminate steady-state errors, but excessively large coefficients can lead to sluggish system response or overshoot. These coefficients usually need to be tuned according to the specific dynamic characteristics of the system and the control performance requirements, for example, by using the Ziegler-Nichols tuning method, the critical proportional gain method, or the empirical trial-and-error method for optimization.

[0065] Discrete sampling period This refers to the time interval during which the control system samples and calculates the active power of the transmission line. The selection of this period requires a trade-off between the control system's response speed and computational resource consumption. A smaller interval... It can improve the system's response speed and control accuracy, but it will increase the computational burden; a larger Conversely, usually. The value will be determined by expert experience based on the dynamic characteristics of the power system and the performance of the controller hardware. For example, it can be set to a fraction of the fundamental period of the power system.

[0066] The solution in this application introduces a discretized power-impedance proportional-integral adjustment model to accurately calculate the basic target equivalent impedance of the series compensation device. This model uses the initial reference static impedance as a reference. Based on this, two key adjustment terms were superimposed: a power deviation ratio adjustment term. and power deviation integral adjustment term In each discrete sampling period The controller first obtains the real-time active power of the transmission line. and the expected active power The current power deviation is obtained by comparison. The proportional control term utilizes this instantaneous deviation to provide an immediate and proportional impedance adjustment, enabling the system to respond quickly to transient power changes. Meanwhile, the integral control term continuously accumulates the impedance adjustment from the first sampling period to the current period. By correcting for all historical power deviations, the system effectively eliminates steady-state errors that may occur during long-term operation, ensuring that the actual active power of the transmission line accurately tracks the desired active power. This discretized control strategy, combining proportional and integral actions, enables the basic target equivalent impedance to be accurately tracked. The calculation not only adapts quickly to current operating conditions but also compensates for historical deviations, thus providing a stable, accurate, and forward-looking impedance benchmark for the series compensation device in a dynamically changing power system environment. This aligns with the steps in S10 described above: extracting the deviation between the real-time active power and the expected active power of the transmission line and obtaining the basic target equivalent impedance required by the series compensation device through a closed-loop control model. This makes the calculation of the basic target equivalent impedance more refined and accurate, providing high-quality input for subsequent correction of the thermal-electric cross-coupling asymmetric penalty factor, thereby improving the robustness and control accuracy of the entire control method.

[0067] As a specific implementation, the aforementioned discretized power-impedance proportional-integral adjustment model can be deployed in the digital controller of the series compensation device, for example, using a high-performance digital signal processor (DSP) or field-programmable gate array (FPGA) as the core computing unit. In each discrete sampling period... (For example, it can be set to 200 microseconds, corresponding to a sampling frequency of 5 kHz.) The controller first acquires the real-time voltage and current signals of the transmission line through an analog-to-digital converter (ADC) and calculates the real-time active power. At the same time, the system will preset a desired active power. The controller will and By comparison, the power deviation is obtained. Subsequently, according to the pre-set proportional adjustment coefficient and integral adjustment coefficient Calculate the proportional adjustment term and the integral adjustment term. For example, It can be set to 0.01 ohms per watt according to the system response speed requirements. The steady-state error elimination requirement can be set to 0.0005 ohms per watt-second. The accumulation of the integral term can be implemented in software, i.e., multiplying the current power deviation by a certain factor in each sampling period. This is then accumulated into the historical integral values. Finally, the initial reference static impedance is... (For example, it can be set to 10 ohms) Adding this to the calculated proportional and integral adjustment terms yields the basic target equivalent impedance for the current cycle. This calculation process is repeated within each sampling period to ensure... It can reflect the power demand of transmission lines in real time and accurately.

[0068] Through the above technical solution, this application effectively solves the problems of response lag and steady-state error in traditional control logic when facing power fluctuations in transmission lines. The discretized proportional-integral (PI) control model, by introducing a proportional control term, enables the system to respond quickly to current power deviations, significantly improving the tracking speed of the desired active power. Simultaneously, the cumulative correction of historical power deviations by the integral control term completely eliminates steady-state error during steady-state operation, ensuring the accuracy of the basic target equivalent impedance calculation. This control strategy, combining instantaneous response and historical cumulative correction, enables the series compensation device to continuously provide a stable and accurate basic target equivalent impedance under complex and variable power grid conditions, providing a reliable reference input for subsequent thermal-electrical cross-coupling correction, thereby enhancing the robustness, control accuracy, and adaptability to power grid changes of the entire control system.

[0069] Preferably, the method for determining the equivalent current weights of the forward and reverse thyristors in step S20 is as follows:

[0070] The equivalent current-carrying coefficient of the forward thyristor and the equivalent current-carrying coefficient of the reverse thyristor are both based on the reference half-wave conduction weight.

[0071] The equivalent current-carrying coefficient of the forward thyristor is the reference half-wave conduction weight minus the asymmetric offset, and the equivalent current-carrying coefficient of the reverse thyristor is the reference half-wave conduction weight plus the asymmetric offset.

[0072] The asymmetric offset is positively correlated with the ratio of the difference between the positive and negative half-wave triggering delay time of the thyristor to the fundamental period of the system AC current.

[0073] Specifically, in S20, the specific calculation formula for determining the equivalent current-carrying weights of the forward and reverse thyristors based on the trigger delay time difference is as follows:

[0074]

[0075]

[0076] in, and They represent the first The equivalent current-carrying coefficients of the forward and reverse thyristors for each sampling period. This represents the time difference between the positive and negative half-wave triggering delays of the thyristor (in seconds). The fundamental period of the system's alternating current (in seconds). The baseline half-wave conduction weight (typically set to 0.5). Indicates asymmetric offset;

[0077] The method for independently recursively obtaining the observed values ​​of the forward and reverse thyristor junction temperatures for the current cycle in S20 is as follows:

[0078] The current period's forward thyristor junction temperature observation value is obtained by superimposing the previous period's forward thyristor junction temperature observation value with the heat source temperature rise increment during the current sampling period, and subtracting the environmental heat dissipation temperature drop decrease during the current sampling period.

[0079] The temperature rise increment of the heat source is positively correlated with the product of the equivalent current coefficient of the forward thyristor and the square of the effective current of the thyristor branch, and is directly proportional to the equivalent on-resistance of the thyristor and inversely proportional to the equivalent heat capacity.

[0080] The reduction in ambient heat dissipation temperature drop is positively correlated with the temperature difference between the observed value of the forward thyristor junction temperature in the previous cycle and the external ambient temperature, and is inversely proportional to the equivalent thermal resistance and equivalent heat capacity.

[0081] The junction temperature observation value of the reverse thyristor is obtained synchronously and recursively in the same way as that of the forward thyristor, combined with the equivalent current coefficient of the reverse thyristor.

[0082] Specifically, in S20, the specific calculation formula for independently recursively obtaining the observed values ​​of the forward and reverse thyristor junction temperatures for the current cycle by combining the equivalent current coefficient is as follows:

[0083]

[0084]

[0085] in, and These represent the observed junction temperatures of the forward and reverse thyristors in the current cycle (in degrees Celsius). and These represent the observed junction temperatures of the forward and reverse thyristors in the previous cycle (in degrees Celsius). Indicates the discrete sampling period (in seconds). It represents the equivalent heat capacity (in joules per degree Celsius). This indicates the effective current of the thyristor branch (in amperes). and This represents the equivalent current-carrying coefficient of the forward and reverse thyristors. This represents the equivalent on-resistance (in ohms). This indicates the ambient temperature (in degrees Celsius). It represents the equivalent thermal resistance (unit: degrees Celsius per watt). Indicates the increase in temperature of the heat source and , This indicates the reduction in temperature drop due to environmental heat dissipation.

[0086] Equivalent flow coefficient and Used to quantify the effective current share carried by the forward and reverse thyristors under asymmetric triggering conditions, they represent the time difference between the positive and negative half-wave triggering delays of the thyristors. This electrical asymmetry is converted into a correction factor for the current carrying capacity, thus reflecting the actual thermal stress distribution of the thyristor in different directions. This coefficient can be understood as the proportion of the actual conduction time of the thyristor in half a fundamental cycle to the ideal half-wave conduction time, or its weight in the total current contribution. Thyristor positive and negative half-wave trigger delay time difference. It refers to the same sampling period Within this range, the actual trigger time of the forward and reverse thyristors is the difference between their ideal trigger time and the actual trigger time. This difference can be caused by various factors, such as inherent delay differences in the hardware drive circuit, quantization errors in the control algorithm, harmonic distortion of the mains voltage, or system noise interference. This time difference can be obtained by measuring the actual time interval between the thyristor gate trigger signal and the zero-crossing point of the main circuit current using a high-precision timer and calculating the difference between the positive and negative half-waves; alternatively, it can be obtained by analyzing the waveforms of the voltage or current flowing through the thyristor to identify its conduction start point, thereby calculating the actual trigger delay time and obtaining the difference between the positive and negative half-waves. The fundamental period of the system's AC current. This refers to the period of AC voltage or current in a power system. It is the basis for calculating the proportion of thyristor conduction time. This period can be obtained in real time by tracking the frequency of the grid voltage or current using phase-locked loop (PLL) technology; alternatively, if the system frequency is stable, it can be preset to a fixed value, such as for a 50Hz system. For a 60Hz system, the value is 20 milliseconds. It is 16.67 milliseconds. Reference half-wave conduction weight. This represents the proportion of the total current carried by a single half-wave thyristor under ideal symmetrical conduction conditions. (In the absence of a trigger delay time difference) At this time, the forward and reverse thyristors should each bear half of the current carrying capacity, therefore The value is typically set to 0.5. This weight can also be fine-tuned based on the actual design and operating characteristics of the thyristor valve assembly. For example, in some special applications, if the design allows for slight asymmetry, It can deviate slightly by 0.5. Asymmetric offset. Based on the time difference between the positive and negative half-wave triggering of the thyristor and fundamental frequency period The calculated value is used to quantify the deviation of the current weight from the baseline due to trigger asymmetry. The degree of this offset directly reflects the impact of electrical asymmetry on the thermal stress distribution of the thyristor. Observed junction temperatures of the forward and reverse thyristors. and The current sampling period The actual temperature of the thyristor PN junction, estimated through a thermal model, is measured in real-time and dynamically. These observations reflect the temperature changes caused by current heating and environmental heat dissipation during thyristor operation. They are key parameters for assessing thyristor thermal stress, predicting lifespan, and implementing thermal protection. These junction temperature observations can be directly displayed on the monitoring interface for operator reference; they can also serve as input to subsequent control algorithms, such as for generating the thermal-electrical cross-coupling asymmetry penalty factor. The previous cycle's forward and reverse thyristor junction temperature observations are also included. and These are the initial conditions for performing junction temperature recursive calculations in each sampling period. At the beginning, the system will utilize the previous sampling period. The junction temperature value calculated at the end of the cycle is used as the starting point of the current cycle, thus achieving continuous dynamic tracking of the junction temperature. This recursive method makes the junction temperature estimation time-continuous and can accurately reflect the cumulative effect of the junction temperature. Discrete sampling period This is the time interval between data acquisition and algorithm calculations performed by the control system. This period is usually set according to the real-time requirements and computing resource capabilities of the control system; for example, it can be set to the millisecond level or a smaller value. It can improve the real-time performance and accuracy of junction temperature observations, but it will increase the computational burden; a larger... Conversely, Precise control can be achieved using a system clock or timer to ensure that each calculation is performed within a fixed time interval. Equivalent heat capacity. This represents the amount of heat absorbed by a thyristor when the temperature increases by one degree Celsius. It reflects the thyristor device's response speed to changes in heat, i.e., its thermal inertia. This information can usually be obtained from the thyristor manufacturer's datasheet or through experimental testing (such as a step heating response test) to identify the system's effective current in the thyristor branch. This refers to the current sampling period. The effective value of the alternating current flowing through the thyristor valve group is the main source of heat generation in the thyristor. The product of its square and the on-resistance represents the instantaneous power consumption of the thyristor. The equivalent on-resistance can be obtained in real time through current measuring devices such as current transformers or Hall sensors, and then processed digitally (e.g., by root mean square calculation). This represents the equivalent resistance of the thyristor in the on-state, when current flows through the thyristor. It generates Joule heating, which is a major component of the internal heat source of the thyristor. This information can usually be obtained from the datasheet provided by the thyristor manufacturer, or by measuring the voltage drop and current of the thyristor at different currents and performing a linear fit. Ambient temperature. This refers to the ambient temperature of the thyristor valve assembly. This temperature serves as a reference for the thyristor to dissipate heat to the external environment. The equivalent thermal resistance can be obtained in real time by a temperature sensor (such as a thermistor or thermocouple) installed near the thyristor valve assembly. This represents the heat transfer resistance between the thyristor junction and the environment. It reflects the thyristor's heat dissipation capability, that is, the increase in junction temperature relative to ambient temperature per unit power consumption. This information can usually be obtained from the datasheet provided by the thyristor manufacturer, or through systematic identification via experimental testing (such as steady-state thermal resistance testing). Heat source temperature rise increment. Indicates the discrete sampling period Internally, due to the power consumption inside the thyristor (caused by the current) Equivalent flow coefficient and equivalent on-resistance The portion of the junction temperature increase caused by the decision (and the portion of the ambient heat dissipation temperature drop reduction). This indicates that within the same cycle, due to the thyristor junction temperature... Higher than ambient temperature Through thermal resistance The portion of the junction temperature decrease due to heat dissipation to the environment. These two terms together constitute the physical model of the dynamic equilibrium of the thyristor junction temperature, accurately describing the real-time evolution of the junction temperature.

[0087] This application's solution, by introducing an equivalent current-carrying coefficient and a junction temperature recursive observation model based on this coefficient, achieves a precise mapping from electrical asymmetry to thermal state, thereby solving the problem of the inability to accurately perceive the uneven distribution of internal thermal stress in thyristors in real time in traditional control. Specifically, in the control method of the series compensation device, firstly, in step S10, the system calculates the required basic target equivalent impedance based on the deviation between the real-time active power and the desired active power of the transmission line using a discretized power-impedance proportional-integral adjustment model. Building upon this, to more precisely consider the thermal characteristics of the thyristor, step S20 introduces real-time observation of the thyristor's thermal state. The core of this observation mechanism lies in first measuring or estimating the difference in trigger delay time between the positive and negative half-waves of the thyristor. And combined with the fundamental period of the system's alternating current. and reference half-wave conduction weight The equivalent current-carrying coefficient of the forward thyristor was calculated. The equivalent current coefficient of the reverse thyristor These coefficients quantify the uneven current distribution between the positive and negative half-wave thyristors due to triggering asymmetry, thus transforming electrical asymmetry into a direct factor influencing thermal stress distribution. Subsequently, these equivalent current-carrying coefficients are used... and Combined with the effective value current of the thyristor branch Equivalent on-resistance Equivalent heat capacity Equivalent thermal resistance and external ambient temperature The observed junction temperature of the forward thyristor was calculated using independent recursive formulas. and reverse thyristor junction temperature observation values These two recursive formulas consider the heat source temperature rise increment (Joule heat generated by current and current-carrying coefficient) and the ambient heat dissipation temperature drop decrease (heat dissipation driven by the temperature difference between the junction and the environment), thus enabling dynamic and real-time tracking of the junction temperature changes of the forward and reverse thyristors. This independent recursive approach allows the system to accurately perceive the junction temperature difference caused by current asymmetry even when the total current is the same, providing accurate thermal feedback for subsequent thermo-electrical cross-coupling control. Through the above mechanism, the scheme of this application accurately quantifies and tracks in real time the thermal stress caused by electrical asymmetry, which was originally difficult to quantify directly, using the equivalent current-carrying coefficient and dynamic junction temperature observation model. This allows the control system to expand from single electrical parameter feedback to deep cross-coupling that simultaneously considers electrical and thermal parameters, providing a solid foundation and accurate data support for generating the thermo-electrical cross-coupling asymmetry penalty factor and correcting the target equivalent impedance in the subsequent S30 step, and for extracting the real-time evolution rate of the highest junction temperature as a thermal inertia feedforward intervention variable in the S40 step. This precise mapping from electrical asymmetry to thermal state significantly improves the accuracy, real-time performance, and reliability of series compensation device control, effectively avoiding the risk of device overheating and failure caused by uneven thermal stress in traditional control.

[0088] The following is a concrete example. For instance, in a series compensation device, the control system can adjust the output in 1 millisecond (i.e., ... The system operates with a discrete sampling period of 0.001 seconds. The fundamental frequency period of the system's AC current... It can be 20 milliseconds (corresponding to a 50Hz power grid). Reference half-wave conduction weight. It can be set to 0.5. During a certain sampling period... The system can detect the time difference between the positive and negative half-wave triggering of the thyristor. The value is 0.5 milliseconds. At this point, the equivalent flow coefficient can be calculated using the formula: ; This indicates that the current weight of the forward thyristor is slightly higher than that of the reverse thyristor, reflecting the difference in current distribution caused by trigger asymmetry. Simultaneously, the system can measure the effective current of the thyristor branch in real time. 100 amperes, ambient temperature The equivalent heat capacity of a thyristor is 40 degrees Celsius. Equivalent on-resistance and equivalent thermal resistance These parameters can be obtained from the device datasheet, for example... 10 joules per degree Celsius It is 0.001 ohms. The value is 0.5 degrees Celsius per watt. Assuming the previous sampling period... Observed junction temperature of forward thyristor The observed junction temperature of the reverse thyristor is 80 degrees Celsius. The temperature is 75 degrees Celsius. Therefore, the current cycle... Observed junction temperature of forward thyristor It can be calculated recursively as follows: Degrees Celsius. Similarly, the observed junction temperature of the reverse thyristor. It can be calculated recursively as follows: Temperature in degrees Celsius. Through the above calculations, the system can obtain the junction temperature observations of the forward and reverse thyristors in real time, accurately reflecting their respective thermal states even when trigger asymmetry leads to differences in current weights. These precise junction temperature observations will serve as important inputs for subsequent thermo-electric cross-coupling control, ensuring the stable and safe operation of the series compensation device.

[0089] Through the above technical solution, this application can accurately quantify the asymmetric current conduction characteristics caused by the trigger delay time difference between the positive and negative half-waves of the thyristor, and on this basis, observe the junction temperature evolution state of the forward and reverse thyristors in real time and independently. Specifically, by introducing an equivalent current conduction coefficient, the triggering asymmetry at the electrical level is transformed into a direct correction of the current-thermal effect, enabling the junction temperature calculation to accurately reflect the real thermal stress borne by the thyristor in different directions. Furthermore, the junction temperature recursive observation model constructed based on this equivalent current conduction coefficient can dynamically balance the temperature rise of the heat source inside the thyristor and the temperature drop of heat dissipation to the environment, thereby providing high-precision junction temperature observation values ​​for both forward and reverse thyristors. This precise junction temperature observation capability overcomes the limitation of traditional methods that cannot directly quantify the real thermal stress based solely on the trigger delay time difference, significantly improving the accuracy and real-time performance of thyristor thermal state perception. When combined with a fundamental power-impedance closed-loop control model (such as a discretized power-impedance proportional-integral control model), the obtained precise junction temperature observations can serve as reliable thermodynamic feedback quantities, providing a solid data foundation for the subsequent generation of the thermal-electric cross-coupling asymmetric penalty factor and the extraction of thermal inertia feedforward intervention variables. This enables the control system of the series compensation device to more effectively and deeply cross-couple thermal and electrical parameters, achieving refined management of thyristor thermal stress unevenness, thereby improving the operational reliability of the device, extending device life, and effectively avoiding the risk of commutation failure or thermal breakdown due to transient thermal deterioration.

[0090] Preferably, the mechanism for generating the thermal-electric cross-coupling asymmetric penalty factor in S30 is as follows:

[0091] The thermo-electric cross-coupling asymmetric penalty factor is obtained by adding the baseline physical asymmetric gain to the thermo-electric coupling dynamic increment;

[0092] The thermoelectric coupling dynamic increment is the product of the absolute junction temperature difference between the forward and reverse thyristors and the thermoelectric coupling sensitivity coefficient, which is used to characterize the negative feedback depth of asymmetric thermal stress on the control system.

[0093] Specifically, in step S30, the specific calculation formula for generating the thermal-electric cross-coupling asymmetric penalty factor is as follows:

[0094]

[0095] in, This represents the asymmetric penalty factor for thermal-electrical cross-coupling. Indicates the reference physical asymmetric gain. It represents the thermoelectric coupling sensitivity coefficient (in units of one part per Celsius). and These represent the observed junction temperatures (in degrees Celsius) of the forward and reverse thyristors, respectively. This represents the absolute junction temperature difference between the forward and reverse thyristors (in degrees Celsius). This represents the dynamic increment of thermoelectric coupling;

[0096] The method for calculating the corrected target equivalent impedance in S30 is as follows:

[0097] The modified target equivalent impedance is the product of the base target equivalent impedance and the asymmetric amplification factor;

[0098] The asymmetric amplification factor is an amplification function with a base of 1, and its super-base increment is positively correlated with the thermal-electric cross-coupling asymmetric penalty factor, and is positively proportional to the square of the ratio of the thyristor positive and negative half-wave trigger delay time difference to the fundamental period.

[0099] Specifically, in S30, the specific calculation formula for calculating the corrected target equivalent impedance using the thermal-electric cross-coupling asymmetric penalty factor is as follows:

[0100]

[0101] in, This indicates the corrected target equivalent impedance (in ohms). This represents the basic target equivalent impedance (in ohms). This represents the asymmetric penalty factor for thermal-electrical cross-coupling. This indicates the time difference between the positive and negative half-wave triggering delays of the thyristor (in seconds). Indicates the fundamental frequency period (in seconds). Indicates the asymmetric magnification factor. This represents the incremental portion of the superbase.

[0102] Among them, the thermal-electric cross-coupling asymmetric penalty factor This is a dynamically adjusted coefficient used to quantify the impact of thyristor forward and reverse thermal imbalance on the system's electrical characteristics. It reflects the strength of the correction required to the target equivalent impedance under specific operating conditions due to thermal stress asymmetry. As a feedback mechanism, it transforms the thermal state difference of the thyristor into a correction signal for the electrical control quantity. (Reference physical asymmetry gain) This refers to the gain resulting from the inherent physical asymmetry of the system, independent of its thermal state. Even under ideal thermal symmetry conditions, some electrical asymmetry may still exist due to factors such as device manufacturing tolerances and circuit layout. To compensate for this reference asymmetry, a basic, constant asymmetry correction is provided. This gain can be determined through experimental testing or simulation analysis, or it can be set based on empirical values. Thermoelectric coupling sensitivity coefficient. This coefficient characterizes the sensitivity of the thyristor junction temperature difference change to the thermoelectric coupling asymmetry penalty factor. It determines the magnitude of the dynamic increment in thermoelectric coupling caused by a unit change in junction temperature difference and is used to adjust the contribution weight of the junction temperature difference to the penalty factor. This coefficient can be calibrated using the device's thermal characteristic curves, simulation models, or actual operating data, or it can be adjusted online using optimization algorithms. The specific steps for calibration using actual operating data are as follows: First, allow the thyristor valve group to operate under perfectly ideal and symmetrical triggering conditions (trigger delay time difference...). = 0) Operation, measuring the reference physical asymmetry gain of the system due to inherent factors such as manufacturing tolerances. In the control driver, a stepped trigger delay time difference is manually set (e.g., setting...). (The intervals are 0.1ms, 0.2ms, 0.5ms, etc.). This asymmetric triggering leads to uneven heating of the forward and reverse thyristors. After the system reaches thermal steady state, the absolute junction temperature difference of multiple sets of forward and reverse thyristors is recorded. Under each set of manually defined junction temperature difference conditions, the impedance correction of the system is adjusted manually or through a high-precision outer loop control algorithm until the system can both meet the electrical compensation requirements and prevent further deterioration of thermal imbalance. The corresponding thermal-electric cross-coupling asymmetric penalty factor is recorded at this point. According to the formula Multiple sets of measured data were plotted on a two-dimensional coordinate system (X-axis for absolute junction temperature difference, Y-axis for dynamic penalty factor). Linear regression fitting was performed using the least squares method to obtain a straight line. The slope of this line is the calibrated thermoelectric coupling sensitivity coefficient. The absolute junction temperature difference between forward and reverse thyristors This quantifies the degree of thermal imbalance between the forward and reverse thyristors within the current sampling period. It is the absolute value of the difference between the observed junction temperatures of the two thyristors, serving as a thermodynamic feedback quantity. This directly reflects the thermal stress asymmetry of the thyristors and is the core input for generating the thermal-electrical cross-coupling asymmetry penalty factor. This junction temperature difference is obtained by real-time monitoring or estimation of the junction temperatures of the forward and reverse thyristors, followed by difference calculation. (Corrected target equivalent impedance) Based on the equivalent impedance of the basic target Based on this, the final target equivalent impedance, after nonlinear correction by the thermo-electric cross-coupling asymmetric penalty factor, comprehensively considers the system's active power regulation requirements and the thyristor's thermal imbalance state. It serves as the basis for subsequent firing angle generation, ensuring that the series compensation device meets electrical performance requirements while also balancing the thyristor's thermal stress. This impedance is obtained by multiplying the basic target equivalent impedance by the asymmetric amplification factor. (Asymmetric amplification factor) This is a dynamically changing multiplicative factor used to nonlinearly amplify or correct the equivalent impedance of the base target. This coefficient consists of 1 plus the super-base increment, where the super-base increment reflects the combined effect of the thermoelectric coupling asymmetry penalty factor and the trigger delay time difference. Based on the thyristor's thermal imbalance and trigger asymmetry, the target equivalent impedance is dynamically adjusted to achieve thermo-electric synergistic control. This coefficient is obtained by calculating the square of the thermo-electric cross-coupling asymmetry penalty factor and the trigger delay time difference, followed by addition and multiplication operations. (Super-base increment) It is the dynamic incremental part of the asymmetric amplification factor other than the reference value of 1. It is composed of the thermal-electric cross-coupling asymmetric penalty factor. The square of the difference between the normalized trigger delay time and the normalized trigger delay time Multiplying these values ​​yields a quantified amount of additional correction to the equivalent impedance of the basic target under the combined effects of thermal imbalance and triggering asymmetry.

[0103] This application's solution achieves a leap from simple electrical control to thermo-electric synergistic control by introducing a thermo-electric cross-coupling mechanism. First, the absolute junction temperature difference between the forward and reverse thyristors is calculated and used as a thermodynamic feedback quantity. Combined with the reference physical asymmetry gain and the thermo-electric coupling sensitivity coefficient, a thermo-electric cross-coupling asymmetric penalty factor is generated. The significance of this process lies in quantifying the thermal stress imbalance state inside the thyristor into a controllable penalty factor, thereby capturing the potential impact of the thermal state on electrical performance. Subsequently, this penalty factor is used to nonlinearly correct the basic target equivalent impedance, introducing an asymmetric amplification factor based on the square of the trigger delay time difference. This correction method not only considers the direct electrical deviation caused by the trigger delay but also transforms the degree of thermal imbalance into a correction quantity for impedance adjustment through the penalty factor, enabling the final corrected target equivalent impedance to dynamically adapt to changes in the thyristor's thermal state. Through this thermo-electric cross-coupling nonlinear correction, the system can actively compensate for impedance control deviations caused by uneven thermal stress, thereby suppressing the interference of thermal imbalance on the output performance of the series compensation device at its source.

[0104] The following is a concrete example to illustrate this. Suppose that in a certain sampling period... The observed junction temperature of the forward thyristor was calculated using the above method. The observed junction temperature of the reverse thyristor is 85℃. If the absolute junction temperature difference between the forward and reverse thyristors is 80℃, then... The temperature is 5°C, and at the same time, it is assumed that the reference physical asymmetric gain is 5°C. Thermoelectric coupling sensitivity coefficient is set to 0.01. If set to 0.005 (1 / ℃), then the thermal-electric cross-coupling asymmetric penalty factor is... It can be calculated as follows: Furthermore, assuming the current sampling period... Thyristor positive and negative half-wave trigger delay time difference The fundamental period of the system's alternating current is 0.0005 seconds. If it is 0.02 seconds, then the square of the normalized trigger delay time difference is... for Superbase incremental part for Asymmetric magnification factor for If the basic target equivalent impedance is obtained through a closed-loop adjustment model... If the value is 10 ohms, then the corrected target equivalent impedance is... It can be calculated as follows: Ohm. This corrected impedance. This will serve as input for subsequent steps, thereby incorporating the effects of thermal imbalance and electrical asymmetry into the final control decision.

[0105] Through the above technical solution, this application can dynamically quantify the thermal stress imbalance state of the thyristor by combining the absolute junction temperature difference—the thermodynamic feedback quantity—between the observed junction temperatures of the forward and reverse sides of the thyristor with the reference physical asymmetry gain and the thermoelectric coupling sensitivity coefficient. Based on this, the penalty factor is used to nonlinearly correct the basic target equivalent impedance, generating a corrected target equivalent impedance. This correction method not only considers the direct electrical deviation caused by the trigger delay time difference between the positive and negative half-waves of the thyristor, but more importantly, it transforms the degree of thermal imbalance into a correction quantity for impedance adjustment through the penalty factor. This allows the final corrected target equivalent impedance to dynamically adapt to changes in the thermal state of the thyristor, thereby achieving deep thermo-electric cross-coupling in the electrical control loop. Through this nonlinear correction of thermo-electric cross-coupling, the system can actively compensate for impedance control deviations caused by uneven thermal stress, effectively suppressing the interference of thermal imbalance on the output performance of the series compensation device, and significantly improving the control robustness and operational reliability of the device under complex operating conditions.

[0106] Preferably, in step S40, the mechanism for calculating the real-time evolution rate and the basic trigger angle includes:

[0107] The real-time evolution rate is equal to the ratio of the highest temperature value in the current cycle of the bidirectional thyristor minus the highest temperature value in the previous cycle to the discrete sampling cycle.

[0108] The basic firing angle is obtained by nonlinear quadratic polynomial mapping of the corrected target equivalent impedance, which includes a constant bias term, a linear term based on the corrected target equivalent impedance, and a quadratic parabolic term.

[0109] Specifically, in S40, the specific calculation formulas for calculating the real-time evolution rate and generating the basic firing angle based on the corrected target equivalent impedance mapping are as follows:

[0110]

[0111]

[0112] in, This indicates the real-time evolution rate (in degrees Celsius per second). and This represents the observed junction temperature for the current period (in degrees Celsius). and This represents the observed junction temperature value (in degrees Celsius) from the previous cycle. Indicates the discrete sampling period (in seconds). Indicates the base trigger angle (in radians). This represents the constant term (constant bias term, in radians) of the fitted polynomial. This represents the coefficients of the first-order term of the fitted polynomial (in radians per ohm). This represents the coefficients of the quadratic term in the fitted polynomial (in radians per square ohm). This indicates the corrected target equivalent impedance (in ohms). This represents a linear term based on the corrected target equivalent impedance. This represents the quadratic parabolic term based on the corrected target equivalent impedance.

[0113] The control logic in S40 for generating the feedforward pre-compensation phase angle and synthesizing the final target trigger angle is as follows:

[0114] When the real-time evolution rate is less than or equal to zero, the thermal inertia feedforward pre-compensation angle is zero.

[0115] When the real-time evolution rate is greater than zero, the thermal inertia feedforward pre-compensation angle is activated, and its magnitude is equal to the product of the real-time evolution rate, the thermal inertia feedforward coefficient, and the impedance state margin ratio; the impedance state margin ratio is the ratio of the corrected target equivalent impedance to the maximum reference static impedance.

[0116] The final target trigger angle is the sum of the base trigger angle and the thermal inertia feedforward pre-compensation angle. When the sum is less than the minimum allowable trigger angle, the final target trigger angle is hard-bounded and truncated at the minimum allowable trigger angle.

[0117] Specifically, in S40, the specific calculation process for generating the feedforward pre-compensation phase angle and synthesizing the final target trigger angle is as follows:

[0118]

[0119]

[0120] in, This represents the thermal inertia feedforward pre-compensation angle (in radians). It represents the thermal inertia feedforward coefficient (unit: seconds-radians per degree Celsius (s·rad / ℃)). This indicates the real-time evolution rate (in degrees Celsius per second). This indicates the corrected target equivalent impedance (in ohms). This represents the maximum reference static impedance (in ohms). Indicates the final target trigger angle (in radians). Indicates the minimum permissible trigger angle (in radians). Indicates the base trigger angle (in radians). This indicates the impedance state margin ratio.

[0121] In step S40 of this method, the real-time evolution rate is first calculated, and the basic firing angle is generated based on the modified target equivalent impedance mapping. The real-time evolution rate... This refers to the thyristor with the highest junction temperature in the thyristor valve group during the current discrete sampling period. The rate of change of junction temperature within the thyristor serves to quantify the transient trend of thermal stress, providing a dynamic and real-time basis for subsequent thermal feedforward control. This rate can be acquired in real time by a digital signal processor (DSP) or microcontroller (MCU) for the current cycle. Compared to the previous cycle Observed junction temperature of forward thyristor , and the observed junction temperature of the reverse thyristor , After performing a difference operation, divide by the discrete sampling period. Obtained. Base trigger angle. It is based on the corrected target equivalent impedance Calculated using a polynomial approximation method, it represents the thyristor firing angle required to achieve the target equivalent impedance without considering thermal inertia feedforward interference. Its function is to provide an accurate reference firing angle directly related to the electrical quantity (impedance), ensuring the basic electrical control functions of the series compensation device. This base firing angle can be obtained by pre-storing a set of corrected target equivalent impedances derived from experimental data or simulation models in the control system. With base trigger angle The corresponding data points are obtained, and the constant term of the fitting polynomial is obtained using the least squares method or other curve fitting algorithms. coefficient of the first term and quadratic coefficient In actual operation, the results will be calculated in real time. Substituting into the polynomial yields the following result. .

[0122] Further, in step S40, the feedforward pre-compensation phase angle is generated and the final target firing angle is synthesized. (Feedforward pre-compensation phase angle) Based on real-time evolution rate and impedance state margin ratio Dynamically generated, this system adjusts the firing angle in advance when the thyristor junction temperature shows an upward trend, actively suppressing further increases in junction temperature. Its function is to introduce thermal inertia feedforward control, enabling proactive early warning and intervention of thyristor thermal stress. The control system can acquire data in real time. and ,when When it is greater than zero, With thermal inertia feedforward coefficient and impedance state margin ratio Multiply, we get .like If not greater than zero, then Set to zero. Final target trigger angle. It is the base trigger angle Phase angle with feedforward pre-compensation The final control command, synthesized and then subjected to physical boundary limiting, ensures that the output firing angle meets both electrical control requirements and the predictability of thermal protection, while remaining within the physical limits of safe thyristor operation. In the control algorithm, the calculated base firing angle is first... Phase angle with feedforward pre-compensation The results are then superimposed, and the superimposed result is compared with the preset minimum allowable trigger angle. Compare the two values ​​and take the larger one as the average. Besides the lower limit and amplitude limit In addition, an upper limit limit can be introduced, such as the maximum allowed trigger angle. ,make sure Always fall Within the range.

[0123] The solution in this application deeply integrates the transient thermal characteristics of the thyristor with the electrical control circuit through the aforementioned mechanism. Firstly, it achieves this by real-time monitoring of the forward and reverse junction temperatures of the thyristor. and Combined with the junction temperature observations from the previous cycle and The real-time evolution rate of the thyristor valve group was calculated. This rate quantifies the transient change trend of thyristor thermal stress, providing a crucial input for subsequent dynamic compensation. Simultaneously, the system calculates the target equivalent impedance based on the thermal-electric cross-coupling asymmetric penalty factor. By using a pre-established polynomial approximation model, the basic trigger angle is accurately mapped and generated. This basic firing angle serves as the electrical reference for achieving the target equivalent impedance, ensuring the fundamental electrical control functions of the series compensation device. Building upon this, this method further utilizes the calculated real-time evolution rate. and corrected target equivalent impedance With maximum reference static impedance The ratio (i.e., impedance state margin ratio) generates the thermal inertia feedforward pre-compensation angle. When an upward trend in junction temperature is detected (i.e.) When the junction temperature changes, the pre-compensation angle is activated and dynamically adjusted based on the rate of junction temperature evolution and the impedance state margin. This design allows the control system to predict the deterioration trend of the thyristor junction temperature and take preventative measures. Finally, this dynamically generated thermal inertia feedforward pre-compensation angle is... With base trigger angle The composite image is then processed and limited by physical boundaries to obtain the final target trigger angle. This final target trigger angle The design comprehensively considers electrical control requirements and predictable thermal protection, ensuring that the thyristors operate within a safe operating range. Real-time evolution rate. The introduction of this feature enables the control system to shift from passive static temperature threshold protection to active dynamic thermal early warning. When the thyristor junction temperature rises rapidly, the feedforward pre-compensation angle... The trigger angle is adjusted promptly, thereby reducing thermal stress on the thyristor by changing its conduction state before the junction temperature reaches a dangerous threshold. This effectively avoids the problem of lag response and potential thermal breakdown that can occur with traditional control strategies under extreme conditions. This strategy, which combines thermal inertia feedforward intervention variables with the corrected target equivalent impedance to generate a feedforward pre-compensation phase angle and synthesize it with the base trigger angle, enables the series compensation device to not only respond to power changes in the power grid but also actively manage the thermal state of the thyristor.

[0124] The following is a concrete example. In the controller of a series compensation device, a high-performance digital signal processor (DSP), such as the TI TMS320F28379D series DSP, can be used as the core control unit. This DSP possesses powerful floating-point arithmetic capabilities and abundant on-chip peripherals, enabling it to execute complex control algorithms in real time. In step S40, to calculate the real-time evolution rate... The DSP will use a preset discrete sampling period. (e.g., 1 millisecond) Read the current cycle from memory Compared to the previous cycle Observed junction temperature of forward thyristor , , and These junction temperature observations can be recursively calculated using the thermal model described in the preceding steps. The DSP determines the highest junction temperature in the current and previous cycles by comparing the current and reverse junction temperatures, as well as the previous cycle's forward and reverse junction temperatures. For example, if... 100℃ If the temperature is 95℃, then the current highest junction temperature is 100℃. If... It is 98℃. If the temperature is 93℃, then the highest junction temperature in the previous cycle was 98℃. Then, the DSP performs subtraction and division operations to calculate... °C / second. Simultaneously, the DSP will adjust the target equivalent impedance based on the current correction. To generate the basic trigger angle Assume that the constant term of the fitting polynomial has been obtained through offline fitting. coefficient of the first term and quadratic coefficient ,For example, It can be 1.5 radians. It can be 0.05 radians / ohm. It can be -0.001 radians per square ohm. If the current... If it is 10 ohms, then the DSP calculates... Radius. Next, the DSP calculates... and Generate feedforward pre-compensation phase angle Assuming thermal inertia feedforward coefficient Maximum reference static impedance is 0.0001 s·radians / degrees Celsius. It is 20 ohms, because The DSP will calculate Radius. Finally, the DSP will determine the base trigger angle. Phase angle with feedforward pre-compensation Perform the synthesis. Assume the minimum allowable firing angle. It is 1.8 radians. DSP calculation. Radius. Then, the DSP performs a limiting operation. Radius. This is the final target trigger angle. It will then be sent to the thyristor's trigger execution unit to control the thyristor's conduction.

[0125] Through the above technical solution, this application effectively solves the technical problem that under extreme conditions such as power surges or short circuits in transmission lines, the thyristor junction temperature undergoes rapid transient evolution, and traditional control systems suffer from lag in response, making it impossible to effectively and proactively intervene in thermal breakdown. Specifically, this method dynamically captures the transient change trend of thyristor thermal stress by calculating the real-time evolution rate, providing the control system with forward-looking thermal state information. Based on this, by combining the modified target equivalent impedance to generate a thermal inertia feedforward pre-compensation angle, the control system can adjust the thyristor firing angle in advance when the junction temperature deterioration trend becomes apparent, thereby actively suppressing further increases in junction temperature. This control strategy, which deeply integrates the thermal evolution rate with the impedance state, realizes the transformation from passive thermal protection to proactive thermal early warning, significantly enhancing the thermal stability and operational reliability of the series compensation device in complex power grid environments, and effectively avoiding the risk of thyristor commutation failure or thermal breakdown due to excessive thermal stress.

[0126] Preferably, in this embodiment, a certain Taking the Controllable Series Compensator (TCSC) deployed in an AC transmission system as an example, this demonstrates how it performs in a single control interruption (the first... Within a discrete sampling period, the controller executes the complete quantization calculation process of the control algorithm of the present invention (steps S10-S40).

[0127] Substituting the system's initial state and preset parameters, at the... When a discrete sampling period is triggered, the underlying module of the control system reads the following sensor data and preset system parameters:

[0128] Power grid and operating parameters: Discrete sampling period (Right now (Control frequency); fundamental period (Right now ); Expected active power Real-time active power in the current period Historical cumulative power deviation integral term ; RMS current of thyristor branch .

[0129] Hardware physical and thermodynamic parameters: Time difference between positive and negative half-wave triggering delays Ambient temperature thyristor equivalent on-resistance Equivalent thermal resistance Equivalent heat capacity (Note: Previous cycle) Junction temperature observation: positive reverse ).

[0130] Controller preset adjustment coefficient: initial reference static impedance Maximum impedance of the device proportionality coefficient Integral coefficient Thermoelectric coupling sensitivity coefficient Reference asymmetric gain Thermal inertia feedforward coefficient .

[0131] Mapping polynomial parameters: constant term , one item quadratic term Physical limit minimum trigger angle .

[0132] Detailed calculation steps and process

[0133] S10: Calculation of the equivalent impedance of the basic target based on transmission power error

[0134] According to the closed-loop control formula:

[0135]

[0136] Proportional adjustment item: ;

[0137] Integral adjustment item: ;

[0138] Calculation results: ;

[0139] S20: Independently recursive junction temperature observations in both forward and reverse directions

[0140] 1. Calculate the equivalent flow weight:

[0141] Time difference percentage: ;

[0142] Positive coefficient: ;

[0143] Reverse coefficient: .

[0144] 2. Forward junction temperature recursive calculation:

[0145] Forward heating power: ;

[0146] Positive temperature increase increment: ;

[0147] Forward heat dissipation reduction: ;

[0148] Forward junction temperature update: .

[0149] 3. Reverse junction temperature recursive calculation:

[0150] Reverse heating power: ;

[0151] Reverse temperature rise increment: ;

[0152] Reverse heat dissipation reduction: ;

[0153] Reverse junction temperature update: .

[0154] S30: Thermal-electric cross-coupling correction

[0155] 1. Calculate the thermoelectric coupling asymmetry penalty factor:

[0156] Absolute junction temperature difference: ;

[0157] Punishment factor: .

[0158] 2. Calculate the corrected target equivalent impedance:

[0159] Asymmetric magnification factor: ;

[0160] Corrected impedance: .

[0161] S40: Thermal Feedforward Intervention and Output

[0162] 1. Calculate the real-time evolution rate:

[0163] The current highest junction temperature is positive. The highest junction temperature in the previous cycle was positive. .

[0164] Evolution rate: .

[0165] 2. Calculate the base firing angle:

[0166]

[0167] 3. Calculate the feedforward pre-compensation phase angle (because...) (Trigger activation):

[0168] Impedance margin ratio: ;

[0169] Compensation angle: .

[0170] 4. Synthesize and limit the final trigger angle output:

[0171] Target trigger angle: .

[0172] A controller for a series compensation device employs the control method described above for the series compensation device.

[0173] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A control method for a series compensation device, characterized in that, include: S10. Extract the deviation between the real-time active power and the expected active power of the transmission line in the current discrete sampling period, and obtain the basic target equivalent impedance required by the series compensation device through the closed-loop adjustment model. S20. Obtain the trigger delay time difference between the positive and negative half-waves of the thyristor. Based on the asymmetric current conduction characteristics characterized by the trigger delay time difference, determine the equivalent current conduction weights of the forward thyristor and the reverse thyristor respectively, and independently recursively obtain the observed junction temperature values ​​of the forward thyristor and the reverse thyristor in the current cycle. S30. Extract the absolute junction temperature difference between the observed junction temperature of the forward thyristor and the observed junction temperature of the reverse thyristor as a thermodynamic feedback quantity, generate the thermo-electric cross-coupling asymmetric penalty factor, and use the thermo-electric cross-coupling asymmetric penalty factor to perform nonlinear correction on the basic target equivalent impedance to obtain the corrected target equivalent impedance. S40. Extract the real-time evolution rate of the highest junction temperature of the thyristor valve group as the thermal inertia feedforward intervention variable. Combine the real-time evolution rate with the corrected target equivalent impedance to generate the feedforward pre-compensation phase angle. Combine the feedforward pre-compensation phase angle with the basic trigger angle generated based on the corrected target equivalent impedance mapping. After physical boundary limiting, output the final target trigger angle and trigger the execution unit to execute.

2. The control method for the series compensation device according to claim 1, characterized in that, In step S10, when calculating the basic target equivalent impedance, the basic target equivalent impedance is a linear superposition of the initial reference static impedance, the power deviation proportional adjustment term, and the power deviation integral adjustment term. The power deviation proportional adjustment term is directly proportional to the proportional adjustment coefficient and the deviation between the real-time active power and the expected active power in the current sampling period; the power deviation integral adjustment term is directly proportional to the integral adjustment coefficient, the discrete sampling period, and the cumulative amount of active power deviation from the past to the current sampling period.

3. The control method for the series compensation device according to claim 1, characterized in that, The method for determining the equivalent current weights of the forward and reverse thyristors in S20 is as follows: The equivalent current-carrying coefficient of the forward thyristor and the equivalent current-carrying coefficient of the reverse thyristor are both based on the reference half-wave conduction weight. The equivalent current-carrying coefficient of the forward thyristor is the reference half-wave conduction weight minus the asymmetric offset, and the equivalent current-carrying coefficient of the reverse thyristor is the reference half-wave conduction weight plus the asymmetric offset. The asymmetric offset is positively correlated with the ratio of the thyristor's positive and negative half-wave trigger delay time difference to the fundamental period of the system's AC current.

4. The control method for the series compensation device according to claim 3, characterized in that, The method for independently recursively obtaining the observed values ​​of the forward and reverse thyristor junction temperatures for the current cycle in S20 is as follows: The current period's forward thyristor junction temperature observation value is obtained by superimposing the previous period's forward thyristor junction temperature observation value with the heat source temperature rise increment during the current sampling period, and subtracting the environmental heat dissipation temperature drop decrease during the current sampling period. The temperature rise increment of the heat source is positively correlated with the product of the equivalent current coefficient of the forward thyristor and the square of the effective current of the thyristor branch, and is directly proportional to the equivalent on-resistance of the thyristor and inversely proportional to the equivalent heat capacity. The reduction in ambient heat dissipation temperature drop is positively correlated with the temperature difference between the observed value of the forward thyristor junction temperature in the previous cycle and the external ambient temperature, and is inversely proportional to the equivalent thermal resistance and equivalent heat capacity. The junction temperature observation value of the reverse thyristor is obtained synchronously and recursively in the same way as that of the forward thyristor, combined with the equivalent current coefficient of the reverse thyristor.

5. The control method for the series compensation device according to claim 1, characterized in that, The mechanism for generating the thermo-electric cross-coupling asymmetric penalty factor in S30 is as follows: The thermo-electric cross-coupling asymmetric penalty factor is obtained by adding the baseline physical asymmetric gain to the thermo-electric coupling dynamic increment; The thermoelectric coupling dynamic increment is the product of the absolute junction temperature difference between the forward and reverse thyristors and the thermoelectric coupling sensitivity coefficient, which is used to characterize the negative feedback depth of asymmetric thermal stress on the control system.

6. The control method for the series compensation device according to claim 5, characterized in that, The method for calculating the corrected target equivalent impedance in S30 is as follows: The modified target equivalent impedance is the product of the base target equivalent impedance and the asymmetric amplification factor; The asymmetric amplification factor is an amplification function with a base of 1, and its super-base increment is positively correlated with the thermal-electric cross-coupling asymmetric penalty factor, and is positively proportional to the square of the ratio of the thyristor positive and negative half-wave trigger delay time difference to the fundamental period.

7. The control method for the series compensation device according to claim 1, characterized in that, In step S40, the mechanism for calculating the real-time evolution rate and the basic trigger angle includes: The real-time evolution rate is equal to the ratio of the highest temperature value in the current cycle of the bidirectional thyristor minus the highest temperature value in the previous cycle to the discrete sampling cycle. The basic firing angle is obtained by nonlinear quadratic polynomial mapping of the corrected target equivalent impedance, which includes a constant bias term, a linear term based on the corrected target equivalent impedance, and a quadratic parabolic term.

8. The control method for the series compensation device according to claim 7, characterized in that, The control logic in S40 for generating the feedforward pre-compensation phase angle and synthesizing the final target trigger angle is as follows: When the real-time evolution rate is less than or equal to zero, the thermal inertia feedforward pre-compensation angle is zero. When the real-time evolution rate is greater than zero, the thermal inertia feedforward pre-compensation angle is activated, and its magnitude is equal to the product of the real-time evolution rate, the thermal inertia feedforward coefficient, and the impedance state margin ratio; the impedance state margin ratio is the ratio of the corrected target equivalent impedance to the maximum reference static impedance. The final target trigger angle is the sum of the base trigger angle and the thermal inertia feedforward pre-compensation angle. When the sum is less than the minimum allowable trigger angle, the final target trigger angle is hard-bounded and truncated at the minimum allowable trigger angle.

9. A controller for a series compensation device, characterized in that, The control method of the series compensation device according to any one of claims 1-8 is adopted.

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