Digital control method for split-phase voltage regulation voltage stabilizer based on silicon controlled rectifier gear switching

Abstract

The invention discloses a digital control method for a split-phase voltage-regulating voltage stabilizer based on silicon controlled gear switching, and relates to the technical field of voltage-regulating voltage stabilizer control. The method comprises the following steps: executing closed-loop control in each power supply cycle in a gear switching transition period: pre-judging a circulation increment according to initial trigger angles of a new gear and an old gear, and comparing the circulation increment with a safety threshold; if the threshold is exceeded, calculating a critical overlapping starting angle, segmenting an overlapping conduction interval by taking the critical overlapping starting angle as an anchor point, calculating a residual ratio, and selecting a segmentation correction strategy to correct the initial trigger angle; calculating an effective energy transmission proportion reflecting an actual transition progress based on the corrected trigger angle, and adaptively generating a target weight of a next power cycle based on the effective energy transmission proportion; monotonicity and saturation constraints are applied to the target weight to obtain an execution weight, the execution weight is mapped into an initial trigger angle of a next power supply cycle, and a cycle-by-cycle closed loop is formed; and when the execution weight reaches a final value, executing steady state locking to complete switching. The circulating current is safe and controllable, and the transition process is smooth and free of impact.

Description

Technical Field

[0001] This invention relates to the field of voltage regulator control technology, and more specifically, to a digital control method for phase-by-phase voltage regulators based on thyristor range switching. Background Technology

[0002] In a phase-splitting voltage regulator based on thyristor switching, in order to achieve a smooth transition of the output voltage, it is necessary to control the old and new thyristors to conduct alternately during the switching process. During this process, due to the voltage difference between the two transformer tap windings and the existence of loop leakage inductance, circulating current will be generated between the two windings. Excessive circulating current will not only increase the losses and thermal stress of the devices and transformers, but may also damage the thyristors or cause protection to activate, affecting the continuity of power supply. In existing technologies, fixed safety thresholds or fixed time-angle switching curves are often used to control circulating current. However, these methods have significant shortcomings: in the initial stage of switching, the system has a relatively strong capacity to withstand circulating current, and fixed thresholds or overly conservative curves can limit the transition speed, resulting in a slow switching process. In the final stage of switching, when the old mode is about to be phased out, the circulating current needs to be suppressed to an extremely low level to prevent interference. Fixed thresholds or curves may not be able to effectively suppress the circulating current due to insufficient margin, causing shocks. In addition, due to factors such as load changes and power grid fluctuations, the preset fixed switching trajectory is prone to deviating from the dynamic response of the actual system, resulting in an unsmooth transition process and fluctuations or steps in the output voltage. To address the above problems, this invention proposes a solution. Summary of the Invention

[0003] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a digital control method for a phase-by-phase voltage regulator based on thyristor range switching, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: The digital control method for a phase-splitting voltage regulator based on thyristor range switching includes the following steps: During each power cycle of the range switching transition period, the overlapping conduction interval and its overlap start angle of the two ranges are determined according to the initial trigger angle set for the new range and the old range. The voltage difference within the overlapping conduction interval is integrated and combined with the sum of the leakage inductance of the windings of the new and old ranges to calculate the predicted value of the circulating current increment. The predicted value of the circulating current increment is compared with the safety threshold. When the predicted value of the circulating current increment exceeds the safety threshold, it is determined to be an over-limit state and the critical overlap start angle is calculated. Using the critical overlap start angle as the anchor point, the overlapping conduction interval is divided into the first sub-segment and the second sub-segment. The residual ratio is calculated based on the critical overlap start angle. Based on the comparison result between the residual ratio and the residual ratio judgment threshold, the dominant correction strategy of the subsequent conduction level or the two-level collaborative correction strategy is selected to correct the initial trigger angle and output the corrected trigger angle. Based on the corrected trigger angle, the actual conduction angle span of the old and new stages is calculated respectively, and the effective energy transmission ratio reflecting the actual power supply ratio of the new stage is obtained. The effective energy transmission ratio is used as the starting point of trajectory planning. The difference between the starting point of trajectory planning and the transition final value weight is evenly distributed in the remaining cycles to obtain the adaptive weight increment, which is added to the effective energy transmission ratio to obtain the target weight of the next power supply cycle. The execution weight is obtained by applying monotonicity and saturation constraints to the target weight. The execution weight is then mapped to the initial trigger angle of the next cycle through a complementary conduction strategy. When the execution weight reaches the transition terminal weight, steady-state locking is performed to complete the gear shift transition.

[0005] In a preferred embodiment, the initial trigger angle for the new gear and the old gear is obtained as follows: when the gear switching transition period is in the first power cycle, the transition weight of the first power cycle is set to 1 divided by the total number of power cycles in the transition period. The initial trigger angle of the new gear in the first power cycle is equal to the difference between the natural turn-off phase multiplied by 1 and the transition weight of the first power cycle. The initial trigger angle of the old gear is equal to the natural turn-off phase multiplied by the transition weight of the first power cycle. The initial trigger angle of the second power cycle and subsequent power cycles during the gear switching transition period is determined by the execution weight of the previous power cycle output. The initial trigger angle of the new gear is equal to the difference between the natural shutdown phase multiplied by 1 and the execution weight of the previous power cycle, and the initial trigger angle of the old gear is equal to the natural shutdown phase multiplied by the execution weight of the previous power cycle.

[0006] In a preferred embodiment, the circulating current increment prediction value is calculated as follows: the overlap start angle is obtained by taking the larger of the initial trigger angles of the new and old gears; the voltage difference within the overlap conduction interval is integrated from the overlap start angle to the natural turn-off phase to obtain the volt-second product, which is equal to the quotient of the peak voltage difference divided by the power frequency angular frequency, and then multiplied by the cosine of the overlap start angle minus the cosine of the natural turn-off phase, and the peak voltage difference is the absolute value of the difference between the peak voltage of the new gear tap and the peak voltage of the old gear tap; the volt-second product is divided by the sum of the leakage inductance of the new and old gear windings to obtain the circulating current increment prediction value; wherein, the overlap conduction interval is the intersection of the conduction intervals of the new and old gears.

[0007] In a preferred embodiment, the safety threshold is designed as a sequence that decreases with the power supply cycle number. The safety threshold of the nth power supply cycle is equal to the product of the initial threshold coefficient and the rated current, minus the product of the decreasing step size coefficient, the rated current and the difference between the power supply cycle number and 1. The critical overlap initiation angle is obtained by inversely solving the expression of the circulating current increment prediction value. Specifically, the safety threshold is multiplied by the sum of the power frequency angular frequency and the leakage inductance of the old and new windings, and then divided by the peak voltage difference to obtain the intermediate value. The intermediate value is added to the cosine value of the natural turn-off phase and the inverse cosine is taken as the critical overlap initiation angle.

[0008] In a preferred embodiment, the specific way to divide the overlapping conduction interval into the first sub-segment and the second sub-segment is as follows: the overlapping conduction interval is divided into two consecutive sub-segments with the critical overlap start angle as the dividing point; The starting boundary of the first sub-segment is set to the current overlap initiation angle, and the ending boundary is set to the critical overlap initiation angle; the starting boundary of the second sub-segment is set to the critical overlap initiation angle, and the ending boundary is set to the natural turn-off phase. The voltage difference within the second segment is integrated from the critical overlap initiation angle to the natural turn-off phase to obtain the volt-second product of the second segment; the residual ratio is the ratio of the volt-second product of the second segment to the total volt-second product of the overlap conduction interval. It is calculated by subtracting the cosine of the natural turn-off phase from the cosine of the critical overlap initiation angle, and dividing by the cosine of the current overlap initiation angle minus the cosine of the natural turn-off phase.

[0009] In a preferred embodiment, based on the comparison result between the residual ratio and the residual ratio determination threshold, a post-conduction gear dominant correction strategy or a two-gear collaborative correction strategy is selected. Specifically, based on the relationship between the initial trigger angles of the old and new gears, the gear with the larger trigger angle is determined as the post-conduction gear, and the gear with the smaller trigger angle is determined as the pre-conduction gear. When the residual ratio is not greater than the residual ratio judgment threshold, the subsequent conduction mode is selected as the dominant correction strategy, that is, the trigger angle of the subsequent conduction mode is set as the critical overlap start angle, and the trigger angle of the first conduction mode remains unchanged at its initial value. When the residual ratio is greater than the residual ratio judgment threshold, a two-level collaborative correction strategy is selected. The trigger angle of the subsequent conduction is set as the critical overlap start angle, and then the second sub-segment is further divided to allocate the additional correction amount of the two levels. Based on the preset segmented integral accumulation ratio parameter, the voltage difference function is integrated along the phase angle increase direction from the starting end of the second sub-segment, i.e., the critical overlap start angle. When the integral accumulation value reaches the product of the volt-second product of the second sub-segment and the preset segmented integral accumulation ratio parameter, the corresponding phase angle is the dividing point. The dividing point divides the second sub-segment into a front sub-segment and a rear sub-segment, where the front sub-segment is the interval from the critical overlap start angle to the dividing point, and the rear sub-segment is the interval from the dividing point to the natural turn-off phase. The ratio of the volt-second product of the front sub-segment to the volt-second product of the second sub-segment is used as the additional correction responsibility coefficient of the subsequent conduction, and the ratio of the volt-second product of the rear sub-segment to the volt-second product of the second sub-segment is used as the correction responsibility coefficient of the pilot conduction. The circulating current reduction is determined based on the preset safety margin coefficient, and the additional correction angle of the two levels is allocated according to each responsibility coefficient.

[0010] In a preferred embodiment, the additional correction angle in the two-stage collaborative correction strategy is determined as follows: The reduction in circulating current is equal to the product of the safety margin coefficient and the current cycle safety threshold. The reduction in circulating current is multiplied by the sum of the leakage inductance of the old and new windings and converted into the volt-second product that needs to be eliminated. The volt-second product that needs to be eliminated is then converted into the angle increment that needs to be delayed by the overlap start angle. Introducing indirect effect reduction factor This is used to reflect that the indirect effect of the pilot pass's trigger angle change on the initial boundary of the overlapping section is weaker than the direct effect of the subsequent pass; the additional correction angle of the subsequent pass. Additional correction angle for pilot pass Calculate using the following formulas respectively: ; ; in This is an additional correction liability factor for the subsequent conduction file. The correction liability coefficient for the pilot pass. This requires an additional angle increment to delay the overlap initiation angle; After the trigger angle is corrected by the post-conduction mode After the pilot pass is corrected, the trigger angle is adjusted. They are respectively: ; ; in The initial trigger angle for the pilot pass. The critical overlap start angle is the nth power cycle, where n is the power cycle number.

[0011] In a preferred embodiment, the actual conduction angle span between the old and new stages is calculated based on the corrected firing angle, thereby obtaining the effective energy transfer ratio reflecting the actual power supply ratio of the new stage, specifically: The actual conduction angle span of the new gear is equal to the natural turn-off phase minus the new gear's corrected trigger angle, and the actual conduction angle span of the old gear is equal to the natural turn-off phase minus the old gear's corrected trigger angle; the effective energy transfer ratio is equal to the actual conduction angle span of the new gear divided by the sum of the actual conduction angle spans of the new and old gears, and its value range is between 0 and 1. The adaptive weight increment is calculated by dividing the difference between the transition final value weight and the effective energy transmission ratio by the remaining transition cycles, where the remaining transition cycles are equal to the total power supply cycles during the transition period minus the current power supply cycle number; the target weight for the next power supply cycle is equal to the current effective energy transmission ratio plus the adaptive weight increment.

[0012] In a preferred embodiment, the modification further includes: The trigger angle after the first conduction pass is corrected shall not exceed the trigger angle after the second conduction pass is corrected minus the preset minimum sequence interval. If this constraint is not met, the trigger angle after the first conduction pass is forcibly set to the trigger angle after the second conduction pass is corrected minus the minimum sequence interval, so as to maintain the timing of the first and second conductions without reversal. The modified back conduction trigger angle is used as the new overlap starting angle and substituted into the calculation formula of the circulating current increment prediction value for verification. If the verification result shows that the circulating current still exceeds the safety threshold, the controllability segmentation and correction allocation process is repeated with the modified trigger angle as the new starting point until the circulating current drops below the safety threshold or the maximum number of iterations is reached.

[0013] In a preferred embodiment, the monotonicity constraint is to take the larger value between the target weight and the current effective energy transmission ratio as the execution weight, so as to ensure that the execution weight of the next cycle is not lower than the actual transmission ratio of the current cycle. Saturation constraint limits the upper limit of the execution weight to the weight saturation limit, corresponding to the final state where the new file is fully activated and the old file is completely deactivated; The complementary conduction strategy is that the initial trigger angle of the new frame is equal to the difference between the natural shutdown phase multiplied by 1 and the ratio of the execution weight to the weight saturation limit, and the initial trigger angle of the old frame is equal to the ratio of the natural shutdown phase multiplied by the execution weight to the weight saturation limit. Steady-state locking includes stopping the cycle-by-cycle closed-loop iterative calculation, canceling the trigger signal of the old thyristor, and locking the new thyristor in steady-state operation mode.

[0014] The technical effects and advantages of this invention are as follows: A digital control method for a phase-by-phase voltage regulator based on thyristor range switching. This invention achieves proactive suppression and closed-loop management of circulating current throughout the switching process by accurately predicting the incremental circulating current before each power cycle is executed and comparing it with a dynamically decreasing safety threshold. This effectively prevents equipment damage caused by excessive circulating current. Based on a segmented correction strategy using the critical overlap initiation angle, the optimal correction strategy can be intelligently selected according to the residual ratio, minimizing intervention in the transition process while ensuring safety and guaranteeing switching speed. By observing the transition state in real time through the effective energy transfer ratio and adaptively generating subsequent weights based on this, the control trajectory always closely matches the actual system response, avoiding oscillations or overshoots caused by the disconnect between the preset model and reality, and achieving a truly smooth and shock-free voltage transition. Finally, through a complete closed loop from circulating current safety prediction to trigger angle correction and adaptive weight generation, the discrete switching action of power electronic devices is transformed into a continuous and controllable energy migration process, significantly improving the reliability, stability, and overall system performance of gear switching. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to the present invention. Figure 2 This is a schematic diagram of residual ratio determination and second segment division correction in the digital control method of phase-by-phase voltage regulator based on thyristor range switching of the present invention. Figure 3 This is a schematic diagram of the new and old tap windings and the thyristor trigger control in the digital control method for phase-by-phase voltage regulator based on thyristor range switching of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example

[0018] Please see Figure 1 As shown, this invention discloses a digital control method for a phase-by-phase voltage regulator based on thyristor range switching, comprising the following steps: Step 1: During each power cycle of the gear switching transition period, calculate the overlap start angle of the conduction interval of the two gears based on the initial trigger angle of the old and new gears. Integrate the voltage difference in the overlapping conduction interval and convert it to obtain the circulating current increment prediction value. Compare the circulating current increment prediction value with the safety threshold. When the circulating current increment prediction value exceeds the safety threshold, it is determined to be an over-limit state and the critical overlap start angle is calculated. The purpose of this step is to: before the thyristor triggering of each power cycle during the gear switching transition period, based on the trigger angle values ​​of the old and new gears of the current power cycle, analyze the overlap relationship of the two gear conduction intervals on the power frequency sinusoidal voltage waveform, calculate the integral value of the instantaneous voltage difference between the old and new gear transformer tap windings in the overlapping interval with respect to time, convert this integral value into a predicted value of the circulating current increment to be generated by the power cycle, and compare the predicted value with a preset safety threshold decreasing per power cycle to determine whether the current initial trigger angle combination is safe, providing circulating current over-limit judgment results and correction target parameters for subsequent steps; the transition period mentioned in this invention refers to the time period from the moment the digital controller makes the gear switching decision, for example, switching from gear k to gear k+1, until the new gear completely takes over the load current, i.e., the weight of the new gear reaches 1.0; this transition period consists of several consecutive power frequency cycles, and the total number of power cycles in the transition period is denoted as M; It should be noted that, in this invention, a thyristor refers to the precise control of energy transmission in a power system achieved by controlling the thyristor's on and off states. The thyristor's operating state, i.e., on or off, directly affects the quality and stability of power transmission. Therefore, in the digital control method of this invention, precise adjustment of the power output is achieved based on the adjustment of the thyristor's on-angle. Taps refer to different contacts on a transformer or inductor, which are used to obtain different voltage values ​​or adjust the current distribution. In this invention, taps refer to multiple winding contacts connected to the thyristor circuit, used to adjust the voltage output and current characteristics of the power supply. In the first power cycle of the transition period, i.e., the first power cycle with n=1 and n representing the power cycle number, since the feedback execution weight of the previous power cycle has not yet been generated, the digital controller uses a preset first power cycle transition weight to calculate the initial trigger angle. The first power cycle transition weight is defined as the smallest step unit of the transition process. The specific process for this step is as follows: During the nth power cycle of the transition period, the digital controller determines the initial firing angle of the old circuit based on the transition weight of the current power cycle. And the initial trigger angle of the new file For a thyristor voltage regulator, the conduction range of each thyristor is determined by its firing angle: conduction begins from the phase corresponding to the firing angle and continues until the thyristor naturally turns off due to the current crossing zero. This invention defines the phase corresponding to the turn-off moment as the natural turn-off phase. Once the firing angles of the old and new ranges are known, the conduction range of each range is determined, i.e., from their respective firing phases to their respective natural turn-off phases. Until then; the intersection of two conduction intervals is the overlapping conduction interval. In a phase-controlled voltage regulation topology, two thyristors alternately conduct the same phase load current, and their turn-off is triggered by the zero-crossing of the phase load current. Therefore, they share the same natural turn-off phase, and the characteristics of the overlapping region are entirely determined by its initial boundary, which is equal to the larger of the two trigger angles. This invention defines this initial boundary as the overlap start angle, which is obtained by taking the maximum value of the two trigger angles. ; Within the overlapping conduction range, both the old and new thyristors are in the conducting state, and both transformer tap windings supply voltage to the load circuit. Due to the different tap positions of the old and new taps, there is a difference in the instantaneous voltage between the two windings. This instantaneous voltage difference drives circulating current through the leakage inductance circuit of the two windings. Since the power supply voltage varies sinusoidally, the instantaneous voltage difference between the two windings also varies sinusoidally with the phase angle. Its peak value is equal to the absolute value of the difference between the peak values ​​of the two tap voltages. This invention defines it as the peak voltage difference. ; To quantify the cumulative driving effect of the voltage difference over the entire overlap interval, it is necessary to calculate the integral of the voltage difference with respect to time. This integral value physically corresponds to the total change in magnetic flux applied to the leakage inductance circuit by the voltage difference. This invention defines it as the volt-second product. The larger the volt-second product, the stronger the cumulative driving effect of the voltage difference, and the greater the increase in circulating current. The sinusoidal voltage difference function is analytically integrated from the overlap initiation angle to the natural turn-off phase. In this invention, the natural turn-off phase is denoted as... This represents the phase angle at which the thyristor turns off due to the natural decay and zero crossing of the current within the current power supply cycle; for the same power supply cycle, the natural turn-off phase... Treated as a known constant, it serves as the upper limit of the integral of the voltage difference during the overlapping conduction interval; the natural turn-off phase. It can be obtained by current zero-crossing detection, or estimated by the controller based on load characteristics and historical cycle information; when using voltage zero-crossing approximation, the natural turn-off phase... π can be taken as a special case; let the voltage difference within the overlapping conduction interval be sinusoidal, with its peak value being the peak voltage difference; let the phase angle θ characterize the independent variable of the voltage difference function, then from the overlapping start angle... To the point of phase cutoff The volt-second product is defined as the time integral over the voltage difference: ; Obtained from the analytic integral of the sine function: Where ω is the power frequency angular frequency, representing the angular frequency of the power supply voltage, determined by the measured or nominal value of the power supply frequency; when the natural turn-off phase... When taking π, ; In obtaining the volt-second product Then, the magnitude of the circulating current to be generated by the power supply cycle can be further calculated; according to the volt-ampere characteristic of the inductor, the change in current generated by the volt-second product applied to the leakage inductance circuit is equal to the volt-second product divided by the sum of the leakage inductance of the old and new windings in the circuit; therefore, the above volt-second product... Divide by the sum of the leakage inductance of the old and new windings That is, to obtain the predicted value of the circulating current increment of the power supply cycle. After combining the expression for the volt-second product with the leakage inductance division, the predicted value of the circulating current increment is uniquely determined by four parameters: the peak value of the voltage difference between the old and new voltage levels, the angular frequency, the sum of the leakage inductance, and the overlap initiation angle. Among them, the sum of the leakage inductance of the old and new windings. It is the sum of the nominal values ​​of the leakage inductance of the old and new windings, obtained from the transformer's factory parameters or offline measurement; After obtaining the predicted value of the circulating current increment, a judgment criterion needs to be established to determine whether the predicted value is within an acceptable range. However, this judgment criterion should not use a fixed single threshold, because the transition process itself has the characteristics of dynamic evolution: in the early stage of the transition, the old level still dominates, the new level participates less, and the power imbalance between the two levels makes the system relatively strong in terms of the ability to withstand circulating current. At this time, a larger circulating current can be allowed to ensure the transition speed. As the transition progresses to the middle and late stages, the weight of the new level gradually increases and will eventually take over the power supply completely. At this time, it is necessary to ensure that the old level exits smoothly and does not cause disturbance to the steady-state operation of the new level. Therefore, the circulating current must be reduced to a level close to zero.

[0019] Based on the above analysis, this invention designs the safety threshold as a sequence that decreases with the power supply cycle number. Let M be the total number of power supply cycles during the transition period; then the safety threshold sequence contains M thresholds. The first term of the sequence corresponds to the maximum allowable circulating current in the initial transition phase, determined by the initial threshold coefficient. With rated current The product is determined; the decreasing pattern of the sequence is determined by the decreasing step size coefficient. It is decided that the threshold will decrease by one step for each power frequency advancement, and the safe threshold for the nth power frequency... Expressed as: ; Where the initial threshold coefficient A typical value of 0.12 indicates that the allowable peak circulating current of the first power supply cycle during transition is 12% of the rated current; the decreasing step size factor The typical value is 0.02, which means that the rated current drops by 2% per power supply cycle threshold. This decreasing rule ensures that the allowable circulating current of the power supply cycle at the end of the transition approaches zero, which matches the physical requirement of completely exiting the old range. The rated current is the effective value of the single-phase output rated current of the phase-by-phase voltage regulator in the range to be switched, i.e., the old range or the new range. It is a fixed nameplate parameter of the equipment or a preset storage by the controller. In one optional implementation, the digital controller may also receive voltage sampling signals or current sampling signals for operation status monitoring, protection criteria, and engineering tuning and verification of parameters such as threshold coefficients. It should be noted that the rated current used in the safety threshold sequence may be a preset parameter. The above sampling is not necessary for implementing the present invention, but is only used to improve engineering feasibility and operational robustness, and does not constitute a limitation on the scope of protection of the present invention. And predict the incremental value of circulation The absolute safety threshold of the current power frequency Comparison: when When the current initial firing angle combination is determined to be in a safe state, the digital controller directly uses the old initial firing angle. And the initial trigger angle of the new file Execute the thyristor trigger. This step outputs a safety flag and does not proceed to the subsequent correction process. Proceed directly to step three. when When the current initial trigger angle combination is determined to be in an over-limit state, the trigger angle needs to be adjusted to compress the overlapping conduction interval. This step outputs an over-limit flag and further calculates the critical overlap initiation angle required to make the circulating current increment just drop to the threshold. The critical overlap initiation angle means that if the initiation angle of the overlapping conduction interval is not less than the critical overlap initiation angle. If the circulating current increment does not exceed the current power supply cycle threshold; Then the critical overlap start angle The calculation method is as follows: The absolute safety threshold is... Multiply by power frequency angular frequency The sum of leakage inductance of the old and new windings The product of the products is then divided by To obtain an intermediate value, the natural shutdown phase will be determined. The critical overlap initiation angle is obtained by adding the cosine value of z to the median value z and then taking the inverse cosine. The expression: ;in, ;when When the value exceeds [−1, 1], it is truncated according to the boundary value. The critical overlap initiation angle This indicates that if the initial boundary of the overlapping conduction interval is not less than the critical overlap initiation angle... Then the circulating current increment will not exceed the safety threshold of the current power cycle; This step will include the over-limit sign and the critical overlap initiation angle. and the current overlap start angle It is passed to step two as the quantization target and calculation starting point for the trigger angle orientation correction in step two.

[0020] Please see Figure 2 As shown, step two: Based on the current overlap start angle and the critical overlap start angle, the overlap conduction interval is divided into the first sub-segment and the second sub-segment with the critical overlap start angle as the anchor point. The ratio of the volt-second product of the second sub-segment to the total volt-second product of the overlap conduction interval is calculated to obtain the residual ratio. The correction strategy is determined based on the comparison result between the residual ratio and the residual ratio judgment threshold, and the corrected trigger angle is output. After step one determines that the circulating current exceeds the limit, receive the current overlap start angle output from step one. Critical overlap starting angle This is designed to provide targeted correction for unsafe initial firing angles, specifically: First, based on the relationship between the trigger angles of the old and new gears before correction, determine the pilot gear and the rear gear. Mark the gear with the smaller trigger angle as pilot gear E, and denot its trigger angle as... The setting with the larger firing angle is designated as the rear conduction setting L, and its firing angle is denoted as... As can be seen from the analysis in step one, the current overlap starting angle is... Equal to the trigger angle of the back conductor Therefore, increasing the trigger angle of the subsequent conduction will directly delay the starting boundary of the overlapping interval; Subsequently, starting with the critical overlap angle As the anchor point, for the current overlapping conduction interval Controllable segmentation is performed, and the segmentation process is as follows: The critical overlap initiation angle is... Current overlap starting angle and natural phase off Numerical comparisons are performed, and the interval is divided into two continuous segments based on the position of the critical overlap initiation angle within the overlap interval. The starting boundary of the first sub-segment is set to the current overlap start angle. The termination boundary is set as the critical overlap start angle. Phase span of the first sub-segment ; The physical characteristic of this segment is: when the trigger angle of the rear conduction switch changes from the current value... Increase to the critical overlap initiation angle At that time, overlapping conduction intervals The starting boundary will be from the current overlap starting angle. Delayed to the critical overlap start angle The volt-second product contribution that originally fell within the first segment will be completely eliminated; therefore, the circulating drive energy within the first segment can be eliminated by adjusting the firing angle of the rear conduction stage only, without the participation of the first conduction stage. The starting boundary of the second sub-segment is set as the critical overlap starting angle. The termination boundary is set as the natural turn-off phase. Phase span of the second sub-segment ; The physical characteristic of the second segment is: even if the trigger angle of the subsequent conduction is... Increased to the critical overlap initiation angle The second segment still belongs to the corrected overlapping conduction interval, and its volt-second product contribution continues; due to the critical overlap initiation angle The extreme position is obtained by inverse solving based on the safety threshold in step one, followed by the trigger angle of the conduction switch. equal to the critical overlap initiation angle The corresponding circulation increment is exactly equal to the threshold, and the circulation corresponding to this threshold is driven by the volt-second product of the second segment. After completing the above segmentation, perform independent volt-second product calculations on the second sub-segment, and calculate the sinusoidal voltage difference function from the critical overlap starting angle. To the natural shutdown phase Integrate to obtain the volt-second product of the second sub-segment and record it as the volt-second product of the second sub-segment. ; The second sub-segment volt-second product Total volt-second product with overlapping conduction interval Divide them to obtain the residual ratio ρ: The residual ratio ρ ranges from 0 to 1. When ρ∈[0,1], the residual ratio ρ characterizes the proportion of the original total circulating driving energy remaining when the overlap initiation angle is postponed to the critical overlap initiation angle; Based on the obtained residual ratio ρ, let the residual ratio judgment threshold be... Its typical value is 0.5, and the residual ratio ρ is compared with the residual ratio judgment threshold. Comparison to determine the correction strategy: when When the first segment contributes more than 50% of the residual ratio of the total volt-second product of the overlapping conduction interval, the subsequent conduction stage alone can eliminate the main circulating current driving energy; at this time, the subsequent conduction stage-dominant correction strategy is adopted: the firing angle of the subsequent conduction stage is adjusted. Directly set as the critical overlap start angle The pilot pass trigger angle remains unchanged. The corrected circulation increment remains unchanged and is exactly equal to the safety threshold. It is in a critical state of meeting the standard; After the trigger angle is corrected by the post-conduction mode After the pilot pass is corrected, the trigger angle is adjusted. They are respectively: ; when When the contribution of the first segment is insufficient, the residual ratio of the total volt-second product of the overlapping conduction interval is less than 50%, and the coverage of the subsequent conduction segment alone is limited. Although the circulating current is numerically equal to the threshold after the subsequent conduction segment is corrected to the critical overlap initiation angle, the system is in a critical state at the threshold boundary and lacks a safety margin. At this point, a pilot switch is needed to assist in the correction, reducing the actual circulating current below the threshold to increase the safety margin. When the pilot pass participates in the correction, it is necessary to determine the correction amount allocation ratio between the two passes. This invention introduces a piecewise integral accumulation ratio parameter for the second sub-segment. Further division is performed, with a typical value of 1 / 3; starting from the beginning of the second sub-segment. Initially, the voltage difference function is integrated along the direction of increasing phase angle. When the accumulated value reaches the second segment volt-second product... of When the phase angle is doubled, the resulting phase angle is determined as the dividing point. The dividing point Divide the second sub-segment into the first sub-segment, i.e., starting from the critical overlap starting angle. To the cumulative proportional parameter of piecewise integration Its volt-second product accounts for a proportion of the volt-second product of the second sub-segment. This ratio serves as an additional correction liability factor for the subsequent conduction phase. The latter sub-segment starts from the split point. To the natural shutdown phase The volt-second product ratio of the latter segment is used as the correction liability coefficient for the leader pass. ; The dividing point satisfies: ;in, The percentage of the volt-second product in the latter sub-segment; And based on the preset safety margin coefficient Its typical value is 0.2, indicating that the target circulation should be less than 20% of the threshold; the amount of circulation reduction corresponding to the safety margin coefficient. The calculation is as follows: ; Reduce circulation Converted to volt-second product that needs to be eliminated : ; Then, the volt-second product that needs to be eliminated additionally... Converted to the angle increment that requires additional delay of the overlap start angle Since the volt-second product is linearly related to the cosine of the overlap initiation angle, the angle increment can be obtained through difference approximation or exact inverse solution. Therefore, an indirect effect reduction factor is introduced. Its typical value is 0.3, used to reflect that the indirect effect of the pilot pass firing angle change on the starting boundary of the overlapping interval is weaker than the direct effect of the subsequent pass; the additional correction angles for the two passes are allocated as follows: ; ; After the post-conduction correction, the trigger angle is equal to the critical overlap start angle. Plus additional corrections After the pilot pass is corrected, the trigger angle is equal to its original value. Plus additional corrections : ; Preferably, it further includes constraining the trigger angle after the pilot pass correction to not exceed the trigger angle after the subsequent pass correction minus the minimum sequence interval. Its typical value is 5° to maintain the sequential conduction timing without reversal; if this constraint is violated, the trigger angle of the first conduction position will be forcibly reverted to the corrected trigger angle of the second conduction position minus [the value of the angle]. The constraints are: ; If the above constraints are not met, the trigger angle after the first pass is corrected will be forcibly set to the trigger angle after the second pass is corrected minus the minimum sequence interval. The corrected back-conductor trigger angle The new overlap starting angle is substituted into the circulation increment calculation formula in step one for verification; if the verification result shows that the circulation still exceeds the safety threshold, the above controllability segmentation and correction allocation process is repeated with the corrected trigger angle as the new starting point, iterating until the circulation drops below the threshold or the maximum number of iterations is reached. Its typical value is 4; Based on the correspondence between the pilot and follower passes and the old and new passes, the corrected trigger angle is restored to the old pass's corrected trigger angle. And the trigger angle after the new file was corrected This step outputs the two corrected firing angles and the residual ratio ρ, which are then passed to step three for calculating the actual output voltage.

[0021] Step 3: Based on the corrected trigger angle, calculate the actual conduction angle span of the old and new stages respectively. The ratio of the actual conduction angle span of the new stage to the sum of the conduction angle spans of the two stages is used to obtain the effective energy transmission ratio. The effective energy transmission ratio is used as the starting point of trajectory planning. The difference between the trajectory planning starting point and the transition final value weight is evenly distributed in the remaining cycles to obtain the adaptive weight increment. This is added to the effective energy transmission ratio to obtain the target weight of the next power supply cycle. Receive the corrected trigger angle from the old file output in step two. And the trigger angle after the new file was corrected Based on the conduction characteristics of thyristors, the effective power supply duration of each thyristor to the load is determined by the difference between its firing angle and its natural turn-off phase; utilizing the natural turn-off phase... Calculate the actual conduction angle span of the old and new settings in the current power supply cycle; the actual conduction angle span of the new setting. Equals the natural shutdown phase minus the trigger angle after the new setting correction, expressed as Actual conduction angle span of the old file Equals the natural shutdown phase minus the trigger angle after old file correction, expressed as The larger the conduction angle span, the longer the effective conduction time of the thyristor in the current power cycle, and the greater its contribution to the power supply of the load. After obtaining the actual conduction angle spans of the old and new gears, the ratio of the actual conduction angle span of the new gear to the sum of the conduction angle spans of the two gears is defined as the effective energy transfer ratio. This percentage represents the actual contribution of the new frequency band to the total power supply in the current power cycle: The proportion of effective energy transmission This is a real-time observation of the current power supply cycle system's transient state, with a value range between 0 and 1; this observation extracts transient progress information from the corrected firing angle value: When the transition value is close to the final value, it indicates that the new generation has almost completely taken over the power supply and the transition is nearing completion. When the value is close to the middle value, it indicates that the old and new levels each bear about half of the power supply task, and the transition is in the middle stage. When the value approaches the initial value, it indicates that the old mode still dominates the power supply and the transition is in the initial stage. Through this observation, the digital controller gains the ability to perceive the actual transition state of the system in real time, rather than blindly controlling it by relying solely on a preset theoretical trajectory. Among them, the typical value of the transition terminal value is 1.0, the typical value of the intermediate value is 0.5, and the typical value of the initial value is 0; Next, the effective energy transfer ratio will be compared with the expected transition trajectory to quantify the deviation between the current observation state and the theoretical expectation; let the total power frequency during the transition period be... Then, the expected weight of the nth power supply cycle, determined according to the linear increasing law, is: ; Calculate trajectory deviation The difference between the expected weight and the effective energy transfer ratio: Among them, trajectory deviation A positive value indicates that the actual observed transition progress lags behind the linear expected trajectory, a zero value indicates that the actual progress is consistent with the expectation, and a negative value indicates that the actual progress is ahead of the expectation; the quantification of this deviation provides state feedback information for the subsequent adaptive weight generation. Based on the real-time observed effective energy transfer ratio, this step uses an adaptive algorithm to generate the target weight for the next power cycle; the core idea of ​​the generation strategy is to use the currently observed effective energy transfer ratio... As the actual starting point for trajectory planning, the weight difference between this starting point and the transition endpoint is evenly distributed across the remaining power cycles, ensuring that the weight increment for each subsequent power cycle remains smooth. This strategy ensures that the weight sequence is always planned based on the actual physical state of the system, rather than mechanically following a preset trajectory that may be out of touch with reality. Let the weight of the transition endpoint be... Its typical value is 1.0, corresponding to the new stage fully taking over the power supply, with the remaining transition power supply frequency being [number missing]. ; Calculate adaptive weight increment The remaining weight difference from the current observation state to the transition endpoint is divided by the remaining power supply cycles: ; Based on this adaptive increment, the target weight for the next power cycle is calculated. Add an adaptive increment to the current effective energy transfer percentage: ; The adaptive weight generation algorithm has the following characteristics: First, it guarantees continuity: the target weight for the next power cycle is calculated by superimposing the currently observed effective energy transfer ratio, rather than based on theoretical expectations that may be out of sync with reality. This ensures that the weight sequence remains continuous between power cycles without command jumps caused by differences between theoretical and actual values. Second, it guarantees convergence: as the power cycle number n approaches the total number of power cycles M, the denominator... Gradually decrease, adaptive increment The corresponding increase forces the system to converge to the endpoint weights at the end of the transition. This ensures the new generation completely takes over the power supply; secondly, it guarantees adaptability: when the observed actual progress exceeds the linear expectation, that is... Greater than The algorithm automatically reduces the subsequent weight growth rate to avoid overshoot; when the actual progress lags behind, the algorithm evenly distributes the difference in the remaining power supply cycles to catch up smoothly and avoid drastic changes at the end. This step outputs the current percentage of effective energy transfer. Trajectory deviation and adaptively generated target weights for the next power cycle The data is then passed to step four for trigger timing mapping and transition completion determination.

[0022] Please see Figure 3 As shown, step four: apply monotonicity constraints and saturation constraints to the output target weight to obtain the execution weight, map the execution weight to the initial trigger angle of the old and new gears through the complementary conduction strategy and use it as the input of the next cycle to form a cycle-by-cycle closed loop, and when the execution weight reaches the transition final value weight, execute steady-state locking to complete the gear switching transition; The specific process for this step is as follows; First, the target weights output in step three are physically constrained and verified. During the thyristor phase-by-phase voltage regulation transition, to ensure the monotonic stability of the output voltage and prevent voltage fluctuations from disturbing the load, the weight sequence must satisfy a monotonically increasing constraint; that is, the conduction ratio of the new stage can only increase or remain constant and cannot decrease. This invention introduces a monotonicity locking mechanism to impose a lower limit constraint on the target weights: the target weights output in step three... Compared with the current effective energy transfer ratio The two values ​​are compared, and the larger value is taken as the execution weight. ; This constraint ensures that the execution weight of the next power cycle is never lower than the actual transmission proportion of the current power cycle, preventing weight rollback due to grid voltage fluctuations, load abrupt changes, or numerical calculation disturbances. Simultaneously, a saturation constraint is introduced to limit the execution weight: let the weight saturation upper limit be... Its typical value is 1.0, which strictly limits the upper limit of the execution weight to this saturation value, corresponding to the final state where the new file is fully connected and the old file is completely deactivated; the execution weight after bilateral constraints satisfy Scope requirements; After obtaining the execution weights with constraints, they are converted into trigger control parameters of the thyristors. For the phase-splitting voltage regulator, in order to maintain the integrity of the output voltage waveform and avoid the power supply vacuum between the old and new ranges, the thyristors of the old and new ranges adopt a complementary conduction strategy, that is, the increase of the conduction angle of the new range corresponds to the equal decrease of the conduction angle of the old range, and the conduction of the two ranges forms a complementary relay in timing. Based on the geometric relationship between the trigger angle and the conduction interval described in step one, this invention establishes an inverse mapping model from the execution weight to the trigger angle. For a new-range thyristor, its firing angle determines the starting moment when the new-range voltage is connected to the load; in order to achieve execution weighting The corresponding energy transfer ratio, the new trigger angle should be relative to the natural turn-off phase. The corresponding proportion should be advanced; the initial trigger angle of the new file. The calculation is the natural shutdown phase multiplied by the complement of the execution weights relative to the saturation cap: ; The physical meaning of this mapping relationship is: when the execution weight approaches the saturation limit... When the trigger angle of the new gear approaches zero or the minimum trigger angle allowed by the system, the new gear thyristor immediately turns on after triggering and maintains it until natural turn-off, achieving the maximum conduction time; when the execution weight is small, the trigger angle of the new gear is large, the new gear thyristor delays conduction, and the effective conduction time is shortened accordingly. For the old-type thyristor, its firing angle determines the starting time when the old-type voltage exits the load; according to the complementary conduction principle, the conduction range of the old-type should be time-complementary with that of the new-type; the initial firing angle of the old-type... The calculation is the natural shutdown phase multiplied by the ratio of the execution weight to the saturation cap: ; The physical meaning of this mapping relationship is: when the execution weight approaches the saturation upper limit, the trigger angle of the old file approaches the natural shutdown phase. The conduction window of the old-type thyristor is completely compressed to the closed state, and the old-type thyristor is completely de-energized; when the execution weight is small, the old-type trigger angle is small, the old-type thyristor turns on earlier, and still maintains a long effective conduction time; The initial trigger angle of the new file calculated above and the initial trigger angle of the old file The proposed trigger angle for the (n+1)th power cycle is fed back to step one as the input parameter for predicting the circulating current increment of that power cycle. This forms a closed-loop architecture for prediction and correction execution from step one to step four: the initial trigger angle of the next cycle generated in step four is fed back to step one. Step one calculates the overlap initiation angle and volt-second product based on the trigger angle, and then predicts the circulating current increment of the (n+1)th power cycle and compares it with the (n+1)th threshold in the decreasing safety threshold sequence. If the prediction result indicates a safe state, the digital controller directly executes the thyristor triggering according to the trigger angle. If the prediction result indicates an over-limit state, step two is entered to perform controllable segmentation and constrained orientation correction of the critical overlap initiation angle anchoring, and obtains the corrected trigger angle that meets the circulating current safety constraints. Then, step three interprets it from the transition progress dimension and generates the target weight of the next power cycle. This closed-loop architecture ensures that every issued physical trigger pulse has undergone dual verification of circulating current safety prediction and transition progress optimization. In one implementation, the digital controller generates trigger pulses for the new and old SCRs within each power supply cycle. To ensure a unified timing reference for the trigger angle, the digital controller uses a zero-crossing detection circuit to obtain the zero-crossing moment of the power supply voltage as the timing reference for that power supply cycle. The trigger angle, measured in angular terms, is converted into a trigger delay, measured in time terms, according to the power frequency. Then, a hardware timer outputs a trigger pulse to drive the SCR gate to conduct when the corresponding delay arrives. The zero-crossing detection, circuit timing, and gate driving described above can all be implemented using conventional methods in the art, and their structural forms are not limited, nor are they considered as limitations on the innovative points of this invention. After the firing angle is confirmed to be safe through closed-loop verification, the digital controller executes a physical firing operation; the zero-crossing detection circuit captures the zero-crossing moment of each phase power supply voltage as a timing reference, and the firing angle is divided by the power supply angular frequency. Convert the trigger delay to a time value; configure the hardware timer to start timing after detecting the zero crossing moment. When the timing reaches the delay duration corresponding to the new trigger angle, drive the gate of the new trigger SCR to generate a trigger pulse. When the timing reaches the delay duration corresponding to the old trigger angle, drive the gate of the old trigger SCR to generate a trigger pulse. After each power cycle is completed, it is determined whether the gear shift transition process meets the termination condition; the determination is based on the execution weight. Has the transitional terminal value weight been reached? When the execution weight reaches the transition terminal weight. When the new gear has completely taken over the load current supply and the old gear has completely exited the conduction sequence, the transition process meets the termination condition. At this time, the digital controller performs a steady-state lockout operation: at the logic level, it stops the iterative calculation of steps one to three and resets the power frequency counter; at the physical level, it permanently removes the trigger signal of the old gear thyristor to prevent interference and false triggering, and locks the new gear thyristor in the steady-state operation mode; the voltage regulator officially enters the steady-state operation stage of the new gear, and the gear switching transition process ends. Through the synergistic effect of steps one through four, this invention establishes a dual-utilization architecture for the trigger angle in both the circulation control and transition progress dimensions. Step one calculates the overlap interval and volt-second product based on the trigger angle before triggering, predicts the circulation increment, compares it with a decreasing safety threshold, and outputs an over-limit judgment and a critical overlap initiation angle as safety boundary parameters. Step two uses the critical overlap initiation angle as an anchor point to perform controllable segmentation of the overlap interval, calculates the residual ratio to evaluate the post-conduction correction coverage, and performs constrained trigger angle directional correction accordingly, outputting a corrected trigger angle that satisfies circulation safety constraints. Step three solves the transition progress dimension... After reading the corrected trigger angle, the effective energy transfer ratio is calculated as the real-time observation value of the actual transition state of the system. Based on this observation value, the target weight of the next power cycle is adaptively generated. In step four, physical constraints are applied to the target weight and mapped to the trigger timing parameters. The data is then fed back to step one to form a closed loop, and the transition termination condition is determined. The decreasing safety threshold sequence drives the correction amount in step two to decrease one power cycle at a time. The effective energy transfer ratio observed in step three increases one power cycle at a time and converges to the final value. The weight sequence remains smooth and continuous under the adjustment of the adaptive algorithm, and finally, a smooth and shock-free gear switching transition is achieved under the condition of controlled circulation.

[0023] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0024] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0025] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0026] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0027] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0028] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A digital control method for a phase-by-phase voltage regulator based on thyristor range switching, characterized in that, Includes the following steps: During each power cycle of the gear switching transition period, the overlapping conduction interval and its overlap start angle of the two gears are determined according to the initial trigger angle set for the new gear and the old gear. The voltage difference in the overlapping conduction interval is integrated and combined with the sum of the leakage inductance of the windings of the new and old gears to calculate the circulating current increment prediction value. The circulating current increment prediction value is compared with the safety threshold. When the circulating current increment prediction value exceeds the safety threshold, it is determined to be an over-limit state and the critical overlap start angle is calculated. Using the critical overlap start angle as the anchor point, the overlapping conduction interval is divided into the first sub-segment and the second sub-segment. The residual ratio is calculated based on the critical overlap start angle. Based on the comparison result between the residual ratio and the residual ratio judgment threshold, the dominant correction strategy of the subsequent conduction level or the two-level collaborative correction strategy is selected to correct the initial trigger angle and output the corrected trigger angle. Based on the corrected trigger angle, the actual conduction angle span of the old and new stages is calculated respectively, and the effective energy transmission ratio reflecting the actual power supply ratio of the new stage is obtained. The effective energy transmission ratio is used as the starting point of trajectory planning. The difference between the starting point of trajectory planning and the transition final value weight is evenly distributed in the remaining cycles to obtain the adaptive weight increment, which is added to the effective energy transmission ratio to obtain the target weight of the next power supply cycle. The execution weight is obtained by applying monotonicity and saturation constraints to the target weight. The execution weight is then mapped to the initial trigger angle of the next cycle through a complementary conduction strategy. When the execution weight reaches the transition terminal weight, steady-state locking is performed to complete the gear shift transition.

2. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 1, characterized in that, The method for obtaining the initial trigger angle for the new and old gears is as follows: When the gear switching transition period is in the first power cycle, the transition weight of the first power cycle is set to 1 divided by the total number of power cycles in the transition period. The initial trigger angle of the new gear in the first power cycle is equal to the difference between the natural shutdown phase multiplied by 1 and the transition weight of the first power cycle. The initial trigger angle of the old gear is equal to the natural shutdown phase multiplied by the transition weight of the first power cycle. The initial trigger angle of the second power cycle and subsequent power cycles during the gear switching transition period is determined by the execution weight of the previous power cycle output. The initial trigger angle of the new gear is equal to the difference between the natural shutdown phase multiplied by 1 and the execution weight of the previous power cycle, and the initial trigger angle of the old gear is equal to the natural shutdown phase multiplied by the execution weight of the previous power cycle.

3. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 1, characterized in that, The method for calculating the predicted value of the circulating current increment is as follows: the overlap start angle is obtained by taking the larger value of the initial trigger angles of the new and old gears; the voltage difference within the overlap conduction interval is integrated from the overlap start angle to the natural turn-off phase to obtain the volt-second product, which is equal to the quotient of the peak voltage difference divided by the power frequency angular frequency, and then multiplied by the cosine of the overlap start angle minus the cosine of the natural turn-off phase. The peak voltage difference is the absolute value of the difference between the peak voltage of the new gear tap and the peak voltage of the old gear tap; the predicted value of the circulating current increment is obtained by dividing the volt-second product by the sum of the leakage inductance of the new and old gear windings; where the overlap conduction interval is the intersection of the conduction intervals of the new and old gears.

4. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 1, characterized in that, The safety threshold is designed as a sequence that decreases with the power supply cycle number. The safety threshold of the nth power supply cycle is equal to the product of the initial threshold coefficient and the rated current, minus the product of the decreasing step size coefficient, the rated current and the difference between the power supply cycle number and 1. The critical overlap initiation angle is obtained by inversely solving the expression of the circulating current increment prediction value. Specifically, the safety threshold is multiplied by the sum of the power frequency angular frequency and the leakage inductance of the old and new windings, and then divided by the peak voltage difference to obtain the intermediate value. The intermediate value is added to the cosine value of the natural turn-off phase and the inverse cosine is taken as the critical overlap initiation angle.

5. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 1, characterized in that, The specific method for dividing the overlapping conduction interval into the first sub-segment and the second sub-segment is as follows: the overlapping conduction interval is divided into two continuous sub-segments with the critical overlap start angle as the dividing point; The starting boundary of the first sub-segment is set to the current overlap initiation angle, and the ending boundary is set to the critical overlap initiation angle; the starting boundary of the second sub-segment is set to the critical overlap initiation angle, and the ending boundary is set to the natural turn-off phase. The voltage difference within the second segment is integrated from the critical overlap initiation angle to the natural turn-off phase to obtain the volt-second product of the second segment; the residual ratio is the ratio of the volt-second product of the second segment to the total volt-second product of the overlap conduction interval. It is calculated by subtracting the cosine of the natural turn-off phase from the cosine of the critical overlap initiation angle, and dividing by the cosine of the current overlap initiation angle minus the cosine of the natural turn-off phase.

6. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 5, characterized in that, Based on the comparison results of the residual ratio and the residual ratio judgment threshold, the following strategy is selected: the rear conduction gear dominant correction strategy or the two gears cooperative correction strategy. Specifically, based on the relationship between the initial trigger angles of the old and new gears, the gear with the larger trigger angle is determined as the rear conduction gear and the gear with the smaller trigger angle is determined as the first conduction gear. When the residual ratio is not greater than the residual ratio judgment threshold, the subsequent conduction mode is selected as the dominant correction strategy, that is, the trigger angle of the subsequent conduction mode is set as the critical overlap start angle, and the trigger angle of the first conduction mode remains unchanged at its initial value. When the residual ratio is greater than the residual ratio judgment threshold, a two-level collaborative correction strategy is selected. The trigger angle of the subsequent conduction is set as the critical overlap start angle, and then the second sub-segment is further divided to allocate the additional correction amount of the two levels. Based on the preset segmented integral accumulation ratio parameter, the voltage difference function is integrated along the phase angle increase direction from the starting end of the second sub-segment, i.e., the critical overlap start angle. When the integral accumulation value reaches the product of the volt-second product of the second sub-segment and the preset segmented integral accumulation ratio parameter, the corresponding phase angle is the dividing point. The dividing point divides the second sub-segment into a front sub-segment and a rear sub-segment. The front sub-segment is the interval from the critical overlap start angle to the dividing point, and the rear sub-segment is the interval from the dividing point to the natural turn-off phase. The ratio of the volt-second product of the front sub-segment to the volt-second product of the second sub-segment is used as the additional correction responsibility coefficient of the subsequent conduction, and the ratio of the volt-second product of the rear sub-segment to the volt-second product of the second sub-segment is used as the correction responsibility coefficient of the leading conduction. The amount of circulation reduction is determined based on the preset safety margin coefficient, and two additional correction angles are allocated according to each responsibility coefficient.

7. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 6, characterized in that, The method for determining the additional correction angle in the two-stage collaborative correction strategy is as follows: The reduction in circulating current is equal to the product of the safety margin coefficient and the current cycle safety threshold. The reduction in circulating current is multiplied by the sum of the leakage inductance of the old and new windings and converted into the volt-second product that needs to be eliminated. The volt-second product that needs to be eliminated is then converted into the angle increment that needs to be delayed by the overlap start angle. Introducing indirect effect reduction factor This is used to reflect that the indirect effect of the pilot pass's trigger angle change on the initial boundary of the overlapping section is weaker than the direct effect of the subsequent pass; the additional correction angle of the subsequent pass. Additional correction angle for pilot pass Calculate using the following formulas respectively: ； ； in This is an additional correction liability factor for the subsequent conduction file. The correction liability coefficient for the pilot pass. This requires an additional angle increment to delay the overlap initiation angle; After the trigger angle is corrected, the follow-through is restored. After the pilot pass is corrected, the trigger angle is adjusted. They are respectively: ； ； in The initial trigger angle for the pilot pass. The critical overlap start angle is the nth power cycle, where n is the power cycle number.

8. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 1, characterized in that, Based on the corrected firing angle, the actual conduction angle span of the old and new stages is calculated separately, and the effective energy transfer ratio reflecting the actual power supply ratio of the new stage is obtained, specifically: The actual conduction angle span of the new setting is equal to the natural turn-off phase minus the new setting's corrected trigger angle; the actual conduction angle span of the old setting is equal to the natural turn-off phase minus the old setting's corrected trigger angle. The effective energy transfer ratio is equal to the actual conduction angle span of the new gear divided by the sum of the actual conduction angle spans of the old and new gears, and its value range is between 0 and 1. The adaptive weight increment is calculated by dividing the difference between the transition final value weight and the effective energy transmission ratio by the remaining transition cycles, where the remaining transition cycles are equal to the total power supply cycles during the transition period minus the current power supply cycle number; the target weight for the next power supply cycle is equal to the current effective energy transmission ratio plus the adaptive weight increment.

9. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 6, characterized in that, The revisions also include: The trigger angle after the first conduction pass is corrected shall not exceed the trigger angle after the second conduction pass is corrected minus the preset minimum sequence interval. If this constraint is not met, the trigger angle after the first conduction pass is forcibly set to the trigger angle after the second conduction pass is corrected minus the minimum sequence interval, so as to maintain the timing of the first and second conductions without reversal. The modified back conduction trigger angle is used as the new overlap starting angle and substituted into the calculation formula of the circulating current increment prediction value for verification. If the verification result shows that the circulating current still exceeds the safety threshold, the controllability segmentation and correction allocation process is repeated with the modified trigger angle as the new starting point until the circulating current drops below the safety threshold or the maximum number of iterations is reached.

10. The digital control method for a phase-by-phase voltage regulator based on thyristor range switching according to claim 1, characterized in that, The monotonicity constraint is to take the larger value between the target weight and the current effective energy transmission ratio as the execution weight, so as to ensure that the execution weight of the next cycle is not lower than the actual transmission ratio of the current cycle. Saturation constraint limits the upper limit of the execution weight to the weight saturation limit, corresponding to the final state where the new file is fully activated and the old file is completely deactivated; The complementary conduction strategy is that the initial trigger angle of the new file is equal to the difference between the natural shutdown phase multiplied by 1 and the ratio of the execution weight to the weight saturation limit, and the initial trigger angle of the old file is equal to the ratio of the natural shutdown phase multiplied by the execution weight to the weight saturation limit. Steady-state locking includes stopping the cycle-by-cycle closed-loop iterative calculation, canceling the trigger signal of the old thyristor, and locking the new thyristor in steady-state operation mode.

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