Excitation inrush current and phase jump suppression method and system for transformer switching

Abstract

The invention relates to the technical field of transformer equipment protection and operation control, and provides a method and a system for suppressing excitation inrush current and phase jump of transformer switching, which are characterized in that an excitation inrush current suppression mechanism is integrated into a control system of an energy storage converter, and sine wave pulse width modulation is adopted to generate an output voltage waveform. At the moment of switching of the transformer, the controller firstly detects the instantaneous current change of the output end in real time, and when it is monitored that the current value rapidly rises and overcurrent occurs, the modulation depth coefficient is automatically adjusted by adopting a fuzzy logic control algorithm according to an error interval. The modulation depth coefficient is used as a control parameter to determine the amplitude of the output voltage so as to influence the current input intensity. And then, according to a feedback current value, if the detected current is reduced below a rated value, gradually increasing the PWM pulse duty ratio, so that the output voltage is gradually recovered to a normal level, meanwhile, ensuring the continuity and smooth transition of a voltage phase, and finally realizing a control closed loop of the transformer from a switching-on state to a stable operation state.

Description

Technical Field

[0001] This invention relates to the technical field of transformer equipment protection and operation control in power systems including power storage converters (PCS), specifically to a method and system for suppressing inrush current and phase jump during transformer switching. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In the mining industry, microgrid systems, due to their unique operating environment and complex load characteristics, face the practical need for frequent transformer switching, with an average of 100 to 200 operations per year, far exceeding that of conventional industrial power grids. The root causes of this phenomenon are twofold: First, mining power loads exhibit typical high-impact characteristics. Large equipment such as crushers and ball mills often have single-unit power ratings in the MW range. During frequent start-ups and shutdowns, these devices generate starting current surges of 6 to 8 times their rated current within a very short time, causing severe disturbances to the power grid. The apparent power peak can even reach 9 to 13 times the rated power, lasting for several seconds. To maintain the stability of the bus voltage, the system often needs to frequently switch standby transformers or adjust tap changes, resulting in high-frequency transformer switching operations. Second, the operating mode of mining microgrids is complex, requiring frequent switching between grid-connected and islanded modes. Furthermore, due to long transmission lines, complex terrain, and a high incidence of line faults caused by natural factors such as lightning strikes, the system must possess rapid recovery capabilities. During such faults or operating mode switching, transformers must be put into use quickly. However, switching transformers under no-load or light-load conditions can easily generate high-amplitude inrush currents, with peak values ​​reaching 6 to 12 times the rated current. In severe cases, this can cause voltage drops, harmonic amplification, and protection malfunctions, posing a serious threat to system stability and equipment safety. Therefore, researching and implementing a method to effectively control and suppress inrush currents during transformer switching is of significant engineering importance and practical application value for ensuring the stability, safety, and continuous power supply capability of mine microgrid systems.

[0004] Currently, traditional techniques for suppressing inrush current during transformer switching rely heavily on hardware control methods on the power system side. These include controlling the closing phase angle of circuit breakers, adding series current-limiting resistors, or using closing synchronization devices to avoid or reduce inrush current. However, these methods have significant limitations: firstly, circuit breaker control depends on precise matching of closing timing, and optimal phase angle control is difficult to guarantee during frequent switching or when system disturbances are significant, still easily leading to inrush current problems; secondly, while series current-limiting resistors can reduce peak current to some extent, they introduce additional power consumption and voltage drop, and have poor adaptability to transformers of different capacities. Furthermore, traditional power conversion systems (PCS) generally employ proportional-integral-derivative (PID) control strategies, which are slow to respond to transient processes like inrush current, failing to intervene in control in time at the initial stage of current surges. This results in long inrush durations and large amplitudes, affecting the safe operation of downstream equipment and the power quality of the system. Therefore, existing technologies are insufficient to meet the practical needs of mine microgrids, which require high-frequency switching, strong disturbance response, and complex operating modes. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method and system for suppressing inrush current and phase jump during transformer switching. It innovatively embeds a fuzzy logic control algorithm into the PCS control system, and achieves rapid suppression of inrush current and smooth phase recovery during transformer switching by dynamically adjusting the PWM duty cycle, thereby improving the system's response speed and operational stability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for suppressing inrush current and phase jump during transformer switching, applied to a power system including an energy storage converter, wherein the energy storage converter supplies power to the transformer, comprising the following steps: The output voltage of the energy storage converter is controlled by a sinusoidal pulse width modulation algorithm, and the instantaneous current value at the output terminal of the energy storage converter is obtained in real time to determine whether an overcurrent has occurred. If an overcurrent is detected, the modulation depth coefficient is determined using a fuzzy logic control algorithm based on the current current error range, and the duty cycle of the next PWM pulse cycle is dynamically calculated and adjusted to achieve current limiting. When the instantaneous current value is less than the rated operating current set by the energy storage converter, the duty cycle of the PWM pulse is gradually increased to restore normal output. By increasing the PWM pulse, the duty cycle value gradually becomes consistent with the normal value, thereby restoring the output voltage and phase of the energy storage converter.

[0007] A second aspect of the present invention provides a transformer switching inrush current and phase jump suppression system, comprising: The current judgment module is configured to control the output voltage of the energy storage converter through a sinusoidal pulse width modulation algorithm, acquire and detect the instantaneous current value at the output terminal of the energy storage converter in real time, and determine whether an overcurrent has occurred. The current limiting module is configured to, if an overcurrent is detected, determine the modulation depth coefficient based on the current current error range using a fuzzy logic control algorithm, dynamically calculate and adjust the duty cycle of the next PWM pulse cycle to achieve current limiting. The output voltage and phase recovery module is configured to gradually increase the PWM pulse duty cycle to restore normal output when the instantaneous current value is less than the rated operating current set by the energy storage converter. By gradually increasing the PWM pulse to match the normal duty cycle value, the output voltage and phase of the energy storage converter are restored.

[0008] A third aspect of the present invention provides an electronic device, including a memory and a processor, and computer instructions stored in the memory and running on the processor, wherein the computer instructions, when executed by the processor, perform the steps in the above-described method for suppressing inrush current and phase jump during transformer switching.

[0009] A fourth aspect of the present invention provides a computer-readable storage medium for storing computer instructions, which, when executed by a processor, perform the steps in the above-described method for suppressing inrush current and phase jump during transformer switching.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention overcomes the technical bottleneck of traditional control methods relying on external hardware devices such as current-limiting resistors or closing synchronizers. By combining rapid current limiting and phase jump resistance methods, it achieves excitation control functionality when a transformer is directly switched on. First, the control strategy is fully embedded within the PCS, eliminating the need for additional electrical equipment, resulting in a simpler structure and lower cost. Second, by using fuzzy logic algorithms instead of traditional PID control, it can respond quickly in the early stages of current surges, improving suppression efficiency, significantly shortening the duration of inrush current, and reducing its peak value. Third, the dynamic adjustment of the modulation depth coefficient enhances the system's adaptability, automatically adapting to changes in transformer capacity and operating conditions. Furthermore, this method enables synchronous optimization of the current and voltage recovery processes, avoiding phase jump problems caused by voltage surges, and improving power quality and system stability. Even with significant differences in equipment capacity or frequent changes in system operating conditions, effective control of the transformer switching process can be achieved.

[0011] The advantages of the present invention, as well as its additional advantages, will be described in detail in the following specific embodiments. Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute a limitation thereof.

[0013] Figure 1 This is a flowchart of a method for suppressing inrush current and phase jump during transformer switching according to Embodiment 1 of the present invention; Figure 2 This is a flowchart illustrating a specific example of the method process in Embodiment 1 of the present invention; Figure 3 This is the current error in Embodiment 1 of the present invention. Membership function graph; Figure 4 This is a membership function graph of the weight coefficient M in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the PWM duty cycle recovery method in Embodiment 1 of the present invention. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0016] It should be noted that the terminology used herein is for describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. It should be noted that, without conflict, the various embodiments and features within those embodiments can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0017] Example 1 In one or more of the technical solutions disclosed in the embodiments, such as Figures 1 to 5 As shown, a method for suppressing inrush current and phase jump during transformer switching is applied to a power system containing a power storage converter (PCS), which supplies power to the transformer through the power storage converter (PCS). The method includes the following steps: Step 1: Control the output voltage of the PCS using the Sinusoidal Pulse Width Modulation (SPWM) algorithm, obtain the instantaneous current value at the output terminal of the PCS in real time, and determine whether an overcurrent has occurred. Step 2: If overcurrent is detected, the modulation depth coefficient is determined using a fuzzy logic control algorithm based on the current current error range. The duty cycle of the next PWM pulse cycle is then dynamically calculated and adjusted to achieve current limiting. Step 3: When the instantaneous current value is less than the rated operating current set by the PCS, gradually increase the PWM pulse duty cycle to restore normal output. By gradually increasing the PWM pulse value to match the normal duty cycle value, the output voltage and phase of the PCS are restored. This embodiment integrates the inrush current suppression mechanism into the control system of the energy storage converter PCS, employing sinusoidal pulse width modulation (SPWM) technology to generate the output voltage waveform. At the moment of transformer switching, the PCS controller first detects the instantaneous current change at the output terminal in real time. When a rapid rise in current and overcurrent are detected, a fuzzy logic control algorithm is used to automatically adjust the modulation depth coefficient of the SPWM waveform based on the error range. The modulation depth coefficient, as a control parameter, determines the amplitude of the output voltage, thus affecting the current input intensity. Subsequently, based on the feedback current value, if the current drops below the rated value, the PWM pulse duty cycle is gradually increased to gradually restore the output voltage to a normal level, while ensuring the continuity and smooth transition of the voltage phase, ultimately achieving a closed-loop control from transformer closing to stable operation. In the initial stage of transformer closing, the system automatically reduces the duty cycle to limit the input voltage and suppress current surges; as the magnetic field is established, the duty cycle is gradually increased to achieve a smooth transition to steady-state operation, avoiding system overcurrent or voltage drops.

[0018] This implementation method overcomes the technical bottleneck of traditional control methods that rely on external hardware devices such as current-limiting resistors or closing synchronizers. By combining methods such as rapid current limiting and phase jump resistance, it achieves excitation control functionality when the transformer is directly switched on. First, the control strategy is completely embedded within the PCS, eliminating the need for additional electrical equipment, resulting in a simpler structure and lower cost. Second, by using fuzzy logic algorithms instead of traditional PID control, it can respond quickly in the early stages of current surges, improving suppression efficiency, significantly shortening the duration of excitation inrush current, and reducing its peak value. Third, the dynamic adjustment of the modulation depth coefficient enhances the system's adaptability, automatically adapting to changes in transformer capacity and operating conditions. Furthermore, this method enables synchronous optimization of the current and voltage recovery processes, avoiding phase jump problems caused by voltage surges, and improving power quality and system stability. Even with significant differences in equipment capacity or frequent changes in system operating conditions, effective control of the transformer switching process can be achieved.

[0019] First, let's explain the specific control scenario. The transformer is used for energy conversion between different voltage levels and is a core device for grid connection. The power storage converter (PCS) connects the energy storage system and the grid, realizing bidirectional flow control of electrical energy and serving as an important interface for grid regulation. In islanded operation or PCS-based power supply scenarios, the PCS directly supplies power to the transformer (e.g., through medium-voltage side, low-voltage side, etc.), and the control behavior directly acts on the transformer. The method described in this embodiment suppresses inrush current by controlling the output voltage of the PCS to act on the transformer. In the initial stage of transformer no-load switching, by adjusting the amplitude and rise rate of the PCS output voltage, the rate of change of the transformer's magnetic flux is controlled, thereby effectively suppressing the generation of excitation inrush current or reducing its amplitude and duration.

[0020] Step 1: Control the PCS output voltage using a sinusoidal pulse width modulation (SPWM) algorithm; The principle of Sinusoidal Pulse Width Modulation (SPWM) is to adjust the equivalent output voltage by changing the duty cycle of the output square wave. The core of SPWM technology is that the width of the modulation pulse is arranged according to the sine wave law, so that the output waveform can be close to the sine wave output after appropriate filtering, effectively reducing the high-order harmonic components in the load current.

[0021] During the control process, the AC output half-cycle is divided into several interrupt cycles. The corresponding PWM duty cycle is calculated within each interrupt cycle using the following formula: (1); In the formula, For the first Duty cycle of each waveform interrupt, This represents the interruption cycle value. The modulation depth coefficient is used to modulate based on the output voltage and current. For the first A waveform interruption, The total number of interrupts required to generate a half-cycle waveform.

[0022] The real-time output voltage value can be obtained by multiplying the duty cycle by the DC bus voltage. The calculation formula is as follows: (2); In the formula, No. Output voltage at the moment of waveform interruption This is the DC bus voltage.

[0023] Optionally, the total number of interrupts N is calculated using the switching frequency of the power devices and the AC output frequency; Specifically, taking an AC side voltage frequency of 50 Hz (period 20 ms) as an example, the number of interruptions within the positive half-cycle (10 ms) is analyzed: When the switching frequency of the power device is 1kHz, the number of interrupts generated in the positive half-cycle is N=1000 / (1000 / 10)=10; When the switching frequency of the power device is 2kHz, the number of interrupt pulses is N=10000 / (1000 / 2)=20.

[0024] Preferably, the number of interrupt cycles is adjusted according to the switching frequency of the power device, and increases as the switching frequency increases.

[0025] To better control the PWM duty cycle of instantaneous overcurrent, formula (1) is optimized as follows: The optimized duty cycle calculation formula is: (3); In the formula, The adjustment coefficient is set to control instantaneous overcurrent.

[0026] Step 1, the method for obtaining the instantaneous current value at the output of the real-time detection PCS and determining whether an overcurrent has occurred, includes the following steps: Step 11: Convert the instantaneous current value at the output of the PCS to a per-unit value and compare it with the per-unit value of the rated current value of the power conversion system (PCS). Step 12: If the per-unit value of the instantaneous current is greater than the per-unit value of the rated current of the power conversion system (PCS), that is... If so, it is judged as an overcurrent; Step 2: If overcurrent is detected, based on the current current error range, a fuzzy logic control algorithm is used to determine the modulation depth coefficient, dynamically calculate and adjust the duty cycle of the next PWM pulse cycle to achieve current limiting. This includes: Step 21: Set a first threshold. If the instantaneous current value at the PCS output is not less than the first threshold, then calculate the duty cycle adjustment coefficient. Calculate the duty cycle to reduce the instantaneous current value at the PCS output terminal; Step 22: When the instantaneous current value at the output of the PCS is overcurrent and less than the first threshold, the modulation depth coefficient M is determined by the fuzzy logic control algorithm to reduce the instantaneous current value at the output of the PCS. In step 21, the duty cycle adjustment factor is calculated. Calculating the duty cycle and reducing the instantaneous current value at the PCS output is a cyclical process that includes the following steps: Step 211: If an overcurrent occurs, determine whether it exceeds the set first threshold. If it is not less than the set first threshold... The adjustment factor used to calculate the duty cycle Based on transformer capacity adjustment, the larger the capacity, the greater the adjustment coefficient. The smaller the value, the better the value for the next duty cycle will be; Optional, an adjustment factor for calculating the duty cycle. The initial value is 1; In this embodiment, the first threshold is set as a multiple K1 of the rated current value of the power conversion system (PCS). The multiple K1 can be 1.2 to 2 times, preferably 1.5 times. Specifically, after the overcurrent occurs, the first step is to determine... ;in, Convert the detected instantaneous current value into a per-unit value. This is the per-unit value of the rated operating current set according to the power device capacity; Furthermore, the value of the next duty cycle calculated in this step satisfies the constraint that the duty cycle is greater than the set minimum duty cycle value. When the calculated duty cycle is less than the minimum duty cycle value, the calculated duty cycle is updated to the minimum duty cycle value, as shown below: like: ,but: ; If modulated ,but This ensures that the transformer's magnetic field is established with a continuous minimum current during the control period.

[0027] Optionally, the minimum duty cycle can be set to 10%, and the minimum duty cycle can be adjusted according to the inrush current suppression situation.

[0028] Step 212: Adjust the width of the output PWM pulse signal based on the calculated duty cycle to control the output voltage and current of the PCS for modulation; Step 213: Obtain the instantaneous current value of the modulated PCS output terminal and determine whether it is lower than the first threshold. If not, repeat steps 211 to 212 until the number of cycles is met or the instantaneous current value is less than the first threshold. If the set number of interrupt cycles is reached and the instantaneous current value of the PCS output terminal is still not less than the first threshold, an alarm is triggered and the process ends. If the instantaneous current value of the PCS output terminal is less than the first threshold, proceed to the next step. Specifically, judgment If the count exceeds the set number of interrupt cycles, such as 200, an alarm will be triggered, and then the process will jump to the end. If the count does not exceed the set number of interrupt cycles, the process will jump to step 21.

[0029] In this embodiment This means the actual current exceeds 1.5 times the maximum capacity of the PCS. To protect the PCS, the traditional method is to diagnose it as a short-circuit fault, exceeding the energy conversion system's capacity, and shut it down directly. However, as a transformer load, if the transformer is switched on and off after shutdown, a large inrush current will also be generated. Under overcurrent conditions, if the downstream transformer is continuously energized, once an induced electromotive force is established inside the transformer, the current will gradually decrease under the same input voltage.

[0030] Step 21 of this embodiment provides a method for automatically setting the PWM duty cycle based on the transformer capacity. The larger the transformer capacity, the smaller its input impedance. This method sets the duty cycle to the reciprocal of the transformer capacity. Thus, the larger the capacity, the smaller the duty cycle in the next PWM cycle. However, the PWM duty cycle is not set to 0. This allows the duty cycle to be automatically adjusted according to the capacity of the connected transformer after the overcurrent condition, satisfying a 2-3 second switching time to achieve full power-on operation of the transformer. The adjustment coefficient... The calculation formula is available; (4); In the formula, A coefficient set for the capacity of the connected transformer.

[0031] In this example, if the transformer capacity is less than or equal to 500kW, If the transformer capacity is greater than 500kW and less than 1MW, If the transformer capacity is greater than or equal to 1MW, The selection of the above coefficients can be adjusted according to the actual situation.

[0032] In step 22, when the instantaneous current value at the PCS output terminal is overcurrent and less than the first threshold, the adjustment coefficient for calculating the duty cycle is set. The initial value is used to determine the modulation depth coefficient M through a fuzzy logic control algorithm, thereby reducing the instantaneous current value at the PCS output. Specifically, if and By adjusting formula (3) The value controls the next duty cycle, and is adjusted according to fuzzy logic rules. The value is then used to obtain the duty cycle at time (k+1). .

[0033] Furthermore, the method for determining the modulation depth coefficient M using a fuzzy logic control algorithm includes the following steps: Step 221: Calculate the current error between the instantaneous current value at the PCS output and the rated current value of the power conversion system (PCS). The per-unit value; Step 222: Establish the membership function of the current error, and determine the value of the modulation depth coefficient M corresponding to the current current error according to the fuzzy rules; like Figure 3 and Figure 4 As shown, based on the range of variation of the per-unit value of the current error, it is divided into 7 segments: {-1.5, -1.3, -1.2, 1.0, 1.2, 1.3, 1.5}; And these correspond to the following 7 types of fuzzy linguistic variables: {NB,NM,NS,ZE.PS,PM,PB}; The corresponding values ​​are -1.5 for NB, -1.3 for NM, -1.2 for NS, 0 for ZE, 1.2 for PS, 1.3 for PM, and 1.5 for PB. Current error Membership function The expression is: {-1.5, -1.3, -1.2, 1.0, 1.2, 1.3, 1.5} → {NB, NM, NS, ZE.PS, PM, PB} like Figure 3 As shown, the membership function of the modulation depth coefficient M in this embodiment {NB,NM,NS,ZE.PS,PM,PB}→{0.2, 0.4, 0.6, 0, 0.6, 0.4, 0.6}; According to the fuzzy rules, the modulation depth coefficient M value corresponding to the current current error is determined. Specifically, the fuzzy values ​​of the modulation depth coefficient {NB, NM, NS, ZE.PS, PM, PB} are obtained according to the fuzzy logic rule table. Through defuzzification, the fuzzy values ​​of the modulation depth coefficient are converted into the actual value M. For example, if the per-unit value of the current current error varies within -1.5, then the fuzzy value of the modulation depth coefficient is NB, and the modulation depth coefficient M is 0.2, and so on. This embodiment uses the fuzzy logic rule table shown in Table 1 to defuzzify the fuzzy values ​​of the mapped weight coefficients, for example... For PM, For PM, M takes the value of 0.4 through its membership function; the adaptive adjustment weight coefficient M is substituted into formula (3) to realize the adaptive adjustment of the duty cycle and complete the automatic adjustment of the duty cycle based on the transformer switching period.

[0034] Table 1. Fuzzy Logic Rule Table;

[0035] This embodiment achieves real-time adaptive adjustment of the modulation depth coefficient M through dynamic mapping and defuzzification operations of fuzzy logic rules, effectively suppressing the instantaneous current surge during transformer switching and improving the dynamic response accuracy and stability of the system. By real-time acquisition of the current error and its rate of change during the transformer switching process, combined with preset membership functions and fuzzy rule tables, the system can dynamically output the optimal modulation depth coefficient M, ensuring smooth duty cycle adjustment and rapid response. Experimental results show that this method significantly reduces current overshoot, shortens adjustment time, and improves power quality and equipment operational reliability.

[0036] After an overcurrent signal occurs, step 2 above adjusts M to limit the PCS current, which disrupts the voltage amplitude and phase of the PCS output. After the current error decreases to 1.0 times the rated current for several consecutive interrupt cycles, the SPWM voltage output sequence is gradually restored by real-time comparison and adjustment of the duty cycle to ensure the voltage amplitude and phase of the PCS output.

[0037] Step 3 is the method for voltage pulse and phase recovery after the excitation inrush current disappears. Specifically: when the instantaneous current value is less than the rated operating current set by the PCS, and when the instantaneous current value is less than the rated operating current set by the PCS within the set interruption period, the duty cycle is gradually increased. By increasing the number of pulses, the voltage and phase are gradually restored to match the normal duty cycle value.

[0038] Recovery is initiated when the instantaneous current value within the set interruption period is less than the rated operating current set by the PCS, i.e., when the following conditions are met: The instantaneous current is less than the rated operating current of the PCS for multiple consecutive interruption cycles (such as the set S cycles); The inrush current has disappeared, and the system has entered a stable state.

[0039] Furthermore, in step 3, the duty cycle is gradually increased to gradually match the normal duty cycle value, thereby restoring the voltage and phase. This method includes the following steps: Step 31: Generate the duty cycle data for each PWM cycle during normal operation in advance according to formula (1), and store it as a comparison database; This database serves as the target reference for recovery, ensuring that the recovered duty cycle sequence conforms to a sinusoidal pattern (SPWM modulation requirement). Step 32: Determine the duty cycle deviation: Calculate the difference between the duty cycle suppressed by the fuzzy logic algorithm (i.e., the duty cycle obtained in step 22) and the normal duty cycle. The calculation formula is: ; in, Indicates the normal duty cycle; This represents the duty cycle after suppression based on the fuzzy logic algorithm; Step 33: When the instantaneous current value within the set interrupt cycle is less than the rated operating current set by the PCS, in each subsequent interrupt cycle, a new duty cycle is obtained by adding a set multiple of the difference to the duty cycle suppressed by the fuzzy logic algorithm, which is then used as the duty cycle for the next interrupt cycle. This process is repeated for multiple interrupt cycles until the voltage amplitude and phase output by the PCS are restored.

[0040] In the If the instantaneous current is less than the PCS rated operating current for multiple consecutive interrupt cycles (e.g., S cycles), then the status label will be displayed. The duty cycle deviation is obtained through the above 32 steps. ,Will Add 0.5 times to In this way, the PWM duty cycle is restored through several interrupt cycles, thereby restoring the voltage amplitude and phase of the PCS output.

[0041] (5); like Figure 5 As shown, Figure 4 The lower middle section represents the PWM duty cycle during current suppression. The upper section represents the PWM duty cycle when the output voltage is normal. By using the duty cycle recovery calculation formula (5) mentioned above, the output voltage amplitude and phase can be gradually recovered.

[0042] The above process is based on the fuzzy logic control algorithm integrated inside the energy storage converter (PCS). It uses the current error segmented membership function and fuzzy inference rules to realize the real-time dynamic adjustment of the SPWM duty cycle, thereby suppressing the inrush current during transformer switching without relying on external circuit breaker control or needing a series current limiting resistor.

[0043] This embodiment proposes a dynamic control method for transformer inrush current suppression, using an energy storage converter as the control core and integrating fuzzy logic and SPWM modulation algorithms. It exhibits significant technological advancements in control strategy, system integration capabilities, and adaptability to complex operating conditions. First, unlike existing hardware solutions relying on circuit breaker phase angle control or series current-limiting resistors, this invention achieves software integration of the inrush current control algorithm, requiring no additional hardware modifications and offering greater flexibility and compatibility. Second, by introducing a fuzzy logic reasoning mechanism, it achieves intelligent identification and adaptive adjustment of transformer capacity, current surge amplitude, and overcurrent state, overcoming the technical bottlenecks of traditional PID control's sluggish response and difficulty in parameter adjustment under nonlinear strong disturbance scenarios. Third, this solution is specifically designed for multi-mode operation, high-impact load, and high-frequency switching environments such as mining microgrids, possessing strong robustness and wide adaptability, significantly improving system operational stability and equipment safety.

[0044] To illustrate the implementation process of the above embodiments, a specific example is given below, wherein the first threshold is set as follows. The following is combined with Figure 2 The flowchart in the document provides a detailed explanation of the methods for suppressing inrush current generated during transformer switching and the subsequent phase recovery. Step 1: Real-time detection of the instantaneous current value at the downstream end of the power device, and obtaining the value based on the rated current value of the power conversion system (PCS). .

[0045] Step two, if an overcurrent occurs, first determine... ,in Convert the detected instantaneous current value into a per-unit value. This is the per-unit value of the rated operating current set according to the capacity of the power device.

[0046] Step 3, if Adjust according to formula (4) To control the value of the next duty cycle. Set it in advance according to the capacity of the downstream transformer. If after modulation ,but The minimum current is maintained during the guarantee period to establish the magnetic field of the transformer.

[0047] Step 4, make a judgment If the number of interrupt cycles exceeds the set maximum number, such as 200, an alarm will be triggered, and then the process will jump to the end; if it does not exceed the maximum number, the process will jump to step three. Step 5, if and If an overcurrent is detected in the power device, and the power device can operate within the overcurrent range, proceed to step six.

[0048] Step six, in formula (3), set By adjusting This controls the value of the next duty cycle; based on the current error, the range of per-unit current error values ​​is divided into 7 segments, and adjustments are made according to fuzzy logic rules. The value is then used to obtain the duty cycle at time (k+1). .

[0049] Step 7, Determine and If the count exceeds the set maximum number, such as 200, an alarm will sound and the process will end. If the count does not exceed the maximum number, proceed to step five.

[0050] Step 8, if judgment If yes, proceed to step nine; otherwise, repeat step eight.

[0051] Step 9, Determine Check if the count has reached S interrupt cycles. If yes, execute step ten, the phase recovery method. Depending on the actual situation, S can be 3-5 interrupt cycles. If not, repeat step nine.

[0052] Step 10: By comparing the duty cycle values ​​before and after current suppression, gradually increase the duty cycle according to the proposed method, and gradually match the normal duty cycle value by increasing the pulse, thereby realizing the recovery of voltage and phase. The transformer switching inrush current and phase jump suppression method provided in this embodiment addresses the high-frequency, high-impact, and strong-disturbance operating environment of mining microgrids. It overcomes the limitations of traditional PID control or electrical switching devices, which suffer from slow response and poor adaptability. By employing a control strategy integrated within the energy storage converter (PCS), and through the synergistic effect of SPWM modulation and fuzzy logic algorithms, real-time, dynamic, and precise control of the inrush current is achieved. Actual project verification shows that the energy storage converter (PCS) can withstand transformer inrush currents up to 150% of its rated capacity, effectively handling the impact of large-capacity transformer switching without requiring additional energy storage. This method significantly reduces the peak and duration of the excitation current, ensuring system voltage stability, preventing protection malfunctions, and improving the operational reliability and adaptability of the microgrid. Experimental data shows that even when transformer switching causes a brief voltage drop or overshoot on the medium-voltage bus, the system maintains stable operation, providing customers with continuous and reliable power security.

[0053] Example 2 Based on Embodiment 1, this embodiment provides a transformer switching inrush current and phase jump suppression system, including: The current judgment module is configured to control the output voltage of the energy storage converter through a sinusoidal pulse width modulation algorithm, acquire and detect the instantaneous current value at the output terminal of the energy storage converter in real time, and determine whether an overcurrent has occurred. The current limiting module is configured to, if an overcurrent is detected, determine the modulation depth coefficient based on the current current error range using a fuzzy logic control algorithm, dynamically calculate and adjust the duty cycle of the next PWM pulse cycle to achieve current limiting. The output voltage and phase recovery module is configured to gradually increase the PWM pulse duty cycle to restore normal output when the instantaneous current value is less than the rated operating current set by the energy storage converter. By gradually increasing the PWM pulse to match the normal duty cycle value, the output voltage and phase of the energy storage converter are restored.

[0054] It should be noted that each module in this embodiment corresponds one-to-one with each step in embodiment 1, and their specific implementation process is the same, so it will not be repeated here.

[0055] Example 3 Based on Embodiment 1, this embodiment provides an electronic device, including a memory and a processor, as well as computer instructions stored in the memory and running on the processor. When the computer instructions are executed by the processor, they complete the steps in the transformer switching inrush current and phase jump suppression method described in Embodiment 1.

[0056] Example 4 Based on Embodiment 1, this embodiment provides a computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, they complete the steps in the method for suppressing inrush current and phase jump of transformer switching as described in Embodiment 1.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0058] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for suppressing inrush current and phase jump of transformer switching, applied to a power system comprising an energy storage converter, the energy storage converter supplies power for the transformer, characterized in that, The method comprises the following steps: The output voltage of the energy storage converter is controlled by a sine wave pulse width modulation algorithm, and the instantaneous current value of the output end of the energy storage converter is obtained in real time, and it is determined whether overcurrent occurs; If overcurrent is detected, the modulation depth coefficient is determined according to the interval in which the current error is located by using a fuzzy logic control algorithm, the duty cycle of the next PWM pulse period is dynamically calculated and adjusted, so as to realize current limitation; When the instantaneous current value is less than the rated operating current of the energy storage converter, the PWM pulse duty cycle is gradually increased to restore normal output, and the PWM pulse is gradually increased to be consistent with the normal duty cycle value, so as to realize the recovery of the output voltage and phase of the energy storage converter.

2. The transformer switching inrush current and phase jump suppression method according to claim 1, characterized in that: The duty cycle calculation formula is: ； wherein, for controlling the current instantaneous overcurrent, for the first duty cycle of the waveform interruption, for the number of interruption periods, for the modulation depth coefficient, which modulates according to the output voltage and current conditions; for the first duty cycle of the waveform interruption, for the total number of interruptions required for the generation of a half-cycle waveform.

3. A method of transformer inrush and phase jump suppression by switching, according to claim 1, characterized in that: The method for obtaining the instantaneous current value of the output end of the energy storage converter in real time and determining whether overcurrent occurs comprises the following steps: The instantaneous current value of the output end of the energy storage converter is converted into a per-unit value, and the per-unit value is compared with the per-unit value of the rated current value of the energy conversion system; If the per-unit value of the instantaneous current value is greater than the per-unit value of the rated current value of the energy conversion system, it is determined that overcurrent occurs.

4. A method of transformer inrush and phase jump suppression by switching as claimed in claim 1, characterized in that: If overcurrent is detected, the modulation depth coefficient is determined according to the interval in which the current error is located by using a fuzzy logic control algorithm, the duty cycle of the next PWM pulse period is dynamically calculated and adjusted, so as to realize current limitation. A first threshold is set, and if the instantaneous current value at the output end of the energy storage converter is not less than the first threshold, an adjustment coefficient of the duty cycle is calculated The duty cycle is calculated, and the instantaneous current value at the output end of the energy storage converter is reduced. When the instantaneous current value of the output end of the energy storage converter is overcurrent and less than the first threshold value, the modulation depth coefficient M is determined by using a fuzzy logic control algorithm, and the instantaneous current value of the output end of the energy storage converter is reduced.

5. The transformer switching inrush current and phase jump suppression method according to claim 4, characterized in that: Adjusting factor for duty cycle The process of calculating the duty cycle and reducing the instantaneous current value at the output of the energy storage converter is as follows: Step 211, if overcurrent occurs, it is judged whether the set first threshold is exceeded, if not less than the set first threshold, the adjustment coefficient for calculating the duty cycle Based on transformer capacity adjustment, the larger the capacity, the smaller the adjustment coefficient The smaller, the value for calculating the next duty cycle; Step 212: The width of the output PWM pulse signal is adjusted based on the calculated duty cycle, and the output voltage and current of the energy storage converter are controlled for modulation; Step 213: The instantaneous current value of the output end of the energy storage converter after modulation is obtained, and it is determined whether the instantaneous current value is less than the first threshold value. If not, steps 211 to 212 are executed in a loop until the number of cycles is met or the instantaneous current value is less than the first threshold value. If the number of cycles is reached and the instantaneous current value of the output end of the energy storage converter is still not less than the first threshold value, an alarm is given, and the process is ended. If the instantaneous current value of the output end of the energy storage converter is less than the first threshold value, the next step is executed.

6. A method of transformer inrush and phase jump suppression by switching, according to claim 4, characterized in that: When the instantaneous current value at the output end of the energy storage converter is overcurrent and less than a first threshold value, an adjustment coefficient for calculating the duty cycle is set The modulation depth coefficient M is determined by a fuzzy logic control algorithm as an initial value, and the instantaneous current value at the output end of the energy storage converter is reduced.

7. A method of transformer inrush and phase jump suppression by switching, according to claim 4, characterized in that: The method for determining the modulation depth coefficient M by using a fuzzy logic control algorithm comprises the following steps: calculating a current error between an instantaneous current value at an output of the energy storage converter and a rated current value of the energy conversion system in units of per unit A current error membership function is established, and the modulation depth coefficient M value corresponding to the current current error is determined according to a fuzzy rule.

8. A transformer inrush and phase jump suppression system for switching, characterized by, It comprises: The current judgment module is configured to control the output voltage of the energy storage converter by a sine wave pulse width modulation algorithm, and to obtain the instantaneous current value of the output end of the energy storage converter in real time, and to determine whether overcurrent occurs; The current limitation module is configured to, if overcurrent is detected, determine the modulation depth coefficient according to the interval in which the current error is located by using a fuzzy logic control algorithm, dynamically calculate and adjust the duty cycle of the next PWM pulse period, so as to realize current limitation. The output voltage and phase recovery module is configured to gradually increase the duty cycle of the PWM pulse to recover normal output when the instantaneous current value is less than the rated operating current set by the energy storage converter, and gradually consistent with the normal duty cycle value through the increase of the PWM pulse, so as to realize the recovery of the output voltage and phase of the energy storage converter.

9. An electronic device, comprising: The computer program product comprises a memory and a processor, and computer instructions stored in the memory and run on the processor, and when the computer instructions are run by the processor, the steps of the transformer switching excitation inrush current and phase jump suppression method in any one of claims 1-7 are completed.

10. A computer-readable storage medium, characterized in that, The computer program product is used for storing computer instructions, and when the computer instructions are executed by the processor, the steps of the transformer switching excitation inrush current and phase jump suppression method in any one of claims 1-7 are completed.

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