Super-capacitor direct-current power supply and back-up power supply switching method

Abstract

The invention discloses a switching method for a back-up power supply of a super-capacitor direct-current power supply, relates to the technical field of direct-current power supply of a power system, and can at least partially solve the problems of low fault identification accuracy, large impact current and loose switching flow connection in the switching process of the existing direct-current back-up power supply. The method comprises the steps that main supply line current, bus voltage, new energy output power, load power and the state of an energy storage device are collected, and filtering processing and power correction are carried out; calculating a harmonic energy distribution coefficient and a sudden change value thereof, performing island state judgment in combination with an electrical quantity threshold value, and triggering a spare power automatic switching process; a source load power difference value is calculated, a dynamic penalty function optimization model is constructed, and a storage consumption coordinated regulation strategy is executed according to power surplus or gap; after the grid-connected condition is verified, the standby line switch is closed, the system stability coefficient is calculated, and the energy consumption resistor is gradually withdrawn. According to the invention, automatic switching of the direct-current back-up power supply with high fault identification accuracy, small impact current and controllable voltage fluctuation is realized.

Description

Technical Field

[0001] This invention relates to the field of DC power supply technology for power systems, and specifically to a method for switching backup power supplies from supercapacitor DC power supplies. Background Technology

[0002] Supercapacitors have become the core choice for DC backup power supplies due to their advantages such as high power density, fast charging and discharging speed, and long cycle life, but their switching technology still has many pain points.

[0003] In terms of fault identification, traditional methods rely on single voltage and current threshold detection, which is susceptible to harmonic interference, resulting in low fault identification accuracy. Industrial scenarios are characterized by significant electromagnetic interference, and single threshold detection methods are prone to misjudgments, leading to malfunctions or failures to operate in automatic transfer switch systems, thus affecting power supply reliability.

[0004] Regarding switching impacts, the lack of precise source-load power calculation and dynamic adjustment mechanisms means that the inrush current during switching can reach three times the rated current, easily damaging switchgear and new energy units. Traditional switching methods do not consider the fluctuations in new energy output power due to environmental factors, making precise power matching impossible.

[0005] Regarding optimization strategies, existing strategies are static and cannot adapt to dynamic changes in the system, resulting in a switching success rate of only about 95%. Static parameter settings cannot cope with dynamic scenarios such as fluctuations in renewable energy power and load changes, leading to severe voltage fluctuations and significant frequency shifts during the switching process.

[0006] In terms of process integration, the transition between different stages is loosely connected and lacks effective feedback and verification. Data transfer between steps is inefficient, and there is a lack of closed-loop control mechanisms, making it impossible to adjust strategies in a timely manner when anomalies occur during the transition.

[0007] Although existing AC system backup automatic transfer strategies introduce source-load-storage balance and dynamic penalty function optimization, DC systems lack phase characteristics, are sensitive to voltage ripple, and the charging and discharging characteristics of supercapacitors differ significantly from those of AC energy storage devices, making direct transfer impossible.

[0008] Therefore, there is an urgent need to develop a supercapacitor DC backup power switching method that is streamlined, logically interconnected, and balances speed and stability. Summary of the Invention

[0009] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a method for switching backup power supply for supercapacitor DC power supply.

[0010] To achieve the above objectives, the present invention provides a method for switching backup power from a supercapacitor DC power supply, comprising: The system collects the main power supply line current, bus voltage, new energy output power, load power, and energy storage device status. It filters the collected electrical signals, corrects the new energy output power based on environmental parameters to obtain the corrected new energy power, and calculates the system equivalent reactance. The harmonic energy distribution coefficient and its abrupt change value are calculated based on the filtered electrical signal. When the abrupt change value is greater than the preset abrupt change threshold, the bus voltage is in the preset residual voltage range, and the main power supply line current is less than the preset current threshold, it is determined to be an island state. If the duration of the island state reaches the preset time threshold, the backup automatic transfer process is triggered and the main power supply line switch is blocked. The source-load power difference is calculated based on the corrected new energy power and the load power. A dynamic penalty function optimization model is constructed, which includes energy storage power, energy consumption resistor power and constraint penalty terms. When the source-load power difference is positive, the number of energy consumption resistors is calculated and the charging power of the energy storage device is adjusted. When the source-load power difference is negative, the discharging power of the energy storage device is adjusted. When the closing inrush current, bus voltage fluctuation, and system frequency offset all meet the preset constraints and continue to meet the preset grid connection time, a closing command is sent to the standby line switch. After grid connection is completed, the system stability coefficient is calculated. When the system stability coefficient reaches the preset stability threshold and continues to meet the preset stability time, the installed energy-consuming resistors are gradually removed and the energy storage device is adjusted to standby status.

[0011] Furthermore, the filtering process employs the Kalman filtering algorithm, with a sampling frequency of not less than 1 kHz; The formula for correcting the output power of new energy sources is as follows: ; in, To correct the output power of the new energy source, Real-time power output for new energy sources This is the temperature correction factor. For real-time ambient temperature, Standard reference temperature; When the new energy source is wind power This is the wind speed correction factor. For real-time wind speed, The rated wind speed of the fan; When the new energy source is photovoltaics This is the illumination correction factor. For real-time light intensity, Rated light intensity for photovoltaic modules.

[0012] Furthermore, the formula for calculating the equivalent reactance of the system is as follows: ; in, The equivalent reactance of the system is... For the grid-side equivalent reactance, For the equivalent reactance on the new energy side, This is the equivalent reactance of the load.

[0013] Furthermore, the formula for calculating the harmonic energy distribution coefficient is as follows: ; in, For the first Energy distribution coefficient of subharmonics For the first The instantaneous energy of subharmonics This represents the total number of harmonics involved in the calculation; The formula for calculating the mutation value is: ; in, The abrupt change value of the harmonic energy distribution coefficient. The sampling interval is... The first sampling time of the previous sampling time Subharmonic energy distribution coefficient.

[0014] Furthermore, the preset mutation threshold is 0.15, the preset residual voltage range is 0.3 to 0.7 times the system rated voltage, the preset current threshold is 0.05 times the system rated current, and the preset time threshold is 50ms.

[0015] Furthermore, the formula for calculating the source-load power difference is as follows: ; in, The difference between source and load power. The corrected new energy power, Real-time load power; The objective function of the dynamic penalty function optimization model is: ; in, To broaden the objective function, This represents the real-time power of the energy storage device. This represents the total power consumed by the energy-consuming resistor. As a dynamic penalty factor, To constrain penalty items.

[0016] Furthermore, the formula for calculating the constraint penalty term is as follows: ; in, to To constrain the weighting coefficients, This is the closing inrush current. The rated current of the system. This refers to the bus voltage fluctuation. The system's rated voltage. This is the system frequency offset. This represents the maximum charging and discharging power of the energy storage device. The update formula for the dynamic penalty factor is: ; in, This represents the current iteration number. The maximum number of iterations, and This is the adjustment constant.

[0017] Furthermore, when the source-load power difference is positive, the formula for calculating the number of energy-consuming resistors to be connected is: ; in, This refers to the number of energy-consuming resistors that need to be installed. This is the power redundancy factor. It is a rounding function. The rated power of a single power-consuming resistor; The formula for calculating the charging power of the energy storage device is as follows: ; in, Power to charge energy storage devices, This represents the state of charge (SBC) value of the energy storage device. The rated capacity of the energy storage device, For charging efficiency, Adjust the charging time step; When the source-load power difference is negative, the formula for calculating the discharge power of the energy storage device is: ; in, This refers to the discharge power of the energy storage device. This refers to the discharge efficiency.

[0018] Furthermore, the formula for calculating the system stability coefficient is as follows: ; in, The system stability coefficient, The system's rated frequency; The preset stability threshold is 0.95, and the preset stability time is 100ms.

[0019] Furthermore, the formula for gradually withdrawing the installed energy-consuming resistors is as follows: ; in, For grid connection The remaining number of energy-consuming resistors in operation at any given time. The number of energy-consuming resistors put in at the previous moment. The duration after grid connection, The time constant for removing the energy-consuming resistor; The process of adjusting the energy storage device to standby mode involves adjusting the charging and discharging of the energy storage device to restore its state of charge value to a range of 0.5 to 0.8 times the rated capacity of the energy storage device.

[0020] The beneficial effects of this invention are as follows: This invention integrates harmonic characteristics and electrical quantity thresholds as dual criteria, resulting in strong anti-interference capabilities and an identification accuracy rate exceeding 99.5%, completely resolving the failure problem of traditional automatic transfer switch criteria. Through coordinated adjustment of energy storage and dynamic penalty function optimization, the closing inrush current is controlled within twice the rated current, reducing it by more than 60% compared to traditional methods, effectively protecting switchgear and new energy units. When the power source exceeds the load, energy consumption and energy storage work together to absorb the surplus power. When the power source is less than the load, energy storage discharges to supplement the power gap. There is no need to cut off new energy sources or loads. Voltage fluctuations are controlled within ±0.07 times the rated voltage, and frequency deviations are controlled within ±1Hz. New energy sources are not disconnected throughout the process. Through dynamic optimization to adapt to power fluctuations, the utilization rate of new energy sources is increased to over 90%, taking into account both the economic efficiency and reliability of power supply. Attached Figure Description

[0021] Figure 1 A flowchart of a supercapacitor DC power supply backup power switching method according to a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the automatic backup switching system according to a specific embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application. It should be understood that the specific embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0023] like Figure 1 and Figure 2 As shown in the specific embodiment of the present invention, the supercapacitor DC power supply backup power switching method is applied to a 110kV substation automatic transfer system with a doubly-fed wind turbine. The core system parameters include: system rated voltage. 110kV, rated current 500A, rated frequency The frequency is 50Hz; the new energy module uses a doubly-fed wind turbine with a rated power of 5MVA and a rated wind speed of 50Hz. 12 m / s, temperature correction factor Wind speed correction factor: 0.002 / ℃ The value is 0.01; the energy storage module uses a supercapacitor with a rated capacity of It has a capacity of 100kWh and a maximum charge / discharge power. It has a power output of 500kW and a charge / discharge efficiency of [missing information]. and All are 0.95; the rated power of a single energy-consuming resistor module For 50kW, the maximum number of units that can be put into operation There are 10; real-time load power of load modules It is 3MW.

[0024] The automatic transfer switch system of this invention includes a main power supply module, a backup power supply module, a new energy module, an energy storage module, an energy-consuming resistor module, a load module, a multi-dimensional monitoring module, and a central control module. The main power supply module is connected to the busbar via a switch and is responsible for supplying power under normal operating conditions. The backup power supply module is connected to the busbar via a switch and takes over power supply when the main power supply line fails. The new energy module includes a doubly-fed induction generator (DFIG) and its control system, connected to the busbar via a transformer. The energy storage module includes a supercapacitor bank and its charging and discharging control system, connected to the busbar via a bidirectional converter. The energy-consuming resistor module includes multiple sets of switchable energy-consuming resistors, connected to the busbar via a switch. The load module includes various electrical devices, connected to the busbar via feeders. The multi-dimensional monitoring module includes current transformers, voltage transformers, power metering devices, and energy storage status monitoring devices distributed at various nodes. The central control module receives data from the multi-dimensional monitoring module and implements closed-loop control of the automatic transfer switch system according to the method steps of this invention.

[0025] The supercapacitor DC power supply backup power switching method of the present invention includes the following steps: Step 1: Multi-dimensional electrical quantity monitoring and new energy power correction.

[0026] This step is fundamental to the entire automatic transfer switch (ATS) process. Its core purpose is to collect comprehensive and accurate system operation data and adjust the output power of renewable energy sources to eliminate environmental interference. First, the main power supply line current is simultaneously collected using a high-frequency sampling module. Bus voltage New energy output power Load power And the status of energy storage devices. The sampling frequency is set to 1kHz to ensure that rapidly changing electrical signals such as fluctuations in new energy power and voltage surges during faults are captured.

[0027] In this embodiment, the main power supply line current is collected. 480A, bus voltage 108kV, wind turbine output power 4MW, real-time ambient temperature 30℃, real-time wind speed 13 m / s, energy storage state of charge It is 0.6.

[0028] The Kalman filter algorithm is used to denoise the acquired signals. Kalman filtering can effectively eliminate the influence of measurement noise and system noise, improve the accuracy and stability of electrical quantity data, and provide a reliable data foundation for subsequent islanding detection and power optimization.

[0029] To address the randomness of renewable energy output being affected by temperature and wind speed, a correction is made to the renewable energy output power. Increased temperature reduces the photoelectric conversion efficiency of photovoltaic modules and the heat dissipation performance of wind turbine windings, while wind speed deviations from rated values ​​directly alter the wind turbine's output power. The corrected renewable energy power calculation formula is as follows: ; in, The corrected output power of the new energy source is expressed in MW. This refers to the real-time output power of new energy sources, measured in MW. This is a temperature correction factor, with units of 1 / ℃. In this embodiment, the value is 0.002 / ℃. This is the real-time ambient temperature, in °C. The standard reference temperature is fixed at 25℃. The wind speed correction factor is 0.01 in this implementation method; Real-time wind speed, in m / s; The rated wind speed of the fan is given in m / s; in this implementation, it is taken as 12 m / s. Substituting the values, we get: .

[0030] Simultaneously, the system's equivalent reactance is calculated, comprehensively considering the reactance characteristics of the grid side, the renewable energy side, and the load side. The formula for calculating the system's equivalent reactance is: ; in, The system equivalent reactance is expressed in units of 1. ; The equivalent reactance on the grid side is expressed in units of 1. In this embodiment, the value is 12. ; The equivalent reactance on the new energy side is expressed in units of 1. In this embodiment, the value is 5. ; The equivalent reactance of the load is expressed in units of 1. In this embodiment, the value is 3. Substituting the numerical values, we get: .

[0031] This step also calculates the voltage phase shift at the grid connection point, a parameter that directly reflects the degree of power imbalance between the source and load. The formula for calculating the voltage phase shift is: ; in, The voltage phase change at the grid connection point, in units of Substituting the numerical values, we get: All processing results from this step are transmitted in real time to the next step, forming a complete data link that lays the foundation for islanding detection and power optimization adjustment.

[0032] Step 2: Island status determination and backup self-disconnection triggering.

[0033] This step, based on the preprocessed data from Step 1, addresses the issue of traditional automatic switchover criteria failing, achieving accurate identification of islanded states. Traditional methods rely solely on voltage and current threshold detection, making them susceptible to electromagnetic interference in industrial environments, leading to misjudgments. This method integrates harmonic characteristics and electrical quantity thresholds as dual criteria, improving the reliability of the judgment.

[0034] First, calculate the harmonic energy distribution coefficient. Under normal system operation, the harmonic energy distribution is relatively stable; however, when the main power supply line is disconnected and islanding occurs, the system impedance changes abruptly, causing a drastic change in the harmonic energy distribution. This coefficient effectively captures this characteristic. The formula for calculating the harmonic energy distribution coefficient is: ; in, For the first Energy distribution coefficient of subharmonics; For the first The instantaneous energy of a subharmonic wave is expressed in kJ. The total number of harmonics included in the calculation is set to 5 by default.

[0035] Calculate the abrupt change value of the harmonic energy distribution coefficient: ; in, This represents the abrupt change in the harmonic energy distribution coefficient. The sampling interval is a fixed value of 1ms; The first sampling time of the previous sampling time Subharmonic energy distribution coefficient.

[0036] When the following three conditions are met, it is preliminarily determined to be in an islanded state: abrupt change in the harmonic energy distribution coefficient. Greater than 0.15; bus voltage It falls within the range of 0.3 to 0.7 times the system's rated voltage, i.e. Corresponding to 33kV to 77kV; main power supply line current Less than 0.05 times the system rated current, i.e. , corresponding to 25A.

[0037] To avoid false triggering caused by momentary faults, a 50ms state duration check is set. Only when the islanded state remains stable for 50ms will the automatic transfer switch be triggered, and the main power supply line switch be blocked to prevent the main power supply line from being accidentally closed and aggravating the fault.

[0038] In this embodiment, When the main power supply line fails, data is collected. A less than 25A, bus voltage kV is in the range of 33kV to 77kV, and the harmonic energy distribution coefficient has a sudden change value. If the value is greater than 0.15, and the islanding state persists for 60ms, the automatic transfer switch is triggered, and the main power supply line switch is blocked. This step, through dual criteria and time verification, improves the islanding identification accuracy to over 99.5%, ensuring the reliability of the automatic transfer switch triggering.

[0039] Step 3: Optimize the balance between source, load and storage and coordinate the regulation of storage and consumption.

[0040] This step is crucial for suppressing the closing inrush current and balancing system power. It works directly based on the corrected power from step one and the standby automatic transfer trigger signal from step two. First, the source-load power difference is calculated to determine whether the system is in a power surplus or power deficit state. The formula for calculating the source-load power difference is: ; in, This represents the power difference between the source and load, measured in MW. A positive value indicates a power surplus in the system, while a negative value indicates a power deficit in the system. The corrected power output of new energy sources is expressed in MW. This represents the real-time power of the load, in MW. In this embodiment, If the value is positive, the system is in a power surplus state.

[0041] Subsequently, a dynamic penalty function optimization model is constructed. The core of the augmented objective function is to minimize the power imbalance between source and load and the penalty for constraint violation, ensuring that the regulation strategy satisfies both power balance and system safety constraints. The augmented objective function is: ; in, To broaden the objective function; This represents the real-time power of the energy storage device, measured in MW. Positive values ​​indicate discharging, and negative values ​​indicate charging. This represents the total power consumed by the energy-consuming resistor, expressed in MW. It is a dynamic penalty factor; To constrain penalty items.

[0042] The constraint penalty term incorporates key constraints such as closing inrush current, voltage fluctuation, frequency deviation, and energy storage output limits into the optimization. When a constraint is violated, the penalty term increases accordingly, forcing a correction in the optimization direction. The formula for calculating the constraint penalty term is: ; in, to To constrain the weighting coefficients, all are set to 1.0; This is the closing inrush current, in kA. The rated current of the system is 500A in this embodiment; This represents the bus voltage fluctuation, in kV. The system's rated voltage is 110kV in this embodiment; This represents the system frequency offset, in Hz. The maximum charging and discharging power of the energy storage device is 500kW in this embodiment.

[0043] The dynamic penalty factor adaptively adjusts with the number of iterations, improving the accuracy of solving the objective function. The formula for updating the dynamic penalty factor is: ; in, This represents the current iteration number; The maximum number of iterations is a fixed value of 20. This is the adjustment constant.

[0044] In this embodiment, the initial penalty factor is calculated. .

[0045] A power surplus scenario is addressed by implementing a coordinated power storage and consumption adjustment strategy. When calculating the number of energy-consuming resistors to be installed, prioritize the use of these resistors to quickly dissipate excess power. The formula for calculating the number of energy-consuming resistors to be installed is: ; in, The number of energy-consuming resistors to be installed is given in units. This is the power redundancy factor; It is a rounding function; The rated power of a single power-consuming resistor is 50kW in this embodiment. Substituting the values, we get: Due to the maximum number of units that can be put into operation, 10 units were actually put into operation, with a total power consumption of 500kW.

[0046] The charging power of the energy storage device is adjusted, constrained by the current state of charge, rated capacity, and charging efficiency to avoid overcharging. The formula for calculating the charging power of the energy storage device is: ; in, The charging power of energy storage devices, measured in MW; The value of the state of charge of the energy storage device is 0.6 in this embodiment; The rated capacity of the energy storage device is 100 kWh in this embodiment; For charging efficiency, this embodiment uses a value of 0.95; The charging adjustment time step is fixed at 0.01s. Substituting the values, we get: Due to the limitation of maximum charge and discharge power, the actual charging power is 500kW.

[0047] For power deficit scenarios, when At this time, adjusting the discharge power of the energy storage device directly compensates for the power shortfall without disconnecting any load. The formula for calculating the discharge power of the energy storage device is: ; in, The discharge power of the energy storage device is expressed in MW. For discharge efficiency, this implementation uses a value of 0.95. The discharge power is constrained by the remaining energy storage capacity and discharge efficiency to avoid over-discharge and ensure power supply continuity.

[0048] This step, through energy storage and energy consumption coordination and dynamic optimization, strictly suppresses the closing inrush current to within twice the rated current, and controls voltage fluctuations and frequency deviations within the system's allowable range. The charging and discharging power constraints of the energy storage device meet the requirements. Energy state constraints satisfy .

[0049] Step 4: Simultaneous grid connection and system stability recovery.

[0050] This step, based on the adjustment results of step three, achieves smooth grid connection and system reset, forming a closed-loop control. First, the adjusted system electrical quantities are verified. Synchronous grid connection is only satisfied when the following three grid connection conditions are met and maintained stably for more than 10ms, thus avoiding equipment surges during grid connection: closing inrush current. That is, not exceeding 1000A; voltage fluctuation That is, not exceeding 7.7kV; frequency offset .

[0051] In this embodiment, the closing inrush current was detected after adjustment. Less than 1000A, voltage fluctuation Less than 7.7kV, frequency offset The frequency is less than 1 Hz and the duration is 15 ms to meet the grid connection requirements.

[0052] After the grid connection conditions are met, a closing command is sent to the standby line switch. The grid connection operation is completed after the switch is reliably closed. The detection delay for reliable switch closure is set to 100ms. In this embodiment, the standby line switch is closed, and grid connection is detected successfully 100ms later.

[0053] After grid connection is completed, the system's operating status is continuously monitored, and the system stability coefficient is calculated. The system stability coefficient integrates three major indicators: voltage stability, frequency stability, and power balance. The formula for calculating the system stability coefficient is: ; in, This is the system stability coefficient, with a value ranging from 0 to 1; The system's rated frequency is a fixed value of 50Hz. Substituting the values, we get: Continued monitoring will continue until... .

[0054] when When the duration reaches 100ms, the system is considered to have reached a stable operating state. Subsequently, the installed energy-consuming resistors are gradually withdrawn, using a gradient withdrawal method to avoid secondary voltage fluctuations during the withdrawal process. The formula for withdrawing the energy-consuming resistors is: ; in, The remaining number of energy-consuming resistors at time t after grid connection, expressed in units; This represents the number of energy-consuming resistors that were activated at the previous moment. The duration after grid connection, in milliseconds (ms). ms is the time constant for removing the power-consuming resistors, measured in milliseconds. In this embodiment, 10 power-consuming resistors are gradually removed, and all are removed after 200ms.

[0055] Simultaneously, the charging and discharging state of the energy storage device is adjusted to a standby state with a state of charge (SBC) of 0.5 to 0.8 times the rated capacity of the energy storage device, preparing for automatic backup switching in the event of a subsequent fault. In this embodiment, the energy storage device is charged to a SBC of 0.7 to restore the standby state. If the grid connection test fails, the process returns to step three to update the penalty factor and adjustment strategy until the grid connection conditions are met.

[0056] In summary, the embodiments disclosed herein have at least the following technical effects: This invention integrates harmonic characteristics and electrical quantity thresholds as dual criteria, resulting in strong anti-interference capabilities and an identification accuracy rate of over 99.5%, completely solving the problem of failure of traditional automatic transfer switch criteria. This invention controls the closing inrush current to within twice the rated current through coordinated regulation of energy storage and dynamic penalty function optimization, reducing it by more than 60% compared to traditional methods, effectively protecting switchgear and new energy units. When the power source is overloaded, energy consumption and energy storage work together to absorb the surplus power. When the power source is underloaded, energy storage discharges to supplement the power gap. There is no need to cut off new energy sources or loads. Voltage fluctuations are controlled within ±0.07 times the rated voltage, and frequency deviations are controlled within ±1Hz. This invention does not disconnect the new energy source throughout the entire process. By dynamically optimizing and adapting to power fluctuations, the utilization rate of the new energy source is increased to over 90%, taking into account both the economic efficiency and reliability of power supply. The data links between each step of this invention are closely connected, forming a complete closed-loop control mechanism. When the grid connection conditions are not met, it can automatically return to the adjustment link for re-optimization, ensuring that the switching success rate reaches more than 99%.

[0057] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for switching backup power to a supercapacitor DC power supply, characterized in that, include: The system collects the main power supply line current, bus voltage, new energy output power, load power, and energy storage device status. It filters the collected electrical signals, corrects the new energy output power based on environmental parameters to obtain the corrected new energy power, and calculates the system equivalent reactance. The harmonic energy distribution coefficient and its abrupt change value are calculated based on the filtered electrical quantities. When the abrupt change value is greater than the preset abrupt change threshold, the bus voltage is in the preset residual voltage range, and the main power supply line current is less than the preset current threshold, it is determined to be an island state. If the duration of the island state reaches the preset time threshold, the backup automatic transfer process is triggered and the main power supply line switch is blocked. The source-load power difference is calculated based on the corrected new energy power and the load power. A dynamic penalty function optimization model is constructed, which includes energy storage power, energy consumption resistor power and constraint penalty terms. When the source-load power difference is positive, the number of energy consumption resistors is calculated and the charging power of the energy storage device is adjusted. When the source-load power difference is negative, the discharging power of the energy storage device is adjusted. When the closing inrush current, bus voltage fluctuation, and system frequency offset all meet the preset constraints and continue to meet the preset grid connection time, a closing command is sent to the standby line switch. After grid connection is completed, the system stability coefficient is calculated. When the system stability coefficient reaches the preset stability threshold and continues to meet the preset stability time, the installed energy-consuming resistors are gradually removed and the energy storage device is adjusted to standby status.

2. The method for switching backup power to a supercapacitor DC power supply according to claim 1, characterized in that, The filtering process employs the Kalman filtering algorithm, with a sampling frequency of not less than 1kHz. The formula for correcting the output power of new energy sources is as follows: ； in, To correct the output power of the new energy source, Real-time power output for new energy sources This is the temperature correction factor. For real-time ambient temperature, Standard reference temperature; When the new energy source is wind power This is the wind speed correction factor. For real-time wind speed, The rated wind speed of the fan; When the new energy source is photovoltaics This is the illumination correction factor. For real-time light intensity, Rated light intensity for photovoltaic modules.

3. The method for switching backup power to a supercapacitor DC power supply according to claim 2, characterized in that, The formula for calculating the equivalent reactance of the system is as follows: ； in, The equivalent reactance of the system is... For the grid-side equivalent reactance, For the equivalent reactance on the new energy side, This is the equivalent reactance of the load.

4. The method for switching backup power to a supercapacitor DC power supply according to claim 1, characterized in that, The formula for calculating the harmonic energy distribution coefficient is as follows: ； in, For the first Energy distribution coefficient of subharmonics For the first The instantaneous energy of subharmonics This represents the total number of harmonics involved in the calculation; The formula for calculating the mutation value is: ； in, The abrupt change value of the harmonic energy distribution coefficient. The sampling interval is... The first sampling time of the previous sampling time Subharmonic energy distribution coefficient.

5. The method for switching backup power to a supercapacitor DC power supply according to claim 1, characterized in that, The preset mutation threshold is 0.15, the preset residual voltage range is 0.3 to 0.7 times the system rated voltage, the preset current threshold is 0.05 times the system rated current, and the preset time threshold is 50ms.

6. The method for switching backup power to a supercapacitor DC power supply according to claim 1, characterized in that, The formula for calculating the power difference between the source and load is: ； in, The difference between source and load power. The corrected new energy power, Real-time load power; The objective function of the dynamic penalty function optimization model is: ； in, To broaden the objective function, This represents the real-time power of the energy storage device. This represents the total power consumed by the energy-consuming resistor. As a dynamic penalty factor, To constrain penalty items.

7. The method for switching backup power to a supercapacitor DC power supply according to claim 6, characterized in that, The formula for calculating the constraint penalty term is as follows: ； in, to To constrain the weighting coefficients, This is the closing inrush current. The rated current of the system. This refers to the bus voltage fluctuation. The system's rated voltage. This is the system frequency offset. This represents the maximum charging and discharging power of the energy storage device. The update formula for the dynamic penalty factor is: ； in, This represents the current iteration number. The maximum number of iterations, and This is the adjustment constant.

8. The method for switching backup power to a supercapacitor DC power supply according to claim 6, characterized in that, When the power difference between the source and load is positive, the formula for calculating the number of energy-consuming resistors to be installed is: ； in, This refers to the number of energy-consuming resistors that need to be installed. This is the power redundancy factor. It is a rounding function. The rated power of a single power-consuming resistor; The formula for calculating the charging power of the energy storage device is as follows: ； in, Power to charge energy storage devices, This represents the state of charge (SBC) value of the energy storage device. The rated capacity of the energy storage device, For charging efficiency, Adjust the charging time step; When the source-load power difference is negative, the formula for calculating the discharge power of the energy storage device is: ； in, This refers to the discharge power of the energy storage device. This refers to the discharge efficiency.

9. The method for switching backup power to a supercapacitor DC power supply according to claim 1, characterized in that, The formula for calculating the system stability coefficient is as follows: ； in, The system stability coefficient, The system's rated frequency; The preset stability threshold is 0.95, and the preset stability time is 100ms.

10. The method for switching backup power to a supercapacitor DC power supply according to any one of claims 1 to 9, characterized in that, The formula for gradually withdrawing the installed energy-consuming resistors is as follows: ； in, For grid connection The remaining number of energy-consuming resistors in operation at any given time. The number of energy-consuming resistors put in at the previous moment. The duration after grid connection, The time constant for removing the energy-consuming resistor; The adjustment of the energy storage device to standby status includes: adjusting the charging and discharging power of the energy storage device to restore its state of charge value to the range of 0.5 to 0.8.

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