Box transformer substation UPS continuous power supply system and control method

Abstract

The invention belongs to the technical field of box transformer substation UPS power supply, and relates to a box transformer substation UPS continuous power supply system and a control method, and the method comprises the steps: obtaining the photovoltaic power generation power, the commercial power voltage, and the charge state of a storage battery pack, and obtaining a comprehensive score value according to the photovoltaic power generation power, the commercial power voltage, and the charge state of the storage battery pack; switching different energy sources on the basis of the comprehensive score value and different preset score threshold values; and when different energy sources are switched, smooth seamless switching is carried out through a continuously changing switching proportion. According to the method, different energy sources are switched according to the priorities through the comprehensive score value and the preset different score threshold values, smooth seamless switching is carried out through the continuously changing switching proportion, and the problems that an existing box transformer substation UPS lacks special control logic for different energy sources during continuous power supply, and smooth seamless switching of different energy sources cannot be achieved are solved.

Description

Technical Field

[0001] This invention relates to the field of UPS power supply technology for prefabricated substations, and specifically discloses a continuous power supply system and control method for UPS in prefabricated substations. Background Technology

[0002] Box-type transformers (i.e., prefabricated transformers) are core node equipment in photovoltaic power plants, wind farms, and urban power distribution networks. The monitoring and control devices, communication terminals, and remote actuators configured inside all rely on UPS systems for backup power. A UPS system typically consists of a rectifier module, an inverter module, and a battery bank. During normal operation, it is powered by the mains power and simultaneously float-charges the battery. When the mains power fails, it automatically switches to battery power to maintain continuous operation of the load.

[0003] Although the design life of batteries is 3-5 years, their actual lifespan is only 2-3 years. Moreover, with the increase in the frequency of battery use, batteries generally experience irreversible performance degradation, resulting in insufficient backup power and a significant increase in equipment offline rate. Therefore, batteries are usually replaced. However, battery replacement is costly and requires power outages for construction, which affects power generation revenue. In this case, photovoltaic energy and UPS systems are generally connected in parallel to provide continuous power supply to improve endurance and extend battery life. However, this method lacks dedicated control logic for different energy sources and cannot achieve smooth and seamless switching between different energy sources. Summary of the Invention

[0004] The purpose of this invention is to provide a continuous power supply system and control method for transformer substations, which solves the problem that existing transformer substation UPS continuous power supply systems lack dedicated control logic for different energy sources and cannot achieve smooth and seamless switching between different energy sources.

[0005] The specific solution of the present invention is as follows:

[0006] A method for continuous power supply control of a transformer substation UPS includes:

[0007] The system obtains photovoltaic power generation, mains voltage, and battery state of charge, and then calculates a comprehensive score based on these parameters.

[0008] Based on the comprehensive score and preset different score thresholds, different energy sources are switched;

[0009] When switching between different energy sources, a smooth and seamless transition is achieved through continuously varying switching ratios.

[0010] The preferred formula for calculating the overall score is as follows:

[0011] ,

[0012] in, Photovoltaic power generation; This is the preset rated photovoltaic power generation capacity; Mains voltage; The preset rated mains voltage; This is the preset maximum voltage deviation; The state of charge of the battery pack; The preset photovoltaic energy weight; The preset mains power weight; The preset weight of stored energy; .

[0013] Preferably, based on a comprehensive score and preset different score thresholds, different energy switching is performed, including:

[0014] The scoring thresholds include a first scoring threshold and a second scoring threshold, with the first scoring threshold being greater than the second scoring threshold;

[0015] Determine if the overall score is less than the first score threshold. If no, continue using photovoltaic energy. If yes, determine if the overall score is less than the second score threshold and greater than zero. If no, switch from photovoltaic energy to grid power. If yes, switch from grid power to energy storage.

[0016] Preferably, smooth and seamless switching is achieved through continuously varying switching ratios, including:

[0017] Get the current switching time, and calculate the switching ratio based on the current switching time and the preset total switching time;

[0018] Based on the switching ratio, the power of the withdrawing energy source and the power of the input energy source are simultaneously controlled by a proportional control valve to achieve a smooth and seamless switching until the input energy source is used for power supply.

[0019] Preferably, the formula for calculating the switching ratio is:

[0020] ,

[0021] The formula for calculating the power output of the energy source is:

[0022] ,

[0023] The formula for calculating the power of the input energy is:

[0024] ,

[0025] and

[0026] in, The switching ratio is the current switching time t; t is the current switching time, which is in the range (0, T); T is the preset total switching time. To reduce the power output of energy source A; The power of energy input B.

[0027] This invention also relates to a continuous power supply system for a transformer substation UPS, used to implement the above-mentioned continuous power supply control method for a transformer substation UPS, comprising:

[0028] Solar photovoltaic panel modules, MPPT photovoltaic controllers, intelligent switching modules, communication modules, rectifier modules, inverter modules, proportional control valves, battery packs, and mains power;

[0029] The solar photovoltaic module is connected to the MPPT photovoltaic controller. The MPPT photovoltaic controller, the mains power and the battery pack are all connected to the proportional control valve. The proportional control valve is connected to the rectifier module. The rectifier module is connected to the inverter module. The communication module is connected to the MPPT photovoltaic controller, the mains power, the battery pack, the intelligent switching module and the proportional control valve respectively.

[0030] Preferably, the solar photovoltaic panel is a flexible monocrystalline silicon photovoltaic panel, and the tilt angle of the photovoltaic panel of the flexible monocrystalline silicon photovoltaic panel is in the range of 0°-10°.

[0031] Preferably, it also includes an online battery compensation module, which includes:

[0032] The current-limiting resistor, resettable fuse, LED status indicator, anti-reverse diode, and TVS transient suppression diode are connected in sequence. The positive terminal of the battery pack is connected to the negative terminal of the anti-reverse diode and the anode of the TVS transient suppression diode, respectively, and the negative terminal of the battery pack is connected to the cathode of the TVS transient suppression diode.

[0033] Preferably, it also includes a BMS slave module for dynamically adjusting the charging current limit value according to the battery health status. The BMS slave module is connected to the MPPT photovoltaic controller, the mains power, the communication module and the battery pack respectively.

[0034] Preferably, the formula for calculating the charging current limit value is:

[0035] ,

[0036] in, This is the charging current limit value; This is the preset rated maximum charging current; For battery health; This is the preset safety factor.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] 1. This invention evaluates the quality of photovoltaic energy, mains power, and energy storage through a comprehensive score. Based on the comprehensive score and preset different score thresholds, it enables the switching of different energy sources in order of priority: photovoltaic energy, mains power, and energy storage. During the switching of different energy sources, the power of the withdrawn energy source and the power of the input energy source are dynamically adjusted by continuously changing the switching ratio, so as to achieve a smooth and seamless switching between withdrawn and input energy sources. This improves the driving range, extends the battery life, and reduces the offline rate.

[0039] 2. The present invention uses flexible monocrystalline silicon photovoltaic modules and photovoltaic panels with a tilt angle range of 0°-10°, which allows the solar photovoltaic panel modules to not only be installed on the top of the transformer substation, but also to fit snugly against the top of the transformer substation, thus improving stability.

[0040] 3. This invention uses an online battery compensation module to prevent the battery from discharging back to the photovoltaic panel when the photovoltaic panel generates insufficient power at night. This suppresses charging current spikes at startup and under abnormal operating conditions, and absorbs surge voltage in the charging circuit to prevent damage to the controller from lightning strikes or operational overvoltages.

[0041] 4. This invention dynamically adjusts the charging current through the BMS slave control module, which significantly extends the remaining service life of aging batteries. Attached Figure Description

[0042] Figure 1 This is a flowchart of a continuous power supply control method for a transformer substation UPS in an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of a UPS continuous power supply system for a transformer substation according to an embodiment of the present invention.

[0044] Figure reference numerals: 1-Solar photovoltaic panel module, 2-MPPT photovoltaic controller, 3-Main power, 4-Battery pack, 5-Intelligent switching module, 6-Proportional control valve, 7-Communication module, 8-Rectifier module, 9-Inverter module, 10-Battery online compensation module, 11-BMS slave control module. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0046] A method for continuous power supply control of a transformer substation UPS, such as Figure 1 As shown, it includes the following steps:

[0047] S1. Obtain photovoltaic power generation, mains voltage, and battery state of charge, and obtain a comprehensive score based on photovoltaic power generation, mains voltage, and battery state of charge;

[0048] The communication module 7 collects real-time data on photovoltaic power generation, mains voltage, and battery state of charge, and transmits this data to the intelligent switching module 5. The intelligent switching module 5 calculates a comprehensive score based on the photovoltaic power generation, mains voltage, battery state of charge, and preset weights for photovoltaic energy, mains energy, and battery energy. The formula for calculating the comprehensive score is as follows:

[0049] ,

[0050] in, Photovoltaic power generation; This is the preset rated photovoltaic power generation capacity; Mains voltage; The preset rated mains voltage; This is the preset maximum voltage deviation; The state of charge of the battery pack; The preset photovoltaic energy weight; The preset mains power weight; The preset weight of stored energy; .

[0051] Battery pack state of charge This refers to the percentage of the battery pack's current remaining charge relative to its total capacity when fully charged.

[0052] The quality of photovoltaic energy, grid power, and energy storage is evaluated through a comprehensive scoring system to ensure sufficient backup power supply.

[0053] S2. Based on the comprehensive score and preset different score thresholds, switch between different energy sources;

[0054] Energy sources include photovoltaic energy, grid power, and energy storage; the scoring thresholds include a first scoring threshold and a second scoring threshold, with the first scoring threshold being greater than the second scoring threshold.

[0055] The UPS for the transformer substation prioritizes photovoltaic (PV) energy. The system checks if the overall score is less than the first threshold. If it is negative, the PV energy is normal and can meet the UPS load requirements, so PV energy continues to be used. If it is positive, the PV energy is abnormal and cannot meet the UPS load requirements. The system then checks if the overall score is less than the second threshold but greater than zero. If negative, the mains power is normal and can meet the UPS load requirements, so the PV energy is switched to mains power. If positive, the mains power is also abnormal and cannot meet the UPS load requirements, but the battery storage is normal and can meet the UPS load requirements, so the mains power is switched to battery storage.

[0056] By combining comprehensive scores and preset different scoring thresholds, the system automatically switches between photovoltaic energy, grid power, and energy storage according to their priorities, thereby improving range, extending battery life, and reducing offline rate.

[0057] For example, if the weight of photovoltaic energy is 0.6, the weight of mains power energy is 0.3, the weight of energy storage is 0.1, the photovoltaic power generation capacity is 40KW, the rated photovoltaic power generation capacity is 100KW, the mains voltage is 216V, the rated mains voltage is 220V, the preset maximum voltage deviation is 20, and the battery pack's state of charge is 80%, then the comprehensive score is... The first scoring threshold is 70, and the second scoring threshold is 33. It can be seen that if the comprehensive score is less than the first scoring threshold and greater than the second scoring threshold, it indicates that the photovoltaic energy is abnormal, but the mains power energy is normal. Therefore, the power supply of the transformer substation UPS is switched from photovoltaic energy to mains power energy.

[0058] S3. When switching between different energy sources, a smooth and seamless switching is achieved through continuously changing switching ratios.

[0059] During energy switching, the current switching time is acquired in real time. Based on the current switching time and the preset total switching time, the switching ratio is obtained. According to the switching ratio, the power of the deactivated energy source and the input energy source are simultaneously controlled by the proportional control valve 6 to achieve a smooth and seamless switch. This allows the deactivated energy source to gradually decrease and the input energy source to gradually increase until the input energy source is used for power supply. By dynamically adjusting the power of the deactivated energy source and the input energy source through continuously changing switching ratios, a smooth and seamless switch between the deactivated and input energy sources is achieved.

[0060] The formula for calculating the switching ratio is:

[0061] ,

[0062] in, The switching ratio is the current switching time t; t is the current switching time, and the range of the current switching time is (0, T); T is the preset total switching time.

[0063] Throughout the entire process of switching between deactivated and activated energy sources, the sum of the power of the deactivated energy source and the power of the activated energy source must be satisfied. The power of the exiting energy source A remains constant at the current switching time t. The power of energy input B And satisfy: .

[0064] This invention also relates to a continuous power supply system for a transformer substation UPS, used to implement the aforementioned continuous power supply control method for a transformer substation UPS, such as... Figure 2 As shown, it includes:

[0065] 1. Solar photovoltaic panel module; 2. MPPT photovoltaic controller; 5. Intelligent switching module; 7. Communication module; 8. Rectifier module; 9. Inverter module; 6. Proportional control valve; 4. Battery pack; and 3. Mains power.

[0066] The solar photovoltaic panel module 1 is connected to the MPPT photovoltaic controller 2. The MPPT photovoltaic controller 2, the mains power 3, and the battery pack 4 are all connected to the proportional control valve 6. The proportional control valve 6 is connected to the rectifier module 8. The rectifier module 8 is connected to the inverter module 9. The communication module 7 is connected to the MPPT photovoltaic controller 2, the mains power 3, the battery pack 4, the intelligent switching module 5, and the proportional control valve 6.

[0067] Solar photovoltaic panel module 1, used to produce photovoltaic energy.

[0068] MPPT PV Controller 2 is a maximum power point tracking solar controller with a tracking efficiency of ≥99.5%. It features three-stage charging and temperature compensation. The three-stage charging includes constant current charging, constant voltage charging, and float charging. Temperature compensation means the charging voltage automatically adjusts with ambient temperature, with a compensation coefficient of -3mV / ℃ / cell to -5mV / ℃ / cell. MPPT PV Controller 2 coordinates the energy flow between photovoltaic energy, the battery, and the load, preventing overcharging, over-discharging, short circuits, and overloads, ensuring safe and stable system operation.

[0069] Communication module 7 is used to collect and transmit various data information in real time, including photovoltaic power generation, mains voltage, battery pack charge status, etc. It supports three wireless communication modes: RS485, CAN and 4G / 5G. It has Modbus-RTU and IEC104 protocol conversion capabilities and can be directly connected to existing new energy power station monitoring systems, dispatch data networks or third-party IoT platforms.

[0070] The proportional control valve 6 is used to control the valve opening degree of the proportional control valve 6 according to the proportion of the energy to be switched. The proportional control valve includes three ports, which are respectively used to connect to the mains power, photovoltaic energy and energy storage.

[0071] The intelligent switching module 5 is used to obtain a comprehensive evaluation value based on the photovoltaic power generation, mains voltage, and battery pack state of charge. Based on the comprehensive evaluation value and different preset evaluation thresholds, it switches different energy sources and obtains the proportion of energy to be switched based on the current switching time and the preset total switching time during the switching process, so as to achieve smooth and seamless switching of multiple energy sources.

[0072] Preferably, the solar photovoltaic panel module 1 is a flexible monocrystalline silicon photovoltaic module, and the tilt angle of the photovoltaic panel of the flexible monocrystalline silicon photovoltaic module is in the range of 0°-10°.

[0073] The thickness of solar photovoltaic module 1 is ≤5mm, and its weight is only 4kg / ㎡-6kg / ㎡. It is fixed to the top of the transformer substation by structural adhesive or bolt pressing. The tilt angle of the flexible monocrystalline silicon photovoltaic module is 0°-10°. Due to careful consideration of the special working conditions of the transformer substation top: ① The transformer substation top is a curved surface or a slightly tilted plane, and conventional photovoltaic modules are rigid and difficult to fit snugly against the top; ② The load-bearing capacity of the transformer substation top is limited, and the weight of conventional photovoltaic modules is approximately 12kg / ㎡-15kg / ㎡, far exceeding the design load of the transformer substation top; ③ The transformer substation experiences continuous low-frequency vibration during operation, and conventional supports are prone to loosening. Therefore, flexible monocrystalline silicon photovoltaic modules are directly bonded, eliminating the need for supports and completely solving the technical problem of not being able to install photovoltaic modules on the top of the transformer substation.

[0074] Preferably, it also includes a battery online compensation module 10, which includes:

[0075] The current-limiting resistor, resettable fuse, LED status indicator, anti-reverse diode, and TVS transient suppression diode are connected in sequence. The positive terminal of the battery pack 4 is connected to the negative terminal of the anti-reverse diode and the anode of the TVS transient suppression diode, respectively, and the negative terminal of the battery pack 4 is connected to the cathode of the TVS transient suppression diode.

[0076] Anti-reverse diodes are used to prevent the battery from discharging in reverse to the photovoltaic panel when the photovoltaic panel generates insufficient power at night; current-limiting resistors are used to suppress charging current spikes at startup and under abnormal operating conditions; self-resetting fuses are used to automatically disconnect when the circuit is overcurrent and automatically reset after the fault is cleared; TVS transient voltage suppressor diodes are used to absorb surge voltage in the charging circuit to prevent damage to the controller from lightning strikes or operational overvoltages; LED status indicator lights are used to indicate the charging status.

[0077] Preferably, it also includes a BMS slave control module 11 for dynamically adjusting the charging current limit value according to the battery health status. The BMS slave control module 11 is connected to the MPPT photovoltaic controller 2, the mains power 3, the communication module 7 and the battery pack 4 respectively.

[0078] The BMS slave module 11 is used to monitor the parameters of the battery pack 4 in real time, including voltage, current, internal resistance, and temperature. The BMS slave module 11 integrates a battery health status assessment unit (i.e., a SOH assessment unit), which assesses the remaining battery life by analyzing the battery's internal resistance change curve, capacity decay rate, and charge / discharge cycle count to obtain the battery health status. Based on the battery health status, it dynamically adjusts the charging current limit value and automatically sends a charging current limit adjustment command to the MPPT photovoltaic controller 2. The formula for calculating the charging current limit value is:

[0079] ,

[0080] in, This is the charging current limit value; This is the preset rated maximum charging current; This represents battery health, with a value ranging from 0 to 1 (1 for 100% healthy, 0 for complete failure). The preset safety factor ranges from 0.8 to 0.95.

[0081] As the battery pack 4 operates for a long time, the battery ages and its internal resistance increases. If it is still charged at the rated maximum charging current, it will cause the battery to overheat, gas evolution, accelerated corrosion of the positive plate, and even thermal runaway bulging. Therefore, by dynamically adjusting the charging current through the BMS slave control module 11, the remaining service life of the aging battery can be significantly extended.

[0082] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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.

Claims

1. A method for continuous power supply control of a transformer substation UPS, characterized in that, include: The system obtains photovoltaic power generation, mains voltage, and battery state of charge, and then calculates a comprehensive score based on these parameters. Based on the comprehensive score and preset different score thresholds, different energy sources are switched; When switching between different energy sources, a smooth and seamless transition is achieved through continuously varying switching ratios.

2. The method for continuous power supply control of a transformer substation UPS according to claim 1, characterized in that, The formula for calculating the overall score is: ， in, Photovoltaic power generation; This is the preset rated photovoltaic power generation capacity; Mains voltage; The preset rated mains voltage; This is the preset maximum voltage deviation; The state of charge of the battery pack; The preset photovoltaic energy weight; The preset mains power weight; The preset weight of stored energy; .

3. The method for continuous power supply control of a transformer substation UPS according to claim 1, characterized in that, The switching of different energy sources based on a comprehensive score and preset different score thresholds includes: The scoring thresholds include a first scoring threshold and a second scoring threshold, wherein the first scoring threshold is greater than the second scoring threshold; Determine if the overall score is less than the first scoring threshold. If not, continue using photovoltaic energy. If yes, determine if the overall score is less than the second scoring threshold. If no, switch from photovoltaic energy to grid power. If yes, switch from grid power to energy storage.

4. The method for continuous power supply control of a transformer substation UPS according to claim 1, characterized in that, The smooth and seamless switching achieved through continuously varying switching ratios includes: Get the current switching time, and calculate the switching ratio based on the current switching time and the preset total switching time; Based on the switching ratio, the power of the withdrawing energy source and the power of the input energy source are simultaneously controlled by a proportional control valve to achieve a smooth and seamless switching until the input energy source is used for power supply.

5. The continuous power supply control method for a transformer substation UPS according to claim 4, characterized in that, The formula for calculating the switching ratio is: ， The formula for calculating the power output of the energy source is: , The formula for calculating the power of the input energy is: ， and in, The switching ratio is the current switching time t; t is the current switching time, which is in the range (0, T); T is the preset total switching time. To reduce the power output of energy source A; The power of energy input B.

6. A continuous power supply system for a transformer substation UPS, characterized in that, A method for implementing a continuous power supply control of a transformer substation UPS according to any one of claims 1-5 includes: a solar photovoltaic panel assembly, an MPPT photovoltaic controller, an intelligent switching module, a communication module, a rectifier module, an inverter module, a proportional control valve, a battery pack, and mains power. The solar photovoltaic panel assembly is connected to the MPPT photovoltaic controller. The MPPT photovoltaic controller, the mains power supply, and the battery pack are all connected to the proportional control valve. The proportional control valve is connected to the rectifier module. The rectifier module is connected to the inverter module. The communication module is connected to the MPPT photovoltaic controller, the mains power supply, the battery pack, the intelligent switching module, and the proportional control valve.

7. A continuous power supply system for a transformer substation UPS according to claim 6, characterized in that: The solar photovoltaic panel is a flexible monocrystalline silicon photovoltaic panel, and the tilt angle of the photovoltaic panel of the flexible monocrystalline silicon photovoltaic panel is in the range of 0°-10°.

8. A continuous power supply system for a transformer substation UPS according to claim 6, characterized in that, It also includes a battery online compensation module, which comprises: The current-limiting resistor, resettable fuse, LED status indicator, anti-reverse diode, and TVS transient suppression diode are connected in sequence. The positive terminal of the battery pack is connected to the negative terminal of the anti-reverse diode and the anode of the TVS transient suppression diode, respectively, and the negative terminal of the battery pack is connected to the cathode of the TVS transient suppression diode.

9. A continuous power supply system for a transformer substation UPS according to claim 6, characterized in that: It also includes a BMS slave control module for dynamically adjusting the charging current limit value according to the battery health status. The BMS slave control module is connected to the MPPT photovoltaic controller, the mains power, the communication module and the battery pack respectively.

10. A continuous power supply system for a transformer substation UPS according to claim 9, characterized in that, The formula for calculating the charging current limit is: ， in, This is the charging current limit value; This is the preset rated maximum charging current; For battery health; This is the preset safety factor.

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