Substation Distributed DC Power Supply System

Abstract

The present invention relates to a distributed DC power supply system for a substation, which belongs to a DC backup power supply system for a substation. The system includes a plurality of string battery units, each of which includes a backup battery group, an active charging execution module, a passive discharge execution module, a string battery monitoring and maintenance module, and a string battery management unit. The string battery management unit is responsible for the data collection of the single cell voltage, the string battery voltage, the string battery current, the string battery temperature, the ambient temperature, and the control of the conversion of each working state of the distributed power supply. The present invention adopts a dispersed arrangement working mode of the string battery capacity, realizes automatic battery balancing, full-capacity online automatic maintenance, and at least two groups of batteries are configured in parallel, providing a safe electrical environment for the battery monomer, convenient access to the string battery, strong redundancy of the backup function, and high reliability.

Description

Technical Field

[0001] The invention belongs to a DC backup power supply system for a substation, and in particular relates to a distributed DC power supply system for a substation. Background Art

[0002] The DC backup power supply system is an important part of the substation system. It operates independently without being affected by the generator, factory power and operating mode. In the event of an external AC power outage, it provides uninterrupted DC power for some important loads, relay protection and monitoring devices, and telecontrol communication devices, and provides lighting power for the accident site.

[0003] With the improvement of intelligence, digitization and automation level of DC system in substation, higher requirements are put forward for the performance, safety and maintenance-freeness of DC system in substation. Most battery packs in substations adopt full-capacity configuration of single-string batteries, and can only operate at half capacity during daily capacity loading. After 3 to 5 years, the short board effect of battery pack will become more and more obvious, which will cause greater uncertainty in the daily operation of substation and require replacement of battery pack again. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a substation distributed DC power supply system, which is used to solve the problem that the battery pack of the current substation DC power supply system is difficult to maintain and has a short safe service time.

[0005] To achieve the above object, the present invention provides a distributed DC power supply system for a substation, including a backup power mode formed by at least two string battery units connected in parallel, various modules of the string battery units are connected in parallel on the bus of the substation DC system according to the bus and the state of the string battery, the string battery unit includes a string battery switch, a backup battery group, an active charging execution module, a passive discharge execution module, a string battery monitoring and maintenance module and a string battery management unit, one end of the passive discharge execution module and the active charging execution module connected in parallel is connected to the string battery switch, the other end of the passive discharge execution module and the active charging execution module connected in parallel is connected in series with one end of the string monitoring and maintenance module and the string battery connected in parallel, and the other end of the string monitoring and maintenance module and the string battery connected in parallel is grounded;

[0006] The string battery management unit is responsible for collecting data on single cell voltage, string battery voltage, string battery current, string battery temperature, switch status, bus status, ambient temperature, and control of each working state conversion. Each string battery unit independently completes charging, discharging, floating charging, and maintenance operations through the string battery management unit. The string monitoring and maintenance module monitors the operating temperature, bus voltage, battery pack voltage, battery pack current, and battery single cell voltage of the battery pack in real time to ensure stable and reliable operation of the distributed power system.

[0007] Preferably, the battery string switch may be a manual air switch or an electrically controlled operating switch.

[0008] Preferably, the backup battery group is set according to the DC bus capacity requirement of the substation, and the string batteries can be lead-acid string batteries or lithium string batteries or a mixture of lead-acid string batteries and lithium string batteries.

[0009] Preferably, the active charging execution module includes a controlled charging switch and an anti-shock module. The active charging execution module can start charging through the controlled charging switch according to the state of the string battery group, and prevent the string battery voltage from matching the bus voltage through the anti-shock module.

[0010] Preferably, the passive charging execution module can automatically allocate the discharge time according to the power when the distributed power source discharges to the bus, so as to ensure balanced and orderly discharge of each battery string.

[0011] Preferably, the string battery monitoring and maintenance module includes a string battery maintenance module, a string battery information collection module, a single cell active balancing module, and a single cell information monitoring module. The string battery monitoring and maintenance module is responsible for implementing daily maintenance and information collection functions for the entire battery group.

[0012] Preferably, the string battery management unit reasonably adjusts and controls the state of the battery group according to the battery state, and uploads and summarizes various states, actions, and alarm information of the string battery units through differential communication.

[0013] Preferably, the anti-shock module has an autonomous constant current function, so that the distributed power supply multiple string battery groups are always in a safe working state.

[0014] Beneficial effects of the present invention:

[0015] The various modules of the string battery unit are connected in parallel on the busbar of the DC system of the substation according to the status of the busbar and the string battery. Each string battery unit independently completes the charging, discharging, floating charging and maintenance operations through the string battery management system, and monitors the operating temperature of the battery pack, busbar voltage, battery pack voltage, battery pack current and battery single cell voltage in real time through the single cell balancing module and the monitoring module to ensure the stable and reliable operation of the distributed power system.

[0016] By adding a balancing system, it is ensured that each battery is always within the set safe working range during operation, effectively avoiding overcharging and over-discharging problems in conventional battery systems, and greatly delaying the time when the barrel effect appears in the string battery; by operating multiple string batteries in parallel, on the one hand, the scope of influence of the barrel effect is effectively reduced, avoiding the situation where the entire battery group loses power due to the failure of one battery, and enhancing the backup power capacity of the substation battery system; on the other hand, under the premise of ensuring the backup power function, the multiple string battery system does not rely on external battery groups, and can achieve full-capacity online maintenance through its own control, which is convenient for operation and maintenance; by adding PTC anti-shock elements, string batteries can be incorporated in any case under the premise of ensuring the safety of system operation, which enhances the access applicability and backup power capacity of the system string batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the implementation of the present invention and do not constitute a limitation of the present invention.

[0018] Figure 1 A schematic diagram of system operation state conversion for implementing the present invention;

[0019] Figure 2 A schematic diagram of a charging operation state provided for implementing the present invention;

[0020] Figure 3 A schematic diagram of a floating charge operation state provided for implementing the present invention;

[0021] Figure 4 A schematic diagram of a discharge operation state provided for implementing the present invention;

[0022] Figure 5 A schematic diagram of the maintenance operation status provided for implementing the present invention;

[0023] Figure 6 It is a connection diagram of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and by the implementation of a distributed power supply system using lead-acid batteries as a backup power supply; it should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention. For those skilled in the art, other systems, methods and / or features of this embodiment will become apparent after reviewing the following detailed description. It is intended that all such additional systems, methods, features and advantages are included in this specification, included within the scope of the present invention, and protected by the appended claims.

[0025] Embodiment 1:

[0026] A distributed DC power supply system for a substation described in this embodiment includes a backup power mode of at least two string battery units connected in parallel. Various modules of the string battery units are connected in parallel on the bus of the substation DC system according to the bus and the status of the string batteries. The string battery units include a string battery switch, a backup battery group, an active charging execution module, a passive discharge execution module, a string battery monitoring and maintenance module, and a string battery management unit. The string battery switch adopts an electronically controlled operation switch. One end of the passive discharge execution module and the active charging execution module connected in parallel is connected to the string battery switch, and the other end of the passive discharge execution module and the active charging execution module connected in parallel is connected in series with one end of the string monitoring and maintenance module and the string battery connected in parallel. The other end of the string monitoring and maintenance module and the string battery connected in parallel is grounded.

[0027] The string battery management unit is responsible for collecting data on single cell voltage, string battery voltage, string battery current, string battery temperature, switch status, bus status, ambient temperature, and control of the conversion of various working states of the distributed power supply. Each string battery unit independently completes charging, discharging, floating charging, and maintenance operations through the string battery management unit. The string battery management unit reasonably adjusts and controls the battery pack according to the battery status, and uploads and summarizes various states, actions, and alarm information of the string battery unit through differential communication. The string battery monitoring and maintenance module includes a string battery maintenance module, a string battery information acquisition module, a single cell active balancing module, and a single cell information monitoring module. The string monitoring and maintenance module monitors the operating temperature, bus voltage, battery pack voltage, battery pack current, and battery single cell voltage of the battery pack in real time. The string battery monitoring and maintenance module is responsible for implementing daily maintenance and information collection functions for the entire battery pack to ensure stable and reliable operation of the distributed power supply system.

[0028] Preferably, the backup battery group is set according to the DC bus capacity requirement of the substation, and the string batteries can be lead-acid string batteries.

[0029] Preferably, the active charging execution module includes a controlled charging switch and an anti-shock module. The active charging execution module can start charging through the controlled charging switch according to the state of the string battery group, and prevent the string battery voltage from not matching the bus voltage through the anti-shock module. The anti-shock module has an autonomous constant current function, so that the distributed power supply multi-string battery group is always in a safe working state.

[0030] Preferably, the passive charging execution module can automatically allocate the discharge time according to the power when the distributed power source discharges to the bus, so as to ensure balanced and orderly discharge of each battery string.

[0031] like Figure 1As shown in the figure, in order to ensure that the distributed power system can complete tasks under various conditions, a complete system operation strategy has been formulated. The entire system completes various functions by configuring electric switches. The operating status and state transition are shown in the figure. When the substation bus is powered, it includes three states: charging (power replenishment + balancing), floating charging, and maintenance. When the substation bus loses power, it includes one state of discharging. When the substation suddenly loses power, the system can switch from any state when the bus voltage is online to discharging, completing the battery system backup function.

[0032] New installation or replacement of string batteries. There are more than two string batteries in the system. When new installation or replacement is performed, the initial state of the battery group is full of power and there is a certain degree of self-discharge. The battery group voltage is generally 2.25~2.35*n. First, the string battery switch is placed in the disconnected state, and the new battery group is connected to the distributed power supply. Then, the string battery switch is closed, and the string battery voltage is maintained at the bus voltage through the passive discharge module or the active charging module. The battery group maintenance module is subject to daily management to maintain the best power storage state.

[0033] Charging status Figure 2 As shown, system charging includes two processes: power replenishment and balanced replenishment, which are completed by the active charging module and the battery pack maintenance module respectively.

[0034] After the system has fulfilled its backup function when the AC power fails, it is necessary to recharge the string batteries. The string battery management unit connects the string batteries to the DC bus system of the substation through the active charging execution module according to the current string battery status. In this state, the battery group voltages on the bus are the same, the anti-shock constant current module exits the working state, and the bus voltage follows the string battery voltage to complete the power recharge process. When the string battery voltage reaches the preset voltage or any string cell reaches the preset voltage, the string battery management unit switches the string battery to the active balanced recharge state, so that each battery is in an independent balanced charging state until the preset voltage is reached.

[0035] When the voltages of the battery strings on the bus are inconsistent, the string battery management unit enables the anti-shock constant current module, and uses the anti-shock constant current module to make the voltage or energy difference between the battery groups consistent in a constant current manner, completing the power replenishment process, and further entering the balanced replenishment process through the balancing module.

[0036] Float charge status Figure 3 As shown, after the charging process is completed, the state remains unchanged, and each battery in the string is float-charged at a fixed set voltage for a long time under the control of the string battery management unit, and the lead-acid battery is 2.25V.

[0037] Maintenance status Figure 4As shown, in order to ensure the backup power function, at least one string battery is guaranteed to be in bus charging or floating charging state during the maintenance period. The maintenance process includes two processes: discharge capacity and replenishment. (1) Discharge capacity: The capacity string battery is connected to the maintenance load. The string battery management unit puts the corresponding string into the maintenance-discharge capacity state according to the setting. The capacity is achieved by full-capacity discharge according to the preset program. The string battery management unit records the voltage, current, time, and temperature information of the maintenance process for query. (2) Replenishment: The string battery is connected to the maintenance charger. Under the control of the string battery management unit, the corresponding string battery enters the charging state. The battery group voltage is charged to the preset value through the charger. During this period, the voltage, current, and time information of the string battery and each battery are recorded. After charging is completed, the energy and voltage balance of the battery group between the strings is completed through the charging anti-shock constant current module. The string battery group further enters the balance and floating charging state to achieve the normal battery backup state of the substation.

[0038] Discharge status Figure 5 As shown, when the substation loses power and the DC bus charging power supply is lost, the system immediately automatically supplies power to the 110V / 220V DC bus through the passive discharge execution module, and then the string battery management unit adjusts the current state of each string to enter the discharge state, ensuring that the distributed power system is only in the discharge state of powering the bus.

[0039] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical scheme and technical concept of the present invention without creative mental work, which all fall within the scope of protection of the present invention.

Claims

1. A distributed DC power supply system for a substation, characterized in that: The invention comprises a backup power mode in which at least two string battery units are connected in parallel, and various modules of the string battery units are connected in parallel on the bus of the DC system of the substation according to the bus and the state of the string battery. The string battery unit comprises a string battery switch, a backup battery group, an active charging execution module, a passive discharge execution module, a string battery monitoring and maintenance module and a string battery management unit. One end of the passive discharge execution module and the active charging execution module connected in parallel is connected to the string battery switch, and the other end of the passive discharge execution module and the active charging execution module connected in parallel is connected in series with one end of the string monitoring and maintenance module and the string battery connected in parallel, and the other end of the string monitoring and maintenance module and the string battery connected in parallel is grounded; The string battery management unit is responsible for the data collection of single cell voltage, string battery voltage, string battery current, string battery temperature, switch status, bus status, ambient temperature and the control of the conversion of each working state of the distributed power supply. Each string battery unit independently completes the charging, discharging, floating charging and maintenance operations through the string battery management unit. The string monitoring and maintenance module monitors the operating temperature, bus voltage, battery pack voltage, battery pack current and battery single cell voltage of the battery pack in real time to ensure the stable and reliable operation of the distributed power supply system. The active charging execution module includes a controlled charging switch and an anti-shock module. The active charging execution module can start charging through the controlled charging switch according to the state of the string battery group, and prevent the mismatch between the string battery voltage and the bus voltage through the anti-shock module; The string battery monitoring and maintenance module includes a string battery maintenance module, a string battery information collection module, a single cell active balancing module, and a single cell information monitoring module. The string battery monitoring and maintenance module is responsible for implementing daily maintenance and information collection functions for the entire battery group. The anti-shock module has an autonomous constant current function, which keeps the distributed power supply multi-string battery group in a safe working state at all times; the system charging includes two processes: power replenishment and balanced replenishment, which are completed by the active charging module and the battery group maintenance module respectively; After the system has fulfilled the backup function when the AC power fails, the string battery management unit connects the string battery to the DC bus system of the substation through the active charging execution module according to the current string battery status. In this state, the battery group voltages on the bus are the same, the anti-shock constant current module exits the working state, and the bus voltage follows the string battery voltage to complete the power replenishment process; when the string battery voltage reaches the preset voltage or any string cell reaches the preset voltage, the string battery management unit switches the string battery to the active balanced charging state, so that each battery is in an independent balanced charging state until the preset voltage is reached; When the voltages of the battery strings on the bus are inconsistent, the voltage or energy difference between the battery groups is made consistent through the anti-shock constant current module in a constant current manner to complete the power replenishment process, and then the balanced replenishment process is further transferred through the balanced module; During the maintenance period, at least one battery string is guaranteed to be in busbar charging or floating charging state. The maintenance process includes two processes: discharging and replenishing. Discharge core capacity, core capacity string batteries are connected to maintenance loads, the string battery management unit puts the corresponding string into maintenance-discharge core capacity state according to the settings, and achieves the core capacity purpose by full capacity discharge according to the preset program. The string battery management unit records the voltage, current, time, and temperature information of the maintenance process for query; Recharging: The string battery is connected to the maintenance charger. Under the control of the string battery management unit, the corresponding string battery enters the charging state. The battery group voltage is charged to the preset value through the charger. During this period, the voltage, current and time information of the string battery and each battery are recorded. After charging is completed, the energy and voltage balance of the battery groups between the strings is completed through the charging shock prevention constant current module. The string battery group further enters the balancing and floating charging state to achieve the normal battery backup state of the substation; In the discharge state, when the substation loses power and the DC bus charging power supply is lost, the system immediately automatically supplies power to the 110V / 220V DC bus through the passive discharge execution module, and then the string battery management unit adjusts the current state of each string to enter the discharge state, ensuring that the distributed power system is only in the discharge state of the bus power supply.

2. A distributed DC power supply system for a substation according to claim 1, characterized in that: The string battery switch can be a manual air switch or an electrically controlled operating switch.

3. A distributed DC power supply system for a substation according to claim 1, characterized in that: The backup battery group is set according to the DC bus capacity requirement of the substation, and the string batteries are lead-acid string batteries or lithium string batteries or a mixture of lead-acid string batteries and lithium string batteries.

4. A distributed DC power supply system for a substation according to claim 1, characterized in that: When the distributed power source discharges to the bus, the passive charging execution module can automatically allocate the discharge time according to the power, ensuring balanced and orderly discharge of each battery string.

5. A distributed DC power supply system for a substation according to claim 1, characterized in that: The string battery management unit reasonably adjusts and controls the battery group according to the battery status, and uploads and summarizes the various status, action, and alarm information of the string battery units through differential communication.

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