Novel direct current charging and discharging device

Abstract

The utility model discloses a novel direct current charging and discharging device in the technical field of a secondary direct current system of a power grid. The novel direct current charging and discharging device comprises an AC-DC loop, a storage battery charging and discharging loop, a storage battery pack, a DC-DC loop and a control unit, the output side of the AC-DC loop is connected with one side of the storage battery charging and discharging loop and the input side of the DC-DC loop at the same time. The other side of the storage battery charging and discharging loop is connected with the storage battery pack; the input side of the DC-DC loop is used for receiving the voltage output by the AC-DC loop or the discharging current of the storage battery charging and discharging loop; the control unit is used for collecting current and voltage of the AC-DC loop input and output side and the DC-DC loop input and output side and controlling the current magnitude and loop on-off. The device is also used for collecting current and voltage of a storage battery charging and discharging loop and controlling current and loop on-off. A plurality of novel direct current charging and discharging devices run in parallel to perform charging and discharging tests on a specific storage battery pack, so that the reliability of a secondary direct current system is improved, and the maintenance cost is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of power grid secondary DC system, especially relates to a novel DC charging and discharging device. BACKGROUND

[0002] Because the DC power can continuously and stably supply power, and when the AC power is lost, the secondary power system can maintain stability for a certain time through the discharge of the battery, the secondary control system in the power grid generally adopts the DC system power supply to ensure the high reliability of the secondary system operation in the station. The secondary DC system of the substation, switching station, ring network cabinet and the like in the power grid generally converts the AC power in the station into DC through the high-frequency charging module, and the DC power supplies power to the secondary equipment in the station, and is connected with the battery pack. When the system AC power is lost due to failure, the battery pack supplies power to the secondary equipment in the station to ensure the stability and reliability of the secondary equipment power supply.

[0003] The above-mentioned traditional DC system relies on the battery pack for the standby power supply, and therefore the operation status of the battery pack is very critical to the operation reliability of the entire DC system. In particular, for the switching station, ring network cabinet and the like in the distribution network, because they are almost at the end of the power grid, the AC system often cannot meet the requirement of double power supply, and once the fault occurs at the incoming line end, the AC system in the station will lose power first, resulting in that the secondary system in the station relies on the battery pack for power supply at the first time, and therefore the operation status of the battery pack directly determines the reliability of the DC system at this time.

[0004] The switching station, ring network cabinet and the like in the distribution network have a large number of devices, poor operation environment and insufficient maintenance, and many battery packs have been damaged in the actual operation process. In the traditional DC system, the battery pack is always in the floating charge state during the normal operation of the system, and the capacity shortage or damage of the battery pack cannot be found, especially for the distribution network system which is difficult to carry out the DC system inspection, it is almost impossible to find such hidden troubles, which greatly affects the DC reliability of the existing switching station and ring network cabinet.

[0005] At present, the automation level of the distribution network is gradually improving, and the protection, measurement and control, and communication equipment in the switching station and ring network cabinet are increasing. In order to ensure the reliable operation of the secondary system of the distribution network, a high-reliability and low-maintenance DC system is urgently needed. UTILITY MODEL CONTENTS

[0006] The application provides a novel DC charging and discharging device, solves the problems of poor reliability and difficult maintenance of the existing battery pack of the distribution network, improves the reliability of the secondary DC system, and reduces the maintenance cost.

[0007] The application provides a novel DC charging and discharging device, which comprises an AC-DC loop, a battery charging and discharging loop, a battery pack, a DC-DC loop and a control unit.

[0008] The input side of the AC-DC circuit inputs wide-range alternating current of 50Hz or 60Hz, and the output side outputs a first direct current voltage, the output side of the AC-DC circuit is connected with one side of the battery charging and discharging circuit and the input side of the DC-DC circuit,

[0009] The other side of the battery charging and discharging circuit is connected with the battery pack, so as to charge and discharge the battery pack;

[0010] The input side of the DC-DC circuit is connected with one side of the battery charging and discharging circuit and the output side of the AC-DC circuit, so as to receive the first direct current voltage output by the AC-DC circuit or the discharge current of the battery pack through the battery charging and discharging circuit, and the output side of the DC-DC circuit outputs a second direct current voltage;

[0011] The control unit is electrically connected with the AC-DC circuit, the battery charging and discharging circuit and the DC-DC circuit respectively, the control unit is used to collect the current and voltage of the input and output sides of the AC-DC circuit and the input and output sides of the DC-DC circuit, and control the output current size and the on-off of the AC-DC circuit and the DC-DC circuit; the control unit is also used to collect the current and voltage of the battery charging and discharging circuit and control the current size and the on-off of the battery charging and discharging circuit.

[0012] On the basis of the above embodiment, the application can be further improved, specifically as follows:

[0013] In one of the embodiments of the application, the battery pack is a plurality of small battery packs arranged in parallel, and the small battery pack is a series combination of one or more batteries.

[0014] In one of the embodiments of the application, the battery is a standard lead-acid battery.

[0015] In one of the embodiments of the application, the second direct current voltage is one or more direct current voltages, such as 110V, 220V or 48V.

[0016] In one of the embodiments of the application, the AC-DC circuit is a one-way conversion circuit, which can only convert from the input side to the output side, and the reverse conversion will be cut off.

[0017] In one of the embodiments of the application, the DC-DC circuit is a one-way conversion circuit, which can only convert from the input side to the output side, and the reverse conversion will be cut off.

[0018] In one of the embodiments of the present application, the control unit has a human interaction interface, which is convenient for setting parameters and displaying the current and voltage of the AC-DC circuit, the DC-DC circuit and the battery charging and discharging circuit.

[0019] In one of the embodiments of the present application, the control unit can communicate with other same control units through a CAN bus.

[0020] In one of the embodiments of the present application, the control unit is used to send and receive soft messages according to a protocol, which includes alarm messages, current and voltage collection messages and control messages.

[0021] In one of the embodiments of the present application, the control unit is used to output hard contact alarm signals, including module failure, DC ground, insufficient battery capacity and battery failure.

[0022] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0023] 1. N+1 (N>=1) new DC charging and discharging devices run in parallel, which can perform charging and discharging tests on specific battery groups under the premise that the secondary system can meet reliable power supply. During the test, the target battery group is in reverse discharge state by reducing the AC input of the target battery group and reducing the DC output of other groups, and the control unit is used to monitor the discharge time and load current of the target battery group to determine whether the battery and DC output are normally operated; at the same time, the AC input of other groups is normal, which ensures that the secondary system can meet reliable power supply. The test is performed in turn according to groups, and the charging and discharging test of all battery groups can be completed.

[0024] 2. N+1 (N>=1) new DC charging and discharging devices run in parallel, and when AC power loss occurs due to failure, multiple parallel running battery groups are discharged to the secondary system through the DC-DC system, so that even if a battery group is damaged, the discharge process of other battery groups is not affected, thereby ensuring higher reliability of the DC system.

[0025] 3. The battery group of the new DC charging and discharging device is designed as multiple small battery groups running in parallel, when a small battery group fails and is damaged, the new DC charging and discharging device can timely find the battery activation and send it to the master station for timely replacement, and only the battery group needs to be replaced, and other groups of batteries do not need to be replaced, which greatly reduces the battery operation and maintenance replacement cost. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference signs. In the drawings, the elements or parts are not necessarily drawn according to the actual proportions.

[0027] Figure 1 A structure block diagram of a new DC charging and discharging device in the embodiments of the present application;

[0028] Figure 2 A structure schematic diagram of a DC system in which multiple new DC charging and discharging devices run in parallel;

[0029] Among them, 1. AC-DC loop, 2. Battery charging and discharging loop, 3. Battery pack, 4. DC-DC loop, 5. Control unit. DETAILED DESCRIPTION

[0030] The present application will be further illustrated below in conjunction with the specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not used to limit the scope of the present application. After reading the present application, various equivalent modifications of the present application made by those skilled in the art all fall within the scope defined by the claims of the present application.

[0031] It should be noted that: similar signs and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0032] In the description of the present application, it should be noted that the terms "first", "second", "third" and the like are only used to distinguish description and cannot be understood as indicating or implying relative importance. Unless otherwise explicitly specified and limited, the terms "set", "install", "connect", "connect" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] The embodiments of the present application provide a new DC charging and discharging device, which solves the problems of poor reliability and difficult maintenance of the existing power distribution network battery pack, improves the reliability of the secondary DC system, and reduces the maintenance cost.

[0034] The technical solutions in the embodiments of the present application are as follows to solve the above problems:

[0035] Embodiment:

[0036] like Figure 1 As shown, a novel DC charging and discharging device includes an AC-DC circuit 1, a battery charging and discharging circuit 2, a battery pack 3, a DC-DC circuit 4, and a control unit 5.

[0037] The input side of AC-DC circuit 1 receives a wide-range AC current of 50Hz or 60Hz, and the output side outputs a first DC voltage. The output side of AC-DC circuit 1 is simultaneously connected to one side of battery charging / discharging circuit 2 and the input side of DC-DC circuit 4. The other side of battery charging / discharging circuit 2 is connected to battery pack 3 for charging and discharging battery pack 3. That is, the first DC voltage can charge battery pack 3 through battery charging / discharging circuit 2, and similarly, battery pack 3 can also achieve the function of discharging through battery charging / discharging circuit 2. Battery pack 3 consists of multiple small battery packs 3 operating in parallel, and small battery pack 3 is a series combination of one or more batteries. The input side of DC-DC circuit 4 is simultaneously connected to one side of battery charging / discharging circuit 2 and the output side of AC-DC circuit 1 to receive the first DC voltage output by AC-DC circuit 1 or the discharge current of battery pack 3 through battery charging / discharging circuit 2. The output side of DC-DC circuit 4 outputs a second DC voltage, which is one or more DC voltages, such as 110V, 220V, or 48V.

[0038] The control unit 5 is electrically connected to AC-DC circuit 1, battery charging and discharging circuit 2 and DC-DC circuit 4 respectively. The control unit 5 is used to collect the current and voltage on the input and output sides of AC-DC circuit 1 and DC-DC circuit 4, and to control the output current of AC-DC circuit 1 and DC-DC circuit 4 and the circuit connection and disconnection. The control unit 5 is also used to collect the charging and discharging current and voltage of battery pack 3 in battery charging and discharging circuit 2 and to control its current magnitude and the circuit connection and disconnection.

[0039] Furthermore, control unit 5 can communicate with other identical control units 5 via CAN bus, serial port, or remote signaling.

[0040] Furthermore, the control unit 5 has a user interface that supports parameter setting. It can monitor and display the current and voltage status of AC-DC circuit 1, DC-DC circuit 4, and battery charging / discharging circuit 2, and issue alarms according to the set logic. The control unit 5 can send and receive soft messages according to the protocol, including alarm messages, current and voltage acquisition messages, control messages, etc., and simultaneously output hard contact alarm signals.

[0041] Furthermore, AC-DC circuit 1 is a unidirectional conversion circuit, which can only be converted from the input side to the output side; the reverse conversion will be cut off.

[0042] Further, the DC-DC circuit 4 is a one-way conversion circuit, and can only convert from the input side to the output side, and the reverse conversion is cut off.

[0043] Due to the chemical properties of lead-acid batteries, any damage to a single battery of a lead-acid battery pack requires replacement of the entire battery pack. The existing charging and discharging device generally has 18 or 9 batteries in a group, resulting in high replacement cost after the battery pack is damaged. The new DC charging and discharging device has 4 or 2 batteries in a group, and only 4 or 2 batteries need to be replaced each time, thereby reducing maintenance cost.

[0044] The CPU model of the optional control chip is STM32F103RCT6.

[0045] In use, the specific implementation process of the new DC charging and discharging device is as follows:

[0046] Suppose that a DC system in a 10kV switching station of a distribution network system is composed of multiple new DC charging and discharging devices in parallel, and the control unit can communicate with a DTU through a serial port or remote signaling. The structure is as shown in Figure 2 The different devices communicate through a CAN bus. Generally, the DC system has three working states.

[0047] First, in a normal operating state, the AC input of each group is converted through the corresponding AC-DC circuit, and the output DC voltage supplies power to the secondary system in the station. At the same time, the battery charging and discharging circuit charges each battery pack, and each battery pack is in a floating state. Each control unit monitors the state of the device in real time, can monitor and display the current and voltage conditions and grounding conditions of the AC-DC circuit, the DC-DC circuit, and the battery charging and discharging circuit, communicates with other control units through the CAN bus, and alarms according to the set logic. When an external distribution network line fails, the secondary system in the switching station is in a reliable power supply state, and the relay protection can act to remove the fault in time to ensure the safe operation of the distribution network.

[0048] Second, the battery test state, that is, the battery packs in each new DC charging and discharging device operating in parallel are tested one by one. When the new DC charging and discharging device operates to the activation period, it automatically detects the activation condition and enters the activation state after the activation condition is met. In particular, when the system detects that the battery pack in another charging and discharging device fails or is in a charging state, the charging and discharging test of the device cannot start until the abnormal operating state of the other device disappears. At the same time, when a charging and discharging device in the system receives a signal and starts the charging and discharging test, other groups of devices cannot enter the charging and discharging test state to ensure reliable power supply of the secondary system during the charging and discharging test.

[0049] After the start of the charge and discharge test, interrupt the AC input of the test battery pack, the test battery pack will supply power to the secondary system through the charge and discharge circuit and the DC-DC circuit at once, and the control circuit will detect the discharge current and voltage of the battery pack to comprehensively judge the capacity and state of the battery pack. After the activation is completed, according to the activation result, each control unit communicates with the DTU through remote signaling, and the DTU reports the activation result to the master station, such as battery normal or battery failure. The operation and maintenance personnel check the information received by the master station, and if it is a battery failure, replace the corresponding battery pack. During the entire test process, the secondary system of the switching station is always in a reliable power supply state, which ensures the reliability of the secondary system while checking the operation of each battery pack.

[0050] Thirdly, the AC input is faulty, and the battery pack is in a discharging state. On the one hand, when the AC input of the system loses, the control unit will control the battery pack to discharge through the battery charge and discharge circuit and the DC-DC circuit, and supply power to the secondary system together with other normally operating devices, and stop discharging after the battery pack is discharged to a certain voltage, so as to reduce the life loss of the battery. On the other hand, when the external AC input is lost, all battery packs in the new type DC charge and discharge device discharge through the battery charge and discharge circuit and the DC-DC circuit, and at the same time, the devices communicate with each other, balance the discharge current, and stop discharging when reaching a certain voltage, so as to ensure reliable power supply of the secondary system of the switching station within a certain time. When the external AC input is restored, the discharged battery pack will enter the charging state. In particular, compared with the traditional DC system, when a battery pack itself has a fault, the use of the new type DC charge and discharge device does not affect the power output of other battery packs, which greatly improves the reliability of the DC system.

[0051] Although the embodiments of the utility model have been shown and described above, and three field conditions have been shown. It can be understood that the above-mentioned embodiments are exemplary, and cannot be understood as the limitation of the utility model, and the ordinary skilled in the art can change, modify, replace and modify the above-mentioned embodiments within the scope of the utility model.

Claims

1. A novel direct current charging and discharging device, characterized by, The AC-DC circuit, the battery charging and discharging circuit, the battery pack, the DC-DC circuit and the control unit are connected. The input side of the AC-DC circuit inputs alternating current, and the output side of the AC-DC circuit is connected with one side of the battery charging and discharging circuit and the input side of the DC-DC circuit. The other side of the battery charging and discharging circuit is connected with the battery pack, so as to charge and discharge the battery pack. The input side of the DC-DC circuit is connected with one side of the battery charging and discharging circuit and the output side of the AC-DC circuit. The control unit is electrically connected with the AC-DC circuit, the battery charging and discharging circuit and the DC-DC circuit, respectively, and is used to collect the current and voltage of the input and output sides of the AC-DC circuit and the input and output sides of the DC-DC circuit, and control the output current size and the circuit on-off of the AC-DC circuit and the DC-DC circuit. The control unit is also used to collect the current and voltage of the battery charging and discharging circuit and control the current size and the circuit on-off of the battery charging and discharging circuit.

2. The novel DC charging and discharging device according to claim 1, characterized in that: A plurality of the novel direct current charging and discharging devices are in communication and run in parallel in a secondary direct current system.

3. The novel DC charging and discharging device according to claim 2, characterized in that: The battery pack is a plurality of small battery packs arranged in parallel, and the small battery pack is a series combination of one or more batteries.

4. The novel DC charging and discharging device according to claim 1, characterized in that: The battery is a lead-acid battery.

5. The novel DC charging and discharging device according to claim 1, characterized in that: The output side of the DC-DC circuit outputs a second direct current voltage, and the second direct current voltage is one or more direct current voltages.

6. The novel DC charging and discharging device according to claim 1, characterized in that: The AC-DC circuit is a one-way conversion circuit, which can only convert from the input side to the output side, and the reverse conversion will be cut off.

7. The novel DC charging and discharging device according to claim 1, characterized in that: The DC-DC circuit is a one-way conversion circuit, which can only convert from the input side to the output side, and the reverse conversion will be cut off.

8. The novel DC charging and discharging device according to claim 1, characterized in that: The control unit has an artificial interactive interface, which is used to set parameters and display the current and voltage of the AC-DC circuit, the DC-DC circuit and the battery charging and discharging circuit.

9. The novel DC charging and discharging device according to claim 8, characterized in that: The control unit can communicate with the outside through the CAN bus.

10. The novel DC charging and discharging device according to claim 8, characterized in that: The control unit is used to send and receive soft messages according to the protocol, and the soft messages include alarm messages, current and voltage collection messages and control messages. The control unit is used to output hard contact alarm signals, and the alarm signals include module failure, direct current grounding, insufficient battery capacity and battery failure.

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