CN105006867B - The battery unit connection circuit of energy-storage system applied to high power high voltage operating mode - Google Patents

Abstract

A kind of battery unit the present invention provides energy-storage system applied to high power high voltage operating mode connects circuit, first single battery is connected to form major loop, branched major loop is connected in parallel, often row single battery parallel connection on major loop is formed into minor loop again, major loop undertakes carries out the permutable access of electricity with external, minor loop undertakes sampling monitoring, the hard protection of overcurrent fusing, it is balanced, the multi-functionals such as back work, it is in certain ratio to connect resistance between connection resistance and minor loop unit between the major loop battery unit, major loop on minor loop with being both provided with fuse.The present invention makes energy-storage system show higher energy efficiency by the setting in primary and secondary circuit, it is the good combination that energy-storage system is balanced and works normally, realize the dynamic equalization between batteries in parallel connection unit, the uniformity under working condition is enhanced, the effective time of energy-storage system high-power operation can be extended.

Description

Battery unit connection lines for energy storage systems used in high-power and high-voltage conditions

technical field

The invention relates to an energy storage system, in particular to a composition structure of an energy storage system, a battery unit connection circuit and a unit monitoring and management method for high-power and high-voltage applications.

Background technique

With the advancement of battery energy storage system technology, the specific energy of its energy storage has increased rapidly, and the unit cost has gradually decreased. In addition, the battery energy storage system itself has the characteristics of fast response and convenient setting, making the application of battery energy storage system in It is also becoming more and more common in high-power and high-voltage working conditions.

Normally, a battery energy storage system is composed of a large number of single batteries connected in series and parallel to form a complete system to realize the storage and release of electric energy of a certain scale. In occasions that need to meet high-power and high-voltage working conditions (such as port rubber-tyred gantry crane oil-electric hybrid power system), due to the large power capacity that the energy storage system needs to meet, it is often inconvenient to install too many protection devices on the working circuit , such as fuses, these high-power protection devices themselves need to consume power, and may cause a decrease in the reliability of the energy storage system due to the poor consistency of these protection devices. Furthermore, the high voltage of the energy storage system means that the number of single cells connected in series is large, so the problem of its consistency is particularly prominent. If there is no better solution to achieve the dynamic consistency of the energy storage system during use, the energy storage system often needs to operate with limited capacity or limited power, which cannot well meet the needs of actual working conditions.

In order to solve this problem, a balance management module is generally set in the BMS (battery management system). The commonly used balance method is to add a hardware structure circuit in the BMS (battery management system) as a balance management module. When the system is running, turn on the balance mode to consume the excess power in the high-voltage or high-SOC single battery in the system, and adjust the voltage and charge of the single battery to the target level set by the system to achieve the purpose of balance. However, this method has the problems of high equilibrium management cost and low equilibrium efficiency.

Contents of the invention

Aiming at the defects in the prior art, the present invention aims to provide a battery unit connection circuit that can be applied to an energy storage system under high power and high voltage conditions. The present invention realizes by following scheme:

The structure of the energy storage battery unit adopts the method of main series and secondary parallel. First, n single batteries are connected in series to form a battery pack to form a main circuit, m main circuits are connected in parallel, and then each row of monomers between each main circuit is connected. The batteries are connected in parallel to form a secondary circuit, and the way of the parallel connection is that one end of the connecting wire is respectively connected to the positive pole or negative pole of each single battery in the same row, and the other end of the connecting wire is connected to the copper bar. The ratio of the connection resistance between the main circuit battery units to the connection resistance between the secondary circuit units is in the range of 1:1˜1:200, preferably 1:20˜1:100. The setting of the connection resistance ratio can well realize the realization of different functions of the two types of circuits, that is, the main circuit is responsible for the energy exchange path between the energy storage system and the outside, and the secondary circuit is responsible for the internal line sampling monitoring of the energy storage system, BMS protection, current Multiple functions such as over-current fuse hard protection, equalization, and auxiliary work.

The total negative pole or the total positive terminal of the main circuit is connected in series with the first fuse (5), the second fuse (6) and the third fuse (7) are connected between the secondary circuit units, and the second fuse (6) ) and the rated current of the third fuse (7) are 5% to 20% of the rated current of the first fuse. The setting of the second fuse, the third fuse and their rated current can not only meet the purpose of internal automatic balance of each battery unit of the energy storage system due to performance differences under normal conditions, but also meet the safety requirements of the energy storage system under abnormal conditions. protection and rapid isolation requirements.

At the same time, in order to combine the new structural features of the energy storage system, a battery management unit for monitoring the secondary circuit unit is specially provided. The setting of the battery management unit for secondary circuit monitoring further enhances the dynamic management capability of the energy storage system, especially the monitoring of unit consistency is fundamentally strengthened, so its safety and reliability are strengthened and guaranteed.

Compared with prior art, the present invention has following advantage:

1. Energy storage systems exhibit higher energy efficiency. As the working circuit, the main circuit is responsible for the energy exchange path between the energy storage system and the outside. Since there is no need to consider the influence of internal parallel circulation and no additional protection devices such as FUSE, the connection resistance and voltage drop of the main circuit are very low. , the line losses are small under high-power operating conditions, leading to higher overall efficiency of the energy storage system.

2. Efficient and fast equalization can be achieved. As an auxiliary circuit, the secondary circuit realizes the parallel connection between the battery cells, so it can achieve the purpose of dynamic balance between the parallel battery cells.

3. A good combination of balance and normal operation of the energy storage system can be achieved. Since the main circuit and the secondary circuit are separated, it will not affect the high-power work of the energy storage system. On the contrary, due to the existence of the secondary circuit, the dynamic balance between the parallel battery units can be realized, which enhances the consistency of the energy storage system in the working state. It can prolong the effective time of high-power operation of the energy storage system.

Description of drawings

Fig. 1 is the combined structural diagram of the energy storage system of the comparative example of the present invention;

Fig. 2 is a combined structure diagram of an energy storage system according to an embodiment of the present invention;

Fig. 3a is a voltage-time curve diagram of the discharge column unit of the Ni-MH battery energy storage system according to the embodiment of the present invention.

Fig. 3b is a graph showing the voltage-time curve of the discharge column unit of the Ni-MH battery energy storage system of the comparative example of the present invention.

Fig. 4 is a graph showing cell voltage-time curves of the discharge line of the Ni-MH battery energy storage system according to the embodiment of the present invention.

Fig. 5 is a voltage-time graph of single battery and row unit of the Ni-MH battery energy storage system according to the embodiment of the present invention.

Detailed ways

Example 1

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments. This embodiment uses a nickel metal hydride D-type 1.2V6Ah battery and an energy storage system composed of this type of single battery for illustration. The energy storage system is composed of 3360 single batteries. The rated voltage of the energy storage system is 576V and the rated energy is 24.2kWh.

Figure 1 shows the combined structural form of the energy storage system of the comparative example. First, 480 single cells 1 are connected in series to form a column, and a relay 4 is provided at the place where the positive pole of each column is connected to the total positive 2, and a fuse 5 is provided at the place where the negative pole of each column is connected to the total negative 3. Then the same 7 columns of negative poles are connected in parallel to the total negative 3, and the 7 columns of positive poles are connected in parallel to the total positive 2. BMS (Battery Management System) monitors the voltage, temperature, and current of each column of the smallest management unit, calculates the SOC of each column, and implements management and control of the energy storage system. Since the energy storage system is composed of 3360 single batteries, in order to reduce the cost of management, the smallest management unit is usually composed of 6 single batteries in series, that is, the BMS detects the voltage of the smallest management unit composed of 6 single batteries in series , temperature, current per column. The energy storage system with this structure has the following problems: First, since the minimum management unit monitored by the BMS is composed of as many as 6 batteries in series, its voltage characteristics are the superposition of the characteristics of 6 single batteries, due to the inconsistency of single batteries The superimposed characteristics often cannot accurately reflect the actual characteristics of the single battery, so it brings uncertainty to the management and control of the energy storage system, and it is easy to cause overcharge and overdischarge of the single battery, which will bring safety in severe cases. risk. Secondly, multiple factors such as the inconsistency of the intrinsic characteristics of the single battery, the inconsistency of the use environment, and the inconsistency of the combination are superimposed. During the use of the energy storage system, the differences between the monomers often show a tendency to expand. If the difference reaches a certain level, the energy storage system needs to be shut down for maintenance. However, since the BMS can only judge the voltage deviation between the minimum management unit, that is, the six series assemblies, it is difficult to judge the voltage deviation between the single cells, so there is a small deviation of the minimum management unit. In fact, the voltage between the single cells The case where the deviation is already large. Untimely judgment will further accelerate the failure and deterioration of the energy storage system. Third, there is no effective balancing method to eliminate the inconsistency between monomers. Since the cells are fully connected in series, they can only be balanced by the column, but the column balance may be exactly the opposite of the cell balance requirement, that is, the column is charging in equalization but there is a high-capacity and high-voltage battery in it. The single battery just needs to be discharged. Fourth, the maintainability of the energy storage system is poor, and the usable energy range is greatly reduced. Since the BMS cannot effectively feedback the state of the single battery and the lack of an effective balancing method between the single cells, in order to ensure safety during the use of the energy storage system, the range of energy that can be used is often reduced. At the same time, the energy storage system does need When performing maintenance, reliable maintenance methods cannot be obtained.

Fig. 2 shows the combined structural form of the energy storage system of the embodiment of the present invention. First, 480 single cells 1 are connected in series to form a column, which is called the main circuit, and a relay is provided where the positive pole of each column is connected to the total positive 2, and a first relay is provided at the place where the negative pole of each column is connected to the total negative 3. Fuse 5. Then the same 7 columns of negative poles are connected in parallel to the total negative 3, and the 7 columns of positive poles are connected in parallel to the total positive 2. Next is each row, a total of 480 rows. The single cells 1 in the same row are connected in parallel through the parallel conductor 8, which is called the secondary circuit. A row fuse, namely the second fuse 6, is set at the place where the positive pole of the single battery is connected to the parallel conductor. , a third fuse 7 is provided at the place where the negative pole of the single battery is connected to the parallel conductor.

The series connection between 480 single batteries in each row, in order to make the energy storage system have the ability to work for more than 3 minutes with a rated power output of 200kW, so the connection resistance of the main circuit (the connection resistance from a to b shown in Figure 2, that is R _ab ) is as small as possible to reduce the loss of the loop itself during operation. Secondly, the secondary circuit undertakes the function of equalizing the single cells in the same line, and needs to have the ability to pass a certain current, but it cannot be equivalent to the function of the main circuit. Therefore, the connection resistance of the secondary circuit (the connection from c to d shown in Figure 2 The setting of the resistance, that is, R _cd ), is very necessary (the resistance of the parallel conductor 8 adopts copper bars, the total resistance is 0.2mΩ, and the resistance value between each adjacent two rows of batteries is 0.033mΩ, and the resistance value of the parallel conductor 8 is much smaller than R _cd ) . In this embodiment, the ratio of the connection resistance between the cells in the main circuit of the energy storage system to the connection resistance between the cells in the secondary circuit is 1:80 (R _ab =0.05mΩ, R _cd =4.0mΩ). The setting of the resistance ratio value, on the one hand, can meet the needs of the main circuit to undertake the energy exchange path between the energy storage system and the outside, and can also meet the needs of the secondary circuit to undertake the internal line sampling monitoring of the energy storage system, BMS protection, current overcurrent fuse hard protection, equalization , auxiliary work and other multiple functions. Since the resistance of the secondary circuit is significantly higher than that of the main circuit, the secondary circuit can automatically perform equalization when the cells in the same line are unbalanced, and the greater the deviation between the cells, the more obvious the equalization effect.

A second fuse 6 is provided at the place where the positive pole of the single battery is connected to the parallel conductor, and a third fuse 7 is provided at the place where the negative pole of the single battery is connected to the parallel conductor, and the second fuse 6 and the third fuse are disconnected. The rated current of the fuse 7 is 5% to 20% of the rated current of the first fuse 5 . In this embodiment, the rated working current of each row of the energy storage system is 60A, the first fuse 5 with a rated current of 60A is used, and the second fuse 6 and the third fuse 7 with a rated current of 10A are used. As an auxiliary parallel equalization circuit, the secondary circuit can effectively improve the consistency of the energy storage system. However, when the consistency deviation of the energy storage system exceeds the allowable range, or an abnormal problem occurs such as an internal short circuit of a row of single cells, then Due to the setting of the second fuse 6 and the third fuse 7, the secondary circuit can quickly isolate faults and protect the safety of the energy storage system. This method is different from the commonly used main parallel mode. If the main parallel mode needs safety protection under abnormal fault conditions, fuses or other protection devices are set on the parallel circuit, but this will increase the power consumption of the entire main circuit and On the contrary, if the main parallel mode does not set a protection device and directly connects the single cells in parallel, the safety of the entire energy storage system will have a greater risk.

The BMS of the embodiment of the present invention is provided with a monitoring secondary circuit, that is, a management unit of single cells connected in parallel in parallel. That is to say, compared with the comparative example, the BMS (battery management system) of the present invention monitors the voltage of each row and the voltage of each column. The current and the temperature of the minimum temperature management unit calculate the SOC of each column, and implement the management and control of the energy storage system. Since the row units of the secondary circuit are formed by auxiliary parallel connection of single cells, the voltage of each single cell in the idle state is consistent, and in the working state (that is, charging or discharging of the energy storage system) due to the consistent voltage between the single cells in the same row The polarity deviation is dynamically balanced through the secondary circuit at all times, so the voltage between the individual cells is also basically the same. Therefore, the voltage of each row detected by the BMS can well reflect the actual state of the single battery in the row, and can effectively avoid the occurrence of overcharge and overdischarge. At the same time, it also fundamentally improves the maintainability of the energy storage system.

Fig. 3a shows the voltage-time curve diagram of the minimum management unit (hereinafter referred to as 7.2V unit) composed of 6 single batteries in 4 similar rows during the 42A constant current discharge process of the energy storage system according to the embodiment of the present invention . It can be seen from Figure 3 that during the discharge process of the energy storage system, the 7.2V unit showed good consistency. This is because the existence of the secondary circuit can balance the monomer batteries in the same row, and the voltage deviation of the batteries in each row is very large. Small, the end result is that the voltage consistency of the 4 7.2V cells also performed well, with a maximum voltage deviation of 30mV. Compared with 42A constant current discharge under the same discharge current condition, Figure 3b shows the voltage-time curve diagram of the four similar 7.2V units in the comparative example, the voltage consistency of the four 7.2V units is poor, and the voltage deviation is the largest It is 130mV, which is 3 times higher than that of the embodiment.

Fig. 4 shows the voltage-time curves of 12 cells in a similar row (hereinafter referred to as 1.2V cells) extracted during the 42A constant current discharge process of the energy storage system according to the embodiment of the present invention. It can be seen from Figure 4 that during the discharge process of the energy storage system, the 1.2V cells did not show good consistency. This is because the batteries in each row often have inconsistencies, such as capacity. The balance between the bulk cells, but the difference between the lines cannot be reduced. Therefore, it is reflected in the discharge process that the voltage of each row unit is very different. If the row unit voltage is not used as the protection control of discharge, there will be overdischarge. For example, the 11th row unit monitored in Figure 4 has serious overdischarge phenomenon. . In order to verify the authenticity of the cell voltage in row 11, that is, whether the voltage in this row can represent the 7 single cells in the row, the voltage of each cell in the row was monitored. Figure 5 shows the comparative voltage-time curves. It can be seen from Figure 5 that the cell voltage of this row overlaps well with the voltages of the 7 single cells, which can represent the actual condition of the single cells in this row.

Therefore, based on the above Figure 2, Figure 3, Figure 4, and Figure 5, the technical solution adopted by the embodiment of the present invention is: the energy storage system adopts the main series auxiliary parallel mode in structure, that is, the main body adopts a series structure, which is called the main circuit , the main circuit is responsible for the energy exchange path between the energy storage system and the outside; at the same time, there is also a parallel structure, called the secondary circuit or auxiliary circuit, and the secondary circuit is responsible for the internal line sampling and monitoring of the energy storage system, BMS protection, and current overcurrent fusing hardware. Protection, balance, auxiliary work and other multiple functions.

The ratio of the connection resistance between the main circuit units to the connection resistance between the secondary circuit units is between 1:20 and 1:100. The setting of the connection resistance ratio can well realize the realization of different functions of the two types of circuits, that is, the main circuit is responsible for the energy exchange path between the energy storage system and the outside, and the secondary circuit is responsible for the internal line sampling monitoring of the energy storage system, BMS protection, current Multiple functions such as over-current fuse hard protection, equalization, and auxiliary work.

A second fuse and a third fuse are connected between the secondary circuit units, and the rated current of the second fuse and the third fuse is 5% to 20% of the rated current of the first fuse. The setting of the second and third fuses and their rated current can not only meet the purpose of internal automatic balancing of the battery units of the energy storage system due to performance differences under normal conditions, but also meet the safety protection and safety requirements of the energy storage system under abnormal conditions. Rapid quarantine requirements.

At the same time, in order to combine the new structural features of the energy storage system, a battery management unit for monitoring the secondary circuit unit is specially provided. The setting of the battery management unit for secondary circuit monitoring further enhances the dynamic management capability of the energy storage system, especially the monitoring of unit consistency is fundamentally strengthened, so its safety and reliability are strengthened and guaranteed.

Compared with the prior art, the nickel-hydrogen battery energy storage system of the present invention has the following advantages:

(1) The energy storage system exhibits higher energy efficiency. As the working circuit, the main circuit is responsible for the energy exchange path between the energy storage system and the outside. Since there is no need to consider the influence of internal parallel circulation and no additional protection devices such as FUSE, the connection resistance and voltage drop of the main circuit are very low. , the line losses are small under high-power operating conditions, leading to higher overall efficiency of the energy storage system.

(2) Efficient and fast equalization can be realized. As an auxiliary circuit, the secondary circuit realizes the parallel connection between the battery cells, so it can achieve the purpose of dynamic balance between the parallel battery cells.

(3) A good combination of balance and normal operation of the energy storage system can be achieved. Since the main circuit and the secondary circuit are separated, it will not affect the high-power work of the energy storage system. On the contrary, due to the existence of the secondary circuit, the dynamic balance between the parallel battery units can be realized, which enhances the consistency of the energy storage system in the working state. It can prolong the effective time of high-power operation of the energy storage system.

Although the present invention is described by taking a nickel-metal hydride battery energy storage system as an example, it is also applicable to an energy storage system or an energy module composed of a rechargeable battery system such as a lithium-ion battery, a nickel-cadmium battery, or a lead-acid battery.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, these improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (4)

1. the battery unit connection circuit of the energy-storage system applied to high power high voltage operating mode, n single battery is in column direction Series connection forms a major loop, and major loop arranges m branch in line direction, and parallel connection forms energy-storage battery unit to m branch major loop again, special Sign is：By every a line single battery formation minor loop in parallel between every major loop, and the mode of the parallel connection is same Anode, the cathode of each single battery of row are connected respectively by connecting wire with parallel conductor, and a single battery corresponds to two companies Connect conducting wire, with each single battery of a line corresponding two parallel conductors jointly, connection resistance between the major loop battery unit with The scope that the ratio between resistance is connected between minor loop unit is 1：1~1：200；The major loop carries out electric energy for energy-storage system with external The access of exchange, the minor loop is for sampling monitoring, the hard protection of overcurrent fusing, balanced and back work.

2. the battery unit applied to the energy-storage system of high power high voltage operating mode connects circuit as described in claim 1, It is characterized in that：Ranging preferably from for the ratio between resistance is connected between connection resistance and minor loop unit between the major loop battery unit 1：20~1：100.

3. the battery unit applied to the energy-storage system of high power high voltage operating mode connects circuit as claimed in claim 1 or 2, It is characterized in that：Total cathode of the major loop or total positive terminal series connection first fuse (5), in the minor loop, each monomer Be serially connected with second fuse (6) in connecting wire between the anode and parallel conductor of battery, the cathode of each single battery with simultaneously The 3rd fuse (7) is serially connected in connecting wire between connection conductor.

4. the battery unit applied to the energy-storage system of high power high voltage operating mode connects circuit as claimed in claim 3, It is characterized in that：The rated current of the second fuse (6) and the 3rd fuse (7) is first fuse (5) rated current 5%~20%.