A device and method for controlling electrolyte temperature of a flow battery for a multi-cell stack

Abstract

The present application relates to the technical field of liquid flow batteries, and in particular to a liquid flow battery electrolyte temperature control device and method for a multi-cell stack group. It includes an energy storage system, a refrigeration system, a buffered thermal reaction system, and a battery management system; during the operation of the system, the battery management system uses a PID adjustment method to control the ratio of the opening of the regulating valves on the positive and negative electrode outlet branches to adjust the electrolyte flow; calculate the total heat output of the branch stack group, the required cooling capacity, the refrigerant flow, the opening of the cooling capacity regulating valve, and the frequency of the freezing pump; adjust the opening of the branch cooling capacity regulating valve and the frequency of the freezing pump to achieve the liquid flow battery electrolyte temperature control of the multi-cell stack group. The battery management system BMS will be used to control the liquid temperature of various parts of the system by adjusting the parameters such as the load of the refrigerator evaporator compressor, the frequency of the pump, and the opening of the regulating valve, so as to achieve the purpose of improving the safety and efficient operation of the entire system.

Description

Technical Field

[0001] The present application relates to the technical field of liquid flow batteries, and in particular to a liquid flow battery electrolyte temperature control device and method for a multi-cell stack group. Background Art

[0002] The electrolyte in the flow battery energy storage system circulates throughout the energy storage system, and the positive and negative electrolytes undergo redox reactions on both sides of the ion exchange membrane inside the battery stack to achieve the storage and output of electrical energy. At the same time, the existence of battery side reactions will also generate heat to increase the battery temperature. Excessive temperature will cause battery stack failure, which in turn affects the normal operation of the entire system.

[0003] At present, liquid flow battery systems mostly use heat exchange devices for temperature control. However, in a heavy-loaded, large-scale, multi-branch battery stack system, the heat generated by each branch varies greatly, and under different control conditions, the heat generation also varies greatly, which brings safety and efficiency challenges to the overall thermal energy control of the system. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present application provides a device and method for detecting and controlling the electrolyte temperature of a liquid flow battery for a multi-stack group.

[0005] This application provides a technical solution:

[0006] A liquid flow battery electrolyte temperature control device for multiple battery stacks, comprising an energy storage system, a refrigeration system, a buffered thermal reaction system, and a battery management system (20); the energy storage system comprises: battery stacks (01) of each branch, a liquid storage tank (04), a liquid flow pump (06), an electrolyte return side sensor and a valve group (08), a battery stack inlet sensor and a valve group (11), a battery stack outlet sensor and a valve group (12), an electrolyte short-circuit switch valve (15), an inter-group series flow switch valve (16), and an electrolyte liquid level balance valve (19); the battery stack (01) is connected to the liquid storage tank (04); the refrigeration system comprises: a plate heat exchanger (02) of each branch, a refrigerator evaporator (03), a freezing pump (07), a refrigerant outlet side sensor and a valve group (09), a refrigerant return side sensor and The invention relates to a valve group (10), a plate heat exchanger inlet side sensor and a valve group (13) of each branch, a plate heat exchanger outlet side sensor and a valve group (14) of each branch, a buffer water tank inlet valve (17) and a buffer water tank outlet valve (18); the plate heat exchanger (02) is connected to the refrigerator evaporator (03); the buffer thermal reaction system comprises: a buffer water tank (05); the battery stack group (01) and the liquid storage tank (04) in the energy storage system are respectively connected to the plate heat exchanger (02) in the refrigeration system; the liquid storage tank (04) in the energy storage system is connected to the buffer water tank (05) in the buffer thermal reaction system; the refrigerator evaporator (03) in the refrigeration system is connected to the buffer water tank (05) in the buffer thermal reaction system; the battery management system is connected to the energy storage system, the refrigeration system and the buffer thermal reaction system in an electrically connected manner.

[0007] Preferably, the stack inlet sensor and valve group (11) are arranged between the liquid storage tank (04) and the stack group (01); the stack outlet sensor and valve group (12) are arranged between the stack group (01) and the plate heat exchanger (02); the electrolyte short-circuit switch valve (15) is arranged between the stack inlet sensor and valve group (11) and the buffer water tank (05); an inter-group series flow switch valve (16) is arranged between the positive electrode electrolyte outlet pipes of different stack groups (01); an inter-group series flow switch valve (16) is arranged between the negative electrode electrolyte outlet pipes of different stack groups (01); and the electrolyte liquid level balance valve (19) is arranged between the liquid storage tank (04) and the buffer water tank (05).

[0008] Preferably, the plate heat exchanger liquid inlet side sensor and valve group (13) are arranged between the plate heat exchanger (02) and the refrigerator evaporator (03); the plate heat exchanger liquid outlet side sensor and valve group (14) are arranged between the plate heat exchanger (02) and the refrigerator evaporator (03); the buffer water tank inlet valve (17) is arranged between the refrigerator evaporator (03) and the buffer water tank (05); and the buffer water tank outlet valve (18) is arranged between the refrigerator evaporator (03) and the buffer water tank (05).

[0009] A method for controlling electrolyte temperature of a flow battery for a multi-stack group comprises the following steps:

[0010] Step S1: The battery management system uses the PID adjustment method to control the ratio of the opening of the regulating valves on the positive and negative electrode outlet branches, adjust the electrolyte flow, and maintain the electrolyte pressure balance on both sides of the diaphragm in the battery stack. The calculation formula for the ratio of the regulating valve opening is: ;

[0011] Where: It is the ratio of the opening of the regulating valve on the positive and negative electrode liquid outlet branches; is the instantaneous error between the positive branch inlet pressure and the negative branch inlet pressure; It is the proportional coefficient in the PID regulation process; It is the integral time constant in the PID adjustment process; It is the differential time constant in the PID adjustment process; It is the PID adjustment time.

[0012] Step S2: Collect the positive electrode electrolyte inlet temperature, the positive electrode electrolyte outlet temperature, the negative electrode electrolyte inlet temperature, and the negative electrode electrolyte outlet temperature, and calculate the total heat output of the branch stack group. The calculation formula is: ;

[0013] Where: is the total heat produced by the branch stack group; is the positive electrode electrolyte inlet temperature; is the negative electrode electrolyte inlet temperature; is the outlet temperature of the positive electrode electrolyte; is the outlet temperature of the negative electrode electrolyte; is the positive electrode flow value; is the negative electrode flow value; is the cathode electrolyte density at 50% state of charge (SOC); is the negative electrode electrolyte density at 50% SOC; is the specific heat capacity of the cathode electrolyte at 50% SOC; is the specific heat capacity of the negative electrode electrolyte at 50% SOC.

[0014] Step S3: Calculate the cooling capacity required by the branch stack group as:

[0015] ;

[0016] Where: is the cooling capacity required by the branch stack group, is the heat transfer efficiency of the heat exchanger.

[0017] Step S4: Calculate the refrigerant flow rate of the branch through the heat exchanger according to the cooling capacity required by the branch stack group. The calculation formula is:

[0018] ;

[0019] Where: is the refrigerant flow rate through the heat exchanger in the branch; The branch cooling temperature; is the branch return cooling temperature; is the heat transfer efficiency of the branch heat exchanger; is the density of the refrigerant; is the specific heat capacity of the refrigerant.

[0020] Step S5: The refrigerant flow rate of the branch passing through the heat exchanger is used to calculate the opening of the branch cooling regulating valve. The calculation formula is:

[0021] ;

[0022] Where: is the opening degree of the branch cooling regulating valve; Branch flow The instant error of To adjust the proportional coefficient of the branch cooling regulating valve; To adjust the integral time constant of the branch cooling regulating valve; To adjust the differential time constant of the branch cooling regulating valve; To adjust the time.

[0023] Step S6: Accumulate the refrigerant flow of each branch, calculate the total refrigerant flow that should be supplied during the refrigeration process of the multi-stack liquid flow battery system, and determine the frequency of the refrigeration pump. The calculation formula is: ;

[0024] Where: is the frequency of the refrigeration pump; is the instant error of the total required refrigerant flow rate; To adjust the proportional coefficient of the refrigeration pump frequency; The integral time constant for adjusting the frequency of the refrigeration pump; The differential time constant for adjusting the frequency of the refrigeration pump; To adjust the time; adjust the opening of the branch cooling regulating valve and the frequency of the freezing pump to achieve electrolyte temperature control of the liquid flow battery of the multi-stack group.

[0025] Preferably, when the branch liquid inlet temperature in step S2 is lower than 10° C., the positive and negative electrolytes of the branch are placed in a buffer water tank mixing tank for mixing.

[0026] Preferably, the heat exchange efficiency of the heat exchanger in step S3 is equal to the total heat output of the branch stack group. There is a positive correlation. When the heat exchange efficiency of the heat exchanger is greater than 50%, the pipelines of each branch fuel cell group are not interconnected. When the heat exchange efficiency of the heat exchanger is less than or equal to 50%, the pipelines of adjacent branch fuel cell groups are interconnected, and the battery management system will close the pipeline switch between the branch fuel cell group and the heat exchanger.

[0027] Preferably, when the refrigerant flow rate in step S6 is lower than 30% of the rated flow rate, the refrigerant flow rate reaches 30% by activating the refrigerant circulation between the refrigeration system and the buffer thermal reaction system and increasing the frequency of the refrigeration pump.

[0028] The beneficial technical effects of this application are:

[0029] 1. When the system is working, it can control the heat generated by the stack side branch and calculate the heat generated by the branch. At the same time, according to the heat generated by each stack group branch, the total cooling capacity is determined while ensuring the efficiency of the evaporator compressor, and the amount of refrigerant in each refrigeration branch is reasonably allocated, thereby reducing the energy loss during the operation of the energy storage system and improving the overall operating efficiency of the flow battery.

[0030] 2. The system can restore the normal temperature of the electrolyte when the local electrolyte temperature of a branch battery group is too low due to changes in the charging and discharging methods and the operation control mode. At the same time, it can control the rate of increase in electrolyte temperature to avoid excessive temperature increase that affects system operation.

[0031] 3. The system can improve the heat transfer efficiency of the plate heat exchanger while ensuring the performance of the battery stack by mixing the flow at the liquid outlet of the large-scale heavy-load battery stack, thereby achieving the goal of controlling the temperature and reducing the internal energy consumption of the energy storage system, thereby improving the overall operating efficiency of the liquid flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the device structure of the present application.

[0033] Figure 2 It is a schematic diagram of the energy storage system structure of this application.

[0034] Figure 3 It is a schematic diagram of the refrigeration system structure of the present application.

[0035] Figure 4 It is a schematic diagram of the structure of the buffered thermal reaction system of the present application.

[0036] Figure 5 It is a schematic diagram of heat exchange between the branch stack and the plate heat exchanger of the present application.

[0037] Figure 6It is a schematic diagram of the partial structure of the main circuit circulation of the electrolyte positive electrode side of an embodiment of the present application.

[0038] Figure 7 It is a schematic diagram of the partial structure of the main circuit circulation of the electrolyte negative electrode side of an embodiment of the present application.

[0039] Figure 8 It is a schematic diagram of the local structure of the battery stack side of an embodiment of the present application.

[0040] Fig. 9 It is a schematic diagram of the local structure of the cooling side of the refrigeration circuit of an embodiment of the present application.

[0041] Fig.10 It is a schematic diagram of the local structure of the plate heat exchanger side of an embodiment of the present application.

[0042] Figure numerals: 01, battery stack; 02, plate heat exchanger; 03, refrigerator evaporator; 04, liquid storage tank; 05, electrolyte heating buffer water tank; 06, liquid flow pump; 07, freezing pump; 08, electrolyte return side sensor and valve group; 09, refrigerant outlet side sensor and valve group; 10, refrigerant return side sensor and valve group; 11, branch battery stack inlet sensor and valve group; 12, branch battery stack outlet sensor and valve group; 13, branch plate inlet side sensor and valve group; 14, branch plate outlet side sensor and valve group; 15, electrolyte short-circuit switch valve; 16, inter-group series flow switch valve; 17, buffer water tank inlet valve; 18, buffer water tank outlet valve; 19, electrolyte liquid level balance valve; 20, battery management system;

[0043] 031, refrigerator evaporator compressor; 051, buffer water tank mixing tank; 052, buffer water tank level gauge; 053, buffer heat reaction coil; 091, refrigeration liquid outlet valve; 092, refrigeration liquid outlet temperature sensor; 093, refrigeration liquid outlet pressure sensor; 101, refrigeration liquid return valve; 102, refrigeration liquid return temperature sensor; 103, refrigeration liquid return pressure sensor; 104, refrigeration liquid return flowmeter; 131, branch cooling temperature sensor; 141, branch cooling regulating valve; 142, branch cooling temperature sensor; 143, branch cooling flowmeter;

[0044] 04P, positive electrode liquid storage tank; 04N, negative electrode liquid storage tank; 06P, positive electrode liquid flow pump; 06N, negative electrode liquid flow pump; 15P, positive electrode electrolyte short-circuit switch valve; 15N, negative electrode electrolyte short-circuit switch valve; 16P, positive electrode inter-group series flow switch valve; 16N, negative electrode inter-group series flow switch valve; 19P, positive electrode electrolyte liquid level balance valve; 19N, negative electrode electrolyte liquid level balance valve;

[0045] 041P, positive electrode liquid storage tank level sensor; 041N, negative electrode liquid storage tank level sensor; 081P, positive electrode electrolyte return valve; 082P, positive electrode electrolyte return temperature sensor; 083P, positive electrode electrolyte return pressure sensor; 084P, positive electrode electrolyte return flow sensor; 111P, positive electrode branch inlet switch valve; 112P, positive electrode branch inlet temperature sensor; 113P, positive electrode branch inlet pressure sensor ; 111N, negative branch liquid inlet switch valve; 112N, negative branch liquid inlet temperature sensor; 113N, negative branch liquid inlet pressure sensor; 121P, positive branch liquid outlet regulating valve; 122P, positive branch liquid outlet temperature sensor; 123P, positive branch liquid outlet pressure sensor; 121N, negative branch liquid outlet regulating valve; 122N, negative branch liquid outlet temperature sensor; 123N, negative branch liquid outlet pressure sensor;

[0046] 01A, branch A battery stack; 01B, branch B battery stack; 111AP, branch A positive branch liquid inlet switch valve; 112AP, branch A positive branch liquid inlet temperature sensor; 113AP, branch A positive branch liquid inlet pressure sensor; 111AN, branch A negative branch liquid inlet switch valve; 112AN, branch A negative branch liquid inlet temperature sensor; 113AN, branch A negative branch liquid inlet pressure sensor; 111BP, branch B positive branch liquid inlet switch valve; 112BP, branch B positive branch liquid inlet temperature sensor; 113BP , branch B positive electrode branch inlet pressure sensor; 111BN, branch B negative electrode branch inlet switch valve; 112BN, branch B negative electrode branch inlet temperature sensor; 113BN, branch B negative electrode branch inlet pressure sensor; 121AP, branch A positive electrode outlet regulating valve; 122AP, branch A positive electrode outlet temperature sensor; 123AP, branch A positive electrode outlet pressure sensor; 121AN, branch A negative electrode outlet regulating valve; 122AN, branch A negative electrode outlet temperature sensor; 123AN, branch A negative electrode outlet pressure sensor; 12 1BP, branch B positive electrode outlet regulating valve; 122BP, branch B positive electrode outlet temperature sensor; 123BP, branch B positive electrode outlet pressure sensor; 121BN, branch B negative electrode outlet regulating valve; 122BN, branch B negative electrode outlet temperature sensor; 123BN, branch B negative electrode outlet pressure sensor; 131A, branch A cooling temperature sensor; 131B, branch B cooling temperature sensor; 141A, branch A cooling capacity regulating valve; 142A, branch A return cooling temperature sensor; 143A, branch A return cooling flowmeter; 141B, Branch B cooling capacity regulating valve; 142B, branch B return cooling temperature sensor; 143B, branch B return cooling flowmeter; 15AP, branch A positive electrolyte short-circuit switch valve; 15BP, branch B positive electrolyte short-circuit switch valve; 15CP, branch C positive electrolyte short-circuit switch valve; 15AN, branch A negative electrolyte short-circuit switch valve; 15BN, branch B negative electrolyte short-circuit switch valve; 15CN, branch C negative electrolyte short-circuit switch valve; 16AP, branch A positive group series flow switch valve; 16AN, branch A negative group series flow switch valve. DETAILED DESCRIPTION

[0047] The following is combined with Figure 1-Figure 10 This application is described in further detail.

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] like Figure 1 A flow battery electrolyte temperature control device for a multi-stack group is shown, comprising an energy storage system, a refrigeration system, a buffered thermal reaction system and a battery management system.

[0050] Figure 2 The schematic diagram of the energy storage system structure in the device is shown in the figure. The connection mode of each component in the system is shown in the figure. The installation position of each sensor and valve group should meet the following requirements: the electrolyte return side sensor and valve group 08 should be installed on the electrolyte return main pipe according to their polarity; the battery stack group inlet sensor and valve group 11 of each branch should be installed on the battery stack group inlet pipe of each branch according to their polarity; the battery stack group outlet sensor and valve group 12 of each branch should be installed on the battery stack group outlet pipe of each branch according to their polarity; the electrolyte short-circuit switch valve 15 of each branch should be installed on the electrolyte short-circuit branch pipe according to its polarity; the series flow switch valve 16 between each group should be installed on the branch electrolyte series flow pipe according to its polarity; the electrolyte liquid level balance valve 19 should be installed on the electrolyte liquid level balance pipe. The electrolyte supply pipeline starts from the liquid storage tank 04, passes through the electrolyte supply main pipe and is divided into the liquid inlet pipe of each branch of the battery stack group, and then enters the battery stack group 01 of each branch, and then enters the refrigeration system through the battery stack group outlet pipe of each branch; the battery stack group outlet pipes of each branch are connected through the branch electrolyte series flow pipe; the electrolyte return pipeline starts from the plate heat exchanger 02 of each branch of the refrigeration system, converges into the electrolyte return main pipe, and then returns to the electrolyte storage tank.

[0051] Reference Figure 3, the installation positions of each sensor and valve group should meet the following requirements: the freezing pump 07 and the refrigerant outlet side sensor and valve group 09 should be installed on the cold supply main pipe; the refrigerant return side sensor and valve group 10 should be installed on the return cold main pipe; the plate heat exchanger inlet side sensor and valve group 13 of each branch should be installed on the plate heat exchanger cold supply pipe of each branch; the plate heat exchanger outlet side sensor and valve group 14 of each branch should be installed on the plate heat exchanger return cold pipe of each branch. The plate heat exchanger 02 of each branch is connected to the outlet pipe of the battery stack group from each branch of the energy storage system according to its polarity. After the electrolyte in it is cooled by the plate heat exchanger 02A of each branch, it passes through the electrolyte return pipe of each branch and is collected into the electrolyte return main pipe according to its polarity. The cooling dry pipe and the cooling return dry pipe are connected to the electrolyte heating buffer water tank 05 in the buffer thermal reaction system through the buffer water tank inlet pipe and the buffer water tank outlet pipe before the cooling pipe of the plate heat exchanger of each branch and the cooling return pipe of the plate heat exchanger of each branch.

[0052] Figure 4 This is a schematic diagram of the structure of the buffer thermal reaction system of the device, wherein the main body is a buffer water tank 05 on which a buffer water tank level gauge 052 is mounted; the buffer thermal reaction coil 053 and the buffer water tank mixing tank 051 are immersed in the refrigerant in the buffer water tank 05. As shown in the figure, the electrolyte short-circuit switch valve 15 can be divided into 15AP, branch A positive electrolyte short-circuit switch valve; 15BP, branch B positive electrolyte short-circuit switch valve; 15CP, branch C positive electrolyte short-circuit switch valve; 15AN, branch A negative electrolyte short-circuit switch valve; 15BN, branch B negative electrolyte short-circuit switch valve; 15CN, branch C negative electrolyte short-circuit switch valve; the stack group inlet pipe of each branch is connected to the buffer water tank mixing tank 051 in the buffer thermal reaction system through the electrolyte short-circuit branch pipe, through the buffer thermal reaction coil 053 in the buffer thermal reaction system, and then connected to the positive and negative electrolyte liquid level balance pipes where the electrolyte liquid level balance valve 19 is located through the buffer water tank return pipe.

[0053] Figure 5The schematic diagram of heat exchange between the branch stack and the plate heat exchanger of the present application is shown in the figure. As shown in the figure, the branch stack group inlet sensor and valve group 11 include a positive branch liquid inlet switch valve 111P, a positive branch liquid inlet temperature sensor 112P, and a positive branch liquid inlet pressure sensor 113P on the positive side; include a negative branch liquid inlet switch valve 111N, a negative branch liquid inlet temperature sensor 112N, and a negative branch liquid inlet pressure sensor 113N on the negative side; the branch stack group outlet sensor and valve group 12 include a positive branch liquid outlet regulating valve 121P, a positive branch liquid outlet temperature sensor 122 on the positive side. P, positive branch liquid outlet pressure sensor 123P; on the negative side, it includes a negative branch liquid outlet regulating valve 121N, a negative branch liquid outlet temperature sensor 122N, and a negative branch liquid outlet pressure sensor 123N; the branch plate liquid inlet side sensor and valve group 13 includes a branch cooling temperature sensor 131; the branch plate liquid outlet side sensor and valve group 14 includes a branch cooling regulating valve 141, a branch return cooling temperature sensor 142, and a branch return cooling flowmeter 143; the figure shows the pipeline connection relationship between the battery stack group 01 in a single branch energy storage system and the plate heat exchanger 02 in the refrigeration system.

[0054] Reference Figure 6 , Figure 7 The liquid storage tank 04, liquid flow pump 06, electrolyte return side sensor and valve group 08, electrolyte level balance valve 19 can be divided into positive liquid storage tank 04P and negative liquid storage tank 04N according to their polarity, which respectively include positive liquid storage tank level sensor 041P and negative liquid storage tank level sensor 041N; positive liquid flow pump 06P and negative liquid flow pump 06N, positive electrolyte return side sensor and valve group 08P and negative electrolyte return side sensor and valve group 08N, positive electrolyte level balance valve 19P and negative electrolyte level balance valve 19N. The energy storage system is connected to the buffer thermal reaction system through the electrolyte short-circuit branch pipe.

[0055] Reference Figure 8 , Fig.10The stack group 01 can be divided into branch A stack group 01A, branch B stack group 01B... plate heat exchanger 02 according to the branch to which it belongs. The stack group 01 can be divided into branch A plate heat exchanger 02A, branch B plate heat exchanger 02B... The branch stack group inlet sensor and valve group 11 respectively include branch A positive branch liquid inlet switch valve 111AP, branch A positive branch liquid inlet temperature sensor 112AP, branch A positive branch liquid inlet pressure sensor 113AP, branch A negative branch liquid inlet switch valve 111AN, branch A negative branch liquid inlet temperature sensor 112AN, branch A negative branch due to the difference in polarity and the branch to which it belongs. The branch stack outlet sensor and valve group 12 respectively includes a branch A positive electrode liquid outlet regulating valve 121AP, a branch A positive electrode liquid outlet temperature sensor 122AP, a branch A positive electrode liquid outlet pressure sensor 123AP, a branch B positive electrode liquid outlet pressure sensor 124BP, a branch B negative electrode liquid outlet switching valve 111BN, a branch B negative electrode liquid outlet temperature sensor 112BN, and a branch B negative electrode liquid outlet pressure sensor 113BN due to the difference in polarity and the branch to which it belongs. A branch negative electrode liquid outlet regulating valve 121AN, branch A negative electrode liquid outlet temperature sensor 122AN, branch A negative electrode liquid outlet pressure sensor 123AN, branch B positive electrode liquid outlet regulating valve 121BP, branch B positive electrode liquid outlet temperature sensor 122BP, branch B positive electrode liquid outlet pressure sensor 123BP, branch B negative electrode liquid outlet regulating valve 121BN, branch B negative electrode liquid outlet temperature sensor 122BN, branch B negative electrode liquid outlet pressure sensor 123BN... The branch plate replacement liquid inlet side sensor and valve group 13 respectively include branch A cooling temperature sensor 131A, branch B cooling temperature sensor 131B due to the different branches to which they belong... The branch plate liquid side sensor and valve group 14 includes branch A cooling capacity regulating valve 141A, branch A return cooling temperature sensor 142A, branch A return cooling flow meter 143A, branch B cooling capacity regulating valve 141B, branch B return cooling temperature sensor 142B, branch B return cooling flow meter 143B... The inter-group series flow switch valve 16 can include branch A positive electrode inter-group series flow switch valve 16AP, branch A negative electrode inter-group series flow switch valve 16AN according to its polarity and the branch it belongs to... The figure shows the connection relationship between the branches, that is, the liquid outlet pipes of the battery stack group of each branch are connected in sequence through the branch electrolyte series flow pipe.

[0056] Reference Fig. 9The refrigerant liquid outlet side sensor and valve group 09 includes a refrigerated liquid outlet valve 091, a refrigerated liquid outlet temperature sensor 092, and a refrigerated liquid outlet pressure sensor 093; the refrigerant liquid return side sensor and valve group 10 includes a refrigerated liquid return valve 101, a refrigerated liquid return temperature sensor 102, a refrigerated liquid return pressure sensor 103, and a refrigerated liquid return flowmeter 104; the figure shows the connection relationship between the refrigeration system and the buffer thermal reaction system, that is, the cold supply dry pipe and the buffer water tank are directly connected through the buffer water tank inlet pipe, and the pipeline is controlled by the buffer water tank inlet valve 17; the cold return dry pipe and the buffer water tank are directly connected through the buffer water tank return pipe, and the pipeline is controlled by the buffer water tank return valve 18.

[0057] The principle of detecting and controlling the electrolyte temperature of the flow battery of the multi-stack group in the embodiment of the present application is:

[0058] During the normal charging and discharging process of the energy storage system, due to the change in charging and discharging power, the energy efficiency of the battery stack is also changing, and the heat generated is also changing dynamically. Figure 5-Figure 8 , the calorific value of the branch stack group can be calculated through the positive electrode inlet temperature sensor 112P (negative electrode inlet temperature sensor 112N), the positive electrode outlet temperature sensor 122P (negative electrode outlet temperature sensor 122N), and the positive electrode branch flowmeter 123P (negative electrode branch flowmeter 123N) of the stack group. Due to the characteristics of the ion conduction membrane in the stack, when a pressure difference appears on both sides of the positive and negative electrodes, the electrolyte will flow from one electrode to the other, which will cause hydrogen and oxygen evolution side reactions on the surface of the electrode material, which will not only bring operational risks, but also reduce the coulomb efficiency of the stack and increase heat. By adjusting the positive electrode stack outlet regulating valve 121P (negative electrode stack outlet regulating valve 121N), the positive and negative electrode flow rate acceleration / deceleration balance of the same stack group can be controlled, thereby reducing the generation of waste heat. The positive branch liquid inlet switch valve 111P (negative branch liquid inlet switch valve 111N) is interlocked with the contactor of the battery stack circuit to control whether the branch is enabled or not.

[0059] For one of the battery stack branches, the ratio of the opening of the positive branch outlet regulating valve 121P to the negative branch outlet regulating valve 121P is The pressure values ​​measured by the positive branch liquid inlet pressure sensor 113P and the negative branch liquid inlet pressure sensor 113N are and , the proportional coefficient in the adjustment process is , the integration time constant is , the differential time constant is ,pressure and The instantaneous error is When the valve opening is not less than the minimum setting opening, the battery management system 20 responds Control is performed as follows:

[0060] Formula (1);

[0061] At this time, by controlling the liquid outlet valve on the battery stack side, one of the positive and negative electrode liquid outlet valves is opened to the maximum, and the other is adjusted according to this ratio, the additional heat generated can be minimized as much as possible.

[0062] The temperature value measured by the positive branch inlet temperature sensor 112P is The temperature value measured by the negative electrode branch inlet temperature sensor 112N is The temperature value measured by the positive branch outlet temperature sensor 122P is The temperature value measured by the negative electrode branch outlet temperature sensor 122N is , the flow rate measured by branch flowmeter 123 is The temperature value measured by the branch cooling temperature sensor 131 is The temperature value measured by the branch return cooling temperature sensor 142 is , the flow rate measured by the branch return flow meter 143 is ; The density and specific heat capacity of the cathode electrolyte are , ; The density and specific heat capacity of the negative electrode electrolyte are , ; The density and specific heat capacity of the refrigerant are , The heat transfer capacity of the plate heat exchanger, that is, the minimum total cooling demand of a single branch for:

[0063] Formula (2);

[0064] Cooling capacity supply value of a single branch It can be expanded into the formula:

[0065] Formula (3);

[0066] in satisfy:

[0067] Formula (4);

[0068] From equations (2), (3) and (4), we can get the flow rate of each cooling branch: The control should satisfy the following formula:

[0069] Formula (5);

[0070] The opening degree of the branch cooling regulating valve 141 is , the proportional coefficient in the automatic adjustment process is , the integration time constant is , the differential time constant is , flow rate The instantaneous error is When the valve opening is not less than the minimum setting opening, the battery management system 20 responds Control is performed as follows:

[0071] Formula (6);

[0072] The heat transfer efficiency of the plate heat exchanger is The heat transfer efficiency of each branch is different. The value is related to the heat transfer amount, and the overall characteristic curve is basically positively correlated. According to equations (2) and (4), at the inlet and outlet temperatures of the positive and negative electrodes of a branch, and When closer, smaller, the branch corresponds to is also low. When it is less than or equal to 50%, open the inter-group series flow switch valve 16, connect the branch with a larger load in series flow with the branch to transfer the cooling demand of the branch to other branches, and at the same time close the positive branch liquid outlet regulating valve 121P (negative branch liquid outlet regulating valve 121N) and the branch cooling capacity regulating valve 141, disable the cooling side of the branch, and let other branches perform cooling control for the branch.

[0073] Since the heat production of each branch is different, the heat exchange of each branch is also different. By controlling the refrigerant delivery ratio of each branch through the cold capacity regulating valve 141 on the freezing pipe, the total load on the refrigeration side can be reduced, and the cold capacity delivery of all branches can be avoided in accordance with the requirements of the most unfavorable side due to excessive demand on one branch, which leads to an increase in the internal energy consumption of the energy storage system. At the same time, when the total branch flow measured by the return cold flow meter 143 of each branch is lower than 30% of the rated flow, the battery management system 20 will control the buffer water tank inlet valve 17 and the buffer water tank outlet valve 18 to open to maintain the basic chilled water circulation volume, and make a judgment after the evaporator compressor 031 and the freezing pump 07 are adjusted and run stably. When the load can maintain safe and stable operation, the buffer water tank inlet valve 17 and the buffer water tank outlet valve 18 can be closed again.

[0074] The opening value of the branch cooling regulating valve 141 is , this value is Positive correlation, it can be approximately considered that each branch meets the following proportional relationship:

[0075] Formula (7);

[0076] When the temperature inside a branch of a battery stack is too low, it is necessary to mix the charged solution introduced into the battery stack to release heat to quickly heat up in a short time. In order to avoid the temperature rising too fast and bring risks to the operation state of the battery stack, after opening the electrolyte short-circuit switch valve 15, the electrolyte will be mixed in the buffer water tank mixing tank 051 through the mixed solution coil immersed in the electrolyte heating buffer water tank 05. Afterwards, according to the different charging and discharging states, the battery management system 20 measures and compares the corresponding liquid tank level sensor 041 on the liquid storage tank 04, opens the electrolyte level balance valve 19 corresponding to the liquid storage tank with a lower liquid level, and forms an electrolyte liquid circuit loop and a battery stack circuit short-circuit loop, so as to achieve the purpose of slowing down the heating rate of the branch battery stack while the battery stack is heating up.

[0077] During the adjustment process, if the load of the refrigerator evaporator compressor 031 is less than or equal to 40% of the rated power, open the buffer water tank inlet valve 17 and the buffer water tank outlet valve 18 to maintain the load of the refrigerator evaporator compressor 031 by circulating the refrigerant inside the buffer water tank 05 through the electrolyte heating.

[0078] The battery management system calculates the heat generated during the charging and discharging process and calculates the current heat exchanger efficiency through the plate heat exchanger efficiency and heat exchange relationship curve provided by the manufacturer. Taking branch A as an example, the heat exchange efficiency of plate heat exchanger 02 in branch A is When less than or equal to 50%, Fig.10 In order to improve the heat exchange efficiency of the plate heat exchanger, the positive electrode group series flow switch valve 16AP (negative electrode group series flow switch valve 16AN) of branch A between the battery stack and the plate heat exchanger will be opened to mix the electrolyte of branch A into branch B, and disable the heat exchange on the cooling side of branch A, so that the plate heat exchanger 02 in use can exchange heat at a higher heat exchange efficiency as much as possible.

[0079] The temperature value measured by the refrigeration liquid outlet temperature sensor 092 is The temperature value measured by the refrigeration return liquid temperature sensor 102 is , the flow rate measured by the refrigeration return flow meter 104 is Combined with the previous formula (3), the total cooling capacity output on the cooling side is for:

[0080] Formula (8);

[0081] Formula (9);

[0082] Since the total amount of heat generated by each stack group 01 is determined, the temperature control of the refrigerator evaporator compressor 031 and the frequency control target of the refrigeration pump 07 can be determined accordingly. Controlling the outlet water temperature of the refrigerator evaporator 03 and making the refrigerator evaporator compressor 031 operate at a load rate of more than 50% can greatly reduce the energy consumption of the refrigerator evaporator compressor 031. At the same time, the frequency of the refrigeration pump 07 is used to control the refrigerant flow on the refrigeration side.

[0083] According to formula (8), when the total cooling demand decreases, the frequency of the refrigeration pump 07 can be reduced. , and correspondingly reduce the total refrigerant flow rate , thereby achieving the purpose of reducing refrigeration energy consumption. The proportional coefficient in the automatic adjustment process of adjusting the refrigeration pump 07 is , the integration time constant is , the differential time constant is , actual flow pressure and required flow rate The instantaneous error is When the load rate is not less than 50%, the battery management system 20 should Control is performed as follows:

[0084] Formula (10);

[0085] When the total cooling demand is still too large and the frequency of the refrigeration pump 07 has been reduced to a low value that affects the operation of the compressor 031, according to formula (8), it can be seen that the outlet water temperature of the compressor should be increased to improve , thereby reducing and At this time, the energy consumption of the host can be reduced and the output of cooling capacity can be reduced.

[0086] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A flow battery electrolyte temperature control device for a multi-stack group, characterized in that: The invention comprises an energy storage system, a refrigeration system, a buffer thermal reaction system, and a battery management system (20); the battery management system (20) controls the valve opening of the inlet sensor and valve group (11) of the energy storage system battery stack group, the outlet sensor and valve group (12) of the battery stack group, the electrolyte short-circuit switch valve (15), and the inter-group series flow switch valve (16); it also controls the refrigeration frequency of the refrigerator evaporator (03) and the freezing pump (07) of the refrigeration system; it also controls the valve opening of the plate exchange liquid inlet side sensor and valve group (13) of each branch of the refrigeration system, and the plate exchange liquid outlet side sensor and valve group (14) of each branch; it also controls the valve opening of the buffer water tank inlet valve (17) and the buffer water tank outlet valve (18) of the buffer thermal reaction system. The energy storage system further comprises a battery stack group (01) of each branch, a liquid storage tank (04), a liquid flow pump (06), an electrolyte return side sensor and a valve group (08), and an electrolyte level balance valve (19); the battery stack group (01) is connected to the liquid storage tank (04); the refrigeration system further comprises a plate heat exchanger (02) of each branch, a refrigerant liquid outlet side sensor and a valve group (09), and a refrigerant return side sensor and a valve group (10); the plate heat exchanger (02) is connected to the refrigerator evaporator (03); the buffer thermal reaction system further comprises a buffer water tank (05); the battery stack group (01) and the liquid storage tank (04) in the energy storage system are respectively connected to the plate heat exchanger (02) in the refrigeration system The liquid storage tank (04) in the energy storage system is connected to the buffer water tank (05) in the buffer thermal reaction system; the refrigerator evaporator (03) in the refrigeration system is connected to the buffer water tank (05) in the buffer thermal reaction system; the inlet sensor and valve group (11) of the battery stack group are arranged between the liquid storage tank (04) and the battery stack group (01); the outlet sensor and valve group (12) of the battery stack group are arranged between the battery stack group (01) and the plate heat exchanger (02); the electrolyte short-circuit switch valve (15) is arranged between the inlet sensor and valve group (11) of the battery stack group and the buffer water tank (05); an inter-group series flow switch valve (16) is arranged between the positive electrode electrolyte outlet pipes of different battery stack groups (01); An inter-group series flow switch valve (16) is provided between the negative electrode electrolyte outlet pipes of different battery stack groups (01); the electrolyte liquid level balance valve (19) is provided between the liquid storage tank (04) and the buffer water tank (05); the plate heat exchanger liquid inlet side sensor and valve group (13) are provided between the plate heat exchanger (02) and the refrigerator evaporator (03); the plate heat exchanger liquid outlet side sensor and valve group (14) are provided between the plate heat exchanger (02) and the refrigerator evaporator (03); the buffer water tank water inlet valve (17) is provided between the refrigerator evaporator (03) and the buffer water tank (05); and the buffer water tank water outlet valve (18) is provided between the refrigerator evaporator (03) and the buffer water tank (05).

2. A control method for the electrolyte temperature control device of a flow battery of a multi-stack group according to claim 1, characterized in that: The following steps are involved: Step S1: The battery management system uses the PID adjustment method to control the ratio of the opening of the regulating valves on the positive and negative electrode outlet branches, adjust the electrolyte flow, and maintain the electrolyte pressure balance on both sides of the diaphragm in the battery stack. The calculation formula for the ratio of the regulating valve opening is: ; Where: It is the ratio of the opening of the regulating valve on the positive and negative electrode liquid outlet branches; is the instantaneous error between the positive branch inlet pressure and the negative branch inlet pressure; It is the proportional coefficient in the PID regulation process; It is the integral time constant in the PID adjustment process; It is the differential time constant in the PID adjustment process; It is the PID adjustment time; Step S2: Collect the positive electrode electrolyte inlet temperature, the positive electrode electrolyte outlet temperature, the negative electrode electrolyte inlet temperature, and the negative electrode electrolyte outlet temperature, and calculate the total heat output of the branch stack group. The calculation formula is: ; Where: is the total heat produced by the branch stack group; is the positive electrode electrolyte inlet temperature; is the negative electrode electrolyte inlet temperature; is the outlet temperature of the positive electrode electrolyte; is the outlet temperature of the negative electrode electrolyte; is the positive electrode flow value; is the negative electrode flow value; is the cathode electrolyte density at 50% state of charge (SOC); is the negative electrode electrolyte density at 50% SOC; is the specific heat capacity of the cathode electrolyte at 50% SOC; is the specific heat capacity of the negative electrode electrolyte at 50% SOC; Step S3: Calculate the cooling capacity required by the branch stack group as: ； Where: is the cooling capacity required by the branch stack group, is the heat transfer efficiency of the heat exchanger; Step S4: Calculate the refrigerant flow rate of the branch through the heat exchanger according to the cooling capacity required by the branch stack group. The calculation formula is: ； Where: is the refrigerant flow rate of the branch passing through the heat exchanger; The branch cooling temperature; is the branch return cooling temperature; is the heat transfer efficiency of the branch heat exchanger; is the density of the refrigerant; is the specific heat capacity of the refrigerant; Step S5: Calculate the opening of the branch cooling regulating valve according to the refrigerant flow rate of the branch passing through the heat exchanger. The calculation formula is: ； Where: is the opening degree of the branch cooling regulating valve; Branch flow The instant error of To adjust the proportional coefficient of the branch cooling regulating valve; To adjust the integral time constant of the branch cooling regulating valve; To adjust the differential time constant of the branch cooling regulating valve; To adjust the time; Step S6: Accumulate the refrigerant flow of each branch, calculate the total refrigerant flow that should be supplied during the refrigeration process of the multi-stack liquid flow battery system, and determine the frequency of the refrigeration pump. The calculation formula is: ; Where: is the frequency of the refrigeration pump; is the instant error of the total required refrigerant flow rate; To adjust the proportional coefficient of the refrigeration pump frequency; The integral time constant for adjusting the frequency of the refrigeration pump; The differential time constant for adjusting the frequency of the refrigeration pump; To adjust the time; Adjust the opening of the branch cooling control valve and the frequency of the refrigeration pump to achieve electrolyte temperature control of the multi-stack flow battery.

3. The control method according to claim 2, characterized in that: When the branch liquid inlet temperature in step S2 is lower than 10° C., the positive and negative electrolytes of the branch are placed in a buffer water tank mixing tank for mixing.

4. The control method according to claim 2, characterized in that: The heat exchange efficiency of the heat exchanger in step S3 is equal to the total heat output of the branch stack group. There is a positive correlation. When the heat exchange efficiency of the heat exchanger is greater than 50%, the pipelines of each branch fuel cell group are not interconnected. When the heat exchange efficiency of the heat exchanger is less than or equal to 50%, the pipelines of adjacent branch fuel cell groups are interconnected, and the battery management system will close the pipeline switch between the branch fuel cell group and the heat exchanger.

5. The control method according to claim 2, characterized in that: When the refrigerant flow rate in step S6 is lower than 30% of the rated flow rate, the refrigerant flow rate reaches 30% by activating the refrigerant circulation between the refrigeration system and the buffer thermal reaction system and increasing the frequency of the refrigeration pump.

Images