Compressor rotating speed control method, heat management system and energy storage system applying same

Abstract

The invention discloses a compressor rotating speed control method, a heat management system and an energy storage system applying the heat management system, and relates to the technical field of heat management systems and control methods thereof. The method comprises the steps that multiple sets of battery cluster operation condition data and corresponding battery cluster calorific value data are collected in advance, and a calorific value reference model is established; and the battery cluster operation condition real-time data serve as input data and are input into the calorific value reference model to obtain battery cluster calorific value reference data output by the calorific value reference model, and the battery cluster calorific value reference data serve as the refrigerating capacity of the compressor to control the initial rotating speed of the compressor. The invention mainly solves the problem of how to provide a reasonable, stable, reliable, energy-saving and efficient control method for the thermal management system. The reasonable, stable, reliable, energy-saving and efficient control method is provided for the compressor of the heat management system, and the undesirable phenomena that overshoot happens to the heat management system or the heat management system cannot reach the steady state all the time and the like are effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal management systems and control methods thereof, and in particular to a compressor speed control method, a thermal management system and an energy storage system using the same. Background Art

[0002] An energy storage system is a system used to store and release electrical energy. It involves the conversion between electrical energy and chemical energy, as well as the conversion between electrical energy and electrical energy. In the above process, a lot of heat will be generated. If the heat cannot be discharged in time, the temperature of the energy storage system will rise, bringing safety hazards, and thus affecting the performance, life and normal operation of the energy storage system.

[0003] In order to control the temperature of the energy storage system and improve the charging and discharging efficiency of the energy storage system, it is necessary to configure a thermal management system in the energy storage system. For example, the Chinese invention patent publication number CN117458048A, entitled "Refrigeration capacity control method of liquid cooling unit, liquid cooling unit and energy storage system", discloses a typical thermal management system structure.

[0004] The thermal management system in the prior art still has at least the following technical problems:

[0005] Thermal management systems usually rely on automatic control systems for closed-loop control. The automatic control system uses the actual temperature of the thermal management object (e.g., the battery cluster of the energy storage system) as input, and calculates the temperature difference e(t) between the actual temperature of the thermal management object and the target temperature, and then performs closed-loop control on controllable working devices such as the compressor, expansion valve, and water pump in the thermal management system, so as to control the temperature difference e(t) between the actual temperature of the thermal management object and the target temperature within a certain range as much as possible, or even make the temperature difference e(t) roughly disappear; however, the above control method only considers the actual temperature of the thermal management object, but lacks consideration for the heat generation of the thermal management object, which can easily cause the automatic control system to overshoot, or always fail to reach a steady state and other undesirable phenomena.

[0006] In summary, how to provide a reasonable, stable, reliable, energy-saving and efficient control method for the thermal management system has become an urgent problem to be solved. Summary of the invention

[0007] The object of the present invention is to provide a compressor speed control method, a thermal management system and an energy storage system using the same, which can provide a reasonable, stable, reliable, energy-saving and efficient control method for the compressor of the thermal management system.

[0008] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a compressor speed control method is applied in a thermal management system, the thermal management system is used to perform thermal management for a battery cluster of an energy storage system; the thermal management system includes a compressor, a condenser with a fan, an expansion valve, and an evaporative heat exchanger suitable for heat exchange with the battery cluster; the refrigerant channels of the compressor, the condenser, the expansion valve and the evaporative heat exchanger are connected in sequence, so that the refrigerant can circulate among the refrigerant channels of the compressor, the condenser, the expansion valve and the evaporative heat exchanger;

[0009] The method includes:

[0010] S1. Collecting several groups of battery cluster operating condition data and corresponding battery cluster heat generation data in advance;

[0011] S2, using the battery cluster operating condition data as an independent variable and the battery cluster heat data as a dependent variable to establish a heat generation reference model;

[0012] S3. When the energy storage system and the thermal management system are put into operation, real-time data on the operating conditions of the battery cluster is collected;

[0013] S4, inputting the real-time data of the battery cluster operating condition as input data into the calorific value reference model to obtain the calorific value reference data of the battery cluster output by the calorific value reference model;

[0014] S5, using the heating value reference data of the battery cluster as the cooling capacity of the compressor to control the initial rotation speed of the compressor;

[0015] S6. After the energy storage system and the thermal management system are put into operation and reach predetermined conditions, the system temperature difference e(t) is used as the input of the automatic control system to perform closed-loop control on the speed of the compressor;

[0016] The system temperature difference e(t) is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster.

[0017] In the above technical solution, the battery cluster operating condition data and the battery cluster operating condition real-time data both include the battery cluster capacity and the battery cluster charge and discharge rate.

[0018] In the above technical solution, the calorific value reference model is specifically a regression model which takes the battery cluster capacity and the battery cluster charge and discharge rate as independent variables and takes the battery cluster calorific value data as the dependent variable.

[0019] In the above technical solution, step S5 specifically includes:

[0020] S5.1. Using the heat generation reference data of the battery cluster as the cooling capacity Q of the compressor, calculate the refrigerant mass flow rate required by the compressor according to the cooling capacity calculation formula Q=cmΔt.

[0021] Wherein, Q is the cooling capacity of the compressor, c is the specific heat capacity of the refrigerant used in the thermal management system, and Δt is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster;

[0022] S5.2, according to the mass flow-volume flow conversion formula q m =ρq v , calculate the refrigerant volume flow required by the compressor

[0023] Among them, q m is the refrigerant mass flow rate n calculated in step S5.1, and ρ is the density of the refrigerant used in the thermal management system;

[0024] S5.3, according to the compressor speed calculation formula (refrigerant volume flow q v = compressor displacement * compressor speed), calculated

[0025] S5.4. Using the compressor speed calculated in step S5.3 as the initial speed of the compressor, control the operation of the compressor.

[0026] In the above technical solution, in step S6, the automatic control system specifically includes a PID controller;

[0027] The input-output function relationship of the PID controller is:

[0028] u(t)=K p *e(t)+K i *∫(e(τ)dτ)+K d *(de(t) / dt)

[0029] Wherein, u(t) is the speed value at which the compressor needs to increase or decrease the frequency, e(t) is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster, K p is the proportionality coefficient, K i is the integration coefficient, K d is the differential coefficient.

[0030] In the above technical solution, in step S6, the actual temperature of the battery cluster is sampled at a preset time interval to calculate the system temperature difference e(t), and the speed of the compressor is closed-loop controlled.

[0031] In the above technical solution, the evaporative heat exchanger of the thermal management system performs direct contact heat exchange with the battery cluster.

[0032] In the above technical solution, the thermal management system also includes a water pump and a liquid-cooled heat exchanger capable of exchanging heat with the battery cluster; the water pump, the evaporative heat exchanger and the liquid-cooled medium channels of the liquid-cooled heat exchanger are connected in sequence, so that the liquid-cooled medium can circulate among the water pump, the evaporative heat exchanger and the liquid-cooled medium channels of the liquid-cooled heat exchanger.

[0033] A thermal management system applies the above compressor speed control method.

[0034] An energy storage system comprises the above-mentioned thermal management system.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows: the compressor speed control method, thermal management system and energy storage system using the same of the present invention, by collecting several groups of battery cluster operating condition data and corresponding battery cluster heating data, establish a heating value reference model. In the initial stage of operation of the thermal management system, the battery cluster heating value reference data is used as the cooling capacity of the compressor to control the initial speed of the compressor, thereby providing a reasonable, stable, reliable, energy-saving and efficient control method for the compressor of the thermal management system, effectively avoiding undesirable phenomena such as overshoot of the thermal management system or the inability to reach a steady state. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is one of the structural views of the thermal management system of the present invention.

[0037] Figure 2 This is the second structural view of the thermal management system of the present invention.

[0038] The reference numerals in the drawings are: 1. compressor; 2. condenser; 3. fan; 4. expansion valve; 5. evaporative heat exchanger; 6. heater; 7. battery cluster; 8. water pump; 9. liquid-cooled heat exchanger. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0040] The present embodiment provides a compressor speed control method, which is applied in a thermal management system to control the speed of the compressor in the thermal management system, so that the operation of the thermal management system is more stable, reliable, energy-saving and efficient.

[0041] The thermal management system includes a compressor 1 , a condenser 2 with a fan 3 , an expansion valve 4 , and an evaporative heat exchanger 5 suitable for exchanging heat with a battery cluster 7 .

[0042] Among them, the compressor 1 is a compressor used to compress refrigerant in the refrigeration system, specifically a variable frequency compressor; the condenser 2 is a condenser used for condensing refrigerant in the refrigeration system, which dissipates heat through its own fan 3; the expansion valve 4 is an expansion valve used to throttle refrigerant in the refrigeration system, specifically an electronic expansion valve.

[0043] The refrigerant channels of the compressor 1, condenser 2, expansion valve 4 and evaporative heat exchanger 5 are connected in sequence, so that the refrigerant can circulate among the refrigerant channels of the compressor 1, condenser 2, expansion valve 4 and evaporative heat exchanger 5. With this arrangement, the refrigeration function of the thermal management system can be realized.

[0044] It is understandable that the thermal management system or its upper system at least includes a control device, such as a programmable controller, an embedded system and an industrial computer.

[0045] It should be noted that the evaporative heat exchanger 5 is an evaporator in the refrigeration system for evaporating the refrigerant and absorbing heat, and has a heat exchange function.

[0046] See also Figure 1 In some possible embodiments, the evaporative heat exchanger 5 of the thermal management system performs direct contact heat exchange with the battery cluster 7, that is, the evaporative heat exchanger 5 is directly attached to the battery cluster 7, or the evaporative heat exchanger 5 is buried in the battery cluster 7, so that the evaporative heat exchanger 5 and the battery cluster 7 can directly exchange heat.

[0047] See also Figure 2 In some other possible embodiments, the thermal management system further includes a water pump 8 and a liquid-cooled heat exchanger 9 capable of exchanging heat with the battery cluster 7; the liquid-cooled medium channels of the water pump 8, the evaporative heat exchanger 5 and the liquid-cooled heat exchanger 9 are sequentially connected, so that the liquid-cooled medium can circulate among the water pump 8, the evaporative heat exchanger 5 and the liquid-cooled medium channels of the liquid-cooled heat exchanger 9, thereby achieving heat exchange between the evaporative heat exchanger 5 and the battery cluster 7; in addition, the thermal management system can also selectively be configured with a heater 6 (connected between the evaporative heat exchanger and the liquid-cooled heat exchanger) for heating the liquid-cooled medium to keep the battery cluster 7 warm.

[0048] The compressor speed control method of this embodiment includes:

[0049] S1. Collecting several groups of battery cluster operating condition data and corresponding battery cluster heat generation data in advance;

[0050] S2. Using the battery cluster operating condition data as the independent variable and the battery cluster heat data as the dependent variable, a heat generation reference model is established;

[0051] S3. When the energy storage system and thermal management system are put into operation, real-time data on the operating conditions of the battery cluster is collected;

[0052] S4, inputting the real-time data of the battery cluster operating conditions as input data into the calorific value reference model to obtain the calorific value reference data of the battery cluster output by the calorific value reference model;

[0053] S5, using the heat generation reference data of the battery cluster as the cooling capacity of the compressor to control the initial speed of the compressor;

[0054] S6. After the energy storage system and the thermal management system are put into operation and reach the predetermined conditions, the system temperature difference e(t) is used as the input of the automatic control system to perform closed-loop control on the speed of the compressor;

[0055] The system temperature difference e(t) is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster.

[0056] It is understandable that the actual temperature of the battery cluster may be directly acquired through a sensor disposed at the battery cluster, or may be fed back from a management chip / management device of the battery cluster.

[0057] Specifically, the battery cluster operating condition data and the battery cluster operating condition real-time data both include the battery cluster capacity (in Ah) and the battery cluster charge and discharge rate (in C). The battery cluster capacity is one of the rated data of the battery cluster and is provided by the manufacturer when the battery cluster leaves the factory. The battery cluster charge and discharge rate is specifically calculated as follows: The charging and discharging current (in A) of the battery cluster may be fed back from the management chip / management device of the battery cluster.

[0058] Specifically, the calorific value reference model is a regression model that takes the battery cluster capacity and the battery cluster charge and discharge rate as independent variables and takes the battery cluster calorific value data as the dependent variable.

[0059] In fact, by using computer mathematical software, inputting several groups of battery cluster capacities (as independent variables), battery cluster charge and discharge rates (as independent variables) and battery cluster calorific value data (as dependent variables), and performing linear or nonlinear fitting, a calorific value reference model can be obtained.

[0060] Specifically, step S5 includes:

[0061] S5.1. Take the heat generation reference data of the battery cluster as the cooling capacity Q of the compressor, and calculate the refrigerant mass flow rate required by the compressor according to the cooling capacity calculation formula Q = cmΔt. (Unit: g / s);

[0062] Wherein, Q is the cooling capacity of the compressor (in W, i.e. J / s), c is the specific heat capacity of the refrigerant used in the thermal management system (in J / (g·℃), Δt is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster (in ℃);

[0063] S5.2, according to the mass flow-volume flow conversion formula q m =ρq v , calculate the refrigerant volume flow required by the compressor (Unit: m 3 / h);

[0064] Among them, q m is the refrigerant mass flow m calculated in step S5.1, and ρ is the density of the refrigerant used in the thermal management system (in g / cm 3 );

[0065] S5.3, according to the compressor speed calculation formula (refrigerant volume flow q v = compressor displacement * compressor speed), calculated

[0066] The unit of compressor displacement is cc / rev and the unit of compressor speed is rpm.

[0067] S5.4. Using the compressor speed calculated in step S5.3 as the initial speed of the compressor, the operation of the compressor is controlled.

[0068] It is understandable that the parameters in the above calculations can be converted into units according to actual conditions, but the calculation methods are the same.

[0069] Specifically, in step S6, after the energy storage system and the thermal management system are put into operation and reach the predetermined conditions, the system temperature difference e(t) is used as the input of the automatic control system to perform closed-loop control on the speed of the compressor, wherein the "predetermined conditions" mentioned above can specifically be a predetermined time, such as 0.5 min, 1 min, 2 min or 10 min.

[0070] Specifically, in step S6, the automatic control system specifically includes a PID controller;

[0071] The input-output function relationship of the PID controller is:

[0072] u(t)=K p *e(t)+K i *∫(e(τ)dτ)+K d *(de(t) / dt)

[0073] Where u(t) is the speed value that the compressor needs to increase or decrease, e(t) is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster, K p is the proportionality coefficient, K i is the integration coefficient, K d is the differential coefficient.

[0074] It can be understood that the difference e(t) between the actual temperature of the battery cluster and the target temperature of the battery cluster is the data in the mathematical domain of the PID controller, which needs to be converted from the temperature difference data of the physical quantity; the speed value E(t) that the compressor needs to increase or decrease in frequency is also the data in the mathematical domain of the PID controller, which needs to be converted into a physical quantity before it can be used for closed-loop control of the speed of the compressor; the proportional coefficient K p , integral coefficient K i and the differential coefficient K d All of them can be calibrated manually based on engineering experience.

[0075] Furthermore, in step S6, the actual temperature of the battery cluster is sampled at a preset time interval (for example, once every 5 seconds) to calculate the system temperature difference e(t), and the speed of the compressor is closed-loop controlled.

[0076] The following will use a specific case to further illustrate the technical solution of the present invention:

[0077] An energy storage system is established at a certain location according to needs. The battery cluster of the energy storage system adopts the thermal management system of this embodiment for thermal management.

[0078] The refrigerant model of the thermal management system is R410A, whose specific heat capacity c and density ρ are both known; the displacement of the compressor of the thermal management system is 14.9cc / rev.

[0079] First, use the debugging process of the energy storage system to collect several groups of battery cluster operating condition data and corresponding battery cluster heating data, or collect several groups of battery cluster operating condition data and corresponding battery cluster heating data from energy storage systems with the same / similar parameters and operating environment, implement steps S1 and S2, and establish a heating value reference model.

[0080] As a typical case of normal operation of the energy storage system, one set of data shows that when the battery cluster capacity is 280Ah and the battery cluster charge and discharge rate is 0.5C, the battery cluster heat generation data is 5000W.

[0081] When the energy storage system is put into operation, its battery cluster capacity is 280Ah, and its battery cluster charge and discharge rate is 0.5C. The battery cluster capacity of 280Ah and the battery cluster charge and discharge rate of 0.5C are input into the calorific value reference model, and the calorific value reference data of the battery cluster output by the calorific value reference model is 5000W.

[0082] Take the reference data of the battery cluster heat (5000W) as the cooling capacity Q of the compressor, implement step S5.1, calculate the mass flow rate of the refrigerant required by the compressor m = 32g / s, and then implement step S5.2 to calculate the volume flow rate of the refrigerant required by the compressor q v =2.9m 3 / h, and then implement step S5.3 to calculate the compressor speed = 3240 rpm; at this point, 3240 rpm can be used as the initial speed of the compressor to control the operation of the compressor.

[0083] After the energy storage system and thermal management system are put into operation and reach the predetermined conditions (specifically 1 minute), the system temperature difference e(t) is used as the input of the automatic control system to perform closed-loop control on the compressor speed.

[0084] This embodiment also provides a thermal management system, which applies the above-mentioned compressor speed control method.

[0085] This embodiment also provides an energy storage system, which includes the above-mentioned thermal management system.

[0086] The compressor speed control method, thermal management system and energy storage system using the same of the present embodiment establish a heat generation reference model by collecting several groups of battery cluster operating condition data and corresponding battery cluster heat generation data. In the initial stage of operation of the thermal management system, the battery cluster heat generation reference data is used as the cooling capacity of the compressor to control the initial speed of the compressor, thereby providing a reasonable, stable, reliable, energy-saving and efficient control method for the compressor of the thermal management system, and effectively avoiding undesirable phenomena such as overshoot of the thermal management system or the inability to reach a steady state.

[0087] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A compressor speed control method is applied in a thermal management system, wherein the thermal management system is used to perform thermal management for a battery cluster of an energy storage system; The thermal management system includes a compressor, a condenser with a fan, an expansion valve, and an evaporative heat exchanger suitable for heat exchange with the battery cluster; The refrigerant channels of the compressor, the condenser, the expansion valve and the evaporative heat exchanger are connected in sequence, so that the refrigerant can circulate among the refrigerant channels of the compressor, the condenser, the expansion valve and the evaporative heat exchanger; It is characterized in that The method includes: S1. Collecting several groups of battery cluster operating condition data and corresponding battery cluster heat generation data in advance; S2, using the battery cluster operating condition data as an independent variable and the battery cluster heat data as a dependent variable to establish a heat generation reference model; S3. When the energy storage system and the thermal management system are put into operation, real-time data on the operating conditions of the battery cluster is collected; S4, inputting the real-time data of the battery cluster operating condition as input data into the calorific value reference model to obtain the calorific value reference data of the battery cluster output by the calorific value reference model; S5, using the heating value reference data of the battery cluster as the cooling capacity of the compressor to control the initial rotation speed of the compressor; S6. After the energy storage system and the thermal management system are put into operation and reach predetermined conditions, the system temperature difference e(t) is used as the input of the automatic control system to perform closed-loop control on the speed of the compressor; The system temperature difference e(t) is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster.

2. The compressor speed control method according to claim 1, characterized in that: The battery cluster operating condition data and the battery cluster operating condition real-time data both include the battery cluster capacity and the battery cluster charge and discharge rate.

3. The compressor speed control method according to claim 2, characterized in that: The calorific value reference model is specifically a regression model that takes the battery cluster capacity and the battery cluster charge and discharge rate as independent variables and takes the battery cluster calorific value data as a dependent variable.

4. The compressor speed control method according to claim 1, characterized in that: Step S5 specifically includes: S5.

1. Using the heat generation reference data of the battery cluster as the cooling capacity Q of the compressor, calculate the refrigerant mass flow rate required by the compressor according to the cooling capacity calculation formula Q=cmΔt. Wherein, Q is the cooling capacity of the compressor, c is the specific heat capacity of the refrigerant used in the thermal management system, and Δt is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster; S5.2, according to the mass flow-volume flow conversion formula q m =ρq v , calculate the refrigerant volume flow required by the compressor Among them, q m is the refrigerant mass flow m calculated in step S5.1, and ρ is the density of the refrigerant used in the thermal management system; S5.3, according to the compressor speed calculation formula (refrigerant volume flow q v = compressor displacement * compressor speed), S5.

4. Using the compressor speed calculated in step S5.3 as the initial speed of the compressor, control the operation of the compressor.

5. The compressor speed control method according to claim 1, characterized in that: In step S6, the automatic control system specifically includes a PID controller; The input-output function relationship of the PID controller is: u(t)=K p *e(t)+K i *∫(e(τ)dτ)+K d *(de(t) / dt) Wherein, u(t) is the speed value at which the compressor needs to increase or decrease the frequency, e(t) is the difference between the actual temperature of the battery cluster and the target temperature of the battery cluster, K p is the proportionality coefficient, K i is the integration coefficient, K d is the differential coefficient.

6. The compressor speed control method according to claim 1 or 5, characterized in that: In step S6, the actual temperature of the battery cluster is sampled at a preset time interval to calculate the system temperature difference e(t), and the speed of the compressor is closed-loop controlled.

7. The compressor speed control method according to claim 1, characterized in that: The evaporative heat exchanger of the thermal management system performs direct contact heat exchange with the battery cluster.

8. The compressor speed control method according to claim 1, characterized in that: The thermal management system further includes a water pump and a liquid-cooled heat exchanger capable of exchanging heat with the battery cluster; The water pump, the evaporative heat exchanger and the liquid-cooling medium channels of the liquid-cooling heat exchanger are sequentially connected, so that the liquid-cooling medium can circulate among the water pump, the evaporative heat exchanger and the liquid-cooling medium channels of the liquid-cooling heat exchanger.

9. A thermal management system, characterized in that: The compressor speed control method described in any one of claims 1-8 is applied.

10. An energy storage system, characterized in that: Includes the thermal management system as claimed in claim 9.

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