Method for regulating compressor in refrigerant circuit

Abstract

The invention relates to a method for regulating a compressor in a refrigerant circuit. The method comprises the following steps: S1, determining a thermal target state; s2, determining a target heat flow dQSoll or a variable proportional to the target heat flow at least partially according to the heat target state; s3, the actual heat flow dQIst or a variable proportional to the actual heat flow is determined, and the heat flow deviation Q between the actual heat flow dQIst and the target heat flow dQSoll or between the variable proportional to the actual heat flow dQIst and the variable proportional to the target heat flow dQSoll is determined; s4, regulating the compressor by means of a cascade regulation, an inner regulating circuit (R1) of the cascade regulation at least partially regulating the power, in particular the rotational speed, of the compressor as a function of the heat flow deviation Q determined in step S3, and an outer regulating circuit (R2) at least partially regulating the target heat flow dQSoll as a function of the heat target state determined in step S1.

Description

Technical Field

[0001] The invention relates to a method for regulating a compressor in a refrigerant circuit, a control device for a compressor, a refrigerant circuit, a computer program for carrying out the method and a computer-readable data carrier. In particular, the refrigerant circuit can be a refrigerant circuit in a vehicle which is electrically driven by a battery and is provided for temperature control of components, such as a battery. Background Art

[0002] Optimal design of the refrigerant circuit of battery-electric vehicles (BEV for short) is essential for thermal management within the vehicle, since the temperature control of components such as the vehicle battery is energy-intensive and in many applications has to be carried out simultaneously with other tasks such as cooling or heating the passenger compartment.

[0003] In this regard, the regulation of the compressor of the refrigerant circuit plays a central role.

[0004] In the prior art, the speed of the compressor is regulated as a function of the refrigerant pressure upstream of the compressor. The target value is derived from the requirements of the refrigerant circuit, for example from the required operating temperature of the vehicle battery and its deviation from the current actual temperature, or from the required air temperature of the air in the passenger compartment.

[0005] Furthermore, the target value is determined by the technical limit values ​​of the refrigerant pressure upstream of the compressor, in particular in order to maintain temperature limits for the air conditioning system of the vehicle.

[0006] The disadvantage of this approach is that the target value for the refrigerant pressure upstream of the compressor is more complicated to form, since the relationship between the refrigerant pressure and the target variable determined for the heat flow is not linear. This has an effect in particular when cooling a vehicle battery, since the target variable here is clearly the heat flow due to indirect cooling via the cooling circuit.

[0007] The object of the present invention is to provide an alternative or improved method for controlling a compressor in a refrigerant circuit, as well as a control device for a compressor, a refrigerant circuit, a computer program for carrying out the method and a computer-readable data carrier. Summary of the invention

[0008] The object of the invention is achieved by means of a method according to claim 1, by a control device for a compressor according to claim 10, by a refrigerant circuit according to claim 11, by a computer program according to claim 12 and by a computer-readable data carrier according to claim 13. Advantageous developments, additional features and / or advantages of the invention are apparent from the dependent claims and the following description.

[0009] According to a first aspect, the present disclosure discloses a method for regulating a compressor in a refrigerant circuit, the method comprising the following steps:

[0010] S1. Determine the thermal target state;

[0011] S2. Determine a target heat flow dQ based at least in part on the thermal target state Soll or a variable proportional to the target heat flow;

[0012] S3. Determine the actual heat flow dQ Ist or a variable proportional to the actual heat flow and determines the actual heat flow dQ Ist and target heat flux dQ Soll between or with the actual heat flow dQ Ist A variable proportional to the target heat flow dQ Soll Heat flow deviation DQ between proportional variables;

[0013] S4. The compressor is regulated using cascade regulation, wherein the internal control loop of the cascade regulation is at least partially based on the heat flow deviation Δ determined in step S3. Q The power of the compressor, in particular the speed, is adjusted, and the outer control loop adjusts the target heat flow dQ at least partially according to the thermal target state determined in step S1 Soll .

[0014] Within the scope of the present invention, the Arabic numerals in the symbols of the method steps "S1" to "S4" are used only to identify the individual steps and are not intended to define the order of the method steps. In particular, some or more of the steps S1 to S4 can also be performed in parallel or repeatedly in a cycle.

[0015] Refrigeration circuit regulation can thus be separated from temperature regulation of heat sources or sinks, such as batteries or air to the passenger compartment.The above-mentioned nonlinearity in the relationship between heat flow and refrigerant pressure need not be taken into account.

[0016] According to another aspect, the present disclosure discloses a control device for a compressor in a refrigerant circuit, the refrigerant circuit comprising at least: a circulating refrigerant; an electronic expansion valve (EEV); a first heat exchanger, through which the refrigerant circuit is preferably thermally coupled to a coolant circuit; a device for measuring temperature- and pressure variables in the refrigerant circuit and preferably in the coolant circuit; wherein the control device is configured to perform the method described above.

[0017] According to another aspect, the present disclosure discloses a refrigerant circuit, comprising: a circulating refrigerant; at least one compressor; an electronic expansion valve (EEV); a first heat exchanger, through which the refrigerant circuit is preferably thermally coupled to a coolant circuit; a device for measuring temperature- and pressure variables in the refrigerant circuit and preferably in the coolant circuit; and a control device for regulating the compressor, wherein the control device is configured to perform the method described above.

[0018] According to another aspect, the disclosure discloses a computer program for executing the method described above when the computer program is executed by a control device of a compressor in a refrigerant circuit or is stored on a computer-readable data carrier.

[0019] According to another aspect, the present disclosure discloses a computer-readable data carrier on which the computer program described above is stored.

[0020] In the method, the actual temperature value T can be determined at least in part by Ist and temperature target value T Soll The deviation between T The thermal target state in step S1 can be determined, and the thermal target state can be determined in step S2 at least partially based on the deviation Δ T To determine the target heat flow dQ Soll Or a variable that is proportional to the target heat flow.

[0021] In the method, the temperature actual variable T in step S1 can be determined at least partially with the aid of the temperature of a heat source or a heat sink, in particular a vehicle battery. Ist The temperature target value T can be determined at least in part by means of the target temperature of the heat source or heat sink. Soll .

[0022] Cascade regulation can include targeting a target heat flow dQ Soll Or pre-control of a variable proportional to the target heat flow.

[0023] The pre-controlled target heat flow dQ may be obtained at least in part based on a power loss model of the heat source. Sollor pre-controlled with target heat flow dQ Soll Proportional variables.

[0024] Model-based precontrol of the heat flow allows for a more robust and faster regulator parameterization of the compressor control, since the different temporal behavior of both subsystems—temperature control of the battery or the air to the passenger compartment and refrigeration circuit control—can be taken into account.

[0025] Since less superheat is required, i.e. the temperature of the refrigerant rises less than its evaporation temperature, more robust control leads to higher cooling capacity with the same components. Faster control allows the target variable to be reached more quickly and thus, for example, shorter preparation times up to the maximum battery charging rate, which presupposes a certain cooling capacity.

[0026] The pre-controlled target heat flow dQ may be obtained at least in part based on a predetermined temperature gradient at the heat source or heat sink. Soll or pre-controlled with target heat flow dQ Soll Proportional variables.

[0027] The inner control loop can be controlled with a smaller time constant than the outer control loop, so that the inner control loop achieves a faster control than the outer control loop.

[0028] The actual heat flow dQ in step S3 can be determined at least in part by temperature and pressure measurements in the refrigerant circuit. Ist Or the actual heat flow dQ Ist Proportional variables.

[0029] The heat source or heat sink may be cooled or heated by a coolant circuit which is thermally coupled to the refrigerant circuit via a first heat exchanger.

[0030] The actual heat flow dQ can be determined in step S3 at least partly by temperature measurement and pressure measurement at the outlet of the first heat exchanger in the coolant circuit. Ist Or the actual heat flow dQ Ist Proportional variables. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention will be further explained below with the aid of embodiments with reference to the attached schematic and not correctly scaled figures. In the present invention, a feature can be designed to be positive (i.e., present) or negative (i.e., not present). In this specification, a negative feature is not explicitly interpreted as a feature when its absence is not emphasized according to the invention. That is, the invention actually made rather than the invention constructed by the prior art is that the feature is to be omitted. The absence of a feature (negative feature) in one embodiment indicates that the feature is optional. In the merely exemplary drawings (Fig.):

[0032] Figure 1 Schematically shows a refrigerant circuit according to an embodiment of the present invention;

[0033] Figure 2 The structure and working principle of the compressor adjustment according to one embodiment of the present invention are schematically shown. DETAILED DESCRIPTION

[0034] With the help of Figure 1 , the structure and working principle of the refrigerant circuit 10 according to the present invention for a vehicle will be schematically explained below. Figure 1 In the embodiment shown, the refrigerant circuit 10 can be operated both in a heating mode, in which the passenger compartment of the vehicle and / or the vehicle battery are heated, and in a cooling mode, in which the vehicle battery is cooled, for example. The present application in this respect therefore generally relates to the temperature management of a heat source or heat sink 500.

[0035] In the following, the cooling of the vehicle battery 500 is mainly described by way of example, with the heat source or heat sink 500 being taken as a representative. In the illustrated embodiment, the refrigerant circuit 10 and the coolant circuit 20 operate as heat pumps.

[0036] The coolant circuit 20 for conducting the coolant is thermally coupled to the vehicle battery 500 of the vehicle. Reference numeral 205 denotes a line system in which the coolant is conveyed between the individual components of the cooling circuit 20 by means of a coolant pump 6. As a further component, the coolant circuit 20 comprises an electric heating element 212 (positive self-regulating heater, PTC).

[0037] The refrigerant circuit 10 guides the refrigerant and has a compressor 200 and a refrigerant delivery pump (not shown). Reference symbol 105 denotes a corresponding pipe system of the refrigerant circuit 10, in which the refrigerant is delivered. In particular, the refrigerant includes propane (R290) and / or carbon dioxide (R744).

[0038] The first heat exchanger 300 (a battery cooler in the embodiment shown) is thermally coupled not only to the refrigerant circuit 10 but also to the coolant circuit 20. Heat can be transferred between the refrigerant circuit 10 and the coolant circuit 20 as required by the first heat exchanger 300, wherein the first heat exchanger 300 is connected to the refrigerant circuit 10 via a pair of electronically adjustable expansion valves (EEV) 8 and 9.

[0039] The electronic control mechanism (not shown) communicates with the coolant delivery pump, the refrigerant delivery pump, the valve of the coolant circuit 20 and the refrigerant circuit 10 through control technology. Figure 1 The valve connections are shown in FIG.

[0040] Waste heat from the vehicle environment or also from the vehicle's electrical drive train can be used as a heat source for the heat pump. In order to utilize heat from the vehicle environment, the refrigerant circuit 10 has an ambient heat exchanger 600 in the refrigerant circuit 10 .

[0041] exist Figure 2 Further components of the refrigerant circuit 10 of the embodiment shown in the figure include: a battery 270, which serves as an intermediate energy storage device (Zwischentank) for the refrigerant; an electronically regulated expansion valve 220, which is used to expand the refrigerant behind the condenser 240 for heating the passenger compartment in heating mode; an evaporator 230 arranged in front of the first heat exchanger 300; and an electric PTC heating element for the air in the passenger compartment.

[0042] Not explicitly shown in the figure are means for measuring temperature and pressure variables in the refrigerant circuit 10 and in the coolant circuit 20 for monitoring and determining, for example, the refrigerant pressure and temperature and the coolant pressure and temperature.

[0043] The following uses Figure 2 A method for regulating compressor 200 will be described.

[0044] In step S1, preferably by determining the actual temperature value T Ist and temperature target value T Soll Deviation of T To determine the actual thermal state. Actual temperature T IstIt may be a specific enthalpy and in one embodiment of the invention is determined at least in part by means of the current temperature of the vehicle battery 500 , for example by means of a suitably installed temperature sensor in the coolant circuit 20 . In this context, the following applies: Δ T =T lst -T Soll .

[0045] Temperature target value T Soll It is determined at least in part by means of a target temperature of vehicle battery 500 , which may be selected, for example, from the perspective of optimal performance of vehicle battery 500 and in embodiments of the invention at least in part as a function of different operating points, external temperatures, etc.

[0046] In step S2, based at least in part on the deviation Δ T To determine the target heat flow dQ Soll Or a variable proportional thereto. This can be achieved by using the following relationship using a predetermined temperature gradient at the vehicle battery 500:

[0047]

[0048] In this case, in a known manner, the time variation of the variable X is expressed as or To express.

[0049] Furthermore, in Equation 1:

[0050] dQ Soll represents the target heat flow, which is determined here according to the temperature gradient;

[0051] cp Bat represents the thermal capacity of the vehicle battery 500;

[0052] m Bat represents the mass of the vehicle battery 500;

[0053] cp KM Indicates the heat capacity of the coolant;

[0054] m KM Indicates the quality of the coolant;

[0055] Represents the planned temperature gradient.

[0056] In this case, the planned temperature gradient can be represented by a deviation DT. As an alternative to equation 1, the pre-controlled target heat flow dQ can also be obtained at least partially based on the power loss model of the vehicle battery 500 Soll .

[0057] In step S3, the actual heat flow dQ is determined Ist or a variable proportional to it and the actual heat flow dQ Ist and target heat flux dQ Soll Heat flow deviation between Q .

[0058] Here, for example, in order to determine the actual heat flow dQ Ist The following enthalpy models can be used:

[0059]

[0060] in:

[0061] dQ Ist Represents the actual heat flow at the outlet of the heat exchanger;

[0062] represents the coolant mass flow rate at the outlet of the first heat exchanger 300;

[0063] h us，Hx represents the specific enthalpy before the first heat exchanger 300;

[0064] h ds，Hx represents the specific enthalpy after the first heat exchanger 300 .

[0065] As an alternative to Equation 2, the actual heat flow dQ Ist It is also possible to observe variables in the refrigeration circuit, which has dynamic advantages when regulating.

[0066] If pressure and temperature sensors are arranged before the expansion valve 220 and after the condenser 240, as well as after the evaporator 230 and before the compressor 200, the specific enthalpy h can be measured at the usual target operating point, and the actual heat flow dQ can also be determined using equation 2 Ist .

[0067] Other methods for determining the actual heat flow dQ can also be considered. Ist However, here the number of directly measured variables may be small and the actual heat flow dQ obtained is supported by the model required. Ist There may be a significant deviation from the actual situation.

[0068] In step S4, the compressor 200 is regulated using a cascade control, wherein the inner control loop R1 of the cascade control is at least partially dependent on the heat flow deviation Δ Q The power, in particular the speed, of the compressor 200 is regulated, and the outer control loop R2 is at least partially dependent on the deviation Δ determined in step S2. T To adjust the target heat flow dQSoll .

[0069] The regulation loop R1 and R2 are Figure 2 In addition, it can be seen that the cascade regulation includes the target heat flow dQ Soll The pre-control mechanism 211 transmits the corresponding signal to the heat flow controller 213 after the temperature controller 212.

[0070] The heat flow controller 213 and the control component 214 together form an internal regulation loop R1, in which the actual heat flow dQ is obtained. Ist , in the refrigerant circuit 10 to adjust the actual heat flow. The heat flow controller 213 obtains the heat flow deviation Δ by using the information provided by the temperature controller 212 and the control component 214. Q , and at least partially adjust the compressor power based on this. For example, the enthalpy model shown in equation 2 can be implemented in the control component 214.

[0071] The outer control loop R2 is monitored by a temperature controller 212 which determines the actual temperature variable T Ist and temperature target value T Soll The deviation between T And forward this information to the thermal flow controller 213.

[0072] In one embodiment of the present invention, the inner control loop R1 is controlled with a smaller time constant than the outer control loop R2 , thereby enabling the inner control loop to be regulated more quickly than the outer control loop. This contributes to a robust control.

[0073] Some aspects of the invention can be summarized as follows:

[0074] 1) The target variable of compressor regulation is the target heat flow dQ Soll .

[0075] 2) Monitor the actual heat flow dQ Ist .

[0076] 3) From the actual temperature T Ist and temperature target value T Soll The target heat flow dQ is obtained from the deviation Soll .

[0077] 4) There is a target heat flux dQ Soll pre-control.

[0078] The cascade control allows for simple initiation of a pre-control via the heat flow. The pre-controlled heat flow can be determined during battery cooling, for example, via a power loss model and can also be determined via a planned temperature gradient and heat capacity.

[0079] The invention is not limited to the described and illustrated embodiments. On the contrary, the invention also includes all specialized improvements within the scope of the invention defined by the patent claims. In addition to the described and depicted embodiments, other embodiments are also conceivable, which may include other modifications and feature combinations.

Claims

1. A method for regulating a compressor (200) in a refrigerant circuit, the method comprising the following steps: S1. Determine the thermal target state; S2. Determine a target heat flow dQ based at least in part on the thermal target state Soll or a variable proportional to the target heat flow; S3. Determine the actual heat flow dQ Ist or a variable proportional to the actual heat flow and determines the actual heat flow dQ Ist and target heat flux dQ Soll between or with the actual heat flow dQ Ist A variable proportional to the target heat flow dQ Soll Heat flow deviation between proportional variables △ Q ; S4. The compressor (200) is regulated by cascade regulation, wherein the internal regulation loop (R1) of the cascade regulation is at least partially based on the heat flow deviation Δ determined in step S3. Q The power of the compressor (200), in particular the speed, is adjusted, and the external control loop (R2) adjusts the target heat flow dQ at least partially according to the thermal target state determined in step S1. Soll .

2. The method according to claim 1, characterized in that At least in part by determining the actual temperature T Ist and temperature target value T Soll The deviation between T to determine the thermal target state in step S1, and at least in part based on the deviation Δ T To determine the target heat flow dQ in step S2 Soll Or a variable that is proportional to the target heat flow.

3. The method according to claim 2, characterized in that The temperature actual variable T in step S1 is determined at least partially with the aid of the temperature of a heat source or heat sink (500), in particular a vehicle battery. Ist , and determining a temperature target value T at least in part with the aid of a target temperature of a heat source or heat sink (500) Soll .

4. The method according to any one of claims 1 to 3, characterized in that Cascade regulation includes the target heat flow dQ Soll Or pre-control of a variable proportional to the target heat flow.

5. The method according to claim 4, characterized in that A pre-controlled target heat flow dQ is obtained based at least in part on a power loss model of a heat source or heat sink (500) Soll or pre-controlled with target heat flow dQ Soll Proportional variables.

6. The method according to claim 4, characterized in that A pre-controlled target heat flow dQ is obtained based at least in part on a predetermined temperature gradient at a heat source or heat sink (500). Soll or pre-controlled with target heat flow dQ Soll Proportional variables.

7. The method according to any one of claims 1 to 6, characterized in that The inner control loop (R1) performs control with a smaller time constant than the outer control loop (R2), thereby enabling the inner control loop (R1) to be regulated more quickly than the outer control loop (R2).

8. The method according to any one of claims 1 to 7, characterized in that The actual heat flow dQ in step S3 is determined by temperature measurement and pressure measurement in the refrigerant circuit (10). Ist Or the actual heat flow dQ Ist Proportional variables.

9. The method according to any one of claims 3 to 8, characterized in that The heat source or heat sink (500) is cooled or heated by a coolant circuit (20) which is thermally coupled to the refrigerant circuit (10) via a first heat exchanger (300).

10. The method according to claim 9, characterized in that The actual heat flow dQ in step S3 is determined at least in part by temperature measurement and pressure measurement at the outlet of the first heat exchanger (300) in the coolant circuit (20). Ist Or the actual heat flow dQ Ist Proportional variables.

11. A control device (210) for a compressor (200) in a refrigerant circuit (10), the refrigerant circuit (10) comprising at least: Circulating refrigerant; an electronic expansion valve (EEV) (100); a first heat exchanger (300), via which the refrigerant circuit (10) is preferably thermally coupled to the coolant circuit (20); means for measuring temperature and pressure variables in the refrigerant circuit (10) and preferably in the coolant circuit (20); in The control device (210) is configured to carry out the method according to any one of claims 1 to 10.

12. A refrigerant circuit (10), comprising: Circulating refrigerant; at least one compressor (200); an electronic expansion valve (EEV) (100); A first heat exchanger (300), via which the refrigerant circuit (10) is preferably thermally coupled to the coolant circuit (20); means for measuring temperature and pressure variables in the refrigerant circuit (10) and preferably in the coolant circuit (20); and a control device (210) for regulating the compressor (200), wherein the control device (210) is configured to carry out the method according to any one of claims 1 to 10.

13. A computer program for executing the method according to any one of claims 1 to 10 when the computer program is executed by a control device (210) of a compressor (200) in a refrigerant circuit (10) or is stored on a computer-readable data carrier.

14. A computer-readable data carrier on which a computer program according to claim 13 is stored.

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