JP2006317050A - Control device for cooling and heating concurrent operation type air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in a refrigerant circuit for a cooling and heating concurrent operation type air conditioner wherein it is necessary to set a refrigerant state quantity showing capacity required for cooling and a refrigerant state quantity showing capacity required for heating concurrently to control target values from its functional characteristics, but when load of the refrigerant circuit (e.g., operating indoor unit capacity or room temperature) considerably varies, feedback control does not effectively work because the state quantities of the refrigerant interfere with each other in individual feedback control utilized for usual cooling and heating, and as a result, it takes time before converging on the target values again. <P>SOLUTION: When a plurality of indoor heat exchangers 23 are concurrently operated in different uses of cooling and heating in the cooling and heating concurrent operation type air conditioner 3, control is switched to model predictive control of controlling the refrigerant state quantity showing the capacity required for cooling and the refrigerant state quantity showing capacity required for heating, with a model having transfer characteristics of operation quantities and refrigerant state quantities, based on at least two operation quantities that can control the refrigerant state quantities to the control target values. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a technology of a control device for a cooling and heating simultaneous operation type air conditioner.

Conventionally, indoor units are installed in each room for multiple rooms with different loads in building air conditioning, and each room is individually air-conditioned by a cooling / heating mixed multi-room air conditioner connected to one outdoor unit. The technique of distributed air conditioning is known.
Here, when independent control of the refrigerant state quantity indicating the required cooling capacity and the refrigerant state quantity indicating the required heating capacity is performed independently, each refrigerant state quantity is for the same refrigerant cycle, and one of them is operated. Since the influences on the other side affect each other, it becomes difficult to maintain the refrigerant state quantity at a predetermined target value when a large change such as a change in the number of operating indoor units occurs.

By the way, since the refrigerant circuit of the air conditioner has a large dead time and a large time constant, feedback control based on a deviation between the control amount of the refrigerant and the control target value as a control result is promptly adapted to changes in room temperature, outdoor temperature, etc. May not work.
In addition, when the load of the refrigerant circuit (for example, the operating indoor unit capacity or room temperature) changes greatly, it takes time until the refrigerant state quantity such as the suction pressure and the suction superheat degree changes with the feedback control alone. Since the input deviation does not change, feedback control does not work effectively. Moreover, it takes time until the target value is converged again after the change once appears.
Model predictive control is conceivable as a control method having a higher response speed and higher stability than the feedback control described above. The model control is known in Non-Patent Document 1, but the control purpose does not correspond to the simultaneous cooling and heating operation.
JP-A-6-300388 Journal of System Control Information Society Vol.46, No.7, 418-424

Although the above-mentioned Patent Document 1 controls the compression function based on the refrigerant discharge pressure and the refrigerant suction pressure in the simultaneous cooling and heating operation, the control target is only the compressor, and the heat exchange amount of the refrigerant in the outdoor unit can be controlled simultaneously. It wasn't.
An object of the present invention is to apply a model predictive control capable of handling a plurality of input / output signals based on the above-described problems of the prior art to simultaneous operation of cooling and heating, and a refrigerant state quantity indicating a cooling necessary capacity and a refrigerant indicating a heating necessary capacity It is to control the state quantity at the same time and improve the cooling / heating simultaneous operation performance.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, in claim 1, in a heat pump having a compressor, an outdoor heat exchanger, and a plurality of indoor heat exchangers, when the plurality of indoor heat exchangers are operated at the same time divided into different uses for cooling and heating. Communicating the operation amount and the refrigerant state amount based on at least two operation amounts capable of controlling the refrigerant state amount indicating the cooling necessary capacity and the refrigerant state quantity indicating the heating necessary capacity to the control target values Switching to model predictive control in which control is performed using a model having characteristics.

  According to a second aspect of the present invention, in the heat pump according to the first aspect, the refrigerant state quantity indicating the cooling necessary capacity is defined as the compressor suction pressure, and the refrigerant state quantity indicating the heating necessary capacity is defined as the compressor discharge pressure.

  According to a third aspect of the present invention, in the heat pump according to the first aspect, the target of the operation amount is switched depending on the difference between the cooling required capacity and the heating required capacity.

  In claim 4, in the heat pump according to claim 3, when the cooling required capacity is larger than the heating required capacity, the compressor rotation speed and the condensation capacity of the outdoor unit are set as adjustable operation amounts, and the heating required capacity is required to be cooled. When the capacity is larger than the capacity, the operation amount is adjusted so that the compressor rotation speed and the evaporation capacity of the outdoor unit can be adjusted.

  According to a fifth aspect of the present invention, in the heat pump according to the fourth aspect, when the superheat degree of the refrigerant sucked into the compressor becomes a predetermined value or less, the compressor suction pressure control target value is changed.

  As effects of the present invention, the following effects can be obtained.

  In claim 1, the refrigerant state quantity indicating the required cooling capacity and the refrigerant state quantity indicating the required heating capacity can be stably maintained at the target values at the same time, and each room can be rapidly cooled or heated to a desired temperature. Air-conditioning operation can be performed stably.

  In claim 2, the compressor suction pressure sensor and the discharge pressure sensor conventionally used in claim 1 can be used as means for detecting the refrigerant amount, and it is not necessary to provide a new detection means. It is possible to provide a stable air conditioner (cooling / heating device) at low cost simply by changing the above.

  In claim 3, the difference between the cooling required capacity and the heating required capacity can be balanced by the outdoor unit.

  In claim 4, the condensation capacity of the outdoor unit can be controlled by controlling the fan rotation speed of the outdoor unit in claim 3. Also, when the outdoor unit acts as an evaporator, in the case of an engine-driven heat pump equipped with a circuit that takes away the amount of heat in the waste heat recovery unit, the evaporation capacity in the waste heat recovery unit is not affected. In addition, the evaporation capacity can be controlled by the opening degree of the expansion valve.

In claim 5, simultaneous realization of cooling and heating and protection against wet operation of the compressor can be achieved at the same time.
Here, the damp operation of the compressor is a phenomenon in which the compressor sucks the refrigerant containing the liquid, which may cause liquid compression or oil rise of the compressor, leading to a compressor failure. Occurrence is expected when the target suction pressure changes due to fluctuations in the number of indoor units operating or the indoor load, but these can be avoided by changing the compressor suction pressure control target value.

Next, embodiments of the invention will be described.
1 is a block diagram showing a basic algorithm of model predictive control, FIG. 2 is a refrigerant circuit diagram showing a refrigerant circuit configuration according to an embodiment of the present invention, and FIG. 3 is a block diagram of model predictive control. FIG. 4A is a diagram showing an operation change according to Embodiment 1 of the present invention, and FIG. 4B is a diagram showing an operation state change according to Embodiment 2 of the present invention.

<Model predictive control algorithm>
First, a basic algorithm of predictive control applied to the present invention will be described with reference to the block diagram of FIG.
Here, the model predictive controller 1 (hereinafter referred to as MPC) uses the control target value y ^* (t), the operation amount u (t), and the refrigerant control amount y (t) as input signals, and the model parameters of the refrigeration cycle 2; Predictive control is performed using a parametric model (hereinafter referred to as a model) having a transfer characteristic indicating the relationship between the operation amount u (t) and the refrigerant control amount y (t). The predictive control is executed by the following algorithm.

(1) The output of the predictive control model is given by the following equation.
ym (t) = θ ₀ u (t) + θ ₁ u (t−1) +... + θ _n u (t−n)
Here, θ is a model parameter, and θ = [θ ₀ , θ ₁ ,..., Θ _n ]
(2) The predicted value yp (t + p) of the output after p steps is given by the following equation.
yp (t + p) = ym (t + p) + {y (t) -ym (t)}
Here, the difference y (t) −ym (t) between the observed value at the current time t and the calculated value based on the controlled variable model is regarded as a disturbance, and the disturbance having the same magnitude as that in the future will be constant in a stepped manner. It is corrected by assuming that it appears in the controlled variable.
(3) A reference trajectory yr (t + p) whose predicted value is provisionally targeted is given by the following equation.
yr (t + p) -y ^* (t + p) = a {y (t) -y ^* (t)}
Here, a is a control parameter and is set in the range of 0 ≦ a ≦ 1.
(4) The evaluation function J (t) is given by the following equation from yp (t + p) and yr (t + p).

Here, T is set in the range of 0 <T in the prediction interval.
(5) The refrigerant operation quantity sequence U satisfying the following conditions is determined.
Minimize J (t) Subject to Ω∋U
Here, U = [u (t), u (t + 1),..., U (t + T−1)], and Ω is an operation amount restriction region.
The first S of U are output every sampling period.
Here, S is set in the range of 0 ≦ S ≦ T in the output section.
(6) Repeat at time t + S.
The above is the basic predictive control algorithm. Actually, the application of the basic algorithm includes predictive control of a 2-input 2-output interference system, predictive control including disturbance in the 2-input 2-output interference system, and the like.

<Cooling and heating simultaneous operation type refrigerant circuit>
The cooling / heating simultaneous operation type air conditioner 3 according to the present invention is an air conditioner that can be operated simultaneously by connecting a plurality of indoor units 12 that perform cooling operation and heating operation with one outdoor unit 11. In the present embodiment, the refrigerant circuit configuration of the cooling and heating simultaneous operation type air conditioner 3 using an engine-driven heat pump will be described with reference to FIG.

  The engine-driven heat pump has a compressor 21 that obtains power from an engine (not shown) as a drive source and compresses the refrigerant, and is connected to the discharge side of the compressor 21 to switch the refrigerant flow during cooling and heating. The valves 24a and 24b, the outdoor heat exchangers 22a and 22b to which refrigerant is supplied from the compressor 21 through the three-way valves 24a and 24b during cooling, and the refrigerant from the compressor 21 through the three-way valves 24a and 24b during heating It has indoor heat exchangers 23a, 23b, 23c to be supplied, and outdoor heat exchangers 22 and outdoor heat exchanger expansion valves 33a, 33b disposed between the indoor heat exchangers 23a, 23b, 23c. The refrigerant cycle composed of these is used.

  The compressor 21 sucks and compresses the gas refrigerant from the suction side and discharges the high-temperature and high-pressure gas refrigerant. On the other hand, an oil separator 25 for separating the refrigeration oil contained in the gas refrigerant and returning it to the suction side of the compressor 21 is provided on the discharge side of the compressor 21 via a path 61 constituting a discharge line. Yes. That is, the gas refrigerant discharged from the compressor 21 flows into the three-way valves 24a and 24b through the oil separator 25 and is guided in a predetermined direction by the three-way valves 24a and 24b. Further, since the gas refrigerant sucked into the compressor 21 is also guided by the three-way valves 24a and 24b, the refrigerant suction side of the compressor 21 and the three-way valves 24a and 24b are connected by a path 62 that constitutes a suction line. .

The outdoor heat exchangers 22a and 22b have a function of exchanging heat between the refrigerant passing through the outdoor heat exchangers 22a and 22b and the outdoor air by the blowing of the outdoor fan 26. The three-way valves 24a and 24b are connected to one end of the outdoor heat exchangers 22a and 22b, and the other end is connected to the bridge circuit 27 via the outdoor heat exchanger expansion valves 33a and 33b.
Here, the reason why there are two outdoor heat exchangers 22a and 22b via the outdoor heat exchangers 22a and 22b is to adjust the heat exchange capacity, and the details are omitted.

  The receiver 28 capable of temporarily storing the refrigerant liquid is a sealed container, and includes a supercooling heat exchanger 29 inside. Here, the path 63a is a refrigerant inlet of the receiver 28, and the path 63b is a refrigerant outlet. The path 63a and the path 63b connect the receiver 28 and the bridge circuit 27, respectively. The bridge circuit is a circuit in which four check valves are combined, and controls the flow of the liquid refrigerant whose direction is reversed during the cooling operation and the heating operation, and the receiver 28 makes the refrigerant flow one-way.

  The cooling and heating simultaneous operation type air conditioner 3 of the present embodiment is characterized in that it has three connecting pipes that connect the outdoor unit 11 and the indoor unit 12 unlike a normal air conditioner. In this embodiment, the high pressure gas pipe 14, the low pressure gas pipe 15, and the liquid pipe 16 are connecting pipes.

  The engine waste heat recovery unit 30 is provided in a path 64 that branches from the liquid refrigerant outlet path 63 b of the receiver 28 and is connected to the path 62. To the path 64, the waste heat recovery device expansion valve 31, the supercooling heat exchanger 29, and the waste heat recovery device 30 are connected in series toward the path 62.

  The indoor heat exchangers 23a, 23b, and 23c have a role of exchanging heat between the refrigerant that passes through the indoor heat exchangers 23a, 23b, and 23c and the room air by the blowing of the indoor fans 32a, 32b, and 32c. One end of each of the indoor heat exchangers 23a, 23b, and 23c is connected to the refrigerant branch controllers 13a, 13b, and 13c through the indoor heat exchanger expansion valves 34a, 34b, and 34c.

<Cooling operation of a cooling and heating simultaneous operation type air conditioner>
Here, the cooling operation of the simultaneous cooling and heating operation of the cooling and heating simultaneous operation type air conditioner 3 will be described. Here, the description will be made on the assumption that 12a out of the three indoor units 12a, 12b, and 12c perform the cooling operation.
In the cooling operation, the high-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 21 is sent to the outdoor heat exchangers 22a and 22b via the three-way valves 24a and 24b, and the outdoor heat exchangers 22a and 22b. Then, it is condensed by dissipating heat to the outside air blown by the outdoor fan 26, and this condensation heat is dissipated into the outdoor air. Here, the gas refrigerant changes from gas to liquid. The liquefied refrigerant flows from the check valve 35a through the liquid refrigerant receiver inflow path 63a into the receiver 28, and further passes through the liquid refrigerant receiver outlet path 63b through the check valve 35d and the liquid pipe 16 to the room. The heat exchanger reaches the heat exchanger expansion valve 34a, and is rapidly reduced in pressure by the indoor heat exchanger expansion valve 34a to be easily evaporated and led to the indoor heat exchanger 23a. This indoor heat exchanger 23a becomes an evaporator, and the refrigerant takes heat of evaporation from the indoor air and changes from a liquid to a gas, and cools the indoor air. The vaporized refrigerant passes through the path 62 via the low-pressure gas pipe 15 and is sucked and compressed by the compressor 21 and then discharged again.

<Heating operation of a cooling and heating simultaneous operation type air conditioner>
Here, the heating operation at the time of the simultaneous cooling and heating operation of the cooling and heating simultaneous operation type air conditioner 3 will be described. Here, of the three indoor units 12a, 12b, and 12c shown, 12b will be described as performing heating operation.
During the heating operation, the high-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 21 is sent to the indoor heat exchanger 23b via the path 61 and the high-pressure gas pipe 14, and in the indoor heat exchanger 23b. It is condensed by releasing heat to the indoor air blown by the indoor fan 32, and this condensation heat is dissipated into the indoor air and warms the indoor air. Here, the refrigerant changes from gas to liquid. The liquefied refrigerant flows into the receiver 28 from the liquid refrigerant receiver inlet path 63a through the liquid pipe 16 and the check valve 35c, and from the liquid refrigerant receiver outlet path 63b to the outdoor heat exchanger expansion valves 33a and 33b. , And is rapidly reduced in pressure by the outdoor heat exchanger expansion valves 33a and 33b to be easily evaporated and led to the outdoor heat exchangers 22a and 22b. The outdoor heat exchangers 22a and 22b serve as an evaporator, and the refrigerant takes heat of evaporation from the outdoor air, and a part of the refrigerant changes from liquid to gas. The refrigerant evaporated through the outdoor heat exchangers 22a and 22b passes through the path 62 via the three-way valves 24a and 24b, is sucked and compressed by the compressor 21, and is then discharged again.

Furthermore, the waste heat recovery device 30 during heating operation, which is a feature of the engine-driven heat pump, will be described.
The liquid refrigerant branched from the receiver 28 flows through the path 64 as follows. That is, after being depressurized by the waste heat recovery device expansion valve 31, it flows into the supercooling heat exchanger 29 provided in the receiver and is guided to the engine waste heat recovery device 30 via the path 64. The supercooling heat exchanger 29 and the waste heat recovery device 30 serve as an evaporator, and the refrigerant takes the heat of evaporation from the liquid refrigerant in the receiver 28 and the engine waste heat and changes from liquid to gas. The vaporized refrigerant merges with the path 62, is sucked into the compressor 21 and compressed, and then discharged again.

<Cooling and heating simultaneous operation of cooling and heating simultaneous operation type air conditioner>
Next, the cooling / heating mixing operation, which is a feature of the cooling / heating simultaneous operation type air conditioner 3, will be described. Here, of the three indoor units 12a, 12b, and 12c shown, 12a and 12b will be described as being in the cooling operation, and 12c will be described as being in the heating operation. In this case, assuming that the loads of the indoor units are all equal, the capacity of the cooling operation is large as a whole, so that the outdoor unit heat exchanger 22 acts as a condenser.

  First, the flow of the refrigerant from the outdoor unit 22 side will be described. The high-pressure gas discharged from the compressor 21 passes through the path 61 and is guided to the oil separator 25. Then, it branches into the refrigerant | coolant which passes the high pressure gas piping 14, and goes to the indoor unit 12c, and the refrigerant | coolant guide | induced to the outdoor heat exchangers 22a and 22b via the three-way valves 24a and 24b. The latter refrigerant is condensed by dissipating heat to the outside air blown by the outdoor fan 26 in the outdoor heat exchangers 22a and 22b, and this condensation heat is dissipated into the outdoor air. Here, the refrigerant changes from gas to liquid. The liquefied cooling operation refrigerant flows into the receiver 28 from the check valve 35a through the liquid refrigerant receiver inflow path 63a.

Next, the flow of the refrigerant on the indoor units 12a, 12b, and 12c side will be described.
Here, the indoor unit 12c that performs the heating operation will be described. As described above, the refrigerant that has passed through the high-pressure gas pipe 14 toward the indoor unit 12c in the state of high-pressure gas is sent to the indoor heat exchanger 23c, and is blown by the indoor fan 32c in the indoor heat exchanger 23c. It is condensed by dissipating heat to the air, and this condensation heat is dissipated into the indoor air to warm the indoor air. Here, the refrigerant changes from gas to liquid. The liquefied refrigerant flows into the receiver 28 from the liquid refrigerant receiver inlet path 63a through the liquid pipe 16 and the check valve 35c.

  Next, the indoor units 12a and 12b that perform the cooling operation will be described. The liquid refrigerant stored in the receiver 28 as the liquid refrigerant as described above reaches the indoor heat exchanger expansion valves 34a and 34b from the liquid refrigerant receiver outlet path 63b via the check valve 35d and the liquid pipe 16. The indoor heat exchanger expansion valves 34a and 34b are suddenly decompressed and easily evaporated, and are led to the indoor heat exchangers 23a and 23b. The indoor heat exchangers 23a and 23b serve as evaporators, and the refrigerant takes evaporation heat from the indoor air and changes from liquid to gas, and cools the indoor air. The vaporized refrigerant passes through the path 62 via the low-pressure gas pipe 15 and is sucked and compressed by the compressor 21 and then discharged again.

  From the above description, regarding the cooling and heating mixing operation that is a feature of the cooling and heating simultaneous operation type air conditioner 3, when the capacity of the cooling operation in the plurality of indoor units 12 is large, the evaporator of the indoor unit 12c that performs the heating operation is usually However, in this embodiment, it is understood that the indoor units 12a and 12b that are performing the cooling operation are used as the evaporator of the indoor unit 12c. .

<Predictive control of a cooling and heating simultaneous operation type air conditioner>
Next, the cooling and heating simultaneous operation type air conditioner 3 to which the predictive control according to the embodiment of the present invention is applied will be described with reference to FIG.
In FIG. 3, MPC represents the model predictive control controller 1, the signal is transmitted in the direction of the arrow, and at the junction indicated by “◯”, the signal represents a positive coupling with + and a negative coupling with −. The signal branches at the branch indicated by ●.

In FIG. 3, the inside of the broken line indicates the cooling and heating simultaneous operation type air conditioner 3, and G <b> 1 to G <b> 11 within the broken line indicate transfer functions having certain characteristics, respectively. These transfer functions are stored in advance in the MPC 1 and modeled. Further, in the drawing, the feedback of the operation amount shown in FIG. 1 is not shown, but is assumed to be included in the MPC 1.
Here, as the refrigerant state quantity, the compressor low pressure is shown as PL, the compressor high pressure as PH, and the suction superheat degree as SH. Further, Ne as the operation amount is the compressor rotational speed, where the rotational speed of the outdoor fan 26 is Fan and the opening degree of the outdoor heat exchanger expansion valve 33 is EV. Furthermore, the target value of the compressor low pressure is shown as PL ^* , and the target value of the compressor high pressure is shown as PH ^* . In the cooling / heating simultaneous operation type air conditioner 3, the cooling operation indoor unit total capacity is indicated by HCc, and the heating operation indoor unit total capacity is indicated by HCh.

  Here, each transfer function will be described. G1 is the relationship between the compressor rotational speed Ne and the low pressure PL, G2 is the relationship between the compressor rotational speed Ne and the high pressure PH, G3 is the relationship between the rotational speed Fan of the outdoor fan 26 and the low pressure PL, and G4 is the relationship between the outdoor fan 26 and G4. The relationship between the rotational speed Fan and the high pressure PH, G5 is the relationship between the cooling operation indoor unit total capacity HCc and the low pressure PL, G6 is the relationship between the cooling operation indoor unit total capacity HCh and the high pressure PH, and G7 is the heating operation indoor unit total capacity. Relationship between HCh and low pressure PL, G8 is the relationship between the total capacity of heating operation indoor units HCh and high pressure PH, G9 is the relationship between the opening EV of the outdoor heat exchanger expansion valves 33a and 33b and the low pressure PL, and G10 is outdoor heat. The relationship between the opening degree EV of the exchanger expansion valves 33a and 33b and the high pressure PH, and G11 shows the relationship between the opening degree EV of the expansion valves 33a and 33b for the outdoor heat exchanger and the suction superheat degree SH.

Further, in FIG. 3, the switching determination unit 81 compares the cooling operation indoor unit total capacity HCc with the heating operation indoor unit total capacity HCh, and if the cooling operation indoor unit total capacity HCc is larger than the heating operation indoor unit total capacity HCh, If the rotational speed Fan of the outdoor fan 26 is an operation amount and the heating operation indoor unit total capacity HCh is larger than the cooling operation indoor unit total capacity HCc, the outdoor heat exchanger expansion valves 33a and 33b or the waste heat recovery expansion valve 31 Switching is automatically performed so that the degree of opening EV is the operation amount.
Similarly, in FIG. 3, the target value changing unit 82 changes the target value PL ^* of the compressor low pressure if the suction superheat degree SH is equal to or less than a predetermined value.

Hereinafter, how to obtain the above-described refrigerant amount will be described in detail with reference to FIGS.
As the refrigerant state quantity, the compressor low pressure PL is detected by the suction pressure sensor 53, and the compressor high pressure PH is detected by the discharge pressure sensor 54 and input to the MPC 1 respectively. Further, the suction superheat degree SH is obtained by subtracting the saturation equivalent temperature of the compressor low pressure PL detected by the suction pressure sensor 53 from the suction temperature detected by the suction temperature sensor 52, and is input to the target value changing unit 82.
Here, the cooling operation indoor unit total capacity HCc and the heating operation indoor unit total capacity HCh depend on the difference between the indoor temperature sensor 50 provided in each indoor unit, the indoor air conditioning set temperature, and the indoor unit capacity. Determine each capacity.

Further, a specific control method will be described with reference to FIG.
Here, FIG. 4 shows a representative example of the indoor unit operation pattern state change of the cooling and heating simultaneous operation type air conditioner 3 shown in FIG. In FIG. 4, the state of the outdoor unit is expressed by cooling or heating. This means that the outdoor unit is in a heating operation state, that is, it is used as an evaporator, and the outdoor unit is in a cooling operation state. That is, it is used as a condenser. Further, the cooling operation indoor unit total capacity HCc and the heating operation indoor unit total capacity HCh are not determined by the number of indoor units operated, but are the respective capacities of the cooling / heating simultaneous operation type air conditioner 3 as a whole. In the following embodiments, it is assumed that the operating capacities (both cooling and heating) of all indoor units are the same.

First, in the operation pattern change shown in FIG. 4, the indoor units 12a and 12b are in the cooling operation and the indoor unit 12c is stopped (the operation state A in FIG. 4). It is assumed that the machine 12c has started the heating operation (operation state B in FIG. 4).
First, in the operation state A, since only the cooling operation is performed, the target value PL ^* of the compressor low pressure corresponding to the cooling load is set, and the normal feedback control is performed with the compressor rotational speed Ne as the operation amount. Yes.
Next, when the indoor unit 12c starts the heating operation from the above state, the operation is switched to the cooling and heating simultaneous operation type operation. At this stage, the model predictive control according to the embodiment of the present invention is applied. That is, based on the fact that the values of both the cooling operation indoor unit total capacity HCc and the heating operation indoor unit total capacity HCh are input after the state transition, the compressor low pressure target value PL ^* and the compressor high pressure target value PH (1) to (6) described above, where ^* is the target value, the compressor low pressure PL and the compressor high pressure PH of the refrigerant state quantity are control amounts, the compressor rotational speed Ne and the outdoor fan rotational speed Fan are the manipulated variables Predictive control is performed. The details of the predictive control are the same as the basic algorithm described above, and are omitted here. Here, the aforementioned transfer functions G1 to G11 of the cooling and heating simultaneous operation type air conditioner 3 are stored in advance in the MPC1. The control by the MPC 1 is repeated until the compressor low pressure PL and the compressor high pressure PH reach their target values.

Next, in the operation state change shown in FIG. 4, from the above-described operation state B, the indoor unit 12a is stopped from the cooling operation while the indoor unit 12a is in the cooling operation, the indoor unit 12c is in the heating operation (the operation state in FIG. 4). C). Here, model predictive control is applied continuously. That is, the target value PL ^* of the compressor low pressure and the target value PH ^* of the compressor high pressure are set to the target value, the compressor low pressure PL and the compressor high pressure PH of the refrigerant state quantity are controlled, the compressor speed Ne and The predictive control (1) to (6) described above is performed using the rotational speed Fan of the outdoor fan as an operation amount. The control by MPC1 detects that the indoor unit 12b has stopped from the cooling operation as a decrease in the cooling operation indoor unit total capacity HCh, and the compressor low pressure PL and the compressor high pressure based on the stored transfer functions G1 to G11. It repeats until pressure PH becomes each target value.
Here, even in the case where the cooling operation is started from the operation only in the heating operation in the first embodiment, the same control is performed by using the outdoor heat exchanger expansion valve opening EV as the operation amount instead of the rotation speed Fan of the outdoor fan. Needless to say.

Furthermore, a specific control method will be described.
Similarly, in the cooling / heating simultaneous operation type air conditioner 3 shown in FIG. 2, the indoor units 12a and 12b are in the cooling operation and the indoor unit 12c is in the heating operation in the operation pattern change shown in FIG. 4, it is assumed that the indoor unit 12a is in the cooling operation, the indoor units 12b and 12c are in the heating operation (operation state E in FIG. 4), that is, the indoor unit 12b is switched from the cooling operation to the heating operation.
In the present embodiment, the state of transition from the cooling operation state to the heating operation state is changed, that is, the outdoor heat exchangers 22a and 22b play the role of the evaporator from the role of the condenser. In 81, a command is issued to change the manipulated variable from the outdoor fan rotational speed Fan to the outdoor heat exchanger expansion valve opening EV. However, as described above, switching is performed according to the capacity of cooling or heating, not the number of operating units.

Here, the target value PL ^* of the compressor low pressure and the target value PH ^* of the compressor high pressure after the state transition are set as the target values, and the compressor low pressure PL and the compressor high pressure PH of the refrigerant state quantity are controlled and compressed. The predictive control (1) to (6) described above is performed using the machine speed Ne and the outdoor heat exchanger expansion valve opening EV as the manipulated variables. The details of the predictive control are the same as the basic algorithm described above, and are omitted here. Here, the aforementioned transfer functions G1 to G11 of the cooling and heating simultaneous operation type air conditioner 3 are stored in advance in the MPC1. The control by the MPC 1 is repeated until the compressor low pressure PL and the compressor high pressure PH reach their target values.
Here, it is needless to say that the same control is performed even when the operation pattern of the large heating capacity is changed to the operation pattern of the large cooling capacity in the second embodiment.

In the above-described second embodiment, the control by the MPC 1 is repeated until the compressor low pressure PL reaches the target value PL ^* . However, when the target value is the compressor low pressure PL, and is set only in consideration of the cooling capacity, the control is performed in a state where the compressor wet operation cannot be protected. The wet operation of the compressor causes liquid compression and oil rising, which causes a compressor failure.
Therefore, in order to prevent the compressor from being wet, if the refrigerant supercharging amount SH is less than a predetermined value, the target value PL ^* of the compressor low pressure is changed in a timely manner so that the intake superheat SH is reduced. Control is performed so as to be equal to or greater than a predetermined value.

It is the block diagram which showed the basic algorithm of predictive control. It is the refrigerant circuit figure which showed the refrigerant circuit structure which concerns on embodiment of this invention. It is a block diagram of prediction control similarly. (A) The figure which showed the driving | running state change which concerns on Example 1 of this invention, (b) The figure which showed the driving | running state change which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Model prediction controller 3 Cooling and heating simultaneous operation type air conditioner 81 Switching determination part 82 Target value change part

Claims (5)

In a heat pump having a compressor, an outdoor heat exchanger, and a plurality of indoor heat exchangers,
When the plurality of indoor heat exchangers are operated at the same time divided into different uses for cooling and heating, the refrigerant state quantity indicating the cooling necessary capacity and the refrigerant state quantity indicating the heating necessary capacity are controlled to the control target values. A heat pump characterized in that, based on at least two manipulated variables that can be performed, switching to model predictive control in which control is performed with a model having a transfer characteristic between the manipulated variable and the refrigerant state quantity. The heat pump according to claim 1, wherein
A heat pump characterized in that a refrigerant state quantity indicating a cooling necessary capacity is a compressor suction pressure, and a refrigerant state quantity indicating a heating necessary capacity is a compressor discharge pressure. The heat pump according to claim 1, wherein
A heat pump characterized in that the target of the operation amount is switched depending on the difference between the cooling required capacity and the heating required capacity. The heat pump according to claim 3, wherein
When the required cooling capacity is greater than the required heating capacity, the compressor speed and the outdoor unit condensation capacity can be adjusted.When the required heating capacity is greater than the required cooling capacity, the compressor speed and the outdoor unit A heat pump characterized by an operation amount with adjustable evaporation capacity. The heat pump according to claim 4, wherein
A heat pump characterized by changing a compressor suction pressure control target value when the degree of superheat of refrigerant sucked into the compressor becomes a predetermined value or less.

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