CN110486896B - Cascade air conditioning system optimization control method based on water chilling unit energy consumption model - Google Patents

Abstract

The invention discloses a cascade air conditioning system optimization control method based on a water chilling unit energy consumption model, which comprises the following steps: collecting relevant data of a cascade air-conditioning refrigeration system, and estimating the ice melting amount and the maximum refrigeration load upper limit of a unit; carrying out energy consumption model modeling on a base load water chilling unit and a double-working-condition water chilling unit in the cascade air-conditioning refrigeration system by adopting a support vector regression machine; calculating the actual unit operation quantity according to the estimated ice melting quantity at the current moment, the maximum refrigeration load upper limit of the unit and the load demand, and realizing the group control of the unit; distributing a base load unit, a double-working-condition unit and an ice melting load, realizing parameter optimization by combining a unit energy consumption model, and minimizing the operation cost while meeting the current load and boundary conditions; and setting an optimization updating period, and re-optimizing after each period is finished. The control method can meet the current load and boundary conditions and simultaneously has the lowest operation cost.

Description

Cascade air conditioning system optimization control method based on water chilling unit energy consumption model

Technical Field

The invention belongs to the field of energy-saving optimization control of a central air-conditioning refrigeration system, and particularly relates to a control method for realizing ice melting plan, unit group control and operation parameter optimization of the central air-conditioning refrigeration system.

Background

The cascade refrigeration system of the central air conditioner generally comprises a base load water chilling unit, a double-working-condition water chilling unit and an ice storage tank, and due to the existence of three cold sources, various operation modes can be combined in actual operation, so that the cascade refrigeration system has the characteristics of strong load adaptability and flexible adjustment mode. However, the excessive operation modes cause that a system control scheme is difficult to select, the operation cost is different due to the difference of the operation modes and the scheme under the same load requirement, and the unreasonable operation modes cause that the operation cost is increased and even the load requirement cannot be met. The complex cascade air-conditioning refrigeration system is generally large in installed capacity, large in operation energy consumption base number and large in energy-saving space.

In actual operation, because the operation condition of the cascade air-conditioning refrigeration system is complex, load coordination distribution among a base load unit, a double-working-condition unit and an ice tank is involved, the conventional unit group control strategy cannot realize automatic operation of the system, usually, an operator manually controls the system according to the previous operation experience, only the load supply requirement can be guaranteed, and the effects of peak load shifting, valley filling, energy saving and consumption reduction of the cascade air-conditioning refrigeration system are not really exerted.

In order to realize the operation optimization of the cascade air-conditioning refrigeration system, coordinate the operation loads among the base load unit, the double-working-condition unit and the ice tank and uniformly manage the operation loads while meeting the load requirements, the cascade air-conditioning system optimization control method based on the water chilling unit energy consumption model is provided.

Disclosure of Invention

The invention aims to provide a cascade air conditioning system optimization control method based on a water chilling unit energy consumption model, which can meet the current load and boundary conditions and simultaneously has the lowest operation cost.

In order to achieve the above purpose, the solution of the invention is:

a cascade air conditioning system optimization control method based on a water chilling unit energy consumption model comprises the following steps:

step 1, collecting temperature, flow and ice tank ice amount data of a cascade air-conditioning refrigeration system, and estimating the ice melting amount and the maximum refrigeration load upper limit of a unit;

step 2, performing energy consumption model modeling on a base load water chilling unit and a dual-working-condition water chilling unit in the cascade air-conditioning refrigeration system by using a support vector regression, inputting variables of chilled water inlet and outlet water temperature, cooling water inlet and outlet water temperature and unit load, and outputting the variables of chilled water inlet and outlet water temperature, cooling water inlet and outlet water temperature and unit load as unit energy efficiency ratio;

step 3, calculating the actual unit operation number according to the estimated ice melting amount at the current moment, the maximum refrigerating load upper limit of the unit and the load demand, and realizing the group control of the unit;

step 4, distributing the base load unit, the double-working-condition unit and the ice melting load, realizing parameter optimization by combining a unit energy consumption model, and minimizing the operation cost while meeting the current load and boundary conditions;

and 5, setting an optimization updating period, and re-optimizing after each period is finished.

In the step 1, the ice melting amount is estimated by adopting a weighted average method, and the weighting coefficient K per hour at the time of the power price and in the peak time period is set by taking the hour as a unit_iThen, the ice melting amount at the current moment is estimated as:

wherein Q is_rThe unit is kW which is the ice melting amount at the current moment; q_iceThe unit of the residual ice amount of the ice tank at the current moment is kWh; k_nowA current time ice melting weighting coefficient; now denotes the current time, and end denotes the last planned ice-melt time of the day.

In the step 1, the method for estimating the output of the water chilling unit comprises the following steps: calculating historical maximum refrigerating load Q 'of base-mounted water chiller unit'_{max_b}And historical maximum refrigerating load Q 'of double-working-condition water chilling unit'_{max_d}And then, the maximum refrigerating load upper limit of the unit is as follows:

wherein Q is_{max_b}The unit is kW which is the actual load upper limit of the base load unit; eta_bThe load safety factor of the base load unit is a constant of 0-1; q_{max_d}The unit is the actual load upper limit of the double-working-condition unit, and the unit is kW; eta_dThe load safety factor of the double-working-condition unit is a constant of 0-1.

In the step 2, when the base-load water chilling unit is modeled, the input variables adopt the chilled water inlet/outlet water temperature, the cooling water inlet/outlet water temperature and the unit load, and the output is the unit energy efficiency ratio, namely:

COP_b＝f(T_ei，T′_eo，T_{ci_b}，T_{co_b}，Q_{e_b})

wherein COP _ b is the energy efficiency ratio of the base load unit; t is_eiThe temperature of the inlet water of the chilled water is the unit of ℃; t is_e'_oThe temperature of the outlet water of the chilled water is shown in unit of ℃; t is_{ci_b}The unit is the water inlet temperature of cooling water of the base load unit; t is_{co_b}The outlet water temperature of cooling water of the base load unit is measured in unit; q_{e_b}The unit is kW for the load of the base load unit;

when modeling the double-working-condition unit, the chilled water is uniformly used as a reference, the input quantity adopts plate exchange inlet and outlet water temperature, cooling water inlet and outlet water temperature and unit load, and the output is a unit energy efficiency ratio, namely:

COP_d＝f(T′_eo，T_eo，T_{ci_d}，T_{co_d}，Q_{e_d})

wherein COP _ d is the energy efficiency ratio of the double-working-condition unit; t'_eoThe temperature of inlet water is changed for the plate, and the unit is; t is_eoThe temperature of the outlet water is changed for the plate, and the unit is; t is_{ci_d}The unit of the inlet water temperature of the cooling water of the double-working-condition unit is; t is_{co_d}The outlet water temperature of the cooling water of the double-working-condition unit is measured in unit; q_{e_d}The unit is kW for the load of the double-working-condition unit.

In the step 3, when the group control of the units is realized, a rolling calculation control strategy with the priority of ice melting and the priority of starting the base-load water chilling unit is adopted.

The specific content of the step 3 is as follows: operating the double-working-condition water chilling unit by n_dSet to zero, gradually increase the running number n of the base load water chilling unit_bIf the base load water chilling unit is fully opened and still does not meet the load requirement, a dual-working-condition water chilling unit is added, the base load unit is gradually increased from zero, and the circulation is performed until the load requirement is met:

Q_r+Q_{max_b}×n_b+Q_{max_d}×n_d＞Q

wherein Q is_rThe unit is kW for the ice melting amount; q_{max_b}The unit is kW which is the upper limit of the load of the base load unit; q_{max_d}The unit is the upper limit of the load of the double-working-condition unit, and the unit is kW; q is the actual load demand in kW.

In the step 4, parameter optimization is realized by adopting an exhaustion method, and the optimization result is the set value of the outlet temperature of the base load water chilling unit.

The specific content of the step 4 is as follows:

setting temperature calculation step length, and enabling chilled water to enter plate exchange temperature T'_eoStep by T_eiRise to T_eoEstimating the unit energy efficiency ratio under each temperature calculation step length by combining the energy consumption models of the base load unit and the double-working-condition unit, and calculating the actual energy consumption under each temperature step length; considering the actual upper limit of the operation load and the operation load requirement of the unit, the actual alternative scheme meets the following conditions:

wherein F is the flow rate of the chilled water with the unit of kg/s;

wherein Q is_{max_b}The unit is kW which is the actual load upper limit of the base load unit; q_{max_d}The unit is the actual load upper limit of the double-working-condition unit, and the unit is kW; n is_bThe number of running water chilling units is the base load; n is_dThe number of running water chilling units is two; c is the specific heat capacity of water, and the value is 4.2kJ/(kg DEG C); q_rThe unit is kW which is the ice melting amount at the current moment; COP _ b is the energy efficiency ratio of the base load unit; t is_{ci_b}The unit is the water inlet temperature of cooling water of the base load unit; t is_{co_b}The outlet water temperature of cooling water of the base load unit is measured in unit; COP _ d is the energy efficiency ratio of the double-working-condition unit; t is_{ci_d}The unit of the inlet water temperature of the cooling water of the double-working-condition unit is; t is_{co_d}The outlet water temperature of the cooling water of the double-working-condition unit is measured in unit;

at the moment, the unit equipment calculates the power consumption N under each temperature step length_e' is:

gradually increasing T 'according to step length'_eoOn the premise of satisfying the boundary condition, the power consumption N is searched_e'minimum T'_eoI.e. the optimizing result.

By adopting the scheme, the invention can realize the group control function of the unit of the cascade air-conditioning refrigeration system, carry out coordinated distribution and unified management on the operation loads among the base load unit, the double-working-condition unit and the ice tank, and realize the optimal operation cost of the system while meeting the load requirement of the air-conditioning system. Meanwhile, the cycle optimization of the operation parameters is adopted, so that the unstable operation of the system caused by the inertia of the air conditioning system is avoided.

Drawings

FIG. 1 is a flow chart of the present invention;

fig. 2 is a schematic structural diagram of a conventional cascade air conditioning system according to the present invention.

Detailed Description

The technical solution and the advantages of the present invention will be described in detail with reference to the accompanying drawings.

As shown in fig. 1, the invention provides a cascade air conditioning system optimization control method based on a water chilling unit energy consumption model, which comprises the following steps:

acquiring conventional easily-acquired data such as temperature, flow and ice tank ice amount of a cascade air-conditioning refrigeration system, and estimating the ice melting amount and the output of a water chilling unit;

the data collected includes: the water inlet/outlet temperature of the chilled water, the water inlet/outlet temperature of the cooling water, the flow rate of the chilled water, the power consumption of the unit and the ice amount of the ice tank of the base-load water chiller and the double-working-condition water chiller. And the output and energy efficiency ratio of the unit can be calculated by using the collected data.

The method comprises the following steps of according to a heat calculation formula and a unit energy efficiency ratio calculation formula:

wherein Q is a machineGroup refrigeration load, unit is kW; c is the specific heat capacity of water, and the value is 4.2kJ/(kg DEG C); q is the fluid flow rate in kg/s; delta t is the temperature difference of the chilled water supply and return water, and the unit is; COP is the energy efficiency ratio of the water chilling unit; n is a radical of_eThe input power is in kW.

The data acquired and calculated in real time are subjected to historical storage, and the historical maximum refrigerating load Q 'of the base-mounted water chilling unit can be calculated through statistics'_{max_b}And historical maximum refrigerating load Q 'of double-working-condition water chilling unit'_{max_d}Then, the upper limit of the actual load of the unit can be estimated as follows:

wherein Q is_{max_b}The unit is kW which is the actual load upper limit of the base load unit; eta_bThe load safety factor of the base load unit is a constant of 0-1; q_{max_d}The unit is the actual load upper limit of the double-working-condition unit, and the unit is kW; eta_dThe load safety factor of the double-working-condition unit is a constant of 0-1.

The ice melting amount is calculated by only considering the time interval of the power price at the normal time and the peak time, the ice melting amount is estimated by adopting a weighted average method, and the weighting coefficient K of each hour in the time interval of the power price at the normal time and the peak time is set by taking the hour as a unit_iThen, the ice melting amount at the current moment is estimated as:

wherein Q is_rThe unit is kW which is the ice melting amount at the current moment; q_iceThe unit of the residual ice amount of the ice tank at the current moment is kWh; k_iThe weighting coefficients of the ice melting at the electricity price and in the peak time period per hour; k_nowA current time ice melting weighting coefficient; now denotes the current time, and end denotes the last planned ice-melt time of the day.

And step two, performing energy consumption model modeling on the base load water chilling unit and the double-working-condition water chilling unit in the cascade air-conditioning refrigeration system by using a Support Vector Regression (SVR).

The support vector regression expression is as follows:

wherein alpha is_iIs Lagrange multiplier;

are support vector coefficients; k (x, x)_i) For the kernel function, a gaussian radial basis kernel function (RFB) is used, which is calculated as follows:

wherein x is an input variable, x_iFor the support vector, σ is the kernel width parameter, and | … | | | is the norm calculation.

As shown in FIG. 2, the structure of the cascade air-conditioning refrigeration system is shown, the temperature of the chilled water passing through the base-load water chilling unit is T_eiIs reduced to T'_eoThen the temperature of the chilled water is changed by a double working condition unit/ice cold storage plate'_eoDown to T_eo。

When modeling the base load water chilling unit, input variables adopt chilled water inlet/outlet water temperature, cooling water inlet/outlet water temperature and unit load, and output is unit energy efficiency ratio, namely:

COP_b＝f(T_ei，T′_eo，T_{ci_b}，T_{co_b}，Q_{e_b})

wherein COP _ b is the energy efficiency ratio of the base load unit; t is_eiThe temperature of the inlet water of the chilled water is the unit of ℃; t'_eoThe temperature of the outlet water of the chilled water is shown in unit of ℃; t is_{ci_b}The unit is the water inlet temperature of cooling water of the base load unit; t is_{co_b}The outlet water temperature of cooling water of the base load unit is measured in unit; q_{e_b}The unit is kW for the load of the base load unit.

When modeling the double-working-condition unit, for convenient optimization calculation, the chilled water is uniformly used as a reference, the input quantity adopts the temperature of plate exchange inlet and outlet water, the temperature of cooling water inlet and outlet water and the unit load, and the output is the unit energy efficiency ratio, namely:

COP_d＝f(T′_eo，T_eo，T_{ci_d}，T_{co_d}，Q_{e_d})

wherein COP _ d is the energy efficiency ratio of the double-working-condition unit; t'_eoThe temperature of inlet water is changed for the plate, and the unit is; t is_eoThe temperature of the outlet water is changed for the plate, and the unit is; t is_{ci_d}The unit of the inlet water temperature of the cooling water of the double-working-condition unit is; t is_{co_d}The outlet water temperature of the cooling water of the double-working-condition unit is measured in unit; q_{e_d}The unit is kW for the load of the double-working-condition unit.

And step three, calculating the actual unit operation quantity according to the ice melting quantity at the current moment, the unit maximum refrigeration load estimation and the load demand. Operating the double-working-condition water chilling unit by n_dSet to zero, gradually increase the running number n of the base load water chilling unit_bIf the base load water chilling unit is fully opened and still does not meet the load requirement, a dual-working-condition water chilling unit is added, the base load unit is gradually increased from zero, and the circulation is performed until the load requirement is met:

Q_r+Q_{max_b}×n_b+Q_{max_d}×n_d＞Q

wherein Q is_rThe unit is kW for the ice melting amount; q_{max_b}The unit is kW which is the upper limit of the load of the base load unit; q_{max_d}The unit is the upper limit of the load of the double-working-condition unit, and the unit is kW; q is the actual demand load, and the unit is kW; n is_bThe number of the base load units is the number of the base load units; n is_dThe number of the double-working-condition units is the number of the double-working-condition units.

Step four, setting a temperature calculation step length, and enabling the chilled water to enter a plate exchange temperature T'_eoStep by T_eiRise to T_eoThe energy efficiency ratio of the unit under each temperature calculation step can be estimated by combining the energy consumption models of the base load unit and the double-working-condition unit, and meanwhile, the actual energy consumption under each temperature step can be calculated. Considering the actual upper limit of the operation load and the operation load requirement of the unit, the actual alternative scheme should meet the following conditions:

wherein F is the flow rate of the frozen water, and the unit is kg/s.

At the moment, the unit equipment calculates the power consumption N under each temperature step length_e' is:

gradually increasing T 'according to step length'_eoOn the premise of satisfying the boundary condition, the power consumption N is searched_e'minimum T'_eoI.e. the optimizing result.

And step five, setting an optimization updating period, and updating the unit operation quantity and the outlet temperature fixed value of the base load unit obtained by each optimization calculation periodically or in non-real time so as to prevent frequent adjustment of the control strategy.

By the optimization control method of the series air conditioning system, the ice melting amount, the unit group control and the unit water supply temperature fixed value can be optimized while the cooling load is required, the lowest operation cost is realized, and meanwhile, due to the adoption of a fixed-period optimization strategy, the frequent adjustment of the strategy can be effectively avoided, and the operation stability of the system is improved.

The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.

Claims (6)

1. A cascade air conditioning system optimization control method based on a water chilling unit energy consumption model is characterized by comprising the following steps:

step 1, collecting temperature, flow and ice tank ice amount data of a cascade air-conditioning refrigeration system, and estimating the ice melting amount and the maximum refrigeration load upper limit of a unit;

step 2, performing energy consumption model modeling on a base load water chilling unit and a dual-working-condition water chilling unit in the cascade air-conditioning refrigeration system by using a support vector regression, inputting variables of chilled water inlet and outlet water temperature, cooling water inlet and outlet water temperature and unit load, and outputting the variables of chilled water inlet and outlet water temperature, cooling water inlet and outlet water temperature and unit load as unit energy efficiency ratio;

step 3, calculating the actual unit operation number according to the estimated ice melting amount at the current moment, the maximum refrigerating load upper limit of the unit and the load demand, and realizing the group control of the unit;

step 4, distributing the base load unit, the double-working-condition unit and the ice melting load, realizing parameter optimization by combining a unit energy consumption model, and minimizing the operation cost while meeting the current load and boundary conditions;

step 5, setting an optimization updating period, and re-optimizing after each period is finished;

in the step 4, parameter optimization is realized by adopting an exhaustion method, and the optimization result is the set value of the outlet temperature of the base load water chilling unit;

the specific content of the step 4 is as follows:

setting temperature calculation step length, and enabling chilled water to enter plate exchange temperature T'_eoStep by T_eiRise to T_eoEstimating the unit energy efficiency ratio under each temperature calculation step length by combining the energy consumption models of the base load unit and the double-working-condition unit, and calculating the actual energy consumption under each temperature step length; considering the actual upper limit of the operation load and the operation load requirement of the unit, the actual alternative scheme meets the following conditions:

wherein F is the flow rate of the chilled water with the unit of kg/s;

wherein Q is_{max_b}The unit is kW which is the actual load upper limit of the base load unit; q_{max_d}The unit is the actual load upper limit of the double-working-condition unit, and the unit is kW; n is_bThe number of running water chilling units is the base load; n is_dThe number of running water chilling units is two; c is the specific heat capacity of water, and the value is 4.2kJ/(kg DEG C); q_rThe unit is kW which is the ice melting amount at the current moment; COP _ b is the energy efficiency ratio of the base load unit; t is_{ci_b}The water inlet temperature of cooling water of the base load unitIn units of; t is_{co_b}The outlet water temperature of cooling water of the base load unit is measured in unit; COP _ d is the energy efficiency ratio of the double-working-condition unit; t is_{ci_d}The unit of the inlet water temperature of the cooling water of the double-working-condition unit is; t is_{co_d}The outlet water temperature of the cooling water of the double-working-condition unit is measured in unit;

at this time, the unit device calculates the power consumption N 'at each temperature step'_eComprises the following steps:

gradually increasing T 'according to step length'_eoSeeking to make the power consumption N 'on the premise of satisfying the boundary condition'_eMinimum T'_eoI.e. the optimizing result.

2. The cascade air conditioning system optimization control method based on the water chilling unit energy consumption model as claimed in claim 1, characterized in that: in the step 1, the ice melting amount is estimated by adopting a weighted average method, and the weighting coefficient K per hour at the time of the power price and in the peak time period is set by taking the hour as a unit_iThen, the ice melting amount at the current moment is estimated as:

wherein Q is_rThe unit is kW which is the ice melting amount at the current moment; q_iceThe unit of the residual ice amount of the ice tank at the current moment is kWh; k_nowA current time ice melting weighting coefficient; now denotes the current time, and end denotes the last planned ice-melt time of the day.

3. The cascade air conditioning system optimization control method based on the water chilling unit energy consumption model as claimed in claim 1, characterized in that: in the step 1, the method for estimating the output of the water chilling unit comprises the following steps: calculating historical maximum refrigerating load Q 'of base-mounted water chiller unit'_{max_b}And historical maximum refrigerating load Q 'of double-working-condition water chilling unit'_{max_d}And then, the maximum refrigerating load upper limit of the unit is as follows:

wherein Q is_{max_b}The unit is kW which is the actual load upper limit of the base load unit; eta_bThe load safety factor of the base load unit is a constant of 0-1; q_{max_d}The unit is the actual load upper limit of the double-working-condition unit, and the unit is kW; eta_dThe load safety factor of the double-working-condition unit is a constant of 0-1.

4. The cascade air conditioning system optimization control method based on the water chilling unit energy consumption model as claimed in claim 1, characterized in that: in the step 2, when the base-load water chilling unit is modeled, the input variables adopt chilled water inlet/outlet water temperature, cooling water inlet/outlet water temperature and unit load, and the output is a unit energy efficiency ratio, namely:

COP_b＝f(T_ei，T′_eo，T_{ci_b}，T_{co_b}，Q_{e_b})

wherein COP _ b is the energy efficiency ratio of the base load unit; t is_eiThe temperature of the inlet water of the chilled water is the unit of ℃; t'_eoThe temperature of the outlet water of the chilled water is shown in unit of ℃; t is_{ci_b}The unit is the water inlet temperature of cooling water of the base load unit; t is_{co_b}The outlet water temperature of cooling water of the base load unit is measured in unit; q_{e_b}The unit is kW for the load of the base load unit;

when modeling the double-working-condition unit, the chilled water is uniformly used as a reference, the input quantity adopts plate exchange inlet and outlet water temperature, cooling water inlet and outlet water temperature and unit load, and the output is a unit energy efficiency ratio, namely:

COP_d＝f(T′_eo，T_eo，T_{ci_d}，T_{co_d}，Q_{e_d})

wherein COP _ d is the energy efficiency ratio of the double-working-condition unit; t'_eoThe temperature of inlet water is changed for the plate, and the unit is; t is_eoThe temperature of the outlet water is changed for the plate, and the unit is; t is_{ci_d}For cooling double-working-condition unitsThe water inlet temperature is measured in units of; t is_{co_d}The outlet water temperature of the cooling water of the double-working-condition unit is measured in unit; q_{e_d}The unit is kW for the load of the double-working-condition unit.

5. The cascade air conditioning system optimization control method based on the water chilling unit energy consumption model as claimed in claim 1, characterized in that: in the step 3, when the group control of the units is realized, a rolling calculation control strategy with the priority of ice melting and the priority of starting the base-load water chilling unit is adopted.

6. The optimal control method of the cascade air conditioning system based on the water chilling unit energy consumption model as claimed in claim 5, wherein: the specific content of the step 3 is as follows: operating the double-working-condition water chilling unit by n_dSet to zero, gradually increase the running number n of the base load water chilling unit_bIf the base load water chilling unit is fully opened and still does not meet the load requirement, a dual-working-condition water chilling unit is added, the base load unit is gradually increased from zero, and the circulation is performed until the load requirement is met:

Q_r+Q_{max_b}×n_b+Q_{max_d}×n_d＞Q

wherein Q is_rThe unit is kW for the ice melting amount; q_{max_b}The unit is kW which is the upper limit of the load of the base load unit; q_{max_d}The unit is the upper limit of the load of the double-working-condition unit, and the unit is kW; q is the actual load demand in kW.

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