A control-oriented aggregate modeling method for variable frequency air conditioning loads

Abstract

The present invention discloses a control-oriented aggregate modeling method for variable frequency air conditioner loads, comprising the following steps: (1) determining a controllable frequency range according to user comfort requirements, and obtaining a frequency control model based on a variable slope coefficient; (2) establishing an aggregate variable frequency air conditioner load model under dynamic response and a forced response load model of the aggregate variable frequency air conditioner according to the obtained frequency control model, and obtaining the corresponding frequency change rate; (3) discretizing the operating frequency of the variable frequency air conditioner compressor based on the finite difference method, and establishing an aggregate variable frequency air conditioner load model under dynamic response and forced response for control. Finally, the effectiveness of the aggregate variable frequency air conditioner load model is verified by simulation. The present invention realizes the unified dispatching and control of large-scale variable frequency air conditioners, and provides a theoretical basis for the decision-making of the dispatching center and the load agent.

Description

Technical Field

[0001] The present invention belongs to the field of power system auxiliary services and demand-side response, and relates to an aggregate modeling method for temperature control loads, in particular to an aggregate modeling method for control-oriented variable frequency air-conditioning loads. Background Art

[0002] The large-scale access of new energy sources represented by wind power and photovoltaic power has put forward higher requirements on the adjustable capacity of the power grid. The traditional method of increasing spare capacity to maintain the balance of supply and demand in the power system not only increases the operating cost of the system, but also has low efficiency. With the development of the Internet of Things and smart grid technology, demand-side load, as an excellent dispatchable resource, can play an increasingly important role in improving the reliability and economy of the power system by providing fast load tracking, spinning reserve and other auxiliary services.

[0003] Inverter air conditioners are a demand-side resource with great dispatchable potential and good energy storage characteristics. Inverter air conditioners maintain room temperature stability through continuous changes in frequency and power. They have faster response speeds and lower energy consumption at low frequencies. Therefore, the aggregate modeling of large-scale inverter air conditioners is one of the core technologies for studying the various auxiliary services that inverter air conditioners provide to power systems, and plays an important role in realizing the participation of inverter air conditioners in demand response. Summary of the invention

[0004] The purpose of the present invention is to establish a control-oriented aggregate variable frequency air conditioner load model to solve the problem of ignoring the frequency operation characteristics of the variable frequency air conditioner group during the demand response process, that is, failing to accurately track the temperature setting value or treating the frequency change rate as a constant. The present invention provides a variable frequency air conditioner frequency control model suitable for participating in demand response. The control strategy not only takes into account user comfort, but also avoids load rebound; and based on this, a control-oriented aggregate variable frequency air conditioner load model is derived and established, and finally the effectiveness of the aggregate variable frequency air conditioner load model is verified through simulation.

[0005] The problem described in the present invention is achieved by the following technical solution:

[0006] A control-oriented variable frequency air conditioning load aggregation modeling method includes the following steps:

[0007] (1) Determine the controllable frequency range according to user comfort requirements and obtain a frequency control model based on a variable slope coefficient;

[0008] (2) establishing a dynamic response aggregate variable frequency air conditioning load model and a forced response load model of the aggregate variable frequency air conditioning according to the obtained frequency control model, and obtaining the corresponding frequency change rate;

[0009] (3) Based on the finite difference method, the operating frequency of the variable frequency air-conditioning compressor is discretized, and an aggregated variable frequency air-conditioning load model under control-oriented dynamic response and forced response is established.

[0010] Specifically, in step (1), the frequency control model based on the variable slope coefficient is:

[0011]

[0012] Where: f(Hz) is the operating frequency of the variable frequency air conditioner compressor, f max (Hz) is its maximum operating frequency, u and v are constants, f set (Hz) is the operating frequency of the compressor running stably at the temperature setting value, f min =((f max -f set ) / v)·u+f set is the minimum operating frequency of the variable frequency air conditioner compressor, k f =(f max -f set ) / u is the slope of the straight line, ΔT(℃) is the indoor temperature T in With the set temperature T set From formula (1), it can be seen that the change of temperature setting value will affect the change of slope, thereby changing the relationship between f-ΔT and rapidly changing the change of frequency. When the frequency setting value changes, according to the user's comfort requirements, the lowest operating frequency f that the user can accept is set. user , the frequency control model described in formula (1) becomes:

[0013]

[0014] f user Different values ​​can be set according to the comfort requirements of different users. At this time, the slope of the frequency expression in the load model of a single variable-frequency air conditioner no longer changes.

[0015] Specifically, in step (2), the frequency change rate of the variable frequency air conditioner under dynamic response is:

[0016]

[0017] Where: k f is the slope in the frequency control model, a (kW / Hz) and b (kW) are the expressions for the cooling capacity of the variable frequency air conditioner Q AC = constant coefficient in af+b, T out and T inare the outdoor temperature and indoor temperature respectively, R and C are the equivalent thermal resistance and equivalent heat capacity of the room respectively, the growth rate of load concentration can be expressed by the difference between the inflow and outflow divided by the frequency change, and the inflow is stipulated to be positive and the outflow is negative, and the aggregate variable frequency air conditioning load model under dynamic response can be obtained:

[0018]

[0019] Where: X(t,f) is the load quantity of the variable frequency air conditioner group at frequency f at time t, λ f is the frequency change rate under dynamic response; when the frequency setting value f set When a change occurs, the rate of change of frequency under forced response is:

[0020]

[0021] in: is the rate of change of the frequency setting value. When the frequency setting value changes, the forced response load model of the aggregate variable frequency air conditioner is:

[0022]

[0023] Where: u is the frequency change rate under forced response.

[0024] Specifically, in step (3), the finite difference method is used to establish an aggregate variable frequency air conditioning load model under control-oriented dynamic response and forced response, and the specific process is as follows:

[0025] Discretize the operating frequency of the variable frequency air conditioner compressor, and replace the frequency of each discrete interval with the middle value of the frequency in this interval, and use the initial value T set by the temperature set0 Approximately T in , use the frequency setting value initial value f set0 Approximately replace f set , from which the discretized frequency change rate can be obtained:

[0026]

[0027] Where: f i is the middle value of the ith frequency interval, λ fi and λ ui are the frequency change rates of the aggregate variable frequency air conditioner load model and the forced response load model of the aggregate variable frequency air conditioner under the discretized dynamic response, respectively;

[0028] In the discrete process, when the load transfer rate under the forced response is negative relative to the dynamic response process, that is, λ u<0, it is necessary to select the forward difference of the space quantity, otherwise it is necessary to select the backward difference of the space quantity. The following is a control-oriented aggregate variable frequency air conditioning load model established for different situations;

[0029] Case 1: Assuming the frequency setting value f set Falling on the Mth segment, according to the operating characteristics of the variable frequency air conditioner group, in [f min ,f set ) is positive, and the load flow direction in the range of (f set ,f max ] is negative, and the aggregate variable frequency air conditioning load model in formula (4) is discretized to obtain the aggregate variable frequency air conditioning load model expression under control-oriented dynamic response:

[0030]

[0031] Where: m (kW / Hz) and n (kW) are the power expressions of variable frequency air conditioners P AC = constant coefficients in mf+n, x(t)=[x1(t),x2(t),…,x N (t)] T is an N×1 state vector, A1 is an N×N state matrix, B1=0, E=[1,1,…,1] 1×N is a 1×N output vector, y(t) represents the total power of the aggregate variable frequency air conditioner, C matrix is ​​an N×N state output matrix, and the expressions of A1 and C are:

[0032]

[0033] Case 2: When demand response requires load reduction, in order to ensure the effectiveness of load reduction, it is assumed that all load flows are negative, that is, λ u <0, discretize the forced response load model of the aggregate variable frequency air conditioner in formula (6), and obtain the load model expression of the aggregate variable frequency air conditioner during the load reduction in the forced response stage for control:

[0034]

[0035] Among them, A2 is the N×N state matrix, B2 is the N×N input matrix, and A2 and B2 are:

[0036]

[0037]

[0038] Case 3: Contrary to the load reduction process, when the demand response requires an increase in load, in order to ensure the effectiveness of load reduction, it is assumed that all load flows are positive, that is) u> 0, discretize the forced response load model of the aggregate variable frequency air conditioner in formula (6), and obtain the load model expression of the aggregate variable frequency air conditioner when the load increases in the forced response stage for control:

[0039]

[0040] Among them, A3 is the N×N state matrix, B3 is the N×N input matrix, and the expressions of A3 and B3 are:

[0041]

[0042] Considering the user's comfort requirements, it is necessary to limit the rate of change of the frequency setting value. min <f user When , the f-ΔT relationship becomes equation (2), and the above equation (7) should be updated according to the following equation:

[0043]

[0044] Where: fi and λ ui f min <f user The frequency change rate of the aggregate variable frequency air conditioning load model and the forced response load model of the aggregate variable frequency air conditioning under the dynamic response.

[0045] The technical solution provided by the present invention has the following beneficial effects:

[0046] The frequency control model based on variable slope coefficient is based on changing the f-ΔT electrical quantity relationship, which can accurately track the temperature setting value. The change of slope can significantly adjust the power output and effectively improve the demand response effect. A finite-dimensional state space model of aggregated variable frequency air conditioning load under dynamic response and forced response is established, and user comfort is considered to update the model parameters, realizing the control of variable frequency air conditioning load in a wide frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will be further described below in conjunction with the accompanying drawings:

[0048] Figure 1 is a flow chart of the present invention;

[0049] Figure 2 It is a schematic diagram of the variable slope coefficient frequency model;

[0050] Figure 3 Schematic diagram of uncontrolled free response process;

[0051] Figure 4 This is a schematic diagram of the load reduction process in the forced response stage;

[0052] Figure 5 Add a load process diagram for the forced response stage;

[0053] Figure 6 This is a comparison curve between the aggregate variable frequency air conditioning load model and the Monte Carlo simulation. Specific implementation plan

[0054] like Figure 1 As shown, the present invention proposes a control-oriented variable frequency air conditioning load aggregation modeling method. Figures 2 to 6 , which is specifically described in the following steps. The theoretical derivation of the present invention is described in detail in the following description, but the present invention can be implemented in many different ways than described here, so the present invention is not limited to the specific implementation disclosed below.

[0055] Step 1: Determine the controllable frequency range according to user comfort requirements and obtain a frequency control model based on a variable slope coefficient.

[0056] like Figure 2 As shown, taking load reduction as an example, due to the frequency setting value f set Moving downward along the vertical line of ΔT=0, curve l1 becomes curve l2. The frequency reduction of the variable frequency air conditioner load corresponding to the curve includes two parts: 1) from A to B, which describes the thermodynamic change process, and the reduction is Δf1; 2) from B to C, which represents the f set The frequency change caused by the change is reduced by Δf2, from which the frequency control model based on the variable slope coefficient can be obtained as follows:

[0057]

[0058] Where: f(Hz) is the operating frequency of the variable frequency air conditioner compressor, f max (Hz) is its maximum operating frequency, u and v are constants, f set (Hz) is the operating frequency of the compressor running stably at the temperature setting value, f min =((f max -f set ) / v)·u+f set is the minimum operating frequency of the variable frequency air conditioner compressor, k f =(f max -f set ) / u is the slope of the straight line, ΔT(℃) is the indoor temperature T in With the set temperature T set From formula (1), it can be seen that the change of temperature setting value will affect the change of slope, thereby changing the relationship between f-ΔT and rapidly changing the change of frequency. When the frequency setting value changes, according to the user's comfort requirements, the lowest operating frequency f that the user can accept is set. user, the frequency control model described in formula (1) becomes:

[0059]

[0060] f user Different values ​​can be set according to the comfort requirements of different users. At this time, the slope of the frequency expression in the load model of a single variable-frequency air conditioner no longer changes.

[0061] Step 2: The dynamic change process of the variable frequency air conditioner load is described by the equivalent thermodynamic parameter (ETP) model, and a single variable frequency air conditioner load model is established according to the frequency control strategy based on the variable slope coefficient.

[0062]

[0063] Where: Refrigeration capacity Q AC and air conditioning power P AC is a linear function of the compressor operating frequency. The frequency f can be obtained according to equations (18) and (19). a, b, m and n are constant coefficients. The thermodynamic dynamic characteristics of the variable frequency air conditioner are simulated according to the equivalent thermodynamic parameter (ETP) model:

[0064]

[0065] Where: T out and T in are the outdoor and indoor temperatures respectively, R and C are the equivalent thermal resistance and equivalent heat capacity of the room respectively. When ΔT<u, the compressor operates at the minimum frequency f min When ΔT>u, the compressor operates at the highest frequency f max During the demand response phase, the variable frequency air conditioning load participates in the response in the following ways:

[0066]

[0067] Where ΔP up and ΔP dn are the target power to be increased and reduced during demand response, respectively, and f target Corresponding to ΔP up and ΔP dn The target frequency is set to

[0068] Step 3: Establish the aggregate variable frequency air conditioning load model under dynamic response and the forced response load model of aggregate variable frequency air conditioning, and obtain the corresponding frequency change rate.

[0069]

[0070] Among them, X(f,t) is the load quantity of the variable frequency air conditioner group at frequency f at time t, F(f,t) is the load flow, is the change of frequency over time, which is called the flow rate of the load. Then the frequency change rate of the aggregate variable frequency air conditioning load model under dynamic response is:

[0071]

[0072] The growth rate of load concentration can be expressed by dividing the difference between inflow and outflow by the frequency change, and the inflow is defined as positive and the outflow is defined as negative. The aggregate variable frequency air conditioning load model under dynamic response can be obtained:

[0073]

[0074] Where: f is the frequency change rate under dynamic response; when the frequency setting value f set When a change occurs, according to the conservation relationship, the increment of X(f,t) is determined by the net increment and external factors. At this time, the load flow can be written as:

[0075]

[0076] The frequency change rate under forced response is:

[0077]

[0078] It can be concluded that when the frequency setting value changes, the forced response load model of the aggregate variable frequency air conditioner is:

[0079]

[0080] Where: u is the frequency change rate under forced response.

[0081] Step 4: Discretize the operating frequency of the variable frequency air conditioner compressor based on the finite difference method, and establish an aggregated variable frequency air conditioner load model under control-oriented dynamic response and forced response.

[0082] After discretizing the operating frequency of the variable frequency air conditioner compressor, we can get:

[0083]

[0084] Where: N is [f min ,f max ] is the number of discretized intervals, df is the interval length, the middle value of each frequency interval in formula (29) is used to replace the frequency of this interval, and the initial value T of the temperature setting is used. set0 Approximately T in , use the frequency setting value initial value f set0 Approximately replace f set , from which we can get the discretized frequency change rate:

[0085]

[0086] Where: f i is the middle value of the ith frequency interval, λ fi and λ ui are the frequency change rates of the aggregate variable frequency air conditioner load model and the forced response load model of the aggregate variable frequency air conditioner under the discretized dynamic response, respectively;

[0087] In the discrete process, when the load transfer rate under the forced response is negative relative to the dynamic response process, that is, λ u <0, it is necessary to select the forward difference of the space quantity, otherwise it is necessary to select the backward difference of the space quantity. The following is a control-oriented aggregate variable frequency air conditioning load model for different situations;

[0088] Case 1: If Figure 3 As shown, assuming the frequency setting value f set Falling on the Mth segment, according to the operating characteristics of the variable frequency air conditioner group, at this time [f min ,f set ) is positive, and the load flow direction in the range of (f set ,f max ] is negative, and the aggregate variable frequency air conditioning load model in formula (25) can be obtained by discretizing it:

[0089]

[0090] x i (t) represents the number of loads in the i-th segment at time t, Δf is the discretized frequency length. According to the flow conservation law, the x1 and x2 nodes only have outflows at this time, and the M node only has inflows, that is, all loads eventually flow to the frequency setting value. The boundary conditions of the aggregate variable frequency air conditioning load model under uncontrolled dynamic response can be obtained as follows:

[0091]

[0092] From this, we can get the expression of the aggregate variable frequency air conditioning load model under control-oriented dynamic response:

[0093]

[0094] where x(t)=[x1(t),x2(t),…,x N (t)] T is an N×1 state vector, A1 is an N×N state matrix, B1=0, E=[1,1,…,1] 1×N is a 1×N output vector, y(t) represents the total power of the aggregate variable frequency air conditioner, C matrix is ​​an N×N state output matrix, and the expressions of A1 and C are:

[0095]

[0096] Case 2: If Figure 4 As shown in the figure, when the demand response requires load reduction, in order to ensure the effectiveness of load reduction, it is assumed that all load flows are negative, that is, λ u <0, the forced response load model of the aggregate variable frequency air conditioner in formula (11) can be discretized to obtain:

[0097]

[0098] According to the flow conservation principle, the x1 node only flows into the flow, and x N The node only flows out, that is, all loads eventually flow to the node with the minimum frequency. The boundary conditions of the load reduction model in the forced response stage can be obtained as follows:

[0099]

[0100] Therefore, the aggregate variable frequency air conditioning load model expression for load reduction in the forced response stage for control can be obtained:

[0101]

[0102] Among them, A2 is the N×N state matrix, B2 is the N×N input matrix, and A2 and B2 are:

[0103]

[0104]

[0105] Case 3: If Figure 5 As shown in the figure, in contrast to the load reduction process, when the demand response requires an increase in load, in order to ensure the effectiveness of load reduction, it is assumed that all load flows are positive, i.e., λ u > 0, discretizing the forced response load model of the aggregate variable frequency air conditioner in formula (28) yields:

[0106]

[0107] According to the law of conservation of flow, x N The node only has inflow traffic, and the x1 node only has outflow traffic, that is, all loads eventually flow to the node with the maximum frequency. The model boundary condition of load increase in the forced response stage can be obtained as follows:

[0108]

[0109] From this, we can get the expression of the aggregate variable frequency air conditioning load model when the load increases in the forced response stage for control:

[0110]

[0111] Among them, A3 is the N×N state matrix, B3 is the N×N input matrix, and the expressions of A3 and B3 are:

[0112]

[0113] Considering the user's comfort requirements, it is necessary to limit the rate of change of the frequency setting value. min <f user When , the f-ΔT relationship becomes equation (19), and the above equation (30) should be updated according to the following equation.

[0114]

[0115] Where: fi and λ ui f min <f user The frequency change rate of the aggregate variable frequency air conditioning load model and the forced response load model of the aggregate variable frequency air conditioning under the dynamic response.

[0116] In order to verify the effectiveness of the aggregate variable frequency air conditioner load model proposed in this paper, the Monte Carlo method is used to simulate the actual operation of a variable frequency air conditioner group consisting of 3000 variable frequency air conditioners. The aggregate variable frequency air conditioner can change the load of the variable frequency air conditioner at any time by changing f set The output power is changed according to the value of the frequency setting value. In the simulation, the frequency setting value excitation signal is reduced by 1.8Hz at a rate of 0.1Hz / h in 0.1h, and then restored to the initial frequency setting value at the same rate in 0.3h. The comparison between the aggregate variable frequency air conditioning load model and the Monte Carlo simulation results is as follows Figure 6 The parameters used in the simulation are shown in Table 1:

[0117] Table 1 Parameter settings of variable frequency air conditioner and user room

[0118]

[0119] Depend on Figure 6 The simulation results show that in the forced response process of reducing or increasing load, the aggregate variable frequency air conditioning load model not only has a good response speed, but also has a high model accuracy. The error of reducing and increasing power is very small, which fully meets the accuracy requirements of power system demand response. It is only because of the approximation in formula (30), |λ u | is slightly smaller than the true value. In the uncontrolled dynamic response process, the power change is slightly delayed compared with the Monte Carlo simulation, but the final power curve is still stable near the Monte Carlo simulation result, and there is no load rebound after the frequency is restored to the initial value.

Claims

1. A control-oriented variable frequency air conditioning load aggregation modeling method, characterized by: The steps include: (1) Determine the controllable frequency range according to user comfort requirements and obtain a frequency control model based on a variable slope coefficient; (2) establishing a dynamic response aggregate variable frequency air conditioning load model and a forced response load model of the aggregate variable frequency air conditioning according to the obtained frequency control model, and obtaining the corresponding frequency change rate; (3) Based on the finite difference method, the operating frequency of the variable frequency air conditioner compressor is discretized, and an aggregate variable frequency air conditioner load model under control-oriented dynamic response and forced response is established; In the step (1), the frequency control model based on the variable slope coefficient is: Where: f(Hz) is the operating frequency of the variable frequency air conditioner compressor, f max (Hz) is its maximum operating frequency, u and v are constants, f set (Hz) is the operating frequency of the compressor running stably at the temperature setting value, f min =((f max -f set ) / v)·u+f set is the minimum operating frequency of the variable frequency air conditioner compressor, k f =(f max -f set ) / u is the slope of the straight line, ΔT(℃) is the indoor temperature T in With the set temperature T set From formula (1), we can see that the change of temperature setting value will affect the change of slope, thus changing the relationship between f-ΔT and rapidly changing the frequency. When the frequency setting value changes, according to the user's comfort requirements, the lowest operating frequency f that the user can accept is set. user , the frequency control model described in formula (1) becomes: f user Different values ​​can be set according to the comfort requirements of different users. At this time, the slope of the frequency expression in the variable frequency air conditioning load model will no longer change; In step (2), the frequency change rate of the variable frequency air conditioner under dynamic response is: Where: k f is the slope in the frequency control model, a (kW / Hz) and b (kW) are the expressions for the cooling capacity of the variable frequency air conditioner Q AC = constant coefficient in af+b, T out and T in are the outdoor temperature and indoor temperature respectively, R and C are the equivalent thermal resistance and equivalent heat capacity of the room respectively, the growth rate of load concentration can be expressed by the difference between the inflow and outflow divided by the frequency change, and the inflow is stipulated to be positive and the outflow is negative, and the aggregate variable frequency air conditioning load model under dynamic response can be obtained: Where: X(t,f) is the load quantity of the variable frequency air conditioner group at frequency f at time t, λ f is the frequency change rate under dynamic response; when the frequency setting value f set When a change occurs, the rate of change of frequency under forced response is: in: is the rate of change of the frequency setting value. When the frequency setting value changes, the forced response load model of the aggregate variable frequency air conditioner is: Where: u is the frequency change rate under forced response; In the step (3), the finite difference method is used to establish an aggregate variable frequency air conditioning load model under control-oriented dynamic response and forced response. The specific process is as follows: Discretize the operating frequency of the variable frequency air conditioner compressor, and replace the frequency of each discrete interval with the middle value of the frequency in this interval, and use the initial value T set by the temperature set0 Approximately T in , use the frequency setting value initial value f set0 Approximately replace f set , from which the discretized frequency change rate can be obtained: Where: f i is the middle value of the ith frequency interval, λ fi and λ ui are the frequency change rates of the aggregate variable frequency air conditioner load model and the forced response load model of the aggregate variable frequency air conditioner under the discretized dynamic response, respectively; In the discrete process, when the load transfer rate under the forced response is negative relative to the dynamic response process, that is, λ u <0, it is necessary to select the forward difference of the space quantity, otherwise it is necessary to select the backward difference of the space quantity. The following is a control-oriented aggregate variable frequency air conditioning load model established for different situations; Case 1: Assuming the frequency setting value f set Falling on the Mth segment, according to the operating characteristics of the variable frequency air conditioner group, in [f min ,f set ) is positive, and the load flow direction in the range of (f set ,f max ] is negative, and the aggregate variable frequency air conditioning load model in formula (4) is discretized to obtain the aggregate variable frequency air conditioning load model expression under control-oriented dynamic response: Where: m (kW / Hz) and n (kW) are the power expressions of variable frequency air conditioners P AC = constant coefficients in mf+n, x(t)=[x1(t),x2(t),…,x N (t)] T is an N×1 state vector, A1 is an N×N state matrix, B1=0, E=[1,1,…,1] 1×N is a 1×N output vector, y(t) represents the total power of the aggregate variable frequency air conditioner, C matrix is ​​an N×N state output matrix, and the expressions of A1 and C are: Case 2: When demand response requires load reduction, in order to ensure the effectiveness of load reduction, it is assumed that all load flows are negative, that is, λ u <0, discretizing the forced response load model of the aggregate variable frequency air conditioner in formula (6) can obtain the load model expression of the aggregate variable frequency air conditioner during the load reduction in the forced response stage for control: Among them, A2 is the N×N state matrix, B2 is the N×N input matrix, and A2 and B2 are: Case 3: Contrary to the load reduction process, when the demand response requires an increase in load, in order to ensure the effectiveness of load reduction, it is assumed that all load flows are positive, that is, λ u > 0, discretize the forced response load model of the aggregate variable frequency air conditioner in formula (6), and obtain the load model expression of the aggregate variable frequency air conditioner when the load increases in the forced response stage for control: Among them, A3 is the N×N state matrix, B3 is the N×N input matrix, and the expressions of A3 and B3 are: Considering the user's comfort requirements, it is necessary to limit the rate of change of the frequency setting value. min <f user When , the f-ΔT relationship becomes equation (2), and the above equation (7) should be updated according to the following equation: Where: fi and λ ui f min <f user The frequency change rate of the aggregate variable frequency air conditioning load model under the dynamic response and the forced response load model of the aggregate variable frequency air conditioning.

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