A control method of a variable air volume ventilation air conditioner and an air conditioning system

Abstract

The application discloses a control method and air conditioning system of a variable air volume ventilation air conditioner, and relates to the technical field of heating ventilation control. The control method collects real-time evaporation temperature of refrigerant, updates target evaporation temperature, inputs total load, real-time evaporation temperature and target evaporation temperature into a load controller, calculates speed error of a compressor, then inputs real-time current and speed error into a speed controller, and updates input current of the compressor. In the control process of the variable air volume ventilation air conditioner, the feedforward control part of the load controller is constantly updated. Since the real-time updated feedforward control part contains magnetic resistance change of the compressor itself, the driving error is calculated when the compressor is in sleep, the magnetic resistance coefficient of the speed controller is updated, and the feedforward control part is initialized according to the updated magnetic resistance coefficient, so that the control precision of the air conditioner compressor is improved.

Description

Technical Field

[0001] This invention relates to the field of HVAC control technology, and in particular to a control method and air conditioning system for variable air volume ventilation and air conditioning. Background Technology

[0002] Existing building HVAC systems typically employ variable frequency closed-loop control technology, which adjusts the compressor's output parameters based on feedback from the cooling load at the output end. However, in this closed-loop feedback control system, compressor parameters inevitably fluctuate. Chinese patent application CN201811529668.X discloses a method and apparatus for controlling the speed of an air conditioning compressor. This method calculates the difference between the target angular velocity fluctuation and the first angular velocity output of the phase-locked loop regulator, obtaining a filtered angular velocity after filtering out at least some of the angular velocity fluctuation. This filtered angular velocity is then input to the speed loop regulator in the compressor control speed loop to obtain the output torque of the speed loop regulator. This method improves the effectiveness of suppressing air conditioning compressor speed fluctuations by using the angular velocity difference. This technical solution mainly considers the impact of the operating environment on the equipment's output values. As the air conditioning system continues to operate, the parameters of the hardware gradually change due to factors such as refrigerant blockage and magnetic reluctance drift. Pre-tuned parameters of the speed loop regulator, current regulator, etc., can actually affect the accuracy of subsequent system response. Therefore, further improvements to the existing technology are necessary. Summary of the Invention

[0003] To address the shortcomings of the existing technology, this invention proposes a control method and air conditioning system for variable air volume ventilation air conditioning. This invention continuously adjusts the control parameters of the load controller and speed controller according to the operating conditions to improve the control accuracy of the compressor.

[0004] The technical solution of this invention is implemented as follows:

[0005] A control method for a variable air volume (VAV) ventilation and air conditioning system includes the following steps:

[0006] Step 1: Receive the start signal, determine the target evaporation temperature of the refrigerant, identify the start angle of the compressor rotor, and generate the start speed of the compressor;

[0007] Step 2: Input the starting speed to the speed controller to generate the compressor input current. The compressor pumps refrigerant to the evaporator through the expansion valve of each indoor unit to maintain the target evaporation temperature.

[0008] Step 3: Collect the valve opening of the expansion valve of each indoor unit, and generate the total load based on the multiple valve openings;

[0009] Step 4: Collect the real-time evaporation temperature of the refrigerant, update the target evaporation temperature, input the total load, real-time evaporation temperature and target evaporation temperature into the load controller, and calculate the compressor speed error;

[0010] Step 5: Collect the real-time current of the compressor, input the real-time current and speed error to the speed controller, and update the compressor's input current;

[0011] Step 6: Combine the total load at multiple sampling times to update the feedforward control unit of the load controller. If a standby signal is received, disconnect the input current and proceed to step 7; otherwise, return to step 3.

[0012] Step 7: Identify the first braking angle of the rotor, predict the second braking angle of the rotor based on the compressor's starting angle and real-time speed, update the reluctance control unit of the speed controller based on the first and second braking angles, initialize the feedforward control unit of the load controller, and end the task.

[0013] In this invention, in step 1, pulse voltages are injected sequentially into the six magnetic pole directions of the compressor, the peak current in each direction is detected, the direction of the maximum current is extracted to generate an interval angle, the first peak current and the second peak current are extracted according to the direction of the maximum current to generate an offset angle, and the starting angle is calculated by combining the interval angle and the offset angle.

[0014] In this invention, in step 3, the flow rate of the indoor unit is calculated based on the valve opening of the indoor unit, the supply water temperature and return water temperature are collected, the terminal load of the indoor unit is calculated, and the total load of the compressor is generated based on the terminal loads of multiple indoor units.

[0015] In this invention, in step 4, the load controller includes a feedforward control unit and a temperature PI unit. It calculates the temperature error between the target evaporation temperature and the real-time evaporation temperature, inputs the temperature error to the temperature PI unit to generate a speed adjustment amount, calculates the compressor's feedforward speed by combining the speed adjustment amount and the real-time speed, generates the compressor's feedforward load, generates a load error by combining the feedforward load and the total load, inputs the load error to the feedforward control unit to generate a speed feedforward amount, and generates a speed error by combining the speed feedforward amount and the speed adjustment amount.

[0016] In this invention, in step 5, the speed controller includes a reluctance control unit and a DC PI unit. The reluctance control unit generates a reluctance component, updates the torque constant of the DC PI unit by combining the permanent magnet component and the reluctance component, inputs the speed error to the DC PI unit to generate a direct-axis adjustment amount, and generates an input current by combining the direct-axis adjustment amount and the real-time current.

[0017] In this invention, in step 6, the feedforward control unit has a feedforward gain, extracts multiple sampling moments when the total load variable is less than a threshold, and updates the feedforward gain by combining the temperature error and the speed feedforward amount of the multiple sampling moments.

[0018] In this invention, in step 7, the real-time current and real-time quadrature axis component of the compressor are collected, the reluctance coefficient of the generated reluctance component is adjusted, the displacement influence number of the compressor is calculated based on the reluctance coefficient, and the displacement influence number is deleted from the feedforward gain.

[0019] An air conditioning system implementing the control method for the variable air volume (VAV) ventilation air conditioning system includes: an outdoor unit, multiple indoor units, and a control subsystem. The outdoor unit includes a compressor, and the indoor units include an expansion valve and an evaporator. The compressor is configured to pump refrigerant to the evaporator via the expansion valve. The control subsystem includes:

[0020] The indoor unit control unit is configured to control the valve opening of the expansion valve;

[0021] The outdoor unit control unit is configured to update the target evaporation temperature of the outdoor unit.

[0022] The compressor control unit is configured to update the compressor's input current based on the load controller and speed controller.

[0023] Upon receiving a start signal, the compressor control unit periodically updates the load controller; upon receiving a standby signal, the compressor control unit updates the speed controller and initializes the load controller.

[0024] In this invention, the control subsystem further includes: a first temperature sensor and a valve sensor installed in each indoor unit, and a second temperature sensor and a pressure sensor installed in the outdoor unit.

[0025] The first temperature sensor is configured to collect the supply and return water temperatures of the indoor unit; the valve sensor is configured to collect the valve opening degree of the expansion valve; the second temperature sensor is configured to collect the outdoor temperature; and the pressure sensor is configured to collect the real-time evaporation pressure of the refrigerant and convert it into real-time evaporation temperature.

[0026] The indoor unit control unit generates the terminal load of each indoor unit based on the supply water temperature, return water temperature, and valve opening.

[0027] The outdoor unit control unit updates the target evaporation temperature of the outdoor unit according to the outdoor temperature, and generates the total load according to multiple sets of terminal loads;

[0028] The load controller updates the speed error based on the total load, real-time evaporation temperature, and target evaporation temperature, while the speed controller updates the input current based on the speed error.

[0029] In this invention, the control subsystem further includes: an encoder and a current excitation unit installed on the compressor. The encoder is configured to acquire the real-time rotational speed of the compressor, and the current excitation unit is configured to acquire the rotor's starting angle and first braking angle.

[0030] The compressor control unit updates the feedforward control unit of the load controller based on the total load at multiple sampling times; the compressor control unit also calculates the drive error and updates the reluctance coefficient of the speed controller.

[0031] The control method and air conditioning system for variable air volume (VAV) ventilation air conditioning, as described in this invention, have the following beneficial effects: This invention outputs the target speed of the compressor through a load controller, and then generates an input current through a speed controller. When the indoor unit's airflow changes, the feedforward control unit of the load controller can provide a feedforward amount close to the total load, allowing the cooling output value to quickly follow changes in cooling demand. In the control process of the VAV ventilation air conditioning, this invention continuously updates the feedforward control unit. Because the real-time updated feedforward control unit includes the compressor's own reluctance changes, it calculates the drive error when the compressor is in sleep mode, updates the reluctance coefficient of the speed controller, and initializes the feedforward control unit based on the updated reluctance coefficient. This avoids the compressor's operating conditions affecting the feedforward amount predicted by the feedforward control unit, further improving the control accuracy of the VAV ventilation air conditioning. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the outdoor unit of the air conditioning system of the present invention;

[0033] Figure 2 This is a schematic diagram of the indoor unit of the air conditioning system of the present invention;

[0034] Figure 3 This is a flowchart of a control method for a variable air volume ventilation and air conditioning system according to the present invention;

[0035] Figure 4 This is a control principle diagram of the compressor of the present invention;

[0036] Figure 5 This is a schematic diagram of the compressor structure of the present invention;

[0037] Figure 6 This is a schematic diagram of the magnetic poles of the compressor rotor of the present invention;

[0038] Figure 7 This is a schematic diagram of the load controller of the present invention;

[0039] Figure 8 This is a schematic diagram of the temperature PI section of the present invention;

[0040] Figure 9 This is a schematic diagram of the speed controller of the present invention;

[0041] Figure 10 This is a schematic diagram of the DC PI section of the present invention;

[0042] Figure 11This is a curve of a preferred real-time evaporation temperature according to the present invention;

[0043] Figure 12 This is a preferred real-time rotational speed curve of the present invention;

[0044] Figure 13 This is a preferred input current curve of the present invention;

[0045] Figure 14 This is a block diagram of an air conditioning system that implements the variable air volume ventilation and air conditioning control method of the present invention.

[0046] The reference numerals in the attached drawings are as follows: condenser 110, compressor 120, stator 121, permanent magnet pole 122, rotor 123, gate valve 130, booster 140, expansion valve 210, evaporator 220, filter 230, coil 240, fan 250, air inlet 260, air return outlet 270, and three-way valve 280. Detailed Implementation

[0047] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments. Example 1

[0048] like Figures 1 to 13 As shown, the control method for variable air volume (VAV) ventilation and air conditioning systems of the present invention is used for HVAC regulation in building VRF systems. In VRF systems, the terminal load of the indoor unit changes continuously, causing the refrigerant flow rate and temperature entering the evaporator of the indoor unit to change continuously. The compressor needs to update its speed in real time to operate at the target evaporation temperature. The present invention outputs the compressor speed through a load controller and then generates current through a speed controller. When the indoor unit load changes, the feedforward control unit of the load controller can provide a feedforward amount close to the load variable, so that the cooling output value can quickly follow the change in indoor unit load. The control method for VRF ventilation and air conditioning systems in this embodiment includes the following steps.

[0049] Step 1: Receive the start signal, determine the target evaporation temperature of the refrigerant, identify the start-up angle of the compressor rotor, and generate the compressor's start-up speed. The target evaporation temperature is usually determined by the outdoor temperature, operating conditions, and cooling demand, and is typically between 2°C and 8°C. Maintaining the air conditioning system at the target evaporation temperature ensures stable operation with low power consumption. The core objective of the air conditioning system's cooling control is to continuously bring the real-time evaporation temperature closer to the target evaporation temperature. The start-up speed is the minimum speed at which the compressor can operate stably, determined by the compressor's parameters. The minimum speed for consumer-grade compressors is typically 360 rpm. In this embodiment, pulse voltages are injected sequentially into the six magnetic pole directions of the compressor, the peak current in each direction is detected, the direction of the maximum current is extracted to generate an interval angle, and the first and second peak currents are extracted based on the direction of the maximum current to generate an offset angle. The start-up angle is calculated by combining the interval angle and the offset angle. The optimal identification steps for the start-up angle are described in Embodiment 2.

[0050] Step 2: The starting speed is input to the speed controller to generate the compressor's input current. The compressor pumps refrigerant to the evaporator through the expansion valve of each indoor unit to maintain the target evaporation temperature. In a multi-split air conditioner, each indoor unit has an evaporator. The flow rate of refrigerant entering the evaporator is controlled by the expansion valve, thereby regulating the temperature of the HVAC zone. The starting speed is input to the speed controller to generate a direct-axis target quantity, which is then converted into an input current through two-phase transformation and vector pulse width modulation. The speed controller control process is as described in Example 4.

[0051] Step 3: Collect the valve opening of the expansion valve of each indoor unit, and generate the total load based on the multiple valve openings. For a multi-split unit with K indoor units, first calculate the total load based on the valve opening A of indoor unit k. k Calculate flow rate m k , C1 is the refrigerant flow coefficient. ρ is the density of the refrigerant, determined by the type of refrigerant. P in P out These are the inlet and outlet pressures of the refrigerant at the evaporator, respectively. The supply water temperature T1 and return water temperature T2 are collected to calculate the terminal load Q of the indoor unit. k Q k =C2ρm k (T2-T1), where C2 is the specific heat capacity of the refrigerant. The total compressor load Q is generated based on the terminal loads of multiple indoor units. load , .

[0052] Step 4: Collect the real-time evaporation temperature of the refrigerant, update the target evaporation temperature, and input the total load, real-time evaporation temperature, and target evaporation temperature into the load controller to calculate the compressor speed error. The load controller includes a feedforward control unit G1(ΔQ) and a temperature PI unit G2(ΔT). G1() is the transfer function of the feedforward control unit, and G2() is the transfer function of the temperature PI unit. Calculate the temperature error ΔT between the target evaporation temperature and the real-time evaporation temperature, and input the temperature error ΔT into the temperature PI unit to generate the speed adjustment amount ΔN1. Combine the speed adjustment amount ΔN1 and the real-time speed N1 to calculate the compressor's feedforward-free speed N0, N0 = N1 + ΔN1, and then generate the compressor's feedforward-free load Q. comp Q comp =(h dis -h evap )VN0ρ / 60. h dis and h evap The specific enthalpy of the refrigerant at the evaporator outlet and inlet are respectively obtained by measuring the pressure and temperature and consulting the refrigerant property table. dis Typically, 400~420 kJ / kg, h evap Typically, 240~260 kJ / kg is used. V is the compressor displacement, determined by the compressor's structure. ρ is the refrigerant density. Therefore, the load error ΔQ = Q load -Q comp The load error ΔQ is input to the feedforward control unit to generate the speed feedforward quantity ΔN2. The speed adjustment quantity ΔN1 and the speed feedforward quantity ΔN2 are combined to generate the speed error ΔN3, where ΔN3 = ΔN1 + ΔN2. The optimized algorithm structure of the load controller is further as described in Embodiment 3.

[0053] Step 5: Collect the real-time current of the compressor, input the real-time current and speed error to the speed controller, and update the compressor's input current. The speed controller includes a reluctance control unit G3(i d The transfer function of the reluctance control unit is G3(), and the transfer function of the DC PI unit is G4(). The real-time current i of the compressor is collected. d The real-time current, i.e., the direct-axis component, is the real-time current i. d The input magnetoresistive control unit generates a magnetoresistive component R2, R2=G3(i d The torque constant R of the DC PI unit is updated by combining the permanent magnet component R1 and the reluctance component R2, where R = R1 + R2. The proportional coefficient K of the DC PI unit is then retuned based on the torque constant R. 2p Integral coefficient K 2i The optimal algorithm structure for the speed controller is further as described in Embodiment 4.

[0054] This invention inputs the speed error to a DC PI converter to generate a direct-axis adjustment, and combines the direct-axis adjustment with the real-time current to generate an input current. In a permanent magnet rotor compressor, the input current is the direct-axis component. After undergoing two-phase and three-phase transformations, the input current generates an IPMSM control signal. This IPMSM control signal is then connected to the three-phase circuit to control the current entering the compressor. Figures 11 to 13 The graph shows the real-time evaporator temperature, real-time speed, and input current of a 160kW medium-sized commercial central air conditioner when it is not in standby mode. Figure 12 and Figure 13 During operation, the compressor's real-time speed varies with the input current. The compressor's input current and real-time speed are lower at night and steadily increase during the day. During the midday break, both the compressor's real-time speed and input current drop. It should be noted that some air conditioning systems have a standby time. This invention estimates the change in the compressor's reluctance coefficient based on the rotor position during standby. The reluctance coefficient is updated once for each received standby signal. The shorter the standby interval (sampling time), the more accurate the reluctance coefficient update.

[0055] Step 6: Update the feedforward control unit of the load controller based on the total load at multiple sampling times. If a standby signal is received, disconnect the input current and proceed to step 7; otherwise, return to step 3. The feedforward control unit has a feedforward gain K. ff In the feedforward control unit, ΔN2=G1(ΔQ)=K ff ΔQ(h dis -h evap ), h dis and h evap These are the refrigerant specific enthalpy at the evaporator outlet and inlet, respectively. Multiple sampling moments with stable total load are extracted; since disturbances are small at these sampling moments, they can be used to update the feedforward gain. The average temperature error T' and the average speed feedforward N' are calculated by combining the temperature error and speed feedforward at t sampling moments, respectively, and then the feedforward gain K is updated. ff Updated feedforward gain K ff (t+1)=(1-β1)K ff (t)+(β1β2T' / N')K ff (t), K ff (t) represents the feedforward gain before the update. β1 is the learning rate, which can be set to 0.1 to 0.3. β2 is the adjustment coefficient, which can usually be equal to the proportional gain K of the load controller. 1p .

[0056] Step 7: Identify the first braking angle of the rotor, predict the second braking angle of the rotor based on the compressor's starting angle and real-time speed, update the reluctance control unit of the speed controller based on the first and second braking angles, then initialize the feedforward control unit of the load controller, and end the task. This invention collects the real-time current and real-time quadrature-axis component of the compressor and adjusts the reluctance coefficient of the reluctance control unit. Simultaneously, since the change in the reluctance coefficient affects the compressor's response to the load, this invention calculates the compressor's displacement influence number V' based on the reluctance coefficient, as described in Example 4. The displacement influence number is used to predict the influence of the reluctance coefficient on the compressor's actual displacement. Deleting the displacement influence number V' from the feedforward gain Kff(t+1) yields the initialized feedforward gain Kff(t+1)', i.e., Kff(t+1)' = (1-V')Kff(t+1). Example 2

[0057] This embodiment further discloses a preferred method for calculating the starting angle and the first braking angle of the rotor 123 according to the present invention. (Refer to...) Figure 5 and Figure 6 The compressor stator 121 has three sets of permanent magnet poles 122, corresponding to six magnetic pole directions: +A phase, -C phase, +B phase, -A phase, +C phase, and -B phase. The corresponding angle intervals for these six directions are 0, 1 / 3π, 2 / 3π, π, 4 / 3π, and 5 / 3π, respectively. Clockwise is defined as positive, and counterclockwise as negative. Before starting the compressor, the following steps can be performed to identify the starting angle.

[0058] Step 101: Inject pulse voltage sequentially into the six magnetic poles of the compressor. The pulse voltage is, for example, 15V-45V, and the pulse width is, for example, 0.5ms-3ms.

[0059] Step 102: Determine the interval angle. Detect the peak current i in the six magnetic pole directions. k k=1,2,…,6. Extract the maximum current i. max The peak currents in the two directions that differ from the direction of the maximum current by 2 / 3π are respectively denoted as the first peak current i. m1 Second peak current i m2 Since the direction of the maximum current is close to the direction of the rotor magnetic poles, the interval angle α1 is determined based on the direction of the maximum current. The starting angle of rotor 123 is within the interval angle α1 of the direction of the maximum current, that is, α3 is within a range of 1 / 3π centered on the direction of the maximum current. For example, when i max When i = i2, i m1 =i6, i m2 =i4, α1=1 / 3π, at this time the starting angle α3 is between 1 / 6π and 1 / 2π.

[0060] Step 103: Calculate the starting angle. The first and second peak currents are far from the direction of the rotor 123 magnetic poles and can be used to estimate the offset angle α2. Based on the first peak current i m1 Second peak current i m2 Determine the first peak current difference Δi m1 The difference between the second peak current and the peak current Δi m2 Δi m1 =i m1 -i avg , Δi m2 =i m2 -i avg i avg This is the average of the peak currents in the six magnetic pole directions. Combined with the first peak current difference Δi m1 The difference between the second peak current and the peak current Δi m2 Calculate the offset angle α2. Then, combining the interval angle α1 and the offset angle α2, calculate the starting angle α3, where α3 = α1 + α2. Figure 6 In this case, α2 is negative, meaning α3 < α1. Similarly, by performing the above steps after the compressor is braked, the first braking angle θ1 of rotor 123 can be identified. Example 3

[0061] like Figure 7 and Figure 8 This embodiment further discloses a preferred algorithm structure for the load controller. The load controller of the present invention includes a feedforward control unit G1 (ΔQ) and a temperature PI unit G2 (ΔT).

[0062] The temperature PI controller can be a conventional PI controller, which typically does not include a differential loop. The input to the temperature PI controller is the temperature error ΔT, and the output is the speed regulation ΔN1. The temperature PI controller has the form ΔN1 = K. 1p ΔT+K 1i ∫ΔTdt. The integration interval is the current sampling interval. K 1p K 1i These are the proportional coefficient and integral coefficient of the temperature PI part, respectively. K 1p K 1i The tuning can be referenced from existing technologies such as the IMC method and the critical proportionality method.

[0063] The feedforward control unit is used to sense the load variable at the terminal in advance, adjust the speed in advance, and accelerate system convergence. The input of the feedforward control unit G1(ΔQ) is the load variable ΔQ, and the output is the speed feedforward amount ΔN2. In this embodiment, combined with the compressor working model, ΔN2=G1(ΔQ)=K ff ΔQ(h dis -h evap ), K ffFor feedforward gain, h dis h evap These are the refrigerant specific enthalpy at the evaporator outlet and inlet, respectively. In another embodiment, the evaporation temperature T can be collected. e and condensation temperature T c Combined with the compressor at this evaporation temperature T e and condensation temperature T c The characteristic curve is used to generate G1(ΔQ). Furthermore, a PID module can be embedded in the feedforward control unit to improve tuning stability. ff The setting can be referred to in the existing technology, etc.

[0064] To improve feedforward accuracy, this invention continuously collects total load data during operation to update the feedforward control unit, i.e., updates the feedforward gain of the feedforward control unit. The initial value of the feedforward gain can be Vρ / 60, where V is the compressor displacement and ρ is the refrigerant density. Specifically, the total load variable Q is extracted. load Less than threshold Q max For t sampling times, the mean speed error N' and mean temperature error T' are calculated based on the speed error and the speed feedforward amount at each of the t sampling times. T' / N' can be used to characterize the feedforward speed of the speed feedforward amount; the smaller T' / N' is, the slower the speed feedforward speed, and the larger T' / N' is, the faster the speed feedforward speed. The feedforward gain K is updated based on the mean speed error N' and the mean temperature error T'. ff (t), updated feedforward gain K ff (t+1)=(1-β1)K ff (t)+(β1β2T' / N')K ff (t). β1 is the learning rate, which can be set to 0.1 to 0.3. β2 is the adjustment coefficient, which can usually be equal to the proportional coefficient K of the load controller. 1p .

[0065] This embodiment uses total load data to update the feedforward gain. The adjustment strategy involves first determining the time interval for load stability, then decoupling the disturbance from this stable time interval, determining the gain of the disturbance on the adjustment, and finally updating the feedforward gain. In another embodiment, the feedforward gain can be updated based on a gradient descent method using performance feedback or an adaptive method based on Lyapunov stability. Example 4

[0066] like Figure 9 and Figure 10 This embodiment further discloses a preferred algorithm structure for the speed controller. The speed controller includes a reluctance control unit G3(i d ), DC PI section G4(ΔN3).

[0067] Magnetoresistive control unit G3(i dThis is used to predict the torque constant. Specifically, the electromagnetic torque T output by the compressor is divided into the permanent magnet torque T1 driven by the quadrature-axis current and the reluctance torque T2 driven by both the direct-axis and quadrature-axis currents, i.e., T = T1 + T2. Permanent magnet torque T1 = R1i q R1 is the permanent magnet component, determined by the permanent magnet structure of the motor, and is usually a constant value. Reluctance torque T2 = R2i q R2 is the reluctance component, determined by the reluctance coefficient. q Let R1i be the quadrature component of the compressor. Then T = R1i q +R2i q =(R1+R2)i q Collect the real-time current i of the compressor. d The real-time current, i.e., the direct-axis component, is the real-time current i. d The input magnetoresistive control unit generates a magnetoresistive component R2, i.e., R2 = G3(i d The torque constant R of the DC PI unit is updated by combining the permanent magnet component R1 and the reluctance component R2, where R = R1 + R2. In this embodiment, R1 = 3Pψ / 2, R2 = 3PL0i d / 2. Where P is the number of pole pairs, typically 2~6. ψ is the flux linkage, typically 0.1~0.3 Wb. L0 is the reluctance coefficient, which is related to the compressor's d-axis and q-axis inductances. Therefore, the torque constant R = 3PL0i d / 2+3Pψ / 2. The reluctance coefficient may degrade in actual operation, and the update method is as described in Example 5.

[0068] The DC PI unit G4(ΔN3) can be a conventional PID controller. The input of the DC PI unit is the speed error ΔN3, and the output is the direct-axis adjustment Δi. d The DC PI section is shaped like Δi. d =K 2p ΔN3+K 2i ∫ΔN3dt. The integration interval is the current sampling interval. K 2p K 2i These are the proportional and integral coefficients of the DC PI section, respectively. 2p K 2i It is tuned by the torque constant R.

[0069] This embodiment discloses the method of setting the proportional coefficient K based on the torque constant R. 2p Integral coefficient K 2iThe preferred method is as follows: First, determine the system parameters K0 and performance indices w and ζ. K0 = (60R) / (2πJ), where J is the total moment of inertia of the compressor, in kg·m². ζ is typically selected from 0.7 to 1.0. ζ = 0.7 provides approximately 5% overshoot, striking a balance between speed and smoothness. ζ = 1.0 provides no overshoot, but the response is slightly slower. w determines the speed controller bandwidth, which is typically selected as 1 / 10 to 1 / 5 of the current sampling bandwidth. Then, calculate the PI parameter K. 2p and K 2i K 2p =w 2 / K0, unit is A / rpm. K 2i =2ζw / K0, the unit is A / (rpm·s).

[0070] Because this invention continuously updates the feedforward gain based on the current operating conditions during operation, to avoid the feedforward gain and reluctance coefficient repeatedly considering the current operating conditions, before the end of each task, this invention removes the displacement influence number from the feedforward gain Kff(t+1) to initialize the feedforward control unit. This invention does not limit the method of removing the displacement influence number.

[0071] In this invention, the displacement influence number V' of the speed controller is calculated based on the reluctance coefficient. The displacement influence number refers to the ratio of the influence of the reluctance coefficient on the torque constant before and after adjustment. The mean value i of t direct-axis components between sampling times 1 and t is calculated. d Let the reluctance coefficient before adjustment be L0, then the torque constant before adjustment is R = 3PL0i d Let the adjusted reluctance coefficient be L0', then the adjusted torque constant R' = 3PL0'i d ' / 2+3Pψ / 2. Calculate the displacement influence number V' based on the torque constants R and R' before and after adjustment, V'=(R'-R) / R=(L0'i d '-L0i d ') / (L0i d The displacement influence number is removed from the feedforward gain Kff(t+1) to obtain the initialized feedforward gain Kff(t+1)', i.e., Kff(t+1)'=(1-V')Kff(t+1). This invention provides a preferred method for updating the feedforward gain. Those skilled in the art can combine existing deep learning tools to optimize the adjustment speed of the feedforward gain. In another embodiment, a learning rate less than 1 can be set to slow down the update step size of the feedforward gain and avoid adjustment oscillations. Example 5

[0072] This embodiment further provides a preferred method for updating the reluctance coefficient of the speed controller. Updating the reluctance coefficient is a problem of time-varying system identification. As the equipment is used, the operating parameters of the compressor drift, so it is necessary to update the reluctance coefficient to improve the control accuracy of the air conditioning system.

[0073] In the power system of an air conditioning compressor, the electromagnetic torque output by the compressor is T=Ri. q =(3Pψ / 2-3PL0i d / 2)i q Where P is the pole pair number, ψ is the magnetic flux linkage, and i d i q These are the direct-axis and quadrature-axis components, respectively. L0 is the reluctance coefficient, usually L0 = L... d -L q L d For the d-axis inductance, L q For q-axis inductance, L is typically defined based on design parameters. d and L q The q-axis inductance is prone to drift, affecting the reluctance coefficient of the compressor, and consequently, the compressor speed. The preferred method for updating the reluctance coefficient in this invention is as follows.

[0074] Step 701: Predict the second braking angle of the rotor based on multiple sets of instantaneous rotor angles. In this embodiment, the second braking angle θ2 is predicted based on the integral of the rotor's instantaneous angle ω, i.e., θ2 = α3 + ∫ωdt. The integration interval is the compressor's operating time. In another embodiment, the instantaneous angles can also be discretized, and the second braking angle can be calculated by cumulative summation.

[0075] Step 702: Calculate the driving error based on the first braking angle θ1 and the second braking angle θ2. In this embodiment, the driving error ω e The differential component of the braking angle, i.e., ω e =d(θ2-θ1) / dt. This method can avoid the amplification of noise signals caused by cumulative integration. In another embodiment, the difference in braking angle can be directly used as the driving error, i.e., ω. e =(θ2-θ1) / Δt, where Δt is the sampling duration.

[0076] Step 703: Construct the relationship between electromagnetic torque and its observed values. Based on the dynamic equation of electromagnetic torque J(dω) e / dt)=T'-T-Bω e The relationship between the electromagnetic torque T and its observed quantity T' can be obtained as T'-T=J(dω) e / dt)+Bω e In the formula, J is the total rotational inertia of the compressor, which can be tracked and predicted according to load changes during compressor operation. B is the viscous friction coefficient, with units of N·m·s / rad.

[0077] Step 704: Update the reluctance coefficient. Collect the real-time current and real-time quadrature-axis component of the compressor, and calculate the average real-time current i. d 'and real-time cross-axis component mean i q Let the reluctance coefficient before adjustment be L0, then the torque constant before adjustment is R = 3PL0i d Let the adjusted reluctance coefficient be L0', then the adjusted torque constant R' = 3PL0'i d ' / 2+3Pψ / 2. Because T'-T=(R'-R)i q =3P(L0'-L0)i d 'i q ' / 2=J(dω e / dt)+Bω e Then the reluctance adjustment amount L0'-L0=2[J(dω) e / dt)+Bω e ] / (3Pi d 'i q Furthermore, the adjusted reluctance coefficient L0' = L0 + 2[J(dω)] e / dt)+Bω e ] / (3Pi d 'i q '). Example 6

[0078] like Figure 1 , Figure 2 , Figure 4 as well as Figure 14 As shown in the figure, an air conditioning system for implementing the control method of variable air volume ventilation air conditioning in this embodiment includes: an outdoor unit, multiple indoor units and a control subsystem.

[0079] The outdoor unit includes a condenser 110 and a compressor 120, and the indoor unit includes an expansion valve 210 and an evaporator 220. The refrigerant used in this invention is, for example, water. In the outdoor unit, the compressor 120 is configured to pump refrigerant to the evaporator 220 via the expansion valve 210. The condenser 110 transfers heat to the outside via a cooling water pipe, which may also be equipped with a booster 140 to regulate the heat exchange rate. A gate valve 130 is connected in series with the compressor 120 to control the refrigerant flow rate in the main pipe. In the indoor unit, the evaporator 220 may be connected in series with a filter 230, a coil 240, and a fan 250. The filter 230 is used to block bacteria and dust, and the refrigerant transfers cooling energy in the coil 240 of the evaporator 220. The fan 250 pumps cooling energy to the air inlet 260 of the indoor area, and the return air vent 270 can return to the indoor unit via a three-way valve 280.

[0080] The control subsystem includes an indoor unit control unit, an outdoor unit control unit, and a compressor control unit. The indoor unit control unit is configured to control the valve opening of the expansion valve 210. The outdoor unit control unit is configured to update the target evaporation temperature of the outdoor unit. The compressor control unit is configured to update the input current of the compressor 120 based on the load controller and the speed controller. This invention outputs the target speed of the compressor 120 through the load controller and then generates the input current through the speed controller. When the indoor unit airflow changes, the feedforward control unit of the load controller can provide a feedforward amount close to the total load, allowing the cooling output value to quickly follow changes in cooling demand. Figure 4 The compressor control unit receives the direct-axis component of the input current. After the input current passes through a two-phase conversion unit and a vector pulse width modulation unit to obtain a three-phase pulse width modulation signal, it is then used by the inverter to generate a three-phase control signal. The three-phase control signal controls the three-phase current entering the compressor. Similarly, after acquiring the three-phase current, it passes through a three-phase conversion unit and a two-phase conversion unit to obtain the real-time direct-axis component of the current.

[0081] Upon receiving a start signal, the compressor control unit periodically updates the load controller. Upon receiving a standby signal, the compressor control unit updates the speed controller and initializes the load controller. In the variable air volume control process of ventilation and air conditioning, this invention continuously updates the feedforward control unit. When the compressor 120 is in sleep mode, this invention calculates the drive error, updates the reluctance coefficient of the speed controller, and initializes the feedforward control unit based on the updated reluctance coefficient.

[0082] like Figure 14 The control subsystem further includes: a first temperature sensor and a valve sensor installed in each indoor unit; a second temperature sensor and a pressure sensor installed in the outdoor unit; and an encoder and a current excitation unit installed in the compressor 120. The first temperature sensor is configured to collect the supply water temperature and return water temperature of the indoor unit, and the valve sensor is configured to collect the valve opening degree of the expansion valve 210. The second temperature sensor is configured to collect the outdoor temperature, and the pressure sensor is configured to collect the real-time evaporation pressure of the refrigerant and convert it into a real-time evaporation temperature. The encoder is configured to collect the real-time speed of the compressor 120, and the current excitation unit is configured to collect the rotor's starting angle and first braking angle. Figure 14 In the diagram, the solid line represents the electrical signal path, and the dashed line represents the heat exchange path.

[0083] The indoor unit control unit generates the terminal load for each indoor unit based on the supply and return water temperatures and valve opening. The outdoor unit control unit updates the target evaporation temperature of the outdoor unit based on the outdoor temperature and generates the total load based on multiple sets of terminal loads. The load controller updates the speed error based on the total load, real-time evaporation temperature, and target evaporation temperature, and the speed controller updates the input current based on the speed error. The compressor control unit updates the feedforward control unit of the load controller based on the total load at multiple sampling times. The compressor control unit also calculates the drive error and updates the reluctance coefficient of the speed controller.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control method for a variable air volume (VAV) ventilation and air conditioning system, characterized in that, Includes the following steps: Step 1: Receive the start signal, determine the target evaporation temperature of the refrigerant, identify the start angle of the compressor rotor, and generate the start speed of the compressor; Step 2: Input the starting speed to the speed controller to generate the compressor input current. The compressor pumps refrigerant to the evaporator through the expansion valve of each indoor unit to maintain the target evaporation temperature. Step 3: Collect the valve opening of the expansion valve of each indoor unit, and generate the total load based on the multiple valve openings; Step 4: Collect the real-time evaporation temperature of the refrigerant, update the target evaporation temperature, input the total load, real-time evaporation temperature and target evaporation temperature into the load controller, and calculate the compressor speed error; Step 5: Collect the real-time current of the compressor, input the real-time current and speed error to the speed controller, and update the compressor's input current; Step 6: Combine the total load at multiple sampling times to update the feedforward control unit of the load controller. If a standby signal is received, disconnect the input current and proceed to step 7; otherwise, return to step 3. Step 7: Identify the rotor's first braking angle, predict the rotor's second braking angle based on the compressor's starting angle and real-time speed, update the reluctance control unit of the speed controller based on the first and second braking angles, then initialize the feedforward control unit of the load controller, and end the task. In step 1, pulse voltages are injected sequentially into the six magnetic pole directions of the compressor, and the peak current in each direction is detected. The direction of the maximum current is extracted to generate an interval angle. Then, the first and second peak currents are extracted based on the direction of the maximum current to generate an offset angle. The starting angle is calculated by combining the interval angle and the offset angle. In step 7, after the compressor brakes, the same steps as calculating the starting angle are performed to calculate the first braking angle.

2. The control method for variable air volume ventilation and air conditioning according to claim 1, characterized in that, In step 3, the flow rate of the indoor unit is calculated based on the valve opening of the indoor unit, the supply water temperature and return water temperature are collected, the terminal load of the indoor unit is calculated, and the total load of the compressor is generated based on the terminal loads of multiple indoor units.

3. The control method for variable air volume ventilation and air conditioning according to claim 1, characterized in that, In step 4, the load controller includes a feedforward control unit and a temperature PI unit. It calculates the temperature error between the target evaporation temperature and the real-time evaporation temperature, inputs the temperature error to the temperature PI unit to generate a speed adjustment amount, combines the speed adjustment amount and the real-time speed to calculate the compressor's feedforward speed, generates the compressor's feedforward load, combines the feedforward load and the total load to generate a load error, inputs the load error to the feedforward control unit to generate a speed feedforward amount, and combines the speed feedforward amount and the speed adjustment amount to generate a speed error.

4. The control method for variable air volume ventilation and air conditioning according to claim 1, characterized in that, In step 5, the speed controller includes a reluctance control unit and a DC PI unit. The reluctance control unit generates a reluctance component, updates the torque constant of the DC PI unit by combining the permanent magnet component and the reluctance component, inputs the speed error to the DC PI unit to generate a direct-axis adjustment, and generates an input current by combining the direct-axis adjustment and the real-time current.

5. The control method for variable air volume ventilation and air conditioning according to claim 3, characterized in that, In step 6, the feedforward control unit has a feedforward gain, extracts multiple sampling moments when the total load variable is less than a threshold, and updates the feedforward gain by combining the temperature error and the speed feedforward amount of the multiple sampling moments.

6. The control method for variable air volume ventilation and air conditioning according to claim 5, characterized in that, In step 7, the real-time current and real-time quadrature axis component of the compressor are collected, the reluctance coefficient of the generated reluctance component is adjusted, the displacement influence number of the compressor is calculated based on the reluctance coefficient, and the displacement influence number is deleted from the feedforward gain.

7. An air conditioning system implementing the control method for variable air volume ventilation and air conditioning as described in claim 1, characterized in that, include: An outdoor unit, multiple indoor units, and a control subsystem, wherein the outdoor unit includes a compressor, and the indoor units include an expansion valve and an evaporator, the compressor being configured to pump refrigerant to the evaporator via the expansion valve, and the control subsystem includes: The indoor unit control unit is configured to control the valve opening of the expansion valve; The outdoor unit control unit is configured to update the target evaporation temperature of the outdoor unit. The compressor control unit is configured to update the compressor's input current based on the load controller and speed controller. Upon receiving a start signal, the compressor control unit periodically updates the load controller; upon receiving a standby signal, the compressor control unit updates the speed controller and initializes the load controller.

8. The air conditioning system according to claim 7, characterized in that, The control subsystem further includes: a first temperature sensor and a valve sensor installed in each indoor unit, and a second temperature sensor and a pressure sensor installed in the outdoor unit. The first temperature sensor is configured to collect the supply and return water temperatures of the indoor unit; the valve sensor is configured to collect the valve opening degree of the expansion valve; the second temperature sensor is configured to collect the outdoor temperature; and the pressure sensor is configured to collect the real-time evaporation pressure of the refrigerant and convert it into real-time evaporation temperature. The indoor unit control unit generates the terminal load of each indoor unit based on the supply water temperature, return water temperature, and valve opening. The outdoor unit control unit updates the target evaporation temperature of the outdoor unit according to the outdoor temperature, and generates the total load according to multiple sets of terminal loads; The load controller updates the speed error based on the total load, real-time evaporation temperature, and target evaporation temperature, while the speed controller updates the input current based on the speed error.

9. The air conditioning system according to claim 8, characterized in that, The control subsystem further includes: an encoder and a current excitation unit installed on the compressor. The encoder is configured to acquire the real-time speed of the compressor, and the current excitation unit is configured to acquire the rotor's starting angle and first braking angle. The compressor control unit updates the feedforward control unit of the load controller based on the total load at multiple sampling times.

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