A heating, ventilation, and air conditioning system and its control method

Abstract

The present invention discloses a heating, ventilation and air conditioning (HVAC) system and its control method. The control method includes the steps of: when receiving a control instruction to start operation, the control device controls the first regulating valve and the third regulating valve to be completely closed, controls the second regulating valve to be completely opened, and controls the chilled water pump, the low-temperature system and the high-temperature system to start working; the control device calculates the medium-temperature supply and return water pressure difference ΔPz and the low-temperature supply and return water pressure difference ΔPd; the control device adjusts the opening degrees of the first regulating valve, the second regulating valve and the third regulating valve according to ΔPz; the control device adjusts the operating frequency of the chilled water pump according to ΔPd and the opening degree of the first regulating valve. The control method disclosed in this application adjusts the opening degrees of the first regulating valve, the second regulating valve and the third regulating valve according to ΔPz, and adjusts the operating frequency of the chilled water pump according to ΔPz and the opening degree of the first regulating valve, so as to adjust the connection relationship among the low-temperature system, the medium-temperature system, the water supply pipe and the water return pipe, and realize the stable series operation of the medium-temperature system and the low-temperature system.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning systems, and particularly to a heating, ventilation and air conditioning (HVAC) system and a control method thereof. Background Art

[0002] The operating energy consumption of an HVAC system accounts for about 65% of the total building energy consumption. Improving the operating energy efficiency of the HVAC system will bring significant economic and environmental benefits.

[0003] In industrial plants, such as pharmaceutical, lithium battery, and electronics plants, in addition to the dehumidification areas that require low-temperature chilled water supply, there are some areas with low dehumidification requirements or low temperature requirements. Medium-temperature chilled water can be provided to these areas. By increasing the supply water temperature of the chilled water required in some areas, the operating energy efficiency of the refrigeration system can be improved. For plants that need to supply both low-temperature and medium-temperature chilled water, there are two traditional methods: First, two independent systems, a medium-temperature system and a low-temperature system, are set up in the plant. The medium-temperature chilled water is provided by the medium-temperature system, and the low-temperature chilled water is provided by the low-temperature system. Second, only a low-temperature system is set up in the plant, and all the chilled water is supplied by the low-temperature system. Setting up two independent systems requires two sets of main engines, water pumps, water towers and other equipment, as well as two sets of independent control equipment and pipeline systems. Moreover, the two independent systems are not applicable to the independent medium-temperature systems in small and scattered areas. The system is complex, costly, and lacks flexibility. If only a low-temperature system is set up to supply chilled water, the supply water temperature is low, resulting in low operating energy efficiency and energy inefficiency of the system.

[0004] To achieve the purpose of energy conservation, the method of connecting the medium-temperature system and the low-temperature system in series can be adopted. By connecting in series, the supply water temperature can be increased, the system temperature difference can be enlarged, and the system energy efficiency can be improved. Currently, the medium-temperature and low-temperature series connection technology is only applied to single equipment, only involving the series connection of two coils, a low-temperature coil and a medium-temperature coil, before and after a single equipment, and cannot meet the series connection requirements of single-coil terminal equipment in the system. Moreover, an electric control valve needs to be added to control each medium-temperature and low-temperature series connection terminal, resulting in high cost, lack of flexibility, and complex control.

[0005] It can be seen that the existing technology still needs to be improved. Summary of the Invention

[0006] In view of the deficiencies of the above-mentioned existing technology, the purpose of the present invention is to provide a control method for an HVAC system, which can realize the stable series operation of the medium-temperature system and the low-temperature system, enlarge the supply water temperature difference of the HVAC system, and improve the energy efficiency of the HVAC system.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A control method for a heating, ventilation and air conditioning (HVAC) system, the HVAC system comprising a control device, a water supply pipe, a water return pipe, a chilled water pump, and one or more medium-low temperature series systems, the medium-low temperature series systems comprising a medium temperature system, a low temperature system, a first regulating valve, a second regulating valve, a third regulating valve, a medium temperature return water pressure sensor, a medium temperature supply water pressure sensor, a low temperature return water pressure sensor, and a low temperature supply water pressure sensor, which are respectively electrically connected to the control device, the water supply pipe is respectively connected to the input end of the low temperature system and one end of the first regulating valve through the chilled water pump, the other end of the first regulating valve is connected to the input end of the medium temperature system, the output end of the low temperature system is connected to the input end of the medium temperature system through the second regulating valve and is connected to the water return pipe through the third regulating valve, and the output end of the medium temperature system is connected to the water return pipe; the control method comprises the steps:

[0009] When receiving a control instruction to start operation, the control device controls the first regulating valve and the third regulating valve to be fully closed, controls the second regulating valve to be fully opened, and controls the chilled water pump, the low temperature system, and the high temperature system to start working;

[0010] The control device acquires the pressure information real-time feedback by the medium temperature return water pressure sensor and the medium temperature supply water pressure sensor, and calculates the medium temperature supply and return water pressure difference, denoted as ΔPz;

[0011] The control device acquires the pressure information real-time feedback by the low temperature return water pressure sensor and the low temperature supply water pressure sensor, and calculates the low temperature supply and return water pressure difference, denoted as ΔPd;

[0012] The control device adjusts the opening degrees of the first regulating valve, the second regulating valve, and the third regulating valve according to the medium temperature supply and return water pressure difference ΔPz to adjust the connection relationship among the low temperature system, the medium temperature system, the water supply pipe, and the water return pipe; the control device adjusts the operating frequency of the chilled water pump according to the low temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve.

[0013] In the control method of the HVAC system, the control device adjusts the opening degrees of the first regulating valve, the second regulating valve, and the third regulating valve according to the medium temperature supply and return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump according to the low temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve, specifically including:

[0014] When the medium temperature supply and return water pressure difference ΔPz is equal to the preset medium temperature supply and return water pressure difference setting value, the control device controls the first regulating valve and the third regulating valve to remain in the fully closed state, and controls the second regulating valve to remain in the fully opened state;

[0015] When the low temperature supply and return water pressure difference ΔPd is greater than the preset low temperature supply and return water pressure difference setting value, the control device reduces the operating frequency of the chilled water pump;

[0016] When the low-temperature supply and return water pressure difference ΔPd is less than the preset low-temperature supply and return water pressure difference set value, the control device increases the operating frequency of the chilled water pump.

[0017] In the control method of the HVAC system described above, the control device adjusts the opening degrees of the first regulating valve, the second regulating valve, and the third regulating valve according to the medium-temperature supply and return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump according to the low-temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve, specifically including:

[0018] When the medium-temperature supply and return water pressure difference ΔPz is greater than the preset medium-temperature supply and return water pressure difference set value, the control device controls the second regulating valve to remain fully open, controls the first regulating valve to remain fully closed, and controls the opening degree of the third regulating valve to gradually increase;

[0019] When the third regulating valve is fully open and the medium-temperature supply and return water pressure difference ΔPz is still greater than the preset medium-temperature supply and return water pressure difference set value, the control device controls the opening degree of the second regulating valve to gradually decrease until it is fully closed;

[0020] When the low-temperature supply and return water pressure difference ΔPd is greater than the preset low-temperature supply and return water pressure difference set value, the control device decreases the operating frequency of the chilled water pump;

[0021] When the low-temperature supply and return water pressure difference ΔPd is less than the preset low-temperature supply and return water pressure difference set value, the control device increases the operating frequency of the chilled water pump.

[0022] The control method of the HVAC system described above further includes the steps:

[0023] When the medium-temperature supply and return water pressure difference ΔPz is less than the preset medium-temperature supply and return water pressure difference set value, the control device controls the first regulating valve to remain fully closed, the third regulating valve to remain fully open, and controls the opening degree of the second regulating valve to gradually increase;

[0024] When the second regulating valve is fully open and the medium-temperature supply and return water pressure difference ΔPz is still less than the preset medium-temperature supply and return water pressure difference set value, the control device controls the opening degree of the third regulating valve to gradually decrease until it is fully closed.

[0025] In the control method of the HVAC system described above, the control device adjusts the opening degrees of the first regulating valve, the second regulating valve, and the third regulating valve according to the medium-temperature supply and return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump according to the low-temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve, specifically including:

[0026] When the medium-temperature supply and return water pressure difference ΔPz is less than the preset medium-temperature supply and return water pressure difference set value, the control device controls the second regulating valve to remain fully open, controls the third regulating valve to remain fully closed, and controls the opening degree of the first regulating valve to gradually increase;

[0027] When the first regulating valve is fully open and the medium-temperature supply-return water pressure difference ΔPz is still less than the preset medium-temperature supply-return water pressure difference setting value, the control device increases the operating frequency of the chilled water pump;

[0028] When the low-temperature supply-return water pressure difference ΔPd is greater than the preset low-temperature supply-return water pressure difference setting value, the control device decreases the operating frequency of the chilled water pump;

[0029] When the low-temperature supply-return water pressure difference ΔPd is less than the preset low-temperature supply-return water pressure difference setting value, the control device increases the operating frequency of the chilled water pump.

[0030] In the control method of the HVAC system described above, it further includes the steps:

[0031] When the first regulating valve is fully open and the medium-temperature supply-return water pressure difference ΔPz is still less than the preset medium-temperature supply-return water pressure difference setting value, and when the low-temperature supply-return water pressure difference ΔPd is greater than the preset low-temperature supply-return water pressure difference setting value, the control device obtains the information fed back by the medium-temperature system and the low-temperature system, and adjusts the working state of the chilled water pump according to the fed-back information to meet the requirements of the most unfavorable signal control;

[0032] The control device controls the opening degree of the first regulating valve ≤ the preset maximum opening degree.

[0033] In the control method of the HVAC system described above, the control device obtains the pressure information fed back in real time by the medium-temperature return water pressure sensor and the medium-temperature supply water pressure sensor, and calculates the medium-temperature supply-return water pressure difference, denoted as ΔPz. Specifically:

[0034] The control device obtains the pressure information P1 fed back in real time by the medium-temperature return water pressure sensor;

[0035] The control device obtains the pressure information P2 fed back in real time by the medium-temperature supply water pressure sensor;

[0036] The control device calculates the medium-temperature supply-return water pressure difference ΔPz, ΔPz = P1 - P2.

[0037] In the control method of the HVAC system described above, the control device obtains the pressure information fed back in real time by the low-temperature return water pressure sensor and the low-temperature supply water pressure sensor, and calculates the low-temperature supply-return water pressure difference, denoted as ΔPd. Specifically:

[0038] The control device obtains the pressure information P3 fed back in real time by the low-temperature return water pressure sensor;

[0039] The control device obtains the pressure information P4 fed back in real time by the low-temperature supply water pressure sensor;

[0040] The control device calculates the medium-temperature supply-return water pressure difference ΔPd, ΔPd = P3 - P4.

[0041] The present invention also correspondingly provides a heating, ventilation and air conditioning (HVAC) system, which realizes working control by adopting the control method of the HVAC as described above; the HVAC system includes a control device, a water supply pipe, a water return pipe, a chilled water pump, and one or more medium-low temperature series systems. The water supply pipe is respectively connected to a plurality of the medium-low temperature series systems through the chilled water pump, and the water return pipe is respectively connected to a plurality of the medium-low temperature series systems; a plurality of the medium-low temperature series systems are connected in parallel; the medium-low temperature series system includes a medium temperature system, a low temperature system, a first regulating valve, a second regulating valve, a third regulating valve, a medium temperature return water pressure sensor, a medium temperature supply water pressure sensor, a low temperature return water pressure sensor, and a low temperature supply water pressure sensor which are respectively electrically connected to the control device. The water supply pipe is respectively connected to the input end of the low temperature system and one end of the first regulating valve through the chilled water pump. The other end of the first regulating valve is connected to the input end of the medium temperature system. The output end of the low temperature system is connected to the input end of the medium temperature system through the second regulating valve and is connected to the water return pipe through the third regulating valve. The output end of the medium temperature system is connected to the water return pipe; the medium temperature return water pressure sensor is arranged on the connecting pipeline between the output end of the medium temperature system and the water return pipe for detecting the return water pressure of the medium temperature system; the medium temperature supply water pressure sensor is arranged on the connecting pipeline between the other end of the first regulating valve and the input end of the medium temperature system for detecting the supply water pressure of the medium temperature system; the low temperature return water pressure sensor is arranged on the connecting pipeline between the output end of the low temperature system and the input end of the medium temperature system for detecting the return water pressure of the low temperature system; the low temperature supply water pressure sensor is arranged on the connecting pipeline between the output end of the chilled water pump and the input end of the low temperature system for detecting the supply water pressure of the low temperature system; the control device is also electrically connected to the chilled water pump.

[0042] In the described HVAC system, the medium temperature system includes a plurality of medium temperature terminals connected in parallel, and a first terminal regulating valve is arranged at the input end of the medium temperature terminal. The low temperature system includes a plurality of low temperature terminals connected in parallel, and a second terminal regulating valve is arranged at the input end of the low temperature terminal. The control device is respectively electrically connected to the first terminal regulating valve and the second terminal regulating valve, and the control device adjusts the opening degrees of the first terminal regulating valve and the second terminal regulating valve according to the indoor load demand.

[0043] Beneficial effects:

[0044] The present invention provides a control method for a heating, ventilation, and air conditioning (HVAC) system. The opening degrees of a first regulating valve, a second regulating valve, and a third regulating valve are adjusted according to ΔPz to adjust the connection relationships among a low-temperature system, a medium-temperature system, a water supply pipe, and a water return pipe. Moreover, the operating frequency of a chilled water pump is adjusted according to ΔPd and the opening degree of the first regulating valve to achieve stable series operation of the medium-temperature system and the low-temperature system. This can increase the water supply temperature difference of the HVAC system, improve the operating energy efficiency of the HVAC system, and achieve the purpose of energy conservation. Further, the medium-temperature system and the low-temperature system can be operated in series, enabling the HVAC system to be applicable to various usage scenarios with different requirements, including scenarios where the medium-temperature and low-temperature regions are relatively dispersed and scenarios where the medium-temperature and low-temperature loads differ significantly. It has the advantages of a wide application range and strong usage flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is the first flowchart of the control method provided by the present invention;

[0046] Figure 2 is the second flowchart of the control method provided by the present invention;

[0047] Figure 3 is the third flowchart of the control method provided by the present invention;

[0048] Figure 4 is the fourth flowchart of the control method provided by the present invention;

[0049] Figure 5 is a schematic structural diagram of an HVAC system provided by the present invention;

[0050] Figure 6 is another schematic structural diagram of an HVAC system provided by the present invention.

[0051] MAIN ELEMENT SYMBOL DESCRIPTION: 1 - water supply pipe, 2 - water return pipe, 3 - chilled water pump, 411 - medium-temperature terminal, 412 - first terminal regulating valve, 421 - low-temperature terminal, 422 - second terminal regulating valve, 43 - first regulating valve, 44 - second regulating valve, 45 - third regulating valve, 46 - medium-temperature return water pressure sensor, 47 - medium-temperature supply water pressure sensor, 48 - low-temperature return water pressure sensor, 49 - low-temperature supply water pressure sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The present invention provides an HVAC system and its control method. To make the objectives, technical solutions, and effects of the present invention clearer and more explicit, the following further elaborates on the present invention with reference to the accompanying drawings and by way of examples.

[0053] In the description, claims and the above drawings of the present invention, the terms "first", "second", "third", "fourth", etc. are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the term "comprising" or "having" and any variation thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0054] Please refer to Figures 1 to 4 , the present invention provides a control method for a heating, ventilation and air conditioning (HVAC) system. The HVAC system includes a control device, a water supply pipe 1, a water return pipe 2, a chilled water pump 3, and one or more medium-low temperature series systems. The medium-low temperature series systems include a medium temperature system, a low temperature system, a first regulating valve 43, a second regulating valve 44, a third regulating valve 45, a medium temperature return water pressure sensor 46, a medium temperature supply water pressure sensor 47, a low temperature return water pressure sensor 48, and a low temperature supply water pressure sensor 49, which are respectively electrically connected to the control device. The water supply pipe 1 is connected to the input end of the low temperature system and one end of the first regulating valve 43 through the chilled water pump 3. The other end of the first regulating valve 43 is connected to the input end of the medium temperature system. The output end of the low temperature system is connected to the input end of the medium temperature system through the second regulating valve 44 and is connected to the water return pipe 2 through the third regulating valve 45. The output end of the medium temperature system is connected to the water return pipe 2. The control method includes the steps:

[0055] S101. When receiving a control instruction to start operation, the control device controls the first regulating valve 43 and the third regulating valve 45 to be fully closed, controls the second regulating valve 44 to be fully opened, and controls the chilled water pump 3, the low temperature system, and the high temperature system to start working. The water supply pipe 1 transports the refrigerant carrier to the low temperature system through the chilled water pump 3. The output end of the low temperature system is connected to the input end of the medium temperature system. The low temperature system outputs the heat-exchanged refrigerant carrier to the medium temperature system for reuse. The medium temperature system outputs the heat-exchanged refrigerant carrier to the water return pipe 2, that is, the medium temperature system and the low temperature system are completely connected in series for operation. In this embodiment, the control instruction to start operation can be triggered by the user through the power-on button.

[0056] S102. The control device obtains the pressure information real-time feedback by the medium temperature return water pressure sensor 46 and the medium temperature supply water pressure sensor 47, and calculates the medium temperature supply and return water pressure difference, denoted as ΔPz. The medium temperature supply and return water pressure difference ΔPz is updated in real time.

[0057] S103. The control device obtains the pressure information feedback in real time by the low-temperature return water pressure sensor 48 and the low-temperature supply water pressure sensor 49, and calculates the low-temperature supply and return water pressure difference, denoted as ΔPd, and the low-temperature supply and return water pressure difference ΔPd is updated in real time.

[0058] S104. The control device adjusts the opening degrees of the first regulating valve 43, the second regulating valve 44 and the third regulating valve 45 according to the medium-temperature supply and return water pressure difference ΔPz, so as to adjust the connection relationship among the low-temperature system, the medium-temperature system, the water supply pipe 1 and the water return pipe 2; the control device adjusts the operating frequency of the chilled water pump 3 according to the low-temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve.

[0059] The control method of the HVAC system disclosed in this application adjusts the opening degrees of the first regulating valve 43, the second regulating valve 44 and the third regulating valve 45 according to the medium-temperature supply and return water pressure difference ΔPz, so as to adjust the connection relationship among the low-temperature system, the medium-temperature system, the water supply pipe 1 and the water return pipe 2, and adjusts the operating frequency of the chilled water pump 3 according to the low-temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve, realizing the stable series operation of the medium-temperature system and the low-temperature system, which can increase the water supply temperature difference of the HVAC system, improve the operating energy efficiency of the HVAC system, achieve the purpose of energy saving, and one HVAC system can meet the two temperature requirements of medium temperature and low temperature, reducing the production and transportation costs; further, the medium-temperature system and the low-temperature system can be connected in series, so that the HVAC system can be applied to various usage occasions with different requirements, including occasions where the medium-temperature and low-temperature areas are relatively scattered and occasions where the medium-temperature and low-temperature loads vary greatly, having the advantages of wide application range and strong usage flexibility.

[0060] Further, when there are multiple medium-low temperature series systems, the multiple medium-low temperature series systems are connected in parallel, and the regulating valves of each medium-low temperature series system are adjusted according to the requirements at the end of the medium-temperature system and the requirements at the end of the low-temperature system; when it comes to the adjustment of the operating frequency of the chilled water pump, collect the chilled water pump operating frequency control signals (fed back by the valve opening degree or the low-temperature supply and return water pressure difference signal) fed back by each medium-low temperature series system. If any medium-low temperature series system feeds back that the operating frequency of the chilled water pump needs to be increased, the chilled water pump increases the frequency to meet the requirements of all up-frequency signals. If all medium-low temperature series systems feed back that the operating frequency of the chilled water pump needs to be decreased, the chilled water pump decreases the frequency to meet the requirements of the minimum down-frequency signal.

[0061] Further, please refer to Figure 2 , the control device adjusts the opening degrees of the first regulating valve 43, the second regulating valve 44 and the third regulating valve 45 according to the medium-temperature supply and return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump 3 according to the low-temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve 43, specifically including:

[0062] S201. When the medium-temperature supply-return water pressure difference ΔPz is equal to the preset medium-temperature supply-return water pressure difference setting value, that is, when the flow rate corresponding to the medium-temperature system load is equal to the flow rate corresponding to the low-temperature system load, the control device controls the first regulating valve 43 and the third regulating valve 45 to remain in a fully closed state, and controls the second regulating valve 44 to remain in a fully open state, that is, the medium-temperature system and the low-temperature system operate in series completely; in this embodiment, the medium-temperature supply-return water pressure difference setting value is set by the designer according to the design parameters and operation requirements of the HVAC system.

[0063] S202. When the low-temperature supply-return water pressure difference ΔPd is greater than the preset low-temperature supply-return water pressure difference setting value, the control device reduces the operating frequency of the chilled water pump 3; in this embodiment, the low-temperature supply-return water pressure difference setting value is set by the designer according to the design parameters and operation requirements of the HVAC system

[0064] S203. When the low-temperature supply-return water pressure difference ΔPd is less than the preset low-temperature supply-return water pressure difference setting value, the control device increases the operating frequency of the chilled water pump 3.

[0065] In this embodiment, when the medium-temperature supply-return water pressure difference ΔPz is equal to the preset medium-temperature supply-return water pressure difference setting value, that is, when the flow rate corresponding to the medium-temperature system load is equal to the flow rate corresponding to the low-temperature system load, the control device adjusts the operating frequency of the chilled water pump 3 according to the comparison result between the low-temperature supply-return water pressure difference ΔPd and the preset low-temperature return water pressure difference setting value, ensuring that the working states of the medium-temperature system and the low-temperature system meet the indoor load requirements and guaranteeing the safe operation of the medium-temperature system and the low-temperature system.

[0066] Further, please refer to Figure 3 , the control device adjusts the opening degrees of the first regulating valve 43, the second regulating valve 44 and the third regulating valve 45 according to the medium-temperature supply-return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump 3 according to the low-temperature supply-return water pressure difference ΔPd and the opening degree of the first regulating valve 43, specifically including:

[0067] S301. When the medium-temperature supply-return water pressure difference ΔPz is greater than the preset medium-temperature supply-return water pressure difference setting value, that is, when the flow rate corresponding to the medium-temperature system load is less than the flow rate corresponding to the low-temperature system load, the control device controls the second regulating valve 44 to remain in a fully open state, controls the first regulating valve 43 to remain in a fully closed state, and controls the opening degree of the third regulating valve 45 to gradually increase; the supply pipe 1 conveys the refrigerant carrier to the low-temperature system through the chilled water pump 3, and part of the refrigerant carrier output by the low-temperature system is input to the medium-temperature system through the second regulating valve 44, and part returns to the return pipe 2 through the third regulating valve 45, and the refrigerant carrier output by the medium-temperature system returns to the return pipe 2.

[0068] S302. When the third regulating valve 45 is fully opened and the medium-temperature supply-return water pressure difference ΔPz is still greater than the preset medium-temperature supply-return water pressure difference set value, the control device controls the opening of the second regulating valve 44 to gradually decrease until it is fully closed; when the second regulating valve 44 is fully closed, the supply pipe 1 conveys the coolant to the low-temperature system through the chilled water pump 3, and the coolant output by the low-temperature system returns to the return pipe 2 through the third regulating valve 45. The medium-temperature system has no load and the low-temperature system operates independently.

[0069] During the execution of steps S301 and S302, the operating frequency of the chilled water pump 3 is adjusted according to the low-temperature supply-return water pressure difference ΔPd.

[0070] S303. When the low-temperature supply-return water pressure difference ΔPd is greater than the preset low-temperature supply-return water pressure difference set value, the control device reduces the operating frequency of the chilled water pump 3;

[0071] S304. When the low-temperature supply-return water pressure difference ΔPd is less than the preset low-temperature supply-return water pressure difference set value, the control device increases the operating frequency of the chilled water pump 3.

[0072] In this embodiment, when adjusting the working states of the third regulating valve 45 and the second regulating valve 44 according to the comparison result of the medium-temperature supply-return water pressure difference ΔPz and the preset medium-temperature supply-return water pressure difference set value, the operating frequency of the chilled water pump 3 is adjusted simultaneously according to the comparison result of the low-temperature supply-return water pressure difference ΔPd and the preset low-temperature return water pressure difference set value, realizing real-time and precise control adjustment of the medium-temperature system and the low-temperature system, and achieving the goals of energy conservation of the HVAC system and carbon reduction of the building while ensuring the safe operation of the HVAC system.

[0073] Further, in step S302, when the second regulating valve 44 is fully closed and the low-temperature system operates independently, as time goes by, the load of the medium-temperature system gradually increases from zero. Please refer to Figure 3 , the control method of the HVAC system further includes the step:

[0074] S305. When the medium-temperature supply-return water pressure difference ΔPz is less than the preset medium-temperature supply-return water pressure difference set value, the control device controls the first regulating valve 43 to remain in the fully closed state, the third regulating valve 45 to remain in the fully open state, and controls the opening of the second regulating valve 44 to gradually increase; the supply pipe 1 conveys the coolant to the low-temperature system through the chilled water pump 3, part of the coolant output by the low-temperature system is input to the medium-temperature system through the second regulating valve 44, and part returns to the return pipe 2 through the third regulating valve 45. The coolant output by the medium-temperature system returns to the return pipe 2;

[0075] S306. When the second regulating valve 44 is fully opened and the medium-temperature supply-return water pressure difference ΔPz is still less than the preset medium-temperature supply-return water pressure difference setting value, the control device controls the opening degree of the third regulating valve 45 to gradually decrease until it is fully closed. When the third regulating valve 45 is fully closed, the supply pipe 1 conveys the coolant to the low-temperature system through the chilled water pump 3. The output end of the low-temperature system is connected to the input end of the medium-temperature system. The low-temperature system outputs the heat-exchanged coolant to the medium-temperature system for reuse, and the medium-temperature system outputs the heat-exchanged coolant to the return pipe 2. The flow rate corresponding to the medium-temperature system load gradually tends to the flow rate corresponding to the low-temperature system load.

[0076] In this embodiment, according to the comparison result between the medium-temperature supply-return water pressure difference ΔPz and the preset medium-temperature supply-return water pressure difference setting value, the opening degrees of the second regulating valve 44 and the third regulating valve 45 are adjusted, so that the operating state of the HVAC system is gradually converted to the series operation of the medium-temperature system and the low-temperature system, increasing the temperature difference of the HVAC system and improving the operating energy efficiency of the HVAC system.

[0077] Further, please refer to Figure 4 , the control device adjusts the opening degrees of the first regulating valve 43, the second regulating valve 44 and the third regulating valve 45 according to the medium-temperature supply-return water pressure difference ΔPz. The control device adjusts the operating frequency of the chilled water pump 3 according to the low-temperature supply-return water pressure difference ΔPd and the opening degree of the first regulating valve 43, specifically including:

[0078] S401. When the medium-temperature supply-return water pressure difference ΔPz is less than the preset medium-temperature supply-return water pressure difference setting value, that is, when the flow rate corresponding to the medium-temperature system load is greater than the flow rate corresponding to the low-temperature system load, the control device controls the second regulating valve 44 to remain fully open, controls the third regulating valve 45 to remain fully closed, and controls the opening degree of the first regulating valve 43 to gradually increase. The supply pipe 1 conveys part of the coolant to the low-temperature system through the chilled water pump 3 and conveys part of the coolant to the medium-temperature system through the first regulating valve 43. The coolant output by the low-temperature system is input to the medium-temperature system through the second regulating valve 44, and the coolant output by the medium-temperature system returns to the return pipe 2.

[0079] S402. When the first regulating valve 43 is fully opened and the medium-temperature supply-return water pressure difference ΔPz is still less than the preset medium-temperature supply-return water pressure difference setting value, the control device increases the operating frequency of the chilled water pump 3. When the first regulating valve 43 is fully opened, the supply pipe 1 conveys the coolant to the medium-temperature system through the first regulating valve 43. The output end of the medium-temperature system is connected to the return pipe 2, and the low-temperature system has no load, and the medium-temperature system operates independently.

[0080] S403. When the low-temperature supply-return water pressure difference ΔPd is greater than the preset low-temperature supply-return water pressure difference setting value, the control device decreases the operating frequency of the chilled water pump 3;

[0081] S404. When the low-temperature supply and return water pressure difference ΔPd is less than the preset low-temperature supply and return water pressure difference setting value, the control device increases the operating frequency of the chilled water pump 3.

[0082] In this embodiment, when adjusting the working state of the first regulating valve 43 according to the comparison result of the preset medium-temperature supply and return water pressure difference setting value of the medium-temperature supply and return water pressure difference ΔPz, at the same time, adjust the operating frequency of the chilled water pump 3 according to the comparison result of the low-temperature supply and return water pressure difference ΔPd and the preset low-temperature return water pressure difference setting value, so as to realize the real-time and accurate control and adjustment of the medium-temperature system and the low-temperature system. While ensuring the safe operation of the HVAC system, the goals of energy saving of the HVAC system and carbon reduction of the building are achieved.

[0083] Further, please refer to Figure 4 , the control method of the HVAC system further includes the steps:

[0084] S405. When the first regulating valve 43 is fully opened and the medium-temperature supply and return water pressure difference ΔPz is still less than the preset medium-temperature supply and return water pressure difference setting value, that is, when there is a conflict in the control signal of the operating frequency of the chilled water pump 3; and when the low-temperature supply and return water pressure difference ΔPd is greater than the preset low-temperature supply and return water pressure difference setting value, the control device obtains the information fed back by the medium-temperature system and the low-temperature system, and adjusts the working state of the chilled water pump 3 according to the fed-back information; specifically, the control device first meets the control requirements of the most unfavorable signal, such as the control device adjusts the operating frequency of the chilled water pump 3 according to the system that outputs the alarm signal first.

[0085] S406. The control device controls the opening degree of the first regulating valve 43 ≤ the preset maximum opening degree. In this embodiment, the preset maximum opening degree is 95%.

[0086] In this embodiment, when the first regulating valve 43 is fully opened, its opening degree is 95%.

[0087] Further, the control device obtains the pressure information fed back in real time by the medium-temperature return water pressure sensor 46 and the medium-temperature supply water pressure sensor 47, and calculates the medium-temperature supply and return water pressure difference, denoted as ΔPz. Specifically:

[0088] S501. The control device obtains the pressure information P1 fed back in real time by the medium-temperature return water pressure sensor 46;

[0089] S502. The control device obtains the pressure information P2 fed back in real time by the medium-temperature supply water pressure sensor 47;

[0090] S503. The control device calculates the medium-temperature supply and return water pressure difference ΔPz, ΔPz = P1 - P2.

[0091] Further, the control device acquires the pressure information real-time feedback by the low-temperature return water pressure sensor 48 and the low-temperature supply water pressure sensor 49, and calculates the low-temperature supply-return water pressure difference, denoted as ΔPd, specifically as follows:

[0092] S601. The control device acquires the pressure information P3 real-time feedback by the low-temperature return water pressure sensor 48;

[0093] S602. The control device acquires the pressure information P4 real-time feedback by the low-temperature supply water pressure sensor 49;

[0094] S603. The control device calculates the low-temperature supply-return water pressure difference ΔPd, ΔPd = P3 - P4.

[0095] Further, the medium-temperature system includes a plurality of medium-temperature terminals 411 connected in parallel. A first terminal regulating valve 412 is provided at the input end of the medium-temperature terminal 411. The low-temperature system includes a plurality of low-temperature terminals 421 connected in parallel. A second terminal regulating valve 422 is provided at the input end of the low-temperature terminal 421. The control device is electrically connected to the first terminal regulating valve 412 and the second terminal regulating valve 422 respectively. The control method further includes the steps:

[0096] S701. The control device acquires the indoor load demand of the medium-temperature terminal 411 and the indoor load demand of the low-temperature terminal 421;

[0097] S702. The control device adjusts the opening degree of the first terminal regulating valve 412 according to the indoor load demand of the medium-temperature terminal 411, and adjusts the opening degree of the second terminal regulating valve 422 according to the indoor load demand of the low-temperature terminal 421. Specifically, when the indoor load demand increases, the control device increases the opening degrees of the first terminal regulating valve 412 and the second terminal regulating valve 422. When the indoor load demand decreases, the control device decreases the opening degrees of the first terminal regulating valve 412 and the second terminal regulating valve 422.

[0098] Please refer to Figure 5 and Figure 6, the present invention also correspondingly provides a heating, ventilation and air conditioning (HVAC) system, and the HVAC system realizes working control by adopting the control method of the HVAC as described in any one of the above; the HVAC system includes a control device, a water supply pipe 1, a water return pipe 2, a chilled water pump 3, and one or more medium-low temperature series systems. The water supply pipe 1 is respectively connected to a plurality of the medium-low temperature series systems through the chilled water pump 3, and the water return pipe 2 is respectively connected to a plurality of the medium-low temperature series systems; a plurality of the medium-low temperature series systems are connected in parallel; the medium-low temperature series system includes a medium temperature system, a low temperature system, a first regulating valve 43, a second regulating valve 44, a third regulating valve 45, a medium temperature return water pressure sensor 46, a medium temperature supply water pressure sensor 47, a low temperature return water pressure sensor 48, and a low temperature supply water pressure sensor 49, which are respectively electrically connected to the control device. The water supply pipe 1 is respectively connected to the input end of the low temperature system and one end of the first regulating valve 43 through the chilled water pump 3. The other end of the first regulating valve 43 is connected to the input end of the medium temperature system. The output end of the low temperature system is connected to the input end of the medium temperature system through the second regulating valve 44 and is connected to the water return pipe 2 through the third regulating valve 45. The output end of the medium temperature system is connected to the water return pipe 2; the medium temperature return water pressure sensor 46 is arranged on the connecting pipeline between the output end of the medium temperature system and the water return pipe 2 for detecting the return water pressure of the medium temperature system; the medium temperature supply water pressure sensor 47 is arranged on the connecting pipeline between the other end of the first regulating valve 43 and the input end of the medium temperature system for detecting the supply water pressure of the medium temperature system; the low temperature return water pressure sensor 48 is arranged on the connecting pipeline between the output end of the low temperature system and the input end of the medium temperature system for detecting the return water pressure of the low temperature system; the low temperature supply water pressure sensor 49 is arranged on the connecting pipeline between the output end of the chilled water pump 3 and the input end of the low temperature system for detecting the supply water pressure of the low temperature system; the control device is also electrically connected to the chilled water pump 3 for adjusting the operating frequency of the chilled water pump 3; in one embodiment, the first regulating valve 43, the second regulating valve 44, and the third regulating valve 45 are electric regulating valves.

[0099] Further, please refer to Figure 5 and Figure 6 , the medium temperature system includes a plurality of medium temperature terminals 411 connected in parallel, and a first terminal regulating valve 412 is arranged at the input end of the medium temperature terminal 411. The low temperature system includes a plurality of low temperature terminals 421 connected in parallel, and a second terminal regulating valve 422 is arranged at the input end of the low temperature terminal 421. The control device is respectively electrically connected to the first terminal regulating valve 412 and the second terminal regulating valve 422, and the control device adjusts the opening degrees of the first terminal regulating valve 412 and the second terminal regulating valve 422 according to the indoor load demand.

[0100] It will be understood that those of ordinary skill in the art can make equivalent substitutions or changes based on the technical solution of the present invention and its inventive concept, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A control method for a heating, ventilation, and air conditioning (HVAC) system, characterized in that, the HVAC system includes a control device, a water supply pipe, a water return pipe, a chilled water pump, and one or more medium-low temperature series systems. The medium-low temperature series system includes a medium temperature system, a low temperature system, a first regulating valve, a second regulating valve, a third regulating valve, a medium temperature return water pressure sensor, a medium temperature supply water pressure sensor, a low temperature return water pressure sensor, and a low temperature supply water pressure sensor, which are respectively electrically connected to the control device. The water supply pipe is respectively connected to the input end of the low temperature system and one end of the first regulating valve through the chilled water pump. The other end of the first regulating valve is connected to the input end of the medium temperature system. The output end of the low temperature system is connected to the input end of the medium temperature system through the second regulating valve and is connected to the water return pipe through the third regulating valve. The output end of the medium temperature system is connected to the water return pipe. The control method includes the steps: When receiving a control instruction to start operation, the control device controls the first regulating valve and the third regulating valve to be fully closed, controls the second regulating valve to be fully opened, and controls the chilled water pump, the low temperature system, and the high temperature system to start working; The control device obtains the pressure information real-time feedback by the medium temperature return water pressure sensor and the medium temperature supply water pressure sensor, and calculates the medium temperature supply and return water pressure difference, denoted as ΔPz; The control device obtains the pressure information real-time feedback by the low temperature return water pressure sensor and the low temperature supply water pressure sensor, and calculates the low temperature supply and return water pressure difference, denoted as ΔPd; The control device adjusts the opening degrees of the first regulating valve, the second regulating valve, and the third regulating valve according to the medium temperature supply and return water pressure difference ΔPz to adjust the connection relationship among the low temperature system, the medium temperature system, the water supply pipe, and the water return pipe; the control device adjusts the operating frequency of the chilled water pump according to the low temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve.

2. The control method for an HVAC system according to claim 1, characterized in that, the control device adjusts the opening degrees of the first regulating valve, the second regulating valve, and the third regulating valve according to the medium temperature supply and return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump according to the low temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve, specifically including: When the medium temperature supply and return water pressure difference ΔPz is equal to the preset medium temperature supply and return water pressure difference setting value, the control device controls the first regulating valve and the third regulating valve to maintain a fully closed state, and controls the second regulating valve to maintain a fully opened state; When the low temperature supply and return water pressure difference ΔPd is greater than the preset low temperature supply and return water pressure difference setting value, the control device reduces the operating frequency of the chilled water pump; When the low temperature supply and return water pressure difference ΔPd is less than the preset low temperature supply and return water pressure difference setting value, the control device increases the operating frequency of the chilled water pump.

3. The control method for an HVAC system according to claim 1, characterized in that, the control device adjusts the opening degrees of the first regulating valve, the second regulating valve, and the third regulating valve according to the medium temperature supply and return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump according to the low temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve, specifically including: When the medium-temperature supply and return water pressure difference ΔPz is greater than the preset medium-temperature supply and return water pressure difference set value, the control device controls the second regulating valve to remain fully open, controls the first regulating valve to remain fully closed, and controls the opening degree of the third regulating valve to gradually increase; When the third regulating valve is fully open and the medium-temperature supply and return water pressure difference ΔPz is still greater than the preset medium-temperature supply and return water pressure difference set value, the control device controls the opening degree of the second regulating valve to gradually decrease until it is fully closed; When the low-temperature supply and return water pressure difference ΔPd is greater than the preset low-temperature supply and return water pressure difference set value, the control device reduces the operating frequency of the chilled water pump; When the low-temperature supply and return water pressure difference ΔPd is less than the preset low-temperature supply and return water pressure difference set value, the control device increases the operating frequency of the chilled water pump.

4. A control method for a heating, ventilation and air conditioning system according to claim 3, wherein, it further includes the steps: When the medium-temperature supply and return water pressure difference ΔPz is less than the preset medium-temperature supply and return water pressure difference set value, the control device controls the first regulating valve to remain fully closed, the third regulating valve to remain fully open, and controls the opening degree of the second regulating valve to gradually increase; When the second regulating valve is fully open and the medium-temperature supply and return water pressure difference ΔPz is still less than the preset medium-temperature supply and return water pressure difference set value, the control device controls the opening degree of the third regulating valve to gradually decrease until it is fully closed.

5. A control method for a heating, ventilation and air conditioning system according to claim 1, wherein, the control device adjusts the opening degrees of the first regulating valve, the second regulating valve and the third regulating valve according to the medium-temperature supply and return water pressure difference ΔPz; the control device adjusts the operating frequency of the chilled water pump according to the low-temperature supply and return water pressure difference ΔPd and the opening degree of the first regulating valve, specifically including: When the medium-temperature supply and return water pressure difference ΔPz is less than the preset medium-temperature supply and return water pressure difference set value, the control device controls the second regulating valve to remain fully open, controls the third regulating valve to remain fully closed, and controls the opening degree of the first regulating valve to gradually increase; When the first regulating valve is fully open and the medium-temperature supply and return water pressure difference ΔPz is still less than the preset medium-temperature supply and return water pressure difference set value, the control device increases the operating frequency of the chilled water pump; When the low-temperature supply and return water pressure difference ΔPd is greater than the preset low-temperature supply and return water pressure difference set value, the control device reduces the operating frequency of the chilled water pump; When the low-temperature supply and return water pressure difference ΔPd is less than the preset low-temperature supply and return water pressure difference set value, the control device increases the operating frequency of the chilled water pump.

6. A control method for a heating, ventilation and air conditioning system according to claim 5, wherein, it further includes the steps: When the first regulating valve is fully open and the medium-temperature supply and return water pressure difference ΔPz is still less than the preset medium-temperature supply and return water pressure difference set value, and when the low-temperature supply and return water pressure difference ΔPd is greater than the preset low-temperature supply and return water pressure difference set value, the control device obtains the information fed back by the medium-temperature system and the low-temperature system, and adjusts the working state of the chilled water pump according to the fed-back information to meet the most unfavorable signal control requirements; The control device controls the opening degree of the first regulating valve ≤ the preset maximum opening degree.

7. A control method for a heating, ventilation and air conditioning system according to claim 1, wherein, The control device acquires the pressure information real-time feedback by the medium-temperature return water pressure sensor and the medium-temperature supply water pressure sensor, and calculates the medium-temperature supply-return water pressure difference, denoted as ΔPz. Specifically: The control device acquires the pressure information P1 real-time feedback by the medium-temperature return water pressure sensor; The control device acquires the pressure information P2 real-time feedback by the medium-temperature supply water pressure sensor; The control device calculates the medium-temperature supply-return water pressure difference ΔPz, where ΔPz = P1 - P2.

8. The control method of a heating, ventilation, and air conditioning (HVAC) system according to claim 1, characterized in that The control device acquires the pressure information real-time feedback by the low-temperature return water pressure sensor and the low-temperature supply water pressure sensor, and calculates the low-temperature supply-return water pressure difference, denoted as ΔPd. Specifically: The control device acquires the pressure information P3 real-time feedback by the low-temperature return water pressure sensor; The control device acquires the pressure information P4 real-time feedback by the low-temperature supply water pressure sensor; The control device calculates the low-temperature supply-return water pressure difference ΔPd, where ΔPd = P3 - P4.

9. A heating, ventilation, and air conditioning (HVAC) system, characterized in that The HVAC system realizes working control by using the control method of the HVAC according to any one of claims 1-8; the HVAC system includes a control device, a water supply pipe, a water return pipe, a chilled water pump, and one or more medium-low temperature series systems. The water supply pipe is respectively connected to multiple medium-low temperature series systems through the chilled water pump. The water return pipe is respectively connected to multiple medium-low temperature series systems; multiple medium-low temperature series systems are connected in parallel; the medium-low temperature series system includes a medium-temperature system, a low-temperature system, a first regulating valve, a second regulating valve, a third regulating valve, a medium-temperature return water pressure sensor, a medium-temperature supply water pressure sensor, a low-temperature return water pressure sensor, and a low-temperature supply water pressure sensor respectively electrically connected to the control device. The water supply pipe is respectively connected to the input end of the low-temperature system and one end of the first regulating valve through the chilled water pump. The other end of the first regulating valve is connected to the input end of the medium-temperature system. The output end of the low-temperature system is connected to the input end of the medium-temperature system through the second regulating valve and is connected to the water return pipe through the third regulating valve. The output end of the medium-temperature system is connected to the water return pipe; the medium-temperature return water pressure sensor is arranged on the connecting pipeline between the output end of the medium-temperature system and the water return pipe for detecting the return water pressure of the medium-temperature system; the medium-temperature supply water pressure sensor is arranged on the connecting pipeline between the other end of the first regulating valve and the input end of the medium-temperature system for detecting the supply water pressure of the medium-temperature system; the low-temperature return water pressure sensor is arranged on the connecting pipeline between the output end of the low-temperature system and the input end of the medium-temperature system for detecting the return water pressure of the low-temperature system; the low-temperature supply water pressure sensor is arranged on the connecting pipeline between the output end of the chilled water pump and the input end of the low-temperature system for detecting the supply water pressure of the low-temperature system; the control device is also electrically connected to the chilled water pump.

10. The heating, ventilation, and air conditioning (HVAC) system according to claim 9, characterized in that The medium-temperature system includes multiple medium-temperature terminals connected in parallel. A first terminal regulating valve is provided at the input end of the medium-temperature terminals. The low-temperature system includes multiple low-temperature terminals connected in parallel. A second terminal regulating valve is provided at the input end of the low-temperature terminals. The control device is electrically connected to the first terminal regulating valve and the second terminal regulating valve respectively. The control device adjusts the opening degrees of the first terminal regulating valve and the second terminal regulating valve according to the indoor load demand.

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