4489 results about "Electronic expansion valve" patented technology

The invention provides an adjusting method of an electronic expansion valve for an air conditioning unit. The method comprises the steps of detecting indoor environment temperature Ti, outdoor environment temperature To and compressor running frequency f when the air conditioning unit is stared and runs, determining the initial opening degree P1 of the electronic expansion valve through the formula of P1= A*Ti + B*To + C*f + D, controlling the initial opening degree of the electronic expansion valve according to the P1, detecting the actual exhaust gas temperature T of a compressor after the air conditioning unit runs stably, enabling the electronic expansion valve to maintain a current opening degree state when the T is in an optimum target exhaust gas temperature range, reducing the opening degree of the electronic expansion valve when the T is lower than the lower limiting value of the optimum target exhaust gas temperature range, increasing the opening degree of the electronic expansion valve when the T is higher than the upper limiting value of the optimum target exhaust gas temperature range, and returning to a former step. The adjusting method reduces the time needed for adjusting the electronic expansion valve, and improves the reliability of the running of the air conditioning unit. The invention further provides an adjusting device of the electronic expansion valve for the air conditioning unit.

The present invention relates to a directly-expanded type solar heat pump air conditioning and water-heating system, the directly-expanded type solar heat pump and ice cold-storage air conditioner are combined organically, and it is mainly formed from solar heat collector / evaporator, compressor, condenser, electronic expansion valve, four-way reverse valve, heat water storage tank, hot water tank, air conditioner tail end cover and system control component. The solar heat collector / evaporator adopts the plate type heat collector which has no cover plate and whose bottom is heat insulated and whose surface is coated with solar spectrum absorbing material, and the energy storage device adopts a closed pressure-bearing heat storage water tank whose interior is equipped with high-effective heat exchange equipment which can store heat in winter and can store ice in summer.

An intelligent multi-loop thermal management system for and electric vehicle has components including a battery pack, an electric-drive module, an on-board charger a DC / DC converter, a battery radiator, a battery refrigerator, a motor radiator, an electric water pump, an electric oil pump, an expansion tank, a PTC heater, a heat exchanger, an electric compressor, a condenser, an evaporator, a receiver drier, and a heater core. The system also includes an electric-drive module having a drive motor and a motor control unit. The components are thermally connected to each other by using a pipeline and a four-way valve, a three-way valve, a straight-through valve, and an electronic expansion valve that are disposed in the pipeline, to form a plurality of loops that separately performs thermal management and control the battery pack, the electric-drive module, and a passenger compartment air conditioner.

The invention discloses a control method of a multiple connected air conditioning system. The control method comprises the following steps of: calculating a target temperature by using a fuzzy control algorithm according to operating parameters of an air conditioning system; converting an actual pressure measured by a pressure sensor into a saturated refrigerant temperature as an actual temperature and calculating a difference value of the actual temperature and the target temperature; and calculating and adjusting capacity output of a compressor, wind speed of an outdoor fan and openings of indoor and outdoor electronic expansion valves by using a proportion integration differentiation algorithm according to the difference value of the actual temperature and the target temperature, a change rate of the actual pressure and a change rate of the actual temperature and the target temperature so that the actual temperature and the target temperature are consistent. The invention also discloses the multiple connected air conditioning system. The air conditioning system has little wave property, stability, favorable refrigeration and heating effects and favorable energy saving effect.

The invention discloses a defrosting control method of an air conditioner. The control method comprises the following steps that environment temperature and the temperature of an outdoor heat exchanger outlet or the temperature of a super cooling section are obtained; whether the defrosting condition is met or not is judged according to the environment temperature and the temperature of the outdoor heat exchanger outlet or the temperature of the super cooling section; when the judgment result shows that the defrosting condition is met, the wind speed of an indoor fan is decelerated, an electronic expansion valve is controlled to be lowered to the first opening degree state, an outdoor fan is closed, a compressor is regulated to the defrosting frequency, after the preset time, and the first ascending speed is used for controlling the electronic expansion valve to be raised to the second opening degree state, wherein the opening degree value of the second opening degree state is greater than the opening value of the first opening degree state. The defrosting control method of the air conditioner has the advantages that the defrosting can be realized without stopping the compressor, the method is simple, and the reliability is high. The invention also provides the air conditioner.

An air conditioner has a refrigeration circuit formed by sequentially connecting a compressor 1, a condenser 2, an electronic expansion valve 4 and an evaporator 7 by pipes (6, 10). A compressor bypass pipe 12 is provided to connect an outlet of the evaporator 7 with an inlet of the condenser 2. A first on-off valve 11 is located in the bypass pipe 12. The air conditioner is controlled to switch to either a forced circulation operation or a natural circulation operation. In the forced circulation operation, the first on-off valve 11 is closed, the expansion valve 4 is opened to a first degree to allow refrigerant to pass therethrough, and the compressor 1 is operated in a running state. In the natural circulation operation, the first on-off valve 11 is opened, the expansion valve 4 is opened to a second degree, different from the first degree, to allow refrigerant to pass therethrough, and the compressor 1 is stopped.

A process and method for monitoring and selectively controlling the capacity and power demand within a transport unit is disclosed. Specifically, the present invention teaches the combined controls of an electronic suction modulation valve, and electronic expansion valve, and / or an electronic hot gas valve in communication with a microcontroller and a number of sensors in order to monitor and control power consumption and capacity, preferably without the use or presence of compressor unloaders, mechanical throttling devices, or other mechanical power control devices.

The invention is applicable to an air conditioner control technology and provides a system for controlling an electronic expansion valve of an air conditioner. The system comprises a system starting unit, a superheat degree acquisition unit, and a judgment and regulation unit, wherein the system starting unit is used for opening the electronic expansion valve based on initial openness according to the environment temperature; the superheat degree acquisition unit is used for acquiring the exhaust temperature superheat degree of a compressor regularly; the judgment and regulation unit is used for judging whether the exhaust temperature superheat degree is within a preset reasonable temperature range and regulating the initial openness based on preset regulation amplitude when the exhaust temperature superheat degree is not within the preset reasonable temperature range, thus to enable the exhaust temperature superheat degree of the compressor to be within the preset reasonable temperature range. The system for controlling the electronic expansion valve of the air conditioner has the advantages that the openness of the electronic expansion valve is adjusted according to the exhaust temperature superheat degree of the compressor; due to larger permissible error range of the exhaust temperature superheat degree, the openness of the compressor cannot deviate from the optimum openness even if errors are smaller, so that a multi-split air conditioner system can be keep well operating under an optimum state.

The invention relates to a method for controlling a machine room air conditioner based on a variable frequency compressor. The method comprises the following steps of: 1, initializing the machine room air conditioner, and returning an electronic expansion valve to zero; 2, starting an evaporator, and regulating the air velocity of a fan of the evaporator according to air suction pressure Ps; 3, starting the variable frequency compressor, and regulating the frequency H of the variable frequency compressor according to the indoor temperature T0 and the preset temperature TA; 4, starting a condenser in time T2 after the variable frequency compressor is started, and controlling the air velocity of a fan of the condenser according to exhaust pressure PD and the air inlet temperature TD; and 5, controlling the opening Pm of the electronic expansion valve, and performing corresponding compensation on the opening Pm of the electronic expansion valve according to the frequency of the variable frequency compressor. By adopting the method for controlling the machine room air conditioner based on the variable frequency compressor, the temperature is controlled more stably and the fluctuation is low; and the opening of the expansion valve is compensated through the variable frequency compressor, so that the superheat degree is more stable and close to the expected target value.

The invention discloses a thermostat dehumidification control method of an air conditioner. The air conditioner comprises a compressor, a condenser, an electronic expansion valve, an evaporator, a four-way reversing valve, an outdoor fan, an indoor fan, an indoor temperature sensor, an indoor humidity sensor and an outdoor temperature sensor; and the evaporator is divided into a heating section and a dehumidifying section by a dehumidifying electromagnetic valve. The dehumidifying operating mode of the air conditioner is divided into a cold room dehumidification control mode and a thermostat dehumidification control mode according to the difference between the temperature detected by the indoor temperature sensor and the temperature set by a remote controller. When the air conditioner is in the thermostat dehumidification control mode, the thermostat dehumidification control mode is further subdivided into three control areas according to the relative humidity detected by the indoor temperature sensor, thus the purposes of reducing the indoor temperature and keeping the temperature constant are achieved by controlling the frequency of the compressor, the rotation speed of the outdoor fan and various valves, and a conformable indoor environment is provided for the user.

The present invention provides a control method of an electronic expansion valve, the electronic expansion valve is provided in a refrigerant circulation loop of equipment, the circulation loop is also provided with an evaporator, characterized in that the control method includes following steps: S10: starting the electronic expansion valve to process initialization, setting the opening of the electronic expansion valve in a predetermined initial value; S20: after starting the predetermined time, determining the real superheat / subcooling of the electronic expansion valve according to the difference between the outlet temperature and the inlet temperature of the evaporator; S30: comparing the object superheat / subcooling with the real superheat / subcooling, determining the optimal opening range of the electronic expansion valve; S40: adjusting the opening of the electronic expansion valve to the optimal opening range. The invention realizes the automatic control of refrigerant volume and throttle degree of equipment, and capable of adapting the working condition to control automatically, so as to protect the optimal state in the system operation ,ensuring credibility and safety operation.

The invention provides a control system for air-conditioning heating and frosting. The control system comprises an air-conditioning system, wherein the air-conditioning system comprises an outdoor unit heat exchanger (3), an electronic expansion valve (8), a compressor (1) and an outdoor motor (4), and further comprises an outer ring temperature detecting element (6) and an outer tube temperature detecting element arranged on the outdoor unit heat exchanger (3) as well as a controller electrically connected with the elements, wherein the controller (7) outputs a control signal to one or more of the electronic expansion valve (8), the compressor (1) and the outdoor motor (4). According to the control system provided by the invention, frostless control can be carried out on a frosting process of an outdoor unit, so that indoor heating comfort is improved; a frosting period is prolonged, so that defrosting action in a using process of a user is reduced; the process is simple and the cost is reduced; and active defrosting is carried out to overcome the defects of passive defrosting. The invention further relates to a control method for carrying out frosting control by utilizing the system.

The invention provides an air-conditioner defrosting control method. The air-conditioner defrosting control method comprises the following steps that when the outdoor environmental temperature is higher than 0 DEG C and lower than 5 DEG C, an air-conditioner works in a heating mode, and whether defrosting conditions are met or not is judged; if the defrosting conditions are met, the air-conditioner enters a defrosting mode, the defrosting mode is that a frequency of a compressor is controlled to be a defrosting frequency, and meanwhile, an aperture of an electronic expansion valve is controlled to be a defrosting aperture to enable the surface temperature of an outdoor heat exchanger to be kept at 0 DEG C; and the defrosting frequency is lower than the real-time operational frequency of the compressor in the heating mode, the defrosting aperture is larger than the real-time aperture of the electronic expansion valve in the heating mode, and the air-conditioner keeps operating the defrosting mode till the situation that an exit condition is met is judged. Meanwhile, an air-conditioner defrosting control device and an air-conditioner are further disclosed. According to the air-conditioner defrosting control method, switching between the heating mode and a refrigeration mode is not needed in the defrosting process, defrosting is conducted by using air heat, and the air-conditioner defrosting control method has the advantages that energy consumption is low, and user experience is good.

The invention discloses an electronic expansion valve, which comprises an electrical control part and a mechanical part. The electrical control part comprises a bus signal reception / transmission module, a central processing module and a stepper motor driving module; wherein the bus signal reception / transmission module is used for receiving a bus control signal and transmitting the bus control signal to the central processing module; the central processing module is used for extracting valve opening information included in the bus control signal, generating a corresponding pulse control signalin combination with current position information of a stepper motor read from a data storage module, and outputting the pulse control signal to the stepper motor driving module; and the stepper motordriving module is used for driving the stepper motor to adjust the valve opening according to the pulse control signal. The invention also discloses a stepper motor and a reversing valve. The number of drive wires directly connected with a main control board can be reduced, the structure of the main control board can be simplified, and the manufacturing cost can be saved.

The invention provides a method for controlling opening of an electronic expansion valve in a central air-conditioning unit, which comprises the following steps of: 1, changing the opening of the electronic expansion valve according to difference of T suction and T target; and 2, after the opening of the electronic expansion valve is changed, when a compressor in the central air-conditioning unitoperates to a first preset time, if T exhaust is not in a preset range of exhaust superheat degree, changing the T target and turning to the step 1, otherwise setting T target to be T0 target and returning to the step 1, wherein T suction refers to an actual suction superheat degree of the compressor in the central air-conditioning unit, T exhaust refers to an actual exhaust superheat degree of the compressor, T target refers to an actual target suction superheat degree of the compressor, and T0 target refers to an initial target suction superheat degree of the compressor. By the control method, interference resistance of the central air-conditioning unit is improved, and the reliability of the central air-conditioning unit is improved.

The present invention discloses a refrigerant flow rate intelligent distribution system for one-driving-multiple air conditioners, comprising a compressor and at least three indoor units, wherein, each indoor unit comprises a control valve regulation module for intelligently regulating an electronic expansion valve of each indoor unit. The present invention also discloses a refrigerant flow rate intelligent distribution method for one-driving-multiple air conditioners, which first regulates the electronic expansion valve of each indoor unit to a datum opening degree when the compressor begins to operate, and then does not regulate the electronic expansion valve of each indoor unit in an operation period of the compressor, and finally regulates the electronic expansion valve of each indoor unit according to valve regulation cycles after the compressor overruns the operation period. Through the intelligent distribution to the refrigerant flow rate of one-driving-multiple air conditioners, the present invention realizes the refrigerant flow rate distribution of one-driving-multiple air conditioners according to needs.

The invention relates to a high-heat-discharge-quantity refrigerating and heating temperature control system for a reaction kettle. The high-heat-discharge-quantity refrigerating and heating temperature control system comprises a reaction kettle, wherein one end of the reaction kettle is sequentially connected with a heating pipe, an electric proportioning regulating valve, a first cold storage tank and an evaporation heat exchanger through a fourth pipeline, the output end of the evaporation heat exchanger is sequentially connected with a first circulation pump, a first one-way valve, an expansion tank and an exhaust valve through a first pipeline, the exhaust valve is connected to the other end of the reaction kettle through a fifth pipeline, the two ends of the evaporation heat exchanger are connected with a refrigerating machine, the refrigerating machine is structurally characterized in that one end of the evaporation heat exchanger is sequentially connected in series with a gas-liquid separator, a compressor, an oil separator, a condenser, a drying filter, a second cold storage tank, an electromagnetic valve and an expansion valve through a third pipeline, the outer end of the expansion valve is connected with the other end of the evaporation heat exchanger through an eighth pipeline, the refrigerating machine is positioned between the electromagnetic valve and the second cold storage tank and is connected with the third pipeline through the second pipeline, and an electronic expansion valve is arranged on the second pipeline. The work reliability is good.

The invention provides a vapor-injected air-conditioning system, a vapor-injected air-conditioning control method and an air-conditioner, which can solve the problems of incapability of refrigerant flow adjustment, complex structure, poor refrigerating / heating effect and the like of the prior art. The technical scheme includes that the vapor-injected air-conditioning system comprises a compressor, a controller, a four-way valve, a condenser, an evaporator, a flash evaporator, an electromagnetic valve and refrigerant pipes. Two refrigerant pipe connector ends of the flash evaporator are arranged at the refrigerant pipes between the evaporator and the condenser and connected with the refrigerant pipes on the respective side, a refrigerant outlet at one end of the flash evaporator is connected with the compressor through one refrigerant pipe provided with a one-way valve and the electromagnetic valve, and an electronic expansion valve is arranged on the refrigerant pipe arranged between the condenser and the flash evaporator. A vapor-injected flow control system is simplified, cost is reduced, refrigerant flow control of the system is optimized by using the electronic expansion valve for controlling, and refrigerating and heating performances are improved.

The invention provides a method and a system for low-frequency oil return control for an air conditioner. The method comprises the following steps: detecting a running frequency, a suction gas superheat degree, an indoor environment temperature and an outdoor environment temperature of a compressor; when detecting that the running frequency of the compressor is kept for a preset time in the case that the running frequency is lower than a preset oil return frequency, enabling the air conditioner to enter an oil return mode, selecting an initial openness degree of an electronic expansion valve in the air conditioner, an initial rotational speed of an outdoor fan and an initial rotational speed of an indoor fan according to the indoor environment temperature and the outdoor environment temperature, adjusting the openness degree of the electronic expansion valve to be the initial openness degree, adjusting the rotational speed of the outdoor fan to be the initial rotational speed, and adjusting the rotational speed of the indoor fan to be the initial rotational speed; and adjusting the openness degree of the electronic expansion valve, the rotational speed of the outdoor fan and the rotational speed of the indoor fan according to the detected suction gas superheat degree. According to the invention, an oil return effect is achieved by virtue of a pipeline pressure difference, and various adverse factors brought by the traditional increasing-frequency oil return are overcome in case of no influence on the refrigerating capacity need and the running reliability of low-frequency running.

The invention discloses a refrigerant flow control method for a multi-connected air-conditioning system during heating. The refrigerant flow control method controls the refrigerant flow in the system by adjusting the opening of an electronic expansion valve in a switched-off indoor unit, and comprises the following steps: a. enabling the air-conditioning system to enter a heating operational mode; b. switching off or switching on the valve according to the condensing pressure and evaporating pressure of the system; c. switching on the valve according to the exhaust temperature of a compressor; and d. switching off or switching on the valve according to the condensing saturation temperature converted from the condensing pressure or according to the coil temperature of the switched-on indoor unit, the coil temperature of the switched-off indoor unit, the outlet temperature of a heat exchanger in the switched-off indoor unit and the inlet temperature of the heat exchanger in the switched-off indoor unit. The dynamic equilibrium control strategy for a refrigerant provided by the invention can automatically adjust the opening of the electronic expansion valve in the switched-off indoorunit according to the system operation conditions, thereby avoiding energy waste and reduced heating effect caused by overlarge deviation of the opening of the expansion valve, and improving the heating performance of the air-conditioning system.

The invention discloses an air conditioner and a control method thereof. The control method comprises the following steps: detecting the discharge temperature of a compressor of the air conditioner; detecting the pipeline temperature of a heat exchanger of the air conditioner; calculating a difference value between the former two temperatures to obtain the exhaustion superheat degree of the air conditioner; comparing the exhaustion superheat degree with a range of a target exhaustion superheat degree to obtain a relation; and when the exhaustion superheat degree is not within the range of the target exhaustion superheat degree, adjusting the opening degree of an electronic expansion valve of the air conditioner to allow the exhaustion superheat degree to be within the range of the target exhaustion superheat degree. According to the invention, the electronic expansion valve of a system is adjusted based on the exhaustion superheat degree with top and bottom limitation set in the adjusting process, so that the air conditioner can always keep the exhaustion superheat degree stable, no matter what environmental temperature is, so that the long-time running stability and reliability of the air conditioner are greatly increased.

The invention is applicable to the field of air conditioner controlling and provides an integrated control method and circuit for an electronic expansion valve of an air conditioner. The method includes: calculating a first openness adjustment of the electronic expansion valve according to exhaust temperature; calculating a second opening adjustment and adjusting time of the electronic expansion valve according to superheat degree of return gas of a compressor; selecting one of the first opening adjustment and the second opening adjustment as a final opening adjustment of the electronic expansion valve according to size relationship between the first and second opening adjustments, correspondingly adjusting opening of the electronic expansion valve according to the final opening adjustment, and keeping the opening of the electronic expansion valve unchanged in an adjusting period of time. An effective control scheme is provided by combining a control method for superheat degree of the return gas of the compressor and a control method for target temperature of exhaust of the compressor; the defects of the existing two control methods can be overcome; quick response of the electronic expansion valve is achieved; control with optimal energy efficiency is achieved.

The invention discloses a throttle opening degree control method for a varied-frequency air-conditioner. The method comprises the following steps of: S1) making an electronic expansion valve standby at the opening degree of P0; S2) determining a frequency band Fn of a compressor frequency value according to the compressor frequency value and a corresponding initial target opening degree Pn; adjusting the opening degree of the electronic expansion valve to be Pn; if the frequency of a compressor is increased, adjusting the opening degree of the electronic expansion valve to be the initial target opening degree corresponding to a real-time frequency; and if the frequency of the compressor is reduced, adjusting the opening degree of the electronic expansion valve to be the initial target opening degree corresponding to the real-time frequency after a delay of 60 seconds; and S3) after the electronic expansion valve is operated for t minutes at the opening degree of Pn, modifying the opening degree of the electronic expansion valve every other m seconds. By the method, the optimum efficiency of the operation of a refrigeration system can be ensured at various frequencies and under various working conditions.

The invention discloses a control method for an electronic expansion valve, a self-adaptive control method for a heat pump, and a device thereof; wherein, the control method for the electronic expansion valve comprises the steps as follows: S110: the electronic expansion valve is started and initiated; a controller arranges the openness of the electronic expansion valve as an initial value; S120: after starting prearranged time, the controller determines the practical over-heat degree of the electronic expansion valve; S130: controller compares the practical over-heat degree with a destination over-heat degree so as to determine the optimum openness value domain of the electronic expansion valve, and S140: the controller adjusts the openness of the electronic expansion valve to the optimum openness value domain. Therefore, automatic regulation of refrigerant flux and throttling degree of the heat pump device according to the working conditions can be ensured, the system is protected and runs at a best state, the optimum openness of the electronic expansion valve can be quickly gained, the lag time is greatly reduced, and the throttling degree of the system can be adjusted according to the running state.

The invention relates to a central air-conditioning system, in particular to a duct air conditioner, namely an enhanced vapor injection air-conditioning circulating system. A vapor injection side electronic expansion valve of the system is subject to discharge superheat control instead of vapor injection superheat control; high discharge superheat is guaranteed, and heating capacity of the system can be further improved by vapor injection; the system is especially applicable to variable frequency compressors; high heating capacity is kept even under different operating frequencies; the system operates stably and fluctuates little. The enhanced vapor injection air-conditioning circulating system comprises a controller, a compressor, a four-way valve, a vapor-liquid separator, an economizer, a solenoid valve and a coolant pipe. The compressor is a variable frequency compressor. The economizer is a plate economizer. The electronic expansion valve controls vapor injection. The vapor injection electronic expansion valve is subject to discharge superheat control instead of vapor injection superheat control; accordingly, high discharge superheat is guaranteed, and heating capacity of the system is further improved by vapor injection. The system is especially applicable to variable frequency compressors; the heating capacity is kept even under different operating frequencies; the system operates stably and fluctuates little.

The invention relates to a multipurpose intelligent control method for an electronic expansion valve of a heat pump system of a refrigeration air-condition, belonging to the technical field of the independent heat and cold energy supply of buildings. The method comprises the steps of(1) determining two or more controlled parameters affected by the electronic expansion valve,(2) determining a set value for each controlled parameter and carrying out detection in real time, (3)comparing the detection value and the set value of each controlled parameter, calculating deviation and deviation change rate, then carrying out indistinct processing to generate the control quantity of respective electronic expansion valve,(4) obtaining the control quantity of each electronic expansion valve by being calculated by the step (3) to be taken as the input layer of a neural network controller and obtaining the right value of each controlled parameter by being trained by a single neuron neural network and (5) obtaining the feedback control quantity of the electronic expansion valve according to each controlled parameter value detected in real time. Due to the adoption of the method, operating parameters can be intelligently adjusted, so that intelligent heat and cold supply and stable and efficient operation under a variety of climatic conditions are realized.

The invention provides an air conditioner and a self-cleaning control method of an indoor unit of the air conditioner. An indoor unit heat exchanging assembly of the air conditioner comprises a first indoor heat exchanger and a second indoor heat exchanger which are in tandem connection. The second indoor heat exchanger is connected to a compressor through a refrigerant flow direction switching device. An electronic expansion valve is arranged between the first indoor heat exchanger and the second indoor heat exchanger. The control method comprises the following steps that a trigger signal that the air conditioner starts a self-cleaning function is received, and the refrigerant flow direction switching device is adjusted to a state that the compressor provides a compress refrigerant for the indoor unit heat exchanging assembly; by adjusting the opening degree of the electronic expansion valve, the first indoor heat exchanger is made to conduct refrigerating firstly and then heating so as to constantly frost on the surface of the first indoor heat exchanger in a refrigerating stage; and defrosting is conducted in a heating stage, attached contaminants are taken away by water formed by defrosting, and self cleaning of the first indoor heat exchanger is achieved. According to the scheme, drastic fluctuation of temperature is avoided, and better using experience is brought to users.

The invention discloses a refrigerant flow control method and device for a multi-connected air conditioning system. The device comprises control modules; each control module is provided for each indoor unit of the multi-connected air conditioning system. Each control module for the corresponding indoor unit comprises a sensor unit and a master control panel; the sensor unit used for acquiring data of the indoor unit comprises a high pressure sensor, a return air temperature sensor, a supply air temperature sensor and a liquid pipe temperature sensor; the master control board is used for receiving user-set temperature and acquiring data from the sensor unit to calculate target supercooling degree and actual supercooling degree when each sampling period is up; a difference between the actual supercooling degree and the target supercooling degree is used as a supercooling degree difference; an opening signal of an electronic expansion valve is adjusted to control opening of the electronic expansion valve of the corresponding indoor unit according to a difference between the supercooling degree difference of the current sampling period and the supercooling degree difference of previous sampling period. Through the use of the refrigerant flow control method and device, heating effect of each indoor unit can be guaranteed and energy consumption can be avoided.

The invention discloses a method for controlling a direct current frequency conversion air-conditioner while operating in a refrigeration mode. The method is used for controlling the direct current frequency conversion air-conditioner when the lowest capacity output of the outdoor unit is higher than the capacity requirement of the inner unit, and comprises the following steps: step 1, setting different target low pressure values for various sections of the outdoor ambient temperature; step 2, reducing the operation frequency of a direct current frequency conversion compressor to the lowest operation frequency during the operation process of the direct current frequency conversion air-conditioner according to the requirements on the capability of the indoor unit; and step 3, controlling a first throttle electronic expansion valve, a second throttle electronic expansion valve and an unloading electromagnetic valve to execute corresponding actions according to the low pressure values when the direct current frequency conversion compressor operates in the lowest operation frequency, or controlling the direct current frequency conversion air-conditioner to be started or stopped. With the adoption of the method, the excess capacity output of the outdoor unit is counterbalanced, so that capacity output of the outdoor unit is matched with the lowest capacity requirement of the indoor unit, the normal and stable operation of the direct current frequency conversion air-conditioner is maintained, and the phenomenon that a small trolley is drawn by a horse having large power is prevented.

The invention relates to a VRF (varied refrigerant volume) air conditioning system, which comprises a compressor, an evaporator, a condenser, an outdoor environment temperature sensor and an electronic expansion valve opening degree control device, wherein the electronic expansion valve opening degree control device comprises a controller, temperature sensors, a pressure sensor and an electronic expansion valve, the temperature sensors, the pressure sensor and the electronic expansion valve are respectively in electric signal connection with the controller, the temperature sensors are respectively arranged on an exhaust pipe of each compressor for detecting the exhaust temperature value, the pressure sensor is arranged on a main exhaust pipe of a plurality of compressors for detecting the total exhaust pressure, and the electronic expansion valve is arranged at the back end of the condenser for realizing the throttling on an outdoor unit. The invention also discloses a control method of the VRF air conditioning system. The control method avoids the defects that in the practical use, when the exhaust temperature is too low, excessive coolants are deposited at the air return side of the system, the compression with liquid of the compressor is caused, when the exhaust temperature is too high, the compressor is overheated, and the lubricating oil carbonization of the system is caused. The stable and efficiency operation of the whole system is guaranteed.