CN106052031A - Frequency conversion control system and method for outdoor unit of constant temperature and humidity equipment - Google Patents

Abstract

The invention discloses a variable frequency control system and method of an outdoor unit of constant temperature and humidity equipment, wherein the system comprises: a temperature sensor for measuring an actual condensing temperature of the condenser; the PID controller is used for calculating the frequency value of the frequency converter to be executed through a PID algorithm according to the deviation between the measured actual condensation temperature and the set ideal condensation temperature; the D/A conversion unit is used for converting the frequency value of the frequency converter calculated by the PID controller into an analog signal which can be identified by the frequency converter; and the frequency converter is used for adjusting the rotating speed of the fan according to the corresponding analog signal, so that the condensing temperature of the condenser is controlled in real time to reach the ideal condensing temperature, and the condensing pressure is higher than the evaporation limiting pressure. The invention has reasonable design and can realize the perennial stable operation of the equipment.

Description

Frequency conversion control system and method for outdoor unit of constant temperature and humidity equipment

technical field

The present invention relates to the technical field of constant temperature and humidity equipment, and more specifically relates to a frequency conversion control system and method for an outdoor unit of constant temperature and humidity equipment.

Background technique

The existing constant temperature and humidity equipment generally relies on freezing and dehumidification in consideration of its economy and stability. When the constant temperature and humidity equipment is running at low temperature, the surface temperature of the evaporator must be lower, but the temperature will be lower than 0°C for a long time, which will cause evaporation. The evaporator is frosted, and defrosting will cause temperature and humidity fluctuations, so long-term operation and need to be used as low-temperature and low-humidity constant temperature and humidity equipment must limit the evaporator temperature to not be too much lower than 0°C, and the evaporator temperature is determined by the evaporation pressure of the refrigerant It was decided that limiting the evaporator temperature would limit the evaporating pressure.

The compressor absorbs the refrigerant vapor from the evaporator, increases the pressure (compression), and flows to the condenser to condense. After condensation, the refrigerant flows to the evaporator through the throttle valve, so that the refrigerant completes the refrigeration cycle. During this process, the refrigerant flows from high pressure to low pressure powered by pressure. When the ambient temperature of the condenser is too low (below -10°C in winter in the north), and the condensation temperature is lower than the limited evaporation temperature of the evaporator, that is, when the condensation pressure is lower than the evaporation limit pressure, the refrigerant cannot complete the refrigeration cycle. The refrigeration and dehumidification effect, the equipment cannot operate normally, so the year-round operation of the equipment cannot be realized.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects in the prior art, and provide a frequency conversion control system and method for outdoor units of constant temperature and humidity equipment, which can make the constant temperature and humidity equipment realize stable operation all year round.

In order to achieve the above object, the first aspect of the present invention provides a frequency conversion control system for the outdoor unit of constant temperature and humidity equipment, the outdoor unit of the constant temperature and humidity equipment is set as a condenser with a fan, and the fan is equipped with frequency converter, the system includes:

A temperature sensor for measuring the actual condensation temperature of the condenser;

The PID controller is used to calculate the frequency value of the inverter to be executed through the PID algorithm according to the deviation between the measured actual condensing temperature and the set ideal condensing temperature;

The D/A conversion unit is used to convert the frequency value of the inverter calculated by the PID controller into an analog signal that can be recognized by the inverter;

The frequency converter is used to adjust the fan speed according to the corresponding analog signal, so as to control the condensing temperature of the condenser in real time to achieve the ideal condensing temperature, and to make the condensing pressure higher than the evaporation limit pressure.

Preferably, the constant temperature and humidity equipment further includes an evaporator and a compressor, the condenser is respectively connected to the evaporator and the compressor, and the evaporator is connected to the compressor.

Preferably, a throttling valve is connected between the condenser and the evaporator, and an evaporation pressure regulating valve is connected between the evaporator and the compressor.

Preferably, the ideal condensation temperature is higher than 0°C and the evaporation temperature of the evaporator.

Preferably, the ideal condensation temperature is set at 11-14°C.

Preferably, the analog signal is set as a 0-10V analog signal.

The second aspect of the present invention provides a frequency conversion control method implemented by the frequency conversion control system of the outdoor unit of the constant temperature and humidity equipment described in the above technical solution, including the following steps:

Measure the actual condensation temperature of the condenser through the temperature sensor;

According to the deviation between the measured actual condensing temperature and the set ideal condensing temperature, the PID controller uses the PID algorithm to calculate the frequency value of the inverter to be executed;

The D/A conversion unit converts the frequency value of the inverter calculated by the PID controller into an analog signal that can be recognized by the inverter;

The frequency converter adjusts the fan speed according to the corresponding analog signal, so as to control the condensing temperature of the condenser in real time to make it reach the ideal condensing temperature, and make the condensing pressure higher than the evaporation limit pressure.

As preferably, described PID controller is made up of proportional unit, integral unit and differential unit, and the relation of its input e(t) and output u(t) is:

u(t)=kp[e(t)+1/TI∫e(t)dt+TD*de(t)/dt];

In the formula, the upper and lower limits of integral are 0 and t respectively;

The transfer function is: G(s)=U(s)/E(s)=kp[1+1/(TI*s)+TD*s];

Among them, kp is the proportional coefficient, TI is the integral time constant, and TD is the differential time constant.

Compared with prior art, the beneficial effect of the present invention is:

The invention measures the actual condensing temperature of the condenser through a temperature sensor, uses the PID algorithm to calculate the frequency value of the frequency converter to be executed according to the deviation between the actual condensing temperature and the ideal condensing temperature, and then converts the frequency value of the frequency converter through the D/A conversion unit It can be converted into an analog signal that can be recognized by the frequency converter, so as to control the frequency of the frequency converter to adjust the speed of the condenser fan, control the condensation temperature by controlling the heat dissipation, and make the condensing pressure higher than the evaporation limit pressure of the evaporator, so as to realize the equipment. It operates stably all year round.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are For some embodiments of the present invention, those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the structural representation of constant temperature and humidity equipment provided by the present invention;

Fig. 2 is the structural block diagram of the frequency conversion control system of the outdoor unit of constant temperature and humidity equipment provided by the present invention;

Fig. 3 is a working principle diagram of the frequency conversion control system of the outdoor unit of the constant temperature and humidity equipment provided by the present invention.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Please refer to Figure 1, which shows a constant temperature and humidity equipment, which includes an outdoor unit, an evaporator 7 and a compressor 8 located indoors, wherein the outdoor unit of the constant temperature and humidity equipment is set as a fan 1 The condenser 2 is connected to the evaporator 7 and the compressor 8 respectively, and the evaporator 7 is connected to the compressor 8 . In addition, a throttle valve 9 is connected between the condenser 2 and the evaporator 7 , and an evaporation pressure regulating valve 10 is connected between the evaporator 7 and the compressor 8 . During specific assembly, the exhaust port of compressor 8 is connected to one end of condenser 2 by pipeline, and the other end of condenser 2 is connected to throttle valve 9 by pipeline and then connected to one end of evaporator 7 by pipeline, and the end of evaporator 7 The other end is finally connected to the suction port of the compressor 8 by a pipeline, so as to realize the connection process of a complete refrigeration system.

When working, the low-temperature and low-pressure refrigerant gas that has been heat-exchanged (heat-absorbed) by the evaporator 7 in the system is sucked by the compressor 8 and passed (compressed) into a high-pressure and high-temperature gas that is transported to the condenser 2 through pipelines (cooling and releasing heat ) into a medium-temperature and high-pressure liquid and then send the medium-temperature and high-pressure liquid to the throttle valve 9 (throttling and decompression) through the pipeline. Evaporation absorbs surrounding heat, and this continuous cycle of heat exchange completes the entire refrigeration cycle.

Please refer to Fig. 2, an embodiment of the present invention provides a frequency conversion control system for an outdoor unit of constant temperature and humidity equipment, the system includes a temperature sensor 4, a PID controller 5, a D/A conversion unit 6 and a fan 1 Frequency converter 3, the present embodiment will be described in detail below in conjunction with the accompanying drawings.

The temperature sensor 4 is used to measure the actual condensation temperature of the condenser 2 .

Wherein, the temperature sensor 4 can be installed on the pipeline between the condenser 2 and the throttle valve 9 and close to the condenser 2 .

The PID controller 5 is used to calculate the frequency value of the frequency converter 3 to be executed through the PID algorithm according to the deviation between the measured actual condensing temperature and the set ideal condensing temperature.

During specific implementation, the ideal condensing temperature must be higher than 0°C and the evaporation temperature of the evaporator 7, but it should not be too high. If it is too high, the condensation efficiency will be low and the refrigeration effect will be poor. Generally speaking, the ideal condensing temperature can be set at 11-14°C , For example: 12°C. Of course, the value can also be selected in other ranges according to the actual situation.

The D/A conversion unit 6 is used to convert the frequency value of the frequency converter 3 calculated by the PID controller 5 into an analog signal that can be recognized by the frequency converter 3 .

During specific implementation, the analog signal can preferably be set as a 0-10V analog signal, which fully considers its uniformity, and all frequency converters on the market support 0-10V analog signals.

The frequency converter 3 is used to adjust the speed of the fan 1 according to the corresponding analog signal, so as to control the condensing temperature of the condenser 2 in real time to achieve an ideal condensing temperature, and to make the condensing pressure higher than the evaporation limit pressure.

As shown in Figure 3, a frequency conversion control method realized by a frequency conversion control system of an outdoor unit of constant temperature and humidity equipment, the method includes the following steps:

(1) measure the actual condensation temperature of condenser 2 by temperature sensor 4;

(2) The PID controller 5 uses the PID algorithm to calculate the frequency value of the frequency converter 3 to be executed according to the deviation between the measured actual condensing temperature and the set ideal condensing temperature;

Specifically, the PID element consists of three parts: measure, compare and execute. The key to measuring is the actual value of the controlled variable, compared with the expected value, and using this deviation to correct the response of the system to perform regulatory control. In engineering practice, the most widely used regulator control law is proportional, integral, differential control, referred to as PID control, also known as PID regulation.

The PID controller 5 is composed of a proportional unit, an integral unit and a differential unit. The relationship between its input e(t) (i.e. the difference between the actual condensing temperature and the ideal condensing temperature) and the output u(t) (i.e. the frequency value) is:

u(t)=kp[e(t)+1/TI∫e(t)dt+TD*de(t)/dt];

In the formula, the upper and lower limits of integral are 0 and t respectively;

The transfer function is: G(s)=U(s)/E(s)=kp[1+1/(TI*s)+TD*s];

Among them, kp is the proportional coefficient, TI is the integral time constant, and TD is the differential time constant.

(3) The D/A conversion unit 6 converts the frequency value of the frequency converter 3 calculated by the PID controller 5 into an analog signal that can be recognized by the frequency converter 3;

(4) The frequency converter 3 adjusts the speed of the fan 1 according to the corresponding analog signal, so as to control the condensation temperature of the condenser 2 in real time so that it reaches an ideal condensation temperature, and makes the condensation pressure higher than the evaporation limit pressure.

In the frequency conversion speed regulation system, according to the formula n=60f/p, it can be known that changing the frequency f can change the speed n, reducing the frequency f, the speed will become smaller: that is, 60f↓/p=n↓, increasing the frequency f, the speed will increase Large: namely 60f↑/p=n↑.

When the condensing temperature is lower than the evaporating temperature limited by the evaporator, that is, when the condensing pressure is lower than the evaporating limiting pressure, the refrigerant cannot complete the refrigeration cycle. At this time, there is no cooling and dehumidification effect, and the equipment cannot operate normally. Therefore, it needs to be operated all year round and condensed For outdoor constant temperature and humidity equipment, when the ambient temperature is too low, it must be controlled to make the condensation temperature reach an ideal value, so that the equipment can operate in an ideal state.

In summary, the present invention can collect the condensation temperature and control the frequency of the frequency converter in combination with the PID control principle to adjust the speed of the condenser fan, control the condensation temperature by controlling the heat dissipation, and make the condensation pressure higher than the evaporation limit pressure of the evaporator , so as to realize the stable operation of the equipment all year round.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (8)

1. a frequency-changing control system for the outdoor unit of thermostatic constant wet equipment, the outdoor unit of described thermostatic constant wet equipment is arranged For the condenser with blower fan, it is characterised in that be provided with converter in described blower fan, this system includes:

Temperature sensor, for measuring the actual condensation temperature of condenser；

PID controller, for the deviation according to the preferable condensation temperature measuring actual condensation temperature and the setting arrived, passes through PID Algorithm removes to calculate the frequency values of the converter needing execution；

D/A converting unit, can allow converter identification for being converted into by the frequency values of calculated for PID controller converter Analogue signal；

Converter, for going to adjust rotation speed of fan according to corresponding analogue signal, thus controls the condensation temperature of condenser in real time Reach preferable condensation temperature, and make condensing pressure be higher than evaporation restriction pressure.

The frequency-changing control system of the outdoor unit of thermostatic constant wet equipment the most according to claim 1, it is characterised in that described Thermostatic constant wet equipment also includes that vaporizer and compressor, described condenser are connected with vaporizer and compressor respectively, described steaming Send out device to be connected with compressor.

The frequency-changing control system of the outdoor unit of thermostatic constant wet equipment the most according to claim 2, it is characterised in that described Being connected between condenser with vaporizer and have choke valve, being connected between described vaporizer and compressor has evaporating pressure regulating valve.

The frequency-changing control system of the outdoor unit of thermostatic constant wet equipment the most according to claim 2, it is characterised in that described Preferable condensation temperature is higher than the evaporating temperature of 0 DEG C and vaporizer.

The frequency-changing control system of the outdoor unit of thermostatic constant wet equipment the most according to claim 4, it is characterised in that described Preferable condensation temperature is set to 11～14 DEG C.

The frequency-changing control system of the outdoor unit of thermostatic constant wet equipment the most according to claim 1, it is characterised in that described Analogue signal is set to 0～10V analogue signal.

7. the VFC system of the outdoor unit of the thermostatic constant wet equipment utilized in claim 1～6 described in any one The method for controlling frequency conversion that system realizes, it is characterised in that the method comprises the following steps:

By the actual condensation temperature of temperature sensor measurement condenser；

PID controller, according to the deviation of the preferable condensation temperature measuring actual condensation temperature and the setting arrived, is gone by pid algorithm Calculate the frequency values of the converter needing execution；

The frequency values of calculated for PID controller converter is converted into and can allow the mould of converter identification by D/A converting unit Intend signal；

Converter goes to adjust rotation speed of fan according to corresponding analogue signal, thus the condensation temperature controlling condenser in real time makes it reach To preferable condensation temperature, and condensing pressure is made to be higher than evaporation restriction pressure.

The VFC side that the frequency-changing control system of the outdoor unit of thermostatic constant wet equipment the most according to claim 7 realizes Method, it is characterised in that described PID controller is made up of proportional unit, integral unit and differentiation element, its input e (t) and output The relation of u (t) is:

U (t)=kp [e (t)+1/TI ∫ e (t) dt+TD*de (t)/dt]；

In formula, the bound of integration is 0 and t respectively；

Transmission function is: G (s)=U (s)/E (s)=kp [1+1/ (TI*s)+TD*s]；

Wherein, kp is proportionality coefficient, and TI is integration time constant, and TD is derivative time constant.