Heating and cooling PID control system

Abstract

The present invention relates to a heating and cooling proportional-integral-differential (PID) control system comprising: a heater for raising the temperature of a chamber; a freezer for lowering the temperature of the chamber; and a PID controller that controls the heater and the freezer in a PID control method, wherein the operation of the freezer is stopped while operating the heater, and the operation of the heater is stopped while operating the freezer. According to the present invention, in a system having a freezer and a heater together, energy efficiency is increased by removing an energy waste element, precise temperature control is possible, and a temperature increase and decrease speed can be improved.

Description

Heating and Cooling PID Control System

[0001] The present invention relates to a PID (Proportional-Integral-Differential) control system, and more particularly, to a PID control technique in a system that operates a heater and a refrigerator simultaneously, such as a thermostat or a thermo-hygrostat.

[0002] Thermostats and thermo-hygrostats, which must control both high and low temperatures, operate the refrigerator and heater simultaneously, even when raising temperatures from low to high. This not only slows the temperature rise rate but also reduces energy efficiency. Conversely, the temperature-lowering section is also controlled in the same way, consuming significant energy.

[0003] In the case of the traditionally used “ON / OFF compressor,” if the compressor is turned ON / OFF frequently in a short period of time, durability is reduced and precise control is not possible, so the refrigerator is operated continuously and the temperature is controlled with a heater.

[0004] To address these shortcomings, efforts have been made to improve energy efficiency by bypassing the refrigerator during the rising section. However, this method complicates the system due to the need for numerous bypass valves to accommodate various situations. Furthermore, the refrigerator cannot provide precise control at low temperatures, requiring the heater to be operated simultaneously with the refrigerator.

[0005] Thus, equipment that must control both above and below room temperature operates both refrigerators and heaters simultaneously, slowing down the rate of temperature rise and fall and reducing energy efficiency. The reality is that complex systems designed to address these shortcomings lead to higher failure rates and higher unit costs.

[0006] Figure 1 is a block diagram illustrating a control system for operating an existing heater and refrigerator together, and Figure 2 is a graph for explaining a heater and refrigerator control method in a control system for operating an existing heater and refrigerator together.

[0007] As shown in Figures 1 and 2, the existing control system that competitively controls the heater and the refrigerator applies an “ON / OFF compressor” and requires the addition of a supplementary “bypass valve” to increase the temperature rise and fall speed. In addition, since multiple bypass valves must be operated to respond to various situations, the system becomes complex and is a cause of failure. However, since precise temperature control is still not possible with the “ON / OFF compressor,” there is a problem that precise temperature control must ultimately be achieved with the heater while the refrigerator is running. In this way, the existing control method can be said to have a separate and competitive relationship in controlling the heater and the refrigerator.

[0008] The present invention has been devised to solve the above problems, and its purpose is to provide a heating and cooling PID (Proportional-Integral-Differential) control system with an inverter compressor that can implement a cooperative control system in which the heater is automatically turned off when the refrigerator is in operation, and conversely, the refrigerator is automatically turned off when the heater is in operation, in a competitive control system in which the refrigerator and the heater are operated together.

[0009] The purpose of the present invention is not limited to the purposes mentioned above, and other purposes not mentioned will be clearly understood by those skilled in the art from the description below.

[0010] To achieve the above purpose, the present invention relates to a heating and cooling PID control system, comprising a heater for raising the temperature of a chamber, a refrigerator for lowering the temperature of the chamber, and a PID controller for controlling the heater and the refrigerator in a PID (Proportional-Integral-Differential) control manner, while the heater is in operation, stopping the operation of the refrigerator, and stopping the operation of the heater while the refrigerator is in operation.

[0011] The above refrigerator may include an inverter compressor that can be driven by a PID control method.

[0012] When the mode for operating the heater is called a heating mode and the mode for operating the refrigerator is called a cooling mode, the PID controller can control by setting the P (Proportional Band) value differently in the heating mode and the cooling mode.

[0013] The above PID controller can apply the same integral time value and differential time value in the heating mode and the cooling mode.

[0014] According to the present invention, in a system having both a refrigerator and a heater, energy efficiency can be improved by eliminating energy-wasting elements, precise temperature control can be achieved, and the temperature rising and falling speeds can be improved.

[0015] In addition, according to the present invention, since the bypass valve can be significantly reduced in a system equipped with both a refrigerator and a heater, there is an effect of enabling the system to be implemented simply.

[0016] Figure 1 is a block diagram illustrating a control system that operates an existing heater and refrigerator together.

[0017] Figure 2 is a graph for explaining a heater and refrigerator control method in a control system that operates an existing heater and refrigerator together.

[0018] FIG. 3 is a block diagram illustrating the configuration of a heating and cooling PID control system according to one embodiment of the present invention.

[0019] FIG. 4 is a graph showing PID results in a heating and cooling PID control system according to one embodiment of the present invention.

[0020] FIG. 5 is a block diagram illustrating a detailed configuration of a heating and cooling PID control system according to one embodiment of the present invention.

[0021] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0022] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0023] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0024] In addition, when describing with reference to the attached drawings, identical components will be assigned the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing the present invention, if a detailed description of a related known technology is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0025] FIG. 3 is a block diagram illustrating the configuration of a heating and cooling PID control system according to one embodiment of the present invention.

[0026] Referring to FIG. 3, a heating and cooling PID control system according to one embodiment of the present invention includes a PID controller (100), a heater (200), and a refrigerator (300).

[0027] In the present invention, the chamber (400) is used in equipment that is controlled to a high temperature state and a low temperature state by using a heater (200) and a refrigerator (300) simultaneously, and can be applied to various systems such as a constant temperature bath, a constant temperature and humidity chamber, or a photostability chamber, for example.

[0028] The heater (200) serves to raise the temperature of the chamber (400).

[0029] The refrigerator (300) serves to lower the temperature of the chamber (400). In one embodiment of the present invention, the refrigerator (300) may include an inverter compressor that can be driven by a PID control method.

[0030] The PID controller (100) controls the heater (200) and the refrigerator (300) using a PID (Proportional-Integral-Differential) control method, but stops the operation of the refrigerator (300) while the heater (200) is operating, and stops the operation of the heater (200) while the refrigerator (300) is operating.

[0031] In the present invention, when the mode for operating the heater (200) is referred to as a heating mode and the mode for operating the refrigerator (300) is referred to as a cooling mode, the PID controller (100) can control by setting the P (Proportional Band) value differently in the heating mode and the cooling mode, respectively.

[0032] At this time, the PID controller (100) can apply the same integral time and differential time values ​​in the heating mode and the cooling mode to ensure stability of the system.

[0033]

[0034] FIG. 4 is a graph showing PID results in a heating and cooling PID control system according to one embodiment of the present invention.

[0035] In Fig. 4, the PID result values ​​output from the PID controller (100) in the heating mode and cooling mode of the present invention are shown.

[0036] Referring to FIG. 4, the PID controller (100) can control the operation of the refrigerator (300) from 100% (maximum output) to 0% (operation stop) in the cooling mode, and can control the operation of the heater (200) from 0% (operation stop) to 100% (maximum output) in the heating mode. Here, DB (Dead Band) means an area in which neither the heater (200) nor the refrigerator (300) operates.

[0037] In the present invention, the DB can be set. Increasing the DB in a positive direction expands the area where the heater and refrigerator do not operate. In well-insulated environments with no disturbances, setting the DB relatively large reduces energy consumption, which is advantageous. However, in environments with disturbances, setting the DB relatively large can lead to unstable temperature control in the DB area.

[0038] Conversely, if DB is increased in the negative direction, a part (cross band) where the heater (200) and the refrigerator (300) overlap and operate occurs, and the heater and refrigerator compete with each other to achieve precise control, thereby increasing energy consumption.

[0039] In one embodiment of the present invention, when there is a disturbance (i.e., an uninsulated case), DB can be set to 0 to -10%, and when there is no disturbance (i.e., an insulated case), DB can be set to 10 to 0%.

[0040] FIG. 5 is a block diagram illustrating a detailed configuration of a heating and cooling PID control system according to one embodiment of the present invention.

[0041] In Fig. 5, PV represents a measured value (Process Variable), SV represents a target value (Set Variable), DB represents a dead band of heating output and cooling output, PB represents a proportional band on the heating side, PBc represents a proportional band on the cooling side, Ti represents an integral time, Td represents a differential time, and DV represents a deviation variable. In the present invention, DB can be arbitrarily set, for example, it can be set to 5%. In addition, DV can be calculated as SV - PV.

[0042] And, MV represents the output value (Manipulate Variable), HV-Heat represents the heating output value, and MV_Cool represents the cooling output value.

[0043] Referring to FIG. 5, in a heating and cooling PID control system according to one embodiment of the present invention, a PID controller (100) may include a PID unit (110), a heating PID unit (120), and a cooling PID unit (130).

[0044] In the present invention, the deviation (DV) can be calculated as DV = SV-PV using a preset target value (SV) and a measured value (PV) fed back from the chamber (400).

[0045] The PID unit (110) calculates the output value (MV) using the deviation (DV). In the present invention, the output value (MV) can be calculated using the following mathematical formula.

[0046] [Mathematical Formula 1]

[0047]

[0048]

[0049] The heating PID unit (120) calculates a heating output value (MV_Heat) using the output value (MV) and DB, and controls the heater (200) using the heating output value. In the present invention, the heating output value (MV_Heat) can be calculated using the following mathematical formula.

[0050] [Equation 2]

[0051] MV_Heat = (MV - DB / 2 - 50%)×2, (0 ≤ MV_Heat ≤ 100%)

[0052]

[0053] The cooling PID unit (130) calculates a cooling output value (MV_Cool) using the output value (MV) and DB, and controls the refrigerator (300) using the cooling output value. In the present invention, the cooling output value (MV_Cool) can be calculated using the following mathematical formula.

[0054] [Equation 3]

[0055] MV_Cool = (50% - DB / 2 - MV)×2×(PB / PBc), (0 ≤ MV_Cool ≤ 100%)

[0056] While the present invention has been described using several preferred embodiments, these embodiments are illustrative and not limiting. Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit and scope of the invention as set forth in the appended claims.

Claims

1. Heater to raise the temperature of the chamber; A refrigerator for lowering the temperature of the chamber; and A PID controller that controls the heater and the refrigerator using a PID (Proportional-Integral-Differential) control method, and stops the operation of the refrigerator while the heater is operating, and stops the operation of the heater while the refrigerator is operating. Heating and cooling PID control system including.

2. In claim 1, A heating and cooling PID control system characterized in that the refrigerator comprises an inverter compressor that can be driven by a PID control method.

3. In claim 1, When the mode for operating the above heater is called the heating mode and the mode for operating the above refrigerator is called the cooling mode, A heating and cooling PID control system characterized in that the PID controller controls by setting the P (Proportional Band) value differently in the heating mode and the cooling mode.

4. In claim 3, A heating and cooling PID control system characterized in that the PID controller applies the same integral time value and differential time value in the heating mode and the cooling mode.

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