DESC:TECHNICAL FIELD
[001] The present invention relates to control systems and more specifically to a system and a method for controlling an electronic expansion valve in a heat pump system for heating and cooling of water majorly used in swimming pools or domestic applications.

BACKGROUND
[002] Generally, a chiller is used to heat/cool water in an evaporator. The heating and cooling take place in a plate type heat exchanger having water on one side and refrigerant on the other side and heat exchange takes place between said water and refrigerant. The heated/cooled water is then used for various applications ranging from swimming pools to cooking/washing utensils and other domestic applications. The refrigerant circulates throughout a heat pump system by means of a refrigerant loop. In the refrigerant loop, the refrigerant leaves the evaporator and enters a compressor where the pressure of the refrigerant is increased. The compressed refrigerant leaves the compressor and enters a condenser where it is condensed from a vapor to a liquid refrigerant by heat exchange. The liquid refrigerant is then returned, by means of an expansion device, to the evaporator to continue the cycle through the refrigerant. A four-way valve located at outlet of the compressor controls the path of refrigerant and in turn controls whether refrigerant is used for heating application or for cooling application.
[003] Referring Figure 1 shows the refrigerant circuit of a standard heat pump system used for heating and cooling of water in a plate heat exchanger (PHE). During heating cycle (as illustrated by a dotted line in Figure 1), high pressure refrigerant gas from the compressor enters the water-cooled heat exchanger (PHE), where it condenses into high pressure liquid refrigerant resulting in the heat getting transferred to the water in the PHE. The low-pressure liquid refrigerant then converts into a low-pressure liquid refrigerant in the electronic expansion valve (EXV). The electronic expansion valve also controls the flow of refrigerant into the evaporator of the unit. The low-pressure refrigerant then enters the evaporator of the unit. The evaporator for the heat cycle is fin and tube type air cooled heat exchanger in which the low-pressure refrigerant liquid gets converted into low pressure refrigerant vapour. The low-pressure refrigerant vapour then enters the compressor where it converts into high pressure refrigerant vapour and the cycle continues. During the cooling cycle (as illustrated by solid line in Figure 1), the high-pressure refrigerant enters the fin and tube type heat exchanger which acts as a condenser of the system and converts the refrigerant into high pressure liquid.
[004] The electronic expansion valve converts the high-pressure liquid refrigerant into low pressure liquid refrigerant which enters the PHE. In the PHE the refrigerant absorbs heat from the water and converts into low refrigerant vapour which results in the water getting cooled. The low-pressure refrigerant vapour then enters the compressor where it converts into high pressure refrigerant vapour and the cycle repeats. The expansion device used in such systems is an electronic expansion valve which modulates the refrigerant flow to the Evaporator. The electronic expansion valve is commonly controlled by on board controller based on plurality of input parameters received from a plurality of sensors. The functionality of EXV control is to ensure that no liquid refrigerant enters the compressor and at the same time ensure sufficient quantity of refrigerant enters the compressor. Opening the EXV more than requirement can cause liquid refrigerant flood-back in the compressor leading to compressor failure while closing the EXV more than requirement can lead to tripping of the system on low pressure. Such conventional EXV control systems have inherent limitations as they employ multiple sensors for both heat mode and cool mode for measuring suction temperatures and PHE in and out temperatures and outdoor unit (ODU) heat exchanger in and out temperatures, the cost of such systems is also high. Further, there is no secondary protection available to protect the system against a refrigerant liquid flood back in case of incorrect sensing by sensors.
[005] Therefore, there is a need to provide a method and system to overcome one or more of the aforementioned problems.

SUMMARY
[006] Accordingly, an exemplary aspect of the present invention discloses method for controlling an electronic expansion valve in a heat pump system, said method comprising sensing and determining, by a controller in communication with a plurality of sensors, after start of a compressor connected through an inverter drive, a plurality of first group of parameter values and a second group of parameter value, said plurality of sensors located in the heat pump system; calculating, by the controller having at least one processor, an ideal discharge temperature value using the determined values of the plurality first group of parameter values and the second group of parameter value individually for a heating mode operation and a cooling mode operation of the heat pump system; calculating, by the controller, a differential temperature value using said calculated ideal discharge temperature value minus a determined discharge temperature value from the plurality first group of parameters individually for said heating mode operation and said cooling mode operation of the heat pump system; adjusting, by the controller, steps of said electronic expansion valve with a pre-defined adjust pulse value for a pre-defined time interval based on said calculated differential temperature value; and controlling, by the controller, operation of said electronic expansion valve based on said calculated differential temperature value by invoking a first control signal for closing of said electronic expansion valve when said calculated differential temperature value is incremental within said pre-defined time interval and a second control signal for opening of said electronic expansion valve when said calculated differential temperature value is decremental within said pre-defined time interval.
[007] According to another exemplary aspect, the present invention discloses a system for operating an electronic expansion valve in a heat pump system.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[008] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
[009] Figure 1 illustrates a conventional refrigerant system of a standard heat pump system used for heating and cooling of water in a plate heat exchanger (PHE);
[010] Figure 2 illustrates a block diagram of a controller for a heat pump system, according to an exemplary aspect of the present invention; and
[011] Figure 3 illustrates a flow chart of a method for controlling an electronic expansion valve in the heat pump system, according to an exemplary embodiment of the present invention.
[012] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to the other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference signs are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION
[013] While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiment illustrated. Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. Embodiments of the present disclosure will now be described with reference to the accompanying drawings. Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to a person skilled in the art. Numerous details are set forth relating to specific components to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
[014] In general, the present invention claims, a method and a system for controlling an electronic expansion valve in a heat pump system. After start of a compressor connected through an inverter drive, a plurality of sensors, determine a plurality of first group of parameter values and a second group of parameter value and a controller calculates an ideal discharge temperature value, a differential temperature value, and adjusts steps of said electronic expansion valve with a pre-defined adjust pulse value based on said calculated differential temperature value. The controller controls operation of opening/closing of said electronic expansion valve based on said calculated differential temperature value.
[015] Accordingly, the present invention removes the extra sensors required for electronic expansion valve (EXV) control in a heat mode operation and a cool mode operation of the heat-cool pump. The controller that ensures no refrigerant flood-back even in case of malfunction of sensors. The system of the present invention operating in heat mode and a cool mode includes sensors, compressor, inverter, a plate water-cooled heat exchanger (PHE) for cool mode, refrigerant gas, electronic expansion valve (EXV), evaporator for heat mode with a fin and tube type air cooled heat exchanger, and a controller having a memory and in communication with at least a processor. The determined, calculated and measured values by the controller are stored in the memory.
[016] The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. As used in the present disclosure, the forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises,” “comprising,” “including,” “made of” and “having,” are open ended transitional phrases and therefore specify the presence of stated elements, units and/or components, but do not forbid the presence or addition of one or more other elements, components, and/or groups thereof.
[017] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. All the terms and expressions in the description are only for the purpose of the understanding and nowhere limit the invention.
[018] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein may be made without departing from the scope of the invention. Terms plurality, first, second, third, parameter values, control signal, desired values, threshold values, pre-defined time interval, pre-defined pulse values and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof. The control system for control of electronic expansion valve referred in the description for the purpose of the understanding and nowhere limit the invention and said system logic disclosed in the present invention can be adapted to other systems of like as well. Thus, while particular type of structure, refrigerant circuit, controller, input values, temperatures, pressures, predetermined values, number of sensors, number of parameters, time intervals, parameters have been disclosed, it will be appreciated that the embodiments may be manufactured with other design parameters and configurations as well and are not limited to those described herein above and may be as per operational requirements and nowhere limits the scope of the invention and are provided only for reference and for understating purpose of the invention.
[019] Referring Figure 2 shows the controller (200) of the heat pump system, according to an exemplary embodiment of the present invention. The controller (200) may include but not limited to at least one processor, in communication with a memory and said plurality of sensors positioned at various components of the system. According to the exemplary embodiment of the present invention, the controller during initial start-up condition of the compressor, ensures that the EXV opens at a pre-set pulse in the range of 48-480 pulse for a predetermined time interval between 2-5 minutes. The initial EXV opening for heat and cool mode operation is different.
[020] According to an exemplary aspect, the present invention discloses a system for operating an electronic expansion valve in a heat pump system, in said system, a controller (200) is in communication with at least one processor for processing a logic and controlling operation of said heat pump system. After startup condition, the controller (200) may retrieve inputs using plurality of sensors, a plurality of first group of parameters information values from a compressor (220) connected through an inverter drive (210) and at least a heat exchanger but not limited to a water inlet temperature (EWT) (230) measured and determined at an inlet of the plate heat exchanger (PHE), a water outlet temperature (LWT) (240) measured and determined at an outlet of the plate heat exchanger (PHE), an outdoor unit (ODU) mid coil refrigerant temperature (Tcoil) (250) measured and determined at the u-bend of a fin and tube heat exchanger, a discharge refrigerant temperature (Tdis) (260) measured and determined at an outlet of the compressor and an ambient temperature (Tamb) (270) measured and determined at the inlet of the fin and tube heat exchanger. Further, the controller retrieves the second group of parameter value from the compressor (220) which is the mechanical frequency/speed (RPS) (280) at which the compressor (220) is running by the inverter drive (210). The feedback of the speed of the compressor i.e., compressor frequency (RPS) is taken as an input for the EXV control by the controller. The determined plurality of first group of parameter values and the second group of parameter value are stored in the memory.
[021] According to the exemplary embodiment of the present invention, after initial period is completed, based on the information values obtained from plurality of first group of parameter values and the second group of parameter value as an input to the controller, the controller (200) is capable of calculating an ideal discharge temperature value individually/ separately for a heating mode operation and a cooling mode operation of the heat pump system based on the following:
Heat mode operation:
Target/ ideal Tdis = LWT + H1 + (H2* Tamb) + (H3*Tcoil) + (H4*RPS)
Where H1, H2, H3 and H4 are constants.
Cool mode operation:
Target/ ideal Tdis = C1+ (C2*EWT) + (C3*Tamb) + (C4*RPS) + (Tcoil)
Where C1, C2, C3 and C4 are constants.
[022] According to the exemplary embodiment, the calculated values of said ideal discharge temperature are stored in the memory. The calculated values of said ideal discharge temperature and the determined discharge temperature for heat mode operation and cool mode operation is different. The controller (200) ensures that the EXV opens, and closes based on the calculated ideal discharge temperature and determined discharge temperature obtained by the controller, after competition of said predetermined time interval.
[023] According to the exemplary embodiment of the present invention, based on the calculated values of said ideal discharge temperature value minus the determined value of a discharge temperature value (260) from the plurality first group of parameters, the controller (200) calculates differential temperature value individually/separately for said heating mode operation and said cooling mode operation of the heat pump system based on the following:
differential temperature value ?t2= calculated ideal DLT temperature – determined DLT temperature

[024] According to the exemplary embodiment of the present invention, calculated differential temperature value is stored in the memory. The Controller, then looks-up a pre-defined adjust pulse value range from the memory, and then adjusts the electronic expansion valve EXV steps / pulses with said pre-defined adjust pulse value for a pre-defined time interval based on said calculated differential temperature value. The adjustment in said pulses is done in the EXV steps at the predetermined time interval ranging from 10 to 120 seconds. The pre-defined adjust pulse value is determined based on calculated differential temperature value and is stored in the memory by the controller.
[025] According to the exemplary embodiment of the present invention, the controller (200) controls operation of said electronic expansion valve based on said calculated differential temperature value by invoking a first control signal for closing of said electronic expansion valve when said calculated differential temperature value is incremental within said pre-defined time interval and a second control signal for opening of said electronic expansion valve when said calculated differential temperature value is decremental within said pre-defined time interval i.e. increase in calculated differential temperature value ?t2 for control of discharge temperature results indicates in a faster closing of the EXV, while decrease in calculated differential temperature value ?t2 for control of discharge temperature results indicates in a faster opening of the EXV.

[026] The controller of the system also ensures sensor malfunction protection. Incorrect installation or malfunction of sensors results in incorrect calculation of target discharge temperature resulting in failure of compressor due to liquid refrigerant entering it. Accordingly, an exemplary embodiment of the present invention, ensures that the controller (200) continuous monitoring of the operation of the electronic expansion valve for said pre-defined time interval. The controller determines the number of said adjusted electronic expansion valve steps and stores the determined value of number of said adjusted electronic expansion valve steps in the memory.
[027] According to the exemplary embodiment, the controller (200) limits maximum EXV steps / pulses in any condition both for heat mode and cool mode. The controller (200) determines a threshold number of electronic expansion valve steps value using the determined values of the plurality first group of parameters and the second group of parameter value individually for said heating mode operation and said cooling mode operation of the heat pump system based on the following:
Heat mode operation:
Max EXV Steps= (H5*RPS) + (H6*LWT) + H7
Where H5, H6 and H7 are constants.
Cool mode operation:
Max EXV Steps= (C5*RPS) + (C6*Tamb) + C7
Where C5, C6 and C7 are constants.

[028] According to the exemplary embodiment, the controller then stores the determined value of said threshold number of electronic expansion valve steps in the memory. Further, the controller compares the determined value of number of said adjusted electronic expansion valve steps with said determined value of said threshold number of electronic expansion valve steps. According to the exemplary embodiment, the controller (200) based on said compared values invokes a third control signal, indicative of a malfunction of at least a sensor or said plurality of sensors, when said determined value of number of said adjusted electronic expansion valve steps is equal to said determined value of said threshold number of electronic expansion valve steps, thereby protecting said compressor from a potential refrigerant flood-back.
[029] Referring Figure 3 illustrates a flow chart of a method (300) for controlling an electronic expansion valve in a heat pump system. The method (300) comprising the steps of after start of a compressor connected through an inverter drive, sensing and determining (310), by a controller in communication with a plurality of sensors, a plurality of first group of parameter values and a second group of parameter value, said plurality of sensors located in the heat pump system. The method (300) includes the step of storing, by the controller having at least one processor, said determined plurality of first group of parameter values and the second group of parameter value in a memory. The method (300) includes the step of calculating (320), by the controller, an ideal discharge temperature value using the determined values of the plurality first group of parameter values and the second group of parameter value individually for a heating mode operation and a cooling mode operation of the heat pump system and storing, by the controller, said calculated value of said ideal discharge temperature value in the memory.
[030] According to the exemplary embodiment, the method (300) includes the step of calculating (330), by the controller, a differential temperature value using said calculated ideal discharge temperature value minus a determined discharge temperature value from the plurality first group of parameters individually for said heating mode operation and said cooling mode operation of the heat pump system and storing, by the controller, said differential temperature value in the memory. The method (300) includes the step of adjusting (340), by the controller, steps of said electronic expansion valve with a pre-defined adjust pulse value for a pre-defined time interval based on said calculated differential temperature value and determining, by the controller, number of said adjusted electronic expansion valve steps. The method then includes storing, by the controller, said determined value of number of said adjusted electronic expansion valve steps in the memory.
[031] According to the exemplary embodiment, the method (300) includes the step of continuous monitoring and controlling (350), by the controller, operation of said electronic expansion valve based on said calculated differential temperature value by invoking a first control signal for closing of said electronic expansion valve when said calculated differential temperature value is incremental within said pre-defined time interval and a second control signal for opening of said electronic expansion valve when said calculated differential temperature value is decremental within said pre-defined time interval.
[032] According to the exemplary embodiment, the method (300) includes the step of determining (360), by the controller, a threshold number of electronic expansion valve steps value using the determined values of the plurality first group of parameters and the second group of parameter value individually for said heating mode operation and said cooling mode operation of the heat pump system and storing, by the controller, said determined value of said threshold number of electronic expansion valve steps in the memory. The method (300) includes the step of comparing (370), by the controller, said determined value of number of said adjusted electronic expansion valve steps with said determined value of said threshold number of electronic expansion valve steps and invoking a third control signal, indicative of a malfunction of said plurality of sensors or at least a sensor, when said determined value of number of said adjusted electronic expansion valve steps is equal to said determined value of said threshold number of electronic expansion valve steps, thereby protecting said compressor from a refrigerant flood-back.
[033] According to the present invention, the cost of the system for controlling an electronic expansion valve in a heat pump system reduces substantially as minimum of sensors without any additional sensors are required, when compared to existing systems that have plurality of sensors added to control the electronic expansion valve apart from other existing sensors. The Controller operates efficiently and EXV control ensures precise control of the expansion valve in both heat and cool modes. The controller of the system of the present invention ensures that the sensor malfunction protection is provided such that the compressor is protected from any refrigerant flood-back.
[034] There have been described and illustrated herein several embodiments of exemplary indicative implementation of a method and a system for controlling an electronic expansion valve in a heat pump system. The heat pump system in the present invention is a heat cool air to water heat pump system. It will be also apparent to a skilled person that the embodiments described above are specific examples of a single broader invention, which may have greater scope than any of the singular descriptions taught. There may be many alterations made in the description without departing from the scope of the invention. The present invention is simple in construction and design, integrated, cost effective and easy to manufacture and assembly. While particular embodiments of the invention have been described, it is not intended that the invention be limited said configuration disclosed thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise not restrictive to the terminology described herein above. Any discussion of embodiments included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
NOMENCLATURE
EWT - Water In Temperature Tdis - Discharge Temperature
LWT - Water Out Temperature Tamb - Ambient Temperature
Tcoil: ODU Mid Coil Temperature RPS - Compressor Frequency
EXV - Electronic Expansion Valve

,CLAIMS:
1. A method for controlling an electronic expansion valve in a heat pump system, said method comprising:
sensing and determining, by a controller in communication with a plurality of sensors, after start of a compressor connected through an inverter drive, a plurality of first group of parameter values and a second group of parameter value, said plurality of sensors located in the heat pump system;
calculating, by the controller having at least one processor, an ideal discharge temperature value using the determined values of the plurality first group of parameter values and the second group of parameter value individually for a heating mode operation and a cooling mode operation of the heat pump system;
calculating, by the controller, a differential temperature value using said calculated ideal discharge temperature value minus a determined discharge temperature value from the plurality first group of parameters individually for said heating mode operation and said cooling mode operation of the heat pump system;
adjusting, by the controller, steps of said electronic expansion valve with a pre-defined adjust pulse value for a pre-defined time interval based on said calculated differential temperature value; and
controlling, by the controller, operation of said electronic expansion valve based on said calculated differential temperature value by invoking a first control signal for closing of said electronic expansion valve when said calculated differential temperature value is incremental within said pre-defined time interval and a second control signal for opening of said electronic expansion valve when said calculated differential temperature value is decremental within said pre-defined time interval.

2. The method as claimed in claim 1, further comprising continuous monitoring, by the controller, the operation of the electronic expansion valve for said pre-defined time interval.

3. The method as claimed in claim 1, further comprising:
determining, by the controller, a number of said adjusted electronic expansion valve steps;
determining, by the controller, a threshold number of electronic expansion valve steps value using at least the determined values of the plurality first group of parameters and the second group of parameter value individually for said heating mode operation and said cooling mode operation of the heat pump system;
comparing, by the controller, said determined value of number of said adjusted electronic expansion valve steps with said determined value of said threshold number of electronic expansion valve steps and invoking a third control signal, indicative of a malfunction of at least said sensor, when said determined value of number of said adjusted electronic expansion valve steps is equal to said determined value of said threshold number of electronic expansion valve steps, thereby protecting said compressor from a refrigerant flood-back.

4. The method as claimed in anyone of the preceding claims 1-3, wherein said values of plurality of first group of parameters include values of a water inlet temperature, a water outlet temperature, an outdoor unit (ODU) mid coil temperature, a discharge temperature and an ambient temperature.

5. The method as claimed in anyone of the preceding claims 1-4, wherein said second group of parameter values include a feedback value of a speed of the compressor (rps)

6. The method as claimed in anyone of the preceding claims 1-5, wherein said pre-defined time interval is 10 to 120 seconds and said pre-defined adjust pulse value is determined based on calculated differential temperature value and is stored in a memory by the controller.

7. A system for operating an electronic expansion valve in a heat pump, said system comprising:
a memory configured to store a plurality of values, after start of a compressor connected through an inverter drive;
a plurality of sensors, located in the heat pump system, configured for sensing and determining a plurality of first group of parameter values and a second group of parameter value; and
a controller in communication with plurality of sensors and said memory, controller configured to:
receive the determined plurality of first group of parameter values and the second group of parameter value,
calculate an ideal discharge temperature value based on the determined values of the plurality first group of parameter values and the second group of parameter value individually for a heating mode operation and a cooling mode operation of the heat pump system,
calculate a differential temperature value based on said calculated ideal desired discharge temperature values minus a determined value of a discharge temperature value from the plurality first group of parameters individually for said heating mode operation and said cooling mode operation of the heat pump system,
look-up a pre-defined adjust pulse value range from the memory,
adjust steps of said electronic expansion valve with said pre-defined adjust pulse value obtained from the memory based on said calculated differential temperature value,
control operation of said electronic expansion valve based on said calculated differential temperature value by invoking a first control signal for closing of said electronic expansion valve when calculated differential temperature value is incremental within a pre-defined time interval and a second control signal for opening of said electronic expansion valve when said calculated differential temperature value is decremental within said pre-defined time interval.

8. The system as claimed in claim 7, wherein said controller is further configured to:
determine a number of said adjusted electronic expansion valve steps,
determine a threshold number of electronic expansion valve steps value using the determined values of the plurality first group of parameters and the second group of parameter value individually for said heating mode operation and said cooling mode operation of the heat pump system,
compare said determined value of number of said adjusted electronic expansion valve steps with said determined value of said threshold number of electronic expansion valve steps and invoking a third control signal, indicative of a malfunction of at least said sensor, when said determined value of number of said adjusted electronic expansion valve steps is equal to said determined value of said threshold number of electronic expansion valve steps, thereby protecting said compressor from a refrigerant flood-back.

9. The system as claimed in any of the preceding claims 7-8, wherein said controller is in communication with at least one processor for processing a logic and controlling operation of said heat pump system.