Patent Grant
12140977
This application claims priority to Italian Patent Application No. 102021000025670 filed on Oct. 7, 2021, the contents of which are incorporated by reference in their entirety.
The present invention relates to the field of systems for controlling temperatures and mass or volumetric flow rates inside (thermal) energy distribution systems.
In particular, the present invention relates to a regulation system for a thermo-hydraulic circuit configured to jointly control the temperature and mass or volumetric flow rate in a thermal energy distribution system, such as for example, but not exclusively, heating and cooling systems used in residential buildings or in industrial plants for the distribution of energy from a thermal machine (or from a thermal energy storage) to the radiator or between heat pump and one or more thermal energy storages.
The current automated management technologies allow implementing highly efficient temperature control systems or can be associated with pre-existing thermoregulation systems to optimize the performance thereof.
The known thermoregulation systems for thermo-hydraulic circuits are generally managed so as to ensure a desired temperature in one or more volumes to be heated or cooled, e.g., the temperature of the air in the case of one or more residential units of a building and/or in individual rooms thereof, or the temperature of a carrier fluid inside a chamber or duct at a given point to be controlled, e.g., at the inlet of one or more industrial machines.
The systems controlling the opening or closing of a three-way valve within such regulating systems suitably mix the delivery carrier fluid of the plant with the return carrier fluid.
An example of the aforesaid systems is described in document WO2020/065417.
However, the systems of the prior art, and in particular the related thermoregulation control systems, do not allow adequately managing quick achievement of the desired optimal temperature. Indeed, the control systems of the prior art require several iterative cycles to reach the optimal operation of the plant as a function of the available control parameters (typically, the opening/closing of the three-way valve alone).
Therefore, the need is strongly felt to provide a regulation system for a thermo-hydraulic circuit and a control method for a regulation system for a thermo-hydraulic circuit capable of overcoming the drawbacks of the prior art.
Such a need is met with a regulation system for a thermo-hydraulic circuit and a control method as described and claimed herein. Preferred or advantageous embodiments of the present invention are also described.
The features and advantages of the regulation system for a thermo-hydraulic circuit and the control method for the regulation system for a thermo-hydraulic circuit will be apparent from the following description of preferred embodiments thereof, given by way of a non-limiting indication, with reference to the accompanying drawings, in which:
With reference to the drawings, reference numeral 1000 indicates a regulation system for a thermo-hydraulic circuit as a whole, i.e., a system for controlling the temperature of a fluid in a volume intended to be heated or cooled. For example, the regulation system for a thermo-hydraulic circuit is a heating system or a cooling system or an air conditioning system for a building comprising the thermo-hydraulic circuit, where the volume be heated or cooled is, for example, the volume of air of a room of the building or of the whole building, or is a volume of fluid inside heat exchange terminals or radiators.
The regulation system 1000 for a thermo-hydraulic circuit, an embodiment of which is diagrammatically shown in greater detail in
The thermo-hydraulic circuit 20 further comprises a carrier fluid circulation system 20′ adapted to allow the circulation of a carrier fluid inside the thermo-hydraulic circuit 20. The carrier fluid circulation system 20′ includes a delivery duct 102 for transferring the carrier fluid from the thermal machine 100 to the heat exchange terminal 101, and a return duct 103 for transferring the carrier fluid from the heat exchange terminal 101 towards the thermal machine 100.
A three-way valve 1 is arranged along the delivery duct 102 and is fluidically connected to the thermal machine 100 and the return duct 103. The three-way valve 1 is operable to mix the carrier fluid in the delivery duct 102 with the carrier fluid in the return duct 103.
The delivery duct 102 allows the carrier fluid to flow from the thermal machine 100 to the heat exchange terminal 101, and possibly to other elements (not shown) of the thermo-hydraulic circuit 20, such as a boiler/tank for domestic hot water, for example.
The return duct 103 allows a carrier fluid flow from the heat exchange terminal 101 to return towards the thermal machine 100 and towards the three-way valve 1.
A pump 2 is installed on the delivery duct 102 and is adapted to pump the carrier fluid through the carrier fluid circulation system.
According to a variant (not shown), the pump 2 is installed on the return duct 103 upstream of the three-way valve 1, i.e., before the three-way valve 1 and downstream of the heat exchange terminal 101, in the circulating direction of the carrier fluid (diagrammatically indicated by the arrows in
Preferably, the three-way valve 1 is arranged on the delivery duct 102 between the thermal machine 100 and the pump 2, along the delivery duct 102. The three-way valve 1 may be activated to mix the carrier fluid from a thermal machine outlet 8 of the thermal machine 100 (e.g., a “hot” carrier fluid of the thermal machine) with the “cold” carrier fluid from a radiator outlet 11 of the heat exchange terminal 101 so as to regulate—in particular, to lower in the case of “hot” fluid from the thermal machine or to heat in the case of “cold” fluid from the thermal machine—the temperature of the carrier fluid in the delivery duct 102 leaving the three-way valve 1. In other words, the delivery duct 102 comprises a first duct portion 102′ connecting the thermal machine outlet 8 to a first inlet 1′ of the three-way valve and in which carrier fluid directly from the thermal machine 100 circulates. Moreover, the delivery duct 102 also comprises a second duct portion 102″ which is directly connected to a valve outlet of the three-way valve 1 and in which a mixed carrier fluid circulates, i.e., a carrier fluid obtained by mixing the carrier fluid directly from the thermal machine 100 with the carrier fluid from the heat exchange terminal 101, in particular from the radiator outlet 11 of the heat exchange terminal.
The thermo-hydraulic circuit 20 comprises at least a first temperature sensor 4 installed on the delivery duct 102 downstream of the three-way valve 1, i.e., preferably on the second duct portion 102″, and even more preferably downstream of pump 2. The first temperature sensor 4 is adapted to measure the post-valve delivery temperature ϑ1 of the carrier fluid downstream of the three-way valve 1 in the flowing direction of the carrier fluid.
The thermo-hydraulic circuit 20 also comprises at least a second temperature sensor 5 installed on the delivery duct 102 or inside the thermal machine 100, upstream of the three-way valve 1, i.e., preferably on the first duct portion 102′. The second temperature sensor 5 is adapted to measure the pre-valve delivery temperature ϑ2 of the carrier fluid upstream of the three-way valve 1 in the flowing direction of the carrier fluid.
The thermo-hydraulic circuit 20 further comprises at least a third temperature sensor 6 installed on the return duct 103 or inside the heat exchange terminal 101 and adapted to measure the temperature ϑ3 of the carrier fluid downstream of the heat exchange terminal 101 in the flowing direction of the carrier fluid. Such a third temperature sensor 6 is further installed upstream of the three-way valve 1.
Moreover, at least one flow or flow rate sensor 3 is installed in the fluid circulation system to measure a mass or volumetric flow rate {dot over (m)}1 of the carrier fluid in an area of the fluid circulation system 20′. Preferably, the flow or flow rate sensor 3 is installed on the return duct 103, even more preferably is installed downstream of the heat exchange terminal 101 and upstream of a second inlet 1″ of the three-way valve 1.
According to an advantageous embodiment, the flow or flow rate sensor 3 is installed before a point 7 of bifurcation of the return duct 103 into two duct branches 71, 72, where a first branch 71 of the two branches 71, 72 is connected to the second inlet 1″ of the three-way valve 1 and the second branch 72 of the two branches is connected to the thermal machine 100, and in particular to the machine inlet 9 of the thermal machine 100.
The electronic control unit 14 is operatively connected to the three-way valve 1, the pump 2, the first temperature sensor 4, the second temperature sensor 5, the third temperature sensor 6, and the flow or flow rate sensor 3, to read parameters or control the activation thereof.
The electronic control unit 14 is configured to acquire the post-valve delivery temperature ϑ1, the pre-valve delivery temperature ϑ2, the carrier fluid temperature ϑ3 downstream of the heat exchange terminal 101, the value of mass or volumetric flow rate {dot over (m)}1 of the carrier fluid, from the respective sensor.
Moreover, the electronic control unit 14 comprises a storage device 140 in which a model function {circumflex over (V)} of the operation of the valve connected to the thermo-hydraulic circuit 20 is stored, and a processing unit 141 configured to calculate the values of certain signals described hereinbelow and which will be better understood with reference to
The processing unit 141 is configured to calculate a valve control signal u adapted to determine an opening value of the three-way valve 1 for mixing the carrier fluid from the thermal machine 100 and from the heat exchange terminal 101 as a function of (i.e., according to a processing of) the opening value of the three-way valve 1.
Moreover, the processing unit 141 is configured to calculate a pump control signal pg adapted to regulate the value of power delivered by the pump, i.e., the mass or volumetric flow rate of the carrier fluid flow.
The processing unit 141 is further configured to calculate an estimated post-valve delivery temperature value and an estimated mass flow rate value
as output values of the model function {circumflex over (V)} of the thermo-hydraulic circuit 20.
In particular, the processing unit 141 is further configured to jointly calculate the estimated post-valve delivery temperature value and an estimated mass flow rate value
as output values of the model function {circumflex over (V)}, i.e., in the same calculating iteration.
The processing unit 141 is further configured to calculate a carrier fluid delivery temperature error eϑ. The carrier fluid delivery temperature error eϑ
.
Moreover, the carrier fluid mass or volumetric flow rate error is calculated by the processing unit 141 as a function of a desired mass or volumetric flow rate value
, the value of measured mass or volumetric flow rate {dot over (m)}1 of the carrier fluid and the estimated mass or volumetric flow rate value
.
Therefore, the valve control signal u and the pump control signal pg are calculated as a function of the mass flow rate error and the carrier fluid delivery temperature error eϑ
According to an embodiment, the model function {circumflex over (V)} consists of a family of similar transformations combined with one another by a fuzzy system of the Takagi-Sugeno type.
According to an advantageous embodiment, the valve control signal u and the pump control signal pg are also calculated as a function of the desired mass or volumetric flow rate value , the desired post-valve delivery temperature value rϑ
Preferably, the estimated post-valve delivery temperature value is calculated through a third delay line (e.g., a transfer function which delays the signal) from a first post-valve delivery temperature value
output by the model function {circumflex over (V)} and the estimated mass flow rate value
is calculated by adding a second predefined time delay to a first mass flow rate value
output by the model function {circumflex over (V)}.
According to an embodiment, the delayed pre-valve delivery temperature ϑ5, the delayed temperature ϑ6 carrier fluid downstream of the heat exchange terminal 101 are calculated as a function of the delayed valve control signal u according to a predetermined delay range and the delayed control signal pg to pump 2 according to a second predetermined delay range.
According to an advantageous embodiment, the delayed pre-valve delivery temperature ϑ5, the delayed temperature ϑ6 of carrier fluid downstream of the heat exchange terminal 101 and the estimated post-valve delivery temperature are calculated through auxiliary delay lines which process the value of mass or volumetric flow rate signals
,
and
estimated by the model function {circumflex over (V)}, respectively, which in turn calculates them by processing the value of the control signal u to valve 1 and the value of the control signal pg to pump 2.
With particular reference to
According to the embodiment in
The block {circumflex over (V)} is the model (or observer) function which allows estimating values of a status of not directly observable parameters. The model function {circumflex over (V)} together with the special delay blocks indicated on the right in
The block indicated by Ĉ(z) is the controller, i.e., the series of code instructions executed by the processing unit 141 to calculate the valve control signal u and the pump control signal pg.
The further blocks D1, D2 and D3 instead are particular delay lines provided with two inlets, one for the quantity to be delayed, the other for a quantity of the volumetric or mass flow rate type, employed in order to obtain a delay depending on the values taken by the latter in past instants.
According to an embodiment, the value of the quantity output from the particular delay line (, ϑ5 or ϑ6) is calculated by linearly interpolating the last two elements of a circular queue containing pairs of values representing the value taken by the quantity at the input of the particular delay line (
, ϑ2 or ϑ3) in past instants and the current position of each of these values within the delay line. In an advantageous formulation, the positions are iteratively updated in a proportional manner to the fluid flow rate (
,
or
) and the integration step. Each time the position of the last element in the queue exceeds a characteristic length associated with the special delay line (violation of the condition on the position), such an element is removed from the queue and re-introduced at the beginning of the queue, thus decreasing its positional coordinate of the characteristic length of the special delay line and assigning to the value of the input quantity, the value of the input quantity that this has when the violation of the condition on the position is detected.
An example of model function {circumflex over (V)} is shown in
This means that, according to an embodiment, the quantities and
are the result of a similar transformation of the quantities pg, u, ϑ5 and ϑ6, where the coefficients of the transfer matrix and the known term are in turn determined as a function of the variables u and pg, for example as
Similarly, the quantities , and
are the result of a similar transformation of the quantities u and pg, where the coefficients of the transfer matrix and the known term are in turn determined as a function of the variables u and pg, for example as
Moreover, the transfer matrixes {circumflex over (P)}1(u, pg), {circumflex over (P)}2(u, pg), {circumflex over (P)}3(u, Pg) and the known terms {circumflex over (b)})u, pg), ĉ(u, pg) are obtained as a convex combination of a certain number of similar models with constant coefficients, where the combiners are the membership functions of the variables u and pg in a suitable two-dimensional grid of fuzzy sets.
According to an alternative embodiment, the quantities and
are calculated as a convex combination of the images of the quantities pg, u, ϑ5 and ϑ6 through a certain number of similar transformations where the combiner coefficients are the membership functions of the variables pg and u in a two-dimensional grid of fuzzy sets. Similarly, the quantities
and
are calculated as a convex combination of the images of the quantities pg, u through the same number of similar transformations, where the combiners are the same membership functions the variables pg and u in the two-dimensional grid of fuzzy sets.
An example of controller with Ĉ(z) is shown in
The function of the open chain component Ĉ(z) of the controller is that of obtaining a particular inverse of the model function {circumflex over (V)} which exactly returns those values of the control variables uFF and Pg given at the input of block {circumflex over (V)}−1 together with the values ϑ5 and ϑ6.
In a convenient embodiment, such a block can be implemented by employing the generalized Newton-Raphson method for the multi-variable case.
The feedback component Ĉ(z) of the controller is shown in
The design of the feedback block can occur with various state-of-the-art techniques, but in an advantageous embodiment, this component is obtained using two controllers with one input and one output of proportional, integral and derivative type, one for the control chain related to the temperature (Π1(z)), the other for that related to the volumetric or mass flow rate (Π2(z)), connected in series to a decoupler element P1−1 which can be the inverse Jacobian matrix of the model function calculated at point uFF, pg
The experimental determination of the coefficients of the Takagi-Sugeno models, and in general the parameters of the model function {circumflex over (V)}, can take place through the application, around the most significant working points, of linear identification techniques known at the state of the art or through the application of any other method of identifying parametric models known at the current or future state of the art.
The correct determination of the characteristic length of the special delay lines D1, D2 and D3 is equally important. These parameters can be determined with identification methods known at the state of the art, but even better they can be determined based to the on-site measurement of the distance travelled by the fluid between the body of the three-way valve 1 and the temperature sensors 4, 5, 6, respectively.
As for the design and the resulting calibration of the coefficients of control block K(z), it can take place by virtue of the use of the model function {circumflex over (V)}, the inverse function {circumflex over (V)}−1, and the delay lines D1, D2 and D3, using any technique known at the state of the art.
Innovatively, the present invention allows brilliantly overcoming the aforementioned drawbacks with respect to the control systems for regulating thermo-hydraulic plants of the known art.
In particular, the regulation system for a thermo-hydraulic circuit 1000 of the present invention advantageously allows controlling the three-way valve and the pump in a coupled manner to obtain a more timely, adequate and efficient response for the desired temperature set point in the considered volume of fluid. In other words, by virtue of the possibility of jointly controlling the pump and the three-way valve, it is possible to carry out a control such as to act simultaneously on the valve and the pump to change the value of the flow rate alone or of the temperature alone. This is particularly distinctive with respect to the systems of the prior art which do not include controlling both the valve and the pump.
Furthermore, by virtue of the presence of an adequately calibrated model function, the system of the present invention may provide accurate tracking of pre-programmed trajectories (i.e., known in the future in terms of temperature and volumetric or mass flow rate). This specific quality also makes the invention very useful within the context of controlling industrial processes where simultaneously controlling temperature and flow rate of an energy carrier fluid is required.
In order to meet specific needs, those skilled in the art may make variations to the embodiments of the present invention or replace elements with other functionally equivalent ones.
Such variants are also contained in the scope of protection as described and claimed herein.
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| 102021000025670 | Oct 2021 | IT | national |
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