EP0781965A1 - Domestic hot water producing system with a gas heater and method for controlling the temperature of the domestic hot water in such a system - Google Patents

Abstract

The hot water system includes a device (40) measuring the flow (Qecs) of sanitary hot water in the circuit (11,14), and a further device (30) measuring the temperature (Ts) of this water at the output of the heat exchanger (13). A control system (100) controls the modulation valve (20) in response to the detected temperature and a reference temperature (Tc). A module (103) providing proportional control action adjusts the valve (Qecs) adjusting the pulsed flow of gas to the burner, thus providing a continuously adjusted and controlled burner output in response to the measured conditions. The proportional action operates according to a control formula taking account of the flow and temperature measurements, and the known characteristics of the boiler.

Description

The subject of the present invention is an installation for producing domestic hot water for a gas boiler with an atmospheric burner, comprising a boiler hearth equipped with a burner supplied with gas by means of an electrically controlled modulation valve, and at least one heat exchanger between said hearth and a domestic hot water production circuit comprising a cold water inlet line and a domestic hot water drawing line.

The invention also relates to a process for regulating the temperature of domestic hot water in an installation for producing domestic hot water by heat exchange with a gas boiler hearth comprising an atmospheric burner whose gas supply rate is modulated from a servo system.

In known installations for producing domestic hot water by gas boiler, it is well known that the outlet temperature of domestic hot water tends to vary as a function of the quantity of hot water consumed by the users. Thus, in the event of an increase in the flow rate for drawing hot water by a user taking a bath or a shower, or due to the commissioning of another device consuming hot water, such as a washing machine - dishes, the outlet temperature of the hot water produced tends to drop. To overcome this drawback, provision has already been made for regulating the flow rate of gas supplied to the boiler burner, this flow rate being controlled by an electrically controlled modulation valve.

The various known control systems, mechanical or electronic, however, have not been shown to be effective enough to guarantee a constant temperature of the hot water consumed, even in the event of sudden variations in flow rate, which are however frequent in practice, in particular when several users obtain hot water from the same hot water production installation.

The object of the invention is to remedy the aforementioned drawbacks and to allow the outlet temperature of the domestic hot water supplied by a domestic hot water production system by gas boiler to be kept at a constant and stable value. that is the flow of water drawn, including when the variations in flow are very sudden due to the starting or stopping by a user of a device for consuming hot water.

These goals are achieved by means of a domestic hot water production installation for an atmospheric burner gas boiler, comprising a boiler hearth equipped with a burner supplied with gas by means of an electrically controlled modulation valve, and at least one heat exchanger between said hearth and a domestic hot water production circuit comprising a cold water inlet line and a domestic hot water drawing line, characterized in that it further comprises a device for measuring the flow rate (Q _DHW ) of drawing domestic hot water from the domestic hot water production circuit, a device for measuring the temperature (Ts) of the domestic hot water leaving the heat exchanger heat and an electrically controlled modulation valve control system, the modulation valve control system comprising a closed loop regulation module of the modulation valve from the a temperature (Ts) measured by said device for measuring temperature and a set temperature (Tc), a proportional action module for direct regulation of the modulation valve on the basis of the information (Q _DHW ) supplied by the device flow rate measurement (Q _DHW ), and a pulse control module of the modulation valve from the flow variations detected by the flow measurement device, the pulse control module generating a signal creating a peak in the flow d '' gas supply to the burner by the modulation valve at each significant abrupt change in domestic hot water drawing rate (Q _DHW ) measured by said measuring device, the peak being positive or negative depending on whether the variation corresponds to an increase or a reduction in this flow, the initial and final values of the peak being zero and the amplitude of a peak being proportional to the variation in flow detected.

où

• k₁ est un coefficient dont la valeur est comprise entre 0 et 1,
• k₂ est un paramètre positif réglé en fonction du type de chaudière,
• Q_G3(n) et Q_G3(n-1) désignent la valeur de pic du débit de gaz (Q_G3) aux instants n et n-1, et
• Q_ECS(n) et Q_ECS(n-1) désignent la valeur du débit de puisage d'eau sanitaire aux instants n et n-1.

More particularly, the impulse regulation module comprises means for generating a sampled signal creating a gas flow peak (Q _G3 ) whose value is obtained as a function of the domestic hot water drawing rate (Q _DHW ) by the following sampled formula: $${\text{Q}}_{\text{G3}}{\text{(n) = k1.Q}}_{\text{G3}}{\text{(n-1) + k2. (Q}}_{\text{DHW}}{\text{(n) - Q}}_{\text{DHW}}\text{(n-1)),}$$

or

• k ₁ is a coefficient whose value is between 0 and 1,
• k ₂ is a positive parameter adjusted according to the type of boiler,
• Q _G3 (n) and Q _G3 (n-1) denote the peak value of the gas flow rate (Q _G3 ) at times n and n-1, and
• Q _DHW (n) and Q _DHW (n-1) designate the value of the domestic water drawing flow at times n and n-1.

According to a particular embodiment, the impulse regulation module comprises means for defining the positive parameter k ₂ adjusted as a function of the type of boiler, on the basis of the following information: heat capacity (Cp) of water, efficiency (η) of the installation, lower calorific value (PCI) of the gas, set temperature (Tc) and cold water temperature (Tef) introduced into the domestic hot water circulation circuit, according to the formula $${\text{k}}_{}$$$${}_{\text{2}}\text{= Cp. (Tc - Tef) / η.PCI.}$$

Advantageously, the closed-loop regulation module comprises a servo circuit of the PID (Proportional-Integral-Derivative) type, the input quantity of which is constituted by the difference between the temperature (Ts) measured by said device for measuring temperature and the set temperature (Tc).

According to another advantageous embodiment, the closed loop regulation module comprises a fuzzy controller receiving as input temperature error information E corresponding to the difference between the temperature (Ts) measured by said temperature measuring device and the set temperature (Tc), as well as information corresponding to the derivative with respect to time of the temperature error information.

In this case, preferably, the closed-loop regulation module further includes a PI (Proportional-Integral) type servo circuit placed at the output of the fuzzy controller and receiving as input (dQ _G ) flow variation gas supply to the burner.

This avoids possible instabilities or oscillations of the system.

• . f(0-) = 0
• . f(0+) = k₂ ΔQ_ECS, avec k₂ coefficient positif,
• . f est décroissante (resp. croissante) sur ]0, + ∝[
• . lim f(t) = 0
  t → + ∝.

The invention also relates to a process for regulating the temperature of domestic hot water in an installation for producing domestic hot water by heat exchange with a gas boiler hearth comprising an atmospheric burner whose gas supply rate is modulated from a servo system, characterized in that that the flow rate (Q _G ) of gas supply to said burner is controlled from the measurement of the flow rate (Q _DHW ) of domestic hot water drawing, on the one hand, by direct regulation with proportional action from said measurement of the flow rate (Q _DHW ) of domestic hot water drawing and, on the other hand, by impulse regulation from significant jumps (ΔQ _DHW ) of the measured value of the flow rate (Q _DHW ) of water drawing domestic hot water, the impulse regulation acting on the flow rate (Q _G ) of gas supply to said burner so as to create a peak according to a "peak" function f (t) such that, if t = 0 is the instant of the jump ΔQ _DHW positive, respectively negative, the function f (t) is defined by:

• . f (0-) = 0
• . f (0+) = k ₂ ΔQ _DHW , with k ₂ positive coefficient,
• . f is decreasing (resp. increasing) on] 0, + ∝ [
• . lim f (t) = 0
  t → + ∝.

In this case, the positive coefficient k ₂ can be adjusted according to the type of boiler, from the following information: heat capacity (Cp) of water, efficiency (η) of the installation, lower heat capacity (PCI) of gas, set temperature (Tc) and cold water temperature (Tef) introduced into the domestic hot water circulation circuit, according to the formula: $${\text{<figure-callout id="2" label="k" filenames="imgf0001.png,imgf0002.png" state="{{state}}">k</figure-callout>}}_{\text{2}}\text{= Cp. (Tc - Tef) / η.PCI.}$$

Advantageously, the flow rate (Q _G ) of gas supply to said burner is further controlled from the difference between the actual temperature (Ts) of the domestic hot water produced and a set temperature (Tc) according to a control closed-loop PID (Proportional-Integral-Derivative) type.

According to another advantageous embodiment, the flow rate (Q _G ) of gas supply to said burner is further controlled, by a fuzzy command, from temperature error information E corresponding to the difference between the temperature real temperature (Ts) of the domestic hot water produced and a set temperature (Tc), and from information corresponding to the derivative with respect to time of the temperature error information E.

In this case, preferably, the flow rate (Q _G ) of gas supply to said burner is further controlled from the output information of the fuzzy control according to a PI type control (Proportional-Integral).

• la Figure 1 est un schéma-bloc d'ensemble d'une installation de production d'eau chaude sanitaire selon l'invention ;
• la Figure 2 est un diagramme montrant un exemple d'évolution brusque, en fonction du temps du débit Q_ECS d'eau chaude sanitaire puisée dans une installation telle que celle de la Figure 1 ;
• la Figure 3 est un diagramme montrant de façon comparative l'évolution de la température de sortie d'eau chaude sanitaire produite dans une installation classique et dans l'installation de la Figure 1, lorsque le débit d'eau chaude puisée évolue selon le diagramme de la Figure 2 ;
• la Figure 4 est un diagramme montrant l'évolution en fonction du temps de la quantité de gaz foumie au brûleur de l'installation de la Figure 1, lorsque le débit d'eau chaude puisée évolue selon le diagramme de la Figure 2;
• la Figure 5 est un schéma-bloc d'une variante de réalisation de l'installation de production d'eau chaude sanitaire selon l'invention qui met en oeuvre un contrôleur flou ;
• la Figure 6 montre un exemple de table d'inférence pouvant être associée au contrôleur flou de l'installation de la Figure 5 ;
• la Figure 7 montre un exemple de fonctions d'appartenance d'une variable d'entrée (écart de température E) du contrôleur flou de l'installation de la Figure 5 ;
• la Figure 8 montre un exemple de fonctions d'appartenance d'une autre variable d'entrée (dérivée par rapport au temps de l'écart de température E) du contrôleur flou de l'installation de la Figure 5 ; et
• la Figure 9 montre un exemple de fonctions d'appartenance de la variable de sortie (écart de débit d'alimentation en gaz dQ_G) du contrôleur flou de l'installation de la Figure 5.

Other characteristics and advantages of the invention will emerge from the following description of particular embodiments, given by way of examples, with reference to the appended drawings, in which:

• Figure 1 is an overall block diagram of a domestic hot water production installation according to the invention;
• Figure 2 is a diagram showing an example of an abrupt change, as a function of time, in the _DHW flow rate of domestic hot water drawn from an installation such as that of Figure 1;
• Figure 3 is a diagram showing in a comparative manner the evolution of the outlet temperature of domestic hot water produced in a conventional installation and in the installation of Figure 1, when the flow of hot water drawn changes according to the diagram of Figure 2;
• Figure 4 is a diagram showing the evolution over time of the amount of gas supplied to the burner of the installation of Figure 1, when the flow of hot water drawn changes according to the diagram of Figure 2;
• Figure 5 is a block diagram of an alternative embodiment of the domestic hot water production installation according to the invention which implements a fuzzy controller;
• Figure 6 shows an example of an inference table that can be associated with the fuzzy controller of the installation of Figure 5;
• Figure 7 shows an example of membership functions of an input variable (temperature difference E) of the fuzzy controller of the installation of Figure 5;
• Figure 8 shows an example of membership functions of another input variable (derived with respect to time from the temperature difference E) of the fuzzy controller of the installation of Figure 5; and
• Figure 9 shows an example of membership functions of the output variable (gas supply flow difference dQ _G ) of the fuzzy controller of the installation of Figure 5.

Figure 1 schematically shows a domestic hot water production installation comprising a gas boiler hearth 10 equipped with an atmospheric burner 12 supplied by a flow rate Q _G of gas at from an electrically controlled modulation valve 20. The domestic hot water production circuit comprises an inlet 11 for supplying cold water at a temperature Tef, a heat exchanger 13 between the cold water and the heat released in the hearth 10 by the flame from the burner 12 and an outlet 14 for supplying domestic hot water at an outlet temperature Ts and with a flow rate _DHW .

In a domestic installation, the _DHW flow rate of domestic hot water drawn by users varies suddenly and unpredictably depending on the number of hot water consumption devices switched on or off (shower, sink, bathtub , dishwasher,...). If the quantity of heat produced in the furnace of the boiler 10 remains constant, the variations in the flow rate _DHW will automatically lead to variations of the same order for the temperature Ts of the domestic hot water produced, which is unpleasant for the users. This is why the installation according to the invention is equipped with a system 100 for controlling the regulating valve 20 so as to be able to adjust in real time the gas flow rate Q _G supplied to the burner 12 and thus ensure constant maintenance. or almost constant of the temperature Ts leaving the domestic hot water.

For this, the installation includes a flow meter 40 placed on the domestic hot water production circuit in order to continuously measure the actual flow of hot water drawn. The domestic hot water outlet temperature Ts is likewise measured by a temperature probe 30 provide, by lines 41, respectively 32, information on the values of the flow rate _DHW and of the temperature Ts at control system 100 for regulating valve 20, which may include a microcontroller associated with analog-digital converters (for input information) and a digital-analog converter (for controlling valve 20).

A set temperature value Tc, at which the outlet temperature Ts of the domestic hot water must be maintained, can be defined once and for all in the control system 100 or be provided from external information applied by a line 31 through a communication interface between the control system 100 and the users.

According to the invention, the control system 100 comprises a regulation module 104 which receives as input, via line 41, information supplied by the flow meter 40 concerning the flow rate Q _DHW of water hot domestic hot water. The module 104 detects significant sudden variations in the flow rate _DHW which constitute jumps in flow rate of a value ΔQ _DHW , and generates at the output, on a line 141, a control signal tending to instantly cause a peak in the flow rate of gas Q _G3 to be supplied by the modulation valve 20 to the burner 12, as soon as such a flow jump ΔQ _DHW occurs.

• les pics de débit de gaz Q_G3 sont provoqués uniquement par détection de variations du débit de gaz mesuré par le débitmètre 40,
• les valeurs initiale et finale du pic sont nulles,
• l'amplitude des pics est proportionnelle à la variation ΔQ_ECS du débit de puisage de l'eau chaude sanitaire,
• le pic a lieu dans le même sens que la variation ΔQ_ECS du débit de puisage, c'est-à-dire que le pic est positif lorsque le débit Q_ECS d'eau chaude augmente et le pic est négatif lorsque le débit Q_ECS d'eau chaude diminue.

The properties of the module 104 generating the gas flow peaks Q _G3 at the time of the sudden variations in the flow rate ΔQ _DHW are as follows:

• the gas flow peaks Q _G3 are caused only by detection of variations in the gas flow measured by the flow meter 40,
• the initial and final values of the peak are zero,
• the amplitude of the peaks is proportional to the variation ΔQ _DHW of the domestic hot water drawing flow,
• the peak takes place in the same direction as the variation ΔQ _DHW of the draw-off flow, that is to say that the peak is positive when the Q _DHW flow of hot water increases and the peak is negative when the Q _DHW flow hot water decreases.

• . f(0-) = 0
• . f(0+) = k₂ ΔQ_ECS, avec k₂ > 0,
• . f est décroissante (resp. croissante) sur ]0, + ∝[
• . lim f = 0
  t → + ∝.

In general, the "peak" function f (t) giving the configuration of the peak as a function of time during a flow jump ΔQ _DHW positive (resp. Negative) can be expressed as follows:
let t = 0 the instant of the flow jump ΔQ _DHW positive (resp. negative), then the function f (t) is defined by:

• . f (0-) = 0
• . f (0+) = k ₂ ΔQ _DHW , with k ₂ > 0,
• . f is decreasing (resp. increasing) on] 0, + ∝ [
• . lim f = 0
  t → + ∝.

The positive coefficient k ₂ is a constant whose value is determined according to the type of boiler and the nature of the combustible gas used.

• capacité calorifique de l'eau Cp
• rendement de l'installation η
• pouvoir calorifique inférieur du gaz PCI
• température de consigne Tc et
• température Tef de l'eau froide introduite dans le circuit de foumiture d'eau chaude.

For example, the coefficient k ₂ can be defined from the following information:

• heat capacity of water Cp
• installation efficiency η
• lower calorific value of PCI gas
• setpoint temperature Tc and
• temperature Tef of the cold water introduced into the hot water supply circuit.

In this case, the formula giving k ₂ can be written: $${\text{<figure-callout id="2" label="k" filenames="imgf0001.png,imgf0002.png" state="{{state}}">k</figure-callout>}}_{\text{2}}\text{= Cp. (Tc - Tef) / η. PCI}$$

For example, the temperature of the cold water Tef can be between 5 ° C and 15 ° C with an average value of 10 ° C; the set temperature can be 50 ° C, the value of the heat capacity of the water Cp can be taken equal to 4180 J / kg; the lower calorific value of PCI gas for natural gas can be of the order of 10,000 and the efficiency η of the boiler and the heat exchangers (i.e. the difference between the power supplied by the boiler and the power recovered by the water) can be between 0.7 and 0.95.

Under typical operating conditions, the coefficient k ₂ can thus have a value of the order of 20.

With such an example, in the event of a positive flow rate (resp. Negative) ΔQ _DHW of 6 liters per minute, i.e. 0.1 kg / s, the value of the additional gas flow Q _G3 supplied by the burner 12 should be at peak point level of the order of 2 m ³ / h.

In practice, the control system 100 equipped with a microcontroller acts by time step and the function f (t) mentioned above, which must define a peak with a sudden growth then a slower decrease, is expressed in a sampled form.

où

0 < k₁ < 1

(k₁ étant lié à la période d'échantillonnage des mesures et à l'inertie de l'installation),

k₂

est un coefficient positif réglé en fonction de la chaudière, par exemple de la façon indiquée plus haut,

Q_G3(n) et Q_G3(n-1)

désignent la valeur du pic de débit de gaz aux instants n et n-1

Q_ECS(n) et Q_ECS(n-1)

désignent la valeur du débit d'eau chaude sanitaire mesurée par le débitmètre 40 et échantillonné aux instants n et n-1.

Thus, the "peak" function provided by the regulation module 104 and giving the value of the additional gas flow rate Q _G3 to be supplied to the burner 12 can be linked to the instantaneous domestic hot water flow rate Q _DHW by the following sampled formula: $${\text{Q}}_{\text{G3}}{\text{(n) = <figure-callout id="1" label="k" filenames="imgf0001.png" state="{{state}}">k</figure-callout>}}_{\text{1}}{\text{. Q}}_{\text{G3}}{\text{(n-1) + <figure-callout id="2" label="k" filenames="imgf0001.png,imgf0002.png" state="{{state}}">k</figure-callout>}}_{\text{2}}{\text{. (Q}}_{\text{DHW}}{\text{(n) - Q}}_{\text{DHW}}\text{(n-1))}$$

or

0 <k ₁ <1

(k ₁ being linked to the measurement sampling period and the inertia of the installation),

k ₂

is a positive coefficient adjusted according to the boiler, for example as indicated above,

Q _G3 (n) and Q _G3 (n-1)

denote the value of the gas flow peak at times n and n-1

Q _DHW (n) and Q _DHW (n-1)

designate the value of the domestic hot water flow rate measured by the flow meter 40 and sampled at times n and n-1.

For example, if the measurement sampling period is 0.5 seconds, k ₁ can be chosen to be 0.8 and the value of the peak will be brought back to a value close to zero after 5 seconds.

The diagrams in FIGS. 2 to 4 make it possible to better visualize the role of the regulation module 104.

Figure 2 shows a curve 210 giving the evolution of the domestic hot water flow Q _DHW as a function of time, with a first section 211 corresponding to a relatively regular Q _DHW flow ₁ corresponding for example to the consumption of hot water by a user taking a shower or bath. A second section 212 corresponds to a flow of hot water drawn Q _ECS2 increased between times t ₁ and t ₂ due to the withdrawal of hot water by another user or device such as a dishwasher. A third section 213 after time t ₂ corresponds to a return to the conditions prior to time t ₁ , that is to say the stopping of additional hot water withdrawal. As can be seen in Figure 2, the withdrawal of an additional flow of hot water causes a sudden jump in flow at time t ₁ , in the direction of an increase and a sudden jump in flow, but in the direction of a decrease, at time t ₂ .

Figure 3 shows a curve 220 giving the outlet temperature Ts of the domestic hot water produced by the installation according to the invention. It can be seen that this outlet temperature Ts remains permanently equal to or very close to the setpoint temperature Tc.

The temperature Ts remains equal to the setpoint temperature Tc both on a section 221, prior to the instant t ₁ , and during most of the section 223 between the instants t ₁ and t ₂ or on the section 225 after the instant t ₂ . A very slight residual negative point 222 or a very slight residual positive point 224 may be present in the vicinity of the instants t ₁ and t ₂ taking into account the reaction time of the burner 12, but these fluctuations are much less than in the case of a modulation system not comprising the impulse regulation module 104 creator of selective positive or negative gas flow peaks.

There is thus shown in dotted lines in FIG. 3 the evolution of the outlet temperature Ts of the domestic hot water in the case where the impulse regulation module 104 is absent, but where the control system 100 comprises only one more classic 103 proportional control module. Such a regulation module 103 (FIG. 1) receives information from the flow meter 40 and provides, at the switching valve 20, a signal controlling the evolution of the gas flow rate Q _G2 supplied to the burner 12, according to a law of proportionality. In the case where such a direct regulation module 103 is used alone, in the event of an abrupt variation in the hot water flow rate Q _DHW , as at times t ₁ and t ₂ , the temperature Ts deviates much more strongly from the value Tc setpoint and takes longer to return to this value (sections 226 and 227 with dotted lines in Figure 3).

In the control system 100 according to the invention, the two regulation modules 103 and 104 coexist and deliver, by lines 142, 141, to a summing circuit 105 of the signals controlling an evolution of the gas flow rate Q _G according, on the one hand , a proportional evolution Q _G2 and, on the other hand, an impulse evolution Q _G3 . The valve 20 is controlled by the signals from the summing circuit 105.

FIG. 4 shows a curve 230 giving the evolution, as a function of time, of the gas flow rate Q _G applied to the burner 12 by the modulation valve 20 when the latter receives control signals from the summing circuit 105 whose inputs are connected, by lines 142 and 141, to regulation modules 103 and 104.

In the period prior to time t ₁ (mason 231), the flow rate Q _G of gas is equal to the flow rate Q _G2 of gas fixed by the proportional regulation module 103 as a function of the regular hot water flow rate of the section 211 of Figure 2. At time t ₁ when a jump in hot water flow rate ΔQ _DHW is detected by the impulse control module 104, it immediately comes into action and provides a gas flow peak Q _G3 (reference 232) which greatly attenuates, or even eliminates, the temperature drop Ts after time t ₁ . Q _G3 gas flow peak returns progressively to zero, but the proportional regulation module 103 has meanwhile entered into action to readjust the gas flow Q _G2 to a value greater than the value of the gas flow Q _G2 prior to time t ₁ , to take account of increasing the hot water flow rate Q _DHW . The tip 232 is thus followed by a section 233 in the form of a plateau until the instant t ₂ . At time t ₂ , the regulation process is identical to that of time t ₁ , but in reverse. The impulse regulation module 104 detects a jump in the hot water flow rate ΔQ _DHW negative and causes a negative peak in the gas flow Q _G3 which is subtracted from the previous gas flow Q _G2 , then this gas flow peak Q _G3 ( reference 234) returns to zero but, taking into account the downward readjustment of the gas flow rate Q _G2 defined by the proportional regulation module 103, the overall value Q _G of the gas flow rate supplied to the burner 12 returns to a value substantially equal to that preceding the instant t ₁ (section 235).

The pulse type regulation through the regulation module 104 and the direct or proportional type regulation through the regulation module 103 both overlap and exploit the flow information supplied by the flow meter 40.

Advantageously, a third type of regulation can be superimposed on the two preceding modes of regulation. Thus, we see in Figure 1 a closed loop regulation circuit 102 which generates, on an output line 143, a control signal of the closed loop gas flow which is applied to the summing circuit 105 to allow, by the through the modulation valve 20, to provide the burner 12 with a gas flow Q _G1 adjusted as a function of the value of the water temperature Ts measured by the temperature probe 30. A comparator 101 makes it possible to compare the value Ts of the temperature of the domestic hot water measured, applied by a line 32, to the set temperature Tc supplied by a line 31. The temperature difference E constitutes the input of the closed-loop regulation module 102.

The closed loop regulation module 102 can include a PID (Proportional-Integral-Derivative) type servo.

However, according to an advantageous alternative embodiment, which is illustrated in FIG. 5, the closed-loop regulation module 102 comprises a fuzzy controller 122 and constitutes a fuzzy control system with fuzzy control rules, membership functions and an inference table.

The fuzzy controller 122 receives as input temperature error information E which corresponds to the difference made by the comparator 101 between the temperature Ts measured by the temperature probe 30 and the setpoint temperature Tc.

The fuzzy controller 122 receives on a second input, via a differentiator circuit 121, connected to the comparator 101, information corresponding to the derivative dE / dt of the temperature error information. The fuzzy controller 122 provides information relating to the variation of the gas flow rate dQ _G1 which must be applied to the burner of the assembly 10, 20 for heating the domestic water.

FIG. 6 shows an example of an inference table which may be suitable for the fuzzy controller 122. The abbreviations ZE, NG, PG respectively represent the terms zero, large negative, large positive which characterize the difference E or the derivative of the difference dE / dt previously defined as input variables of the fuzzy controller 122, as well as the output variable dQ _G1 .

For example, according to one of the rules, if the difference E is positive large, and the derivative of the difference dE / dt is also positive and large, then the output variable dQ _G1 must be negative and large, c that is to say, the gas flow rate Q _G1 applied to the burner should be significantly reduced as a result of the control of the regulating module 102.

If, according to another possible case, the difference E is negative large and the derivative of the difference dE / dt is positive and large, the output variable dQ _G1 will be zero, that is to say that there n there will be no correction to be made by the regulation loop 102.

For the various cases of this particular example, reference should be made to the inference table in Figure 6 which constitutes a matrix table with double entry.

Naturally, each of the input variables E, dE / dt and output dQ _G1 was previously associated with the fuzzy characteristics NG, ZE and PG previously mentioned.

Thus, by way of example, it can be considered that the temperature difference E provided by the comparator 101 is large negative if it is between -20 ° and + 10 ° and positive large if it is between +10 ° and + 20 ° or above.

Similarly, by way of example, the input variable dE / dt provided by the differentiator 121 can be considered as negative large if it is between -2 ° / s and -1 ° / s or below, zero if it is between-1 ° / s and + 1 ° / s and positive large if it is between + 1 ° / s and + 2 ° / s or beyond.

The output variable dQ _G1 can itself, for example, be considered to be equal to a value of -2 m ³ / h if it must be negative large, zero if it must be equal to zero, or equal to a value of + 2m ³ / h if it must be positive large.

Figures 7, 8 and 9 show examples of membership functions relating to the fuzzy characteristics applicable respectively to the temperature difference E, to the derivative of the temperature difference dE / dt with respect to time and to the variation dQ _G1 of the gas flow.

We will refer to Figures 7 to 9 to see the form of these membership functions which correspond for each variable given to a term or a fuzzy characterization (NG, ZE, PG). We find triangular membership functions (for ZE applied to variables E and dE / dt) for NG and PG (applied to variables E and dE / dt), or punctual (singletons for NG, ZE and PG applied to output variable dQ _G1 ). These membership functions have overlap zones and are between zero and one for the variables E and dE / dt.

Naturally, it is possible to choose a number of fuzzy characteristics greater than three for each of the input variables, according to the desired precision, without however choosing too large a number which would produce saturation of the system.

The fuzzy controller 122 includes a fuzzification input stage making it possible to provide fuzzy input variables from the variables E and dE / dt by taking account of the membership functions of these input variables. A fuzzy output is then determined, in a fuzzy inference stage, from predefined control rules and fuzzy inputs from the fuzzification stage.

Finally, in a defuzzification stage of the fuzzy controller 122, there is produced a control signal for the variation of the gas flow rate dQ _G1 to be applied to the burner by the valve 20. The control signal can be obtained from a fuzzy output value by a method such as determining the center of gravity of the set of rules predefined whose synthesis served to constitute the associated inference table.

At the output of the fuzzy controller 122, it is possible to have a regulation block of the PI (Proportional-lntégrale) type which makes it possible to stabilize possible oscillations of the system. The control signals from the fuzzy control module 102 are applied to the summing circuit 105 which receives, in the same manner as indicated above with reference to FIG. 1, signals from the proportional regulation module 103 and from the pulse regulation module 104.

Claims (11)

Installation for producing domestic hot water by gas boiler with atmospheric burner, comprising a boiler hearth (10) equipped with a burner (12) supplied with gas by means of an electrically controlled modulation valve (20) , and at least one heat exchanger (13) between said hearth (10) and a circuit (11, 14) for producing domestic hot water comprising a line (11) for cold water and a line (14 ) domestic hot water drawing,
characterized in that it further comprises a device (40) for measuring the flow rate (Q _DHW ) of drawing domestic hot water from the circuit (11, 14) for producing domestic hot water, a device (30) for measuring the temperature (Ts) of the domestic hot water at the outlet of the heat exchanger (13) and a system (100) for controlling the electrically controlled modulation valve (20), the system (100) for control of the modulation valve (20) comprising a module (102) for closed-loop regulation of the modulation valve (20) from the temperature (Ts) measured by said device (30) for measuring temperature and a set temperature (Tc), a module (103) with proportional action for direct regulation of the modulation valve (20) from the information (Q _DHW ) provided by the device (40) for measuring the flow rate (Q _DHW ), and a module (104) for pulse regulation of the modulation valve (20) from variations detected by the flow measurement device (40), the impulse regulation module (104) generating a signal creating a peak in the gas supply flow to the burner (12) by the modulation valve (20) at each abrupt significant variation in domestic hot water drawing flow (Q _DHW ) measured by said measuring device (40), the peak being positive or negative depending on whether the variation corresponds to an increase or a decrease in this flow, the initial values and final of the peak being zero and the amplitude of a peak being proportional to the variation in flow detected. Installation according to claim 1, characterized in that the pulse regulation module (104) comprises means for generating a sampled signal creating a gas flow peak (Q _G3 ) whose value is obtained as a function of the drawing flow of domestic hot water (Q _DHW ) by the following sampled formula: $${\text{Q}}_{\text{G3}}{\text{(n) = k1.Q}}_{\text{G3}}{\text{(n-1) + k2. (Q}}_{\text{DHW}}{\text{(n) - Q}}_{\text{DHW}}\text{(n-1)),}$$

or k ₁ is a coefficient whose value is between 0 and 1, k ₂ is a positive parameter adjusted according to the type of boiler. Q _G3 (n) and Q _G3 (n-1) denote the peak value of the gas flow rate (Q _G3 ) at times n and n-1, and Q _DHW (n) and Q _DHW (n-1) designate the value of the domestic water drawing flow at times n and n-1. Installation according to claim 2, characterized in that the pulse regulation module (104) comprises means for defining the positive parameter k ₂ adjusted according to the type of boiler, from the following information: heat capacity (Cp) of the water, efficiency (η) of the installation, lower calorific value (PCI) of the gas, set temperature (Tc) and cold water temperature (Tef) introduced into the domestic hot water circulation circuit, depending on the formula $${\text{k}}_{\text{2}}\text{= Cp. (Tc - Tef) / η.PCI.}$$

Installation according to any one of claims 1 to 3, characterized in that the closed-loop regulation module (102) comprises a servo circuit of the PID (Proportional-Integral-Derivative) type whose input quantity is made up by the difference between the temperature (Ts) measured by said device (30) for measuring the temperature (Ts) and the set temperature (Tc). Installation according to any one of claims 1 to 3, characterized in that the closed loop regulation module (102) comprises a fuzzy controller (122) receiving as input temperature error information E corresponding to the difference between the temperature (Ts) measured by said device (30) for measuring the temperature and the set temperature (Tc), as well as information (dE / dt) corresponding to the derivative with respect to time of the error information of temperature. Installation according to claim 5, characterized in that the closed-loop control module (102) further comprises a circuit servo control (123) of PI (Proportional-Integral) type placed at the output of the fuzzy controller (122) and receiving at the input an information (dQ _G ) of variation of the gas supply flow rate of the burner. Method for regulating the temperature of domestic hot water in an installation for producing domestic hot water by heat exchange with a gas boiler hearth comprising an atmospheric burner whose gas supply rate is modulated from a servo system,
characterized in that the flow rate (Q _G ) of gas supply to said burner is controlled from the measurement of the flow rate (Q _DHW ) of domestic hot water drawing, on the one hand, by direct regulation with proportional action from said measurement of the flow rate (Q _DHW ) of domestic hot water drawing and, on the other hand, by impulse regulation from significant jumps (ΔQ _DHW ) of the measured value of the flow rate (Q _ESC ) domestic hot water, the impulse regulation acting on the flow rate (Q _G ) of gas supply to said burner so as to create a peak according to a "peak" function f (t) such that, if t = 0 is the instant of the flow jump ΔQ _DHW positive, respectively negative, the function f (t) is defined by: . f (0-) = 0 . f (0+) = k ₂ ΔQ _DHW , with k ₂ positive coefficient, . f is decreasing (resp. increasing) on] 0, + ∝ [ . lim f (t) = 0
t → + ∝. Method according to claim 7, characterized in that the positive coefficient k ₂ is adjusted as a function of the type of boiler, on the basis of the following information: heat capacity (Cp) of the water, efficiency (η) of the installation, power lower calorific value (PCI) of the gas, set temperature (Tc) and cold water temperature (Tef) introduced into the domestic hot water circulation circuit, according to the formula: $${\text{k}}_{\text{2}}\text{= Cp. (Tc - Tef) / η.PCI.}$$

Method according to either of Claims 7 and 8, characterized in that the flow rate (Q _G ) of gas supply to said burner is further controlled from the difference between the actual temperature (Ts) of the water domestic hot water produced and a set temperature (Tc) according to a closed loop control of the PID (Proportional-Integral-Derivative) type. Method according to either of Claims 7 and 8, characterized in that the flow rate (Q _G ) of gas supply to said burner is further controlled, by a fuzzy command, on the basis of temperature error information E corresponding to the difference between the actual temperature (Ts) of the domestic hot water produced and a set temperature (Tc), and from information corresponding to the derivative with respect to time of the information E d ' temperature error. Method according to claim 10, characterized in that the flow rate (Q _G ) of gas supply to said burner is further controlled from the output information of the fuzzy control according to a PI type control (Proportional-Integral) .

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