WO2007091175A1

WO2007091175A1 - Method for modulating electric power to a lamp and device implementing this method

Info

Publication number: WO2007091175A1
Application number: PCT/IB2007/000372
Authority: WO
Inventors: Fernando MEGOZI
Original assignee: Spes S.C.P.A.
Priority date: 2006-02-07
Filing date: 2007-02-07
Publication date: 2007-08-16
Also published as: ITAN20060008A1; EP1982564A1

Abstract

The present invention relates to a method for modulation of the electrical power transferred to a lamp, connected to a public-lighting network and supplied electrically via said network. According to the invention, the modulation method consists in the first place in determining one or more time values on the basis of at least one historical piece of information regarding operation of the lamp, and then in making a variation of the electrical power transferred to the lamp at the time values previously determined, said time values being measured starting from a predetermined operating condition regarding the lamp. Also described is a regulation device designed to implement the method according to the invention.

Description

"METHOD FOR MODULATING ELECTRIC POWER TO A LAMP AND DEVICE IMPLEMENTING THIS METHOD"

DESCRIPTION

Field of the invention The present invention relates to a method for modulation of the electrical power transferred to a lamp, said lamp being connected to a public-lighting network and being supplied electrically via said network, as well as a regulation device, designed to be installed between a lamp and a source of electrical energy, in particular a public-lighting network. In greater detail, the present invention falls within the sector of public-lighting systems in urban and/or extra-urban areas and tackles in particular the question of energy saving at night, in which the traffic is limited.

It is known, in fact, with reference, for example, to an urban area, how the light intensity that is deemed necessary for guaranteeing the regular circulation of urban traffic in conditions of safety, markedly depends upon the conditions of the traffic itself, there being required a higher degree of visibility when the traffic is more intense. This means that, at night when the traffic is statistically much lower, it is possible to reduce the light intensity of the lamps of a public lighting system, obtaining considerable benefits in terms of energy saving, without jeopardizing in any way the safety of citizens. Background art

In the various countries, there exist standards that regulate the modality of safe reduction of the light intensity of a public lighting system in order to prevent useless waste of electrical energy during those night hours in which the traffic is statistically very low. Said standards generally refer to the night time, during which the light intensity of the lamps can be reduced by a given amount, typically distinguishing between areas in which the hours of dusk and dawn are markedly different on account of a different geographical location.

To meet the aforesaid need of reduction of energy consumption by a public lighting system, it is necessary to use appropriate systems that enable modulation of the power supplied to the light points of the lighting system itself, typically consisting of gas-discharge lamps, which use, for example, high-pressure sodium (HPS lamps), or else low-pressure sodium, or else mercury vapours, or else metallic halogenides, and so forth. Various regulation systems are known that adopt different methods for differentiating, as required, the amount of the power supplied to a given public- lighting network. Said regulation systems can, for reasons of simplicity, be classified in two general categories: ones that adopt a regulation of a centralized type and ones that, instead, use a regulation distributed locally at a level of the individual light points.

In the case of centralized systems, the regulation is made upstream, directly in the station that supplies a given public-lighting network, in which the instant of start and end of a "lighting session", i.e., of the interval of time during which the lighting system is kept active, is also managed in an automatic or manual way. In this case, the differentiation of light between night hours with different traffic situations is typically made in the following two ways: by varying the intensity of the a.c. voltage applied to the lighting network or else by supplying the light points with two separate electrical lines, so that two contiguous lamps are never supplied by the same electrical line. In the second case, deactivation of one of the two lines causes turning-off of the corresponding light points and produces a regular alternation of lamps that are active and of lamps that are turned off, the evident advantage of which is a reduction in the energy consumption of 50%, but the even more evident disadvantage of which is the creation of areas of shade that can at times be very dangerous for circulation. For said reason, this technique of variation of the light, which has been widely used in the past, is progressively replaced with the one indicated in the first case, based upon the variation of the intensity of the a.c. voltage that supplies the public-lighting network.

The systems belonging to the aforesaid first case consequently use appropriate variations of the amplitude of the a.c. mains voltage, which supplies the lighting system, for regulating the light intensity of the lamps, passing from the value of rated voltage, used for guaranteeing the full brightness of each individual lamp, to a predetermined voltage value, lower than the rated value, to which there corresponds a reduced brightness and a consequent reduction of the absorbed electrical power. To obtain the aforesaid reduction of the amplitude of the a.c. voltage of the lighting network, appropriate regulating control units are used, equipped with electronic control systems and appropriate power devices.

Said systems appear simple and effective, but have in actual fact the following limits: they have a high cost, since they involve the use of sophisticated high-power voltage regulators, they cannot exceed, in order to guarantee adequate levels of reliability, given values of power that can be supplied, consequently limiting the maximum number of light points that can be managed, and finally they do not guarantee, in the condition of reduced lighting (the so-called "energy- saving mode"), definite operation of the individual lamps, above all when these are not equipped with appropriate circuits for activation/re-activation of the discharge of the gas, such as, for example, the so-called "electronic ballasts", which are able to function even at voltages lower than the rated one. hi systems of a distributed type, unlike the case of the centralized ones just discussed, the modulation of the power supplied is made locally (namely, at the individual light points), through appropriate high-efficiency electronic regulating systems (electronic ballasts). This enables the limits of the centralized systems to be overcome, but requires synchronization of the individual light points so as to guarantee that the variations of brightness of the lamps occur always at the same instant.

Synchronization systems are known based upon exchange of information between the central control system and the control systems of the individual light points, said exchange of information being made through an appropriate communication line, for example a radio-frequency communication line or else one based upon the so-called "conveyed waves" (power-line communication). Said systems also have the advantage of enabling direct monitoring of the state of operation of each light point (for example, detected through the mechanism of self-diagnosis with which the same control system of each light point can be equipped) by the central control system, but present the drawback of being very costly, because they require the presence, in each light point, of an appropriate electronic control system capable not only of performing the function of regulation of the power supplied to the lamp (electronic-ballast function), but also of guaranteeing a stable and reliable communication, in any operating condition, with the central control system.

Likewise known are lighting systems in which the instant of day-time activation of the supply voltage is used, by the control system of each light point, as starting synchronism of a timer, which, after a given fixed time, activates the mechanism of reduction of the power supplied to the lamp, without the need for a direct dialogue with the central control system. Said solution is quite economical, because it does not require, in each light point, the presence of a communication system, but presents the drawback of managing in a fixed way the start of operation in "energy-saving" mode, without taking into account the variations of duration of night hours according to the seasonal period and the geographical location.

In order to take into consideration the seasonal period and the geographical location, it would be necessary to associate to each light point a programmable control system, for example using a low-cost microcontroller, that is able to manage internally a clock with calendar and the appropriate information regarding the logic of activation of the "energy-saving" mode, but this would require the presence of a battery for keeping the system active in the hours of daylight during which the a.c. mains voltage is not applied to the lighting line, and would impose the need moreover for a complex and costly activity of maintenance to guarantee the constant alignment of the clocks and of the calendars of the control systems of the individual lamps.

Purpose of the invention

The purpose of the present invention is to present a method that is able to manage in an effective and inexpensive manner the function of energy saving of a public-lighting system, overcoming the various drawbacks described above, and a device that manages each light point through the implementation of said method.

The above and further purposes are achieved by means of the method that constitutes the subject of the present invention and that is designed to manage modulation of the electrical power transferred to a lamp, which is connected to a public-lighting network and is supplied electrically via said network.

The method according to the present invention comprises the steps of: i) determining one or more time values on the basis of at least one historical piece of information regarding operation of a lamp; and ii) making a variation of the electrical power transferred to said lamp at the aforesaid one or more time values, which are measured starting from a predetermined condition of operation of said lamp, said operating condition being preferably represented by the initial instant of activation of said lamp at each lighting session. The method forming the subject of the present invention, which regards a public-lighting network and has the purpose of reducing the consumption of electrical energy in accordance with the standards currently in force regarding energy saving, can be conveniently implemented within the control system of one or more light points belonging to one and the same public-lighting system. In fact, the control system of each light point is able to determine, for example at the start of each lighting session, one or more time values on the basis of at least one historical item of information regarding previous lighting sessions, and then to implement, during the current lighting session, a variation of the electrical power transferred to the lamp of the light point at said one or more time values, measured starting from the occurrence of a predetermined condition of operation of said lamp, said operating condition being represented preferably by the instant of activation of said lighting session.

Brief description of the drawings

The subject of the present invention is described in greater detail with the aid of a few figures, which are provided purely by way of non-limiting example and in which:

- Figure 1 is a schematic illustration of the architecture of a regulation device, designed to be installed between a lamp and a source of electrical energy, in particular a public-lighting network, according to the invention; - Figure 2a is a schematic illustration of a possible evolution, during the year, of the hours of sunset and sunrise;

- Figure 2b is a schematic illustration of the evolution of the duration (in hours) of the night during the year, where the night period is defined as the interval of time comprised between sunset and sunrise; - Figure 2c is a schematic illustration of the evolution, during the year, of the interval of time (in hours) that elapses between sunset and midnight hours in the various days of the year;

- Figure 3 a is a schematic illustration of a first profile of supply of electrical power to the light point, which represents a first possible embodiment of the method for modulation of the electrical power transferred to a lamp according to the invention;

- Figure 3b is a schematic illustration of a second profile of supply of electrical power to the light point, which represents a second possible embodiment of the method for modulation of the electrical power transferred to a lamp according to the invention; and

- Figure 3 c is a schematic illustration of a third profile of supply of electrical power to the light point, which represents a third possible embodiment of the method for modulation of the electrical power transferred to a lamp according to the invention. Detailed description of the invention The device for regulation of the light intensity of a lamp 40 according to the invention, represented in Figure 1, comprises the following parts:

- a power feeder 15 of an ac-dc type that is able to generate, by drawing electrical power from the lighting line 10, the a.c. voltage necessary for supplying the electronic control system (30, 35, 25) that manages said regulation device, indicated with 50;

- a microcontroller 30, which is able to perform the following functions: detection, through an appropriate input ZCD, of the zero-crossing pulses, i.e., the zero crossings of the a.c. voltage of the lighting line 10; timely identification, always through the same input ZCD, of the possible absence of said a.c. voltage; management, using appropriate electronic means 25, of the electronic-ballast function modulating the quantity of the power supplied to the lamp 40; and saving day after day of the information useful for pursuing the purposes of the invention, such as for example the duration of the current lighting session, on a nonvolatile memory 35; reading from said nonvolatile memory of the historical information accumulated day after day; and for implementation, through an appropriate software program, of the method forming the subject of the present invention;

- a nonvolatile memory 35 represented by an EEPROM or else by a flash memory, in the latter case said memory being preferably contained within said microcontroller 30;

- an electronic driver 25, constituted by appropriate actuator means, by means of which the microcontroller 30 carries out regulation of the amount of power supplied to the lamp 40 in accordance with the method forming the subject of the present invention; said electronic driver can also contain appropriate means of diagnosis, which are able to detect possible malfunctioning of the lamp 40 and/or of the electronic driver 25 itself and to signal them to the microcontroller 30 through appropriate electrical signals.

We shall consider a lighting line 10, to which a given number of light points 50, 40 is connected, for example the lamps that characterize an urban and/or extra-urban lighting system, each light point being made up of a lamp 40 and a device 50 for regulation of the power supplied to said lamp, set between the same lamp and said lighting line. A lighting session starts when a given a.c. voltage is applied to the lighting line 10, for example 230 Vac or some other value, said a.c. voltage being characterized by a given frequency, for example equal to 50 Hz or some other value, and terminates¹ at the instant when said a.c. voltage is suppressed. At the moment when said a.c. voltage is applied to the lighting line 10, each light point receives supply and starts to perform its function of lighting, managed through the regulation device 50 and the corresponding lamp 40. At the instant when a light point receives supply, the microcontroller 30 starts to function executing the power-on routine, i.e., a specific software program dedicated to initialization of the variables of the control system of the light point 50, 40 itself. By means of said routine the microcontroller 30 starts counting the duration of the current lighting session, fetches from the nonvolatile memory 35 the historical information necessary for calculating the instants in which the power supplied to the lamp must be varied, and carries out said calculations.

Said historical information, stored in the form of mathematical relations and/or of data appropriately organized in tables, regards the duration of the last lighting session, the durations of the immediately preceding sessions, the statistical data regarding the preceding sessions and all the other information necessary for identifying the exact instants in which, starting from the instant of activation of the current lighting session, the quantity of electrical power supplied to the lamp 40 must be varied.

At the instant when the lighting session terminates, each light point is deprived of the supply, and the corresponding microcontroller 30 immediately terminates measurement of the duration of said lighting session and its storage in the nonvolatile memory 35.

Counting of time is performed using preferably the pulses of zero crossing of the a.c. voltage applied to the lighting line, in this way obtaining synchronization of all the light points of said line. In fact, taking as time basis the period associated to the frequency of the a.c. voltage that supplies the lighting network, the microcontroller 30 of each light point 50, 40 is able to measure the time in an absolutely identical manner, all the light points being supplied with the same a.c. voltage, thus guaranteeing the necessary synchronism at the moments of variation, according to the invention, of the power supplied to the respective lamps. Furthermore, since the aforesaid measurement of the duration of the interval of time that elapses between the instant of activation of the lighting session and that of its deactivation is effected at the instant when the supply voltage is set to zero, the feeder 15 of the control system of each light point is equipped, according to the invention, with filter capacitors 20, appropriately sized in such a way as to accumulate the energy necessary to keep the microcontroller 30 active for a time such as to enable conclusion of the aforesaid measurement and to store the value of said measurement in the nonvolatile memory 35. For said purpose, the microcontroller has available an input ZCD through which it detects continuously the zero crossing of the a.c. supply voltage so as to be able to perform the following two operations: measurement of the time, through counting the number of zero crossings of the supply voltage; and early identification of a lack of said supply voltage through detection of the absence of signals on said input ZCD. The present invention, consequently, regards a method for reducing the consumption of electrical energy in a public-lighting network, characterized in that:

- the power absorbed by each individual light point 50, 40 is managed through an appropriate control system 30, 35, associated to said light point and equipped with appropriate means 25, for example the ones typical of an electronic ballast, for autonomous regulation of the amount of power transferred to the corresponding lamp 40;

- the instant of activation of said lighting network, for each day of the solar year, is managed by an appropriate central control system, which, through appropriate means, supplies said lighting network with an appropriate a.c. voltage having a predetermined amplitude and frequency;

- the instant of deactivation of said lighting network, for each day of the solar year, is likewise managed by the same central control system, which, at said instant of deactivation, sets said a.c. supply voltage to zero; - the duration of each "lighting session", constituted by the interval of time that elapses between the instant of activation and that of deactivation of said lighting network, depends, for each day of the solar year, upon the interval of time that elapses between the instant in which the sun sets and that in which the sun rises and is thus characteristic of each day of the solar year; and - the energy-saving function, associated to each lighting session of said network, is managed autonomously by the control system of each light point according to the method forming the subject of the present invention.

According to the present invention, the microcontroller 30 of the electronic control system of each light point 50, 40 contains, in its nonvolatile memory 35, information regarding the estimated hours in which, day after day throughout the year, the sun sets and rises, as described in Figure 2a. On the basis of said information said microcontroller is able to determine, day after day, the duration of the night, as represented in Figure 2b.

Since the interval of time that elapses between the start of a lighting session and its end is in strict relation with the hours of sunset and sunrise, it follows that the control system of each light point is also able to trace back, through appropriate software processing operations, to the day of the year through the comparison of the duration of said lighting session with the information contained in its nonvolatile memory. Once the day of the year has been identified through a historical piece of information, such as for example the duration of the immediately previous lighting session or else the average duration calculated on the basis of a predefined number of durations of preceding lighting sessions, said historical piece of information is used by the control system of each light point to define, according to the invention, one or more time values at which, starting from the instant of activation of the lighting session, a variation of the power supplied to the corresponding lamp must be made.

It is consequently evident that, at the moment of activation of a given session of power supply, the control system of each light point determines, through appropriate processing software, said one or more time values on the basis of the durations of the previous sessions. In particular, the duration of the lighting session immediately preceding the one in course may be taken as reference, or else an average of the durations of a predetermined number of lighting sessions immediately prior to the current session, carrying out if necessary filtering, i.e., elimination, of the possible values of duration that, for any reason, diverge too much from the values of the duration of chronologically adjacent sessions. A filtering mode, indicated purely by way of non-limiting example, may be the one described in what follows: in the calculation of said average duration, one or more lighting sessions are excluded when the ratio between the duration of said one or more lighting sessions and said average duration is lower than a predetermined validation coefficient.

As regards the number of variations of the power transferred to the lamp of each light point, the present invention envisages at least one variation, which necessarily takes the form of a reduction in said power. In a first embodiment of the present invention, a single negative variation of the electrical power transferred to the lamp 40 is made in accordance with the profile of power supply represented in Figure 3 a, where the reduction in the power supplied to the lamp of each light point belonging to one and the same lighting line is effected, purely by way of example, at midnight. In this case the microcontroller 30 determines a single time value, so that, starting from said time value, the consumption of electrical energy by the lamp 40 is reduced.

For a clear representation of the corresponding evolution of the supply of electrical power to the light point 50, 40, Figures 3a, 3b and 3c give on the ordinate the percentage value of the power supplied, the value 100 corresponding to the rated power. From the analysis of the historical data represented in Figures 2b and 2c it emerges that, if the distance in time of midnight from the instant of activation of the lighting session is equal to X and the duration of said session is equal to Y, the ratio between X and Y is approximately 0.45. This means that, if the duration of the current session is known on the basis of historical information regarding the immediately preceding sessions, it is possible to calculate the interval X associated to midnight through a simple mathematical operation of multiplication. More in general it may be stated that, according to the invention, the ratio between the time value X, associated to the instant at which the first variation of the power supplied to the lamp is made, and Y, associated to the duration of the lighting session, is comprised between a minimum value and a maximum value respectively lower and higher than the coefficient 0.45: for example, the value of said ratio can be comprised between 0.35 and 0.55.

In the aforesaid first embodiment of the present invention, the time value at which the negative variation of the electrical power transferred to the lamp is made (time value that corresponds to midnight in Figure 3 a) is obtained by multiplying the historical information regarding operation of the lamp 40 by a predetermined timing coefficient preferably comprised between 0.35 and 0.55.

As an alternative to the use of the aforesaid mathematical calculation it is possible to use, as already mentioned above, relations of a tabular type contained in the nonvolatile memory of the control system 30, 35 of the light point 50, 40.

In a second embodiment of the present invention, the variations of the power supplied to the lamp are more than one, with the possibility of obtaining profiles of power absorption suited to the various night-time hours with different traffic intensities, as illustrated for example in Figure 3b, where, in addition to a first reduction of power made towards midnight, there is indicated also a second further reduction towards 3 o'clock in the morning.

According to a third embodiment of the present invention, it is finally possible, in the case where the variations of power are more than one, that at least one variation is of a positive type, i.e., such as to increase the power supplied to the lamp, as indicated in Figure 3 c, where the light intensity is given at the maximum value during the first hours of the day, when the traffic starts to intensify.

As already indicated for the first variation of the power supplied to the lamp, so also for the subsequent variations the time value associated to each can be calculated by multiplying the aforesaid duration Y by a given timing coefficient, or else be obtained from appropriate tables contained in the nonvolatile memory of the control system of each light point.

It is clear that various modifications may be made, with reference in particular to the software processing operations through which the control system of each light point determines the instants of variation of the power supplied on the basis of the durations of the previous lighting sessions, without thereby departing from the claimed scope.

Claims

1. A method for modulation of the electrical power transferred to a lamp, said lamp being connected to a public-lighting network and being supplied electrically via said network, said method comprising the steps of: i) determining one or more time values on the basis of at least one historical piece of information regarding operation of said lamp; and ii) making a variation of the electrical power transferred to said lamp at said one or more time values, said one or more time values being measured starting from a predetermined condition of operation of said lamp.

2. The method according to Claim 1 , wherein said predetermined operating condition is activation of said lamp at the start of a lighting session.

3. The method according to Claim 2, wherein said historical information is generated on the basis of the duration of lighting sessions prior to said activation.

4. The method according to Claim 2 or 3, wherein said historical information is the duration of the lighting session immediately preceding said activation.

5. The method according to Claim 2 or 3, wherein said historical information is the average duration of a predetermined number of lighting sessions immediately prior to said activation.

6. The method according to Claim 5, wherein, in the calculation of said average duration, one or more lighting sessions are excluded, in the case where the ratio between the duration of said one or more lighting sessions and said average duration is lower than a predetermined validation coefficient.

7. The method according to any one of the preceding claims, wherein a single time value is determined and wherein, at said time value, a negative variation of the electrical power transferred to said lamp is made in order to reduce the consumption of electrical energy by said lamp starting from said time value.

8. The method according to any of Claims 4-6 and Claim 7, wherein said time value is determined by multiplying said historical information by a timing coefficient, said timing coefficient being predetermined and preferably comprised between 0.35 and 0.55.

9. The method according to any one of Claims 1 to 6, wherein a plurality of time values is determined and wherein, at the first of said time values, a negative variation of the electrical power transferred to said lamp is made.

10. The method according to Claim 9, wherein, at the last of said time values, a positive variation of the electrical power transferred to said lamp is made.

11. The method according to any of Claims 4-6 and any of Claims 9-10, wherein said plurality of time values is determined by multiplying said historical information by a plurality of timing coefficients, said timing coefficients being predetermined and the first of said timing coefficients being preferably comprised between 0.35 and 0.55.

12. A regulation device, designed to be installed between a lamp and a source of electrical energy, in particular a public-lighting network that supplies said device with a.c. voltage, characterized in that said device configured to regulate the electrical power transferred to said lamp by means of the modulation method according to any one of the preceding claims.

13. The device according to Claim 12, said device comprising electronic control means, in particular a microcontroller, and actuator means, said actuator means being designed to transfer electrical power from said source of electrical energy to said lamp, wherein said electronic control means control said actuator means, so as to make, through said actuator means, a variation of the electrical power transferred to said lamp at said one or more time values.

14. The device according to Claim 13, said control means comprising also storage means, in particular a memory of a nonvolatile type, wherein said storage means contain relations, in particular relations in the form of tables, designed to determine said one or more time values on the basis of said at least one historical piece of information regarding said lamp.

15. The device according to Claim 14, wherein said electronic control means are designed to measure the duration of said lighting sessions of said lamp and to store said duration in said storage means.

16. The device according to any of Claims 13-15, wherein said control means are designed to generate diagnostic information regarding said lamp, on the basis of electrical signals coming from said actuator means.

17. The device according to Claim 15, wherein the measurement of said duration is made taking as time basis the period associated to the frequency of said a.c. voltage.

18. The device according to any one of Claims 14 to 17, wherein said device also comprises means designed for timely detection of an interruption of the supply of said device by said public-lighting network.

19. The device according to Claim 18, wherein said device also comprises means for accumulation of energy, designed to guarantee operation of said electronic control means during a time period immediately subsequent to said interruption.

20. The device according to Claim 19, wherein said energy-accumulation means comprise at least one capacitor.

21. The device according to Claim 19 or 20, wherein, during the time period immediately subsequent to said interruption, said electronic control means conclude measurement of the duration of the lighting session and store the value of said measurement in said storage means.

22. A public-lighting system, characterized in that it comprises at least one device according to any one of Claims 12 to 21.