WO2016120786A1

WO2016120786A1 - Power-supply voltage regulating device and method

Info

Publication number: WO2016120786A1
Application number: PCT/IB2016/050378
Authority: WO
Inventors: Severino BIAVA
Original assignee: Delta Electric Srl
Priority date: 2015-01-27
Filing date: 2016-01-26
Publication date: 2016-08-04
Also published as: EP3251471A1

Abstract

To improve the general energy efficiency, a method is described for adjusting the power supply voltage (VL) of a lamp (LI - Ln), e.g. a lamp for street lighting, wherein the lamp is supplied with a voltage having amplitude that gradually decreases from a maximum voltage (VI) down to a minimum working voltage (V6), characterized by (i) sequentially switching the lamp between a plurality of n voltages (VI - V6), n> = 2, wherein the amplitude of each voltage of the plurality is fixed and the amplitudes of the plurality's voltages are gradually decreasing in value from a maximum voltage down to a minimum working voltage, (ii) maintaining then the voltage on the lamp at the minimum working voltage (V6); so that the voltage on the lamp (a) starts from one initial maximum voltage, then (b) has a transient with an only-decreasing envelope, and afterwards (c) remains at a minimum voltage.

Description

Power-supply Voltage Regulating Device and Method

DESCRIPTION

The invention relates to a method, and to a relative regulator device, for regulating the electrical power supply voltage, in particular for regulating the light intensity of lamps, in particular for street lighting lamps hereafter taken as example.

To save electric energy used in street lighting very often the light intensity of the lamps is regulated to levels below the nominal one. On the other hand, it is not always necessary that the lamps emit their maximum light intensity, e.g. in the dead of the night. Also, reduced-power lamps work at lower temperature, and their service life increases.

Known systems provide to supply the lamps from a Variac, by gradually decreasing the power-supply voltage down to a minimum value. The voltage control, however, is very inaccurate because it occurs mechanically by translating a slider on the Variac's windings. In addition to giving off sparks and wearing out the sliding contacts, the Variac-based systems generate voltage transient or dips not tolerated by the lamps, which switch off. Finally, the Variac- based systems are little efficient, and generate inside them a power dissipation that degrades the system performance. The main object of the invention is to provide a method, and a relative regulator device, for regulating the electrical power supply voltage, in particular for lamps, more in particular for lamps used in public or street lighting, which allows energy savings during the use of the lamps.

Another object is to enable an easy and precise regulation of the power supply voltage without the lamps turning off.

Another object is to easily adapt the regulator device to different networks of lamps.

Another object is to build a regulator device which is easily interfaced to processing means capable of managing all the working, regulation and safety controls of the lamps, as well as of managing data relating to the presence of potential faults or history data for the evaluation of consumption or for the management of the transmission of said data to the outside, for the remote control or supervision.

The method is for adjusting the power supply voltage of a lamp, e.g. a lamp for street lighting, wherein the lamp is supplied with a voltage having (e.g. maximum or peak) amplitude that gradually decreases from a maximum voltage down to a minimum working voltage, characterized by

(i) sequentially switching the lamp between a plurality of n voltages, n> = 2, wherein the amplitude of each voltage of the plurality is fixed and the amplitudes of the plurality's voltages are gradually decreasing in value from a maximum voltage down to a minimum working voltage,

(ii) maintaining then the voltage on the lamp at the minimum working voltage; so that the voltage on the lamp (a) starts from one initial maximum voltage, then

(b) has a transient with an only-decreasing envelope, and afterwards

(c) remains at a minimum voltage.

In this way, a voltage transient is generated across the lamp that makes it illuminate less but without turning off. By only-decreasing envelope here it is meant the ordinary meaning, i.e. that the envelope of the voltage across the lamp starts from an initial maximum value and then decreases toward a minimum final value with decreasing or constant trend, but without local increases. That is to say that during the transient between the maximum voltage and the minimum voltage the envelope over time only and always takes a value lower than or equal to that in a previous instant.

To maximize the probability of not turning off the lamp, the method provides that said envelope is strictly decreasing. By strictly decreasing here it is meant the ordinary meaning, namely that the envelope of the voltage across the lamp starts from an initial maximum value and then decreases toward a minimum final value with a trend being always and only decreasing. That is to say that during the transient between maximum and minimum voltage the envelope over time always and only assumes a lower value than that in a previous instant.

The plurality of voltages of the method (and in the device defined below) may be of various types, e.g. square or triangular waves. Preferably the plurality of voltages is constituted of sinusoidal voltages, to avoid harmonic emissions and to exploit the public mains. In this case, the plurality of voltages may be constituted of voltages derived from the public mains through a windings system and by magnetic induction (e.g. via a transformer or au to transformer) , and preferably for each voltage a tapping terminal is provided. The passage or switching from one voltage of the plurality to the other may occur according to several criteria. Preferably the lamp is switched from one voltage of the plurality to the other after a voltage of the plurality has remained across the lamp (load) for (about) one half-wave thereof. This avoids steep-fronted voltages on the load and allows low voltage switching with reduced noise. Even more preferably the lamp is switched from one voltage of the plurality to the other in correspondence with the zero crossing of the voltage across the lamp (load). This has the advantage to avoid transients and to form the voltage across the load out of those in the plurality without steps and in uniform manner. By knowing the frequency of the voltages, also timers and/ or synchronizers may be used to determine the switching instant, in particular the zero-crossing switching instant.

Preferably the lamp is switched by connecting it to each of the n voltages via the parallel of n switches, each switch having one terminal connected to the lamp and the other terminal to a different voltage of the plurality. Therefore, the sequential turn on of one switch of the n and the simultaneous turn off of all the others ensures both a single voltage across the lamp and a voltage having a gradually decreasing value.

The lamp may be switched from one voltage of the plurality to the other by switching the conductive state of a solid-state electronic switch, in order to make the commutations precise and repeatable. To improve efficiency, the excitation state of a relay placed in parallel to the solid-state switch may be switched. The solid-state switch and the paralleled relay may constitute one or each of said n switches. Preferably a delay is set between the switching of the conductive state and the excitation state, to stabilize the voltages at play.

To implement the method a device may be used for adjusting the power supply voltage of a lamp, e.g. a lamp for street lighting, adapted to supply the lamp with a voltage having amplitude that gradually decreases from a maximum voltage down to a minimum working voltage, characterized by comprising

- a voltage generator for generating a plurality of n voltages, n >= 2, available at n separate terminals, wherein the (e.g. maximum or peak) amplitude of each voltage of the plurality is fixed, and the amplitudes of the plurality's voltages has a gradually-decreasing value from a maximum voltage down to a minimum working voltage,

- n switches, each placed between the lamp and one of the n terminals,

- a processing unit (e.g. a PC or PLC or a microprocessor, or a discrete- component PCB circuit) adapted to control the conductive state of the n switches so as to supply the lamp with a decreasing-envelope voltage by connecting sequentially to it one at a time each of the n terminals, so that the voltage on the lamp, after one single transient with only-decreasing envelope, starts from an initial maximum voltage and comes to and remains at a minimum working voltage (V6).

Preferably, the plurality of voltages is constituted of n sinusoidal voltages. For example the device may comprise a windings system and by magnetic induction it can generate the n voltages from a single sinusoidal voltage. Preferably, the device comprises a transformer or an autotransformer to derive the n voltages at one secondary or more secondary windings.

Preferably, the processing unit is programmed or configured to switch the lamp from one voltage of the plurality to the other after one voltage of the plurality has remained across the lamp (load) for (about) one half-wave thereof.

Even more preferably, the processing unit is programmed or configured to switch the lamp from one voltage of the plurality to the other in correspondence with the zero-crossing of the voltage across the lamp. To this aim, the device may comprise a zero-voltage detector circuit or a zero-crossing voltage detector circuit for the voltage across the lamp or load, the circuit being able to generate for the processing unit a synchronization signal in correspondence of said zero.

Preferably, the n switches are placed in parallel to each other, and each switch has one terminal connected to the lamp and the other terminal to a different voltage of the plurality (or to a different terminal of the n terminals) , and the processing unit is programmed or configured to sequentially turn on all the n switches one at a time while keeping the other (n- 1) turned-off.

Preferably, one or each of the n switches comprises or is constituted of a solid-state electronic switch, e.g. a SCR or a power Mosfet. Preferably, a power relay, whose conductive state is controlled by the unit, is placed in parallel to one or each of the n switches.

Preferably, the processing unit is programmed or configured to determine a delay between the commutations of the conductive state of a solid-state switch and the excitation state of the relative relay placed in parallel. Another aspect of the invention is a method and a device for controlling the operational state of a lamp. The method (or device) for controlling comprises:

(i) means for - or the step of - detecting the voltage across the lamp in the vicinity of the lamp (e.g. on or inside a street lamp pole);

(ii) means for - or the step of - determining the operational state by processing the detected voltage;

(iii) means for - or the step of - electrically disconnecting the lamp from the power supply if the operational state is inefficient or defective.

The lamps to be supplied by the device or the method are, for example. Neon type, mercury vapor type, high and low pressure Sodium type and Metal Halide type.

The device or method may be used advantageously to drive public and private lighting plants, with single-phase or three-phase network power systems.

The device for controlling can advantageously be interfaced with said device for adjusting, preferably with said processing unit to communicate with it and from it to receive control signals. This way the device for adjusting can also monitor the state of the loads in the network it supplies. A preferred embodiment of the invention is hereinafter described with reference to the accompanying drawing, wherein:

- Fig. 1 illustrates a block diagram of the device;

- Fig. 2 illustrates a circuit diagram for synchronism generation;

- Fig. 3 shows a voltage trend across the load;

- Fig. 4 shows a control device for a lamp.

A power supply device 10, of the single-phase type, comprises a transformer 12 whose primary is connected to the hot and neutral sinusoidal voltages of the public mains Vrete (e.g. 220 V) and whose secondary comprises six windings, connected to respective terminals TV1 - TV6 which are therefore six sinusoidal voltage outputs VI - V6 being strictly-decreasing compared to a common terminal TVG, namely it holds that:

VI > V2 > V3 > V4 > V5 > V6.

For simplicity only VI is shown.

In the example the rms values of the voltages VI - V6 are:

VI = 230 V; V2 = 210 V; V3 = 195 V; V4 = 185 V; V5 = 175 V and V6 = 165 V. For not strictly-decreasing voltages one might have: VI >= V2 >= V3 => V4 >= V5 => V6.

The transformer 12 may also be an auto transformer, wherein the outputs on the secondary windings are tapped from a single secondary winding (this is the particular case of Fig. 1). The lamps to be supplied are identified with the references LI, L2, ...; Ln, etc.

Each of the terminals TV1 - TV6 is independently connected in series to the load, consisting of the lamps Ll-Ln, by means of equal power switches 11 - 16 that allow switching between the various voltage levels VI - V6 on the lamps Ll- Ln.

E.g. each of the switches II - 16 is current-bidirectional and is constituted of a pair 30 of antiparallelly-arranged SCRs able to be short-circuited by means of a relay Rl - R6 placed in parallel thereto (only Rl is shown in the figure). The relays Rl - R6 may sustain 60 A, while the SCRs 40 to 50 A.

Control lines Jl - J6 carrying power-on/off signals to the SCRs and excitation or de-excitation signals for relays Rl - R6 arrive to the switches 11 - 16 from an electronic board 40. To the input of the board 40 arrives a signal generated by a circuit 42 (Fig. 2) which senses the voltage VI for detecting the zero-crossing of the voltages VI - V6 (with an auto transformer just one needs to be detected). The voltage VI is rectified by a diode bridge PD3 and sent to the gate of a MOSFET Q3 which by turning on supplies a photodiode, which sends a signal used inside the board 40 as a synchronization instant to switch the switches II - 16 in turn.

The switching between the voltages VI - V6 on the load is carried out substantially in synchronism with the zero-crossing of the sinusoidal voltage VI (and therefore of all the voltages VI - V6).

In particular, the board 40 sends signals on lines Jl - J6 so that the switching phase of switches II - 16, starting from an unpowered load, takes place in general in the following way:

I. turn-on of an SCR in the switch II when the voltage VI has come at substantially 0 V (all the other SCRs of the device 10 are turned off);

II. (optional) waiting for a delay, e.g. a few hundred ms; III. closing of the relay Rl in parallel to the just turned-on SCR;

IV. waiting for a predetermined time wherein the load is powered by the voltage VI, e.g. the time of a half- wave for VI - V6;

V. opening of relay R 1 ;

VI. (optional) waiting for a delay, e.g. a few hundred ms; VII. removal of the turn-on command for the SCR in the switch II (which is now being turned off);

VIII. waiting for the zero Volt crossing of the actual voltage on the load;

IX. closing command to the switch relative to the next voltage, here 12; X. return to phase II, mutatis mutandis for the switch 12 and subsequent ones.

This sequence is respected for positive and negative half-waves of VI - V6. Therefore across the load the voltage can have an overall course VL as shown in Fig. 3. There is a first half- wave with rms value VI, then another half- wave with rms value V2, and so on down to the value V6 which remains stationary on the load.

The train of half-waves with decreasing amplitude and alternating polarity allows disturbing little a turned-on lamp and not to turn it off. One can thus achieve a much lower final voltage value, thereby gaining greater energy efficiency.

The number of half- waves in VL for each voltage VI - V5 may also be different from what is illustrated, and the same applies to the values VI - V6. E.g. V6 in certain installations may also go down to 145 V. VI - V6 usually vary depending on the types of lamps used in the plants to be supplied.

The zero-voltage switching permits not to turn off or perturb a lamp, because it avoids a voltage deformation across the load that would destabilize the lamp; and this solves the problem of interference of a voltage VI - V6 when switching to another. Furthermore, the lamps LI - Ln are powered during turn-on without a steep voltage front, which gives them time to (again) turn on stably. In particular, see case of Fig. 3, advantageously the SCRs are commutated when the voltages VI - V6 are zero (or almost zero), therefore disturbances are not generated and the devices are stressed less. In addition, this prevents a voltage "hole" on the load, since the voltage already is at 0 V. Although the presence of relays R 1 - R6 is optional, they allow a reduction in the power dissipated by the switches 11 - 16 because they maintain the voltage across their terminals to practically zero. A SCR has a voltage drop of approximately 1.2 V when it is traversed by a current of about 30 A. With the relays R1-R6 the power dissipation is much lower because the voltage drop across their contacts is almost zero.

Another big advantage is that such voltage is nearly zero especially when the voltages VI - V6 arrive at their peak, and a voltage drop on the SCRs or generally on the switches 11 - 16 could destabilize a lamp and bring it to turn off. The SCRs in the switches 11 - 16 allow - for their part - a fast, reliable, accurate and repeatable initial switching of the voltages VI - V6.

Preferably the SCRs are driven by pulse transformers, to ensure switching of the electronic switches. The board 40 may advantageously be programmable and comprise one or more microprocessors 44, adapted e.g. to run a program for managing the timing of the signals on the lines Jl - J6. By changing the program one can meet the needs of different plants. In particular, field tests have shown that the output voltage adjustment through the board 40 has enabled an energy saving of up to 50%.

A microprocessor 44 may be programmed to store and manage historical data of the plant, for evaluations and immediate feedback on consumption and potential faults.

A microprocessor 44 may be programmed to manage the transmission signals outside the board 40 both for the polling and for the remote control. To this aim, the board 40 comprises a section 46 comprising e.g. a radio interface or a USB interface, or a GSM interface, or a network card for connecting to the Internet,

Through the transceived data from the section 46 one can implement a control system to remotely manage the lightings. E.g. it is possible to build an APP that, loaded and run on a smartphone, allows programming or controlling the lamps Ll-Ln.

The data communication from /to the device 10 to /from the outside may allow supplying, individually or in groups, lamps kept under maintenance, so as to allow the identification and repair of the fault quickly and without the need of having to resort to the costly power-up of all the lighting fixtures connected to a single supply / distribution framework.

The device 10 may be associated with a system 60 for monitoring the operational state of the single lighting elements; in particular capable of signaling a fault and the relative disconnection of the faulty lamp so as not to leave the power supplies voltage-powered and thereby ensuring a further energy saving. In this regard see FIG. 4. In the vicinity of each lamp Ll-Ln or on the stem of a lamp post 50 is arranged a detector circuit 56 connected to electrical supply lines 52, 54, e.g. those outgoing from the device 10 (see. fig. 1). The circuit 56 is able to detect the voltage and the current on lines 52, 54 in order to determine if the lamp in the lamp post 50 is working or not. Through a data communication circuit, e.g. via radio, GSM or PLT on the same lines 52, 54, the circuit 56 can inform a remote central unit about the operational state of the lamp post 50. In case of failure, automatically or by remote control, the circuit 56 may drive a switch or circuit breaker 58 placed in series with the load to isolate it, thus avoiding unnecessary energy consumption and contributing to a longer working life of the lighting components, such as power supplies, lighters, and lamps, to the advantage of a lower maintenance cost.

Note that the circuit 56 allows verifying the actual working of the streetlight 50 and it is possible to check also remotely the state of the lamps, without having to go on site.

Note that the system 60 is exploitable regardless of the device 10, and vice versa, although together they enable a complete, efficient and automatic management of a lighting network. In particular, the system 60 may be operated remotely from the device 10 and/ or from the unit 44. In general, the device 10 and/or the circuit 56 may perform optional additional functions:

- it may manage the automatic by-pass by means of a relay or a switch placed at the output of the power board, e.g. upstream or downstream of the switches II - 16, for opening or closing contacts in the absence of or with reduced output voltage; and /or

- it may verify the working of individual lamps Ll-Ln connected to the power board by means of a PLT transmitter. For this purpose it may comprise a module or circuit for a lamp with a circuit for checking the absorption of a lamp or the phase shift between voltage and current. This data is then sent online by the transmitter; and/or

- it may be managed remotely and may comprise a GSM radio transmission card (for texts or an APP for smartphones) capable of transmitting data, in particular to report alarms or faults to one or more pre-selected telephone numbers. Conversely, the GSM card can be used for polling or programming remotely the operation of the device 10 and /or the circuit 56.

Claims

1. Method for adjusting the power supply voltage (VL) of a lamp (LI - Ln), e.g. a lamp for street lighting, wherein the lamp is supplied with a voltage having amplitude that gradually decreases from a maximum voltage (VI) down to a minimum working voltage (V6) , characterized by

(i) sequentially switching the lamp between a plurality of n voltages (VI - V6), n> = 2, wherein the amplitude of each voltage of the plurality is fixed and the amplitudes of the plurality's voltages are gradually decreasing in value from a maximum voltage down to a minimum working voltage,

(ii) maintaining then the voltage on the lamp at the minimum working voltage (V6); so that the voltage on the lamp

(a) starts from one initial maximum voltage, then

(b) has a transient with an only-decreasing envelope, and afterwards

(c) remains at a minimum voltage.

2. Method according to claim 1, wherein the plurality of voltages is constituted of sinusoidal voltages.

3. Method according to claim 1 , wherein the plurality of voltages is constituted of voltages derived from the public mains (Vrete) through a windings system and by magnetic induction, e.g. via a transformer or autotransformer (12).

4. Method according to any one of the preceding claims, wherein the lamp is switched from one voltage of the plurality to the other after one voltage of the plurality has remained across the lamp for about one half-wave thereof.

5. Method according to any one of the preceding claims, wherein the lamp is switched from one voltage of the plurality to the other in correspondence with the zero crossing of the voltage across the lamp.

6. Method according to any one of the preceding claims, wherein the lamp is switched from one voltage of the plurality to the other by switching the conductive state of a solid-state electronic switch (30) and by switching the excitation state of a relay (Rl - R6) placed in parallel to the solid-state switch.

7. Method according to claim 6, wherein a delay is set between the switching of the conductive state and the excitation state.

8. Method according to any one of the preceding claims, wherein the voltage across the lamp during said transient has strictly-decreasing envelope.

9. Device (10) for adjusting the power supply voltage (VL) of a lamp (LI - Ln), e.g. a lamp for street lighting, adapted to supply the lamp with a voltage having amplitude that gradually decreases from a maximum voltage down to a minimum working voltage, characterized by comprising

- a voltage generator (12) for generating a plurality of n voltages (VI - V6), n> = 2, available at n separate terminals (TV1 - TV6), wherein the amplitude of each voltage of the plurality is fixed, and the amplitudes of the plurality's voltages has a gradually-decreasing value from a maximum voltage down to a minimum working voltage,

- n switches (II - 16), each placed between the lamp and one of the n terminals,

- a processing unit (40) adapted to control the conductive state of the n switches so as to supply the lamp with a decreasing-envelope voltage by connecting sequentially to it one at a time each of the n terminals, so that the voltage on the lamp, after one single transient with only-decreasing envelope, starts from an initial maximum voltage and comes to and remains at a minimum working voltage (V6) .

10. Device according to claim 9, wherein the plurality of voltages is constituted of n sinusoidal voltages.

1 1. Device according to claim 10, wherein the device comprises a windings system (12) and by magnetic induction can generate the n voltages from a single sinusoidal voltage.

12. Device (10) according to claim 9 or 10 or 1 1, comprising a zero-voltage detector circuit (42) for the voltage across the lamp, the circuit being able to generate for the processing unit a synchronization signal in correspondence of said zero, and the processing unit being programmed or configured to switch the lamp from one voltage of the plurality to the other in correspondence with the zero-crossing of the voltage across the lamp.

13. Device (10) according to claim 9 or 10 or 1 1 or 12, wherein the n switches are placed in parallel to each other, and each switch has one terminal connected to the lamp and the other terminal to a different terminal of the n terminals, and the processing unit is programmed or configured to sequentially turn on all n switches one at a time while keeping the other (n- 1) turned-off.

14. Device (10) according to claim 9 or 10 or 11 or 12 or 13, wherein a power relay, whose conductive state is controlled by the unit, is placed in parallel to one or each of the n switches.