FR2807883A1 - Voltage drop compensator for electric distribution systems, uses switched secondary shunt device to generate correction which is applied to series transformer - Google Patents

Abstract

The compensator has a switched-secondary transformer (110) across the incoming voltage (VE), with its output connected to a second transformer (118) in series between incoming and outgoing supplies to add a correction to incoming voltage. The compensator output voltage (VS) is measured (116) and applied to a controller (112), which selects switch position on the first transformer (110).

Description

The present invention relates to a voltage adapter assembly intended in particular, but not exclusively, to compensate for voltage variations of a power supply line of the electrical energy distribution network.

The power supply lines of the network deliver a voltage that changes over time, Indeed, when the power demanded suddenly increases, there are voltage drops in particular end line.

Overvoltages can also be caused by switching on the lines - they can come from switching on the power transformers, commissioning of highly inductive rotating machines, or unbalance of the three-phase network.

However, the standards provide, for example in France in rural areas to date, that the effective voltage of the low voltage network must be in the range 230 V + 6 / -10%, that is to say between 207 and 244 V.

Indeed, the voltage variations have drawbacks because there are many electrical and electronic devices whose power supply voltage variations must not exceed a given percentage of the nominal supply voltage under penalty of permanent damage or momentary.

In order to overcome these drawbacks, voltage regulating devices have been devised using transformers with variable ratios but whose self-consumption is important or whose supply interruptions during the change of transformation ratio are undesirable.

Moreover, such devices have high response times, it can cause overvoltages for unacceptable times from the point of view of the electricity distributor, when one or more users disconnect a load suddenly. An object of the present invention is to provide a voltage adapter assembly capable of responding rapidly to supply line voltage variations, in particular in the event of an overvoltage, which does not produce breaks or micro-cuts on the line.

To achieve this object, according to the invention, the voltage adapter assembly is characterized in that it comprises - voltage matching device comprising an input for receiving the input voltage VE to be adapted, dividing means of voltage to develop an additional voltage Vp equal to kVE,. means for summing said input voltage VE and a fraction of said voltage Vp by which an output voltage - means for applying said voltage <B> VS </ B> to the output of said device is obtained; adapting means for measuring said output voltage <B> VS </ B>; and control means for producing information representative of the ratio k to be applied to said voltage divider.

It is understood that the voltage VE is the voltage of the supply line and that the output voltage <B> VS </ B> is the voltage that is delivered to the user.

The measuring means which make it possible to measure the output voltage of the adapter provide information representative of said output voltage to the control means which elaborate information able to apply an additional voltage to the input voltage VE in the case of a voltage drop relative to the nominal voltage or information capable of reducing the input voltage VE in the case of a voltage higher than the nominal voltage. In this case, k takes negative values.

This additional voltage is advantageously developed by the voltage divider means, which comprises a primary winding to which said input voltage VE is applied, a secondary winding having a plurality of dividing outputs, a plurality of switches, each switch being connected to a division output of the secondary winding and to the output of said voltage division means, and means for controlling the open or closed state of each switch.

It is understood that the additional voltage is developed from the input voltage VE, which is applied to the primary winding terminals. A secondary winding having a plurality of outputs corresponding to a given number of turns of the winding makes it possible to obtain an additional voltage VD at the terminals of two outputs.

choosing a determined transformation ratio, at the output means voltage division, is realized by the control means provide information to the control means for closing two determined switches on the output terminals of the voltage dividing means in order to obtain at these terminals the additional voltage VD.

According to a preferred embodiment, said means for summing voltages comprise a primary winding to which said additional voltage VD is applied and a secondary winding to which a fraction of said additional voltage VD equal to K'.VD is applied. at the input voltage VE the complementary voltage, representing a fraction of the additional voltage VD depending on the transformation ratio of the transformer such that k 'VD. = kk' VE.

It is understood that this device allows to add a voltage value in the case where there is a voltage drop on the supply line. Given its configuration, this device allows to add an uninterruptible voltage, since the voltage is added series on line.

In the case of an overvoltage, according to yet another preferred embodiment, the adapter assembly further comprises an overvoltage switch and an anti-overvoltage resistor mounted parallel with said primary winding means for the sum of voltages, and means for controlling the open or closed state of said switch.

Thus, when a voltage increase occurs, most often related to a load disconnection in the user, the surge resistor is connected to the terminals of the primary winding means to sum the voltages, so as to compensate drop charge. This resistance thus makes it possible to damp the voltage rise, while the voltage divider means adapt to the new state of the line.

The anti-overvoltage resistor is connected to the secondary terminals by a switch actuated by control means which are able to receive a closing signal developed by the control means. Advantageously, the control means further comprise means for comparing said measured output voltage <B> VS </ B> with a predetermined voltage Vmax and means for developing a signal for closing said overvoltage switch if said output voltage is greater than Vmax- It is understood that the control means analyze the output voltage VS and a predetermined voltage Vmax corresponding to a voltage threshold to be exceeded. This voltage threshold corresponds to a certain percentage of the nominal voltage supplied by the power supply line. The analysis consists of comparing the output voltage VS with a predetermined value and of connecting the surge resistor if this value is exceeded.

As will be explained in more detail, the measurement of the output voltage VS and the comparison with the predetermined value Vmax are performed at a high frequency so as to intervene very quickly on line in case of overvoltage.

Preferably, the measuring means deliver an output voltage value with a periodicity T, and said control means comprise means for developing a predicted voltage value Vpred at a measurement instant t from the output voltage measurements. at times t, t - aT and t - 2aT.

Thus, according to a particular characteristic, a predicted voltage Vpred, which is an estimate of the voltage value for the future taking into account the past evolution of the output voltage Vs, is developed.

It is understood that this estimate makes it possible to prepare a correction to be applied to the voltage taking into account the possible drift that is observed.

After determining that the line was not overvoltage, according to a preferred embodiment, the control means, comprising means for comparing the predicted voltage with a predetermined value Vmin (Vmin <Vmax), triggers a procedure of fast control if Vpred <Vmin.

 Vmin a configurable threshold value below which predicted value Vpred must not go under penalty of overflow. In fact we realize a forecast of what will be the voltage in the future, and if this forecast is below a certain threshold Vmin, decides to regulate the voltage according to a mode called "fast regulation" that will detail in following the description and which makes it possible to return very quickly to the setpoint voltage.

When the future voltage value has been taken into account and the predicted value is greater than the threshold value, the rate of variation of the voltage is taken into account.

Thus, advantageously, the control means comprise means for calculating the variation of the output voltage OV on number n of measurement periods, and means for comparing, Vpred> Vmin, said calculated voltage variation with a predetermined value. of voltage variation and to trigger a control procedure in so-called "fast" mode if AV> Vv and to trigger control procedure in so-called "slow" mode in the opposite case The fast and slow control procedures will be described in more detail in following the description.

Advantageously, the control means furthermore comprise means for comparing said measured voltage output voltage <B> VS </ B> with a predetermined voltage Vinf <Vmin and means for triggering said fast control procedure if said measured lower output voltage Vinf. It is understood that the output voltage must not fall below a certain voltage threshold Vinf. When this is the case, an additional voltage is added to the output voltage at the output of the adapter assembly, according to the fast regulation mode.

Other features and advantages of the invention will become apparent from reading the following description of particular embodiments of the invention, given by way of indication but not limitation, with reference to the attached drawings in which - Figure 1 is a view schematic diagram of the circuit of the voltage adapter assembly, - Figure 2 is a schematic view of the circuit of the voltage matching device comprising an input, voltage divider means, means for summing the input voltage and means for applying the voltage VS to the output of the adaptation device; - Figure 3 is a schematic view of the circuit according to the figure to which the means for measuring the output voltage, the control means and the means for 4 is a schematic view of a flowchart showing the three possible control procedures, and FIG. 5 is a schematic view of a flowchart of FIG. presenting the regulation strategy of the adapter set.

Referring first to Figure 1 to describe the general principle of operation of the voltage adapter assembly.

The adapter device comprises an input E for receiving an input voltage VE to be adapted which corresponds to the power supply and an output S for outputting an output voltage VS corresponding to a suitable voltage delivered to the user.

The device also comprises dividing means 110 or switching transformer which is a variable ratio transformer k for developing an additional voltage. This additional voltage is equal to k.ve. The additional voltage value is determined by the control means 112 by the control means 114 which determine the transformation ratio k to be applied as a function of the value of the output voltage VS given by the measuring means 116. also make the input E of the voltage adapter assembly.

The divider means 110 are connected to means 118 for summing the input voltage VE and a fraction k'Np of the additional voltage so as to obtain the output voltage VS, where k 'is the transformation ratio fixed means for sum 118 which are, in this case, a fixed ratio transformer, said coupling transformer.

Reference will now be made to FIG. 2 to describe in more detail the switching transformer and the coupling transformer, as well as the anti-surge means.

The switching transformer 210 comprises a primary winding across which is applied the input voltage VE and a secondary winding 230 comprising, for example, six dividing outputs: 232, 234, 236, 238, 240, and, 242, respectively connected to six switches C232, C234, C236, C238, C240 and C242, which are also connected to the output of the voltage dividing means 210. In addition, a seventh switch connects the division output 232 to the output of the switching means. Thus, by choosing a switching of two switches, it is possible to vary the additional voltage, for example, from -8 to + 24% of the input voltage.

The coupling transformer 118 comprises a secondary winding 246 to which the complementary voltage k'Mp is applied and a primary winding 248 to which the additional voltage VD is applied. This transformer is a fixed ratio k 'and allows to add to the input voltage VE an additional voltage equal to k.k'. VE = K. VE.

In addition, the adaptation device comprises an overvoltage switch and an anti-surge resistor 252 mounted in parallel with the primary winding 248.

FIG. 3 shows the diagram of FIG. 2 to which control means for controlling switches, control means and means for measuring the output voltage VS have been added.

At the base of any regulating device, it is necessary to have measuring means. In FIG. 3, measurement means 354 measure the output voltage of the adaptation device at a frequency that is the same as that of the electrical network, for example 1000 Hz for a frequency voltage of 50 Hz or a periodicity of 1 ms. In fact the signal is sampled by the measuring means so as to calculate the rms value of the voltage. In order not to weigh down the description, we will talk about the voltage value for the rms value of the voltage.

Consequently, the measuring means 354 are able to provide a measurement of the output voltage value VS to control means 360.

The control means 360 comprise comparison means 361 for comparing the output voltage VS measured by the measuring means 354 with a predetermined voltage Vmax which must not be exceeded or exceeded as short as possible. This voltage Vmax corresponds, for example, to low voltage distributed electrical energy in France in rural areas to an excess of 6% of the nominal value 230 V, ie 244 V. When the output voltage VS is greater than the predetermined voltage Vmax, means 362 develop a signal capable of ordering the control means 363 closing the surge switch 250.

The anti-surge device is activated as a priority. In addition, its activation is followed by a switch switching process C332 and C337 so as to be on a transformation ratio K equal to 1 for a period of time may be equal to 1 s. The deactivation of the surge protection switch 350 occurs as soon as the switching of the switches C332 and C337 has been performed.

This device makes it possible both to reduce the peak voltage and the duration during which the voltage is greater than Vmax is 244 V.

The control means comprises means 364 for generating a predicted voltage value Vpred at a measurement instant t from the output voltage measurements at times t, t - aT and t - 2aT; T is the period between two measurements of the voltage and has an integer. According to a particular example, T is 1 ms and a is 10. Thus, the predicted voltage value Vpred is produced at a time t, from the output voltage values measured at times t-10ms and t-20ms. An example of calculation of the predicted voltage is given by the following formula V2pred (t) = 18333.V2 (t) + 0.3333.V2 (t - 10ms) - 1,1667.V2 (t - 20ms).

This predicted value corresponds to an estimated output voltage value in a given future, taking into account the values of the voltage output at time t, at time t less than half a signal period and at time t minus a period of the signal.

In addition, the control means comprise comparison means 365 for comparing the predicted voltage Vpred to a configurable voltage Vmin. When the predicted voltage Vpred is lower than the threshold value Vmin, means 368 produce a signal capable of supplying information to the control means 363 so that they control switches according to a so-called "fast" regulation procedure aimed at immediately return to a value Vcible equal to the setpoint voltage Vc. This setpoint will generally be chosen close to the nominal value of the network. This procedure will be described in detail in the following description.

The control means also comprises means 367 for calculating the variation speed OV of the output voltage VS over n preceding periods and for comparing this variation rate with a predetermined value V.sub.v. This value is taken close to the product of the nominal voltage by the magnitude AK which is the difference between two consecutive ratios K. For example, Vv will be worth 6 V per ms, the variation being measured over 3 periods of the voltage. When the speed of variation is greater than Vv means 368 develop a signal capable of providing information to the control means 363 so that they control closing switches according to a so-called fast procedure, and when AV is less than Vv means 369 develop a signal capable of providing information to the control means 363 so that the so-called "slow" procedure is continued.

The regulation modes known as the "slow" procedure and the "fast" procedure will be described in greater detail in the remainder of the description.

In addition, preferably and for safety reasons, the comparison means 361 also compare the output voltage <B> VS </ B> to a predetermined voltage Vinf <Vmin, this voltage being close to the low threshold of the contract value of the distributor. When the output voltage Vs is lower than Vinf, the means 368 produce a signal capable of supplying information to the control means 363 so that they control the closing of the switches according to a so-called "fast" procedure. Reference will now be made to Figure 4 to describe the three regulation procedures.

In the case of slow regulation, the new transformation ratio will take into account the previous transformation ratio, a target voltage Vcible and the value of the voltage to be regulated Vreg, as we will explain it in more detail in As a result of the description, the value of the target voltage Vcible can be taken equal to the value of the target voltage, which will generally be close to the nominal voltage of the network The voltage to be regulated Vreg may itself be worth the output voltage Vs measured at the instant t of the fast regulation, or the predicted voltage Vpred at the same time.

Slow regulation is a substitute for the fast regulation of the triple condition that the output voltage is not less than Vinf, the predicted voltage is not less than Vmin, and the variations of the output voltage are slow (0V < Under these conditions, it is allowed to change the transformation ratio by one notch (that is to say that the ratio immediately below or above that previously activated) is changed to at least ntemp seconds ( ntemp integer) after the previous switching of the switches The duration of this delay ntemp is calculated so as to keep the flicker below the level of discomfort (this level of discomfort is characterized by an empirical curve connecting the voltage variation to the frequency this variation ).

The "fast" control mode is the main mode of regulation. It is called in several cases, and in a different way in each case: the difference lies in the target voltage values Vcible and voltage to be regulated Vreg which are involved in the calculation of the new transformation ratio. The "slow" regulation procedure allows the transition from one transformation report to another consecutive and to the one of a delay equaling ntemp seconds (ntemp integer). The target voltage Vcible is then the target voltage and the voltage to be regulated Vreg is the output voltage. As a result, the difference between the output voltage <B> VS </ B> and the target voltage (which may be the rated voltage of the network) will be reduced by an increase or decrease in the immediately higher transformation ratio or immediately below, which corresponds, in the example considered, to a change of about 2% of the output voltage.

This procedure is called "slow" because the threats to the deviations of the output voltage Vs from the nominal voltage of 230 V are low. Indeed, the predicted value does not exceed predetermined threshold, that is to say that the output voltage does not seem to deviate significantly from the nominal voltage in a given future, and given its speed of variation it does not seems no more deviate from the nominal voltage in the near future.

Consequently, the difference found between the output voltage Vs and the nominal voltage or the target voltage will be reduced by an increase or decrease in the immediately higher or immediately lower transformation ratio, which corresponds, in the example under consideration, to a change of about 2% of the output voltage. elsewhere, the timer is in this mode, for example, 18 s, that is to say that is maintained for at least 18 s this transformation ratio. Given the speed of evolution of the output voltage, it is reasonable to assume that the voltage differences will not occur in the following 18 s, on the one hand, and the fact that switching occurs all the 18 s avoids generating an annoying flicker for users when the voltage variation is 2%. The "fast" regulation mode is called, in a first when the output voltage is lower than Vinf. If the reliability index one of the predicted voltage value Vpred is good, the target value V target for calculating the new transformation ratio will be worth the nominal voltage VC (close to the nominal voltage generally), and in the opposite case , Target will be worth between Vinf and VC. The notion of reliability index will be described in the complete description of the flowchart.

In a second case, it is called when Vpred is less than Vmin. If the reliability index is good, V will be worth VC, and the voltage to be regulated Vreg will be worth the output voltage VS. In the case where the reliability is insufficient, no action is triggered. It is understood that this test makes it possible to anticipate a decrease in VS below Vinf, but the regulation is then triggered only if this prediction is reliable.

In a last case, the "fast" regulation is called when the output voltage variation is greater than Vv. As in the previous case, no action is triggered if the reliability is insufficient. The "slow" regulation procedure is chosen for the other cases, that is to say when the output voltage VS is less than Vmax under the triple condition that Veff is greater than Vinf, that Vpred is greater than Vmin and V is less than Vv.

In both modes of regulation is developed according to the transformation ratio to be applied to return as quickly V target target. In the case of fast control, if the test means 471 shows that this ratio is not equal to the previous one, it determines which contactors to close 474 and activates the control procedure In the case of slow control; it passes on the transformation ratio immediately lower or immediately higher according to 473 then develops a signal capable of giving the control means indications on the switches to close, said control means activating 475 and disabling the corresponding switches.

will refer to Figure 5 to describe the complete flowchart operation of the voltage adapter assembly.

This flowchart comprises a test step corresponding to a conditional choice of regulation as a function of the reliability index of the predicted voltage value Vpred already mentioned in the description. This reliability index makes it possible to know whether the prediction that has been made of the voltage value in a given future is good or bad. Advantageously, this reliability index is measured by calculating the variance associated with calculating the predicted value. As for the calculation of the predicted voltage, in general, one calculates at time t, as a function of the values of the voltage at times t, t - aT and t - 2aT, associated variance. Using the example given for calculating Vpred at times t, t - 10 ms and t - 20 ms, the associated variance is calculated as the expression Var (t) = 0.8975.V2 (t) - 1.795.V2 (t - 10ms) + 0.8975; V2 (t - 20ms) The lower the variance, the better the prediction on the voltage value. Consequently, a threshold is determined above which the value of the predicted voltage Vpred is considered to be bad, and it is this threshold variance value which determines, in certain cases, this or that regulation.

Preferably, the regulation process is controlled by a programmable controller which according to said flowchart FIG. 4 first orders, according to the first test 582, to compare the value of the output voltage <B> VS </ B> with the maximum voltage Vmax- If the output voltage is higher than Vmax, the surge protection mode 583 is tripped. Nevertheless, there is a case where the anti-surge resistor will not be connected when <B> VS </ B>> Vmax: it is the one where the overvoltage caused by an imbalance of the network. case is detected by the fact that one has an overvoltage even though transformation ratio .k 'is lower than the upper bound provided the norm, or 6% in case of rural areas in France.

In the case where the output voltage is less than Vmax, the processor of the PLC carries out a second test 584 comparing the value of the output voltage with the value Vinf equivalent, for example, to 207 V (that is to say - 10% of the 230 V nominal value). If the output voltage is lower than Vinf, the processor performs a third test 585 on the variance and if it is below the threshold it triggers the "fast" control mode 586, with a value Vcible equal to the setpoint VC, otherwise it triggers the "fast" control mode 587 with a target value V target between Vmin and VC.

If the output voltage is greater than Vinf, a fourth test 588 on the value of the predicted voltage is performed. If Vpred is less than Vmin, a fifth 589 test on the variance is performed, and if it is below the threshold, the "fast" control mode 590 is triggered; otherwise no new control mode is triggered.

If the predicted voltage is greater than Vmin, a sixth test 591 compares the rate of change of the voltage over the last n periods (for example n = 3) and if this variation aV is less than Vv, the test 595 is carried out, if its result is negative, the end of the delay is expected and if its result is positive the "slow" control mode 593 is triggered, if this variation AV is greater than V "a last test 592 compares variance associated with the value of the predicted voltage at threshold value At the end of this comparison, the "fast" regulation mode 594 is triggered if the variance is lower than said threshold, with target value Vcible equal to the output voltage n periods earlier and a value to regulate Vreg equal to the output voltage at time t, otherwise no new regulation mode is triggered.

The description made above envisages carrying out a regulation on a single-phase network. In contrast, preferably, the adapter assembly according to the invention further comprises, in the case of a three-phase network, a plurality of means for summing the voltages each of the phases. Said means being physically independent on each of the phases.

Indeed, this configuration eliminates the electromagnetic coupling between phases at the transformers. The voltage divider means remain with a star coupled primary.

Claims (2)

<U> CLAIMS </ U> 1. Voltage adapter assembly, characterized in that comprises - voltage matching device having an input for receiving the input voltage VE to be adapted, voltage divider means (110) for developing additional voltage VD equal to kVE means for summing (118) said input voltage and a fraction of said voltage VD equal to k'MD by which output voltage <B> VS is obtained; </ B> - means for applying said voltage <B> VS </ B> to the output of said matching device, - means for measuring (116, 354) said output voltage VS, and - control means (112) for producing representative information report k to apply to said voltage divider. 2. An adapter assembly according to claim 1, characterized in that the voltage divider means (110) comprise - a primary winding (220) to which said input voltage VE is applied, - a secondary winding 230 comprising a plurality of division outputs (232, 234, 236, 238, 240, 242) - plurality of switches (C232, C234, C236, C238, C240, C242), each switch being connected to a division output of the secondary winding (230) and to the output said voltage division means (110), and means (114) for controlling the open or closed state of each switch (C232, C234, C236, C238, C240, C242). An adapter assembly according to any one of claims 2, characterized in that said means for summing (118) the voltages comprise a primary winding (248) to which said additional voltage Vp is applied and a secondary winding (246) to which a fraction of said additional voltage Vp equal to K'.Vp is applied. Adapter assembly according to claim 3, characterized in that it further comprises an overvoltage switch (250) and an anti-overvoltage resistor (252) connected in parallel with said primary winding means for summing the voltages, and means 363 for controlling the open or closed state of said switch (250). An adapter assembly according to claim 4, characterized in that said control means 112 further comprises means for comparing (361) said measured output voltage <B> VS </ B> to a predetermined voltage Vmax and means (362) for developing a closing signal of said surge switch (250) if said output voltage is greater than Vmax. An adapter assembly according to claim 5, characterized in that said measuring means (354) outputs an output voltage value with a periodicity T, and in that said control means comprises means (364) for developing a value predicted voltage Vpred at a measurement instant t from the output voltage measurements at times tt-aT and t-2aT. 7. An adapter assembly according to claim 6, characterized in that said control means (360) comprise means (365, 368) for comparing the predicted voltage with a predetermined value Vmin (Vmin Vmax) and for triggering a fast control procedure if Vpred Vmin. Adapter assembly according to claim 7, characterized in that said control means (360) comprise means (367) for calculating the variation of the output voltage AV over a number n of measurement periods, and means (367). ) to compare, if Vpred> Vmin, said calculated voltage variation with a predetermined value of voltage variation and to trigger a control procedure in "fast" mode if AV> Vv and to trigger regulation procedure in "slow" mode 9. The adapter assembly according to claim 7, characterized in that said control means (360) further comprises means (361) for comparing said measured output voltage <B> VS </ B> with a predetermined voltage Vinf <Vmin and means (368) for triggering, if said measured voltage is lower than Vinf, said fast control procedure 10. Adapter assembly according to any one of the claims ns 1 to 9, characterized in that it further comprises, in the case of a three-phase network, a plurality of means for summing voltages on each of the phases, whereby said means for summing voltages are physically independent on each of the phases.