Background of the invention
The invention relates to an uninterruptible power supply, and more particularly to a control circuit of the DC component of the voltage of an uninterruptible power supply.
An uninterruptible power supply (UPS) or static uninterruptible power supply (ASSC), also known in English under the name "Uninterruptible Power System" or UPS, is a power electronic device that allows to provide a stable AC voltage and without failure or micro-cut to a load, whatever occurs in the electrical network.

The UPS are typically used to provide electrical energy for buildings such as data centers or "data center" in English, such as hosting data centers or industrial sites.

The term inverter, or "inverter" in English, is frequently used by abuse of language to describe the entire device. This is the case, for example, for the "inverters" which is inserted between the distribution network and the servers in a data center.

A UPS consists of an alternating voltage converter DC voltage called rectifier, an energy storage device such as a storage battery or supercapacitor, and a converter generating an AC voltage from a DC voltage is also called inverter and operating at a fixed frequency. In some cases, the energy storage device may be replaced by a device for producing and storing energy such as photovoltaic generation system or an inertial storage type "flywheel".

In some cases, the AC voltage UPS output must be adapted to obtain a higher voltage, and in some of these cases it is necessary to use galvanic isolation. To achieve electrical isolation and / or increasing the AC voltage, a transformer or autotransformer is electrically coupled between

the UPS and the load powered by the UPS. Depending on the configuration, processors may be part of the UPS, the fed-batch, or the feed network supplied by the UPS.

In the case where a DC component is present in the AC voltage output from the inverter of the UPS, the DC voltage component generates a DC component of current in the primary winding of the transformer associated with the UPS which does saturate the transformer core.

The saturation of the transformer core causes a malfunction of the transformer and / or the UPS.

The reasonable quality standard isolation transformers could support a DC component of a few tens of millivolts before the core saturates. However, such DC component generates overheating and acoustic noise not negligible compared to nominal operation and induces deformation of the output voltages of the transformer to saturation.

Such a DC voltage component of some tens of millivolts, for example of the order of 40 mV, can generate a DC component of high current on the primary winding of transformer, since it can reach a value of about ten amperes.

This saturation is shown in the equivalent electrical circuit of the transformer shown in Figure 1 by the magnetizing inductance Lm, also called magnetizing inductance. Lcc the reference represents the leakage inductance, or "leakage inductance" in English, which is not saturable, RI, the winding resistance, R f, the equivalent resistance of the iron loss of the transformer core, and the m transformation ratio of the ideal transformer.

The situation is worse for autotransformers zigzag having a very low current magnetization which can not withstand a DC voltage component of about ten millivolts or less, if no over-sizing is done.

The document drafted by Merlin Gerin entitled "Effect of Direct current DC transformers are," says a DC high current 5 A on a distribution transformer requires the use of special oversized transformer to carry the current. And over 30 A, the kernel must be changed very significantly by integrating including gaps, or "airgaps" in English. In the previous example, a DC component of 240 mV at the output of the UPS, or one thousandth of the AC component of the output voltage of the UPS, generate a continuous current of 30 A.

To overcome this problem, it is known to oversize the transformer. However, oversizing the transformer causes an increase in the financial cost of producing the transformer and therefore the UPS so that increasing the size of the UPS when the UPS includes the transformer. If the transformer is outside, it is the electrical system that will be more expensive.

Another known solution for overcoming this problem is to control the UPS output current by means of a feedback in the control loop that would cancel the DC component of the current.

However, this solution can not be applied as for supplying loads consuming a current with a DC component such as half-wave rectifiers.

Another solution compatible with the loads consuming the current with a DC component is by using the voltage measuring circuit in the UPS to control once the AC component and the DC component of the output AC voltage.

But the precision and dynamics of the voltage measurement circuit is not sufficient to control fairly precisely the DC component. The problem arising from the fact that we must measure a DC ten thousand times smaller than the fundamental component.

It is known from JP 2006/136107 an output voltage control circuit of a power supply unit continuously connected at the output to a transformer. The control circuit comprises a transmission of a voltage setting module, a first current sensor coupled to the output of the UPS and configured to measure the output current of the inverter of the UPS, and a module regulating the UPS output voltage configured to determine switches driving instructions controlled inverter of the UPS

from measurements of the measuring module. The control circuit also includes a second current sensor and a measuring transformer measuring the secondary voltage of the transformer, the second current sensor and the transformer being connected in output of the transformer to the output of the inverter. The control circuit further comprises a unit configured to determine the DC component of the voltage output of the inverter of the UPS from the measurement current, said block comprising a low-pass filter and an amplifying unit configured for amplifying the filtered signal from the filter before measuring the DC component.

However, a transformer transmits only the AC components and not the DC components of the signal.

It is also known from document JP H07 231676 a voltage control circuit of an inverter, the control circuit comprising a measuring module of the output current of the inverter, and a control module of the output voltage the inverter configured to determine control set points of the controlled switches of the inverter.

Purpose and Summary of the Invention

The invention aims to provide an uninterruptible power supply voltage controlled to generate an output AC voltage with no DC component or with negligible DC component, and more particularly to provide a specific circuit to accurately measure the DC component and the AC component of the output voltage of an uninterruptible power supply unit and for controlling power including power transformers or autotransformers coupled out of a power supply unit without interruption.

In an object of the invention, there is provided an output voltage control circuit of a power supply unit without interruption comprising a DC voltage source such as a battery coupled between a power rectifier and an electrical inverter , said circuit being intended to be coupled between the output terminals of a power supply unit without interruption, and a transformer or an autotransformer, the control circuit comprising:

- a transmission module of a voltage setpoint,

- a measurement module of the output characteristics of said power unit, and

- an output voltage regulator module, said unit configured to determine the switches of the driving instructions of said controlled unit from measurements of the measuring module,

said measurement module comprising:

- a first measurement unit configured to measure the output current of said unit,

- a second measurement unit configured to measure the AC component of the output voltage of said unit, and

- a third measuring unit configured to measure the DC component of the output voltage of said unit.

According to a general characteristic of the invention, said third measuring unit includes a low pass filter configured to attenuate the alternating voltage component measured without changing the DC component of the measured voltage, and means for measuring the dc component the output voltage of the power supply unit without interruption, the measuring means comprising an amplifying unit configured to amplify the filtered signal from the filter before measuring the DC component.

The control circuit according to the invention allows to control a power supply unit without interruption so that it outputs an alternating current voltage free of any DC component or with negligible DC component, which also enables power supply a transformer or an autotransformer with a suitable signal.

In addition, a power supply unit without interruption, the output voltage is controlled by the control circuit according to the invention does not include a transformer or autotransformer. Such uninterrupted power supply is called "turn-less" in English. The supply unit continuously being free transformer or autotransformer, it can feed

simultaneously motors, transformers or autotransformers, and more conventional fillers.

Sometimes these loads naturally absorb a direct current to operate. This has the consequence that it is not possible to rely on information current to prevent transformer saturation "remote" in which the unit is connected. The control circuit according to the invention allows to precisely control the DC voltage output of the power supply unit without interruption, in addition to the alternating voltage, with an extremely accurate measurement of the DC component of the voltage which is the only relevant information available, the accuracy of this measurement, in particular from the fact that the measurement is made at the output of the power supply unit without interruption and upstream of the transformer or autotransformer.

Electronic circuits typically known to regulate the tensions can not directly manage the regulation of high voltages. The signal should be attenuated to be compatible with integrated circuits conventionally known regulation. For high voltage means higher voltages manageable tensions directly by electronic circuits lows.

Attenuating signals conventionally, the continuous AC voltage component of output of the power supply device is also, so that the imperfection (offset, input currents, noise) generates electronic circuits of significant errors in the measurements.

The third measuring unit of the measuring module of the control circuit of the invention uses a low-pass filter for attenuating the AC component of the voltage measured on the first connection terminals, that is to say the output of the 'feed unit. The low pass filter attenuates the AC component while keeping the same DC. The attenuation performed by the filter and allows the amplification performed by the means for measuring the amplification block amplifies only the signal related to the DC component. The gain applied to the DC component is calibrated so that the signal on the DC component is as large as possible while remaining consistent with the electronic circuits. This gain makes it easier to measure the DC component and to improve the accuracy of its measurement.

As a result of the attenuation performed by the low-pass filter, the peak to peak amplitude of the voltage complies with the characteristics of standard amplifier circuits.

The third measuring unit and the second measuring unit and allows the control module to generate the power supply unit driving instructions for controlling the output voltage of the power supply device and thus to minimize or even eliminate, the DC component of the output voltage and controlling the AC component.

The control circuit according to the invention allows for example to reduce the DC component of the output voltage signal of an uninterruptible power supply unit to less than 20 mV for an effective voltage of 231 Vrms and a frequency identical to that of electrical distribution network, and more particularly from 50 to 60 Hz. such a reduction of the DC component is more than sufficient to avoid saturation of the core of a transformer or autotransformer standard coupled out of such a feed unit.

The control circuit can be adapted to both a power supply device that multiphase phase.

The control circuit according to the invention allows to extract a DC component from a +/- 100 mV signal, which provides greater accuracy of this measurement approximately 500pV quantization.

According to a first aspect of the control circuit, the control module may comprise:

- a first comparator configured to determine a first signal from the difference between the desired voltage and the AC component measured by said second measuring unit,

- a second comparator configured to determine a second signal from the difference between said first signal and a signal relating to the DC component determined from the measurement made by said third measuring unit, said second signal corresponding to the error made the voltage between the voltage reference and the AC and DC components measured at the output of the power supply unit, and

- correction means configured to determine said driving instructions from the second signal.

The first comparator for determining the error between the voltage reference and the voltage output of the supply unit. The second comparator is then used to process the first signal for the driving instructions then determined make it possible to remove the DC component of the unit of output voltage signal.

According to a second aspect of the control circuit, the correction means may comprise:

- a first correction block configured for determining a current setpoint for canceling the error in the voltage from said second signal,

- a third comparator configured to determine a third signal from the difference between the reference current supplied by the first correction block and the current measured by the first measuring unit, said third signal corresponding to the error made on the current between the current setpoint and the measured current, and

- a second correction block configured to determine said driving instructions from the third signal.

The determination of driving instructions is performed in three steps, with first determining a current set from the error voltage and a determination of the error on the stream, and determination instructions. The markers used can be of different types depending on the needs and constraints of the expected dynamics of the output voltage when the load current disturbances.

The markers may, for example, be conventionally proportional-integral-derivative type or corrective-feedback condition, markers based on sliding mode or predictive markers.

According to a third aspect of the control circuit, the control module further comprises a correction block configured to apply a correction integral proportional to the DC component measured by said third measuring unit before said DC component measured is taken into account by the second comparator.

Correction proportional integral type allows to eliminate the static error signal and so enable the generation of steering instructions to perfectly remove the DC component of the voltage signal at the output of the supply unit.

In another object of the invention, there is provided an interruption without power supply device comprising at least a first connection terminal for coupling to a supply network, at least a second connection terminal intended to be coupled to a load via a transformer or an autotransformer, and at least a supply unit without interruption comprising a rectifier coupled to said at least one first connection terminal, an inverter coupled to said at least one second connection terminal, and voltage source, such as a storage battery coupled between the rectifier and the inverter.

According to a general characteristic of this object, the device further comprises, for each power unit without interruption, a control circuit of the output voltage of a power supply unit without interruption as defined above, each circuit control being coupled between a power supply unit without interruption, and said at least one first connection terminal.

According to one aspect of the power supply device, the device may further comprise, for each power unit without interruption, a transformer or an autotransformer coupled to the output of the power supply unit to which it is associated between the module and measuring said at least one first connection terminal

In another object of the invention, there is provided a method of controlling the output voltage of a power supply unit without interruption comprising a DC voltage source such as a battery, coupled between an electrical rectifier and power inverter, the method being implemented by a control circuit to be coupled between the power unit output terminals without interruption and a transformer or an autotransformer, the method comprising:

- emission of a voltage setpoint,

- a measurement of the output characteristics of said power unit, and

- regulating the output voltage of said power supply unit configured to determine control set points of the controlled switches of said power supply unit from the measurements carried out,

measuring the output characteristics comprising a current measurement output of said power unit, a measure of the alternating component of the output voltage of said power unit, and a measurement of the DC component of the output voltage said supply unit.

According to a general feature of this object, the measurement of the DC component comprises a low-pass filtering of the output voltage signal of said power supply and an amplification of the filtered power signal before measuring said DC component of the output voltage.

According to a first aspect of the control method, the control may comprise:

- a first comparison delivering a first signal from the voltage difference between the setpoint and the measured AC component,

- a second comparison outputting a second signal from the difference between said first signal and a signal relating to the measured dc component, said second signal corresponding to the error made on the voltage between the voltage reference and the AC and DC components measured at the outlet of the supply unit, and

- a correction step wherein said control set points are determined from the second signal.

According to a second aspect of the control method, the correcting step may comprise:

- determining a current setpoint for canceling the error on the output voltage from said second signal,

- determining a third signal from the difference between said reference current and the measured current, said third signal corresponding to the error made on the current between the reference current and the measured current, and

- a determination of said control instructions from the third signal.

According to a third aspect of the control method, the control may include applying a correction integral proportional to said DC component measured before the second comparison is performed.

Brief description of the drawings.

The invention will be better understood by reading given below, for information purposes but not limited to, reference to the accompanying drawings, wherein:

- Figure 1, already described, shows an equivalent circuit diagram of a transformer coupled as input to a power supply device without interruption according to the prior art;

- Figure 2 schematically shows power supply device continuously according to an embodiment of the invention;

- Figure 3 shows a flowchart of a method of controlling the output voltage of an uninterrupted power supply device according to an implementation mode of the invention.

Detailed description of embodiments

In Figure 2 is schematically shown a device 100 for uninterrupted power supply according to an embodiment of the invention.

100 power supply device comprises three first terminals 2 for connection to be coupled to a three-phase supply network, and three second terminals 3 for connection to be coupled to a load. The three terminals here represent the three phases of a three-phase circuit, the neutral has not been shown for reasons of clarity of the figure.

100 power supply device further comprises a plurality of units 1 each uninterruptible power supply comprising a rectifier coupled to the first connection terminal 2, an inverter coupled to the second connecting terminals 3, and a DC voltage source , such as a storage battery coupled between the rectifier and the inverter. For the sake of clarity in Figure 2, a single unit 1 uninterruptible power supply has been shown in FIG.

Each unit 1 power supply, 100 power supply device comprises a filter 4, a transformer or an autotransformer 5, and a circuit 6 for controlling the output voltage of the unit 1 power.

The filter 4 is an LC type of passive filter comprising an inductance L and a capacitance C for each phase at the output of unit 1 power supply and more particularly the output of the inverter unit 1. The filter 4 enables filtering the output signal to have a harmonic-free voltage cutting.

In the embodiment illustrated in Figure 2, the transformer 5 is part of the 100 power supply device. Alternatively, there may be, for each line of the device 100 having a supply unit 1, a transformer coupled between the device 100 and the load.

The filter 4 is electrically coupled to three output terminals 20 of the unit 1 and the power transformer 5, and the circuit controller 6 is also electrically coupled between the three output terminals 20 of the unit 1 Power and the transformer 5.

The circuit controller 6 comprises a transmission module 7 of a reference voltage V ref , a measurement unit 8 of the output characteristics of the unit 1 power supply, and a module 9 for regulating the output voltage Single 1 power Co configured to determine control set points of the controlled switches of the inverter unit 1 power from measurements performed by the 8 measurement module.

8 measurement module includes a first measuring unit 81 configured to measure the current I to the output terminals 20 of the unit 1 feeding a second measuring block 82 configured to measure the AC component V A c of the voltage output of the unit 1 power supply, and a third measuring unit 83 configured to measure the DC component V D c of the output voltage of the unit 1 power.

In the embodiment illustrated in Figure 2, the first measurement block 81 is coupled between the three output terminals 20 of the unit 1 and feeding the inductance L of the filter 4. Alternatively, the first block 81 of measurement may be coupled downstream, relative to direction of the current, inductances L of the filter 4, that is to say between the inductors L and the connection node of the capacitors C of the filter 4. this latter configuration with the first measurement block 81 between the inductors L and the node of connection of the filter capacity C has an increased robustness vis-à-vis the electromagnetic compatibility.

The third measuring unit 83 further comprises a low-pass filter 84 and a measurement means 85 of the DC component V DC of the output voltage of the unit 1 power. The low pass filter 84 is configured to attenuate the AC component V A c of the measured voltage V without changing the DC component V D c of the measured voltage V.

The measuring means 85 includes an amplifying unit for amplifying the filtered signal from the low pass filter 84 of the third measuring unit 83 before measuring the DC component VDC- the low-pass filter 84 attenuates the AC component VAC while maintaining the DC component V D c unchanged before amplifying, with the amplification block measuring means 85, the signal output from the low pass filter 84 which mainly comprises that the DC component V DC of the output voltage V of the unit 1 power. The gain applied to the DC component is calibrated so that the signal on the DC component V D c is as large as possible while remaining consistent with the electronic circuits. This gain allows for easy measurement of the DC component V D c and improve the accuracy of its measurement.

The control module 9 includes a first comparator 91 receiving voltage V setpoint input re f issued by the transmitter module 7 and the AC component VAC of the output voltage V of the unit 1 power delivered by the second measuring unit 82. the first comparator 91 is configured for outputting a first signal from the difference between the desired voltage V re f and the AC component V a c measured by said second measuring unit 82.

The control module 9 further includes a second comparator 92 receiving as input the first signal from the first comparator 91 and a corrected signal of the DC component VDC supplied by the third measuring block 83. The corrected signal of the DC component V D c corresponds to the signal delivered by a proportional integral corrector 93 receiving as input the DC content signal V D c delivered by the third measuring unit 83. the second comparator 92 is configured to output a second signal ε ν from the difference between the first signal and the DC component corrected output from the proportional integral corrector 93. the second signal ε ν is the error made on the voltage V between the voltage reference V re f and the AC and DC components V AC VDC and measured output of the unit 1 power.

The control module 9 finally comprises a correction means 94 configured to determine the Co driving instructions from the second signal ε.

The correction means 94 comprises a first correction unit 95 configured to determine a current command value I c for canceling the error voltage ε ν from said second signal ε ν . The first correction block 75 thus makes it possible to oppose the harmonic distortion created by the load current and by imperfections inverter converter (dead time, minimum pulse or draws min). The correction means 94 further comprises a third comparator 96 configured to determine a third ι signal from the difference between the current set point the output from the first correction block 95 and the current signal I delivered by the first block measurement 81 of the measurement module 8, and a second correction unit 97 configured to determine the Co piloting set point of the inverter unit 1 power from the third ει signal output from the third comparator 96. the third ει signal is the error made on the current between the reference current and the measured current I. the second correction block 97 is configured to improve the harmonic content of the voltage.

Co driving instructions are then supplied to the unit 1 uninterruptible power insulated gate for controlling the switches (IGBT) of the inverter unit 1 uninterruptible power supply for supplying a voltage output Single 1 diet free of any DC component V DC , or with negligible DC component, that is to say for supplying a transformer or a conventional autotransformer 5 without the risk of saturation of the transformer core 5.

In Figure 3 is shown a flowchart of a method of controlling the output voltage of a unit 1 of uninterruptible power supply according to an embodiment of the invention.

In a first step 300, the 5 emission module delivers a setpoint V re f of output voltage of the unit 1 power.

In a second step 310, the measurement unit 8 performs measurement of the output characteristics of the unit 1 power. This step 310 of measuring the characteristics comprises a measurement 312 of the current I output by using the first measuring unit 81 which carries out a survey of the shape and amplitude of the signal, a measurement 314 of the signal component alternative V a c of the output voltage V of the power unit 1 using the second measurement block 82, filter 316, voltage signal V using the low-pass filter 84 of the third block measuring 83 prior to performing a measurement of the signal 318 of the DC component V DC of the output voltage V of the unit 1 power using measuring means 85 of the third measuring unit 83.

In a next step 320, the control module 9 determines the Co pilot instructions of the inverter unit 1 power supply for generating an output voltage V of the power unit 1 in which the DC component V D c has been reduced or eliminated. In step 320, the first comparator 91 sends in a step 322 a subtraction between the first voltage command signal V re f and the signal of the AC component V A c of the output voltage of the unit 1 of power, and then, in a next step 324, the second comparator 92 of the control unit 9 performs a second subtraction between the signal delivered by the first comparator 71 and the corrected signal from the VDC DC component outputted from the proportional integral corrector 93 having received as input the DC content signal V D c delivered by the third measurement block 83.

In a next step 330, the correction means 94 of the control unit 9 carries out, in a first step 332, a determination of the current instruction from the voltage error ε on, then in a second step 334, a determination of ει error on the current from the subtraction between the current setpoint and the current I measured by the first measuring unit 81, then, in a final step 140, a determination of Co driving instructions for controlling the controlled switches of the inverters of the uninterruptible power supply units of the device 1 from the error on the ει current steering Co instructions being sent by the control unit 9 of the control circuit 6 to the unit 1 Uninterruptible power.

The control circuit and the implementation process of the control circuit used to perform an uninterruptible power supply voltage controlled to generate an output AC voltage with no DC component or with negligible DC component. More particularly, the control circuit of the invention enables to accurately measure the DC component and the AC component of the output voltage of an uninterruptible power supply and control power for the particular power transformers or autotransformers in Release uninterrupted power supply.

CLAIMS
1. A control circuit (6) of the output voltage of a power supply unit without interruption (1) having a DC voltage source coupled between a power rectifier and an electric inverter, said control circuit (6) being designed to be coupled between the output terminals (20) of the unit (1) uninterruptible power supply and a transformer or an autotransformer (5), the control circuit (6) comprising:

- a module (7) for emitting a reference voltage (V ref ),

- a module (8) for measuring the output characteristic of said feed unit (1), and

- a module (9) for regulating the output voltage of said unit (1) configured to supply to determine control set (Co) of the controlled switches of the inverter of said unit (1) Power from measurements of the measuring module (8),

said measurement module (8) comprising:

- a first measuring unit (81) configured to measure the current output of said unit (1) feed,

- a second measuring unit (82) configured to measure the AC component (V A c) of the output voltage of said unit (1) power, and

- a third measuring unit (83) configured to measure the DC component of the output voltage (V) of said unit

(1) Power,

characterized in that said third measuring unit (83) comprises a low pass filter (84) configured to attenuate the AC component (V A c) of the voltage measured without changing the DC component (V D c) of the measured voltage (V), and a measuring means (85) of the continuous component (V D c) of the output voltage of the unit (1) uninterruptible power supply, the measuring means (85) comprising a block of amplification configured to amplify the filtered signal output from said filter (84) before measuring the DC component (V D c).

2. A control circuit (6) according to claim 1, wherein said control module (9) comprises:

- a first comparator (91) configured to determine a first signal from the difference between the desired voltage (V re f) and the AC component (V A c) measured by said second measuring unit (82),

- a second comparator (92) configured to determine a second signal (ε v ) from the difference between said first signal and a signal relating to the DC component (V D c) determined from the measurement made by said third block measuring (83), said second signal corresponding to the error (ε v ) performed on the voltage between the voltage reference (V ref ) and the AC and DC components measured at the output of the unit (1) power and

- correcting means (94) configured to determine said control set (Co) from the second signal (εν).

3. A control circuit (6) according to claim 2, wherein the correction means (94) comprises:

- a first correction unit (95) configured to determine a current set point (I c ) for canceling the error in the voltage (ε v ) from said second signal (ε v ),

- a third comparator (96) configured to determine a third signal (ει) from the difference between the reference current (I c ) supplied by the first equalizer block (95) and the measured current (I) by the first measuring block (91), said third signal (ει) corresponding to the error made on the current between the reference current (I c ) and the measured current (I), and

- a second correction unit (97) configured to determine said control set (Co) from the third signal (¾).

4. A control circuit (6) according to one of claims 1 to 3, wherein said control module (9) further comprises a correction block (93) configured to apply a correction type

proportional integral to the DC component (V D c) detected by said third measuring unit (83) of the measuring module (8) before said DC component measured (V D c) is taken into account by the second comparator (92 ) of the control module (9).

5. The device (100) without interrupting the power supply comprising at least a first connecting terminal (2) intended to be coupled to a supply network, at least a second connecting terminal (3) to be coupled to a load via a transformer or an autotransformer (5), and at least one unit (1) uninterruptible power supply comprising a rectifier coupled to said at least a first connecting terminal (2), an inverter coupled to said at least one second connection terminal (3), and a storage battery coupled between the rectifier and the inverter,

characterized in that it further comprises, for each unit (1) uninterruptible power supply, a control circuit (6) of the output voltage of an inverter unit (1) the uninterruptible power according to one of claims 1 to 4, each control circuit (6) being coupled between a unit (1) uninterruptible power supply and said at least one second connecting terminal (3).

6. The device (100) power supply without interruption according to claim 5, further comprising, for each unit (1) uninterruptible power supply, a transformer or an autotransformer (5) coupled to the output of the unit ( 1) power to which it is associated between the measuring module (8) and said at least one second connecting terminal (3).

7. A method of voltage control of an output unit (1) uninterruptible power supply comprising a DC voltage source coupled between a power rectifier and a power inverter, the method being implemented by a control circuit ( 6) to be coupled between the output terminals of the power supply unit without interruption (1) and a transformer or an autotransformer (5), the method comprising:

- a transmission (300) of a voltage setpoint (V re f)

- measuring (310) the output characteristics of said unit (1) power, and

- a control (320 and 330) of the output voltage (V) of said unit (1) configured to supply to determine control set (Co) of the controlled switches of the inverter unit (1) of power from the measurements carried out,

measuring (310) the output characteristics comprising a measuring (312) the current (I) at the output of said unit (1) power, a measure (314) of the AC component (V A c) of the voltage output (V) of said unit (1) power, and a measurement of the DC component (V D c) of the output voltage (V) of said unit (1) feed,

characterized in that the measurement of the DC component (V D c) comprises a filter (316) low-pass output voltage signal (V) of said unit (1) and power amplification of the filtered signal before measuring (318) said DC component (V D c) of the output voltage (V).

8. A control method according to claim 7, wherein the control unit (320 and 330) comprises:

- a first comparison (322) delivering a first signal from the difference between the voltage reference (V ref ) and the measured AC component (V A c),

- a second comparison (324) delivering a second signal

(ε v ) from the difference between said first signal and a signal relating to the measured DC component (V D c), said second signal corresponding to the error (εν) performed on the voltage between the voltage reference (V ref ) and the AC and DC components measured at the output of the unit (1) for feeding, and

- a correction step (330) wherein said control set points are determined (Co) from the second signal

(E).

9, The control method according to claim 8, wherein the correction step (330) comprises:

- a determination (332) of a reference current (I c ) for canceling the error in the voltage (ε v ) from said second signal (εν)

- determining a third signal (ει) from the difference between said reference current (I c ) and the measured current (I), said third signal (ει) corresponding to the error made on the current between the current setpoint (Ic) and the measured current (I), and

- a determination of said control set (Co) from the third signal (ει).

10. Control method according to one of claims 7 to 9, wherein the control unit (320 and 330) comprises applying a correction integral proportional to said measured DC component (V D c) before the second comparison (324) is performed.