WO2018069636A1

WO2018069636A1 - Method for controlling an active parallel filter for networks with interference and associated active filter

Info

Publication number: WO2018069636A1
Application number: PCT/FR2017/052783
Authority: WO
Inventors: Maurice Fadel; Antoine HANNA NOHRA; Hadi KANAAN
Original assignee: Institut National Polytechnique De Toulouse; Centre National De La Recherche Scientifique
Priority date: 2016-10-11
Filing date: 2017-10-10
Publication date: 2018-04-19
Also published as: FR3057405B1; FR3057405A1

Abstract

The invention concerns a method for controlling an active parallel filter suitable for filtering an electrical network that is unbalanced and/or with interference, comprising an electrical voltage supply source (1) and a non-linear load (7) connected to the supply source (1) by an assembly of supply wires comprising n supply wires, where n ≥ 1, connected to the load at n common coupling points, and by a neutral wire, comprising a step of injecting current, referred to as the injected current, by the active filter into each wire of the assembly of supply wires in such a way that the non-linear load (7) is supplied by a total current that is the sum of the current delivered by the electrical supply source (1) and the injected current. The control method is characterised in that the injected current i _r <sb /> injected into each supply wire of the assembly of supply wires is equal to (I).

Description

METHOD FOR CONTROLLING PARALLEL ACTIVE FILTER FOR DISTURBED NETWORKS

AND ACTIVE FILTER

1. Technical field of the invention

The invention relates to a method for controlling an active filter. In particular, the invention relates to a method of controlling an active filter for filtering a single-phase or three-phase electrical network comprising a power source and a non-linear load, thereby reducing the flow of harmonic currents and reducing the reactive power. at the level of the supply network. 2. Technological background

The supply of non-linear loads by a power source in an electrical network is frequently subject to disturbances and / or imbalances in the supply network to which the consumer load is connected.

The disturbances of the supply network designate the presence of harmonics on the supply voltage, which is then not sinusoidal, as well as the circulation of a reactive power carried too much. The imbalances of the supply network designate, in a polyphase network (in particular three-phase), a poor distribution of the supply voltages on the different phases.

In addition, in a distribution network type public network, these disturbances or imbalances may be subject to regulation of the energy supplier: the customers of the supplier, having the non-linear load to feed, must set up a device for minimize these disturbances and imbalances under penalty of termination of the contract or financial penalties.

Active filtering is used to inject current into the load to reduce disturbances. However, the active filterings of the prior art do not effectively balance the supply currents, and may even be ineffective to reduce disturbances if the supply voltages are unbalanced and / or disturbed. In addition, the active filterings of the prior art are generally not usable both in single phase or polyphase, nor with a wire of neutral.

The inventors have therefore sought to provide active filtering whose performance is improved compared to the prior art.

3. Objectives of the invention

The invention aims to overcome at least some of the disadvantages of known active filtering.

In particular, the invention aims to provide, in at least one embodiment of the invention, a method for controlling an active filter which makes it possible to reduce the disturbances of the supply current of a non-linear load, by particularly reduce the presence of harmonics and reactive power transport especially when the network is unbalanced and / or disturbed.

The invention also aims to provide, in at least one embodiment, a method for controlling an active filter which makes it possible to reduce imbalances in the supply current of a non-linear load when the network is unbalanced and / or disturbed.

The invention also aims to provide, in at least one embodiment of the invention, a method for controlling an active filtering adapted to single-phase or multiphase supply networks, in particular three-phase.

The invention also aims to provide, in at least one embodiment, a method for controlling an active filter for reducing the neutral current of the supply network.

The invention also aims to provide, in at least one embodiment, a method of controlling an active filter for obtaining a sinusoidal system balanced current when the voltages are disturbed and / or unbalanced.

The invention also aims to provide, in at least one embodiment, a method of controlling an active filter for obtaining the value of the injection stream or currents in a minimum of operations.

4. Presentation of the invention

To do this, the invention relates to a method for controlling a parallel active filter adapted to filter an electrical network comprising a source of electrical voltage supply and a non-linear load connected to the power source by a set of supply wires comprising n supply wires, with n> 1, connected to the load at n common coupling points, and a neutral wire, comprising a current injection step, said injected current , by the active filter in each wire of the set of supply wires, so that the non-linear load is fed by a total current, sum of the current delivered by the power source and the injected current, said current injected being provided by at least one capacitor of the active filter,

and characterized in that the value of the injected current i _r in each supply wire of the set of supply leads is:

with i _L the instantaneous current in the non-linear load, P _s the active power delivered by the source, Vf the fundamental rms value of the voltage at the common coupling point of said supply wire, Σl ^ _n the sum n effective values of the fundamentals of the voltages at the common coupling points of each supply wire of the set of supply wires, and Vf the fundamental value of the voltage at the common coupling point of said supply wire. 'food.

A method of controlling an active filter according to the invention thus makes it possible to reduce the disturbances of the supply current and thus obtain a sinusoidal supply current, in particular by reduction of the harmonics, and to reduce the reactive power transported in the network. , thus allowing an increase in the power factor. In addition, the current flowing in the neutral wire to the power source is zero because the currents flowing in the phases are balanced.

The supply circuit can be either single-phase, in which case it comprises a single power supply wire (and a neutral wire), or polyphase, in particular three-phase, comprising a first supply wire, said first phase (whose associated values are referenced with the suffix a in the equations), a second feed wire, called second phase (whose associated values are referenced with the suffix b in the equations), a third feed wire, called third phase (whose associated values are referenced with the suffix c in the equations) and a neutral thread. When the supply circuit is single-phase, n = 1, Σl ^ _n is equal to Vf and therefore the equation can be written in the form:

Ps

When the supply circuit is three-phase, n = 3, Σ Vf _n is equal to Vf _a + Vf _b + Vf _C and therefore the equation can be written in the form:

for the first phase:

Ps

for the second phase:

Ps

lrb ^{~ l} Lb v _fb ru. V _fc ) ^V f ^b

X (Vf a + Vfb +

for the third phase:

Ps

l ^{rc = lLc ~} v _fc x (v _fa + v _fb + v _fc ) ^Vfc

In the case of a three-phase supply circuit, the injection of the current in each phase thus allows a balancing of the currents in each phase. In particular, even if the power supply is unbalanced and / or disturbed (the filter has no direct control over the balancing of the supply voltages), the fact that the voltages of each phase are taken into account in the fundamental equation to obtain a balancing of the currents at the level of the load.

The values used are either measured directly or calculated using other values easily measurable by those skilled in the art. In particular, for a user of the non-linear load and the active filter, certain values related to the source, in particular the active power delivered by the source, may not be directly measurable and must be calculated according to the values related to the load and to the filter. In all cases, the number of operations required to calculate the injection currents is less than that of the methods p-q and p-q-r of the prior art.

The electrical network may be an onboard low voltage or medium voltage electrical network, for example in a vehicle (aircraft, automobile, railway), a low, medium or high voltage distribution network between an electricity producer and a consumer load, a high electrical transport network voltage, etc.

Advantageously and according to the invention, the value P _s of the active power delivered by the power source is deduced from the measurement of the active power P _C harge active consumed by the power source and the power P utre active consumed by the active filter, according to the equation:

^- charge P filter)

According to this aspect of the invention, this power can be deduced from measurements accessible to the user, related to the load and the active filter. Advantageously and according to the invention, the electrical network is a three-phase network, the power source and the load being connected by three supply wires, constituting three phases, and the current injection step allowing the injection of current in the three phases of the power grid. According to a variant of the invention, the network comprises a neutral wire.

According to this aspect of the invention, the introduction of this active filter control method in a three-phase electrical network allows, as previously described, both the reduction of disturbances and the balancing of currents on the phases.

The invention also relates to a parallel active filter adapted to filter an electrical network comprising a source of electrical voltage supply and a non-linear load connected to the power source by a set of supply son comprising n supply son , with n> 1, connected to the load at n common coupling points, and by a neutral wire, configured to allow injection of current, called injected current, into each wire of the set of power leads so that the non-linear load is fed by a total current sum of the current delivered by the power source and the injected current, said injected current being supplied by at least one capacitor of the active filter, and characterized in that it comprises a module for calculating the current injected \ _m in each supply of all power wire son, the injected current being equal to:

with i _L the instantaneous current in the nonlinear load, P _s the active power delivered by the source, Vf the fundamental rms value of the voltage at the common coupling point of said supply wire, ΣV n the sum of the n effective values of the fundamental of the voltages at the common coupling points of each supply wire of the set of supply wires, and Vf the fundamental value of the voltage at the common coupling point of said wire of food.

The term module refers to a software element, a subset of a software program, that can be compiled separately, either for independent use, or to be assembled with other modules of a program, or a hardware element, or a combination of a hardware element and a software subprogram. Such a hardware element may comprise an application-specific integrated circuit (better known by the acronym ASIC for Application-Specific Integrated Circuit in English) or a programmable logic circuit (better known by the acronym FPGA for Field-Programmable Gate Array in English), or a dedicated microprocessor circuit (better known by the acronym DSP for Digital Signal Processor in English) or any equivalent hardware. In general, a module is an element (software and / or hardware) that ensures a function.

Advantageously, an active filter according to the invention comprises an inverter comprising a set of power switches arranged in parallel with one or more capacitors, said power switches being controlled between a conducting state and blocked according to a cyclic ratio calculated as a function of the current to be injected.

The active filter according to the invention is adapted to be controlled by the control method according to the invention.

The control method according to the invention is adapted to control the active filter according to the invention.

The invention also relates to an electrical distribution network, comprising a power source and a power consumption load connected to the power source by a set of power leads comprising n supply wires, with n> 1, connected to the load at n points of common couplings, and by a neutral wire, characterized in that it comprises an active filter according to the invention configured to inject current into each supply wire of the set of supply son.

Used in an electrical distribution network, the active filter reduces load disturbances from the point of view of the power source, thus enabling a better quality of electrical distribution and reducing the risk of fines or penalties due to a load disturbing the network.

The invention also relates to a control method, an active filter and an electrical distribution network characterized in combination by all or some of the characteristics mentioned above or below. 5. List of figures

Other objects, features and advantages of the invention will become apparent on reading the following description given solely by way of non-limiting example and which refers to the appended figures in which:

FIG. 1 is a schematic view of a single-phase electrical network comprising an active filter controlled by a control method according to a first embodiment of the invention,

FIG. 2 is a schematic view of a three-phase electrical network comprising an active filter controlled by a control method according to a second embodiment of the invention. 6. Detailed description of an embodiment of the invention

The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments may also be combined to provide other embodiments. In figures, scales and proportions are not strictly respected, for purposes of illustration and clarity.

Figures 1 and 2 schematically show electrical networks comprising an active filter controlled by a control method according to a first and a second embodiment of the invention. Figure 1 shows a single-phase electrical network and Figure 2 shows a three-phase electrical network. The operation of the active filter being similar in the two networks, the two figures are described together and their differences specified.

The electrical networks comprise a power supply source 1 for supplying a non-linear load 7. The power source 1 is connected to the load 7 by at least one power supply wire:

a feed wire in the embodiment of FIG.

three supply wires, a first supply wire said first phase Ph _a , a second supply wire said second phase Ph _b , a third supply wire said third phase Ph _c , in the embodiment of the figure 2.

For the sake of clarity, the three phases Ph _abc are represented by the same line.

In addition, the power source and the load 7 are connected by a neutral wire. The voltage supply source represents a power distribution network, for example a public network.

At the power source, each power line has a line inductance, represented by a coil 2.

The power source delivers a voltage supply v _a between the phase and the neutral (for the single-phase network figure 1) or v _abc between each phase and the neutral (for the three-phase network figure 2). The supply current (i _sa for the phase of the single-phase network FIG. 1, i _{its bc} for each phase of the three-phase network FIG. 2) flows on the supply line to supply the load 7.

The power source is connected to the load 7 at a common coupling point (PCC). The common coupling point (point of common coupling) is defined by the International Electrotechnical Commission as the point of a power supply network, the closest electrically to a load particular, to which other charges are or can be connected.

The active filter consists of a voltage inverter 11 and an inductor 8, and a module for calculating the current to be injected into the phase or phases.

The voltage inverter 11, of conventional operation, comprises several power switches 12 (for example IGBT type), four in number for the single-phase network Figure 1 and six for the three-phase network.

The power switches 12 are connected to one or more capacitors 13. The inverter 11 is further connected to the neutral wire at a PCC of the neutral wire.

The control of the power switches 12 allows the injection of current in the phase or phases of the network, as well as in the neutral wire. The power switches 12 are thus controlled according to a control method according to one embodiment of the invention, and in particular this method comprises a current injection step in each phase whose value is calculated here by the calculation module. of the injected current.

The calculation module makes it possible to calculate the injected current by measuring different values at the level of the load 7 and the filter, in particular:

measurement of i _{> bc} (reference 6): the current or currents flowing in each phase of the load 7 by one or more current sensors,

if _abc measurement (reference 10): the current (s) flowing in the active filter by one or more current sensors 9,

measurement of v _abc (reference 4): the voltage or voltages between each phase and the neutral wire by one or more voltage sensors 3,

measuring V _c , the voltage of the capacitor of the active filter of the single-phase network (reference 15, FIG. 1) measured by a voltage sensor 14, or V _ch and V _cb , the voltages respectively of the capacitor C _h up and capacitor C _b bottom of the active filter of the three-phase network (reference 15 and 15 ', Figure 2) respectively measured by the sensors 14 and 14' of tension.

The current i _r injected in each phase is equal to:

i _r corresponds to i _ra for the single phase of the single-phase network or for the first phase of the three-phase network, i _rb for the second phase of the three-phase network and i _rc for the third phase of the three-phase network.

The term i _L of the equation, the instantaneous current in the nonlinear load 7, corresponds to i _La for the single phase of the single-phase network or for the first phase of the three-phase network, to i _Lb for the second phase of the three-phase network and i _Lc for the third phase of the three-phase network. It is measured by the current sensor.

The term Vf corresponds to the fundamental value of the voltage at the common coupling point of a phase, referenced Vf _a for the single phase of the single-phase network (FIG. 1) or Vf _abc for the three phases of the three-phase network (FIG. 2). This value is obtained by processing the values v _abc by a band pass filter 31 (BPF noted for Band-Pass Filter in English). The band pass filter 31 has the function of transfer:

B. p

p ² + B. p + O) Q

with ω ₀ = 2.π.ί ₀ the network pulse, f ₀ being the frequency of the center of the band and B = 2.ji.f _b ; f _b being the bandwidth in Hz. For example, for a 50 Hz network, and a bandwidth of 5 Hz, ω ₀ = 314 rd / s and B = 31.4 rd / s.

The term Vf corresponds to the fundamental rms value of the voltage at the common coupling point of a phase, and is deduced from Vf. In particular Vf is calculated in the block referenced 35, comprising a multiplier 32, a low-pass filter 33 (denoted LPF for Low-Pass Filter in English) and a mathematical function

34 square root, so to calculate V for each phase according to the equation:

The calculation of V for each phase also makes it possible to obtain the value Vf:

in the three-phase network, Σ Vf = Vf _a + Vf _b + Vf _C , obtained by means of an adder 36, with Vf _at the fundamental value of the voltage at the coupling point and in the first phase, Vf _b la effective value of the fundamental of the voltage at the coupling point as in the second phase and Vf _C the fundamental rms value of the voltage at the coupling point as in the third phase, ie Vf xΣVf = Vf _a x (Vf _a + Vf _b + Vf _C ) in the calculation of the current injected into the first phase, Vf xΣ Vf = Vf _b x (Vf _a + Vf _b + Vf _C ) in the calculation of the current injected into the second phase, and Vf xΣVf =

Vfc ^x (Vfa + Vfb + Vfc in the calculation of the current injected in the third phase.

When the power grid is an on-board network on which a user can obtain all the data and measurements, the measurement of the power P _s active delivered by the source can be obtained by direct measurement on the source (measurement of voltage across source and output current for example). However, the direct measurement of the active power P _s delivered by the source is generally not possible for a user holding only the load 7 and the active filter. This value is, however, deductible from the powers consumed by the load 7 and the active filter.

In particular, the Boucherot theorem makes it possible to write that:

Ps ^~ charge P filter)

With charge, the active power absorbed by the load 7 and P _rer the active power absorbed by the active filter. This operation is carried out by an adder 23.

Pcharge is equal to the average value of the instantaneous power p _{c /} , _arge (t) which is measured by the measurement of the instantaneous voltage or voltage _abc by the voltage sensor (s) 3 and the current (s) i _{La> bc} instantaneous by the current sensor (s) 5: in the single-phase network: v _load (t) = v _a (t). i _The (t)

in the three-phase network: p _cha rge (t) = v _a t). i _The t) + v _b t). i _Lb t) + v _c t). i _Lc t) The value _C harge (t) is then passed to a low-pass filter 24 to obtain P charge _'

The active filter must not carry active power except the active power necessary to compensate for the losses in it. The losses of the active filter only result in a discharge of the capacitor or capacitors of the inverter 11 which must be compensated by a sampling of equivalent equal currents on each phase of the network. The capacitor or capacitors constitute the energy storage means for supplying the injected current. The active filter is thus a capacitive active filter.

Starting from the instantaneous active power P / v _be (t) consumed by the filter, it can be deduced that:

Pfiltre ⁼ lpertes ^x (Vf a + Vfb + Vfc)

With p _e nes the rms value of the instantaneous loss current in the active filter.

The value l _losses can be deduced from the voltage difference across the capacitor or capacitors of the inverter 11 with the value of the reference voltage across the capacitor or capacitors, that is to say the value of the voltage which should be measured across the capacitor (s) in the absence of losses.

In the single-phase network, the error ε _ν is calculated between the value V _c of the voltage at the terminals of the capacitor and the value V _Cre f of the reference voltage across the capacitor (reference 29, FIG. 1) via an adder. and multipliers 28 and 30:

εν ⁼ Vcref ^~ Vc

The error ε _ν is then successively processed in a regulator 26 PI and then in a low-pass filter 25 to give / _losses .

The value l _losses is then multiplied by V _fa previously calculated to give

Pfiltre-

In the three-phase network, the error s _vh is calculated from the value V _ch of the voltage at the terminals of the high capacitor and the value of the reference voltage at the terminals of the high capacitor (reference 29 FIG. 2) via an adder 27 and multipliers 28 and 30:

^£ vh ⁼ Vctiref ^~ ^ Ch

and calculating the error e _vb from the value V _cb of the voltage at the terminals of the low capacitor and the value V _cbref of the reference voltage across the terminals of the low capacitor (reference 29 'figure 2) via an adder 27' and multipliers 28 'and 30':

^£ vb ⁼ Vcbref ^~ ^ Cb

The errors s _vh and s _vb are then each treated successively in a PI regulator (referenced 26 and 26 ') then added and passed into a low-pass filter to give / _losses .

The value of the _loss is then multiplied by Vf _a + _b + ^ Vf calculated above to give P /, _{/ be.}

Once all the parameters of the equation giving the value of the injected current i _{r have been} calculated, the value of i _r is compared for each phase with the value /) of the intensity flowing in the active filter. In particular, the mistake

is calculated in an adder 22 for each phase, injected into a regulator 21 PI, giving the values of the reference voltages V _Lref across the inductance 8 of the filter. With these values V _Lref , at or the voltages at the terminals of the capacitor or capacitors of the filter and at the voltage i / _{o fc c} of each phase, a duty cycle a is calculated in a block 20 of calculation of duty cycle. This duty cycle has passed into a limitation block 18 and a comparison block 16 to a carrier 19 to derive a control logic Q and a complementary control logic Q (obtained via an inverter 17) for controlling the power switches 12 of the inverter 11 of the active filter between an on state and a off state.

The set of operations described constitutes a number of operations less than the number of operations generally performed in the active filters of the prior art (about -20% compared to the methods pq and about -40% compared to the method pqr ), for a better result.

The invention is not limited to the embodiments described. In particular, measurements and / or calculations of the values required for the determination of the injected current can be made by different methods, and the injected current can be injected by an active filter having different components and / or a different configuration.

Claims

1. A method for controlling a parallel active filter adapted to filter an unbalanced and / or disturbed electrical network comprising a source (1) of supply voltage and a load (7) non-linear connected to the source (1) d supplying by a set of supply wires comprising n supply wires, with n> 1, connected to the load at n common coupling points, and a neutral wire, comprising a current injection step , said injected current, by the active filter in each wire of the set of supply wires so that the load (7) is linear powered by a total current sum of the current delivered by the source (1) d power supply and the injected current, said injected current being supplied by at least one capacitor of the active filter,

with i _L the instantaneous current in the nonlinear load, P _s the active power delivered by the source, Vf the fundamental rms value of the voltage at the common coupling point of said supply wire, ΣV n the sum of the n effective values of the fundamental of the voltages at the common coupling points of each supply wire of all the supply wires, and Vf the fundamental value of the voltage at the common coupling point of said wire of food

2. Control method according to claim 1, characterized in that the value P _s of the active power delivered by the supply source (1) is deduced from the measurement of the power P _C active harge consumed by the source (1 ) and the power P /, _/ active being consumed by the active filter, according to the equation:

Ps ^~ charge P filter)

3. Control method according to one of claims 1 or 2, characterized in that the electrical network is a three-phase network, the source (1) of power and the load (7) being connected by three power supply son, constituting three phases, and the current injection step for the injection of current in the three phases of the electrical network.

4. Parallel active filter adapted to filter an electrical network comprising a source (1) for supplying electrical voltage and a load (7) non-linear connected to the source (1) of supply by a set of supply son comprising n supply wire, with n> 1, connected to the load at n common coupling points, and by a neutral wire, configured to allow a current injection, called injected current, in each wire of the set supplying wires so that the non-linear load is fed by a total current sum of the current delivered by the power source and the injected current, said injected current being supplied by at least one capacitor of the active filter,

and characterized in that it comprises a module for calculating the injected current i _ra in each supply wire of the set of supply wires, the injected current being equal to:

with i _L the instantaneous current in the non-linear load, P _s the active power delivered by the source, Vf the fundamental rms value of the voltage at the common coupling point of said supply wire, Σl ^ _n the sum n effective values of the fundamentals of the voltages at the common coupling points of each supply wire of the set of supply wires, and Vf the fundamental value of the voltage at the common coupling point of said feed wire. 'food.

Active filter according to claim 4, characterized in that it comprises an inverter (11) comprising a set of power switches (12) arranged in parallel with one or more capacitors (13), said power switches ( 12) being controlled between an on state and blocked according to a duty cycle (a) calculated according to the current to be injected.

6. Power distribution network, including a source (1) of power a power supply (7) connected to the electrical power source (1) by a set of power supply wires comprising n feed wire, with n> 1, connected to the load at n common coupling, and by a neutral wire, characterized in that it comprises an active filter according to one of claims 4 or 5 configured to inject current into each supply wire of the set of supply son.