DE102011108255A1 - Method for adaptive control of the supply voltage in local networks - Google Patents

Abstract

Method for the adaptive control of the supply voltage in local networks, in which electrical energy, in particular in the form of solar and / or photovoltaic energy can be fed and removed by consumers, using at least one transformer, which is provided between a medium voltage and a low voltage network by different State variables of at least one of the feeders / consumers, in particular current, voltage, consumption, energy supply, energy loss or the like, are determined within the respective local network, these state variables per chamfer are fed to a controller, in particular a multivariable controller, the respective controller these state variables as input values compares with setpoint / reference values and generates at least one manipulated variable, which is provided to an electronically controlled transformer, via which the respective local network within specifiable levels deviates from the determined state variable calibrating regulated mains voltage is set, which can be measured at a predefinable point of the local network.

Description

The invention relates to a method for the adaptive control of the supply voltage in local networks.

Electrical energy is generated primarily by nuclear power plants, coal, gas or hydroelectric power plants today.

In addition to hydropower plants as regenerative energy producers, more renewable energy generation facilities, such as wind energy and solar power plants, have increasingly been added in recent years.

While the first-mentioned systems have hitherto brought about a stable energy supply within tolerable fluctuation ranges, the latter-mentioned energy producers, as feeders, in particular in local networks, lead to considerable supply voltage fluctuations. This in view of the fact that the regenerative energy sources, such as wind and sun, are not constantly available and thus, seen over the day, changing supply voltages must be managed within the local networks, which are noticeable by voltage fluctuations in the local network consumers.

Typically, the energy generated and transported is transported in so-called high and medium voltage networks over land and in the already mentioned local networks via transformers to the voltage level of the end user (eg 400 volts) translated.

While it was relatively easy in the past, due to known requirements on the medium and low voltage side transformers to dimension so that the electrical energy on the low voltage side within predeterminable tolerances could be provided easily, lead the new renewable energy sources, in particular energy feed into local networks , to control problems, since they are not constantly available in the same feed quantity.

In the Act on the Renewable Energy Sources Act in the Electricity Sector (2004 Renewable Energy Sources Act), the incentives for a widespread introduction of renewable energy generation systems compared to the first Renewable Energy Sources Act of 2000 were significantly increased. The goal is to increase the share of renewable energies by 2020 to more than 20% of total electricity generation.

Today's power grids are dimensioned in their mode of operation to the load flow from the power plant to the consumer. The quality management at the network operator usually ensures that the quality criteria for the voltage quality accordingly DIN EN 50160 be complied with at all consumer connections of the respective network.

• – Messen eines Eingangsstroms des Transformators, eines Ausgangsstroms des Transformators, einer Ausgangsspannung des Transformators sowie eines Phasenwinkels zwischen Ausgangsstrom und Ausgangsspannung,
• – Bestimmen des Übersetzungsverhältnisses und einer Admittanz eines Quergliedes eines p-Ersatzschaltbildes des Transformators der Außenstation mit Hilfe des gemessenen Eingangsstroms, des gemessenen Ausgangsstroms, der gemessenen Ausgangsspannung und des Phasenwinkels zwischen dem Ausgangsstrom und der Ausgangsspannung,
• – Ermitteln der Eingangsspannung des Transformators der Ortsnetzstation auf der Basis des bestimmten Übersetzungsverhältnisses und der bestimmten Admittanz des Quergliedes des p-Ersatzschaltbildes.

Of the DE 10 2009 048 509 A1 is a method for determining an input voltage of a transformer of a local network station, which includes the following steps:

• Measuring an input current of the transformer, an output current of the transformer, an output voltage of the transformer and a phase angle between output current and output voltage,
• Determining the transmission ratio and an admittance of a cross-member of a p-equivalent circuit diagram of the transformer of the outdoor station with the aid of the measured input current, the measured output current, the measured output voltage and the phase angle between the output current and the output voltage,
• - Determining the input voltage of the transformer of the local network station on the basis of the specific gear ratio and the specific admittance of the cross-member of the p-equivalent circuit diagram.

The DE 10 2009 014 243 A1 relates to a local network transformer or circuit for an electrical distribution transformer for controlling and / or regulating the voltage range per phase for the low voltage level, wherein a distribution transformer at least one transformer with at least one primary and one secondary development is connected downstream, the secondary side in series with the phase is switched by the distribution transformer and the winding of the primary side by means of a switching matrix of power semiconductor switches short-circuited or supplied with a gleichfasigen or gegenfasigen voltage by fast switching and the output voltage during the switching operations remains uninterrupted.

Of the DE 10 2007 037 277 A1 a method for demand control of electrical energy in the low-voltage network can be seen, in which electrical energy is obtained from the low-voltage network and the power control of the energy by active variation of the mains voltage within the tolerance band of the standard voltage.

The DE 10 2006 050 509 A1 discloses a method for the controlled decoupling of electrical energy from the low voltage grid. The use of a voltage controllable is addressed Transformers, in order to influence the load behavior of decentralized power feeders in the supplied low-voltage network segment and thereby control the reference or the supply of electrical energy in the higher-level medium-voltage level. The variable secondary voltage is used within the tolerance band of the standard voltage as a signal carrier for the request of the regulated power.

By the DE 10 2009 035 699 A1 an arrangement of a tap changer to a control transformer has become known, wherein the tap changer comprises a mechanical contact system for selecting a tap of a control winding of the control transformer and a load switch for actual load switching, wherein the control transformer has an oil-filled boiler in which there are at least one iron yoke and windings and wherein the boiler is closed at the top by a transformer cover. The mechanical contact system of the on-load tap-changer is located inside the boiler below the transformer cover and above the iron yoke. The diverter switch of the tap changer has power electronic switching elements, in particular thyristors or IGBTs for uninterrupted load switching.

The object of the subject invention is to provide a method by which, regardless of the nature of the given on the low voltage or medium voltage side supply voltage, in the DIN EN 50160 defined permissible voltage band is not left, in particular, the influences of the decentralized on the low-voltage side regenerative regenerative energy generator can be compensated in such a way that no or only insignificant voltage fluctuations are given on the consumer side.

In addition, it is an object of the subject invention, high or medium voltage side voltage drops, which arise in particular by industrial consumers with high power output to compensate.

Furthermore, decentralized generation plants in the form of z. As wind turbines, Bioheizkraftwerke, oil cogeneration plants and others, which raise the potential, especially on the medium voltage level, are regulated by an electronically controlled transformer.

Finally, it is an object of the subject invention, taking into account energy flows in all directions within the voltage levels and over the voltage levels, to ensure the maintenance of voltage quality in local networks, whereby the capacity of existing networks can be increased.

This object is achieved by a method for adaptive control of the supply voltage in local networks, in which electrical energy, in particular in the form of solar and / or photovoltaic energy can be fed and removed by consumers, using at least one transformer, which is between a medium voltage and a low-voltage network is provided by different state variables of at least one of the feeders / consumers, in particular electricity, voltage, consumption, energy, energy loss or the like, are determined within the respective local area network, these state variables per chamfer at least one controller, in particular a multivariable controller, are fed in that the respective controller adjusts these state variables as input values with desired / reference values and generates at least one manipulated variable which is made available to an electrically regulated transformer via which the respective local network can be preset within predefinable stages one of the determined state variable deviating regulated mains voltage is set, which is measurable at a predetermined location of the local network.

Advantageous developments of the subject invention can be found in the subclaims according to the method.

• – kurzschlussfeste Wicklungsanzapfungen in Form von mehreren Stufen,
• – mindestens ein Leistungsmodul,
• – mindestens ein Steuer- und Regelmodul,

wobei innerhalb des Leistungsmoduls unter Einsatz von Halbleiterschaltern das Transformatorübersetzungsverhältnis unter Last und ohne Unterbrechung der Energieversorgung in Abhängigkeit von der Netzlast und dem Spannungsniveau im Niederspannungsnetz zwischen den einzelnen Stufen der Wicklungsanzapfungen umschaltbar ist, und wobei die Verbindung zwischen dem Leistungsmodul und dem Steuer- und Regelmodul über Lichtwellenleiter herbeiführbar ist.This object is also achieved by a transformer for regulating the voltage between a medium-voltage network and a low-voltage network, at least including

• - Short-circuit proof winding taps in the form of several stages,
• - at least one power module,
• - at least one control module,

wherein within the power module using semiconductor switches, the transformer ratio is switchable under load and without interruption of the power supply depending on the network load and the voltage level in the low voltage network between the individual stages of the winding taps, and wherein the connection between the power module and the control module over Fiber optic can be brought.

Advantageous developments of the transformer according to the invention can be found in the associated subject subclaims.

As a semiconductor switch come thyristors and other types of switching elements, such. As IGBT's, used by which the transformer ratio between the winding taps in response to the network load and the voltage level in the low-voltage network is switched.

Depending on the use of the transformer, for example for a 10 or 20 kV medium-voltage network, stages between 0 and +2 and -2, but in particular between 0, +2, +4, -2 and -4% may be present.

The winding taps of the respective stages are, according to a further idea of the invention, led into a terminal box, in which the power electronics is at medium voltage potential.

A control and regulating module is used to acquire measured values and control the power modules according to a predefined control algorithm.

Status data and fault messages, for example, via a GSM radio modem via SMS to a service center to be transmitted.

In the power module, the ratio of the transformer is switched under load and without interrupting the power supply between the winding taps with the help of the addressed semiconductor switch. After switching, each phase of the conductive thyristors can be bridged by a contact, so that availability and reliability of the controllable transformer is just as high as in conventional transformers.

The subject invention is illustrated by means of an embodiment in the drawing and will be described as follows. Show it:

1 Schematic diagram of a power flow plan of a local network with multiple feeders / consumers using a variable transformer;

2 Schematic diagram of a control scheme for the in 1 illustrated local area network;

3 Basic structure of the transformer according to the invention;

4 Schematic diagram of the function of in 2 illustrated regulator;

5 Schematic diagram of a stepwise regulation of the transformer.

1 shows as a schematic diagram a power flow plan for a local network 1 , In the local network 1 are given as consumer homes H1 to H14. The houses H1, H2, H3 to H11, H14 represent consumers, while in the houses H4, H12 and H13 on their roofs photovoltaic systems PVA different performance are mounted. The houses H4, H12 and H13 are among the so-called feeders and consumers. At the entrance of the local network 1 there is a transformer 2 which translates a mean voltage of 10 kV in this example to the local voltage of 0.4 kV. Only indicated is another transformer 3 between a 110 kV high voltage grid and the medium voltage grid of 10 kV in this example. On the side of the medium-voltage grid of 10 kV is another feeder in the form of a wind turbine 4 as well as an industrial consumer 5 currently not considered further.

The assumed mean voltage of 10 kV is merely an example, could also be 20 kV.

• – Verbrauchern H1, H8
• – Einspeiser/Verbraucher H13
• – Einspeiseknoten 6

For information only, it should be noted that both the given on the medium voltage side industrial consumers 5 and the feeder 4 to lead to voltage fluctuations on the medium voltage side, which is via the transformer 2 also in the local network 1 can affect. According to the power flow plan, the state variables power, voltage and / or current are measured by way of example, namely:

• - consumers H1, H8
• - Feeder / consumer H13
• - Feed-in node 6

Various state variables can be measured, such as the voltage, the current, the energy supply, the energy loss, or the like within the local network 1 , In this example, only the voltage U of the consumers / feeders involved as well as the one at the feed node 6 be measured. The measured state variables are - here only simplified - a multivariable controller 7 abandoned, which can be a fuzzy controller if necessary. Inside the controller 7 the respective input values are compared with reference / reference values, whereby the controller 7 then generates a manipulated variable, via which an electronic stepwise regulation within here also only indicated power modules 8th of the transformer 2 can be brought about. Depending on the voltage drop / voltage increase, the power module is measured via the measured parameters 8th abandoned a different voltage value, the voltage initially measured in the local network 1 is set to be so within the in the DIN EN 50160 specified tolerances a long-term voltage constancy, regardless of consumption, respectively the supply of electrical energy to maintain. At the feed-in node 6 This superimposed voltage can be measured.

2 shows as a schematic diagram a single - ended control scheme for the in 1 illustrated local area network 1 , Recognizable are the multivariable controller 7 and the Power control modules 8th the transformer not shown 2 , where the power modules 8th integral part of the transformer 2 are. The in the local network 1 recorded state variables U _K1 to U _Kn (P _K1 to P _Kn / I _K1 to I _Kn ) are the controller 7 supplied and adjusted with appropriate reference / reference values U _Ksoll (P _Ksoll , I _Ksoll ). The regulator 7 generates one or more manipulated variables (U ₁ to U _n , P ₁ to P _n , I ₁ to I _n ) corresponding to the power modules 8th be made available, in turn, with a (positive or negative) value U _Tr the voltage in the local network 1 to adjust.

U_K1

Spannung am ersten Messknoten

U_Kn

Spannung am n-ten Messknoten

P_K1

Leistung am ersten Messknoten

P_Kn

Leistung am n-ten Messknoten

I_K1

Strom am ersten Messknoten

I_Kn

Strom am n-ten Messknoten

U_Ksoll

Sollspannung am jeweiligen Knoten

P_Ksoll

Sollleistung am jeweiligen Knoten

I_Ksoll

Sollstrom am jeweiligen Knoten

U₁

erste Stellgröße des Reglers

U_n

n-te Stellgröße des Reglers

U_Tr

Ausgangsspannung des geregelten Transformators

P_Tr

Ausgangsleistung des geregelten Transformators

I_Tr

Ausgangsstrom des geregelten Transformators

The abbreviations used are given as follows:

U _K1

Voltage at the first measuring node

U _Kn

Voltage at the nth measuring node

P _K1

Power at the first measuring node

P _Kn

Power at the nth measurement node

I _K1

Current at the first measuring node

I _Kn

Current at the nth measuring node

U _Ksoll

Target voltage at the respective node

P _Ksoll

Target power at the respective node

I _Ksoll

Target current at the respective node

U ₁

first manipulated variable of the controller

U _n

nth manipulated variable of the controller

U _Tr

Output voltage of the regulated transformer

P _Tr

Output power of the regulated transformer

I _Tr

Output current of the regulated transformer

3 shows the basic structure of the transformer according to the invention 2 , Recognizable is the controller 7 as well as the three power modules of the outer conductors L1, L2, L3, within a flange housing 8th are arranged. The power modules L1-L3 are at medium voltage potential. Also indicated are winding taps 9 . 10 . 11 of the local power transformer 2 , The power modules L1, L2, L3 in this example can be regulated within voltage tolerances between -4% and + 4%. They are controlled by the controller 7 , in which - here only indicated - the state variables of the local network 1 be fed. The function of the controller 7 was already in 2 closer illuminated. The flange housing 8th and the transformer housing 8th' are filled with insulating oil. The oil flows through both partial housings 8th . 8th' , By not shown openings between the two sub-housings 8th . 8th' become the connecting lines from the transformer windings 9 . 10 . 11 led to the power modules L1, L2, L3.

The regulator 7 is via a radio modem 12 with a central control center, not shown in connection and transmitted within predeterminable time window state variables of the transformer 2 ,

4 shows the principle one-phased construction of the 2 illustrated regulator 7 , The differences of the reference / reference values and actual state values, ie the control deviations, e ₁ -e _n , are transferred to the controller 7 fed on its left side. Only shown are e ₁ as the first control deviation and e _n as the last (n-th) control deviation. The controller, which is designed as a fuzzy controller in this example, generates by appropriate comparison with reference / reference values 7 one or more manipulated variables, then the power level 8th (not shown here) of the transformer 2 to provide.

5 shows a chamfer of power levels, e.g. B. L1, the transformer, not shown here.

The electronic control of the transformer is done by controlling electronic switches at different taps of the primary transformer winding. As a result, the number of turns of the primary winding and thus the transmission ratio of the entire transformer are changed. The taps required for the control cause a percentage change in the primary number of turns, which affects the gear ratio and results in a change in the transformer output voltage.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009048509 A1 [0009]
• DE 102009014243 A1 [0010]
• DE 102007037277 A1 [0011]
• DE 102006050509 A1 [0012]
• DE 102009035699 A1 [0013]

Cited non-patent literature

• DIN EN 50160 [0008]
• DIN EN 50160 [0014]
• DIN EN 50160 [0037]

Claims (13)

Method for the adaptive control of the supply voltage in local networks, in which electrical energy, in particular in the form of solar and / or photovoltaic energy can be fed and removed by consumers, using at least one transformer, which is provided between a medium voltage and a low voltage network by different State variables of at least one of the feeders / consumers, in particular current, voltage, consumption, energy supply, energy loss or the like, are determined within the respective local network, these state variables per chamfer are fed to a controller, in particular a multivariable controller, the respective controller these state variables as input values compares with reference / reference values and generates at least one output that is made available to an electronically controlled transformer over which the local network within specifiable levels deviates from the determined manipulated variable calibrating regulated mains voltage is set, which can be measured at a predefinable point of the local network. A method according to claim 1, characterized in that the measured values are transmitted via a GSM radio modem, in particular by SMS, to the multivariable controller. A method according to claim 1 or 2, characterized in that in compact power modules using semiconductor switches, the transmission ratio of the transformer is switched under load and without interrupting the power supply between the winding taps. Method according to one of the preceding claims, characterized in that the measurements carried out at the relevant network nodes in the local network on consumer and / or feeder side using digital counter. Method according to one of the preceding claims, characterized in that the switching of the low-voltage side mains voltage between winding taps of the transformer is three-phase on the medium voltage level without interrupting the power supply. Method according to one of the preceding claims, characterized in that the line electronics required for switching leads medium-voltage potential as a reference voltage. Method according to one of the preceding claims, characterized in that compact power modules using optical waveguides receive control commands to ensure the respective switching and to transmit status messages to a control and regulation module. Method according to one of the preceding claims, characterized in that operating state and fault messages are transmitted in particular via a GSM radio modem via SMS or e-mail to a central control center. Transformer for regulating the voltage between a medium-voltage network and a low-voltage network, at least including - Short-circuit proof winding taps in the form of several stages, - at least one power module, - at least one control module, wherein within the power module using semiconductor switches, the transformer transmission ratio under load without interruption of the power supply depending on the network load and the voltage level in the low voltage network between the individual stages of the winding taps is switchable and wherein the connection between the power module and the control module via optical fibers brought about is. Transformer according to claim 9, characterized in that within the power module using thyristors as semiconductor switches, the transformer transmission ratio between the winding taps is switchable. Transformer according to claim 9 or 10, characterized in that winding taps at least the levels +2 to -2% voltage deviation, in particular +4 to -4%, include. Transformer according to one of claims 9 to 11, characterized in that the winding taps of the respective stages are feasible in a terminal box, in which the power electronics is at medium voltage potential. Transformer according to one of claims 9 to 12, characterized in that the control and regulating module includes a multivariable controller per chamfer, in particular a fuzzy controller.

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