EP3336650B1 - Longitudinal voltage regulator - Google Patents

Description

technical field

The invention relates to a direct-axis voltage regulator, in particular for use in a single-phase or multi-phase power distribution network, for example a medium-voltage network or a low-voltage network, according to the preamble of patent claim 1.

background

The CN 2 814 480 Y discloses a longitudinal voltage regulator of this type EP 0 637 122 A1 shows a method for controlling an output voltage in response to an input voltage. The US 5,568,398A discloses a voltage regulator with a memory unit and the EP 2 390 750 A1 shows a voltage regulator and a toroidal transformer.

In recent years, the share of renewable energies in the energy supply has risen sharply. These renewable energies include energies generated by means of photovoltaic systems or by means of other alternative energy sources. There are regions in which the amount of energy generated is significantly greater than the energy demand, so that excess energy has to be fed into the existing energy grid and transmitted over comparatively long distances to places where the energy demand is greater than the amount of energy generated there.

This feeding of energy into the existing energy distribution grid brings many conventional energy distribution grids to their limits and requires additional interventions in these conventional energy distribution grids, with these additional interventions being associated with high costs and a great deal of effort.

Particularly with regard to the planned shutdown of further nuclear power plants, it is to be expected that the share of renewable energies will continue to rise, so that it is foreseeable that the distribution problem mentioned will also increase.

The European standard EN 50160 defines the requirements for the voltage in distribution grids and stipulates, among other things, that the voltage must remain within +/-10% of the nominal voltage.

In general, voltage increases of only 2% are currently occurring in the supply lines of medium-voltage networks. The exact value of this Increases in voltage depend on the settings made by the respective network operators and on the current load and/or feed-in situation in the respective supply line.

On longer supply lines, where feeds are made at different distances or line positions, the respectively specified planning value for the voltage tolerance can easily be undesirably exceeded and it is necessary to take countermeasures, for example disconnecting some of the generators from the grid. This can occur more frequently on days when there is only a comparatively low energy requirement. This means that in many cases supply lines of medium-voltage grids are not limited because of their capacity, but because of undesired voltage increases. This problem can be reduced by modifying the network architecture. However, this is expensive and also time-consuming.

As an alternative to changing the network architecture, there is the option of using longitudinal voltage regulators in the area of the supply lines of the medium-voltage networks.

In current power distribution networks, voltage regulation is carried out by an HV-MV transformer, which converts a supplied high voltage into a medium voltage. This voltage regulation can ensure that the voltage arriving at connected consumers is in the range of +/- 10% of the nominal voltage.

If a direct-axis voltage regulator is used in the area of the supply lines of the medium-voltage network between the mentioned HV-MV transformer and the connected consumers, then this can achieve better stabilization of the voltage in the area of the supply lines and also the possibility of feeding in energy provided by means of alternative energy sources in the supply lines of the medium-voltage network can be improved.

The optimal positioning of a direct-axis voltage regulator depends on the particular medium-voltage network present and on the feed-in points for the energy, which is supplied in particular by large photovoltaic systems or other alternative energy sources.

When positioning a longitudinal voltage regulator, it should also be noted, among other things, that if several supply lines of the medium-voltage network are connected to the HV-MV transformer, changing the transformer tapping point used affects all supply lines of the medium-voltage network, whereas a longitudinal voltage regulator only increases the voltage of the supply line on which problems occur. This is particularly important in view of the fact that the feeds occurring on the various supply lines and the loads on the various supply lines can differ greatly from one another.

A longitudinal voltage regulator is usually installed in a housing that is suitable for outdoor installation, for example in a concrete housing, and because of its dimensions and weight it has to be transported to the desired place of use by means of a low-loader. If a repositioning of the longitudinal voltage regulator in the area of the medium-voltage grid is necessary or if additional longitudinal voltage regulators are to be used in the medium-voltage grid, then this is associated with a comparatively high level of effort, since this in turn requires low-loaders that transport the respective longitudinal voltage regulator to the desired location. There it is then placed on a prepared concrete platform using a crane.

The invention is defined in claim 1. Preferred developments are specified in the dependent claims.

The invention provides a direct-axis voltage regulator which has a voltage source for generating an additional voltage and a transformer for coupling the additional voltage into an input voltage, the transformer being designed both for generating the additional voltage and for coupling the additional voltage into the input voltage.

Such a series voltage regulator has a much more compact structure than known series voltage regulators, since it has only one transformer, which is designed to generate the additional voltage and to couple this additional voltage into the supply line. This more compact structure enables the direct-axis voltage regulator to be reduced in size and weight. This reduction in the weight and dimensions of the series voltage regulator also reduces the dimensions and weight of the housing in which the series voltage regulator is installed. This improves the portability of the longitudinal voltage regulator. Such a longitudinal voltage regulator can be moved to the desired installation site, for example can also be transported on the loading area of a truck, which is associated with considerably less effort than transporting a longitudinal voltage regulator using a low-loader. At the installation site itself, the housing of the longitudinal voltage regulator, including the built-in longitudinal voltage regulator, is placed on a prepared foundation using a crane. Further advantages of a longitudinal voltage regulator according to the invention are that its acquisition costs are lower than the acquisition costs of known longitudinal voltage regulators and that its energy efficiency is significantly increased.

The transformer has an input winding and an output winding, with the output winding being arranged in a supply line. This supply line can be a supply line provided in a medium-voltage network or a supply line provided in a low-voltage network. Such a supply line can, for example, be assigned to a single-phase power distribution network or to one phase of a three-phase power distribution network. A three-phase power distribution network requires three such power supply lines.

The polarity of the additional voltage can preferably be changed. As a result, the desired voltage regulation can take place both positively and negatively. In the first-mentioned case, the input voltage is superimposed in phase with the additional voltage, so that the additional voltage is added to the input voltage. In the second case mentioned, the input voltage is superimposed in phase opposition with the additional voltage, so that the additional voltage is subtracted from the input voltage.

The polarity of the additional voltage can advantageously be changed by changing the direction of the current.

According to the invention, one terminal of the input winding of the transformer can be connected to a reference potential and the other terminal of the input winding can be connected to an output terminal of the series voltage regulator, and one terminal of the output winding of the transformer can be connected to an input terminal of the series voltage regulator and the other terminal of the output winding can be connected to the output terminal of the series voltage regulator. In this embodiment, the additional voltage is superimposed in phase with the input voltage.

According to a further embodiment, one connection of the input winding of the transformer can be connected to the reference potential and the other connection of the input winding to the input connection of the series voltage regulator and one connection of the output winding of the transformer to the input connection of the series voltage regulator and the other connection of the output winding to the output connection of the series voltage regulator be.

According to an advantageous embodiment, the input winding of the transformer can have a plurality of taps which are connected to the output terminals of a tap changer, the input terminal of the tap changer being connected to a reference potential. This allows a gradual change in the additional voltage provided. This possibility of switching on the additional voltage in stages allows the additional voltage to be adapted to the fluctuation range of the input voltage supplied.

According to a preferred embodiment, the input winding of the transformer can have five taps. This number of taps has proven to be useful and sufficient in practice and offers a good compromise between effort and effect. Alternatively, the number of taps can also be seven, for example.

It has proven to be advantageous to distribute the positions of the taps over the number of turns of the primary winding of the transformer in a non-linear manner in such a way that a continuous change in the selection of the tap enables a linear change in the additional voltage.

As an alternative to this, the input winding of the transformer can also be designed without tapping according to an example in which no tap changer is used.

Further advantages of the invention result from the following exemplary explanation based on the drawings.

Brief description of the drawings

• The figure 1 shows a sketch to explain the basic structure of a direct-axis voltage regulator.
• The figure 2 shows a sketch of a longitudinal voltage regulator, in which the in the figure 1 voltage source shown is realized by means of a supply transformer.
• The figure 3 shows a sketch of a longitudinal voltage regulator according to a first embodiment of the invention.
• The figure 4 shows a sketch of a longitudinal voltage regulator according to a second embodiment of the invention.

Detailed description

The principle of operation of a direct-axis voltage regulator is to add or subtract an additional voltage to an input voltage. The boost voltage is provided using a variable voltage source that is powered from the utility line. The additional voltage provided by the voltage source is coupled into the supply line using a booster transformer. By means of such a direct-axis voltage regulator, the input voltage is regulated and an additional voltage provided by a voltage source is coupled into the input voltage.

The figure 1 shows a sketch to explain the basic structure of a direct-axis voltage regulator described above. This longitudinal voltage regulator 1 is used in a supply line 3 of a medium-voltage network, which is provided, for example, between a high-voltage-medium-voltage transformer (HV-MV transformer, not shown) and a low-voltage network, also not shown, in which loads are arranged. An input voltage or system voltage U _L subject to voltage fluctuations is present at the input connection 2 of the longitudinal voltage regulator 1 . A regulated output voltage or a regulated system voltage U _R is provided at the output connection 4 of the longitudinal voltage regulator 1 . The following applies: $${\mathrm{u}}_{\mathrm{R}}={\mathrm{u}}_{\mathrm{L}}-{\mathrm{u}}_{\mathrm{B}}.$$

U _B is a voltage that drops across the output winding 5b of a booster transformer 5 that is inserted into the supply line 3 . This voltage U _B is an additional voltage coupled into the supply line 3 . In order to generate this additional voltage, the direct-axis voltage regulator 1 has a variable voltage source 6 and the booster transformer 5 already mentioned. The voltage source 6, which is supplied with energy from the supply line 3, is a variable voltage source, by means of which an additional voltage U _RB is generated, which is present at the input winding 5a of the booster transformer 5 and is coupled into the supply line 3 by means of the booster transformer.

Another transformer can be used as the variable voltage source 6, which is referred to below as the supply transformer. This is in the figure 2 illustrated. This shows a sketch of a longitudinal voltage regulator, in which the in the figure 1 voltage source 6 shown is formed by such a supply transformer 7 .

Also with the one in the figure 2 In the direct-axis voltage regulator 1 shown, an input or system voltage U _L that is subject to fluctuations is present at the input connection 2 of the booster transformer 5 on a supply line 3 . A regulated output voltage or a regulated system voltage U _R is provided at the output connection 4 of the longitudinal voltage regulator 1 . The same applies to this as in the figure 1 the following relationship: $${\mathrm{u}}_{\mathrm{R}}={\mathrm{u}}_{\mathrm{L}}-{\mathrm{u}}_{\mathrm{B}}.$$

The longitudinal voltage regulator 1 has a variable voltage source 6 and a booster transformer 5 . An additional voltage U _RB drops across the input winding 5a of the booster transformer 5, which is connected to the variable voltage source 6. This is coupled by means of the booster transformer 5 into the secondary winding 5b of the booster transformer 5, which is inserted into the supply line 3 and across which a voltage U _B drops, which is the additional voltage U _RB coupled to the secondary side of the booster transformer 5 acts.

The variable voltage source 6 of the direct-axis voltage regulator 1 is formed by a supply transformer 7 . This has a primary winding 7a and a secondary winding 7b. The primary winding 7a of the supply transformer 7 is connected to the supply line 3 with one of its terminals. The other terminal of the primary winding 7a is connected to a reference potential N. The secondary winding 7b of the supply transformer 7 is connected to one connection of the primary winding 5a of the booster transformer 5 and with its second connection to the other connection of the primary winding 5a of the booster transformer 5 tied together. This second connection of the secondary winding 7b of the supply transformer interacts with an uninterruptible tap changer 8 with five connections in such a way that the tapping point used on the secondary winding 7b can be switched over without interruption.

The disadvantage of using the figure 2 explained longitudinal voltage regulator 1 is that it has comparatively large dimensions and a comparatively high weight due to the fact that it requires two transformers, together with the housing in which it is used.

The figure 3 shows a sketch of a longitudinal voltage regulator 1 according to a first embodiment of the invention. In this longitudinal voltage regulator are compared to that in the figure 2 shown longitudinal voltage regulator reduces the dimensions and weight.

This longitudinal voltage regulator 1 can be used in a supply line 3 of a medium-voltage network, which is provided, for example, between a high-voltage-medium-voltage transformer (HV-MV transformer, not shown) and a low-voltage network, also not shown, in which loads are arranged. An input voltage subject to voltage fluctuations or the system voltage U _L subject to fluctuations is present at the input connection 2 of the longitudinal voltage regulator 1 . A regulated output voltage or a regulated system voltage U _R is provided at the output connection 4 of the longitudinal voltage regulator 1 . The following applies: $${\mathrm{u}}_{\mathrm{R}}={\mathrm{u}}_{\mathrm{L}}-{\mathrm{u}}_{\mathrm{B}}.$$

U _B is a voltage that drops across the output winding 5b of a booster transformer 5 that is inserted into the supply line 3 . This voltage U _B is an additional voltage coupled into the supply line 3 or transformed into the supply line 3 . In order to generate this additional voltage, the direct-axis voltage regulator 1 has a variable voltage source 6 which is formed by the booster transformer 5 already mentioned, which interacts with a tap changer 8 . The voltage source 6, which is supplied with energy from the supply line 3, is a variable voltage source, by means of which an additional voltage U _RB is generated, which is applied to the input winding 5a of the booster transformer 5 and is coupled into the supply line 3 or boosted by means of the booster transformer 5 .is transformed into the supply line 3.

The booster transformer 5 is consequently designed in such a way that it both generates the additional voltage and couples it into the supply line 3 .

For this purpose, in the first exemplary embodiment shown, one connection of the input winding 5a of the booster transformer 5 is connected to the reference potential N via the tap changer 8 and the other connection of the input winding 5a of the booster transformer 5 is connected to an output connection 4 of the longitudinal voltage regulator 1. Furthermore, one connection of the output winding 5b of the booster transformer 5 is connected to an input connection 2 of the series voltage regulator 1 and the other connection of the output winding 5b is connected to the output connection 4 of the series voltage regulator 1 . The additional voltage U _B coupled into the supply line 3 or transformed into the supply line 3 drops across the output winding 5b of the booster transformer 5 .

The variable voltage source 6 of the longitudinal voltage regulator 1 is formed by the primary winding 5a of the booster transformer 5, which interacts with the tap changer 8. In the exemplary embodiment shown, the primary winding 5a has five taps which are connected to output terminals of the tap changer 8 . The input of the tap changer 8 is connected to the reference potential N. The tap changer 8 can be switched in such a way that one of its total of 5 output connections is connected to the output connection 4 via the turns of the primary winding 5a remaining between the reference potential N and the output connection 4 . The additional voltage generated by means of the variable voltage source can be changed by switching over the tap changer 8, for example by 2% from tap to tap of the primary winding 5a. For this purpose, the taps of the primary winding 5a of the booster transformer 5 and the associated output connections of the tap changer 8 are distributed non-linearly over the number of turns of the primary winding 5a in such a way that a change in the selection of the tap used from tap to tap results in a linear change the provided additional voltage U _RB allows. This possibility of changing the additional voltage advantageously allows the additional voltage to be adapted to the voltage fluctuations occurring on the supply line 3 .

The figure 4 shows a sketch of a longitudinal voltage regulator 1 according to a second embodiment of the invention. Also with this longitudinal voltage regulator are compared to that in the figure 2 shown longitudinal voltage regulator reduces the dimensions and weight.

This longitudinal voltage regulator 1 can also be used in a supply line 3 of a medium-voltage network, which is provided, for example, between a high-voltage-medium-voltage transformer (HV-MV transformer, not shown) and a low-voltage network, also not shown, in which loads are arranged. An input voltage subject to voltage fluctuations or the system voltage U _L subject to fluctuations is present at the input connection 2 of the longitudinal voltage regulator 1 . A regulated output voltage or a regulated system voltage U _R is provided at the output connection 4 of the longitudinal voltage regulator 1 . The following applies: $${\mathrm{u}}_{\mathrm{R}}={\mathrm{u}}_{\mathrm{L}}-{\mathrm{u}}_{\mathrm{B}}.$$

U _B is a voltage that drops across the output winding 5b of a booster transformer 5 that is inserted into the supply line 3 . This voltage U _B is an additional voltage coupled into the supply line 3 or transformed into the supply line 3 . In order to generate this additional voltage, the direct-axis voltage regulator 1 has a variable voltage source 6 which is formed by the booster transformer 5 already mentioned, which interacts with a tap changer 8 . The voltage source 6, which is supplied with energy from the supply line 3, is a variable voltage source, by means of which an additional voltage U _RB is generated, which is present at the input winding 5a of the booster transformer 5 and is coupled into the supply line 3 or boosted by means of the booster transformer 5. is transformed into the supply line 3.

The booster transformer 5 is consequently designed in such a way that it both generates the additional voltage and couples it into the supply line 3 .

For this purpose, in the second exemplary embodiment shown, one connection of the input winding 5a of the booster transformer 5 is connected to the reference potential N via the tap changer 8 and the other connection of the input winding 5a of the booster transformer 5 is connected to the input connection 2 of the longitudinal voltage regulator 1. Furthermore, one connection of the output winding 5b of the booster transformer 5 is connected to the input connection 2 of the series voltage regulator 1 and the other connection of the output winding 5b is connected to the output connection 4 of the series voltage regulator 1 . The additional voltage U _B coupled into the supply line 3 or transformed into the supply line 3 drops across the output winding 5b of the booster transformer 5 .

The variable voltage source 6 of the direct-axis voltage regulator 1 is formed by the primary winding 5a of the booster transformer 5 which interacts with the tap changer 8 . In the exemplary embodiment shown, the primary winding 5a has five taps which are connected to output terminals of the tap changer 8 . The input of the tap changer 8 is connected to the reference potential N. The tap changer 8 can be switched in such a way that one of its total of 5 output connections is connected to the input connection 2 via the turns of the primary winding 5a remaining between the reference potential N and the input connection 2 . The additional voltage generated by means of the variable voltage source can be changed by switching over the tap changer 8, for example by 2% from tap to tap of the primary winding 5a. For this purpose, the taps of the primary winding 5a of the booster transformer 5 and the associated output connections of the tap changer 8 are distributed non-linearly over the number of turns of the primary winding 5a in such a way that a change in the selection of the tap used from tap to tap results in a linear change the provided additional voltage U _RB allows. This possibility of changing the additional voltage advantageously allows the additional voltage to be adapted to the voltage fluctuations occurring on the supply line 3 .

The invention described with reference to the exemplary embodiments described above has a number of advantages.

A major advantage of a direct-axis voltage regulator according to the invention is that it requires only one transformer. This is designed both to generate the additional voltage and to couple this additional voltage into the supply line. This enables a more compact structure compared to known direct-axis voltage regulators. This more compact structure in turn is accompanied by a reduction in the dimensions of the direct-axis voltage regulator and a reduction in its weight. This reduction in the weight and dimensions of the series voltage regulator also reduces the dimensions and weight of the housing in which the series voltage regulator is installed. For example, a concrete housing with built-in longitudinal voltage regulator according to the prior art has a length of 2.50 m, a width of 6.00 m and a height of 3.20 m Height a reduced width, which is for example 4.00 m.

Due to the mentioned reduction in its weight and dimensions, the transportability of a longitudinal voltage regulator built into a housing is improved. Such a longitudinal voltage regulator can be transported to the desired installation site, for example on the loading area of a truck, which is associated with considerably less effort than transporting a longitudinal voltage regulator using a low-loader, as was necessary with known longitudinal voltage regulators. At the installation site itself, the housing of the longitudinal voltage regulator, including the built-in longitudinal voltage regulator, is placed on a prepared foundation using a crane.

The improved portability of a direct-axis voltage regulator is particularly advantageous when additional energy sources, in particular alternative energy sources, are to be connected to the electricity distribution network when there is a need to expand an electricity distribution network. This often means that no longer tolerable voltage fluctuations occur in the area of the supply lines, which must be reduced by suitable voltage regulation. For such a voltage regulation, it is possible to place one or more longitudinal voltage regulators, which have the features according to the invention, at suitable positions within the power distribution network.

Further advantages of a series voltage regulator according to the invention are that its acquisition costs are lower than the acquisition costs of known series voltage regulators, since it has fewer components than conventional series voltage regulators. In particular, the costs for the supply transformer used in conventional series voltage regulators are saved, which is used in known series voltage regulators in addition to the booster transformer.

Furthermore, the energy efficiency of a series voltage regulator according to the invention is significantly increased compared to the energy efficiency of conventional series voltage regulators. A series voltage regulator according to the invention generates less waste heat than a known series voltage regulator because it requires fewer transformers and therefore has fewer losses.

Furthermore, due to the reduction in the number of components used, the likelihood of defects occurring is also reduced.

Furthermore, the design of a direct-axis voltage regulator according to the invention is simplified compared to a design of known direct-axis voltage regulators.

Direct-axis voltage regulators with the features according to the invention can be used in particular in single-phase or multi-phase power distribution networks such as medium-voltage networks or low-voltage networks.

Reference List

1

Longitudinal voltage regulator, phase regulator

2

Input connection of the longitudinal voltage regulator

3

supply line

4

Output connection of the longitudinal voltage regulator

5

Booster Transformer

5a

Booster transformer input winding

5b

Booster transformer output winding

6

Variable voltage source

7

supply transformer

7a

Input winding of the supply transformer

7b

Output winding of the supply transformer

8th

step switch

N

reference potential

UB

transformed additional voltage on the supply line

UL

input voltage, system voltage

ur

Output voltage, regulated system voltage

urb

additional voltage

Claims (5)

1. Series voltage regulator (1) having:

   - an input connection (2) which is connected to a supply line (3), wherein the supply line (3) can be connected to an input voltage (U_L),

   - an output connection (4) which is configured to provide a regulated output voltage (U_R),

   - a voltage source (6),

   - a transformer (5) for generating an additional voltage (U_RB) and for coupling the additional voltage (U_RB) into the input voltage, and

   - a tap changer (8),

   wherein the transformer (5) has an input winding (5a) and an output winding (5b),

   wherein the output winding (5b) is arranged in the supply line (3),

   wherein a connection of the output winding (5b) of the transformer (5) is connected to the input connection (2) of the series voltage regulator (1) and the other connection of the output winding (5b) is connected to the output connection (4) of the series voltage regulator (1),

   wherein the input winding (5a) of the transformer (5) has a plurality of taps which are connected to output connections of the tap changer (8),

   wherein the voltage source (6) is formed by the input winding (5a) of the transformer (5), which is configured to interact with the tap changer (8) in order to generate the additional voltage (U_RB),

   wherein an input connection of the tap changer (8) is connected to a reference potential (N),

   wherein a connection of the input winding (5a) of the transformer (5) is connected to the reference potential (N) via the tap changer (8) and the other connection of the input winding (5a) is connected to the output connection (4) of the series voltage regulator (1),

   or wherein a connection of the input winding (5a) of the transformer (5) is connected to the reference potential (N) via the tap changer (8) and the other connection of the input winding (5a) is connected to the input connection (2) of the series voltage regulator (1),

   characterized in that the positions of the taps are distributed in a non-linear manner over the number of turns of the input winding (5a) of the transformer (5) in such a manner that a change in the selection of a tap enables a linear change in the additional voltage (U_RB).
2. Series voltage regulator according to Claim 1, wherein the polarity of the additional voltage can be changed.
3. Series voltage regulator according to Claim 2, wherein the polarity of the additional voltage can be changed by changing the current direction.
4. Series voltage regulator according to one of the preceding claims, wherein the number of taps of the input winding (5a) of the transformer (5) is five.
5. Use of a series voltage regulator having the features stated in one of the preceding claims in a single-phase or multi-phase electricity distribution network.

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