DE102005052013A1 - Wind energy plant operating method for generation of electrical current, involves separating generator from network during falling of nominal voltage under given threshold value and outflow of reactive power - Google Patents

Abstract

The method involves connecting an electrical generator to a network (N) operated with given network nominal voltage, where the generator transmits electrical active and reactive powers to a network connection point (NP). The generator is automatically separated from the network by a separator (1) during falling of the nominal voltage in the connection point under a given threshold value of the nominal voltage and outflow of the reactive power which is directed from the network to the generator. An independent claim is also included for a wind energy plant.

Description

The The invention relates to a method for operating at least one wind turbine According to the preamble of claim 1. It further relates to a wind turbine according to the preamble of claim 15.

The This invention relates generally to the field of production and transportation of electricity. For generating electric power can several Wind turbines combined into a so-called "wind farm" and at a common Network connection point to be connected to a network. The net is going on a given voltage level, z. B. 110 kV, 220 kV or 380 kV, operated. It can over Transformers be connected to other networks, which on one be operated at different voltage level.

From the DE 197 56 777 B4 It is known to regulate the output to a network by means of a wind turbine power in response to the mains voltage to avoid Spannungsüberschwankungen.

From the EP 1 040 564 B1 It is known to operate a wind turbine without power to the grid when the mains voltage is less than a predetermined mains voltage value.

Of Further, it is according to the prior art in the event of a fault Waste of mains voltage known, wind turbines automatically disconnect from the network. It is thus tried to counteract the disturbance and to narrow down their cause. Depending on territorial extent the disorder will u.U. a variety of wind turbines disconnected from the grid. After fixing the fault usually takes a relatively long time to complete Wind turbines are connected to the grid again and electrical power feed.

task The invention is to the disadvantages of the prior art remove. In particular, a method is to be specified, with the one inadmissible Voltage drop in the network is counteracted. Furthermore, a to execution the method suitable wind turbine can be provided.

These The object is solved by the features of claims 1 and 15. Advantageous embodiments The invention will become apparent from the features of claims 2 to 14 and 16 to 31.

To the method according to the invention it is envisaged that if there is a drop in mains voltage at the grid connection point below a predetermined first limit of the mains voltage and a simultaneous one From the grid to the generator directed outflow of reactive power of Generator is automatically disconnected from the mains. - In contrast to the state of Technique will be in case of an inadmissible voltage drop first only those generators disconnected from the grid which have no reactive power feed into the network. This is a by a reactive power deficit caused voltage drop counteracted. The disorder can be eliminated or at least reduced. As in the case the disorder only part of the wind turbines are disconnected from the grid the network relatively quickly back to a proper state be offset.

modeling the fault processes and practice show that the critical or first limit expediently 85% of the mains voltage. An undesirable Waste of the mains voltage can thus be counteracted at an early stage. To In another embodiment, the mains voltage is the largest of the three chained mains voltages. If only one or two of the chained mains voltages fall below the first limit, there is still no separation of the generator from the grid. A disorder, which only to a drop in one or two of the chained mains voltages below leads the first limit, remains unconsidered. The elimination of such a disorder usually succeeds with usual other measures and does not require disconnecting the generator quickly from the grid.

To a particularly advantageous embodiment of the invention is the Generator with a first time delay of at most 1 second, preferably 0.4 to 0.6 seconds, disconnected from the mains. This is a separation of the generator only when it occurs a short-term drop below the limit. The generator remains connected to the grid and can by feeding in reactive power Counteract the voltage dip. That contributes to a particularly high network stability at.

According to a further embodiment, it is provided that the generator is automatically disconnected from the network after the expiry of the first time delay and a simultaneous in the grid connection point to the grid inflow of reactive power when a voltage applied to a low voltage side of the generator downstream transformer voltage falls below a second threshold, which is less than a lower value of a generator voltage band. - As a result of a voltage drop due to the Generator has not been disconnected from the network because of an existing inflow of reactive power in the grid connection point is checked according to the proposed embodiment, whether the second limit value of the generator voltage is exceeded. It is then the generator of those wind turbines disconnected from the grid, in which a voltage applied to a low voltage side of the generator downstream of the transformer generator voltage falls below the second limit. The second threshold is chosen to be less than a lower value of the generator voltage band. This selectively separates other wind turbines from the grid, which do not counteract the disturbance strongly enough. In practice, it has proven expedient that the lower value of the generator voltage band is 5% below the rated generator voltage. The second limit is expediently 0.8 times the lower value. In the case of a rated generator voltage of 690 V, for example, the lower value is 690 V × 0.95 = 655.5 V. The second limit value is then 655.5 V × 0.8 = 525 V.

To A further embodiment provides that the generator only after a second time delay disconnected from the network. Each wind turbine can have a predefined one Value for the Time Delay be assigned. The predetermined value is expediently selected from a group of predefined values. The group for the second Time Delay In particular, it may contain the following values: 1.5, 1.8, 2.1, and 2.4 seconds. A greatest value the second time delay is less than 3.0 seconds. Ie. at the latest with a time delay of less than 3.0 seconds from the fall below the second limit are all Generators disconnected from the grid, their generator voltages smaller as the second limit.

In practice is common a plurality of wind turbines combined to form a wind farm and connected to the network together at the network connection point. The Wind turbines of a wind farm can in equal proportions the selected from the group Values for the second time delay be assigned. In the above example, so 25% of wind turbines a value of 1.5 seconds, another 25% a value of 1.8 seconds, another 25% a value of 2.1 seconds and another 25% a value of 2.4 seconds for the second time delay be assigned. The values for the second time delay can be selected at an interval of preferably 1.0 to 3.0 seconds. This makes it possible the wind turbines in groups according to the respective value of the second Time Delay time-separated from the network. This measure also contributes to this at, the network as long as possible stable. Only when proposed by the invention Gradual separation of an increasing number of wind turbines The network has not eliminated the voltage dip more wind turbines disconnected from the grid. The inventive method counteracts in particular a territorial extension of the disturbance and carries thus to a high network stability.

To further requirement the invention is in a wind turbine, in particular for execution of the method according to the invention, a first separator for automatically disconnecting the generator provided by the network, which at a drop of a mains voltage in the grid connection point below a predetermined first limit of Mains voltage and a simultaneous from the mains to the generator directed Outflow of reactive power responds. The first separator can z. B. include a first voltage monitor with which the three interconnected mains voltages and the direction of the Flow of reactive power can be determined. Such a first voltage monitor can comprise a timing element that is adjustable to the first time delay is. With the first voltage monitor can depend on a preset first limit of the mains voltage and in further dependency a pre-set direction of the flow of reactive power a first Circuit breaker for disconnecting the generator at the grid connection point automatically after the first time delay open become. This can be counteracted quickly and effectively a fault in the network become.

Because of the configuration of the first limit value is based on the preceding ones References.

The The first separating device can in particular be set so that the generator with a first time delay of at most 1 second, preferably 0.4 to 0.6 seconds, disconnected from the mains becomes. Conveniently, the first separator is set so that the first time delay is 0.5 Seconds counting from the occurrence of the disturbance. To set the first Time Delay For example, the first separator may comprise a timer.

According to a further advantageous embodiment, a second disconnecting device is provided for automatically disconnecting the generator from the mains, which responds when the generator voltage falls below a second limit value on a low-voltage side of a transformer downstream of the generator, which is smaller than a lower value of the generator voltage band. If the first separator due to an inflow of reactive power in the grid connection point does not respond, the wind turbine can still be disconnected from the network by means of the second separator when the second limit of the undervoltage has been reached. This allows a selective separation of certain wind turbines, a wind farm, which does not counteract the disturbance strong enough. This selective separation can be done in groups by choosing different values for the second time delay. For this purpose, each wind turbine can be assigned a predetermined value for the second time delay. The predetermined value may be selected from a group of predetermined values. The group for the second time delay may contain the following values: 1.5, 1.8, 2.1 and 2.4 seconds. A maximum value of the second time delay is less than 3.0 seconds.

The second separator may comprise a second voltage monitor, with the three mutually linked generator voltages measurable are. The second voltage monitor may comprise a further time switching element, which on the second Time Delay is adjustable. With the second voltage monitor can depend on a preset second limit value of the generator voltage a second circuit breaker for disconnecting the generator after second time delay automatically opened become.

To an advantageous embodiment of the invention separates the second Separator the generator from the transformer. Ie. the second Separator is between the transformer and the generator connected.

Conveniently, are a plurality of wind turbines combined to form a wind farm and connected to the network together at the network connection point. In this Case can the wind turbines, especially those combined in a wind farm Wind turbines, in groups according to the respective value of the second Time Delay be separated from the grid at certain times. Here are the respective Groups about the same size.

To the Connection of a wind farm in the grid connection point is common a mains connection transformer is provided. According to an advantageous embodiment In accordance with the invention, the first separator separates the power supply transformer of the wind farm from the network. The first and / or the second separating device includes / suitably a circuit breaker and a voltage monitor with, preferably adjustable, Time Delay. Such separators are known in the art and can out individual voltage relays, time relays and reactive power directional relays be assembled. They are expediently programmable.

following is an embodiment of Invention explained in more detail with reference to the single figure.

The single figure shows a connection diagram for a connection of several to a wind farm WP combined wind turbines W1, W2 to a network N.

The network N is via a first circuit breaker 1 connected to the wind farm WP at a grid connection point NP.

Each wind turbine W1, W2 has a rotor 2 on, with a (not shown here) generator for generating electrical power, ie active and reactive power can be driven. The generator is via a second circuit breaker 3 with a transformer 4 connected. An undervoltage side of the transformer 4 is designated by the reference numeral U, a high-voltage side by the reference numeral O. The high-voltage side O of the transformer 4 is, if necessary, with the interposition of other circuit breakers 5 , via a mains connection transformer 6 with the first circuit breaker 1 connected.

The first circuit breaker 1 is connected to a first voltage monitor (not shown here). The first voltage monitor measures the mains voltage applied to the grid connection point NP. In addition, it is continuously determined whether reactive power is supplied from wind farm WP to grid N or vice versa. The first voltage monitor is set to a predetermined first limit value for the mains voltage and a predetermined value for the first time delay.

If the first limit value for the mains voltage is undershot and at the same time an inflow of reactive power from the grid N to the wind farm WP is detected, the first voltage monitor with the first time delay automatically opens the first circuit breaker 1 causes and thus the wind farm WP separated from the network N.

The second circuit breaker 3 is connected to a (not shown here) second voltage monitor, which has a generator voltage on the low voltage side U of the transformer 4 measures. The second voltage monitor is set to a predetermined second limit and a predetermined second time delay. If the measured generator voltage falls below the second limit value, the second power switch automatically becomes the second time delay 3 opened and thus the generator from the transformer 4 separated.

following becomes the method according to the invention explained in more detail.

The For example, grid N is at a voltage level with a grid voltage operated by 110 kV. In grid N, the grid voltage drops in the grid connection point NP below the limit from which z. B. 85% of the rated network voltage is, d. H. to a value of less than 110 kV × 0.85 = 93.5 kV.

The first voltage monitor monitoring the grid connection point NP is set to a first time delay of 0.5 seconds. If the drop of the mains voltage to the value of less than 93.5 kV lasts longer than 0.5 seconds and at the same time reactive power flows from the grid N to the wind farm WP, the first circuit breaker 1 opened and the wind farm WP separated from the network N.

If the shutdown conditions for the first voltage monitor are not met, the first circuit breaker remains 1 closed, ie the wind farm WP remains connected to the network N. The detected supply of reactive power counteracts the voltage drop in the network N and contributes to a stabilization of the network N.

At the same time, the respectively supplied generator voltages are checked with the second voltage monitors of the individual wind turbines W1, W2 and disconnected from the grid N when the second limit value falls below a predetermined second time delay. The procedure is as follows:
With the second voltage monitor, the generator voltage at the low voltage side U of the transformer 4 measured. If the applied generator voltage, the second limit, z. B. 525 V, is less than the second time delay, the second power switch 3 the affected wind turbine W1, W2 activated and opened.

at a wind farm WP with a plurality of wind turbines W1, W2 can the respective second voltage monitors on different second Time delay values be set, which expediently from a value range of 1.0 to 3.0 seconds from the Admission of the disorder selected are. For example, the second voltage monitor in a first quarter of the wind turbines W1, W2 to 1.5 seconds, in a second quarter to 1.8 seconds, in a third quarter to 2.1 seconds and a fourth quarter to 2.4 seconds be set. In this case, successively all those wind turbines can W1, W2 are separated from the network N, in spite of the already made separations the second limit of the generator voltage is still below becomes.

The inventive method allowed in easier and less expensive Way a dynamic and accurate metered response of wind turbines W1, W2 and wind farms WP in the event of a fault. It will be successive only those wind turbines W1, W2 separated from the network N, which the disorder do not counteract strong enough. This allows the network N in case of disorders quickly and simply stabilized.

1

first breakers

2

rotor

3

second breakers

4

transformer

5

Another breakers

6

Power supply transformer

N

network

NP

Grid connection point

O

HV side

U

Low Side

W1, W2

Wind turbine

WP

wind farm

Claims (31)

Method for operating at least one wind turbine (W1, W2) with one from a rotor ( 2 ), wherein the generator for transmitting active electrical power and reactive electrical power at a grid connection point (NP) is connected to a network (N) operated with a predetermined nominal line voltage, characterized in that at a fall of a mains voltage in the grid connection point (NP) a predetermined first limit of the rated network voltage and a simultaneous from the network (N) directed to the generator outflow of reactive power, the generator is automatically disconnected from the network (N). The method of claim 1, wherein the first threshold 85% of the rated network voltage. Method according to one of the preceding claims, wherein the mains voltage is the largest of the three chained mains voltages. Method according to one of the preceding claims, wherein the generator with a first time delay of at most 1 second, preferably 0.4 to 0.6 seconds, is disconnected from the network (N). Method according to one of the preceding claims, wherein the generator is automatically disconnected from the network (N) after the expiration of the first time delay and a simultaneous inflow of reactive power directed at the grid connection point (NP) to the grid (N), if one on a low-voltage side (U) a generator downstream of the transformer ( 4 ) generator voltage falls below a second limit, which is smaller than a lower value of a generator voltage band. Method according to one of the preceding claims, wherein the lower value of the generator voltage band is 5% below one Generator rated voltage is. Method according to one of the preceding claims, wherein the second limit is 0.8 times the lower value. Method according to one of claims 5 to 7, wherein the generator after a second time delay is disconnected from the network (N). The method of claim 8, wherein each wind turbine (W1, W2) a predetermined value for the further time delay is assigned. The method of claim 9, wherein the predetermined Value is selected from a group of predefined values. The method of claim 10, wherein the group for the further Time Delay contains the following values: 1.5, 1.8, 2.1, 2.4 seconds. Method according to one of claims 8 to 11, wherein a largest value the further time delay is less than 3.0 seconds. Method according to one of the preceding claims, wherein a plurality of wind turbines (W1, W2) to a wind farm (WP) summarized and together in the network connection point (NP) with the Network (N) are connected. Method according to one of claims 8 to 13, wherein the wind turbines (W1, W2) in groups according to the respective one Value of the further time delay time staggered from the network (N) are separated. Wind energy plant (W1, W2), in particular for carrying out the method according to one of the preceding claims, with one of a rotor ( 2 ), wherein the generator for transmitting electrical active power and reactive electrical power at a grid connection point (NP) is connected to a network (N) operated with a predetermined nominal line voltage, characterized in that a first disconnecting device ( 1 ) is provided for automatic disconnection of the generator from the network (N), which responds to a fall in a grid voltage in the grid connection point (NP) below a predetermined first limit of the nominal network voltage and a simultaneous from the network (N) directed to the generator outflow of reactive power. Wind turbine (W1, W2) according to claim 15, wherein the first limit is 85% of the nominal network voltage. Wind energy plant (W1, W2) according to claim 15 or 16, where the mains voltage is the largest of the three chained mains voltages is. A wind turbine (W1, W2) according to any one of claims 15 to 17, wherein the first separator (W1, W2) 1 ) is set so that the generator with a first time delay of at most 1 second, preferably 0.4 to 0.6 seconds, separated from the network (N). Wind turbine (W1, W2) according to one of claims 15 to 18, wherein a second separator ( 3 ) is provided for automatically disconnecting the generator from the network (N), which responds when a generator voltage on a low-voltage side (U) of a generator downstream of the transformer ( 4 ) is less than a second threshold which is less than a lower value of a generator voltage band. Wind turbine (W1, W2) according to claim 19, wherein the lower value of the generator voltage band is 5% below one Generator rated voltage is. Wind energy plant (W1, W2) according to claim 19 or 20, wherein the second limit is 0.8 times the lower value. Wind energy plant (W1, W2) according to one of claims 19 to 21, wherein the second separation device ( 3 ) is set so that the generator after a second time delay from the network (N) is disconnected. Wind turbine (W1, W2) according to claim 22, wherein each wind turbine (W1, W2) a predetermined value for the second Time delay assigned is. Wind turbine (W1, W2) according to claim 23, wherein the predetermined value is selected from a group of predetermined values. Wind energy plant (W1, W2) according to claim 24, wherein the group for the second time delay contains the following values: 1.5, 1.8, 2.1, 2.4 seconds. Wind energy plant (W1, W2) according to one of claims 22 to 25, being a greatest value the second time delay is less than 3.0 seconds. Wind energy plant (W1, W2) according to one of claims 22 to 26, wherein the second separating device ( 3 ) the generator from the transformer ( 4 ) separates. Wind energy plant (W1, W2) according to one of claims 15 to 27, wherein a plurality of wind turbines (W1, W2) to a Wind Farm (WP) summarized and together in the network connection point (NP) are connected to the network (N). Wind energy plant (W1, W2) according to one of claims 22 to 28, wherein the wind turbines (W1, W2) in groups according to the respective Value of the second time delay time staggered from the network (N) are separated. Wind turbine (W1, W2) according to claim 29, wherein the first separator ( 2 ) a mains connection transformer ( 6 ) of the wind farm (WP) separates from the grid (N). Wind energy plant (W1, W2) according to one of claims 15 to 30, wherein the first ( 1 ) and / or the second separating device ( 3 ) comprises / comprises a circuit breaker and a voltage monitor with, preferably adjustable, time delay.