EP3991264A1

EP3991264A1 - Method for optimizing the active power supply of a wind farm

Info

Publication number: EP3991264A1
Application number: EP20734931.7A
Authority: EP
Inventors: Eckard Quitmann
Original assignee: Wobben Properties GmbH
Current assignee: Wobben Properties GmbH
Priority date: 2019-06-26
Filing date: 2020-06-25
Publication date: 2022-05-04
Also published as: WO2020260504A1; CN114026763A; CA3143410A1; US20220263320A1; CA3143410C; US11764582B2; DE102019117169A1

Abstract

The invention relates to a method for supplying electrical power to an electrical supply grid at a grid connection point (118) by means of a wind farm (112) having a plurality of wind turbines (100), wherein the wind turbines (100) are connected to the grid connection point (118) by transmission means; a farm controller is provided for transmitting active and reactive power specifications to the wind turbines (100); a first power range (401) is specified at each of the wind turbines (100), which first power range spans a value range for active and reactive power to be supplied, and which can differ between the wind turbines (100), wherein the first power range (401) has an active power limit (411) to be maintained by the wind turbine (100) and a reactive power limit which is achievable by the wind turbine; a second power range (402) is specified at the grid connection point (118), which second power range spans a value range for active and reactive power to be supplied, wherein the second power range (402) has an active power limit (411) to be maintained by the wind farm at the grid connection point (118) and a reactive power limit which is achievable by the wind farm at the grid connection point (118); at least one, a plurality or all of the wind turbines (100) generate active and reactive power, in each case in consideration of the specifications of the farm controller, and transfer said active and reactive power to the grid connection point (118), said one, plurality or all of the wind turbines each exceeding the active power limit (411) thereof of the first power range (401), wherein the active power limit (411) to be maintained is exceeded in each case such that the second power range (402) is maintained at the grid connection point (118) by the wind farm.

Description

PROCESS FOR OPTIMIZING THE ACTIVE POWER INFEED IN A WIND FARM

The present invention relates to a method for feeding electrical power into an electrical supply network by means of a wind farm. The invention also relates to a wind farm which can carry out such a method.

Wind energy plants are known; they generate electrical power from wind and feed this into an electrical supply network. Often, several wind turbines are combined in a wind farm that feed into the electrical supply network via a common network connection point. Such a common network connection point can in particular have what is known as a network transformer, via which the electrical supply network is fed, even if this is not absolutely necessary. The grid connection point can also be referred to as a feed-in point. In any case, such network connection points are designed for a feed-in power that must not be exceeded. Exceeding this would often lead to the triggering of a safety device; in particular, the feed would be interrupted by a mains disconnector in such a case. The maximum feed-in power is usually contractually agreed with the network operator.

In order to be able to ensure compliance with the designed feed-in power, the wind turbines are dimensioned or adjusted accordingly to this power limit at the grid connection point, or the power limit at the grid connection point is matched to the total power of the wind turbines in the park when it was planned. In the simplest and most illustrative case, this can mean that the wind turbines in the wind farm are designed in such a way that, when the wind speed is nominal, they all together generate exactly as much power as can and may be fed in at the grid connection point.

The respective operating setting of each wind energy installation often takes into account not only the real power that can be generated, but also that an exchange of reactive power that may be required by the network operator can also be guaranteed. Every wind turbine is designed to feed in a predetermined active power under corresponding wind conditions while at the same time being able to feed in correct reactive power. The reactive power can be fed in or taken up, which corresponds to the behavior of an overexcited or underexcited synchronous generator. In the following, the term reactive power feed is used for the sake of simplicity, which includes feed and consumption. However, if the potentially available reactive power is not called up at an operating point, even at nominal wind speed, a wind turbine could still increase its feed-in active power, which, however, could prevent compliance with the active power limit of the grid connection point. The wind power plant in question would then not be optimally used, at least as long as the potentially available reactive power is not called up.

A remedy could be created by increasing the power limit of the grid connection point. Such a measure can, however, be very costly and sometimes it can also be impossible, namely if the power limit of the network connection point is limited by the properties of the electrical supply network in the area of this network connection point.

In the priority application for the present application, the German Patent and Trademark Office researched the following prior art: US 2014/0248123 A1;

DE 10 2005 032 693 A1; US 2016/0308369 A1 and US 2011/0133461 A1.

The present invention is therefore based on the object of addressing at least one of the problems mentioned above. In particular, a solution is to be proposed in which a network connection point is used as efficiently as possible when feeding electrical power. At least an alternative solution to previously known solutions should be proposed.

According to the invention a method according to claim 1 is proposed. Such a method thus relates to the feeding of electrical power into an electrical supply network. The feed-in is carried out at a grid connection point by means of a wind farm. Such a wind park has a number of wind energy installations and thus these, as intended, feed their power into the electrical supply network at one network connection point. To carry out the method, the wind turbines are connected to the grid connection point by transmission means. Such means of transmission are especially transmission lines (overhead lines or underground cables). But there are also, especially in addition, transformers that can be used to change a voltage level.

In addition, a park controller is provided for regulating active and reactive power specifications at the grid connection point, which transmits the active and reactive power specifications derived therefrom to the wind turbines. Such a park controller is therefore seen to perform a control for the wind park. In particular, the park regulator can be used to regulate power management. For this purpose, the farm controller has in particular a measuring device at the grid connection point, algorithms for analysis and calculation, and the option of sending active and reactive power specifications to one, several or all wind turbines in the wind farm. The active and reactive power specifications can, for example, be transmitted individually to each wind turbine as specific power values, or as percentage values, to name another example.

It is further proposed that a first power range is specified at each of the wind energy installations, which spans a range of values for an active and reactive power to be fed in, and which can differ between the wind energy installations. This first performance range is particularly predetermined by two limits. This is because it has an active power limit to be complied with by the wind energy installation, and a reactive power limit that can be achieved by the wind energy installation.

The real power limit to be complied with is therefore a limit which, in terms of its magnitude, specifies maximum values for the real power. These values should not be exceeded during operation. The achievable reactive power limit is a limit that the wind turbine must be able to reach. The wind turbine must therefore be able to feed in reactive power up to the reactive power limit if this is called up.

Particular attention is paid to the fact that these two limits can be related. In particular, the reactive power that can be achieved can depend on a set active power. Both the active power and the reactive power here basically refer to the power to be delivered by the wind energy installation. The relationship between these limits can be shown particularly in an active power / reactive power diagram and in this the limits form an area or enclose an area. For example, a reactive power limit can specify a minimum reactive power value that is to be achieved, which, however, only has to be able to be achieved within likewise specified active power limits or ranges. For example, it can be provided that this predetermined reactive power value does not have to be achieved with small active powers, but that, for example, the reactive power in kV Ar does not need to be greater than the active power in kW.

Furthermore, the method is designed in such a way that a second power range is specified at the grid connection point, which spans a range of values for active and reactive power to be fed in, the second power range having an active power limit to be observed by the wind farm at the grid connection point and one for the wind farm at the grid connection point has attainable reactive power limit.

Basically, a second power range is therefore specified at the network connection point in the same way as is specified as the first power range at a wind energy installation. However, the first performance range and the second performance range can differ in terms of the values and possibly also the type or shape. In particular, the power values of the second power range, both the active power limit to be complied with and the achievable reactive power limit at the grid connection point, will be greater, in particular many times greater, than the values at each wind energy installation. Ideally, what is mentioned here only for the purpose of explanation, each limit of the second power range could result from the sum of all corresponding limits of the first power range of the relevant wind power plants. In fact, this can only be assumed in an idealized way and influences of the means of transmission also play a role. The grid operator usually specifies the specific reactive power value a wind farm must achieve at the grid connection point in a certain situation. This point lies within the second performance range, the maximum range that the wind farm must be able to implement in principle.

All of these wind energy installations in the wind farm then work in such a way that they generate active and reactive power in each case, taking into account the specifications of the farm regulator, and transmit them to the grid connection point. It is also possible that, for example, a wind energy installation or several wind energy installations fail temporarily and then only the remaining wind energy installations generate corresponding active and reactive power and transmit it to the network connection point. At least one of the wind turbines should do that. Furthermore, it is provided that the individual wind turbines each exceed their effective power limit of the first power range to be observed. It can apply to all wind turbines, several wind turbines or at least one of the wind turbines. It is therefore proposed that at least one or more wind turbines specifically generate more power and transmit it to the grid connection point than is actually permitted or provided on the basis of the active power limit of the relevant first power range to be observed. The result is therefore that the wind energy installations, at least one wind energy installation, no longer comply with the first power range. To this end, however, it is proposed at the same time that the active power limit to be observed for the respective wind energy installation is exceeded in each case in such a way that the wind farm adheres to the second working area at the network connection point.

The first performance range is therefore deliberately exceeded, but the second performance range must be strictly adhered to. Here it was particularly recognized that it is even possible to exceed the first performance range without leaving the second performance range. It was particularly recognized here that the influence of the transmission means can result in a distortion of the power ranges, so that leaving the first power range does not have to lead to leaving the second power range. However, the wind turbines that each leave the first power range do so only taking into account the specifications of the park controller. In this way, these wind energy systems are at least guided by the park controller. In particular, the farm controller can monitor compliance with the second power range at the network connection point and, depending on this, transmit appropriate specifications, namely, particularly for the active and reactive power to be fed in, to the respective wind energy installations.

This can also mean in particular that the park controller records the active and reactive power currently fed in at the grid connection point and also determines a distance between this active / reactive power and the limits of the second power range and, depending on this, sets corresponding specifications for active and reactive power the respective wind turbines transmits. This can in particular also depend on what active and reactive power specifications were previously transmitted to the corresponding wind turbines. If, for example, it is recognized that the active power currently fed in at the network connection point could be increased by 10% due to the active power limit to be observed at the network connection point, this can be implemented, for example, in such a way that all active power specifications are increased by 10%. Each wind turbine then checks whether it can increase its active power by 10% or less and thereby exceed its first power range in a controlled manner. However, this is only an illustrative example and it can also be provided, for example, that a change in the active and reactive power specifications for the individual wind turbines is individual. It was also recognized that leaving the second power range, in particular exceeding the active power limit to be complied with at the grid connection point, must be avoided, and can often even lead to a compulsory separation of the wind farm from the electrical supply network. In particular, safety precautions can lead to the opening of corresponding safety contactors. However, such a consequence is not to be expected immediately with the respective wind turbines in the wind farm. It was also recognized that the design of the wind power plant, which includes such a specification, especially the active power limit to be complied with at the respective wind power plant, is always based on design limits, which, however, do not have to be present in the specific case. For example, an active power limit can be used to protect against overheating. However, such overheating is usually not achieved if an active power limit specified for protection is briefly exceeded. Depending on how much the active power limit is exceeded, it may even be acceptable to permanently exceed it, for example at particularly cold ambient temperatures. Whether such an effective power limit must always be strictly adhered to at a wind energy installation can depend on many factors, of which others are also described below, and is basically accessible to an individual assessment.

According to one embodiment, it is proposed that at least one, several or all of the wind turbines are each controlled in such a way that a reactive power limit of the first power range cannot be reached, whereas the wind farm can reach the reactive power limit of the second power range. The main consideration here is that the means of transmission have a particularly large influence on the transmission of reactive power. This can mean, for example, that an operating point on the wind turbine that is defined by the active power and reactive power that the wind turbine emits leads to a distortion due to the transmission to the grid connection point in such a way that this operating point of a wind turbine becomes an operating point at the grid connection point, which has a larger proportion of reactive power.

Furthermore, it was recognized that especially the output of a very high active power component of the wind energy installation, especially if this is above the active power limit of this wind energy installation, only enables the output of a comparatively low reactive power component. This can be caused, for example, by a current limitation that limits the apparent current. If a high active power is emitted and thus a high active current, the upper limit for the apparent current is almost reached and only a little additional reactive current can be emitted before the apparent current reaches the stated current limit.

The transmission of this apparent current via the transmission means to the network connection point can lead to a shift in the phase position of the current, for example due to an inductive behavior of the transmission line, which can lead to a higher reactive current component and thus reactive power component. This shift can lead to the fact that the wind turbine apparently does not or cannot provide sufficient reactive power, but due to the influence of the transmission infrastructure in relation to the grid connection point, sufficient reactive power is or could be provided.

This is also based on the knowledge that such a reactive power specification on the wind energy installation actually only serves to ensure sufficient reactive power at the network connection point. Frequently, such a reactive power output possibility, which could also be referred to as reactive power adjustment capability, is only required at the grid connection point, namely to support the local voltage of the electrical supply network. Compliance with such a reactive power limit at the wind energy installation can generally only have been specified as an indirect requirement for compliance with the achievable reactive power at the network connection point.

While the park regulator, or a sensor provided for this, immediately ensures compliance with the active power limit at the network connection point Measuring or evaluating a measurement can check, a different way is proposed for the reactive power to be maintained. In order to maintain the achievable reactive power at the network connection point, it is particularly proposed that the properties of the transmission means be taken into account arithmetically or in a simulation. For this purpose, the properties can be measured or derived from the physical conditions. A simulation can also be used to derive how long the corresponding transmission lines are and what electrical properties they have from the physical conditions. In addition or as an alternative, the phase angle obtained during a current and voltage measurement can be used to determine the transmission behavior with regard to the reactive power.

It is also possible that the change in this reactive power is derived by the transmission means from the output power of the wind energy installations and the reactive power established at the network connection point. To illustrate this with a simple example that assumes a linear behavior, a reactive power of 10% emitted by the wind turbine could lead to a reactive power at the grid connection point of 20%. If a reactive power of 40% has to be achieved at the grid connection point, this would mean that the wind turbine would have to achieve a reactive power of 20%.

According to one embodiment, it is proposed that at least one, several or all of the wind turbines are each controlled in such a way that they each output an output power with an active and a reactive power component for transmission to the grid connection point. To this end, it is proposed that the output power exceed the effective power limit of the first power range to be observed. The real power is therefore greater than would be permissible according to the first real power limit to be complied with at the wind energy installation according to the stationary design criteria.

In addition or as an alternative, it is proposed that the output power have an apparent power value which is so large that the reactive power limit of the first power range cannot be reached without reducing the active power component. In this case too, too large an active power component is thus generated and output at the wind energy installation. The fact that the active power component is too high can mean that it is below the active power limit to be observed, but leads to such a large apparent power value that the reactive power limit of the first power range, i.e. at the wind turbine, cannot be reached. The reactive power limit could only be reached if the active power component was reduced. However, there is also the possibility that the active power output is still so high that it exceeds the active power limit to be complied with at the wind turbine.

For both of these variants or at least one of them, however, it is proposed that the transmission means lead completely or partially to such a change in the output power that the second power range, that is to say the power range at the network connection point, is maintained. The active power generation and output at the wind energy installation are therefore deliberately exhausted and even overexcited, but in such a way that the resulting values at the grid connection point are maintained. For this purpose, a known property of the transmission means, in particular a topology of the wind park network, at least a part thereof, can be taken into account when generating the active and reactive power or outputting it to the wind energy installation. It is also possible, however, for the wind farm controller to report back current information about the situation at the grid connection point to the wind power plants and for them to control the described overstimulation of power generation and output as a function of this.

It was particularly recognized here that such over-stimulation, i.e. increasing the active power, is possible and thus the yield can be increased. In particular, a previous strict adherence to the first power range, that is to say the power range at the wind energy installation, has proven to be too cautious in some cases. In particular, it was also recognized here that an isolated consideration of active power on the one hand and reactive power on the other hand is not optimal and it is therefore proposed that the output power be considered with active and reactive power components, namely especially with regard to the first and second power ranges to be observed.

According to one embodiment, it is proposed that the transmission means reduce the output active power portion of the output power output for transmission through thermal consumption in such a way that the active power limit of the second power range is maintained. In particular, for example, ohmic losses or the ohmic behavior of the transmission medium can be known and taken into account when generating and outputting the active power portion of the individual wind energy installation when operating outside the first power range. It was particularly recognized here that active power might be wasted, i.e. less power is taken from the wind and converted into active electrical power than would be possible if such losses were not taken into account. In such a case, an active power range could be maintained at the wind turbine to allegedly protect the grid connection point, although ultimately less effective power arrives at the grid connection point and thus the active power range that would be possible at the grid connection point is not exhausted. It was recognized that exhausting the possible active power range at the grid connection point in this way can mean exceeding a limit at the wind energy installation. However, if it is permissible to exceed a limit for the active power to a certain extent, this can be a sensible option.

In addition or as an alternative, it is proposed that the transmission means lead to such a change in the reactive power portion of the output power output that the reactive power limit of the second power range is reached, i.e. in particular the reactive power value that is typically specified by the network operator and is within the reactive power limit of the second power range are to be achieved. Here, too, it was recognized that in some situations the reactive power limit at the wind turbine does not have to be reached because the transmission means, in particular, causes a phase shift of the transmitted current so that the reactive power limit of the second area, i.e. at the grid connection point, can still be reached. Here, too, a higher active power can be fed in, because to this extent active and reactive power are related and, if it is possible to reduce the reactive power, this can lead to an increase in the active power. According to one embodiment, it is proposed that the sum of all output powers of the wind turbines does not comply with the second power range before transmission by means of the transmission means, whereas the sum of all output powers transmitted to the grid connection point at the grid connection point complies with the second power range. This is based on the knowledge that it is possible, in particular, to adhere to the active power limit at the grid connection point, although all wind turbines together generate and transmit more active power to the grid connection point than would be permitted at the grid connection point. However, the same can also apply to the reactive power, namely insofar as it is possible that all wind energy installations together would not be able to reach the reactive power limit with the sum of their achievable reactive powers at the grid connection point and yet, after transmission via the wind farm's transmission means, the reactive power limit at the grid connection point can be reached.

According to one embodiment, it is proposed that one, several or all wind energy installations exceed their effective power limit of the first power range to be complied with, that is to say at the respective wind energy installation, depending on several test conditions. The active power limit to be observed in each case cannot be exceeded without further ado, but a special test is required to determine whether this is acceptable. As at least one test condition, compliance with a parking specification of the parking controller is proposed. The wind farm controller can thus specify how, for example, an active power upper limit is to be divided between the individual wind turbines. The wind energy installation then only exceeds the active power limit to be complied with, however, insofar as this test condition, namely here compliance with the park specification of the park controller, is guaranteed.

In addition or as an alternative, compliance with a system condition of the respective wind energy system is checked as at least one test condition. Such a system condition is explained in more detail below; it can relate, for example, to maintaining a maximum temperature on a component of the wind energy system. At least one parking specification and at least one system condition are preferably checked, that is to say both types of conditions are checked.

At least two system conditions are preferably checked. For example, it is therefore checked whether a temperature range is maintained on the wind energy installation and whether a mechanical load limit is observed on the wind energy installation. It was particularly recognized here that the active power limit to be observed in the first power range, i.e. at the wind turbine, should not be easily exceeded and that very different individual load limits must be taken into account, which can also be independent of one another, so that a single condition can be considered is insufficient or insufficient. In particular, it was recognized that, to stay with the above example, a mechanical limit can be adhered to without adhering to a thermal limit, and vice versa. Therefore, at least two plant conditions are preferably checked. According to one embodiment, it is proposed that the system condition is one of the conditions described below. If several system conditions are checked, this can be several of the conditions described below. One possible system condition is the maintenance of an extended power range at the respective wind energy system, which is at least partially larger than the first output range of the same wind energy system. A further one is thus placed around the first power range, which can thus ensure that when the first power range is exceeded, it is at least not exceeded to an arbitrary extent. A first safety limit can thus be created.

Another or different system condition can be maintaining a predetermined maximum temperature in the respective wind energy system. For this purpose, critical components can be considered, particularly for power generation or feed-in. This can be, for example, a temperature at a power semiconductor switch that is used for frequency inverting. A temperature at a winding of the generator can also be considered.

It was particularly recognized here that some of the power limitations that serve to protect the system are actually aimed at preventing overheating. In this respect, such power limitations are also useful to protect against overheating and should not be ignored carelessly. Nevertheless, in the light of the temperature in question or when several temperatures are taken into account, an excess of power may be permissible.

On the one hand, the idea plays a role here that an increased output, in particular associated with an increased current, does not immediately lead to overheating, because most systems are significantly slower with regard to their thermal behavior than with regard to their electrical behavior. In addition, temperature behavior also depends on ambient temperatures. For example, if the ambient temperatures are comparatively low, namely lower than a design temperature, a greater or longer increase in output may be acceptable before overheating occurs. A further or alternative condition is compliance with a predetermined maximum current in the respective wind energy installation. Such a maximum current can be a current be in the generator, especially a stator current. Such a current can create a specific load for corresponding elements, such as the generator in this example.

However, for example, an output current that the wind energy installation outputs can also be considered. This can also lead to immediate loads and it is therefore proposed that compliance with a predetermined maximum current be checked as a system condition.

As a further or alternative condition, compliance with a predetermined mechanical maximum load on the respective wind energy installation is proposed. The underlying idea here is that too high an active power output can also mean that a correspondingly high power is drawn from the wind. This leads to a corresponding mechanical load on the affected components. Particular mention should be made of the rotor blades and the rotor hub. In the case of gearless systems, an axle journal can also be considered, which carries the rotor hub together with the rotor blades, and which also carries the generator, at least the rotor of the generator. The transitions of the elements mentioned and also other attachments, especially of the generator on the rest of the nacelle, can also be mechanically heavily loaded with a high active power output.

It was also particularly recognized here that exceeding a mechanical limit is less tolerable than exceeding a power limit, which could only lead to a temperature increase after a time delay. In particular, it was recognized that exceeding the active power limit to be observed can at least temporarily lead to well-tolerable temperature values, particularly at ambient temperatures that are below the design temperatures, while at the same time it can lead to intolerable mechanical loads.

In addition, a strong mechanical load, especially if it leads to a break, cannot be tolerated even if it occurs only once, whereas thermal loads tend to reduce the service life of the wind power plant. This can be acceptable, especially if the reduction in service life leads to an overall service life that is still longer than the approved operating time. In particular, it is preferably proposed that the active power limit of the first power range is specified and / or monitored as a function of a predicted service life of the wind energy installation.

It is preferably proposed that the exceeding of the first power range while adhering to the extended power range is only permissible if at least one criterion of the previously explained system conditions, which in this respect form a list of conditions, is complied with. In particular, it is proposed that it is only permissible as long as at least two criteria in the list of conditions are complied with, and further preferably as long as all criteria in the list of conditions are complied with. In particular, a simplified test criterion is used here, in which the first performance range is limited by the further performance range being exceeded. In a first step, a safety limit is drawn for exceeding the limit. It is then additionally checked whether at least one of the further conditions is met and if the at least one condition, the several conditions or all other conditions are met, the first power range can be exceeded. As a result, additional active power can be fed in, while at the same time binding conditions are taken into account, thus avoiding a plant hazard. Of course, the criterion that the second power range is maintained at the grid connection point must also always be observed. This can be achieved, for example, by adhering to setpoints or limit values that the park controller transmits to the relevant wind energy installation.

It is therefore preferably proposed that the exceeding of the first power range while maintaining the extended power range, if the second power range at the network connection point is also observed, is always permissible if at least one of the criteria of the specified list of conditions is met, at least if several or all of them Criteria of the list of conditions are met. This enables a positive and final test. In particular, it was recognized that the conditions mentioned in the list of conditions, at least if all are complied with, can be sufficient to define such an exceptional situation for exceeding the first performance range.

In addition or as an alternative, it is proposed that the extended power range may be exceeded for a predetermined exceptional period of time if the predetermined maximum mechanical load is observed, and in particular the other criteria the list of conditions are complied with, or at least one of them. This means that even more power can be fed in if even the extended power range is exceeded. By adhering to the conditions, and especially by adhering to the predetermined maximum mechanical load, a risk to the system can be excluded.

In addition or as an alternative, it is proposed that the predetermined maximum temperature be predetermined as a function of a predetermined tolerance period. This is based in particular on the idea that too high a temperature can often lead to intolerable damage only in the event of a permanent load or at least prolonged load, and this predetermined time limit of the predetermined maximum painting temperature is therefore proposed by means of the predetermined tolerance period.

It is preferably proposed to improve this even further, namely to specify at least a first predetermined maximum temperature for a first predetermined tolerance period and to specify at least a second predetermined maximum temperature for a second predetermined tolerance period, the first predetermined maximum temperature being smaller than the second predetermined maximum temperature and the first vorbe certain tolerance period is greater than the second predetermined tolerance period. Different maximum temperatures, that is, temperature limit values, can be specified for different lengths of time. A first, longer tolerance period is predetermined for the first, smaller maximum temperature, and the second predetermined maximum temperature can be selected higher, but only for a shorter time, namely only for the shorter second predetermined tolerance period.

The underlying idea here is that, depending on the situation, namely particularly depending on the overall situation of the wind farm and / or at the grid connection point, sometimes a smaller increase in output can be more appropriate for a longer period of time, whereas in other situations there is not much time available and in this one as much power as possible should be fed in. If, for example, the exceeding of the power at the wind turbine is severely limited by a comparatively small margin due to compliance with the second power range at the network connection point, then a correspondingly small power increase would be more sensible, which is then preferably carried out for as long as possible. In addition or as an alternative, it is proposed that the predetermined maximum current may be exceeded for a predetermined second exception period if the predetermined maximum mechanical load is observed and in particular the other criteria of the list of conditions are observed. It was recognized that a time limit can also be useful for the maximum current. On the one hand, a high current, sometimes only after a long period of time, can cause damage that is no longer tolerable or impairment that is no longer tolerable, on the other hand, a high current can also lead to thermal stress, namely on an element, whose temperature is not measured so that the temperature cannot be checked and the current is monitored instead.

It was also recognized that a mechanical load should also be observed and it was particularly recognized that a high current can lead to a mechanical load. This is especially true with a high stator current, which can lead to a high generator torque. However, it can also apply to other currents which, for example, can indirectly lead to a high generator current and to a generator torque.

In addition or as an alternative, it is generally proposed that compliance with the maximum mechanical load that has been specified must always be guaranteed. This is based in particular on the knowledge that a temporal consideration, as is proposed for thermal loads and explained above, does not apply to mechanical loads. In addition, it was recognized that the mechanical load is only reached when the power is significantly exceeded, so that observing the mechanical maximum load allows a comparatively large excess, especially of the active power limit to be observed, but is comparatively intolerant for further excess or mechanical overload .

According to one embodiment, it is proposed that the park specification include at least one park specification value output to each wind energy installation. The park default value can be an active power maximum value to be observed by each wind power installation, or it can be a reactive power value to be achieved by each wind power installation. Several park default values can also be provided, of which at least one is the active power maximum value to be maintained, or has this as a value, and at least one other, which is the minimum reactive power value to be achieved by each wind energy installation, or has this value. To comply with the second performance range It is therefore proposed that the park controller generate corresponding park default values for this purpose and transmit at least one park default value to the wind energy plants.

For this purpose, it is preferably proposed that the at least one park default value is determined by the park controller as a function of the second power range and a current power fed in at the network connection point. The park controller therefore checks to what extent the second power range is currently being observed and can then adjust the park default values accordingly. If the park controller detects, for example, that active power is currently being fed in at the grid connection point that is 20% below an active power limit at the grid connection point, the park default value can be increased accordingly if it relates to the maximum active power value to be maintained. Provision is preferably made for an upper limit to be provided for such a variable maximum effective power value, which the park controller regularly redetermines.

The at least one parking default value is preferably output as a relative value. In particular, a percentage value that relates to the nominal power of the wind energy installation comes into consideration here. In this way, different wind turbine sizes can be taken into account in a simple manner. In particular, it can be provided here that the maximum active power value to be maintained for the individual wind energy installation is set to values of over 100% if the active power fed in at the network connection point is below an active power limit at the network connection point. A value of 120% can be provided as an upper limit, for example, at which it is assumed that each wind energy installation cannot or only maximally exceed its active power limit to be maintained. It is also possible to determine such a value through simulations or a corresponding system analysis. According to one embodiment, however, it can be proposed that the park target values, at least one of them, be determined individually for each wind energy installation. This makes it possible to specify specific power or reactive power values, but also with individual consideration it is possible to determine and output relative, in particular percentage values from the park controller. By using such individual values, it can be taken into account, for example, that different maximum values would be useful for different wind energy installations.

According to the invention, a wind farm is also proposed. Such a wind park has several wind energy plants and the wind park feeds at a network connection point into an electrical supply network. This grid connection point can be viewed as a boundary and part of the wind farm.

The wind farm has transmission means for connecting the wind energy installation to the network connection point and in particular the wind energy installations are connected to the network connection point via the transmission means. In particular, such transmission means are designed as transmission lines. But there can also be other elements such as transformers or switching means.

In addition, a park controller is provided, which is prepared to transmit active and reactive power specifications to the wind turbines. These active and reactive power specifications can be referred to as specifications of the park regulator. In this way, the farm controller can specify how much real power the wind turbines may generate and transmit and / or how much reactive power the wind turbines must be able to generate - and transmit.

Each of the wind power plants is characterized by a predetermined first power range which spans a range of values for active and reactive powers to be fed in, namely for this respective wind power plant. This first power range can differ between the wind turbines. If only identical wind energy installations are set up in the wind park, it is also possible that these first power ranges do not differ. This first power range is characterized in that it has an active power limit to be observed by the wind energy installation and that it has a reactive power limit that can be reached by the wind energy installation. With regard to the significance of these different limits, reference is also made to the statements made above on the embodiments of the method for feeding described above.

The grid connection point is characterized by a second specified power range that spans a range of values for the active and reactive power to be maintained, where the second power range has an active power limit to be maintained by the wind farm at the grid connection point and a reactive power limit that can be reached by the wind farm at the grid connection point. For explanation, reference is also made here to the above embodiments of the method for feeding. At least one, several or all of the wind power plants have a plant control which is each prepared to control the wind power plant in question as a function of the specifications of the park regulator. In particular, such a system control can be prepared, for example, have corresponding receiving devices, or be connected to such, to receive the specified specifications of the park controller and then, depending on them, to control the relevant wind energy system.

In addition, at least one feed device is provided in each case, which is prepared to generate active and reactive power depending on the specifications of the park controller, and to transmit it to the grid connection point. The system control is also prepared to control the respective wind energy system in such a way that it exceeds the active power limit of the first power range to be complied with and only exceeds the active power limit to be complied with in such a way that the wind farm complies with the second power range at the grid connection point. This can be achieved in particular by the fact that the wind energy installation adheres to the specifications of the park controller. It is particularly proposed here that the system control and the park regulator are prepared so that the wind energy system complies with the second power range at the network connection point. This can in particular be an interaction between the park specifications determined and transmitted by the park controller and the control of the respective wind energy installation carried out as a function thereof by means of the system control.

In particular, it is proposed that the wind farm is prepared to carry out at least one method in accordance with at least one of the embodiments described above. In particular, the park controller and / or the respective system control of the wind energy system is prepared accordingly for this. Such a preparation can ensure that corresponding process computers or control computers are provided on which the corresponding method or the corresponding part of the method is programmed. In addition, there are corresponding transmission means and / or evaluation means and / or sensors that enable or at least support the execution of these methods. The invention is explained in more detail below using exemplary embodiments with reference to the accompanying figures. 1 shows a wind energy installation in a perspective illustration.

2 shows a wind farm in a schematic representation.

Fig. 3 shows schematically a first and second power range in one

P-Q diagram. FIG. 1 shows a wind energy installation 100 with a tower 102 and a nacelle 104. A rotor 106 with three rotor blades 108 and a spinner 110 is arranged on the nacelle 104. The rotor 106 is set in rotation by the wind during operation and thereby drives a generator in the nacelle 104.

In addition, the wind energy installation 100 has a control unit 130 which is coupled to a communication unit 132 and has a communication interface 133 in order to communicate with a central park control unit. To detect an outside temperature, an outside temperature sensor 134 is also provided, which can transmit its measured values to the control unit 130 for evaluation, or which is activated by the control unit 130 for measurement. Furthermore, a transformer 136 is also provided, which is assigned to the wind energy installation 100 and can be referred to as a wind energy installation transformer.

FIG. 2 shows a wind park 112 with, by way of example, three wind energy installations 100, which can be the same or different. The three wind turbines 100 are therefore representative of basically any number of wind turbines in a wind park 112. The wind turbines 100 provide their output, namely in particular the generated electricity, via an electrical park network 114. The currents or powers generated in each case by the individual wind energy installations 100 are added up. In the case of wind farms with a grid connection point, which can also be referred to synonymously as a grid connection point, or PCC, a transformer 1 16 is provided on the high or extra high voltage grid, which steps up the voltage in the park, and then at the grid connection point 1 18 in the network of a Network operator 120 feed. FIG. 2 is only a simplified illustration of a wind farm 112, which, for example, shows no control, although a control is of course present. The park network 114 can also be designed differently, for example, in that, for example, a transformer is also present at the output of each wind energy installation 100, to name just one other exemplary embodiment. FIG. 2 also shows a central park control unit 140, which can also be referred to as a park controller or park controller. A parking measuring unit 141 is also provided which can measure the current and voltage at the network connection point 118. The active and reactive power currently fed in at grid connection point 1 18 can be recorded from this. The park control unit or the park regulator receive this information and can transmit setpoint values or other information to the individual wind energy plants 100 based thereon. The spatial separation shown in FIG. 2 is only used for better illustration, in which the transmission of setpoint values or other information is in the foreground. The parking control unit 140 and the parking measuring unit 141 can also be arranged at the same location, namely in particular at the feed point, and preferably form a unit. Figure 3 shows schematically two PQ diagrams, namely in the left representation a first power range 401 and in the right diagram a second power range 402. In particular, it should be made clear in the left diagram that the first power range 401 is increased by an active power limit 41 1 - is limited, which indicates the maximum active power in continuous operation and under design conditions. Usually this is the nominal power Pnenn. Above this, a possible raised area 416 is shown hatched. This can be used if necessary. In this increase range 416, the first power range 401 can therefore be left. But this is only possible for a short time and / or under certain boundary conditions such as generally low temperatures. It is only possible as long as the sum of all active powers, but taking into account the effects of change and / or distortion caused by the transmission means of the wind farm, does not leave the maximum active power limit of the second power range 402 at the grid connection point.

This raised area 416 forms an expanded power range and is limited at the top by a circular section which is limited by a maximum current load of power semiconductors of an inverter that generates the current. Correspondingly, this limit, shown approximately in dotted lines, forms a limit which is referred to here as the power semiconductor limit 460. Since this limit is given by the current level, it essentially forms a circle around the origin of the P-Q diagram. The phase angle of the current is basically irrelevant for this current limitation or the resulting current load.

The same applies to the continuous current limit 462, which is also drawn in, and which can be specified in particular by a transformer. This continuous current limit 462 is also shown at a distance from the circuit breaker limit 460 and thus at a distance from the increased area 416. If possible, it should not be reached or exceeded. The increase region 416 can also, additionally or alternatively, be predetermined by a first predetermined maximum temperature for a first predetermined tolerance period, wherein the continuous current limit 462 can then be predetermined by a second predetermined maximum temperature for a second predetermined tolerance period. In this case, a temperature limit up to the first predetermined maximum temperature can be exceeded for longer than up to the second predetermined maximum temperature. In addition, a mechanically determined limit 464 is drawn, which indicates a maximum effective power that is caused by an upper limit for mechanical loads, such as loads on the rotor blades, for example. This mechanically determined limit 464 describes a predetermined mechanical maximum load and thus essentially only relates to active power and is therefore designed as a horizontal line parallel to the Q-axis.

In addition to all the limits to be observed in accordance with the diagram on the left, it must be ensured that the second power range 402 is not left. The variant of the second power range 402 shown as an example in the right diagram in FIG. 3 has an active power lower limit 425 near the Q-axis, which essentially states that the feed-in of reactive power in a regulated form is only required from a certain minimum active power. However, such a lower limit is a special case, so that this limit does not have to exist in other embodiments. In this respect, this lower limit is irrelevant. In particular, a solution has now been created which enables a wind energy installation to be operated, at least for a short time, with an effective power above nominal power.

As a result, the best possible utilization of a P-Q actuating capacity of a wind energy installation can be achieved as a goal, while at the same time compliance with grid connection rules by the wind farm as a whole. In particular, this can also increase the yield of the wind power plants without endangering the fulfillment of grid connection rules (grid codes).

This also solved a problem in which the PQ diagram of the wind turbine was basically cut off horizontally at the nominal output. Operation above the rated output was therefore not permitted. However, it was recognized that such a strict limitation is not absolutely necessary. This limit for the nominal power is not absolutely necessary in every case for the fulfillment of regulations at the grid connection point (PCC), nor is operation with a momentary active power above the nominal power generally technically impossible, as has now been recognized. It has been recognized that if a wind turbine receives and can convert at least nominal wind, and at a point in time does not have to generate its reactive power, it can be operated at an operating point at which its active power P exceeds its nominal active power (Pnenn) can. To this end, it is proposed that a wind farm controller, i.e. a central farm control unit, at the same time ensure that the wind farm feeds in a total of the required reactive power at the grid connection point, while at the same time not exceeding the maximum permissible active power at the grid connection point of the wind farm.

For this purpose, it was also recognized that the active power of the individual wind turbines can be increased beyond their nominal power until at least the lowest of the following possible limits is reached: a. An active power limit of the generator. b. An apparent power limit of the converter used in the wind energy installation, a DC cable, or another element in the wind energy installation that limits the apparent power. c. An apparent power limit of a transformer assigned to the wind energy installation. d. A mechanical load limit that is particularly a load limit for the rotor blades or towers. For this purpose, it was also recognized that the utilization of thermal inertia, for example in the case of a generator or transformer, can even allow the component concerned to be temporarily overloaded. It was also recognized that the occurrence of nominal wind and simultaneous retrieval of a high or even maximum reactive power usually do not take place permanently together. In order to enable such increased operation, especially leaving the first power range without endangering, it is proposed to monitor all critical components thermally or mechanically and, if necessary, to reduce the active power operating point to a normal characteristic. It was also recognized that in a wind farm only very rarely do all wind turbines experience nominal wind at the same time and each deliver nominal active power (Pnenn), which can also be referred to as nominal power for simplicity and synonymy. The maximum reactive power is also rarely required from the wind farm at the grid connection point. Nevertheless, each individual wind turbine has so far been limited to its individual limits, especially to its individual nominal power PN as the upper limit, even if more active power could be fed in at the grid connection point according to the maximum active power of the wind farm (PN_WP) permitted by the network operator, because, for example, other winds Due to their wind conditions, energy plants do not use their maximum nominal power PN (PN_WEA) that can be generated.

It was taken into account that grid connection rules, which are also generally referred to as grid codes, generally refer to the maximum permissible feed-in power at the grid connection point of the wind farm. It is usually the case that for each active power operating point of the wind farm, a reactive power setting range specified by the network operator must be made available to the wind farm at the same time. Depending on the type of construction and electrical permits to be applied, it may be permissible that individual wind turbines are operated under certain circumstances with an output above their nominal output, as long as the wind farm as a whole complies with the requirements of the grid connection rules at the grid connection point. If these relationships are taken into account, which is proposed according to the invention, depending on the situation, more yield can be achieved for the wind farm. Better utilization of the generally different wind conditions in a wind farm can also be achieved.

In addition, the capacity of the network at the network connection point and in the upstream network for transporting power to consumers is better utilized. Specifically, the equipment at the network connection point and beyond can achieve a higher number of hours with high utilization, which in turn is economically advantageous for network operation.

The additional yield that can be achieved for a wind energy installation can depend on the frequency of strong wind conditions at the relevant location. The frequency with which the maximum reactive power is called up also plays a role, as does its temporal correlation with the wind conditions and the outside temperatures. If the working range of an individual wind turbine is limited to the nominal output, you can be sure that technical components will not be overloaded, but possibly the technically possible maximum will not be extracted from the hardware. In the meantime, a wind farm controller usually exists in every newly built wind farm. Retrofitting is usually technically possible even with old stocks. It makes it possible to ensure compliance with the grid code conditions, and in particular the maximum active power at the grid connection point, at all times, even if individual wind turbines are operated above their nominal power. It is therefore preferable to use it for this and to program it accordingly.

It is therefore proposed that the wind power installation be expressly permitted to be operated outside of a nominal P-Q setting range. In particular, it is proposed that if the current wind speed at the wind energy installation in question allows more active power than nominal power to be fed in, that this is done as long as other limiting factors do not prohibit this.

Such limiting factors are: a. A limitation within the wind turbine, for example if a generator magnetization has a maximum value; a deflection of the rotor blades has a maximum value, a transformer temperature has reached a maximum value, or a temperature of DC cables has reached a maximum value, to name just a few examples. In the case of electrical components that are in the power flow from the generator to the electrical supply network, i.e. to the network connection point, the rated current or a permanent maximum current is preferably not decisive, but the temperature can also be decisive and it is suggested that the temperature the component concerned to be monitored dynamically. b. A limitation signal from the wind farm controller to prevent a permissible total active power of the wind farm from being exceeded at the grid connection point. c. A reactive power to be taken into account that is requested by a network operator. The wind farm controller is prompted to give the individual wind energy systems corresponding control commands that lead to the corresponding reactive power output from the wind energy systems. It would have to be taken into account here whether the wind energy installation in question is already carrying the maximum apparent current at this moment. In this case, it is proposed to shift the working point accordingly, namely especially along a curve that indicates a maximum apparent power (a Smax curve). In this case, it is suggested that reactive power be prioritized, because this is usually a mandatory specification of the network operator, while active power feed-in is acceptably dependent on the current wind speed.

Claims

Expectations

1. A method for feeding electrical power into an electrical supply network at a network connection point (1 18) by means of a wind park (1 12) with a plurality of wind turbines (100), wherein

- the wind turbines (100) are connected to the grid connection point (1 18) by transmission means,

a park controller is provided for transferring active and reactive power specifications to the wind turbines (100),

a first power range (401) is specified at each of the wind energy installations (100), which has a range of values for active and

Reactive power spans, and which can differ between the wind turbines (100), the first power range (401) an active power limit (41 1) to be maintained by the wind turbine (100) and

- has a reactive power limit that can be achieved by the wind turbine,

a second power range (402) is specified at the grid connection point (1 18), which spans a range of values for active and reactive power to be fed in, the second power range (402)

- An active power limit (41 1) to be maintained by the wind farm at the grid connection point (1 18) and

has a reactive power limit that can be reached by the wind farm at the grid connection point (1 18),

at least one, several or all of the wind turbines (100) generate active and reactive power, each taking into account the specifications of the farm controller, and transmit it to the grid connection point (1 18),

these at least one, these several or all wind turbines each exceed their effective power limit (41 1) of the first power range (401) to be complied with, wherein

- the active power limit (41 1) to be observed is exceeded in each case in such a way that the wind farm maintains the second power range (402) at the grid connection point (1 18). 2. The method according to claim 1, characterized in that

At least one, several or all of the wind turbines (100) are each controlled in such a way that a reactive power limit of the first power range (401) cannot be reached, whereas the wind farm can reach the reactive power limit of the second power range (402), in particular namely, a reactive power value requested by a network operator (120) at a point in time can reach the reactive power limit.

3. The method according to claim 1 or 2,

characterized in that

at least one, several or all of the wind turbines (100) are each controlled in such a way that they each emit an output power with an active and a reactive power component for transmission to the grid connection point (1 18), wherein

the output power exceeds the effective power limit (41 1) of the first power range (401) to be complied with, and / or

the output power has an apparent power value that is so great that the reactive power limit of the first power range (401) cannot be reached without reducing the active power component, the transmission means leading to such a change in the output power in whole or in part that the second power range (402 ) is observed.

4. The method according to any one of the preceding claims,

characterized in that

- The transmission means reduces one or the output active power portion of an or the output power output for transmission by thermal consumption so that the active power limit (41 1) of the second power range (402) is complied with, and / or

the transmission medium leads to such a change in one or the reactive power component of a or the output power output that the

Reactive power limit of the second power range (402) is reached. 5. The method according to any one of the preceding claims, characterized in that

the sum of all output powers of the wind turbines (100) does not comply with the second power range (402) before transmission by means of the transmission means, whereas

the sum of all output power transferred to the grid connection point (1 18) at the grid connection point (1 18) complies with the second power range (402).

Method according to one of the preceding claims,

characterized in that

these at least one, these several or all wind energy installations (100) exceed their one effective power limit (41 1) of the first power range (401) to be maintained, in each case as a function of several test conditions, wherein

Compliance with a parking specification of the parking controller is checked as at least one test condition and / or

Compliance with a system condition of the respective wind energy system is checked as at least one test condition, wherein preferably at least one park specification and at least one system condition are checked and in particular

at least one parking requirement and at least two system conditions are checked.

Method according to one of the preceding claims,

characterized in that

one or the system condition is a condition selected from the condition list having:

Maintaining an extended power range at the respective wind power plant, which is at least partially larger than the first power range of the same wind power plant (100),

Maintaining a predetermined maximum temperature in the respective wind turbine,

Maintaining a predetermined maximum current in the respective wind energy installation (100), and

Compliance with a predetermined maximum mechanical load on the respective wind energy installation (100). 8. The method according to claim 7,

characterized in that

the respective wind energy installation (100) is controlled such that

Exceeding the first performance range (401) while maintaining the extended performance range is only permitted if at least one criterion of the list of conditions is met, in particular as long as at least two criteria, preferably all criteria of the list of conditions, are met,

the extended performance range may be exceeded for a predetermined exceptional period if the predetermined maximum mechanical load is observed and in particular the other criteria in the list of conditions are observed,

the predetermined maximum temperature is predetermined as a function of a predetermined tolerance period, in particular

- At least a first predetermined maximum temperature is specified for a first vorbe certain tolerance period and

at least one second predetermined maximum temperature is specified for a second predetermined tolerance period, wherein

the first predetermined maximum temperature is less than the second predetermined maximum temperature and the first predetermined tolerance period is greater than the second predetermined tolerance period,

the predetermined maximum current may be exceeded for a predetermined second exception period if the predetermined mechanical maximum load is observed and in particular the other criteria of the list of conditions are observed, and / or

Compliance with the predetermined maximum mechanical load must always be guaranteed.

9. The method according to any one of the preceding claims,

characterized in that

- one or the park specification at least one for each wind energy installation

(100) includes output parking default value, selected from the list having:

an active power maximum value to be maintained by each wind energy installation (100), and

- A minimum reactive power value to be achieved by each wind energy installation (100), wherein the at least one parking default value is determined by the parking controller as a function of the second power range (402) and a current power fed in at the grid connection point (1 18), and the at least one parking default value preferably as a relative value, in particular as a percentage value of a nominal power (Pnenn) of the Wind energy installation is output, and / or is determined individually for each wind energy installation.

10. Wind park with several wind turbines for feeding electrical power into an electrical supply network at a network connection point (1 18), including send

- Transmission means for connecting the wind turbines to the grid connection point (1 18),

a park controller for transmitting active and reactive power specifications to the wind turbines, whereby

Each of the wind turbines is characterized by a predetermined first power range (401), which spans a range of values for active and reactive power to be fed in, and which can differ between the wind turbines, the first power range (401) being one of the wind turbine (100) Active power limit to be observed (41 1) and

- has a reactive power limit that can be achieved by the wind energy installation (100),

the grid connection point (1 18) is characterized by a second predetermined power range that spans a range of values for active and reactive power to be fed in, the second power range (402) - one from the wind farm (1 12) at the grid connection point (1 18) being observed tending active power limit (41 1) and

has a reactive power limit that can be reached by the wind farm (1 12) at the grid connection point (1 18),

at least one, several or all of the wind energy installations (100) each have a system control which is prepared to control the wind energy installation (100) in question as a function of the specifications of the park regulator, and

each have a feed device that is prepared to generate active and reactive power depending on the specifications of the park controller and to transmit it to the grid connection point (1 18), the system control being prepared to to control the respective wind energy installation in such a way that they exceed their effective power limit (41 1) of the first power range (401) to be observed, and wherein

the system control and / or the park regulator are prepared to control the respective wind energy system (100) in such a way that the

Active power limit (41 1) is only exceeded in each case in such a way that the wind farm maintains the second power range (402) at the grid connection point (1 18).

1 1. Wind farm according to claim 1 0,

characterized in that

the wind farm (1 12) is prepared to carry out at least one method according to one of claims 1 to 9.