METHOD FOR FEEDING ELECTRICAL POWER INTO AN ELECTRICAL SUPPLY GRID

Abstract

A method for exchanging electrical power between an infeed unit, in particular a wind power installation or a wind farm, and an electrical supply grid at a grid connection point is provided. The exchange comprises exchanging active and reactive power, and the exchange of the active power is controlled based on a frequency-dependent and voltage-dependent active power control function. The active power control function specifies an additional active power to be fed in based on a captured grid frequency and a captured grid voltage. The exchange of the reactive power is controlled based on a frequency-dependent and voltage-dependent reactive power control function, where the reactive power control function specifies an additional reactive power to be fed in based on the captured grid frequency and the captured grid voltage. The control functions are set based on at least one grid characteristic and/or at least one grid state of the grid.

Claims

1. A method for exchanging electrical power between an infeed device and an electrical supply grid at a grid connection point, wherein: the electrical supply grid has a variable grid voltage and a variable grid frequency and is associated with a nominal voltage and a nominal frequency, and the exchange of electrical power includes exchanging active and reactive power, and wherein the method comprises: controlling the exchange of the active power based on an active power control function that is frequency-dependent and voltage-dependent, wherein the active power control function sets an additional active power to be fed in, in addition to a basic active power value, based on a determined grid frequency and a determined grid voltage; and controlling the exchange of the reactive power based on a reactive power control function that is frequency-dependent and voltage-dependent, wherein the reactive power control function sets an additional reactive power to be fed in, in addition to a basic reactive power value, based on the determined grid frequency and the determined grid voltage, and the active power control function and the reactive power control function are each set based on: at least one grid characteristic, and/or at least one grid state of the electrical supply grid.

2. The method as claimed in claim 1, wherein the infeed device is a wind power installation, a wind farm or a photovoltaic installation.

3. The method as claimed in claim 1, wherein: the at least one grid characteristic is a static converter proportion, and the static converter proportion represents a ratio of: power capable of being fed into the electrical supply grid or a grid section of the electrical supply grid by converter-controlled infeed devices to an overall power capable of being fed into the electrical supply grid or the grid section by all infeed devices, and/or the at least one grid characteristic is a resistance to a reactance (R/X) ratio at the grid connection point.

4. The method as claimed in claim 3, wherein: the converter-controlled infeed devices include a wind power installation, a wind farm or a photovoltaic installation, and all infeed devices include a generator that is not converter-controlled or a power plant that is not converter controlled.

5. The method as claimed in claim 1, wherein the at least one grid state is: a grid fault, and/or switch positions for setting or adjusting a grid topology, and/or a dynamic converter proportion, wherein the dynamic converter proportion represents a ratio of: power fed into the electrical supply grid or a grid section of the electrical supply grid by converter-controlled infeed devices to an overall power fed into the electrical supply grid or the grid section by all infeed devices.

6. The method as claimed in claim 1, comprising: changing at least one control function, selected from the active power control function and the reactive power control function, or changing one or more control subfunctions of a plurality of control subfunctions of the at least one control function by: selecting the at least one control function or the one or more control subfunctions from a plurality of predetermined control functions, and/or changing a parameterization, and/or changing a functional characteristic, wherein the functional characteristic is at least one characteristic from a list including: a width and/or a position of a dead band range of the at least one control function or of the one or more control subfunctions, a limit value of the at least one control function or the one or more control subfunctions, and a gradient or a slope of the at least one control function or the one or more control subfunctions.

7. The method as claimed in claim 6, wherein selecting the at least one control function or the one or more control subfunctions from the plurality of predetermined control functions includes: selecting the at least one control function from a set of curves or a set of characteristic areas.

8. The method as claimed in claim 1, wherein at least one control function, selected from the active power control function and the reactive power control function, or one or more control subfunctions of a plurality of control subfunctions of the at least one control function varies based on a weighting or a weighting factor.

9. The method as claimed in claim 8, comprising: setting the at least one control function or the one or more control subfunctions by setting the weighting or the weighting factor.

10. The method as claimed in claim 1, comprising: implementing the active power control function using: an active power frequency function that is a first control subfunction of the active power frequency function and represents a relationship between the determined grid frequency and a first active power value, and an active power voltage function that is a second control subfunction of the active power voltage function and represents a relationship between the determined grid voltage and a second active power value, determining the additional active power based on the first and second active power values; setting the active power frequency function using an active power frequency weighting; setting the active power voltage function using an active power voltage weighting; and changing the first or second control subfunction by: changing at least one of the active power frequency weighting or the active power voltage weighting to cause an active power weighting quotient to change, wherein the active power weighting quotient is a quotient between the active power frequency weighting and the active power voltage weighting is changed.

11. The method as claimed in claim 10, wherein the additional reactive power is a sum of the first and second active power values.

12. The method as claimed in claim 1, comprising: implementing the reactive power control function using: a reactive power frequency function that is a first control subfunction of the reactive power control function and represents a relationship between the determined grid frequency and a first reactive power value, and a reactive power voltage function that is a second control subfunction of the reactive power control function and represents a relationship between the determined grid voltage and a second reactive power value; determining the additional reactive power based on the first and second reactive power values; setting the reactive power frequency function using a reactive power frequency weighting; setting the reactive power voltage function using a reactive power voltage weighting; and changing the first or second control subfunction by: changing at least one of the reactive power frequency weighting or the reactive power voltage weighting to cause a reactive power weighting quotient to change, wherein the reactive power weighting quotient is a quotient between the reactive power frequency weighting and the reactive power voltage weighting.

13. The method as claimed in claim 12, wherein the additional reactive power is a sum of the first and second reactive power values.

14. The method as claimed in claim 12, comprising: in response to a static converter proportion increasing or a dynamic converter proportion increasing, changing the first and second control subfunctions to: reduce an active power weighting quotient, and/or increase the reactive power weighting quotient, and/or reduce a magnitude of an active power ratio, wherein the active power ratio represents a ratio of an average normalized slope of an active power frequency function to an average normalized slope of an active power voltage function, and/or increase a magnitude of a reactive power ratio, wherein the reactive power ratio represents a ratio of an average normalized slope of the reactive power frequency function to a normalized reactive power voltage function.

15. The method as claimed in claim 14, wherein: the active power ratio represents a ratio of an average normalized slope of the active power frequency function to an average normalized slope of the active power voltage function, wherein: a slope of the active power frequency function is normalized to a quotient of a nominal power of the infeed device to a maximum permissible frequency deviation of the grid frequency from the nominal frequency, and a slope of the active power voltage function is normalized to a quotient of the nominal power of the infeed device to a maximum permissible voltage deviation of the grid voltage from the nominal voltage, and a magnitude of the active power ratio decreases in response to an increasing static converter proportion and/or an increasing dynamic converter proportion, and the magnitude of the active power ratio has a value that is less than 1 in response to the static converter proportion and/or the dynamic converter proportion reaching or exceeding 80%.

16. The method as claimed in claim 12, wherein: a reactive power ratio represents a ratio of an average normalized slope of the reactive power frequency function to a normalized reactive power voltage function, wherein a slope of the reactive power frequency function is normalized to a quotient of a nominal power of the infeed device to a maximum permissible frequency deviation of the grid frequency from the nominal frequency, and a slope of the reactive power voltage function is normalized to a quotient of a nominal power of the infeed device to a maximum permissible voltage deviation of the grid voltage from the nominal voltage, and a magnitude of the reactive power ratio increases in response to an increasing static converter proportion and/or in response to an increasing dynamic converter proportion, and the magnitude of the reactive power ratio has a value that is greater than 1 in response to the static converter proportion and/or the dynamic converter proportion reaching or exceeding 80%.

17. An infeed device for exchanging electrical power between the infeed device and an electrical supply grid at a grid connection point, wherein the electrical supply grid has a variable grid voltage and a variable grid frequency and is associated with a nominal voltage and a nominal frequency, and wherein the infeed device comprises: a controller configured to: control the exchange of the electrical power, wherein the exchange of electrical power includes exchanging active and reactive power; control the exchange of the active power based on an active power control function that is frequency-dependent and voltage-dependent, wherein the active power control function sets an additional active power to be fed in, in addition to a basic active power value, based on a determined grid frequency and a determined grid voltage; control the exchange of the reactive power based on a reactive power control function that is frequency-dependent and voltage-dependent, wherein the reactive power control function sets an additional reactive power to be fed in, in addition to a basic reactive power value, based on the determined grid frequency and the determined grid voltage, and the active power control function and the reactive power control function are each set based on:  at least one grid characteristic; and/or  at least one grid state of the electrical supply grid.

18. The infeed device as claimed in claim 17, comprising: one or more converters configured to exchange the electrical power with the electrical supply grid, wherein the controller is configured to control the one or more converters.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0124] The invention is explained in more detail below by way of example on the basis of embodiments with reference to the accompanying figures:

[0125] FIG. 1 shows a perspective illustration of a wind power installation.

[0126] FIG. 2 shows a schematic illustration of a wind farm.

[0127] FIG. 3 shows a schematic control structure for carrying out a proposed method.

[0128] FIG. 4A shows a control subfunction for determining an additional active power.

[0129] FIG. 4B shows a control subfunction for determining an additional active power.

[0130] FIG. 5A shows a control subfunction for determining an additional reactive power.

[0131] FIG. 5B shows a control subfunction for determining an additional reactive power.

[0132] FIG. 6 shows a simplified illustration of a generalized grid section of an electrical supply grid.

DETAILED DESCRIPTION

[0133] FIG. 1 shows a perspective illustration of a wind power installation. The wind power installation 100 has a tower 102 and a nacelle 104 on the tower 102. An aerodynamic rotor 106 having three rotor blades 108 and spinner 110 is provided on the nacelle 104. The aerodynamic rotor 106 is caused to rotate by the wind during operation of the wind power installation and therefore also rotates an electrodynamic rotor of a generator which is directly or indirectly coupled to the aerodynamic rotor 106. The electrical generator is arranged in the nacelle 104 and generates electrical energy. The pitch angles of the rotor blades 108 can be changed by means of pitch motors on the rotor blade roots 109 of the respective rotor blades 108.

[0134] In this case, the wind power installation 100 has an electrical generator 101 which is indicated in the nacelle 104. The generator 101 can be used to generate electrical power. In order to feed in electrical power, provision is made of an infeed unit (infeed device) 105 which may be in the form of an inverter, in particular. A three-phase infeed current and/or a three-phase infeed voltage can therefore be generated according to amplitude, frequency and phase for feeding in at a grid connection point PCC. This may be carried out directly or together with further wind power installations in a wind farm. An installation controller 103 is provided for the purpose of controlling the wind power installation 100 and also the infeed unit 105. The installation controller 103 may also receive specified values from the outside, in particular from a central farm computer.

[0135] FIG. 2 shows a wind farm 112 having, by way of example, three wind power installations 100 which may be identical or different. The three wind power installations 100 are therefore representative of fundamentally any desired number of wind power installations in a wind farm 112. The wind power installations 100 provide their power, specifically in particular the generated current, via an electrical farm grid 114. In this case, the respectively generated currents or powers of the individual wind power installations 100 are added and are fed into the supply grid 120 at the infeed point 118, which is also generally referred to as the PCC. A transformer 116 is usually provided and steps up the voltage in the farm at the infeed point 118. FIG. 2 is only a simplified illustration of a wind farm 112. The farm grid 114, for example, may have a different configuration by virtue of there also being a transformer, for example, at the output of each wind power installation 100, to name just one other exemplary embodiment.

[0136] The wind farm 112 also has a central farm computer 122 which can synonymously also be referred to as a central farm controller. It can be connected to the wind power installations 100 via data lines 124, or in a wireless manner, in order to thereby interchange data with the wind power installations and, in particular, to receive measured values from the wind power installations 100 and to transmit control values to the wind power installations 100.

[0137] FIG. 3 shows a control structure for controlling, in particular specifying, power to be exchanged with the electrical supply grid. The control structure (e.g., controller) 300 exhibits a power specification block 302 which specifies an active power basic value PG. This can be effected in response to a request and/or on the basis of available power. If it is effected on the basis of available power, specifically wind power, in particular in the case of wind power installations, this need not mean that the active power value PG corresponds to the maximum available power at that moment. The value may also be selected to be lower in order to specifically provide potential room for action for further power components. Furthermore, provision is made of an active power frequency block 304 which comprises an active power frequency function P(f) in order to determine a first active power value P.sub.1 on the basis of the captured grid frequency f.

[0138] Provision is also made of an active power voltage block 306 which comprises an active power voltage function P(V) in order to determine a second active power value P.sub.2 on the basis of the captured grid voltage V. The first active power value and the second active power value are then added at the first summation point 308 to form an additional active power P.sub.z to be additionally fed in.

[0139] That active power frequency block 304 and the active power voltage block 306, together with the second summation point 308, therefore implement an active power control function. The three elements mentioned can therefore be combined to form an active power control block 310. Accordingly, the active power control block 310 is illustrated as a dashed block which combines the three elements mentioned.

[0140] The active power control block 310 therefore outputs the additional active power P.sub.z on the basis of the captured grid frequency f and the captured grid voltage v. This is added to the active power basic value P.sub.G at the second summation point 312, thus resulting in the active power P to be fed in overall.

[0141] The procedure is very similar for taking the reactive power into account. Provision is made here of a reactive power frequency block 314 which comprises a reactive power frequency function. It therefore determines a first reactive power value Q.sub.1 on the basis of the captured grid frequency f. A reactive power voltage block 316 determines a second reactive power value Q.sub.2 on the basis of the captured grid frequency. For this purpose, the reactive power voltage block 316 comprises a reactive power voltage function. The first and second reactive power values Q.sub.1 and Q.sub.2 are added at the third summation point 318 to form the additional reactive power Q.sub.z.

[0142] The reactive power frequency block 314, the reactive power voltage block 316 and the third summation point 318 can therefore be logically combined to form a reactive power control block 320. The reactive power control block therefore implements the method of operation of a reactive power control function.

[0143] For the reactive power, provision is often not made for a reactive power basic value that differs from 0 to actually exist or to be additionally specified. Therefore, no equivalent to the power specification block 302 for the active power is provided here for the reactive power. However, such a block may nevertheless be provided if a reactive power basic value is additionally intended to be specified. This could then be added to the additional reactive power value Q.sub.z. However, if such a reactive power basic value is not available, as in the variant shown in FIG. 3, the additional reactive power Q.sub.z corresponds to the reactive power Q to be fed in or exchanged.

[0144] The active power P to be fed in and the reactive power Q to be fed in are then transformed or converted into a current Ito be fed in in the conversion block 322. In this case, the current Ito be fed in is characterized by its amplitude and additionally by its phase angle φ. Accordingly, the result from the conversion block 322 is a current to be fed in according to amplitude I and phase φ. This result can be passed to a converter which generates a corresponding current according to magnitude and phase and feeds it into or takes it from the electrical supply grid.

[0145] FIG. 4A shows an example active power frequency function. FIG. 4A shows an example active power voltage function. FIG. 4A represents an active power frequency function P(f). It indicates a relationship between the captured grid frequency f and a first active power value P.sub.1. At the origin of the representation, the first active power value is 0 and the frequency f is nominal frequency f.sub.N. There is also a dead band range there between the frequency values f′.sub.1 and f.sub.1. This dead band range 402 can be changed, both in terms of its width and in terms of its position, by changing the frequency values f′.sub.1 and f.sub.1. However, the dead band range 402 is often symmetrical with respect to the origin, that is to say with respect to the nominal frequency f.sub.N.

[0146] Otherwise, this active power frequency function P(f) at the lowermost frequency f′.sub.2 falls continuously from the nominal power value P.sub.N to 0 at the lower dead band frequency f.sub.1′. After the dead band range 402, the active power frequency function P(f) falls to the value −P.sub.N, specifically from the upper dead band frequency f.sub.1 to the uppermost frequency f.sub.2.

[0147] The active power frequency function P(f) shown can be considered to be a basic function which can be weighted for use. In particular, it can be weighted, for weighting, with an active power frequency weighting G.sub.P1 which is provided here as a factor. The result is then a modified active power frequency function P*(f) which is illustrated using dashed lines in FIG. 4A. There is no difference in the dead band range 402.

[0148] In the illustration of FIG. 4A, the weighting factor approximately has the value 0.5 (G.sub.P1=0.5).

[0149] FIG. 4B illustrates an active power voltage function P(V). The active power voltage function P(V) likewise has a dead band range 404. The latter is between the lower dead band voltage V′.sub.1 and the upper dead band voltage V.sub.1. Otherwise, the active power voltage function P(V) is such that it falls from the lowermost voltage V′.sub.2 at nominal power P.sub.N to 0 at the lower dead band voltage V′.sub.1. From the upper dead band voltage V.sub.1, it falls further to the uppermost voltage V.sub.2 at negative nominal power −P.sub.N.

[0150] In this case too, the active power voltage function P(V) is intended to form a basic function which is also intended to be weighted with an active power voltage weighting which is also implemented here as a weighting factor G.sub.P2. Accordingly, the result is the modified active power voltage function P*(V).

[0151] In this case too, the weighting factor P.sub.P2 approximately has the value 0.5, which results in a flattening of the modified active power voltage function P*(V) with respect to the unmodified active power voltage function P(V).

[0152] An approach has been proposed here in which both the unmodified active power frequency function P(f) and the unmodified active power voltage function P(V) have been selected to have a maximum value, specifically such that they extend to the nominal power P.sub.N and to the negative value of the nominal power −P.sub.N. For use, they can be multiplied by the respective weighting factor which is proposed here to be a value between 0 and 1.

[0153] In particular, it is proposed that the active power frequency weighting factor G.sub.P1 and the active power voltage weighting factor G.sub.P2 in total result in a maximum of 1. The reason for this can be explained on the basis of the comparison of FIGS. 4A and 4B.

[0154] As a result of the fact that both functions are multiplied by a weighting factor of <1, both functions are flattened. As a result of the fact that the sum of the two weighting functions should not exceed the value 1, at most the value of the nominal power P.sub.N also results, in terms of magnitude, during the sum of the functions. It naturally also comes into consideration that even reaching nominal power is not desirable, in particular because the additional active power P determined thereby is also intended to be added to an active power basic value PG, as can be gathered from the control structure 300 in FIG. 3. Accordingly, the weightings can be selected in such a manner that in total they are below, in particular considerably below, the value 1.

[0155] It can likewise be discerned that the corresponding function or the characteristic curve illustrated therefor in the graph becomes flatter, that is to say its slope falls, as a result of the multiplication by the respective weighting factor. For the example illustrated in Figures A and 4B4, the two weighting factors G.sub.P1 and G.sub.P2 are intended to be the same, specifically 0.5. Accordingly, the two modified functions, that is to say the modified active power frequency function P*(f) and the modified active power voltage function P*(V), are also flatter and have a flatter slope. They have the same slope, at least according to the selected representation. Since, apart from the respective dead band range, only one slope is present here, this slope is also simultaneously the average slope in each case.

[0156] In order to now assess the weighting, a quotient of these two slopes may be formed and, since they are the same in the selected example in FIGS. 4A and 4B, this quotient has a factor of 1. The two weighting factors are likewise the same and their quotient is likewise 1. The ratio of the two weighting factors and the ratio of the two slopes can therefore lead to the same or a similar result. If the functions were more complex, differences could naturally arise.

[0157] In any case, the same values are selected here for the two weighting factors and the two functions have the same slopes and this is proposed, according to one embodiment, for a small proportion of conventional infeed units in the electrical supply grid. It is also proposed, in particular, if the static converter proportion and/or the dynamic converter proportion is/are at least 80%.

[0158] FIGS. 5A and 5B correspond to FIGS. 4A and 4B, but functions for the reactive power are shown. Therefore, FIG. 5A shows a reactive power frequency function Q(f) and FIG. 5B shows a reactive power voltage function Q(V). The amplitudes are also here each normalized to nominal power P.sub.N, as in FIGS. 4A and 4B. In physical terms, although the unit for reactive power Q differs from the unit for active power P, the value of the nominal power P.sub.N can nevertheless also be used to normalize the reactive power functions Q(f) and Q(V).

[0159] In FIG. 5A, the same values as in FIG. 4A have been selected as frequency values, specifically a lowermost frequency f′.sub.2, a lower dead band frequency f′.sub.1, an upper dead band frequency f.sub.1 and an uppermost frequency f.sub.2. A dead band range 502 is likewise provided and the reactive power frequency function Q(f) therefore respectively indicates a first reactive power value Q.sub.1 on the basis of the captured grid frequency f. The profiles likewise analogously correspond to the active power frequency function P(f) in FIG. 4A. However, they may also be different and other frequency values may also be used. However, it is preferably proposed to use similar or analogously identical functions, as illustrated in FIGS. 4A, 4B, 5A and 5B.

[0160] It is likewise proposed to use the reactive power frequency function Q(f) as a basic function or unmodified reactive power frequency function. It can then be multiplied by a reactive power voltage weighting factor G.sub.Q1 which may be between 0 and 1 in order to thereby flatten the reactive power frequency function Q(f). The modified reactive power frequency function Q*(f) is illustrated using dashed lines in FIG. 5A.

[0161] A corresponding situation is also proposed for the reactive power voltage function Q(V) which, for weighting, is multiplied by a reactive power voltage weighting factor G.sub.Q2. This factor should be between 0 and 1 and results in a flattening of the reactive power voltage function Q(V). The result is the modified reactive power voltage function Q*(V).

[0162] In this case too, it is preferably proposed that the two weighting factors G.sub.Q1 and G.sub.Q2 in total do not exceed the value 1.

[0163] In particular, the reactive power frequency function Q(f) and the reactive power voltage function Q(V) may each be weighted differently by means of these weightings, that is to say in particular these two weighting factors G.sub.Q1 and G.sub.Q2. This makes it possible to vary the influence of the captured grid frequency f, on the one hand, and the captured grid voltage V, on the other hand.

[0164] In particular, the influence of the frequency may be selected to be large and the influence of the voltage may be selected to be small or vice versa depending on a grid state and/or a grid characteristic.

[0165] The same moreover also applies to the two weighting factors G.sub.P1 and G.sub.P2 in FIGS. 4A and 4B or the functions explained there.

[0166] Moreover, the same voltage axis as in FIG. 4B has also been selected in FIG. 5B. A lowermost voltage value V′.sub.2, a lower dead band voltage value V′.sub.1, an upper dead band voltage value V.sub.1 and an uppermost voltage value V.sub.2 are therefore also provided. A dead band range 504 is likewise provided.

[0167] FIG. 6 symbolically shows a grid section 600. In this case, the grid section 600 has an equivalent voltage source 602. An equivalent voltage source 602 indicates an idealized voltage source with a fixed voltage. In this sense, the equivalent voltage source 602 indicates the fixed grid voltage V.sub.G. The voltage from an equivalent voltage source 602 is assumed to be fixed, that is to say does not change as a result of the connection. Effects caused by a connection or load are taken into account by further elements.

[0168] The grid impedance Z.sub.G is such a connection which is specifically connected between the equivalent voltage source 602 and the grid connection point P.sub.CC. The wind power installation 604 is connected to the grid connection point P.sub.CC and therefore feeds power into the electrical supply grid or the grid section 600 via this grid connection point P.sub.CC. In this respect, it feeds in an infeed current I.sub.G. The result is a grid connection point voltage V.sub.CC at the grid connection point P.sub.CC. This depends on the equivalent voltage source 602 or the grid voltage V.sub.G and the grid impedance Z.sub.G and the current IG which has been fed in.

[0169] It is therefore proposed to consider this grid impedance Z.sub.G which specifically influences the feeding-in by the infeed unit, that is to say the wind power installation 604 here.

[0170] In this case, it has been recognized, in particular, that the magnitude of the ratio of non-reactive resistance R to reactance X, that is to say the magnitude of the ratio of the resistance R to the reactance X, may be relevant. The smaller this ratio, the more dominant the reactance X and the greater a phase shift at the grid impedance Z.sub.G when feeding in the infeed current I.sub.G.

[0171] It is therefore proposed, in particular, to take this ratio into account; in particular, such an R/X ratio is a grid characteristic and is preferably intended to be taken into account when setting the active power control function and the reactive power control function.

[0172] Described herein is expanding conventional phase angle control and power control in order to function both in conventional electrical supply grids, in which there is a high proportion of conventional infeed units, and in grids with a high penetration of converters. This is achieved by means of a multiply weighted function which changes the weighting and/or the characteristic depending on a grid state variable. In addition to a grid state variable, at least one grid characteristic may also be taken into account for the purpose of changing this weighting of the multiply weighted functions and/or for the purpose of changing their characteristic.

[0173] A penetration of converters may be taken into account using a static converter proportion or a dynamic converter proportion.

[0174] In particular, the described solution is proposed for converter-controlled infeed units, in particular converter-controlled regenerative infeed units. Converter-controlled infeed units may synonymously also be referred to as converter-based infeed units. Infeed units may synonymously also be referred to as infeed apparatuses or infeed devices.

[0175] The proposed method is proposed both for conventional electrical supply grids and for electrical supply grids which have a high penetration of converters or have a high static and/or dynamic converter proportion.

[0176] It has been recognized, in particular, that grid support measures may have a different effect depending on the grid characteristic. Conventional grids which therefore have exclusively or predominantly conventional infeed units react to a power change almost exclusively in terms of a frequency and to a reactive power change in terms of the voltage. In the case of a very high penetration of converters, that is to say a small proportion of conventional infeed apparatuses, this dependence may be shifted, however, to a dependence of the frequency on the reactive power and a dependence of the voltage on the active power. In between, both the grid frequency and the grid voltage may have a dual dependence and may each depend both on the active power and on the reactive power.

[0177] An important point of the underlying idea is to perform both phase angle control and active power control with multiple dependence on the basis of the grid state. The phase angle control controls or regulates a phase angle of the current to be fed in and therefore a reactive power component. The weighting and/or the functional characteristic of both the phase angle control, that is to say the reactive power control, and the active power control can therefore be set in this case on the basis of the grid state.

[0178] FIGS. 4A, 4B, 5A and 5B illustrate, in particular, an adaptation with the aid of a weighting. However, a change of the dead band ranges is a change in the functional characteristic. The dead band ranges can accordingly be changed by changing the lower and upper dead band frequencies or the lower and upper dead band voltages. As a result, the functional characteristic can be changed.

[0179] However, it naturally also comes into consideration to carry out both types of change, that is to say both a change using the weighting and simultaneously a change of the dead bands or another change. For example, instead of a straight slope, the branch before and after the respective dead band range can also be selected differently than using a linear function. One possibility would be to take a quadratic function as a basis, that is to say to specify the characteristic curve branch on the basis of a square of the frequency or voltage, to name just one example. However, a piecewise composition, specifically in addition to the piecewise composition of the two oblique arms shown and of the dead band range, also comes into consideration. Each oblique arm may have, for example, two different slope regions, to name a further example.

[0180] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.