DE102013207816A1 - Method and system for controlling voltage and frequency in a utility network - Google Patents

Abstract

System and method for regulating voltage and frequency in a supply network with a central controller that maximizes a phase stability reserve and a voltage stability reserve by simultaneously setting an operating point of the supply network and controllers of the supply network distributed by controller parameters.

Description

The invention relates to a method and a system for controlling voltage and frequency in a supply network, in particular a low-voltage supply network having a plurality of nodes which are interconnected via supply lines.

Supply networks, in particular electrical power supply networks, serve to distribute electrical energy to consumers. Power supply networks or power supply networks have generators that generate electrical energy. This energy is transported via supply lines and consumed by consumers or loads. A power supply network may include multiple distribution networks connected to a transport network. The stresses in a transport network are much higher than in a distribution network to which consumers, such as households, are connected. While the transport network is a high voltage network that transports electrical energy over long distances, the distribution network is a medium or low voltage network with relatively low voltage levels. For the stability of a supply network, the rapid control or regulation of a voltage amplitude U of the network and a frequency f is indispensable. The utility network typically forms a meshed network with a plurality of nodes interconnected by utility lines. Each supply line has a certain resistance R and a certain reactance or inductance X. In high voltage networks, the ratio between the reactance and the impedance of a supply line is nearly zero. It is therefore possible to decouple the regulation of the voltage amplitude U and the line frequency f in such high-voltage networks, since the voltage amplitude is influenced mainly by the reactive power Q and the mains frequency mainly by the active power P. It is therefore possible in high-voltage networks to use distributed proportional controllers which set an active power P as a function of the locally measured network frequency f and a reactive power Q as a function of a locally measured voltage amplitude. This decoupling of the voltage and frequency control is possible due to the fact that the ratio between the reactance and impedance in the supply line of the high voltage network is low.

However, in the medium and low voltage networks, the ratio between the resistance R and the reactance X of a supply line is not negligible and may in many cases be greater than one. Therefore, the voltage and frequency depend on both the real power P and the reactive power Q. Consequently, the resulting voltage and frequency dynamics depend on each other, i. It is a so-called MIMO (Multiple Input Multiple Output) system. Therefore, for such a MIMO system it is possible to decouple the active and reactive power control P (f) and Q (u), but the analysis and design of such regulators requires the analysis of a complete MIMO system, i. both the voltage and frequency dynamics. Therefore, the conventional techniques for designing regulators used in high and medium voltage power networks can not be used for low voltage power network regulators. Conventional regulators can also result in an unstable supply network due to their lower stability reserve, i. the supply network equipped with such regulators is relatively sensitive to load changes or load jumps.

It is therefore an object of the present invention to provide a system and method for controlling voltage and frequency in a utility network where the utility network is insensitive to load transients and always stable.

This object is achieved by a system having the features specified in claim 1.

The invention thus provides a system for controlling voltage and frequency in a supply network having a central controller which maximizes a phase stability reserve and a voltage stability margin by simultaneously setting an operating point of the supply network and regulator parameters of distributed regulators of the utility network.

In one possible embodiment of the system according to the invention, the supply network is a meshed network with a multiplicity of nodes, which are connected to one another via supply lines.

In one possible embodiment of the system according to the invention, the supply network is a low-voltage network in which the ratio between resistance R and reactance X of the supply lines is significantly greater than zero.

In another possible embodiment of the system according to the invention, the low-voltage power supply network has a voltage of less than 20 kVolt.

In another possible embodiment of the system according to the invention, the regulators provided at the nodes of the supply network are Droop controllers.

In one possible embodiment of the system according to the invention, the controllers, in particular Droop controllers, receive controller parameters and an operating point of the supply network set for the respective node from the central controller of the supply network via a communication connection.

In one possible embodiment of the system according to the invention, the communication link between the central controller and the respective controller of the node via a communication network.

In an alternative embodiment of the system according to the invention, the communication link between the central controller and the respective controller via the supply network itself.

In a further possible embodiment of the system according to the invention, the controller provided at a node of the supply network locally controls a generator located at the node.

In one possible embodiment of the system according to the invention, the controller provided at a node of the supply network locally regulates the generator located at the node as a function of the operating point obtained for the node, the controller parameters obtained and local measured variables.

In one possible embodiment of the system according to the invention, the generator is an inverter of a photovoltaic system.

In a further possible embodiment of the system according to the invention, the generator is an inverter of a battery.

wobei p_i0, q_i0, u_i0, ω₀ durch den Regler von der zentralen Steuerung empfangene Werte des für den Knoten eingestellten Betriebspunktes innerhalb des Versorgungsnetzwerkes hinsichtlich der Wirkleistung, Blindleistung, Spannung und Kreisfrequenz an dem jeweiligen Knoten N_i,
k ~_qi ein Reglerparameter des Reglers und K_i eine Droop-Matrix, insbesondere eine nicht-diagonale Droop-Matrix, ist. In a further possible embodiment of the system according to the invention, the controller of a node provides an active power p _i and a reactive power q _{i of} the generator of the node as a function of a measured local voltage u _i and in dependence on a phase angle θ _i or a local network frequency θ. _i of the node as follows:

where p _i0 , q _i0 , u _i0 , ω ₀ values received by the controller from the central controller of the operating point set for the node within the supply network with regard to the active power, reactive power, voltage and angular frequency at the respective node N _i ,
k ~ _qi a controller parameter of the controller and K _{i is} a droop matrix, in particular a non-diagonal Droop matrix.

wobei p_i0, q_i0, u_i0, ω₀ durch den Regler von der zentralen Steuerung erhaltene Werte des eingestellten Betriebspunktes des Knotens innerhalb des Versorgungsnetzwerkes hinsichtlich der Wirkleistung, Blindleistung, Spannung und Kreisfrequenz an den jeweiligen Knoten N_i und
k ~_qi ein Reglerparameter und
K_i eine Droop-Matrix, insbesondere eine nicht-diagonale Droop-Matrix, ist. In a further possible embodiment of the system according to the invention, the controller of a node sets a phase angle θ _{i of} the node and a local voltage u _{i of} the generator of the node as a function of a measured active power p _i and a measured reactive power q _i as follows:

where p _i0 , q _i0 , u _i0 , ω ₀ values obtained by the controller from the central controller of the set operating point of the node within the supply network with respect to the active power, reactive power, voltage and angular frequency at the respective nodes N _i and
k ~ _qi a controller parameter and
K _{i is} a Droop matrix, in particular a non-diagonal Droop matrix.

In another possible embodiment of the system according to the invention, the non-diagonal Droop matrix is calculated by a calculation unit of the controller of the node in dependence on a compensation matrix KM as follows:

In another possible embodiment of the system according to the invention, the compensation matrix KM of the node is calculated as a function of a compensation rotation angle φ _i as follows:

ϕ_ijmax

der maximale Rotationswinkel der an dem betreffenden Knoten N_i angeschlossenen Versorgungsleitungen und

ϕ_ijmin

der minimale Rotationswinkel der an dem betreffenden Knoten N_i angeschlossenen Versorgungsleitungen ist.

In a further possible embodiment of the system according to the invention, the compensation rotation angle φ _i is calculated by the calculation unit of the controller as a function of the rotation angle φ _{ij of} all supply lines connected to the respective node of the supply network as follows: φ _i = 1/2 (φ _ijmax - φ _ijmin ), in which

φ _ijmax

the maximum angle of rotation of the supply lines connected to the respective node N _i and

φ _ijmin

is the minimum angle of rotation of the supply lines connected to the respective node N _i .

wobei x_ij die Reaktanz der jeweiligen Versorgungsleitung und r_ij der Widerstand der jeweiligen Versorgungsleitung ist. In one possible embodiment of the system according to the invention, the rotation angle φ _{ij of} a supply line is calculated as follows:

where x _{ij is} the reactance of the respective supply line and r _{ij is} the resistance of the respective supply line.

The invention further provides a method having the features specified in claim 15.

The invention thus provides a method for controlling voltage and frequency in a utility network, wherein a phase stability reserve and a voltage stability reserve of the utility network is maximized by simultaneously setting an operating point of the utility network and controller parameters of distributed controllers of the utility network.

In the following, possible embodiments of the method and system according to the invention will be explained in more detail with reference to the attached figures.

Show it:

1 shows a diagram illustrating a supply line between two nodes of the supply network to explain the operation of the system according to the invention and the method according to the invention for controlling voltage and frequency in the supply network;

2 shows a simple example of a multi-node supply network for explaining the method and system for controlling voltage and frequency in the utility network according to the invention;

3A . 3B show embodiments of controllers used in the system according to the invention for controlling voltage and frequency in the supply network;

4 shows a simple block diagram for explaining the operation of the method and system for controlling voltage and frequency in a supply network according to the invention;

5 shows a diagram illustrating a provided for the system and method stability reserve for the supply network.

How to get out 1 can recognize, there is a supply network VNW of a plurality of nodes N _i , N _j , which may be connected to each other via supply lines VL _ij . The supply network can be a power supply network. The supply lines are thereby formed by voltage or power supply lines that connect nodes of the network with each other. Each of the nodes N _i , N _j has a node phase angle θ _i , θ _j, and a voltage U _i , U _j . As in 1 1, an active power P _i , P _j and a reactive power Q _i , Q _j flows into each node on the two sides of the supply line. The supply line has a resistance R _ij and a reactance or inductance X _ij . By the impedance X _{ij of} the supply line VL _ij and by the reactance R _{ij of} the supply line VL _ij a rotation angle φ _{ij of} the supply line is determined. The rotation angle φ _ij is

auf, wobei ϕ_ij der Rotationswinkel der Stromversorgungsleitung bzw. Powerline ist. Dabei gilt r_ij = r_ji > 0, x_ij = x_ji > 0 und z_ij > 0, und ϕ_ij ∊ [0, π / 2]. The utility network VNW may be a partially or fully meshed network in which a plurality of nodes are interconnected via utility lines VL. From each node N _i , N _j , one or more supply lines VL may go to other neighboring nodes. Each power line has a constant complex impedance

where φ _{ij is} the rotation angle of the power supply line. Where r _ij = r _ji > 0, x _ij = x _ji > 0 and z _ij > 0, and φ _ij ε [0, π / 2].

wobei u_i, u_j, θ_i, θ_j:R → R zeitabhängige reelle Funktionen sind. At the two nodes N _i , N _{j in} each case a complex voltage u _i , u _{j is} as follows:

where u _i , u _j , θ _i , θ _j : R → R are time-dependent real functions.

The power transmitted via the supply line can be divided into an active power p _ij and a reactive power q _ij :

The entire power network can have N nodes. It therefore has a set of nodes N = {1, ..., N}. The sentence N _i = | N _i | is the set of all nodes J ∈ N connected to node i.

On the basis of the Energy Conservation Act, all active powers p _i and all reactive powers q _i supplied to the power supply network at a node i are equal to the sum of all active and reactive powers that leave the node in the direction of one of its neighboring nodes J ε N _i :

wobei gilt:

This can also be expressed as follows:

where:

Consequently, the utility network VNW can be specified as follows:

als Rotationsmatrix bezeichnet wird. Diese Gleichungen werden auch als gekoppelte Energiegleichungen bezeichnet. In which

is called a rotation matrix. These equations are also called coupled energy equations.

2 shows an example of a supply network VNW with a plurality of nodes N _i , which are interconnected via supply lines VL. In the illustrated simple example of 2 has the supply network VNW seven nodes N1, N2, N3, N4, N5, N6, N7, which are respectively connected via supply lines or power supply lines. Each node N _i may be connected to one or more adjacent nodes via one or more supply lines. Each node has a bus or a rail. In the illustrated example, each node has a device that is connected to the supply lines via a bus or a rail. In the 2 Devices V1, V2, V3, V4, V5, V6, V7 shown preferably each have a decentralized controller R. The devices V _i may contain generators and / or loads. As in 2 In addition, the supply network VNW has a central controller CU which can control or adjust the controller R _i contained in the devices V _i . The controllers are preferably so-called droop controllers. At the in 2 The supply network VNW shown is preferably a medium or low-voltage supply network, with each supply line VL or power supply line the ratio between resistance R and reactance X of the supply line VL being significantly greater than zero, in particular greater than 0.5. In one possible embodiment, the medium or low voltage power supply network as shown in FIG 2 is shown, a voltage level of less than 20 kVolt. The provided in the supply network of the devices within VNW V _i R _i controller can receive control parameters from the central controller CU via a communication link. In addition, the controllers R _i also receive a set operating point OP of the respective node from the central controller CU of the supply network. The communication connection is in 2 shown in dashed lines. In one possible embodiment, the communication link between the central controller CU at the respective controller R _i within the device V _{i is} a connection which is established via a communication network, in particular a wireless or wired communication network. Alternatively, the communication connection can also be established via the supply network VNW itself, for example via powerline communication.

3A . 3B show exemplary embodiments of regulator R _i within the device V _{i of} the supply network VNW, wherein in the illustrated embodiments, the devices V _i each include a generator G _i . The generator G _i may preferably be an inverter of a photovoltaic system. Furthermore, it is possible that the generator G _i is an inverter for one or more batteries at the node. Furthermore, the generator G _{i can} also be, for example, an inverter of a wind power plant. As in the 3A . 3B 2, the regulators R _i within the devices V _{i are} connected via a bidirectional communication link to the central controller CU of the supply network VNW. In one possible embodiment, the controllers or the sensors contained in the device supply measured variables to the central controller CU. This is also in 4 clarified. In this case, local voltages U of the node or a corresponding vector U are preferably transmitted as measured variables. Furthermore, the local network frequency f _i = θ. _i transmitted over the communication link to the remote central controller CU of the network. Furthermore, the respective active power and reactive power feed P _i and Q _i are preferably transmitted to the central controller CU for a node N _i , which evaluates the measured quantities or measured variable vectors obtained. For this purpose, the central controller CU may contain one or more processors that execute a corresponding program. The central controller CU provides an operating point OP of the utility network, as in 4 indicated, for each node of the supply network VNW a set reference _voltage U _i0 , a reference _{network frequency} f _i0 , a set reference active power P _i0 and a set reference _{reactive power} Q _i0 calculated and transmitted over the communication link. In addition, the respective controller R _i within the device V _i receives controller parameters RP, which are gain factors k _p , k _q and / or time constants k ~ _q can act.

Inverters controlled by a droop regulator can represent both generators, such as photovoltaic inverters, and loads, such as rectifiers. The regulators R _i can be proportional and / or PID controllers.

wobei p_i0, q_i0, u_i0, ω₀ die durch den Regler R_i von der zentralen Steuerung CU empfangenen Werte des eingestellten Betriebspunktes OP des Versorgungsnetzwerkes an den Knoten hinsichtlich der Wirkleistung, Blindleistung, Spannung und Kreisfrequenz an dem jeweiligen Knoten,
k ~_qi ein Reglerparameter des Reglers R_i und
K_i eine Droop-Matrix, insbesondere eine nicht-diagonale Droop-Matrix, ist. The 3A . 3B show two alternative embodiments for a used in a node N _{i of} the supply network VNW controller R _i . At the in 3A In the illustrated embodiment, the controller R _i controls an active and reactive power of the generator as a function of a local voltage u _i and a local phase angle θ _i or a local frequency θ. _i as follows:

where p _i0 , q _i0 , u _i0 , ω _{0 are} the values of the set operating point OP of the supply network at the node received by the controller R _i with respect to the active power, reactive power, voltage and angular frequency at the respective node,
k ~ _qi a controller parameter of the controller R _i and
K _{i is} a Droop matrix, in particular a non-diagonal Droop matrix.

wobei p_i0, q_i0, u_i0, ω₀ die durch den Regler R_i von der zentralen Steuerung CU erhaltenen Werte des eingestellten Betriebspunktes OP des Versorgungsnetzwerkes hinsichtlich der Wirkleistung, Blindleistung, Spannung und Kreisfrequenz an den jeweiligen Knoten N_i,
k ~_qi ein Reglerparameter und
K_i die eine Droop-Matrix, insbesondere eine nicht-diagonale Droop-Matrix, ist. At the in 3B In the alternative embodiment illustrated, the controller R _{i of} a node N _i sets a phase angle θ _{i of} the node and a local voltage u _{i of} the generator of the node as a function of a locally measured active power P _i and measured reactive power Q _i as follows:

where p _i0 , q _i0 , u _i0 , ω _{0 are} the _values , obtained by the controller R _i, of the set operating point OP of the supply network with regard to the active power, reactive power, voltage and angular frequency at the respective node N _i ,
k ~ _qi a controller parameter and
K _i is a droop matrix, in particular a non-diagonal droop matrix.

In one possible embodiment of the system according to the invention, each controller R _i receives a special calculation unit which calculates the non-diagonal droop matrix K _i as a function of a compensation matrix KM:

The calculation unit calculates the compensation matrix KM of the node as a function of a compensation rotation angle φ _i as follows:

The compensation rotation angle φ _i is calculated by the calculation unit of the controller in one possible embodiment as a function of the rotation angles φ _{ij of} all supply lines VL connected to the respective node N _{i of} the supply network VNW as follows: φ _i = 1/2 (φ _ijmax - φ _ijmin ), where φ _{ijmax is} the maximum rotation _{angle of} the supply lines VL and connected to the node N _i
φ _{ijmin is} the minimum _angle of rotation of the supply lines VL connected to the node in question.

wobei x_ij die Impedanz der jeweiligen Versorgungsleitung VL und r_ij die Reaktanz der Versorgungsleitung VL ist. The rotation angle φ _{ij of} a supply line VL is generally constant and depends on properties of the supply line. The rotation angle φ _{ij of} a supply line connected to the node N _i containing the device V _i is:

where x _{ij is} the impedance of the respective supply line VL and r _{ij is} the reactance of the supply line VL.

vernachlässigbar und nahe null. The resistance and the reactance of the supply line VL are usually fixed, so that the rotation angle φ _{ij of} the supply lines can be stored in a local memory on the the respective controller R _{i of} the device V _{i has} access. In a power supply network with non-negligible resistance, the method and system according to the invention for controlling voltage and frequency can be used particularly advantageously. The non-negligible resistance occurs especially in a medium and low voltage power supply network. In contrast, in a high voltage power supply network usually the ratio between resistance and reactance, ie

negligible and close to zero.

The dynamic behavior of the frequency and voltage of the power supply network VNW can be calculated as follows:

welche durch die Reaktanzen der Versorgungsleitung VL hervorgerufen wird. Die Droop-Matrix K_i kann wie folgt berechnet werden:

The droop matrix K _i used here compensates for the rotation matrix

which is caused by the reactances of the supply line VL. The droop matrix K _i can be calculated as follows:

In one possible embodiment, the compensation rotation angle φ _{i is} calculated as a function of all rotation angles φ _{ij of} all supply lines connected to the respective nodes. In one possible implementation, the compensation rotation _angle φ _i depends on a maximum rotation _angle φ _ijmax and a minimum rotation _angle φ _ijmin . In one possible implementation, the average value between the maximum rotation angle and the minimum rotation angle is set or calculated as the compensation rotation angle φ _i . This calculated compensation rotation angle determines the droop matrix K _i .

zieht dieser stabile Zustand asymptotisch alle Anfangsbedingungen innerhalb eines rautenförmigen Gebietes:

an, die um den stabilen Betriebspunkt OP (u*, ϑ*, Ω) liegen, wobei c⁺(t) und c^–(t) wie folgt definiert werden können:

mit ũ_i = u_i – u * / i, ϑ_i = θ_i – θ * / i und den Designparameter κ > 0, falls

wobei

mit ∆ϕ_ij = ϕ_i – ϕ_ij, sinc(x) = sin(x) / x und ε > 0 als Designparameter des Versorgungsnetzwerkes VNW. If the system already has a stable state (u *, θ *, Ω), where θ * = 1Ωt + θ *, which is determined by the solution of the stationary equation of state:

Asymptotically, this stable state draws all initial conditions within a rhombic area:

which lie around the stable operating point OP (u *, θ *, Ω), where c ⁺ (t) and c ^- (t) can be defined as follows:

With ũ _i = u _i - u * / i, θ _i = θ _i - θ * / i and the design parameter κ> 0 if

in which

With Δφ _ij = φ _i -φ _ij , sinc (x) = sin (x) / x and ε> 0 as a design parameter of the utility network VNW.

5 illustrates the stability reserve SR of the supply network VNW formed by the system and method according to the invention. One recognizes in 5 the diamond-shaped form of the stability reserve, which is formed by a phase stability reserve PSR and a voltage stability reserve SSR. The central control CU of the supply network VNW maximizes the in 5 illustrated stability reserve of the supply network VNW to set the operating points for all nodes N _{i of} the supply network and to calculate corresponding control parameters of the decentralized Droop controller R _i , as in 4 indicated.

The phase stability reserve PSR denotes the maximum permissible deviation of the phase of a node of the supply network VNW from the stationary phase position in the stationary operating point OP at any time. The voltage stability reserve SSR denotes the maximum permissible deviation of the voltage of a node of the supply network VNW from the voltage in the stationary operating point OP at any time. The calculation of the stability reserve, ie the phase stability reserve PSR and the voltage stability reserve SSR, is preferably triggered by a specific event in the supply network VNW, for example by an occurring load step or load change. The inventive method then regulates the voltage and frequency of the supply network, the central control CU of the supply network, the phase stability reserve PSR and simultaneously the voltage stability reserve SSR by simultaneously setting an operating point or operation point OP of the supply network and controller parameters of distributed controller R _{i of} the supply network VNW maximized.

The non-negligible non-zero ratio between resistance and reactance in medium and low voltage networks leads to a rotation between voltage and frequency dynamics. For each supply line or power line, a rotation matrix is created with a rotation angle that depends on the resistance-to-reactance ratio. With the method and system according to the invention, a compensation matrix KM is used in the controller R _i , so that the product results in almost an identity matrix between this compensation matrix KM and the rotation matrix for all connected supply lines VL. This can be achieved, for example, by calculating an angle between the inverse rotation matrix and the average of the largest and smallest rotation angles of all connected supply lines VL. Due to this compensation matrix, the voltage and frequency dynamics are largely decoupled, depending on the differences between the R / X ratios of the different supply lines VL. The inventive method and system for controlling voltage and frequencies in the supply network VNW provides a particularly stable and robust supply network VNW, which is insensitive to load changes within the network. In one possible embodiment, all nodes N _{i of} the network VNW have a corresponding droop regulator R _i . In an alternative embodiment, only a few nodes of the network have a corresponding controller. The method and system according to the invention are particularly suitable for medium and low-voltage supply networks. It is also possible to use the system according to the invention in high-voltage power supply networks, in which case the stability gain is lower. The topology of the utility network may vary. The supply network can also have ring structures or tree structures in addition to linear structures. The spatial extent of the supply network VNW can also vary. In one possible embodiment, the supply network VNW is an island network or a smaller local supply network. In an alternative embodiment, the utility network is a wide-span utility network with nodes far apart.

In one possible embodiment variant, the achieved stability reserve is displayed to a user, for example in a control center, via a user interface. For each relevant event, such as a load jump, a new stability reserve can be calculated and displayed to the user. In a possible embodiment, the achieved stability reserve SR corresponds to the area of the 5 shown rhombus. In one possible embodiment variant, this variable can also be displayed to the user in the control center, so that the latter can recognize whether the stability reserve has risen or fallen due to a load jump. In another possible embodiment, the historical development of the stability reserve SR is logged. The evaluation of the stability reserve can take place in connection with the events occurring in the network by an evaluation unit of the control center in order to investigate effects of events on the stability reserve SR and to be able to prepare or execute the corresponding countermeasures in the supply network VNW.

Claims (15)

System for controlling voltage and frequency in a supply network (VNW) with a central control (CU) having a phase stability reserve (PSR) and a voltage stability reserve (SSR) by simultaneously adjusting an operating point of the utility network (VNW) and controller parameters (R) of the utility network (VNW). The system of claim 1, wherein the utility network (VNW) is a meshed network having a plurality of nodes (N _i ) interconnected by utility lines (VL). A system according to claim 1 or 2, wherein the utility network (VNW) is a medium or low voltage network in which the ratio between resistance and reactance of the supply lines (VL) is approximately one. The system of claim 3, wherein the medium or low voltage power supply network has a voltage of less than 20 kVolt. System according to one of the preceding claims 1 to 4, wherein the controllers (R) provided at the nodes of the supply network (VNW) are Droop controllers, which controller parameters and an operating point (VNW) of the supply network (VNW) set for the respective node (N _i ) the central control (CU) via a communication link. A system according to claim 5, wherein the communication link between the central controller (CU) and the respective controller (R) is via a communication network or the utility network. System according to any one of the preceding claims 1 to 6, wherein the at a node (N _i) of the power supply network (V NW) intended controller (R) a to the node (N _i) located generator (G _i) locally in dependence on the obtained operating point , governed by the obtained controller parameters and local measured variables. The system of claim 7, wherein the generator (G _i ) is an inverter of a photovoltaic system or a battery or the inverter of a wind turbine. System according to one of the preceding claims 1 to 8, wherein the controller (R _i ) of a node (N _i ) an active power (p _i ) and a reactive power (q _i ) of the generator (G _i ) of the node (N _i ) in dependence of a measured local voltage (u _i ) and a phase angle (θ _i ) or a frequency (θ _i ) of the node (N _i ) is set as follows:

where p _i0 , q _i0 , u _i0 , ω ₀ are values received by the controller (R _i ) from the central control (CU) of the supply node's operating point set for the node in terms of active power, reactive power, voltage and angular frequency at the respective node ( N _i ), k ~ q _i a controller parameter of the controller and K _{i is} a droop matrix, in particular a non-diagonal Droop matrix. System according to one of the preceding claims 1 to 8, wherein the controller (R _i ) of a node (N _i ) a phase angle (θ _i ) of the node and a local voltage (u _i ) of the generator of the node in dependence on a measured active power ( p _i ) and a measured reactive power (q _i ) is set as follows:

where p _i0 , q _i0 , u _i0 , ω ₀ by the controller (R _i ) from the central controller (CU) received values of the node set operating point of the supply network (VNW) in terms of active power, reactive power, voltage and angular frequency of the respective nodes (N _i ), k ~ _qi a controller parameter and K _{i is} a droop matrix, in particular a non-diagonal droop matrix. A system according to claim 9 or 10, wherein the non-diagonal Droop matrix is calculated by a calculation unit of the controller (R _i ) of the node (N _i ) in dependence on a compensation matrix (KM) as follows:

System according to claim 11, wherein the compensation matrix (KM) of the node is calculated as a function of a compensation rotation angle φ _i as follows:

A system according to claim 12, wherein the compensation rotation angle φ _i is calculated by the controller (R) calculating unit as a function of the rotation angle φ _{ij of} all supply lines (VL) connected to the respective node (N _i ) of the utility network as follows: φ _i = 1/2 (φ _ijmax - φ _ijmin ), where φ _{ijmax is} the maximum rotation _{angle of} the supply lines (VL) connected to the respective node (N _i ) and φ _{ijmin is} the minimum rotation _{angle of} the supply lines (VL) connected to the node (N _i ) concerned, the rotation angle φ _{ij of} a supply line ( VL) of the supply network

where x _{ij is} the reactance of the supply line (VL) and r _{ij is} the resistance of the supply line (VL). Low-voltage network with a system according to one of Claims 1 to 13. Method for controlling voltage and frequency in a supply network (VNW), wherein a phase stability reserve (PSR) and a voltage stability reserve (SSR) of the supply network (VNW) are set by simultaneously setting an operating point of the supply network (VNW) and controller parameters of distributed controllers (R) of the supply network Supply network (VNW) is maximized.

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