EP4073898A1

EP4073898A1 - Method and stabilisation controller for operating an island network

Info

Publication number: EP4073898A1
Application number: EP20804258.0A
Authority: EP
Inventors: Jörn Runge; Christian Feltes
Original assignee: RWE Renewables GmbH
Current assignee: Rwe Offshore Wind GmbH
Priority date: 2019-12-09
Filing date: 2020-11-10
Publication date: 2022-10-19
Also published as: US20220294229A1; DE102019133566A1; WO2021115702A1

Abstract

The invention relates to a method for operating at least one subscriber in an island network comprising the following steps: coupling at least one subscriber of the island network to a stabilisation controller, determining an impedance between an output of the stabilisation controller and a network node of the island network and controlling the voltage on the network node by means of the stabilisation controller depending on the determined impedance.

Description

Process and stabilization controller for operating an island network

The subject matter relates to a method for operating an island network, in particular an island network of a wind park, in particular an offshore wind park. In addition, the subject matter relates to a stabilization regulator set up to carry out the method.

In the area of wind power plants, but also in other plants with generating facilities, a stable network frequency and voltage is usually necessary in order to be able to operate the participants. In particular, the inverters that connect the generating device to the supply network often require an externally applied network frequency and voltage in order to be able to feed electrical power into the supply network. In the network, electrical generators, in particular those that are fed from renewable sources, can only be operated regularly if a stable network frequency and a stable voltage are specified.

However, this is not always the case when an island network is operated. Wind turbines usually have their own voltage regulation. If several wind turbines are operated together in an island network, the voltage controls of the individual wind turbines can oscillate, which leads to considerable instabilities.

In the event of a blackout, when the energy supply network has to be started up again, it makes sense to first start up the wind turbines together as a stand-alone network, in order to then realize a network connection.

In addition, it is necessary to operate the wind turbines at a minimum power when commissioning a wind farm. Such an achievement must be however, they can be discharged via a load. With an installed capacity of 100 MW, a load of approx. 0-10%, for example 1 MW, must be able to absorb excess capacity. If the wind turbines are not yet connected to an energy supply network, such a power output cannot take place. This means that the wind turbines cannot be put into operation. As already mentioned, this is also of enormous importance in the event of restarting after a blackout.

When operations are resumed, especially when connecting to the grid for the first time and after a grid failure, it must be possible to operate consumers within the island grid and / or the wind power plants. These are, for example, motors, air conditioning systems, control computers and the like. These are fed by the wind turbines themselves, but do not offer the possibility of additional load absorption, so that a variable load is also necessary for their supply by the wind turbines.

For the reasons mentioned, the object of the subject matter was to provide a method for operating a subscriber in a stand-alone network, in which the stand-alone network is operated with a stable voltage and frequency.

This object is achieved by a method according to claim 1 and a stabilization regulator according to claim 19.

A participant in an island network can in particular be a generating plant for electrical power. This can in particular be a system for generating electrical power from renewable sources. A participant can in particular be a wind power plant (also called a wind power plant or wind turbine), a photovoltaic plant, a biogas plant, a CHP plant or the like. A subscriber can be an electrical producer or an electrical load. An electrical generator is, for example, a photovoltaic system or a wind turbine. Operation is described below with reference to a Wind turbine described, an analog application on inverters from other participants thus enclosed. A load can, for example, be a piece of equipment in a wind power plant or a photovoltaic plant or a consumer in a transformer station or the like. One or more participants can be operated together in a stand-alone network.

Within an island network, a participant is coupled with a stabilization controller.

An island network is, in particular, such an electrical network in which a plurality of participants are connected to one another, but in addition to which they are not connected to a (supra-regional) energy supply network. An island network can be operated when a wind farm is being built, in particular before the wind farm is connected to the energy supply network. An island network can also arise after a blackout if the voltage falls below a lower voltage limit for too long. If a wind farm or any other number of participants is disconnected from the energy supply network, this island network must continue to be operated or its operation must be restarted.

A stabilization regulator in the stand-alone network can in particular have an electrical storage device, in particular an electrical battery storage device, as well as a converter and / or a generator. Storage and / or generator can be understood as electrical feeders. The converter can electrically connect the storage system to the stand-alone grid. A diesel generator can also be provided on the stabilization regulator. The stabilization regulator can also have an additional load, for example an ohmic resistor. The converter of the stabilization regulator can be controlled via a voltage control loop and / or a phase control loop described below and impress a frequency and / or a voltage and / or a phase in the island network. The feeder is preferably connected to the stand-alone grid via the converter. This island network is separable and connected to a supra-local electrical supply network. In the event of a power failure, it can make sense to disconnect the stand-alone grid from the supply network. When starting up the participants (e.g. the wind park or the solar park), however, it must be ensured that the consumers within the island grid that are necessary for this start-up are supplied with sufficient electrical power. In addition, the participants must form a stable electrical network together with the feeder and strive for a target frequency,

When rebuilding the island network and / or to connect the island network to the grid, the stabilization regulator provides a voltage and / or a frequency and / or a phase between current and voltage to the island grid, in particular on the busbar, but the specified phase position is not necessarily a phase position between Current and voltage, but can be a fixed reference phase angle for the network. This enables the feeder to supply loads in the stand-alone grid. In addition, network impedances between the busbar and a participant can be compensated. The participant is synchronized with the stabilization controller through the impressed frequency. The participant then feeds real power into the stand-alone grid.

If the active power of a participant exceeds the load in the stand-alone grid, the stabilization controller can be operated as a load and absorb active power. A corresponding phase control can also cause the participants to consume active power in motor operation. If the participants who have already started up together with the feeder no longer adequately feed the loads, further participants can be switched on. Further loads and participants are gradually switched on so that the stand-alone grid is transferred / maintained in stable operation. In order to feed active power into the stand-alone grid or to draw it as a load from the stand-alone grid, the feeder is coupled to the stand-alone grid via a stabilization controller. The feeder can have at least one electrical store, for example a battery store and / or a generator.

In turn, the participants are coupled to the stabilization controller via the stand-alone grid. For this purpose, the lines of the participants can be brought together on one or different busbars.

In order to now ensure that the stand-alone grid can be converted to stable operation, in particular with a setpoint frequency and a setpoint active power, it is proposed that a frequency setpoint for the stabilization controller and / or a phase setpoint for the stabilization controller be at least dependent on a measured grid frequency of the stand-alone grid and / or a state of charge and / or an active power of the feeder is regulated in a phase-locked loop. The stabilization regulator can have a phase locked loop.

The phase-locked loop can have a nominal power value, in particular a nominal active power value, as a reference variable. This reference variable can be supplied from a voltage control loop with / without subordinate current control, in particular a d / q voltage control. An intermediate circuit voltage regulator can be provided in the voltage control loop. The DC link voltage regulator can be used to maintain the charge status of the feeder. The DC link voltage regulator can use a voltage setpoint and an actual voltage value from the feeder.

A deviation of the reference variable from a measured actual active power value can be determined and this value can be fed to a controller, in particular an I controller. A power setpoint for a participant can be determined from this. On the one hand, it is possible to communicate the power setpoint as a frequency value or as a power value to a participant via telecontrol technology. On the other hand is It is also possible to use the output of the controller, in particular to limit a positive value if necessary, as a frequency component in a frequency control of the phase-locked loop.

An active and / or reactive component or a d component and a q component of a nominal voltage at the output of the stabilization regulator can be regulated in a voltage control loop depending on a state of charge of the feeder and / or a measured mains voltage on the stabilization regulator. The stabilization regulator can also use a measured and a setpoint network voltage.

In order to be able to determine correct voltage setpoints taking into account the network impedance, it is proposed that an impedance between an output of the stabilization regulator and a network node of the island network be determined, and that the active and / or reactive component or a d component and a q component of a target voltage is regulated for the stabilization regulator depending on the specific impedance in the voltage control loop.

A subordinate current control can be provided within the voltage control loop. In the current control, a control element can be dependent on the network impedance, in particular on the impedance between an output of the stabilization regulator and a network node. This enables voltage pre-control to take place. The line impedance can furthermore depend on the reactance of the transformer of the feeder, the type of busbar, the line reactor and / or the cable between the stabilization regulator and / or the busbar.

It is proposed that a forward connection in the voltage control loop is dependent on the specific reactance. The forward connection in the voltage control loop can also be a crossover between a q component and a d component in accordance with the Park transformation of the regulated voltage. The regulation can in principle also in other coordinates or Component systems are implemented, such as the Clarke transformation (alpha, beta, 0) or the three components of the three-phase system (u, v, bj or the extended components according to Park transformation (d, q, 0), the voltage regulation can in particular using the control loop according to "New Control of Wind Turbines Ensuring Stable and Secure Operation Following Islanding of Wind Farms", I. Erlich et. AL, IEEE 2017. An active current setpoint for the phase-locked loop can be tapped from this voltage control for the participants.

In particular, a difference between the nominal voltage of the feeder and the actual voltage of the feeder can be routed via a PI controller and the output can be used as a q-component of a nominal current. This output can be understood as the output of an intermediate circuit voltage regulator. The output can on the one hand be used in the voltage control loop as a reference variable for a subordinate current control and on the other hand as a reference variable for a phase-locked loop. A corresponding conversion can be used to determine an active power setpoint for the feeder on the phase-locked loop from the q-component of the setpoint current. An active current setpoint value, in particular ad component of a setpoint current from the voltage control loop, can thus be coupled into the phase locked loop.

It is proposed that a power setpoint or a frequency setpoint for the subscriber is output from the phase-locked loop via a communication link or that a power setpoint for the subscriber is output via a frequency setpoint for the stabilization controller. The phase-locked loop can output a nominal power value or a nominal frequency value via a communication device. This setpoint can be used by an inverter or converter on the subscriber to set a corresponding power. The stabilization controller, in particular the converter a frequency can be impressed on the island network. This allows a

Set the active power at the participant.

In order to be able to set the active and reactive power depending on the network frequency, a frequency setpoint, which can be output as a controlled variable on the phase-locked loop, is fed back. The frequency setpoint at the output of the phase-locked loop can be fed back to the frequency setpoint for a participant. A difference from this can be used as a manipulated variable for the phase-locked loop.

It is also proposed that a phase setpoint for the stabilization controller be fed back in the phase locked loop. In particular, the measured voltage around the converter can be transformed into a q component of the voltage using the feedback phase.

The stabilization regulator is operated taking into account an impedance between an output of a stabilization regulator and a network node of the island network. A network node can be, for example, a busbar, in particular a medium-voltage busbar, on which the connections of several participants in the island network are brought together.

The impedance between the output of the stabilization regulator and the network node can be measured or calculated. The impedance can be measured once before commissioning, at intervals during operation, in particular regularly or also once during operation. The impedance can also be calculated from model parameters that result from the data sheets of the equipment involved, such as transformers, cables, switchgear, overhead lines, etc., which are located between the stabilization controller and the network node.

It is also possible to couple signals with one or different frequencies at the output of the stabilization regulator and to control the frequency response of the system measure up. For example, frequencies between 50 and 5 kHz, preferably between 50 and 2.5 kHz, can be coupled in and a measurement can be made per frequency or per frequency band. Here it is possible, for example, either to couple the signals to the stabilization controller and measure them at the network node, or the other way round, namely to couple them to the network node and measure them at the stabilization controller. In the latter case, a measurement signal can be coupled in at the network node.

To operate the subscriber, the stand-alone grid is regulated in a voltage-controlled manner; the setpoint voltage is set in particular at one or the defined network node. The converter of the stabilization regulator is operated in such a way that destabilization tendencies, which result from the regulation of the wind turbines themselves, are counteracted.

In the case of voltage regulation, in particular d / q regulation can take place. The voltage coupled into the stabilization regulator by the line-side converter (LSG) is relevant for the amplitude of the island grid voltage and the active power. A power flow results as a function of the impedance and the voltage influencing the active power is only completely in the q-axis in purely inductive networks. In the offshore island networks there is also a significant ohmic component, so that the voltage component in the d-axis can also influence the active power.

The portion of the fed-in voltage in the direction of the d-axis results from a regulation of the amplitude of the mains voltage. The portion of the fed-in voltage in the q-axis results from a regulation of the active power (or the intermediate circuit voltage) in the network.

With this voltage regulation, there is an overall decoupling between the target value of the voltage and the current feed to the stabilization regulator.

At least the q-component of the voltage is indirectly via the fed-in current on Stabilization controller, i.e. the active power (or via the control of the

DC link voltage) set on the stabilization controller For the setpoints of the

Limits can be introduced for currents.

The impedance between the stabilization regulator and the network node is measured in particular for a fundamental frequency.

Harmonic components are preferably not taken into account. The speed of the regulation of the stabilization regulator is preferably set so that it is decoupled from the participant's regulator. The bandwidth of the frequency response of the stabilization regulator is selected to be greater than the bandwidth of the frequency response of at least one, preferably all, of the participants' converters. The bandwidth of the stabilization regulator is in particular at least twice as large as the bandwidth of at least one converter of the subscribers. This results in the temporal decoupling of the two controllers.

Attenuators which are set to the most important natural frequencies of the system can be arranged within the stabilization regulator. In particular, this can be the resonance frequencies of the stand-alone network, taking into account one or all of the network impedances and the converters of the participants. The attenuators are built into the control loops in such a way that they can cause both active and reactive power changes and can thus act in both axes of the d / q voltage regulation.

If a diesel generator is used as a stabilization controller, the attenuators can only act in one axis via the excitation device.

Because the bandwidth of the stabilization controller is greater than the bandwidth of the converter, preferably at least twice as large, controller oscillations between the stabilization controller and the converter of the participants are minimized. Controller oscillations between the inverters of the participants are minimized or suppressed by the fact that the stabilization controller acts like a stiff network with high short-circuit power due to its high bandwidth.

According to one exemplary embodiment, it is proposed that the stabilization regulator have at least one attenuator. The stabilization controller can have a P, PI or PID controller. In particular, a subordinate current regulation system can have a regulator without an I component.

The subordinate current regulation is essentially used to implement a current limitation so that overloading of the stabilization regulator due to overcurrents can be safely excluded. The current regulators in the d- and q-axes are purely proportional regulators with a pre-control, which sets the steady-state output voltages of the regulator via the network impedance known (from the measurement or calculation) from the current setpoints by applying Ohm's law.

The proportional controllers in both axes only serve to compensate for a possible error in the specific network impedance and to improve the controller dynamics. The current setpoints are determined from the output variables of the superimposed voltage and active power controllers. Since these are voltage components, the conversion can also be carried out using Ohm's law, taking into account the known network impedances and the voltage measured at the network node.

An attenuator can be dimensioned in such a way that it is adapted to the natural frequencies of the island network. Natural frequencies can result from the grid impedances and the converters of the wind turbines. The attenuators are preferably arranged in both controller branches, i.e. in both the q and d branches, and thus act on both axes through changes in active and reactive power. According to one exemplary embodiment, it is proposed that an attenuator be dependent on the impedance of the island network, in particular the impedance between the output of the stabilization regulator and the network node. The attenuator can also be adapted to a transmission function of a converter of the subscriber.

With the help of the attenuators it is possible to minimize or avoid controller oscillations between the stabilization controller and the participant: In particular, the different control speeds ensure that the stabilization controller acts like a rigid network towards the participants.

As already explained, it is proposed according to an exemplary embodiment that the stabilization regulator feed in active and / or reactive power. The active and / or reactive power fed in can be influenced by the attenuator.

According to one exemplary embodiment, it is proposed that the stabilization regulator is operated at a fixed frequency and that an active power of the participant is changed by telecontrol technology as a function of a change in power at the participant. With the fixed nominal frequency of the stabilization controller, this has no relation to the power balance in the stand-alone grid. In order to be able to set the power balance in the stand-alone grid, a regulation is necessary for the participants. If the participant's power fluctuates, for example due to gusts of wind or sudden load changes, the stabilization controller reacts briefly with an angle change in the applied voltage. As a result, the participant's output power can be reduced or increased depending on the direction of the change in power (including change in angle). This changed output power prevents the converter from being overloaded.

If the stabilization regulator is operated with a fixed frequency, the power of the participant cannot be adjusted by adjusting the frequency. It is therefore necessary that a Communication takes place between the stabilization controller and the participant. As part of this communication, a new power setpoint is sent to the

Subscriber transmitted so that after a short balancing process, the fixed frequency can be maintained again. The adjustment of the output power at the stabilization regulator in the event of a power fluctuation of the participant is done by the fact that the voltage vector in the vector diagram follows the voltage vector of the participant, which is leading due to the increase in power or which is quickly ending due to a power reduction, with a minimum delay. If the participant's voltage vector hurries ahead, the lag of the voltage vector of the stabilization regulator results in a short-term

Frequency increase. Conversely, if the voltage indicator lags behind, there is a brief frequency reduction.

It is also possible for the stabilization controller to be operated with a variable frequency. Communication between the subscriber and the stabilization controller can then be dispensed with due to the frequency control. With the help of frequency control, active power control is possible without communication. A lead lag compensator on the stabilization controller can briefly modify the active power output in such a way that it counteracts the change in frequency. A lead lag compensator can also be implemented on the participant. For this purpose, for example, when the frequency is reduced, energy is briefly withdrawn from the inertia of the rotating component of the participant, for example the wind turbine drive train, as a result of which the speed is reduced. As a result, the wind turbine is operated briefly at a new operating point. After adjusting the pitch angle of the rotor blades, the speed is then increased again and the

The wind turbine returns to its optimal working point.

As already described, active power control within the stand-alone grid is possible both via communication and via frequency control. For the active power control, a setpoint value for a converter of the subscriber can be dependent on a frequency and / or a power flow on the stabilization controller to be determined. For this purpose, the setpoint can be permanently set on the stabilization controller. The active power requirement of the stand-alone grid can be determined either from the frequency or from the power flow on the stabilization controller, and the setpoints for the individual wind turbines can be determined from this.

In order to ensure that power fluctuations at the subscriber can be compensated for by the stabilization controller, it is proposed that a

Output power of the participant is less than a maximum power of the stabilization regulator.

It is also proposed that a load forecast be made taking into account typical load profiles of the consumers. The load profiles can be dependent on environmental conditions, such as the outside temperature. These load forecasts are set in the participants or specified via lookup tables. The stand-alone network is then stabilized exclusively by the stabilization controller, since there is no communication between the stabilization controller and the subscriber and frequency control is not necessary. In exceptional cases, however, the subscriber must be switched on and / or off manually, especially if the load forecast is not adhered to.

Power fluctuations at the subscriber, for example caused by gusts of wind or load jumps, can be compensated for by the subscriber's power control. A high level of accuracy is necessary here, so that changes in power do not exceed the converter output of the stabilization regulator, the output of the storage device and / or the output of the load on the stabilization regulator. This means that the stabilization controller is always able to compensate for fluctuations in power.

According to one embodiment, the stabilization regulator acts as a slack bus. Within the scope of its current and voltage limits, the stabilization controller acts like a slack bus, so that the power flow at the associated converter is automatically changed Adapts to needs in the stand-alone grid. The stabilization regulator maintains • the voltage amplitude and angle! stationary constant at a defined network node as long as it works within its current and voltage limits. As soon as the stabilization regulator runs into its current or voltage limits, it automatically limits the output power or voltage so that the voltage and frequency in the island network can no longer be temporarily maintained. By regulating the frequency and voltage of the participants, a new operating point is set, which means. the stabilization controller can return to its normal operating range.

As mentioned, the participants' powers must be quickly adjusted to avoid overloading the stabilization controller. The reactive power of the individual participants can be set depending on the active power at the respective participant and / or the active power of the stabilization regulator. Here, a dependency between active and reactive power can be stored in a lookup table, so that a reactive power can be set corresponding to an active power.

It is also possible for the reactive power to take place via a control loop on the stabilization controller and reactive power measurement on the stabilization controller.

A setpoint specification for the respective participant can be made via communication from the stabilization controller to the participant.

The stabilization controller is designed for the basic frequency of the island network. Harmonics that can occur in stand-alone grid operation can be dampened by additional filters. Active compensation and / or damping of harmonics can also take place in the control loop of the stabilization controller. The stabilization regulator is preferably provided in a container or standard container so that it can be used on the move for commissioning wind farms can be. It can be assumed that a mobile stabilization controller can be used in a variety of ways. A stabilization controller may be necessary in particular for the commissioning of wind farms, as some wind farms have to be operated in the stand-alone grid before they are connected to the grid (e.g. if the grid connection is delayed), in particular to feed loads on the wind turbines, such as air conditioning, motors Lighting and the like.

The active power required for this is made available by the wind power plants, which are provided with a stable network by the stabilization controller.

After the wind farm has been commissioned, the stabilization regulator can be brought to a new wind farm in the standard container. In the container or containers or standard containers, in particular a transformer, in particular a medium-voltage transformer, a converter and a memory can be provided. The transformer and / or converter can be provided for connection to the medium-voltage level. A transformer of a diesel generator, which is provided for the emergency power supply, can also be used. An ohmic load can also be installed in the standard container in order to absorb power peaks.

As already explained, the stabilization regulator provides a voltage and a frequency at a network node. Such a network node is in particular a busbar via which the wind turbines are connected. The stabilization regulator supplies loads and compensates for the reactive power requirement for the cable capacities and / or transformer inductances. The cable capacitance to a first wind turbine can be compensated by the stabilization controller if the cable network is not compensated by compensation coils.

In the case of start-up, the stabilization regulator provides the voltage and frequency and supplies the loads that are necessary for start-up. The first wind power plant is synchronized with the frequency of the island grid and feeds in real power. In order to enable the wind turbine to deliver a minimum technical active power, the stabilization regulator serves as a load. After a first wind turbine has been started up, additional loads and wind turbines are added as loads. By connecting the loads, the active power of both the wind power plant and the storage unit can become too low, so that the next wind power plant is switched to generator mode in a timely manner, synchronized with the island grid and fed in active power. Even then, too much active power fed in is taken up again by the stabilization controller. This means that all the wind turbines in a wind farm can gradually be put into operation and feed their minimum active power into the island grid.

The subject is explained in more detail below with the aid of a drawing showing an exemplary embodiment. In the drawing show:

Fig. 1 shows a standard container with a stabilization regulator obsolete chen;

2 shows a wind farm with participants who are connected to a stabilization controller via a busbar;

3 shows a voltage control loop according to an exemplary embodiment;

Fig. 4 shows a phase locked loop according to an embodiment.

FIG. 1 shows a standard container 2, for example a 20, 30 or 40 foot long container. The container 2 is connected to a distribution network, in particular in a wind farm, via a connection 4. The connection 4 is in particular a connection in the medium voltage level at a voltage level of 20 kV, 33 kV or 66 kV. A stabilization regulator 6 is connected to the connection 4. A control algorithm for a converter, which is also part of the stabilization controller 6, is stored in the stabilization controller 6. The stabilization regulator 6 is connected to the connection 4 via an optional transformer 8, for example a medium-voltage transformer.

The stabilization regulator 6 is connected on the other side to a battery storage 10 and to an ohmic load 12. The load 12 can be switched separately. The load 12 can be connected in parallel to the battery storage device with the stabilization regulator 6.

In addition to the memory 10, a generator 14 can be provided. The generator 14 can be used to charge the energy store 10 u and to bridge periods with a generation deficit (e.g. due to a long calm wind). The load 12 can be connected on the three-phase side between the converter and transformer 8.

The generator 14 can also be connected directly to the stabilization controller 6. The components described can all be arranged together completely or at least partially within the container 2.

FIG. 2 shows the container 2, which is connected with the connection 4 to a busbar 16 within an island network 20. The island network 20 is formed in parts by the stabilization regulator 6 and the busbar 16 as well as wind turbines 22 connected to it. Each of the wind turbines 22 has a generator with a connected load 22a. The wind turbines 22 are also connected to one another with the busbar 16. For an island network operation, the stabilization regulator 6 is operated taking into account the impedance between the connection 4 and the busbar 16, so that it can carry out a voltage regulation.

The impedance is taken into account differently depending on the implementation variant. In the case of direct voltage control without subordinate current control, the impedance is taken into account in the voltage limitation of the controller, which results in this the voltage limit from the product of the maximum permissible current and the impedance, which implements an indirect current limitation. In the case of a subordinate current control, the impedance, as described above, is first required to convert voltage setpoints into current values and then used in the current control in the precontrol.

The following statements are purely exemplary. Any elements of the control loops can be replaced or omitted if necessary. The elements can be combined with one another as required.

FIG. 3 shows a voltage regulation of the stabilization regulator 6 as d / q regulation.

A reference voltage 26a and a measured voltage 26b are fed in as reference variables. The reference voltage 26a results from the need for the memory 12 to have a minimum state of charge. The measured voltage 26b can be measured at the output of the memory 12.

The difference value 26c is fed to a control element, for example a PI controller 28. The output value 30 can be used as the d component of a current setpoint (and using the voltage as the active power setpoint) in a phase-locked loop, as described below.

A measured current component 31 d-of the component of the nominal current can be fed via an attenuator 32. The amount of the difference can be limited. The resulting current reference value 33 can, on the one hand, be conducted via a proportional controller 34, which is dependent on the ohmic resistance between the stabilization controller and the busbar, and output as a d component of the voltage 38. The d component of the voltage 38 can also be limited in terms of amount. Furthermore, the d component of the voltage 38 can be compensated for via an attenuator 40 and / or a measured voltage 42. The resulting current reference value 33 can, on the other hand, be output via a pre-control 44, depending on the reactance of the transformer, the busbar, the choke coil and / or the line to the busbar as a proportion of the q component of the setpoint voltage 46. The q component of the nominal voltage 46 can also be limited in terms of amount. Furthermore, the q component of the nominal voltage 46 can be compensated for via an attenuator 48.

The stabilization regulator 6 can have a measured line voltage 50a and a setpoint value for the line voltage 50b as further reference variables. A difference value 52 can be carried out via a proportional controller 54. A resulting voltage value 56 can be limited.

The resulting q-component of the setpoint current 56 can on the one hand be routed via a proportional regulator 34, which is dependent on the ohmic resistance between the stabilization regulator and the busbar, and output as a q component of the setpoint voltage 46. The q component of the nominal voltage 46 can also be limited in terms of amount. Furthermore, the q component of the setpoint voltage 46 can be compensated for via an attenuator 48.

The resulting current reference value 56 can, on the other hand, be output via a precontrol 44, which depends on the reactance of the transformer, the busbar, the choke coil and / or the line to the busbar as a proportion of the d component of the setpoint voltage 38.

The pre-controls 44 can be understood as a forward connection in the voltage control loop. These are cross-connected with the d and q components of the current control.

The d component of the setpoint current 30 can be fed to a phase-locked loop according to FIG. 4 using a setpoint voltage as the setpoint active power 60a. A difference value from the target active power 60a and an actual active power 60b at the feeder can be conducted via a limiting I controller 62 with a maximum target frequency of the island network. On the one hand, as shown, the output can be used as an additional component of a frequency control or communicated to the participants via telecontrol technology. The frequency setpoint 64 can also be understood as a power setpoint for the subscriber.

A target frequency component 64 can be determined via the controller 62 from a difference between the target active power 60a and an actual active power 60b. If the output of the controller 62 is limited, e.g. B. between 0 and a maximum frequency deviation, the frequency component can be used to limit the power of the participants. A setpoint frequency 66 is subtracted from a reference frequency 80. From the

Difference, a q component of the voltage, which is fed to a measured q component of the voltage 72, is determined via a factor 82. If the active power is too high at the feeder, it can be supplied accordingly via the setpoint frequency component 64 via the controller 62.

The phase-locked loop can have a measured mains voltage 68 as a reference variable, which is transformed in block 70 into a coordinate system rotating with the mains frequency. The q component 72 of the measured voltage results from this. The coordinate transformation 70 is fed from the nominal phase 74 and the measured mains voltage 68.

The setpoint frequency 66 can be determined via a PI controller 84 and a setpoint phase 74 is determined via a further I controller 86. The phase-locked loop described and the voltage-locked loop described are purely exemplary.

Claims

Patent claims

1. A method for operating at least one participant in a stand-alone network, comprising:

Coupling of an electrical feeder, in particular an electrical storage unit and / or a generator, to the island network via a stabilization controller,

Coupling at least the subscriber to the stabilization controller, characterized in that a frequency setpoint for the stabilization controller and / or a phase setpoint for the stabilization controller is regulated in a phase-locked loop at least as a function of a measured network frequency of the island network and / or a state of charge and / or an active power of the feeder .

2. The method according to claim 1, characterized in that the active and / or reactive component, in particular d- and q-components, of a set voltage at the output of the stabilization regulator is controlled in a voltage control loop depending on a state of charge of the feeder and / or a measured mains voltage on the stabilization regulator .

3. The method according to claim 1 or 2, characterized in that an impedance between an output of the stabilization regulator and a network node of the island network is determined, that the active and / or reactive component, in particular the d and q components of the nominal voltage for the stabilization regulator is regulated as a function of the specific impedance in the voltage control loop.

4. The method according to claim 2, characterized in that a forward connection in the voltage control loop is dependent on the specific impedance.

5. The method according to any one of the preceding claims, characterized in that an active current setpoint, in particular ad component of a setpoint current from the voltage control loop is coupled into the phase locked loop.

6. The method according to any one of the preceding claims, characterized in that a power setpoint for the subscriber is output from the phase-locked loop via a communication link or that a power setpoint for the subscriber is output from the phase-locked loop via the frequency setpoint for the stabilization controller.

7. The method according to any one of the preceding claims, characterized in that a frequency setpoint for the stabilization controller is fed back in the phase-locked loop and / or that a phase setpoint for the stabilization controller is fed back in the phase-locked loop.

8. The method according to any one of the preceding claims, characterized in that in the phase locked loop from the difference between an actual power value at the feeder and a power setpoint at the feeder a first Frequency setpoint is determined and that a difference between the first frequency setpoint and the feedback frequency setpoint is determined for the stabilization controller.

9. The method according to any one of the preceding claims, characterized in that the impedance for the fundamental visual oscillation frequency is measured.

10. The method according to any one of the preceding claims, characterized in that the bandwidth of the frequency response of the stabilization controller is greater than the bandwidth of the frequency response of a converter of the subscriber.

11. The method according to any one of the preceding claims, characterized in that the stabilization controller has at least one attenuator, and that the attenuator is dependent on the impedance and / or a natural frequency of the island network and / or a transfer function of a converter of the subscriber, which is the attenuator is at least such that the stabilization regulator is stable.

12. The method according to any one of the preceding claims, characterized in that the stabilization controller feeds in active or reactive power depending on the attenuator

IS. Method according to one of the preceding claims, characterized in that a power balance of the stabilization controller and subscriber is regulated by power measurement at the subscriber and communication between the subscriber and the stabilization controller.

14. The method according to any one of the preceding claims, characterized in that the stabilization controller is frequency-controlled, the stabilization controller having a lead-lag compensator.

15. The method according to any one of the preceding claims, characterized in that the lead-lag compensator modifies an active power output at the stabilization controller in such a way that it counteracts the change in frequency.

16. The method according to any one of the preceding claims, characterized in that an output power of the participant is lower than a maximum power of the stabilization regulator.

17. The method according to any one of the preceding claims, characterized in that the stabilization controller is operated als.Slack-Bus.

18. The method according to any one of the preceding claims, characterized in that a reactive power of the participant is set depending on an active power of the participant and / or an active power of the stabilization regulator, in particular that a dependency between active and reactive power is stored in a look-up table .

19. Stabilization regulator for performing a method according to any one of the preceding claims, wherein the stabilization regulator, at least in part, together with a medium-voltage transformer and an electrical energy store in one

Standard container is installed.