Method for operating an island system, and island system

Patent metadata

Field	Value
Publication number	US-11005270-B2
Application number	US-201916727215-A
Country	US
Kind code	B2
Filing date	Dec 26, 2019
Priority date	Jun 28, 2017
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

A method for operating an island system is disclosed. The island system includes a group of voltage-controlling converters, wherein each of the voltage-controlling converters of the group are configured to convert power of respectively connected regenerative power sources into AC power in accordance with a respective frequency-power characteristic curve. The island system also includes a load having a power consumption that depends on a voltage amplitude of an AC voltage of the island system, and a control unit that is configured to transmit a default value of the voltage amplitude to the group of voltage-controlling converters. The method adapts the power to be consumed by the load.

First claim

The invention claimed is:

1. A method for operating an island system, the island system comprising
a group of voltage-controlling converters, wherein each of the voltage-controlling converters of the group is configured to convert power of respectively connected regenerative power sources into AC power in accordance with a respective frequency-power characteristic curve,
a load having a power consumption that depends on a voltage amplitude of an AC voltage of the island system, and
a control unit that is configured to transmit a default value of the voltage amplitude to the group of voltage-controlling converters,
wherein the method comprises the following acts for adapting a power to be consumed by the load:

modifying the frequency-power characteristic curve of at least one of the voltage-controlling converters as a function of an available power of the respective regenerative power source,
wherein the frequency-power characteristic curve is modified, at least in sections, to a higher frequency at a given power in order to check whether the available power of the regenerative power source lies above the current power, and
wherein the frequency-power characteristic curve is modified, at least in sections, to a lower frequency at a given power if the regenerative power source cannot yield the power associated with the current frequency according to the frequency-power characteristic curve,

determining a frequency of the AC voltage in the island system as a consequence of the modifying of the frequency-power characteristic curve by the control unit, and
predetermining a default value of the voltage amplitude and transmitting the redetermined default value to the group of voltage-controlling converters by means of the control unit, wherein the default value is increased if the determined frequency lies above a nominal frequency, and wherein the default value is reduced if the determined frequency lies below the nominal frequency.

2. The method as claimed in claim 1 , further comprising, prior to increasing the default value of the voltage amplitude:
performing a check as to whether a power flowing through the at least one voltage-controlling converter exceeds, or threatens to exceed, a power limit thereof, wherein the default value of the voltage amplitude is not increased if the power limit will be exceeded with an increased default value of the voltage amplitude, or
performing a check as to whether the power consumption of the load exceeds, or threatens to exceed, a maximum admissible power consumption of the load, wherein the default value of the voltage amplitude is not increased if the maximum admissible power consumption of the load will be exceeded with an increased default value of the voltage amplitude.

3. The method as claimed in claim 2 , further comprising ascertaining the power limit of the corresponding voltage-controlling converter on the basis of maximum permitted current and/or voltage values of the voltage-controlling converter.

4. The method as claimed in claim 2 , further comprising adapting the power to be consumed by the load in the case of known values of the power limit of the converter, of the regenerative power source associated with the converter and/or of the maximum admissible consumption P max,Last of the load in such a way that
the power flowing through the at least one voltage-controlling converter lies by at least one preset tolerance value below the power limit of the corresponding voltage-controlling converter and/or of the regenerative power source associated with the converter, or
a power consumption of the load lies by at least one preset tolerance value below the maximum admissible consumption of the load.

5. The method as claimed in claim 1 , further comprising measuring a voltage value at a DC link circuit associated with the corresponding voltage-controlling converter during a check as to whether the regenerative power source can yield the power associated with the current frequency according to the frequency-power characteristic curve.

6. The method as claimed in claim 5 , further comprising signaling that the regenerative power source is unable to yield the power associated with the current frequency according to the frequency-power characteristic curve if the measured voltage value drops below a voltage threshold.

7. The method as claimed in claim 1 , wherein the modifying of the frequency-power characteristic curve includes a parallel displacement of at least one section of the frequency-power characteristic curve in a direction parallel to the frequency axis.

8. The method as claimed in claim 1 , wherein the frequency-power characteristic curve is described by a straight line in at least one section thereof, wherein the change in the frequency-power characteristic curve includes a change in a straight-line slope in the at least one section.

9. The method as claimed in claim 1 , wherein the group contains a multiplicity of voltage-controlling converters, which are each configured to convert power of connected regenerative power sources into AC power in accordance with a frequency-power characteristic curve, and wherein the modification of the frequency-power characteristic curve as a function of the available power of the power source associated with the converter is implemented for each individual converter.

10. The method as claimed in claim 1 , wherein the acts of adapting the power to be consumed by the load are performed repeatedly in order to track a change of the maximum available power of the regenerative power source over time or in order to track a power limit of the corresponding converter over time.

11. An island system, comprising:
a group of voltage-controlling converters each comprising a DC/AC converting module, wherein the input of each voltage-controlling converter is connected to a respective regenerative power source and an output thereof is connected to an AC conductor of the island system,
wherein each of the voltage-controlling converters is configured to control an AC voltage in the island system as a function of a frequency-power characteristic curve associated with the respective voltage-controlling converter,
a load having a power consumption that depends on a voltage amplitude of the AC voltage in the island system,
a control unit configured to control the group of voltage-controlling converters, wherein the control unit is configured to transfer to the group a default value of the voltage amplitude for the AC voltage of the island system, and
a detection unit configured to determine a frequency of the AC voltage in the island system, wherein the detection unit is connected to the control unit,
wherein the control unit, in adapting a power to be consumed by the load, is further configured to:
modify the frequency-power characteristic curve of at least one of the voltage-controlling converters as a function of an available power of the respective regenerative power source,
wherein the frequency-power characteristic curve is modified, at least in sections, to a higher frequency at a given power in order to check whether the available power of the regenerative power source lies above the current power, and
wherein the frequency-power characteristic curve is modified, at least in sections, to a lower frequency at a given power if the regenerative power source cannot yield the power associated with the current frequency according to the frequency-power characteristic curve,

determine a frequency of the AC voltage in the island system as a consequence of the modifying of the frequency-power characteristic curve, and
predetermine a default value of the voltage amplitude and transmitting the redetermined default val

Assignees

• Sma Solar Technology Ag

Inventors

• Falk Andreas
• Hardt Christian
• Bechtel Neidhardt
• Hermeling Dirk

Classifications

• H02J2101/28

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• H02J2101/10

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