AT514766B1 - Method for stabilizing an energy distribution network - Google Patents

Abstract

Method for stabilizing an energy distribution network (3) including an energy management system (1) of at least one building (2), where - in the energy distribution network (3) at a point in the area from the network connection point of the building to the energy distribution cabinet network connection point of the building in the area up to the The transformer of the energy distribution network (3) closest to the building is measured, - the measured voltage values are compared with a given voltage-active and reactive power characteristic curve that ensures network stability and / or the current measured values are compared with a given current active and reactive power that ensures network stability -Characteristic curve are compared, - the difference between the measured values and the characteristic curve is forwarded to the energy management system and - if the range specified by the reactive power characteristic curve or the active power characteristic curve is exceeded, the energy management system (1) calculates which Components of the building have to change their output in order to return to the area within the active or reactive power characteristic curve, and the change in output is carried out by component (7).

Description

description

PROCESS FOR STABILIZING AN ENERGY DISTRIBUTION GRID

TECHNICAL AREA

The invention relates to a method for stabilizing an energy distribution network, including an energy management system of at least one building, and a corresponding device.

[0002] The planning and operation of energy-related generation and consumption units belongs to energy management. The goals are resource conservation as well as climate protection and cost reductions, while safeguarding the users' energy needs.

STATE OF THE ART

The classic network operation in the electricity supply is facing major challenges due to the increasing penetration of decentralized, mostly renewable energy generation systems (DEA). In addition, there is the development of electromobility and thus an increase in the substitution of other forms of energy transmission by electricity. The so-called “Smart Grid” is seen as a solution to these problems. The smart grid or intelligent power network comprises the communicative networking and control of power generators, storage systems, electrical consumers and network operating resources in the energy transmission and distribution networks of the electricity supply.

The network stability in energy transmission and energy distribution networks can be jeopardized mainly in two areas: The predominant problem in rural networks is voltage maintenance, which is also referred to as the "U problem". In urban networks, which have rather short line lengths due to the load density, it is less the voltage maintenance than the problem of the utilization of equipment that is predominant. This is also known as the "I problem". Decentralized feeders initially reduce the high utilization of lines and transformers. In the rarest of cases, however, the performance limits are also violated when regenerating.

And it can also e.g. in suburban areas network sections within a network area tend to have both a rural and an urban character. In order to still adhere to the voltage limits specified by standards (e.g. EN50160) for the last participant and not to overload the equipment, either network expansion must be carried out or an active network management system must be used. The latter accesses producers, flexible consumers or storage in the network in a targeted manner in order to maintain network operation in accordance with standards.

In the future, so-called “smart buildings”, also referred to as intelligent houses or intelligent buildings, will also contain components such as fluctuating generators (e.g. photovoltaic systems, small wind turbines), flexible consumers and storage devices for electrical energy, or the charging infrastructure for electric vehicles. The building becomes "smart" or intelligent through the use of a modern building automation system. Building automation comprises the entirety of monitoring, control, regulation and optimization devices in buildings. The aim is to carry out functional processes across components independently (automatically) and according to specified setting values (parameters). All sensors, actuators, operating elements, consumers and other technical units in the building are networked with one another. Processes can be summarized in scenarios. The distinguishing feature is the continuous networking by means of a bus system.

The building automation systems of the Smart Buildings, or the energy management systems as part of the building automation systems, must therefore optimize the internal requirements of electrical and thermal energy for the individual components of the building, create local forecasts (related to the building) and provide flexible tariff specifications that market- or also

have network-specific shares.

This means, however, that the smart grid cannot have access to the individual components of a smart building, because otherwise the building-internal optimization, such as the so-called day-ahead optimization, would no longer be possible.

For electricity generation systems> 100kW, it is therefore provided in Germany, for example, due to the so-called medium voltage directive (directive for connection and parallel operation of generation systems on the medium voltage network) that the electricity generation systems must contribute to static and dynamic network stabilization by themselves. Smaller electricity generation systems, such as those in smart buildings, could therefore also meet similar requirements in the future.

DISCLOSURE OF THE INVENTION

The aim of the present invention is to provide a solution for smart buildings that feed electrical power into the energy distribution network, which makes at least a contribution to static network stabilization.

With static network stabilization, inverters must be able to feed inductive or capacitive reactive power into the network at the request of the network operator in order to compensate for the reactive power balance in the network and to keep the network voltage in the medium-voltage network stable.

In addition, it should be possible to automatically reduce the active power as a function of the network frequency. In accordance with the medium-voltage directive, this is done using a characteristic curve called statics (40% per Hz) from leaving the normal frequency band at 50.2 Hz (upper frequency limit of the primary control) to switching off the generating unit at a frequency greater than 51.5 Hz Taken from the TransmissionCode 2007 so that medium-voltage systems behave in the same way as power plants on the transmission network with regard to the global size of the network frequency.

In contrast to this, the dynamic network stabilization causes the voltage to be maintained in the event of small, controllable network faults in order to prevent unintentional simultaneous disconnection of the feed power and thus entire network breakdowns. According to the medium-voltage directive, the generating plants cannot simply switch themselves off in the event of faults in the network and must provide a defined short-circuit current in the event of a short circuit in the public network.

In both static and dynamic grid stabilization, the producers in smart buildings should be actively involved in the operation of the smart grid, on the other hand, the producers should be involved in the internal optimization processes of the smart building and would not or only to a limited extent the network stabilization of the smart grid are available.

It is therefore the object of the present invention to create a balance between these contradicting requirements.

This object is achieved by a method having the features of claim 1 by

- the voltage is measured in the energy distribution network at a point in the area from the network connection point of the building to the building's energy distribution cabinet and / or at a point remote from the network connection point of the building in the area up to the transformer of the energy distribution network electricity closest to the building,

- the measured voltage values are compared with a specified active and reactive power characteristic curve that ensures network stability and / or the measured current values are compared with a specified active and reactive power characteristic curve that ensures network stability,

- the difference between the measured values and the characteristic curve is forwarded to the energy management system and

- if the reactive power characteristic curve or the active power

The energy management system calculates which components of the building have to change their output in order to return to the area within the active or reactive power characteristic curve.

- and the performance change is carried out by the component.

According to the invention, the voltage measurement takes place near the building, that is to say somewhere between the network connection point (including this) and the energy distribution cabinet of the building. The current measurement should not take place at the network connection point of the building, but at a point in the area up to the next transformer or where a high power load is to be expected.

The change in performance can be provided by one component of the building or by several components.

The fact that the energy management system calculates how the externally specified active and reactive power characteristics are maintained, the needs of the building can be taken into account accordingly.

In the case of voltage measurement, it is advantageous if the voltage is measured at the network connection point from the building to the energy distribution network. In doing so, but also in general, either only the voltage of one phase is measured or an average value is formed over all phases, depending on whether one can assume that there is no or uneven load on the phases.

In the case of current measurement, it is advantageous if the current is measured on the closest transformer and / or on the most heavily loaded line segment of the network line from which the building is supplied. In the case of negligible generation capacity in the line under consideration, the line segment with the highest load is usually the first line segment starting from the transformer. If there is a high level of penetration with generators, this can also be a different line segment. In general, either only the current in one phase is measured or an average value is formed over all phases, depending on whether there is no load or an unequal load on the phases.

So that the distribution network operator can change the active and reactive power characteristics depending on the time of day or season, a variant of the invention provides that the reactive power characteristics, which are stored in the energy management system, changed by the operator of the energy distribution network via a data connection to the energy management system, in particular continuously will.

Another problem in low-voltage networks is the uneven loading of the infrastructures and thereby overloading or violation of the voltage limits of individual phases. If the method according to the invention is also to be used to reduce such asymmetries in the load, in the case of voltage measurement it is provided that the voltage of several phases, in particular of all three phases, is measured and, in the case of an uneven load distribution between the phases, the energy management system calculates from which phases active or reactive power is reduced or increased in order to reduce the uneven load distribution, and a corresponding switching of components of the building from one to another phase takes place.

Similarly, in the case of current measurement, it can be provided that the current is measured in several phases, in particular in all three phases, and in the event of an uneven load distribution between the phases, the energy management system calculates the phases of which active or reactive power is reduced or increased, in order to reduce the uneven load distribution, and a corresponding switching of components of the building from one to another phase takes place.

The component of the building whose power is changed can be an inverter of a photovoltaic system.

One possible device for performing the method according to the invention is

characterized in that

- In the energy distribution network close to the building, i.e. at a point away from the building's network connection point in the area up to the transformer of the energy distribution network closest to the building, at least one measuring device for measuring electricity and / or at a point in the area from the building's network connection point to the power distribution cabinet of the Building is provided with at least one measuring device for measuring voltage,

- An energy management system is provided with which the measured voltage values can be compared with a given voltage-active and reactive power characteristic curve that ensures network stability and / or the measured current values can be compared with a given current-active and reactive power characteristic curve that guarantees network stability,

- With the energy management system, if the range specified by the active or reactive power characteristic is exceeded, it can be calculated which components of the building must change their output in order to return to the area within the reactive power characteristic, and

- Data connections of the energy management system to the components are provided in order to carry out the change in performance by the component.

[0027] Further design variants of the device according to the invention are specified in the dependent device claims.

The invention offers the following advantages:

Because the control is based on the power, in the event that several buildings in a network section of the power distribution network work according to the invention, several or even all buildings work together to stabilize the network, but at the same time they only contribute according to their performance at. The system therefore does not overshoot, as would be the case with an uncoordinated control.

By appropriately coordinating the setting parameters of the energy management systems of the individual buildings, it can be ensured that buildings with “weak” network connection points are not disproportionately influenced in the internal optimization, in that constant adjustments to the performance are required.

With the method according to the invention, the available network capacity of the energy distribution network can also be better utilized. Expensive expansion through increasing feed-in with renewable generators with low full load hours (which causes a high output load) or due to the load increase through the substitution of other forms of energy can be avoided or delayed.

[0032] If guidelines similar to those of the German medium-voltage guideline should also be issued for smart buildings, then these could be met with the present method.

The new functionality of the Smart Buildings can lead to an increase in added value through the energy management system, in that the contribution to network stability is offered to the network operator in return for appropriate compensation.

BRIEF DESCRIPTION OF THE FIGURES

To further explain the invention, reference is made in the following part of the description to the figures, from which further advantageous embodiments, details and developments of the invention can be found. Show it:

1 shows a diagram of a device according to the invention,

[0036] FIG. 2 shows an example of a combined active and reactive power characteristic curve as a function of the voltage,

3 shows an example of a combined active and reactive power characteristic as a function of the current.

CARRYING OUT THE INVENTION

1 shows an example of the scheme of an energy management system 1 of a building 2, namely a smart building that is connected to the energy distribution network 3.

So-called energy management generally coordinates the procurement, conversion, distribution and use of energy, here electrical energy. The coordination is forward-looking, organized, systematic and taking ecological and economic objectives into account.

An energy management system is understood to mean the implementation of energy management and the implementation of the necessary organizational and information structures, including the necessary technical measures such as e.g. Software. According to the invention, an energy management system therefore comprises at least one computer or a PLC with energy management software as well as data connections (e.g. data lines) to information sources, measuring devices and the components of the building 2 to be controlled.

Only part of the energy management system 1 is shown here, namely the so-called Building Energy Agent (BEA) 4, which is usually implemented by software. It exchanges information with the individual components of the building via data connections (here generally shown with double-line arrows), which are essentially divided into three groups: consumers 5, storage units 6 and generators (producers) 7. It is an input option 8 provided for customer requests, by means of which users of the building 2 can influence the energy distribution in the building themselves and, for example, start or stop the loading of memories 6 by the generators 7.

The BEA 4 is used to optimize consumers 5, stores 6, generators 7 and possibly also electromobility (for example in the form of a charging station for electric vehicles) through so-called day-ahead deployment planning under external influencing variables (meteorological data, market prices of the energy exchange ( EEX), customer requests, ...).

The BEA 4 and the components consumer 5, memory 6 and generators 7 are also in connection with the intelligent electricity meter (smart meter) 9 of the building 2. This shows the connection user the actual energy consumption and the actual usage time and is in that Communication network of the energy distribution network integrated. These smart meters 9 are usually controlled by a microprocessor and can automatically transmit the data collected to the energy supply company. Via the connection line measured by the smart meter 9, electrical energy, generally represented here by simple black arrows, is drawn from or fed into the energy distribution network 3.

The BEA 4 is also connected to data sources outside of the building 2, for example to those for weather forecasts 10 or for the energy market 11 (in particular with regard to the development of electricity prices). With this, the BEA 4 can plan when energy has to be absorbed from outside into building 2 (e.g. because no sunshine is expected and the photovoltaic system as generator 7 is supplying less energy) or should (because the electricity price is currently low).

Essential to the invention, however, is a component of the BEA 4, which forms a formal access point to the energy distribution network 3, in particular to a smart grid, namely the so-called building-to-grid adapter for ensuring network stability, BGA-SN, 12 for short. Due to the functionality of the BGA-SN 12, specific critical network conditions, e.g. actively prevented as a result of deviations from the day-ahead deployment planning of the BEA 4. The main goal is to prevent possible violations of the applicable standards for voltage limits or overloading of the equipment of the energy distribution network 3 and thus also to actively contribute to the protection of damage to components of the energy distribution network 3, such as transformers, through to blackout avoidance.

The BGA-SN 12 has a data connection, shown here by a dashed arrow, using a first protocol P1 to the measuring point for the voltage

and / or the electricity. The BGA-SN 12 is connected to the Building Energy Agent (BEA) 4 with a further data connection and using a second protocol P2, which in turn is connected to the distribution network operator 13 via a data connection and using a third protocol P3.

To solve a U problem by means of the BGA-SN 12, the procedure is as follows: at the connection point (network connection point) of the building 2 to the power distribution network 3, a three-phase measurement of the voltage takes place with a high resolution. This requires so-called power quality measuring devices or smart meters of the appropriate suitability. The measuring devices transmit the data with a first protocol P1 (e.g. M-Bus radio, MODBUS, 1EC60870-5-104, ...) to the BGA-SN 12.

The network connection point is depending on the power consumption of the building 2 in network level seven (in the low-voltage network), in network level six (low-voltage busbar of the network transformer) or in network level five (in the medium-voltage network). Depending on the situation, the following settings for the operational management system or active network management system must be coordinated in the medium or low voltage level.

Based on the medium voltage directive regarding the type of possible influence of a network operator, the BGA-SN 12 ensures a fictitious P (U) / Q (U) characteristic curve for the smart grid according to FIG. 2. The distribution network operator 13 can use the third protocol P3 influence the impressed characteristic curve by changing the characteristic curve support points.

As can be seen from FIG. 2, there is a need for four-quadrant operation for active and reactive power. Via the BGA-SN 12, the BEA 4 reduces or increases the active or reactive power according to the voltage value at the connection point. If necessary, a suitable temporal mean value formation from the temporally high-resolution voltage values is also necessary. If the variant of the invention is used to compensate for unequal loads on the individual phases, the voltages must be measured individually in each phase - otherwise the phases could also be averaged.

An example of a relative characteristic curve is given in FIG. However, after appropriate parameterization, an absolute characteristic can also be impressed. The quotient of the voltage difference AU (measured voltage U minus the nominal voltage Unom) and the nominal voltage Unom is plotted on the horizontal axis, the quotient of the difference in reactive power AQ (measured reactive power Q minus the nominal reactive power Qnenn) and the nominal reactive power Qnenn as well as the quotient from the difference in power is plotted on the vertical axis AP (measured electrical power P minus nominal power Pnenn) and nominal power Pnenn.

Specifically, the BGA-SN 12 reports the currently necessary active or reactive power change to the BEA 4 via protocol P2 according to the set characteristic curve. This decides according to the momentary optimization through which component of the building 2 these changes are to be made to the building-internal Interfere with optimization as little as possible. Protocol P2 is also used to pass on this information.

The protocol P3 for data transmission between BEA 4 and distribution network operator 13, more precisely its active network management system, is used to change the characteristic curve support points not only once by engineering, but also dynamically (e.g. depending on the time of day or season).

The BGA-SN 12 can also contribute to solving an II problem: for this expression, the same requirements apply as for solving a U problem, it follows analogously, only that instead of a voltage measurement, a current measurement using the Protocol P1 takes place.

Based on the medium-voltage guideline regarding the type of possible influence of a network operator, the BGA-SN 12 ensures a fictitious P (1) / Q (l) characteristic curve for the smart grid according to FIG. 3. The distribution network operator 13 can use the third protocol P3 influence the impressed characteristic curve by changing the characteristic curve support points.

As can be seen from FIG. 3, there is a need for four-quadrant operation for active and reactive power. Via the BGA-SN 12, the BEA 4 reduces or increases the active or reactive power according to the current value at the measuring point. If necessary, a suitable temporal mean value formation is also necessary from the current values with high temporal resolution. If the variant of the invention is used to compensate for unequal loads on the individual phases, an individual measurement of the current in the individual phases is required, otherwise averaging over the phases could also be carried out.

An example of a relative characteristic curve is given in FIG. However, after appropriate parameterization, an absolute characteristic can also be impressed. The quotient of the current difference Al (measured current | minus nominal current Inenn) and nominal current Inenn is plotted on the horizontal axis, and the quotient of the power difference AP (measured electrical power P minus nominal power Pnenn) and nominal power Pnenn is plotted on the vertical axis.

The two versions with voltage or current measurement can be used separately depending on the network version, in the case of suburban networks, for example, where U and I problems occur in combination, can also be used in combination.

If there are asymmetries between the individual phases of the power distribution network 3, in the event of a U problem after measuring the voltage of all three phases from the BGA-SN 12, a suggestion can be calculated as to which phases active or reactive power is reduced and at which should be increased. According to the invention, the BGA-SN 12 only provides a suggestion, e.g. Reduce active power on phase L1 by 20kW. The BEA 4 then uses optimization to decide how the proposal will be implemented. The components controlled by the BEA 4, such as The inverters of the photovoltaic system have a physical switching device (e.g. with three-phase photovoltaic inverters), which can change the phase assignment.

In the case of an I problem, the procedure is analogous, but instead of the voltage, a three-phase current measurement is used in order to reduce or compensate for any asymmetries with regard to the load in critical network components (transformer, certain line sections with the highest load).

REFERENCE CHARACTERISTICS LIST:

1 energy management system

2 buildings (Smart Building)

3 Energy distribution network

4 Building Energy Agent (BEA)

5 consumers

6 memories

7 generators (producers)

8 Input option for customer requests 9 Intelligent electricity meter (Smart Meter) 10 Data source for weather forecasts

11 Data source for the energy market

12 Building-to-Grid adapter to ensure grid stability (BGA-SN) 13 Distribution network operator (operator of the energy distribution network)

P1 first protocol

P2 second protocol

P3 third protocol

Claims (14)

Claims 1. A method for stabilizing an energy distribution network (3) including an energy management system (1) of at least one building (2), wherein - The voltage is measured in the energy distribution network (3) at a point in the area from the building's network connection point to the building's energy distribution cabinet and / or current is measured at a point remote from the building's network connection point in the area up to the transformer of the energy distribution network (3) closest to the building, - the measured voltage values are compared with a specified active and reactive power characteristic curve that ensures network stability and / or the measured current values are compared with a specified active and reactive power characteristic curve that ensures network stability, - the difference between the measured values and the characteristic curve is forwarded to the energy management system and - If the range specified by the reactive power characteristic or the active power characteristic is exceeded, the energy management system (1) calculates which components of the building have to change their output in order to return to the area within the active or reactive power characteristic, - and the change in performance is carried out by component (7). 2. The method according to claim 1, characterized in that the voltage at the network connection point from the building (2) to the energy distribution network (3) is measured. 3. The method according to claim 1 or 2, characterized in that the current is measured on the closest transformer and / or on the most heavily loaded line segment. 4. The method according to any one of claims 1 to 3, characterized in that the active and reactive power characteristics that are stored in the energy management system (1) are changed by the operator of the energy distribution network (13) via a data connection to the energy management system (1). 5. The method according to any one of claims 1 to 4, characterized in that the measurement of current and / or voltage takes place on a single phase or on several phases with subsequent averaging over the phases. 6. The method according to any one of claims 1 to 4, characterized in that the voltage of several phases, in particular of all three phases, is measured and, in the event of an uneven load distribution between the phases, the energy management system (1) calculates which phases are active or reactive power is reduced or increased in order to reduce the uneven load distribution, and a corresponding switching of components (7) of the building (2) from one to another phase takes place. 7. The method according to any one of claims 1 to 4 or 6, characterized in that the current is measured in several phases, in particular in all three phases, and in the event of an uneven load distribution between the phases, the energy management system (1) calculates from which phases Active or reactive power is reduced or increased in order to reduce the uneven load distribution, and a corresponding switching of components (7) of the building (2) from one to another phase takes place. 8. The method according to any one of claims 1 to 7, characterized in that the component of the building whose power is changed is an inverter of a photovoltaic system. 9. Device for performing a method according to one of claims 1 to 8, wherein - in the energy distribution network (3) at a point remote from the network connection point of the building (2) in the area up to the transformer of the energy distribution network (3) closest to the building (2) a measuring device for measuring current and / or at least one measuring device for measuring voltage is provided at a point in the area from the network connection point of the building (2) to the energy distribution cabinet of the building (2), - An energy management system (1) is provided, with which the measured voltage values are compared with a given voltage-active and reactive power characteristic that ensures network stability and / or the measured current values are compared with a given current-active and reactive power characteristic that ensures network stability can be _ - with the energy management system (1), if the range specified by the active or reactive power characteristic is exceeded, it can be calculated which components (7) of the building (2) must change their output in order to return to the area within the reactive power characteristic, and - Data connections of the energy management system to the components are provided in order to carry out the change in performance by the component (7). 10. The device according to claim 9, characterized in that the measuring device for measuring the voltage at the network connection point from the building (2) to the energy distribution network (3) is provided. 11. The device according to claim 9 or 10, characterized in that the measuring device for measuring the current is provided at least on the closest transformer and preferably also on the line segment with the highest load. 12. Device according to one of claims 9 to 11, characterized in that a data connection between the distribution network operator (13) and the energy management system (1) is provided to the active and reactive power characteristics that are stored in the energy management system (1) through the Distribution system operator (13) to be able to change continuously. 13. Device according to one of claims 9 to 12, characterized in that the measuring device for measuring the voltage and / or the current is connected to several phases, in particular all three phases, and the energy management system (1) is designed such that it can calculate from which phases active or reactive power is reduced or increased in order to reduce an uneven load distribution, and the components (7) of the building (2) have a switching device for changing the phase assignment. 14. Device according to one of claims 9 to 13, characterized in that the component of the building (2), the power of which can be changed by the energy management system (1), is an inverter of a photovoltaic system. For this purpose 2 sheets of drawings