Method and system for determining and controlling an electricity feed to an electricity grid from a load side of an electric circuit

Abstract

The invention relates to a method for controlling an electricity feed to an electricity grid (12) from a load side of an electric circuit (5), comprising the steps of: a) Providing a electricity feed with an associated feed duration to a controller (13) of an electric power converter (7); b) The controller (13) commissioning the electric power converter (7) to provide the electricity feed, until the electricity feed and feed duration is provided anew or until the feed duration expires. The invention further relates to a system for controlling an electricity feed of an electric source.

Claims

1. A method for controlling an electricity feed from a load side of an electric circuit (5) to an electricity grid (12), comprising the steps of: determining at least one installation parameter of the electric circuit (5); determining repeatedly an electricity load on the load side of the electric circuit (5), wherein each time the electricity load is determined, the following steps are executed: (i) determining with a computer an information on an electricity feed and an associated feed duration based on the at least one installation parameter and the electricity load, such that a temperature of the electric circuit (5) remains below a predefined maximum temperature during the feed duration; (ii) providing the information on the electricity feed with the associated feed duration from the computer to a controller (13) of an electric power converter (7), wherein the controller comprises a timer; (iii) the controller (13) commissioning the electric power converter (7) to provide the electricity feed, until one of the following conditions are met: the information on the electricity feed and the associated feed duration are provided anew by the computer or the associated feed duration expires, wherein in case the associated feed duration expires, the electricity feed is reduced to a minimum electricity feed to prevent an overheating of the electric circuit.

2. The method according to claim 1, wherein the at least one installation parameter is a nominal current of a fuse (11) protecting the electric circuit (5); a maximum contact load; a maximum wire load; a type of wall of a facility comprising the electric circuit (5); a kind of fuse; and/or a number of fuses for the electric circuit (5).

3. The method according to claim 1, wherein a temperature is determined repeatedly or continuously, wherein the information on the electricity feed and the feed duration are determined also based on the temperature.

4. The method according to claim 3, wherein the temperature is an electric circuit temperature.

5. The method according to claim 4, wherein the electric circuit temperature is estimated recursively from a surrounding temperature of the electric circuit, the electricity load on the load side of the electric circuit (5), a currently fed electricity feed and the at least one installation parameter.

6. The method according to claim 1, wherein the electricity load is estimated as an electric current load or an electric power load, wherein the electric current load is particularly determined from the electric power load, particularly from an effective power load, particularly assuming a phase angle between the electric current and the electric voltage such that the modulus of the cosine of the phase angle is not less than a predefined phase shift value.

7. The method according to claim 1, wherein the electricity load is determined for elapsed time intervals, wherein within each elapsed time interval, a predefined amount of electricity has been supplied to the load side of the electric circuit (5), wherein at the end of each time interval the electricity load is determined.

8. The method according to claim 1, wherein the electricity load is determined for elapsed time intervals, wherein the time intervals are spaced regularly and the electricity load is determined at the end of each time interval, particularly wherein the electricity load is determined from a mains connection meter (4) reading or from a mains connection measurement with a current clamp (3).

9. A system for controlling an electricity feed of an electric source comprising: an electric power converter (7); a controller (13), for controlling an electricity feed from the electric power converter (7) to an electric circuit (5); the controller (13) comprising a data storage and a timer; a computer (2) connected to the controller (13) and configured to provide information on an electricity feed and an associated feed duration to the controller (13); wherein the controller (13) is configured to repeatedly receive an information on the electricity feed and the associated feed duration from the computer (2) and to store the information on the data storage; wherein the controller (13) is further configured to commission the electric power converter (7) to provide the electricity feed and wherein the controller (13) is further configured to commission the electric power converter (7) to autonomously end the electricity feed in case the feed duration is expired even in the absence of a stop-signal or an updated information on the feed duration provided by the computer, such that a fail-safe operation mode is maintained that prevents overheating of the electric circuit in case the computer or a communication between the computer and the controller breaks down.

10. The system (1) according to claim 9, wherein the system (1) further comprises: the electric circuit (5) secured with a fuse (11); an electricity source (6) connected to the electric power converter (7) , wherein the electric power converter (7) is connected to the load side of the electric circuit (5) that is secured by the fuse (11); an electricin load sensor (3) arranged for recording data on an electricity load of the electric circuit (5); wherein the computer (2) is further connected to the electricity load sensor (3), wherein the computer (2) is configured to: (i) determine an electricity load on the electric circuit (5) from the recorded data provided by the electricity load sensor (3); (ii) determine the information on the electricity feed and the associated feed duration from the determined electricity load; (iii) provide the information on the electricity feed and the feed duration to the controller (13).

11. The system (1) according to claim 10, wherein the electricity load sensor (3) is a current clamp.

12. The system (1) according to claim 10, wherein the electricity load sensor (3) is arranged at or in a mains connection meter (4), wherein the electricity load sensor (3) either provides a power reading of the mains connection meter (4), or wherein the electricity load sensor (3) provides a signal to the computer (2) each time a predefined amount of electricity has been provided to the load side of the electric circuit (5).

13. The system (1) according to claim 9, wherein the system (1) comprises a temperature sensor (10) arranged and configured for measuring the surrounding temperature of the electric circuit (5), wherein the temperature sensor (10) is connected to the computer (2).

14. The method according to claim 1 wherein the method is executed on a system according to claim 9.

Description

(1) Further features and advantages of the invention shall be described by means of a detailed description of embodiments with reference to the figures. It is shown in

(2) FIG. 1 a schematic drawing of an electric circuit with a first embodiment of the system according to the invention;

(3) FIG. 2 a schematic drawing of an electric circuit with a second embodiment of the system according to the invention; and

(4) FIG. 3 a schematic drawing of an electric circuit with a third embodiment of the system according to the invention.

(5) In FIG. 1, FIG. 2 and FIG. 3 a system 1 according to the invention is shown. The system 1 comprises an electric circuit 5 with a plurality of power sockets 9. In one of the power sockets 9 a power consuming appliance 8 is plugged in. An electricity source 6 is connected to or comprises an inverter 7 that is connected to another power socket 9. A controller 13 is connected to the inverter 7, wherein the controller 13 is configured to control the inverter 7 and thus the power output of the combination of the electric source 6 and the inverter 7. The electric source 6 is configured to supply an electricity feed to electric circuit 5. Furthermore, the controller 13 is connected to a computer 2, wherein the computer 2 is configured to send control signals to the controller 13, which enable the controller to control the electricity feed of the electric source 6 into the electric circuit 5. The connection can be established by wire but also wirelessly. Communication with the controller 13 is checksum-secured.

(6) The external electricity grid 12 provides the electric circuit 5 with electricity. The power consumption is metered with a mains connection meter 4 that determines a power or a current provided to the electric circuit 5. The power is provided in three lines L1, L2, L3 with shifted phase and a PE line PEN.

(7) There is a variety of different kinds of mains connection meters 4 available. Some mains connection meters 4 are based on a turning wheel. Each turn of the wheel indicates a certain amount of electricity provided to the electric circuit 5, wherein the predefined amount of electricity is for example 375 turns per kilowatt (which corresponds to 2.67 W/turn) or 2000 turns per kilowatt (which corresponds to 0.5 W/turn.

(8) Therefore, the duration of a turn depends on the electricity load on the electric circuit 5. This means that a reading of the provided electricity, which is based on the determination of a completed turn, happens in sporadic time intervals whose duration cannot be predicted accurately.

(9) On the other hand, there are modern, so-called smart meters which allow an electricity reading at any time and also for fixed time intervals.

(10) The system 1 according to the invention comprises an electricity load sensor 3, connected to the electric circuit 5 that allows the estimation of the provided electricity to the electric circuit 5 on the load side.

(11) The electricity load sensor 3 can be realised as a device attached to a mains connection meter (see c.f. FIG. 3) with a turning wheel, wherein the electricity load sensor records 3 the turns of the wheel and provides a signal to the computer 2 each time a turn is completed. By additionally providing the amount of electricity per turn of the meter to the computer 2, the electricity load on the electric circuit 5 from the elapsed time interval (between two signals) can be determined by the computer 2. Modern meters 4 have integrated electricity load sensors 3 or provide in regular intervals the provided amount of electricity. In this case, the computer can be directly attached to the meter. However, a connection via internet or another network is possible as well (see c.f. FIG. 1). The electricity load on the electric circuit 5 can be determined by the computer 2 in regular intervals or even continuously, when a modern or a smart-meter is used.

(12) Alternatively, the electricity load can be estimated by a current clamp 3 (see c.f. FIG. 2). In this embodiment, the electricity load sensor 3 is the current clamp attached to a wire (L1, L2 or L3) of the electricity circuit 5 (two alternative locations of the current clamp are shown in FIG. 2, however only one has to be realized). This embodiment also allows a determination of the electric load in regular time intervals.

(13) Depending on the kind of electricity load sensor 3 the computer 2 will estimate an electric feed that can be safely provided to the electric circuit 5 without overloading the electric circuit 5 based on the determined electricity load on the electric circuit 5.

(14) However, it is only possible to determine the electric load from a past time point. Therefore, the computer 2 determines the electricity feed with an associated feed duration. The feed duration corresponds to a time point at which the temperature of the electric circuit 5 would have reached a predefined temperature, for PVC insulated wires 70° C., in case the electricity load on the electric circuit 5 would increase to its maximum (that corresponds to the nominal current of the fuse 11) right after the electricity load has been determined by the computer 2.

(15) At 70° Celsius the plasticisers of the wires and other components of the electric circuit 5 start taking damage.

(16) According to the invention, the computer controls the electricity feed such that a maximum electricity feed can be fed into the electric circuit 5 while the electric circuit reserve is never exceeded, i.e. the predefined maximum temperature is not exceeded.

(17) For this reason the computer 2 is configured to send control signals to the controller 13 that in turn is controlling the feed duration received from the computer 2 autonomously until a new feed duration and a new electricity feed are received from the computer 2.

(18) In case the feed duration has expired and no new data from the electricity load sensor 3 has been provided to the computer 2, the electricity feed will be reduced to a minimal electricity feed according to the generally recognized rules of the technology by the controller 13.

(19) Within this limit of the minimal electricity feed, the temperature will never exceed 70° but the circuit will most likely will cool down.

(20) The electric circuit 5 is secured by a fuse 11 with a nominal current.

(21) The electric reserve can be estimated from installation parameters such as the nominal current of the fuse 11, the type of wall in which the wires of the electric circuit 5 are arranged, the type of fuse and/or the number of fuses.

(22) The electric reserve of the electric circuit 5 is often times higher than the nominal current of the fuse 11. For example, if the wires of the electric circuit 5 are installed in a concrete wall, a current of 22.5 Ampere can be applied to the wires with the temperature of the wires never exceed 70° C.

(23) Therefore, if the fuse 11 has a nominal current of 16 A, even on full load on the electric circuit 5, i.e. 16 Ampere are provided to electricity consuming appliances, there is still 6.5 A reserve of the electric circuit 5 that can be permanently used for the electricity feed of the electric source 6.

(24) In case a higher electricity feed is provided to the electric circuit 5, the circuit 5 will heat up with time. The time it takes to heat up above the predefined temperature of 70° C. depends on the magnitude of the electricity feed and can be estimated by the computer 2.

(25) In another case, where the walls are dry walls, the permanent reserve of the wires is only 15.5 Ampere which is even lower than a potential nominal current of the fuse. Therefore, the permanent reserve of the electric circuit is 0 Ampere, which means under full load no additional electricity can be fed into the electric circuit.

(26) This situation is considerably improved by the system 1 and the method according to the invention. Here, the electricity load is determined (at least for a past interval) and based on the electricity load, the electricity feed and an associated feed duration is determined, wherein the electricity feed is particularly using the full available electricity circuit reserve. By providing the feed duration, it is ensured that the electric circuit 5 cannot overheat, i.e. heating up more than 70° C.

(27) In most cases however, a new electric load is determined before the feed duration expires. Then, the electricity feed does not need to be reduced to the minimum but can be recalculated based on the latest reading of the electricity load. Also a new associated feed duration will be determined based on the latest reading of the electricity load.

(28) This way, the system 1 and method is updating its status repeatedly, while maintaining a failsafe operation mode that is particularly ensuring that, if for example a communication between the computer and any of the other components is broken or malfunctioning, the electric circuit is not overheating, as the system falls back to a safe operating state after the latest determined feed duration has expired.

(29) If, additionally to the electricity load, also the temperature of the electric circuit 5 is estimated, the calculation of the electricity feed and the feed duration can account also for the temperature of the electric circuit 5. If a temperature reading is not available a more conservative approach for calculating the electricity feed and duration has to be chosen.

(30) The temperature of the electric circuit 5 can be recursively estimated by measuring the surrounding temperature of the electric circuit and assuming an initial temperature of the electric circuit of 70°. The method and the system 1 will then calculate based on material constants and dissipation characteristics of the electric circuit 5 the electricity feed and its associated duration as well as the temperature of the electric circuit 5 each time a new electricity load (and the surrounding temperature) is provided.

(31) Therefore, the initially assumed electric circuit temperature of 70° C., will successively reach an actual electric circuit temperature.

(32) The temperature of the surrounding can be determined with a temperature sensor 10.