METHOD FOR SYNCHRONIZING A GENERATOR WITH A POWER SUPPLY NETWORK

Description

[0001] The present invention relates to a method for synchronizing a generator with a mains frequency power supply network having the features of the preamble of claim 1, an internal combustion engine for driving a generator, a computer program product for synchronizing a generator with a mains frequency power supply network having the features of the preamble of claim 10, and a computer-readable storage medium with such a computer program product.

[0002] Typical methods for synchronizing a generator with a power supply network operating at a grid frequency include the following steps: Mechanically driving the generator by means of an internal combustion engine, in particular a gas engine, generating a generator speed that corresponds to a generator frequency generated by the generator at the given generator speed; regulating or controlling the internal combustion engine so that the generator frequency is within a tolerance range, wherein the grid frequency is within the tolerance range; detecting a phase angle difference between a current and / or voltage generated by the generator on the one hand and a grid current and / or grid voltage on the other; synchronizing the voltage and / or current generated by the generator on the one hand with the grid voltage and / or grid current on the other by reducing, in particular minimizing, the phase angle difference; electrically connecting the generator to the power supply grid.

[0003] To synchronize the generator with the power grid, it is known to be necessary to first increase or decrease the generator speed to a value corresponding to the current frequency and subsequently to regulate it accordingly, whereby the phase angle of the generator must be brought essentially into agreement with that of the power grid.

[0004] This is described, for example, in EP 2 651 000 A2, which states that after the generator speed is increased, a waiting period is observed until the phase angle of the generator and the power grid match within certain limits, and then the generator is electrically connected to the power grid. This procedure involves a relatively long synchronization time.

[0005] EP 3 561 988 A1 describes a method for reducing synchronization time by selectively interrupting either the fuel supply or the ignition for specific cylinder units. Particularly in the case of turbocharged combustion engines, where the mixture is already formed before entering a cylinder unit (and thus the combustion chamber), interrupting the ignition when using, for example, natural gas as fuel results in high methane emissions, which are released unburned into the atmosphere via the exhaust system.

[0006] Furthermore, the emission of unburned fuel-air mixtures via the exhaust system (which usually has high temperatures) leads to deflagrations (also known as misfires), which can cause significant noise pollution, damage and unwanted emissions.

[0007] Other methods known from the prior art can be found, for example, in WO 2017 / 051156 A1, US 2012 / 175876 A1 or EP 2 433 355 B2.

[0008] The object of the present invention is therefore to provide a method for synchronizing a generator with a power supply network which at least partially improves the aforementioned disadvantages of the prior art and / or shortens the synchronization time between the generator and the power supply network and / or reduces emissions during synchronization and / or provides a more resource-efficient method for synchronization.

[0009] According to the invention, this is achieved by a method for synchronizing a generator with a power supply network having a mains frequency according to the features of claim 1, an internal combustion engine with the features of claim 9, a computer program product with the features of claim 10 and a computer-readable storage medium with such a computer program product.

[0010] According to the invention, a method for synchronizing a generator with a power supply network having a mains frequency comprises the following steps: a) Mechanically driving the generator by means of an internal combustion engine, in particular a gas engine, generating a generator speed corresponding to a generator frequency produced by the generator at the given generator speed; b) Regulating or controlling the internal combustion engine so that the generator frequency lies within a tolerance range; c) Detecting a phase angle difference between a current and / or voltage generated by the generator on the one hand and a grid current and / or grid voltage on the other; d) Synchronizing the voltage and / or current generated by the generator on the one hand with the grid voltage and / or grid current on the other by reducing, in particular minimizing, the phase angle difference; e) Electrically connecting the generator to the power supply network wherein the reduction of the phase angle difference is achieved by at least a temporary change in the ignition timing of at least one cylinder unit of the internal combustion engine.

[0011] By temporarily changing the ignition timing of at least one cylinder unit of the internal combustion engine according to the invention, the power output or engine speed can be changed with high precision over very short periods, so that the phase angle difference can be reduced without changing the speed to such an extent that the generator frequency would leave the tolerance range. Nevertheless, complete combustion of the supplied fuel-air mixture can take place simultaneously in the at least one cylinder unit, thus preventing any significant increase in the emissions emitted by the internal combustion engine.

[0012] Of course, the invention may also additionally provide for the use of changing the ignition timing to adjust the speed of the internal combustion engine.

[0013] Furthermore, misfires or deflagrations in the exhaust system of the combustion engine are prevented, as the unburned fuel-air mixtures no longer reach it.

[0014] By temporarily – preferably intermittently – adjusting the ignition timing, a very quick and uncomplicated change in the phase angle difference can still be made, which allows for very quick synchronization between the generator and the power supply network in order to connect the generator electrically to the power supply network.

[0015] Especially when using stationary combustion engines for generating and feeding electrical energy into a power grid, this has the significant advantage that these stationary combustion engines can be started up very quickly and connected to the power grid in order to stabilize sudden instabilities in the power grid (for example, caused by the collapse of an energy supply from an alternative energy source - photovoltaic system) in order to avoid possible power grid collapses.

[0016] Especially in view of the increasing number of alternative energy sources, it is becoming increasingly necessary (since alternative energy sources, such as photovoltaic systems, can generate massive energy fluctuations in a power supply network by obscuring the sun with clouds) to take stabilization measures for a power supply network.

[0017] In order to stabilize these fluctuations in the power supply network and to prevent a possible grid collapse, it is necessary to be able to replace these short-term and short-term drops in alternative energy sources with alternatives. Therefore, it is of high priority to be able to connect corresponding energy sources to a power supply network as quickly as possible, as is permitted by the present invention under still acceptable conditions with regard to emissions, energy consumption and the environment.

[0018] Corresponding electrical power supply systems are also referred to as gensets, in which a stationary combustion engine - preferably a gas engine - drives a generator which can be electrically connected to a power supply network.

[0019] A method according to the invention can also be used in already known embodiments of the prior art, as described, for example, in the introduction to the description, and can be installed subsequently.

[0020] In a particularly preferred embodiment of the invention, the reduction of the phase angle difference can be achieved primarily solely by the inventive temporary change of the ignition timing of at least one cylinder unit of the internal combustion engine. Secondary changes to maintain the engine speed within the tolerance range (for example, slightly opening the throttle valve) must, of course, still be carried out if necessary.

[0021] The temporary change in ignition timing can be made for all cylinders of the internal combustion engine, for individual cylinders, or for groups of cylinders. It is particularly preferred that the temporary change in ignition timing be made for all cylinders of the internal combustion engine.

[0022] To connect the generator rotor to the power grid, a connection criterion may be required. Such a criterion could, for example, include the generator speed being within a predefined tolerance range and the phase angle difference being within a further predefined tolerance range.

[0023] A power supply network can refer to a public electrical local or long-distance supply network, but also to applications where one or a few producers provide an energy supply for one or a few consumers (this is often also referred to as an island network).

[0024] Advantageous embodiments of the invention are defined with reference to the dependent claims.

[0025] Preferably, it can be provided that at least one temporary change in the ignition timing ( t temp ) according to a switching instruction (S), wherein the switching instruction (S) is a function S = f Δ n g soll , Δ φ a deviation from the target generator speed (Δ n gsoll ) and the phase angle difference (Δ φ ) is.

[0026] For example, it may be stipulated that the switching condition (S) is fulfilled (S=0) if the rotational speed is within the specified tolerance range and the phase angle difference is within a further specified tolerance range.

[0027] It may be provided that the temporary change in ignition timing occurs under the condition S > e this is done, whereby S = ε if Δ n gsoll = Δ φ = 0. ε can, for example, be chosen to be zero (=0).

[0028] This means it can be provided that the temporary change in ignition timing occurs under the condition S > 0 occurs, with particular preference being exercised when S > 0 the ignition timing is retarded or advanced to reduce the engine speed and / or it may be provided that a temporary change in the ignition timing is possible under certain conditions. S < 0 is set back to the nominal ignition timing in order to increase the speed of the internal combustion engine.

[0029] It is intended that the temporary change in the ignition timing will occur relative to a predetermined nominal ignition timing.

[0030] It is provided that the ignition timing is temporarily changed relative to the predefinable, nominal ignition timing. This means that the nominal ignition timing can be temporarily set to "retarded" or "advanced." Preferably, it is provided that in step d) the system switches from the nominal ignition timing to the retarded or advanced modified ignition timing and vice versa.

[0031] This means that the ignition timing can be briefly retarded or advanced, then reverted to the nominal timing to precisely adjust the phase angle difference. This process can be repeated until the phase angle difference is acceptably reduced—in particular, minimized. In other words, the ignition timing can be intermittently changed from the nominal timing to the modified timing.

[0032] It may be intended that the ignition timing is changed abruptly by 15 to 20° crank angle (also °CA).

[0033] Depending on the speed and phase angle behavior, this state (change in ignition timing) can be maintained for up to ~2 s.

[0034] If the speed and phase angle difference are within a range that would allow synchronization, the ignition timing is constantly changed intermittently (either nominal ignition timing or modified ignition timing), with a switching state usually being held for less than 0.2 s before it is switched back (to the nominal ignition timing t nom ).

[0035] This allows the speed and phase angle difference to be maintained within the synchronization window until the generator switch closes. This entire synchronization process (from regulator activation) typically takes 2 to 3 seconds – meaning the ignition timing can be continuously and abruptly changed during this time. Ideally, the process should be active for a maximum of 15 seconds.

[0036] It may be provided that the temporary change in the ignition timing occurs essentially in discrete steps.

[0037] It is provided that a throttle valve of the internal combustion engine is controlled or regulated in such a way that the generator speed increases during step d) if the ignition timing would remain essentially at the predeterminable nominal ignition timing.

[0038] Put simply, this means that the throttle valve can be opened slightly when the phase angle difference is reduced.

[0039] It may be provided that the temporary change in the ignition timing ends when the generator is connected to the power grid.

[0040] Furthermore, protection is sought for an internal combustion engine, in particular a gas engine, comprising at least one cylinder unit and a control or regulating unit, wherein the control or regulating unit is configured to control and / or regulate the internal combustion engine according to a method according to the invention.

[0041] With regard to a computer program product according to the invention for synchronizing a generator with a power supply network having a mains frequency, commands are provided which cause an executing computer to: a) to drive an internal combustion engine, in particular a gas engine, for the mechanical drive of the generator, generating a generator speed, wherein the generator speed corresponds to a generator frequency generated by the generator at the given generator speed; b) to regulate or control the internal combustion engine so that the generator frequency lies within a tolerance range, wherein the grid frequency lies within the tolerance range; c) to receive or calculate at least one detection signal, which detection signal corresponds to a phase angle difference between a current and / or voltage generated by the generator on the one hand and a grid current and / or grid voltage on the other; d) to drive the internal combustion engine to synchronize the voltage and / or current generated by the generator on the one hand with the grid voltage and / or grid current on the other, by measuring the phase angle difference (Δ φ ) is reduced, in particular minimized; e) to issue a trigger signal to electrically connect the generator to the power supply network, wherein the commands cause the computer to reduce the phase angle difference by at least a temporary change in the ignition timing of at least one cylinder unit of the internal combustion engine.

[0042] Protection is also sought for a computer-readable storage medium containing a computer program product according to the invention.

[0043] Further details, advantages and features of the present invention are explained by way of example with reference to the figures and the following description of the figures. Fig. 1 shows a first embodiment of a gene set, and Figs. 2a-2e show measurements and control signals from the implementation of an embodiment of a method according to the invention.

[0044] Fig. 1 shows a first embodiment of a gene set 1.

[0045] The genset 1 comprises an internal combustion engine 2, which is connected to a generator 3 for power generation via a mechanical shaft 5 (for example, this can also be implemented as an extension of the crankshaft of the internal combustion engine 2).

[0046] In principle, a gearbox could also be present between the crankshaft of the internal combustion engine.

[0047] In this embodiment, the internal combustion engine 2 has several cylinder units 9, wherein the cylinder units 9 can be controlled or regulated via a central control or regulating unit 6 during the operation of the internal combustion engine 2, by, for example, controlling or regulating the ignition, the fuel supply, the air supply and / or other parameters of the combustion by means of appropriate valves, control or regulating elements using the control or regulating unit 6.

[0048] The generator 3 can be connected to a power supply network 4 via an electrical connection 10, wherein the electrical connection 10 can be designed as a switch which connects the electrical lines of the generator 3 to the power supply network 4.

[0049] Furthermore, a first sensor 7 is provided to determine a characteristic parameter for the generated voltage or current of the generator 3.

[0050] Using this characteristic parameter of the generated voltage or current of the generator 3, a frequency of the voltage and / or current of the generator 3 can be determined via the control unit 6.

[0051] In this embodiment, the first sensor 7 is configured as a speed sensor on the shaft 5, with the measured speed corresponding to the generator speed of the generator 3. If a gearbox were present, the generator speed could be determined based on a known gear ratio. The known generator speed provides the frequency of the current and voltage generated by the generator 3.

[0052] Furthermore, in this embodiment a second sensor 8 is shown, with the help of which a frequency of the current and / or the voltage of the power supply network 4 can be determined and supplied to the control unit 6.

[0053] Furthermore, it may be provided that the control or regulating unit 6 is connected to the electrical connection 10, whereby the control or regulating unit 6 can generate and / or interrupt the electrical connection 10 between generator 3 and power supply network 4.

[0054] The control or regulating unit 6 can be configured to start the combustion engine 2 when needed to drive the generator 3.

[0055] The control unit 6 can now control or regulate the speed of the combustion engine 2 and thus the generator frequency so that the generator frequency approaches the mains frequency until the generator frequency is within the tolerance range 12 around the mains frequency.

[0056] This results in a phase angle difference between the grid voltage and / or current on the one hand and the generator voltage and / or current on the other. In order to connect the generator to the power supply network 4 for the delivery of electrical energy, the phase angle difference must generally be reduced, in particular minimized (which is also referred to as synchronizing the generator 3 with the power supply network 4).

[0057] According to the invention, this is achieved by changing the ignition timing of at least one cylinder unit 9 of the internal combustion engine 2.

[0058] Measured values ​​and control signals from a method according to the invention for synchronizing the generator 3 with the power supply network 4 are separated by the Figuren 2a bis 2e shown, whereby (as in Fig. 2a (as shown) an internal combustion engine 2 with a coupled generator 3 is accelerated from standstill until a desired generator speed is reached.

[0059] Fig. 2a This shows the behavior of the generator speed during the synchronization time with the power supply network 4.

[0060] Through Fig. 2b Figure 3 shows a phase angle difference of the current and / or voltage between the generated current and / or voltage of the generator 3 and the current and / or voltage of the power supply network 4.

[0061] Fig. 2c Figure 1 shows a control signal from the control unit 6 for the ignition timing of at least one cylinder unit 9 of the internal combustion engine 2, i.e., a control signal for determining the ignition timing. This ignition timing is indicated in this figure with respect to a rotation angle of the crankshaft of the internal combustion engine 2 before top dead center (as is common in the prior art).

[0062] Fig. 2d shows a control or regulation signal of the control or regulation unit 6 with respect to a throttle valve of the internal combustion engine 2, where the diagram shows an opening of the throttle valve between "1" (fully open) and "0" (fully closed).

[0063] Fig. 2e Figure 1 shows a control signal from the control unit 6 for the electrical connection 10 of the generator 3 with the power supply network 4, distinguishing between a closed connection "1" (control signal to close the electrical connection 10) and an open connection "0". As can be seen, the connection 10 of the generator 3 with the power supply network 4 is established as soon as the phase angle difference is stabilized within a further tolerance range 12 for an acceptable phase angle difference (connection criterion).

[0064] These measured values ​​or control signals were simultaneously acquired during the execution of the exemplary embodiment of a method according to the invention on an internal combustion engine 2, the time scale of which Figuren 2a bis 2e agrees.

[0065] It can be seen that the combustion engine 2 is initially started up until a desired generator speed is exceeded, whereby the throttle valve is initially fully opened to allow the combustion engine 2 to accelerate as quickly as possible.

[0066] To gradually decelerate the acceleration, the throttle valve is closed shortly before reaching the desired speed, thus reducing the acceleration, and vice versa, to reach the desired tolerance range 11 of the speed (or equivalently the generator frequency). Prior to this, there is an oscillation of the phase angle difference ( Fig. 2b ) to be observed, which is of course due to the generator frequency not matching the grid frequency.

[0067] In Fig. 2c It can be seen that at approximately second 10, the synchronization begins by shifting the nominal ignition timing t nom of a cylinder unit "late" to a modified ignition timing t temp, and this is reset after each cycle or after a predefinable number of cycles to adjust the speed of the internal combustion engine (as Fig. 2a shows) and thus also the

[0068] to bring the generator speed into a predetermined speed range in which a phase angle difference between the power supply network 4 and generator 3 is minimized (or ideally eliminated).

[0069] Furthermore, it can be determined by Fig. 2d The throttle valve is slightly opened at the start of synchronization. This opening allows the engine speed 2 to increase when the ignition timing corresponds to the nominal ignition timing tnom and to decrease when the ignition timing corresponds to the modified ignition timing ttemp. This allows for improved control response during synchronization.

[0070] Once the phase angle difference has been minimized to the extent that it meets a connection criterion, the generator 3 is connected to the power supply network 4 via the electrical connection 10 by the control unit 6 and the generator 3 can be switched to a normal operating mode by the control unit 6.

[0071] The connection criterion includes, for example, that the generator speed (see Fig. 2a ) is within a predefinable tolerance range 11 and that the phase angle difference (see Fig. 2a ) is located within a predefinable further tolerance range of 12.

[0072] Then, after connecting the generator 3 to the power supply network 4, the throttle valve is continuously opened to increase the power output of the combustion engine 2 and thus the power supplied to the power supply network 4. Reference symbol list:

[0073] 1Genset 2Internal combustion engine 3Generator 4Power supply network 5Shaft 6Control or regulating unit 7First sensor 8Second sensor 9Cylinder unit 10Electrical connection 11Tolerance range 12Tolerance range t nom Nominal ignition timing t temp Modified ignition timing

Claims

1. A method for synchronizing a generator (3) with a power supply grid (4) having a mains frequency, comprising the following steps: a) mechanically driving the generator (3) by means of an internal combustion engine (2), in particular a gas engine, while generating a generator speed that corresponds to a generator frequency generated by the generator (3) at the present generator speed; b) regulating or controlling the internal combustion engine (2) so that the generator frequency is within a tolerance range, wherein the mains frequency is within the tolerance range; c) detecting a phase angle difference between a current generated by the generator (3) and / or a voltage generated by the generator (3) on the one hand and a mains current and / or mains voltage on the other hand; d) synchronizing the voltage generated by the generator (3) and / or the current generated by the generator (3) on the one hand with the mains voltage and / or mains current on the other hand by reducing, in particular minimizing, the phase angle difference (Δφ); e) electrically connecting the generator (3) to the power supply grid (4); characterized in that to reduce the phase angle difference (Δφ), at least a temporary change in the ignition timing of at least one cylinder unit (9) of the internal combustion engine (2) is carried out, and the temporary change in the ignition timing is relative to a predeterminable nominal ignition timing (tnom), wherein a throttle valve of the internal combustion engine (2), in particular a gas engine, is controlled and / or regulated such that the generator speed increases during step d) if the ignition timing would remain essentially at the predeterminable nominal ignition timing (tnom).

2. The method according to claim 1, characterized in that the at least one temporary change in the ignition timing is carried out according to a switching instruction (S), wherein the switching instruction (S) is a function S = f Δ n g soll , Δ φ of a deviation from the nominal generator speed (Δngsoll) and the phase angle difference (Δφ).

3. The method according to claim 2, characterized in that the temporary change in the ignition timing takes place under the condition S > ε, wherein S = ε if Δngsoll = Δφ = 0.

4. The method according to at least one of the preceding claims, characterized in that an ignition timing (ttemp) changed according to the temporary change of the ignition timing is temporarily changed relative to the predeterminable nominal ignition timing(tnom).

5. The method according to at least one of the preceding claims, characterized in that in step d) - preferably intermittently - switching is performed from the nominal ignition time (tnom) to the changed ignition timing (ttemp) and vice versa.

6. The method according to at least one of the preceding claims, characterized in that the nominal ignition timing (tnom) corresponds to the ignition timing in step b) and / or c).

7. The method according to at least one of the preceding claims, characterized in that the temporary change of the ignition timing is carried out essentially in discrete steps.

8. The method according to at least one of the preceding claims, characterized in that the temporary change in the ignition timing is terminated by connecting the generator (3) to the power supply grid (4).

9. An internal combustion engine, in particular gas engine, comprising at least one cylinder unit and a control and / or regulating unit (6), wherein the control and / or regulating unit (6) is configured to control or regulate the internal combustion engine (2) according to the method according to at least one of the preceding claims.

10. A computer program product for synchronizing a generator (3) with a mains frequency power supply grid (4) with commands that cause an executing control or regulating unit (6) to perform, a) controlling an internal combustion engine (2), in particular a gas engine, for mechanically driving the generator (3) while generating a generator speed, wherein the generator speed corresponds to a generator frequency generated by the generator (3) at the present generator speed; b) regulating or controlling the internal combustion engine (2) so that the generator frequency is within a tolerance range, wherein the mains frequency is within the tolerance range; c) receiving or calculating a detection signal, which detection signal corresponds to a phase angle difference between a current generated by the generator (3) and / or a voltage generated by the generator (3) on the one hand and a mains current and / or mains voltage on the other hand; d) controlling the internal combustion engine for synchronizing the voltage generated by the generator (3) and / or the current generated by the generator (3) on the one hand with the mains voltage and / or mains current on the other hand by reducing, in particular minimizing, the phase angle difference (Δφ); e) outputting a trigger signal for electrically connecting the generator (3) to the power supply grid (4); characterized in that the commands cause the control or regulating unit (6) to perform at least at least a temporary change of an ignition timing of at least one cylinder unit of the internal combustion engine (2) to reduce the phase angle difference, wherein the temporary change in the ignition timing occurs relative to a predeterminable nominal ignition timing (tnom), wherein the control or regulating unit (6) controls and / or regulates a throttle valve of the internal combustion engine (2), such that the generator speed increases during step d) if the ignition timing would remain essentially at the predeterminable nominal ignition timing (tnom).

11. Computer-readable storage medium comprising a computer program product according to claim 10.