Regulating methods for operating an internal combustion engine upon network fault detection

Abstract

A method of operating an internal combustion engine, wherein a fuel-air mixture is burnt in the internal combustion engine and the internal combustion engine drives a generator, wherein the generator is connected to a power supply network and delivers power to the power supply network and wherein upon or after detection of a dynamic network fault by which the power delivery of the generator into the power supply network is reduced acceleration of the internal combustion engine is prevented or limited, wherein upon or after the detection of the network fault in the power supply network the fuel feed to the internal combustion engine is increased.

Claims

1. A method of operating an internal combustion engine, the method comprising: connecting a generator to a power supply network; providing a fuel feed, at a prevailing fuel feed value, from an at least one fuel metering device to the internal combustion engine, the fuel feed comprising a fuel-air mixture; burning, via an ignition means, the fuel-air mixture in the internal combustion engine; driving the generator with the internal combustion engine to deliver electrical power to the power supply network; detecting a dynamic network fault, the dynamic network fault causing an increase in a rotary speed of the internal combustion engine or of the generator; upon or after detecting the dynamic network fault, deactivating the ignition means of the internal combustion engine, while at a same time as the deactivating, increasing the fuel feed from the at least one fuel metering device to the internal combustion engine; detecting the rotary speed of the internal combustion engine or of the generator; maintaining the increased fuel feed until the detected rotary speed decreases to a predeterminable minimum speed; and reactivating the ignition means when the predeterminable minimum speed has been reached so as to assist in restoring a network voltage of the power supply network.

2. A method as set forth in claim 1, wherein increasing the fuel feed from the at least one fuel metering device to the internal combustion engine occurs at a time t.sub.ign off and the increased fuel feed is maintained until a time t.sub.ign on, at which time the fuel feed is restored to the prevailing fuel feed value being provided prior to the dynamic network fault.

3. A method as set forth in claim 1, wherein increasing the fuel feed to the internal combustion engine is achieved by a lowering of a lambda value of the fuel-air mixture burnt in the internal combustion engine.

4. A method as set forth in claim 1, wherein increasing the fuel feed to the internal combustion engine is achieved by increasing an amount of a gas supplied to at least one port injection valve.

5. A method as set forth in claim 1, wherein increasing the fuel feed to the internal combustion engine is achieved by increasing a charge pressure.

6. An internal combustion engine system comprising: an electrical generator connected to a power supply network; an internal combustion engine for driving the generator to deliver electrical power to the power supply network; at least one sensor for detecting a dynamic network fault of the power supply network, the dynamic network fault causing an increase in a rotary speed of the internal combustion engine or of the generator; a rotary speed sensor for detecting the rotary speed of the internal combustion engine or of the generator; a control unit for controlling the internal combustion engine; the internal combustion engine comprising: at least one fuel metering device for providing a fuel feed, at a prevailing fuel feed value, to the internal combustion engine, the fuel feed comprising a fuel-air mixture; at least one ignition means for burning the fuel-air mixture in the internal combustion engine; wherein the control unit is configured to perform the following steps: upon or after detection of the dynamic network fault, deactivating the ignition means of the internal combustion engine, while at a same time as the deactivating, increasing the fuel feed from the at least one fuel metering device to the internal combustion engine; receiving, from the rotary speed sensor, the detected rotary speed of the internal combustion engine or of the generator; maintaining the increased fuel feed until the detected rotary speed decreases to a predeterminable minimum speed; and reactivating the ignition means when the predeterminable minimum speed has been reached so as to assist in restoring a network voltage of the power supply network.

Description

(1) The invention will be described in greater detail hereinafter by reference to the Figures in which:

(2) FIG. 1 is a diagrammatic view of an internal combustion engine with the accompanying control members, and

(3) FIG. 2 shows a schematic graph of the control interventions in relation to time.

(4) FIG. 1 shows a diagrammatic view of an internal combustion engine 1 having an exhaust gas turbine 4, a compressor 5, a gas metering device 6, a compressor bypass valve 7, a mixture intercooler 8 and a throttle valve 9. The actual engine block of the internal combustion engine 1 is denoted by reference 100. Gas is fed to the gas metering device 6. The feed of air A is effected in this view downstream of the gas metering device 6. It is naturally also possible for gas G and air A to be fed in a common device, for example a venturi mixer.

(5) The internal combustion engine 1 has an ignition means 10. Optionally it is possible to provide a port injection valve 11 through which fuel can be fed to the combustion chambers of the internal combustion engine 1 directly upstream of the inlet valves. The port injection valve 11 is only shown by way of example. In the configuration of FIG. 1 this involves a mixture-charged engine in which fuel metering is effected by way of the gas metering device 6 (for example a gas mixer).

(6) The ignition means 10 and the port injection valve 11 are shown in simplified form only for one cylinder.

(7) A generator 2 is connected to the internal combustion engine by way of a shaft. The generator 2 is shown here in the form of a 3-phase synchronous generator. The generator 2 feeds electric power into the power supply network 3. The rotary speed n.sub.act can be detected at the shaft between the internal combustion engine 1 and the generator 2, for example by way of a rotary speed measuring means. The corresponding sensor is not shown here.

(8) An open-loop and closed-loop control unit 12 sends commands by way of signal lines to the control members gas metering device 6, a compressor bypass valve 7, a throttle valve 9, an ignition means 10, and a port injection valve 11. The open-loop and closed-loop control unit 12 also receives signals in respect of engine and/or generator parameters, for example the speed n.sub.act.

(9) The arrangement of an internal combustion engine 1 with generator 2 is referred to as the genset 13.

(10) FIG. 2 shows a graph in respect of events and control interventions in relation to time.

(11) The curve n.sub.act shows the variation in the rotary speed n.sub.act of the internal combustion engine before, during and after the network fault. It will be seen that the rotary speed firstly rises due to the reduction in power output by virtue of the network fault at the time t.sub.0.

(12) With a delay, the measure ignition off occurs at the time t.sub.ign off and the rotary speed falls. When a predeterminable minimum speed is reached the ignition means is re-activated. It is also possible to see post-oscillation effects after the network fault dies away.

(13) The curve U.sub.grid shows the variation in the network voltage in relation to time. At the time t.sub.0 a voltage drop in the network is to be observed, which persists to the time t.sub.1.

(14) The curve Ign diagrammatically shows the status of the spark ignition of the internal combustion engine. In that respect the high position of the curve denotes the ignition state in normal operation while the low position of the curve denotes deactivation of the ignition means. At the time t.sub.ign off the ignition means is deactivated as a reaction to the network fault, for example a voltage drop. At the time t.sub.ign on the ignition means is set back again to the ignition mode prevailing prior to the network fault.

(15) The triggering aspect for resetting the ignition to the original ignition mode is for example the rotary speed signal, that is to say when a drop in the speed is observed the ignition means is re-activated or reset to the ignition mode prevailing prior to the network fault.

(16) As an alternative to the rotary speed signal it is possible to use for example a rotor signal.

(17) In the curve therebeneath the lambda value being the ratio of combustion air to fuel, is plotted in relation to time. The term combustion air ratio lambda is sufficiently well known. A lambda of 1 denotes the stoichiometric condition, that is to say there is precisely as much air available as is required for stoichiometric combustion of the fuel. A lambda of <1 denotes a sub-stoichiometric, that is to say rich, mode of operation while a lambda>1 denotes an over-stoichiometric, that is to say leaner, mode of operation. It will be seen from the illustrated variation in lambda that, after detection of the voltage drop at the time t.sub.ign off the lambda of the mixture fed to the internal combustion engine is reduced, that is to say the mixture is enriched. Before the network fault dies away the combustion air ratio lambda is restored to the value prevailing prior to the voltage drop. As explained for intervention in ignition the rotary speed signal can be used as a trigger for resetting to the initial value.

(18) The particular advantage of the method according to the invention is that, after the voltage drop dies away, the internal combustion engine is restored to nominal load again substantially more quickly than is possible with the methods known from the state of the art.

(19) By virtue of enrichment during the voltage drop a regulating reserve is so-to-speak implemented in the direction of higher loads. For short run-up times (referred to as ramp-up), meaning retrieval of the nominal load, maintenance of or even a reduction in the fuel feed during the voltage drop has proven to be disadvantageous.

(20) For, when the regular network voltage is restored a high braking moment can be exerted by the generator on the internal combustion engine so that, even with the fuel feed being maintained, a drop in the speed of the internal combustion engine is to be observed when the network voltage is restored.

(21) In contrast, with the method according to the invention and the apparatus according to the invention that overshoot can be compensated and the internal combustion engine presents a fast ramp-up without rotary speed reduction.

(22) It is preferably provided that detection of the network fault is effected by observing the parameters voltage (of the generator), current (of the generator) and frequency (of the generator). Accordingly therefore there is no need to follow the generator power (active, reactive or apparent power)for example at the connecting terminals, but the far more sensitive indicators of voltage, current and frequency of the generator are used.

(23) It should be added for explanation purposes that the voltage drops referred to in the context of this disclosure are typically of a duration of below 500 milliseconds (ms). The BDEW Transmission Code of 2007 (Network and System Rules of the German Transmission System Operators) provides for example that production plants may not disconnect from the network at voltage drops to 0% of the network voltage of a duration of less than/equal to 150 ms.

LIST OF REFERENCES USED

(24) 1 internal combustion engine 2 generator 3 power supply network 4 exhaust gas turbine 5 compressor 6 gas metering device 7 compressor bypass valve 8 mixture/charge air intercooler 9 throttle valve 10 ignition means 11 port injection valve 12 open-loop and closed-loop control unit 13 genset 100 engine block n.sub.act rotary speed at the generator shaft p.sub.2 charge pressure upstream of the mixture/charge air intercooler T.sub.2 temperature upstream of the mixture/charge air intercooler P.sub.2 charge pressure downstream of the mixture/charge air intercooler T.sub.2 temperature downstream of the mixture cooler/charge air intercooler A air G gas