METHOD FOR CONTROLLING AND REGULATING AN INTERNAL COMBUSTION ENGINE WITH GENERATOR AND ASYNCHRONOUS MACHINE, AND INTERNAL COMBUSTION ENGINE

Description

[0001] The invention relates to a method for controlling and regulating an internal combustion engine with a generator and asynchronous machine as well as an internal combustion engine with a generator and asynchronous machine and with a control and regulating device.

[0002] US 2014 / 0015257 A1 describes a power generation system with a motor, an electric generator, and a system controller, and thus, in principle, such a method for controlling and regulating an internal combustion engine with a generator. The motor is configured to generate mechanical power and includes an engine controller and a turbocharger for increasing the air pressure to a boost pressure. The turbocharger is controlled by the engine controller during steady-state operation of the system. A system controller is configured to receive a signal indicating an electrical load on the generator. During a transient condition in which the electrical load increases, the system controller is configured to directly control the turbocharger to change the configuration of the turbocharger to increase the boost pressure.

[0003] On the other hand, in the design and operation of internal combustion engines such as combustion engines with generators, asynchronous motors are often used as load motors for various applications, for example, as drive motors for fans, pumps, and hoists. Asynchronous motors are among the most widely used electrical machines because they can be produced simply and cost-effectively. Due to their design, high starting currents, up to eight times the rated current, occur when asynchronous motors are connected. These high starting currents cause a brief power surge. This causes the speed of, for example, the combustion engine with a synchronous generator to drop significantly. The speed control of the combustion engine must then react to this drop.For example, DE 196 24 343 A1 describes a method for at least controlling the speed of an internal combustion engine to a predeterminable speed, in particular an idling speed, at least as a function of operating parameters and / or ambient parameters of the internal combustion engine, wherein the control also takes place as a function of a disturbance variable that is independent of the operating parameters and the ambient parameters of the internal combustion engine. The disturbance variable is determined in a corresponding program, e.g. the voltage of the on-board electrical system is measured. There is a query as to whether control (pre-control) should be carried out, whereby control can be omitted, for example, if the disturbance variable (the speed) of the internal combustion engine is generally below or above a predeterminable value (e.g. above the idling speed) at which the starting or stopping of the electrical consumer no longer has any effect.When the control is to be performed, the program branches to a control that executes the corresponding pre-control by controlling the injection device accordingly (e.g., increasing or decreasing the injected fuel quantity or the throttle valve position). After the control is completed, the program then branches back to its original starting point or back to the aforementioned determination.

[0004] Several components already exist on the drive technology market that minimize the problem of high starting currents; examples include star-delta starting, soft starting, and frequency converters. The most commonly used method is the star-delta connection. When starting in a star connection, power and torque are reduced by approximately one-third. After the start-up time, the contactors are switched to delta operation. With appropriate configuration or programming, frequency converters can start asynchronous motors smoothly and in line with the load.

[0005] However, in safety-critical applications, direct starting of asynchronous motors is still desirable to achieve a lower probability of failure through a smaller number of components and, if possible, to eliminate expensive power electronic components. At the same time, a drop in the engine's speed should be avoided.

[0006] This object is achieved according to a first aspect of the invention by a method of claim 1. The method for controlling and regulating an internal combustion engine, in particular a diesel engine or gas engine, with a generator and asynchronous machine comprises: Detecting at least one electrical characteristic of the generator, wherein the electrical characteristic is selected from current, voltage or frequency, determining a characteristic change of the electrical characteristic of the generator in a predetermined time interval, comparing the characteristic change with a first limit value in the event that the characteristic change is greater than the first limit value, changing from a standard speed control of the internal combustion engine to a feedforward control.

[0007] The invention includes the discovery that, in particular, by detecting an initial current surge when the asynchronous machine starts up and subsequently switching from standard speed control to feedforward control, the start-up process of the asynchronous machine can be absorbed by the internal combustion engine without the internal combustion engine's speed initially dropping. With the aid of feedforward control, additional power electronic components are obsolete, and direct starting of the asynchronous machine is possible. A predictive response to a load application is therefore possible, and there is no need to wait for a speed drop before initiating countermeasures. With conventional load application, a torque is applied by the electrical load. This torque brakes the internal combustion engine, causing its speed to drop.Only now can the load increase be reliably detected and countermeasures initiated. Depending on the drop in engine speed, the fuel quantity is increased and an attempt is made to accelerate the engine back to the specified target speed.

[0008] Due to this configuration of speed control, the state of the art requires waiting for a response from the entire internal combustion engine-generator system. Countermeasures can only be initiated after a drop in speed. With the aid of the method according to the invention, such waiting is obsolete. By detecting the first current surge via the change in characteristic variables at a predetermined time interval, the load connection can be precisely detected and immediate countermeasures can be initiated via the pre-control. This can improve the load switching capability of the entire system. Furthermore, the invention can prevent strong speed fluctuations. In addition, larger loads can be connected while adhering to limit values. Furthermore, thanks to the rapid prediction of the load, the units no longer need to be oversized as much. This leads to cost savings and a smaller installation space.The unit also runs in better operating ranges due to higher utilization.

[0009] According to the invention, the pre-control comprises determining an adjusted target injection quantity. The adjusted target injection quantity can be selected from stored target injection quantities. According to the invention, the adjusted target injection quantity is determined based on a degree of the parameter change. From the degree of the parameter change, an estimate of the rated power of the asynchronous machine, i.e. the load, can be made, for example using a predictive algorithm. This information can then be used to estimate the impending load on the combustion engine and determine an adjusted target injection quantity. The speed control of the combustion engine can thus be optimized using the adjusted target injection quantity. The parameter change can be determined as the gradient of a parameter curve over time.

[0010] According to the invention, the method further comprises: Re-determining the change in the characteristic value. Comparing the change in the characteristic value with a second limit value which is smaller than the first limit value. In the event that the change in the characteristic value is smaller than the second limit value, switching from the feedforward control back to the standard speed control.

[0011] These additional steps determine whether the start-up phase of the asynchronous machine has ended by checking whether the characteristic change has decreased to a sufficiently low level below the second limit. If this is the case, standard speed control is reactivated. If the characteristic change is still greater than the second limit, the feedforward control remains active.

[0012] The standard speed control includes a continuous determination of a standard target injection quantity based on a comparison between the target speed and the actual speed of the internal combustion engine.

[0013] According to a second aspect, the invention relates to an internal combustion engine, in particular a diesel engine or gas engine, with a generator and asynchronous machine, comprising a control and regulating device. The control and regulating device for an internal combustion engine with a generator and asynchronous machine is designed to carry out a method according to the first aspect of the invention.

[0014] The control and regulating device and the internal combustion engine with generator and asynchronous machine share the advantages of the method for control and regulation according to the first aspect of the invention.

[0015] Advantageous further developments of the method are described below. The additional features of the exemplary embodiments can be combined with one another to form further developments, unless they are expressly described as alternatives to one another in the description.

[0016] It is preferable if the adjusted target injection quantity is larger the greater the change in the characteristic. Furthermore, the adjusted target injection quantity is advantageously determined taking into account a measured maximum starting current of the asynchronous machine. The maximum starting current enables a further improved estimation of the rated power of the asynchronous machine and thus an improved starting behavior of the entire system consisting of the internal combustion engine, generator, and asynchronous machine. Furthermore, the precontrol can provide additional measures to improve the load-switching capability, such as a brief voltage reduction at the generator.

[0017] It is particularly preferred if the control and regulating device comprises a speed controller and a system controller, wherein the speed controller is designed to carry out the standard speed control and the system controller is designed to carry out the pre-control and the control and regulating device is designed to cause a change from a dominance of the speed controller to a dominance of the system controller in the event that the characteristic deviation or the characteristic change is greater than the first limit value.

[0018] Embodiments of the invention are now described below with reference to the drawing. These are not necessarily intended to represent the embodiments to scale; rather, where useful for explanation, the drawing is schematic and / or slightly distorted. With regard to additions to the teachings immediately apparent from the drawing, reference is made to the relevant prior art. It should be noted that numerous modifications and changes to the form and detail of an embodiment can be made without deviating from the general idea of the invention. The features of the invention disclosed in the description, in the drawing and in the claims can be essential for the further development of the invention, both individually and in any combination.Furthermore, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiments shown and described below, or limited to an object that would be more limited than the object claimed in the claims. In the case of specified dimensioning ranges, values within the stated limits are also intended to be disclosed as limit values and to be used and claimed as desired. For the sake of simplicity, the same reference numerals are used below for identical or similar parts or parts with identical or similar functions.

[0019] Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawing, which shows: Fig. 1 shows a schematic representation of an exemplary course of a starting current of an asynchronous machine over time; Fig. 2 shows a schematic representation of a preferred embodiment of a control and regulating device; Fig. 3 shows a schematic representation of a preferred embodiment of an internal combustion engine with a generator and asynchronous machine; Fig. 4 shows a schematic representation of a preferred embodiment of a method for controlling and regulating an internal combustion engine with a generator and asynchronous machine.

[0020] In Fig. 1 is shown as an example of a curve of a starting current of an asynchronous machine over time. The starting current I initially increases sharply up to a maximum starting current I max and then falls to an operating level IB at which the asynchronous machine operates after the start-up phase. The sharp increase in the current curve at the beginning of the start-up phase is expressed in the gradient di / dt, i.e. the change in the characteristic variable in a specific time interval. According to the invention, this increase is recorded as an electrical change in the characteristic variable and, if the change in the characteristic variable lies above a first limit value, a change is made from standard speed control of an internal combustion engine connected to the asynchronous machine to pre-control. As part of the pre-control, a target injection quantity for the internal combustion engine is determined. This can be done from predetermined values or based on a measure of the change in the characteristic variable.In addition to current, voltage and frequency are also considered as electrical parameters.

[0021] Fig. 2 shows a schematic representation of an embodiment of a control and regulating device SR for an internal combustion engine BK with generator and asynchronous machine comprising a speed controller nR and a system controller AS. The speed controller nR is designed to carry out a standard speed control which includes continuously determining a standard target injection quantity Q1 based on a comparison between the target speed nSL and the actual speed nIST of the internal combustion engine BK. In the exemplary embodiment shown, a filter F is additionally used to determine the actual speed nIST from a detected speed n. The control and regulating device SR is designed to detect at least one electrical characteristic of the generator, wherein the electrical characteristic is selected from current I, voltage U or frequency f and to determine a characteristic change dI / dt, dU / dt, df / dt of the electrical characteristic of the generator in a predetermined time interval.Furthermore, the control and regulating device is designed to compare the characteristic variable change dI / dt, dU / dt, df / dt with a first limit value and, in the event that the characteristic variable deviation or the characteristic variable change is greater than the first limit value, to initiate a change from a dominance of the speed controller nR to a dominance of the system controller AS. The system controller AS is designed to perform a pre-control. In the exemplary embodiment shown, the pre-control comprises determining an adjusted target injection quantity Q2 based on a measure of the characteristic variable change, wherein the adjusted target injection quantity is greater the greater the characteristic variable change.Furthermore, the control and regulating device SR is designed, after re-determining the change in the characteristic variable, to compare the change in the characteristic variable with a second limit value that is smaller than the first limit value and, if the change in the characteristic variable is smaller than the second limit value, to initiate a change from the pilot control back to the standard speed control. The change from the pilot control to the standard speed control and vice versa is represented in the exemplary embodiment shown by changing a switch position of the switch from 2 to 1 or 1 to 2. A target injection quantity Q output to the internal combustion engine BK is therefore, depending on the dominance, either the adjusted target injection quantity Q2 or the standard target injection quantity Q1.

[0022] Fig. 3 shows a schematic representation of an embodiment of an internal combustion engine BK with a generator G and an asynchronous machine ASM. The internal combustion engine BK further comprises a control and regulating device which includes a speed controller and a system control AS. The speed controller is designed here as part of the engine control unit ECU. At least one electrical characteristic of the generator G selected from current I, voltage U and frequency f is recorded by the system control AS and an associated characteristic change is determined in a predetermined time interval. The characteristic change is compared by the control and regulating device with a first limit value and in the event that the characteristic change is greater than the first limit value, the control and regulating device switches from standard speed control of the internal combustion engine by the speed controller to feedforward control by the system control.In the embodiment shown, the system control AS is further designed to switch on the asynchronous machine via a switch S.

[0023] Fig. 4shows a schematic representation of a method for controlling and regulating an internal combustion engine with a generator and an asynchronous machine. At least one electrical characteristic of the generator selected from current, voltage and frequency is recorded in step S1 and an associated characteristic change Δ is determined in a predetermined time interval in step S2. The characteristic change Δ is compared with a first limit value GW1 in step S3 and, if the characteristic change Δ is greater than the first limit value GW1, a change occurs from standard speed control of the internal combustion engine to pre-control in step S4. In the exemplary embodiment shown, the pre-control comprises determining an adjusted target injection quantity based on a measure of the characteristic change, the adjusted target injection quantity being greater the greater the characteristic change. List of reference symbols

[0024] IStarting current I max Maximum starting current IB Operating level SRControl and regulation device BKCombustion engine GGenerator ASMASynchronous machine nRSpeed controller ASSystem control Q1Standard target injection quantity nSLTarget speed nISTActual speed nRecorded speed Q2Adjusted target injection quantity QTarget injection quantity FFilter SSwitch GW1First limit value ΔChange in characteristic value

Claims

1. Method for the open-loop and closed-loop control of an internal combustion engine having an open-loop and closed-loop control device (SR), in particular for the open-loop and closed-loop control of a diesel engine or gas engine, and having a generator and having an asynchronous machine (ASM), wherein the asynchronous machine (ASM) is activated by means of a switch (S) and the method comprises the steps of: - detecting at least one electrical characteristic variable of the generator (G), wherein the electrical characteristic variable is selected from current or voltage, - determining a change (Δ) in the electrical characteristic variable of the generator (G) in a predetermined time interval, - comparing the change (Δ) in the characteristic variable with a first threshold value (GW1), - in the event that the change (Δ) in the characteristic variable is greater than the first limit value (GW1), changing over from standard speed control to feed-forward control of the open-loop and closed-loop control device (SR) of the internal combustion engine, wherein - the standard speed control comprises continuously determining a standard target injection quantity (Q1) based on a comparison between the target speed (nSL) and the actual speed (nIST) of the internal combustion engine, and - the feed-forward control comprises determining an adjusted target injection quantity (Q2) based on an extent of the change (Δ) in the characteristic variable, and - again determining the change (Δ) in the characteristic variable, - comparing the change (Δ) in the characteristic variable with a second limit value (GW2), which is smaller than the first limit value (GW1), and, - in the event that the change (Δ) in the characteristic variable is smaller than the second limit value (GW2), changing over from feed-forward control back to standard speed control.

2. Method according to Claim 1, in which the adjusted target injection quantity (Q2) increases the greater the change (Δ) in the characteristic variable.

3. Method according to either of Claims 1 and 2, in which the adjusted target injection quantity (Q2) is determined taking into account a measured maximum starting current (Imax) of the asynchronous machine (ASM).

4. Method according to any of the preceding claims, characterized in that by detecting a first surge in a starting current (I) when starting the asynchronous machine (ASM) the change (Δ) in the characteristic variable is determined in the predetermined time interval and the changeover from the standard speed control to the feed-forward control of the open-loop and closed-loop control device (SR) of the internal combustion engine is then made in the event that the change (Δ) in the characteristic variable is greater than the first limit value (GW1).

5. Method according to any of the preceding claims, in which the change (Δ) in the characteristic variable in the predetermined time interval comprises a gradient (dl / dt, dU / dt) of current (I) or voltage (U).

6. Internal combustion engine, in particular diesel engine or gas engine, having a generator (G) and having an activatable asynchronous machine (ASM) and having an open-loop and closed-loop control device (SR) which is designed to carry out a method according to any of Claims 1 to 5 and which comprises a speed governor (nR) and a system controller (AS), wherein the speed governor (nR) is designed to carry out the standard speed control and the system controller (AS) is designed to carry out the feed-forward control and the system controller (AS) is designed to activate the asynchronous machine (ASM) by means of a switch (S).