CN105402041B - Diesel speed control method and device - Google Patents

Abstract

The present invention relates to a method and device for controlling the rotational speed of a diesel engine. The method includes monitoring the rotational speed of the engine and the rate of change of the rotational speed in real time; The threshold value is compared, and the value of the first rotational speed setting value is adjusted according to the comparison result, so as to control the fuel supply amount of the engine according to the numerical value of the first rotational speed setting value. The invention detects the actual speed of the engine and the change rate of the speed to prevent the instantaneous commissioning rate from exceeding the limit, and when the engine speed has dropped to a safe range, it intervenes in the speed control in advance to prevent pits or oscillations in the engine speed, reducing the The workload of parameter calibration is controlled, the cost of software design and manufacture is reduced, and the operation stability of the power system is improved to a certain extent.

Description

Diesel engine speed control method and device

technical field

The invention relates to the field of diesel engine control, in particular to a method and device for controlling the rotational speed of a diesel engine.

Background technique

Diesel engines are often used as engines for generating sets due to their fuel economy, high thermal efficiency, high reliability, and low harmful emissions. As shown in Figure 1, the existing technical solutions usually adopt closed-loop control (such as PID control), by making a difference between the set speed of the engine and the actual speed, the speed deviation is calculated, and the PID will calculate and update according to this deviation The amount of fuel injected by the engine, the fuel system of the engine injects the corresponding fuel to do work on the engine combustion, and then controls the engine speed.

Load changes on generating equipment are often unpredictable. For example, when the load suddenly increases, if the PID parameter is small, the PID controller will adjust the fuel supply too slowly, and the output power of the engine is less than the power required by the load, resulting in an excessive drop in the actual speed of the engine. , The instantaneous rate of regulation (that is, the percentage of the instantaneous fluctuation of the engine speed when the load changes) exceeds the maximum limit (generally 10% of the set engine speed). If the PID parameter is large, although the PID controller can adjust the oil supply to follow the change of the load to ensure that the speed change rate is within a reasonable range, if the load suddenly decreases at this time, the output power of the engine will be reduced. greater than the power demanded by the load. However, because the output of the PID controller needs to wait for the speed deviation to change, and requires a certain response time, the actual speed of the engine will rise too much, and the instantaneous speed regulation will exceed the maximum limit. At constant speed, the fuel supply at this time is usually zero, and the speed will further drop. Because the PID control parameters are large at this time, the adjustment of the fuel supply of the PID controller is too fast, so that the actual speed of the engine will rise again. , making the droop exceed the maximum limit again. Once the instantaneous speed regulation exceeds the maximum limit, the generator set will be disconnected from the grid due to its own protection, which will seriously affect the operation stability of the power system. On the other hand, if the PID parameters are constantly adjusted according to the change of the load, the calibration workload will be heavy, and the software design cost will also increase.

Contents of the invention

In order to improve the operation stability of the power system and reduce the calibration workload, the present invention proposes a diesel engine speed control method, which includes:

Real-time monitoring of the rotational speed of the engine and the rate of change of said rotational speed;

Comparing the current rotational speed and the current rate of change of the engine with the first rotational speed threshold and the first rate of change threshold respectively, and adjusting the numerical value of the first rotational speed setting value according to the comparison result, so that according to the numerical value of the first rotational speed Control the fuel supply to the engine.

Preferably, the adjustment of the value of the first rotational speed setting value according to the comparison result is specifically:

When the current rotational speed is greater than the first rotational speed threshold and the current rate of change is greater than the first rate of change threshold, the value of the first rotational speed setting value is assigned as the current rotational speed, so as to eliminate the relationship between the current rotational speed and The deviation between the first rotational speed setpoints.

Preferably, said controlling the fuel supply of the engine according to the numerical value of the first rotational speed setting value is specifically:

Controlling the fuel supply of the engine through a closed-loop control method according to the value of the first rotational speed setting value, the control law of the closed-loop control method includes an integral link of the deviation;

Correspondingly, assigning the numerical value of the first rotational speed set value as the current rotational speed to eliminate the deviation between the current rotational speed and the first rotational speed set value also includes the integral link of the deviation cleared.

Preferably, after controlling the fuel supply of the engine according to the numerical value of the first rotational speed setting value, the method further includes:

Comparing the current rotational speed and the current rate of change of the engine with a second rotational speed threshold and a second rate of change threshold respectively, when the current rotational speed is less than the second rotational speed threshold and the current rate of change is less than the second rate of change When the threshold is reached, the value of the first rotational speed setting value is assigned as the second rotational speed setting value.

Preferably, the closed-loop control algorithm is a proportional-integral-derivative PID control algorithm.

On the other hand, the present invention also proposes a diesel engine speed control device, which includes:

a rotational speed monitoring unit, configured to monitor the rotational speed of the engine and the rate of change of said rotational speed in real time;

The rotational speed setting value assignment unit is used to compare the current rotational speed and the current change rate of the engine with the first rotational speed threshold and the first change rate threshold respectively, and adjust the numerical value of the first rotational speed set value according to the comparison result, so as to The numerical value of the first rotational speed setting value controls the fuel supply amount of the engine.

Preferably, the speed setting value assignment unit is further used for:

When the current rotational speed is greater than the first rotational speed threshold and the current rate of change is greater than the first rate of change threshold, the value of the first rotational speed setting value is assigned as the current rotational speed, so as to eliminate the relationship between the current rotational speed and The deviation between the first rotational speed setpoints.

Preferably, the rotational speed setting value assigning unit is further configured to control the fuel supply of the engine through a closed-loop control method according to the value of the first rotational speed setting value, and the control law of the closed-loop control method includes the deviation the scoring link;

Correspondingly, the speed setting value assigning unit is also used to clear the integral link of the deviation to zero.

Preferably, the speed setting value assignment unit is also used for:

Comparing the current rotational speed and the current rate of change of the engine with a second rotational speed threshold and a second rate of change threshold respectively, when the current rotational speed is less than the second rotational speed threshold and the current rate of change is less than the second rate of change When the threshold is reached, the value of the first rotational speed setting value is assigned as the second rotational speed setting value.

Preferably, the closed-loop control algorithm is a proportional-integral-derivative PID control algorithm.

The invention can reduce the calibration workload of control parameters, reduce software design and manufacturing costs, and improve the operation stability of the power system to a certain extent.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are For some embodiments of the present invention, those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 shows the structural block diagram of the engine speed closed-loop control system in the prior art;

Fig. 2 shows the graph of engine speed and fuel injection quantity in the prior art;

Fig. 3 shows the flowchart of the diesel engine speed control method of an embodiment of the present invention;

Fig. 4 shows the structural block diagram of the engine speed closed-loop control system of another embodiment of the present invention;

Fig. 5 shows the flow chart of the diesel engine speed control method of another embodiment of the present invention;

Fig. 6 shows a structural block diagram of a diesel engine speed control device according to an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are the Some, but not all, embodiments are invented. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Fig. 2 shows the graph of engine speed and fuel injection quantity in the prior art; As shown in Figure 2, engine speed corresponds to the left coordinate axis, and its setting value N is 1500 turns; The current fuel injection quantity of engine corresponds to the right side Axis. It can be seen from the first speed peak of the engine speed that when the parameters of the closed-loop control algorithm (such as the PID control algorithm) are fixed, when the engine load suddenly decreases, since the PID controller will not act until the deviation occurs, a certain response is required Time, the oil quantity will drop to zero after a certain period of time, and the engine speed will drop. At this time, the instantaneous speed regulation has exceeded the maximum limit; since the fuel injection quantity of the engine is zero at this time, the actual engine speed will change from the first The peak falls, and the PID controller does not intervene in the control before the actual speed drops back to the speed setting value N. When the actual engine speed is equal to the speed setting value of 1500 rpm, the fuel injection amount of the engine is zero at this time. Due to friction and other reasons, the engine The speed will continue to drop. Due to the large current PID parameters and small load, the excessive fuel injection volume will cause overshoot and produce a second peak, which will cause the instantaneous speed regulation to exceed the maximum limit again, causing the generator set to go off-grid and affect the power. System stability. Based on this, the present application proposes embodiments to solve the above technical problems.

Fig. 3 shows the flow chart of the diesel engine speed control method of an embodiment of the present invention; As shown in Fig. 3, this method comprises:

S1: Real-time monitoring of the engine speed n2 and the change rate dn2 of the speed;

S2: Comparing the current speed n2 and the current change rate dn2 of the engine with the first speed threshold N1 and the first change rate threshold dN1 respectively, adjusting the value of the first speed setting value n1 according to the comparison result, so as to The numerical value of a rotational speed setting value n1 controls the fuel supply of the engine.

This embodiment can reduce the calibration workload of control parameters, reduce software design and manufacturing costs, and improve the operation stability of the power system to a certain extent.

As a preference of this embodiment, the value of the first rotational speed setting value n1 is adjusted according to the comparison result in step S2, specifically:

When the current speed n2 is greater than the first speed threshold N1, and the current change rate dn2 is greater than the first change rate threshold dN1, the value of the first speed setting value n1 is assigned as the current speed n2( That is, n1=n2), so as to eliminate the deviation between the current rotational speed n2 and the first rotational speed setting value n1.

Further, the above-mentioned control of the fuel supply amount of the engine according to the numerical value of the first rotational speed setting value is specifically:

According to the value of the first rotational speed setting value, the oil supply amount of the engine is controlled through a closed-loop control method, and the control law of the closed-loop control method includes the integral link of the deviation, for example, the closed-loop control algorithm is proportional-integral - Differential PID control algorithm, then the integral link is I;

Correspondingly, assigning the value of the first rotational speed setting value n1 to the current rotational speed n2 to eliminate the deviation between the current rotational speed n2 and the first rotational speed setting value n1 also includes setting the The integral link I of the deviation is cleared.

Optionally, after controlling the fuel supply of the engine according to the numerical value of the first rotational speed setting value, the method may further include:

Comparing the current speed n2 of the engine (that is, the monitored current speed of the engine) and the current change rate dn2 with the second speed threshold N2 and the second change rate threshold dN2 respectively, when the current speed n2 is less than the second The rotational speed threshold N2, and when the current change rate dn2 is smaller than the second change rate threshold dN2, the value n1 of the first rotational speed setting value is assigned as the second rotational speed setting value N.

Fig. 4 shows a structural block diagram of an engine speed closed-loop control system according to another embodiment of the present invention. As shown in Figure 4, this system adds an overspeed detection link on the basis of the existing PID speed closed-loop control system. By monitoring the actual speed n2 of the engine, when the speed rises, it is judged in advance whether the instantaneous speed regulation will exceed the maximum limit. If it is judged that the actual instantaneous speed regulation of the engine will exceed the maximum limit, then the The deviated rotational speed setting value n1 is switched to the actual rotational speed n2, and at the same time, the PID controller is made to clear the integral. Since the speed setting value n1 has been switched to the current actual speed n2, and the integral is cleared, the fuel injection amount calculated by the PID controller is zero at this time, the engine does not perform combustion and work, and the speed will drop. When the speed drops to within a reasonable deviation range, the overspeed detection module will slowly transition the speed setting value n1 used to calculate the speed deviation from the current actual speed n2 to the engine speed setting value N (at this time n1 >N), let the deviation appear in advance, and the PID will respond in advance to prevent the speed from falling below the set value of the speed, thereby preventing the actual speed of the engine from oscillating.

Fig. 5 shows a flowchart of a method for controlling the rotational speed of a diesel engine according to another embodiment of the present invention. As shown in Figure 5, the method includes the following steps:

A1: First judge whether the engine speed closed-loop control is enabled: if the speed closed-loop control is turned on, it will enter overspeed detection;

A2: Real-time detection of the actual speed n2 of the engine and the change rate dn2 of the speed: if the actual engine speed n2 exceeds the first speed threshold N1, and the change rate dn exceeds the first change rate threshold dN1, the counter C is incremented by 1, otherwise the counter is cleared zero;

A3: Judging whether the counter C is greater than the preset calibration value Num: If the counter C is greater than the calibration value Num, it is determined that the current instantaneous speed regulation of the engine will exceed the maximum limit, and the state of the overspeed detection state is set (for example: the state bit includes 1 , 0 and two status bits, 1 means that the overspeed detection state is set, and 0 means that the overspeed detection state is not set); otherwise, continue to detect whether the actual engine speed n2 is less than the threshold N2 and the change rate dn is less than the calibration threshold. If the above conditions are met, it means that the engine If the speed has dropped to the safe range, reset the overspeed detection status bit; if it is not satisfied, no operation will be performed;

A4: Determine whether the state of the overspeed detection state is set: if so, switch the speed setting value n1 used to calculate the speed deviation to the actual speed n2, and at the same time initialize the value of the integrator of the PID controller to zero;

A5: If the overspeed detection status is not set, then further judge whether the speed setting value n1 is greater than the sum of the speed setting value N and the preset gradient value dN:

If n1 is greater than the sum of N and dN, update the current value of n1 to the value of n1 in the previous step minus the gradient value dN, so that the speed setting value transitions from the current actual speed n2 to the set value when exiting overspeed. Fixed speed N, intervene in speed control in advance to prevent pits or oscillations in the actual speed;

If n1 is not greater than the sum of N and dN, it means that the transition is completed, update the value of n1 to N, and perform conventional closed-loop control of the speed;

A6: Finally, check whether the controller is powered off. If not, continue the control of the next cycle; if it is powered off, end the control.

In this embodiment, by detecting the actual speed of the engine and the rate of change of the speed, it prevents the instantaneous commissioning rate from exceeding the limit, and when the engine speed has dropped to a safe range, it intervenes in the speed control in advance to prevent pits or oscillations in the engine speed and reduce the engine speed. The workload of control parameter calibration is reduced, the cost of software design and manufacture is reduced, and the operation stability of the power system is improved to a certain extent.

Fig. 6 shows a structural block diagram of a diesel engine speed control device according to an embodiment of the present invention. As shown in Figure 6, the device includes:

The speed monitoring unit 11 is used to monitor the speed n2 of the engine and the change rate dn2 of the speed in real time;

The rotational speed setting value assignment unit 12 is used to compare the current rotational speed n2 and the current change rate dn2 of the engine with the first rotational speed threshold N1 and the first change rate threshold dN1 respectively, and adjust the first rotational speed set value according to the comparison result The numerical value of n1 is used to control the oil supply amount of the engine according to the numerical value of the first rotational speed setting value.

The diesel engine speed control device described in this embodiment can be used to implement the above method embodiments, and its principles and technical effects are similar, and will not be repeated here.

As a preference of this embodiment, the rotational speed setting value assigning unit 12 is further used for:

When the current speed n2 is greater than the first speed threshold N1, and the current change rate dn2 is greater than the first change rate threshold dN1, the value of the first speed setting value n1 is assigned as the current speed n2( That is, n1=n2), so as to eliminate the deviation between the current rotational speed n2 and the first rotational speed setting value n1.

Furthermore, the rotational speed setting value assigning unit 12 is further used to control the fuel supply of the engine through a closed-loop control method (such as PID) according to the value of the first rotational speed setting value n1, and the control of the closed-loop control method The integral part of the law that includes the deviation;

Correspondingly, the speed setting value assignment unit is also used to clear the integral link I of the deviation to zero.

Optionally, the speed setting value assigning unit 12 is also used for:

Comparing the current speed n2 of the engine (which is the speed of the engine at this time) and the current change rate dn2 with the second speed threshold N2 and the second change rate threshold dN2 respectively, when the current speed n2 is less than the second speed threshold N2, and when the current change rate dn2 is less than the second change rate threshold dN2, the value n1 of the first rotational speed setting value is assigned as the second rotational speed setting value N.

The diesel engine speed control device described in this embodiment can be used to implement the above method embodiments, and its principles and technical effects are similar, and will not be repeated here. As for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and for related parts, please refer to the part of the description of the method embodiment.

The present invention can use a set of closed-loop control parameters to meet the requirements of the instantaneous speed regulation not exceeding the limit under complex load changes, reduce the user's calibration workload, reduce software design and manufacturing costs, and improve to a certain extent stability of the power system.

The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be described in the foregoing embodiments Modifications are made to the recorded technical solutions, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (6)

1. A kind of 1. diesel speed control method, it is characterised in that including：

   The rate of change of the rotating speed of monitoring engine and the rotating speed in real time；

   By the current rotating speed of the engine and current rate of change respectively with the first rotary speed threshold value and the first rate of change threshold value It is compared, the numerical value of the first speed setting value is adjusted according to comparative result, with the numerical value control according to first speed setting value Make the fuel delivery of the engine；

   The numerical value that the first speed setting value is adjusted according to comparative result, it is specially：

   Rotating speed is more than first rotary speed threshold value before deserving, and the current rate of change is more than the first rate of change threshold value When, the numerical value of first speed setting value is entered as rotating speed before deserving, deserves preceding rotating speed and first rotating speed to eliminate Deviation between setting value；

   The fuel delivery of the engine according to the Numerical Control of first speed setting value, it is specially：

   The fuel delivery of the engine, the closed loop are controlled by closed loop control method according to the numerical value of first speed setting value The integral element of the deviation is included in the control law of control method；

   Correspondingly, the numerical value by first speed setting value be entered as deserve before rotating speed, with eliminate deserve before rotating speed with Deviation between first speed setting value, in addition to the integral element of the deviation is reset.
2. 2. diesel speed control method according to claim 1, it is characterised in that described according to first speed setting After the fuel delivery of engine described in the Numerical Control of value, this method also includes：

   By the current rotating speed of the engine and current rate of change respectively with the second rotary speed threshold value and the second rate of change threshold value It is compared, rotating speed is less than second rotary speed threshold value before deserving, and the current rate of change is less than the described second change speed During rate threshold value, the numerical value of first speed setting value is entered as the second speed setting value.
3. 3. diesel speed control method according to claim 1, it is characterised in that the closed loop control algorithm be than Example-integration-differential pid control algorithm.
4. A kind of 4. diesel engine rotating-speed controller, it is characterised in that including：

   Rotation speed monitoring unit, for monitoring the rotating speed of engine and the rate of change of the rotating speed in real time；

   Speed setting value assignment unit, for by the current rotating speed of the engine and current rate of change respectively with the first rotating speed Threshold value and the first rate of change threshold value are compared, and the numerical value of the first speed setting value is adjusted according to comparative result, should with basis The fuel delivery of engine described in the Numerical Control of first speed setting value；

   The speed setting value assignment unit is further used for：

   Rotating speed is more than first rotary speed threshold value before deserving, and the current rate of change is more than the first rate of change threshold value When, the numerical value of first speed setting value is entered as rotating speed before deserving, deserves preceding rotating speed and first rotating speed to eliminate Deviation between setting value；

   The speed setting value assignment unit is further used for passing through closed-loop control side according to the numerical value of first speed setting value Method controls the fuel delivery of the engine, and the integral element of the deviation is included in the control law of the closed loop control method；

   Correspondingly, the speed setting value assignment unit is additionally operable to the integral element clearing of the deviation.
5. 5. diesel engine rotating-speed controller according to claim 4, it is characterised in that the speed setting value assignment unit It is additionally operable to：

   By the current rotating speed of the engine and current rate of change respectively with the second rotary speed threshold value and the second rate of change threshold value It is compared, rotating speed is less than second rotary speed threshold value before deserving, and the current rate of change is less than the described second change speed During rate threshold value, the numerical value of first speed setting value is entered as the second speed setting value.
6. 6. diesel engine rotating-speed controller according to claim 5, it is characterised in that the closed loop control algorithm be than Example-integration-differential pid control algorithm.