JPS6245800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for digitally controlling the speed of an electric motor using a power converter that supplies power to the electric motor as an operating terminal, and particularly to a method for digitally controlling the speed of an electric motor that can be advantageously implemented using a microcomputer. Related to digital control method.

When a power converter is used as an operating end to control the speed of a DC motor or other motor that can be similarly controlled, it is required to be stable and quick to respond to all load conditions.

For example, control of DC motors powered by thyristor converters connected to the grid power supply is currently carried out exclusively by analog control. In this case, the current supplied from the thyristor converter to the DC motor during no load or light load is intermittent, and in such an intermittent current state, the gain of the current control system decreases and the time constant disappears, so that
It is known that the response of the current control system deteriorates, and in the worst case, the control system becomes unstable and may even become inoperable. In order to improve these problems when the current is intermittent, there are methods to increase the gain by installing various minor loops in the current control system, and methods to increase the loop gain by switching to a different regulator gain than when the current is continuous. It is considered.

On the other hand, there have been attempts to digitize the control device using a microcomputer, but the above-mentioned problems also arise in this case. In the case of digital control using a microcomputer, there is a method corresponding to analog control, that is, a method of switching adjustment parameters (for example, proportional gain, integration time, etc.) for current adjustment calculations depending on whether the current is continuous or when the current is interrupted. Various types of countermeasures can be considered using software, including little or no additional hardware. In any case, information on whether the current is continuous or intermittent is required. This information can be obtained by determining the current flow angle using hardware, by comparing the current with zero using a comparator, or by determining the current target value that is the result of speed adjustment calculations. Methods are being considered. However, the first and second methods require additional hardware, and the third method has the disadvantage that it does not make a determination based on the actual current value.

An object of the present invention is to provide an optimal and simple method that can accurately distinguish between an intermittent current state and a continuous current state and determine which state the current state is.

This purpose, according to the invention, is to determine whether the current is in an intermittent or continuous state depending on whether the actual current value immediately before the ignition signal is applied to the thyristor of the converter is zero. This is achieved by

The invention will now be explained in more detail with reference to preferred embodiments shown in the drawings.

FIG. 1 is a block diagram showing an example of a hardware configuration for controlling the speed of a DC motor using the digital control method according to the present invention, and FIG. 2 is a flowchart showing an example of arithmetic processing in the control method according to the present invention.

In Fig. 1, 1 is a 3-phase thyristor pure bridge connection thyristor converter with anti-parallel connection without circulating current, and the AC side is connected to 3-phase thyristor converter through a power transformer 2.
It is connected to the phase AC power supply 3. A DC motor 4 is connected to the DC side of this converter. A microcomputer 5 is composed of a CPU 51, a memory 52, and an input/output interface 53, and performs arithmetic processing for controlling the speed of the DC motor according to the present invention. A digitally displayed speed target value to be input into the microcomputer 5 is given by a speed setter 6. Also, the actual current value is detected via the current transformer 7 rectifier 8 and the A/
It is converted into a digital quantity by the D converter 9 and input to the microcomputer 5. Further, a synchronizing signal to be guided to the microcomputer 5 is provided by a synchronizing signal step-down transformer 10 and a quantization circuit 11 connected to the AC power supply 3. Also,
The actual speed value is input in digital form to the microcomputer 5 via the A/D converter 13 by a speed detection generator connected to the DC motor 4. Microcomputer 5 outputs a firing signal for the firing pulse to pulse amplifier 14 . The pulse amplifier 14 supplies a firing pulse to a predetermined thyristor via a pulse transformer 15 or 16 in accordance with the firing signal.

An embodiment of the digital control method according to the present invention, which can be executed by the hardware described above, will be described with reference to the flowchart shown in FIG.

The microcomputer 5 determines the phase of the thyristor to be fired based on the synchronization signal from the power supply by counting up the counter for adjusting the firing angle (~). Next, read the actual current value at that point and store it in the register (). Then, it outputs an ignition signal for giving an ignition pulse to the thyristor determined by (). Next, it is checked whether the actual current value read in is zero, and if it is zero, it is determined that the current is intermittent, and if it is not zero, it is determined that the current is continuous (). If the current is continuous, the flow will be ~, if the current is intermittent, ~
Switch the program flow to this flow.

If the current is continuous, read the new actual current value based on the result of the ignition signal and the stored current target value obtained from the previous speed adjustment calculation result, and perform current adjustment calculation according to a known method such as PI calculation. (), and the calculation result is △ corresponding to the change in firing angle.
If the n-th firing angle is set in the counter as m _o ( ), and α _o represents the nth firing angle, Δm _o can be expressed as Δm _o =α _o −α _o-1 . When Δm _o ⁼⁰ , that is, in order to make the (n-1)th firing angle α _o-1 equal to the nth firing angle α _o , the (n-1)th firing angle The nth ignition signal may be generated when a time equivalent to 60 degrees has elapsed from the time when the signal was generated.
Therefore, when △m _o ≠ 0, it is sufficient to generate the n-th firing signal when a time equivalent to 60° + △m _o has elapsed from the time when the (n-1)th firing signal was generated. . Therefore, the interval between the (n-1)th execution and the second execution is 60° + △m
Just set the count value so that the time corresponds to _o . Next, the actual speed value and target speed value are read, speed adjustment calculation is performed, and the result is output as the target value for the next current adjustment calculation (). While this speed adjustment calculation is being processed, the counter set in is performing a counting operation, and even after the calculation is completed, other calculations are being performed until the count is up.
For example, it performs calculations to display speed and current values, but
It idles and waits for the count-up ().

If it is determined that the current is intermittent at , the flow is changed to . In this case, the current adjustment calculation that is performed when the current is continuous is not performed, but the speed adjustment calculation is performed immediately (). And equivalent to the firing angle change △m _o obtained by the speed adjustment calculation
Set the counter value according to (). Then, in the same way as when the current is continuous, it performs other calculations or idles until the count up, and waits for the count up ().

It goes without saying that in the speed adjustment calculations in and, adjustment calculation parameters suitable for continuous current and intermittent current should be selected, respectively. Furthermore, it is sufficient to perform each calculation for continuous current and intermittent current once every ignition time interval.

As can be seen from the above description, according to the present invention,
When executing different predetermined calculation processes depending on whether the current is intermittent or continuous, the actual current value immediately before the ignition signal is generated is used to determine whether the current is intermittent or continuous. This is done depending on whether or not is zero. The hardware for detecting the actual current value can be common to the hardware for detecting the actual current value required for the current regulation calculation, and therefore no hardware is required to perform the above-mentioned determination. The determination result is extremely accurate because it does not require any additional wear and is essentially an optimal determination method that uses actual current. In particular, as in the embodiment shown in FIG. 2, the firing signal generation point is used as the reference point for the next firing signal generation point, and from this reference point, the steady-state firing interval of 60° is corrected according to the adjustment calculation result. The present invention is very effective when combined with a firing angle adjustment method in which the next firing signal is generated when a time corresponding to the variable interval obtained by this method has elapsed. In Fig. 2, the time from the time of count-up to the time of outputting the ignition signal is constant, and since this constant time is taken into account in the count-up of , immediately before the time of outputting the ignition signal of There is no difficulty in determining the point in time when reading the actual current value io for determining the current state of .

The adjustment calculations for the continuous current of ~ and the adjustment calculations for the continuous current of ~ are performed using extremely simple software processing without adding any hardware to compensate for changes in the characteristics of the motor current circuit that depend on the current state, and to adjust the current of all loads. Although desired control responsiveness and stability can be obtained over a wide range, the present invention is not limited to this and can be modified in various ways.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a hardware configuration for controlling the speed of a DC motor according to the control method according to the present invention, and FIG. 2 is a block diagram for explaining an embodiment of the control method according to the present invention. It is a diagram. 1...Power converter (thyristor converter), 4...
...Electric motor (DC motor), 5...Microcomputer, 6...Speed setting device, 7...Current transformer, 8...
... Rectifier, 9 ... A/D converter, 10 ... Step-down transformer for synchronization signal, 11 ... Quantization circuit, 12 ...
Speed detection generator, 13...A/D converter, 14
...Pulse amplifier, 15...Pulse transformer.

Claims (1)

[Claims] 1 The speed of the motor is controlled by a digital arithmetic processing unit using the power converter that supplies power to the motor as an operating terminal, and depending on whether the current supplied from the power converter to the motor is in an intermittent or continuous state. A method for digital speed control of an electric motor, in which a predetermined and different regulating operation is executed for each one, the execution of the regulating operation being an ignition for each controllable electric valve in a power converter. Synchronized with the signal, each time an ignition signal for any controllable electric valve occurs,
The time point at which the ignition signal is generated is used as the reference time point for determining the time point at which the ignition signal of the controllable electric valve to be fired is generated next, and the ignition signal generation interval in the steady state is used as the result of each adjustment calculation. The next ignition signal is generated when a time corresponding to the variable interval obtained by correcting the ignition signal has elapsed, and the actual value of the current is read in immediately before the ignition signal is generated. A digital speed control method for a motor speed, characterized in that whether the motor is in an intermittent state or a continuous state is determined based on whether an actual value read immediately before generating an ignition signal is zero.