JPS6252560B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chopper control device, and more particularly to a chopper control device suitable for controlling a thyristor chopper whose commutation time varies greatly depending on the magnitude of its load current.

Generally, in a thyristor chopper, commutation failure occurs if the next gate pulse is applied within the commutation time to make the chopper conductive.
Therefore, even if the off signal of the chopper is shifted to the on signal as far as possible, it cannot be brought close to within the commutation time.

Incidentally, the commutation time of the chopper changes depending on the value of the load current, for example, depending on the value of the motor current in a chopper device that controls a DC motor. In other words, the commutation time is longer when the motor current is small;
As it grows, it becomes shorter. Therefore, the setting value to bring the off signal closest to the on signal is:
It is regulated when the motor current is controlled to be the smallest.

In this case, when the motor current is large, the flow time of the chopper becomes shorter than necessary, and the control range of the chopper becomes narrower.

A method for eliminating this drawback has been proposed in Japanese Patent Application No. 17638/1983, particularly for chopper devices in which the commutation time varies greatly depending on the magnitude of the motor current.
This detects the commutation time using a hardware configuration from a chopper circuit, and prevents an ON signal from entering within this range.

On the other hand, the use of a microcomputer is being considered for the gate control of Chiyotsupa, but one of its major purposes is to minimize the hardware configuration by maximizing the functions of the microcomputer. . Furthermore, since the operating frequency of a microcomputer is a high frequency of several MHz, in order to eliminate malfunctions such as noise, it is preferable to limit the signals taken in from the main circuit of large current and high voltage as much as possible.

That is, the hardware configuration proposed in the above-mentioned Japanese Patent Application No. 17638/1983 is inappropriate for a microcomputer system.

SUMMARY OF THE INVENTION An object of the present invention is to provide a chopper control device using a microcomputer that eliminates the drawbacks of the prior art described above and can always make maximum use of the chopper control range.

The present invention focuses on the fact that the commutation time of a thyristor chopper is uniquely determined by the thyristor current value when an off signal is applied to the thyristor. The microcomputer is provided with a program for calculating the current value, and has a function of controlling so that the next on signal does not enter within the commutation time determined from the current value when the off signal is applied. It is something.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a wiring diagram when an electric motor is controlled by a general chopper CH. Power supply (voltage V
_S ), electric motor M, smoothing reactor MSL and chiyotsupa
CH is connected in series, motor M and smoothing reactor
A freewheel diode D _F is connected in parallel with MSL. The configuration of the chopper CH is a parallel arc-extinguishing type, in which an auxiliary thyristor ATh, a series circuit of a commutating reactor L ₀ and a commutating capacitor C ₀ are connected in parallel with the main thyristor MTh via a reverse blocking diode D _S. ing.

FIG. 2 is an explanatory diagram of the commutation operation of the chopper CH. In FIG. 2, it is assumed that the inductance of the motor circuit is large and the motor current I _M has no pulsation and is pure direct current.

When the main thyristor MTh in FIG. 1 is made conductive by the on signal S _ON , a motor current I _M flows from the power supply voltage V _S to the motor M, the smoothing reactor MSL, and the main thyristor MTh. Next, the auxiliary thyristor
The commutation operation that occurs when the off signal _Spff is applied to ATh will be explained with reference to FIG. The direction of the voltage v _cp of the commutating capacitor C ₀ before the off signal S _pff is applied (time t ₀ ) is in the direction of the arrow in FIG. 2, which is defined as the positive direction. When the off signal S _pff is given to the auxiliary thyristor ATh at time t ₀ , the commutating capacitor C ₀
→ Commutation reactor L ₀ → Commutation current i ₀ (positive in the direction of the arrow) flows in the auxiliary thyristor ATh circuit. The half period τ _p of this commutation current i ₀ is τ _p =π√ _{0 0} (1).

At time _t1 , the commutation current _i0 becomes zero, and thereafter the direction is opposite to the arrow in FIG. At time t ₂ when this current i ₀ reaches the same magnitude in the opposite direction as the motor current I _M flowing through the main thyristor MTh, the main thyristor MTh becomes non-conductive. Furthermore, at time t ₂ ,
Since the commutating capacitor voltage v _CP is lower than the power supply voltage V _S , the commutating current i ₀ in the opposite direction continues to flow through the commutating capacitor C ₀ to perform charging. Then, the commutating capacitor voltage v _CP increases to become v _CP =V _S at time t ₃ . The time τ _q from time t ₂ to time t ₃ is τ _q =V _S +(v _cp )t ₂ / _IM ·C ₀ (2).

Furthermore, even after reaching v _cp =V _s , the commutating capacitor voltage v _cp continues to rise further due to the commutating reactor L ₀ and the wiring inductances Ll1, Ll2, Ll3, etc. shown by dotted lines in FIG. At time _t4 , when the current I _CH flowing through the chopper CH reaches zero, the commutation operation is completely completed. That is, the motor current I _M completely flows through the freewheel diode D _F . Time τ _r from time t ₃ to time t ₄
is τ _r =π/2√( ₀ +1+2+3)・C ₀ …(
3) becomes.

Note that during the time from time t ₁ to time t ₂ , the maximum value of current i ₀ in the previous period τ _p is 3 to 4 times larger than motor current I _M , so at time t ₂ The time for commutation current i ₀ to reach I _M is τ
It is sufficiently small compared to _p , τ _q , and τ _r and can be ignored.

From the above, it can be seen that the commutation time τ ₀ is approximately given by the sum of (1) to (3), and among these, τ _q in (2) changes depending on the motor current I _M.

Next, Figure 3 shows a block diagram of a typical control method for DC motor control using the chopper CH shown in Figure 1.
As shown in the figure. That is, command value I _p and motor current I _M
, the phase shifter APS is applied via the control element G(s) to the deviation of
Connect the output of the phase shifter APS to the pulse converter PC
The on signal S p is converted into a pulse by S _p
o , gives an off signal _Spff to perform constant motor current control. FIG. 4 shows the motor speed V vs. motor current I _M characteristic under such control. Desired maximum motor current (I _M ) Minimum motor current (I _M ) _nio when controlled by _nax is the intersection point P with running resistance line RL.
becomes. From this, the commutation time τ ₀ shown in Fig. 2
is known to vary as the motor current I _M varies in the range from (I _M ) _nax to (I _M ) _nio .

In the present invention, by knowing the commutation time τ ₀ of the chopper according to the motor current, the control range of the chopper can always be effectively controlled to the maximum as illustrated below.

FIG. 5 shows the hardware configuration of an embodiment of the present invention, in which the control block diagram of FIG. 3 is constructed by a microcomputer system. That is, an analog-to-digital converter A/D converts the analog values of motor current I _M and command value I _p into digital values, and an oscillator that generates an interrupt signal every operating cycle of the chopper.
It consists of an OSC, a microprocessor MPU that calculates control elements, a programmable timer PTM that converts the calculation results into phase-shifted output, and a pulse converter PC that converts the phase-shifted output into chopper on/off pulses. /D is connected by data bus AB.

FIG. 6 shows the software configuration of an embodiment of the present invention, and is a schematic diagram of the hardware configuration shown in FIG. 5. In addition to the main routine, the oscillator shown in FIG.
It consists of an interrupt routine that is activated by the OSC every operating cycle of the chopper. In the interrupt routine, the deviation ε between the motor current I _M and the command value I _P and the multiplication of the deviation ε by the control element are calculated, and the results are transferred to the programmable timer PTM.

FIG. 7 shows the characteristics of the commutation time τ ₀ in the range from (I _M ) _nax to (I _M ) _nio explained in FIG.
This is obtained from (1) to (3). The data table shown in FIG. 6 is a memory area in which the characteristics shown in FIG. 7 are stored as data.

FIG. 8 is a program flow diagram of the interrupt routine of FIG. First, in step 100, the A/D conversion values of the command value I _p and the motor current I _M are determined. Then, in step 101, find the deviation ε=I _p -I _M ,
Performs an operation with the control element and sets the result as DUTY. Next, in step 102, the commutation time τ ₀ corresponding to the A/D converted value of the motor current I _M is read from the data table. From this, the maximum value of DUTY (DUTY) _n transferred to the programmable timer PTM is the difference obtained by subtracting the commutation time τ ₀ read earlier from the chopper period T _CH , that is,
(DUTY) _n =T _CH -τ ₀ , so this is calculated in step 103. So step 104, 105, 106
Now, let's look at the results obtained from the calculations with the control elements.
When DUTY is larger than (DUTY) _n , DUTY is set to (DUTY) _n ; when it is smaller, DUTY is transferred as is to the programmable timer PTM.

FIG. 9 is a time chart of the output obtained in the flow chart of FIG. Assuming that the calculation results of the control elements in Fig. 8 are transferred as they are to the programmable timer PTM, even if the output is DUTY shown by the dotted line, the actual output of the programmable timer PTM is (DUTY) _n , and the motor current I _M A commutation time τ ₀ corresponding to the off signal Spff is secured, and an on signal is given after τ ₀ from the off signal _Spff . Further, when the motor current I _M is large and τ ₀ is small, the chopper can be made to flow through the chopper with a signal DUTY in a correspondingly wider range. Furthermore, since the only amount taken in from the large power system is the motor current I _M , which is processed through A/D conversion, the influence of noise from the main circuit can also be suppressed.

In the chopper circuit of FIG. 1, the commutation time τ ₀ with respect to the motor current I _M is almost a straight line as shown in FIG. 102, −(τ ₀ ) _nax −(τ ₀ ) _nio /(I _M ) _nax
It is clear that the following calculation may be performed: -(I _M ) _nio ×I _M +(τ ₀ ) _nio .

Furthermore, in practical motor control using a chopper, the motor current I _M includes ripples as shown in FIG. In this case, the current value that affects the commutation time τ ₀ is the value (I _M ) _p at the time when the off signal _Spff is applied to the chopper. Therefore, A/D conversion is performed in synchronization with the off signal S _pff , and (I _M ) _p
What is necessary is to read the commutation time corresponding to the data table from the data table.

In the above embodiment, the chopper circuit has the configuration shown in FIG. 1, but the present invention is not limited to this configuration. Needless to say, the present invention can be applied to any device in which the chopper commutation time τ ₀ is varied depending on the motor current I _M .

In addition, although the hardware and software configurations in Figures 5 to 8 are explained for the case where the motor current is controlled to the command value, the operation and effect are the same even when the motor voltage and speed are controlled to the command value. be.

In addition, regarding the hardware configuration in Figure 5, various
Even if LSI is used, the functions and effects of the present invention are the same.

As is clear from the above description, according to the present invention, in a chopper control device of a microcomputer system, the influence of noise from the main circuit is eliminated, and the control range of the chopper is adjusted to the motor current by a simple hardware configuration. The effect is that it can be used as effectively as possible regardless of the situation.

[Brief explanation of the drawing]

Figures 1 and 2 are an example of a chopper circuit for motor control and an explanatory diagram of its operation, Figure 3 is a block diagram showing a chopper control method, and Figure 4 is a diagram of operating characteristics of the motor under the control shown in Figure 3. , FIG. 5 to FIG. 8 are diagrams showing one embodiment of the present invention, FIG. 9 is an explanatory diagram of operation in one embodiment of the present invention, and FIG. 10 is an actual motor current waveform diagram. CH...Chiyotsupa, τ ₀ ... Commutation time, I _M ...
Motor current, MPU...microcomputer,
OSC...Oscillator, A/D...Analog-to-digital converter, PTM...Programmable timer, PC
...Pulse converter.

Claims (1)

[Scope of Claims] 1. A first means for digitizing a detected value and a command value of an input chopper current, and a chipper for determining a deviation between the command value and the detected value digitized by the first means. a second means for calculating the conduction time corresponding to the deviation of the thyristor constituting the thyristor; a third means for estimating the commutation time of the thyristor from the digitized detected value; The maximum flow time obtained by subtracting the commutation time obtained by the third means from the flow time and the flow time calculated by the second means are compared, and the smaller value is determined as the actual flow time. A chopper control device comprising a fourth means and a fifth means for outputting a gate pulse corresponding to the conduction time determined by the fourth means to the thyristor. 2. The chopper control device according to claim 1, wherein the second, third, and fourth means are constituted by a microcomputer. 3. The third means is configured by providing the commutation time for the chopper current to the microcomputer in advance as a data table. Chiyotsupa control device. 4. Claims 1 and 2, characterized in that the third means is configured by providing the microcomputer with a formula program for calculating the commutation time for the chopper current. The chiotspa control device described.