JPH02151203A - Inverter controller - Google Patents

Abstract

PURPOSE:To enable stabilized control by not feeding back the output from an effective operating circuit to a control system but feeding back the total value of motor current to the control system in the low frequency zone where the effective value operating circuit produces an unstable output. CONSTITUTION:When a vehicle is started to increase the speed gradually, the output from an inverter frequency setting section 13, i.e. an inverter frequency finv, also increases gradually. When the inverter frequency reaches to a preset current feedback system switching frequency, a current feedback system switch 9 is switched to the side of maximum current feedback system. When the speed is decreased during regenerative brake operation, the switch 9 is switched to the side of total motor current feedback system through function of a judging section 10 upon droppage of the inverter frequency finv, i.e. the vehicle speed, to the preset current feedback system switching frequency. By such arrangement, stabilized acceleration/deceleration control is realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable voltage variable frequency inverter control device that obtains an AC output through pulse width modulation, and is particularly suitable for stable speed control of an AC motor of an electric vehicle. The present invention relates to an inverter control device.

[Conventional technology]

[f! ! "2O2 commuter type DC train (top) (bottom)" published in the February/March 987 issue of Kisha no Kagaku Jl.
As described in , in a conventional inverter-controlled electric vehicle, the value of the current fed back to the control system is based on the total value of the currents of a plurality of motors controlled by one inverter device. This method has the disadvantage that it is difficult to operate the control system in the direction of re-sticking the vehicle when it slips or skids. This point will be explained using FIG. 3 as an example.

Now, consider that in a control system in which four induction motors are controlled by one inverter, the rotational speed fr of each motor takes a different value. If any of the shafts slips or slips, the motor current driving that shaft decreases, as is clear from FIG. As mentioned above, the current value fed back to the control system is the sum of each motor current (IMz + IM2 + IM3 + IM4), so if even one motor current decreases due to slipping or skidding, the current value fed back to the control system will change. decreases. The control system has a current pattern that corresponds to the inverter frequency at that time, and control is performed so that the current pattern and the feedback value of the motor current always match. If the motor current feedback value becomes larger than the current pattern, the slip frequency fs will be decreased and the motor current will be reduced; conversely, if the motor current feedback value becomes smaller than the current pattern, all operations will be performed. It operates to increase the frequency fs and increase the motor current. As mentioned above,
Since the motor current feedback value decreases due to slipping and sliding, the control system increases the slip frequency fs in an attempt to increase the motor current. In an inverter-controlled electric vehicle, when driving, the inverter frequency f +ov= f r+
f s , fl during regenerative braking, and v = fr - fs, the inverter frequency f lnV corresponding to the current motor rotation speed f is calculated, and the speed of the electric vehicle is controlled. In the conventional control method that increases the slip frequency fs during slipping and skidding, the inverter frequency f InV also changes with the change in the motor rotation speed fr during regenerative braking.
The value of the slip frequency fs, which is the difference between ftnv and f, does not change, and the position of the slipping/sliding axis on the characteristic diagram does not change. That is, the electric motor side receives the same current from the inverter device side as when slipping/sliding occurs, continues to output the same torque, and the control system does not move in the direction of re-sticking.

Therefore, if the value obtained by multiplying the maximum value of each motor current by four is fed back to the control system,
For example, even if frz in Fig. 3 is idling, a current value four times the maximum motor current IMa due to fr4 is always fed back to the control system, so the value of f5 can be increased or decreased in the control system. There is no change in fIIIV even if there is a change in f at the time of slipping or skidding. If the inverter frequency f lnV does not change, the change in f due to slipping/sliding will be in the direction approaching flllV, that is,
This is a change in the direction of decreasing fs, and without any special control from the outside, due to the characteristics of the motor itself, the current and torque will decrease, and the motor will naturally re-stick.

In this way, the system in which the maximum value of the motor current is fed back to the control system allows the vehicle to naturally re-stick when it slips or skids, depending on the characteristics of the motor itself.

[The problem that the invention aims to solve]

However, as shown in FIG. 2, in the above conventional technology, fI motor current detection units are required at three locations per motor, and twelve locations in total in a general system in which two inverters drive the motor. becomes. In order to reduce the number of detectors and the number of wires, if there is only one current detector per motor, the AC current - phase component will be input to the effective value calculation circuit shown in Figure 2. There occurs a point where the phase of the current input changes, that is, a point where the input current value becomes zero. The effective value calculation circuit 1 shown in FIG. 5 is equipped with a division section 28 due to its circuit configuration, and when the input becomes zero, division by zero is performed. Detection part 2
6 detects from the magnitude of the input current value, and the holder 27
sends a hold signal to

The holder that receives this hold signal holds the input current value immediately before the hold signal is sent, thereby preventing the divider from dividing by zero.

However, the holder used for this execution value calculation circuit.

Good control responsiveness is required, and those with long retention times are generally not available. As long as zero input of the input current value is detected based on the magnitude of the input current value, the lower the frequency of the input current value, the longer the holding time by the holder will be, and it will be difficult to keep the input current value constant. This becomes impossible, and the effective value calculation output becomes extremely unstable while the holding signal is being sent to the holder.

In the prior art, as shown in FIG. 2, the speed of the vehicle does not depend on the value of the inverter frequency.

The mechanism is such that the output of the effective value calculation circuit is always fed back to the control system, and even when the vehicle speed is near zero, that is, the input current is 0 (near z), the output of the effective value calculation circuit is The current value is fed back to the control system, and no consideration is given to the fact that the unstable current value is fed back to the control system, which poses a problem in controlling the speed of the vehicle in a low frequency range, that is, a low speed range.

The object of the present invention is to adopt a control system in which the current detection section is placed in one place per motor and the maximum current value is fed back to the control system, and stable control is possible even in the low speed range, resulting in smooth control. An object of the present invention is to provide an inverter control device with acceleration/deceleration performance.

[Means to solve the problem]

As shown in Fig. 4, the purpose of the above is to avoid feeding back the output of the effective value calculation circuit to the control system in the low frequency range where the effective value calculation circuit produces unstable output. This is achieved by providing feedback to

By feeding back the total value of the motor current at low speeds, the maximum current value feedback system can prevent idling and
Although the advantage of readhesion control during skidding will be lost, it is necessary to determine the frequency range in which the unstable output of the effective value calculation circuit continues, and then adjust the motor current sum value feedback at the lowest possible frequency. This can be dealt with by optimizing the setting of the current feedback switching frequency for switching from the mode to the maximum current value feedback mode.

[Effect]

That is, as shown in FIG. 4, the characteristics of the effective value calculation circuit are determined in advance, and the current feedback method switching frequency is set to a certain inverter frequency at a level that does not impede the characteristics of the maximum current feedback control method.
When the vehicle speed is low, the total value of the motor current is fed back to the control system, and when the current feedback method switching frequency is higher than the current feedback method switching frequency, that is, when the vehicle speed is higher than the set inverter frequency, the maximum value of each motor is Feedback the current to the control system. Thereby.

Stable acceleration/deceleration control can be performed without unstable current values being fed back to the control system, making it possible to use the maximum current feedback control method, and also making it possible to utilize the excellent re-adhesion control effect when slipping or skidding. The current feedback type switching function makes it possible to use a circuit that takes in one phase of the motor current and calculates the effective value, so it is only necessary to install one motor current detection section per motor. It is possible to reduce the number of current detection devices and the number of wires associated with it.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, an inverter device 1 controls the speed of a plurality of induction motors 4 by comparing the current value from the current detecting section 2 or 3 with the pattern current value from the current pattern generating section 12, and setting the perfect frequency. The section 11 outputs the slip frequency fs. By matching the slip frequency fs and the rotor frequency f from the motor rotation speed detection section 5, the inverter frequency setting section 13 outputs an inverter frequency f tnv.

In FIG. 1, when the vehicle is started, the current feedback method selector switch 9 is set to feed back the total value of the motor current to the control system.

When the vehicle starts and the speed gradually increases, the inverter frequency f InV which is the output of the inverter frequency setting section 13
will also gradually increase. When the value of finv reaches the preset current feedback method switching frequency,
The operation of the current feedback switching frequency determining section 10 switches the current feedback method changeover switch 9 to the maximum current feedback method side. From then on, always #J
The changeover switch 9 continues to enter the maximum current feedback method side, and acceleration continues.

Next, when decelerating during regenerative braking, contrary to when accelerating, the maximum current feedback method is first used, and the inverter frequency fll1M, that is, the vehicle speed decreases, until the preset current feedback method switching frequency is reached. Then, by the operation of the current feedback switching frequency determining section 10, the current feed pack method selector switch 9 is switched from the maximum current feedback method side to the motor current sum value feedback method side. 6 in the figure is a current value adding section.

That is, as shown in FIG. 3, in a region where f lnV is smaller than the current feedback method switching frequency, the total value of the motor current is fed back to the control system.

In the region where f 1nV is larger than the current feedback system switching frequency, the maximum value of the motor current will cause the control system to
It will be backed up.

According to this embodiment, below the preset current feedback method switching frequency, the sum total of the motor current is always fed back to the control system, and the effective value calculation circuit 7 in the low frequency range A stable current value is always fed back to the control system without feeding back unstable output to the control system, making stable acceleration/deceleration control possible.

Furthermore, in the region above the current feedback method switching frequency, the maximum value of the electric machine current is always fed back to the control system, providing excellent readhesion control characteristics when the vehicle is slipping or skidding.

Further, the number of motor current detection sections can be reduced to one per motor, making it possible to significantly reduce the number of current detection sections and the number of wires associated with it.

〔Effect of the invention〕

According to the present invention, (1) A stable current value can always be fed back to the control system, making stable acceleration/deceleration control possible.

(2) Excellent re-adhesion control can be performed when the vehicle is spinning or skidding;

(3) It is sufficient to install one motor current detection section per motor, making it possible to reduce the number of current detection devices and the number of wires associated with it.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of an embodiment of the present invention, Fig. 2 is a control block diagram of conventional maximum current feedback, and Fig. 3 is a control block diagram of an embodiment of the present invention.
The figure is a characteristic diagram of the current of the induction motor, 1 Herc and frequency, Figure 4 is an explanatory diagram of the feedback method of the present invention, and Figure 5
The figure is a block diagram of a motor current effective value calculation circuit according to the present invention. 1... Inverter device, 4... Induction motor, 7...
・Each electric station 1st ward 2nd cause 3rd figure 4th figure

Claims (1)

[Scope of Claims] 1. A device for controlling an induction motor by a variable voltage variable frequency inverter device, which adopts a control method in which the one with the largest current value among the plurality of induction motors is fed back to the control system, An inverter control device characterized in that each current detection section of an induction motor is performed by a single detection device. 2. The inverter control device according to claim 1, wherein the detection unit for the current to be fed back is switched at a predetermined constant inverter frequency for feedback to the control system.