JP3217564B2 - Output voltage control device for power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for driving a large number of electric motors, and more particularly to an output voltage control device for a power converter which is a power supply for driving a hysteresis motor. .

[0002]

2. Description of the Related Art A conventional example of an output voltage control method of an inverter, which is a power supply device for operating a number of electric motors in parallel, will be described with reference to the circuit diagram of FIG. In the figure,
The AC voltage of the AC input power supply 1 is rectified by the rectifier 2 and input to the chopper circuit 3. The output voltage of the chopper circuit 3 is voltage-controlled by the voltage control circuit 4 and input to the inverter circuit 5. The inverter circuit 5 outputs a constant AC voltage of V / F according to the level of the output voltage of the chopper circuit 3, and drives the motors 7 _{l to} 7 _n . 6 _{l to} 6 _n are output filter circuits for improving power factor and distortion factor, motors 7 _{l to} 7 _n are hysteresis motors, and 8 is a voltage detector for the inverter output voltage.

The voltage control circuit 4 comprises a voltage reference generation circuit 9 for an inverter output voltage, a PI control circuit 10, a voltage detection circuit 11 for detecting the inverter output voltage, and an adder 12.

Next, an output voltage control system of the inverter shown in FIG. 2 will be described. First, the output voltage _Vinv of the inverter circuit 5 is detected by the voltage detector 8 and the voltage detection circuit 11. This detected inverter output voltage detection value _Vfb is compared with the reference voltage _Vref * of the voltage reference generation circuit 9 by the comparison adder 12, and the difference _Verr is input to the PI control circuit 10.
Controlling the output voltage of the chopper circuit 3 at the output E _c of the PI control circuit 10 controls the output voltage V _inv inverter.

The filter circuits 6 _{l to} 6 _n are composed of AC reactors 6 _{la to} 6 _na and capacitors 6 _{lb to} 6 _nb . These filter circuits 6 _{l to} 6 _n are output filters for improving the power factor and improving the output waveform, and are turned on when the inverter performs a rated operation.

In the voltage detection, it is necessary to supply a constant inverter output voltage _Vinv to a large number of motors (hysteresis motors) 7 _{l to} 7 _n in a lump and to detect the voltage of each motor end. Since the circuit configuration becomes complicated, voltage detection at each motor end is not performed, and the output voltage _Vinv of the inverter circuit 5 is detected and used as a feedback voltage for voltage control.

In the conventional voltage control circuit configuration described above, when the filter circuits 6 _{1 to} 6 _n are turned on during the operation of the inverter, a voltage drop occurs due to the reactance L of the AC reactors 6 _{la to} 6 _na , and , The voltages V _{m1 to} V _mn at the motor end are lower than the output voltage V _inv .

Further, the load current / power factor may fluctuate due to the characteristics of the hysteresis motor. For example, when the output voltage of the inverter is reduced, the hysteresis motor is over-excited, the current is reduced by about 10% of the normal, and the power factor is improved by about twice the normal. That is, since the voltage drop in the filter circuits 6 _{1 to} 6 _n changes due to the load fluctuation of the hysteresis motor, the voltages V _{m1 to} V _mn at the motor terminals fluctuate.

[0009]

[Problems that the Invention is to Solve Thus, controlled from the inverter output circuit after the voltage (voltage V _m1 ~V _mn of the motor end) can not be monitored, the voltage V _m1 ~V _mn of the motor end constant There was a drawback that it was not possible.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawback, and an object of the present invention is to provide a filter circuit, and to keep the output voltage at the motor end constant even if the load current / power factor fluctuates. An output voltage control device for a power conversion device is provided.

[0011]

In order to achieve the above object, a first aspect of the present invention is to output a chopper circuit and an AC voltage having a constant V / F corresponding to the level of the output voltage of the chopper circuit. An inverter circuit, and a filter circuit provided between the inverter circuit and each or a plurality of motors.
With the door, in the output voltage control apparatus of the power converter in parallel operation the electric motor by the output of the inverter circuit, the output voltage of the inverter circuit, a detecting means for detecting a power factor of the output current and the current, and the detected from the size and the power factor of the output current of the voltage drop at the pre-notated filter circuit
A calculating means for calculating a variation amount, out of the inverter circuit
Enter the difference between the force voltage and its reference value and the variation.
It is PI control means for controlling the output voltage of the chopper circuit
Has the door, characterized in that the voltage of the electric motor end with a voltage control means for controlling the constant.

[0012]

[0013]

[0014]

According to the output voltage control device of the power converter of the present invention, the voltage at the motor end can be controlled to be constant without affecting the fluctuation of the load current / power factor.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of one embodiment of the present invention, and the same portions as those of FIG. 2 which is the conventional example described above are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, a voltage control circuit 4A includes a voltage reference generation circuit 9, a PI control circuit 10, a voltage detection circuit 11, a comparison adder 12, a current detection circuit 13, and a power factor (phase) detection circuit 14.
And an output voltage correction circuit 15. A current detector 16 detects an output current of the inverter circuit 5.

[0017] Thus, the power factor (phase) detection circuit 14 detects the power factor from the inverter output voltage V _inv and the inverter output current I _inv (reactor current I _L) (phase). The output voltage correction circuit 15 outputs an output corresponding to a voltage drop due to fluctuation from the inverter output current detection value _Ifb detected by the current detector 16 and the current detection circuit 13 and the power factor Pf of the power factor (phase) detection circuit 14. and outputs the variation V _c voltage. Variation V _c and the inverter output voltage detection value V _fb comparison adder with voltage reference value V _ref ^* from the voltage reference generator circuit 9 12
And the difference V _err is input to the PI control circuit 10,
Controlling the output voltage of the chopper circuit 3 at the output E _c of the PI control circuit 10 controls the output voltage V _inv of the inverter circuit 5.

Next, FIG. 3 shows a voltage / current vector diagram of the inverter output in the case of three phases. In the figure, Vinv
= Inverter output voltage, V _m = motor end voltage, I _m =
Motor current, V _L = reactor voltage of filter circuit,
Reactor current of I _L = filter circuit, the capacitor current I _c = filter circuit, when the reactance of L = reactor, voltage V _m of the motor end is as follows.
(Note that the vector display dots are omitted here.)

[0019]

(Equation 1) The output voltage V _m0 at the motor end when there is no load fluctuation is

[0020]

(Equation 2) The voltage correction V _c due to the load fluctuation

[0021]

(Equation 3)

That is, the current flowing in the AC reactor of the filter circuits 6 _{1 to} 6 _n (= inverter output current I _L )
By detecting the phase θ (power factor fp) and calculating the above equation (1), the voltages V _{m1 to} V _mn at the motor end are obtained, and the voltage variation V _{c corresponding} to the voltage drop by the filter circuit is calculated . Can be.

[0023] Therefore, the load current / power factor of the motor is varied, the output voltage correction circuit 15 feedback voltage variation V _c from the act that PI control circuit 10, the inverter output voltage V _inv is the filter circuit 6 _l to 6 The voltage at the motor end is kept constant by raising / lowering by the amount of the voltage drop at _n .

When the power factor fluctuation of the motor is small,
The voltage drop of the filter circuit is corrected only by the output current l _inv without providing the power factor detection circuit, and the voltage V at the motor end is corrected.
_{m1 to Vmn} can be made constant. Also, in the case where the filter circuits are collectively provided for the individual motors, the voltage at the motor terminals can be made constant by the control method of the present invention.

[0025]

As described above, according to the present invention,
The voltage at the motor end can be controlled to be constant without affecting the fluctuation of the load current / power factor, and a stable voltage can be supplied to the motor.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of voltage control according to the present invention.

FIG. 2 is a circuit configuration diagram of a voltage control system of a conventional voltage source inverter.

FIG. 3 is a voltage / current vector diagram of an inverter output in the case of three phases.

[Explanation of symbols]

1: AC input power supply, 2: Rectifier, 3: Chopper circuit, 4
... voltage control circuit, 5 ... inverter circuit, 6 _{l to} 6 _n ... filter circuit, 7 _{l to} 7 _n ... electric motor (hysteresis motor), 8 ... voltage detector, 9 ... voltage reference generation circuit, 10 ... P
I control circuit, 11: voltage detection circuit, 12: adder, 13: current detection circuit, 14: power factor (phase) detection circuit, 15: output voltage correction circuit, 16: current detector.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02P 7/63 302 H02P 7/63 303 H02P 7/74

Claims (1)

(57) [Claims] 1. A chopper circuit, an inverter circuit for outputting a constant V / F AC voltage corresponding to an output voltage level of the chopper circuit, and a filter circuit provided between the inverter circuit and each or a plurality of electric motors equipped with a door,
In the output voltage control apparatus of the power converter in parallel operation the electric motor by the output of said inverter circuit, a detecting means for detecting a power factor of the output voltage, output current and current of the inverter circuit, the magnitude of the detected output current a calculating means for calculating a fluctuation amount of the voltage drop at the pre-notated filter circuit from the to power factor, the output voltage and its of the inverter circuit
PI control means for receiving a difference between the reference value and the amount of variation and controlling an output voltage of the chopper circuit ,
Output voltage control apparatus of a power conversion apparatus characterized by comprising a voltage control means for controlling the voltage of the electric motor end constant.