JPH04133667A - Voltage type pwm inverter - Google Patents

Abstract

PURPOSE:To make the utilization factor of voltage 100% by adding the voltage deviation between the absolute value of the phase, where the absolute value is the maximum among AC voltage command values even if the load whose load properties change is connected, and the voltage limiting value to the voltage command value to the phase other than the phase where the absolute value is the maximum so as to compensate it. CONSTITUTION:Two-phase AC voltage command values Vu, Vv, and Vw are operated. Next, the absolute value ¦Vu¦ of the voltage command value of phase (u) and the absolute value ¦Vv¦ of the voltage command value of phase (v) are compared with each other. If the absolute value ¦Vu¦ of the voltage command value of phase (u) is larger, the absolute value ¦Vu¦ of the voltage command value of phase (u) and the absolute value ¦Vw¦ of the voltage of phase (w) are compared with each other. If the absolute value ¦Vu¦ of the voltage command value of phase (u) is larger, the value Vmax is put as the value ¦Vu¦. Then, the voltage deviation V is operated by V=Vlim-Vmax. Next, the compensating voltage command value is operated. And the compensating voltage command value is outputted to an inverter controller 23 through output interface 64.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a voltage-type PWM inverter, and particularly to a voltage-type PWM inverter that makes it possible to achieve voltage utilization efficiency of 100%.
Regarding inverters.

[Prior art] In order to control the rotation speed and torque of an AC servo motor to predetermined values, a bridge-connected semiconductor switch is used as a PWM switch.
BACKGROUND ART An inverter that turns on and off using a pulse width modulation method to obtain three-phase AC having a predetermined voltage and frequency from DC supplied from a DC power source is well known (for example, Japanese Utility Model Application No. 57-135892).

In such an inverter, the input DC is generally obtained by converting the three-phase AC into DC using a converter using diodes connected in a three-phase bridge. The subsequent DC voltage value is L7 times the three-phase AC voltage.

When this DC is reversely converted into three-phase AC by a switching element connected in a three-phase bridge, PWM is performed using a predetermined output voltage target value and frequency target value as command signals.
The method determines the switching pattern of the switching element.

[Problem to be solved by the invention 1 However - In the PWM inverter used for boat fishing, the control algorithm is designed so that the output voltage is the maximum voltage at the peak value of 1/2 of the input voltage. Designed.

That is, FIG. 5 is an explanatory diagram of the voltage relationship between the input and output of the inverter. If the effective value of the line voltage of the three-phase AC power supply that supplies power to the converter 1 is 2·■ (volt), then the converter The output voltage Vdc of 1 is Vdc=2 ・5 tons・■ (1)
becomes.

A commonly used PWM inverter has V d
It can be considered that point E at c/2 is a virtual ground point, and voltages of ±2·■ and −2·■ are applied to the inverter 2 from point E.

Therefore, the phase voltage V of the three-phase AC reversely converted by inverter 2
acp is Va c p= (, I”T/2) ・V (
2).

Therefore, for example, when a load such as an AC servo motor is connected with a foot type, the line voltage Vs is Vs = r
Ding・V (3).

Therefore, for the input three-phase AC line voltage of the inverter,
The ratio of maximum output line voltage of the converter is: =E/2
#0.87 (4), and the voltage utilization rate remains at about 87%.

In addition, so-called general-purpose inverters that have perfect periodicity in their output voltage have a method of storing a voltage command value that has been compensated in advance so that the voltage utilization rate is 100%, but such as a servo motor. For loads that require constant stop operation and accurate constant control of rotation speed and output torque, it is necessary to generate an output voltage that does not have periodicity because the load characteristics change over time. It is not possible to program the switching patterns of the elements in advance.

The present invention has been made in view of the above problems, and even when it is necessary to generate an output voltage without periodicity in a case where the load characteristics change, such as with a servo motor, the voltage utilization rate can be improved. Voltage type PW that enables 100%
The purpose is to provide an M inverter.

[Means for Solving the Problems] The basic configuration of the voltage type PWM inverter according to the present invention is as follows.
As shown in the figure, in a voltage-type PWM inverter that outputs three-phase alternating current of a predetermined voltage by controlling the switching pattern of switching elements connected in a three-phase bridge to direct current supplied from a direct current power supply, a predetermined output AC voltage command value generation means that generates a three-phase AC voltage command value based on the voltage command and output frequency command, and selecting the phase with the largest absolute value among the voltage command values generated from the AC voltage command value generation means. a voltage command absolute value maximum value selection means for calculating a deviation between a voltage command absolute value of a phase selected by the voltage command absolute value maximum value selection means and a predetermined output voltage limit value of a voltage type PWM inverter; voltage calculation means; and the deviation voltage calculated by the deviation voltage calculation means is applied to a phase other than the phase selected by the voltage command absolute value maximum value selection means of the three-phase AC voltage command value generated by the AC voltage command value generation means. and compensation voltage command value calculation means for performing additive compensation for the voltage.

[Function] According to the voltage type PWM inverter according to the present invention, even when a load whose load characteristics fluctuate, such as a servo motor, is connected, the absolute value of the phase with the maximum absolute value among the AC voltage command values By adding and compensating the voltage deviation from the predetermined voltage limit value to the voltage command value for the phases other than the phase with the maximum absolute value, the phase-to-phase voltage of the inverter output is made equal to the phase-to-phase voltage of the AC voltage of the converter input. The voltage utilization rate is 1
00%.

[Embodiment 1] FIG. 2 is a block diagram of the present invention when it is configured by a controller using a microprocessor.

In FIG. 2, converter 1 has six sets of diodes ll
a...Ilf are connected in a three-phase bridge, and the AC supplied from the three-phase AC power supply 4 is full-wave rectified.

The inverter 2 is composed of switching transistors 21a...21f and feedback diodes 22a...22f connected in parallel to each other in a three-phase bridge connection, and each switching transistor 21a...
・The gate of 21f is inverter gate controller 2
Connected to 3.

Then, the DC output from the converter is reversely converted into three-phase AC of a predetermined frequency and voltage by switching, but the voltage and frequency of this three-phase AC match the target frequency and target voltage given to the inverter gate controller 23. Inverter gate controller 23 to
controlled by

A capacitor 3 is installed between the converter 1 and the inverter 2 in order to remove ripples in the direct current obtained by full-wave rectification of the three-phase alternating current.

The output of the inverter 2 is connected to a load 5, such as an AC servo motor.

For example, when the load is an AC servo motor, a command signal for the inverter gate controller 23 is calculated by inputting measurement results from a measuring device (not shown) that measures the operating state of the load, such as the rotational speed or current. A controller 6 is installed for this purpose.

This controller 6 is composed of a microprocessor 61, a memory 62, an input interface 63, an output interface 64, and a path 65 connecting these.

Further, the calculation result of the microprocessor sensor 61 is outputted to the inverter gate controller 23 via the output interface 64 of the controller 6.

FIG. 3 is a flowchart of a routine for calculating a voltage control command value to be output to the inverter gate controller 23 in order to make the voltage utilization rate 100%, and is executed at predetermined intervals.

In step 301, the three-phase AC voltage command values Vu, Vv, Vw are
is calculated.

This can be obtained, for example, by reading out the amplitude data stored in the memory using clock pulses corresponding to a predetermined frequency.

In step 302, the absolute values Vu1 and V of the voltage command value of the U phase are determined.
The absolute value 1■v1 of the phase voltage command value is compared.

If the absolute value IVul of the U-phase voltage command value is larger, an affirmative determination is made in step 302, and the process proceeds to step 303.
The absolute value 1■u of the U-phase voltage command value is compared with the absolute value IVw1 of the W-phase voltage.

Absolute value of U-phase voltage command value] If Vu1 is larger, an affirmative determination is made in step 303, and Vma is determined in step 304.
Let x be]■u1.

If the determination in step 302 is negative, step 30
Proceeding to step 5, the absolute value Vvl of the voltage command value of the ■phase is compared with the absolute value 1■w1 of the voltage command value of the W phase.

■If the absolute value of the voltage command value of the phase 1■■1 is larger, an affirmative determination is made in step 305, and in step 306 Vm
Let ax be 1Vv1.

If negative determinations are made in steps 303 and 305, then in step 307 Vmax is set to VWl.

After that, in any case, the process proceeds to step 308, and the voltage deviation ΔV is calculated as follows: ΔV=V 1 tm−Vmax (5) However, the output voltage limit value Vlim is VIim=r d−V ■=converter input interphase voltage/2 (6) is calculated in advance.

Next, in step 309 and subsequent steps, a compensation voltage command value is calculated.

That is, in step 309, it is determined whether the phase with the maximum absolute value of the voltage command value is the U phase. If the determination is affirmative, the process proceeds to step knob 310.

In step 310, the sign of the U-phase voltage command value is determined,
If positive, the process proceeds to step 311, where the compensation voltage command values Vvc and Vwc for the V phase and W phase are calculated as follows: Vvc=Vv+Δ■ VWc=Vw+Δ■ (7).

Then, in step 312, the compensation voltage command value Vuc for the U phase is calculated as Vuc=VI im (8).

When the sign of the U-phase voltage command value is negative, in step 313, Vvc=Vv-Δ■ Vwc=Vw-Δ■ (9)
In step 314, Vuc=-
It is calculated as V 1 im (10).

Similarly, when the absolute value of the V-phase voltage command value is the maximum, an affirmative determination is made in step 315, and steps 316 to 32
0, the compensation voltage command value is calculated.

Also, if the absolute value of the W-phase voltage command value is the maximum, step 3
In steps 21 to 325, a compensation voltage command value is calculated.

Then, in step 326, these complementary rj and voltage command values are output to the inverter gate controller 23 via the output interface 64.

FIG. 4 is a voltage waveform diagram showing the relationship between the voltage command value and the output voltage of the voltage-type PWM inverter controlled by the method described above, with the horizontal axis representing time and the vertical axis representing voltage.

That is, the voltage command values Vu, Vv, and Vw of the U-phase, ■-phase, and W-phase shown by the solid lines are sine waves with a maximum amplitude of 2·F/3 with a phase shift of 120°, respectively.

However, the amplitude of the output phase voltage of the inverter cannot exceed the output limit voltage Vlim.

Considering the period from time t to t3 in FIG. 4, since the voltage command value of the beam phase has the maximum absolute value and is positive during this period, the compensation voltage command value Vuc for the U phase is Vli
m.

For the (2) phase and the W phase, compensation voltage command values Vvc and Vwc are calculated based on the voltage deviation Δ■ between the voltage command value Vu of the U phase and the output voltage limit value Vlim.

That is, for example, at time t2, the voltage deviation Δ■ is equal to the line segment a
It is expressed as b.

A line segment cie with the same length as the line segment ab corresponding to this Δ■
is added to the V-phase and W-phase voltage command values, resulting in compensation voltage command values Vvc and Vwc shown by broken lines.

And these compensation voltage command values Vuc, Vvc and Vw
c is output to the inverter controller 23.

Therefore, the interphase voltage between the U phase and the V phase or W phase at time t2, which is represented by the line segment be, is equal to the interphase voltage of the voltage command value, which is represented by the line segment ad.

Therefore, the maximum amplitude of the inverter's output voltage is Vlim, but by setting the line voltage between each phase to a value equal to the voltage command value, it becomes possible to maintain the voltage between each phase at a predetermined value. .

[Effects of the Invention] As can be understood from the above explanation, according to the present invention, even when a load whose load characteristics constantly change, such as an AC servo motor, is connected to a voltage-type PWM inverter, the phase-to-phase voltage remains constant. It becomes possible to maintain a value equal to the voltage command value, and the ratio (voltage utilization rate) between converter input voltage and inverter output voltage can be made 100%.

[Brief explanation of the drawing]

Figure 1 is a functional block diagram showing the basic configuration, Figure 2 is a configuration diagram when the present invention is configured using a microprocessor, Figure 3 is a flowchart explaining control operation, and Figure 4 is a voltage command value. FIG. 5 is an explanatory diagram of the voltage relationship between the inverter's human power and the output. DESCRIPTION OF SYMBOLS 1...Converter, 2...Inverter, 3...Capacitor, 4...AC power supply, 5...Load, 6...Controller.

Claims (1)

[Claims] 1. In a voltage-type PWM inverter that outputs three-phase alternating current of a predetermined voltage by controlling the switching pattern of switching elements connected in a three-phase bridge to direct current supplied from a direct current power supply, AC voltage command value generation means for generating a three-phase AC voltage command value based on the output voltage command and output frequency command of the AC voltage command value generating means; A voltage command absolute value maximum value selection means for selecting a phase, and a voltage command absolute value of the phase selected by the voltage command absolute value maximum value selection means and a predetermined output voltage limit value of the voltage type PWM inverter. deviation voltage calculation means for calculating a deviation; and voltage command absolute value maximum value selection means for the three-phase AC voltage command value generated by the AC voltage command value generation means, using the deviation voltage calculated by the deviation voltage calculation means. A voltage type PWM inverter comprising compensation voltage command value calculation means for performing additive compensation for phases other than the selected phase.