JPH04138063A - Power converter - Google Patents

Abstract

PURPOSE:To suppress a rush current when a power source is turned ON and to rapidly interrupt an overcurrent by composing at least part of rectifiers of a bridge type rectifier circuit of a controlled rectifier, and controlling a conducting angle. CONSTITUTION:A bridge type rectifier circuit RC is composed by bridge- connecting thyristors SCR1, SCR2 as controlled rectifiers and diodes D3, D4. Reverse polarity self-extinguishing type semiconductor elements S1, S2 are connected in parallel at both ends of the diodes D3, D4. The conducting angles of the elements SCR1, SCR2 are controlled when an AC power source is turned ON to suppress a rush current. The conducting angle is reduced when the AC power source is turned ON, and the angle is so controlled as to increase the angle through a predetermined time. The angle is gradually increased from 0 degree to 180 degrees in a predetermined period of time. Thus, the rush current when a power source switch SW is closed can be effectively suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power converter, and specifically, an AC-DC conversion in which an AC input current has a sinusoidal waveform with a predetermined phase with an AC power supply voltage. This relates to a power converter of the formula.

[Prior Art] As a technique for making the AC input current waveform of a rectifier circuit into a sine waveform with a predetermined phase relationship with the AC power supply voltage, for example,
Presentation No. 3 at the National Conference of the Institute of Electrical Engineers of Japan.

509 "Low loss high power factor converter circuit" etc. The converter circuit presented at this conference has the configuration shown in FIG. This circuit consists of power switch S
It is constructed by connecting W1 reactor L1 diodes D1 to D4, self-extinguishing semiconductor elements S1 and S2 such as gate turn-off thyristors (GTo) and transistors, and smoothing capacitor C as shown in the figure. Note that β is a load, and a control device (not shown) controls the on/off operation of the self-arc-extinguishing semiconductor elements S1 and S2. The control device controls the self-extinguishing semiconductor elements S1 and S2 using a pulse width modulation signal, that is, a PWM signal whose pulse width appropriately increases or decreases in response to changes in the instantaneous value of the power supply voltage, and controls the input current from the AC power supply 1. The waveform is made to be a sine waveform with a predetermined phase relationship with the AC power supply voltage.

In this circuit, when the power switch SW is turned on, a large rush current flows into the smoothing capacitor C through the bridge type rectifier circuit made up of the diode Di-D4. Generally, as a means for suppressing this rush current, a configuration is adopted in which a parallel connection circuit of a current limiting resistor R and a shorting switch SWI is connected in series with the switch SW, as shown in FIG.

In this circuit, when the power switch SW is turned on, the shorting switch SWI is opened and the charging current of the capacitor C is suppressed by the resistor R, and when the voltage of the capacitor C reaches a predetermined value, the shorting switch SWI is closed. The on/off operation of the self-extinguishing semiconductor elements s1 and S2 is started.

[Problem to be solved by the invention] In the conventional power converter as described above, the current limiting resistor R
A device with a large rated power must be used for the short-circuiting switch SWI, and if a malfunction occurs in the operation of the short-circuiting switch SWI, there is a risk that the resistor R will be burnt out. Furthermore, the number of components increases to prevent inrush current, which is uneconomical. Furthermore, when an abnormality such as a short circuit occurs in the load β and an overcurrent flows, the diodes of the bridge rectifier circuit continue to conduct even if the self-extinguishing semiconductor elements St and S2 are turned off, so that the diode of the bridge rectifier circuit continues to conduct. cannot cut off overcurrent.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a power converter that can easily and reliably suppress rush current when power is turned on.

Another object of the present invention is to provide a power converter that can suppress inrush current when the power is turned on and can quickly cut off overcurrent.

[Means for Solving the Problems] In the invention of claim 1, a bridge type rectifier circuit configured by connecting rectifying elements in a bridge to convert alternating current to direct current, a smoothing capacitor, and a chopper control semiconductor element are provided. The object of the present invention is to improve a power converter including a chopper circuit that performs chopper control on the output of a bridge rectifier circuit.

At least a part of the rectifying elements of the bridge type rectifier circuit is composed of a controlled rectifying element, and the bridge type rectifying circuit is characterized by comprising a control device that suppresses inrush current by controlling the conduction angle of the controlled rectifying element when the AC power is turned on. In the invention of claim 2, when the AC power is turned on, the control device gradually increases the conduction angle until the DC forward voltage of the bridge rectifier circuit is saturated;
After the DC voltage is saturated, the conduction angle is immediately increased to 180 degrees. In one preferred embodiment, the conduction angle is gradually increased from 0 degrees to 90 degrees, and as soon as the conduction angle reaches 90 degrees, the conduction angle is immediately increased.

The invention according to claim 3 is characterized in that the control device further includes a configuration that cuts off an overcurrent that occurs due to a short circuit accident by turning the control rectifier element and the chopper control semiconductor element into a non-conducting state. In the invention according to claim 4, the chopper control semiconductor element is composed of a self-arc-extinguishing semiconductor element, and the rectifying elements on at least two adjacent sides of the bridge type rectifier circuit are each provided with a self-arc-extinguishing semiconductor element. In the invention of item 5, a reactor is provided in series with the bridge type rectifier circuit, a chopper control semiconductor element of the chopper circuit is controlled by pulse width modulation, and at least a part of the rectifier elements of the bridge type rectifier circuit are configured from a control rectifier element. death,
The present invention is characterized in that it is provided with a control device that controls the conduction angle of the control rectifying element to suppress or cut off inrush current when AC power is turned on and overcurrent that occurs due to a short circuit accident.

[Function] In the power converter according to the first aspect, when the AC power source is turned on, the conduction angle of the control rectifying element is controlled to suppress inrush current. The control device controls the conduction angle such that the conduction angle is made small when the AC power is turned on, and the conduction angle is made large after a predetermined period of time. The method of controlling the conduction angle is not constant, but a typical method is to gradually increase the conduction angle from 0 degrees to 180 degrees over a predetermined period of time.

In the invention of claim 2, since there is no need to suppress the rush current after the DC output voltage is saturated, the conduction angle is increased to 180 degrees immediately after the DC voltage is saturated. Therefore, according to the present invention, the operation time at startup can be shortened.

In the invention of claim 3, when an overcurrent occurs due to a short circuit accident, etc., if both the control rectifying element and the chopper control semiconductor element are made non-conductive to cut off the overcurrent, all the paths through which the overcurrent flows are eliminated. Therefore, the overcurrent can be cut off rapidly.

By controlling the conduction angle of the controlled rectifying element to suppress overcurrent as in the fifth aspect of the invention, so-called drooping characteristics can be obtained.

[Example code] explain.

In the embodiment shown in Fig. 1, the power switch
, the AC input terminal of the Buri-Soji type rectifier circuit RC is connected via the reactor L. 1) The Soji type rectifier circuit RC includes thyristors 5CRI and 5 as control rectifier elements.
CR2 and diodes D3 and D4 are bridge-connected.
Self-portrait semiconductor elements Sl, 82 with opposite polarities are connected in parallel.

These self-arc-extinguishing semiconductor elements 81 and 826 constitute a chopper control semiconductor element of a boost chopper circuit. The self-arc-extinguishing semiconductor element S1 is turned on and off by PWM III control, and controls half-waves of one polarity passing through the thyristor 5CR1. In addition, the self-arc-extinguishing semiconductor element S2 performs PWM control (by which it is turned on and off and chopper-controls the half-wave of one polarity that passes through the thyristor 5CR2. A smoothing capacitor C is connected between the DC output terminals of the bridge rectifier circuit RC. A load is connected in parallel to the output terminals T1 and T2 of this device.

Although the control device for controlling the thyristors 5CRI and 5CR2 and the self-extinguishing semiconductor elements Sl and 32 is not shown, in this embodiment, the thyristors 5CRI and 5CR2 are
, 5CR2 and the self-extinguishing semiconductor element St, 82 are controlled as follows. First, when the power switch SW is turned on, the conduction angle of each of the gates of thyristors 5CRI and 5CR2 is gradually changed from 0 degrees to 180 degrees as a predetermined time elapses, depending on the positive or negative polarity of the voltage of the AC power source AC. A gate signal is supplied as needed. As a result, the smoothing capacitor C is gradually charged from zero voltage to a DC voltage that is approximately the peak value of the voltage of the AC power source AC. This reliably suppresses inrush current when the power switch SW is turned on.

FIG. 2 is a waveform diagram showing the above operation. FIG. 2 (A) shows the AC power supply voltage V1, FIG. 2 (B) shows the gate signal g s 1 of the thyristor 5CRI, and FIG.
The gate signal gs2 in the figure (D shows each waveform of the terminal voltage Vc of the capacitor C).

The self-extinguishing semiconductor elements St and S2 are connected to a power switch SW.
The thyristors 5CRI and 5CR2 remain in the off state from when they are turned on until the conduction angle of the thyristors 5CRI and 5CR2 reaches 180 degrees. After the conduction angle reaches 180 degrees, the on/off operation by PWM control is started, and the terminal voltage of capacitor C is set to a predetermined set voltage, and the input current waveform is set to a sine with a predetermined phase relationship with the AC power supply voltage. Waveform.

As is clear from Figure 2 (D), the charging voltage Vc of the smoothing capacitor C is saturated at a value close to the peak value of the voltage of the AC power supply AC near the conduction angle of 90 degrees. . Therefore, the period from 90 degrees to 180 degrees is a period in which the conduction angle does not need to be controlled. Therefore, when using a DC voltage detection circuit that detects the saturation of the charging voltage of the smoothing capacitor C, the control of the conduction angle is stopped when the saturation of the charging voltage is detected, and the conduction angle is immediately set to 180 degrees. Arc-extinguishing semiconductor element 81. The PWM control of S2 may be started to set the terminal voltage of the flat groove capacitor C to a predetermined set voltage.

Note that if a DC voltage detection circuit is not used, the conduction angle is 90
The conduction angle control may be stopped at the point in time.

Next, a case will be explained in which an abnormality such as a short circuit occurs in the load and an overcurrent flows.
By reducing the conduction angle of 5CR2 or making it zero, the DC output voltage can be lowered to zero voltage, and overcurrent to the load can be suppressed or stopped.

Figure 3 is a waveform diagram for explaining the operation when an overcurrent occurs, and (A) shows the AC power supply voltage V1 (B).
is the gate signal gs1 of thyristor 5CR1, the same figure (C)
is the gate signal gS2 of thyristor 5CR2, the same figure (D)
is the PWM control signal cs of the self-extinguishing semiconductor element Sl
l sThe same figure (E) shows the PWM of the self-extinguishing semiconductor element S2.
The control signal C82 (F) in the same figure shows each waveform of the terminal voltage of the capacitor C. The figure shows that when an overcurrent occurs at time if, self-extinguishing semiconductor elements 81 and 82 are turned off, and the terminal voltage Vc of the smoothing capacitor C is reduced.
Furthermore, the state is shown over time when the conduction angle of the thyristors 5CRI and 5CR2 is decreased to reduce the terminal voltage Vc of the capacitor C to zero voltage at time t2.

FIG. 4 is a block diagram schematically showing an example of a control device used in the present invention to perform the above control operations. In the figure, when an AC power supply monitoring circuit 1 detects input of an AC power supply voltage, a timer circuit 2 operates and sends a command signal to a thyristor phase control circuit 3 for a predetermined period of time. Based on this command signal, the thyristor phase control circuit 3 outputs a gate signal that gradually increases the conduction angle of the thyristors 5CRI and 5CR2 from 0 degrees to 180 degrees for each positive and negative half wave of the AC input voltage. Note that when measuring the charging voltage of the smoothing capacitor C by providing the DC voltage detection circuit 4 as shown in the figure,
A signal may be output from the DC voltage detection circuit to the thyristor phase control circuit 3 to stop the phase control when the saturation of the charging voltage of the smoothing capacitor C is detected. The thyristor drive circuit 5 amplifies the power of the gate signal and drives the thyristors 5CR1 and 5CR2. Thyristor 5CR
When the conduction angle of I, 5CR2 reaches 180 degrees (when DC voltage detection circuit 4 is used, when voltage saturation is detected), switching circuit 6 operates and self-extinguishing semiconductor element control circuit 7 The self-arc-extinguishing semiconductor element control circuit 7 sends a drive signal to the self-arc-extinguishing semiconductor element 31, 32.
A control signal is output to turn on and off by PWM control.

The self-turn-off type semiconductor element driving circuit 8 amplifies the power of this control signal and drives the self-turn-off type semiconductor element S1.82.

Next, when an overcurrent flows, the overcurrent detection circuit 27 operates and first stops the output of the control signal from the self-arc-extinguishing semiconductor element control circuit 7, thereby causing the self-arc-extinguishing semiconductor element to S1. Turn off S2 to lower the DC output voltage.

On the other hand, when the output of the control signal from the self-extinguishing semiconductor element control circuit 7 is stopped, an operation control signal is sent to the thyristor phase control circuit 3 via the switching circuit 6. If the reduction in the DC output voltage is still insufficient and the overcurrent detection circuit 9 still detects an overcurrent state, the thyristor phase control circuit 3 is controlled to turn off the gate control signal to the thyristors 5CRI and 5CR2. The angle is gradually reduced or zeroed out. This reduces the DC output voltage to zero voltage. Note that when overcurrent is detected, thyristor 5
Of course, the gate signal may be cut off instantaneously without gradually decreasing the conduction angle of the gate control signal to CRI and 5CR2.

Next, main parts of other different embodiments of the present invention are shown in FIGS.
This will be explained using Figure 0. In these drawings, the same parts as in the embodiment of FIG. 1 are given the same reference numerals.

The embodiment of FIG. 5 has two thyristors 5CRI.

The cathodes of 5CR3 are commonly connected to simplify the insulation of the gate drive circuit.

When two thyristors are used, they may also be arranged and connected as shown in FIGS. 6 and 7.

In the embodiment shown in FIG. 8, the emitters of the self-arc-extinguishing semiconductor element 82°S3 are connected in common, and the self-arc-extinguishing semiconductor element S2
, 33 has a structure that can simplify the insulation of the drive circuits.

FIG. 9 and FIG. 10 show still other modified examples,
The modification shown in FIG. 9 includes four self-extinguishing semiconductor elements Sl,
S2. S3. S4 is connected to a bridge circuit to enable regenerative operation, but even in this case, circuit examples using two thyristors may be as shown in FIGS. 6 and 7. .

The modification shown in FIG. 10 is of a type in which 81 self-extinguishing semiconductor elements operate on and off to act as a boost chopper, and include two thyristors 5CRI.

5CR2 and two diodes D3. D4 constitutes a bridge circuit, and a reactor L is connected between the DC output of the bridge circuit.
A series circuit of a self-arc-extinguishing semiconductor element S is connected in parallel, and a series circuit of a diode D and a smoothing capacitor C is connected in parallel to the self-arc-extinguishing semiconductor element S.

[Effects of the Invention] According to the power converter of the first aspect, the conduction angle of the control rectifying element can be controlled when the AC power source is turned on, thereby reliably suppressing inrush current.

According to the invention of claim 2, the operating time at startup can be shortened.

According to the invention of claim 3, when an overcurrent occurs due to a short circuit accident, etc., both the control rectifying element and the chopper control semiconductor element are made non-conductive to cut off the overcurrent, so the overcurrent can be quickly stopped. Can be blocked.

According to the fifth aspect of the invention, the conduction angle of the controlled rectifying element can be controlled to obtain so-called drooping characteristics.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the main parts of an embodiment of the present invention, FIGS. 2 and 3 are waveform diagrams for explaining the operation of the embodiment, and FIG. 4 is a control device used in the present invention. 5 to 10 are circuit diagrams showing main parts of other different embodiments of the present invention, and FIG. 11 and FIG.
Both figures are circuit diagrams showing the main parts of a conventional power converter. AC...AC power supply, L...reactor, 5CRI~
5CR4...Control rectifier (thyristor), 81~S
4... Self-extinguishing semiconductor element, Di-D4... Rectifying element, C... Smoothing capacitor, 1... AC power supply monitoring circuit, 2... Timer circuit, 3... Thyristor phase Control circuit, 4... DC voltage detection circuit, 5... Thyristor drive circuit, 6... Switching circuit, 7... Self-extinguishing semiconductor element control circuit, 8... Self-extinguishing semiconductor element Drive circuit, 9... overcurrent detection circuit. Figure Figure Figure Figure

Claims (5)

[Claims] (1) A chopper that includes a bridge type rectifier circuit configured by connecting rectifier elements in a bridge connection and converts alternating current into direct current, a smoothing capacitor, and a semiconductor element for chopper control, and performs chopper control on the output of the bridge type rectifier circuit. In the power converter comprising a circuit, at least a part of the rectifying elements of the bridge type rectifier circuit are constituted by controlled rectifying elements, and the conduction angle of the controlled rectifying elements is controlled by the inrush current when AC power is turned on. A power converter characterized by comprising a control device that suppresses (2) The control device gradually increases the conduction angle until the DC output voltage of the bridge type rectifier circuit is saturated when the AC power is turned on, and immediately increases the conduction angle to 180 degrees after the DC voltage is saturated. 2. The power converter according to claim 1, wherein the power converter increases to . (3) The control device further includes a configuration that cuts off an overcurrent that occurs due to a short circuit accident or the like by making the control rectifying element and the chopper control semiconductor element non-conductive. Or the power converter according to 2. (4) The chopper control semiconductor element is composed of a self-arc extinguishing semiconductor element, and the self-arc extinguishing semiconductor element is connected in parallel to each of the rectifying elements on at least two adjacent sides of the bridge rectifier circuit. The power converter according to claim 5. (5) A bridge type rectifier circuit configured by connecting rectifier elements in a bridge manner to convert alternating current to direct current, a smoothing capacitor, a reactor connected in series to the bridge type rectifier circuit, and a semiconductor for chopper control. a chopper circuit that chopper-controls the output of the bridge-type rectifier circuit, the power converter comprising a chopper circuit that performs pulse-width modulation control of the chopper-control semiconductor element of the chopper circuit, the power converter comprising: At least a part of the rectifying element is composed of a controlled rectifying element, and includes a control device that controls the conduction angle of the controlled rectifying element to suppress or cut off an inrush current when AC power is turned on and an overcurrent that occurs due to a short circuit accident, etc. A power converter characterized by: