JPS61132082A - Current type inverter - Google Patents

Abstract

PURPOSE:To economically transmit power to a load even in a range that the frequency is high by composing a power inverter of a series unit of a diode and a transistor. CONSTITUTION:A power reactor 1 has power modules 17-19 of thyristors, and a power inverter 6 has power modules 61, 62 of transistors and power modules 65-68 of diodes. The base drive circuit 7 of the transistor has a base drive signal generator 70 and base drive amplifiers 71-74. The generator 70 generates a timing signal of switching the modules 61, 62 of the transistors with a voltage zero point as a reference from the signal of a voltage detector 35 for the load voltage at normal time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a power conversion device that converts AC power at a commercial frequency to AC power at a frequency higher than 1, particularly a high-frequency inverter. It is something.

[Conventional technology]

FIG. 7 is a circuit diagram showing a conventional current source inverter.
In the figure, (1) is a forward conversion circuit consisting of a bridge connection of thyristor (b) to QIS, (2) is a forward conversion circuit consisting of a bridge connection of thyristor (b) to QIS, (2) is a reverse conversion circuit consisting of a bridge connection of thyristor (6) to -. The conversion circuit (4) receives the load voltage detection signal and converts the thyristor (
6) ~ate 01) ~ Gate control circuit that outputs a signal to fire @4, (5) is the capacitor S υ and Coil A/lZ
It is a parallel resonant circuit consisting of

Next, the operation will be explained. The thyristors (B) to αQ of the forward converter (1) conduct at the phase angle at which the load voltage reaches a predetermined value according to the gate signal of the gate control circuit (4), and connect to the terminal R.
The power from the three-phase AC side of the 8T is converted to DC voltage and output to terminals P, N. DC reactor A/ (2) is as follows.

The inverse conversion circuit (3) acts to smooth the current in the closed circuit passing through the parallel resonant circuit (5) to such an extent that it can be regarded as an approximately constant current. Thyristors (2) to - of the inverse conversion circuit (3)
Since it does not have a self-extinguishing ability, it is always operated with a leading power factor as shown in the voltage and current waveforms of each part shown in Fig. 8, and a reverse voltage period of tTs, which is longer than the thyristor turn-off time shown in Fig. 8 (b), is provided. This is controlled by the gate control circuit (4). (to) is a voltage detector for detecting the zero point of the load voltage, which is the reference point for determining the timing. Thyristor 6]) CI41. ! 1. By repeating alternate conduction of the thyristors), a sinusoidal voltage V and a square wave current i as shown in FIG. 5(al) are applied to the parallel conimage circuit (5).

[Problem that the invention seeks to solve]

As described above, in the conventional current source inverter, in order to operate the thyristor normally without commutation failure, it is necessary to provide a reverse voltage time longer than the turn-off time of one thyristor. Therefore, even if the frequency becomes high and the period of one cycle becomes short, it will always take a certain period of time (approximately 80
μs! Since the reverse voltage time (c), that is, six voltage-current phase difference times is required, there is a problem that the power factor becomes extremely poor, making it impossible to economically send power to the load. In this case, it may be possible to use a thyristor with a short turn-off time, but if the rated voltage is the same, it would be difficult to manufacture and therefore expensive.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a current source inverter that is inexpensive and can economically send power to a load even in a high frequency range.

[Means for solving problems]

A current source inverter according to the present invention includes an inverse conversion circuit formed of a series configuration of a diode and a transistor, and a base drive circuit for the transistor.

[Effect]

Seventh aspect of the present invention is that the inverse conversion circuit is configured by driving the base of a transistor, so that the time required before the voltage reaches zero point is reduced compared to the inverse voltage time of the thyristor type.

〔Example〕 .

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) is the power modulation/L of the thyristor.
/(b) ~ Forward conversion circuit composed of Q-shaped cells, (2) is DC reactor μ, (6) is transistor power modi-I
L/@14m and diode power mod LV---
(5) is a parallel resonance port 1 path composed of capacitor II and coil/I/w s@l is a voltage detector, - is a current detector, (7) is a pace drive signal It consists of a generation circuit and a pace drive amplifier υ (741). It is a base drive circuit of a transistor.

Next, the operation of the current source inverter configured as described above will be explained. However, since the operation of the forward conversion side circuit is the same as the conventional one, the explanation will be omitted.

The base drive signal generation circuit σq calculates the power modulus of the transistor lvmill with reference to the voltage zero point from the signal of the voltage detector (to) for the load voltage at one steady state.
1B switching timing signal is generated.

The signal is applied to the base drive amplifier ff1l-H, t
Yes, the internal transistors (61a) (62b) and (61b) (62a
) are alternately driven to switch the output current path.

During this switching operation, there is a moment when all transistors are in communication, and the overlapping period differs depending on the load conditions. Therefore, check the zero point of the load current using the signal from the 1 current detector,
The timing of the base drive (In (70a) (70b) is controlled by feedback 2-p so that the voltage zero point and current zero point are within a certain range.
) is a pair of base drive amplifier υ and a transistor (
In the detailed diagram of 61a), base drive amplifier 0 is connected from terminal (71a) to (71a) while driving transistor (61a).
b).

A driving base current IB of the transistor shown in the current waveform of FIG. 8(B) is applied to drive the 8R Darlington connection type transistor (61a) in the saturation region Cζ.

In the next half-circuit μ, a voltage is applied from the terminal (71b) to (71a) to flow a current for discharging the accumulated carriers of IB2 shown in the current waveform to quickly cut off the current of the transistor (61a), and then A bias voltage is applied to prevent malfunction due to weak disturbances.

Note that when the drive base current IB1 of the transistor is applied, the current I (I) flows from the collector to the emitter of the transistor with a delay of about 1μ2, but even if the carrier absorption current IB2 for transistor cutoff is applied, the current IB2 continues to flow. During this period, the current blocking ability of the transistor has not recovered, and the current Ic continues to flow from the collector to the emitter for a fairly long time (5 to 20 μs!c). ) can automatically ensure a period of conduction for all transistors even if they are mutually inverted at the same timing.However, if the overlapping period is longer than the period of natural commutation, the load capacitor '6Q Since a discharge circuit is formed and a large current flows, the duty of the transistor increases rapidly, and there is a risk that it may eventually be destroyed.
A connection is necessary.

Conversely, if there is a blank period in which the signals of terminals (70a) and (7ob) are both at rest, the transistor (61aX61b)
(62a) and (62b) are all blocked. At this time, the DC reactor /l/ (2) acts to continue the current and generates a high voltage, which acts to block current flow and cause dielectric breakdown of the transistor.

Therefore, in order to prevent this phenomenon, it is necessary to commutate the current to ensure a circuit in which the current of the DC reactor 1v(2) continues, and to switch alternately.

This circuit basically requires no reverse voltage time, so unlike the thyristor type, it is possible to operate with a lagging power factor, but in the case of a lagging power factor, the reverse voltage is increasing in the circuit to be commutated, resulting in a leading power factor. Since the driving force for commutation is weak compared to the state of However, there is a great risk of destroying the transistor.

Therefore, in order to ensure stability and safety, Figure 2 (a) to (i)
), the operation is controlled with a slight lead power factor.

Therefore, the timing of the base drive signal is controlled in such a manner that the commutation time can be secured in consideration of the transistor's cut-off operation time (the time until IB2 is completely turned off). Since the commutation type normally has a time of about 6 μm, it is possible to obtain a timing of 5 to 20 μm before the voltage zero point, which is much shorter than the reverse voltage time of the thyristor type (80 μm or more), and even at high frequencies. Power factor operation becomes possible.

FIG. 4 shows the relationship between the commutation portion in FIG. 2 and the base drive current in FIG. 8(B) 1 on an enlarged time axis.

In this figure, the collector-emitter current IC decreases regardless of whether carriers are absorbed or not, and the commutation is completed because the direction of the voltage in the load circuit assists the commutation since the paired transistors have started conducting.

The transistor at this time is different from the case where the carrier absorption current IB2 is caused to flow when the current k is flowing to block the current flow, and the current flow is blocked from a much deeper state of saturation, and the flow from the collector to the base [ Since there is no pressure applied and the carrier moving force is weak, the voltage zero point (T, ~T,
) is short, as shown in T4, after the current k flows again, the current is blocked, and this current cutoff generates an overvoltage proportional to the circuit inductance ζ of the bridge to which the transistor is connected. do. In other words, during operation, it takes time equivalent to the leading power factor of about 2 ops from T1 to T.
(force) and current within the range i within which the overvoltage is within the allowable value.

In another embodiment of the present invention, as shown in FIG. 5, the base drive circuit (7) for the transistor (61a) includes a first circuit unit σO connected to the base and emitter, and a second circuit unit σO connected to the collector and base. It consists of a circuit unit @■.

FIG. 6 explains the operation in this case and shows the same point in time as FIG. 4. The flow of currents IB1 and IB2 here is the same as in FIG. 4, but the difference is that current 15IE, ie, current x, is flowed from the collector to the base in synchronization with the current IB2. Since a voltage is applied between the collector and the base while flowing IB2, carriers between the collector and the base become a current Ix and are quickly absorbed. Therefore, the current IB2 ends flowing in a time of 60 inches or less (approximately 10a type) compared to the flow time of the current IB2 shown in FIG. 4, and the current flow is blocked.

In the above embodiment, the configuration of the inverse conversion circuit (6) is 2.
In-element heron-shaped transistor power module ρll11
1121 and 1 element diode power module
- is shown, but conversely, it is also possible to have a configuration in which /L/4 one-element transistor power modules are connected to the DC side and two two-element diode power modules are connected to the high-frequency output side.

〔Effect of the invention〕

As described above, according to the present invention, since the thyristor is replaced with a transistor and a diode of a general-purpose power module, the device can be made at low cost and can be used at a higher frequency than the thyristor type.

[Brief explanation of the drawing]

FIG. 1 is a conceptual circuit diagram showing a current source inverter according to an embodiment of the present invention, and FIG. 2 is a waveform diagram illustrating the circuit operation.
FIG. 8 is a diagram showing the details of the connection of the base drive circuit in FIG. 1 and the drive current waveform, FIG. 4 is a waveform diagram explaining the operation at the time of commutation in FIG. 8, and FIG. 6 is a waveform diagram explaining the operation at the time of commutation in FIG. 6, FIG. 7 is a circuit conceptual diagram of a conventional thyristor type current source inverter, and FIG. 7 is a waveform diagram illustrating the operation of the circuit shown in FIG. 7. FIG. In the figure, (5) is a parallel resonant circuit, (6) is an inverse conversion circuit, (7) is a base drive circuit,
1- is a transistor, and - to - are diodes. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (2)

[Claims] (1) In a current source inverter having a parallel resonant circuit as a load, each side of the bridge-connected inverse conversion circuit is configured with a transistor and a reverse current blocking diode connected in series, and a base drive circuit for the transistor is provided. A current source inverter featuring: (2) The base drive circuit includes a first circuit unit that applies a reversible voltage between the base and the emitter to flow the base current during ON operation and the accumulated carrier discharge current at the junction between the base and emitter during OFF operation, and the collector. A second circuit unit that applies a voltage to the base and causes a discharge current of accumulated carriers in the collector-base junction to flow in synchronization with a discharge current of accumulated carriers in the junction between the base and emitter. A current source inverter according to range 1.