JPH0429521A - Overcurrent protective circuit for pwm power converter - Google Patents

Abstract

PURPOSE:To protect respective switching elements reliably by detecting overcurrent to be fed from a smoothing capacitor and providing signals for stopping the switching operation to a voltage type converter and a voltage type inverter. CONSTITUTION:An overcurrent detector is eliminated and a capacitor current detector 24 is connected in series with a smoothing capacitor 5. An overcurrent to be fed from the smoothing capacitor 5 due to short circuit of arms of a voltage type converter and a voltage inverter is detected instantaneously through a capacitor current detector 24. When the overcurrent exceeds an overcurrent set value Ip provided from an overcurrent setter 23, signals are provided to comparators 16 on the sides of the voltage type converter and the voltage type inverter in order to interrupt driving pulse supply to a switching element. Consequently, switching element of the voltage type converter 4 can be protected without requiring a fuse 3.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an overcurrent protection circuit for a PWM power converter. More specifically, the present invention relates to an overcurrent protection circuit for a PWM power converter. More specifically, the present invention relates to an overcurrent protection circuit for a PWM power converter. The problem occurred due to an overcurrent caused by a short circuit between the arms of the PWM power converter.

The present invention relates to a circuit that protects a switching element.

Conventional technology A PWM power converter consisting of a voltage-source converter and a voltage-source inverter in which a DC section is coupled with a smoothing capacitor can reduce the power factor on the AC input side to 1 and eliminate harmonics on the AC output side. Because of this, it has become widely used.

A conventional example of such a PWM power converter will be explained with reference to FIG. In FIG. 2, 1 is a three-phase AC power supply, and 4 is a voltage-type converter. An AC input current detector 12, an AC reactor μ2, and a HEAZ 3 are interposed between the three-phase AC power supply 1 and the voltage-type converter 4. A smoothing capacitor 5 with a resistor 6 connected in parallel is connected to the DC side of the voltage source converter 4. This smoothing capacitor 5 is connected to a voltage source inverter 7 via an overcurrent detector 13 using this as a DC power source, and an AC reactor μ8 is connected to the power side of the smoothing capacitor 5.
, an AC filter consisting of an AC capacitor 9, an output transformer 10, and an AC output current checker 14 are connected to each other to obtain a single-phase AC output. It is done like this. That is, the voltage of the smoothing capacitor 5 is compared with the DC reference voltage VDO obtained from the DC reference voltage generator 21, and the obtained DC error voltage is input to the power factor regulator 19 via the DC voltage IIItrI generator 20. The power factor*m device 19 receives an input voltage waveform from the three-phase AC power supply 1 via the transformer 11, amplitude modulates it with the DC error voltage, and detects the AC input by the AC input current detector 12. The resulting AC error voltage is input to the comparator 16 via the input current regulator 18. This comparator 16 compares the signal with the triangular wave obtained from the oscillator 17 and outputs a PWM control signal, which is passed through the pace driver 15 and becomes a driving pulse for the switching element of the voltage source converter 4. With this drive pulse, the power factor on the AC input side can be made 1. On the other hand, the voltage source inverter 7 is controlled as follows. That is, the AC output voltage is generated by the AC reference voltage generator 22.
The obtained AC error voltage is input to the AC voltage regulator 20', the output of which is compared with the AC output current detected by the AC output current detector 14, and the obtained AC error voltage is inputted to the AC voltage regulator 20'. The AC error voltage is input to comparator 16 via output current regulator 18'. This comparator 16 compares the signal with the triangular wave obtained from the oscillator 17 and outputs a PWM control signal, which is passed through the pace driver 15 and becomes a driving pulse for the switching element of the voltage source inverter 4. This drive pulse can eliminate harmonics on the AC output side.

Such a 21M power converter is provided with an overcurrent detector 13 in order to protect the switching elements from an overcurrent caused by a short circuit between the arms of the voltage source inverter 7, and the current detected by the overcurrent detector 13 is Overcurrent setting device 2
When the overcurrent setting value IP obtained from 3 is exceeded, a signal is sent to the comparator 16 to stop the driving pulse of the switching element of the voltage source inverter 7. On the other hand, a fuse 5 is inserted on the AC input side to protect the switching element from overcurrent due to a short circuit between the arms of the voltage source converter 4.

Problems to be Solved by the Invention In the above-described overcurrent protection circuit of the 21M power converter, overcurrent flowing due to a short circuit between the arms of the voltage source inverter 7 or the voltage source converter 4 is first supplied from the smoothing capacitor 5 with low impedance. Therefore, the switching elements of the voltage source inverter 7 can be protected by the overcurrent detector 13, but the switching elements of the voltage source converter 4 are destroyed by the overcurrent flowing from the smoothing capacitor 5 before the fuse 3 blows. There was a drawback that it could be done.

Means for Solving the Problems In order to solve the above problems, the present invention provides a voltage source converter in which a plurality of switching elements are bridge-connected from an AC power source via an AC reactor, and a voltage source converter connected to the DC side of the voltage source converter. A 21M power converter comprising a smoothing capacitor and a voltage source inverter made up of a plurality of switching elements that uses the smoothing capacitor as an IT current power source, and obtains an AC output from the pressure of the voltage source inverter via an AC filter. In the overcurrent protection circuit, a capacitor current detector is provided in series with the smoothing capacitor, and when the output of the capacitor current detector exceeds an overcurrent setting value, switching operation is performed on the voltage source converter and the voltage source inverter. It is characterized by sending out a signal to stop it.

By providing a working capacitor current detector, it is possible to immediately detect an overcurrent caused by a short circuit between the arms of the voltage source inverter or voltage source converter supplied from the smoothing capacitor, thereby protecting both switching elements. I can do it.

EXAMPLES Below, the present invention will be explained in detail with reference to FIG. 1. In FIG. 1, parts having the same functions as those in FIG. 2 are denoted by the same reference numerals, and the following explanation will be omitted. A feature of the present invention is that the overcurrent detector 13 shown in FIG. The overcurrent supplied from 5 is immediately detected by the capacitor current detector 24, and this current is set to the overcurrent setting value I2 obtained from the overcurrent setting device 23.
In this case, a signal is sent to the comparator 16 of the voltage source converter and the comparator 16 of the voltage source inverter to stop the driving pulses of both switching elements. Therefore, by simply replacing the overcurrent detector 13 with the capacitor current detector 24, the voltage source converter 4
The protection of the switching elements can be performed without depending on the fuse 3.

Effects of the Invention As described in detail in the embodiments, the present invention detects an overcurrent supplied from a smoothing capacitor and switches between a voltage source converter and a voltage source inverter.

Since a signal is sent to stop the switching operation, each switching element can be reliably protected.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an overcurrent protection circuit of a PWK power converter according to the present invention, and FIG. 2 is a circuit diagram of an overcurrent protection circuit of a conventional PWM power converter. 3...k use 4...voltage type converter 5...
Smoothing capacitor 7... Voltage type inverter 13.
・・Overcurrent detector 15・Pace driver 16・
... Comparator 23 ... Overcurrent setting device 24 ... Capacitor current detector

Claims (1)

[Claims] It consists of a voltage source converter in which multiple switching elements are bridge-connected from an AC power source via an AC reactor, a smoothing capacitor connected to the DC side of this voltage source converter, and multiple switching elements that use this smoothing capacitor as a DC power source. In an overcurrent protection circuit for a PWM power converter, which comprises a voltage source inverter and obtains an AC output from the output of the voltage source inverter via an AC filter, a capacitor current detector is provided in series with the smoothing capacitor, An overcurrent protection circuit for a PWM power converter, characterized in that when the output of the capacitor current detector exceeds an overcurrent setting value, a signal is sent to the voltage source converter and the voltage source inverter to stop switching operations. .