JPH0670552A - Pwm inverter - Google Patents

Abstract

(57) [Abstract] [Purpose] In a PWM inverter with pulse width modulation control using a triangular wave comparison circuit, when a triangular wave is no longer output, it is gate-blocked and protected. In a PWM inverter for pulse width modulation control using a triangular wave comparison circuit, means 61 for generating a reset signal at a predetermined interval in synchronization with the triangular wave, and counting pulses supplied from an oscillator 62B are used. A preset counter 62A is provided which resets the count value each time a reset signal is input, and a holding circuit 63 which holds the output of the preset counter and outputs a gate block signal when the preset counter overflows. PWM inverter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PWM inverter, and more particularly to a PWM inverter capable of preventing an abnormal voltage from being generated when a carrier wave output from a triangular wave generating circuit disappears.
Regarding data

[0002]

2. Description of the Related Art When the power of a DC power supply is supplied to a load at a constant AC voltage, it is necessary to convert DC to AC through a power converter. In FIG. 5, a battery or
The DC power output from the DC power supply 1, which is a rectifier power supply, is converted into AC power via the inverter circuit 2, which is a power converter, and is supplied to the load 3 as AC power.
The inverter circuit 2 is composed of a PWM inverter 21 and a DC capacitor 22 connected to the DC input side of the PWM inverter 21. The power conversion device here is a device that feeds back and controls the output voltage, and has an output voltage detector 4 that detects the output voltage of the inverter circuit 2. The gate control circuit 5 includes a control calculation circuit 51 and a gate pulse generation circuit 52.
And a triangular wave generating circuit 53. Control arithmetic circuit 51
Compares the voltage reference value Vref with the detection value Vout obtained from the output voltage detector 4 and performs control calculation such as proportional integration of the error to output the output voltage command value V ^{* of the} inverter circuit 2 ^. Is output. The gate pulse generation circuit 52 is a circuit generally called PWM control, and has an output voltage command value V ^*. And the triangular wave signal Tr generated by the triangular wave generating circuit 53 are compared with each other to determine the gate signal GT which is the energization period of the self-extinguishing element forming the PWM inverter. The gate signal GT
The inverter output voltage is adjusted by adjusting the energization period of the self-extinguishing element of the PWM inverter 21. This gate signal GT is the ON / O of the self-extinguishing type element.
This is a switching signal that switches between two states of the FF. In the case of PWM control of normal triangular wave comparison, the output voltage command value V ^* The value of the triangular wave, which is the carrier wave, increases and decreases in a ramp-like manner sufficiently with respect to the change. Therefore, this switching signal is output by the change of triangular wave signal Tr value.
Signal GT changes. That is, the triangle wave signal Tr changes once with a positive slope (from OFF to ON) and with one circuit with a negative slope (from ON to OFF). Therefore, the switching circuit is proportional to the frequency of the triangular wave signal signal Tr.

[0003]

However, in the above configuration, when the carrier wave output from the triangular wave generating circuit 53 of the gate control circuit disappears due to a failure or the like, the gate pulse generating circuit 52 The change in the gate pulse created is gone. Therefore, the inverter output voltage is fixed and DC is supplied to the load 3. If the PWM inverter does not have a monitoring circuit for detecting the DC voltage component, the DC voltage is supplied until the protection such as overcurrent of the power conversion device is activated. Therefore, for example, if there is an insulating transformer on the load side, the transformer on the load side may cause DC bias magnetism, and a failure may occur on the load side. Therefore, the present invention has been made in view of the above points, and a PWM inverter is provided.
Provide a PWM inverter that can detect when a carrier wave disappears due to a failure in the gate control circuit, output a protection signal and block the gate to prevent abnormal voltage from being output from the power converter. The purpose is to do.

[0004]

In order to achieve the above-mentioned object, the present invention provides a PWM inverter for controlling pulse width modulation by using a triangular wave comparison circuit, in which a reset signal is provided at predetermined intervals in synchronization with the triangular wave. A means for generating, a preset counter that counts the pulses supplied from the oscillator and resets the count value each time the reset signal is input, and when this preset counter overflows,
A holding circuit for holding the output and outputting a gate block signal is provided.

[0005]

With the PWM inverter configured as described above, when the carrier wave input to the gate pulse generation circuit disappears due to a failure or the like, the gate block waits for a secondary factor such as overcurrent. Since the protection operation is directly started by extinguishing the carrier wave, the abnormal output of the PWM inverter can be prevented.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the block diagram of FIG. In FIG. 1, the same parts as those in FIG. 5 are designated by the same reference numerals, the description thereof will be omitted, and only different points will be described here. That is, in FIG. 1, the gate control circuit 5
The protection detection circuit 6 is added in the. The protection circuit 6 is interposed between the triangular wave generation circuit 53 and the inverter circuit 2.

FIG. 2 shows a specific example of the protection detection circuit 6. The protection detection circuit 6 includes a comparator 61 and a timer circuit 62.
And a holding circuit 63. Comparator 61
Detects the zero cross of the carrier wave Tr and outputs a pulse CMP synchronized with the zero cross. The timer circuit 62 has six
It consists of a 2B oscillator and a preset counter 62A that is incremented by the clock of the oscillator. The counter 62A resets the count value at the rising edge of the pulse CMP, and when the input of the pulse CMP is lost, the counter 62A is not preset. -Output the flow signal WDT. The holding circuit 63 uses a D-type flip-flop whose input is fixed at "1",
The flow signal WDT is used as a clock.

Next, the operation of the present invention having the above configuration will be described with reference to FIG. In a normal state, the triangular wave carrier Tr is not interrupted. Therefore, the comparator 61 outputs the pulse CMP synchronized with the triangular wave period. That is,
When the carrier wave Tr has a positive slope, the output CMP becomes H level,
When the gradient is negative, the output CMP becomes L level. The preset counter 62A is a counter that resets the count value to CNTO by a rising signal of CMP and continues counting up. Therefore, since the carrier wave has a fixed period,
The count value until the next CMP signal is input from the comparator 61 is always CNT1. Preset counter 62A
Overturns a count value CNT2 that is greater than CNT1.
Use the flow setting value. Therefore, as long as the carrier wave Tr is continuously input, the preset counter 62A is overflowed.
Therefore, the output WDT remains a negative value, the holding circuit 63 is not triggered, the output is fixed to a negative value, and the protection request signal GB is not output.

However, when the carrier wave Tr disappears as shown in FIG. 4, the input is fixed, so that the CMP signal output from the comparator 61 is fixed to a positive or negative value. The counter 62 reset at the rising edge of CMP is not reset and continues counting up. Therefore, the count value exceeds the normally reset count value CNT1 and reaches the counter overflow value CNT2 at time t, causing an overflow. The output WDT of the counter 62 outputs a pulse by overflow. The holding circuit 63 holds this input pulse and outputs the GB signal to the voltage source inverter 21 of FIG. 1 as a protection request signal GB. As a result, the PWM inverter 21 is stopped and the output of the abnormal DC voltage can be prevented.

In this way, in this embodiment, by providing the protection detection circuit 6, the disappearance of the carrier wave Tr output from the triangular wave generation circuit 52 can be detected, and the PWM inverter 21 can be detected.
It becomes possible to protect before the abnormal voltage is output.

By adding the protection detection circuit of the above embodiment to a power converter having an insulation transformer at the output of the PWM inverter, the self-extinguishing type element of the PWM inverter can be improved. It works as a protection function and can improve the reliability of the device. Further, the present invention can be applied to a PWM inverter that operates in synchronization with a system voltage and is used for power generation and storage using a battery power source such as chemical or solar energy, or for system interconnection such as an active filter.

[0012]

As described above, according to the present invention, P
In the gate pulse generation circuit of the WM inverter, even if the carrier wave output from the triangular wave generation circuit disappears due to a failure, etc., a gate block signal is output by detecting the carrier wave disappearance, and the PWM inverter outputs an abnormal voltage. It becomes possible to protect before output.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a PWM inverter showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a specific example of the protection detection circuit of FIG.

FIG. 3 is a time chart when the carrier wave is normal in the PWM inverter of FIG.

FIG. 4 is a time chart when the carrier wave is abnormal in the PWM inverter of [FIG. 1].

FIG. 5 is a block diagram of a conventional PWM inverter.

[Explanation of symbols]

1 ... DC power supply 2 ... Inverter circuit 21 ... PWM inverter 22 ... DC capacitor 3 ... Load 4 ... Output voltage detector 5 ... Gate control circuit 51 ... Control arithmetic circuit 52 ... Gate pulse generation circuit 53 ... Triangle wave generation circuit 6 ... Protection detection circuit 61 ... Comparator 62 ... Timer circuit 62A ... Preset counter 62B ... Oscillator 63 ... Holding circuit

Claims (1)

[Claims] 1. A PWM inverter that performs pulse width modulation control using a triangular wave comparison circuit, and means for generating a reset signal at predetermined intervals in synchronization with the triangular wave.
A preset counter that counts the pulses supplied from the oscillator and resets the count value each time the reset signal is input, and a gate block signal that holds the output when this preset counter overflows. A PWM inverter provided with a holding circuit for outputting.