JPS5910951Y2 - Self-excited inverter device with commutation auxiliary power supply - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a forced commutation type inverter device having a commutation auxiliary power supply circuit.

2. Description of the Related Art Conventionally, the one shown in FIG. 1 is known as a self-excited inverter device having a commutating auxiliary power supply circuit.

In Figure 1, R1, S1, T1 are AC inputs, U, ■
, W are AC outputs, R2, S2, T2 are commutation auxiliary power supply inputs, TH1 to TH6 are thyristors that constitute a DC variable voltage converter, LF and CF are reactors and capacitors that constitute a filter, D7 to D12 and R and CA are diodes, resistors, and capacitors that constitute a commutating auxiliary power supply circuit, and the part surrounded by a broken line A is an inverter circuit.

In the inverter circuit A, M1 to M6 are main thyristors, D1 to D6 are feedback diodes, A1 to A6 are commutating auxiliary thyristors for extinguishing M1 to M6, respectively.
C1 to C6 are commutating capacitors that store the commutating energy.

Furthermore, LU, LV, and LW are commutation reactors.

Next, the commutation mode will be explained.

Since the inverter circuit has the same circuit structure for each phase, the commutation operation for one phase will be explained with reference to FIG.

In FIG. 3, when the main thyristor M1 is conducting and supplying the load current IL from the U-phase terminal, the commutating capacitors C1 and C4 are charged to the illustrated polarity.

In order to turn off M1, the auxiliary thyristor A1 is turned on from this state.

As a result, the charge on C1 cancels out the load current IL, and then
Discharges through A1 → LU → D1 → C1 (current r as shown)
C), the resonance between C1 and LU eventually charges the battery to the opposite polarity.

Similarly, the charge of C4 is CA-+A1→LU-D1→CF
→Discharge through C4 (current ■E shown), and C4 and LU
It is charged to the opposite polarity by the resonance of M4, and prepares for the next extinction of M4.

Therefore, after the load current IL is canceled by the commutation current (IC+IE), a reverse bias voltage is applied to M1 until the polarity of the commutation capacitor C1 is reversed.

When M1 is turned off, M4 is turned on, and commutation is completed.

Since the conventional self-excited inverter device with a commutating auxiliary power source is constructed as described above, the energy of the commutating auxiliary power source is stored in the CF via the commutating current IE.

Therefore, when there is no load, the DC voltage Ed of capacitor CF is
This has the disadvantage that the voltage increases unnecessarily, and it is necessary to make the converter equipped with regeneration or to insert dummy resistors at both ends of the capacitor CF, resulting in an expensive product.

This invention was made to eliminate the drawbacks of the conventional ones as described above, and provides a device that can prevent the DC voltage Ed from increasing by lowering the commutating auxiliary power supply voltage during light loads. It is aimed at something.

An embodiment of this invention will be described below with reference to FIG.

In FIG. 2, TR is a voltage switching transformer, and NFA and NFB are voltage switching switches.

The rest of the structure is the same as that shown in FIG. 1 described above, so a detailed explanation will be omitted.

? In the above structure, when under load, the commutated auxiliary power supply voltage becomes a normal voltage by opening NFA and closing NFB.

Next, when the load is light, the commutating auxiliary power supply voltage is significantly reduced by opening NFB and closing NFA.

As a result, the regenerated energy from the commutated auxiliary power supply to the DC side is greatly reduced (some of the regenerated energy is consumed by normal circuit losses), and an increase in the DC voltage Ed can be prevented.

In the above embodiment, the transformer TR and the switches NFA and NFB were used to switch the voltage, but this part only switches the voltage and may be replaced with an autotransformer or a converter, or the same as in the above embodiment. be effective.

As described above, according to this invention, by switching the commutating auxiliary power supply voltage, stable operation is possible even when the inverter is under light load without adding a regenerative converter or a large dummy resistor.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional self-commutated inverter with auxiliary commutation power supply, Fig. 2 is a circuit diagram showing an embodiment of this invention, and Fig. 3 is a circuit diagram showing one commutation mode of the self-commutated inverter. FIG. In the figure, R. ,S. ,T. is AC input, U, V, W are AC output, R2, S2, T2 are commutated auxiliary power supply input, TH1~
TH6 is a thyristor, LF is a reactor, CF is a capacitor, D7 to D1 are diodes, and A is an inverter circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] At least a pair of main switching elements connected in series and inserted between the output terminals of the main power supply that generates DC output, a filter capacitor connected between the output terminals of the main power supply, and an auxiliary switching element for commutation for each of the main thyristors. A plurality of commutation capacitors are connected in parallel through elements, and a commutation auxiliary power supply is provided to supply commutation energy to these commutation capacitors, and the commutation auxiliary switching element is made conductive and stored in the commutation capacitor. By discharging the commutated energy into a discharge circuit including the filter capacitor, the conductive main switching element is extinguished and commutation is performed, and the load connected to the series connection of the pair of main switching elements is An inverter device configured to supply an amount of alternating current electricity to the inverter, characterized by comprising voltage control means for lowering the output voltage of the commutating auxiliary power source and reducing regenerated power from the commutating auxiliary power source during light loads. Self-excited inverter device with commutation auxiliary power supply.