JP3398878B2 - Stabilization circuit of parallel inverter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric circuit for a parallel inverter using a thyristor as a switching element to operate stably. 2. Description of the Related Art A conventional parallel inverter is shown in FIG. 3, which has a characteristic that the output voltage becomes excessive at a light load, and the commutation is unsold and stops at a heavy load. This is because the charge stored in the commutation capacitor is
This is because discharge through the load eliminates the charge required for commutation.Therefore, when the load is heavy and the power factor of the load is low, a large capacity of the commutation capacitor is required. Is large, the power consumption increases and the conversion efficiency of the inverter deteriorates.Therefore, a high-speed thyristor with a short turn-off time is used and the capacity of the commutation capacitor has been devised to reduce the load state as described above. Therefore, it can be said that the inverter is extremely unstable. For example, the invention disclosed in Japanese Patent Publication No. 38-13963 is provided with a diode for preventing the discharge of a commutation capacitor as shown in FIG. 4. According to the first embodiment, the operating frequency is 400 Hz and the output capacitance is 3
00W. Further, according to the invention described in Japanese Utility Model Application Laid-Open No. 64-16194, as shown in FIG. 2, a series diode type single-phase parallel inverter circuit in which a commutation improvement type circuit is provided with a commutation capacitor discharge prevention diode. Is,
In this embodiment, the provision of the discharge blocking diode having an operation frequency of 60 Hz enables the capacity of the commutation capacitor to be reduced. Further, it is possible to use not only a high-speed thyristor but also a normal type thyristor. However, there are unstable operations described below. [0003] The aforementioned Japanese Utility Model Application Laid-Open No. 64-16
No. 194, the DC input voltage 12 by the series diode type parallel inverter circuit shown in FIG.
V, AC output square wave voltage 125 V, frequency 60 Hz, output capacity 600 VA, with the design and no load, the AC output waveform is shown in FIG. 8 and point (A) across the primary winding of the transformer. The voltage waveform shown in FIG. 9 is shown in FIG. 9. This series-diode-type parallel inverter changes an AC output rectangular wave when a capacitor is connected to the AC output at no load, and operates abnormally depending on the capacitance of the capacitor. It is. For example, when a 10 μF capacitor is connected to the AC output at no load, the AC output waveform shows a 200V sawtooth waveform as shown in FIG. 10, and the waveform at point (A) is shown in FIG. As shown in FIG. 11, when the thyristor, which is originally a switching element, is in the ON state, the valley portion of the rectangular wave shown in FIG. Is observed. Next, when no load is applied, if a 2.5 μF capacitor is connected to the AC output, the AC output waveform becomes an abnormal waveform, as shown in FIG. This means that the peak voltage is 4
It is observed that the voltage is as high as 00 V, at that time (A)
As shown in FIG. 13, a negative voltage is generated in the waveform at the point, and the voltage is observed to be as low as −30 V. This symptom is that even if a load of about 15 W or less is connected, even if a load of about 15 W or less is connected, abnormal operation similar to the above occurs when a 2.5 μF capacitor is connected, but a load of about 15 W or more is connected. When you are
No abnormal operation occurs even if a 2.5 μF capacitor is connected. If you connect and use an electric device of about 15W or less, such as a jujube lamp, radio, or digital display clock, to the AC output of this inverter, connect a 2.5μF capacitor, or use a motor-using device. Then, when a capacitor is inserted to prevent noise and the motor-using device is turned off, only the noise-prevention capacitor is in the connected state, so abnormal operation occurs when the motor-using device is connected. And a peak voltage of 400 V, A
The C output is applied to an electric device such as a radio, which causes a problem that an internal part is broken and a failure occurs. An object of the present invention is to provide an inverter that can stably supply an AC output even under such a load condition. FIG. 1 is a block diagram showing a stable circuit of a parallel inverter according to one embodiment of the present invention. The DC input voltage is 12 V and the AC output is an embodiment. Square wave voltage 125V, frequency 60Hz, output capacity 600V
A. As for the solution to the abnormal operation, which is of the design, there are two means. The first means is to connect a pair of diodes to both ends of the primary winding of the transformer, and to connect the other end to ground. How to connect. In the series diode-type parallel inverter circuit, a waveform when a 2.5 μF capacitor is connected as a load and abnormal operation is performed. As shown in FIG. 13, a negative voltage is generated during abnormal operation. This is a first means for providing a diode, which has a function of clamping so that no voltage is generated. The second means is that if a clamp diode is provided, commutation fails even if the power switch of the inverter is turned on, and an overcurrent protection device such as a fuse of a power supply or a circuit protector operates and does not start. Therefore, as shown in FIG.
When a resistance is set between the power supply ground and the inverter = (power supply voltage-inverter operation required voltage) ÷ inverter no-load operation current = approximately 0.2 ohm, and the inverter power switch is turned on, it starts and operates. I do, but A
Another abnormal operation has occurred in the C output waveform as shown in FIG. To solve this, as shown in FIG. 6 or FIG. 7, the current is forwarded to a pair of thyristors through a diode to prevent the charge of the commutation capacitor from flowing out through a resistor of about 40 ohms from the power supply. I don't know what is equivalent to the thyristor latching current, but anyway, in this example, when 170 mA is supplied, it operates normally and the resistance of 0.2 ohm attached at startup is Even if it is removed, stable operation is performed as it is. FIG. 15 shows an AC output waveform of the ballast circuit when there is no load. The waveform at point (A) is shown in FIG.
6 is shown. 10μF to AC output at no load
FIG. 17 shows an AC output waveform when a capacitor is connected, and A when a 2.5 μF capacitor is connected.
FIG. 18 shows the C output waveform. As can be observed from FIG. 17 and FIG.
Even at 5 μF, the rectangular wave is wavy in the flat part, but no abnormal operation occurs and it is a usable rectangular wave. The AC output waveform when using a 600 W electric stove is shown in FIG. When starting the inverter,
In some cases, the system may not start due to the effect of the residual magnetism of the transformer.
A circuit is provided so that the inverter can be started via a 2-ohm resistor, and is always started when the power switch of the inverter is turned on. This starting resistor is considered necessary for the parallel inverter at the time of starting. In addition to the ballast circuit according to the present invention, it is conceivable that if a capacitor is connected to the AC output at the time of no load and a malfunction occurs, the capacitor may be connected from the beginning. There is also a means to connect a series circuit of a capacitor and a resistor to the output, but this series circuit consumes power and the efficiency of the inverter becomes worse, and above all, the root cause of the main circuit is According to the present invention,
It works effectively by taking two measures. [0007] According to the present invention, the AC of the parallel inverter
Even when a load corresponding to capacitive reactance is connected to the output, A
The C output voltage does not fluctuate and does not operate abnormally. The voltage of the pulse generated during commutation, which is included in the square wave, is small, and the AC output with an improved waveform can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an embodiment of a parallel inverter stabilization circuit according to the present invention. FIG. 2 is a series diode type single-phase parallel inverter circuit described in Japanese Utility Model Application Laid-Open No. 64-16194. Inverter basic circuit [Fig. 4] Parallel inverter circuit using semiconductor controlled rectifier described in Japanese Patent Publication No. 38-13963 [Fig. 5] Starting circuit of parallel inverter [Fig. 6] [Fig. FIG. 8 is a circuit diagram of the means of FIG.
AC output waveform at no load. FIG. 9 shows a series diode type parallel inverter circuit.
The voltage between the terminal (A) of the primary winding of the transformer and ground with no load. FIG. 10 shows a diagram of AC when a capacitor of 10 μF is connected to an AC output by a series diode type parallel inverter circuit.
Output waveform. FIG. 11 is a waveform at a point (A) when a capacitor of 10 μF is connected to an AC output by a series diode-type parallel inverter circuit. FIG. 12 is a diagram illustrating a case where a capacitor of 2.5 μF is connected to an AC output by a series diode-type parallel inverter circuit;
C output waveform. FIG. 13 is a waveform at a point (A) of a series diode-type parallel inverter circuit when a capacitor of 25 μF is connected to an AC output. FIG. 14 is an AC output waveform at the time of no load, in which the first means of the parallel inverter stabilization circuit according to the present invention is employed. FIG. 15 is an AC output waveform at no load by the parallel inverter stabilization circuit according to the present invention. FIG. 16 is a waveform at a point (A) at the time of no load by the stabilizer circuit of the parallel inverter according to the present invention. FIG. 17 is a diagram illustrating a circuit when a capacitor of 10 μF is connected to an AC output by a stabilizing circuit of a parallel inverter according to the present invention;
C output waveform. FIG. 18 is an AC output waveform when a capacitor of 2.5 μF is connected to the AC output by the stabilizer circuit of the parallel inverter according to the present invention. FIG. 19 is an AC output waveform when a 600 W electric stove is connected to the AC output by the parallel inverter stabilization circuit according to the present invention. [Description of Signs] 1 is transformer 2 and 3 is thyristor 4 is commutation capacitor 5 is reactor 6 is DC power supply battery 7 and 8 is discharge prevention diode 9 and 10 is clamp diode 11 and 12 is for current supply and reverse flow The prevention diode 13 is a current supply resistor 14 is an AC output terminal 15 is a parallel inverter device 16 is a starting resistor A is an operating voltage waveform measurement point

Claims (1)

(57) [Claims 1] An output transformer having an output transformer,
A power supply is connected, and a pair of discharge blocking
A pair of discharge anodes is connected to the anode of the anode.
A pair of thyristor anodes are connected to an anode cathode.
Each connected in series, said pair of discharge blocking diodes,
A commutation capacitor is connected between the series connection points of the pair of thyristors.
Connected to the cathode and rear of the pair of thyristors.
And the other end of the reactor to the common side power supply.
And a pair of terminals at both ends of the primary winding of the output transformer.
The cathode of the diode is connected, and the anode is the common side power supply.
In the parallel inverter circuit connected to
And connect the resistor to the anode of a pair of diodes.
Then, the cathodes of the pair of diodes are connected to the pair of thyristors.
Connected to the anodes of the thyristors, respectively.
Supply the current that flows when the
A parallel inverter circuit.