JP2001186664A - Systematically interconnected inverter devices - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain highly stable systematically interconnected inverter devices that stop oscillations immediately and also quickly discharge the electric potential of an output capacitor connected to the final output stage of the devices if an overvoltage or overcurrent occurs inside the devices. SOLUTION: A DC input power is connected to a voltage-raising converter 2, an inverter 7 comprising switching elements of a full-bridged structure is connected to the converter 2 via a middle-stage capacitor 6, and the output of the inverter 7 is connected to an AC power system via a filter 8. In this structure, an inverter protecting part 13 that stops the oscillating operations of the voltage-raising converter 2 and inverter 7 if a overvoltage or overcurrent occurs inside the structure, and a capacitor discharging part 12 that makes the electric potential accumulated in a capacitor 10 of the filter 8 discharged immediately by the output of the inverter protecting part 13, are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for connecting DC power from a solar cell, a fuel cell or the like to an electric power system and supplying it as AC power.

[0002]

2. Description of the Related Art An example of a conventionally used system interconnection inverter device will be described with reference to FIG. The grid interconnection inverter device 41 includes a boost converter 42 for boosting an input voltage to a voltage higher than the system voltage, an inverter 43 for shaping the output current into a sine wave, and smoothing the voltage boosted by the boost converter 42 to provide a direct current to the inverter 43. An intermediate-stage capacitor 44 for supplying a voltage and a filter 45 for removing high-frequency noise from the output of the inverter 43 are connected to a system of a commercial power supply 46. Especially the boost converter 42
Is constituted by a reactor 49 for energy storage, a switching element 50 for boosting, and a diode 51 for boosting, which smoothes an input voltage of a solar cell 47 or the like with a smoothing capacitor 48.
The inverter has a full bridge configuration using four switching elements Q1 to Q4.

The operation will be described below with reference to FIG. The input power is smoothed by a smoothing capacitor 48 composed of a large-capacity electrolytic capacitor, and the input of the boost converter 42 is reduced in ripple. For example, when the solar cell 47 is used as an input power supply, the solar cell 47 has a rated input of about DC 200 V and the system voltage of the commercial power supply 46 is A
In the case of C200V, the peak of the system voltage reaches 283V. Therefore, it is necessary to increase the input voltage in order to inject power into the system. Become. Therefore, the boosting switching element 5 is controlled by the oscillation control unit 52.
0 is turned on to accumulate energy in the reactor 49, and when the boosting switching element 50 is turned off, the reactor 4
The energy stored in 9 is stored as a voltage in the intermediate-stage capacitor 44 via the boost diode 51. By repeating the above operation at a high frequency, the inverter 43
Is maintained constant. Next, the inverter 43 causes the oscillation control unit 52 to simultaneously switch on Q11 and Q14 or Q12 and Q13 of the four switching elements at the same time to perform switching operation at a high frequency so that the output current becomes a sine wave. The on-time of each is controlled.

[0004]

When an overvoltage or an overcurrent occurs inside the grid-connected inverter device having such a configuration, these abnormalities are promptly detected in order to prevent the destruction of the equipment, and the oscillation of the switching element is started. Although it had a function to stop, when a repair worker cut off the breaker of the switchboard and touched the output terminal part, it stopped without discharging the charge charged in the output capacitor connected to the last stage of the inverter device Because of the state, there is a problem that there is a risk of electric shock.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and stops the oscillating operation of the boost converter and the inverter immediately when an overvoltage or an overcurrent occurs. And a capacitor discharging unit for rapidly discharging the electric charge stored in the output capacitor of the filter by the output of the inverter protecting unit.

As a result, when an overvoltage or an overcurrent occurs inside the device, the oscillation is immediately stopped, and the electric charge of the output capacitor connected to the final output stage of the device is quickly discharged, so that safety is ensured. It is intended to provide a high system interconnection inverter device.

[0007]

According to the first aspect of the present invention, a DC input power smoothed by a capacitor is connected to a boost converter including a reactor, a boost switching element, and a boost diode, and includes a full-bridge switching element. In the configuration where the inverter is connected to the boost converter via an intermediate-stage capacitor and the output of the inverter is connected to the AC power system via a filter composed of a reactor and an output capacitor, when an overvoltage or overcurrent occurs inside the device. An inverter protection unit for quickly stopping the oscillating operation of the boost converter and the inverter, and a capacitor discharging unit for quickly discharging the electric charge accumulated in the output capacitor of the filter by the output of the inverter protection unit. It is provided in.

According to a second aspect of the present invention, there is provided a capacitor discharging unit of a grid-connected inverter device, a discharging circuit in which a discharging resistor and a power transistor are connected in series, a timer circuit for holding a signal from the inverter protecting unit for a predetermined time, And a signal transmission circuit for transmitting the output of the timer circuit to the discharge circuit.

According to a third aspect of the present invention, a capacitor discharge section of a grid-connected inverter device is connected to a discharge circuit in which a discharge resistor and a bidirectional thyristor are connected in series, and a signal from an inverter protection section is transmitted to the discharge circuit. It is constituted by a signal transmission circuit.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a circuit block diagram showing a first embodiment of the present invention. 1 is a capacitor for smoothing DC input power, 2 is a reactor 3, a boosting switching element 4, and a booster. A boost converter including a diode 5; an intermediate stage capacitor 6; an inverter 7 including switching elements Q1 to Q4 in a full bridge configuration; 8 a filter including a reactor 9 and an output capacitor 10;
11 is an oscillation control unit for controlling the oscillation of the boosting switching element 4 and the switching elements Q1 to Q4 in a full bridge configuration, 12 is a capacitor discharging unit for discharging the charge of the output capacitor 10, and 13 is an overvoltage or An inverter protection unit 14 that transmits an abnormal signal to the oscillation control unit 11 and the capacitor discharge unit 12 when an overcurrent occurs, is a system interconnection inverter device including these components, and an input terminal of the inverter device is a solar battery. 15 and a commercial power supply 16 is connected to the output terminal.

The operation of this embodiment will be described below with reference to FIG. The input power is smoothed by a smoothing capacitor 1 composed of a large-capacity electrolytic capacitor, and the input of the boost converter 2 is reduced in ripple. For example, solar cell 15
Is used as an input power source, the solar cell 15 has a rated input of about DC 200 V, and if the system voltage of the commercial power supply 16 is AC 200 V, the peak of the system voltage is 283 V
, It is necessary to boost the input voltage in order to inject power into the system, and if power of about 4 kW is to be output, it is usually necessary to boost the power to about 350 V DC. Therefore, the boosting switching element 4 is turned on by the oscillation control unit 11 to accumulate energy in the reactor 3, and
When the boosting switching element 4 is turned off, the reactor 3
Is stored as a voltage in the intermediate-stage capacitor 6 via the boost diode 5. By repeating the above operation at a high frequency, the input voltage of the inverter 7 is kept constant. Next, the inverter 7 causes the oscillation control unit 1 to simultaneously switch on Q1 and Q4 or Q2 and Q3 of the four switching elements at the same time to perform switching operation at a high frequency, so that the output current becomes a sine wave. The on-time is controlled to inject the output power according to the input power into the system. here,
When an overvoltage or an overcurrent occurs inside the system-connected inverter device due to some abnormality, an abnormal signal is transmitted to the oscillation control unit 11 by the action of the inverter protection unit 13 to prevent the device from being destroyed, and the oscillation is controlled. The control unit 11 is a boost converter 2
And the operation of the inverter 7 is stopped immediately. Further, the inverter protection unit 13 is connected to the capacitor discharge unit 1.
2, the capacitor discharge unit 12 quickly discharges the charge stored in the output capacitor 10.

By this operation, the oscillation is stopped immediately even when an overvoltage or an overcurrent occurs in the system interconnection inverter device 14, and the charge of the output capacitor 10 connected to the final output stage of the device is also quickly reduced. It is possible to provide a highly safe grid-connected inverter device that does not cause an electric shock even when a repair worker detaches the device from the system and performs an operation by touching an output terminal by discharging the device. It is.

(Embodiment 2) FIG. 2 is a circuit block diagram showing a second embodiment of the present invention.
A capacitor discharge unit 12, a discharge circuit 19 in which a discharge resistor 17 and a power transistor 18 are connected in series, a timer circuit 20 for holding a signal from the inverter protection unit 13 for a certain period of time, and an output of the timer circuit 20 as a photocoupler. The signal transmission circuit 22 transmits the signal to the discharge circuit 19 through the signal transmission circuit 21.

The operation of this configuration will be described with reference to FIG. The normal operation of the system interconnection inverter device is the same as that described in the first embodiment and will not be described. Here, if an overvoltage or an overcurrent occurs inside the system-connected inverter device due to some abnormality, an abnormal signal is transmitted to the oscillation control unit 11 by the action of the inverter protection unit 13 in order to prevent destruction of the device. The oscillation control unit 11 stops the operations of the boost converter 2 and the inverter 7 quickly. The inverter protection unit 13 also transmits an abnormal signal from the input terminal 23 to the capacitor discharge unit 12. Since this abnormal signal is often a pulse signal, if this pulse signal is directly sent to the discharge circuit 19 using the power transistor 18, the power transistor 18 turns off without sufficiently discharging the output capacitor 10. There is a risk. Therefore, by transmitting such a pulse signal once through the timer circuit 20, it is possible to keep the power transistor 18 on for a time during which the charge of the output capacitor 10 can be sufficiently discharged.

Here, the output of the timer circuit 20 is supplied to the discharge circuit 1 via a signal transmission circuit 22 having a photocoupler 21.
The purpose of compensating for the difference between the signal of the inverter protection unit 13 and the operating potential of the circuit of the capacitor discharge unit 12 and to isolate the primary and secondary circuits of the photocoupler 21 This is to achieve the purpose of ensuring insulation between the inverter protection unit 13 and the system output.

(Embodiment 3) FIG. 3 is a circuit block diagram showing a third embodiment of the present invention.
It comprises a discharge circuit 26 in which a discharge resistor 24 and a bidirectional thyristor 25 are connected in series, and a signal transmission circuit 28 for transmitting a signal from the inverter protection unit 13 to the discharge circuit 26 via a photocoupler 27.

The operation of this configuration will be described with reference to FIG. The normal operation of the system interconnection inverter device is the same as that described in the first embodiment and will not be described. Here, if an overvoltage or an overcurrent occurs inside the system-connected inverter device due to some abnormality, an abnormal signal is transmitted to the oscillation control unit 11 by the action of the inverter protection unit 13 in order to prevent destruction of the device. The oscillation control unit 11 stops the operations of the boost converter 2 and the inverter 7 quickly. The inverter protection unit 13 also transmits an abnormal signal from the input terminal 29 to the capacitor discharge unit 12. Even if this abnormal signal is a pulse signal and the signal transmission circuit is immediately turned off by the pulse operation, the bidirectional thyristor 2 included in the discharge circuit 26
With the characteristic that it keeps on until it becomes less than the holding current of 5,
This means that the bidirectional thyristor 25 can be kept on for a time period during which the electric charge of the output capacitor 10 can be sufficiently discharged.

Here, the reason why the abnormal signal input from the input terminal 29 is transmitted to the discharge circuit 26 via the signal transmission circuit 28 having the photocoupler 27 is that the signal of the inverter protection unit 13 and the capacitor discharge unit 12 This is to realize the purpose of compensating for the difference in the operating potential of the circuit and the purpose of securing the insulation between the inverter protection unit 13 and the system output by insulating the primary and secondary circuits of the photocoupler 27. .

[0020]

As described above, according to the first aspect of the present invention, when an overvoltage or an overcurrent occurs inside the system interconnection inverter due to some abnormality, the operation of the device is immediately stopped. In addition to preventing the equipment from being destroyed, the output capacitor connected to the output stage of this device is also discharged quickly, so that the repair terminal can be connected to the output terminal when the device is disconnected from the system. It is possible to provide a highly safe grid-connected inverter device that does not cause an electric shock even when touched.

According to the second aspect of the present invention, when an overvoltage or an overcurrent occurs inside the system interconnection inverter due to some abnormality in the system interconnection inverter, even if the abnormality signal is a pulse signal, the timer circuit is used. As a result, the electric charge of the output capacitor can be sufficiently discharged, so that it is possible to provide a highly safe grid-connected inverter device.

Further, according to the third aspect of the present invention, when an overvoltage or an overcurrent occurs in the system interconnection inverter due to some abnormality in the system interconnection inverter, even if the abnormality signal is a pulse signal, the bidirectional inverter is bidirectional. Since the charge of the output capacitor can be sufficiently discharged by the operation of the thyristor, it is possible to provide a highly safe grid-connected inverter device.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram illustrating a system-linked inverter according to a first embodiment.

FIG. 2 is a circuit block diagram illustrating a system interconnection inverter according to a second embodiment;

FIG. 3 is a circuit block diagram illustrating a grid-connected inverter according to a third embodiment;

FIG. 4 is a circuit block diagram showing a conventional example.

[Explanation of symbols]

 2 Boost converter 6 Intermediate stage capacitor 7 Inverter 8 Filter 12 Capacitor discharging unit 13 Inverter protection unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H02M 7/48 H02M 7/48 R (72) Inventor ▲ Taka ▼ Masayuki Kuwa 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Taketoshi Sato 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kiyoshi Izaki 1006 Odaka, Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. 72) Inventor Masafumi Sadahira 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) 5H007 AA06 BB07 CA01 CB05 CC09 CC12 DB01 FA01 FA03 FA14 FA16 GA08

Claims (3)

[Claims] 1. A DC input power smoothed by a capacitor is connected to a boost converter including a reactor, a boost switching element, and a boost diode, and an inverter including a full bridge configuration switching element is connected to the boost converter via an intermediate capacitor. In a configuration in which the output of the inverter is connected to an AC power system via a filter consisting of a reactor and an output capacitor,
An inverter protection unit that stops the oscillating operations of the boost converter and the inverter immediately when an overvoltage or an overcurrent occurs inside the configuration; and an output of the inverter protection unit quickly reduces the charge accumulated in the output capacitor of the filter. A system interconnection inverter device having a capacitor discharging unit for discharging. 2. A capacitor discharging unit includes: a discharging circuit in which a discharging resistor and a power transistor are connected in series; a timer circuit for holding a signal from an inverter protection unit for a certain period of time; and an output of the timer circuit to the discharging circuit. The system interconnection inverter device according to claim 1, wherein the system interconnection inverter device is configured by a signal transmission circuit. 3. The capacitor discharge unit according to claim 1, wherein the capacitor discharge unit includes a discharge circuit in which a discharge resistor and a bidirectional thyristor are connected in series, and a signal transmission circuit that transmits a signal from an inverter protection unit to the discharge circuit. Grid-connected inverter device.