JPH08149843A - Protector of system interconnection inveter - Google Patents

Abstract

PURPOSE: To provide a protector which prevents the occurrence of secondary fault in the other in the case that fault occurs on either the DC side or AC side of an inverter circuit, in a system interconnection inverter which links a solar battery to a commercial power line. CONSTITUTION: This protector is provided with a fault diagnosis part 56 where normal operation province in the relation between the output current i of an inverter circuit 3 and the current amplitude command value lamp of a control circuit 5 is stored. The fault diagnosis part 56 judges the fault by whether the detection value of the output current and the current amplitude command value are in normal operation province or not. When fault is judged, the main controller 53 sends out a gate block signal to a gate circuit 54 so as to stop the operation of the inverter circuit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter protection device for connecting a DC power source such as a solar cell to a commercial power system.

[0002]

2. Description of the Related Art FIG. 4 shows a solar cell (1) as a commercial power system.
The configuration of the grid interconnection inverter for interconnection is shown in (2). In the inverter, the DC power supplied from the solar cell (1) is converted into high frequency power by the high frequency switching circuit (31). The high frequency power is supplied to the rectifier circuit (33) through the high frequency transformer (32) and rectified. The rectified high-frequency power is low-pass filtered and then supplied to the folding circuit (34) to be converted into sinusoidal AC power and output to the commercial power system (2).

The high frequency switching circuit (31) and the folding circuit (34) are each composed of a plurality of switching elements, and are driven by the gate signals A and B supplied from the drive circuits (41) and (42). The drive circuits (41) and (42) are controlled by the control circuit (50).

The output terminal of the inverter circuit (3) has a CT (8)
And PT (81) are provided, and output current i and system voltage v
Are detected and these detected values are supplied to the control circuit (50). In response to this, the control circuit (50) creates a current amplitude command value for obtaining the maximum power and multiplies the current amplitude command value by the system voltage v to generate a target current. Then, a current command value corresponding to the error between the target current and the output current i is created, and a PWM control signal is generated based on the current command value,
This is the drive circuit (41) for the high frequency switching circuit (31).
Supply to Also, a synchronizing signal is generated based on the system voltage v and is supplied to the drive circuit (4) of the folding circuit (34). As a result, the output current having the amplitude corresponding to the current amplitude command value is obtained from the inverter circuit (3).

[0005]

In the conventional grid-connected inverter shown in FIG. 4, when a failure occurs on either the DC side or the AC side of the high frequency transformer (32),
For example, the high frequency switching circuit (31) and the folding circuit (3
If one of the switching elements in 4) fails or one of the gate signal lines from the drive circuits (41) and (42) is broken, the conventional general inverter is not equipped with an overcurrent protection circuit. However, since the protection circuit does not operate as described above, the high frequency switching circuit (31) or the folding circuit (34) in which no failure or disconnection has occurred continues to operate.

As a result, for example, when the switching element on the AC side has failed, the switching element on the DC side continues to operate, resulting in an overvoltage on the DC side of the high-frequency transformer (32), and the overvoltage causes the DC side. The switching element of will also be destroyed. Conversely, when the switching element on the DC side fails, similarly, the switching element on the AC side is destroyed due to the occurrence of overvoltage, and a secondary failure occurs.

An object of the present invention is to provide a protective device which prevents a secondary failure from occurring in the other side of the grid-connected inverter even if a failure occurs in either the direct current side or the alternating current side. It is to be.

[0008]

A protective device for a grid-connected inverter according to the present invention is a storage device in which a normal operating region in a relation between an output current of an inverter circuit (3) and a current amplitude command value is stored in advance. Means, a detecting means for detecting the output current of the inverter circuit (3), and a judging means for judging a failure depending on whether the detected value of the output current and the current amplitude command value are within the normal operating range. , And a protection means for stopping the operation of the inverter circuit (3) when a failure is determined.

Specifically, when a failure is determined, the protection means further causes the disconnection means interposed between the inverter circuit (3) and the commercial power system (2) to be disconnected.

In a more specific configuration, the DC power transmission line extending from the output end of the DC power supply to the inside of the inverter circuit (3) is provided with detection means for detecting a potential difference in a predetermined range of the power transmission line, It is provided with disconnecting means interposed between the power transmission lines and disconnecting control means for causing the disconnecting means to disconnect when an excessive potential difference is detected.

[0011]

In the normal operating state of the inverter, when the current amplitude value command created by the control circuit (5) changes, the output current of the inverter circuit (3) also changes accordingly, and the current amplitude command value and A proportional relationship is established with the output current value. However, when some failure occurs on the DC side or AC side of the inverter circuit (3), the output current of the inverter circuit (3) does not follow the change of the current amplitude value command, and the output current in the normal operating state The current value will be lower than that.

Therefore, in the protection device of the present invention, a normal operation region in the relation between the output current of the inverter circuit (3) and the current amplitude command value in a normal operation condition is defined in advance, and this is determined as a failure determination. It is stored as the standard of. And, in the actual operating condition, the inverter circuit
The output current of (3) is detected, and it is determined whether the detected value and the current amplitude command value at that time are within the normal operating range, and the output current value is lower than the normal value. When it decreases, it is determined that a failure has occurred.

When it is determined that a failure has occurred, the operation of the inverter circuit (3) is stopped, and if necessary, the disconnecting means interposed between the inverter circuit (3) and the commercial power system (2). Disconnect. This makes it possible to prevent secondary failures from occurring.

From the output end of the DC power supply to the inverter circuit (3)
In a specific configuration including a potential difference detection means and a disconnection means in the DC side power transmission line reaching the inside of the, when a current leakage occurs in the DC side power transmission line, a voltage drop due to the current leakage occurs. Upon detection, the disconnecting means is disconnected. This prevents the DC side power transmission line and peripheral components from being burnt out.

[0015]

According to the protection device for the grid-connected inverter according to the present invention, even when a failure occurs on either the DC side or the AC side of the inverter circuit, the other two
The occurrence of the next failure is prevented in advance.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, the solar cell (1) is connected to the commercial power system (2) via the inverter circuit (3), and between the inverter circuit (3) and the commercial power system (2),
The breaker (7) is interposed. The breaker (7) is normally closed, and the power output from the solar cell (1) through the inverter circuit (3) is supplied to the load (6), and the surplus power is supplied to the commercial power system (2). Reverse flow is made.

At the output end of the inverter circuit (3), CT
(8) and PT (81) are installed, and CT (82) and PT (83) are installed at the output end of the solar cell (1). still,
The inverter circuit (3) has the same structure as the conventional circuit shown in FIG. 4, and has a high frequency switching circuit (31) and a folding circuit (34) built therein.

The inverter circuit (3) is driven by the gate signal G from the drive circuit (4) as shown in FIG. The drive circuit (4) is controlled by a control circuit (5) including a microcomputer and a DSP. Control circuit
(5) is output current data i sent from CT (8) through A / D converter (9) and PT (81) is A / D converter (9).
System voltage data v sent via 1), solar cell output current data Idc sent from CT (82) via A / D converter (92), and A / D conversion from PT (83) Based on the solar cell output voltage data Vdc sent through the device (93), the control operation described later is executed.

That is, the output current data i and the system voltage data v are sent to the inverter output control section (51) for use in output control of the inverter, and both data are supplied to the output state calculation means (57). Then, the output power of the inverter circuit (3) is calculated. Also, the solar cell output voltage data Vdc
Is supplied to the current amplitude command value calculation means (52) and the main control section (53). The current amplitude command value calculation means (52) calculates the current amplitude command value Iamp for obtaining the maximum power, based on the solar cell output voltage data Vdc and the output power value from the output state calculation means (57). It The current amplitude command value Ia
mp is supplied to the inverter output control unit (51) via the main control unit (53).

As a result, the inverter output control section (51)
Then, the current amplitude command value Iamp and the system voltage data v are multiplied to create the target current data, and further the current command value corresponding to the error between the target current data and the output current data i is created, and the current command is generated. A PWM control signal is generated based on the value and is supplied to the gate circuit (54). Meanwhile, the main control unit
(53) supplies a signal for releasing the gate block to the gate circuit (54) in a normal operation state. As a result, the PWM control signal from the inverter output control section (51) passes through the gate circuit (54) and is supplied to the drive circuit (4).

Further, the control circuit (5) of FIG. 1 is provided with a failure judging means (55) for monitoring the abnormality such as overcurrent and judging the failure. The failure determination means (55) includes the solar cell output current data Idc, the solar cell output voltage data Vdc,
Also, the inverter output power value is supplied and a well-known failure determination is performed. When the failure is determined by the failure determination means (55), the determination result is sent to the main control unit (53),
In response to this, the main control section (53) issues a gate block signal to the gate circuit (54). As a result, the gate circuit (54) is blocked and the sending of the PWM control signal is cut off.
In addition, if necessary, the main control unit (53) to the breaker (7) OF
The F signal is transmitted and the inverter is disconnected from the commercial power system (2).

Further, the control circuit (5) outputs the output current data i
A failure diagnosis section (56) for diagnosing a failure of the inverter circuit (3) is provided by receiving the current amplitude command value Iamp and the current amplitude command value Iamp. As shown in FIG. 2, the failure diagnosis section (56) outputs the output current data i and the current amplitude command value Iam in the normal operating state.
The proportional relationship between p is stored with an appropriate width. The failure diagnosis section (56) judges whether or not the output current data i and the current amplitude command value Iamp at the time of failure diagnosis are within the normal operation region of FIG. 2, and outputs the data as plotted in FIG. 2, for example. When the current data i is smaller than the normal value, it is diagnosed that a failure has occurred on the DC side or the AC side of the inverter circuit (3).

When the failure diagnosis section (56) diagnoses the occurrence of a failure, the diagnosis result is sent to the main control section (53), and the main control section (53) accordingly responds to the gate circuit (54). ) To the gate block signal. As a result, the gate circuit (54) is blocked and the sending of the PWM control signal is cut off. Further, an OFF signal is sent from the main control unit (53) to the breaker (7) as necessary, and the inverter is disconnected from the commercial power system (2). As a result, the secondary failure of the inverter circuit (3) is prevented.

By the way, in the conventional grid-connected inverter, the AC side is equipped with the disconnecting means such as the breaker (7) shown in FIG. 1, but on the DC side, such disconnecting means is provided. Not equipped. Therefore, when current leakage due to insulation failure or the like occurs in the DC-side power transmission line or circuit from the output end of the solar cell (1) to the inside of the inverter circuit (3), the leakage generation unit There was a risk that peripheral parts would burn out.

Therefore, in the present embodiment, as shown in FIG. 3, the breaker (71) is interposed in the power transmission line extending from the output end of the solar cell (1) to the inlet of the inverter circuit (3), and Potential detector for detecting the potential difference between both ends of the
(84) is provided, and the breaker (71) is opened when an abnormal potential difference is detected.

Also on the DC side inside the inverter circuit (3), a relay (72) is interposed in the transmission line through which direct current flows, and a potential difference detector (85) for detecting the potential difference between both ends of the transmission line. ) Is provided and the relay (72) is opened when an abnormal potential difference is detected.

As a result, burnout in the event of current leakage in the DC power transmission line or circuit is prevented. still,
The breaker means by the breaker (71) or the relay (72) is
Either one may be provided, or both may be replaced by one disconnecting means.

The above description of the embodiments is for the purpose of illustrating the present invention, and should not be construed as limiting the invention described in the claims or limiting the scope. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a grid interconnection inverter according to the present invention.

FIG. 2 is a graph showing a normal operating region in the relationship between the output current of the inverter circuit and the current amplitude command value.

FIG. 3 is a block diagram showing an embodiment for preventing burnout of a DC power transmission line or a circuit of an inverter.

FIG. 4 is a block diagram showing a configuration of a conventional grid interconnection inverter.

[Explanation of symbols]

 (1) Solar cell (2) Commercial power system (3) Inverter circuit (4) Drive circuit (5) Control circuit (56) Fault diagnosis unit i Output current Iamp Current amplitude command value

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H02J 3/38 R 9470-5G (72) Inventor Kuniho Tanaka 2-chome, Keihanhondori, Moriguchi-shi, Osaka 5-5 Sanyo Electric Co., Ltd. (72) Inventor Masahiro Maekawa 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. An inverter circuit (3) for converting DC power supplied from a DC power supply to AC power and outputting the AC power to a commercial power system (2), and the inverter circuit (3) based on a current amplitude command value. In a system interconnection inverter including a control circuit (5) for controlling, a storage unit in which a normal operating region in the relationship between the output current of the inverter circuit (3) and a current amplitude command value is stored in advance, and an inverter circuit. (3) detecting means for detecting the output current, judging means for judging a failure according to whether the detected value of the output current and the current amplitude command value are within the normal operating range, and the failure is judged. A protection device for a grid-connected inverter, which is provided with a protection means for stopping the operation of the inverter circuit (3) when the above condition occurs. 2. The grid connection system according to claim 1, wherein when a failure is determined, the protection means further causes the disconnection means interposed between the inverter circuit (3) and the commercial power system (2) to be disconnected. System inverter protection device. 3. The inverter circuit from the output end of the DC power supply
The DC side power transmission line reaching the inside of (3) is provided with detection means for detecting a potential difference in a predetermined range of the power transmission line, and disconnection means interposed between the transmission lines and an excessive potential difference are detected. The protection device for the grid interconnection inverter according to claim 1 or 2, further comprising: a disconnection control means for disconnecting the disconnection means.