JPH08275397A - System-interconnected system - Google Patents

Abstract

PURPOSE: To prevent the damage of equipments and the lowering of maintenance and safety in system interconnection which are caused by erroneous operation of a manual-reset breaker. CONSTITUTION: In a system-interconnected system which supplies power to a load in interconnection with a commercial power system 3, a contact state of a manual-resed breaker 6 is detected and a parallel-off command signal is transmitted to the breaker 6 immediately after the contact of the breaker 6 comes to the closed state when an inverter circuit 21 is in a faulty state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection system in which an inverter connected to a DC power source such as a solar cell is connected to a commercial power system.

[0002]

2. Description of the Related Art In recent years, a distributed power supply system equipped with a DC power supply with a relatively small capacity of several kW, such as a solar cell, and an inverter that converts the output of the solar power supply into an AC power is connected to a commercial power system to produce home electric appliances. A grid interconnection system that supplies power to the above load has been proposed.

FIG. 3 is a schematic configuration diagram of a conventional system interconnection system. In the figure, 31 is a DC power supply, a solar cell that directly converts the energy of sunlight into a DC voltage, 32 is an inverter for converting the DC power output from the solar cell 31 into AC, and the DC power supply 31 The DC output from is converted into AC by the inverter 32, and then supplied to the load 35 and the commercial power system 36 via the system interconnection relay 33 and the breaker 34.

The relay 33 and the breaker 34 are controlled by a protective relay circuit 37. The protective relay circuit 37
Is the output voltage of the DC power supply 31, the output current of the inverter 32,
The system voltage of the commercial power system 36 is constantly monitored, and when an excess or deficiency of the voltage occurs or when the output current of the inverter 32 becomes excessive, it is judged as an abnormal state and the relay 33 and the breaker 34 Is opened. After that, when the cause of the abnormality is eliminated and the breaker 34 is closed by manual operation, the relay 33 is automatically closed while the operating conditions of the inverter 32 are satisfied, and after a lapse of a predetermined time, the inverter 33 is closed.
32 starts.

[0005]

As described above, in the conventional system, since the breaker of the manual reset type is used as the breaker 34, the user mistakenly inserts the breaker 34 even though the abnormal state has not been eliminated. In such a case, double protection by the relay and breaker cannot be achieved, and there is a possibility that a secondary disaster may occur due to re-input.

For example, when the relay 33 has a failure and is normally closed, that is, welded, the breaker 34 is turned on again to stop the operation of the inverter 32. A current flows from the inverter 36 to the inverter 32, which may shorten the life of the switching element and the control circuit of the inverter 32.

[0007] The present invention has been made in view of the above point, and is capable of preventing the damage of the equipment and the deterioration of the maintenance safety in the system interconnection due to the erroneous operation of the manual reset type breaker. Provide the system.

[0008]

SUMMARY OF THE INVENTION The present invention provides a system interconnection system for connecting an inverter circuit for converting DC power generated from a DC power supply to AC power to a commercial power system to supply power to a load. Automatic reset type grid interconnection relay provided on the output side of the inverter circuit, manual reset type breaker provided between the grid interconnection relay and the commercial power system, and the output voltage of the DC power supply Is below a certain voltage value, or when the interconnection point voltage with the commercial power system is out of a certain range, it is determined that the inverter circuit is in the standby state, and the system interconnection relay is A disconnection command signal is transmitted, and when the output current of the inverter circuit exceeds a certain current value, it is determined that the inverter circuit is in a failure state, and the grid interconnection relay and the breaker are connected. And a protective relay circuit for sending a disconnection command signal, the protective relay circuit detects a contact state of the breaker, and the contact of the breaker is closed when the inverter circuit is in a failure state. In this case, the disconnection command signal is immediately sent to the breaker.

[0009]

According to the present invention, when the user accidentally turns on the manual reset type breaker when the inverter circuit is in a failure state, the breaker contacts are immediately opened.

Further, when the automatic reset type relay is normally closed due to a failure, an overcurrent flows from the commercial power system to the inverter circuit due to a false input of the manual reset type breaker, and a switching element of the inverter circuit and its control circuit, etc. There is no fear of shortening the service life of.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the system interconnection system of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a grid interconnection system of the present invention.

In FIG. 1, the system interconnection system comprises a DC power source 1 composed of solar cells having a rated voltage of 200V,
The DC output of the DC power supply 1 is converted into an AC output for power conversion to supply a predetermined AC voltage to the grid-connected inverter device 2, and the AC output from the grid-connected inverter device 2 is supplied to the commercial power system 3 and the load 4. A system interconnection relay (hereinafter abbreviated as relay) 5 and a breaker 6 that can be supplied,
First current detecting means 7 for detecting the output current of the DC power supply 1.
And a first voltage detecting means 8 for detecting an output voltage of the DC power supply 1, and a second current detecting means provided between the interconnection inverter device 2 and the relay 5 for detecting an output current of the interconnection inverter device 2. 9, a second voltage detection means 10 provided between the breaker 6 and the commercial power system 3 for detecting the system voltage at the interconnection point, the output voltage of the DC power source 1 and the commercial power system 3, and the interconnection. The protective relay circuit 11 controls the open / closed states of the relay 5 and the breaker 6 by detecting the occurrence of an abnormality on the side of the DC power source 1 and the side of the commercial power system 3 depending on the state of the output current of the inverter device 2. .

Here, the relay 5 is an automatic reset type relay, and the open / close state of its contacts can be controlled by inputting a control signal from the protective relay circuit 11. On the other hand, the breaker 6 is a manual reset type breaker and has a protective relay circuit 11
The contact is controlled to an open state by the input of a control signal from, but when closed, the contact is configured only by manual operation.

Further, the protective relay circuit 11 is in an abnormal state of the DC power source 1 and the commercial power system 3 based on the detection results of the first voltage detecting means 8, the second current detecting means 9 and the second voltage detecting means 10. Is detected and a control signal for controlling the open / closed state of the contacts of the relay 5 and the breaker 6 is sent to control the open / closed state of the contact, and as described later, an abnormality in the DC power source 1 and the commercial power system 3 When the occurrence is detected, an abnormal state signal is sent to the interconnection inverter device 2, the contact state of the relay 5 and the breaker 6 is monitored, and the contact state signal is sent to the interconnection inverter device 2.

The interconnection inverter device 2 includes a voltage type current control inverter circuit 21 including a plurality of switching elements.
And its output control unit 22 and main control unit 23.
The output control unit 22 uses the first current detection means 7 as described later.
The output current of the DC power supply 1 detected by the second voltage detection means 8, the output voltage of the DC power supply 1 detected by the first voltage detection means 8, the output current of the inverter circuit 21 detected by the second current detection means 9, Based on the interconnection point voltage detected by the voltage detection means 10, the operating power factor becomes 1 and the inverter circuit 21 is configured to draw the maximum power from the DC power supply 1.
The PWM control signal is supplied to the switching element to control the output current of the inverter circuit 21.

Further, as will be described later, the main control section 23 is supplied with an abnormal state signal and a contact state signal from the protective relay circuit 11, and in accordance with the input signal, an output signal for starting the inverter circuit 21 in the output control section 22. , Or inverter circuit
Sending a stop signal to stop 21.

In the main control section 23, the inverter circuit
Even when the operating conditions of 21 are satisfied, the starting signal is not sent when the contact of the relay 5 is in the closed state due to welding or the like before the start of the starting of the inverter circuit 21.

Specifically, when the output voltage of the DC power supply 1 becomes a predetermined undervoltage value (170 V in this embodiment) or less, or the system voltage of the commercial power system 3 falls within a certain range (this embodiment). 80V ~ 115V), the protection relay circuit 11 judges that the standby state is in effect, and the main control unit
The status signal is input to 23. Also, the inverter circuit
When the output current of 21 becomes a constant current value (45 A in this embodiment) or more, or when the output voltage of the DC power supply 1 becomes a predetermined overvoltage value (300 V in this embodiment) or more,
The protection relay circuit 11 is determined to be in a failure state, and the state signal is input to the main control unit 23. Further, in other cases, it is determined that the inverter circuit 21 is in an operable state in which the operating conditions are satisfied, and the state signal is input to the main control unit 23. Here, when the output current of the inverter circuit 21 becomes a constant current value or more, it is because a failure has occurred in the switching element or the control circuit of the inverter circuit 21. This is also because when the output voltage of the DC power supply 1 exceeds a predetermined overvoltage value, a failure has occurred in the solar cell of the DC power supply 1.

In the main control unit 23, the inverter circuit
Protection relay circuit when 21 is in standby mode and inverter operation is stopped
It is confirmed that the contact of the breaker 6 is in the closed state and the contact of the relay 5 is in the open state according to the contact state signal from 11, and when the above operable state signal is input, A relay interconnection signal is sent to the protective relay circuit 11 and a start signal is sent to the output control unit 22. As a result, the protective relay circuit 11 sends a relay connection command signal (hereinafter referred to as an ON signal) to the relay 5 in accordance with the input of the relay connection signal from the main control unit 23 to the relay 5.

In the main controller 23, the inverter circuit 21
Although the inverter operation is stopped due to a fault condition,
When it is confirmed that the contacts of the breaker 6 are closed, or the contacts of the relay 5 are closed even though the inverter circuit 21 is in the standby state and the inverter operation is stopped. If confirmed, the protective relay circuit
A breaker disconnection signal is sent to 11, and the inverter circuit 21 is disconnected from the commercial power system 3.

In the protective relay circuit 11, the main controller 23
In response to the breaker disconnection signal input from the breaker 6, the breaker command signal for opening the contact of the breaker 6 (hereinafter referred to as OFF
Signal)).

On the other hand, in the protective relay circuit 11, a shortage of the output voltage of the DC power supply 1 occurs during the operation of the inverter circuit 21, or the voltage at the connection point with the commercial power system 3, that is,
When it is determined that the system voltage is in the standby state due to an excess or deficiency voltage, the protective relay circuit 11 first sends an OFF signal to the relay 5 to open the contact of the relay 5,
A standby state signal is sent to the main control unit 22. Then, the main control unit 23 sends a stop signal to the output control unit 22 in accordance with the input of the standby state signal from the protective relay circuit 11, and the output control unit 22 outputs a switching signal for driving and controlling the switching element of the inverter circuit 21. The gate is blocked to stop the supply of the switching signal to the inverter circuit 21.

At this time, in the main control unit 23, the protection relay circuit is
Relay 5 is activated by inputting an OFF signal from relay 11 to relay 5.
Relay circuit that protects whether the contacts are open
Check the contact status signal from 11 and if it is in the open state, the cause of the abnormality is resolved, and as soon as the above operable status signal from the protective relay circuit 11 is input, the protective relay circuit 11
The relay interconnection signal is transmitted to the output control unit 22 and the activation signal is transmitted to the output control unit 22.

On the other hand, when it is confirmed that the contact of the relay 5 is closed regardless of the OFF signal being sent to the relay 5, a breaker disconnection signal is sent to the protective relay circuit 11. When an overcurrent occurs in the inverter output current due to some cause during the operation of the inverter circuit 21, or an overvoltage occurs in the output voltage of the solar cell 1, and the protection relay circuit 11 determines that a failure occurs. The protective relay circuit 11 sends an OFF signal to the relay 5 and the breaker 6, opens the relay 5 and the breaker 6, and sends a failure status signal to the main controller 23. Then, the main control unit 23 inputs a stop signal to the output control unit 22 in accordance with the input of the failure state signal to stop the inverter operation of the inverter circuit 21.

After removing the cause of the failure, the reset switch 11a provided in the protective relay circuit 11 is pressed to send a standby state signal from the protective relay circuit 11 to the main controller 22. . Then, in the main control section 23, it is confirmed that the breaker 6 is closed by manual operation in the standby state and the contact of the relay 5 is opened, and then the operable state signal is input from the protective relay circuit 11. As soon as
A relay interconnection signal is sent to the protection relay circuit 11 and a start signal is sent to the output control unit 22 to connect the interconnection inverter device 2 to the commercial power system 3 and start inverter operation in parallel operation. To perform.

The output control unit 22 includes a power command unit 221, a multiplication means 222, an error amplifier 223, and a PWM comparator 224.
(Pulse width modulation means), the power command section 221 receives a start signal and a stop signal from the main control section 23, and detects the current detected by the first current detection section 8 and the first voltage detection section. The detection voltage of 9 is input at a predetermined sampling cycle (50 μs in this embodiment).

When the activation signal is input from the main control section 23, the power command section 221 outputs the output power Ps of the DC power supply 1 based on the detection values of the first current detection means 8 and the second voltage detection means 9. And the amount of power change ΔPs are calculated, and based on the sign of the amount of power change ΔPs, the direction of change of the voltage command value Vsb, which is the control target value of the operating voltage of the DC power supply 1, is determined, and a constant change width ΔV The voltage command value Vsb is changed by 1.5 V in the example, and the current command value Ib that is the control target value of the output current I of the inverter circuit 21 is calculated based on the voltage command value Vsb. Is input to one end of the multiplication means 222.

On the other hand, when the stop signal is input from the main control unit 23, the power command unit 221 inputs the current command value Ib = 0 to one end of the multiplication means 222, and the PWM control signal to the switching element of the inverter circuit 21. Has been stopped.

Specifically, in the power command unit 221, when the start signal is input from the main control unit 23, first, the voltage command value Vsb of the DC power supply 1 is calculated from the output voltage which is the maximum power point of the DC power supply 1. A high voltage value (set to 210 V in this embodiment) is decreased by the variation width ΔV in the sampling cycle, and the current command value Ib based on the voltage command value Vsb is set. During this period, the power change amount ΔPs takes a positive value, and the output power Ps of the DC power supply 1 increases. When the sign of the power change amount ΔPs changes from positive to negative, that is, when the voltage command value Vsb exceeds the maximum power point voltage, the direction of change of the operating point is reversed to change the voltage command value Vsb. The current command value I based on the voltage command value Vsb is increased by ΔV.
b is set. Similarly, the change direction of the operating point is reversed based on the change in the sign of the power change amount ΔPs. By repeating the above operation, the operating voltage of the DC power supply 1 is maintained near the maximum power point, and the operating point of the DC power supply 1 always follows the maximum power point.

The multiplying means 222 multiplies the output from the power command section 221 by the voltage waveform detected by the second voltage detecting means 11 and uses the multiplication result as one input of the error amplifier 223. That is, in the multiplying means 222, the current command value Ib set in the power command unit 221 and the reference waveform corresponding to the system voltage are input, and both are multiplied, so that the current command value Ib is satisfied. A signal having a sine waveform of the commercial frequency having an amplitude and synchronized with the system voltage waveform is multiplied by the multiplying means 222.
From the error amplifier 223.

The error amplifier 223 amplifies the difference between the input from the multiplying means 222 and the current detected by the second current detecting means 10, and then inputs it to the PWM comparator 224. PWM
The comparator 224 receives the error signal from the error amplifier 223,
The error amplifier 22 is compared with a preset reference triangular wave.
A switching control signal is supplied to the switching element of the inverter circuit 21 so that the error signal from 3 becomes zero.

Next, the contents of the processing operation by the main control unit 23 of the system interconnection system configured as described above will be described with reference to the flowchart of FIG. First, the inverter circuit
It is determined whether the inverter operation by 21 is stopped (S
1) If YES, go to the next step S3, NO
In the case of, it progresses to step S5.

In step S3, it is determined whether or not the breaker 6 is manually closed by a contact state signal from the protective relay circuit 11 before starting the inverter circuit 21, and if YES, the process proceeds to step S7.

In step S7, it is determined whether or not a failure state signal is input from the protective relay circuit 11, and if YES, a breaker disconnection signal is sent to the protective relay circuit 11 (S9) and step S1 is performed. If NO, the process proceeds to step S11.

In step S11, it is judged from the contact state signal from the protective relay circuit 11 whether or not the contact of the relay 5 is open, that is, whether or not the relay 5 is welded, and if YES. Proceeds to step S13, N
If it is O, a breaker disconnection signal is sent to the protective relay circuit 11 (S15) and the process returns to step S1.

In step S13, it is determined whether or not the operable state signal is input from the protective relay circuit 11. If YES, the process proceeds to step S17, and if NO, the process returns to step S3.

In step S17, a relay interconnection signal is sent to the protective relay circuit 11 and a start signal is sent to the output control section 22, and the process proceeds to step S19. In step S19, the inverter operation is started by the input of the activation signal to the output control unit 22, and the process returns to step S1.

On the other hand, if NO at step S1 and proceed to step S5, it is determined whether or not a failure state signal is input from the protective relay circuit 11, and if YES, proceed to step S21. Here, in the protective relay circuit 11, when a failure state is detected, an OFF signal is sent to the relay 5 and the breaker 6 to open the relay 5 and the breaker 6, and the main control unit 23 is broken. A status signal will be sent.

In step S21, in response to the failure status signal input from the protective relay circuit 11 in step S5, a stop signal is sent to the output control section 22 to stop the inverter operation of the inverter circuit 21, and then in step S1. Return.

If NO in step S5, the process proceeds to step S23 to determine whether or not the standby state is detected in the protective relay circuit 11. If YES, the process proceeds to step S25 to determine NO. In that case, the process returns to step S1.

In step S25, the relay 5 is opened by sending the OFF signal from the protective relay circuit 11 to the relay 5 in the previous step S23, and the protective relay circuit 11 sends the signal to the main controller 23. In response to the input of the standby state signal, it sends a stop signal to the output control unit 22 to output the inverter circuit.
The inverter operation of 21 is stopped, and the process returns to step S1.

By performing the above processing, if the user mistakenly inserts the manual reset type breaker 6 in the failure state, the contact point of the breaker 6 is immediately opened, so that the relay and the breaker are always used. Double protection can be achieved, and the secondary disaster due to re-injection can be surely prevented.

Further, when the relay 5 is normally closed due to a failure, overcurrent does not flow from the commercial power system 3 to the inverter circuit 21 due to erroneous turning on of the breaker 6, and the switching element of the inverter circuit 21 and its control circuit. There is no fear of shortening the life of such.

In the above embodiment, the output voltage of the DC power supply 1 and the system voltage of the commercial power system 3 are detected to be abnormal, and it is determined that the inverter circuit 21 is in the standby state. It may be determined that the invar circuit 21 is in the standby state by detecting a decrease or increase in the frequency at the interconnection point with the system 3.

[0045]

As described above, according to the present invention, when the user accidentally turns on the manual reset type breaker when the inverter circuit is in a failure state, the contacts of the breaker are immediately opened. Double protection for commercial power system by relays and breakers can always be achieved.

Further, while the inverter operation is stopped, overcurrent does not flow from the commercial power system to the inverter circuit,
There is no fear that the service life of the switching element of the inverter circuit and its control circuit will be shortened.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a grid interconnection system of the present invention.

FIG. 2 is a flowchart for explaining the processing operation contents of the main control unit 23 of the grid interconnection system of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional grid interconnection system.

[Explanation of symbols]

 1,31 Solar battery (DC power supply) 2 System interconnection inverter device 3,36 Commercial power system 4,35 Load 5,37 System interconnection relay 6,33 Breaker 7 First current detection means 8 First voltage detection means 9 Second current detecting means 10 Second voltage detecting means 11,37 Protection relay circuit 21,32 Inverter circuit 22 Output control section 23 Main control section 221 Power control section 222 Multiplying means 223 Error amplifier 224 PWM comparator (pulse width modulating means)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masahiko Hashimoto 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Masahiro Maekawa 2-5 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A system interconnection system for supplying an electric power to a load by connecting an inverter circuit for converting DC power generated from a DC power supply to AC power to a commercial power system, the system being provided on the output side of the inverter circuit. The automatic recovery type grid interconnection relay, the manual reset type breaker provided between the grid interconnection relay and the commercial power system, and the output voltage of the DC power supply is below a certain voltage value. In this case, or when the voltage of the interconnection point with the commercial power system is out of a certain range, it is determined that the inverter circuit is in the standby state, and a disconnection command signal is sent to the system interconnection relay. When the output current of the inverter circuit is equal to or more than a constant current value, it is determined that the inverter circuit is in a failure state, and a disconnection command signal is sent to the grid interconnection relay and the breaker. And a protective relay circuit, the protective relay circuit detects a contact state of the breaker, and when the contact of the breaker is in a closed state during a failure state of the inverter circuit, the breaker is immediately released. A system interconnection system characterized by transmitting a disconnection command signal to the system.