JPS6111830A - Controlling method of linkage inverter - Google Patents

Abstract

PURPOSE:To utilize a DC power supply based upon a solar battery effectively by supplying control power from the DC power supply side to a control circuit and an electromagnetic contact. CONSTITUTION:When the output voltage of the solar battery 1 is boosted, a capacitor 14 is charged through a diode 15 and the output of a DC/DC converter 13 is applied to the control circuit as a power supply. The output voltage of the solar battery 1 is also applied to a voltage detecting circuit 18, and when the voltage reaches a set point, a detecing signal is applied from the circuit 18 to the circuit 5. Consequently, the electromagnetic switch 2' is turned on and the smoothing capacitor 3 is charged with the output of the solar battery 1. Then, an inverter 4 is started and an AC switch 6 is turned on.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention converts energy obtained from a DC power source such as a solar cell into AC power, connects it to a commercial AC power system, and supplies power to a load. The present invention relates to a method for controlling an inverter.

Conventional technology When controlling an inverter that connects solar cells to an AC power system, the inverter is disconnected from the power grid in the event of a power outage, and restarted smoothly when the power outage is restored, and the inverter system is It is necessary to prevent severe voltages and currents from being applied to the components.

3 is a circuit diagram showing a conventional example of a starting control method for such a series inverter. A solar cell 1, an electromagnetic contactor 2 that short-circuits and opens the output end of the solar cell 1, a smoothing capacitor 3, an inverter 4 that has a function of detecting a power outage and stopping operation of the solar cell 1, and A control circuit 5 having a function of detecting output voltage, an alternating current switch 6 controlled by this control circuit 5, and a switch 7 that automatically opens in the event of a failure or grounding accident of the inverter system.
and a commercial AC power system 8. Further, the main circuit of the onverter 4 includes transistors 9 and 9, as shown in FIG. Feedback diode 10. It is composed of an isolation transformer 11.

In this circuit configuration, after turning on the power, the inverter 4 releases the short-circuited state of the solar cells by turning off the electromagnetic contactor 2, and waits for the solar cell voltage to reach a predetermined value before turning on the AC switch 6. For example, even in the case of recovery from a power outage, the system can be restarted smoothly by controlling the components such as the feedback diode 10, which is a component of the inverter shown in FIG. It is possible to prevent severe voltage and current from being applied to the smoothing capacitor 3 shown in FIG.

The operation of this circuit diagram will be explained using the timing diagram shown in FIG. In this figure, V is the terminal voltage of the smoothing capacitor 3, T is the time, and X is the voltage setting value at which the AC switch 6 should be turned on.

In order to start the inverter system, the system voltage excites the excitation coil of the electromagnetic contactor 2, and the electromagnetic contactor 2 is turned off, thereby releasing the short-circuited state of the solar cells. Here, the inverter is started at point A, and at the same time when the terminal voltage of the smoothing capacitor reaches the set value X (point B), AC switch e is turned on to perform grid-connected operation. At the time of power outage (point 0), the electromagnetic contactor 2 is turned on and the solar cells are short-circuited.

Turn off the AC switch 6. Thereafter, after the power system is restored at point D, the terminal voltage of the smoothing capacitor 3 reaches the set value X (point E), and the inverter system is started again.

In this way, in the circuit configuration described above, after the power is turned on, the inverter 4 releases the short-circuited state of the solar cells by turning off the magnetic contactor 2, waits for the solar cell voltage to reach a predetermined value, and then starts the alternating current. By controlling the switch 6 to turn on, the system can be restarted smoothly even when recovering from a power outage, for example, and the components of the system, such as the feedback diode 10 that is a component of the inverter and the smoothing It is possible to prevent severe voltage and current from being applied to the capacitor 3.

In other words, when the voltage of the smoothing capacitor 3 is low, the power system and the inverter are disconnected, so the charging current for the smoothing capacitor 3 is supplied from the large detection battery, but the large detection battery is a power source with extremely poor regulation. Since the short circuit current is also slightly larger than the normal operating current, the feedback diode 10 and the smoothing capacitor 3 do not have any severe responsibility.

However, in the conventional control method for the grid-connected inverter shown in FIG. 3, the control power for the control circuit 5 and the magnetic contactor 2 is taken from the AC power system. Although there is sufficient power generated by solar cells, the operation has to be stopped.
The drawback is that the power generated by the solar cells cannot be used effectively.

Purpose The present invention connects energy obtained from direct current such as solar cells to a commercial alternating current power system via an inverter.
In a power supply system that supplies power to a load, interconnection that continues to supply power to the load even in the event of a power outage, allows the inverter to start smoothly, and does not impose harsh duties on the components of the inverter system. The purpose of this invention is to provide a control method for an inverter for

Configuration For this reason, the present invention provides a system in which the output of a DC power source such as a solar cell is converted to AC by an inverter, and connected to an AC power system via a switch to supply power to a load.
Wait for the output voltage of the DC power supply to reach a predetermined value, turn on the switch, connect the system, and control the inverter control circuit and switch! The power source is obtained from a DC power supply, so that even in the event of a power outage, the inverter system alone can supply power to the load using the generated power from the DC power supply.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the circuit configuration diagram in FIG. 1 and the starting control timing diagram in FIG. 2.

In Fig. 1, the same symbols as in Fig. 3 indicate the same or equivalent parts, and 2' is an electromagnetic switch installed between the solar cell 1 and the inverter 4, and 7' is an electromagnetic switch that automatically switches the An electromagnetic switch to be opened, 12 a load, and 13 a DC/DC comparator that supplies constant voltage power to the control circuit 5.
5 and 14 are smoothing chemical capacitors, 15 is a backflow prevention diode, and 16 is the terminal voltage of smoothing capacitor 3 (
17 is a discharge resistor for discharging the charge of the smoothing capacitor 3 after opening the electromagnetic switch 2'; 18 is a voltage for detecting the output voltage (X) of the solar cell 1; This is a detection circuit.

The operation of this first circuit configuration diagram will be explained together with the timing diagram of inverter start control shown in FIG.

Nao, V, T, X, , A', in Figure 2
B, C, and D are the same as those in FIG.

When the inverter system is started, when the output voltage of the solar cell 1 increases, the capacitor 14 is charged via the backflow prevention diode 15, and the output of the DC/DC converter 13 is applied to the control circuit 5 as a power source. Further, the output voltage of the solar cell 1 is applied to the voltage detection circuit 18,
The output voltage of the solar cell 1 gradually increases according to its characteristics, and when it reaches the set value X (point B in FIG. 2), the voltage detection circuit 18 operates and provides a detection signal to the control circuit 5. As a result, the electromagnetic switch 2' is turned on at point B in FIG. 2, and the smoothing capacitor 3 is charged with the output of the solar cell 1. At this time, the terminal voltage of the smoothing capacitor 3 becomes as shown between BB' in FIG. Here, the inverter 4 is started at point B, and after waiting for the voltage to reach the set value X again, the AC switch 6 is turned on. As a result, the inverter system of the solar cell 1 and the commercial power grid 8 are interconnected, and power is supplied to the load 12. When performing this interconnection, the output voltage (frequency and phase) of the inverter 4 is connected to the AC power system 8.
However, in this embodiment, the control circuit 5 includes a PLL (Phase Locked Loop) circuit, and this PLL circuit controls the output voltage of the inverter 4 to match the voltage of the AC power system 8. is under control. Further, in the event of a power outage in the AC power system 8, the control circuit 5 controls the inverter 4 using the PLL circuit so that the output voltage of the inverter 4 maintains the state immediately before the power outage. However, since this point is not the gist of the present invention, further detailed explanation will be omitted. By doing so, it is possible to smoothly start up the solar cell from start-up to grid-connected operation, and severe voltage and current are not applied to the components of the inverter system.

In addition, when there is a power outage in the AC power system, the electromagnetic switch 7' is automatically opened as shown between C and D in FIG. Since power for controlling the switch 6 is supplied from the solar cell 1 via the DC/DC converter 13, the inverter system can continue to operate and independently supply power to the load 12.

Effects As described above, according to the present invention, an inverter system can be started up smoothly from the starting state of a DC power source such as a solar battery, and can be operated in connection with an AC power system, and can also be operated without interruption from an AC power system power outage. This makes it possible to continue supplying power to the load even when the load is off.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a timing diagram of starting control of the inverter shown in FIG. 1, FIG. 3 is a conventional circuit configuration diagram, and FIG. 4 is a diagram of the inverter shown in FIG. FIG. 5 is a timing chart for starting control of the inverter shown in FIG. 3. 1...Solar cell, 2...Magnetic contactor, 2'...
Electromagnetic switch, 3... Smoothing capacitor, 4... Inverter, 5... Control circuit, 6... AC switch, 7...
...Switch, 7'...Electromagnetic switch, 8...Commercial AC power system, 9...Transistor, 10...Feedback diode, 11...Isolation transformer, 12...Load, 13 ...DC/DC converter, 14...chemical capacitor. 15... Backflow prevention diode, 16... Voltage detection circuit, 17... Discharge resistor, 18... Voltage detection circuit. Figure 2 Figure 3 Figure $4

Claims (1)

[Claims] In a power supply system that connects a DC power source such as a solar battery to an AC power system via an inverter and supplies power to a load, a grid connection switch is installed after waiting for the voltage of the DC power source to rise to a predetermined value. At the same time, control power for the control circuit of the inverter and the interconnection switch is obtained from the DC power supply, and even in the event of a power outage, the inverter system independently supplies power to the load with the generated power of the DC power supply. A method for controlling a grid-connected inverter, characterized by: