JPH08223816A - Switching method of commercial-system power in inverter system of solar-light power generation - Google Patents

Abstract

PURPOSE: To make good use of solar energy, by constituting a system that modulates an output variation related with solar-light power generation. CONSTITUTION: An inverter system of solar-light power generation is made up of a solar battery 1, a DC/DC converter 2, a DC/AC inverter 3, a battery 4, a control system 5, and a high-speed switch 7. A charging state is detected from the battery 4 to control the operation of the inverter system of solar-light power generation, and the switching to the commercial system power is carried out under control. As to the parallel operation with the battery 4, limiting values for the discharging current and discharging power are previously set to judge the switching timing of to the commercial system power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a photovoltaic power generation inverter system for converting direct current power from a solar cell or the like into alternating current by an inverter and supplying it to a load.

[0002]

2. Description of the Related Art Photovoltaic power generation is a power generation method that uses clean natural energy. However, not only the energy density on the ground surface is low, but also the power generation output is greatly affected by weather conditions and sunshine hours. It is a power source. Further, since the power generated by photovoltaic power generation is direct current, it is necessary to provide an inverter and convert it into alternating current in order to supply it to a normal load, as shown in FIG. That is, the DC power source 101 composed of solar cells is DC
/ Converted to AC power by the AC inverter 102,
Power is supplied to the load through the changeover switch 104, and after sunset, the power is supplied to the load by manually switching to the commercial system power supply 103.

[0003]

Since photovoltaic power generation is an unstable power supply source, it is difficult to increase the utilization rate, and automatic switching to a commercial power supply cannot be easily realized. The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and aims to stabilize the power supplied from the photovoltaic power generation, reduce the frequency of switching to a commercial system, and perform automatic switching. It is possible.

[0004]

A method of switching a photovoltaic power generation inverter system to a commercial system power source according to the present invention is a direct current power source comprising photovoltaic power generation, a DC / DC converter for voltage controlling the direct current power source, and a DC / DC converter DC / AC inverter for converting the output of the DC converter into AC, DC
A solar power generation inverter system configured by a battery connected in parallel to a DC circuit between a DC / DC converter and a DC / AC inverter, and a high-speed switch that switches between an AC output of the DC / AC inverter and a commercial system power source and supplies the load. Then, when the battery is in the charging state, power is supplied to the load by the photovoltaic power generation inverter system, and when the battery is in the discharging state, it is switched to the commercial system power source. In addition, in order to reduce the frequency of switching between the commercial system power supply and the solar power inverter system,
By using the solar power generation inverter system and the battery together, the power supply to the load is stabilized, and when the discharge current of the battery reaches a predetermined value, or DC
/ When the difference between the power supplied from the AC inverter and the power discharged from the battery reaches a predetermined value, the power is switched to the commercial power supply.

[0005]

By providing a battery in the photovoltaic power generation inverter system and operating in parallel, the fluctuation of the photovoltaic power generation output is mitigated to stabilize the power supply, and the frequency of switching to the commercial grid is reduced. Also, in order to avoid over-discharging of the battery, the discharge current and discharge power of the battery are detected to switch to the commercial system, and this detection signal enables automatic switching by a high-speed switch.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of a photovoltaic power generation inverter system according to the present invention. In FIG. 1, the DC power from the solar cell 1 is input to the DC / DC converter 2 to stabilize the DC output voltage, and then DC
It is input to the / AC inverter 3, converted into AC power, and supplied to the load via the high-speed switch 7. DC circuit 8 between the DC / DC converter 2 and the DC / AC inverter 3
A battery 4 is connected in parallel to the battery 4, and the charging current to the battery 4 and the discharging current from the battery 4 are detected by the current transformer 9, and the detection signal is DC / DC.
It is sent to the converter 2 and the control system 5. The control system 5 inputs the detection signal of the charging / discharging current in the battery 4 and the DC voltage described above, and also inputs the voltage signal detected from the commercial system power supply 11 and the power detection signal from the power detection circuit 6 to input the DC / AC inverter. 3 controls the start and stop of 3 and the switching of the high speed switch 7. The output from the output circuit of the DC / AC inverter 3 is constantly detected by the power detection circuit 6 and sent to the control system 5, and is monitored as AC power supplied from the DC / AC inverter 3 to the load. Further, the high-speed switch 7 is provided to switch between the AC output from the DC / AC inverter 3 and the AC power from the commercial system power supply 11, and the switching is controlled by the control system 5.

Next, a method of switching the photovoltaic power generation inverter system according to the present invention to a commercial system power supply will be described. In normal times, the DC power output from the solar cell 1 is input to the DC / DC converter 2 and converted into a constant voltage,
The AC power converted in the DC / AC inverter 3 is configured to be supplied to the load via the high speed switch 7, and the DC circuit 8 between the DC / DC converter 2 and the DC / AC inverter 3 has a battery. 4 are connected in parallel, and the charge / discharge state of the battery 4 is constantly monitored by the control system 5 via the current transformer 9. When it is detected that the battery 4 is in the charging state, the DC power output from the solar cell 1 is the DC / AC inverter 3
Not only is it supplied to the load via the
Since it indicates that the battery is being charged, the operation is continued. On the contrary, when it is detected that the battery 4 is in the discharged state, it indicates that the DC power from the solar cell 1 is insufficient to supply the load and the battery 4 supplies the shortage. Therefore, the DC / AC inverter 3 is stopped and the high speed switch 7 is operated to switch the load to the commercial system power supply 11.

Since the frequency of switching to the commercial system power source increases in the above-described operating method, the frequency of switching can be reduced by stabilizing the output fluctuation of the solar cell 1 by connecting the battery 4 in parallel. The rated capacity of the battery to be installed must be determined in consideration of the output capacity and load capacity of the solar cell, but an example of eliminating the instability during the day by placing the battery assuming a discharge time of around 1 hour There is also. In parallel operation of the solar cell 1 and the battery 4, it is necessary to control so that the battery is not over-discharged, and for this purpose, the following two means are taken. In the first means, the current transformer 10 and the voltage detection point 12 provided in the output circuit of the DC / AC inverter 3 are used.
The power detection circuit 6 for inputting the signal detected from the power detection circuit 6 sends the power detection signal to the control system 5, and the control system 5 receives the detection signals of the discharge current and the DC voltage of the battery 4. Therefore, the discharge power from the battery 4 based on the detection signal and the power supplied to the load based on the power detection signal from the power detection circuit 6 are compared, and when the difference between the two reaches a preset limit value. The DC / AC inverter 3 is stopped and the high speed switch 7 is switched to transfer the load to the commercial system power supply 11.

In the second means, when it is detected that the discharge current of the battery 4 has reached a preset current value, the control signal from the control system 5 stops the DC / AC inverter 3 and the high speed operation is performed. It suffices to switch the switch 7 to transfer the load to the commercial power supply 11, and the circuit configuration in this case is as shown in FIG.

After the DC / AC inverter 3 is stopped, the DC / DC converter 2 charges the battery 4 with the output of the solar cell 1, so that solar energy can be continuously and effectively utilized. Further, when the commercial power supply is out of power, it is possible to supply power to the load even at night until the battery discharge is completed.

[0011]

As described above, the method of switching the photovoltaic power generation inverter system according to the present invention to the commercial power source is the solar cell, the DC / DC converter, the DC / A converter.
A photovoltaic power generation inverter system composed of a C inverter, a battery, a high-speed switch, a control system, etc., which switches between the photovoltaic power generation inverter system and the commercial power supply by detecting the charging / discharging state of the battery to supply power to the load. Supply. Further, the parallel operation of the battery and the photovoltaic power generation inverter system absorbs and stabilizes the output fluctuation of the photovoltaic power generation by discharging the battery, and reduces the frequency of switching to the commercial system power supply. Therefore, it is possible to secure a constant power supply by effectively using solar energy, and it is possible to supply power to the load even at night during a power failure until the battery discharge is completed. In addition, by synchronizing the commercial system power supply with solar power generation and using a high-speed switch as the changeover switch, it has become possible to supply power to the load without interruption.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a photovoltaic power generation inverter system according to the present invention.

FIG. 2 is a block diagram showing the configuration of another photovoltaic inverter system according to the present invention.

FIG. 3 is a block diagram of a conventional photovoltaic power generation inverter system.

[Explanation of symbols]

 1 Solar Cell 2 DC / DC Converter 3 DC / AC Inverter 4 Battery 9, 10 Current Transformer 5 Control System 6 Power Detection Circuit 7 High Speed Switch 8 DC Circuit

Claims (3)

[Claims] 1. A DC power supply comprising a solar cell and a DC / DC for inputting DC power from the DC power supply to control the voltage.
A converter and a DC / AC inverter that converts the DC power output from the DC / DC converter into AC power,
A battery connected in parallel to a DC circuit between the DC / DC converter and the DC / AC inverter, and a high-speed switch that switches between AC power from the DC / AC inverter and AC power from a commercial system power supply to supply the load. A solar power generation inverter system configured by, DC voltage output from the solar cell when it is detected that the output voltage and charge / discharge current of the battery are constantly monitored and the battery is in a charged state. The DC / A
The AC inverter performs AC conversion and then supplies the load to the load through the high-speed switch. When it is detected that the battery is in a discharged state, the DC / AC inverter is stopped and the high-speed switch is switched to switch the commercial system. A method for switching a photovoltaic power generation inverter system to a commercial system power supply, characterized in that AC power is supplied from a power supply to a load. 2. When a DC power from a DC power source composed of a solar cell and a DC power generated by discharging a battery are converted into AC power in a DC / AC inverter and then supplied to a load via a high speed switch, 2. The solar system according to claim 1, wherein when the discharge current reaches a preset current value, the DC / AC inverter is stopped and the load is switched to the commercial system power source via the high speed switch. Method for switching photovoltaic inverter system from commercial power supply. 3. When DC power from a DC power source comprising a solar cell and DC power resulting from battery discharge are converted into AC power in a DC / AC inverter and then supplied to a load via a high-speed switch, the DC / AC When the difference between the load supply power detected from the output circuit of the AC inverter and the discharge output from the battery reaches a preset limit value, the DC / AC inverter is stopped and commercial operation is performed via the high speed switch. 2. The load is switched to a system power supply.
The method for switching the solar power inverter system described in paragraph 1 to the commercial power supply.