JPH04308431A - Control method for photovoltaic power generation linking system - Google Patents

Abstract

PURPOSE:To smooth a rapid fluctuation of output power quantity of a solar battery by A storage battery, further to ensure a charging amount of the storage battery and further so as to actuate the solar battery in the vicinity of optimum operational voltage. CONSTITUTION:A control method for a photovoltaic power generation linking system in which a storage battery 2 is selected so that optimum operational voltage of a solar battery 1 obtains floating charge voltage of the storage battery 2 to detect its voltage, and a power quantity fed to the other AC system 9 from the above-mentioned inverter 3 is controlled so as to decrease, in the case of the voltage of the storage battery 2 lower than the floating charge voltage, and so as to increase in the case of the voltage of the storage battery 2 higher than the floating charge voltage.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a solar power generation interconnection system in which a solar battery and a storage battery are installed as energy storage means, and the power generated by the solar battery is supplied to another AC system via an inverter. This invention relates to a power control method that smoothes the amount of power output from a solar cell while ensuring that the solar cell operates near its optimal operating voltage.

0002

[Prior art and its problems] In a solar power generation interconnection system that supplies power output from solar cells to the grid, the amount of power output from the solar cells depends on the amount of solar radiation and fluctuates rapidly due to changes in weather conditions. If this power is supplied directly to the grid, there is a risk of negative effects such as rapid fluctuations in the voltage and frequency of the grid. To solve this problem, systems have been used that use storage batteries to smooth the amount of power output from solar cells.

[0003] In such conventional solar power generation interconnection systems, the output power of the solar cells is adjusted between the solar cell voltage and the solar cell voltage so that rapid fluctuations in the output power of the solar cells do not have a direct adverse effect on the grid. Control was performed so that the amount of power calculated from the current, etc. and smoothed was the amount of power that the inverter supplied to the grid.

FIG. 3 is a configuration example showing a conventional control method for such a solar power generation interconnection system, and FIG. 4 is a diagram showing waveforms of various parts for explaining the operation. This will be explained below using figures.

FIG. 4A shows an example of variation in the output power amount of the solar cell 1 during a certain period of one day. A control circuit 8' calculates the amount of power generated by the solar cell 1 from the solar cell voltage obtained from the solar cell voltage detector 5' and the solar cell current obtained from the solar cell current detector 6, and generates a smoothed signal. Accordingly, the amount of power that the inverter 3 supplies to the grid 9 is controlled as shown in B of FIG.

That is, when the amount of power generated by the solar cell 1 suddenly decreases, the amount of power supplied from the inverter 3 to the grid 9 is kept constant by discharging from the storage battery 2, and conversely, the amount of power generated by the solar cell 1 decreases. In the case of a sudden increase, the amount of power generated by the solar cell 1 is smoothed by keeping the amount of power supplied from the inverter 3 to the grid 9 constant while charging the storage battery 2.

However, according to this method, charging and discharging of the storage battery 2 occurs, and in order to avoid overcharging and discharging, it is necessary to manage the charging and discharging of the storage battery 2, and in reality, it is necessary to consider the charging and discharging efficiency of the storage battery 2, etc. There is a drawback that the control of the inverter 3 becomes complicated. Further, the charging state of the storage battery 2 is not always fully charged, which may adversely affect the life of the storage battery 2. Further, in this system example, in order to effectively utilize the solar cell 1, another power converter may be used so that the solar cell 1 operates near the optimum operating voltage. In the figure, 4 is an interconnection reactor, 7 is a current detector for detecting the charging and discharging current of the storage battery, and 10 is a backflow prevention element of the solar cell.

[0008]

[Means for Solving the Problems] The present invention selects the number of storage battery cells so that the optimal operating voltage of the solar cell is close to the floating charging voltage of the storage battery, captures only the voltage of this storage battery, and performs floating charging. By controlling the power supplied to the grid by the inverter so that it converges with the voltage, the storage battery smoothes out sudden fluctuations in the output power of the solar cells, secures the amount of charge in the storage battery, and allows the solar cells to operate optimally. It is designed to operate near voltage.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a method of controlling a solar power generation interconnection system according to an embodiment of the present invention, and FIG. 2 is a diagram showing waveforms of various parts to explain the operation. This will be explained below using figures. In the figure, 1 is a solar cell, 2 is a storage battery connected in parallel with the solar cell 1, and the output of the solar cell 1 is smoothed by the storage battery 2, and connected to other power systems via an inverter 3 and a interconnection reactor 4. 9. 5 is a voltage detector for detecting the storage battery voltage; 8' is a control circuit that controls the amount of power that the inverter supplies to other systems;
10 is a backflow prevention element for a solar cell.

FIG. 2A shows an example of the variation in the amount of power of the solar cell 1 during a certain period of the day. If the amount of power generated by the solar cell 1 is less than the amount of power being supplied to the grid 9 by the inverter 3, the storage battery voltage will drop because power is being supplied from the storage battery 2 to the grid, and conversely the power generated by the solar cell 1 will be reduced. When the amount of electric power is greater than the amount of electric power being supplied to the grid by the inverter 3, the storage battery 2 is charged from the solar cell 1, so that the storage battery voltage increases and fluctuates as shown in C in FIG.

Therefore, the control circuit 8 detects the voltage of the storage battery 2 by the voltage detector 5 and controls the amount of power of the inverter 3 so that the voltage converges to the floating charging voltage. In other words, storage battery 2
If the voltage is lower than the floating charging voltage, inverter 3 reduces the amount of power feeding to grid 9, and if it is rising above the floating charging voltage, inverter 3 reduces the amount of power feeding to grid 9. Control is performed to increase the amount of electricity being used.

By operating the storage battery voltage so as to converge it to the floating charging voltage in this manner, it is possible to control the storage battery so that it always converges to a fully charged state and the solar cell to operate near the optimum operating voltage. Furthermore, by performing the above-described control for increasing and decreasing the amount of electric power at a low speed or smoothly, the amount of electric power can be changed as shown in B in FIG. 2. Thereby, sudden fluctuations in the output power of the solar cell 1 can be absorbed.

[0013]

[Effects of the Invention] As described above, according to the present invention, in a solar power generation interconnection system equipped with a storage battery, an inverter supplies power so that only the storage battery voltage is detected and this is converged to a floating charging voltage. By simply controlling the amount of power that is being used, it is possible to smooth the output power of the solar cell and converge the charge amount of the storage battery to a fully charged state, so there is no need to manage the charging and discharging of the storage battery, and the storage battery This has the advantage that there are few negative effects and the solar cell can always be operated near the optimum operating voltage.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a control method for a solar power generation interconnection system according to an embodiment of the present invention.

FIG. 2 is a diagram showing waveforms of various parts for explaining the operation of FIG. 1;

FIG. 3 is a configuration diagram showing a conventional control method for a solar power generation interconnection system.

FIG. 4 is a diagram showing waveforms of various parts for explaining the operation of FIG. 3;

[Explanation of symbols]

1. Solar cells 2 Storage battery 3 Inverter 4 Grid interconnection reactor 5 Voltage detector 8 Control circuit 9 Other power supply systems for power supply

Claims (1)

[Claims] Claim 1: In a solar power generation interconnection system in which power is supplied from a solar cell and a storage battery connected in parallel to another AC system via an inverter, the optimum operating voltage of the solar cell is determined by the floating voltage of the storage battery. A storage battery is selected so as to have a charging voltage, the voltage of the storage battery is detected, and if the storage battery voltage is lower than the floating charging voltage, the amount of power supplied from the inverter to other AC systems is reduced, and the voltage of the storage battery is floating. A control method for a solar power generation interconnection system, characterized in that control is performed to increase the amount of power supplied when the voltage is higher than the charging voltage.