JP2009169800A - Control device of photovoltaic power system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform stop control of a system with increased operation efficiency of the system without being affected by change in solar insolation intensity and generation voltage on a solar battery. <P>SOLUTION: The control device 6 stops power supply to a load 3 when a state where the electric generating capacity of the solar battery 1 is below a fixed level is continued for a stop confirmation time, in addition to cooperative control with the system 2. The control device 6 determines a promising amount of solar insolation in a current time period to the solar battery from the solar insolation intensity, and performs stop confirmation with a value of a setting part 7 in which the stop confirmation time is changed to this amount of solar insolation. The device determines an accumulated electric generating capacity in a time period backward by a fixed time from the current time of the solar battery, and changes the stop confirmation time based on the accumulated electric generating capacity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for a solar power generation system, and more particularly to stop control for stopping power supply from a power generation battery to a load when a power generation amount of the solar battery decreases.

  As shown in the configuration example of FIG. 3, the solar power generation system is connected to the power system 2 using the solar battery 1 as a power source, and supplies the generated power of the solar battery to the load 3, thereby effectively using natural energy. Plan. The interconnection device that links the photovoltaic power generation system to the power system includes an inverter (power converter) 4 that converts the generated power of the solar cell into AC power synchronized with the system (voltage / frequency / phase), and the inverter output. And an interconnection switch (electromagnetic contactor) 5 capable of connecting / disconnecting to / from the system, and a control device 6 having a computer configuration for controlling the operation / stop of the inverter 4 and the opening / closing control of the interconnection switch 5.

  As a power generation system that effectively uses natural energy, there are power generation facilities that use wind power generators or geothermal power sources as power sources, and there are systems that selectively combine these power generation facilities with power generation facilities that use solar cells as power sources. . In addition, these power generation systems include systems that are independent private power generation facilities without being connected to the power system, and there are systems that supply DC power controlled by a DC-DC power converter to a load instead of an inverter. .

  The start / stop control of the photovoltaic power generation system is determined based on the set solar radiation intensity and solar radiation intensity (solar radiation intensity x time), and at night or on cloudy / rainy days when power generation is expected to decrease, The power generation system is disconnected from the grid connection point and placed in a standby state to prevent a reduction in power generation efficiency of the system. That is, continuing the power generation and interconnection with the solar cell while the generated power is reduced continues to supply a loss necessary for the operation of the device (inverter or the like) from the system, resulting in a decrease in system efficiency.

  As a control method for efficiently operating a solar power generation system, there is only one combination of current and voltage that generates maximum power under conditions such as solar radiation output and panel temperature. In some cases, the output of the power generation system is controlled so that the solar cell always operates at the maximum power point (see, for example, Patent Document 1).

(A) of FIG. 4 shows the voltage-current characteristic of the solar cell, (b) shows the voltage-generated power characteristic of the solar cell, and the portion marked with X in the figure is the maximum power point. The control device to be controlled controls, for example, the output current (interconnection current) of the inverter.
JP-A-6-266453

The conventional stop sequence generates power when the generated power (or short-time power generation amount) of the solar cell falls below a preset value or when the generated voltage falls below a preset value for a certain period of time. It is determined that the stop is preferable, and the power generation facility is in a standby state.

  FIG. 5 shows an example of the start / stop sequence. The start-up sequence is when the system is in a stand-by state, and the power generation voltage of the solar cell rises with sunrise. When the voltage exceeds the optimum operating voltage, start check is started and this state continues for a certain period of time (start check time). When this happens, the system starts a grid operation, increases the output current to increase the power generation output, and starts the grid operation that keeps the output constant when the optimum operating voltage is reached. The optimum operating voltage can be sequentially switched and controlled so that the operation is always performed at the maximum power point (see FIG. 4) even when the generated power of the solar cell changes due to a change in solar radiation intensity or the like.

  The stop sequence starts stop confirmation when the generated voltage of the solar cell reaches a predetermined stop DC voltage, or when the generated power reaches the stop output power, and this state is only for a certain time (stop confirmation time). When it continues, it disconnects from the grid, stops the operation of the inverter, and enters a standby state. As the stop condition, the condition of the generated power is set to 5% or less of the rated output after 30 minutes have elapsed, the DC voltage condition is set to 225 V or less and 10 minutes have elapsed, and so on.

  If the stop confirmation time for this stop condition is set short, it will react to sudden fluctuations in solar radiation intensity, resulting in the system repeatedly starting and stopping, as seen from frequent switching of the interconnection switch and the power system It is not preferable in system operation such as the occurrence of disturbance. Conversely, if the stop confirmation time is set longer, useless operation continues and system efficiency is reduced.

  Similarly, if the generated power and DC voltage are set low as the stop confirmation start condition, the stop confirmation may be delayed and the power generation efficiency may be lowered. Conversely, if the generated power and DC voltage are set high, there is a power generation surplus. The power generation is stopped and the generated power cannot be used effectively.

  In particular, when the solar radiation intensity changes greatly or fluctuates in a short time, such as on a cloudy or rainy day, accurate stop control cannot be performed.

  The objective of this invention is providing the control apparatus of the solar power generation system which can perform stop control which raised the operation efficiency of the system, without being influenced by the change of the solar radiation intensity which a solar cell receives, or a generated voltage.

  In order to solve the above problems, the present invention provides a solar cell based on current solar radiation intensity and solar radiation amount received by the solar cell, current generated power and DC voltage of the solar cell, etc. The amount of power generation that can be expected in the current time zone is obtained, and the stop confirmation time is changed based on this amount of power generation.

(1) Solar power provided with a stop sequence for stopping power supply from a power generation system using the solar cell as a power source when a state where the power generation amount of the solar cell is below a certain level continues for a stop confirmation time In the control device of the power generation system,
The present invention is characterized by comprising stop control means for obtaining a power generation amount that can be expected from the solar cell in the current time zone, and changing the stop confirmation time based on the power generation amount.

(2) Solar light with a stop sequence for stopping power supply from the power generation system using the solar cell as a power source when the state where the power generation amount of the solar cell is below a certain level continues for the stop confirmation time In the control device of the power generation system,
Calculate and store the accumulated power generation amount in a time zone that is a certain time retroactive from the present time of the solar cell, and the stop confirmation time based on the cumulative power generation amount when the solar cell power generation amount falls below a certain level It is characterized by comprising stop control means for changing.

(3) When operating the power supply from the solar cell to the load at the maximum power point determined from the combination of the output current and voltage of the solar cell,
The stop control means obtains a power generation amount or a cumulative power generation amount of the solar cell at the maximum power point, and changes the stop confirmation time based on the power generation amount or the cumulative power generation amount.

  As described above, according to the present invention, for the stop control of the system, the amount of power generation that can be expected in the current time zone is obtained for the solar cell, and the stop confirmation time is changed based on this power generation amount. Accurate stop control can always be performed without being affected by changes in the intensity of solar radiation and generated voltage.

  Thereby, useless driving | operation when there is little generated electric power can be suppressed, and the operating efficiency of an apparatus rises. In addition, it is possible to prevent a standby state from being accidentally caused by weather fluctuations. Furthermore, by determining the elapsed time to stop based on the cumulative amount of power generated for a certain elapsed time in the past, it is the same as above even if the generated power is not expected, such as on a cloudy or rainy day, regardless of sunny weather The effect is obtained.

(Embodiment 1)
FIG. 1 is a main part configuration diagram of a photovoltaic power generation system showing the present embodiment, and parts equivalent to those in FIG. 3 are denoted by the same reference numerals.

  The control device 6 incorporates the power supply operation and start / stop sequence of the photovoltaic power generation facility, and the stop confirmation time of the stop sequence is given as a set value according to the current amount of solar radiation received by the solar cell. This set value is set in the stop confirmation time setting unit 7 using table data or the like.

  The stop confirmation time data shown in the setting unit 7 indicates a case where the time from when the amount of solar radiation falls below the stop level to when the stop control is executed is scheduled on a daily time basis in fine weather. In other words, during sunny days, the amount of solar radiation is high only during the daytime hours, and the amount of solar radiation in the early morning and at night is low. Change according to the amount of solar radiation.

  In the schedule shown in the setting unit 7 in the figure, the daytime time zone in which a large amount of solar radiation can be expected is T1 with a long stop confirmation time, and the time zone in which the solar radiation amount cannot be expected is T2 with a short stop confirmation time.

  To control the stop confirmation time, in order to obtain the amount of solar radiation in the current time zone, the measured value of the solar radiation intensity meter 8 is taken into the control device 6, and the control device 6 calculates the average value of the solar radiation intensity per unit time, etc. The amount of solar radiation in the current time zone is obtained every fixed time (10 minutes, etc.), the stop confirmation time set in advance in the setting unit 7 is read according to the amount of solar radiation, and the power generation system stop control is based on this stop confirmation time Determine whether or not.

  In addition, although the case where a stop confirmation time is determined according to the amount of solar radiation is shown in FIG. It is also possible to obtain the amount of power generation that can be expected in step 1, and determine the stop confirmation time based on this amount of power generation. Furthermore, it is preferable to correct the amount of power generation that can be expected based on the current panel temperature or the like.

(Embodiment 2)
FIG. 2 is a configuration diagram of a main part of the photovoltaic power generation system showing the present embodiment, and a part different from FIG. 1 is a time period that goes back a certain time in the past from the time when it falls below a predetermined stop level as a stop condition. This is the stop confirmation time based on the accumulated power generation at In addition, the control device 6 calculates and stores and updates the accumulated power generation amount in a fixed time unit from the direct current voltage (power generation voltage) and the direct current (power generation current) output from the solar cell 1 to the inverter 4, so The stop confirmation time is determined based on the accumulated power generation amount at the present time from when the power generation amount of the battery falls below a predetermined stop level. This determination may be a stop confirmation time proportional to the accumulated power generation amount, or the stop confirmation time may be changed according to history information indicating whether the power generation amount from the present time is increasing or decreasing.

  Therefore, in this embodiment, since the power generation amount moves in proportion to the solar radiation intensity, the stop confirmation time set by the setting unit 7 is determined based on the accumulated power generation amount per unit time. That is, the stop confirmation time is extended if the accumulated power generation amount at the present time is large, but if the accumulated power generation amount is small, it is determined that the power generation amount cannot be expected in the future, and the stop confirmation time is shortened to prevent useless operation.

  In this embodiment, since the stop confirmation time is determined based on the accumulated power generation amount, it is possible to always confirm stop properly even when the amount of solar radiation changes greatly in the daytime time zone such as cloudy or rainy days.

  In addition, although the embodiment until the above shows the case where it applies to the photovoltaic power generation system linked with an electric power system, it is a system which makes it an independent private power generation equipment without being linked with an electric power system, a wind generator, and geothermal power generation It can be applied to a system that is selectively combined with power generation equipment that uses a machine as a power source to obtain the same effect.

  In addition, when operating the power supply from the solar cell to the load at the maximum power point determined from the combination of the output current and voltage of the solar cell, the power generation amount or cumulative power generation amount of the solar cell at this maximum power point is obtained, and this The stop confirmation time can also be changed based on the power generation amount or the accumulated power generation amount.

The principal part block diagram of the solar energy power generation system which shows Embodiment 1 of this invention. The principal part block diagram of the solar energy power generation system which shows Embodiment 2 of this invention. The structural example of a solar power generation system. Solar cell voltage-current / generated power characteristics. An example of a conventional start / stop sequence.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Electric power system 3 Load 4 Inverter (power converter)
5 Linkage switch (electromagnetic contactor)
6 Control device 7 Stop confirmation time setting unit 8 Solar radiation intensity meter

Claims (3)

A solar power generation system having a stop sequence for stopping power supply to a load from a power generation system using the solar battery as a power source when a state where the power generation amount of the solar battery is lower than a certain level continues for a stop confirmation time. In the control device,
A control device for a photovoltaic power generation system, comprising stop control means for obtaining a power generation amount that can be expected from a solar cell in a current time zone and changing the stop confirmation time based on the power generation amount. A solar power generation system having a stop sequence for stopping power supply to a load from a power generation system using the solar battery as a power source when a state where the power generation amount of the solar battery is lower than a certain level continues for a stop confirmation time. In the control device,
Calculate and store the accumulated power generation amount in a time zone that is a certain time retroactive from the present time of the solar cell, and the stop confirmation time based on the cumulative power generation amount when the solar cell power generation amount falls below a certain level A control device for a photovoltaic power generation system, characterized by comprising stop control means for changing the power. When operating the power supply from the solar cell to the load at the maximum power point determined by the combination of the output current and voltage of the solar cell,
The stop control means obtains a power generation amount or a cumulative power generation amount of a solar cell at the maximum power point, and changes the stop confirmation time based on the power generation amount or the cumulative power generation amount. The control apparatus of the solar power generation system of 2.

Images