JP6503155B2 - Output fluctuation suppression system for distributed power supply - Google Patents

Description

  The embodiment of the present invention relates to a distributed power supply output fluctuation suppression system capable of suppressing the output fluctuation of the distributed power supply and reducing the voltage fluctuation and the frequency fluctuation to the electric power system.

  In recent years, interest in the environment and energy has increased, and the introduction of distributed power sources such as solar power generation and wind power generation has been promoted. On the other hand, compared with large-scale centralized power sources such as thermal power plants and nuclear power plants where distributed power sources are widely used in the past, the output fluctuation is large, especially distributed power sources using natural energy, changes in natural conditions Because the generated power fluctuates due to this, when the introduction amount of the distributed power source increases, there is a possibility that adverse effects such as frequency fluctuation and voltage fluctuation may be exerted on the power system connected to it.

  As one of the measures, as described in Patent Document 1 and Patent Document 2, a chargeable and dischargeable power storage device such as a lithium ion battery is provided side by side with a dispersed power supply to suppress fluctuation of output voltage to the power system. Technology has been proposed. In these technologies, the storage device is provided with a control unit for controlling its charge and discharge, and based on the generated power α of the dispersed power source and the difference α-β of its moving average β, the control unit charges and discharges the storage device. By outputting the command, the output fluctuation of the distributed power supply is absorbed by the power storage device, and the output fluctuation from the distributed power supply to the interconnection system is suppressed.

  That is, the control unit provided in the storage device measures the output of the distributed power supply to obtain the moving average β of the distributed power supply output in unit time, and when the generated power α of the distributed power supply exceeds the moving average β, The surplus is charged in the storage device, and when the generated power of the distributed power supply falls below the moving average β, the shortage is discharged from the storage device to smooth the power fluctuation due to the distributed power supply.

Patent No. 4353446 JP, 2013-038960, A

  Fluctuations in output power in photovoltaic power generation widely adopted as distributed power sources depend on weather conditions, but when solar light shielding objects such as clouds cross between the sun and solar cells, 50% or more of the rated power in a short time Fluctuations occur. Since the fluctuation time largely depends on the movement of the shield such as the wind speed, the aspect ratio of the solar cell panel, and the wind direction, a control response commensurate with that is required. However, in the prior art, the charge / discharge operation of the power storage device that absorbs the output fluctuation of the distributed power supply is controlled by the command from the charge / discharge control device calculated based on the generated power α and its moving average β. There is a limit to the speed, and it is difficult to follow weather conditions such as the wind direction which changes instantaneously. As a result, in the prior art, there is a disadvantage that the charge / discharge command for the fluctuation of the generated power is delayed and the fluctuation of the grid power occurs.

  As described above, the distributed power source using natural energy such as a solar panel has a large output fluctuation due to factors such as weather conditions. When a distributed power supply exceeding the allowable value of the transmission and distribution system is connected to the same area, the voltage and frequency of the system fluctuate, and it is necessary to suppress the output fluctuation of the distributed power supply. However, suppressing the output of the distributed power supply will lower the utilization factor of natural energy, so by performing Maximum Power Point Tracking (MPPT), the distributed power supply will always generate power at the maximum efficiency. It is necessary to maintain and control the output fluctuation to the grid.

  Therefore, for example, in the related art of Patent Document 1, maximum power point tracking control can be performed using a grid-connected inverter provided on the output side of the power storage device. However, if maximum power point tracking control is performed using a grid-connected inverter, the system output fluctuates due to power fluctuations derived from maximum power point tracking control that is not related to moving average β, so a command from the control device It is impossible to effectively suppress the output fluctuation even by controlling the charge and discharge of the power storage device.

  Embodiments of the present invention are proposed to solve the problems of the prior art as described above. An object of an embodiment of the present invention is to provide an output fluctuation suppressing system of a distributed power supply which is excellent in charge / discharge response of a power storage device and does not generate fluctuation of grid power even when sudden fluctuation of solar generated power occurs. It is a thing.

  Another object of the embodiment of the present invention is to provide a distributed power supply output fluctuation suppression system in which fluctuation of grid power is effectively suppressed even when maximum power point tracking control is performed.

An output fluctuation suppression system for a distributed power supply according to an embodiment of the present invention is characterized by having the following configuration.
(1) Distributed power supply which is a solar power generation device that outputs DC power.
(2) A first power conversion device that is a DC-DC converter that performs maximum power point tracking control of the solar power generation device, and outputs DC power from the distributed power supply to a DC main circuit.
(3) The second power conversion device that outputs AC power from the DC main circuit to a power supply system.
(4) the second channel output controller for controlling the output of the AC power to the power system from the power conversion device.
(5) A fluctuation suppression calculation device that calculates an output command to the grid output control device based on the generated power of the distributed power supply.
(6) A storage element connected to the DC main circuit and having a characteristic of generating an open end voltage according to a charge state.
Furthermore, the storage element has the following configuration.
(7) and the voltage of the DC main circuit, by performing the charging and discharging based on the battery voltage of the electric storage device, is output from the generated power and the second power converter from the first power converter It is configured to absorb power fluctuations on the DC main circuit based on the AC power difference.
(8) The fluctuation suppression arithmetic device is provided with an input unit for a change rate limit value, and the fluctuation suppression arithmetic device is configured to input the generated change rate restriction value to the second power converter for the generated power. Limit the rate of change of the output voltage of

FIG. 1 is a block diagram showing the configuration of a first embodiment. The block diagram which shows the structure of 2nd Embodiment. The graph which shows an example of the charging rate of a secondary battery, and a voltage characteristic. The graph which shows the setting example of the correction arithmetic unit in a 2nd embodiment. The block diagram which shows the structure of 3rd Embodiment. The graph which shows operation of change rate restriction in a 3rd embodiment. The block diagram which shows the structure of 4th Embodiment.

[1. First embodiment]
(1) Configuration of the embodiment

  As shown in FIG. 1, the distributed power supply system according to the present embodiment includes a distributed power supply 1 such as a solar power generation device, a first power converter 2 connected to the output side of the distributed power supply 1, and A DC main circuit 3 connected to the output side of the power conversion device 2 and receiving power supply from the distributed power supply 1 is provided. As the first power conversion device 2, the output of the distributed power supply 1 is converted into the control voltage range of the second power conversion device 8, and when the distributed power 1 is a solar power generation device, Using a DC-DC converter capable of performing maximum power point tracking control.

  The DC main circuit 3 is provided with a power meter 4 for measuring the generated power α supplied from the distributed power supply 1 to the DC main circuit 3. The output unit of the power meter 4 is a fluctuation suppression arithmetic device 5 (hereinafter referred to as an arithmetic device It is connected to the input section of 5). The output unit of the arithmetic unit 5 is connected to the system output control unit 6 (hereinafter referred to as the control unit 6), and the output unit of the control unit 6 is connected to the second power conversion device 8. The second power conversion device 8 is generally called a grid-connected inverter, and its input part is connected to the DC main circuit 3 and its output part is connected to the power system 11. The power system 11 is connected to a power sensor 7 that measures system power γ.

The arithmetic unit 5 receives the generated power α of the first power conversion device 2 measured by the power meter 4 and performs calculation to suppress the power fluctuation based on the generated power α, and the result is taken as the system output command θ It outputs to the control device 6. In this case, in the arithmetic device 5, for example, the suppression calculation of the change rate can be performed by any one or a plurality of combinations of the following parameters.
(1) Change rate limit: Change rate limit value (% / hour)
(2) Moving average: average sampling number (3) first-order lag filter: time constant

  These parameters may be specified from outside the operation device 5 or may be incorporated into an operation expression preset in the operation device 5. This parameter is not limited to these (1) to (3), and can be set appropriately according to the conditions required by the power system 11 side.

  The control device 6 makes the output power of the second power conversion device 8 equal to the system output command θ based on the system output command θ from the arithmetic device 5 and the system power γ obtained by the power sensor 7. The drive signal is generated to control the output of the second power conversion device 8. That is, the grid output command θ is the output target value of the second power conversion device 8, and the driving amount from the control device 6 is the difference correction amount between the grid power γ and the grid output command θ that is the output target value. The control device 6 acts to eliminate the difference between the grid power γ and the grid output command θ, which is the output target value, by feedback control such as PID calculation.

  A storage element 10 is connected to the DC main circuit 3 in parallel with the DC main circuit capacitor 9. Only the storage element 10 may be provided in the DC main circuit 3 without providing the capacitor 9. As the storage element 10, a secondary battery having a characteristic of generating an open end voltage (OCV) according to a charge state, for example, a lithium ion battery, a lead battery, a nickel hydrogen battery or the like is used. The storage element 10 having such characteristics can perform charging and discharging based on the voltage fluctuation of the DC main circuit 3 and its own battery voltage without providing a control device for controlling the charging and discharging.

(2) Operation of the Embodiment In the present embodiment having the configuration as described above, the voltage of the DC main circuit 3 tends to fluctuate if a difference occurs between the generated power α and the grid output command θ. If the voltage of the DC main circuit 3 is higher than its own voltage, it is charged, and if the voltage of the DC main circuit 3 is lower than its own voltage, the DC main circuit 3 can be in a certain range using the discharge characteristics. Keep it That is, when a difference occurs between the generated power α and the system output command θ, the storage element 10 receives the voltage fluctuation of the DC main circuit 3 and absorbs the difference.

  According to the present embodiment, the DC main circuit is realized by utilizing the charge rate-voltage characteristic of the storage element 10 itself without providing the charge / discharge control device of the storage element 10 as in the prior art in the DC main circuit 3. The voltage fluctuation of 3 can be suppressed. As a result, depending on the type and capacity of the storage element 10, even if the rapid fluctuation of the distributed power supply 1 occurs, the difference is absorbed and the system output is not fluctuated.

  In particular, in the present embodiment, a DC-DC converter capable of maximum power point tracking control is used for the first power conversion device 2, but even when output fluctuation occurs due to the maximum power point tracking control, the second power converter It is not necessary to change the output of the power conversion device 8, and the storage element 10 can absorb the difference in power.

(3) Effects of the embodiment The utilization of natural energy such as solar cells is rapidly spreading from the viewpoint of CO ₂ reduction etc., but the power generation output is influenced by weather conditions etc. regardless of the power supply and demand. fluctuate. In particular, if many or large-scale distributed power supplies are concentrated in the same area, the voltage and frequency maintenance capability of the existing power transmission and distribution system may be exceeded. On the other hand, according to the present embodiment, it is possible to suppress the output fluctuation of the distributed power supply 1 within the allowable value of the power system 11, thereby obtaining a distributed power supply system with less disturbance to the voltage and frequency of the power system 11. There are effects that can be

  In particular, since a device for controlling charging and discharging of the storage element 10 is not necessary, simplification of the configuration of the entire system can be achieved, and the passive constant operation of the storage element 10 causes rapid fluctuation of the distributed power supply 1. In the case where a problem occurs, the voltage fluctuation can be suppressed quickly.

  In addition, although local smart grids predict the power generated by distributed power sources such as solar cells according to seasons and weather conditions, they can not predict short-term fluctuations due to disturbances such as clouds. However, in the present embodiment, when the moving average is used as the fluctuation suppressing operation by the arithmetic device 5, using the moving average for the change rate suppressing operation outputs the generated power with the sudden change due to the disturbance to the power system 11. Can.

  When a DC-DC converter that performs maximum power point tracking control with respect to distributed power supply 1 is used as first power conversion device 2, voltage fluctuations of DC main circuit 3 associated with maximum power point tracking control are also stored. It is possible to absorb by the element 10, and it is possible to effectively suppress the influence of the fluctuation of the output power of the distributed power supply 1 on the power system 11.

[2. Second embodiment]
A second embodiment of the present invention will be described according to FIG. In this embodiment, in addition to the configuration of the first embodiment, a voltmeter 12 for measuring the voltage of the storage element 10, a correction operation device 13 for calculating a correction output based on the measured voltage of the storage element 10, and a power meter An adder 14 is provided to correct the generated power α obtained in 4 in accordance with the output result of the correction operation device 13. That is, the correction arithmetic unit 13 outputs a correction value for the generated power α so as to keep the voltage of the DC main circuit 3 within a fixed range or a fixed value, and this correction value is added to the generated power α by the adder 14 And is input to the arithmetic unit 5.

  Hereinafter, the operation of the correction arithmetic device 13 will be described based on FIGS. 3 and 4. FIG. 3 shows an example of the charging rate and voltage characteristics of a general secondary battery. The storage element 10, which is a secondary battery, has a characteristic that the voltage rises when the charge rate rises, and conversely, the voltage drops when the power reception rate falls. When the charge rate exceeds 100%, overcharge occurs, and when the charge rate is less than 0%, overdischarge occurs. If the charge ratio changes in the process of the storage element 10 absorbing the difference between the generated power α and the system output command θ, an overcharge or an overdischarge may occur. If overcharging or overdischarging occurs, heat generation and performance deterioration of the storage element 10 occur, and therefore it is necessary to maintain the charging rate within the normal use range for battery protection. Generally, since the charging rate is difficult to measure, in the present embodiment, overcharging and overdischarging are prevented by maintaining the battery voltage within a certain range.

  In addition, if the voltage of DC main circuit 3 deviates from the range of the input voltage at which second power conversion device 8 can operate properly, distortion occurs in the output waveform to power system 11, or the conversion efficiency is lowered. Therefore, it is necessary to keep the voltage of the DC main circuit 3 within a certain range. Therefore, in the present embodiment, the voltmeter 12 and the correction operation device 13 are added to the configuration of the first embodiment.

  The voltmeter 12 measures the voltage of the storage element 10, and the voltage of the storage element 10 is also equivalent to the voltage of the DC main circuit 3. FIG. 4 shows an example of the correction operation for the generated power α. In the graph of FIG. 4, the horizontal axis indicates the voltage measured by the voltmeter 12, and the vertical axis indicates the correction amount. In this graph, the correction characteristic (the relationship between the measured voltage and the correction amount) can be arbitrarily set. In this example, the correction characteristics are three straight lines of voltage sections A, B, and C, and the voltage of correction amount = 0 is the rated voltage of the DC main circuit 3. In the voltage section B, when the voltage measured by the voltmeter 12 exceeds the rated voltage, the correction amount increases, and the system output command θ of the second power conversion device 8 is increased. Therefore, the storage element 10 is discharged to compensate for the increase, and the voltage acts to approach the rated voltage.

  That is, when the voltage measured by the voltmeter 12 falls below the rated voltage, the storage element 10 is charged to absorb the decrease, and the voltage acts to approach the rated voltage. The voltage section B is a range of the input voltage in which the second power conversion device 8 can operate properly, and within the range of this voltage, a gentle correction amount is used. The voltage section A is intended to prevent overdischarge, and is a correction amount larger than that of the voltage section B. The voltage section C is for the purpose of preventing overcharge, and has a correction amount larger than that of the voltage section B.

  In the present embodiment having such a configuration, it is possible to keep the charging rate of the storage element 10 in the normal use range, and it is possible to effectively prevent the overcharge and the overdischarge. And there is no risk of performance deterioration.

  In the embodiment, the correction value from the correction arithmetic device 13 is added to the generated power α by the adder 14 to correct the generated power α, but without providing the adder 14, the correction operation is performed. It is also possible to correct the system output command β by directly inputting the correction amount from the device 13 into the arithmetic device 5. However, as in the present embodiment, by adding the correction amount before the arithmetic device 5, the correction amount from the correction arithmetic device 13 can also be a target of fluctuation suppression. In that case, since the purpose of the present embodiment is to suppress the fluctuation of the output to the power system 11, the fluctuation amount is suppressed by the arithmetic device 5 with the correction amount regarding the charge / discharge characteristics of the storage element 10 also as a fluctuation element Is advantageous because it is possible.

[3. Third embodiment]
A third embodiment of the present invention will be described with reference to FIGS. 5 and 6. In this embodiment, in addition to the configuration of the second embodiment, a variation suppressing operation of the system output command θ with respect to a variation of the generated power α as a variation suppressing operation in the arithmetic device 5 is suppressed within a predetermined change width at a predetermined time Δt It is characterized by using a rate limiting operation. Therefore, the calculation unit 5 is provided with the change rate limit value input unit 15. As described above, instead of providing the change rate limit value input unit 15, the change rate limit value may be incorporated in advance in the arithmetic expression set in the arithmetic device 5.

  In the present embodiment having such a configuration, as shown in FIG. 6, when the generated power α input to the arithmetic device 5 changes largely as shown by the dotted line in the figure, the system output command β takes a fixed time Δt. The rate of change limiting operation is performed so as to change stepwise in each step. The limitation calculation of the change rate is calculated at a constant time Δt, and the output fluctuation range by one calculation when the input generated power α changes stepwise is set by the input unit 15 It is limited to the change width which made the change rate limit value the upper limit. This calculation process is repeatedly performed for each fixed time Δt, and the output power from the second power conversion device 8 continues to change gently until the input and the output match.

  In the present embodiment, even when the amount of power generation by natural energy such as sunlight changes rapidly, the command value to the control device 6 is suppressed within a fixed change width at a fixed time Δt. As a result, for example, in the case where a large number of distributed power sources 1 are installed in the same area due to the spread of distributed power sources 1 such as solar cells, the voltage and frequency of the power system fluctuated greatly when the power generation capacity in the same area fluctuated simultaneously. Even in the present embodiment, since the change rate is limited by the arithmetic device 5, the output from the second power conversion device 8 can be suppressed within the allowable fluctuation range of the power system.

[4. Fourth embodiment]
A fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is characterized in that an output command value of a system output input from the outside of the system is added to the arithmetic processing of the arithmetic device 5 in the third embodiment. Therefore, in the present embodiment, the adder 14 is provided with the input unit 16 for the output command value from the outside. The output command value input unit 16 can also be provided directly to the arithmetic device 5.

  The present embodiment having such a configuration has the following effects. That is, when a plurality of distributed power sources 1 are disposed in a wide area, when the output of each distributed power source 1 is remotely controlled from a centralized control center or the like based on the balance of power supply and demand, the generated power of each distributed power source 1 There is a difference between the and the command value from the center. In particular, when the distributed power supply 1 is a solar power generation device, the power generated by each distributed power supply 1 may differ greatly due to the influence of shade etc. It is not preferable to apply it uniformly.

  In this embodiment, since the storage element 10 absorbs the difference between the generated power of the distributed power source 1 and the command value from the center, there is no need to limit or control the amount of power generation on the center side, and the range of the capacity of the storage element 10 If it is inside, the output command value of the system output can be freely set from the center.

[Other embodiments]
Although some embodiments of the present embodiment have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.

1: Distributed power supply 2: First power converter 3: DC main circuit 4: Power meter 5: Fluctuation suppression arithmetic unit 6: System output control unit 7: Power sensor 8: Second power converter 9: DC main circuit Capacitor 10: storage element 11: electric power system 12: voltmeter 13: correction arithmetic device 14: adder 15: change rate limit value input unit 16: output command value input unit

Claims (4)

Distributed power supply, which is a solar power generation device that outputs DC power,
A first power conversion device that performs maximum power point tracking control of the solar power generation device, and outputs DC power from the distributed power supply to a DC main circuit;
A second power converter for outputting AC power from the DC main circuit to a power supply system;
And the system output control device which controls the output of the AC power to the power system from the second power converter,
A fluctuation suppression calculation device that calculates an output command to the grid output control device based on the generated power of the distributed power supply;
A storage element connected to the DC main circuit and having a characteristic of generating a release end voltage according to a charge state;
The storage element performs charge and discharge based on the voltage of the DC main circuit and the battery voltage of the storage element, thereby generating power generated from the first power conversion device and outputting from the second power conversion device Configured to absorb power fluctuations on the DC main circuit based on the difference in AC power ,
The fluctuation suppression arithmetic device is provided with an input unit for a change rate limit value, and the fluctuation suppression arithmetic device outputs an output voltage from the second power conversion device to the generated power based on the inputted change rate restriction value. What is claimed is: 1. A distributed power supply output fluctuation suppression system characterized in that the rate of change is limited . It is a fluctuation control system of distributed power supply according to claim 1,
A voltmeter for detecting the voltage of the DC main circuit;
An output fluctuation suppression system for a distributed power supply, comprising: a correction operation device that adds a correction according to a voltage of a DC main circuit detected by the voltmeter to generated power of the distributed power supply. The fluctuation suppression system of distributed power supply according to claim 1 or claim 2 , wherein
Said fluctuation suppressing arithmetic unit, based on the moving average of the input electric power generated, the output fluctuation suppression of distributed power, characterized by calculating the line output command for controlling the output voltage from the second power converter system. The distributed power supply output fluctuation suppression system according to any one of claims 1 to 3 ,
An output command value input unit for inputting an output command value of a system output from the outside of the system, and the fluctuation suppression arithmetic device performs the fluctuation suppression calculation based on the input output command value and the generated power from the distributed power supply. An output fluctuation suppression system for distributed power supply characterized by

Images