JP2020137292A - Power conversion system - Google Patents

Abstract

To provide a power conversion system capable of securely compensating for power fluctuation of a renewable energy power generation device.SOLUTION: A power conversion system (500) comprising a first power conversion device (101) for performing power conversion on power from a renewable energy power generation device (104) and a second power conversion device (102) for performing power conversion on power from a power storage device (105) controls the first power conversion device on the basis of information acquired through first communication means (107) and controls the second power conversion device so as to compensate for fluctuation in power generated by the renewable energy power generation device to output the first and second power conversion devices' output power to an external system (103). The power conversion system comprises an autonomous control unit (503) for individually controlling the second power conversion device. On the basis of information acquired through second communication means (502) having communication delay smaller than that of the first communication means, the autonomous control unit controls the second power conversion device so as to compensate for fluctuation in power generated by the renewable energy power generation device.SELECTED DRAWING: Figure 5

Description

The present invention relates to a power conversion system that links a renewable energy power generation device and a power system.

In recent years, renewable energy power generation facilities using wind power and solar power as energy sources have become widespread. The renewable energy power generation facility is connected to the power system via a power conversion system, and includes one or more power generation devices depending on the amount of power that can be supplied to the power system.

The technique described in Patent Document 1 is known as a prior art relating to a renewable energy power generation facility including a plurality of power generation devices.

In the technique described in Patent Document 1, the total output power of a plurality of wind power generators is detected, and the central control device controls each of the plurality of wind power generators based on the total output power.

Further, since the renewable energy power generation device uses natural energy, the amount of power generation fluctuates. As a result, if the fluctuation speed of the output power of the power conversion system for grid interconnection becomes large, the power system may become unstable. On the other hand, the prior art described in Patent Document 2 is known.

In the technique described in Patent Document 2, the fluctuation rate of the output power of the renewable energy power source is suppressed by the compensating power from the power storage device.

U.S. Pat. No. 8823193 Japanese Unexamined Patent Publication No. 2010-22122

When the renewable energy power generation facility and the power storage device are controlled by the central control device according to the above-mentioned prior art, the control operation is delayed with respect to the actual power fluctuation, so that the power fluctuation may not be sufficiently suppressed.

Therefore, the present invention provides a power conversion system capable of reliably compensating for power fluctuations in a renewable energy power generation device.

In order to solve the above problems, the power conversion system according to the present invention includes a first power conversion device that converts power from a renewable energy power generation device and a second power conversion device that converts power from a power storage device. , A central control unit that controls the first power conversion device and the second power conversion device, a first communication means that transmits information between the first power conversion device, the second power conversion device, and the central control unit. The central control unit controls the first power conversion device based on the information obtained via the first communication means, and compensates for the fluctuation of the generated power of the renewable energy power generation device. It controls the power conversion device and outputs the output power of the first power conversion device and the second power conversion device to the external system. The autonomous control unit that individually controls the second power conversion device and the first communication. The communication delay is smaller than that of the means, and the second communication means for transmitting information between the power conversion system and the autonomous control unit is provided, and the autonomous control unit is based on the information obtained via the second communication means. , The second power conversion device is controlled so as to compensate for the fluctuation of the generated power of the renewable energy power generation device.

According to the present invention, it is possible to reliably compensate for power fluctuations in a renewable energy power generation device.

Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

The configuration of the power conversion system connected to the power system is shown. The data transmission in the first communication means is shown. The control system in the power conversion system of FIG. 1 is shown. The operation of the power conversion system of FIG. 1 is shown. The configuration of the power conversion system according to the first embodiment is shown. It is a functional block diagram which shows the structure of the control system in Example 1. FIG. The operation of the power conversion system of the first embodiment is shown. The configuration of the power conversion system according to the second embodiment is shown. It is a functional block diagram which shows the structure of the control system in Example 2. FIG. The operation of the power conversion system of the second embodiment is shown.

Before explaining the embodiment of the present invention, first, the power conversion system according to the prior art will be described. The configuration of the power conversion system and its control system described below (FIGS. 1 to 3) is also applied to the examples of the present invention described later.

FIG. 1 shows the configuration of a power conversion system connected to a power system.

As shown in FIG. 1, the power conversion system 100 includes a plurality of (two units in FIG. 1) first power conversion devices 101 and a plurality of (two units in FIG. 1) second power conversion devices 102. The plurality of first power conversion devices 101 are connected in parallel on the output side. The outputs of the plurality of first power conversion devices 101 connected in parallel and multiplex in this way are connected to the external power system 103. Further, the plurality of second power conversion devices 102 are connected in parallel on the output side. The outputs of the plurality of second power conversion devices 102 connected in parallel and multiplex in this way are connected to the power system 103.

The electric power system 103 is composed of a power generation facility including a normal generator made of a rotary electric machine, a facility that consumes electric power, and a power transmission / distribution network to which these facilities are connected.

The first power conversion device 101 includes a main circuit that converts DC power input from the renewable energy power generation device 104 (RE) into AC power (P _RE1 , _{PRE 2} ). This main circuit is a DC / AC converter circuit (inverter circuit) that converts DC power into AC power by turning on / off the semiconductor switching element. The main circuit of the first power conversion device 101 is controlled by the control unit 108. That is, the control unit 108 controls the on / off of the semiconductor switching element of the main circuit according to the output power command value. As a result, the AC power output by the first power conversion device 101 is controlled to be the output power command value.

The renewable energy power generation device 104 (RE) is, for example, a solar power generation device or a wind power generation device. When the renewable energy power generation device outputs AC power, the output power is converted into DC power by an AC / DC converter and then input to the first power conversion device 101.

The second power conversion device 102 includes a main circuit that converts the DC power input from the power storage device 105 into AC power (P _BAT1 , P _BAT2 ). This main circuit is a DC / AC converter circuit (inverter circuit) like the first power conversion device 101. The main circuit of the second power conversion device 102 is controlled by the control unit 108. That is, the control unit 108 controls on / off (switching) of the semiconductor switching element of the main circuit according to the output power command value. As a result, the AC power output by the second power conversion device 102 is controlled so as to be the output power command value.

The power storage device 105 is, for example, a secondary battery or a capacitor.

The plurality of first power conversion devices 101 output the AC power 109 (P _RE ), which is the _sum of the AC powers _PRE1 and _PRE2 output by each of the first power conversion devices 101, to the power system 103. Further, the plurality of second power conversion devices 102 output the AC power 110 (P _BAT ), which is the _{sum of} the AC powers P _BAT1 and P _BAT2 output by each of the second power conversion devices 102, to the power system 103.

A central control unit 106 is provided to control the plurality of first power conversion devices 101 and the plurality of second power conversion devices 102. The central control unit 106 collects information on the operating state (for example, output power) from the plurality of first power conversion devices 101 and the plurality of second power conversion devices 102 via the first communication means 107. Note that this information may be acquired from the control unit 108 included in each power conversion device.

The sensor 700 detects the output power 109 ( _PRE ) of the plurality of first power converters 101. Central control unit 106, the sensor 700, via the first communication means 107, for collecting information about the output power _{P RE.}

The central control unit 106 creates and creates an output power command value of each power conversion device based on the information collected from the plurality of first power conversion devices 101, the plurality of second power conversion devices 102, and the sensor 700. The output power command value is sent to the control unit 108 of each power conversion device via the first communication means 107. The first communication means 107 may be wired or wireless.

The output power _PRE of the plurality of first power conversion devices 101 has a large power fluctuation amount according to natural conditions such as weather due to the intermittent power generation characteristics of the renewable energy power generation device 104 (RE). Such large power fluctuations can destabilize the operation of the generator in the power system 103. Therefore, the power conversion system 100 is required to have the power fluctuation rate of the total output power 111 ( _PSYS ) of the power conversion system 100, that is, the power fluctuation speed within the specified value.

FIG. 2 shows data transmission in the first communication means 107.

Each control unit (M control units # 1 to # M (“108” in FIG. 1) and a central control unit (“106” in FIG. 1)) connected to the first communication means 107 are designated. During the time, the information of the self-control unit is authorized to update all other control units. The authority to update information is handed over to other control units at predetermined time intervals and in a predetermined order. In FIG. 2, the authority to update information is handed over in the order of control unit # 1, control unit # 2, ..., control unit #M, and central control unit during one update cycle of the first communication means.

Such an operation continues between all control units (central control unit and a plurality of control units) connected to each other via the first communication means. Therefore, the more control units are connected, the longer it takes to complete one cycle of data update. This results in a communication delay time.

FIG. 3 shows a control system including a control unit 108 and a central control unit 106 in the power conversion system 100 of FIG.

The central control unit 106 has a power smoothing control unit 302 that smoothes fluctuations in the generated power of the renewable energy power generation device 104. The central control unit 106 collects the output power information _PRE1 and _PRE2 of the plurality of first power conversion devices 101 via the first communication means 107. Central control unit 106 outputs power information _P RE1D that received communication delay due to the first communication means _107, adding the _{P RE2D,} input the total output power information 301 corresponding to the sum _{(P RED)} to the power smoothing control unit 302 To do.

The total output power information 301 ( _PRED ) includes large power fluctuations due to the intermittent power generation of renewable energy. The power smoothing control unit 302 processes the total output power information 301 ( _PRED ) by the rate of change limiter or other filter means to create the smoothed output power command value 303 (P ^* _SYS ). The output power command value 303 (P ^* _SYS ) represents a suitable output power of the power conversion system 100. Therefore, the total compensation power command value according to the plurality of power storage devices 105 ³⁰⁴ _{(P * BAT)} is calculated by subtracting the total output power information 301 _{(P RED)} from the output power command value ³⁰³ _{(P * SYS).}

The central control unit 106 divides the total compensated power command value 304 (P ^* _BAT ) by the number of power storage devices 105, that is, the number of second power conversion devices 102 (two in FIG. 1), thereby converting each second power. Individual compensation power command values (P ^* _BAT1 , P ^* _BAT2 ) for the device 102 are created. That is, in the central control unit 106 of FIG. 1, “P ^* _BAT1 = P ^* _BAT2 = P ^* _BAT / 2”. The compensated power command values P ^* _BAT1 and P ^* _BAT2 are sent to the control unit 108 of each second power conversion device 102 via the first communication means. Each control unit 108 receives the compensated power command value (P ^* _BAT1D , P ^* _BAT2D ) delayed by the first communication means, and outputs the second power conversion device (P _BAT1 , P _BAT2 ) to compensate the power. Control so that it becomes the command value (P ^* _BAT1D , P ^* _BAT2D ).

In an ideal state where there is no information communication delay, large power fluctuations are smoothed by the total output power 110 (P _BAT (= P _BAT1 + P _BAT2 )) of the plurality of second power conversion devices 102, and the output of the power conversion system 100 The fluctuation speed of the electric power 111 ( _PSYS ) falls within the range of the required value. However, in practice, the power conversion system may include a plurality of first power converters and a plurality of second power converters, and in some cases tens or hundreds of first and second power converters. When information is collected from these power conversion devices via the first communication means 107, a communication delay occurs. For example, it takes a maximum of 50 ms to guarantee one data update between 32 power converters. Further, after the individual control unit 108 of the second power conversion device receives the compensation power command value (P ^* _BAT1D , P ^* _BAT2D ) via the first communication means 107, the output power of the second power conversion device (P _BAT1) , P _BAT2 ) There is a delay in control until it matches the compensation power command value.

FIG. 4 shows the operation of the power conversion system of FIG. With reference to this figure, when the power smoothing control is executed in the central control unit 106, the control error of the power smoothing control caused by the above-mentioned communication delay time and control delay time will be described. In this figure, the broken line shows the waveform when the power smoothing control is ideal, and the solid line shows the waveform when an error due to the delay time occurs in the power smoothing control.

First, the waveform 109 shows the electric power due to the renewable energy, but the waveform has a steep electric power fluctuation. In an ideal situation, waveform 301 represents the ideal output of the storage battery for smoothing large power fluctuations in waveform 109, and waveform 302 is the control result (to the grid) when power smoothing control is ideal. Output power _PSYS ) is shown. However, when communication delay time and control delay time occur, these delays are controlled so that the output of the storage battery is delayed from the ideal waveform 301, as shown by the waveform 110.

Hereinafter, embodiments of the present invention will be described with reference to Examples 1 and 2. In each of the embodiments, means for reliably compensating for fluctuations in the amount of power generated by the renewable energy power generation device are added to the configuration shown in FIG. 1-3. Therefore, in the following, the means will be mainly described, and the configuration shown in FIGS. 1-3 will be illustrated, but the description will be omitted.

FIG. 5 shows the configuration of the power conversion system 500 according to the first embodiment of the present invention.

In the first embodiment, a power detection unit 501 (sensor) for detecting the total output power 511 of the power conversion system is provided, and a plurality of detected information is provided via the second communication means 502 (2 in FIG. 5). A part of the second power conversion device 102 (one in FIG. 5) is transmitted to the autonomous control unit 503 that controls individually and independently of the control by the central control unit 106.

Here, the second communication means transmits information by one-to-one communication. Therefore, the communication time delay is smaller than the communication time delay of the first communication means 107. The second communication means 502 may be wired or wireless.

FIG. 6 is a functional block diagram showing the configuration of the control system according to the first embodiment.

This control system includes a central control unit 106 and an autonomous control unit 503. The configuration of the central control unit 106 is the same as the configuration shown in FIG. The autonomous control unit 503 _{issues a} second power command 504 (P ^* _BAT2C ) to some of the second power conversion devices 102, and the total output power 511 of the power conversion system 500 from the power detection unit 501 and the second communication means 502 ( It is set based on the information indicating _PSYS ).

In the first embodiment, the rate limiter 505 (rate limiter) is applied as the control calculation means in the autonomous control unit 503. Since the communication delay of the second communication means 502 is smaller than that of the first communication means 107, the second power command is set prior to the setting of the first power command (P ^* _BAT2D ) by the power smoothing control in the central control unit 106. Set.

The control system shown in Examples 1 and 6 shown in FIG. 5 compensates for the control error caused by the time delay. As a result, the fluctuation rate of the output power of the power conversion system 500 can be satisfactorily managed.

FIG. 7 shows the operation of the power conversion system of the first embodiment. The broken line in FIG. 7 shows an operation waveform when only the central control unit including the power smoothing control unit is applied, as described for the power conversion system 100 in FIG. Further, the solid line in FIG. 7 shows an operation waveform when the power conversion system of the first embodiment shown in FIG. 5 is applied.

In the right diagram of FIG. 7 (an enlarged view of a time scale of a portion of the left (1725~1735sec)), the waveform _P RE (109) is a power from renewable power generator first power converter output Shown. In this waveform, there is a steep power fluctuation. As shown by the waveform _PBAT (110) and the waveform _PSYS (111), the time delay (communication delay and control delay) that occurs in the central control unit compensates the output of the power storage device and the output of the power conversion system. It causes a delay (that is, power fluctuation).

On the other hand, in the first embodiment, the fluctuation of the total output power _PSYS of the power conversion system 500 is monitored. As a result, the autonomous control unit 503 creates a second power command (P ^* _BAT2C ) in order to compensate for the error caused by the time delay, as shown by the waveform 504. As a result, the output power of the power conversion system 500 is controlled so as to suppress the power fluctuation as shown in the waveform 511.

FIG. 8 shows the configuration of the power conversion system 800 according to the second embodiment of the present invention.

In the second embodiment, the sensor 700 detects the total output power 109 ( _PRE ) of the plurality of first power conversion devices 101. The detected total output power 109 ( _PRE ) information is transmitted to the autonomous control unit 803 of the second power conversion device 102 via the second communication means 802. Further, the autonomous control unit 803 uses the first communication means 107 to provide other information regarding the operating state of the power conversion device, for example, information on the output powers _PRE1 and _PRE2 of each first power conversion device as described later. To receive.

Here, the second communication means 802 is a one-to-one communication method, so that the communication delay of the second communication means is smaller than the communication delay of the first communication means.

FIG. 9 is a functional block diagram showing the configuration of the control system according to the second embodiment.

This control system includes a central control unit 106 and an autonomous control unit 803. The configuration of the central control unit is the same as the configuration shown in FIGS. 3 and 6.

The autonomous control unit 803 sets the second power command 805 (P ^* _BAT2C ) for the second power conversion device 102 based on the error 804 between the detected values of the power by the renewable energy power generation device 104.

The error 804 between the detected values includes the total output power detected value ( _PRE ) obtained from the sensor 700 via the second communication means 802 and each first power conversion device 101 acquired via the first communication means 107. It is obtained by calculating the difference from the total output power detection value (P _RE1 + P _RE2 ) obtained by adding the output power detection values P _RE1 and P _RE2 .

The P _RE1 and P _RE2 are distributed from the central control unit 106 to the autonomous control unit 803 after being acquired by the central control unit 106 based on the operation information from the control unit 108 of the first power conversion device 101. The P _RE1 and P _RE2 may be distributed from the control unit 108 of the first power conversion device 101 to the autonomous control unit 803.

The delay unit 806 represents a delay that occurs when the central control unit 106 distributes the power command value of the power storage device 105 to the second power conversion device 102. Since the delay time of the second communication means 802 is short, the power value detected by the sensor 700 is almost the same as the actual power of the plurality of first power conversion devices 101.

In the second embodiment, the power smoothing control unit 807, which is the same power fluctuation compensation unit as the power smoothing control unit 302 in the central control unit 106, is applied to the autonomous control unit 803 that compensates for the control delay including the communication delay. Will be done.

The power smoothing control unit 807 smoothes the error 804 between the detected values (PRE (detected value of the sensor 700) − (P _RE1 + P _RE2 )). The autonomous control unit 803 creates the second compensated power command value 805 (P ^* _BAT2C ) by calculating the difference between the error between the detected values after the smoothing process and the error 804 between the detected values before the smoothing. And output. The control unit 108 of a part (one unit in FIG. 8) of the plurality of second power conversion devices (two units in FIG. 8) is the compensation power command P ^* _BAT2 and the autonomous control unit transmitted from the central control unit 106. The output power _PBAT2 of some of the second power conversion devices is controlled according to the power command to which the second compensating power command created by 803 is added.

According to the second embodiment, since erroneous control due to a control delay including a communication delay can be compensated, the fluctuation speed of the output power of the power conversion system 800 can be surely reduced.

FIG. 10 shows the operation of the power conversion system of the second embodiment. The broken line in FIG. 10 shows an operation waveform when only the central control unit including the power smoothing control unit is applied, as described for the power conversion system 100 in FIG. Further, the solid line in FIG. 10 shows an operation waveform when the power conversion system of the second embodiment shown in FIG. 8 is applied.

In the right view in FIG. 10 (enlarged view of the time scale of a portion of the left (1725~1735sec)), the waveform _P RE (109) is a power from renewable power generator first power converter output Shown. In this waveform, there is a steep power fluctuation.

As the waveform _PRE (201) shows, the time delays (communication delays and control delays) that occur in the central control unit result in delays in the detected waveform of the power of the renewable energy generator. Therefore, as shown by the waveform _PBAT (110) and the waveform _PSYS (111), the output of the power storage device and the output of the power conversion system are erroneously controlled by smoothing control.

In contrast, in Example 2, it is derived by calculating the difference between the waveform 109 in FIG. 10 and the waveform 201 _{(P RE} detected by sensor 700) (delayed _{P RE (= P RE1 + P} RE2)) The error between the detected values of the generated power of the renewable energy power generation device is monitored. Further, according to the second embodiment, the second power command 805 (“P ^* _BAT2C ” in FIG. 9) for the erroneous control compensation function in the autonomous control unit 803 is set. As a result, the output power of the power conversion system 800 is controlled so that the power fluctuation is suppressed as shown by the waveform 811 ( _PSYS ).

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. In addition, it is possible to add / delete / replace a part of the configuration of each example with another configuration.

For example, the number of first power conversion devices, the number of second power conversion devices, and the number of second power conversion devices including an autonomous control unit may be arbitrary depending on the power capacity of the power conversion system.

Further, the power storage device may be used for storing surplus power of the power conversion system, leveling the output of the power conversion system, and the like.

100 power conversion system, 101 first power conversion device, 102 second power conversion device,
103 power system, 104 renewable energy power generator, 105 power storage device,
106 Central Control Unit, 107 First Communication Means, 108 Control Unit,
700 sensor,
500 power conversion system, 501 power detector, 502 second communication means,
503 Autonomous control unit,
800 power conversion system, 802 second communication means, 803 autonomous control unit,

Claims (9)

The first power conversion device that converts the power from the renewable energy power generation device, and
A second power conversion device that converts power from the power storage device,
A central control unit that controls the first power conversion device and the second power conversion device,
A first communication means for transmitting information between the first power conversion device, the second power conversion device, and the central control unit.
With
The central control unit controls the first power conversion device based on the information obtained via the first communication means, and compensates for fluctuations in the generated power of the renewable energy power generation device. 2 Control the power converter,
In a power conversion system that outputs the output power of the first power conversion device and the second power conversion device to an external system.
An autonomous control unit that individually controls the second power conversion device, and
A second communication means that has a smaller communication delay than the first communication means and transmits information between the power conversion system and the autonomous control unit.
With
The autonomous control unit is characterized in that the second power conversion device is controlled so as to compensate for the fluctuation of the generated power of the renewable energy power generation device based on the information obtained via the second communication means. Power conversion system. In the power conversion system according to claim 1,
The first power conversion device includes a plurality of first power conversion units whose outputs are connected in parallel.
The second power conversion device includes a plurality of second power conversion units whose outputs are connected in parallel.
The autonomous control unit is a power conversion system characterized in that it controls a part of the plurality of second power conversion units. The power conversion system according to claim 1, wherein the second communication means transmits information by one-to-one communication. In the power conversion system according to claim 1,
A power conversion system characterized in that the information obtained via the second communication means is a detected value of the total output power of the first power conversion device and the second power conversion device. In the power conversion system according to claim 4,
The autonomous control unit uses a rate of change limiter to compensate for fluctuations in the generated power of the renewable energy power generation device with respect to the second power conversion device based on the detected value of the total output power. A power conversion system characterized by creating an output power command. In the power conversion system according to claim 5,
The power conversion system is characterized in that the autonomous control unit creates the output power command based on the difference between the output of the rate of change limiter and the detected value of the total output power. In the power conversion system according to claim 1,
A power conversion system characterized in that the information obtained via the second communication means is a detected value of the output power of the first power conversion device. In the power conversion system according to claim 7,
The autonomous control unit uses a power smoothing control unit to compensate for fluctuations in the generated power of the renewable energy power generation device with respect to the second power conversion device based on the detected value of the output power. A power conversion system characterized by creating an output power command for. In the power conversion system according to claim 8,
The autonomous control unit includes the output of the power smoothing control unit according to the difference between the detected value of the output power and the output power value of the first power conversion device obtained via the first communication means. , A power conversion system for creating an output power command for compensating the fluctuation of the generated power of the renewable energy power generation device for the second power conversion device based on the difference value from the difference. ..

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