JP7189045B2 - power conversion system - Google Patents

Description

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

In recent years, renewable energy power generation facilities using wind power and sunlight as energy sources are becoming widespread. Renewable energy power generation equipment uses natural energy, so the amount of power generation fluctuates. As a result, when the output power fluctuation speed of the grid-connected power conversion system increases, the power system may become unstable. On the other hand, the prior art described in Patent Document 1 is known.

The technique described in Patent Document 1 compensates for fluctuations in the output power of a natural energy power source with power from a power storage device controlled using a change rate limiter.

JP 2010-22122 A

If a storage battery is provided in a power conversion system by applying the above conventional technology, the cost required for installation and maintenance of the power conversion system increases.

Accordingly, the present invention provides a power conversion system capable of suppressing an increase in cost while including a power storage device.

In order to solve the above problems, a 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. , an electric quantity detection unit that detects the electric quantity of the output of the first power conversion device, and based on the electric quantity detected by the electric quantity detection unit, so as to compensate for fluctuations in the power generated by the renewable energy power generation device, a power control unit that controls the output of the second power conversion device, the power control unit has a smoothing filter that smoothes the detected value of the electric quantity, and the second power conversion device is controlled based on the output of the smoothing filter It controls the output and connects the renewable energy power generation device to the power system. The smoothing filter includes a plurality of smoothing filter units with different characteristics and and a changeover switch unit that selects one of the plurality of smoothing filter units in response.

According to the present invention, since the cost required for the power storage device can be reduced, the cost of the renewable energy power generation device and the power conversion system can be reduced.

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

1 shows a configuration of a power conversion system interconnected to a power system; 2 is a functional block diagram showing the configuration of a power control unit in FIG. 1; FIG. 3 shows a configuration example of a power smoothing filter in FIG. 2 ; FIG. 3 shows another configuration example of the power smoothing filter in FIG. 2 ; 2 illustrates the operation of the power conversion system of FIG. 1; 2 illustrates the operation of the power conversion system of FIG. 1; 1 shows the configuration of a power conversion system that is Embodiment 1. FIG. 4 is a functional block diagram showing the configuration of a power control unit according to the first embodiment; FIG. 4 shows an example of an operating state of a power control unit according to the first embodiment; 4 shows the operation of the power conversion system of Example 1. FIG. The configuration of a power conversion system that is a second embodiment is shown. FIG. 10 is a functional block diagram showing the configuration of a power control unit in Example 2; FIG. 11 shows an example of an operating state of a power control unit according to the second embodiment; FIG. 4 shows the operation of the power conversion system of Example 2. FIG. It is an example of the examination result about the charge energy integrated value and the electrical power amount peak value of various power smoothing filters.

Before describing the embodiments of the present invention, first, a conventional power conversion system will be described. The configurations of the power conversion system and its control system (FIGS. 1 to 4) described below are also applied to embodiments of the present invention described later.

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

As shown in FIG. 1 , the power converter system 100 includes a first power converter 101 and a second power converter 102 . The output of the first power converter 101 and the output of the second power converter 102 are connected to the power grid 103 .

The electric power system 103 is composed of power generating equipment having a normal generator made of a rotating electric machine, equipment consuming electric power, and a power transmission and distribution network to which these equipment are connected.

The first power conversion device 101 includes a main circuit that converts the power (direct current or alternating current) input from the renewable energy power generation device 104 into desired alternating current power (P _RE ). This main circuit performs power conversion by turning on/off a semiconductor switching element. A main circuit of the first power conversion device 101 is controlled by a converter control unit (not shown). That is, the converter control unit controls on/off of the semiconductor switching element of the main circuit according to the output power command value. Thereby, the AC power output by the first power conversion device 101 is controlled to be the output power command value.

Note that the renewable energy power generation device 104 is, for example, a solar power generation device or a wind power generation device. In addition, as the first power conversion device 101, a DC/AC converter, an AC/AC converter, a combination of an AC/DC converter and a DC/AC converter, depending on the power (AC or DC) output by the renewable energy power generation device etc. is applied.

The second power conversion device 102 includes a main circuit that converts DC power input from the storage battery 105 into AC power (P _BAT ). This main circuit is a DC/AC converter circuit. A main circuit of the second power conversion device 102 is controlled by a converter control unit (not shown). That is, the converter control unit 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 (P _BAT ) output by the second power conversion device 102 is controlled to be the output power command value 107 (P ^* _BAT ).

Note that the power storage device 105 is, for example, a secondary battery or a capacitor.

The electric quantity detection unit 109 detects the output power 110 (P _RE ) of the first power conversion device 101 . Power control unit 106 creates output power command value 107 (P ^* _BAT ) based on output power detection value 108 (P _RE ) detected by electric quantity detection unit 109, and outputs created output power command value 107 to 2 to the power converter 102;

Note that the electric quantity detection unit 109, for example, detects the output current and the output current of the first power conversion device 101 by a sensor, calculates the output power 110 (P _RE ) from these detection values, and calculates the calculated power It is output as the detected value of _PRE .

The output power _PRE of the first power conversion device 101 has large power fluctuations according to natural conditions such as weather due to the intermittent power generation characteristics of the renewable energy power generation device 104 . Such large power fluctuations can destabilize the operation of generators in power system 103 . Therefore, the power conversion system 100 is required to keep the power fluctuation rate, that is, the power fluctuation speed, of the total output power 112 (P _SYS ) of the power conversion system 100 within a specified value.

The injection of the output power 111 (P _BAT ) from the second power conversion device 102 by the storage battery 105 compensates for sharp power fluctuations in the output power of the renewable energy power generation device 104 . Therefore, the fluctuation speed of the total output power 112 of the power conversion system 100 is controlled within a predetermined value. This improves the stability of the power system by preventing the normal rotary generator in the external power system from experiencing large unexpected transients. Such a power fluctuation compensation function is provided by the configuration of power control section 106 described below.

FIG. 2 is a functional block diagram showing the configuration of power control section 106 in FIG.

Power control section 106 includes power smoothing filter 201 . The output power detection value 108 (P _RE ) of the first power converter 101 is input to the power smoothing filter 201 . The power smoothing filter creates a total output power command value 202 (P ^* _SYS ) of the power conversion system 100 by smoothing the fluctuation component of the output power detection value 108 (P _RE ), and the created total output power command value 202(P ^* _SYS ).

The power control unit 106 calculates the difference between the total output power command value 202 (P ^* _SYS ) created by the power smoothing filter 201 and the output power detection value 108 (P _RE ), whereby the second power conversion device 102 output power command value 107 (P ^* _BAT ). The power control unit 106 sends the created output power command value 107 (P ^* _BAT ) to the converter control unit (not shown) in the second power converter 102 .

The power smoothing filter 201 removes large fluctuation components due to output fluctuations of the renewable energy power generation device from the output power detection value 108 (P _RE ), and removes the remaining relatively moderately changing components from the total output power command value. 202(P ^* _SYS ). Therefore, the difference (P ^* _SYS - P _RE ) between the total output power command value 202 (P ^* _SYS ) and the output power detection value 108 (P _RE ), that is, the output power command value 107 (P ^* _BAT ) is Cancel large fluctuation components of output power detection value 108 (P _RE ). _Therefore , the total output power ₁₁₂ ( ^P _SYS ) can be suppressed.

FIG. 3 shows a configuration example of the power smoothing filter in FIG.

In this configuration example, the power smoothing filter 201A includes a change rate limiter 301 .

In the power smoothing filter 201A, the output power detection value 108 (P _RE ) and the total output power command value 202 (P ^* _SYS ) at the time T before the input time of the output power detection value 108 (P _RE ), and is calculated, and the calculated difference is input to the change rate limiter 301 . This difference is the fluctuation component of the detected output power value 108 (P _RE ) during time T, and corresponds to the rate of change of the detected output power value 108 (P _RE ).

Here, delay time setting section 304 sets delay time T for total output power command value 202 (P ^* _SYS ). The input/output characteristics of delay time setting section 304 are represented by a transfer function “e ^−sT ” that indicates a time response with dead time T. FIG.

The calculated difference is input to change rate limiter 301 . The change rate limiter 301 outputs the input fluctuation component as it is if it does not exceed a predetermined allowable value, and outputs the allowable value if it exceeds the allowable value. That is, change rate limiter 301 outputs a fluctuation component whose fluctuation speed is suppressed within an allowable value. In FIG. 3, RLIMH (302) and RLIML (303) are the power up and down tolerances, respectively. These allowable values can be set and changed as appropriate.

Power smoothing filter 201A adds the fluctuation component output from change rate limiter 301 and total output power command value 202 (P ^* _SYS ) delayed by delay time setting section 304 to obtain output power detection value 108 ( P _RE ) at the time of inputting the total output power command value 202 (P ^* _SYS ), and the created total output power command value 202 is output.

According to the power smoothing filter 201A of FIG. 3, by using the change rate limiter 301, the total output power command value 202 (P ^* _SYS ) whose power fluctuation speed is within the allowable range can be created.

FIG. 4 shows another configuration example of the power smoothing filter in FIG.

In this configuration example, the output power detection value 108 (P _RE ) of the second power converter is input to the power smoothing filter 201A having the change rate limiter as described above via the moving average filter 201B.

In the moving average filter 201B, N−1 (N is an integer equal to or greater than 2) delay time setting units 401 (having the same configuration as the delay time setting unit 304 in FIG. 3) are connected in series. The output power sense value 108 (P _RE ) is input to this series connection. Moving average filter 201B calculates the sum of output power detection value 108 (P _RE ) and the outputs of N−1 delay time setting units 401 by calculator 402, and further divides the sum by N to obtain , make the input to the power smoothing filter 201A. That is, the moving average filter 201B detects the output power detected value 108 (P _RE ) at each time interval T from the point of time (N−1)T before the input point (current point) of the input output power detection value 108 (P RE ). output the average value of the N output power detection values 108 (P _RE ) of . The input/output characteristics of such moving average filter 201B are represented by a transfer function H(s) as in the following equation.
H(s)=N ^-1 (1+e ^-sT +…+e ^-sT(N-1) )=N ^-1 {(1-e ^-sTN )/(1-e ^-sT )}
According to the configuration example of FIG. 4, the output power detection value 108 (P _RE ) obtained by averaging the magnitude of the fluctuation component over a predetermined time width is input to the power smoothing filter 201A. As a result, as shown in FIG. 2, the difference between the total output power command value 202 (P ^* _SYS ) and the output power detection value 108 (P _RE ) input to the power smoothing filter is calculated to perform the second power conversion. When creating the output power command value 107 (P ^* _BAT ) of the device 102, the instantaneous value of the output power command value 107 (P ^* _BAT ) is prevented from becoming excessively large. Therefore, the power capacity of the storage battery 105 can be reduced.

FIG. 5 shows the operation of the power conversion system of FIG. Note that this figure is a comparative example with respect to Example 1 (FIG. 9) described later.

FIG. 5 shows an example of temporal changes in the total power command value P ^* _SYS of the power conversion system and the output power command value P ^* _BAT of the second power converter. In the figure, the dashed line (202) represents the total power command value P ^* _SYS , and the solid line (107) represents the output power command value P ^* _BAT .

In the figure, cases (1) and (2) correspond to small and large fluctuations in the output power _PRE of the first power converter, respectively. Also, in cases (A) and (B), the power smoothing filter is provided with a change rate limiter (FIG. 3) and a moving average filter (FIG. 4), respectively.

In cases (1)-(A), the power smoothing filter (FIG. 3) produces the same P ^* _SYS as _PRE because the rate limiter does not operate effectively. Therefore, P ^* _BAT output by the power controller (FIG. 2) is almost zero. That is, the storage battery is not charged or discharged.

On the other hand, in the case of (1)-(B), P ^* _BAT generated by the power smoothing filter (FIG. 4) with a moving average filter has negative and positive values, as indicated by the variation of the solid line (107). Take. That is, the storage battery is charged and discharged.

In the cases of (2)-(A) and (2)-(B), as shown by the large fluctuations of each solid line (107), in any case, the power smoothing filter (FIGS. 3 and 4) is , _PRE generates P ^* _BAT to compensate for such variations.

FIG. 6 shows the operation of the power conversion system of FIG. Note that this figure is a comparative example with respect to Example 1 (FIG. 10), which will be described later.

FIG. 6 shows an example of changes over time in the charge/discharge energy integrated value (accumulated energy) and the amount of stored electric power (energy deviation) in the storage battery 105 (FIG. 1). In the figure, the dashed line indicates the integrated value of the absolute value of the output power command value P ^* _BAT of the second power converter, representing the charge/discharge energy integrated value. In the figure, the solid line indicates the integrated value of P ^* _BAT and represents the amount of stored electric power.

Note that the integrated value of the absolute value of P ^* _BAT can be an index related to the life of the storage battery. Also, the integrated value of P ^* _BAT can be an index related to the power capacity required for the storage battery.

In the figure, cases (1) and (2) correspond to small and large fluctuations in the output power _PRE of the first power converter, respectively. Also, in cases (A) and (B), the power smoothing filter is provided with a change rate limiter (FIG. 3) and a moving average filter (FIG. 4), respectively.

Comparing the case of (1)-(A) and the case of (1)-(B), the integrated charge/discharge energy value (broken lines 601A1, 601B1) and the amount of stored power (solid lines 602A1, 602B1) are both (1 )-(A) is smaller than (1)-(B). Therefore, when the fluctuation of the output power _PRE of the first power converter is small, the change limiter is more advantageous than the moving average filter for battery life and capacity.

On the other hand, when comparing the case of (2)-(A) and the case of (2)-(B), the charge/discharge energy integrated value (broken lines 601A2, 601B2) is is smaller than the case of (2)-(B). Also, the amount of stored power (solid lines 602A2, 602B2) is smaller in the case of (2)-(B) than in the case of (2)-(A). Therefore, when the fluctuation of the output power _PRE of the first power converter is large, the change limiter is more advantageous than the moving average filter for the life of the storage battery, but the moving average filter is more advantageous for the capacity of the storage battery. Advantages over limiters.

As discussed above, the rate of change limiter and moving average filter have varying effects on battery life and capacity. For this reason, it is difficult to improve the life of the storage battery and reduce the required capacity in order to reduce the cost of the power conversion system.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below using Examples 1 and 2. FIG. Each embodiment has the system configuration shown in FIG. 1, and uses the change rate limiter shown in FIG. 3 and the moving average filter shown in FIG. 4 in the power smoothing filter. Note that detailed description of the already illustrated configuration is omitted.

FIG. 7 shows the configuration of a power conversion system 700 that is Embodiment 1 according to the present invention.

As shown in FIG. 7, the power conversion system 100 of Example 1 has the same configuration as the power conversion system 100 shown in FIG. Note that the specific configuration of the power control unit 706 is different from the configuration shown in FIG. 2-4, as described below.

FIG. 8 is a functional block diagram showing the configuration of the power control unit 706 according to the first embodiment.

Power control section 706 includes power smoothing filter 801 . The output power detection value 708 (P _RE ) of the first power converter 101 is input to the power smoothing filter 801 . The power smoothing filter 801 creates a total output power command value 802 (P ^* _SYS ) of the power conversion system 700 by smoothing the fluctuation component of the output power detection value 708 (P _RE ). Output the value 802 (P ^* _SYS ).

The power control unit 706 calculates the difference between the total output power command value 802 (P ^* _SYS ) created by the power smoothing filter 801 and the output power detection value 708 (P _RE ), so that the second power converter 102 output power command value 707 (P ^* _BAT ). The power control unit 706 sends the created output power command value 707 (P ^* _BAT ) to the converter control unit (not shown) in the second power converter 102 .

The power smoothing filter 801 removes large fluctuation components due to output fluctuations of the renewable energy power generation device from the output power detection value 708 (P _RE ), and converts the remaining relatively slowly changing components to the total output power command value. 802(P ^* _SYS ). Therefore, the difference (P ^* _SYS - P _RE ) between the total output power command value 802 (P ^* _SYS ) and the output power detection value 708 (P _RE ), that is, the output power command value 707 (P ^* _BAT ) is Cancel large fluctuation components of output power detection value 708 (P _RE ). _Therefore , the total output ^power ₇₁₂ ( P _SYS ) can be suppressed.

As shown in FIG. 8, power smoothing filter 801 has a change rate limiter, and power smoothing filter section 201A (hereinafter simply referred to as "change rate limiter section") having the same configuration as that shown in FIG. , and a moving average filter 201B connected to the change rate limiter (201A) via a changeover switch 803 and having the same configuration as that shown in FIG.

Changeover switch section 803 switches connection and disconnection between the output of moving average filter 201B and the input of change rate limiter section (201A) according to the operation mode of power smoothing filter 801 set by filter operation mode setting section 804. . Note that in the first embodiment, the filter operation mode setting unit 804 outputs an operation mode flag signal indicating the operation mode to be set. The switch unit 803 operates according to this operation mode flag signal.

When moving average filter 201B and change rate limiter section (201A) are connected, output power detection value 708 (P _RE ) is input to change rate limiter section via moving average filter 201B. When moving average filter 201B and change rate limiter section (201A) are not connected, output power detection value 708 (P _RE ) is directly input to change rate limiter section without passing through moving average filter 201B. be. Therefore, in the power smoothing filter 801, the configuration shown in FIG. 3 and the configuration shown in FIG.

The filter operation mode setting unit 804 receives the output power detection value 708 (P _RE ), and combines the input P _RE and the P _RE for which the delay time T is set by the delay time setting unit 805 (that is, the detection value before the time T). ), and the absolute value of the calculated difference is calculated by the absolute value calculator 806 (ABS). Furthermore, the filter operation mode setting unit 804 removes high frequency components from the calculated absolute value using a low-pass filter 807 (LPF), thereby setting a mode selection index 808 ( _PREVIO ) is calculated.

The filter operation mode setting unit 804 compares the calculated P _REVIO with a predetermined threshold value 809 (P _VIOTH ) using the comparison unit 810 (CMP), and sets the operation mode according to the comparison result. In the first embodiment, the filter operation mode setting unit 804 sets the filter operation mode (M0) by the change rate limiter unit without using the moving average filter if _{PRE VIO does not exceed the threshold value P VIOTH ,} 810 outputs an operation mode flag signal 811 indicating the operation mode M0. Further, when _{PRE VIO exceeds the threshold value P VIOTH ,} filter operation mode setting section 804 sets the filter operation mode (M1) by the moving average filter and change rate limiter section, and indicates operation mode M1 from comparison section 810. Outputs an operation mode flag signal.

Changeover switch section 803 connects moving average filter 201B and change rate limiter section (201A) when receiving an operation mode flag signal indicating operation mode M1, and when receiving an operation mode flag signal indicating operation mode M0, switching section 803 connects moving average filter 201B and change rate limiter section (201A). The averaging filter 201B and the change rate limiter section (201A) are disconnected.

Here, _PREVIO represents the magnitude of fluctuation of _PRE in an instant or in a short period of time. Therefore, according to the operation of filter operation mode setting section 804 as described above, when _{PRE VIO does not exceed threshold P VIOTH ,} that is, when the fluctuation of _PRE is relatively small, power smoothing filter 801 operates as a moving average filter. is not used, and the change rate limiter is used (FIG. 3). When _{PRE VIO exceeds the threshold value P VIOTH ,} that is, when the fluctuation of _PRE is relatively large, power smoothing filter 801 has a configuration using a moving average filter and change rate limiter (FIG. 4).

FIG. 9 shows an operation state example of the power control unit 706 (denoted as “power smoothing control unit” in the drawing) according to the first embodiment.

In the figure, cases (1) and (2) correspond to small and large fluctuations in the output power _PRE of the first power converter, respectively.

For each of the cases (1) and (2), the output power detection value _{PRE of the first power converter input to the power control unit 706, the mode selection index 808 (PREVIO :} solid line) and its threshold 809 (P _VIOTH : dashed line) and an operation mode flag signal 811 indicating the operation mode (M0, M1).

For case (1), _{PREVIO (808)<P VIOTH (} 809) as shown in the middle diagram. Therefore, the operation mode M0 is set as shown in the figure below. That is, the power control section 706 uses a change rate limiter section without using a moving average filter.

On the other hand, in the case of (2), as shown in the central diagram, the period of _{PRE VIO (808)<P VIOTH (} 809) and the period of _{PRE VIO (808)≧P VIOTH (} 809) are appear alternately. Therefore, as shown in the figure below, the operation mode _M0 and the operation mode M1 are alternately set according to the magnitude of the variation in PRE. In other words, power control section 706 uses a change rate limiter section without using a moving average filter, or uses a moving average filter and a change rate limiter, depending on the magnitude of fluctuation in _PRE .

10 shows the operation of the power conversion system of Example 1. FIG.

In the figure, cases (1) and (2) correspond to small and large fluctuations in the output power _PRE of the first power conversion device, respectively, similarly to FIG.

For each of the cases (1) and (2), the output power detection value 708 (P _RE ) of the first power conversion device input to the power control unit 706 (denoted as “power smoothing control unit” in the figure), The total output power command value 802 (P ^* _SYS ) of the power conversion system 700, the output power command value 707 (P ^* _BAT ) of the second power conversion device, and the charge/discharge energy accumulated value (accumulated energy ) and energy deviation. In the figure below, the dashed line indicates the integrated value of the absolute value of the output power command value P ^* _BAT of the second power conversion device, representing the charge/discharge energy integrated value. In the lower figure, the solid line indicates the integrated value of P ^* _BAT and represents the amount of stored electric power.

Note that the integrated value of the absolute value of P ^* _BAT can be an index related to the life of the storage battery. Also, the integrated value of P ^* _BAT can be an index related to the power capacity required for the storage battery.

In case (1), as described above with reference to FIG. 9, power control section 706 does not use a moving average filter, but uses a change rate limiter section. Power smoothing filter 801 (FIG. 8) produces P ^* _SYS that is the same as P _RE because the rate of change limiter does not operate effectively due to the small variation of P _PE . Therefore, P ^* _BAT output by power control section 706 (FIG. 7) is approximately zero. That is, the storage battery is not charged or discharged. Therefore, both the accumulated energy of charge and discharge and the energy deviation are zero.

On the other hand, in the case of (2), the power control unit ₇₀₆ , as described above with reference to FIG. A limiter section is used, or a moving average filter and change rate limiter section are used. Therefore, P ^* _BAT output by power control section 706 (FIG. 7) takes a value of zero, plus or minus, depending on the magnitude of variation in _PRE . That is, the storage battery is charged and discharged. As a result, the charge/discharge energy integrated value (accumulated energy) and the amount of stored electric power (energy deviation) take finite values.

The lower diagram in the case of (2) in FIG. 10 shows the accumulated energy and stored energy (energy deviation), and (2)-(A) and (2)-(B) in FIG. Comparing the charge/discharge energy integrated value (accumulated energy) and the stored power amount (energy deviation) in each case, the stored power amount (energy deviation) is the smallest in the first embodiment. In addition, the accumulated charge and discharge energy (accumulated energy) is smaller than in the case of (2)-(B) and smaller than in the case of (2)-(B) In the case of (2)-(A) is equivalent to Therefore, according to the first embodiment, the power capacity required for the storage battery can be reduced, and the life of the storage battery can be improved.

As described above, according to the first embodiment, the power capacity required for the storage battery can be reduced, and the life of the storage battery can be improved, so that the cost required for installation and maintenance of the storage battery can be reduced. As a result, it is possible to reliably reduce the cost of a power conversion system that connects a renewable energy power generation device to an external power system.

Next, Example 2 will be described with reference to FIGS. 11 to 14. FIG. Note that differences from the first embodiment will be mainly described.

FIG. 11 shows the configuration of a power conversion system 1100 that is Embodiment 2 according to the present invention.

In this embodiment, a photovoltaic power generation device is applied as the renewable energy power generation device 104 . The power conversion system 1100 also includes a pyranometer 1113 that detects the amount of solar radiation. The power control unit 1106 selects an operation mode based on the solar radiation amount detection value 1114 (In _RE ) by the pyranometer 1113, as will be described later.

FIG. 12 is a functional block diagram showing the configuration of the power control unit 1106 according to the second embodiment.

In the second embodiment, the filter operation mode setting unit 1204 inputs the solar radiation amount detection value 1114 (In _RE ), and the input In _RE and the In _RE for which the delay time T is set by the delay time setting unit 1205 (that is, The absolute value of the calculated difference is calculated by the absolute value calculator 1206 (ABS). Furthermore, filter operation mode setting section 1204 removes high-frequency components from the calculated absolute value using low-pass filter 1207 (LPF), thereby setting mode selection index 1208 (In _REVIO ) is calculated.

The filter operation mode setting unit 1204 compares the calculated In _REVIO with a predetermined threshold value 1209 (In _VIOTH ) by the comparison unit 1210 (CMP), and sets the operation mode according to the comparison result. In the second embodiment, if In _REVIO does not exceed the threshold value In _VIOTH , the filter operation mode setting unit 1204 sets the filter operation mode (M0) by the change rate limiter unit without using the moving average filter. 1210 outputs an operation mode flag signal 1211 indicating the operation mode M0. Further, when In _REVIO exceeds the threshold value In _VIOTH , filter operation mode setting section 1204 sets the filter operation mode (M1) by the moving average filter and change rate limiter section, and indicates operation mode M1 from comparison section 1210. Outputs an operation mode flag signal.

Changeover switch section 1203 connects moving average filter 201B and change rate limiter section (201A) when receiving an operation mode flag signal indicating operation mode M1, and when receiving an operation mode flag signal indicating operation mode M0, switching section 1203 connects moving average filter 201B and change rate limiter section (201A). The averaging filter 201B and the change rate limiter section (201A) are disconnected.

Here, In _REVIO represents the magnitude of fluctuation of In _RE in an instant or in a short period of time. Therefore, according to the operation of the filter operation mode setting unit 1204 as described above, when In _REVIO does not exceed the threshold value In _VIOTH , that is, when the fluctuation of In _RE is relatively small, the power smoothing filter 1201 uses the moving average filter is not used, and the change rate limiter is used (FIG. 3). Also, when In _REVIO exceeds the threshold In _VIOTH , that is, when the variation of In _RE is relatively large, power smoothing filter 1201 has a configuration using a moving average filter and a change rate limiter (FIG. 4).

FIG. 13 shows an operation state example of the power control unit 1106 (denoted as “power smoothing control unit” in the drawing) according to the second embodiment.

In the figure, (1) is the case where the weather is fine and the variation in the output power _PRE of the first power converter is small. In (2), the weather is cloudy or rainy, and the output power _PRE of the first power conversion device fluctuates greatly.

For each of the cases (1) and (2), the output power detection value 1108 ( _{PRE: solid line) and the solar radiation amount detection value 1114 (In RE :} dashed line) of the first power conversion device input to the power control unit 706 and , a mode selection index 1208 (In _REVIO : solid line) and its threshold 1209 (In _VIOTH : dashed line), and an operation mode flag signal 1211 indicating the operation mode (M0, M1).

In case (1), In _REVIO (1208)<In _VIOTH (1209), as shown in the central figure. Therefore, the operation mode M0 is set as shown in the figure below. That is, power control section 1106 uses a change rate limiter section without using a moving average filter.

On the other hand, in the case of (2), as shown in the central diagram, the period in which In _REVIO (1208)<In _VIOTH (1209) and the period in which In _REVIO (1208)≧In _VIOTH (1209) are appear alternately. Therefore, as shown in the figure below, the operation mode _M0 and the operation mode M1 are alternately set according to the magnitude of the variation in PRE. That is, power control section 1106 uses a change rate limiter section without using a moving average filter, or uses a moving average filter and a change rate limiter, depending on the magnitude of fluctuations in In _RE and _PRE .

FIG. 14 shows the operation of the power conversion system of Example 2. FIG.

In the figure, the cases (1) and (2) are, _similarly to FIG. This is the case where the fluctuation of the output power _PRE of one power converter is large.

For each of the cases (1) and (2), the output power detection value 1108 (P _RE : solid line) of the first power converter input to the power control unit 1106 (denoted as “power smoothing control unit” in the figure) and the solar radiation amount detection value 1114 (In _RE : broken line), the total output power command value 1202 (P ^* _SYS ) of the power conversion system 1100, the output power command value 1107 (P ^* _BAT ) of the second power converter, and the storage battery 105 ( FIG. 11 ) shows the accumulated energy and the energy deviation. In the figure below, the dashed line indicates the integrated value of the absolute value of the output power command value P ^* _BAT of the second power conversion device, representing the charge/discharge energy integrated value. In the lower figure, the solid line indicates the integrated value of P ^* _BAT and represents the amount of stored electric power.

Note that the integrated value of the absolute value of P ^* _BAT can be an index related to the life of the storage battery. Also, the integrated value of P ^* _BAT can be an index related to the power capacity required for the storage battery.

In case (1), as described above with reference to FIG. 13, power control section 1106 does not use a moving average filter, but uses a change rate limiter section. Power smoothing filter 1201 (FIG. 12) produces the same P ^* _SYS as the _PRE , since the rate of change limiter does not operate effectively because the _PRE changes are small due to the small variability of the In _RE . Therefore, P ^* _BAT output by power control section 1106 (FIG. 11) is almost zero. That is, the storage battery is not charged or discharged. Therefore, both the accumulated energy of charge and discharge and the energy deviation are zero.

On the other hand, in the case of (2), the power control _{unit 1106} , as described above with reference to FIG. or a moving average filter and a change rate limiter. Therefore, P ^* _BAT output by power control section 1106 (FIG. 11) takes a value of zero, positive or negative depending on the magnitude of fluctuations in In _RE and _PRE . That is, the storage battery is charged and discharged. As a result, the charge/discharge energy integrated value (accumulated energy) and the amount of stored electric power (energy deviation) take finite values.

The lower diagram in the case of (2) in FIG. 14 shows the accumulated energy and stored energy (energy deviation), and (2)-(A) and (2)-(B) in FIG. Comparing the charge/discharge energy accumulated value (accumulated energy) and the amount of stored electric power (energy deviation) in each case, Example 2 has the smallest charge/discharge energy accumulated value (accumulated energy). In addition, the energy deviation is smaller than in case (2)-(A) and equivalent to case (2)-(B), which is smaller than in case (2)-(A). Therefore, according to the first embodiment, the power capacity required for the storage battery can be reduced, and the life of the storage battery can be improved.

As a modification of the second embodiment, a wind power generator may be applied as the renewable energy power generator 104, and an anemometer may be provided instead of the pyranometer.

As described above, according to the second embodiment, the power capacity required for the storage battery can be reduced, and the life of the storage battery can be improved, so that the costs required for installation and maintenance of the storage battery can be reduced. As a result, it is possible to reliably reduce the cost of a power conversion system that connects a renewable energy power generation device to an external power system. In addition, since the operation mode is switched according to the parameters of natural energy (amount of solar radiation, wind speed), which are direct factors in the amount of power generated by the renewable energy power generation device, fluctuations in the output power (P _RE ) of the first power conversion device are compensated. The followability of the control for doing is improved.

Here, the inventor's examination results regarding the performance of various power smoothing filters will be described.

FIG. 15 shows an example of the results of examination by the present inventor regarding various power smoothing filters regarding accumulated energy and peak energy deviation.

As shown in FIG. 15, it can be seen that Example 1 or Example 2 according to the present invention is advantageous for improving the life of the storage battery and reducing the power capacity.

Each of the above embodiments may be modified as follows.

The power smoothing filter is a plurality of smoothing filter units (in the embodiment, a rate of change limiter and a moving average filter with a rate of change limiter), a plurality of first-order lag filters, and a moving average filter that performs calculations using inputs per unit time. , a limiter that limits the rate of change per unit time, median number calculation means that uses the input per unit time, and means for arbitrarily combining these four methods. In the first-order lag filter, the first-order lag time constant may be adjustable. Also, in the median number calculation means, the unit time width may be adjustable.

In the moving average filter, the unit time width and average calculation coefficient of the moving average filter may be adjustable.

The rate of change limiter that limits the rate of change per unit time may be adjustable in upper and lower limit values of the rate of change.

It may be possible to notify and record information about the smoothing filter section that is in operation among the plurality of smoothing filter sections in the power smoothing filter.

In addition, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Moreover, it is possible to add, delete, or replace a part of the configuration of each example with another configuration.

For example, the first power conversion device and the second power conversion device may be composed of multiple connections of a plurality of power conversion units. Also, the number of renewable energy power generators and storage batteries may be arbitrary.

Also, instead of the storage battery, another power storage device such as a capacitor may be applied. Note that 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.

The electric quantity detection unit may detect the output voltage and the output current in addition to the output power of the first power conversion device. Then, the output power of the second power converter may be controlled so as to compensate for fluctuations in the output voltage and output current. Further, the operation mode setting unit may set the operation mode based on fluctuations in the detected values of the output voltage and output current, or fluctuations in the output (power, voltage, current) of the renewable energy power generation device. .

100 power conversion system, 101 first power conversion device, 102 second power conversion device,
103 power system, 104 renewable energy power generation device, 105 storage battery,
106 power control unit, 109 electric quantity detection unit, 201 power smoothing filter,
201B moving average filter, 301 change rate limiter, 304 delay time setting unit,
401 delay time setting unit, 402 calculator, 700 power conversion system,
706 power control unit, 709 electric quantity detection unit, 801 power smoothing filter,
803 switch unit, 804 filter operation mode setting unit,
805 delay time setting unit, 806 absolute value calculation unit, 807 low-pass filter,
810 comparison unit, 1100 power conversion system, 1106 power control unit,
1109 electric quantity detector, 1113 pyranometer, 1201 power smoothing filter,
1203 switch unit, 1204 operation mode setting unit,
1205 delay time setting unit, 1206 absolute value calculation unit, 1207 low-pass filter,
1210 comparator

Claims (10)

a first power conversion device that converts power from the renewable energy power generation device;
a second power conversion device that converts power from the power storage device;
an electric quantity detection unit that detects the electric quantity of the output of the first power conversion device;
a power control unit that controls the output of the second power conversion device so as to compensate for fluctuations in the power generated by the renewable energy power generation device based on the value of the quantity of electricity detected by the quantity of electricity detection unit;
with
The power control unit has a smoothing filter that smoothes the detected value of the electric quantity, controls the output of the second power conversion device based on the output of the smoothing filter,
In a power conversion system that connects the renewable energy power generation device to a power system,
The smoothing filter is
a plurality of smoothing filter units with different characteristics;
a changeover switch unit that selects one of the plurality of smoothing filter units according to the magnitude of fluctuation in the power generated by the renewable energy power generation device;
A power conversion system comprising: In the power conversion system according to claim 1,
The plurality of smoothing filter units are
a first smoothing filter unit having a change rate limiter for inputting the detected value of the electric quantity;
a second smoothing filter unit having a moving average filter for inputting the detected value of the electrical quantity;
A power conversion system comprising: In the power conversion system according to claim 2,
The power conversion system, wherein the second smoothing filter section has a change rate limiter section connected to the output of the moving average filter. In the power conversion system according to claim 1,
A power conversion system, wherein the quantity of electricity is output power of the first power conversion device. In the power conversion system according to claim 1,
The power conversion system, wherein the changeover switch section selects one of the plurality of smoothing filter sections based on a detected value of a physical quantity that varies with the power generated by the renewable energy power generation device. In the power conversion system according to claim 5,
The power conversion system, wherein the physical quantity is the output power of the first power converter. In the power conversion system according to claim 5,
The renewable energy power generation device is a solar power generation device,
A power conversion system, wherein the physical quantity is an amount of solar radiation. In the power conversion system according to claim 5,
The renewable energy power generation device is a wind power generation device,
The power conversion system, wherein the physical quantity is wind speed. In the power conversion system according to claim 2,
The changeover switch unit selects one of the plurality of smoothing filter units based on a detected value of a physical quantity that varies with the power generated by the renewable energy power generation device,
The changeover switch unit selects the first smoothing filter unit when a magnitude of variation in the detected value of the physical quantity does not exceed a predetermined value, and the magnitude of variation in the detected value of the physical quantity is the predetermined value. is selected, the power conversion system characterized by selecting the second smoothing filter unit. In the power conversion system according to claim 5,
an operation mode setting unit that generates a flag signal for selecting one of the plurality of smoothing filter units according to the magnitude of variation in the detected value of the physical quantity;
The power conversion system, wherein the switch section selects one of the plurality of smoothing filter sections according to the flag signal.

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