WO2018116823A1 - Natural energy power generation system, reactive power controller, or natural energy power generation system control method - Google Patents

Abstract

The purpose of the invention is to provide a natural energy power generation system, a reactive power controller, and a natural energy power generation system control method for suppressing voltage fluctuation at an interconnection point due to reactive power loss of an interconnection transformer. The natural energy power generation system is provided with: a power generation device 12 receiving a natural energy to generate power; a power converter 13 electrically connected to the power generation device 12 and a power system 4; an interconnection transformer 2 disposed between the power converter 13 and the power system 4; and a reactive power controller 16 generating a reactive power command to be output by the power converter 13. Using at least the reactance of the interconnection transformer 2 disposed between the power converter 13 and the power system 4 or the current or the active power output by the power converter 13, the reactive power controller 16 determines the reactive power command so that a sum of the fluctuation component of the voltage at the interconnection point between the power converter 13 and the power system 4 due to the active power and the fluctuation component of the voltage at the interconnection point due to the reactive power becomes substantially constant.

Description

Natural energy power generation system, reactive power controller, or control method of natural energy power generation system

The present invention relates to a natural energy power generation system, a reactive power controller, or a control method for a natural energy power generation system that supplies power generated by using natural energy such as wind or sunlight to an electric power system.

削減 Reducing carbon dioxide emissions, which is thought to cause global warming, has become a major issue. As one means of reducing carbon dioxide emissions, the introduction of natural energy power generation such as solar power generation and wind power generation has become popular. These natural energy power generations are often used in conjunction with the power grid, but there is a concern that the power generation output will fluctuate due to fluctuations in the amount of solar radiation and wind speed, adversely affecting the voltage of the grid. ing.

A proposal has been made to use reactive power as a method for suppressing voltage fluctuation. As methods for suppressing voltage fluctuation at the connection point when the wind power generator is connected to the power system via the power converter, there are Patent Documents 1 to 3.

Patent Document 1 discloses a method for controlling a power converter so as to detect the output of the power converter and compensate for the voltage fluctuation at the interconnection point caused by the effective power output of the power converter. . Specifically, the system parameter α = R _L / X _L is estimated from the effective power output P _{CON of} the power converter and the voltage fluctuation ΔV _{PCC at the connection} point of the power converter generated thereby, and the power converter Reactive power Q _CON obtained by Q _CON = −αP _CON is output. Here, R _L and X _L represent the resistance component and reactance component of the impedance of the interconnection line, respectively.

In Patent Document 2, a predetermined power factor command value PF = P / √ (P ² + Q ² ) at the interconnection point is corrected by using a power factor correction amount set for each wind power generation system. A method for determining a power factor command value for each wind power generation system is disclosed. Here, P and Q represent the active power output and reactive power output of the wind power generation system, respectively. Further, the power factor correction amount is determined based on the reactance component existing between each wind power generation system and the interconnection point.

In Patent Literature 3, a voltage target value or a power factor target value is obtained based on a reactive power measurement value, a voltage measurement value, or a power factor measurement value at a connection point, and invalidity necessary to achieve these target values. A method for outputting electric power from a wind power generation system is disclosed.

JP2007-1224779 WO2009 / 078076 WO2013 / 128986

With regard to the technique of Patent Document 1, since it is intended to suppress voltage fluctuations at the interconnection point caused by the active power output of the power converter, the invalidity consumed by the interconnection transformer connecting the power converter and the interconnection line It is impossible to suppress voltage fluctuations at the interconnection point due to power loss.

Regarding the technique of Patent Document 2, since the reactive power output is controlled by the power factor command, the reactive power output changes in proportion to the active power output. In order to compensate for the reactive power loss of the interconnection transformer, which is also a problem of Patent Document 1, it is necessary to control the reactive power output so as to be proportional to the square of the active power output (or current output). Therefore, the power factor command cannot suppress voltage fluctuations at the interconnection point due to reactive power loss of the interconnection transformer.

Regarding the technology of Patent Document 3, the reactive power command of each wind power generation system is not determined in consideration of the reactive power loss consumed by the interconnection transformer, so the reactive power at the interconnection point matches the target value. I can't let you.

An object of the present invention is to provide a natural energy power generation system, a reactive power controller, or a control method for a natural energy power generation system that suppresses voltage fluctuations at a connection point caused by a reactive power loss of an interconnection transformer.

In order to achieve the object, a natural energy power generation system of the present invention includes a power generation device that generates power by receiving natural energy, a power converter electrically connected to the power generation device and a power system, and the power converter. An interconnection transformer disposed between the power grids, and a reactive power controller that generates a reactive power command output by the power converter, the reactive power controller comprising: the power converter and the power grid. The reactive power command is determined such that a sum of a fluctuation component due to active power at the interconnection point voltage and a fluctuation component due to reactive power at the interconnection point voltage is substantially constant.

Further, the reactive power controller according to the present invention includes a power generation device that receives natural energy to generate power, a power converter that is electrically connected to the power system, and a fluctuation component due to active power in a connection point voltage between the power system and An arithmetic unit is provided that generates a reactive power command output by the power converter so that a sum of fluctuation components due to reactive power in the interconnection point voltage becomes substantially constant.

Furthermore, the control method of the natural energy power generation system according to the present invention includes a power generation device that generates power by receiving natural energy, a power converter electrically connected to the power generation device and a power system, the power converter, and the A method for controlling a natural energy power generation system, comprising: an interconnected transformer disposed between power systems; and a reactive power controller that generates a reactive power command output from the power converter, wherein the power converter and the power The reactive power command is determined so that a sum of a fluctuation component due to active power at a connection point voltage with a system and a fluctuation component due to reactive power at the connection point voltage is substantially constant.

According to the present invention, it is possible to provide a natural energy power generation system, a reactive power controller, or a control method for a natural energy power generation system that suppresses voltage fluctuations at a connection point caused by a reactive power loss of an interconnection transformer.

It is a figure which shows the whole structure of the wind power generation system in Example 1. FIG. It is a figure which shows the structure of the reactive power controller in Example 1. FIG. It is a graph for demonstrating the voltage fluctuation of the connection point in Example 1, (A) is the time change of the active power of a connection point, (B) is the time change of the current of a connection point, (C) is The time change of the reactive power output of the power converter, (D) is the time change of the voltage fluctuation at the interconnection point. It is a graph for demonstrating the determination method of the reactive power command value in Example 1, (A) is the time change of the active power output of a power converter, (B) is the time change of the current output of a power converter, ( C) is a reactive power command for the power converter. It is a graph for demonstrating the voltage fluctuation suppression effect of the connection point in Example 1, (A) is the time change of the reactive power output of a power converter, (B) is the time change of the power control amount of a connection point. , (C) is the time change of voltage fluctuation at the interconnection point. It is a figure which shows the structure of the reactive power controller in the modification 2 of Example 1. FIG. It is a figure which shows an example of the table preserve | saved at the reactive power command value table memory | storage part in the modification 2 of Example 1. FIG. It is a figure which shows the whole structure of the wind farm in Example 2. FIG. It is a figure which shows the structure of the reactive power center controller in Example 2. FIG. It is a figure which shows an example of the table preserve | saved in the current collection structure memory | storage part in Example 2. FIG. It is a figure which shows the whole structure of the wind farm provided with the electric power generation output prediction means in Example 3. FIG. It is a graph for demonstrating the subject of the reactive power command in Example 3, (A) is active power output time change of a power converter, (B) is current output time change of a power converter, (C) is electric power. It is a time change of the reactive power command value of a converter. It is a graph for demonstrating the determination method of the reactive power command value in Example 3, (A) is the active power output time change of a power converter, (B) is the current output time change of a power converter, (C). Is the time change of the reactive power command value of the power converter. It is a table for demonstrating the reactive power command in Example 3. FIG. It is a figure which shows the whole structure of the solar energy power generation system in Example 4. FIG. It is a figure which shows the whole structure of the solar farm in Example 4. FIG. It is a figure which shows the whole structure of the solar farm provided with the power generation output prediction means in Example 4.

DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the invention will be described in detail with reference to the drawings as appropriate.

FIG. 1 is a diagram showing an overall configuration of a wind power generation system which is a natural energy power generation system in the first embodiment. The wind power generation system 1 is connected to the power system 4 via the connection transformer 2 and the connection line 3. The resistance of the impedance of the interconnection line 3 R _L, the reactance and X _L. A point where the interconnection transformer 2 and the interconnection line 3 are connected is defined as an interconnection point 5.

Each part which comprises the wind power generation system 1 is demonstrated. The wind power generation system 1 includes a wind turbine 11, a generator 12 connected to the wind turbine 11 via a main shaft (and a speed increaser as necessary), and a side of the generator 12 opposite to the wind turbine 11 side. A power converter 13 that is electrically connected to adjust the generated power of the generator 11, a sensor 14 that is installed between the power converter 13 and the interconnection transformer 2, an active power controller 15, and a reactive power controller 16. Composed. Wind energy received by the wind turbine 11 is converted into electrical energy by the generator 12 and sent to the power converter 13. The active power controller 15 determines an active power command value P _REF that can be generated by the power generator 12 from the pitch angle or wind speed of the wind turbine 11, and transmits the active power command value P _REF to the power converter 13. The reactive power controller 16 determines a reactive power command value Q _REF that suppresses voltage fluctuations at the interconnection point 5 from the active power output P _CON and the current output I _{CON of the} power converter 13 measured by the sensor 14, and _reacts with the reactive power. Command value Q _REF is transmitted to power converter 13. The power converter 13 controls the active power output P _CON and the reactive power output Q _CON so as to follow the active power command value P _REF and the reactive power command value Q _REF .

FIG. 2 is a configuration diagram of the reactive power controller 16. The reactive power controller 16 acquires the active power output P _CON and the current output I _CON of the power converter 13 measured by the sensor 14 by the receiving unit 161. The reactive power command determination unit 162 includes an active power output P _CON , a current output I _CON , an impedance resistance _RL and reactance X _{L of} the interconnection line 3 stored in the interconnection line parameter storage unit 163, and an interconnection transformer parameter. The reactive power command Q _REF is obtained from the primary side X _TR1 and secondary side X _{TR2 of} the reactance stored in the storage unit 164 and the turn ratio α _TR . The reactive power command Q _REF is output to the power converter 13 via the transmission unit 165.

Reactive power command Q _REF is determined so as to suppress fluctuations in voltage V _PCC (referred to as ΔV _PCC ) at interconnection point 5 shown in FIG. The calculation of the reactive power command Q _REF is performed by the equation (8) described later. Before describing a specific calculation method of reactive power command Q _REF, the principle of generation of voltage fluctuation ΔV _PCC will be described.

The generation principle of the voltage fluctuation ΔV _PCC is expressed by a mathematical expression. As shown in FIG. 1, when active power P _PCC and reactive power Q _PCC flow from interconnection transformer 2 to interconnection point 5, variation component ΔV _PCC 1 due to active power P _PCC at voltage V _{PCC at} interconnection point 5. Then, the fluctuation component ΔV _PCC 2 due to the reactive power Q _PCC can be expressed by the equations (1) and (2), respectively. In addition, about the positive / negative of reactive power, when the reactive power which advances from the power converter 13 to the interconnection transformer 2 flows, it is set as positive.

Here, R _L and X _L are a resistance component and a reactance component of the impedance of the interconnection line 5, respectively.

The active power P _PCC and the reactive power Q _PCC of the interconnection point 5 are respectively obtained from the active power output P _CON and the reactive power output Q _{CON of the} power converter 13 from the active power loss P _LOSS and the power consumed by the interconnection transformer 2. The value is obtained by subtracting the reactive power loss Q _LOSS and can be expressed as the following equations (3) and (4). Incidentally, when the active power loss _{P LOSS} the effective power output _{P CON} is sufficiently small, it may be omitted active power loss _{P LOSS.}

Here, I _CON is the current output of the power converter 13, and R _TR1 and R _TR2 are the primary side (closer to the wind power generation system 1) and the secondary side (closer to the interconnection point 5) of the interconnection transformer 2, respectively. resistance component, the primary side and the secondary side of the reactance component of the impedance of the X _TR1 and X _TR2 are each interconnection transformer 2 of the impedance of the way), the alpha _TR is the turns ratio of the interconnection transformer 2.

(5) (6) is obtained by substituting (3) into (1) and (4) into (2).

From the equations (5) and (6), the voltage fluctuation ΔV _{PCC at the} interconnection point 5 is expressed by the equation (7).

An example of a time-series waveform of the voltage fluctuation ΔV _{PCC in} the equation (7) is shown in FIG. In the equation (7), the variables that vary according to the fluctuation of the natural energy wind speed are the active power output P _CON and the current output I _CON of the power converter 13. Therefore, FIG. 3 shows an example when the active power output P _CON and the current output I _CON fluctuate. The reactive power Q _CON is constant at 0 Var.

Here, _RL is a resistance value determined by the line type and length of the interconnection line, although it changes somewhat with temperature change, is substantially constant, and V _PCC also suppresses voltage fluctuation within a range of several percent. It is usually necessary and still considered to be substantially constant. Therefore, from the equations (A), (D), and (5) in FIG. 3, the voltage fluctuation component ΔV _PCC 1 has a waveform that is substantially proportional to the active power output P _CON .

The turn ratio α _TR is a positive constant determined by the interconnection transformer 2, the resistance component _RL of the impedance of the interconnection line 5 is a positive constant, and the reactance component X _L is dominated by the inductance. Therefore, it is a positive constant. The reactance components _XTR1 and XTR2 of the impedance of the interconnection transformer ₂ are also positive constants because the inductance component is dominant. Since Q _CON = 0 in equation (6) and I _PCC is represented by the waveform in FIG. 3 (B), voltage fluctuations are obtained by equations (B), (C), (D), and (6) in FIG. The component ΔV _PCC 2 has a waveform in which the current output I _CON is squared and the phase is inverted (the waveform is reversed upside down).

3D and 7 regarding the voltage fluctuation, the voltage fluctuation ΔV _PCC is a waveform obtained by combining the voltage fluctuation components ΔV _PCC 1 and ΔV _PCC 2.

Next, a specific method for determining the reactive power command value Q _REF by the reactive power command determination unit 162 serving as an arithmetic device will be described. By _{obtaining the} reactive power command value Q _REF that satisfies the following relational expression, the voltage fluctuation ΔV _PCC at the interconnection point 5 shown in the expressions (D) and (7) of FIG. 3 can be suppressed. In the present embodiment, a case where the voltage fluctuation ΔV _{PCC at the} interconnection point 5 becomes approximately zero has been described as a particularly preferable example. However, from the viewpoint of suppressing fluctuation, ΔV _PCC may be substantially constant.
ΔV _PCC = ΔV _PCC 1 + ΔV _PCC 2 = (5) equation + (6) equation = 0
Specifically, the reactive power output Q _CON of the power converter 13 may be controlled to the reactive power command value Q _REF obtained by the equation (8). That is, the reactive power command determination unit 162 shown in FIG. 2 may obtain the reactive power command value Q _REF using the equation (8). Note that in equation (8), that the impedance ratio of the interconnection line 3 (R _L / X _L) is small, when the first term is sufficiently small relative to the second and third terms, the first term May be omitted.

An example of the time series waveform of the reactive power command value Q _{REF in} the equation (8) is shown in FIG. The active power output P _CON and current output I _CON shown in (A) and (B) of FIG. A part of the reactive power command obtained by the active power output P _CON shown in FIG. 4A and the first term of the equation (8) inverts the phase of the active power output P _CON as shown in FIG. It becomes a waveform (with the upper limit of the waveform reversed). Further, a part of the reactive power command obtained by the current output I _CON shown in FIG. 4B and the second and third terms of the equation (8) has a waveform proportional to the square of the current output I _CON. . A waveform obtained by synthesizing these waveforms is the final reactive power command.

Finally, the effect of suppressing the voltage fluctuation ΔV _{PCC at} the interconnection point 5 by the reactive power controller 16 of the first embodiment will be described with reference to FIG. 5A to 5C show the reactive power output Q _CON of the power converter 13 under the respective conditions shown in the following equations (I) to (III) and (9) to (11). The waveforms of the voltage control amount Y and the voltage fluctuation ΔV _{PCC at} the interconnection point 5 are shown.

(I) This is a condition in which the reactive power Q _CON is constant at 0 Var.

(II) A condition to which the reactive power control method of Patent Document 1 is applied.

(II) Conditions for applying the reactive power control method according to the first embodiment.

Voltage control amount of the interconnection point 5 Y is a (7) the second term of _{((X L / V PCC)} Q CON), obtained by substituting (9) to (11) below. The voltage control amount Y under the conditions (I) to (III) is shown in the equations (12) to (13) and FIG. 5 (B).

The voltage fluctuation ΔV _PCC suppressed by the voltage control amount Y can be obtained by replacing the second term ((X _L / V _PCC ) Q _CON ) in the equation (7) with the equations (12) to (14). The voltage fluctuation ΔV _PCC under the conditions (I) to (III) is shown in the equations (15) to (17) and FIG. 5 (C).

Using (15) to (17) and FIG. 5C, the effect of suppressing the voltage fluctuation ΔV _PCC by the reactive power control methods (I) to (III) is compared. In (I) and (II), the voltage fluctuation ΔV _PCC remains even after the reactive power control, whereas in (III), the voltage fluctuation ΔV _PCC can be suppressed to 0V.

Therefore, according to the first embodiment, in order to suppress the voltage fluctuation at the interconnection point 5, the active power output and current output of the power converter 13, the impedance ratio of the interconnection line 3, the reactance of the interconnection transformer 2, and By using the turn ratio, the reactive power output of the power converter 13 can be controlled to an appropriate value. This eliminates the need for a special device such as a reactive power compensator or a tap-switching transformer for suppressing voltage fluctuations at the interconnection point 5. As described above, the impedance ratio of the interconnection line 3 is small, and as a result, when the first term of the equation (8) is sufficiently smaller than the second term and the third term, the first term Can be omitted, and can be omitted.

In addition, you may obtain _| require the reactive power command value _QREF of the present Example 1 as follows.

<Modification 1 of Example 1>
The current output I _CON is approximated by the effective power output P _CON and the reference line voltage V _BASE at the installation point of the sensor 14 as shown in the equation (18).

Substituting equation (18) into equation (8) yields equation (19). By _{obtaining the} reactive power command value Q _REF using the equation (19), the current output I _CON can be omitted from the equation (8).

<Modification 2 of Example 1>
A table in which the active power output P _{CON is associated} with the reactive power command value Q _REF is created in advance, and the reactive power command value Q _REF is determined with reference to the table. Specifically, as illustrated in FIG. 6, the reactive power controller 16 a has a configuration in which a reactive power command value table creation unit 166 and a reactive power command value table storage unit 167 are added to the reactive power controller 16. The reactive power command value table creation unit 166 calculates the reactive power command Q _REF when the active power output P _CON is changed from 0 kW to the maximum output in predetermined increments using the equation (19). Then, a table associating the active power output P _CON and the reactive power command Q _REF as shown in FIG. 7 is stored in the reactive power command value table storage unit 167. The reactive power command value determination unit 162 determines the reactive power command value Q _REF with reference to the table of the reactive power command value table storage unit 167 every time the active power output P _CON is updated.

FIG. 8 is a configuration diagram of the reactive power controller 16b in the wind power generation system 1 according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in that the wind power generation system 1 (1A, 1B, 1C, 1D) and the interconnection transformers 2 (2I, 2J, 2K) are plural. Further, the reactive power command Q _REF (Q _{REF_A} , Q _{REF_B} , Q _{REF_C} , Q _{REF_D} ) of each wind power generation system 1 is different from that of the first embodiment in that the reactive power controller 16b determines. In the following description, A, B, C, and D are symbols that distinguish individual wind power generation systems 1, and I, J, and K are symbols that distinguish individual interconnection transformers 2.

In this embodiment, the power system side of each power converter of the wind power generation system 1A and the wind power generation system 1B is interconnected, and is interconnected after the connection (the power system side from the connection point of the two wind power generation systems). A transformer 2I is provided. Moreover, the power system side of each power converter of the wind power generation system 1C and the wind power generation system 1D is connected, and after the connection (the power system side from the connection point of the two wind power generation systems), the connection transformer 2J Is provided. An interconnection transformer 2K is further provided on the power system side of both interconnection transformers 2I and 2J. The reactive power controller 16b controls the wind power generation systems 1A to 1D collectively.

The configuration of the reactive power controller 16b is different from the reactive power controller 16 of the first embodiment and has the configuration of FIG. In the reactive power controller 16b, a power collection configuration storage unit 168 that stores a table representing a current collection configuration of the interconnection transformer 2 and the wind power generation system 1, and a power converter rated output storage that stores a rated output of the power converter 13. And a reactive power distribution determining unit 169 that distributes the reactive power output command Q _REF to the wind power generation system 1.

A method for obtaining the reactive power output command Q _REF of the wind power generation system 1 will be described.

First, a method in which the reactive power command determination unit 162b of the reactive power controller 16b determines the total reactive power output command Q _{REF_TOTAL} will be described. In determining the total reactive power output command Q _{REF_TOTAL,} the equation (8) in the first embodiment corresponds to a plurality of wind power generation systems 1 and a plurality of interconnection transformers 2 as shown in the equation (20). A modified function is used.

Here, the first term of the equation (20) is the reactive power obtained from the impedance (R _L , X _L ) of the interconnection line 3 and the active power (P _{CON_A} + P _{CON_B} + P _{CON_C} + P _{CON_D} ) flowing through the interconnection line 3. It is a directive. The second and third terms are _{derived from} the primary and secondary reactances ( _{XTR1_I} , _{XTR2_I} ) of the interconnection transformer 2I and the current flowing through the primary and secondary sides of the interconnection transformer 2I. This is a reactive power command obtained from (I _{CON_A} + I _{CON_B} , (I _{CON_A} + I _{CON_B} ) / α _I ). Similar to the second and third terms, the fourth to seventh terms are reactive power command values corresponding to the interconnection transformer 2J and the interconnection transformer 2K. A value obtained by adding the reactive power commands obtained in the first to seventh terms becomes a total reactive power output command Q _{REF_TOTAL} .

(20) When there are a plurality of wind power generation systems 1 and a plurality of interconnection transformers 2 as in the equation (20), which wind power generation system 1 current output I _CON flows through each interconnection transformer 2 It is necessary to decide. Therefore, the reactive power command determination unit 162b of the reactive power controller 16a reads the current collection configuration table representing the current collection configuration of the interconnection transformer 2 and the wind power generation system 1 from the current collection configuration storage unit 168. An example of the current collection configuration table is shown in FIG. In FIG. 10, when the individual wind power generation system 1 and the individual interconnection transformer 2 intersect with each other, the current output I _CON of the wind power generation system 1 flows through the interconnection transformer 2. Means. In this embodiment, an interconnection mode as shown in FIG. 8 is employed, but a different interconnection method may be adopted. Even in that case, it is possible to determine which wind power generation system 1 current output I _CON flows through each interconnection transformer 2 by referring to the current collection configuration table.

Next, the reactive power distribution determination unit 169 of the reactive power controller 16b shown in FIG. 9 _{sends the} reactive power commands Q _REF (Q _{REF_A} , Q _{REF_B} , Q _{REF_C} , Q ₎ to the individual wind power generation systems 1 from the total reactive power output command Q _{REF_TOTAL} . A method for allocating Q _{REF — D} ) will be described.

The reactive power distribution determining unit 169 includes the rated apparent power S _RAT (S _{RAT_A} ) of the power converter 13 of each wind power generation system 1 (1A, 1B, 1C, 1D) stored in the power converter rated output storage unit 170. S _{RAT_B} , S _{RAT_C} , S _{RAT_D} ) and active power output P _CON (P _{CON_A} , P _{CON_B} , P _{CON_C} , P _{CON_D} ), the reactive power output of the power converter 13 of the wind power generation system 1 using the equation (21) The possible amount Q _UL (Q _{UL_A} , Q _{UL_B} , Q _{UL_C} , Q _{UL_D} ) is obtained.

Then, the total reactive power output command Q _{REF_TOTAL} is distributed to each wind power generation system so that the reactive power command Q _REF ≦ Q _{UL of} each wind power generation system 1 is _satisfied .

According to the second embodiment, in a wind farm composed of a plurality of wind power generation systems 1 and a plurality of interconnection transformers 2, the active power output and the current output of each wind power generation system are detected, and the interconnection is performed. The total reactive power output command Q _{REF_TOTAL} of the wind power generation system is determined using the impedance of the line 3, the reactance of each interconnection transformer, and the table indicating the current collection configuration of the interconnection transformer 2 and the wind power generation system 1. By doing so, the voltage fluctuation of the connection point 5 can be suppressed. Further, by distributing the total reactive power output command Q _{REF_TOTAL} to the individual wind power generation systems 1 so that the reactive power command Q _{REF of} the individual wind power generation systems 1 is less than or equal to the reactive power output possible amount Q _UL , wind power generation It is possible to avoid voltage fluctuation at the interconnection point 5 due to insufficient capacity of the power converter 13 of the system 1.

FIG. 11 is a configuration diagram of the reactive power controller 16c in the wind farm according to the third embodiment of the present invention. The third embodiment is different from the second embodiment in that the reactive power controller 16c allows the wind power generation system 1 to output the active power output P _PRE (P _{PRE_A} , P _{PRE_B} , P _{PRE_C} , P _{PRE_D)} and the current output prediction _{I PRE (I PRE_A, I PRE_B} , I PRE_C, in that inputting the I _{PRE_D).}

As shown in FIG. 12, the reactive power controller 16c detects the active power output P _CON and the current output I _CON of the wind power generation system 1 when a predetermined update time (T1 and T2) is reached (FIG. 12 (A) ( B)), reactive power command Q _REF is determined from active power output P _CON and current output I _CON (FIG. 12C).

A case where reactive power command Q _REF determined at update time T1 is continued until next update time T2 will be described with reference to FIG. The active power output P _CON and the current output I _CON of the wind power generation system 1 change according to the wind speed that changes every moment. Due to these changes, the ideal reactive power command Q _{REF_IDEAL} also changes. The ideal reactive power command Q _{REF_IDEAL} is _obtained by sequentially updating the reactive power command in accordance with changes in the active power output P _CON and the current output I _CON . Therefore, after the update time T1, there is a difference between the ideal reactive power command Q _{REF_IDEAL} and the reactive power command Q _REF maintained from time T1. The effect of suppressing voltage fluctuation is reduced due to the deviation.

Therefore, in the third embodiment, as shown in FIG. 13, at the update time T1, the future active power output prediction value P _PRE and the current output prediction value I _PRE from the power generation output prediction means 6 until the next update time T2 are obtained. get. Then, the reactive power command value Q _REF is obtained for each of the detected values (P _CON , I _CON ) and the predicted values (P _PRE , I _PRE ) of the active power output and the current output. As described above, by determining the reactive power command value Q _REF in a cross section including the future at the update time T1, the deviation from the ideal reactive power command Q _{REF_IDEAL} can be reduced. The power generation output prediction means 6 predicts the active power output predicted value P _PRE and the current output predicted value I _PRE by linear extrapolation from the past detected values of the active power output P _CON and the current output I _CON . However, the prediction method is not limited to linear extrapolation.

FIG. 14 shows an example of the reactive power command value Q _REF sent from the reactive power controller 16c to each wind power generation system 1 (1A, 1B, 1C, 1D) at time T1. In FIG. 14, the reactive power command value Q _REF (30 kVar) for time T1 (0:00:00) is a value obtained from the active power output P _CON and the current output I _CON detected at time T1. Reactive power command value Q _REF (35 kVar, for time T1.25 (0:02:30), time T1.5 (0:05:00), and time T1.75 (0:07:30) 40 kVar and 45 kVar) are values obtained from the predicted active power output value P _PRE and the current output predicted value I _PRE acquired at time T1.

And the wind power generation system 1 operate _| moves so that the reactive power command value _{QREF for} every time shown in FIG. 14 and the reactive power output _QCON may correspond. For example, the reactive power command value Q _{REF in} the period immediately after time T1 (0:00:01) to immediately before time T1.25 (0:02:29) is equal to time T1 (0:00:00). ) Reactive power command value Q _REF (30Var) may be maintained. Alternatively, the reactive power command value Q _REF (30Var, 35Var) at time T1 (0:00:00) and time T1.25 (0:02:30) may be obtained by linear interpolation.

The feature of the third embodiment is that a reactive power command Q _REF of a plurality of time sections is obtained by using future predicted values in addition to detected values of the active power output and current output of the wind power generation system 1, and the time section The method for obtaining each reactive power command value Q _REF is the same as in the first and second embodiments.

According to the third embodiment, compared to a method of updating the reactive power command value and maintaining it until the next update, using the predicted output value of the future wind power generation system, the reactive power command value in the future multiple time sections Therefore, the performance of the voltage fluctuation suppression control can be improved.

Although the wind power generation system 1 of the natural energy power generation system has been described as the first to third embodiments, the present invention is not limited to this. A case where the natural energy power generation system is a solar power generation system 7 will be described as a fourth embodiment with reference to FIGS. In addition, as a natural energy power generation system, since a wind power generation system and a solar power generation system are typical, the Example is shown, However, It is not limited to them.

FIG. 15 is a diagram showing an overall configuration of the solar power generation system 7 in the fourth embodiment. FIG. 16 is a diagram illustrating an overall configuration of a solar farm that includes a plurality of the photovoltaic power generation systems of FIG. 15 and includes a reactive power center controller that determines a reactive power command of each photovoltaic power generation system. FIG. 17 is a diagram showing an overall configuration in which power generation output prediction means is added to FIG.

FIG. 15 shows a configuration of a photovoltaic power generation system corresponding to FIG. 1 (Example 1). FIG. 16 shows a configuration of a solar farm corresponding to FIG. 8 (Example 2). FIG. 17 shows a configuration of a solar farm corresponding to FIG. 11 (Example 3).

The difference between FIG. 1 and FIG. 15 is the difference in whether the power generation system installed in the natural energy power generation system is the wind power generation system 1 or the solar power generation system 7. The wind turbine 11 and the generator 12 in FIG. 1 correspond to the solar cell 71 in FIG. The wind power generator 12 in FIG. 1 corresponds to the solar power converter 72 in FIG. The wind power generation active power controller 15 in FIG. 1 corresponds to the photovoltaic power generation active power controller 74 in FIG. 15. The pitch angle, wind speed, and the like obtained from the wind turbine 11 by the active power controller 15 for wind power generation in FIG. 1 correspond to the voltage and current generated from the solar cell 71 in FIG. The wind power reactive power controller 16 in FIG. 1 corresponds to the solar power reactive power controller 75 in FIG. The wind power generation sensor 14 in FIG. 1 corresponds to the solar power generation sensor 73 in FIG. 15. Similarly, the difference between FIGS. 8 and 16 and the difference between FIGS. 11 and 17 are also differences between the wind power generation system 1 and the solar power generation system 7. The other parts having the same reference numerals are the same and will not be described here.

The configurations in FIGS. 15 to 17 and the operation and effects thereof are the same as those described in the first to third embodiments, and thus detailed description thereof is omitted, but the wind power described in the first to third embodiments is omitted. The effect of the power generation system is the same in the photovoltaic power generation system of the present embodiment.

Note that the present invention is not limited to the first to fourth embodiments described above, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

In addition, each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function may be placed in a memory, a hard disk, a recording device such as an SSD (SolId-State-DrIve), or a recording medium such as an IC card, SD card, or DVD. it can.

DESCRIPTION OF SYMBOLS 1 Wind power generation system 2 Connection transformer 3 Connection line 4 Electric power system 5 Connection point 6 Power generation output prediction means 7 Solar power generation system 11 Wind turbine 12 Generator 13 Power converter 14 Sensor 15 Active power controller 16 Reactive power controller DESCRIPTION OF SYMBOLS 71 Solar cell 72 Power converter for solar power generation devices 73 Sensor for solar power generation devices 74 Active power controller for solar power generation 75 Reactive power controller for solar power generation 161 Receiving unit 162 Reactive power command determining unit 163 Interconnection line parameter storage Unit 164 interconnection transformer parameter storage unit 165 transmission unit 166 reactive power command value table creation unit 167 reactive power command value table storage unit 168 current collection configuration storage unit 169 reactive power distribution determination unit 170 power converter rated output storage unit

Claims (11)

1. A power generation device that receives natural energy to generate power,
   A power converter electrically connected to the power generator and the power system;
   An interconnection transformer disposed between the power converter and the power system;
   A reactive power controller that generates a reactive power command output by the power converter;
   The reactive power controller is:
   Determining the reactive power command so that a sum of a fluctuation component due to active power in a connection point voltage between the power converter and the power system and a fluctuation component due to reactive power in the connection point voltage are substantially constant. Natural energy power generation system characterized by
2. The natural energy power generation system according to claim 1,
   The reactive power controller is:
   Determining the reactive power command using reactance of the interconnection transformer disposed between the power converter and the power system and at least one of current and active power output by the power converter; Natural energy power generation system characterized by
3. The natural energy power generation system according to claim 1 or 2,
   The reactive power controller is:
   Further, the reactive power command is determined using an impedance ratio between the power converter and the interconnection line of the power system.
4. The natural energy power generation system according to claim 3,
   From the active power, the reactance, and the impedance ratio, a control table creating unit that creates a control table that associates at least one of the current or the active power with a reactive power command value;
   A control table storage unit for storing the control table;
   The reactive power command determination unit determines a reactive power command value by using the control table and at least one of the current and the active power.
5. A natural energy power generation system according to claim 3 or 4,
   A plurality of the power generation devices, a plurality of the power converters, and a plurality of the interconnected transformers,
   The reactive power controller is:
   A current collection configuration table storage unit for storing a table showing a current collection configuration of the interconnection transformer and the power converter;
   The reactive power command value determining unit determines a reactive power command value using at least one of the current and the active power, the interconnection transformer reactance, the interconnection impedance ratio, and the current collection configuration table. Natural energy power generation system characterized by
6. The natural energy power generation system according to claim 5,
   The reactive power controller is:
   From the maximum apparent power of the power converter and the active power, a reactive power output possible amount of the power converter is calculated, and a plurality of the powers so that the reactive power command value is equal to or less than the reactive power output possible amount. A renewable energy power generation system comprising a reactive power output distribution determining unit that determines a distribution of reactive power command values in a converter
7. The reactive power controller is:
   Means for obtaining at least one of a predicted current value or a predicted active power value of the power converter;
   The reactive power command value determining unit determines a reactive power command value of a cross section for a plurality of times from the active power predicted value.
   Natural energy power generation system characterized by
8. A natural energy power generation system according to any one of claims 1 to 7,
   A natural energy power generation system, wherein the power generation device is a wind power generation device
9. A natural energy power generation system according to any one of claims 1 to 7,
   Natural power generation system characterized in that the power generation device is a solar power generation device
10. Fluctuation component due to active power in a connection point voltage between the power system and a power converter electrically connected to the power system receiving natural energy and the power system, and a fluctuation component due to reactive power in the connection point voltage A reactive power controller comprising: an arithmetic unit that generates a reactive power command output from the power converter so that a sum of
11. A power generation device that receives natural energy to generate power,
    A power converter electrically connected to the power generator and the power system;
    An interconnection transformer disposed between the power converter and the power system;
    A control method of a natural energy power generation system including a reactive power controller that generates a reactive power command output by the power converter,
    Determining the reactive power command so that a sum of a fluctuation component due to active power in a connection point voltage between the power converter and the power system and a fluctuation component due to reactive power in the connection point voltage are substantially constant. Control method for natural energy power generation system

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