JP2017051038A - Power conversion device, power generation system, and power generation control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device, a power generation system, and a power generation control method, capable of appropriately suppressing output power.SOLUTION: A power conversion device according to an embodiment comprises a control unit for controlling output power to a power system by controlling rotation speed of a power generator depending on the amount of water flowing into a water turbine connected to the power generator. The control unit, when maximum power capable of being output to the power system exceeds set power, controls the power generator so that the rotation speed is higher than rotation speed at which the maximum power can be obtained to limit the output power to the power system to power equal to or lower than the set power.SELECTED DRAWING: Figure 1A

Description

  Embodiments disclosed herein relate to a power conversion device, a power generation system, and a power generation control method.

  2. Description of the Related Art Conventionally, there is known a power conversion device that controls a power generator connected to a water turbine and outputs generated power obtained from the water turbine via the power generator to a power system (see, for example, Patent Document 1). Such a power converter increases the power generation efficiency by controlling the rotation of the water turbine according to the amount of water flowing into the water turbine so that the water turbine efficiency is high.

JP2015-002645A

  However, when the amount of water flowing into the water turbine increases and the power that can be generated exceeds the upper limit of the output power, a member that consumes power, such as a resistor, is connected to suppress the output power. However, the arrangement and cost of such members are problematic.

  Therefore, it is conceivable to suppress the rotation speed of the generator so that the output power does not increase. However, if the rotation speed of the generator is suppressed in this way, an overcurrent may occur.

  One aspect of the embodiments has been made in view of the above, and an object thereof is to provide a power conversion device, a power generation system, and a power generation control method capable of appropriately suppressing output power.

  The power converter device which concerns on 1 aspect of embodiment is provided with the control part which controls the rotational speed of the said generator according to the amount of water which flows into the water turbine connected to the generator, and controls the output electric power to an electric power grid | system. When the maximum power that can be output to the power system exceeds a set power, the control unit controls the generator at a rotational speed faster than the rotational speed at which the maximum power is obtained, and outputs power to the power system. The power is limited to the set power or less.

  According to one aspect of the embodiment, it is possible to provide a power conversion device, a power generation system, and a power generation control method that can appropriately suppress output power.

FIG. 1A is a diagram illustrating an example of a configuration of a power generation system according to an embodiment. FIG. 1B is a diagram illustrating an example of the relationship between the rotational speed of the generator and the generated power. FIG. 2 is a diagram illustrating an example of a configuration of the power conversion device according to the embodiment. FIG. 3 is a diagram showing an example of the characteristics of the shaft torque-rotation speed of the water turbine. FIG. 4 is a diagram illustrating an example of the relationship between the generated power of the generator and the rotation speed. FIG. 5 is a diagram illustrating an example of another configuration of the command generation unit. FIG. 6 is a diagram illustrating an example of still another configuration of the command generation unit. FIG. 7 is a diagram illustrating an example of still another configuration of the command generation unit. FIG. 8 is a flowchart illustrating an example of the power generation control process by the power converter.

  Hereinafter, embodiments of a power conversion device, a power generation system, and a power generation control method disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

  FIG. 1A is a diagram illustrating an example of a configuration of a power generation system according to an embodiment. A power generation system 1 shown in FIG. 1A is provided between a water turbine 2 and an electric power system 3, and converts the rotational force of the water wheel 2 into electric power and outputs the electric power to the electric power system 3. The power generation system 1 is, for example, a small hydropower generation system, but can be applied to power generation systems other than the small hydropower generation system.

  The water turbine 2 is an open circumferential water turbine (also referred to as an open water turbine) such as an open top water turbine or an open bottom water turbine. For example, other types such as a Pelton turbine, a cross-flow turbine, a Francis turbine, etc. It may be a water wheel.

  The power generation system 1 includes a generator 10 and a power conversion device 20. The generator 10 is a rotating electrical machine, for example, a three-phase AC generator such as a permanent magnet synchronous machine. Such a generator 10 is connected to the water turbine 2. For example, the rotating shaft of the generator 10 is linked to the rotating shaft of the water turbine 2 directly or via a gear or the like. The generator 10 may be a generator other than the three-phase AC generator as long as the rotational force of the water turbine 2 can be converted into electric power.

  The power conversion device 20 includes a power conversion unit 21 and a control unit 22. The power conversion unit 21 includes an AC / DC conversion unit 23 and a DC / AC conversion unit 24. The AC / DC converter 23 is controlled by the controller 22 and converts AC power output from the generator 10 into DC power. The DC / AC conversion unit 24 is controlled by the control unit 22, converts the DC power output from the AC / DC conversion unit 23 into AC power, and outputs the AC power to the power system 3.

  For example, the control unit 22 acquires information on the value of the inflow water amount to the water turbine 2 detected by the water amount detection device 4 (hereinafter referred to as the inflow water amount Qw), and the generator 10 determines the amount of the inflow water Qw. The generated power Pi of the generator 10 is controlled by controlling the rotational speed ωi.

  FIG. 1B is a diagram illustrating an example of the relationship between the rotational speed ωi of the generator 10 and the generated power Pi. As shown in FIG. 1B, the generated power Pi of the generator 10 changes according to the rotational speed ωi of the generator 10 even with the same amount of inflowing water.

  The control unit 22 controls the rotational speed ωi of the generator 10 to an optimum rotational speed according to the inflow water amount Qw so that the generated power Pi of the generator 10 becomes the maximum at the current inflow water amount Qw. Thereby, the output electric power Po to the electric power grid | system 3 can be enlarged as much as possible. Hereinafter, the maximum power that can be obtained with an arbitrary inflow water amount Qw is referred to as maximum power Pimax.

  When the inflow water amount Qw is the rated inflow water amount Qwx, the control unit 22 controls the rotation speed ωi of the generator 10 to the rated rotation speed ωix as shown in FIG. Can be. The rated generated power Pix is the maximum power Pimax at the rated inflow water amount Qwx, and is the generated power Pi when the output power Po to the power system 3 becomes the set power Pox (hereinafter referred to as the set output power Pox).

  The set output power Pox (an example of set power) is, for example, the output power Po set by a contract with an electric power company that operates the power system 3, and the output power Po from the power generation system 1 to the power system 3 is It is limited to the set output power Pox or less. When the set output power Pox is 10 [kW] and the power conversion efficiency ηc of the power converter 21 is 90 [%], Pix = 10 ÷ 0.9 = 11.1 [kW].

  By the way, when the inflow water amount Qw exceeds the rated inflow water amount Qwx and becomes an excess water amount, if the rotational speed ωi is controlled so that the output power Po to the power system 3 is maximized, the output power Po to the power system 3 is The set output power Pox will be exceeded.

  In this way, when the inflow water amount Qw is an excess water amount, the generated power Pi is rated by controlling the rotational speed ωi so that the rotational speed ωiz2 (see FIG. 1B) is lower than the rotational speed ωiz from which the maximum power Pimax is obtained. The generated power Pix can be suppressed. However, since the generator 10 is controlled at the rotational speed ωiz2 lower than the rotational speed ωiz, the shaft torque of the generator 10 increases, and the current flowing between the generator 10 and the power converter 20 increases. For this reason, for example, there is a risk of an overcurrent exceeding the upper limit value of the current that can be passed through the generator 10 or the power conversion unit 21.

  Therefore, the control unit 22 controls the rotational speed ωi so that the rotational speed ωiz1 (see FIG. 1B) is higher than the rotational speed ωiz at which the maximum electric power Pimax is obtained when the inflowing water amount Qw is an excess water amount. The power Pi is set to be equal to or lower than the rated generated power Pix, and the output power Po is limited to be equal to or lower than the set output power Pox. Thereby, since the axial torque of the generator 10 can be suppressed and the current flowing between the generator 10 and the power converter 20 can be suppressed, the generator 10 and the power converter 21 are protected from overcurrent. be able to. Hereinafter, the configuration of the power conversion device 20 will be further described.

  When the rotational speed ωi is controlled so that the rotational speed ωiz1 is higher than the rotational speed ωiz from which the maximum power Pimax can be obtained, the generator 10 and the power conversion unit 21 are more affected than when the rotational speed ωi is the rated rotational speed ωix. The applied voltage is further increased.

  Therefore, for example, it is desirable to select the generator 10 having a rated voltage equal to or higher than the voltage applied to the generator 10 in the case of the rated inflow water amount Qwx and the unconstrained state (when Pi = 0). The same applies to the withstand voltage of the power converter 21. It is desirable that the power converter 21 has a rated inflow water amount Qwx and a withstand voltage equal to or higher than the voltage applied to the generator 10 in an unconstrained state.

  Further, when the voltage generated in the generator 10 is larger than the rated voltage of the generator 10 or the withstand voltage of the power conversion unit 21, a part of the generated power of the generator 10 is consumed by resistance or the like, thereby generating the generator. The voltage generated at 10 can also be suppressed.

  For example, in the power converter 21, a series connection circuit of a switch and a resistor is provided between the DC buses connecting the AC / DC converter 23 and the DC / AC converter 24. And when the voltage which arises in the generator 10 becomes larger than the rated voltage of the generator 10, and the proof pressure of the power conversion part 21, the control part 22 controls on / off of a switch, and makes a resistor consume electric power, The voltage generated in the generator 10 is suppressed.

  In this way, even when a power consuming member such as a resistor is provided, the rotational speed ωi is controlled so that the rotational speed ωiz1 is higher than the rotational speed ωiz, so that the rotational speed ωi is changed to the rotational speed ωiz. The size of the power consuming member can be reduced compared to Therefore, the problem of arrangement and cost of the power consuming member can be reduced.

  FIG. 2 is a diagram illustrating an example of a configuration of the power conversion device 20 according to the embodiment. As shown in FIG. 2, the power conversion device 20 includes a power conversion unit 21 and a control unit 22. The power conversion unit 21 includes an AC / DC conversion unit 23, a DC / AC conversion unit 24, current detection units 25 and 27, and voltage detection units 26 and 28.

  The AC / DC converter 23 includes a bridge circuit and a capacitor in which a plurality of switching elements are connected in a three-phase bridge. The DC / AC converter 24 includes a bridge circuit and a capacitor in which a plurality of switching elements are connected in a three-phase bridge. Prepare. Note that the switching element is, for example, a MOS-FET or an IGBT, and the AC / DC converter 23 and the DC / AC converter 24 are not limited to the configuration shown in FIG.

  The current detection unit 25 detects instantaneous values Iu, Iv, and Iw (hereinafter referred to as current Iid) of currents flowing from the U phase, V phase, and W phase of the generator 10 to the power conversion unit 21, respectively. Current detector 27 detects instantaneous values Ir, Is, It (hereinafter referred to as current Iod) of current flowing from power converter 21 to the R phase, S phase, and T phase of power system 3.

  The voltage detection unit 26 detects an instantaneous value Vpn (hereinafter referred to as DC voltage Vpn) of the DC voltage output from the AC / DC conversion unit 23. The voltage detector 28 detects R phase, S phase, and T phase instantaneous voltage values Vr, Vs, and Vt (hereinafter referred to as voltage Vod) of the power system 3.

  The control unit 22 includes an AC / DC conversion control unit 30, a DC / AC conversion control unit 31, and a cutoff control unit 32. The AC / DC conversion control unit 30 generates drive signals S1 to S6 based on the inflow water amount Qw detected by the water amount detection device 4 and outputs the drive signals S1 to S6 to the AC / DC conversion unit 23. Each of the plurality of switching elements constituting the AC / DC converter 23 is on / off controlled by the drive signals S1 to S6. The inflow water amount Qw is, for example, the amount of water that flows into the water turbine 2 per unit time.

  The DC / AC conversion control unit 31 generates drive signals S7 to S12 so that the DC voltage Vpn becomes a predetermined constant voltage, and outputs the drive signals S7 to S12 to the DC / AC conversion unit 24. Each of the plurality of switching elements constituting the DC / AC converter 24 is controlled to be turned on / off by the drive signals S7 to S12, and the DC power output from the AC / DC converter 23 is converted into AC power to be DC / AC. The signal is output from the converter 24 to the power system 3.

  For example, the DC / AC conversion control unit 31 generates a command in synchronization with the voltage Vod detected by the voltage detection unit 28 and the DC voltage Vpn matches a predetermined DC voltage command Vpnr, and responds to the command. Drive signals S7 to S12 are generated. Thereby, the output power Po corresponding to the generated power Pi of the generator 10 is output from the power converter 20 to the power system 3.

  When the DC voltage Vpn exceeds the upper limit voltage Vmax, the cutoff control unit 32 outputs a cutoff request SH to the connection breaker 5, and based on the cutoff request SH, the connection breaker 5 connects the turbine 2 and the generator 10. The water turbine 2 and the generator 10 are disconnected by disconnecting the connection. Thereby, when the state where the generated power Pi exceeds the rated generated power Pix continues, the connection between the water turbine 2 and the generator 10 is released, so that excessive power supply from the generator 10 to the power converter 20 is performed. Can be suppressed.

  The AC / DC conversion control unit 30 includes a command generation unit 41, a subtraction unit 42, a speed control unit 43, a current control unit 44, and a switch drive unit 45. The command generator 41 generates a speed command ωir based on the inflow water amount Qw detected by the water amount detection device 4. The speed command ωir is a command that defines the rotational speed ωi of the generator 10.

  The subtracting unit 42 subtracts the value of the rotational speed ωi of the generator 10 (hereinafter referred to as rotational speed ωid) from the speed command ωir generated by the command generating unit 41. The rotational speed ωod is detected by, for example, the encoder 6 attached to the generator 10, and the subtraction unit 42 acquires the rotational speed ωod from the encoder 6.

  For example, the speed control unit 43 generates a current command Iir by PI (proportional integration) control of the difference between the speed command ωir and the rotational speed ωod so that the deviation between the speed command ωir and the rotational speed ωod becomes zero. . The current command Iir includes, for example, U-phase, V-phase, and W-phase current commands Iur, Ivr, and Iwr.

  For example, the current control unit 44 generates a voltage command Vir by performing PI control on a deviation between the current Iid and the current command Iir so that the current Iid matches the current command Iir. The voltage command Vir includes, for example, U-phase, V-phase, and W-phase voltage commands Vur, Vvr, and Vwr.

  The switch drive unit 45 generates the drive signals S1 to S6 so that the U-phase, V-phase, and W-phase voltages become voltages according to the voltage commands Vur, Vvr, and Vwr. Thereby, the rotational speed ωi of the generator 10 can be set to a rotational speed corresponding to the speed command ωir.

  When the maximum power that can be output from the power conversion unit 21 to the power system 3 (hereinafter referred to as the maximum output power Pomax) is equal to or less than the set output power Pox, the command generation unit 41 can obtain the rotation speed ωi that provides the maximum output power Pomax. The speed command ωir is generated so that the generator 10 rotates.

  On the other hand, when the maximum output power Pomax exceeds the set output power Pox, the command generation unit 41 limits the output power Po to the power system 3 to be equal to or less than the set output power Pox. In this case, the command generation unit 41 causes the generator 10 to rotate at the rotational speed ωi that limits the output power Po to the set output power Pox or less and at a rotational speed ωi that is faster than the rotational speed at which the maximum output power Pomax is obtained. A speed command ωir is generated so as to rotate.

  Here, the characteristics of the water turbine 2 will be described. FIG. 3 is a diagram illustrating an example of a characteristic of the axial torque Trq-rotational speed ωi of the water turbine 2. In the example shown in FIG. 3, it is a figure which shows the outline of the relationship between axial torque Trq and rotational speed (omega) i in three inflow water quantity Qw1, Qw2, Qw3 from which inflow water quantity Qw differs.

As shown in FIG. 3, the shaft torque Trq and the rotational speed ωi are approximately linear functions, and have a negative proportional relationship with an offset. Here, assuming that the shaft torque Trq when the rotational speed ωi is 0 is TI, and the rotational speed ωi when the shaft torque Trq is 0 is ωin, the relationship between the shaft torque Trq and the rotational speed ωi. Can be expressed as, for example, the following expression (1).
Trq = TI−TI × (ωi / ωin) (1)

  Assuming that the loss of the generator 10 is small and can be ignored, the maximum power Pimax that can be obtained with the inflow water amount Qw is the largest value among the values obtained by multiplying the shaft torque Trq and the rotational speed ωi. The multiplication result of the shaft torque Trq and the rotation speed ωi is the largest when the shaft torque Trq and the rotation speed ωi are in the relationship shown in FIG. 3 when ωi = ωin / 2.

Therefore, the maximum power Pimax can be obtained by the following equation (2).
Pimax = Trq × ωin / 2 = TI × ωin / 4 (2)

  In small hydropower generation, heads are determined by dams, weirs, and waterways, and there is no significant change in effective heads depending on the fluctuation of the overflow water level, and hydropower is determined by the amount of water. Then, assuming that the hydropower is determined only by the amount of water, assuming that the rated generated power is 1 and ωi / ωix = 1, the relationship between the generated power Pi and the rotational speed ωi is expressed as shown in FIG. Can do. FIG. 4 is a diagram illustrating an example of the relationship between the generated power Pi and the rotation speed ωi.

Therefore, in this case, the relationship among the generated power Pi, the output power Po, the inflow water amount Qw, and the rotational speed ωi can be generalized as shown in the following equation (3). The command generation unit 41 can calculate the speed command ωir based on the relationship of the following formula (3). Note that α = Qwx / Qw and n = ωi / ωix.
Pi = Po / ηc = −αn ² + 2n (3)

  The command generation unit 41 includes a water amount information acquisition unit 51, a storage unit 52, and a speed command generation unit 54. The water amount information acquisition unit 51 acquires the inflow water amount Qw from the water amount detection device 4. The storage unit 52 stores the generated power Pi for each inflow water amount Qw. In addition, the storage unit 52 stores the inflow water amount Qw, the rotation speed ωi, and the generated power Pi at which the maximum output power Pomax becomes the set output power Pox as the rated inflow water amount Qwx, the rated rotation speed ωix, and the rated generation power Pix.

  The speed command generator 54 determines whether or not the maximum output power Pomax that can be output to the power system 3 is equal to or less than the set output power Pox. The speed command generation unit 54 determines whether or not the maximum output power Pomax is less than or equal to the set output power Pox based on whether or not the inflow water amount Qw acquired by the water amount information acquisition unit 51 is less than or equal to the rated inflow water amount Qwx. To do.

Next, the speed command generation unit 54 determines the speed command ωir based on the inflow water amount Qw acquired by the water amount information acquisition unit 51 and the information stored in the storage unit 52. For example, the speed command generation unit 54 calculates the speed command ωir by calculating the following equation (4).
Pi / Pix = − (Qwx / Qw) × (ωir / ωix) ² +2 (ωir / ωix)
... (4)

  When the inflow water amount Qw is less than or equal to the rated inflow water amount Qwx, that is, when the maximum output power Pomax is less than or equal to the set output power Pox, the speed command generation unit 54 performs the calculation of Equation (4) above as Pi = Pimax. . Thus, when the maximum output power Pomax is equal to or less than the set output power Pox, the maximum output power Pomax can be output to the power system 3.

  On the other hand, when the inflow water amount Qw exceeds the rated inflow water amount Qwx, that is, when the maximum output power Pomax exceeds the set output power Pox, the speed command generation unit 54 sets Pi / Pix = 1 and calculates the above equation (4). I do. Thereby, when the maximum output power Pomax exceeds the set output power Pox, the set output power Pox can be output to the power system 3.

  For example, when Qw / Qwx = 1.3, ωi / ωix = 1.92, and the speed command generator 54 outputs the speed command ωir as ωir = ωix × 1.92. The speed command generator 54 can also output power lower than the set output power Pox to the power system 3 when the maximum output power Pomax exceeds the set output power Pox.

  In the above description, the example in which the speed command generation unit 54 generates the speed command ωir based on the above formula (4) has been described. However, the above formula (4) represents the characteristics of the turbine 2 and the loss of the generator 10. It can be appropriately changed based on the characteristics and the characteristics of the power conversion efficiency ηc of the power converter 21. Thereby, the speed command ωir can be determined with higher accuracy.

  In addition, when the inflow water amount Qw exceeds the rated inflow water amount Qwx, it is only necessary to control the rotation speed ωi so that the rotation speed is higher than the rotation speed at which the maximum power Pimax is obtained. It can be changed as appropriate.

  For example, the speed command generation unit 54 stores a table in which the ratio γ (= Qw / Qwx) between the rated inflow water amount Qwx and the inflow water amount Qw and the speed command ωir is stored in the internal storage unit, and based on the table The speed command ωir may be selected and output from the ratio γ based on the inflow water amount Qw acquired by the water amount information acquisition unit 51.

  Further, the speed command generation unit 54 stores a table in which the inflow water amount Qw and the speed command ωir are associated with each other in an internal storage unit, and based on the table, the speed command generation unit 54 calculates the speed from the inflow water amount Qw acquired by the water amount information acquisition unit 51. The configuration may be such that the command ωir is selected and output.

  The command generation unit 41 is not limited to the configuration illustrated in FIG. 2, and may have the configuration illustrated in FIGS. 5 to 7, for example. Hereinafter, a configuration example of the command generation unit 41 will be further described. FIG. 5 is a diagram illustrating an example of another configuration of the command generation unit 41. In FIG. 5, the same reference numerals are given to the same components as those of the command generator 41 shown in FIG. 2, and the configurations of the power converter 21 and the controller 22 are partially omitted.

  The command generation unit 41 illustrated in FIG. 5 includes a water amount information acquisition unit 51, a storage unit 52, a speed command generation unit 54A, and a power detection unit 55. For example, the power detector 55 detects the output power Po based on the current Iod and the voltage Vod.

  The speed command generation unit 54A can perform the calculation of the above formula (4) by correcting the water flow ratio α (= Qwx / Qw) based on the output power Po. For example, when Po / Pox = β, when β <1, the speed command generation unit 54A sets α ′ = α / β and performs the calculation of the above equation (4) using the corrected running water ratio α ′. . Thereby, the power converter device 20 can optimally adjust the speed command ωir. Note that it is only necessary that the speed command ωir can be adjusted based on the output power Po, and the present invention is not limited to the above-described processing.

  As described above, the command generation unit 41 shown in FIG. 5 performs the correction based on the output power Po to obtain the speed command ωir, so that the speed command ωir can be generated more optimally. Efficiency can be further improved.

  FIG. 6 is a diagram illustrating an example of still another configuration of the command generation unit 41. In FIG. 6, the same reference numerals are given to the same components as those of the command generation unit 41 shown in FIG. 2, and the configuration of the power conversion unit 21 is partially omitted.

  The command generation unit 41 illustrated in FIG. 6 includes a storage unit 52, a speed command generation unit 54, and a water amount estimation unit 56. The memory | storage part 52 and the speed command generation part 54 are the structure and operation | movement similar to the command generation part 41 shown in FIG.

  The water amount estimation unit 56 obtains instantaneous values (hereinafter referred to as voltages Vu, Vv, and Vw) and currents Iu, Iv, and Iw of the U-phase, V-phase, and W-phase of the generator 10 and applies the voltages. Based on Vu, Vv, Vw and currents Iu, Iv, Iw, the generated power Pi is detected (or estimated). The voltages Vu, Vv, and Vw are detected by the voltage detection unit 29 of the power conversion unit 21.

  The water amount estimation unit 56 can estimate the inflow water amount Qw based on the generated power Pi detected based on the currents Iu, Iv, Iw and the voltages Vu, Vv, Vw. For example, the water amount estimation unit 56 determines the largest generated power Pi among the generated power Pi detected when the inflow water amount Qw notified to the speed command generating unit 54 is increased or decreased as the maximum power Pimax, and sets the maximum power Pimax. It is estimated that the corresponding inflow water amount Qw is the current inflow water amount Qw.

  Further, the inflow water amount Qw that the water amount estimation unit 56 notifies to the speed command generation unit 54 is limited to the rated inflow water amount Qwx or less. The water amount estimation unit 56 increases or decreases the inflow water amount Qw if the generated power Pi detected when the inflow water amount Qw is the rated inflow water amount Qwx among the generated power Pi detected by the increase or decrease in the inflow water amount Qw. The current inflow water amount Qw is estimated based on the relationship between the rate of change in the generated power Pi with respect to the rate.

  As described above, for example, the speed command generation unit 54 uses the inflow water amount Qw estimated by the water amount estimation unit 56 and the information stored in the storage unit 52 as parameters based on the above equation (4), as a speed command ωir. Ask for. Since the generated power Pi and the output power Po are in the relationship shown in the above equation (3), the water amount estimation unit 56 can use the output power Po instead of the generated power Pi, and the output power The generated power Pi can also be obtained from Po. For example, the water amount estimation unit 56 performs the same process as in the case of the generated power Pi, based on the output power Po when the rotational speed ωi of the generator 10 is increased or decreased by increasing or decreasing the inflow water amount Qw, The power Pimax can also be estimated. In this case, the water amount estimation unit 56 can detect the output power Po based on the current Iod and the voltage Vod.

  As described above, the command generation unit 41 illustrated in FIG. 6 can estimate the inflow water amount Qw without using the water amount detection device 4 illustrated in FIG. 2, and thus the cost of the entire system can be suppressed. In the command generation unit 41 illustrated in FIG. 5, the water amount information acquisition unit 51 may be replaced with a water amount estimation unit 56.

  FIG. 7 is a diagram illustrating an example of still another configuration of the command generation unit 41. In FIG. 7, the same components as those of the command generation unit 41 shown in FIG.

  The command generation unit 41 illustrated in FIG. 7 includes a water amount information acquisition unit 51, a storage unit 52B, a maximum power calculation unit 53, and a speed command generation unit 54B. The storage unit 52B stores the characteristics of the water wheel 2. For example, the storage unit 52B stores a table in which the shaft torque Trq and the rotational speed ωi are associated with each other for each inflow water amount Qw, an arithmetic expression, or parameters of the arithmetic expression (for example, TI and ωin).

  An arithmetic expression indicating the relationship between the shaft torque Trq and the rotational speed ωi can be expressed as shown in the above expression (1), for example. The above formula (1) is an example, and the accuracy can be improved by using an arithmetic expression according to the relationship between the shaft torque Trq and the rotational speed ωi in the water turbine 2.

  The maximum power calculation unit 53 is based on the inflow water amount Qw acquired by the water amount information acquisition unit 51 and the characteristics of the water turbine 2 stored in the storage unit 52B, and the maximum power that can be extracted from the generator 10 by the current inflow water amount Qw. Pimax is calculated. For example, the maximum power calculation unit 53 acquires parameters (for example, TI and ωix) from the storage unit 52B, and calculates the maximum power Pimax according to (2) above.

  The speed command generation unit 54B determines whether or not the maximum output power Pomax that can be output to the power system 3 is equal to or less than the set output power Pox. For example, the speed command generation unit 54B multiplies the maximum output power Pomax by the power conversion efficiency ηc of the power conversion unit 21 by multiplying the maximum power Pimax by whether or not the maximum output power Pomax is equal to or less than the set output power Pox. Calculate.

  The speed command generation unit 54B compares the maximum output power Pomax and the set output power Pox. When the maximum output power Pomax is equal to or less than the set output power Pox, the rotational speed ωi (for example, ωi = ωix) at which the maximum output power Pomax is obtained. / 2), the speed command ωir is generated so that the generator 10 rotates. Thereby, the generator 10 is controlled so that the rotational speed ωi of the generator 10 coincides with the speed command ωir, and the output power Po to the power system 3 becomes the maximum output power Pomax.

  On the other hand, the speed command generator 54B, when the maximum output power Pomax exceeds the set output power Pox, the speed command ωir so that the generator 10 rotates at a rotational speed ωi faster than the rotational speed at which the maximum output power Pomax is obtained. Is generated. Thereby, the generator 10 is controlled so that the rotational speed ωi of the generator 10 coincides with the speed command ωir, and the output power Po to the power system 3 is limited to the set output power Pox or less.

Here, the set output power Pox can be expressed as the following equation (5) when the above equation (1) holds.
Pox = Pi × ηc
= (Trq × ωir) / ηc
= {TI-TI × (ωir / ωin)} × ωir × ηc (5)

Therefore, in this case, when the maximum output power Pomax exceeds the set output power Pox, the speed command generation unit 54B can generate the speed command ωir by calculating the speed command ωir that satisfies the following expression (6). it can.
ωir ² / ωin−ωir + Pox / (TI × ηc) = 0 (6)

  In addition, the said speed | rate command production | generation part 54B can improve the precision of speed command (omega) ir by making said Formula (6) into the arithmetic expression according to the relationship between the axial torque Trq and the rotational speed (omega) i in the water turbine 2. FIG. .

  Further, the command generation unit 41 described above, when the maximum output power Pomax exceeds the set output power Pox, the speed command ωir so that the generator 10 rotates at a rotational speed ωi that is faster than the rotational speed at which the maximum output power Pomax is obtained. However, the present invention is not limited to such a process.

  For example, even when the maximum output power Pomax exceeds the set output power Pox, the command generation unit 41, for example, if the maximum output power Pomax is up to n (for example, 1.2) times the set output power Pox, for example. The speed command ωir is generated so that the generator 10 rotates at a rotational speed ωi that is slower than the rotational speed at which the maximum output power Pomax is obtained. Even when the generator 10 rotates at a rotational speed ωi corresponding to the speed command ωir generated in this way, an overcurrent does not occur as long as it is up to n times the set output power Pox.

  Then, the command generator 41 speeds the generator 10 to rotate at a rotational speed ωi that is faster than the rotational speed at which the maximum output power Pomax is obtained when the maximum output power Pomax exceeds n times the set output power Pox. A command ωir is generated. In this way, the output power Po can be suppressed, and the current flowing between the generator 10 and the power conversion device 20 can be suppressed while the output power Po is suppressed. 10 and the power converter 21 can be protected from overcurrent.

  FIG. 8 is a diagram illustrating an example of the power generation control process performed by the power conversion device 20. The control unit 22 repeatedly executes the power generation control process shown in FIG. As shown in FIG. 8, the control unit 22 acquires the inflow water amount Qw to the water turbine 2 (step S10), and compares the maximum output power Pomax and the set output power Pox according to the inflow water amount Qw (step S11). .

  Since Pomax / Pox = Qw / Qwx = Pimax / Pox holds, the control unit 22 compares the generated power Pi with the rated generated power Pix instead of the output power Po, and the inflow water amount Qw and the rated inflow water amount. The comparison in step S11 can also be performed based on the comparison with Qwx.

  The control unit 22 determines whether or not the maximum output power Pomax exceeds the set output power Pox (step S12). When it is determined that the maximum output power Pomax exceeds the set output power Pox (step S12; Yes), the control unit 22 has a rotational speed ωi corresponding to the generated power Pi for outputting the set output power Pox, and A speed command ωir for rotating the generator 10 at a rotational speed ωi faster than the rotational speed when the generated power Pi is the maximum power Pimax is generated (step S13).

  On the other hand, when it is determined that the maximum output power Pomax is equal to or less than the set output power Pox (step S12; No), the control unit 22 rotates the generator 10 at the rotational speed ωi when the generated power Pi is the maximum power Pimax. Is generated (step S14).

  When the processes of steps S13 and S14 are completed, the control unit 22 generates drive signals S1 to S6 corresponding to the generated speed command ωir, and outputs them to the power conversion unit 21 (step S15). Thereby, the output power Po can be suppressed, and overcurrent can be suppressed while suppressing the output power Po.

  As described above, in small hydroelectric power generation, a head or the like is determined by a dam, a weir, and a water channel, and there is no significant change in the effective head when the overflow level changes, and the hydropower is determined by the amount of water. Therefore, in the above-described embodiment, the maximum power Pimax is estimated according to the inflow water amount Qw. However, for example, when there is an influence on hydraulic power other than the water amount, such as a change in head or water channel, the command generation unit 41 In addition, the maximum power Pimax can be estimated using a change such as a head or a water channel as a correction value.

  The control unit 22 can also process each command by converting the U-phase, V-phase, and W-phase fixed coordinate systems into components of the dq-axis coordinate system synchronized with the rotation of the generator 10. The d axis is an axis parallel to the magnetic flux of the generator 10, and the q axis is an axis orthogonal to the d axis.

  The control unit 22 is realized by an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The control unit 22 may include, for example, a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), an input / output port, and various circuits. In this case, the CPU of the microcomputer can realize the above-described control by reading and executing the program stored in the ROM.

  In addition, although embodiment mentioned above demonstrated the example in which the power converter device 20 controls the generator 10 by speed control, the power converter device 20 can also control the generator 10 by torque control.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Power generation system 2 Water wheel 3 Electric power system 4 Water quantity detection apparatus 5 Connection interruption machine 10 Generator 20 Power converter 21 Power conversion part 22 Control part 32 Shutdown control part 41 Command generation part 51 Water quantity information acquisition part 52, 52B Storage part 54 54A, 54B Speed command generation unit 55 Power detection unit 56 Water amount estimation unit

Claims (8)

A controller for controlling the output power to the power system by controlling the rotational speed of the generator according to the amount of water flowing into the water turbine connected to the generator;
The controller is
When the maximum power that can be output to the power system exceeds set power, the generator is controlled at a rotational speed faster than the rotational speed at which the maximum power is obtained, and the output power is limited to the set power or less. A power conversion device. The controller is
The power converter according to claim 1, wherein when the maximum power is equal to or less than a set power, the generator is controlled at a rotation speed at which the maximum power is obtained. The water turbine and the generator are connected via a circuit breaker,
The controller is
2. A cut-off control unit that controls the breaker and separates the turbine and the generator when the generated power of the generator exceeds the power for outputting the set power. Or the power converter device of 2. The controller is
The estimation part which estimates the said amount of water or the said maximum electric power based on the electric power output to the said electric power grid when increasing / decreasing the rotational speed of the said generator is provided. The power converter as described in one. The controller is
A water amount information acquisition unit for acquiring information on the amount of water flowing into the water wheel;
A storage unit for storing information on the amount of water from which the maximum power corresponding to the set power is obtained;
A speed command generating unit that generates a speed command that defines a rotational speed of the generator based on a ratio between the water amount information acquired by the water amount information acquiring unit and the water amount information stored in the storage unit. The power converter according to any one of claims 1 to 3, wherein the power converter is provided. A power detection unit for detecting the output power;
The controller is
A speed command generating unit that generates a speed command that defines a rotational speed based on the amount of water flowing into the water wheel;
The speed command generator is
The power conversion apparatus according to claim 1, wherein the speed command is adjusted based on the output power detected by the power detection unit. The power conversion device according to any one of claims 1 to 6,
The power generation system comprising: the power generator connected to the power conversion device. A control step of controlling the output power to the power system by controlling the rotational speed of the generator connected to the turbine according to the amount of water flowing into the turbine,
The control step includes
When the maximum power that can be output to the power system exceeds the set power, the generator is controlled at a rotational speed that is faster than the rotational speed at which the maximum power is obtained, and the output power to the power system is less than or equal to the set power A power generation control method comprising the step of limiting.

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