Wind power generation system and control method therefor

Abstract

To improve the efficiency of a wind power generation system in a wide range of wind speed sections including a low-speed rotation section where the wind speed is low by quickly following an instantaneous change in wind speed.SOLUTION: The wind power generation system includes a lift-type fixed wing fixed to a rotating shaft, a plurality of three-phase AC generators, a step-up / down converter and a resistance load constituting a load of the wind power generator, and a system controller, and the three-phase AC generator has a rectifier unit that converts a three-phase AC output into a DC output. The step-up / down converter may be connected to the rectifier unit, and the system controller may control the load to follow an optimal TSR (λ) suitable for the fixed wing according to a change in wind speed in real time based on a rotation speed of the rotating shaft, information on a super-instantaneous wind speed obtained from an anemometer, an output of the generator, and a state of the load.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a wind power generation system and a control method thereof, and more particularly to a lift-type small wind power generation system and a control method thereof. [Background technology]

[0002] It is considered desirable for small wind power generation systems to have an annual average wind speed of 5 m / s or more. However, there are not many locations where such an average wind speed can be obtained and that are suitable for installing small wind power generation systems. For this reason, wind power generation systems that can generate electricity efficiently even when the wind speed is low have been proposed. Patent Document 1 discloses a power generation system including an AC generator having one rotor and one stator, the stator being provided with multiple stator coils for each phase, a switching circuit that switches the connection of the multiple stator coils for each phase between a series connection and a parallel connection, and a power conversion device that converts AC power output from the AC generator into DC power.The stator of this AC generator is provided with multiple stator coils for each phase, and the multiple stator coils for each phase are switched by the switching circuit between a state in which they are connected in series and a state in which they are connected in parallel. According to the description in Patent Document 1, when the stator coils are connected in series, the number of turns is twice that when they are connected in parallel, so the generator can output the voltage necessary to charge the battery even when the wind speed is low. On the other hand, when the coils are connected in parallel, the number of turns is half that when the stator coils are connected in series, so when the wind speed is high, the voltage output from the generator can be prevented from becoming too high.

[0003] Patent Document 2 proposes a wind power generation system that includes a plurality of generators commonly connected to a single main shaft that rotates together with the wind turbines in order to generate power efficiently in response to changing wind speeds, a power converter connected to at least one of the plurality of generators and supplying the power to an AC power system, and a switch that directly inputs AC power generated by other generators that are not connected to the power converter into the AC power system; when the wind speed is low, only the at least one generator generates power, and when the wind speed exceeds a rated wind speed, power is generated by the at least one generator and the other generators.

[0004] Patent Document 3 discloses an invention for a wind power generation system equipped with a rotor having blades that receive lift generated by wind, the invention including a control device that controls the wind power generation system or equipment mounted thereon, the control device temporarily changing the pitch angle to suppress braking that hinders acceleration of the rotor when the wind speed in the wind power generation system increases while the rotation speed of the rotor is below the rated rotation speed. Specifically, it describes that the TSR (tidal speed ratio) at which the power coefficient Cp and torque coefficient peak is changed to temporarily suppress generator torque. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5590472 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-50181 [Patent Document 3] Patent No. 6650317 Summary of the Invention [Problem to be solved by the invention]

[0006] The invention of Patent Document 1 includes a first relay Ry1 to a seventh relay Ry7 as a switching circuit for switching the connection of multiple stator coils between a series connection and a parallel connection. That is, as shown in FIG. 2A of Patent Document 1, one generator must provide a three-phase output (three wires), while the other generator must draw (output) each phase's output (six wires). Furthermore, as shown in FIG. 3 of Patent Document 1, five SPDT relays and two SPST relays are required, resulting in a complex system with many connections. Furthermore, because three-phase stator coils generating AC voltage are connected in series and parallel, the two generators must have the same pole pair. Furthermore, the two generators must have the same output voltage, frequency, and electrical angle. Therefore, it is difficult to control the generators to obtain sufficient active power while switching between series and parallel operation. Using three or more generators would likely result in a significantly more complex system.

[0007] On the other hand, the invention of Patent Document 2 does not have the same problems as the invention of Patent Document 1 because the two generators are completely independent. However, when the wind speed is low, only one generator generates electricity and the other generator is stopped, so the two generators are not used effectively as a whole system. In particular, there is a problem that sufficient power output cannot be obtained when the wind speed is low.

[0008] The invention in Patent Document 3 relates to a movable blade type wind power generation system with a variable blade pitch angle. However, wind speed in the natural world is constantly changing, and movable blade type wind power generation systems have a large time lag and cannot respond to instantaneous changes in wind speed.

[0009] Although there are known inventions for controlling wind power generation systems by predicting instantaneous changes in wind speed in advance, in reality, wind speed rarely changes instantaneously as predicted. Rather, it is thought that power generation efficiency could be improved if the actual instantaneous changes in wind speed could be detected and the wind power generation system could be controlled to quickly follow them. Furthermore, wind power generation systems typically use three-phase AC generators, whose output voltage is proportional to the rotational speed of the wind turbine rotor. Therefore, when the wind speed is low and the rotor rotation speed is slow, the generator output voltage is low and the battery cannot be charged. It is possible to increase the generator output voltage even when the wind speed is low by increasing the number of turns of the three-phase coil, for example. However, when the wind speed increases, the generator output voltage becomes too high and the generator's output power cannot be used effectively.

[0010] Therefore, in order to generate power efficiently with a wind power generation system, it is desirable to increase the efficiency of the wind power generation system over a wide range of wind speed zones, particularly in zones with low average wind speeds.

[0011] An object of the present invention is to improve the efficiency of a wind power generation system over a wide range of wind speeds by controlling the wind power generation system in a manner that quickly follows instantaneous changes in wind speed. [Means for solving the problem]

[0012] According to one aspect of the present invention, there is provided a wind power generation system having a wind power generator and a load connected to the wind power generator, the wind power generator includes a lift-type fixed blade fixed to a rotating shaft, a plurality of three-phase AC generators, a step-up / step-down converter and a resistive load constituting the load, and a system controller; Each of the three-phase AC generators has a rectifier unit that converts a three-phase AC output into a DC output, the step-up / step-down converter is connected to the rectifier section of each of the three-phase AC generators; the system controller is configured to control the load so as to track in real time an optimum TSR(λ) suited to the fixed blades in response to changes in wind speed, based on the wind turbine specifications, the rotational speed of the rotating shaft, information on super-instantaneous wind speed obtained from an anemometer, the output of the generator, and a state of the load; The rotation speed and the super-instantaneous wind speed are each an average value of at least 10 data points measured at short time intervals of 0.01 seconds or less.

[0013] This invention is based on a fixed-wing wind turbine, and therefore does not require mechanically moving components such as blades to respond to instantaneous changes in wind speed. Instead, it only requires controlling loads such as converters that operate instantaneously with electrical signals. This allows the fixed-wing wind turbine to efficiently convert instantaneously changing wind energy into electrical energy. This allows for high efficiency in wind power generation systems over a wide range of wind speeds, including areas with low average wind speeds. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing the overall system configuration of a wind power generation system according to an embodiment of the present invention. [Figure 2] 1 is a side view of a lift-type small wind power generation system to which the present invention is applied. [Figure 3] FIG. 2 is a functional block diagram of a system controller appearing in FIG. 1. [Figure 4] 2 is a diagram showing the characteristics of battery charging power and resistive load power when generators are connected in series and in parallel in the wind power generation system of FIG. 1. FIG. [Figure 5A] FIG. 10 is a circuit diagram showing a configuration in which two generators are connected in series by a series-parallel switching means. [Figure 5B] FIG. 10 is a circuit diagram showing a configuration in which two generators are connected in parallel by a series-parallel switching means. [Figure 5C] FIG. 10 is a circuit diagram showing a configuration in which three generators are connected in series by a series-parallel switching means. [Figure 6A] FIG. 1 is a circuit diagram showing a configuration of a boost converter. [Figure 6B] FIG. 1 illustrates the operation of a boost converter when switched on. [Figure 6C] FIG. 1 illustrates the operation of a boost converter when switched off. [Figure 7A] FIG. 1 is a circuit diagram showing the configuration of a BUCK converter. [Figure 7B] FIG. 1 illustrates the operation of a buck converter at switch-on. [Figure 7C] FIG. 1 illustrates the operation of a buck converter when switched off. [Figure 8] 10 is a flowchart showing the process of connecting two generators in series and in parallel in response to changes in wind speed. [Figure 9] FIG. 10 is a diagram showing the relationship between wind speed, the total output of the generator, and the output voltage of the generator. [Figure 10] FIG. 4 is a circuit diagram that embodies the functional blocks of the system controller shown in FIG. 3. [Figure 11] FIG. 2 is a block diagram showing details of an input data processing unit of the system controller. [Figure 12] 10 is a flowchart showing the overall processing of the system controller. [Figure 13] FIG. 2 is a block diagram showing details of a TSR processing unit and a PID processing unit #1 of the system controller. [Figure 14] 14 is a flowchart showing the processing of the TSR processing unit and PID processing unit #1 in FIG. 13. [Figure 15] FIG. 10 is a diagram showing the relationship between TSR(λ), power coefficient Cp, and wind speed. [Figure 16] FIG. 10 is a block diagram showing details of a CP processing unit and a PID processing unit #2 of the system controller. [Figure 17] 17 is a flowchart showing the processing of the CP processing unit and PID processing unit #2 in FIG. 16. [Figure 18] 10 is a time chart showing an example of the relationship between average wind speed, instantaneous wind speed, output power (watts), and actual output (limit). [Figure 19] FIG. 11 is a block diagram showing details of a limiter in FIG. 10. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, an example of a wind power generation system in which multiple generators are switched between series and parallel using a series-parallel switching means will be described, but the wind power generation system of the present invention can also be applied to wind power generation systems that do not switch between series and parallel. 1 shows the overall system configuration of a wind power generation system according to one embodiment of the present invention. Two permanent magnet three-phase AC generators 10A and 10B each include a generator section 102A (102B) including a three-phase stator coil, a rectifier section 103A (103B) that converts the AC output of each phase into a DC output, voltage / current sensors 104A (104B), and DC output terminals (+) terminal T10, (-) terminal T11, (+) terminal T20, and (-) terminal T21). The rectifier sections 103A and 103B each include diodes D1 to D6 and a capacitor C1 connected in the forward direction between the coils of each of the three phases of the three-phase AC generator sections 102A (102B). Reference numeral 11 denotes a step-up / step-down converter / series-parallel switching means, which includes a step-up / step-down converter and a series-parallel switching means 113 that switches the connection between series and parallel of two three-phase AC generators 10A and 10B. The step-up / step-down converter (DC / DC converter) is made up of a boost converter 111 that boosts the voltage of the DC output of the three-phase AC generator, and a buck converter 112 that lowers the voltage of the DC output. The boost converter 111 and the buck converter 112 each include a PWM / current circuit 117, 118. Reference numeral 20 denotes a power line.

[0016] System controller 12, which controls the entire wind power generation system, is composed of an FPGA and a CPU. System controller 12 starts and operates two three-phase AC generators 10A and 10B in a series connection. When the total output voltage of the two three-phase AC generators 10A and 10B exceeds a predetermined threshold, system controller 12 controls the two three-phase AC generators 10A and 10B to operate in a parallel connection. Furthermore, system controller 12 effectively utilizes instantaneous wind speeds to operate the wind power generation system efficiently and without stalling, regardless of wind speed. System controller 12 is implemented as a dedicated FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or an IC circuit chip using a general-purpose single-chip microcomputer (CPU), and is mounted on a printed circuit board. This system controller 12 is configured to send and receive various data to and from the voltage / current sensor 104, the step-up / step-down converter / series-parallel switching means 11, etc. via a signal line 21. The system controller 12 has the function of converting various information into, for example, a parallel signal or a serial signal via the signal line 21 and sending and receiving the information to and from the step-up / step-down converter / series-parallel switching means 11, etc. The current of the current sensor is used as a hardware limit value for a comparator or the like within the device. Reference numeral 13 denotes a battery controller, which includes a voltage control circuit 132 and a current control circuit 134 to control the amount of charge from the generators 10A and 10B to the battery 14. An output load 15 is connected to the battery 14. Note that an inverter connected to the power grid may also be connected to the step-up / step-down converter as a load connected to the wind power generator. Reference numeral 16 denotes a resistive load connection means, which has the function of connecting the rectifier sections 103A and 103B of the generator sections 102A and 102B to a resistive load 17 via a switch when the output power of the generator sections 102A and 102B is greater than a threshold value, thereby directly consuming the excessive power without passing through a step-up / step-down converter. The resistive load 17 includes a PWM / current circuit 172. When the output power of the generator sections 102A and 102B falls below the threshold value, the resistive load 17 is disconnected. The connection and disconnection of the resistive load connection means to the generator sections 102A and 102B has a hysteresis characteristic.

[0017] Figure 2 is a side view showing an example of a lift-type small wind power generation system to which the present invention is applied, in which generators 10A and 10B and lift-type vertically elongated blades 30 and 31 as fixed wings constituting a Darrieus wind turbine are connected to a common vertical rotating shaft 32. Note that the wind turbine may be of any type as long as it has lift-type fixed wings, has the function of receiving wind head-on regardless of wind direction, and does not require azimuth control. For example, a downwind propeller wind turbine fixed to a horizontal shaft may also be used. 33 is a frame that supports the rotating shaft, etc., and 184 is a high-precision anemometer. For a specific example of the structure of a lift-type small wind power generation system, the description in Japanese Patent No. 7101416, which is an invention by the same inventor as the present application, is cited.

[0018] 3 is a functional block diagram of the system controller 12. This system controller 12 has the function of controlling the entire wind power generation system, and includes, as blocks for executing each function, an input data processing unit 1210 that processes input data, a series / parallel mode determination unit 1212 that controls the series or parallel connection operation of the two three-phase AC generators 10A, and a control unit 1214 for series / parallel switching means. The system controller 12 also includes a control unit 1216 for resistive load connection means that controls the resistive load according to the output power of the AC generator, and a battery charge control unit 1218. The system controller 12 further includes a calculation unit 122 that calculates a target speed and an optimal output load based on the TSR (tidal speed ratio) and the output coefficient Cp, a calculation unit 123 that calculates a reference load based on Cp and inverse Cp, and the generator output power (watts), a control unit 124 for generator output / resistive load based on the output load, a control unit 125 for generator output / resistive load based on the output power, a limit control unit 126, a converter control unit 127, and a resistive load control unit 128. With these functions, the system controller 12 effectively utilizes the energy of the wind, which changes instantaneously, to control the operation of the wind power generation system so that it operates efficiently and does not stall, from low to high wind speeds. The functions executed by each functional block will be explained in detail later. Note that the classification of each functional block is for the purpose of explaining the concept of the present invention, and it goes without saying that there is no relationship between each functional block and a specific circuit configuration. 1 , various data, such as battery voltage and current 136, are input to the system controller 12. Other data input via the input interface 188 include data from the rotary encoder 182, wind speed measured by the anemometer 184, meteorological data 185 measured by a sensor, wind turbine specifications 186, and a tip speed ratio 1874 provided by a tip speed ratio setting unit 1872. The rotary encoder 182 employs a Hall element, GMR sensor, or optical sensor, and has a high resolution of 20 bits or more per rotation, capable of sampling at a rate of, for example, 20,000 / second. The anemometer 184 also employs a high-precision anemometer capable of sampling at a rate of, for example, 20,000 / second. Data and signals are input and output to and from the system controller 12 via an AD converter or a DA converter.

[0019] Figure 4 is a diagram showing the characteristics of battery charging power and resistive load power when the generators are connected in series and in parallel in the wind power generation system of Figure 1. In both series connection operation and parallel connection operation, the system controller 12 controls the battery charging voltage so that it is below a predetermined threshold. When the charging voltage exceeds the predetermined threshold, the system controller 12 connects the rectifier units 103A and 103B of each generator to the resistive load 17 via a switch, and controls the resistive load 17 to consume excessive output power of the wind power generation system. When an inverter connected to the power grid is also connected to a buck-boost converter, the output power is controlled, including the power consumed by the inverter.

[0020] "Series connection of generators" FIG. 5A is a circuit diagram showing a configuration in which two generators are connected in series by a series-parallel switching means 11. The series-parallel switching means 113 includes a circuit that connects the DC output (+) terminal T10 and (-) terminal T21 of the two generators to the input terminals of the step-up / step-down converters 111 and 112. The series-parallel switching means 113 further includes a first terminal Ts1, a second terminal Ts2, and a changeover switch SW1 that switches between on and off between these terminals. The series-parallel switching means 113 also includes a first diode D13 connected in the forward direction between the DC output (+) terminal T10 of one generator 10A and the DC output (+) terminal T20 of the other generator 10B, and a second diode D14 connected in the forward direction between the DC output (-) terminal T11 of one generator 10A and the DC output (-) terminal T21 of the other generator 10B. The changeover switch SW1 is driven by a relay or the like. In this series connection, the DC output (-) terminal T11 of one generator 10A is connected to the DC output (+) terminal T20 of the other generator 10B via the closed changeover switch SW1 of the series-parallel switching means 113. As a result, the DC output (+) terminal T10 of one generator 10A and the DC output (-) terminal T21 of the other generator 10B are connected to the input terminals of the step-up / step-down converters 111 and 112. With this connection configuration, the DC outputs of the two AC generators are supplied to the step-up / step-down converters. In other words, if the DC output voltages of the AC generators are VA and VB, then V out The power of voltage =VA+VB is supplied to the buck-boost converter. If VA=VB, then V out =2VA is supplied to the buck-boost converter.

[0021] "Parallel connection of generators" FIG. 5B is a circuit diagram showing the configuration when two generators are connected in parallel by the series-parallel switching means 11. When the generators are connected in parallel, the changeover switch SW1 is in an open state. This connects the DC output (+) terminal T10 of one generator 10A to the DC output (+) terminal T20 of the other generator 10B, and the DC output (-) terminal T11 of one generator 10A is connected to the DC output (-) terminal T21 of the other generator 10B. As a result, the two generators 10A and 10B are connected to the step-up / step-down converters 111 and 112 in a parallel connection state. That is, if the DC output voltages of the AC generators are VA=VB, then V out Power with a voltage of =VA=VB is supplied to the buck-boost converter.

[0022] "Series and parallel connection of three or more generators" The series-parallel switching means 11 corresponding to three or more generators is provided with one changeover switch and two diodes connected in the forward direction for each additional generator, in comparison with the series-parallel switching means corresponding to two generators. 5C is a circuit diagram showing a configuration in which three generators 10A, 10B, and 10C are connected in series by series-parallel switching means 11. In this example, series-parallel switching means 113 includes a first changeover switch SW1, a second changeover switch SW2, and first to fourth forward diodes D14 to D17. Changeover switches SW1 and SW2 are linked by a relay or the like and driven simultaneously. In this series connection, the DC output (-) terminal T11 of the first generator 10A is connected to the DC output (+) terminal T20 of the second generator 10B via the changeover switch SW1. The DC output (+) terminal T10 of the first generator 10A is connected to the DC output (-) terminal T31 of the third generator 10C via the changeover switch SW2. Furthermore, the DC output (-) terminal T21 of the second generator 10B is connected to the DC output (-) terminal T11 of the first generator 10A via a first diode D14, and the DC output (+) terminal T20 of the second generator 10B is connected to the DC output (+) terminal T30 of the third generator 10C via a second diode D15. Furthermore, the DC output (-) terminal T21 of the second generator 10B is connected to the DC output (-) terminal T31 of the third generator 10A via a third diode D16, and the DC output (+) terminal T10 of the first generator 10A is connected to the DC output (+) terminal T30 of the third generator 10A via a fourth diode D17. The second diode D15 and the third diode D16 must have a higher withstand voltage than the first diode D14 and the fourth diode D17. With this connection configuration, when the changeover switches SW1 and SW2 are closed, the sum of the DC outputs of the three AC generators is supplied to the buck-boost converter. In other words, if the DC output voltages of the AC generators are VA, VB, and VC, then V out The power of voltage =VA+VB+VC is supplied to the buck-boost converter. If the DC output voltage of each AC generator is VA=VB=VC, then V out On the other hand, when both switches SW1 and SW2 are open, power with a voltage of V = 3VA is supplied to the buck-boost converter. out Power with a voltage of =VA=VB=VC is supplied to the buck-boost converter. Similarly, when the number of generators is increased to four or five, the series-parallel switching means 113 can be configured to add one changeover switch SW and two forward diodes for each additional generator, and to switch simultaneously in cooperation with relays.

[0023] As shown in FIG. 6A, the boost converter 111 is composed of an inductor L, a diode D, a capacitor C, and a switch S. In the boost converter 111, when the switch S is ON (see FIG. 6B), the inductor L is short-circuited to the input side (Vi) and energy is stored, and when the switch is OFF, energy is released from the inductor L to the output side (V0). That is, when the switch S is OFF (see FIG. 6C), the inductor L tries to continue to pass a current (IL), causing a back electromotive force to act, and as a result, the sum of the input voltage and the voltage of the inductor L (current (ID)) is output to the output side (V0) via the diode D. The ratio of the ON time to the switching period of the switch S (duty ratio) is controlled by a PWM signal that drives the switch S, and this determines the step-up ratio of the output voltage to the input voltage.

[0024] As shown in FIG. 7A, the BUCK converter 112 is composed of an inductor L, a diode D, a capacitor C, and a switch S. When the switch S is ON (see FIG. 7B), the diode D is reverse-biased. As a result, magnetic energy is stored in the inductor L. When the switch S is OFF (see FIG. 7C), the inductor L tries to continue to pass current, generating an electromotive force in the inductor L. As a result, the diode is forward-biased, a current (IL) flows, and magnetic energy is released. The duty ratio is controlled by a PWM signal that drives the switch S, which determines the step-down ratio of the output voltage to the input voltage. The boost converter 111 and the buck converter 112 are controlled in an ultra-high speed mode of 1000 times per second (see FIG. 12).

[0025] Next, FIG. 8 is a flowchart showing the process by the system controller 12 for connecting two generators in series and in parallel in response to changes in wind speed. At start, the two generators are connected in series (S701). When the average wind speed exceeds the cut-in wind speed, the generators are activated (S702, S703). When the average wind speed falls below the cut-in wind speed, the two generators are stopped (S704, S705). If the total output voltage of the two generators exceeds a first threshold Vt1, e.g., 350 V, the two generators are switched to a parallel connection (S706, S707). On the other hand, if the total output voltage of the two generators falls below a second threshold Vt2, which is lower than the first threshold Vt1, the two generators are switched to a series connection (S708, S709). Thus, the series-parallel switching has a hysteresis characteristic. Furthermore, if the average wind speed is equal to or greater than the rated wind speed, the two generators are switched to parallel rated operation (S710, S711). This switching also has a hysteresis characteristic. Furthermore, if the instantaneous wind speed corresponds to the strong wind operation mode, the two generators are switched to the strong wind operation mode (S712, S713). Furthermore, if the instantaneous wind speed is equal to or greater than the cutout wind speed, the operation of the generators is terminated by control such as forced stall (S714, S715).

[0026] The average wind speed during cut-in wind speed or series / parallel connection switching is calculated by averaging multiple samples N, for example 20 times, and processing M times per second, for example 1000 times. That is, for super-instantaneous wind speed, wind speed is sampled at 20000 / second, and the average of these 20 times is used as the average wind speed. In other words, wind speed at 1 / 1000 second is used. Furthermore, the average value is not simply calculated as the arithmetic mean value of multiple measurements N, for example, 20 measurements, but is calculated using the following formula: Average value = (previous average value * (N-1) + current sampled value) / N That is, Average value = (previous average value * 19 + current sampled value) / 20

[0027] Figure 9 shows the relationship between wind speed, the total output power P of the generators, and the generator's output voltage. The output voltage of each three-phase AC generator increases in proportion to the wind speed, and the total output power of the two generators increases in proportion to the cube of the wind speed. The two generators start operation in series connection, and when their output voltage reaches a predetermined value, for example, 350 V, they switch to parallel connection and operate. When the average wind speed exceeds a limit value, rated operation is initiated, and the total output power of the two generators is maintained at a predetermined value. For example, the cut-in wind speed is 3 to 5 m / s, the rated wind speed is 8 to 16 m / s, and the cut-out wind speed is 24 to 25 m / s. Furthermore, if the wind speed exceeds 25 m / s for three seconds or more, the system enters shutdown mode. In this case, before stopping, the turbine switches to strong wind operation mode and slows down in three stages: 300 rpm / s, 200 rpm / s, and 100 rpm / s. This control ensures safety even in strong winds and efficiently recovers wind energy, and if the instantaneous wind speed drops to less than 25 m / s for a period of less than three seconds, the turbine will return to rated operation. According to the present invention, when the wind speed is low, the two generators are operated in series connection, which reduces the current flowing through the generators and increases the voltage, thereby achieving high power generation efficiency and expanding the range in which the battery can be charged, even at low wind speeds. On the other hand, when the wind speed is high, the two generators are switched to a parallel connection, which allows the large amount of wind energy to be efficiently converted into electric power. In this way, according to the present invention, sufficient active power can be obtained with high power generation efficiency over a wide range of wind speeds. Furthermore, because the output of each AC generator is switched while rectified to DC of the same voltage, there is no need to consider the frequency, electrical angle, etc. of the output power. Therefore, the series-parallel switching means 113 may have a simple configuration.

[0028] Unlike large wind turbines, most small lift-type wind turbines have a relatively high rotor rotation speed of 100-200 RPM or more. Generally, most use a maximum rated output of 300 RPM. Table 1 shows the specifications of commercially available 2kW class small wind turbines. [Table 1] Looking at the specifications for the 100 RPM range in Table 1, it outputs 50.71V at a constant load. If a 48V battery system were to be charged at this time, a full charge voltage of approximately 55.2V (13.8V x 4) would be required, but since this is not possible, it would be impossible to use in the range below 100 RPM. Another method would be to increase the voltage by increasing the generator windings, but this would have the disadvantage of causing the voltage to become too high in the high speed range. Below is Table 2, which measures the voltage at different rotation speeds when no load is present. [Table 2] According to the present invention, the problem of high voltage during high-speed rotation can be solved while utilizing the low-speed rotation section. Instead of using a single generator per wind turbine, two or more smaller-capacity three-phase AC generators can be used to increase efficiency. In other words, compared to using a single generator, operating multiple generators in series / parallel as in the present invention enables efficient power generation by connecting the generators in series when the wind speed is low and the rotation speed is low, and by connecting the generators in parallel when the wind speed is high and the rotation speed is high, power generation can be achieved at a lower voltage, thereby achieving a greater power output than with a single generator. In particular, by controlling the wind power generation system to quickly follow instantaneous changes in wind speed, the efficiency of the wind power generation system can be increased in the low-speed rotation section where the wind speed is low. Wind power generation generally uses generators with three-phase AC output. To use AC power in series or parallel, the phases of each power source, i.e., the phases U, V, and W of each three-phase AC generator, must be matched. This increases technical difficulty and costs. Therefore, the present invention solves this problem by converting the AC power of the three-phase AC generator into DC power and then connecting this power in series or parallel depending on the load conditions, such as the battery charging voltage.

[0029] Furthermore, the series-parallel switching means 113 of the present invention is basically configured with one changeover switch SW and two forward diodes, and for each additional generator, it is sufficient to add one more changeover switch SW and two forward diodes, so the configuration is simple and the control is easy.

[0030] Next, Fig. 10 is a diagram showing an example of a specific circuit configuration of the system controller 12 shown in Fig. 3. The system controller 12 has a TSR processing unit 1201, a target speed processing unit 1202, a first PID control unit 1203, an output load processing unit 1204, a CP processing unit 1205, an RMS output unit 1206, a reference load processing unit 1207, a second PID control unit 1208, an actual output unit 1209, etc. The system controller 12 repeats digital calculations at an ultra-high speed, for example, every control period (1000 times / second), but due to the response of the converter (which may include an inverter) and the resistive load, analog values ​​are output to the outside of the system controller 12, and a converter is also designed to respond to this. The system controller 12 will be described in detail below.

[0031] FIG. 11 is a block diagram showing an example of the configuration of the input data processing unit 1220 of the system controller 12. The input data processing unit 1220 receives, as input data 18, various data necessary for controlling the converters and other loads on the generators. For example, the generator series-parallel unit 1221 receives voltage and current data for two generators 10A and 10B, and outputs voltage data (A) for the series-parallel connection. The rotational speed processing unit 1222 receives data from a rotary encoder of the rotating shaft of the wind turbine, and outputs rotational speed data (B). The wind speed processing unit 1242 receives data from an anemometer, and outputs super-instantaneous wind speed (C). Generally, "instantaneous wind speed" is defined as the average of anemometer measurements taken at 0.25-second intervals over three seconds (the average of 12 measurements). On the other hand, in the present invention, "super-instantaneous wind speed" is the average value of multiple, at least 10, wind speeds measured at time intervals much shorter than 0.25 seconds, at least 0.01 seconds or less. Weather data such as temperature and humidity are input to air density processing unit 1250, which calculates air density (D) by referring to average air density information 1252. Blade diameter (E) and blade cross-sectional area (F) are input as wind turbine specifications. Reference TSR data (G) is also set based on the tip speed ratio. These basic information on the elements that make up the system, such as generator specifications and wind turbine specifications, are stored in advance as initial setting values ​​in the memory of system controller 12.

[0032] FIG. 12 is a flowchart showing the overall processing of the system controller 12. When the generator starts operating (S1200), the input data processing unit 1220 samples various types of data (S1202). Analog data is sampled, for example, 20,000 times per second. Each piece of data is then filtered and converted into analog form, and for data requiring an average value, an average value is calculated (S1204). The sampled data is converted into digital values, and these converted values ​​are recorded in memory as time-series data. The average value is the average value of multiple samples N, for example, 20 samples. This data is stored in memory (S1206). Furthermore, the system controller 12 executes the following processing at ultra-high speed, for example, 1000 times per second, based on the average value data stored in the memory. First, a determination is made as to whether the generator and resistive load should be connected and switched (S1208). Based on the result of this determination, the system controller 12 executes the following parallel processing. Based on the input data, the optimum output load is calculated (S1214) based on the results of TSR processing (S1210) and target speed calculation (S1212), and further the actual output (O) to be controlled for the generator is calculated (S1216). In addition, the reference load is calculated (S1226) based on the processing of the output coefficient Cp based on the input data (S1220), the acquisition of the actual output (O) (S1222), and the inverse CP processing (S1224), and the output power (watts) of the generator is calculated based on the reference load and the cross-sectional area of ​​the wind turbine blades (S1228). On the other hand, the output power (watts) and actual output (O) are acquired (S1230), and the actual output (O) is controlled within the output power (watts) (S1231). Based on this information, the converter output calculation (S1232), the converter PID / PWM calculation (S1233), the resistive load calculation (S1234), and the resistive load PID / PWM calculation (S1235) are performed. Furthermore, the system operating information is acquired (S1240), and limit control determination is made (S1242). Based on this processed data, output limit control is executed (S1250). Furthermore, the inverse TSR is acquired from the limit control information (S1260), and the reference TSR is updated from the inverse TSR and the peripheral speed ratio (S1262). In this way, the present invention executes multiple ultra-high-speed processes in parallel, for example, at 1,000 times per second. Because the wind power generation system of the present invention is based on fixed-wing wind turbines, the only components that need to be controlled in response to instantaneous changes in wind speed are converters and other devices that are controlled by high-speed electrical signals with almost no time lag. Therefore, the energy of instantaneous changes in wind can be efficiently converted into electrical energy by a fixed-wing wind power generation system. According to the present invention, the efficiency of the wind power generation system can be improved over a wide range of wind speed zones, including zones with low average wind speeds.

[0033] Fig. 13 is a functional block diagram showing details of a TSR processing unit 1301 and a PID processing unit #1 (1306, corresponding to PID #1 in Fig. 10) of the system controller. Fig. 14 is a flowchart showing the processing of the TSR processing unit and the PID processing unit #1 in Fig. 13. Based on the tip speed ratio and inverse TSR, a reference TSR(G) is calculated (1303 in FIG. 13, S1401 in FIG. 14). The TSR processing unit (1301) calculates TSR (=λ) in the following equation based on the rotation speed B, wind speed C (average value of S1204 in FIG. 12, V in FIG. 14, same below), wind turbine specifications (blade diameter E, etc.), and reference TSR(G).

number

[0034] Next, Fig. 16 is a functional block diagram showing details of the CP processing unit (1205) and PID processing unit #2 (1208) of the system controller, and Fig. 17 is a flowchart showing the processing of the CP processing unit and PID processing unit #2 of Fig. 16. The aerodynamic characteristics of a wind turbine blade change depending on the blade shape (F), pitch angle, wind speed (C), and rotor rotation speed (B). According to one-dimensional momentum theory, aerodynamic characteristics can be expressed as the output due to the force in the rotor rotation direction and the thrust due to the force perpendicular to the rotor rotation area, as shown in the following equation:

number

[0035] The relationship between the two sets of PID processes, PID process #1 (first PID process) and PID process #2 (second PID process), performed by the system controller will now be described. These two sets of PID processes, the first PID process and the second PID process, are executed based on synchronized, common sampled data (current data) related to the rotor rotation speed (B) and wind speed (C), acquired in S1204 of FIG. 12. The first PID process updates the current output data of the generator (i.e., the result of generator control based on previous data), calculated based on the generator output voltage and other parameters, based on data such as TSR(λ), the output coefficient Cp, and the current wind speed (see FIG. 15). In other words, this is the primary control system that controls the current flowing through the generator load so that the actual generator output is always optimal. Meanwhile, the second PID process uses the logical value of the output coefficient Cp and calculates the generator output power (watts) based on the current data. The second PID process complements the control performed by the first PID process to ensure efficient operation of the generator without stalling.

[0036] Figure 18 is a time chart showing the relationship between average wind speed, superinstantaneous wind speed, output power (watts), and actual output (limit). The graph in the lower right of Figure 18 shows the change over time in natural wind speed measured outdoors from 4:00 PM to 8:00 PM on October 21, 2023. Natural wind is not constant; it is constantly fluctuating. The graph in the upper right of Figure 18 is an image of superinstantaneous wind speed, showing an enlarged portion of the graph in the lower right. Assume that the wind speed C (corresponding to the average value of S1204 in Figure 12) at each time point t1, t2, and t3 within this interval changes as shown in the figure. Wind energy is proportional to the swept area and to the cube of the wind speed. It is clear that the power obtained as the cube of the wind speed at each point t1, t2, and t3 is greater than the power obtained as the cube of the average wind speed between t1 and t3. If the super-instantaneous wind speed increases rapidly, increasing the generator's output power (watts) will cause the airflow along the wind turbine blades to separate, causing the turbine to stall. Therefore, limit control is performed to prevent the generator's actual output from exceeding the output power (watts).

[0037] Fig. 19 is a functional block diagram showing details of the limiter in Fig. 10. A limit control section 1211 performs limit control in response to various inputs, thereby enabling the control shown in Figs.

[0038] The AC generators to which the present invention can be applied are not limited to permanent magnet types, and other general induction generators or synchronous generators equipped with field coils may also be used. In this case, the control output of the converter may be shared to control the generator's excitation current, rotating field, etc. The converter may also be replaced with one of other general configurations depending on the application. In addition, although the embodiment shows an example of switching between series and parallel connections of two generators, the present invention is not limited to this. For example, three to six generators may be configured to be switched between series and parallel connections within the range of the converter's input design voltage.

[0039] Furthermore, multiple three-phase AC generators may be mounted on different rotating shafts with fixed blades, as long as they have the same specifications. For example, two three-phase AC generators 10A and 10B may be mounted separately on two rotating shafts that extend parallel and close to each other, each with fixed blades. The DC output from the rectifiers of these two three-phase AC generators is switched between series and parallel by a series-parallel switching device and connected to a step-up / step-down converter. In this case, a rotary encoder 182 may be provided for each rotating shaft, and an anemometer 184 may be provided between the two rotating shafts and controlled by a common system controller. Because the switching device switches the DC output of each three-phase AC generator between series and parallel, the frequency and UVW phase of the output power of the two three-phase AC generators do not need to match.

[0040] As described above, the wind power generation system of the present invention can also be applied to a system that includes multiple three-phase AC generators but does not have a series-parallel selector switch. That is, the control of the buck-boost converter and the resistive load by the system controller 12 using ultra-instantaneous wind speed, as described with reference to Figures 3 and 10 and subsequent figures, can also be applied to a wind power generation system in which multiple three-phase AC generators are connected in series or in parallel. For example, the present invention can be applied to a wind power generation system in which two three-phase AC generators 10A and 10B are connected in series by omitting the selector switch SW1 in Figure 5A and configuring the first terminal Ts1 and the second terminal Ts2 to be directly connected. Alternatively, the present invention can be applied to a wind power generation system in which two generators are connected in parallel by omitting the selector switch SW1 in Figure 5B and configuring the first terminal Ts1 and the second terminal Ts2 to be disconnected. In these cases, too, by controlling the wind power generation system to quickly follow instantaneous changes in wind speed, it is possible to increase the efficiency of the wind power generation system over a wide range of wind speed zones, including low-speed zones where the wind speed is low. [Explanation of symbols]

[0041] 10A, 10B three-phase AC generator 102A, 102B generator section 103A, 103B Rectifier section 11 Buck-boost converter / series-parallel switching means 111 BOOST Converter 112 BUCK Converter 12 System Controller 13 Battery Controller 14 Battery 17 Resistive Load 30 Lift-type vertical blade 31 Lift-type vertical blade 32 Rotation axis 1220 Input Data Processing Unit 182 Rotary Encoder Reverse Calculation 184 Anemometer

Claims

1. A wind power generation system having a wind power generator and a load connected to the wind power generator, the wind power generator includes a lift-type fixed blade fixed to a rotating shaft, a plurality of three-phase AC generators, a step-up / step-down converter and a resistive load constituting the load, and a system controller; Each of the three-phase AC generators has a rectifier unit that converts a three-phase AC output into a DC output, the step-up / step-down converter is connected to the rectifier section of each of the three-phase AC generators; the system controller is configured to control the load so as to track in real time an optimum TSR(λ) suited to the fixed blades in response to changes in wind speed, based on the wind turbine specifications, the rotational speed of the rotating shaft, information on super-instantaneous wind speed obtained from an anemometer, the output of the generator, and a state of the load; A wind power generation system characterized in that the rotational speed and the super-instantaneous wind speed are each an average value of at least 10 pieces of data measured at short time intervals of 0.01 seconds or less.

2. A wind power generation system having a wind power generator and a load connected to the wind power generator, the wind power generator includes a lift-type fixed blade fixed to a rotating shaft, a plurality of three-phase AC generators, a step-up / step-down converter and a resistive load constituting the load, and a system controller; Each of the three-phase AC generators has a rectifier unit that converts a three-phase AC output into a DC output, the step-up / step-down converter is connected to the rectifier section of each of the three-phase AC generators; the system controller calculates TSR(λ) defined by the following formula based on the wind turbine specifications, the rotational speed of the rotating shaft, information on super-instantaneous wind speed obtained from an anemometer, the total output of the three-phase AC generator, and the state of the load: [Equation 1] A maximum load P corresponding to the super-instantaneous wind speed obtained based on the Cp logical value is calculated as a reference load, and output power (watts) is calculated from the reference load, the cross-sectional area of ​​the blade, and the generator voltage. Calculate the output coefficient Cp defined by the following equation: [Equation 2] However, P e is the actual power output, ρ is the air density, v is the wind speed (current super-instantaneous wind speed), A is the rotor cross-sectional area, and CP is the power coefficient) The actual output P e The load is controlled so as to track the optimum TSR (λ) suited to the fixed wing in real time according to the change in the super-instantaneous wind speed, within a range not exceeding the value of the output power (watts), A wind power generation system characterized in that the rotational speed and the super-instantaneous wind speed are each an average value of at least 10 pieces of data measured at short time intervals of 0.01 seconds or less.

3. In claim 1 or 2, The wind power generation system includes a series-parallel switching means, the series-parallel switching means has a function of switching the plurality of three-phase AC generators on the output side of the rectifier unit between series and parallel connection and connecting them to the step-up / step-down converter constituting the load, the system controller is configured to start the plurality of three-phase AC generators in a series-connected state, and, when a total output voltage of the plurality of three-phase AC generators exceeds a preset threshold, switch the plurality of three-phase AC generators to a parallel connection using the series-parallel switching means and connect the parallel connection to the step-up / step-down converter.

4. A method for controlling a wind power generation system having a load connected to a wind power generator, comprising: The wind power generation system includes a lift-type fixed blade fixed to a rotating shaft, a plurality of three-phase AC generators, a step-up / step-down converter and a resistive load constituting the load, and a system controller, each of the three-phase AC generators has a rectifier unit that converts a three-phase AC output into a DC output, and the step-up / step-down converter is connected to the rectifier unit, the step-up / step-down converter is connected to the rectifier section of each of the three-phase AC generators; controlling the load so as to track in real time the optimum TSR(λ) suited to the fixed blades due to changes in wind speed, based on the wind turbine specifications, the rotational speed of the rotating shaft, information on super-instantaneous wind speed obtained from an anemometer, the output of the generator, and the state of the load; A method for controlling a wind power generation system, wherein the rotation speed and the super-instantaneous wind speed are each an average value of at least 10 pieces of data measured at short time intervals of 0.01 seconds or less.

Images