Brake control device

Abstract

To improve the power generation efficiency of a power generation system.SOLUTION: A first switch Sw1 and a first resistor R1 are connected to each other in series between a first power line Pu and a second power line Pv, A second switch Sw2 and a second resistor R2 are connected to each other in series between the second power line Pv and a third power line Pw. A third switch Sw3 and a third resistor R3 are connected to each other in series between the third power line Pw and the first power line Pu. When a condition indicating that an abnormality occurs in a power generation system is established, a control part 52 switches states of the first switch Sw1, the second switch Sw2 and the third switch Sw3 between non-conductive states and conductive states on the basis of a duty ratio corresponding to a rotational speed of a power generator 3. The duty ratio is low as the rotational speed of the power generator 3 is high.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a brake control device for a power generation system.

Background Art

[0002] Conventionally, a brake control device for a power generation system has been known. For example, Japanese Patent Application Laid-Open No. 2002-339856 (Patent Document 1) discloses an electric brake device for a permanent magnet type wind power generator. According to the electric brake device, the stopped state of the windmill can be maintained without demagnetizing the permanent magnets constituting the rotor poles of the generator.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a generator for the purpose of wind power generation, a coreless generator is known. Even when the coreless generator is short-circuited, no saturation phenomenon occurs in the torque of the coreless generator. Therefore, by short-circuiting the coreless generator, the braking force increases in proportion to the rotational speed of the coreless generator. Due to such characteristics of the coreless generator, the coreless generator is often used in a system that brakes the generator by short-circuiting the generator. However, the coreless generator has a drawback of poor power generation efficiency.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to improve the power generation efficiency of a power generation system.

Means for Solving the Problems

[0006] The brake control device according to the present disclosure is a brake control device for a power generation system. The power generation system includes a rotating body, a generator, and a control device. The generator is rotated by the rotating body and outputs three-phase power to a first power line, a second power line, and a third power line respectively. The control device receives the three-phase power from the first power line, the second power line, and the third power line respectively, and controls the rotation speed of the rotating body. The brake control device includes a first switch, a second switch, a third switch, a first resistor, a second resistor, a third resistor, and a control unit. The first switch and the first resistor are connected in series between the first power line and the second power line. The second switch and the second resistor are connected in series between the second power line and the third power line. The third switch and the third resistor are connected in series between the third power line and the first power line. The control unit controls each of the first switch, the second switch, and the third switch. When a brake condition indicating that an abnormality has occurred in the power generation system is not satisfied, the control unit sets the state of each of the first switch, the second switch, and the third switch to a non-conducting state. When the brake condition is satisfied, the control unit switches the state of each of the first switch, the second switch, and the third switch between a non-conducting state and a conducting state based on a duty ratio corresponding to the rotation speed of the generator. The higher the rotation speed of the generator, the smaller the duty ratio.

Effect of the Invention

[0007] According to the brake control device of the present disclosure, when the brake condition is satisfied, the control unit switches the state of each of the first switch, the second switch, and the third switch between a non-conducting state and a conducting state based on a duty ratio corresponding to the rotation speed of the generator, and the higher the rotation speed of the generator, the smaller the duty ratio, so that the power generation efficiency of the power generation system can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0010] FIG. 1 is a functional block diagram showing the configuration of the brake control device 5 of the wind power generation system 100 according to the embodiment. The wind power generation system 100 is an example of a horizontal axis type (propeller type) wind power generation system. As shown in FIG. 1, the wind power generation system 100 includes a windmill 1 (rotating body), a generator 3, and a control device 4.

[0011] The windmill 1 includes a main shaft 2. The generator 3 includes a three-phase synchronous generator using permanent magnets. The generator 3 is fastened to the main shaft 2 by a coupling or the like. The windmill 1 is rotated by the kinetic energy of the wind, and the main shaft 2 rotates the generator 3.

[0012] The generator 3 outputs three-phase (U-phase, V-phase, and W-phase) power to the power lines Pu (first power line), Pv (second power line), and Pw (third power line), respectively. If necessary, a speed increaser may be provided between the main shaft 2 and the generator 3.

[0013] The control device 4 receives three-phase power from the power lines Pu to Pw and controls the rotational speed of the windmill 1. The control device 4 includes a power conversion unit 41 and a power storage unit 42. The power conversion unit 41 converts the power received from the power lines Pu to Pw. The power conversion unit 41 includes, for example, an inverter and an AC (Alternate Current) / DC (Direct Current) converter. The power storage unit 42 is charged using the power received from the power lines Pu to Pw.

[0014] When a load is connected to the generator 3 to output power, a braking torque is output from the generator 3 to the windmill 1, and the rotation of the windmill 1 is braked. When the power consumed by the load is increased, the rotational speed of the windmill 1 decreases, and when the power is decreased, the rotational speed of the windmill 1 increases. In the wind power generation system 100, the control device 4 is connected as a load of the generator 3. The control device 4 controls the braking torque of the generator 3 according to the wind speed (wind velocity) received by the windmill 1 to rotate the windmill 1 at an optimal rotational speed.

[0015] The brake control device 5 includes a brake control circuit 51, a control unit 52, and a detection unit 53. The brake control circuit 51 includes a switch Sw1 (first switch), a switch Sw2 (second switch), a switch Sw3 (third switch), a resistor R1 (first resistor), a resistor R2 (second resistor), and a resistor R3 (third resistor). The switch Sw1 and the resistor R1 are connected in series between the power lines Pu and Pv. The switch Sw2 and the resistor R2 are connected in series between the power lines Pv and Pw. The switch Sw3 and the resistor R3 are connected in series between the power lines Pw and Pu.

[0016] The control unit 52 controls the brake control circuit 51. The control unit 52 includes a CPU (Central Processing Unit) and a memory. When a condition (brake condition) indicating that an abnormality has occurred in the wind power generation system 100 is satisfied, the control unit 52 performs control (duty control) to selectively switch the states of the switches Sw1 to Sw3 between a conduction state (ON) and a non-conduction state (OFF) based on a duty ratio (the ratio of the time during which the switch is in the conduction state to the unit time with respect to the unit time) corresponding to the rotation speed of the windmill 1. The control unit 52 causes the power output from the generator 3 to be short-circuited between the power lines Pu to Pw by the resistors R1 to R3, thereby generating a braking torque from the generator 3 to the windmill 1. When the wind power generation system 100 is normal (when the brake condition is not satisfied), the control unit 52 sets the switches Sw1 to Sw3 to the non-conduction state. The brake condition includes at least one of the conditions that the charge amount of the power storage unit 42 is greater than a reference amount, the wind speed is faster than a reference wind speed, the rotation speed of the windmill 1 is faster than a reference rotation speed, the power output from the generator 3 is greater than a reference power, and the voltage of the power output from the generator 3 is higher than a reference voltage. The reference amount, reference wind speed, reference rotation speed, reference power, and reference voltage can be appropriately determined by actual machine experiments or simulations.

[0017] The detection unit 53 detects the charge amount of the power storage unit 42, the wind speed, the rotation speed of the windmill 1, the power output from the generator 3, and the voltage of the power output from the generator 3. The detection unit 53 includes various sensors. The detection unit 53 outputs to the control unit 52 whether the brake condition is satisfied or not at each sampling time.

[0018] FIG. 2 is a flowchart showing the flow of the switching process of the switches Sw1 to Sw3 performed by the control unit 52 in FIG. 1. The process shown in FIG. 2 is called at each sampling time by a main routine (not shown) that integrally controls the brake control device 5. Hereinafter, the steps are simply described as S.

[0019] As shown in FIG. 2, the control unit 52 determines whether or not the brake condition is satisfied in S101. When the brake condition is satisfied (YES in S101), the control unit 52 outputs a brake command to the brake control circuit 51 in S102, performs duty control on the switches Sw1 to Sw3 for a certain period of time, and ends the process. When the brake condition is not satisfied (NO in S101), the control unit 52 sets the states of the switches Sw1 to Sw3 to the non-conducting state in S103 and ends the process.

[0020] FIG. 3 is a functional block diagram showing the configuration of the brake control device 5A of the wind power generation system 100 according to the comparative example. The configuration of the brake control device 5A is a configuration in which the brake control circuit 51 and the control unit 52 in FIG. 1 are replaced with a brake control circuit 51A and a control unit 52A, respectively. The brake control circuit 51A is a configuration in which the resistors R1 to R3 are removed from the brake control circuit 51 in FIG. 1. When the brake condition is satisfied, the control unit 52A simply switches the switches Sw1 to Sw3 to the conducting state without performing duty control on the switches Sw1 to Sw3. Since the rest is the same, the description will not be repeated.

[0021] FIG. 4 is a diagram showing together the relationship (torque characteristics) between the rotational speed of the generator 3 and the braking torque generated from the generator 3 when the switches Sw1 to Sw3 in FIG. 1 are under duty control, the torque characteristics of the generator 3 when the switches Sw1 to Sw3 in FIG. 1 are simply made conductive without duty control, and the torque characteristics of the generator 3 when the switches Sw1 to Sw3 in FIG. 3 are simply made conductive without duty control. In FIG. 4, the curve TC1 represents the torque characteristics of the generator 3 when the switches Sw1 to Sw3 in FIG. 1 are under duty control, the curve TC11 represents the torque characteristics of the generator 3 when the switches Sw1 to Sw3 in FIG. 1 are simply made conductive without duty control, and the curve TC12 represents the torque characteristics of the generator 3 when the switches Sw1 to Sw3 in FIG. 3 are simply made conductive without duty control.

[0022] As shown in Fig. 4, the torque characteristics of the generator 3 differ depending on the resistance values between the power lines Pu, Pv, and Pw. In the generator 3 of Fig. 3, the resistance values between the power lines Pu, Pv, and Pw are mainly the internal resistance value of the generator 3. In the generator 3 of Fig. 1, the resistance values between the power lines Pu, Pv, and Pw are mainly the internal resistance value of the generator 3 and the resistance values of the resistors R1, R2, and R3. The greater the resistance value existing between the power lines Pu, Pv, and Pw, the higher the rotational speed of the generator 3 at which the braking torque becomes maximum. Therefore, the rotational speed at which the braking torque becomes maximum in curve TC11 is higher than the rotational speed at which the braking torque becomes maximum in curve TC12.

[0023] Therefore, in the brake control device 5, when the brake condition is satisfied, the higher the rotational speed of the generator 3, the lower the duty ratio of each of the switches Sw1 to Sw3 is decreased, and the average value of the resistance value between the power lines Pu, Pv, and Pw per unit time is increased. As a result, as shown in curve TC1, the range of the rotational speed at which the maximum value of the braking torque can be maintained can be widened compared to the torque characteristics shown in curves TC11 and TC12.

[0024] Fig. 5 is a diagram showing the relationship between the rotational speed of the generator 3 in Fig. 1 and the duty ratios of the switches Sw1 to Sw3. As shown in Fig. 5, the higher the rotational speed of the generator 3, the smaller the duty ratios of the switches Sw1 to Sw3. For example, the braking torque is usually required in a situation where the rotational speed of the generator 3 is high (for example, 400 min -1 ). Therefore, it is necessary to decrease the duty ratio immediately after the start of the generator 3 and increase the duty ratio in response to the decrease in the rotational speed of the generator 3 after the generation of the braking torque.

[0025] In Fig. 5, the duty ratios of the switches Sw1 to Sw3 are finely controlled for each rotational speed of the generator 3. For the simplification of the software executed by the control unit 52, the relationship between the generator 3 and the duty ratio may be determined in advance as a map for each range of the rotational speed of the generator 3.

[0026] FIG. 6 is a diagram showing the relationship between the rotational speed of the generator 3 in FIG. 1 and the duty ratios of the switches Sw1 to Sw3, which is predefined as a map. The curve DT1 shown by the dotted line in FIG. 6 is the same as the curve shown in FIG. 5. As shown in FIG. 6, the relationship between the rotational speed of the generator 3 and the duty ratios of the switches Sw1 to Sw3 in the wind power generation system 100 in FIG. 1 is such that the rotational speed of the generator 3 is 0 min -1 above and less than Vr1 in the range Rg1, Vr1 or more and less than Vr2 in the range Rg2, and Vr2 or more in the range Rg3, and is predefined as a map of a linear relationship representing a straight line approximating the curve DT1.

[0027] According to the brake control device 5, since it is not necessary to use a coreless generator as the generator 3, the power generation efficiency of the generator 3 can be improved. In addition, the cost of the generator 3 can be reduced, and the generator 3 can be miniaturized. Furthermore, the availability of the generator 3 can be improved.

[0028] As described above, according to the brake control device according to the embodiment, the power generation efficiency of the power generation system can be improved.

[0029] It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Description of Reference Numerals

[0030] 1 Windmill, 2 Main shaft, 3 Generator, 4 Control device, 5, 5A Brake control device, 41 Power conversion unit, 42 Power storage unit, 51, 51A Brake control circuit, 52, 52A Control unit, 53 Detection unit, 100 Wind power generation system, Pu to Pw Power lines, R1 to R3 Resistors, Sw1 to Sw3 Switches.

Claims

1. A braking control device for a power generation system, wherein the power generation system includes a rotating body, a generator rotated by the rotating body and outputting three-phase power to a first power line, a second power line, and a third power line respectively, a control device that receives the three-phase power from the first power line, the second power line, and the third power line respectively and controls the rotational speed of the rotating body, the braking control device includes a first switch and a first resistor connected in series between the first power line and the second power line, a second switch and a second resistor connected in series between the second power line and the third power line, a third switch and a third resistor connected in series between the third power line and the first power line, a control unit that controls each of the first switch, the second switch, and the third switch, the first switch and the first resistor are connected to the second power line without passing through the second switch and the second resistor, the second switch and the second resistor are connected to the third power line without passing through the third switch and the third resistor, the third switch and the third resistor are connected to the first power line without passing through the first switch and the first resistor, when a braking condition indicating that an abnormality has occurred in the power generation system is not satisfied, the control unit sets the states of each of the first switch, the second switch, and the third switch to a non-conducting state, when the braking condition is satisfied, the control unit switches the states of each of the first switch, the second switch, and the third switch between a non-conducting state and a conducting state based on a duty ratio corresponding to the rotational speed of the generator, the higher the rotational speed of the generator, the smaller the duty ratio, the control device is charged by the power output from the generator, the braking condition includes at least one of a condition that the charge amount of the control device is greater than a reference amount, a condition that the wind speed received by the rotating body is faster than a reference wind speed, and a condition that the voltage of the power output from the generator is higher than a reference voltage, a braking control device.

2. The braking control device according to claim 1, wherein the relationship between the rotational speed of the generator and the duty ratio is determined in advance as a map.

3. the rotating body includes a windmill, the control device further includes a power storage unit charged by the power output from the generator, The condition that the charge amount of the control device is greater than the reference amount includes the condition that the charge amount of the power storage unit is greater than the reference amount. The condition that the wind speed received by the rotating body is faster than the reference wind speed includes the condition that the wind speed received by the windmill is faster than the reference wind speed. The brake condition further includes at least one of the condition that the rotational speed of the windmill is faster than the reference rotational speed and the condition that the power output from the generator is greater than the reference power. The brake control device according to claim 1 or 2.

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