JP2016158407A - Power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and inexpensive power generating system.SOLUTION: A small hydraulic power generating system comprises: a water turbine 11 rotationally driven by flowing water; an AC power generator 7 that includes a rotor 9 coupled with a rotating shaft of the water turbine 11 to rotate at the same rotation speed as that of the water turbine 11, and outputs AC voltage VAC1 having a frequency corresponding to the rotation speed of the water turbine 11; a converter 13 for converting the AC voltage VAC1 into DC voltage VDC1; a boost chopper 14 for boosting the DC voltage VDC1 to DC voltage VDC2 having a predetermined value; and an inverter 16 for converting the DC voltage VDC2 into AC voltage having a commercial frequency. Absence of an amplification device for increasing the rotation speed of the rotating shaft of the water turbine 11 to transfer the speed to the rotor 9 makes it possible to implement a small-sized and inexpensive power generating system.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power generation system, and more particularly to a power generation system that generates electric power using the energy of water flowing in rivers, waterways, and the like.

  Patent Document 1 discloses a power generation system that generates electric power using ultra-low drop water level energy or the like. In this power generation system, the rotational speed of the rotating shaft of the ultra-low head water level recovery machine is increased by the speed increasing device and transmitted to the rotating shaft of the DC generator. The DC voltage output from the DC generator and the DC voltage output from the solar battery are supplied to the inverter via the DC voltage balance unit, converted into AC voltage by the inverter, and supplied to the load and the commercial power system. The

JP 2002-262462 A

  However, the conventional power generation system is equipped with a speed increasing device that increases the rotational speed of the rotating shaft of the ultra-low-drop water level recovery machine and transmits it to the rotating shaft of the DC generator. There was a problem of becoming high.

  Therefore, a main object of the present invention is to provide a small-sized and low-cost power generation system.

  The power generation system according to the present invention includes a water wheel that is rotationally driven by running water, and a rotor that is coupled to a rotation shaft of the water wheel and rotates at the same rotation speed as the water wheel, and has a first frequency having a frequency corresponding to the rotation speed of the water wheel. An AC generator that outputs an AC voltage, a converter that converts the first AC voltage into a first DC voltage, and a second DC voltage having a predetermined value are generated by boosting the first DC voltage. A first step-up chopper and an inverter that converts the second DC voltage into a second AC voltage are provided.

  In the power generation system according to the present invention, the rotor of the AC generator is rotated at the same rotational speed as the rotating shaft of the water turbine without providing a speed increasing device. Therefore, it is possible to reduce the size and cost of the system as compared with the conventional case where the speed increasing device is provided. Furthermore, since the first step-up chopper is provided between the converter and the inverter, the input voltage of the inverter can be maintained at a predetermined value even when the output voltage of the AC generator varies.

It is a circuit block diagram which shows the structure of the small hydroelectric power generation system by Embodiment 1 of this invention. It is a circuit diagram which shows the structure of the pressure | voltage rise chopper shown in FIG. FIG. 6 is a circuit block diagram illustrating a modification of the first embodiment. FIG. 10 is a circuit block diagram illustrating another modification of the first embodiment. It is a circuit block diagram which shows the structure of the electric power generation system by Embodiment 2 of this invention.

[Embodiment 1]
FIG. 1 is a circuit block diagram showing a configuration of a small hydraulic power generation system according to Embodiment 1 of the present invention. This small hydroelectric power generation system generates three-phase AC power using the energy of water flowing in a river, a water channel, etc., and supplies the three-phase AC power to a commercial power system 31 and a load 32. In FIG. 1, only a circuit for one phase is shown for simplification of the drawing and description.

  In FIG. 1, this small hydroelectric power generation system includes circuit breakers 1, 19, 20, isolation transformers 2, 18, current detector 3, voltage detector 4, electromagnetic contactor 5, excitation device 6, AC generator 7, connection A water vessel 10, a water wheel 11, a reactor 12, a converter 13, a boost chopper 14, an electrolytic capacitor 15, an inverter 16, an output filter 17, and a control device 21 are provided.

  One terminal of the circuit breaker 1 receives a commercial frequency AC voltage from the commercial power system 31, and the other terminal is connected to the primary terminal of the isolation transformer 2. The secondary terminal of the isolation transformer 2 is connected to the excitation device 6 via the electromagnetic contactor 5. The circuit breaker 1 is normally turned on and is turned off when an overcurrent flows to protect the small hydropower generation system. The insulation transformer 2 outputs an AC voltage having a voltage value corresponding to the AC voltage applied to the primary side terminal to the secondary side terminal.

  The current detector 3 detects an instantaneous value of the output voltage of the isolation transformer 2 and gives a signal indicating the detected value to the control device 21. The voltage detector 4 detects an instantaneous value of the output current of the isolation transformer 2 and gives a signal indicating the detected value to the control device 21. The electromagnetic contactor 5 is controlled by the control device 21 and is turned on when performing small hydraulic power generation, and is turned off when stopping small hydraulic power generation.

  The AC generator 7 is a synchronous generator and includes an excitation winding (stator winding) 8 and a rotor 9. The excitation device 6 is controlled by the control device 21, is driven by AC power supplied from the insulation transformer 2 via the electromagnetic contactor 5, and causes excitation current to flow through the excitation winding 8. The rotor 9 is coupled to the rotation shaft of the water wheel 11 via the coupler 10.

  The water turbine 11 is rotationally driven by the energy of water flowing in a river, a water channel or the like. The rotation speed of the water wheel 11 changes according to the flow rate of water, the amount of water, and the like. When the water wheel 11 is driven to rotate, the rotation speed (rpm) of the rotation shaft of the water wheel 11 is transmitted to the rotor 9 via the coupler 10. The rotor 9 rotates at the same rotational speed (rpm) as the water wheel 11.

  When the rotor 9 is driven to rotate while an excitation current is flowing through the excitation winding 8, an AC voltage VAC <b> 1 is generated in the rotor winding included in the rotor 9. When the excitation current is increased, the amplitude value of the AC voltage VAC1 increases. The AC voltage VAC1 has a frequency with a value corresponding to the rotational speed (rpm) of the water turbine 11. The control device 21 detects the instantaneous value of the AC voltage VAC1, controls the excitation device 6 based on the detection result, and adjusts the excitation current flowing through the excitation winding 8.

  The AC voltage VAC1 output from the rotor 9 of the AC generator 7 is given to the converter 13 via the reactor 12. Reactor 12 forms a low-pass filter, passes AC voltage VAC1, and prevents a signal having a switching frequency generated by converter 13 from passing to AC generator 7 side.

  Converter 13 includes a plurality of switching elements and a plurality of diodes. As the switching element, for example, an IGBT (Insulated Gate Bipolar Transistor) is used. Control device 21 controls converter 13 in synchronization with AC voltage VAC1. Converter 13 is controlled by control device 21 to convert AC voltage VAC to DC voltage VDC1.

  Boost chopper 14 is controlled by control device 21 to boost DC voltage VDC1 and generate DC voltage VDC2 having a predetermined value. As shown in FIG. 2, boost chopper 14 includes input terminals T1, T2, output terminals T3, T4, a reactor L1, a diode D1, and an N-channel MOS transistor Q1.

  DC voltage VDC1 is applied between input terminals T1 and T2. One terminal of the reactor L1 is connected to the input terminal T1. The anode of the diode D1 is connected to the other terminal of the reactor L1, and the cathode is connected to the output terminal T3. The drain of the transistor Q1 is connected to the anode of the diode D1, and the source thereof is connected to the terminals T2 and T4. The gate of transistor Q1 receives a PWM (pulse width modulation) signal φ1 from control device 21. The electrolytic capacitor 15 is connected between the output terminals T3 and T4. The DC voltage VDC2 is output between the output terminals T3 and T4.

  When PWM signal φ1 is set to “H” level, transistor Q1 is turned on, current flows from input terminal T1 through reactor L1 and transistor Q1 to input terminal T2, and electromagnetic energy is stored in reactor L1. When the PWM signal φ1 is set to the “L” level, the transistor Q1 is turned off, the electromagnetic energy of the reactor L1 is released, and a current flows from the input terminal T1 to the input terminal T2 via the reactor L1, the diode D1, and the electrolytic capacitor 15. Flows, and the electrolytic capacitor 15 is charged. VDC2 is a voltage obtained by adding the voltage across the terminals of reactor L1 to VDC1, and VDC2> VDC1.

  The PWM signal φ1 has a predetermined frequency. The ratio between the time for which the PWM signal φ1 is set to the “H” level and the time for one cycle is called a duty ratio. The value of the DC voltage VDC2 increases as the duty ratio increases. By adjusting the duty ratio, the DC voltage VDC2 can be set to a desired voltage value. Control device 21 controls the duty ratio of PWM signal φ1 so that DC voltage VDC2 becomes a predetermined value.

  Returning to FIG. 1, the DC voltage VDC2 generated by the step-up chopper 14 is supplied to the inverter 16 via the DC bus Ldc. Electrolytic capacitor 15 smoothes and stabilizes DC voltage VDC2 of DC bus Ldc.

  Inverter 16 includes a plurality of switching elements and a plurality of diodes. For example, an IGBT is used as the switching element. The control device 21 controls the inverter 16 in synchronization with the AC voltage detected by the voltage detector 4. The inverter 16 is controlled by the control device 21 and converts the DC voltage VDC2 into an AC voltage having a commercial frequency. The AC voltage generated by the inverter 16 is given to the primary side terminal of the isolation transformer 18 via the output filter 17.

  The output filter 17 includes a capacitor and a plurality of reactors. The output filter 17 is a low-pass filter that passes a commercial frequency component of the output voltage of the inverter 16 and prevents a signal having a switching frequency generated by the inverter 16 from passing to the insulating transformer 18 side. In other words, the output filter 17 converts the AC voltage generated by the inverter 16 into a sinusoidal AC voltage VAC2.

  The insulation transformer 18 outputs an AC voltage having a voltage value corresponding to the AC voltage VAC2 applied to the primary side terminal to the secondary side terminal. The phase and voltage value of the AC voltage output from the secondary terminal of the insulation transformer 18 match the phase and voltage value of the AC voltage supplied from the commercial power system 31.

  The circuit breaker 19 is connected between the secondary terminal of the isolation transformer 18 and the load 32, and the circuit breaker 20 is connected between the commercial power system 31 and the load 32. When the load 32 is driven only by the AC power generated by the small hydraulic power generation system, the circuit breaker 19 is turned on and the circuit breaker 20 is turned off.

  When the load 32 is driven only by the AC power supplied from the commercial power system 31 at the time of maintenance of the small hydraulic power generation system, the circuit breaker 19 is turned off and the circuit breaker 20 is turned on. When the AC power generated by the small hydropower generation system is larger than the power consumption of the load 32, both the circuit breakers 19 and 20 are turned on, and surplus power of the small hydropower generation system is supplied to the commercial power system 31.

  Next, the operation of the first embodiment will be described. The circuit breakers 1, 19 and 20 are both turned on. The water turbine 11 is rotationally driven by running water, and the rotational speed of the rotating shaft of the water turbine 11 is transmitted to the rotor 9 of the AC generator 7 by the coupler 10, and the rotor 9 rotates at the same rotational speed as the water turbine 11.

  When the electromagnetic contactor 5 is turned on, AC power from the commercial power system 31 is supplied to the excitation device 6 through the circuit breaker 1, the insulation transformer 2, and the electromagnetic contactor 5, and the excitation device 6 supplies the excitation winding 8. Excitation current is passed, and AC power is generated in the rotor 9. The AC voltage VAC1 output from the rotor 9 is supplied to the converter 13 via the reactor 12, and is converted into the DC voltage VDC1 by the converter 13.

  The DC voltage VDC1 is converted into a DC voltage VDC2 having a predetermined value by the step-up chopper 14, and is converted into an AC voltage having a commercial frequency by the inverter 16. The AC voltage generated by the inverter 16 is converted by the output filter 17 into a sinusoidal AC voltage VAC2. The AC voltage VAC2 is supplied to the load 32 via the insulation transformer 18 and the circuit breaker 19. The load 32 is driven by AC power supplied from the small hydropower generation system. Surplus power of the small hydropower generation system is supplied to the commercial power system 31 via the circuit breaker 20.

  In the first embodiment, a speed increasing device for increasing the rotational speed of the rotating shaft of the water turbine 11 and transmitting it to the rotor 9 is not provided. Therefore, it is possible to reduce the size and cost of the system as compared with the conventional case where the speed increasing device is provided.

  Further, after the AC voltage VAC1 output from the AC generator 7 is converted into the DC voltage VDC2 by the converter 13 and the step-up chopper 14, the DC voltage VDC2 is converted into the AC voltage VAC2 of the commercial frequency by the inverter 16 and the output filter 17. Therefore, the AC voltage VAC2 having a commercial frequency can be generated regardless of the rotational speed of the water turbine 11.

  Further, since the step-up chopper 14 is provided between the converter 13 and the inverter 16, the input voltage VDC2 of the inverter 16 is maintained at a predetermined value even when the rotation speed of the water turbine 11 decreases and the output voltage VDC1 of the converter 13 decreases. can do.

  In the first embodiment, the case where the present invention is applied to a small hydropower generation system that generates three-phase AC power has been described. However, the present invention is also applicable to a small hydropower generation system that generates single-phase AC power. Is possible.

  FIG. 3 is a circuit block diagram showing a modification of the first embodiment, and is a diagram to be compared with FIG. With reference to FIG. 3, this small hydroelectric power generation system is obtained by adding a storage battery 22 and an electromagnetic contactor 23 to the small hydroelectric power generation system of FIG. Storage battery 22 is connected to DC bus Ldc via electromagnetic contactor 23. The electromagnetic contactor 23 is normally turned on and turned off when the storage battery 22 is maintained.

  During normal times when AC power is supplied from the commercial power system 31, a part of the DC power output from the boost chopper 14 is supplied to the storage battery 22, and the storage battery 22 is charged to the DC voltage VDC2 having a predetermined value. In the event of a power failure when the supply of AC power from the commercial power system 31 is stopped, the DC power of the storage battery 22 is supplied to the inverter 16 via the electromagnetic contactor 23 and the DC bus Ldc, and is converted into AC power by the inverter 16. At the time of a power failure, the circuit breaker 20 is turned off. Therefore, even when a power failure occurs, the operation of the load 32 can be continued during the period in which the DC power is stored in the storage battery 22.

  FIG. 4 is a circuit block diagram showing another modification of the first embodiment, which is compared with FIG. Referring to FIG. 4, this small hydroelectric power generation system is obtained by adding an electric double layer capacitor 24 to the small hydroelectric power generation system of FIG. Electric double layer capacitor 24 is connected to DC bus Ldc. During normal times when AC power is supplied from the commercial power system 31, a part of the DC power output from the step-up chopper 14 is supplied to the electric double layer capacitor 24, and the electric double layer capacitor 24 has a DC voltage VDC2 having a predetermined value. Charged. When the AC voltage supplied from the commercial power system 31 drops instantaneously (so-called instantaneous power failure), the DC power of the electric double layer capacitor 24 is supplied to the inverter 16 via the DC bus Ldc. Converted to AC power. Therefore, even when a momentary power failure occurs, the operation of the load 32 can be continued.

[Embodiment 2]
FIG. 5 is a circuit block diagram showing the configuration of the power generation system according to Embodiment 2 of the present invention, and is compared with FIG. Referring to FIG. 5, this power generation system is different from the small hydropower generation system of FIG. 3 in that it is disconnected from commercial power system 31, circuit breaker 1 is removed, and a plurality of sets (three sets in FIG. 5) of solar cells. A panel 25, a step-up chopper 26, and an electromagnetic contactor 27 are added. One set of the solar cell panel 25 and the boost chopper 26 may be used.

  The load 32 is connected to the secondary side terminal of the insulation transformer 18 through the circuit breaker 19 and is connected to the primary side terminal of the insulation transformer 2 through the circuit breaker 20. The circuit breaker 20 is normally turned on and turned off when an overcurrent flows. Each solar cell panel 25 is connected to the DC bus Ldc via a corresponding boost chopper 26 and electromagnetic contactor 27. The electromagnetic contactor 23 is normally turned on, and is turned off when the solar cell panel 25 is maintained.

  Each solar battery panel 25 receives sunlight and converts the solar energy into DC power. Each step-up chopper 26 converts the DC voltage output from the corresponding solar cell panel 25 into a DC voltage VDC2 having a predetermined value. The DC power output from each boost chopper 26 is stored in the storage battery 22, converted into AC power by the inverter 16, and supplied to the load 32 and the excitation device 6.

  The DC power necessary for starting the power generation system is generated by the solar cell panel 25. That is, when the AC generator 7 is started by installing the power generation system, the storage battery 22 is charged to the DC voltage VDC2 having a predetermined value by the solar battery panel 25 and the boost chopper 26, and then the DC power of the storage battery 22 is supplied by the inverter 16. The AC power is converted to AC power, the exciter 6 is activated by the AC power, and an exciting current is passed through the exciting winding 8.

  As a result, AC power is generated by the AC generator 7, and the AC power is converted into AC power of commercial frequency by the converter 13, the step-up chopper 14, and the inverter 16, and the AC power is supplied to the excitation device 6 to generate power. The system is started. If the power switch of the load 32 is turned on after the power generation system is activated, the load 32 can be driven.

  In the second embodiment, since the solar battery panel 25 and the boost chopper 26 for charging the storage battery 22 are provided, AC power having a commercial frequency is generated even in an area where AC power is not supplied from the commercial power system. The load 32 can be driven.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1, 19, 20 Circuit breaker, 2, 18 Insulation transformer, 3 Current detector, 4 Voltage detector, 5, 23, 27 Electromagnetic contactor, 6 Excitation device, 7 Alternator, 10 coupler, 11 Turbine, 12 Reactor, 13 Converter, 14, 26 Boost chopper, Ldc DC bus, 15 Electrolytic capacitor, 16 Inverter, 17 Output filter, 21 Controller, T1, T2 input terminal, T3, T4 output terminal, L1 reactor, D1 diode, Q1 N Channel MOS transistor, 22 storage battery, 24 electric double layer capacitor, 25 solar panel.

Claims (6)

A water wheel that is rotationally driven by running water;
An alternator including a rotor coupled to a rotation shaft of the water wheel and rotating at the same rotation speed as the water wheel, and outputting a first AC voltage having a frequency corresponding to the rotation speed of the water wheel;
A converter for converting the first AC voltage into a first DC voltage;
A first boost chopper that boosts the first DC voltage to generate a second DC voltage having a predetermined value;
A power generation system comprising: an inverter that converts the second DC voltage into a second AC voltage. Further, a DC bus for supplying the inverter with the second DC voltage generated by the first boost chopper;
A power storage device connected to the DC bus and charged to the second DC voltage;
2. The power generation system according to claim 1, wherein when the DC power used by the inverter is insufficient, a shortage of DC power is supplied from the power storage device to the inverter.   The power generation system according to claim 2, wherein the power storage device is a storage battery.   The power generation system according to claim 2, wherein the power storage device is an electric double layer capacitor. A solar cell that receives sunlight and outputs a third DC voltage;
A second boost chopper that boosts the third DC voltage to generate the second DC voltage and outputs the generated second DC voltage to the DC bus. 5. The power generation system according to any one of up to 4. The AC generator is a synchronous generator including the rotor and an excitation winding,
Furthermore, any one of Claim 1-5 provided with the excitation apparatus which is driven by the alternating current power supplied from at least any one of the said inverter and a commercial power system, and supplies excitation current to the said excitation winding. The power generation system according to claim 1.

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