Method for autonomous operation of electricity-generating device

Abstract

When it is not possible for a power generation device to operate coupled to an electric power system, an autonomous operation of connection and disconnection of a load of the power generation device is performed along an efficiency-characteristics curve within a speed range from a rated speed to a maximum speed in the efficiency-characteristics curve of an energy source. During the autonomous operation, an aperture command is outputted to an inlet valve of a water turbine and a first converter is operated in a converter mode when an operation preparation command is outputted by a control unit, a second converter is operated in an inverter mode when a voltage is established by of a DC linkage unit, and the load is connected when the operation preparation is completed.

Claims

1. A method for an autonomous operation of an electricity-generating device interconnected to an electric power system, the electricity-generating device comprising: a permanent magnet power generator coupled to a water turbine; first and second converters having forward/inverse conversion functions; a smoothing capacitor connected to a DC linkage unit between the first and second converters; and a control unit outputting control commands to the first and second converters, wherein, when the autonomous operation of the electricity-generating device is conducted, the autonomous operation is an operation in which the electricity-generating device is separated from the electric power system, the method comprising: controlling, by the first converter, a voltage of the DC linkage unit to be constant, causing a load connected to the electricity-generating device to be connected or disconnected, and always operating the electricity-generating device along an efficiency-characteristics curve, when the autonomous operation of the electricity-generating device is conducted, that corresponds to an aperture of an inlet valve of the water turbine and is based on a shaft input and a rotational speed, only within a speed range from a rated speed, at which the shaft input of the efficiency-characteristics curve becomes maximum, to a maximum speed, at which the shaft input becomes minimum, in the efficiency-characteristics curve of the water turbine.

2. The method for the autonomous operation as claimed in claim 1, further comprising: outputting, during the autonomous operation, a valve-position command to the inlet valve of the water turbine and operating the first converter in a converter mode when an operation preparation command is outputted by the control unit, and operating the second converter in an inverter mode when a voltage is established by the DC linkage unit, and connecting the load when the operation preparation is completed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view showing an interconnection state to an electric power system of an electricity-generating device according to an embodiment of the present invention;

(2) FIG. 2 is a chart showing an autonomous operation range of the electricity-generating device for explanation;

(3) FIG. 3 is an explanatory chart of states at the time of autonomous operation;

(4) FIG. 4 is a view showing the outline of an operation procedure at the time of autonomous operation;

(5) FIG. 5 is a view showing the outline of the operation procedure at the time of autonomous operation;

(6) FIG. 6 is a view showing the outline of the operation procedure at the time of autonomous operation;

(7) FIG. 7 is a view showing an interconnection state to an electric power system of a conventional electricity-generating device; and

(8) FIG. 8 is a view showing an operation range when a permanent magnet power generator is interconnected to the electric power system.

MODE FOR IMPLEMENTING THE INVENTION

(9) FIG. 1 is a schematic diagram showing an electricity-generating device according to the present Embodiment 1. FIG. 1 differs from FIG. 7 which shows a conventional electricity-generating device in a point that a dummy load device is omitted. Other points are the same as FIG. 7, therefore, explanation will be omitted.

(10) FIG. 2 shows efficiency-characteristics curves (hereinafter referred to as Cp characteristics curves) of a water turbine. When a rated capacity of a permanent magnet power generator is f.sub.0 and a rated speed thereof is n.sub.0, the shaft input is increased from a line D to a line A in accordance with an aperture of an inlet value 1a of a water turbine 1, and the generator is operated in the vicinity of the rated speed n.sub.0 at the time of system interconnection.

(11) In the present invention, the autonomous operation is performed with respect to the load capacity which is lower than a rated capacity of the permanent magnet power generator in the case where the system interconnection is difficult to be performed. At the time of performing the autonomous operation, for example, a Cp characteristics curve at an aperture 100% of the line A is used as well as a range in which the speed is the rated speed no or higher is used as a variable speed range as shown in FIG. 3. Hereinafter, a method for the autonomous operation will be explained with reference to FIG. 4 to FIG. 6. In FIG. 4 to FIG. 6, components in an operation state are shown by being hatched.

(12) FIG. 4 (1) to FIG. 6 (3) correspond to the outline showing an operation procedure in the autonomous operation by the electricity-generating device shown in FIG. 1. In FIG. 4 (1), a DC control power supply is connected to a converter panel 10 in the initial state of the electricity-generating device. The inlet value 1a of the water turbine 1 is in a closed state at this time. In FIG. 4 (2), a valve-position command to the inlet valve 1a, input of an electromagnetic switch 16 and an operation preparation command for a first converter (inverter) 11 are outputted from an upper control unit 40. Accordingly, the water turbine 1 starts to rotate and a permanent magnet power generator 3 starts to generate power and generate a voltage. The initial charge to a smoothing capacitor 14 is started by the first converter (inverter) 11 being operated in a converter mode.

(13) In FIG. 4 (3), the flow rate is increased as the aperture of the inlet valve 1a further progresses, and the water turbine 1 is accelerated into a runway speed (the rated speed no or higher). The charging to the smoothing capacitor 14 further progresses accordingly, and an electromagnetic switch 17 and a breaker 18 are inputted at the time when a voltage in a DC linkage unit is established.

(14) In FIG. 5 (1), the water turbine is at the runway speed at the aperture 100% of the inlet valve 1a, an output voltage is set and an output frequency is set with respect to a second converter 12, and the second converter 12 is allowed to have a function of automatically controlling voltage/frequency as an inverter operation to complete the operation preparation. As the device is in a no-load state when the operation preparation is completed, the water turbine rotates at a maximum rotational speed n.sub.m shown in FIG. 3. In FIG. 3, numerals inside square frames correspond to numerals in diagrams of FIG. 4 to FIG. 6.

(15) In FIG. 5 (2), a load input command in a power plant is issued with respect to a breaker CB1 from the upper control unit 40, thereby starting the autonomous operation. When the load is inputted, a load current flows and the voltage in the DC linkage unit is reduced. However, the first converter (inverter) 11 controls the voltage in the DC linkage unit to be constant (AVR), thereby replenishing deficit of energy with rotation energy of the water turbine 1, a flywheel 2 and the permanent magnet power generator 3 as a rotating body and reducing the speed of the permanent magnet power generator 3 and the water turbine. As a result, the rotational speed is reduced along the Cp characteristics curve from the maximum rotational speed n.sub.m, and the device is operated at a rotational speed of n.sub.m1 which corresponds to the load.

(16) When an additional input command of the load is issued and a breaker CB2 is turned on in FIG. 5 (3), the rotational speed of the water turbine is further reduced in accordance with the inputted load amount, and the device is operated at a rotational speed of n.sub.m2. The range in which the load amount can be inputted is within a range of speed from the rated speed no to the maximum speed n.sub.m.

(17) The rotational speed of the water turbine 1 at the time of the autonomous operation has to be the rated speed no or more. The reason is that the rotational speed is reduced due to the overload and the rotation is finally stopped when operated at the rated speed no or less.

(18) Next, a procedure of stopping the electricity-generating device will be explained with reference to FIG. 6. In the case where part of the load is released at the rotational speed n.sub.m2, the breaker CB2 is turned off as shown in FIG. 6 (1), then, the rotational speed is increased along the Cp characteristics curve. Then, the energy balance between the load and the power generation amount is achieved and the increase of rotational speed is stopped at the rotation of n.sub.m1, and the operation is continued at the rotational speed of n.sub.m1.

(19) Furthermore, in a state where all load is released as shown in FIG. 6 (2), the no-load operation is performed at the rotational speed of n.sub.m. In FIG. 6 (3), a stop command is outputted to the second converter 12 and the operation is stopped. After that, a stop command for the electricity-generating device is outputted and the first converter 11 is also stopped, then, a deceleration command is outputted to the inlet valve 1a of the water turbine and the inlet valve 1a is wholly closed to thereby stop the water turbine.

(20) According to the present invention mentioned above, even when parallel-off of the electricity-generating device from the electric power system is performed, the autonomous operation of the electricity-generating device is realized by performing operation at a speed at which the energy balance corresponding to the load is achieved within a speed range of the rated speed or more in the Cp characteristics curve. Accordingly, when it is difficult for the electricity-generating device to perform system interconnection, the autonomous operation control can be performed only by allowing the electricity-generating device to have a software-based autonomous function by the device for interconnection operation without specially preparing devices for an isolated operation such as a dummy resistor device or a high-speed guide vane control unit by an electric servo motor.