JP2809926B2 - Operation control method of pumped storage power plant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling the operation of an AC secondary excitation type variable speed pumped storage power plant using a sine wave PWM controlled inverter / converter.

[0002]

2. Description of the Related Art Recently, a pumped-storage power plant has a generator motor having a winding rotor and a PWM for converting a direct current into a two-stage square wave to provide a variable frequency alternating current to a rotor of the generator motor.
Neutral point clamp (NPC: Neutral Po)
A pumped-storage power plant equipped with an inverter / converter using an ( int Clamped) system is employed.

[0003] Fig. 8 shows an example of the configuration of a conventional AC secondary excitation type variable speed pumped-storage power generation equipment using a sine wave PWM control three-phase bridge type GTO inverter / converter. In addition,
Hereinafter, a case where the generator motor is operated as a generator will be described. In the figure, an AC voltage generated by a generator motor 1 is output to a transmission line (not shown), and a part of the AC voltage is transmitted through a power transformer 2 to a GTO of PWM control.
The DC voltage is supplied to a converter 3 and converted into a DC voltage.
By applying the variable frequency low-frequency alternating current to the TO inverter 5, the winding type rotor of the generator motor 1 is applied.

FIG. 9 is a diagram showing a pulse train generated by a conventional GTO inverter and its fundamental wave component. As shown in the figure, when the GTO inverter 5 applies a low-frequency alternating current to the winding rotor of the generator motor 1, the DC voltage Vd of the DC link capacitor 4 is PWM-controlled by the GTO switching of the GTO inverter 5. To generate a pulse train of the voltage Vd, and output a low-frequency alternating current with the fundamental wave component A generated by the pulse train.

At this time, the GTO inverter 5 outputs a phase voltage of + Vd / 2 or -Vd / 2 as shown in FIG. 8, so that the line voltage is + Vd, as can be seen from FIG.
A low-frequency alternating current is output by outputting pulse trains of 0 and -Vd.

On the other hand, a sine wave PW to which the present invention is applied
FIG. 1 shows an example of the configuration of an AC secondary excitation type variable speed pumped-storage power generation facility using an M-control NPC type GTO inverter. Here, the same portions as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. Only different portions will be described.

That is, FIG. 1 shows a configuration in which the GTO inverter 2 in FIG. 8 is an NPC type GTO inverter 6 and two DC link capacitors 4 are connected in series as one. is there. Next, an operation control method for the pumped storage power plant to which the present invention configured as described above is applied will be described with reference to the drawings.

In the configuration shown in FIG. 1, the principle of generation of the low-frequency alternating current is the same as that of the conventional GTO inverter, but the NP
In the case of the C type GTO inverter, since the DC voltage of one DC link capacitor is Vd / 2, the phase voltage is +
Vd / 2, 0, and -Vd / 2 are output, and as shown in FIG. 2, the line voltage is + Vd,
Since pulse trains of + Vd / 2, 0, -Vd / 2, and -Vd can be output, the conventional GTO inverter shown in FIG.
A similar low-frequency alternating current can be generated by a two-stage square wave train with a finer granularity than the output pulse train described above.

The feature of using the NPC type GTO inverter is that, since the output pulse is fine, the voltage distortion of the main circuit voltage waveform in the generator motor can be improved.
In addition, the reduction in GTO switching loss can increase plant efficiency.

[0010]

However, in a pumped storage power plant using the above-described NPC method, when the output pulse voltage is low, a two-stage rectangular waveform cannot be output, and the main circuit voltage waveform of the generator motor is reduced. It has been difficult to improve the voltage distortion. The reason will be described below.

First, when an output pulse train is generated by the NPC type GTO inverter, the output pulse train is superimposed on the main circuit voltage waveform B of the generator motor 1 as shown in FIG.

FIG. 4 shows an NPC type GTO inverter.
6 shows the characteristics of slip S and voltage distortion C in the data. The horizontal axis represents the magnitude of the low frequency output voltage generated in the fundamental wave component A, or “slip S”, and the vertical axis represents the magnitude of the voltage distortion C. In the figure, it can be seen that as the slip S increases from 0, the voltage distortion C initially increases, but eventually decreases at the local maximum value.

This means that, where the slip S is smaller than the maximum value, + Vd and -Vd of the pulse voltage value (the line voltage value) for generating the fundamental wave component A are the fundamental wave component A.
Does not occur because it is relatively higher than the amplitude of
Since a one-step rectangular waveform with three pulse voltage values of / 2, 0, and -Vd / 2 is output, the voltage distortion C increases as the output voltage (slip S) increases, and when the slip S further increases. , The fundamental wave component A is + Vd, + Vd /
Since five pulse voltage values of 2, 0, -Vd / 2, and -Vd can be generated, the output pulse train has a fine-grained two-stage rectangular waveform, which indicates that the voltage distortion C is improved.

As described above, in the conventional NPC type GTO inverter, when the slip is small and large, the voltage distortion of the main circuit voltage waveform in the generator motor is small. Is output, it is difficult to improve the voltage distortion.

The present invention has been made in view of the above circumstances, and it is possible to improve voltage distortion of a main circuit voltage waveform in a generator motor in a slip intermediate region of an NPC type GTO inverter, which has been difficult in the past. It is an object of the present invention to provide a method of operating a pumped storage power plant.

[0016]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a generator motor having a winding type rotor, a PWM control NPC type inverter for supplying a variable frequency AC to the rotor, and an AC input. Pumping power plant comprising: a converter for converting the DC to DC and outputting the DC to the inverter; and a DC link capacitor provided as a DC voltage source for the inverter between the PWM control inverter and the converter. In the above, the output pulse voltage generated from the inverter is changed to a two-stage square wave by controlling the DC voltage of the DC link capacitor so as to decrease without changing the fundamental wave component output from the inverter. At the same time, the generator motor is operated by reducing the output pulse voltage and increasing the pulse width.

[0017]

Therefore, the output pulse generated from the inverter is converted into a two-stage square wave in the entire operation range by the PWM control.
By using a PC-type inverter-converter converter, the output pulse voltage causing the voltage distortion of the main circuit voltage waveform in the generator motor can be finely divided, and the fundamental wave component generated by the output pulse train Since the output pulse waveform is controlled to be constant, it is possible to improve the voltage distortion of the main circuit voltage waveform while operating the generator motor normally in a constant state.

[0018]

An embodiment of the present invention will be described below with reference to the drawings. The control method of the present invention will be described with reference to, for example, a case where the present invention is applied to the circuit configuration of the power generation equipment shown in FIG. 1 and the generator motor is operated as a generator. In the figure, a wound rotor and a stator are provided, and the stator is connected to a transmission line (not shown) to supply a generated AC voltage. Further, a part of the generated AC voltage is filtered.
A generator motor 1 used for self-excitation by driving back, a power transformer 2 for transforming a part of the generated AC voltage, and a GTO of PWM control for converting an AC voltage supplied from the power transformer 2 into a DC voltage A converter 3, a DC link capacitor 4 serving as a DC voltage source connected in series and charged by the DC voltage, and a DC voltage supplied from the DC link capacitor to convert the variable frequency low frequency pulse AC A PWM control NPC type GTO inverter 6 for generating a voltage and applying a fundamental wave component A generated by the pulsed AC voltage as an excitation voltage to the wound rotor of the generator motor 1.
And converter control means 7 for controlling the GTO converter 3 in accordance with a voltage set value of the DC link capacitor which is predetermined according to the operating conditions of the generator motor 1.

The control of the DC link capacitor voltage by the converter control means 7 is as follows. For example, as shown in a control block diagram in FIG. 5, the optimum DC link capacitor voltage Vd ^* And the present DC link capacitor voltage Vd, the converter output voltage command value V _conv
By controlling the GTO converter 3 based on the PWM, the DC link capacitor voltage is slid.
Is controlled to a voltage value that minimizes the voltage distortion. In FIG. 5, G1 represents the slip S as the optimum DC link capacitor voltage Vd ^*. S-Vd function for converting to G2
Indicates converter control functions for converting the deviation into a converter output voltage command value _Vconv .

In the pumped storage power plant having such a configuration,
Even when an output pulse train having a one-step rectangular waveform appears in the slip intermediate region, for example, the optimum DC link capacitor voltage Vd ^{* of the} converter control means 7 is obtained ^. By reducing G
The DC voltage output from the TO converter 3 is controlled,
Accordingly, the DC voltage Vd supplied from the DC link capacitor 4 to the NPC type GTO inverter 6 also decreases. Therefore, the reduced DC voltage Vd is input to the GTO inverter 6, and the DC voltage Vd
Is relatively large, the output pulse train can be made into a two-stage rectangular waveform by the NPC method. The state of the NPC method at this time will be described with reference to waveforms.

FIG. 6 shows a one-step square-wave output waveform and a fundamental wave component thereof in the slip intermediate region according to the conventional NPC method.
In the figure, Vd indicates the DC link capacitor voltage connected in series, and Vd / 2 indicates the DC link capacitor voltage. Since the amplitude of the fundamental wave component A is small, it is formed only by the pulse train of Vd / 2.

FIG. 7 shows a two-stage rectangular output pulse waveform generated by the inverter when the DC voltage of the DC link capacitor is reduced according to the present invention, and its fundamental wave component.
As shown in the figure, since the DC link capacitor voltage Vd is lowered, the amplitude of the fundamental wave component A becomes relatively larger than Vd, and the fundamental wave component A is created by combining the pulse voltages of Vd / 2 and Vd. Therefore, the output pulse can be made into a two-stage rectangular waveform.

Further, even if a two-step rectangular waveform is generated in the output pulse, PWM control is performed so as to increase the output pulse width while lowering the DC link capacitor voltage Vd, so that the main circuit voltage waveform B of the generator motor 1 Voltage distortion C generated by superimposition can be further improved.

When the PWM control is performed, the area of the voltage / time applied to the generator motor 1 per cycle is also controlled to be constant, so that the generator motor 1 can also operate normally in a constant state.

As described above, in the present embodiment, by controlling the DC link capacitor voltage Vd so as to generate a two-stage rectangular waveform in all operating states, the output pulse train causing the voltage distortion C is always generated. The voltage distortion C of the main circuit voltage waveform B is improved because of the fineness.

In addition, even if a two-stage rectangular waveform is generated in the output pulse train, the DC link capacitor voltage V
Since d is reduced, the voltage distortion C is further improved, and the PWM control is performed so that the area of the voltage / time per cycle of the output pulse train is constant with that of the conventional output pulse train. There is no change in the fundamental wave component A applied to the spiral rotor, so that the generator motor 1 can also operate normally in a constant state.

The above description is for the case where the generator motor 1 is operated as a generator. However, even when the generator motor is operated as a motor at the time of pumping, the same control as described above is performed so that the voltage distortion of the main circuit voltage waveform of the generator motor 1 is obtained. Can be improved. In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.

[0028]

As described above, according to the present invention, the DC voltage of the DC link capacitor is reduced to reduce the DC voltage of the NPC system.
The output pulse generated from the TO inverter is always made into a two-stage rectangular waveform, so that the NPC system G, which has been difficult in the past,
It is possible to provide a method of operating a pumped storage power plant capable of improving voltage distortion of a main circuit voltage waveform in a generator motor in a slip intermediate region of a TO inverter.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an AC secondary excitation type variable speed pumped storage power plant using an NPC type GTO inverter according to one embodiment of the present invention.

FIG. 2 is a diagram showing a pulse train generated by an NPC type GTO inverter and its fundamental wave component.

FIG. 3 is a diagram illustrating a principle of generation of voltage distortion in a main circuit voltage waveform of the generator motor.

FIG. 4 is a diagram showing characteristics of slip and voltage distortion in an NPC type GTO inverter.

FIG. 5 is a control block diagram of a DC link capacitor voltage according to an embodiment of the present invention.

FIG. 6 is a diagram showing a one-stage square wave output waveform and its fundamental wave component in a slip intermediate region according to a conventional NPC method.

FIG. 7 is a diagram showing a two-stage rectangular waveform output pulse waveform generated by an inverter and its fundamental wave component when the DC voltage of the DC link capacitor according to the present invention is lowered.

FIG. 8: Three-phase bridge system GTO inverter / converter
FIG. 1 is a configuration diagram of an AC secondary excitation type variable-speed pumped-storage power generation facility using a motor.

FIG. 9 is a diagram showing a pulse train generated by a GTO inverter and its fundamental wave component.

[Explanation of symbols]

1: generator motor, 2: power transformer, 3: GTO converter
4 ... DC link capacitor 5 ... Three-phase bridge type GTO inverter 6 ... NPC type GTO inverter
7 ... Converter control means.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuyuki Abe 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Inventor Hirokazu Kaneko 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Inside Electric Power Company (72) Inventor Ryoji Sugawara 6-15-1, Ginza, Chuo-ku, Tokyo Power Supply Development Co., Ltd. (72) Inventor Takayoshi Sano 6-15-1, Ginza, Chuo-ku, Tokyo Power Supply Development Co., Ltd. (72) Inventor Kazuo Hachiya 6-15-1, Ginza, Chuo-ku, Tokyo Inside Power Development Co., Ltd. (72) Inventor Kenji Kudo 1-1-1, Shibaura, Minato-ku, Tokyo Inside Toshiba Head Office (56 References JP-A-3-289399 (JP, A) JP-A-3-159570 (JP, A) JP-A-56-121369 (JP, A) JP-A-5-211775 (JP, A) (58)査the field (Int.Cl. ^6, DB name) H02P 9/00 - 9/48

Claims (1)

(57) [Claims] 1. A generator motor having a winding rotor, a PWM-controlled neutral-point-clamped inverter that converts a direct current into a two-stage square wave to provide a variable frequency alternating current to the rotor, and converts an AC input to a DC. And a DC link capacitor provided between the PWM control inverter and the converter as a DC voltage source of the inverter, wherein the fundamental wave component output from the inverter is not changed. An output pulse voltage wave generated by the inverter by controlling the DC voltage of the DC link capacitor to decrease.
The shape is a two-stage square wave, the output pulse voltage is small, and the output pulse
An operation method of the pumped storage power generation facility, wherein the generator motor is operated by increasing the width of the gap.