JPS60106334A - Method of controlling field current of non-utility generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention has a private generator and operates a factory using the electric power generated by the generator and the electric power supplied from the electric power company. The present invention relates to a method of controlling the field current of a private generator before and after the power supply stoppage, taking into consideration the case where the power supply from the electric power company is stopped.

(Prior technology) The automatic voltage adjustment function of private generators is intended to quickly stabilize the grid voltage and maintain a stable supply of power even when the grid is disturbed by changes in the grid load, such as load additions or interruptions. It is something.

As shown in Fig. 1, the output characteristics of a synchronous generator generally include a limited area (■) due to armature current and a limited area (■) due to field current, but it is generally not possible to operate in the field current limited area (■). In many cases, it is possible to perform maximum phase delay operation by field current control. Note that in this figure, θ is the rated slow phase power factor.

Conventionally, a method for improving the power reception rate by slow-phase operation of a private generator is that, as shown in FIG. 2, the private generator 1 performs automatic voltage adjustment operation regardless of whether it is connected to the power company. This is achieved by controlling the field current 4 by changing the reference signal 3 of the automatic voltage regulator 2 to bring it closer to maximum phase lag operation. 5 in the figure is the field of the private generator,
6 is an excitation device, 7 is a step-up transformer, 8 is an instrument transformer, 9
indicates a current transformer, and 10 indicates a load. According to this method, the automatic voltage regulator is used at all times, and even if the connection with the electric power company is cut off, the system voltage continues to be adjusted, so there is no problem with the stable supply of electric power. However, even if the reference signal of the automatic voltage regulator is changed and adjusted to the maximum phase lag operating point, the automatic voltage adjustment function will always act due to voltage fluctuations due to load fluctuations in the system, and the field current will also change. For example, as shown in Fig. 3, even if the operation is at the most delayed phase point M at the output P, a command to increase or decrease the field current is issued by the control signal of the automatic voltage regulator. Since it is limited by (2), it inevitably operates only toward the area side and moves to point N as time passes. That is, the maximum lagging power factor changes from θ to θ2. During grid-connected operation with a power company, operators have always monitored and made adjustments to eliminate the reduction in field current caused by this automatic voltage regulator function.

Even if such adjustments are made frequently, it is not possible to maintain the maximum phase-lag operation trajectory continuously, and on average, the operation trajectory can only be achieved as D', and furthermore, the operating burden on the operator is significant. there were.

(Objective of the invention) The present invention aims to solve this problem and provide a method that can be implemented at a very low cost. There are two cases for private generators: connected operation with the electric power company and standalone operation of the private generator system.When the private generator system is operated independently, it exhibits an automatic voltage adjustment function, and is connected to the electric power company. During system operation, this method trace-controls the rated value of the field current to enable maximum phase-lag operation.

(Structure and operation of the invention) The following is a description based on examples. As shown in FIG. 4, when the interconnection breaker 13 with the electric power company 15 is on, the field control switch 16 is switched to the direction b, and the field current 4 is controlled by the automatic field current tracking device 11. Perform trace control.

By adjusting the reference signal 12 of the field current automatic tracking device 11 and setting the field current 4 to the rated value, maximum phase-lag operation is possible. In this state, the interconnection breaker 1 with the power company
3 is turned off, the field control switch 16 instantly automatically switches to the direction a, thereby exerting an automatic voltage adjustment function, quickly settling the grid voltage, and maintaining a stable supply of electric power.

By this method, when the private generator is connected to the electric power company, the amount of reactive power received at the transaction meter 14 with the electric power company can be reduced, and the power reception ratio can be improved. .

(Effects of the Invention) As shown in FIG. 5, the method of the present invention can improve the operating state of the private generator to an operating trajectory F due to automatic tracking of the field current compared to the conventional operating trajectory E ( ΔPF is a power factor correction formula), and as a result, the amount of reactive power received from the interconnected electric power company can be reduced, and the received power factor can be improved by several times.

[Brief explanation of the drawing]

Figure 1 is an output characteristic diagram of a synchronous generator, Figure 2 is a system overview diagram of a conventional private generator field current control method, and Figure 3
Is the diagram the conventional self-71? Figure 4 is a system diagram of the field current control method according to the embodiment of the present invention. Figure 5 is a diagram showing the maximum phase-lag operation locus during operation using the I'It pressure regulator. Figure 5 is a diagram showing the conventional method and the present invention. It is a comparison diagram of the operating trajectory of a private generator with the method according to the method. 1: Private generator 2: Automatic voltage regulator 3: Automatic voltage regulator reference signal 4: Field current 5: Private generator field 6: Excitation device 7: Step-up transformer 8: Potential transformer 9: Instrument current transformer 10: Load 11: Field current automatic follow-up device 12: Reference signal 1 of field current automatic follow-up device
3: Interrupter for interconnection with electric power company 14: Instrument for transaction with electric power company 15: Electric power company 16: Field control switch ■
: Limited range due to armature current ■: Limited range due to field current ◎: Operating range of overexcitation limiter D: Maximum slow phase operation trajectory due to field current Dl: Average slow phase operation trajectory according to conventional method E: Actual result F : Actual result M of average slow phase operation trajectory in the embodiment of the present invention
: Maximum lag phase operating point N at specific output: Point θ that shifts over time from the maximum lag phase operation point M at output P in the conventional method due to load fluctuations in the grid: θ: Rated phase lag power of the private generator Factor θ1: Maximum lagging power factor θ2 at output P: Maximum lagging power factor θ at output P in the conventional method
, the power factor changes over time due to load fluctuations in the system.Applicant Minoru Aoyagi, patent attorney representing Nippon Steel CorporationFigure 1Figure 2Figure 3

Claims (1)

[Scope of Claims] When operating a factory using the electric power generated by the generator and the electric power supplied from the electric power company, the private generator is connected to the electric power company. When the power supply is disconnected from the electric power company, the system is controlled to trace a constant field current value to enable arbitrary slow-phase power factor operation to improve the power reception rate. Automatic Kk with automatic voltage adjustment function
')ii' A method for controlling a field current of a private generator, characterized in that the grid voltage is quickly stabilized to maintain a stable supply of electric power.