JPH04275028A - Frequency conversion transmission system - Google Patents

Abstract

PURPOSE:To increase power transporting ability by transmitting power, converting into a frequency (usually 10-30Hz) lower than a commercial frequency. CONSTITUTION:Frequency converters 4, 5 are put between a generator 1 and the beginning end of a transmission line 2, and between the termination of the transmission line 2 and a load 3 respectively. Hereupon the frequency of the AC power generated by the generator 1 is 60Hz. But the frequency is converted from 60Hz to 20Hz by the frequency converter 4 on the side of the generator 1, and converted reversely from 20Hz back to 60Hz by the frequency converter 5 on the side of the load 3. Incidentally, the frequency of the power is considered to be 20Hz, but it is judged that a range of 10-30Hz is appropriate. And this constitution makes it possible to transport more power on the same transmission line and to raise the transportation efficiency.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alternating current power transmission system, and more particularly to a frequency conversion power transmission system that transmits power by converting it to a lower frequency.

0002

BACKGROUND OF THE INVENTION There are two types of electric power transportation methods: DC and AC, but AC is the most commonly used method worldwide. This is because alternating current can be transformed, is easy to shut off, is easy to control power flow, and has little magnetic influence. In addition, the commercial frequency for AC systems is approximately 50Hz or 60Hz worldwide, but this is because increasing the frequency in 3-phase systems not only reduces the amount of transmission, but also lowers the transmission rate during light loads. This is because when three-phase unbalance conditions such as a ground fault occur, resonance easily occurs and overvoltage occurs, and conversely, at low frequencies, flickering of the lighting becomes a concern. In addition, the current frequency of AC systems is determined by taking into account the design and manufacturing conditions of generators, etc.

[0003] In an AC system in such a frequency range, in order to use the amount of power transported up to the heat capacity limit of the electric wire, the reactance as AC resistance is usually reduced by 1/2 to 1/2.
A value of about 3 is sufficient. A common method for this purpose is to introduce a series capacitor, but it has limitations due to low frequency axial torsional resonance (SSR). Efforts are also being made to reduce the reactance of power transmission lines, but
The reality is that the line structure is close to its limits.

[0004] Therefore, this invention aims to provide a power transmission system that improves the power transport capacity by introducing a series capacitor and by introducing a new method to replace the low reactance of the power transmission line. Take it as a challenge.

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention adopts a method of transmitting power by converting it to a frequency lower than the commercial frequency (usually 10 to 30 Hz) in the AC power transmission system. .

That is, the transportation power P due to alternating current is expressed by the following equation.

P=(VG ・VL ・sin δ)/X However, VG
: Generation end voltage VL : Load end voltage δ : Phase difference angle between VG and VL Electric wires can transport a lot of power, and in principle, if the frequency is halved, twice as much power can be transported.

[0008]

[Embodiment] Figures 1 to 3 show examples of the system of the present invention, and the one shown in Figure 1 shows the connection between the generator 1 and the starting end of the power transmission line 2, and between the end of the power transmission line 2 and the load. 3, frequency converters 4 and 5 are interposed between them. generator 1
The frequency of the alternating current power generated at Conversely, convert from 20Hz to 60Hz. Therefore, the frequency of the power transported by the power transmission line 2 is 20 Hz.

In the embodiment shown in FIG. 2, a transformer 6 is interposed between the generator 1 and the starting end of the power transmission line 2, and the same frequency conversion as described above is performed between the end of the power transmission line 2 and the load 3. A container 5 is used.

In this case, the frequency of the generator 1 is 20 Hz, so the frequency of the power transmitted by the power transmission line 2 is 20 Hz, which is converted by the frequency converter 5 to 60 Hz.

The embodiment shown in FIG. 3 has a configuration similar to that shown in FIG. 1, but the frequency of the generator 1 in this case is 200 Hz, which is converted to 20 Hz by the frequency converter 4.

[0012] In all of the above embodiments, the frequency of the power transmitted by the power transmission line 2 is 20 Hz, but it is judged that this frequency is appropriate in the range of 10 to 30 Hz. This is because if the frequency is lower than 10 Hz, the turbine and power generation/transformation equipment will be large, and if the frequency exceeds 30 Hz, the weight of the converter cost in the system will become large, making it impractical in terms of cost.

[0013]

[Effect of the invention] As described above, the power transmission method of this invention is
Since power is transmitted at a lower frequency than normal, a large amount of power can be transported on the same transmission line. In other words, it has the effect of increasing the transportation efficiency of existing power transmission lines and reducing the number of routes for new power transmission lines.

[Brief explanation of the drawing]

[Figure 1] Block diagram of the embodiment

[Figure 2] Block diagram of the embodiment

[Figure 3] Block diagram of the embodiment

[Explanation of symbols]

1 Generator 2 Power transmission line 3 Load 4, 5 Frequency converter 6　Transformer

Claims (2)

[Claims] 1. A frequency conversion power transmission method in which power is transmitted by converting it to a frequency lower than the commercial frequency in an AC power transmission method. 2. The frequency conversion power transmission system according to claim 1, wherein the power transmission frequency is 10 to 30 Hz.