DC power flow controller and control method for multi-terminal flexible DC transmission system

A DC power transmission system and DC power flow technology, applied in the field of DC power flow controllers and multi-terminal DC power transmission occasions, can solve problems such as many switching devices, achieve less switching devices, improve control ability, transmission line transmission capacity, and simple circuit structure. Effect

Inactive Publication Date: 2016-03-30
SOUTHEAST UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the circuit structure of these two schemes requires an external power supply to provide power for the adjustable voltage source or absorb its power, and a low-frequency and high-voltage isolation transformer is required for voltage isolation, and more switching devices are required.

Method used

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  • DC power flow controller and control method for multi-terminal flexible DC transmission system
  • DC power flow controller and control method for multi-terminal flexible DC transmission system
  • DC power flow controller and control method for multi-terminal flexible DC transmission system

Examples

Experimental program
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Embodiment 1

[0038] Embodiment 1 and embodiment 2 all adopt figure 1 In the three-terminal ring-network flexible DC power transmission system shown, VSC3 operates in constant DC voltage mode and controls V 3 =150kV, VSC1 and VSC2 operate in constant power mode, respectively injecting P into the system 1 = 160MW and P 2 =80MW power, the parameters of the three-section transmission line are shown in Table 1.

[0039] Table 1 figure 2 Line parameters of the three-terminal flexible DC transmission system shown

[0040] Transmission Line Parameters

Line1

Line2

Line3

Length / km

200

300

100

Resistance / Ω

2

3

1

Inductance / mH

80

120

40

[0041] The transmission line current and the adjustable voltage source voltage V after adding the DC power flow controller of the present invention x , V y The relationship curve is as Figure 10 As shown, the port voltage V 1 , V 2 with adjustable voltage source voltage V ...

Embodiment 2

[0043] Example 2 for power P first by V y pass to V x , after some time by V x pass to V y , power P by V y pass to V x , the sustaining current I 13 is 0.32kA, the power P is determined by V x pass to V y , the sustaining current I 23 0.35kA. Figure 15 The current waveforms of the transmission line before and after the power P transmission direction is changed are given, Figure 16 The port voltage V before and after the power P transfer direction is changed is given 1 and V 2 waveform. Depend on Figure 15 It can be seen that when the power P transmission direction of the power flow controller changes, the currents on the three lines all change, and the DC power flow in Line1 reverses. It shows that the power flow controller of the present invention can meet the requirement of power flow reversal.

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Abstract

The invention discloses a direct-current power flow controller for a multiport flexible direct-current power transmission system and a control method. The direct-current power flow controller comprises two adjustable voltage sources which are respectively connected in two adjacent power transmission lines in series, wherein two by-pass switches are respectively in parallel connection with the two adjustable voltage sources, and four switch tubes and four diodes are distributed on two sides of an inductor after being connected in series. Current of the power transmission line where a certain adjustable voltage source is located is acquired and subtracted from a given current reference value and then is subtracted from acquired voltage of the adjustable voltage source after a PI link and a delay link, PWM drive signals of the switch tubes are obtained by performing the PI link on a difference value, and turning-on and turning-off of the switch tubes are controlled to enable the current of the power transmission line where the adjustable voltage source to serve as a given reference value. The direct-current power flow controller is simple in circuit structure, is provided with few switch devices and does not need an isolation transformer and an external power supply.

Description

technical field [0001] The invention relates to a direct current flow controller, which belongs to the technical field of power electronics and is mainly used in multi-terminal direct current transmission occasions. Background technique [0002] The multi-terminal direct current transmission system is a direct current transmission system consisting of three or more converter stations connected in series, parallel or hybrid. It can realize multi-source power supply and multi-drop power reception. The operation of the system is more economical and flexible, and it is one of the effective technical means to solve the problems of large-scale renewable energy grid integration, large-capacity long-distance power transmission and shortage of transmission corridors that my country is currently facing. Compared with the traditional current source converter, the voltage source converter (voltage source converter, VSC) reverses the direction of the DC current when the power flow reverse...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J1/00H02J3/36
CPCY02E60/60
Inventor 陈武朱旭
Owner SOUTHEAST UNIV
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