Three-phase phase-locked loop based on virtual synchronous damping control and alternating-current microgrid transient stability improving method

A technology of damping control and virtual synchronization, applied in the field of microgrid, can solve problems such as the analysis of stability technology of AC microgrid that is not applicable, and achieve the effect of enhancing transient stability

Pending Publication Date: 2021-01-05
ZHEJIANG UNIV
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  • Summary
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  • Application Information

AI Technical Summary

Problems solved by technology

However, for AC microgrids in an island state, the system voltage is provided by grid support converters, and their control structures will switch under large disturbance
Therefore, the system voltage is time-varying and cannot be modeled as a constant voltage source; in addition, the grid-following converter will also be affected, and a very complex nonlinear interaction will be formed between them
Therefore, the existing research results are not applicable to the stability technical analysis of the AC microgrid in the island state

Method used

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  • Three-phase phase-locked loop based on virtual synchronous damping control and alternating-current microgrid transient stability improving method
  • Three-phase phase-locked loop based on virtual synchronous damping control and alternating-current microgrid transient stability improving method
  • Three-phase phase-locked loop based on virtual synchronous damping control and alternating-current microgrid transient stability improving method

Examples

Experimental program
Comparison scheme
Effect test

experiment example 1

[0023] Experimental case 1: There are only two converters in the AC microgrid, and the experimental waveform comparison results before and after adding virtual synchronous damping control.

[0024] There are only two converters in this experiment, a grid-supporting converter and a grid-following converter. The amplitude of the rated AC bus voltage is 311V, the frequency is 50Hz, and the system load under normal conditions is Z L = 2Ω. Before 0.4s, the system was running in normal state. During 0.4s——0.9s, the system suffers a large disturbance and operates in a fault state, which is equivalent to the system load Z L An additional fault impedance Z is connected in parallel D . After 0.9s, the system returns to the normal state. The relevant control parameters of the grid generating converter and the grid following converter are shown in Table 1 and Table 2.

[0025] Table 1 Relevant control parameters of grid generating converter

[0026]

[0027] Table 2 Relevant con...

experiment example 2

[0032] Experimental case 2: There are four converters in the AC microgrid, and the experimental waveform comparison results before and after adding virtual synchronous damping control.

[0033] In order to verify the effectiveness of the method of virtual synchronous damping control more effectively, an AC microgrid containing 4 converters, including 1 grid-supporting converter (#0) and 3 grid-following converters (#1 , #2, #3). The corresponding control measures remain unchanged, except that the maximum currents of grid following converters #1, #2, and #3 are changed to 50A, 30A and 20A respectively.

[0034] Figure 6 shows that without virtual synchronous damping control, when the system is subjected to perceptual disturbance (Z D =3mH) dynamic response characteristic diagram. It can be seen that in the transient process, the system is difficult to maintain equilibrium. The AC bus voltage and the output currents of the three converters all oscillated, and the phase angl...

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Abstract

The invention relates to a three-phase phase-locked loop control structure based on virtual synchronous damping control, which is characterized in that a frequency deviation feedback channel is addedin the PI control process in the three-phase phase-locked loop control structure, and the frequency deviation output by PI is used as a feedback signal to be transmitted back to the input end of a PIcontroller. The invention further provides an alternating-current microgrid transient stability improving method based on virtual synchronous damping control, and a controller of a power grid following converter in the alternating-current microgrid is designed based on a d-q synchronous rotating coordinate system, wherein the Park transformation and inverse transformation rotation angle [theta]pllis obtained by observing the bus end voltage of the microgrid through a three-phase phase-locked loop control structure. The equivalent damping of the phase-locked loop can be increased under the condition that the steady-state performance of the phase-locked loop is not changed, so that the overshoot in the transient process is reduced, and the transient stability of the alternating-current microgrid is improved.

Description

technical field [0001] The invention relates to a three-phase phase-locked loop based on virtual synchronous damping control and a method for improving transient stability of an AC microgrid, which belongs to the transient stability control technology in the field of microgrids. Background technique [0002] In recent years, with the development of distributed renewable energy, AC microgrid technology has made great breakthroughs. Different from the traditional power system dominated by synchronous generators, AC microgrid is a typical power system dominated by power electronics, and its dynamic characteristics have undergone tremendous changes. The low inertia and low overload capacity of power electronic devices pose serious challenges to the stability of AC microgrids, which greatly affects the reliable and efficient operation of AC microgrids. [0003] The stability of AC microgrid can be divided into small signal stability and transient stability. At present, the rese...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/00H02J3/38H02J3/46
CPCH02J3/00H02J3/388H02J3/46H02J2300/22Y02E10/56
Inventor 何杭航夏杨红韦巍
Owner ZHEJIANG UNIV
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