VSC grid-connected stability domain construction method based on linear matrix inequality optimization method

Abstract

The invention relates to a VSC grid-connected stability domain construction method based on a linear matrix inequality optimization method. The VSC grid-connected stability domain construction method comprises the following steps: establishing a second-order mathematical model of a VSC access weak network system only considering the dynamic state of a phase-locked loop; performing Taylor expansion on a trigonometric function in the second-order mathematical model (A) to n orders; the optimization problem is solved based on LMI optimization; obtaining a stable domain; the control parameters of the VSC accessing to the weak network system are changed, the stability domain boundary of the VSC accessing to the weak network system under different control parameters is obtained, and according to the characteristic that the larger the stability domain area is, the stronger the system transient synchronization stability is, the stability domain area under different control parameters is compared to obtain the stability domain area of the VSC accessing to the weak network system. And qualitatively analyzing the influence of different control parameters on the transient synchronization stability of the VSC grid-connected system.

Description

technical field [0001] The invention belongs to the field of transient stability analysis of a power electronic power system, and aims at the transient synchronization stability problem of a phase-locked loop synchronous VSC connected to a weak network system, and proposes a method for constructing its stable domain. Background technique [0002] In recent years, with the rapid development of renewable energy power generation, the voltage source converter (voltage source converter, VSC) as the grid-connected interface of the renewable energy generation unit plays an increasingly important role in the power system [2-3] . Different from traditional synchronous motors that are kept synchronous by rotating rotors, VSCs are usually synchronized with the AC grid by a phase-locked loop (PLL). The dynamic performance of the PLL depends heavily on the voltage characteristics of the grid-connected point. However, under weak grid conditions, the grid-connected point voltage is easily...

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Problems solved by technology

Although the method proposed in literature [15] can guarantee the validity of the obtained stable domain, this method limits the stable domain to the area where the damping is positive, so it is relatively conservative

In addition, literature [16] used the Sum-of-Square (SOS) programming method to obtain the stable domain of the PLL dynamic equation, but the stable domain estimated by this method is also relatively conservative

[0005]The third is the inverse trajectory method: Literature [13] proposed that the boundary of the real stable domain of the system can be described by using the inverse trajectory method, but the boundary of the stable domain described cannot be used Formal description of the equation, that is to say, it is difficult to use the analytical method to judge whether the initial state of the system is in the stable region. In addition, this method is basically a graphical method, so for high-order systems (more than 3 orders), use this It will become very difficult to describe the stable domain by the method, which greatly limits the scope of application of the method

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