Improved control method for low voltage ride through of renewable energy power generation system

Abstract

The invention discloses an improved control method for low voltage ride through of a renewable energy power generation system. The method specifically comprises the following steps: measuring a three-phase voltage signal of a fault point and equivalent resistance of a transmission circuit between a grid-connected point of the renewable energy power generation system and the fault point; calculating a total instruction value I * of current injected into the power grid by the renewable energy power generation system; the method comprises the following steps: collecting a grid-connected point three-phase voltage signal Us of a renewable energy power generation system, and calculating a virtual terminal voltage signal Uv of a phase-locked loop module of the renewable energy power generation system; a virtual end voltage signal Uv of a phase-locked loop module of the renewable energy power generation system passes through a digital phase-locked loop to obtain an electrical angle theta PLL and a synchronous electrical angular velocity omega g of a positive sequence voltage vector of a power grid, and subsequent control is carried out by adopting a virtual end voltage d-axis orientation mode. According to the invention, through processing and improving control of the phase-locked loop three-phase voltage signal input signal of the renewable energy power generation system, the problem of large interference instability of the renewable energy power generation system during the low voltage ride-through period is avoided.

Description

technical field [0001] The invention relates to the field of new energy power generation, in particular to an improved control method of a renewable energy power generation system during low voltage ride through. Background technique [0002] At present, the conventional wind power / photovoltaic and other renewable energy power generation systems mostly use the phase-locked synchronous control mode based on the phase-locked loop, and its operating characteristics are heavily dependent on the operating state of the power grid. However, with the large-scale and centralized development of renewable energy sources such as wind power / photovoltaic, as well as cross-regional and long-distance transmission, the connection between the renewable energy power generation system and the main grid is tending to weaken. The interaction between the output power flow of the renewable energy power generation system and the grid impedance is becoming more and more obvious, especially during the...

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Problems solved by technology

However, this method can only improve the small-signal stability of the system, and cannot avoid the risk of system out-of-synchronization

Literature [2], starting from the electromechanical time scale, studied the large disturbance instability phenomenon of the double-fed wind power generation system during the low-voltage ride-through period of the weak grid, and found that the large-scale disturbance of the double-fed wind power system during the low-voltage ride-through period was out of step and out of the grid Instability phenomenon, but the literature did not propose corresponding improvement control measures

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