A control method and system for frequency modulation of a wind power grid-connected inverter

Abstract

The invention discloses a wind power grid-connected inverter frequency modulation control method and system. The control method is applied to frequency modulation control in a wind power grid-connected system. The control method comprises the following steps that the wind power grid-connected system uses a double-closed-loop control strategy of a output voltage outer loop and a output current inner loop; a virtual synchronous motor is used for control; the operation frequency of the wind power grid-connected system is obtained; whether the operation frequency is in a frequency range or not isjudged; if so, the virtual synchronous motor is used for performing primary frequency modulation on the wind power grid-connected system; otherwise, the virtual synchronous motor is used for performing secondary frequency modulation on the wind power grid-connected system. The double feed control is performed according to the frequency deviation; the frequency self restoration is realized; meanwhile, the power fluctuation is reduced; no limiting exceeding in the whole frequency regulation process occurs is ensured.

Description

technical field [0001] The invention relates to the field of wind power grid-connected, in particular to a control method and system for frequency modulation of a wind power grid-connected inverter. Background technique [0002] The internal rotor kinetic energy and damping coefficient of traditional synchronous generators can maintain the stability of the grid frequency, while the wind power generation system connected to the grid through the inverter has low inertia and damping characteristics. With the continuous increase of wind power penetration, the grid frequency regulation is restricted. dynamic and steady-state performance. When the frequency of the grid changes suddenly or the load is switched, the wind farm itself is required to have frequency response and adjustment capabilities to meet the needs of the grid for inertial response and primary frequency regulation of the wind farm. [0003] In order to make wind power grid-connected with inertial frequency modulat...

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Problems solved by technology

[0003] In order to enable wind power grid-connected to have inertial frequency modulation similar to that of synchronous motors, a virtual synchronous motor control is proposed. By introducing the motion equation of synchronous motors, the wind power grid-connected inverter has inertial and damping characteristics, which suppresses frequency transient fluctuations. The steady-state primary frequency modulation is realized, which improves the stability of the wind power grid-connected system. However, the virtual synchronous motor has differential control and cannot achieve frequency recovery.

When the grid frequency drops greatly or switches high-power loads, the system frequency exceeding the limit will lead to low-frequency or high-frequency relay protection. Therefore, the stability of the wind power grid-connected system in the prior art is poor. When the power is loaded, there will be a problem that the system frequency exceeds the limit

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