Enhanced low voltage ride-through control method for doubly-fed wind turbines under grid asymmetric faults

Abstract

The present invention discloses a control method capable of enhancing low-voltage ride-through used for a double-fed induction generator under an asymmetrical power grid fault. The method comprises control of a rotor side converter and a grid side converter of the double-fed induction generator. According to the method, by controlling the rotor side converter of the double-fed induction generator, the double frequency fluctuation of the electromagnetic torque of the generator can be effectively suppressed, so that safe and stable fault ride-through operation of a double-fed wind power generation system is realized; meanwhile, on the basis of consideration of converter capacity, a minimum reactive current meeting the requirements of a power grid guide rule can be output, so that the transient voltage level of a power grid during a fault period is improved. According to the method, by controlling the grid side converter of the double-fed induction generator, the double frequency fluctuation of a DC bus voltage can be suppressed, so that the service life of a DC bus capacitor is improved, the double frequency fluctuation of active and reactive power output from the generator can be effectively suppressed via coordinated control with the rotor side converter, and thus the grid-connected power quality is improved. According to the method, by comprehensively considering the capacity of the converter and the operation condition of the generator, the fault ride-through capability of the double-fed induction generator and the power quality of the connected power grid are effectively improved.

Description

technical field [0001] The invention relates to wind power generation technology, in particular to an enhanced fault ride-through control method for a doubly-fed wind generator set under an asymmetric fault of a power grid, and belongs to the field of new energy power generation. Background technique [0002] At present, doubly-fed wind turbines have become one of the mainstream models in wind power generation systems due to their advantages of variable speed and constant frequency operation and small converter capacity. However, since the stator winding is directly connected to the grid, the unit has poor performance against grid disturbances, especially grid voltage drops. Compared with the symmetrical short-circuit fault of the power grid, the probability of the unsymmetrical short-circuit fault of the power grid to occur in the actual system is greater. When an asymmetric drop fault occurs in the power grid, overvoltage and overcurrent will appear in the rotor winding o...

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Problems solved by technology

However, this method causes the doubly-fed wind power system to absorb reactive power from the grid during asymmetric faults in the grid, thereby deepening the degree of fault drop.

Document (3) proposes to increase the use of dynamic voltage restorer to compensate the grid-connected point voltage of the doubly-fed wind power system during the asymmetric fault of the grid, so as to further improve the operating performance of the doubly-fed wind turbine under the grid asymmetrical drop fault, but the use of hardware equipment will inevitably increase the cost of the entire system

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