Three-level wind power converter soft start circuit and control method

Abstract

The invention relates to the technical field of three-level converters of wind generating sets, in particular to a three-level wind power converter soft start circuit. The main loop power supply inputis connected with a converter controller U and a main loop protection switch Q; a main loop grid-connected switch KM2, a filter reactor L, an alternating-current filter capacitor C and a three-levelpower module M1 are sequentially connected in the direction from the main loop protection switch Q to the direct-current bus, a positive bus capacitor C1 and a negative bus capacitor C2 are arranged at the two ends of the main loop protection switch Q, and the converter controller U is connected with the three-level power module M1; a charging alternating-current protection fuse FU1 is connected in the direction from the power distribution source to the direct-current bus side, and a charging contactor KM1, a charging resistor R1, a double-split transformer T1, a rectifier bridge V1, a rectifier bridge V2 and a charging direct-current fuse FU2 are connected in the direction from the charging alternating-current protection fuse FU1 to the direct-current bus side. According to the invention,surge impact of the power supply on the DC capacitor and the AC filter capacitor of the bus can be reduced, damage to related devices due to surge current is avoided, and soft start of the system isrealized.

Description

technical field [0001] The invention relates to the technical field of three-level converters for wind power generators, in particular to a soft-start circuit and a control method for a three-level wind power converter. Background technique [0002] Wind energy has become the renewable clean energy with the most mature technology and the most conditions for large-scale development. The wind power generating set is a set of automatic adjustment and unattended fully automatic equipment; and the converter, which is responsible for the main task of converting electric energy, is an important part of the system. [0003] At present, the available wind resources on land in the wind power industry are nearly saturated. Offshore wind power is the future development direction of the wind power field. Due to the cost of offshore wind power hoisting and maintenance, high-power units are an inevitable trend. It is a difficult problem for existing mainstream designs to increase power uni...

AI Technical Summary

Problems solved by technology

[0005] The current commonly used charging method is mainly to bypass the grid-connected switch, and the grid side is connected to the AC side of the power device at the back end of the grid-side switch through a resistor to charge. After charging, after the DC bus voltage reaches a certain value, the grid-connected switch is closed. Then cut off the resistance circuit. The disadvantage of this method is that after the voltage level of the main circuit is increased, the low-voltage electrical devices of the charging circuit need a higher voltage level (from the conventional 690V to 900V or 1140V). There are few such products in the market, and the price is very high. , poorly replaceable

[0006] In addition, in order to achieve the effect of reducing grid-connected impulse voltage and charge the DC bus and AC filter capacitor at the same time, the charging circuit requires a large capacity, requires more space and cost to meet the requirements, and does not meet the high power density and cost requirements of the wind power industry. The characteristics of the industry; the DC bus and the AC filter capacitor of this kind of charging are in parallel relationship, the charging effect of this circuit alone is poor, and the reverse fast diode inside the power device is used for charging rectification, which affects the three-level power module. service life

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