Wind power station whole low voltage ride through (LVRT) system

Abstract

The invention provides a wind power station whole low voltage ride through (LVRT) system. The system comprises at least one wind turbine and at least one wind turbine set-up transformer which are connected in series at a wind power station side and at least one main step-up transformer at a power grid side. The system further comprises a plurality of current collection busses and a power grid bus, wherein each current collection bus accesses at least one wind turbine and at least one wind turbine step-up transformer which are connected in series; the current collection busses are divided into at least one group, and each group comprises at least one current collection bus; the power grid bus is used for accessing the main step-up transformer at the power grid side; and each group of the current collection busses are respectively connected to the power grid bus through an LVRT device. The invention can achieve the wind power station whole LVRT by using fewer LVRT devices.

Description

technical field [0001] The invention refers to an overall low-voltage ride-through system of a wind farm. Background technique [0002] Low Voltage Ride Through (LVRT for short, Low Voltage Ride Through) refers to the ability of the wind farm to maintain continuous grid-connected operation without disconnecting the grid when the grid fails and after the grid failure causes a voltage drop. [0003] In the early stage of wind power development, because wind turbines generally adopt the Danish concept of fixed-speed asynchronous generator technology, they cannot provide active excitation. When the grid fails, the terminal voltage is difficult to establish. If the wind turbines continue to be connected to the grid, the grid voltage will not be restored. Therefore, when a grid failure occurs and a voltage drop occurs, the method of cutting off the wind turbine is generally adopted to deal with it, because when the proportion of wind power installed capacity is low at that time, i...

AI Technical Summary

Problems solved by technology

[0006] 1) Most of the old-fashioned wind turbines adopt the fixed-speed and fixed-propeller method, and the power has no active adjustment capability; the capacity of a single machine is small, and the number of wind farms with the same capacity is large, so it is difficult to transform LVRT and the cost is very high

[0007] 2) Most of the MW-level wind turbines installed in recent years are double-fed models. When the grid voltage drops, if the machine is not switched off, it is easy to cause overvoltage and overcurrent on the rotor side of the generator and overspeed of the impeller due to a sudden drop in output power

[0008] 3) Doubly-fed units realize LVRT generally by adding Crowbar, suppressing overvoltage and overcurrent through its resistive unit, and damping the oscillation of electromagnetic torque, but it still has certain damage to the unit

[0009] 4) Many domestic doubly-fed units did not reserve crowbar interface and placement space at the beginning of design, so it is very difficult to transform

This is equivalent to transforming the unit into a full-power frequency conversion form. The advantages are obvious, but there are also two obvious problems: first, each unit needs to be modified accordingly, and the construction is difficult, and even the equipment in the tower needs to be re-arranged; second, it is expensive. Calculated according to my country's wind power on-grid electricity price level, the return on capital will be reduced by about two percentage points

Due to the large number of wind turbines, the modification of each unit will lead to very high cost of equipment transformation

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