Low voltage ride through control method for network side inverter of permanent magnet direct drive wind power system

Abstract

The invention discloses a low voltage ride through control method for a network side inverter of a permanent magnet direct drive wind power system. The low voltage ride through control method comprises a power detector a, a power detector b, a power change detector and a control circuit are adopted, wherein the power change detector is used for receiving output signals from the power detectors a and b to record power changes; a comparator is arranged in the power change detector and is used for comparing an output power of a wind motor and an output power of a network side inverter to generate a practical power difference signal delta P, and inputting the signal delta P into an outer loop controller of the control circuit; and the control circuit is used for realizing current decoupling and generating a PWM (pulse width modulation) control signal to drive the inverter. According to the control method using a power outer loop, stability of the system during a voltage drop and a grid connection period can be guaranteed, reactive power can be compensated along with the power grid drop depth, and overcurrent of the network side inverter can be limited at the same time, therefore, the network side inverter can be guaranteed to work stably.

Description

technical field [0001] The invention relates to a low-voltage ride-through control method for a grid-side inverter of a permanent magnet direct-drive wind power system. Background technique [0002] Wind energy is a renewable energy source. It is estimated that the theoretical storage capacity of wind energy on the earth is about 2.74×10 9 MW, the wind energy that can be developed and utilized is 2×10 7 MW, as long as 1% of the wind energy on the earth is used, the global energy demand can be met. However, wind energy is an intermittent energy source, which is unstable and has large regional differences. In addition, my country's wind power industry started late and the level of localization is not high. In particular, there are still many problems in my country's wind power grid connection technology. Frequently, it exposes the lack of low-voltage ride-through capability of current wind turbines. All countries have issued corresponding standards for low-voltage ride-throug...

AI Technical Summary

Problems solved by technology

[0005] 1. Complicate the system, reduce reliability, unload load circuit and SVC are expensive, and increase cost and volume;

[0006] 2. When the grid-connected voltage drops, the working mode needs to be changed, and the grid voltage needs to be monitored quickly and accurately. At the same time, uncontrollable factors of the system are added during the conversion process, which brings transient disturbance to the system;

[0007] 3. It is not easy to determine the timing and degree of unloading load and SVC delivery, the adjustment accuracy is not high, and the adjustment time is long

For the control method, it takes a long time to collect the DC bus voltage as the voltage outer loop. Since the capacitor voltage is collected, the capacitor voltage cannot change suddenly, so the time to collect information is long, the response is slow, and there is a hysteresis phenomenon.

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