A current limiting device and current limiting method of an active power filter

Abstract

The invention provides a current limiting device of an active power filter, comprising a power frequency cycle module, a switching cycle module and a hardware circuit module. The power frequency cyclemodule is used for calculating the current limiting coefficient of the reference current effective value and realizing the current limiting control of the harmonic reference current effective value.The switching cycle module is used for calculating the peak current limiting coefficient of the reference current, realizing the current limiting control of the peak current of the harmonic current, and simultaneously calculating the real-time reference current after twice current limiting; The hardware circuit module corrects the peak current limiting coefficient. The invention also provides a current limiting method of a current limiting device of an active power filter. The invention can carry out more accurate effective value and peak current limiting on APF under each working condition, At the same time, the peak current of IGBT is detected by hardware circuit, and the working state of IGBT is adjusted in real time to avoid overcurrent damage or frequent overcurrent protection of IGBT, and the current stress of IGBT is controlled, which ensures the stable operation of APF under all operating conditions.

Description

technical field [0001] The present invention relates to the technical field of active power filters, in particular to a current limiting device and a current limiting method for an active power filter. Background technique [0002] Active Power Filter (APF), as a current harmonic generator based on a fully controlled rectifier, has a much more complex control system than a current fundamental wave generator based on a fully controlled rectifier, especially for its current limiting technology, for fundamental wave systems (such as photovoltaic inverters, SVG, etc.), the current peak value and effective value are in a fixed proportional relationship, while for APF, since the phase and amplitude proportional relationship of each harmonic varies with the load in real time, its The relationship between the current peak value and the effective value is not fixed, which makes the current limiting technology more complicated. [0003] The invention patent with the application numbe...

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Problems solved by technology

[0002] Active Power Filter (APF), as a current harmonic generator based on a fully controlled rectifier, has a much more complex control system than a current fundamental wave generator based on a fully controlled rectifier, especially for its current limiting technology, for fundamental wave systems (such as photovoltaic inverters, SVG, etc.), the current peak value and effective value are in a fixed proportional relationship, while for APF, since the phase and amplitude proportional relationship of each harmonic varies with the load in real time, its The relationship between the current peak value and the effective value is not fixed, which makes the current limiting technology more complicated

[0003] The invention patent with the application number CN201410074914.2 discloses a current-limiting control method for the compensation current of an active power filter. The patent mentions how to control the harmonic current RMS, but does not consider the peak current limit , which may cause excessive peak current to trigger overcurrent protection or damage the IGBT (IGBT is an insulated gate bipolar transistor)

[0004] The invention patent with the application number CN201410305638.6 discloses a protection method for active power filters. The patent mentions two-stage current limiting strategies, taking into account the effective value and peak current limiting at the same time, but it adopts the truncation current limiting strategy , will increase the high-frequency harmonic components and affect the control effect; at the same time, the final peak value of the actual output current will exceed the peak value of the reference current, which will not achieve the ideal peak current limiting effect

[0005] APF needs to consider peak current limit and RMS current limit at the same time. The existing technology cannot ideally achieve the effect of current limit. There is a possibility of over-current protection, and there will be some working conditions that cannot operate stably.

[0006] At the same time, when the APF modulation ratio changes or the grid voltage waveform is distorted, the ripple current on the inductor will also change, resulting in a more complicated relationship between the peak current actually applied to the IGBT and the limited peak current. Some manufacturers will As a result, the IGBT is damaged, and some manufacturers with perfect protection functions may stop the protection under such working conditions and cannot operate stably.

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