Neutral point clamped power converter fault detection, identification, and protection

Abstract

A fault detection, identification, and protection system for a phase leg of a three-level neutral point clamped (NPC) power converter includes a fault detection circuit, the fault detection circuit configured to determine, based on signals received from the two inner switches and two outer switches via their respective gate drivers, the presence of a fault in the phase leg; a fault identification circuit, the fault identification circuit being configured to determine, based on signals from the fault detection circuit, a location of the fault in the phase leg; and a protection circuit, the protection circuit being configured to turn off at least one of the inner switches or outer switches in response to the identification of the location of the fault by the fault identification circuit.

Description

BACKGROUND OF THE INVENTION[0001]The subject matter disclosed herein relates generally to neutral point clamped (NPC) power converters, and, more particularly, to a method and apparatus for electrical fault detection, identification, and protection in a neutral point clamped (NPC) power converter.[0002]Switching mode power converters are used in many applications, including industry applications, transportation, home appliances, and power production and transmission. A common topology for a switching mode power converter is a voltage source pulse width modulated converter with two-level or multilevel output pulse width modulated voltage. Neutral point clamped (NPC) power converters have become more common due to various advantages over two-level converters. A NPC power converter includes a direct current (DC) bus capacitor comprising two series connected capacitors. The NPC power converter may further include one or more phase legs, and each phase leg may include two NPC diodes. The...

AI Technical Summary

Benefits of technology

The patent describes a system for detecting and protecting faults in a power converter. It uses inner and outer switches with associated diodes and a detection circuit to identify the location of a fault. The system can then turn off one of the switches to prevent damage to the converter. The technical effects of this system are improved reliability and safety in power conversion.

Problems solved by technology

NPC power converters may require relatively complex of control systems for the switches in the various phase legs.

Additionally, fault detection and protection is a complex process.

Without proper fault detection and protection the entire NPC power converter may be destroyed during fault conditions.

Failure of an NPC power converter may include blocking capability collapse of a diode or breakdown of a semiconductor switch.

A result of such a failure is may be a direct short circuit across an energized power capacitor, which is followed by high fault current that may be an order of magnitude higher than the device rated current.

However, the detection circuit may not be able to determine exact position of the faulty device, or distinguish short circuit (SC) fault of a first device from an open circuit (OC) fault of a second device.

The fault case when two devices fail in short circuit may also not be able to be identified.

This may result in a postponed catastrophic failure of the NPC power converter due to improper diagnosis of fault conditions.

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