Distributed hierarchical overvoltage control system and method

Abstract

The invention discloses a distributed level overvoltage control system and method. The system comprises a combined overvoltage protector, an energy absorber, a connecting electric reactor, a power unit, a power unit clamping voltage limiter, a laminated busbar and an IGBT induced voltage clamping device. After the energy absorber is subjected to parallel connection with the connecting electric reactor, one end of the energy absorber and the connecting electric reactor is connected with the combined overvoltage protector, the other end of the energy absorber and the connecting electric reactor is connected with the power unit, and the power unit clamping voltage limiter and the laminated busbar are respectively connected with the power unit. Five-grade defense is adopted in the distributed level overvoltage control system and method, overvoltage energy from various aspects can be suppressed, and damage to an IGBT caused by dangerous overvoltage of cut-off overvoltage, IGBT off-state overvoltage and the like of the device overvoltage invading the connecting electric reactor can be avoided, so that safe and reliable operation of an SVG device is ensured. The system and method are simple to operate and high in working efficiency and prolong the service life of the SVG device.

Description

technical field [0001] The invention relates to the field of electric power, in particular to a distributed hierarchical overvoltage control system and method. Background technique [0002] The medium-voltage static dynamic synchronous compensation device, referred to as SVG, has many advantages such as fast response to signal changes, ability to absorb and emit reactive power for two-way regulation, small footprint, and regulation characteristics that are not affected by grid voltage. In the power quality control technology in the 21st century, it has become an indisputable core product, and has made great progress, and has become an important development direction of power electronics technology in the field of power systems. This technology also has great application prospects in the fields of iron and steel, non-ferrous metals, mines, electrified railways, wind power, etc. Breakdown and explosion cause the device to shut down and fail to operate normally; what’s more, a...

AI Technical Summary

Problems solved by technology

[0003] 1) The medium-voltage SVG belongs to the direct connection mode, and the connection reactor is directly connected to the busbar. All kinds of transient overvoltages and instantaneous overvoltages that occur during the operation of the busbar will act on the links on the SVG through the connection reactor. Each power unit IGBT poses a great threat to the safe operation of the IGBT. If things go on like this, the C and E poles of a weak power unit IGBT may be broken down, resulting in a "straight-through" accident and explosion

[0004] 2) Due to the large capacity and inductance of the connected reactor, especially when there is a large current passing through, the magnetic field energy stored by itself is very high. When the controlled PWM wave acts on each power unit IGBT, when the IGBT is turned off During the conversion process to conduction, due to the rapid switching and truncation of the current, a high overvoltage will inevitably be generated on the connected reactor. The C and E poles of a weak power unit IGBT break down, causing the power unit IGBT to over-current and shut down

[0005] 3) Due to the limitation of the structure of the power unit IGBT, the positive and negative DC bus bars connected between the electrolytic capacitor and the full IGBT are generally assembled with copper bars in a discrete manner. The stray inductance is too large, and when the IGBT is working in the transition process from on to off, a high overvoltage is generated between the C and E poles of the power unit IGBT. The long-term effect will inevitably lead to the insulation of IGBT and E break down

During operation, due to the effects of long-term operation oxidation, vibration, and poor contact, the G and E poles of the power unit IGBT will inevitably be "suspended" due to poor contact. When an alternating high electric field acts on it, power will occur. The "false trigger" of the unit IGBT is turned on, which will cause the IGBT branch of the unit to over-current, at least the SVG will shut down, and the IGBT will explode to form an internal short circuit and cause greater losses.

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