Voltage-type three-level NPC (Neutral Point Clamped) converter direct power control method

Abstract

The invention discloses a voltage-type three-level NPC (Neutral Point Clamped) converter direct power control method. A voltage-type three-level NPC (Neutral Point Clamped) converter is adopted. The method comprises the following steps: 1, ua, ub, uc, ia, ib and ic values are acquired, and instantaneous active power p and instantaneous reactive power q are calculated; 2, according to the ua, ub, and uc values, the located sector thetan is determined; 3, an AC / DC voltage ratio eta is calculated; 4, according to the eta value, a voltage ratio variable Seta is determined; 5, an active power deviation variable Sp and a reactive power deviation variable Sq are determined; 6, a reactive wave variable Srp is determined; 7, a specific vector adopted by a DPC strategy is determined; 8, switching states of VS1 to VS6 are selected to balance DC capacitor voltage; and 9, a switch device is controlled to enable the actual output power of the system to reach set requirements. The method can be applied to any AC / DC voltage ratio, and abnormal fluctuations of instantaneous reactive power are not caused.

Description

technical field [0001] The invention belongs to the technical field of power electronics and relates to a direct power control method of a voltage-type three-level NPC converter. Background technique [0002] The voltage-type three-level neutral point clamped (Neutral Point Clamped or NPC) converter is currently the most commonly used multi-level converter. Compared with the traditional two-level converter, the three-level NPC converter has output It has many advantages such as high power, small output waveform THD, device voltage stress and system EMI, so it is widely used in various high-voltage and high-power occasions. [0003] Since the 1990s, research on three-level NPC converters has emerged in an endless stream, among which high-performance control strategy is a hot issue in the research of three-level NPC converters. At present, in the PWM converter, the most commonly used high-performance control strategy is the voltage-oriented vector control strategy (VoltageOri...

AI Technical Summary

Problems solved by technology

However, due to the particularity and vector complexity of the three-level NPC converter, the application of the DPC strategy is far less extensive than the VOC strategy

In the visible three-level NPC converter DPC strategy research, there is little research on the influence of the important index of AC and DC voltage ratio on the vector selection of DPC vector strategy

Further research found that the existing three-level DPC strategy can cause abnormal fluctuations in instantaneous reactive power in some areas, which greatly increases the THD value of system output voltage and current

Images