The method of DPWM injected offset voltage for control of neutral point voltage using 3-level NPC inverter

摘要

Recently, The necessity of renewable energy be on the rise in as fossil fuel is depleted. Study of offshore wind power generation is being carried out as part of the renewable energy business. The 3-level inverter for use in the offshore wind power system studied is increasing as high capacity about offshore wind power. The 3-level inverter had an advantage that make reference voltage higher than 2-level reference voltage. Also, study of the 3-phase inverter has increased nowadays. However, 3-level NPC (Neutral-Point-Clamped) inverter, two capacitors and the neutral point are connected in series, it can lead to problems reduces stability of the system and unbalance voltage. It is SVPWM (Space Vector Pulse Width Modulation) method. Because DPWM (Discontinuous Pulse Width Modulation) method didn't neutral point control as same method from SVPWM, each DPWM method need a method of neutral point control. This paper proposed a method of applying the offset voltage attem pts to resolve the difficulties of the neutral point voltage control. The equation for the offset voltage to be applied to the system of each DPWM was determined. The proposed method is implemented by comparison of block diagram. The proposed algorithm is verified by the simulation.