Research On Modeling And Simulating Integration Difference Control Of Cascaded Inverter Staircase Wave Synthesizing

Cascaded multilevel inverter is widely used in AC and DC power transmission,high-power motor drive and so on. But there exists the problem of resource wasting.The development of cascaded inverter becomes the hot topic of electric power andelectronics technology again, because adapting to resource conservation andenvironment protecting.The present goal of this paper is to put the2H-bridge cascaded inverter circuit as abasic research platform, studying how to control the conducting angles of each H-bridgein the feedback closed loop control and ensure the quality of output voltage waveform,revealing the relationship of feedback control parameter and switching angles and THD.The main methods used in research work in this paper is simulation method.Effectiveness of control parameter and practicability of integration difference algorithmmodulating staircase wave are verified by simulation.Other methods are the buildingmathematical model of control parameters and comparing switching angle to see if it isavailable.The results of this study are:1.Creates a new algorithm of synthesizing staircasewave, that is, integration difference method. Gives the feedback control parameter ofintegration difference control for staircase wave tracking sine wave and two valuemodel of this parameter.2. Reveals the relationship between integration differencecontrol and switching angel of switches in H-bridge, thus revealing its relationship withthe THD of multilevel inverter’s output voltage.3. Expands the scope of studyingintegration difference control algorithm, promotes integration difference control tosynthesizing PWM staircase wave, namely the research of EPWM and single unitSPWM for staircase waveform.The final conclusion of this paper are:1. Integration difference exists between thereference sine wave and the staircase wave synthesized by cascaded inverter. Thisdifference can be used as control parameter of feedback closed loop control.2. Theexpression of the control parameter has two mathematical models.3. Integrationdifference control parameter and switching angles of switch devices are linked, it canalso reflect the THD in synthesized staircase voltage. This parameter can be selectedaccording to circumstances in practice.4. Integration difference control algorithmsynthesizing smooth staircase wave can be used in staircase PWM, including staircase wave EPWM and staircase wave single unit SPWM.Correspondingly, the integrationdifference control can be combined with the PWM control for applying hybrid controlfor hybrid cascade inverter.