The discrete time control of a three phase 4 wire PWM inverter with variable DC link voltage for simultaneously supply of three phase and single phase load in transformerless stand alone photovoltaic application with battery energy storage (BES) and LC output filter is described. | The Discrete Time Control of a Three Phase 4 Wire PWM Inverter with Variable DC Link Voltage and Battery Storage for PV Application Dipl. Ing. Said El-Barbari and Prof. Dr. W. Hofmann CHEMNITZ UNIVERSITY OF TECHNOLOGY Department of Electrical Machines and Derives Abstract The discrete time control of a three phase 4 wire PWM inverter with variable DC link voltage for simultaneously supply of three phase and single phase load in transformerless stand alone photovoltaic application with battery energy storage BES and LC output filter is described. The whole system consists of a photovoltaic array a battery energy storage two step up boost converter and three phase PWM voltage source inverter with a LC output Filter. The first boost converter is controlled in such a way so that the battery will be always charged at the maximum power point MPP when changes in the insulation or temperature are occurred. The second step up boost converter is connected in series between the Battery energy storage and the DC link capacitor of the PWM inverter. It controls the DC link capacitor voltage. The mathematical model of the linearized system is first obtained. The discretized state space equation of the whole system is derived. A new control method based on the dead beat control algorithm is implemented to control both the output voltage of the LC filter and dc link capacitor voltage so that disturbance of the output voltage due to load unbalances is eliminated. Simulation results for various operation conditions are presented to verify the validity of the control method. Summary Nowadays more attention is paid to PV system and their related technology for domestic application as well as in large central power stations. PV systems are advantageous because they are abundant pollution free and distributed through the earth. The only draw back is that the initial installation cost is considerably high. Figure 1 stand alone photovoltaic system with 3 phase 4 wire PWM voltage source .
