A Three Level Common Mode Voltage Eliminated Inverter with Single Dc Supply Using Flying Capacitor Inverter and Cascaded H-Bridge

ABSTRACT:

A three-level common-mode voltage eliminated inverter with single dc supply using flying capacitor inverter and cascaded H-bridge has been proposed in this paper. The three phase space vector polygon formed by this configuration and the polygon formed by the common-mode eliminated states have been discussed. The entire system is simulated in Simulink and the results are experimentally verified. This system has an advantage that if one of devices in the H-bridge fails, the system can still be operated as a normal three-level inverter at full power. This inverter has many other advantages like use of single dc supply, making it possible for a back-to-back grid-tied converter application, improved reliability, etc.

KEYWORDS:

1.      Common-mode voltage elimination

2.       Hybrid multilevel inverter

3.       Multilevel inverter

4.       Three-level inverter

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig 1 Power circuit for the proposed three level common mode voltage eliminated inverter

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation result for testing the capacitor balancing algorithm. VAO : pole voltage (100 V/div), IA : pole current (5  A/div)  VC 1 :  cap1-voltage (100 V/div), VC 2 : cap2 voltage (50 V/div), VC M : common-mode voltage (50 V/div), time: 500 ms/div.

Fig. 3. Steady-state performance at 10 Hz. VAO : pole voltage (100 V/div),  VA N : phase voltage (100 V/div), VN O : neutral point voltage (20 V/div), IA : phase current (2 A/div), time: 20 ms/div.

Fig. 4. Steady-state performance at 20 Hz. VAO : pole voltage (100 V/div), VA N : phase voltage (100 V/div), VN O : neutral point voltage (20 V/div), IA : phase current (2 A/div), time: 10 ms/div.

Fig. 5. Steady-state performance at 30 Hz. VAO : pole voltage (100 V/div), VA N : phase voltage (100 V/div), VN O : neutral point voltage (20 V/div), IA : phase current (2 A/div), time: 10 ms/div.

Fig. 6. Steady-state performance at 40 Hz. VAO : pole voltage (100 V/div), VA N : phase voltage (100 V/div), VN O : neutral point voltage (20 V/div), IA : phase current (2 A/div).

 CONCLUSION:

In this paper, a three-level common-mode voltage eliminated inverter with single dc supply using flyin capacitor inverter and cascaded H-bridge was proposed and studied. The operation and performance of the proposed inverter  is simulated  in Simulink with induction motor load. Various aspects of the inverter configuration such as the transients and the performance of the capacitor balancing algorithm, have been studied. The proposed inverter is implemented in hardware using IGBT- based inverters. A three-phase Y-connected induction motor is run with the proposed inverter and the performance of the drive is analyzed for both steady-state operation and transient operation during sudden acceleration. In all the cases, the inverter was able to give faithful reproduction of intended voltage levels with negligible capacitor voltage ripple and common mode, thereby improving the life of bearings. This configuration has various advantages like motor being connected in single-ended configuration use of reduced number of switches, use of single dc supply, etc. Also, this configuration has improved reliability.In case of failure of one of the devices in the H-bridge, the inverter can still be operated as a normal three-level inverter  at full power or a two-level common-mode voltage eliminated inverter at full power rating by bypassing the H-bridges, thereby improving the overall reliability of the system greatly.

REFERENCES:

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