03-08-2013, 02:21 PM
MULTI-LEVEL INVERTER CAPABLE OF POWER FACTOR CONTROL WITH DC LINK SWITCHES
MULTI-LEVEL INVERTER.pptx (Size: 434.64 KB / Downloads: 35)
ABSTRACT
This project proposes a new multi-level inverter topology based on a H-bridge structure with four switches connected to the dc-link. Based on a POD (Phase opposition disposition) modulation method, a new PWM method is suggested. The proposed topology requires minimum number of component count to increase the number of voltage level. Operating principle of the proposed inverter is verified through simulation and experiment.
EXISTING SYSTEM
In existing system a SPWM approach was presented to deal with the uneven power transferring characteristics of the conventional SPWM modulation technique. This technique proved to be successful due to the irradiance profile and the use of capacitors to smooth the voltage fluctuation. The system was driven at 2kHz because of speed constrains of the control platform, which required bulk filter components.
PROPOSED SYSTEM
Number of devices of the proposed multi-level inverter is lower than that of the conventional multi-level inverters. Therefore, the proposed system is more reliable and cost competitive than the conventional two-level and multilevel inverters.
In the H-bridge converter are operated at a low frequency. Therefore, switching loss of the four switches almost negligible.
Only one carrier signal is required to generate the PWM signals
The proposed topology can be easily extended to 7-level or higher level with minimized active device component count.
MICROCONTROLLER
FEATURES
4K Bytes of In-System Reprogrammable Flash Memory
Endurance: 1,000 Write/Erase Cycles
Fully Static Operation: 0 Hz to 24 MHz
Three-Level Program Memory Lock
128 x 8-Bit Internal RAM
32 Programmable I/O Lines
Two 16-Bit Timer/Counters
Six Interrupt Sources
Programmable Serial Channel
Low Power Idle and Power Down Modes
OPERATION
In H-bridge four npn transistors (BC547) are used in the switch mode configuration. The emitter and collector of transistors T1 & T2 and of T3 & T4 are connected. The collector of T1& T3 is connected to VCC and emitter of T2& T4 is connected to ground. The base of T1 & T4 and T2 & T3are connected through resistors. The motor is connected as shown in the figure2. When high signal (logic 1) is given at A and low (logic 0) at B, the transistor T1 & T4 will behave as closed switch andT2 & T3 will behave as open switch. As a result of which the current will start flowing from Vcc to T1 to motor to T4 to ground and motor will start running in one direction.
Similarly if B is given high signal and A low, then the transistors T1& T4 are in the cut off state and T2 and T3 are in the saturation state i.e., T1 & T4behave as open switch and T2 & T3behave as closed switch and motor rotates in other direction. We should avoid giving either high or low to both A & B simultaneously.
TRANSISTOR(BC547)
A BC547 transistor is a negative-positive-negative (NPN) transistor that is used for many purposes.
BC547 is a bipolar junction transistor (BJT)
In a typical configuration, the current flowing from the base to the emitter controls the collector current.
CONCLUSION
Therefore based on the given requirement we have successfully design and implemented an multilevel inverter prototype using an 8051 controller.