One of major problems related with PV-applications is common mode currents. The issue can be solved in two ways: galvanic decoupling of AC-grid and chopping the common mode currents by additional actively controlled circuitry. Flyback converter is good solution for MPPT tracking for PV-modules up to 100-150 W with galvanic decoupling. The problem of designing of this type of converter is that most of design guides and literature is dedicated to consumer electronics applications. MPPT converter design have different starting points of calculations. The paper contains the suggested approaches to the calculations, design recommendations, considering the specific nature of PVsources and NOCT model of PV-module.The approach calculations, design guidelines, recommendations and simulation of power electronics part of MPPT converter and experimental results with implemented circuit are presented and discussed. In order to increase the efficiency during tests the circuit was upgraded with active clamp. After the tests active clamp was upgraded to the forward active clamp topology. The efficiencies and key waveforms of voltages are compared and analyzed.Index Terms-active clamp, flyback, forward, MPPT, photovoltaic.
The authors present an analytical model for a voltage step-up/step-down DC/DC converter without transformers. The proposed topology is a combination of classic buck and boost converters in one single circuit but with differing operational principles. The converter is developed for a wind power autonomous supply system equipped with a hydrogen electrolytic tank and a fuel cell for energy stabilization. The main power source of the hydrogen-based autonomous supply system is energized by a synchronous generator operating on permanent magnets and equipped with a diode bridge. The input voltage of the converter in this case varies in the range 0-700 V, while its output DC voltage must be 540 V according to the demand of other parts of the system. To maintain the rated voltage, a special electrical load regulation is introduced. The calculations of the converter, the generator (equipped with a diode bridge) as element of the power system supply joint, and the load replaced by resistance are verified with PSIM software. NOMENCLATURE U 1 -the voltage across the terminals of generator; U ld -the voltage of load; E -the EMF of the generator; n -the speed of rotor in rpm; I d -the current at the output of diode bridge; m 2 -the number of pulsations; X L -the resistance caused by inductive impedance of the generator`s windings; k 1 -a coefficient showing relationship between EMF and rpm; k 2 -a coefficient showing voltage drop caused by the inductivity of stator windings according to the stator current frequency and equivalent resistance of DC voltage source; i 2 -the instantaneous value of the inductor L2 current; I 2max -the maximum value of current i 2 during a duty cycle; D 1 -the duty ratio of TR1 for the step-down mode; D 1b -the duty ratio of TR1 for the step-down mode in the boundary case; D 2 -the duty ratio of TR2 for the step-up mode; D 2b -the duty ratio of TR2 for step-up mode in the boundary case; R -the resistance of load; 30 f -the switching frequency of the converter; L 1 -the inductance of inductor L1; L 2 -the inductance of inductor L2.
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