Abstract: This paper presents a novel three-phase utility
frequency to high frequency soft switching power conversion circuit
with dual mode pulse width modulation and pulse density modulation
for high power induction heating applications as melting of steel and
non ferrous metals, annealing of metals, surface hardening of steel
and cast iron work pieces and hot water producers, steamers and
super heated steamers. This high frequency power conversion circuit
can operate from three-phase systems to produce high current for
high power induction heating applications under the principles of
ZVS and it can regulate its ac output power from the rated value to a
low power level. A dual mode modulation control scheme based on
high frequency PWM in synchronization with the utility frequency
positive and negative half cycles for the proposed high frequency
conversion circuit and utility frequency pulse density modulation is
produced to extend its soft switching operating range for wide ac
output power regulation. A dual packs heat exchanger assembly is
designed to be used in consumer and industrial fluid pipeline systems
and it is proved to be suitable for the hot water, steam and super
heated steam producers. Experiment and simulation results are given
in this paper to verify the operation principles of the proposed ac
conversion circuit and to evaluate its power regulation and
conversion efficiency. Also, the paper presents a mutual coupling
model of the induction heating load instead of equivalent transformer
circuit model.
Abstract: Selective harmonic elimination-pulse width modulation techniques offer a tight control of the harmonic spectrum of a given voltage waveform generated by a power electronic converter along with a low number of switching transitions. Traditional optimization methods suffer from various drawbacks, such as prolonged and tedious computational steps and convergence to local optima; thus, the more the number of harmonics to be eliminated, the larger the computational complexity and time. This paper presents a novel method for output voltage harmonic elimination and voltage control of PWM AC/AC voltage converters using the principle of hybrid Real-Coded Genetic Algorithm-Pattern Search (RGA-PS) method. RGA is the primary optimizer exploiting its global search capabilities, PS is then employed to fine tune the best solution provided by RGA in each evolution. The proposed method enables linear control of the fundamental component of the output voltage and complete elimination of its harmonic contents up to a specified order. Theoretical studies have been carried out to show the effectiveness and robustness of the proposed method of selective harmonic elimination. Theoretical results are validated through simulation studies using PSIM software package.