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Purpose: Induction heating applications aided by power electronic control have become very attractive in the recent past. For cooking applications, power electronics circuits are very suitable to feed power to multi loads with an appropriate control technique. The purpose of this paper is to develop a three leg inverter to feed power to three loads simultaneously and independently. Design/methodology/approach: Pulse density modulation control technique is used to control the output power independently with constant switching frequency. Findings: Multi-load handling converter with independent power control is achieved with reduced number of switching devices (two switches/per load) with simple control strategy. Originality/value: The proposed system is simulated in MATLAB/Simulink, and the thermal analysis is carried out in COMSOL multi-physics software. The hardware realisation is performed for a 1 kW prototype with 20 kHz switching frequency and 10 kHz pulse density modulation frequency. PIC16F877A microcontroller is used to validate the experimental results for various values of control signals (DPDM). The simulation and experimental results are in good agreement and validates the developed system. [ABSTRACT FROM AUTHOR]

Induction heating (IH) applications aided power electronic control and becomes most attractive in recent years. Power control plays a vital role in any IH applications in which the stability of the converter is still a research hot spot due to variable frequency operation. In the proposed work, the stability of the converter is carried out based on the Floquet theory for dual-frequency half-bridge series inverter-fed multiload IH system. The dynamic behaviour of the converter is analyzed by developing a small-signal model of the converter. The system with a dynamic closed-loop controller results in poles and zeros lying outside the unit circle, which has poor closed-loop stability and up-down glitches in the frequency response plot. Hence, a proportional-integral (PI) compensator is used to mitigate the said issue, which results in a better response when compared with the open system and works satisfactorily. However, the system becomes unstable when the frequency is varied and the system also possesses a poor time domain response. Hence, the values of the controller gain are optimized with the Floquet theory, which is based on the Eigenvalues of the time domain model. For the optimized gains, the system possesses better stability for the variations in the switching frequency (20 kHz to 24 kHz), and also, the frequency response of the system is better with minimum time domain specifications. The performance of the system is simulated in MATLAB, and the response is noted for various switching frequencies in open loop, with a PI compensator, and with an optimized PI compensator. The output power is varied from 500 W to 18 W at load 1 and 250 W to 9 W at load 2. It is noted from the output response that the rise time is 0.0085 s, the peak time is 0.0001 s, and the peak overshoot is 0.1% with minimum steady-state error. Furthermore, the IH system is validated using a PIC16F877A microcontroller with the optimized PI controller, and the thermal image is recorded using a FLIR thermal imager. [ABSTRACT FROM AUTHOR]

Summary: Induction heating applications aided by power electronic control have become very attractive in the recent past. For cooking applications, power electronics circuits need to feed power to multi loads with a suitable control technique. The induction heating system requires a superlative converter topology and independent control to deliver power to multi loads. The main idea of this research work is to develop a dual‐frequency half‐bridge series resonant high‐frequency inverter feeding power for multi loads independently. A pulse density modulation (PDM) control technique is used to control the output power independently. The inverter simultaneously powers both loads with constant switching frequency. The proposed system is simulated in MATLAB/Simulink and thermal analysis is carried out in COMSOL multi‐physics software. A 1 kW prototype experimental set up is developed to feed power to dual load with the switching frequencies of 20 and 80 kHz for load 1 and load 2, respectively. The experimental results are provided to validate the system performance for various duty cycles of the PDM signal. The simulation and experimental results are in good agreement. The efficient power control is accomplished by varying the density of the switching pulses. [ABSTRACT FROM AUTHOR]

In recent years, induction heating (IH) applications aided by electronic power control have gained significance. Particularly, for cooking applications, an appropriate control technique is required to feed power from a single source to multiple loads with minimum switching losses. Additionally, when multiple loads are used, it requires independent control and operation for each of the loads. The main idea of this work is to develop a single-stage AC-AC converter topology to feed power to multiple loads independently with a single source, with a reduced number of switching devices and with minimum switching losses. The proposed topology uses a frequency bifurcation concept to feed power to multiple loads by placing the transmitting coil and work coil at a distance of 3 cm. The source is resonated at a 25 kHz switching frequency, with the designed bifurcated frequencies of 20 kHz and 33 kHz. The resonant capacitors are appropriately chosen to operate at those frequencies. For real-time applications, simultaneous and independent power control are inevitable in multi load-fed IH applications. This is achieved through a pulse density modulation scheme with minimum switching losses. The simulation of the proposed system is performed in MATLAB/Simulink, and also the 1 kW system is validated using a PIC16F877A microcontroller. The real-time thermal variation in the load is also recorded using a FLIR thermal imager. The experimental and simulation results are observed, and the obtained efficiency of the system is plotted for various duty cycles of pulse density modulation control. [ABSTRACT FROM AUTHOR]