A HIGH-EFFICIENCY SEPIC BASED DC-DC CONVERTER DESIGN BY ROBUST PID CONTROLLER
Abstract : This work addresses the problem of instability occurring in the voltage control mode of a non-minimum phase Quasi Resonant High Gain, High-Efficiency Single Ended Primary Inductor Converter -based DC-DC converter with continuous input current. To solve this instability issue in the presence of uncertainties and the external disturbances, quantitative feedback theory (QFT) is adapted to systematically design a robust proportional integral derivative (PID) controller, which is realized using only sensed output voltage as feedback. The advantages of the proposed PID design using the QFT are: (i) it eliminates the burden of tedious and ad-hoc tuning of PID gains using the conventional PID design approaches, (ii) current measurement is not required, (iii) disturbance dynamics (input voltage and load current variations) are included in the design stage itself, which further enhances the disturbance rejection performance of the output voltage. Due to soft-switching operation in all switching components, the power dissipations in the converter are significantly alleviated. Thus, the proposed SEPIC can provide high voltage gain whilst achieving a high efficiency.
A DC-to-DC converter is a device that accepts a DC input voltage at one level and converts it to a DC output voltage of another level. Among the DC-DC converters, the SEPIC has unique features like a non-inverted output voltage, and its output is greater than, less than, or equal to its input voltage. The system behavior is completely determined by the coefficients k1 , k2 , k3 and k4 which must be selected so as to satisfy the existing condition and to ensure stability and a fast response, even under large supply and load variations. In order to improve the dynamic performance of the SEPIC, a Sliding Mode Controller (SMC) is developed. There is still exists room for the development of a controller to improve the performance of the SEPIC. A sliding mode controller for the SEPIC is proposed in this paper in order to ensure the stability under any operating conditions, better static and dynamic performances under input voltage disturbances, load changes and component variations. The performance of the SMC is evaluated in terms of output voltage regulation under different operating conditions such as startup transients, line variations, load variations, steady state conditions and component variations. The performance of the SMC versus a PI controller is evaluated in a simulation in terms of robustness and stability.
The different section of the water pumping system such as PV panel, negative output Luo converter and motorpump system are designed in such a way that the system becomes reliable and performs efficiently irrespective of any environmental condition. Every section is designed at all possible test conditions (1000W/m2 , 250 C). First an induction motor of 4kW,1500rpm at 415V and then according to the requirement a SPV array of slightly more than 4kW peak power rating, is selected. PV panel with higher capacity is proposed based on the practical condition wherein there are loses at different section of the given system.
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