Z-source Dc-dc Converter Research Articles

Z-source DC-DC Converter with Fuzzy Logic MPPT Control for Photovoltaic Applications

Abstract Z-source converters are recently premised DC-DC converters which can perform buck and boost operations, offer greater range of DC output voltage, high reliability and reduce in-rush and ripple currents. In photovoltaic (PV) applications, they provide better results compared to conventional DC-DC converters. These converters can be used as power conditioning units, so that the voltage boost and reception of maximum power from the PV array can be achieved. The maximum power point tracking (MPPT) is here achieved by controlling the duty cycle of the converter. A fuzzy logic control based MPPT is developed in this work to track the maximum power point of the PV array under variable solar irradiance and temperature conditions. MATLAB simulation and experimental results are given to establish the developed system.

Closed Loop Control of Bi-Directional Soft Switched Quasi Z-Source DC-DC Converter

Quasi Z-source converter is a single stage soft switched power converter derived from Z-source converter topology, employing an impedance network coupling the source with the converter. The quasi Z-source source converter can buck or boost the voltage and current flow is bidirectional. The duty cycle of the switch can be adjusted to maintain constant voltage during load change. To obtain constant output voltage, proper controller design is a must. This paper presents closed loop control of quasi Z-source converter using PI controller where controller parameters are estimated using the small signal model of the entire system. The transfer function of the system with AC sweep is used to obtain appropriate proportional and integral gain constants to reduce transient dynamics and to reduce steady state error.

A Novel Isolated Quazi Z-Source DC-DC Converter

A Novel Isolated Quazi Z-Source DC-DC Converter

A Modified Maximum Power Point Tracking Control for Bi-Directional Z-Source DC-DC Converter Based Solar Electric Vehicle

A solar electric vehicle is powered by photovoltaic arrays which allow for direct conversion of solar energy into electrical energy. Since space and weight are very limited with any vehicle, it is desired that the maximum possible amount of energy be obtained from the employed photovoltaic arrays. Every photovoltaic array has an optimum operating point, called the maximum power point (MPP), which varies depending on cell temperature and solar insolation level. This paper is focussed to find the mechanism best suited for employment in a moving vehicle to optimally track this point of maximum efficiency under rapid variation of solar insolation and adjust the operating point of the photovoltaic array accordingly. An integral part of any modern day electric vehicle is power electronic circuits comprising DC-DC converters for conversion and conditioning of electrical power. Recently, Z-source DC-DC converters show promising outcomes when integrated with photovoltaic array compared to conventional DC-DC converters. They provide larger range of output dc voltage, improve reliability and can reduce in-rush and harmonic current. A bi-directional Z-source DC-DC converter with a maximum power point tracking (MPPT) technique suitable for electric vehicle applications is developed to incur high electric power from photovoltaic array. The photovoltaic array output voltage is controlled and the maximum power point tracking is attained by controlling the duty cycle. The well known incremental conductance MPPT algorithm is modified by measuring the power in the middle of the sampling interval to prevent the bewilderedness during rapidly changing insolation condition. Computer simulation and experimental results are provided to establish the performance of the proposed system.

전압 스트레스와 맥동이 개선된 양극성 출력 전압을 갖는 LCCT Z-소스 DC-DC 컨버터

This paper proposes the improved LCCT(Inductor-Capacitor-Capacitor-Trans) Z-source DC-DC converter (Improved LCCT ZSDC) which can generate the bipolar output voltages according to duty ratio D. The proposed converter has the characteristic and structure of Quasi Z-source DC-DC converter(Quasi ZSDC) and conventional LCCT Z-source DC-DC converter(LCCT ZSDC). To confirm the validity of the proposed method, PSIM simulation and a DSP based experiment were performed for each converter. In case which the input DC voltage is 70V, the bipolar output DC voltage of positive 90V and negative 50V could generate. Also, as comparison result of the capacitor voltage ripple in Z-network and the input current under the same condition for each converter, the voltage stress and the capacitor voltage in Z-network of the proposed method were lower compared with the conventional methods. Finally, the efficiency for each method was investigated according to load variation and duty ratio D.

Analysis of PWM Z-Source DC-DC Converter in CCM for Steady State

Steady-state analysis of pulse-width modulated (PWM) Z-source dc-dc converter operating in continuous conduction mode (CCM) is presented. Voltage and current waveforms, and their corresponding expressions describing the steady-state operation of the PWM Z-source dc-dc converter have been presented. The input-to-output dc voltage transfer functions, both for ideal and non-ideal PWM Z-source dc-dc converter have been derived. The minimum Z-network inductance required to ensure CCM operation is derived. The voltage ripple due to filter capacitor and its ESR, and their individual effects on the the overall output voltage ripple have been derived and analyzed. Expressions for power loss in each of the components of the PWM Z-source dc-dc converter has been determined. Using the expressions derived to determine the power losses, an expression for the overall efficiency of the PWM Z-source dc-dc has been derived. An example PWM Z-source dc-dc converter is considered. A laboratory prototype is built and the theoretical analysis is in good agreement with the experimental results.