Power Electronic
N. Bagheri; B. Tousi; S.M. Alilou
Abstract
This research offers a high step-up DC-DC converter using a two- winding coupled inductor and voltage multiplier circuit (VMC) including diodes and capacitors for renewable energy (RE) usages such as photovoltaic (PV) and fuel cell (FC). The advantages of this converter are: 1) High voltage gain with ...
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This research offers a high step-up DC-DC converter using a two- winding coupled inductor and voltage multiplier circuit (VMC) including diodes and capacitors for renewable energy (RE) usages such as photovoltaic (PV) and fuel cell (FC). The advantages of this converter are: 1) High voltage gain with small duty cycle of the switch, 2) low voltage stress across switch/diodes, 3) Low number of components, 4) Lower volume and cost, 5) simple structure with only one power switch, 6) small current ripple of the input, 7) zero voltage and current (ZVS and ZCS) of the diodes, 8) improved efficiency, and 9) common grounding of the input and output. Due to the coupled inductor usage, the voltage gain is more flexible, and it can be enhanced by adjusting two different parameters: the turns ratio (N) of the coupled inductor and the duty cycle (D) of the switch. Furthermore, the voltage stresses of the semiconductors are decreased by increasing N. VMC is the other element for the power switch’s voltage stress reduction. The suggested topology could be an appropriate option for RE usage because of the small current ripple of the input and modified efficiency.
T. Qanbari; B. Tousi; M. Farhadi-Kangarlu
Abstract
The conventional space vector pulse-width modulation (SVPWM) for cascaded H-bridge inverters (CHBIs) has problems of computational complexity and memory requirements. Operation in overmodulation mode is the other reason for the complexity in SVPWM. This paper proposes a novel modulation method, named ...
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The conventional space vector pulse-width modulation (SVPWM) for cascaded H-bridge inverters (CHBIs) has problems of computational complexity and memory requirements. Operation in overmodulation mode is the other reason for the complexity in SVPWM. This paper proposes a novel modulation method, named as level vector pulse-width modulation (LVPWM), for voltage control of CHBIs. The concept of the proposed method is similar to the SVPWM but with different vector diagram and dwell times calculations. Unlike the SVPWM, the α and β axes and also their variables are considered separately without gathering in complex variables. The vector diagram has two separated α and β axes each of which contains individual switching vectors and reference vectors. The selection of the vectors to synthesize the reference vectors depends only on the amplitudes of the reference vectors. The computational overhead and memory requirement are independent of the number of cascaded H-bridges. Lower computational overhead and easy and continuous extension to overmodulation region are the advantages of the proposed method compared with the SVPWM-based methods. Moreover, the switching algorithm achieves improved efficiency for the inverter. Simulation and experimental results verify the effectiveness of the proposed algorithm.
T. Qanbari; B. Tousi; M. Farhadi-Kangarlu
Abstract
Abstract- The space vector pulse-width modulation (SVPWM) is a simple and suitable method for voltage control of three-phase two-level voltage source inverters (VSI)s. However, there are plenty of methods to improve the two-level VSIs performance by adding virtual vectors or sub-sectors to the SVPWM ...
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Abstract- The space vector pulse-width modulation (SVPWM) is a simple and suitable method for voltage control of three-phase two-level voltage source inverters (VSI)s. However, there are plenty of methods to improve the two-level VSIs performance by adding virtual vectors or sub-sectors to the SVPWM diagram which cause complexity in implementation of SVPWM for VSIs similar to multilevel inverters. Operation in overmodulation mode is the other reason for complexity in conventional SVPWM. This paper proposes a novel modulation method, named as level vector pulse-width modulation (LVPWM), for voltage control of VSIs. The concept of the proposed method is similar to SVPWM but with different vector diagram and dwell times calculations. Unlike the SVPWM, the α and β axes and also their variables are considered separately without gathering in complex variables. The vector diagram has two separated α and β axes each of which contains individual switching vectors and reference vectors. The selection of the vectors to synthesize the reference vectors depends on only the amplitudes of the reference vectors. With lower computational overhead and easy and continuous extension to overmodulation region, the proposed method is a simple solution to the mentioned problems. Simulation and experimental results and harmonics analysis verify the effectiveness of the proposed algorithm.
Power System Stability
M. Abbasi; B. Tousi
Abstract
In this paper, dynamic performance of a transformerless cascaded PWM static synchronous shunt compensator (STATCOM) based on a novel control scheme is investigated for bus voltage regulation in a 6.6kV distribution system. The transformerless STATCOM consists of a thirteen-level cascaded H-bridge inverter, ...
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In this paper, dynamic performance of a transformerless cascaded PWM static synchronous shunt compensator (STATCOM) based on a novel control scheme is investigated for bus voltage regulation in a 6.6kV distribution system. The transformerless STATCOM consists of a thirteen-level cascaded H-bridge inverter, in which each voltage source H-bridge inverter should be equipped with a floating and isolated capacitor without any power source. The proposed control algorithm uses instantaneous p-q power theory in an innovative way that devotes itself not only to meet the reactive power demand but also to balance the dc link voltages at the same time. DC link voltage balancing control consists of two main parts: cluster and individual balancing. The control algorithm based on a phase shifted carrier modulation strategy has no restriction on the number of cascaded voltage source H-bridge inverters. Comprehensive simulations are presented in MATLAB/ SIMULINK environment for validating the performance of proposed transformerless STATCOM.
