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Conventional photovoltaic (PV) power system connects hundreds and thousands of solar cells to form the PV array to match the power and voltage rating. It has been reported that any mismatch among cells results in significant power loss. PV modular level parallel inverter (MLPI) has attracted significant research attention in order to address the issue and improve system reliability. The MLPI requires...
The paper presents a new four-level voltage source converter (VSC). Compared to conventional four-level converters, this proposed converter has fewer components and can be used for a higher power density system in low and medium voltage applications. Its principles and advantages are studied in this paper. The effect of various redundant switching states on the voltages of flying capacitors is analyzed...
The focus of this paper is on power flow control in the asymmetric quad-active-bridge (QAB) converter and its limitations imposed by uneven values of parasitic elements in the isolation transformer. The QAB converter under study is intended for solid-state transformer applications in asymmetric configuration, where one of the ports is placed at the low voltage side and rated for the threefold power...
In this paper, a novel hybrid DTC scheme is proposed for asymmetric six-phase PMSM drives, which can achieve faster dynamic response of classical ST-DTC scheme and good steady-state performance of classical SVM-DTC scheme. The key is that a completely novel control strategy for torque and stator flux is designed. Different torque control methods are adopted under dynamic mode and steady-state mode...
Aalborg Inverter is a kind of high efficient Buck-Boost inverter. Since it may work in “Buck-Boost” mode, the control bandwidth should be high enough to ensure a good performance under any grid condition. However, during the “Boost” operation, the control bandwidth depends much on the grid impedance if the crossover frequency is traditionally chosen lower than the characteristic frequency of system...
Inverters are widely applied in industrial fields. To acquire the analytical solution of sinusoidal pulse width modulation (SPWM) Single-phase inverters, a traditional harmonic balance based method is extended, in which the double Fourier transform is used to describe the nonlinear switching function of the converter. Thus the steady-state periodic solution of the inverter can be obtained by our approach...
Among various converters, the LLC electric current resonant converter attracts attention because of high power density, low noise and high efficiency. However, this converter cannot apply the analysis of averaging method, and impossible to derivate the transfer function, so designing is difficult. In this study, we devised a method to derive a frequency response characteristic with a transfer function...
This study presents a sensorless static model based with output current estimation method for digital PWM control dc-dc converters. The static model is a feedforward type control method adopted in coordination with the standard PID control and it can improve characteristics of wide input and output range of dc-dc converter by using information of output current. The one of the drawbacks of the static...
This work presents the design of an autonomous, cost-effective and efficient solar powered irrigation pump using a switched reluctance motor (SRM) drive. The proposed system utilizes a modified CSC (Canonical Switching Cell) converter for power optimization of photovoltaic (PV) array. The continuous inductor current mode (CICM) working of DC-DC converter significantly minimizes the stresses on its...
The digital control power supply has been widely used by virtue of its many advantages. However, it may cause limit cycle oscillations due to quantization in the feedback loop when the switching frequency is high. This paper presents an analytical model of buck converter using state space average method and derives the equilibrium expression in steady state, and the requirement for DPWM resolution...
This paper proposes a digitally controlled bipolar converter for dc micro grids. The bipolar converter configuration is based on the combination of SEPIC and CUK converter with the modifications in both the converters. In the proposed bipolar converter, the equivalent series resistance (ESR) of the transfer floating capacitor is increased by inserting a series resistance in the both SEPIC and CUK...
This paper proposed switched fractional order controller (SFOC) for grid connected Wind Energy Conversion System. The SFOC consists of conventional PI controller, fractional order IP controller and decision maker. The SFOC controller is applied to control PMSG connected to the grid. The proposed control aims to extract maximum power under fluctuating wind speed. SFOC controller designed to solve the...
The concept and technologies of fractional calculus have been increasingly applied to model and design circuits and electrical elements. In this work, by combining the principle of harmonic balance and equivalent small parameter method, we develop a new method of steady-state analysis for fractional-order DC-DC converters in discontinuous conduction mode (DCM). The effectiveness of the proposed scheme...
This paper introduces a novel battery cell balancing technique for portable applications, where multiple series connected lithium-ion battery cells are utilized. The equal discharge of the battery cells are achieved through a simple modification of a hybrid step-down dc-dc converter, where only an additional resonant inductor is required. Hybrid converters, combining switched-capacitor and inductor...
Isolated DC-DC converters are widely used as the essential power conversion equipment in recent renewable energy systems. At the same time, such converters are expected for wide input voltage range and fault tolerance. This paper proposes an isolated boost full bridge DC-DC converter with a set of low loss active snubber circuits. To verify the feasibility of the proposed scheme, a 10 kW prototype...
Single stage power factor corrected (SSPFC) AC-DC converters are popular in industrial applications such as telecom because they are cheaper and smaller than conventional two-stage converters. The intermediate DC bus voltage of these converters, however, varies significantly when used in universal voltage range applications. A new AC-DC SSPFC resonant converter that can be operated with universal...
In this paper, a predictive direct power control (P-DPC) strategy for a three level NPC rectifier under ideal grid voltage is proposed, discussed and applied. With the proposed P-DPC strategy, the control targets are the active power, the reactive power and the neutral potential voltage; neither hysteresis comparators nor switching table are needed; sinusoidal input current with low total harmonic...
A novel reaching law of sliding mode control is proposed by using saturation function and power term in this paper, which aims at reducing chatting phenomenon and fastening convergence speed. It is indicated through theoretical analysis that the system under the proposed reaching law has existence and accessibility. The convergence speed is calculated in detail. The sliding mode control system of...
To improve the accuracy of stator flux estimator in Direct Torque Control (DTC) of Interior Permanent-Magnet Synchronous Machine (IPMSM), a pulse response based rotor position estimator is proposed. The current ripples caused by active voltage vectors in DTC are utilized by the rotor position estimator. Then, the estimated rotor position serves as an input for a model-based stator flux estimator in...
A helical-type fusion facility uses a large-scale superconducting DC magnet. To maintain the coil current of this magnet during steady-state operation, a large output current supplied by a very-low-voltage power supply is necessary. For this purpose, a DC power supply using a mechanical contact as a switching device was designed, and a small model of the contact was tested.
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