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This paper presents a division-summation (D-Σ) digital controlled three-phase four-leg voltage source inverter with load impedance estimation for uninterruptible power supply applications. The D-Σ digital control developed for current tracking can accommodate wide filter inductance variation, which has been successfully adopted in grid-tied applications. This paper proposes a load impedance estimation...
This study presents design of D-Σ digital controlled hybrid-frequency inverters with LCL filter for grid-connected applications. Hybrid-frequency inverters consist of inverters with different frequencies and power ratings connected in parallel. The lower frequency inverter has higher power rating, while the higher frequency inverter has lower one. The inverters are controlled to cancel out low-frequency...
This paper presents a three-phase transformerless uninterruptible power supply (UPS) with sinusoidal pulse width modulation (SPWM) based division-summation (D-Σ) digital control. A transformerless UPS controls the power flow between dc link and utility grid, as well as tracks the ac reference voltage. The proposed control law derived with D-Σ digital approach takes into account the effects of dc-link...
There has been a growing demand of using multi-function inverters for grid-connected systems applied to nonconventional energy sources, such as solar, wind and so on. In addition to power quality conditioning, the inverter can also be used for bidirectional active power exchange with a three-phase four-wire grid. Therefore, the inverter acts as a multi-function compensator. The functions of the proposed...
Recently, an appealing switching strategy, named model-based predictive current control (MBPCC), has received much research attention in power electronics and drives. However, MBPCC usually requires system model (in discrete-time form) and the system parameters in its controller design. In order to eliminate these restrictions, a simplified model-free predictive current control (SMFPCC) is proposed...
This paper presents an SVPWM-based division-summation (D-E) digital control for a three-phase grid-connected inverter with wide inductance variation. The proposed D-E approach summarizes all of the individual inductor-current variations over one switching cycle to derive control laws directly, which can overcome the limitation of d-q transformation. The inverter with this control can achieve the functions...
This paper presents a division-summation (D-Σ) digital control for a three-phase bi-directional photovoltaic inverter with wide inductance variation. The bi-directional inverter fulfilling grid connection and rectification with power factor correction has been implemented in the laboratory. The proposed D-Σ approach summarizes the inductor-current variations over one switching cycle to derive control...
This paper presents filter-capacitor current compensation for Division-Summation (D-Σ) digital controlled singlephase bi-directional inverter with LCL filter to reduce grid-current distortion. The single-phase bi-directional inverter allows wide filter-inductance variation and it can operate in grid-connection mode and rectification mode with power factor correction. With the D-Σ digital control,...
This paper presents a load impedance estimation and iterative-learning control for a three-phase four-wire inverter. The topology of a three-phase four wire inverter is adopted to uninterruptible power supply (UPS) applications, which can supply unbalanced load, linear load and rectified load. The proposed load impedance estimation scheme employs an RLC equivalent circuit concept to determine the...
This paper proposes an active clamp interleaved forward converter with a single-capacitor turn-off snubber constructed with a full-bridge inverter for stunning poultry applications. The proposed converter can use active clamp circuit to recover the energy trapped in magnetizing and leakage inductors of transformer and to achieve zero-voltage switching at turn-on transition. In addition, the proposed...
Control systems consisting of a subsystem with discontinuities often cause problems in digital simulation. Real-time simulation of this type of system using conventional fix-step integration algorithms can lead to sizable errors for reasonable step sizes. This paper suggests a new approach which replaces the subsystems with a function table. The dynamic equations of the control subsystem with discontinuities...
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