scholarly journals A Novel Stability Improvement Strategy for a Multi-Inverter System in a Weak Grid Utilizing Dual-Mode Control

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2144 ◽  
Author(s):  
Ming Li ◽  
Xing Zhang ◽  
Wei Zhao
Keyword(s):  
Current Source ◽  
Voltage Source ◽  
Output Current ◽  
Dual Mode ◽  
Improvement Strategy ◽  
Distributed Generations ◽  
Mode Control ◽  
Loop Transfer Function ◽  
Grid Impedance ◽  
Control Scheme

Due to the increasing penetration of distributed generations (DGS) and non-negligible grid impedance, the instability problem of the multi-inverter system operating in current source mode (CSM) is becoming serious. In this paper, a closed-loop transfer function model of such a multi-inverter system is established, by which it is concluded that output current resonance will occur with the increase in the grid impedance. In order to address this problem, this paper presents a novel dual-mode control scheme of multiple inverters: one inverter operating in CSM will be alternated into voltage source mode (VSM) if the grid impedance is high. It is theoretically proved that the coupling between the inverters and the resonance in the output current can be suppressed effectively with the proposed scheme. Finally, the validity of the proposed theory is demonstrated by extensive simulations and experiments.

scholarly journals Modeling a Dual-Mode Controller Design for a Quasi-Resonant Flyback Converter

2019 ◽  
Vol 9 (9) ◽  
pp. 1860
Author(s):  
Ching-Chun Chuang ◽  
Chih-Chiang Hua ◽  
Chong-Yu Huang ◽  
Li-Kai Jhou
Keyword(s):  
Controller Design ◽  
Circuit Simulation ◽  
Equivalent Circuit Model ◽  
Technological Advancement ◽  
Dual Mode ◽  
Heavy Load ◽  
Constant Frequency ◽  
Mode Control ◽  
Control Scheme ◽  
Load Conditions

The proposed system can overcome the disadvantage of a high peak current in quasi-resonant fly-back (QRF) converters when operated under heavy load conditions. The operating mode and control scheme of a QRF converter with dual-mode control were established and analyzed. The dual-mode control scheme not only enabled a valley-switching detection technique that satisfied the zero-voltage switching condition but also provided a constant frequency mechanism to reduce the conduction loss in QRF converters when operated in a continuous conduction mode and under heavy load conditions. The small-signal equivalent circuit model of QRF converter circuits was constructed using an average approximation method. The technological advancement of a QRF converter with a dual-mode controller was presented in this study. The circuit simulation result of the proposed QRF converter with a mix control scheme proved that the derived circuit component parameters meet the requirements of the converter.

A Generalized Three-Phase Multilevel Current-Source Inverter Topology

2011 ◽  
Vol 88-89 ◽  
pp. 373-378
Author(s):  
Jian Yu Bao ◽  
Wei Bing Bao ◽  
Zhong Chao Zhang
Keyword(s):  
Control Strategies ◽  
Current Source ◽  
Voltage Source ◽  
Output Current ◽  
Current Source Inverter ◽  
Multilevel Structure ◽  
Three Phase ◽  
Dc Current ◽  
And Control ◽  
Inverter Topology

A generalized three-phase multilevel current-source inverter (MCSI) topology is proposed by implanting the generalized N-level current cells into a three-phase MCSI topology which is derived from the three-phase multilevel voltage-source inverter (MVSI) topology through dual conversion. In the generalized three-phase MCSI topology, each intermediate dc-link current level can be automatically balanced without adding any external circuits, thus a true multilevel structure is provided. Output current of each phase is independently modulated because of being supplied with two DC current-sources. This allows the wealth of existing knowledge relating to the operations, modulations and control strategies of multilevel VSI to be immediately applied to such multilevel CSI. Simulation results of 5-level and 7-level CSI systems are presented to verify the proposed three-phase MCSI topology.

Analysis and Design of a Dual-Mode Control Boost Rectifier

2012 ◽  
Vol 516-517 ◽  
pp. 1906-1909
Author(s):  
Yu Kang Lo ◽  
Jing Yuan Lin ◽  
Chao Fu Wang
Keyword(s):  
Switching Loss ◽  
Dual Mode ◽  
Analysis And Design ◽  
Design Procedures ◽  
Mode Control ◽  
Extreme Loads ◽  
Control Scheme ◽  
Boost Rectifier ◽  
Heavy Loads ◽  
Mode Tm

This paper presents a dual-mode control scheme for a boost rectifier at both extreme loads. The transition-mode (TM) technique is adopted to reduce the switching loss at light loads. On the other hand, the fixed-off-time (FOT) control with continuous conduction mode (CCM) operation decreases the conduction losses at heavy loads. The principles and design procedures of the proposed dual-mode controller are discussed and analyzed. Finally, a 300-W dual-mode boost rectifier with an output voltage of 380 V is implemented with satisfactory experimental results.

scholarly journals Observer-Based Sliding Mode Control to Improve Stability of Three-Phase LCL-Filtered Grid-Connected VSIs

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1421 ◽  
Author(s):  
Min Huang ◽  
Han Li ◽  
Weimin Wu ◽  
Frede Blaabjerg
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
Voltage Source ◽  
Voltage Source Inverters ◽  
Mode Control ◽  
Impedance Variation ◽  
Three Phase ◽  
Grid Impedance ◽  
The Stability ◽  
Fast Dynamic

Grid-connected voltage source inverters (VSIs) with LCL filters have been widely used for distributed generation systems (DGs). Various control methods have been studied to achieve good performance. Among them, sliding mode control has been applied to LCL-filtered grid-connected VSIs for its fast, dynamic response and strong robustness. However, LCL networks can easily cause instability problems under weak grid conditions such as grid impedance variation. At the same time, the stability design of sliding mode control applied for LCL-filtered grid-connected inverters are important, but they lack detailed parameters design in recent papers. In this paper, a design of observer-based sliding mode control to improve the stability of three-phase LCL-filtered grid-connected VSIs was proposed. The theoretical stability analysis was developed to consider the effect of the system discretization and grid impedance variations. Finally, a 3-kW, 110-V, 50-Hz experimental setup has been built to demonstrate the validation of the proposed method.

LQR Based Control Method for Grid Connected and Islanded DG System

2018 ◽  
Vol 19 (5) ◽  
Author(s):  
Parusharamulu Buduma ◽  
Gayadhar Panda
Keyword(s):  
State Feedback ◽  
Reactive Power ◽  
Control Method ◽  
Current Source ◽  
Superior Performance ◽  
Voltage Source ◽  
Optimization Approach ◽  
Control Scheme ◽  
And Performance ◽  
Comparative Results

AbstractThis paper presents an output and state feedback robust LQR (OSRLQR ) optimal controller for the control of active (P) and reactive power (Q) in grid-connected mode, and voltage (V) and active power in islanded mode of photovoltaic (PV) distributed generation (DG) system. The OSRLQR scheme is comprising of an output and state feedback controllers, which are designed based on LMI-LQR optimization approach. The DG inverter along with proposed controller is configured to work as a current source in grid-connected mode and a voltage source in island mode using P-Q and P-V control scheme respectively. A seamless transition between the grid connected and island modes under the presence of the proposed controller is achieved using a passive island detection and synchronization algorithm along with load shedding. The entire control scheme of the DG system is modelled and analyzed using MATLAB/SIMULINK/Robust Tool-Box, and the practical feasibility of the proposed control scheme is verified using dSPACE. A superior trade-off robustness among the stability and performance is the final outcome of the DG system with proposed control scheme. Performance of the proposed control scheme is compared with conventional PI controller and the comparative results indicate the superior performance of proposed control scheme over the conventional control scheme.

The Application of Sliding Mode Control in Current Source Converter

2014 ◽  
Vol 945-949 ◽  
pp. 2331-2337
Author(s):  
Jing Bai ◽  
Shi Qi Lu ◽  
Jian Liu
Keyword(s):  
Control Strategy ◽  
Sliding Mode ◽  
Current Source ◽  
Variable Structure ◽  
Current Waveform ◽  
Output Current ◽  
Fast Tracking ◽  
Control Scheme ◽  
Existence Domain ◽  
Current Source Converter

Current source converter is a variable structure system due to its switching nature, so that it can easily cause the output current waveform distortion and can not be accurately track the reference current. To solve the above problems, this paper proposes a new variable structure control strategy with fan-shaped sliding domain in the current source converter control system. In the control strategy, the paper deduces the switching surface and switching control law of SMVSC, and calculates the sliding existence domain based on the mathematical model of current source converter. Finally, the simulation results show that the control scheme can make current source converter have better output current waveform, fast tracking the reference current, and strong anti-interference ability. Therefore, the control scheme is correct, effective and feasible.

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