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Single-phase grid-connected inverters with LCL filter are widely used to connect photovoltaic systems to the utility grid. Among the existing control schemes, predictive control methods are faster and more accurate but also more complicated to implement. Recently, the Model Predictive Control (MPC) algorithm for single-phase inverter has been presented, where the algorithm implementation is straightforward...
This paper proposes a DC link controller based on H∞ method for robust and reliable operation of a single-phase grid-connected inverter with an LCL-filter in photovoltaic (PV) applications. The H∞ DC link controller minimizes the bus voltage fluctuations caused by the power variations of PV system. Also, the controller ensures system robustness against such power variations, which conventional controllers...
This paper proposes a fixed frequency based sliding mode (SM) controller for transformer-less single phase inverter for photovoltaic (PV) application with active power decoupling minimizing the capacitance requirement. Unlike conventional power decoupling techniques in full bridge converters, the proposed technique incorporates a large sinusoidal swing of the half-bridge capacitor voltages and a limited...
This paper proposes an improvement of the finite control set model predictive control (FCS-MPC) strategy for enhancing the voltage regulation performance of a voltage source converter (VSC) used for standalone microgrid and uninterrupted power supply (UPS) applications. The modification is based on tracking the voltage reference trajectory derivative using a single step prediction horizon. The main...
To address the DC link voltage regeneration issue in parallel Uninterruptible Power Supply (UPS) system, a DC link voltage protection (DCVP) method through online virtual resistance regulation is proposed. The proposed control strategy is able to protect the DC link from overvoltage that may trigger the protection mechanism of the UPS system. Moreover, a current sharing control strategy by regulating...
Apart from high power density, unified power quality conditioner (UPQC) offers a cost-effective and energy-efficient way to deal with power quality issues. A single-phase transformer-less unified power quality conditioner (TL-UPQC) utilizing four switching devices only is presented. The proposed UPQC consists of two voltage source inverters, one is connected in parallel with the load and another one...
Because of the differences in line impedances, parallel inverters with conventional droop control will have huge circulating current, which does not flow through the loads. To mitigate the circulating current, the research in this paper finds out that parallel-operated inverters should have the impedance in inverse proportion to their capacities, which is difficult to realize in practice. To meet...
This paper presents a unified selective harmonic compensation strategy using DG-interfacing inverter with LCL filter in the presence of nonlinear local loads for both grid-connected and islanded microgrid. Compared with the existing harmonic compensation methods in the literature, the proposed strategy consists of a triple-control-loop in the grid-connected mode to compensate the grid current harmonics...
Microgrids are seen to play an ever increasing role in providing clean energy which is essential to ensure sustainable and equitable growth. A variety of challenges need to be overcome for these microgrids to be successful, varying from stability, power quality issues to protection and management. Various control algorithms are actively being proposed, and emerging challenges still being researched...
Voltage unbalance in a three-phase system introduces oscillations to the DC Link voltage and power. Moreover, it causes performance deterioration of a pulsewidth modulation (PWM) of the back-to back voltage source converter systems (BTB-VSC) by producing the double-line-frequency ripples in the dc link voltage and power. This paper proposes a new control strategy by developing the conventional vector...
In this work it is presented a two-phase open-end winding induction motor (IM) driven by an improved current source inverter (CSI). The proposed inverter has independent full quadrant operation, lower DC-link current value, high magnetics power density, 25% more efficient and high AC output voltage waveform quality compared to conventional CSI solutions. A back-to-back AC-DC-AC current source converter...
At present, the research on the quality of micro-grid power at home and abroad is still at the initial stage, which focuses on the study of the power quality characteristics of micro-sources. There is little research on the quality control of micro-grid power and the power quality adjustment device for microgrid. In particular, there is no literature on the power quality of the microgrids containing...
To avoid the stability problem of grid connected inverter caused by the conventional phase locked loop (PLL), the direct power control of voltage source inverter in virtual synchronous reference frame without PLL is investigated considering grid voltage disturbance in the paper. Based on the small signal analysis methods, comparison between conventional PLL and no PLL is made. It can be found that...
This paper proposes a primary side control for series-series compensated wireless power transfer system. By eliminating the need for a communication link for signal feedback, the control method not only reduces volume and cost of the system, but also improves a dynamic response. This controller only requires the information of the primary side voltage and current to identify the load resistance and...
In order to address the economical dispatch problem in cascaded microgrids, this digest proposes an optimal economical-sharing scheme via decentralized approach only with the local information. This overcomes the limitations of centralized control, where the central controller and external information exchange are needed. The frequency and current are used as carriers driven the distributed generators...
There is an increasing need to model large networks of inverter-based distributed generation due to the limits of existing simulation tools. A deliberate enforcement of intra-feeder coherency between adjacent droop-controlled inverters is a worthwhile objective, as phase angle coherency will allow for a deliberate partitioning of fast and slow dynamics within the network. This partitioning, in turn,...
This paper focuses on the relevant content of the MVDC-connected photovoltaic system based on the modular cascaded structure. This paper proposes a new topology for the DC grid-connected photovoltaic system with a novel capacitor voltage balancing control strategy, including the module input power ratio feed forward and module capacitor voltage closed-loop control. The proposed control strategy is...
An interleaved current-fed capacitor-less DC/AC converter for PV systems is proposed in this paper with the merits low input current ripple, high power density and high reliability. This proposed DC/AC converter is composed of an interleaved current-fed dc/pulsating-dc converter cascaded with a three-phase pulsating-dc/ac inverter through pulsating-dc-link modulation. The pulse width modulation of...
In this paper, a method to diagnose and identify the open-circuit faults of IGBT for a six-level hybrid inverter (6L-HI) is proposed, which is based on the signals of the inner device voltages, the flying capacitor voltages and the phase currents of the inverter. Since the flying capacitor voltage sensors and the output current sensors are already employed for the inverter operation, only one additional...
In Digital Grid which has been proposed as a new electric power grid, multi-inverters are operated in parallel and it may cause the cross-current among those inverters, since inverters do not have synchronizing mechanism. In this study, the authors propose a method to control the cross-current caused by the difference in switching frequencies of multi-inverters in parallel operation. An indirect hysteresis...
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