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Since the capacitor equivalent series resistance (ESR) above 1kHz almost stays constant, dc-link current root-mean-square (RMS) closed form equation is an easy way to evaluate the capacitor losses from the switching harmonic currents (SHCs). But when the ac current contains multiple low order harmonics (LOHs), their impacts on the dc-link has not been systematically studied. In this paper, a straightforward...
This paper presents new constraints for Selective Harmonic Elimination (SHE)-PWM technique utilized in single phase applications. The proposed constraints eliminate all triplen harmonic orders naturally whereas they appear in all single-phase output voltage waveforms conventionally. The specified non-triplen harmonics are also eliminated through calculation of switching angles. Five-level high switching...
Droop control is generally used to realize power sharing without communication lines. VSG (Virtual Synchronous Generator) is a control method that mimics both steady-state droop and dynamic characteristic of SG (Synchronous Generator) to enhance inertia of microgrid. In this paper, the comparison of different damping effect forms in VSG control is given firstly to draw conclusions: For the aspect...
A hybrid impedance model of Islanded MicroGrid with Paralleled Inverters Controlled by Droop and PQ Strategies (IMG-PICDPS) is derived, in which the PQ-controlled Inverters (PQ-Invs) are equivalent to Norton's circuits, while the DRoop-controlled Inverters (DR-Inv) to Thevenin's circuits in this paper. An impedance-based stability analysis method is further proposed according to the Nyquist criterion...
Parallel three-level T-type inverters (3LT2Is) can increase power rating and reliability, but the circulating current problem will arise. Unbalanced conditions including unbalanced filter inductances and unbalanced grid voltage have negative effects on the operation of parallel 3LT2Is. This paper presents an improved repetitive control scheme for circulating current suppression in parallel 3LT2Is...
An analytical approach for accurate calculation of the conduction and switching power losses associated with the switching devices in the 5-Level 3-Phase Back to Back E-Type Converter (5L3ϕ BTB E-Type Converter) has been proposed in this paper. The 5L3ϕ BTB E-Type Converter is composed by two different multilevel topologies: the 5-Level E-Type Inverter and the 5-Level E-Type Rectifier. The power losses...
Photovoltaic units that are connected to the grid through dc/dc converters and inverters in distributed generation, are controlled via a synchronous-generator-like voltage control mechanism. While other control schemes such Synchronverters are used to control the inverter frequency and power at a fixed dc link voltage, the proposed approach considers both the dc-link voltage dynamics and the inverter...
This paper presents a new topology of multilevel converter that allows to increase the number of output voltage levels reducing the numbers of semiconductors necessary in comparison with the standard multilevel converters like Active Neutral Point Clamped (ANPC) and Stacked Multicell Converter (SMC). This new topology called Reduced Multilevel Converter (RMC) consists of a tandem connection of basic...
Paralleled inverters have the merits of high power rating, improved reliability and convenient maintenance, but zero-sequence circulating current (ZSCC) will occur and lead to current distortion and system loss. The ZSCC control is more complicated when adopting three-level topology and increasing paralleled number. This paper addresses the suppression of ZSCC in multi-paralleled three-level T-type...
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...
Advanced control techniques such as Volt-Watt and Volt-VAR Control have been developed for high integration of distributed renewable energy, such as Photovoltaic (PV) resources, on an electric distribution system. However, designing these control parameters which yields the best results in the system is complicated and depends on feeder conditions. This paper proposes a method to properly design the...
This paper proposes a new control method for two stage converters to realize the virtual synchronous generator (VSG) operation, which also can help eliminate circulating power between energy storage (ES) converters. It is proven in this paper that the proposed method shares stronger resemblances with synchronous generators (SGs) than traditional VSG in aspects of power conversion process and mathematical...
In order to ensure the stable operation of the power grid, this paper aims at the modeling of the integrated information system of the photovoltaic power plant, and the model of the PV module is divided into physical characteristics. In order to ensure the stability of the power grid, Model and external characteristic model. The PV module model based on the physical characteristics is based on the...
Electrical energy generation is evolving from centralized towards distributed energy resources (DER) like wind and solar power plants. In such power systems, new challenges arise for the design of voltage source converter (VSC) control strategies. In the last few years synchronverters have gained interest from the research community due to their capability of emulating synchronous machines (SMs) and...
Nowadays, due to the high-scale penetration of photovoltaic systems, reliable and efficient photovoltaic grid-connected systems using the advances of power electronics and advanced control techniques are desirable. In this paper, using the general structure for synchronous dq0 frame, a single-stage three-phase grid-connected photovoltaic inverter with a nonlinear control strategy is developed to generate...
The proportional power sharing has been identified as an important issue to guarantee reliability on the operation of low voltage AC-Microgrids. However, inaccurate reactive power sharing in scenarios with line impedance mismatches, and slow transient response remain important limitations of most of the conventional power sharing controllers. In this context, an improved method for power sharing control...
The common-mode current casued by the parasitic parameters in the transformerless multilevel converters degrades the performance of converters and brings security issues. This paper presents a new zero common-mode voltage space vector modulation for common-mode voltage suppression in the five-level modular composited converter. Firstly, the common-mode equivalent circuit model of five-level modular...
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...
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...
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...
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