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Bulk power transmission across long distances has been mostly based in High Voltage Alternated Current solutions, not only due to their flexibility and cost, but also driven by the broad available portfolio. However, this solution has known physical boundaries which are quite relevant especially under the analysis of long-distance offshore wind farm applications. The aim of this paper is to present...
Internal distribution systems such as photovoltaic parks allow to use DC or AC with a frequency different from 50Hz. In this paper is instead proposed to use more than one frequency at the same time. The grid voltage amplitude at the fundamental frequency can be increased while the voltage peak value is kept constant by adding odd harmonics to the voltage waveform. The currents are decreased for the...
This paper presents a differential current compensation technique for partially shaded PV string. The proposed technique integrates an input parallel output series (IPOS) configuration of DC-DC flyback converters with distributed digital voltage mode control. PV modules in the string are interfaced with IPOS configuration of flyback converters. Each dedicated converter is regulated at the MPP voltage...
This paper presents a simple modulation algorithm which accomplishes the voltage balance across the capacitors of a Cascaded H-bridge (CHB) converter using zero voltage injection. CHB converters are widely used in renewable energy production, especially in solar plants due to their modularity. This advantage can also become a problem when the power generated by the solar cell or consumed by a load...
This paper introduces a new transformerless converter topology for Multiphase-Based Wind Energy Conversion Systems (WECSs). In this topology, a twelve-phase induction generator is integrated to the grid using dual Nine-Switch Converters (NSCs) connected in series forming a high voltage cascaded dc-link. For this generator phase number, this topology reduces the total number of semiconductor devices...
This paper proposes a novel space vector pulse width modulation (SVPWM) technique to address the capacitor voltage balancing issue in MMCs. The MMC topology consists of cascade connected identical and individual controllable submodules (SMs) to generate higher level output voltages. The characteristic of DC floating capacitor of SM complicates the modulation technique for MMC. This work presents a...
In general, the distributed generation (DG) inverters can operate in parallel in islanded microgrids through droop characteristic based control technique. This control technique is suitable for long distance DG inverters to achieve proper power sharing while ensuring good voltage regulation. On the other hand, the traditional droop control shows some disadvantages, such as the requirement for multi-loop...
A novel scheme for the control of three-phase two-level grid-connected power converters is presented in this paper. A cascade-control structure, based on H∞ control and sliding mode control (SMC), is proposed, which simultaneously achieves output voltage regulation and unity power factor under dc-load variations. The overall control strategy contains two main loops: first, a current tracking loop...
Dynamic states in the power grid - deep voltage sags and swells, voltage fluctuation - can cause faults and defects in sensitive loads and in consequence financial losses. This paper presents the concept of a smart distribution transformer, without DC energy storage, to mitigate up to 50% voltage sag/swell and voltage fluctuation and protect sensitive loads against voltage perturbation. The presented...
The paper aims to realize the micro-grid control in presence of distributed generation (DG) sources and the automatic voltage regulators (AVR). The provided analysis had into account highlighting the influence of the hybrid energy systems with consideration of the automatic voltage regulators on the power losses and the voltage level into micro-grids. The obtained results with the highest power/energy...
With a high penetration of renewable energy in the grid, virtual synchronous generator (VSG) technology is proposed to be a solution for stability controlling of micro-source inverter. VSG can effectively solve the problem of renewable energy actively connected to the grid. This paper focuses on the control design and small-signal modeling of multi-parallel VSGs. Simplified virtual inertia controller...
Cascaded Multi-level inverter for synchronization of power generated from PV system to utility grid is reported in this paper. Inverters are prone to several types of faults e.g. switch failure or dc link capacitor failure. Failure mode analysis of cascaded H-Bridge is widely discussed in the literature. Various methods for post-fault operation with reduced capacity (due to module failure) but with...
This paper presents a Lyapunov-function based control approach with cascaded proportional-resonant (PR) controller for single-phase grid-tied LCL-filtered quasi-Z-source inverter (qZSI). The proposed control approach guarantees the global stability of the closed-loop system and zero steady-state error in the grid current. The reference values for the inverter current and capacitor voltage are generated...
In this paper, Active and Reactive power management with the utility grid is achieved by integrating 7-level quasi Impedance Source Inverter (qZSI) with Thyristor based elements (Thyristor Switched Capacitor (TSC) and Thyristor Switched Reactor (TSR)). Major portion of the reactive power is managed by the thyristor based elements and the remaining reactive power is managed by the cascaded qZSI. The...
This paper presents a 27-Level asymmetric multilevel shunt active power filter topology that allows the compensation of a nonlinear load, as well as the DC voltage regulation thanks to a comprehensive control strategy. The topology considers the ratio 9∶3∶1 in order to generate the AC waveform with a simple staircase modulation algorithm. The dynamic model of the proposed topology is obtained and...
Modular multilevel converters generate high voltage ripple in the floating capacitors which increases the harmonic content of arm voltages and currents and consequently the losses and can degrade the control performance. In order to reduce this voltage ripple, a large capacitance is usually employed, but the size and cost of the submodules and the whole converter are increased. In this paper the voltage...
This paper proposes the modeling and control of a Solid-State Transformer built using a three stage conversion topology. First, a rectification stage is used, where a three-phase high-voltage AC signal is converted to a DC level; this stage is then followed by a DC-DC converter, and finally an inverter is used to convert the DC into a three-phase low-voltage AC signal. The adopted topology is modeled...
The paper presents SiC-based three-level T-type modules designed for a high-performance 30kVA DC/AC inverter operating at high frequency 85 kHz with low THD of the output voltage. This inverter system consists of two integrated parts. The first part is active and contains three parallel-connected three-phase T-type modules built with fast-switching SiC power transistors. The second, passive part of...
This paper assesses the dynamic behaviour of an Energy Storage System (ESS) under disturbed grid operating conditions. The ESS is designed, as well as the AC and DC current and voltage controllers, and a Supervisor is developed, that defines the system operation states, and the boundary conditions between them, establishing the references for the currents and voltages to control. Simulation results...
This paper presents a fast and robust control system for a three-phase quasi-Z-source inverter (qZSI) connected to the grid. The topology combines two quasi-Z-source networks with a T-type inverter allowing to obtain AC voltages with multilevel characteristics and properties of the referred networks. To control this system a closed-loop current controller for the AC currents is proposed. The controller...
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