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By intensifying renewable energy sources integration to the power grid and forming the microgrids (MGs) concept, many studies have been done to investigate MGs operation, control, protection, and etc. The performance of loads can play a major role in the MG behavior. Different load models can be implemented in MGs. The voltage and frequency (VF) dependent load is a substantial load model which few...
A model control and a filter suppressing oscillation of the output voltage that can obtain the stable output voltage of a dc-dc converter have been proposed previous. Although there is a problem that the condition on the input side of dc-dc converter is changed when it connects the load equipment to renewable energy generators through the DC bus, since the renewable energy generators are sometimes...
The Compact Fluorescent Lamps (CFLs) are widely adopted in residential and commercial sector. This adoption is proposed following the energy conservation and environmental protection efforts. Despite, the CFLs consume low power, many users using these loads can cause a harmonic impact depending of the Attenuation-Amplification Effect. For instance, if this Effect is neglected (e.g., using Harmonic...
Hybrid AC/DC microgrid (MG) has attracted more and more attention due to its advantages such as better power sharing, improved system dynamics, and optimal management. But the complicated structure brings a great challenge to the modeling and stability analysis. In recent years, dynamic phasor model has been well applied in the modeling of AC MGs. Dynamic phasor tranforms sinusoidal quantities to...
The droop control technology, which can achieve an autonomous power sharing among distributed resources interface converters, provides the advantages of enhanced system reliability and reduced complexity. However, the reactive power sharing accuracy of the conventional Q — V droop method can be degraded due to its dependence on the line impedances. The Q — V droop control method was proposed to reduce...
Multilevel inverters as the best existing solution for high power/ medium voltage applications have been utilized to incorporate renewable energy sources into electric grid. Solar energy, and fuel-cells as two major sources of power can only provide unidirectional power flow. However, utilizing cascaded H-bridge inverters or other inverters with trinary voltage ratios at the input DC links might cause...
Three-phase/level T-type converter has advantages of high efficiency and low current harmonics, which is utilized in power conversion systems for supplying dc loads widely. Three-phase/level T-type converter provides bipolar dc buses with a neutral line at relatively low cost. In order to extend applications for bipolar dc bus structure, voltage independence control of split-dc bus proposed in this...
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...
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...
Modular medium voltage power converters have gained increasing attention in context of Smart Transformers (STs) in the electrical distribution grid. A possible ST architecture can be built by a Cascaded H-Bridge (CHB) converter in the Medium Voltage side and Dual Active Bridges (DABs) in the isolation stage. One of the main issues in the CHB control is represented by the voltage balancing. This work...
This paper proposes the application of advanced modelling and control strategies for a single phase Dual Active Bridge (DAB) based Medium Voltage DC (MVDC) Shipboard Power System (SPS). In these systems the tightly controlled point of load (POL) converters exhibit a constant power load (CPL) behaviour, which has a destabilising effect on the bus voltage. In this work, a Multiple Input Single Output...
Non-inverting Buck Boost converters (NIBB) have been utilized as interfacing converters for energy storage, due to the high steady-state efficiency offered by the asynchronous control. However, classical asynchronous control has inherent poor dynamic performance when the input and output voltages are near. To solve the problem, concept of “dynamic mode switching” is first proposed in this paper. Instead...
The paper proposes a hybrid droop control strategy to enhance the stability and increase maximum constant power loads (CPLs) capability of DC microgrids in a realistic scenario. By capturing the detailed model of inner control loops and hybrid droop control and general dc MG topology, a thorough comparative study is conducted between traditional droop control and hybrid droop control. Enhanced control...
This paper proposes a real time scalar control of induction motor by using RT-LAB software. This method of control leads to be able to adjust the speed of the motor by control the frequency and stator voltage magnitude, the ratio of stator voltage magnitude to frequency should be kept constant, which is called as scalar control of induction motor. The real-time scalar control algorithm is designed...
This paper approaches the topic of robust control for DC-DC power converters. A low-power single-ended primary-inductor converter (SEPIC) has been chosen as a case study, for which the output voltage regulation problem in presence of parameter uncertainties is stated in the Hinf formalism as a disturbance-rejection problem. This approach is assessed by numerical simulations in MATLAB against a classical...
The paper proposes a novel voltage event-triggered P-U control strategy for improving related active power sharing accuracy in low-voltage microgrid (MG). Active power sharing inaccuracy is associated with voltages difference of distributed generation units (DGs) that is basically attributed to mismatched lines impedance. So the inaccuracy is inevitable. The proposed voltage control strategy contains...
This paper presents a smart DC network formed by a multi-terminal VSC-HVDC connecting various micro-grids, independent power generation stations, and passive loads. The corresponding deadbeat current control scheme based on coordinated strategy for multi-terminal VSC-HVDC systems is proposed. The current control scheme is easy to design, implement and has good dynamic response. the case of four-terminal...
To manage the microgrid effectively, it is important to get the power information among multiple distributed generation (DG) units. However, when the droop control method is adopted, as the corresponding DG units cannot be simply modeled as VF or PQ buses, the conventional power flow algorithm may become inapplicable. To solve this issue, a time domain iteration (TDI) based power flow algorithm is...
Microgrids have become an alternative to increase the controlability and resilience of the electrical system due to the local and efficient energy management they provide. Additionally, when the microgrid has a main DC bus it does not require synchronization hence the control scheme is simplified allowing to improve the dynamics of currents and voltages. These DC microgrids are usually controlled...
In this paper, a new distributed cooperative control for voltage unbalance compensation in an islanded microgrid is proposed. In order to decrease the negative impacts of impedance of distributed lines upon conventional negative-sequence reactive power-conductance droop control, a cooperative control component is added to accomplish the trade-off between the accuracy of negative-sequence reactive...
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