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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...
Multilevel inverters has acquire a great attention of modern power electronic systems. It offers less distortion and electro-magnetic interference and hence, it can be used in medium voltage and high power applications. The aim of this research article is to propose a new asymmetric type multilevel inverter with minimum number of power switches. The proposed inverter produces 7-level voltage waveform...
This paper introduces analysis for the performance of voltage source inverter fed from wind energy system. The inverter is used to control the voltage and frequency of an induction motor, so that its speed can be controlled. A self-excited induction generator is used to convert mechanical energy to electrical energy, as it has many advantages in terms of ease of maintenance, self-protection against...
Single phase loads, which constitute the majority of low voltage consumers, give rise to unbalanced load currents in microgrids. As a consequence the voltage unbalance might rise beyond the permissible range. The voltage unbalance can be reduced by injecting a negative sequence (NS) compensation signal into the DERs reference voltage. However, such compensation might cause circulating currents between...
EMTP is one of the useful softwares in power system studies especially in transient and protection analysis. In this software, there are some built-in models for synchronous machine as well as induction machine that could be used to simulate machine-based DG. However, for inverter-based DG there are neither such built-in models nor any reference, which explain simulation procedure in detail. This...
This works deals with the study and control of output voltage of a conversion chain based on wind conversion using a PI controller integrated into the system, and presents a mathematical model that allows the simulation of all under the Matlab environment. This with the implementation of the direct torque control DTC for the synchronous machine supplied with a rectifier installed on the output of...
This paper is devoted to the study and control of output voltage of a conversion chain based on wind conversion PMSM using a PI controller integrated into the system, and presents a mathematical model that allows the simulation of all under the Matlab environment. This with the implementation of the direct torque control DTC for the synchronous machine supplied with a rectifier installed on the output...
The purpose of this paper is to present a multi-inverter control technique to achieve fast dynamics and current sharing. The system is designed for back-up power system applications, especially for base station, etc. The multi-inverter system consists of one master module and several slave modules. The master module is with voltage and current control. The voltage controller is with proportional and...
Power flow control is one of the most important issues for operating the inverter-dominated autonomous microgrid. A technical challenge is how to achieve the accurate active/reactive power sharing of inverters. P-F and Q-V droop control schemes have been widely used for power sharing in the past decades. But it suffers from the poor power sharing in the presence of unequal line impedance. In order...
The variability and intermittency associated with the production of electricity by photovoltaic (PV) systems pose unique challenges to power systems engineers. Overcoming these challenges requires the use of computer models that accurately simulate the behavior of such systems. There is a dearth of such reliable and accurate models for PV systems study. This paper develops models for an integrated...
This paper is mainly to develop a grid-connected photovoltaic simulation system with maximum power point tracking (MPPT) function using MATLAB software in order to simulate and predict the behaviors of the real photovoltaic system. An engineering model of the photovoltaic (PV) cell is first established and then combined with an MPPT algorithm, as well as models of an MPPT controller and a DC-DC converter,...
Based on analyzing the existing series-parallel converted UPS, a new UPS system model is proposed and its principle is described in detail. The proposed UPS system is simulated using the Simulink of MATLAB6.5. The simulation result has shown that the proposed UPS system can reduce the wastage of switch and enhance the whole efficiency of system under condition of satisfying electric equipments' demand...
In this paper, a simple variable integral gain PI controller for a single-phase Inverter is presented. The controller is based on a conventional PI by adding a rule of Fuzzy Logic Control (FLC), the complete mathematical model is derived. Compared with the conventional PI controller, the integral gain of the proposed controller can be adjusted online. The efficacy and feasibility of the proposed methods...
A novel method which can improve medium frequency inverter power supply output waveforms using Delta inverter compensate technology is put forward in this paper. Taking parallel compensation as an example, the theoretical analysis of Delta inverter's compensation principle is given. The novel method can improve inverter output waveform distortion which is caused by voltage source inverter's inherent...
This paper presents a dual-buck full-bridge inverter (DBFBI) with the sinusoidal pulse width modulation (SPWM) and single current sensor. Shoot-through problem does not exist. All the power devices and filter inductors operate at each half line cycle, thus the efficiency can be increased. Only one switch works at high frequency when the reference current and the output voltage have the same polarity,...
Microgrid has become the focus of the researchers around the world because of the more emphasis on the flexibility and reliability of power system and low carbon society. Most of the microsources are connected to the microgrid through inverters, thus the modeling of inverter is quite important to the modeling and analysis of microgrid. Considering only the fundamental component of the input and output...
Unstable problem of PMSM current control system in the overmodulation range of an inverter is a well known problem, however, the cause and mechanism of this problem are still not investigated well. Actually, the main reasons which are large amount of harmonic components and voltage saturation of an inverter in this range are already known. However, the effects from current controller such as PI controller...
New energy generation systems, such as photovoltaic cells or fuel cells are increasing in application on distribution networks. These power sources require an inverter to connect to an AC network. There is the possibility that sub-network containing inverter power sources will be disconnected from the utility system to become isolated networks. This paper focuses on an isolated distribution network...
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