Masoumeh Karimi

An Innovative Scheme of Symmetric Multilevel Voltage Source Inverter With Lower Number of Circuit Devices

In this paper, an advanced configuration for a symmetric multilevel voltage source inverter is proposed. The authority of the proposed inverter versus the conventional cascaded H-bridge inverter and those most recently introduced is verified with provided comparisons. The proposed inverter is able to generate the desired voltage levels using a lower number of circuit devices, including power semiconductor switches and related gate driver circuits of switches. As a result, the total cost is considerably reduced, and the control scheme gets simpler. Moreover, the reduced amount of on-state switches in the suggested configuration decreases voltage drops. Furthermore, power losses are diminished. The given simulation results confirm the feasibility of the proposed configuration. To approve the practicability of the proposed inverter, a prototype of the proposed topology has been implemented. Finally, simulation and experimental results are compared, and the provided comparison shows that the obtained results are in good agreement.

A novel symmetric/asymmetric multilevel current source inverter topology with lower number of components and lowest power rating of switches

ABSTRACT A novel multilevel current source inverter (MCSI) configuration is introduced in this paper. The ability of handling with asymmetrical DC sources is one of the substantial advantages of the proposed inverter. In asymmetric mode, by appropriate selection of DC sources magnitude, a considerable increase can be obtained in the number of output levels without any manipulation on inverters’ hardware. In MCSIs, the number of required circuit devices is very important because the overall costs, circuit size, reliability and control complexity are dependent on them directly. The proposed inverter can generate all desired current levels using a lower number of elements. Besides, it is known that reduction of number of switches from conventional inverters imposes an undesired increase in total semiconductor device power (SDP). But, the total SDP of the proposed inverter is kept equal to conventional inverter. To validate the superiority of the proposed inverter, a full comparison is provided. Also, the computer simulation and experimental results are presented.

Optimal planning of distributed generation with application of multi-objective algorithm including economic, environmental and technical issues with considering uncertainties

ABSTRACT This paper proposes a stochastic multi-objective model for integration of distributed generations (DGs) in distribution networks. The proposed model determines the optimal location and size of DGs by optimising different objective functions dependently and simultaneously subject to the operating constraints. If proper sizes of DGs are located in suitable sites and are also managed properly they can improve integrity, reliability and efficiency of the system. Regarding the widespread impact of uncertainties, some strategies must be devised in order to incorporate them well into power system modelling and hence achieve the best possible strategy to be adopted which its characteristics keep closer to reality. The most important uncertainties in network planning are load forecasting and market price errors. The proposed scheme is solved using non-dominated sorting genetic algorithms II, allowing the distribution company (DisCo) to exercise his/her personal preferences. To validate the effectiveness of the proposed scheme, simulations are carried out on a 33-bus distribution network and finally the attained results are discussed.

A Solution Compatible with Cost-Reliability for Multi-Stage Feeder Routing Problem with Considering Uncertainties

ABSTRACT This paper proposes a stochastic multistage expansion planning method in order to solve the mid-term and long-term optimal feeder routing problem. Pseudo dynamic behaviour of the network parameters and geographical constraints besides the associated uncertainties of future load demand and market price are incorporated into the method. The proposed method is solved from the DisCo viewpoints using particle swarm optimization algorithm which finally converges to a solution with minimum costs. The proposed cost function is the sum of feeders installation costs, power losses cost, cost of active purchased power from power market, and reliability costs. Meanwhile, the final solution must satisfy all the operation aspects of power system in acceptable levels. On the other hand, the implementation of the final strategy obtained from the proposed method of this paper, can increase the responsibility of the power system in lower costs. In this regard, distribution system can power its customers with higher power quality in acceptable reliability level and also in lower costs. The proposed method is applied on a large-scale distribution network and its practicability and also its effectiveness are analysed due to the simulation results.

A developed single-phase cascaded multilevel inverter with reduced number of circuit devices

ABSTRACT In this paper, an advanced configuration for multilevel voltage source inverters is proposed. The proposed topology can be used as symmetric and asymmetric inverter. In asymmetric mode, DC sources’ magnitudes are defined in a way that the number of output voltage levels gets more than the case when the symmetrical DC sources are applied. In this regard, to calculate the magnitudes of required DC voltage sources, several different solutions are proposed. In multilevel inverters, the overall cost, circuit size and so installation area, complexity of control scheme and reliability are directly dependent on the number of circuit devices needed. The provided comparison study among suggested inverter in all defined solutions, CHB and recently proposed converters validates that the proposed modular inverter uses reduced number of circuit devices. The provided simulation and experimental results confirm the feasibility of the proposed structure and show that the obtained results are in good agreements.

Modeling and Analysis of Resilience for Distribution Networks

Electric power distribution networks are constructed and expanded among wide geographical areas. Traditionally the focus of distribution networks planning is mainly on network reliability improvement with minimum cost considering the technical constraints. The aim of such vision is based-on the fact that distribution network outages occurred on the network component because of conventional faults with high frequency and low impact characteristics. Nowadays the power distribution networks encounter with unwanted weather conditions and natural disasters facing the network with high impact low probability events on distribution network that can be damage the network components widely and permanently. It can cause costumer interruption and loss of load with high financial cost. The aim of this chapter is the optimal planning of conventional electric distribution network based-on distribution network resiliency enhancement. In this work the optimal size and site of network component and its topology is determined using optimization algorithm. A resilient-based fitness function is proposed to meet the resilient network requirement. To model the effect of the natural disasters on resilient based distribution network planning, the geographical data for hurricane as a natural disaster is combined to create a spatial risk index map. In this work a new methodology is proposed to establish a rational relation between network component fragility curves, component geographical location and hurricane spatial risk index. The proposed method is tested on a real large scale distribution network.

Risk-based modelling of simultaneous reconfiguration of power distribution networks and allocation of distributed generations

ABSTRACT In this paper, stochastic modelling for optimally siting and sizing of distributed generations (DGs) and network reconfiguration are done simultaneously. Uncertainties of load forecasting and market price are well incorporated into the problem. The main goal of distribution company is to provide high reliability power with the lowest possible costs. So the proposed cost function includes DG units’ installation and operation cost, cost of purchased energy from transmission network, active and reactive power losses cost, reconfiguration cost and line upgrade cost. Besides, risk-based modelling of energy not supplied as an efficient reliability index is incorporated into the cost function in order to improve network reliability. Voltage limitation and thermal limit of feeders are implemented by fuzzy set theory. The Teaching–learning-based optimisation algorithm is used as a powerful tool in order to solve the problem. To validate the effectiveness of the suggested method, simulations are taken and the results are compared with respect to the initial configuration.

Total harmonic distortion minimisation in multilevel inverters using the teaching–learning-based optimisation algorithm

ABSTRACT In this article, the minimisation of total harmonic distortion (THD) of the output voltage of a multilevel inverter is studied. The harmonic component of output voltage in the inverter is reduced in THD minimisation. The output voltage THD in multilevel inverters is minimised by proper selection of switching angles. The teaching–learning-based optimisation algorithm is used to find the optimum switching angles in order to generate the desired voltage value in the possible minimum THD. Experimental and simulation results depict advantages of this approach compared to published papers which discus this concept using genetic algorithm. The experiments conducted on a seven-level inverter confirm the feasibility of this approach.

Multi-objective modelling of simultaneous reconfiguration of NMG-based distribution network and operation of different DERs

ABSTRACT A Micro-Grid (MG) is envisaged with ever increasing distributed energy resources (DERs) e.g. distributed generation, demand response and electrical vehicles. This paper suggests a method based on multi-objective modelling for day-ahead scheduling of Networked-MGs based distribution network in the presence of different DERs and also this method is able to find the daily reconfiguration instants. The proposed scheme is solved using NSGA-II from distribution network operator viewpoints, who is responsible for providing power demand in higher reliability level and lower costs. Besides, in the suggested scheme voltage deviation and voltage stability as efficient power quality criteria in distribution networks and emission pollutant reduction are incorporated as independent objective functions. Moreover, to quantify the influence of different load models, a 33-node distribution network is adopted with a load class mix of residential, industrial and commercial loads. Eventually, the obtained results are reported which verify the efficiency of the proposed method.