Sharif Digital Repository

Accurate power factor definitions are of great importance for industries due to the fact that they affect the billing strategy. They also considerably affect the generation and distribution losses of the power system. At the moment, there are some ambiguities in power definitions to be used for this purpose. In recent years, because of a rapid growth in industry and the use of variable loads such as electrical furnaces and variable speed motors, there is a need for fast compensators that are capable of tracking load changes. One of these facilities is TSC, a capacitor bank that is controlled by static switches (thyristors). In this paper, the performance of these compensators in power factor... 

This paper presents a new nonlinear current control strategy based on backstepping control and high-order sliding mode differentiator in order to employ distributed generation (DG) unit interfacing converters to actively compensate harmonics/interharmonics of local loads. The converter-based DG unit is connected to a weak grid (with uncertain impedance) and local load (that can be parametrically uncertain and topologically unknown) through an LCL filter. The proposed strategy robustly regulates the inverter output currents and delivers pure sinusoidal, three-phase balanced currents to the grid. The new controller demonstrates the robust performance and robust stability of the DG unit system... 

In this paper; control and parallel operation of multi-modular 3-phase inverters are investigated. Active current sharing approach is selected as the fundamental control technique for parallel operation of inverters due to its high reliability. Among different methods for active current sharing; average load sharing is employed due to its acceptable stability. For this purpose; optimal control strategy and Linear Quadratic Regulator (LQR) method is proposed to parallel 3-phase 4-leg inverters. The system is modeled to be compatible and solvable with LQR equations. Using dq technique; 3-phase inverters are paralleled and controlled. The proposed method obtains both current sharing and voltage... 

The vision of advanced long-term evolution (LTE-A) project is set to ultimate increase of network capacity in heterogeneous networks (HetNets). In HetNets with small cell configuration, a considerable majority of user devices is eventually connected to the macrocell base station (MBS), while small base stations (BSs), such as femtocell access points (FAPs), are still without any user. This results in unbalanced load and reduces the data rate of macrocell user equipment (MUE). In this paper, a method is proposed for load balancing among FAPs, while desired throughput is achieved. The proposed method uses the estimated received signal strength from different BSs and adjusted pilot signals.... 

This paper proposes a new control strategy for the islanded operation of a multi-bus medium voltage (MV) microgrid. The microgrid consists of several dispatchable electronically-coupled distributed generation (DG) units. Each DG unit supplies a local load which can be unbalanced due to the inclusion of single-phase loads. The proposed control strategy of each DG comprises a proportional resonance (PR) controller with an adjustable resonance frequency, a droop control strategy, and a negative-sequence impedance controller (NSIC). The PR and droop controllers are, respectively, used to regulate the load voltage and share the average power components among the DG units. The NSIC is used to...