(1990). ENERGY FUNCTION ANALYSIS FOR POWER SYSTEM STABILITY. Electric Machines & Power Systems: Vol. 18, No. 2, pp. 209-210.

Energy function analysis for power system stability

Magnetically controlled reactors (MCRs) are usually used as three-phase shunt reactors. They have low harmonic distortion independent of the third harmonic current because most three-phase MCRs are delta connected. However, as arc suppression coils, MCRs are operated in the single-phase mode, and the harmonics can be much higher than those of three-phase MCRs. In this paper, the structure and the mathematical model of a two-stage saturable MCR (TSMCR) are proposed. There are two stages with different lengths and areas in the iron cores. The stages saturate at different times when the TSMCR outputs reactive current. The current harmonics of the first saturated stage can be compensated for when the second stage begins to saturate, to reduce the total harmonics of the output current. The mathematical model that reveals the distribution characteristics of the current harmonics for the TSMCR is also presented. A study of the mathematical model indicates that there are two key factors that affect the total current harmonics of the TSMCR. One is the parameter k, which represents the area ratio of the second stage to the first stage. The other one is the parameter m, which represents the ratio of the length of the first stage to the total length of the magnetic valve in the iron core. The simulations and experiments show that the maximum current harmonics of the novel MCR can be limited to 3.61% of the rated output current when k and m are chosen according to the theoretical mathematical model.

Modeling and Harmonic Optimization of a Two-Stage Saturable Magnetically Controlled Reactor for an Arc Suppression Coil

The multilevel converter, (MC) had been recommended for high- and medium-level power applications for decades. It is one of the most popular converters due to its ability to decrease the harmonic distortion in the output waveform without decreasing the converter power output. This paper presents the basic concept of four different types of multilevel converter: the neutral-point clamped, flying capacitor, cascaded H-bridge and modular. This paper also reviews five different modulation techniques for multilevel converters: pulse width modulation, space vector pulse width modulation, phase shifted carrier pulse width modulation, sinusoidal pulse width modulation and selective harmonic elimination pulse width modulation. In addition, recent publications regarding developments and improvements of fundamental concern to MCs and modulation techniques are reviewed in this paper. The implementation of MCs within renewable energy systems is also discussed here.

Reviews on multilevel converter and modulation techniques

Optimal energy management and control aspects of distributed microgrid using multi-agent systems

In the case of motors and generators, the benefits of using high-temperature superconducting (HTS) coils could be represented by the reduction of 50% in both losses and sizes compared to the conventional machines of the same rating. However, it is hard to establish the quench detection and protection devices for the HTS coils applied to the rotors of motors and generators. Therefore, the stability of the coils is lower than the quiescent coils applied to NMR, MRI, and so on. Therefore, it is important to improve the self-protection ability of HTS coils. We have been developing a novel self-protection method, which removes the insulation turn-turn winding and inserts various metal tapes instead of the insulation. In our previous research, the higher self-protection ability for the thermal disturbances in the HTS coils removed the insulation and inserted Cu tape has been proved. This paper presents the results of an experimental study for the quench current using the insulated, the noninsulated, and the Brass tape inserted HTS coils in liquid nitrogen and background magnetic fields. Also, the measured quench currents of each coil will be discussed.

The Transient Stability of HTS Coils With and Without the Insulation and With the Insulation Being Replaced by Brass Tape

Comparison of magnetically controlled reactor (MCR) and thyristor controlled reactor (TCR) from harmonics point of view

A power sharing scheme for voltage unbalance and harmonics compensation in an islanded microgrid

Summary
If sensitive loads are connected to the point of common coupling (PCC), compensation should be carried out in order to reduce PCC voltage harmonics. In this case, compensation is performed by the interface converters of distributed generation (DG) units. In this paper, a novel method is proposed for voltage harmonics compensation in islanded microgrids. The proposed method is capable of adjusting compensation percentage in proportion to the existing level of distortion at PCC. Also, this controller provides a proper sharing of compensation workload, considering the nominal capacity of DGs, which will improve the sharing of nonlinear load. Also, to decrease the asymmetry among phase impedances of microgrid, a novel structure is proposed to generate virtual impedance. At fundamental frequency, the proposed structure for the virtual impedance improves the control of the fundamental component of the power, and at harmonic frequencies, it acts to adaptively improve nonlinear load sharing among DG units. In the structures of the proposed harmonics compensator and the proposed virtual impedance, a self-tuning filter is used for separating the fundamental component from the harmonic components. This self-tuning filter decreases the number of the phase-locked loops. The simulation results in MATLAB/SIMULINK environment show the efficiency of the proposed approach in improving load sharing and decreasing voltage harmonics. Copyright © 2016 John Wiley & Sons, Ltd.

Non‐linear load sharing and voltage harmonics compensation in islanded microgrids with converter interfaced units

In this paper, a novel compensator based on Magnetically Controlled Reactor with Fixed Capacitor banks (FCMCR) is introduced and then power system stability in presence of this compensator is studied using an intelligent control method. The problem of robust FC-MCR-based damping controller design is formulated as a multi-objective optimization problem. The multi-objective problem is concocted to optimize a composite set of two eigenvalue-based objective functions comprising the desired damping factor, and the desired damping ratio of the lightly damped and undamped electromechanical modes. The controller is automatically tuned by optimization of an eigenvalue-based multi-objective function using Honey Bee Mating Optimization (HBMO) to simultaneously shift the lightly damped and undamped electromechanical modes to a prescribed zone in the splane so that the relative stability is guaranteed and the time domain specifications concurrently secured. The effectiveness of the proposed controller in damping low frequency oscillations under different operating conditions is demonstrated through eigenvalue analysis and nonlinear time simulation studies. The results show that the tuned HBMO-based FC-MCR controller which is designed by using the proposed multi-objective function has an outstanding capability in damping power system low frequency oscillations and significantly improves the power systems dynamic stability.

http://joape.uma.ac.ir/article_181_afb4e03f853a54808aba03f929a972eb.pdf

A Multi-Objective HBMO-Based New FC-MCR Compensator for Damping of Power System Oscillations

In order to deal with power quality problems under distortional and unbalanced load conditions, this paper presents a new control method for a four-wire three-phase unified power quality conditioner (UPQC) which is based on instantaneous power p-q theory. The proposed control approach is based on instantaneous power and is optimized by using a self-tuning filter (STF), without using any low-pass filters (LPFs) or phase locked loop (PLL), and without measuring load or filter currents. In this approach, the load and source voltages are used to generate the reference voltages of a series active power filter (APF) and source currents are used to generate the reference currents of a shunt APF. Therefore, the number of times that current is measured is reduced and system performance is improved. The performance of the proposed control approach is evaluated in terms of power factor correction, source neutral current mitigation, load balancing and mitigation of the current and voltage harmonics of distortional and unbalanced loads in a three-phase four-wire system. The results obtained by MATLAB/SIMULINK software show the effectiveness of the proposed control technique in comparison to the conventional p-q method.

/pdf/a-new-approach-based-on-instantaneous-power-theory-for-3y2guejtgj.pdf

Mahmoud Ebadian

Papers

Comparison of magnetically controlled reactor (MCR) and thyristor controlled reactor (TCR) from harmonics point of view

A power sharing scheme for voltage unbalance and harmonics compensation in an islanded microgrid

Non‐linear load sharing and voltage harmonics compensation in islanded microgrids with converter interfaced units

A Multi-Objective HBMO-Based New FC-MCR Compensator for Damping of Power System Oscillations

A New Approach Based on Instantaneous Power Theory for Improving the Performance of UPQC Under Unbalanced and Distortional Load Conditions