Nonperiodic Currents Research Articles

Tri-window compensator for loads with non-periodic current

This paper presents a new technique for the compensation of non-periodic load current. The method provides control references for three co-located devices, each corresponding to one moving calculation window and one decomposed part of the compensated current. They are slow compensator with high power rating, large calculation window, and low switching frequency; fast compensator with lower power rating, shorter calculation window, and higher switching frequency; and the reactive compensator which is an ordinary static VAR compensator (SVC). A fuzzy based adaptive window is proposed for the slow compensator to find the optimum window for different load characteristics. The technique is evaluated using real-world data and controller hardware-in-the-loop (HIL) implementation.

Extreme nonperiodic currents on the northeastern shelf of Sakhalin Island

Extreme nonperiodic currents on the northeastern shelf of Sakhalin Island

A four-leg unified series–parallel active filter system for periodic and non-periodic disturbance compensation

This paper presents a three-phase four-leg (3P4L) unified series–parallel active filter (USPAF) system, compensating for both periodic and non-periodic disturbances using a generalized non-active power theory (GNAP) based control strategy. The 3P4L USPAF system is realized by the integration of series and parallel active filters (AFs), composed of the two 3P4L voltage source inverters (VSIs) sharing a common dc-link capacitor. The GNAP theory was implemented previously in the parallel AF. In this study, the theory is proposed for the 3P4L USPAF system to compensate non-sinusoidal periodic and non-periodic currents and voltages. Distorted source voltages and unbalanced non-linear load currents compensation were verified simultaneously through the 3P4L USPAF system experimental prototype. Sub-harmonic and stochastic non-periodic current/voltage compensations were analyzed through simulations with Matlab/Simulink software. The simulation and experimental results showed that the theory proposed for the 3P4L USPAF system was applicable to non-active power compensation in three-phase four-wire (3P4W) systems under periodic and non-periodic disturbances.

A unified series-parallel active filter system for nonperiodic disturbances

This paper presents a 3-phase, 4-wire unified series-parallel active filter (USPAF) system for periodic and nonperiodic disturbance compensation using a generalized nonactive power theory. The USPAF system consists of a series active filter (AF), parallel AF, and split DC-link capacitors with the midpoint of the DC-link connected to the neutral wire. The generalized nonactive power theory is applicable to single-phase or multiphase, sinusoidal or nonsinusoidal, periodic or nonperiodic, and balanced or unbalanced electrical systems. The theory was implemented previously in a parallel AF. In this study, the USPAF system is proposed to compensate for the nonsinusoidal and nonperiodic currents and voltages. Distorted source voltages, source voltage sag, and unbalanced nonlinear load current compensation were simultaneously tested in the experiments. Subharmonic and stochastic nonperiodic current and voltage compensation were simulated in MATLAB/Simulink. Simulation and experimental results verified the validity of the generalized nonactive power theory for the compensation of periodic (nonsinusoidal) and nonperiodic current and voltage disturbances with the USPAF system.

Compensation-based nonactive power definition

This paper presents a new definition of nonactive current from which the definitions of instantaneous active and nonactive power are also derived. The definitions are consistent with the traditional power definitions and valid for single-phase and polyphase systems, as well as periodic and nonperiodic waveforms. The definitions are applied to a shunt compensation system. The paper elaborates on the compensation of three different cases of nonperiodic current: single-phase disturbance, three-phase subharmonics, and three-phase stochastic current. Simulation results give credibility to the applicability of the definition for a diversity of load currents. According to different compensation cases and the goals to be achieved, different averaging time intervals for the compensator are chosen which will determine the compensator's energy storage requirement and the extent of residual distortion in the source current.

Evaluation of a shunt active power conditioner with a modified control scheme under nonperiodic conditions

Nonperiodic waveforms are produced in power systems under various operating conditions; it is convenient to suppress such waveforms via the active filter dedicated to harmonics. An active power conditioner is scrutinised and modified to treat both periodic and nonperiodic waveform distortions. A new consistent and practical index to assess the distortion of nonstationary and nonperiodic signals is established. Its fidelity and potential for real applications are also addressed. The conditioner operation is examined under nonperiodic load currents with different types of nonperiodicity. The proposal is compared with both Fryze's and instantaneous power control techniques. The active conditioner is shown to be competent in compensating periodic and nonperiodic current distortions.

A numerical analysis of time-dependent two-dimensional magnetic fields

The nonlinear diffusion equation as applied to two-dimensional time-dependent magnetic fields is solved with a finite element algorithm. This algorithm permits the analysis of problems possessing complex geometries, induced eddy currents, permanent magnets, and nonperiodic excitation currents. The numerical procedure utilizes implicit time stepping with an iterative scheme no solve the resulting set of equations. Two examples of its application are presented.