No abstract

No abstract

This paper presents variable common mode injection pulse width modulation (VCMIPWM) technique to reduce the neutral-point voltage variations in three-level neutral-point-clamped (NPC) inverter. The neutral-point voltage varies with the modulation index and the variation is high in the low modulation index region. Therefore, proper common mode voltages are calculated for various modulation index regions and are carefully injected with the reference phase voltages. The calculation is based on equalizing the switching times of the zero/redundant vectors in a switching cycle for various modulation index regions. The simulation results show the improvement in the neutral-point voltage balancing of the inverter in the VCMIPWM scheme compared with the sinusoidal pulse width modulation (PWM). The proposed PWM is implemented in field programmable gate array (FPGA) and the experimental results are shown to verify the practicability of the proposed method.

No abstract

Original scientific paper Distributed Generation (DG) units are also called Dispersed Generation, Decentralized Generation and Embedded Generation. They are normally small generating plants, connected directly to either distribution side or customer side. The installation of inverter-based distributed generation (DG) has increased rapidly in recent years. This higher penetration level may result in the increased level of harmonics, which could exceed the permissible harmonic distortion level. The penetration level of DG is restricted by harmonic distortion, because of the nonlinear current injected by inverter based DG units. In this work, the maximum DG penetration level is determined, by considering the harmonic limits. The harmonics are determined by using the Decoupled Harmonic Power Flow (DHPF) approach. The constraints of this proposed problem include power balance equations, bus voltage limits, total and individual harmonic distortion limits specified by IEEE-519 standard. The problem is solved by using Particle Swarm Optimization (PSO) algorithm based optimization technique. Simulation results are obtained by MATPOWER/MATLAB in IEEE 30 and IEEE 57 bus test systems and the results prove the effectiveness of this proposed approach. Keywords: Decoupled Harmonic Power Flow (DHPF); Distributed Generation (DG); harmonic distortion; Particle Swarm Optimization (PSO)Na optimizaciji roja čestica utemeljeno optimalno razmještanje i kapacitet decentralizirane proizvodnje uzimajući u obzir harmonijska ograničenjaIzvorni znanstveni članak Jedinice decentralizirane proizvodnje (DG units) također se nazivaju raspršenom proizvodnjom, decentraliziranom proizvodnjom i ugrađenom proizvodnjom. Uobičajeno su to male elektrane, direktno povezane bilo s distribucijom ili potrošačem. Uspostava decentralizirane proizvodnje na temelju invertera rapidno se povećala zadnjih godina. To može biti rezultat povećane razine sekundarne frekvencije koja može prekoračiti dopušenu razinu harmonijskog izobličenja. Razina prodiranja DG ograničena je harmonijskim izobličenjem zbog nelinearne struje iz DG jedinica na bazi invertera. U ovom je radu određena maksimalna razina penetracije DG, uzimajući u obzir harmonijska ograničenja. Harmonici su određeni pristupom odvojenog harmonijskog protoka snage (DHPF). Ograničenja ovog predloženog problema uključuju jednadžbe balansiranja snage, ograničenja napona sabirnice, ukupne i pojedinačne granice harmonijskog izobličenja specificiranog normom IEEE-519. Problem je riješen primjenom tehnike optimizacije pomoću algoritma optimizacije roja čestica. Rezultati simulacije dobiveni su primjenom MATPOWER/MATLAB u sustavima ispitivanja sabirnice IEEE 30 i IEEE 57, a rezultati dokazuju učinkovitost predloženog pristupa.Ključne riječi: decentralizirana proizvodnja; harmonijsko izobličenje; odvojeni harmonijski protok snage; optimizacija roja čestica