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Voltage source inverters (VSIs) are widely utilized in motor drives and renewable energy integration. Pulsewidth modulation (PWM)-VSIs are employed to generate a controlled alternating current (ac) waveform from a finite direct current (dc) link voltage. When the amplitude of the reference signal exceeds its linearity limit, which is Vdc/2 for sinusoidal PWM (SPWM), a PWM-VSI operates in the overmodulation region which causes a significant reduction in the quality of the output ac voltage and the dc bus utilization (DBU). In this article, first, two adaptive optimal third harmonic injection (AOTHI)-PWM schemes are proposed to minimize voltage total harmonic distortion (THD) (AOTHI-THDv) and maximize DBU (AOTHI-DBU). To validate the effectiveness of the proposed schemes, the resulting THD and DBU values are compared with existing continuous/discontinuous PWM scheme results. Then, to meet the practical implementation in microcontrollers, one generalized AOTHI-PWM is formulated to adaptively generate an optimal injection level using two proposed mathematical models. Aside from the simulation evaluations, the performances of the proposed schemes are also validated through experimental comparisons, which show a superiority over the other PWM schemes. [ABSTRACT FROM AUTHOR]

In this article, an optimal design procedure of shunt RC damped LCL filter is discussed. The proposed design procedure finds the minimum damping resistance to guarantee the stability of the grid-current controller without affecting the effectiveness of the filter. This minimum value is derived using the factorized filter input admittance and filter forward transadmittance. The proposed factorization procedure allows us to have an analytical expression of system poles and zeros. Moreover, the minimum damping resistor is determined upon the desired crossover frequency and the desired phase margin of the grid-current controller. After that, an objective function is assumed, and an optimization problem is formulated to minimize the physical size of the filter by minimizing the total capacitance and inductance and by minimizing the filter ripple content as well. Accordingly, the proposed objective function minimizes the filter physical size and filter power losses and, hence, enhances filter's efficiency. A prototype demonstrates and validates the proposed filter design and analysis experimentally. [ABSTRACT FROM AUTHOR]

Full time-domain analysis of the impact of third-harmonic injection (THI) on the output phase voltage waveform of a two-level voltage source inverter is presented, and the total harmonic distortion (THD) performance of different pulsewidth modulation (PWM) methods is provided. Two well-known third harmonic injection PWM (THIPWM) schemes are adopted from the literature: THIPWM6 and THIPWM4, where the THI amplitude is one-sixth and one-fourth the amplitude of the sine-wave, respectively. In this article, three analysis-derived developments are provided. Global optimal THIPWM ensures minimum THD in all linear region, unlike other THIPWM schemes. A unique THI-level is selected for each modulation index from the proposed curve or the compacted lookup table. The best suboptimal THIPWM method is provided that employs a linear injection applied over the linear modulation. To achieve better THD performance and to satisfy different operation criteria, several suboptimal THIPWM methods are proposed. Comparisons between these schemes must define performance indices, and this is carried out using various objective functions, such as the sum of squared error and area under the curve. The impact on extending the linear region is also presented. This study examines when THIPWM is useful and which injection level is best. Experimental verifications support the presented analysis. [ABSTRACT FROM AUTHOR]

This paper presents the mathematical and harmonic analyses of output phase voltages of three-phase voltage source inverters which employ a hybrid two-dimensional–threedimensional (2-D–3-D) space vector modulation (SVM) voltage control algorithm. The explicit time-domain representation of the harmonic components in addition to the total harmonic distortion (THD) of the output phase voltages is given in terms of system and control parameters. This paper also investigates the harmonic characteristics and THD performance against the linearity of the modulation region which helps in the harmonic performance and design studies of such inverters employing the hybrid 2-D–3-D SVM. The fundamental component of the output voltages follows the reference with lower THD in the linear modulation region rather than the overmodulation region. Experimental results are used to validate these analyses as well as the effectiveness of the hybrid 2-D–3-D SVM algorithm for generating balanced and low THD phase voltages. [ABSTRACT FROM PUBLISHER]