Total Harmonic Distortion Improvement Research Articles

Power quality analysis of grid-connected solar photovoltaic generators in Brazil

The typical electrical distribution system shows a passive characteristic in relation to power flows (i.e. unidirectional power flows from substation to loads along the feeder). However, with the inclusion of solar photovoltaic (PV) generators along the feeder, this behavior is changed, and characteristics related to power quality, such as voltage level and total harmonic distortion (THD), may be affected. This paper presents the analysis of power quality in a feeder of the urban grid in the city of the Florianopolis, Brazil, with the integration of grid-connected PV systems as distributed generation. The analysis of power quality is based on real measurements of THD on an existing 12kWp PV pilot plant installed in the urban environment, and power flow simulations of a hypothetical PV system of 4.2MWp distributed in the same area, using the ANAREDE software. The power flow simulations allowed assessing the voltage level, the direction of power flow and loading of the distribution lines. The introduction of limited amounts of PV generation as distributed generation in the urban environment was found to be beneficial in several aspects: better voltage profile; power loss reduction and improvement in total harmonic distortion of the voltage (THDv). Furthermore, photovoltaics as a distributed generation source can also postpone feeder capacity upgrading investments.

Total harmonic distortion improvement for elliptical miniature loudspeaker based on suspension stiffness nonlinearity

This article reports the effect of geometric modification of diaphragm on the total harmonic distortion (THD) for an elliptical miniature loudspeaker by systematically investigating and modifying suspension stiffness. Three diaphragms, typified by different track patterns on the concave ring are simulated and experimented. Initially, the prototype specimens were tested for stiffness curves and electroacoustic parameters by laser vibrometry. Further, the stiffness curves for three sample designs were numerically modeled using finite element analysis (FEA). The loudspeaker is also modeled using equivalent circuit method (ECM) for simulating THD. As a result of employing Runge- Kutta method for the solution of a coupled system of ordinary differential equations, THD was calculated and subsequently presented as a function of frequency. In addition, their THD was measured in a standard anechoic chamber and compared with simulations. It is found that the effect of track patterns on the sound pressure level is absolutely insignificant. On contrary, effect on THD is observable and leads to the conclusion that the diaphragm with curved tracks outperforms other diaphragms (partial straight and straight tracks). The reliability of simulation and its confirmation with the measurement has assured the possibility of simulating THD by FEA and analytical method for design optimization of track patterns.

Induction Motor Drive THD Improvement with Multi-Level Inverter

Multi-level voltage source inverters offer several advantages such as a better output voltage with reduced total harmonic distortion (THD), reduction of voltage ratings of the power semiconductor switching devices and also the reduced electro-magnetic interference problems etc. This paper presents the application of Fast space vector pulse width modulation (SVPWM) method for multi-level diode clamped inverter feeding a three-phase Induction motor. The algorithm is independent of the number of inverter levels. In this the three vectors nearest to the reference vector are identified and their corresponding duty cycles are found. These values remain same regardless of number of inverter levels and the location of reference vector.

Experimental Verifications and Simulations of Magnetic Motor of Circular Miniature Loudspeaker for Total Harmonic Distortion Improvement

The reduction in total harmonic distortion of miniature loudspeaker is reported by investigating the force factor (Bl(x)). Micro tensile testing is employed to get Bl(x) vs x curves, which verify finite element simulation. Furthermore, magnetic system of miniature loudspeaker is modified to obtain tailor made Bl(x) vs x curves. Based on it, prototypes are fabricated, which is followed by total harmonic distortion and sound pressure level measurements in an anechoic chamber. Measurements reveal a significant reduction in total harmonic distortion without affecting the sound pressure level.

Linearization Technique for Source-Degenerated CMOS Differential Transconductors

A supplementary linearization technique for CMOS differential pairs with resistive source degeneration is proposed. The approach exploits an auxiliary (degenerated) differential pair to drive the bulk terminals of the main pair. Transistor-level simulations on a design using a 0.25-mum process and powered with 2.5 V and 1 mA, show that total harmonic distortion (THD) in the voltage-to-current conversion is decreased by 10 dB (for an input differential signal with a peak amplitude of 0.5 V and for frequencies up to 100 MHz) compared to the traditional source-degenerated transconductor. This THD improvement is achieved with a negligible increase in power consumption.

Application of Double Gate Graded-Channel SOI in MOSFET-C Balanced Structures

This work studies the linearity of conventional and Graded- Channel (GC) Gate-All-Around (GAA) devices when applied in 2- MOS and 4-MOS balanced structures operating as tunable resistors. The study has been performed through device characterization and two-dimensional process and device simulations. Total harmonic distortion (THD) and third order harmonic distortion (HD3) have been evaluated. When taking into account similar on-resistance, the use of the GC GAA transistors in both 2-MOS and 4-MOS structures improves the linearity. The use of GC GAA devices in 2-MOS balanced structures allows a reduction of the gate overdrive voltage of 22.5% without degrading THD and HD3. On the other hand, the use of GC GAA devices in 4-MOS structures leads to an improvement in both HD3 and THD by 7 dB for devices with similar channel length at the same gate voltage overdrive.

Linearity improvement in biquadratic transconductor-C filters

A new technique for improving the linearity performance in biquadratic transconductor-C filters is presented. This improvement has been achieved by applying some modifications to the filter topology which considerably relax the linearity requirement on transconductor circuits. Using very simple transconductors, 30 dB improvement in total harmonic distortion compared to the conventional approach has been observed.

Phase-Plane-Derived Distortion Modeling of a Fast and Accurate Digitizing Sampler

Continued efforts to model the distortion behavior of custom-designed digitizing samplers for accurate measurement of dynamic signals are reported. This work is part of ongoing efforts at the National Institute of Standards and Technology (NIST) to advance the state of the art in waveform sampling metrology. In this paper, an analytic error model for a sampler having a -3-dB 6-GHz bandwidth is described. The model is derived from examination of the sampler's error behavior in the phase plane. The model takes as inputs the per-sample estimates of signal amplitude, first derivative, and second derivative, where the derivatives are with respect to time. The model's analytic form consists of polynomials in these terms, which are chosen from consideration of the voltage dependence of the digitizer input capacitance and the previously studied error behavior in a predecessor digitizer. At 1 GHz, an improvement in total harmonic distortion from -32 to -46 dB is obtained when model-generated sample corrections are applied to the waveform. The effect of timebase distortion in the sampling system is also accounted for and corrected. The inclusion of second-derivative dependence in the model is shown to improve the model's fit to the measured data by providing fine temporal adjustment of the fitted waveform

The nonlinearity of high-radiance light-emitting diodes

Distortion measurements have been performed on a series of Burrus-type LED's as a function of device structure, type of dopant, and dopant concentration in the active layer of devices. The results of measurements show that the total harmonic distortion (THD) in double heterostructure LED's is relatively insensitive to the type and amount of dopant in the active layer provided the ratio of the active layer thickness <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</tex> to diffusion length <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</tex> is less than one. For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d/L &gt; 1</tex> an improvement in THD is observed by about 20 dB to a value of -50 dB at 100 mA dc and 100 mA peak-to-peak modulation currents. The improvement in the linearity is attributed to the reduction of the influence of the heterostructure boundary on the minority carriers in the active layer of LED's.