Inverter Output Waveform Research Articles

Development of a class-D audio amplifier with switch-mode rectifier front-end and its waveform control

This study presents the development of a switch-mode class-D audio power amplifier and its robust waveform control. First, a pulse-width modulated inverter is designed and implemented to have successful high-frequency switching operation. Then a robust two degree-of-freedom control scheme is proposed to let the inverter-fed loudspeaker possess close and robust voltage arbitrary waveform tracking characteristics within wide audio frequency range. The waveform tracking performance of the developed inverter is evaluated under resistor load and loudspeaker load with the commands of varying-frequency sinewave, random signal and actual music signals. Finally, a front-end flyback switch-mode rectifier (SMR) is developed and employed to establish well-regulated and boostable DC-link voltage for the followed inverter. Significant improved inverter output waveform tracking performance can be obtained. Meanwhile, good line drawn power quality is achieved. Some experimental results are provided to demonstrate the performance of the whole SMR-fed switch-mode audio system.

Practical implementation of a digital signal processor controlled multilevel inverter with low total harmonic distortion for motor drive applications

This paper presents a digital signal processor (DSP) based algorithm to generate three-level output voltage using H-Bridge multilevel inverter (MLI). The developed sinusoidal pulse width modulation (SPWM) scheme is employed to achieve lower harmonic contents in the output waveforms of inverter. Since SPWM scheme does not utilize vector positions, any pre-calculated switching states are not required. In addition to this advantage of conventional SPWM, modulators eliminate only base band harmonics due to regular control scheme. Therefore, neglecting the side band harmonics limits the efficiency of SPWM scheme. The harmonics located in the side bands of carrier frequency are also eliminated by the enhanced SPWM scheme proposed in this study. The validation of the modelled system is verified with the total harmonic distortion (THD) analyzes. The control algorithm is developed using TMS320F2812 DSP that is a 32-bit fixed-point processor operating at 150 MHz. The simulation and experimental results are compared to previous studies. The THD ratios of phase voltages and currents are measured loading the inverter with a three- phase 3 kW asynchronous motor. The lowest THD ratios of voltage and current are obtained at 1.9% and 0.4%, respectively.

Modeling the Overshooting Effect for CMOS Inverter Delay Analysis in Nanometer Technologies

With the scaling of complementary metal-oxide-semiconductor (CMOS) technology into the nanometer regime, the overshooting effect due to the input-to-output coupling capacitance has more significant influence on CMOS gate analysis, especially on CMOS gate static timing analysis. In this paper, the overshooting effect is modeled for CMOS inverter delay analysis in nanometer technologies. The results produced by the proposed model are close to simulation program with integrated circuit emphasis (SPICE). Moreover, the influence of the overshooting effect on CMOS inverter analysis is discussed. An analytical model is presented to calculate the CMOS inverter delay time based on the proposed overshooting effect model, which is verified to be in good agreement with SPICE results. Furthermore, the proposed model is used to improve the accuracy of the switch-resistor model for approximating the inverter output waveform.

Performance of grid connected inverter with maximum power point tracker and power factor control

Detailed analysis, simulation and hardware results of grid connected inverter with maximum power point tracker and power factor control in Malaysian climate are presented. A six-switch topology inverter with symmetrical pulse width modulation (PWM) switching technique is used. A low-pass filter is incorporated in the circuit to filter out unwanted harmonics and produce a sinusoidal AC current. Low total harmonic current distortion at the inverter output can be achieved. The three-phase PWM switching pattern was developed using Xilinx FPGA. The developed system is also capable of adjusting the power factor to unity. A 3 kVA power transformer with a 1:2 ratio is constructed to provide galvanic isolation for better circuit performance and circuit protection. Hardware results for proposed solar photovoltaic inverter configuration interconnected to the grid are also presented. From the experimental results, it is confirmed that the harmonic distortion of the inverter output waveform is within the limits laid down by the utility companies.

Three-phase three-level voltage source inverter with low switching frequency based on the two-level inverter topology

A new configuration of the three-phase three-level voltage source inverter has been presented. The proposed inverter is based on the two-level inverter. The inverter is built of one two-level conventional inverter, an auxiliary circuit which comprises of three bidirectional switches, and two bulk capacitor banks. A selected harmonic elimination control scheme is employed to achieve lower harmonic contents in the inverter output waveforms. Two-level inverter switches operate at the line power frequency (50 Hz) whereas the auxiliary circuit switches operate at twice line power frequency (100 Hz). To validate the proposed inverter, a low power prototype inverter has been designed and implemented; analytical, simulation and experimental results have been provided.

Short-circuit energy dissipation modeling for submicrometer CMOS gates

A significant part of the energy dissipation in static complementary metal-oxide-semiconductor (CMOS) structures is due to short-circuit currents. In this paper, an accurate analytical model for the CMOS short-circuit energy dissipation is presented. First, the short-circuit energy dissipation of the CMOS inverter is modeled. The derived model is based on analytical expressions of the inverter output waveform which include the influences of both transistor currents and the gate-to-drain coupling capacitance. Also, the effect of the short-circuiting transistor's gate-source capacitance on the short-circuit energy dissipation, is taken into account. The /spl alpha/-power law MOS model that considers the carriers' velocity saturation effect of submicrometer devices is used. Second, the inverter model is extended to static CMOS gates by using reduction techniques of series- and parallel-connected transistors. The results produced by the suggested model for a commercial 0.8-/spl mu/m process, show very good agreement with SPICE simulations.

Calculation of maximum power in a utility-interactive photovoltaic-generating system by using PWM current-source inverter

In a utility-interactive photovoltaic (PV)-generating system, a PWM inverter is used for the connection between the PV arrays and the utility. The inverter is controlled to keep the output power at the maximum point for the PV. Although the PV power can be easily found by using the measured PV voltage and PV current, the installation of two detectors in the system is indispensable to obtain the exact PV power. In system operation with the maximum power that is fed into the utility, the PV does not always operate at the maximum point of PV output power because of power losses in the system. It has been reported that the use of the measured ac voltage or ac current on the inverter output side can exclude system losses from consideration and achieve system operation with maximum utility power. In this manner, however, since the ac output waveforms of the PWM inverter consist of many pulse trains, a filter circuit may be necessary for the detector to obtain the exact values of the ac output. This paper proposes a method of calculation of the utility power in the PV-generating system by using a PWM-current source inverter. In this system, only the PV current is measured, and it is employed for power calculations in combination with the control parameter of the PWM inverter. Since the proposed approach monitors the utility power instead of the PV power, control that does not need to take system losses into consideration can be achieved. This paper presents a method of calculation of the power for a single-phase–inverter PV system and gives basic experimental characteristics. An application of the proposed method to a three-phase PWM inverter–PV system is also described, and experimental results are given. © 1998 Scripta Technica, Electr Eng Jpn, 125(1): 55–64, 1998

A centroid-based PWM switching technique for full-bridge inverter applications

A novel centroid-based pulse-width-modulation (PWM) switching strategy is proposed which is suitable for full-bridge inverter applications. This method is evaluated, and its performance is compared with existing PWM switching strategies. The performance evaluation and comparison are based on the total harmonic distortion (THD) and number of pulses per cycle of the inverter output waveform. The objective of the new switching strategy is to minimize both the THD and low-order harmonics. Simulation results show that this technique yields a significant improvement in performance. In addition, a hybrid switching sequence is developed for the proposed scheme, which can lead to further reduction in switching losses.

A single-phase delta-modulated inverter for UPS applications

The performance characteristics of the rectangular wave delta modulation (RWDM) scheme for uninterruptible power supply (UPS) applications is investigated. Normalized characteristic curves that show the effect of various modulator parameters on the frequency spectrum of the inverter output voltage are obtained using discrete Fourier transform (DFT) and harmonic analysis techniques. The performance of a single-phase half-bridge inverter with an LC filter is discussed, and experimental results are provided to validate the predicted and simulated results. It is shown that the harmonic content of the inverter output waveform can be controlled through the control of the modulator parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetic noise caused by output waveform harmonics of voltage‐source inverters

AbstractHarmonic components included in the output waveforms of inverter circuits cause magnetic noise, that is, audio noise, from the output transformers or load motors. To estimate the magnetic noise due to the harmonic components, we have already proposed the equivalent noise voltage Es and current Is.In this paper, by applying the aforementioned Es, we compare quantitatively the magnetic noise in the various ordinary voltage‐source inverters, both PWM inverters with multipulse waveforms and PAM inverters with multistep waveforms. Then, to reduce the magnetic noise, the output waveforms of the PWM inverters are improved by applying Es into the idea of harmonic elimination. Moreover, by employing PAM system as voltage regulation in the aforementioned method, the more improved output waveforms can be obtained with lower noise and also lower distortion.

Magnetic Noise Caused by Output Waveform Harmonics of Voltage Source Inverters.

Harmonic components included in the output waveforms of inverter circuits cause magnetic noise, that is, audio noise, from the output transformers or load motors. In order to estimate the magnetic noise due to the harmonic components, we have already proposed the equivalent noise voltage Es and current Is.In this paper, by applying the above Es, we compare quantitatively the magnetic noise in the various ordinary voltage source inverters, both PWM inverters with multi-pulse waveforms and PAM inverters with multi-step waveforms. Then, in order to reduce the magnetic noise, we improve the output waveforms of the PWM inverters by applying Es into the idea of harmonic elimination. Moreover, by employing PAM system as voltage regulation in the above method, we can get the more improved output waveforms with lower noise and also lower distortion.

Study on magnetic noise caused by harmonics in output voltages of PWM inverter

Harmonic components included in the output waveforms of inverter circuits cause magnetic noise from the output transformers or load motors. Functions to estimate the magnetic noise caused by the harmonics are proposed. After confirming the relationship between the proposed functions and the magnetic noise by experiments, the authors compare the magnetic noise qualitatively in several output waveforms of PWM inverters, considering their distortions. By applying those functions, those waveforms that are more noisy can be predicted. >

A Study on Harmonic Elimination Method of PWM Inverter Fed Induction Motor System Using Walsh Series

Microprocessor control of power electronics systems offers the possibility of improvements in variability, maintenance and servicing, and increased control flexibility. This paper describes the new algorithm for elimination of unwanted harmonics and control of the fundamental amplitude in the three phase PWM inverter output waveform. in other words, this paper is presented technique of the particular harmonics eiimination(PHE) by waish series in three phase PWM inverter output waveform. A microprocessor(8086 CPU) - controlled three phase induction motor system realizing this algorithm is presented. It is designed for a three output voltage in the 1~45Hz inverter with the 5th and 7th harmonics eliminated, and with the fundamental wave amplitude proportional to the output frequency. The performance of the proposed method has been greatly improved with respect to an earlier realization proposed by the authors. In the future, the proposed PWM pattern by Walsh series, is effective not only to the induction motor but also to the other electromagnetic machine such as voltage regulator, UPS.

Simulation of unstable oscillations in PWM variable-speed drives

In several recent technical papers, limit-cycle instabilities of voltage source inverter-fed drives at low speeds have been attributed to the switching effects of the inverter or slight jitter in the output waveform of a proprietary LSI pulsewidth-modulated device. A study of such limit-cycle instabilities using two simulation techniques is presented. One is full simulation including the effects of inverter harmonics, anti-overlap delays, open-circuit voltages and output waveform jitter, the other is a reduced-order simulation that neglects inverter output harmonics and other output waveform defects. These simulations form part of a commercial software package under development. The simulation results indicate that the instabilities are inherent in the inverter source impedance/induction motor combination and are relatively independent of inverter output waveform harmonics, jitter, and other defects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Improving PWM inverter output waveform by use of repetitive control with regard to asynchronous interferences.

Improving PWM inverter output waveform by use of repetitive control with regard to asynchronous interferences.

PWM Systems in Power Converters: An Extension of the ``Subharmonic'' Method

In this paper the extension of the subharmonic method for pulse-width modulation (PWM) systems, in the case in which the ratio between modulating and carrier wave amplitudes can be varied from 0 to ?, is studied in an analytical way. This method allows us to obtain an inverter output waveform variable continuously from a nearly sinusoidal to a square wave and to increase somewhat the amplitude of the fundamental output wave without a significant worsening of the harmonic content, a feature particularly useful for drives with wide speed variations or which need an optimized use of dc power supply.

Technique for pulse dropping in pulse-width modulated inverters

The maximum output voltage obtainable from a pulse-width modulated inverter is less than that obtained when the inverter output waveform is a square wave of wanted frequency. Therefore, in order to realise the full potential of the inverter it is necessary to make the transition from a PWM output waveform to a square wave. Due to the practical limitations of the power circuit, it is not possible to reduce the width of unwanted pulses in the PWM waveform gradually to zero, but instead, pulses of a finite width must be dropped abruptly from the waveform. This results in step changes in the output voltage which can produce large current transients in the power circuit and the load. It is shown that the traditional method of pulse dropping is unsatisfactory and a new method is proposed which produces much smaller step changes in output voltage.

Invertor system stability analysis

A single phase bridge inverter system is analyzed. It is assumed that the inverter is used as a closed loop voltage regulated. source of ac power. The inverter output waveform is pulse width modulated to control the output voltage which is supplied to a general linear filter. A feedback signal which is a function of the filter output is compared with a reference constant to deliver the error signal which determines the pulse width. Stability theorems based on Liapunov's methods as applied to discrete control systems are used to determine the conditions for asymptotic stability of the closed loop inverter system. Necessary and sufficient condition for stability are derived. Several digital computer generated plots of the output voltage waveform are shown both for stable and unstable operating conditions. Systems with linear parts which have distinct or repeated eigenvalues that are either real or complex may be analyzed using this method.