Conventional Sinusoidal Pulse Width Modulation Research Articles

Current Control System for PMSM in Overmodulation Range of Inverter

This paper proposes a novel current control system for a PMSM that can stably operate even in the overmodulation range of an inverter. Because an inverter generates harmonic components in this range, an instability problem in the conventional current control system usually occurs. For solving this instability problem, the idea of harmonic current compensation scheme has already been proposed. However, the effectiveness of this method depends directly on the harmonic current estimation accuracy.There are two new topics in harmonic component estimation that we use in our proposed current control system as follows: (1) the harmonic voltage estimation method that is based on the conventional sinusoidal PWM modulation technique, and (2) the harmonic current estimation method that estimates correctly both in the steady state and transient condition. The effectiveness of the proposed methods is confirmed by computer simulation and experimental results.

Inverted sine carrier for fundamental fortification in PWM inverters and FPGA based implementations

This paper deals with a novel natural sampled pulse width modulation (PWM) switching strategy for voltage source inverter through carrier modification. The proposed inverted sine carrier PWM (ISCPWM) method, which uses the conventional sinusoidal reference signal and an inverted sine carrier, has a better spectral quality and a higher fundamental component compared to the conventional sinusoidal PWM (SPWM) without any pulse dropping. The ISCPWM strategy enhances the fundamental output voltage particularly at lower modulation index ranges while keeping the total harmonic distortion (THD) lower without involving changes in device switching losses. The presented mathematical preliminaries for both SPWM and ISCPWM give a conceptual understanding and a comparison of the strategies. The detailed comparison of the harmonic content and fundamental component of the ISCPWM output for different values of modulation index with the results obtained for the SPWM is also presented. Finally, the proposed modulator has been implemented in field programmable gate array (FPGA- Xilinx Spartan 3) and tested with the proto-type inverter.

GENERATION OF CHAOS-BASED SPWM AND ANALYSIS OF ITS SPECTRAL PROPERTY FOR SUPPRESSION OF HARMONICS

There exists cluster harmonics around the multiples of carrier frequency in conventional sinusoidal pulse width modulation (SPWM) output waves. A new strategy for generation of Chaos-based SPWM (CSPWM) is proposed with the aim of reduction harmonic. A one-dimensional tent map is used to vary the frequencies of the triangular carrier wave so that the harmonics can be distributed continuously and equably over a wide frequency range. The new proposed CSPWM scheme is applied to a voltage source inverter. Research results show that it is effective on suppression of harmonics, moreover, it is easy to realize by microprocessor.

A novel modulation technique for a single phase H-bridge inverter

In this paper a novel space vector modulation method for single-phase inverters is presented. Mathematical analysis, simulation and comparison of conventional sinusoidal pulse width modulation (SPWM) techniques with the proposed space vector modulation for single-phase inverter are included. These modulation techniques are compared, evaluated and classified for different single-phase applications, including deadband effects. The proposed modulation method combines the flexibility of the well-known unipolar PWM scheme for single-phase inverters result in maximum harmonic mitigation. The new technique is suitable for simple digital implementation. Experimental results, obtained by a digital signal processor (DSP) board, are included.

Modeling and analysis of a single stage step-up/down three-phase AC to DC converter

In this paper, first the apportioning of null-space-vector duty ratio between two null-space-vectors for the conventional three-phase voltage source sinusoidal pulse width modulation inverter is derived. To achieve clean sinusoidal input current, adjustable power factor and bidirectional power flow and step-up/down output DC voltage, analytic duty cycle control laws based on the derived null-space-vector duty ratio are then derived. As a result, the popularly used state-space technique can be extended easily for modeling a process that allows to obtain any kind of the desired transfer functions and dynamic responses. Based on these dynamic responses obtained the regulators of closed loop control system can be designed or adjusted properly. Finally, some simulated and measured results are presented for demonstration.

Digitally-controlled PWM inverter modulated by multi-random technique with fixed switching frequency

A digitally controlled PWM inverter, modulated by a multi-random technique with a single fixed switching frequency, is proposed for uninterruptible power supplies. Multi-random pulsewidth modulation utilises a random phase-shift PWM scheme and a random pulse position PWM scheme, both driven at the same switching frequency. The multi-random technique reduces harmonics intensity, and thus reduces undesirable acoustic noise and mechanical vibration. The control scheme is based on instantaneous feedback signals of output voltage and capacitor current. The output voltage is therefore well regulated during sudden load disturbance, as confirmed by simulation results. An experimental prototype was built. When compared with the conventional sinusoidal PWM scheme, experimental results show better spectrum performance, very fast dynamic response, and a great reduction of acoustic noise.

Third-harmonic supply current minimization in single-phase AC/DC converters

One effect of the second-harmonic in the load-side current ripple of a single-phase AC/DC converter is to introduce an unwanted third-harmonic into the supply-side current. Although this can be neither eliminated nor reduced by either conventional selective harmonic or natural sinusoidal PWM strategies, it is shown that the use of a modified switching function in the selective strategy enables a considerable reduction to be achieved. Possible applications for the new strategy include single-phase AC/DC converter-fed DC drives and converters providing a DClink for inverter-fed DC drives.

Switching loss minimised space vector PWM method for IGBT three-level inverter

In an inverter-fed motor drive system, inverter output-current distortion is reduced by enhancing the switching frequency and the motor torque ripple; magnetic noise is also reduced as a consequence. However, the system efficiency is also reduced due to the switching loss; this, in turn, sets a limit on any further enhancement of the switching frequency. This is particularly the case for the IGBT three-level inverter, since it is used in high switching frequency applications: the number of switching devices is twice that of the two-level inverter, thus the switching loss problem is more serious. The authors describe a new PWM strategy for the three-level inverter with an ability to reduce switching loss. In comparison with conventional sinusoidal PWM methods generating almost the same distorted load current, every phase of the inverter can have its switching stopped for 120/spl deg/ in one period by this new method. According to the load power factor angle /spl beta/, if /spl beta//spl les/30/spl deg/ the no switching duration can be set just in the centre of the peak value region of the load current, hence the switching loss can be greatly reduced. The reduction of switching loss is not dependent on /spl beta/.

Low torque ripple drive of induction motor by multi-step PWN inverter.

In this paper, we propose a novel multi-step PWM inverter useful for the torque ripple reduction of an induction motor. The PWM waveform can be easily obtained by exchanging alternately neighbour two voltage vectors among six output voltage vectors together with a zero voltage vector every 60 degree interval.The basic principle and characteristics of the PWM inverter are shown at first. It is introduced that the harmonics Cn of the PWM voltage waveform approximately has the enough relation of _??_C6m-1/(6m-1)=C6m-1/(6m+1)_??_ to reduce the torque ripple of an induction motor by the cancellation of the 6m order power ripple components arising from the product of a fundamental component and 6m±1 harmonic components of the PWM waveform.And then, the driving characteristics of an induction motor by the proposed PWM inverter are investigated from some simulation and experimental results comparing with the conventional PAM, rectangular PWM and sinusoidal PWM inverter.The features of the PWM technique are high efficiency and low acoustic noise operations for the low torque ripple drive of an induction motor.The PWM technique may be suitable for the induction motor drive using relatively slow and large switching power devices such as GTOs.

A novel PWM scheme of voltage source inverters based on space vector theory

A novel PWM scheme which can considerably reduce harmonic currents is proposed. It is explained analytically that the harmonic currents depend on the amplitude and phase angle of the reference voltage vector, the inverter output voltage vectors used in a switching period, and the sequence of these output voltage vectors. In the novel PWM scheme, the switching sequence is selected so that the harmonic currents are minimum. An experimental system which generates the PWM patterns by software at real time is constructed. Compared with the conventional sinusoidal PWM scheme, it is confirmed that the current ripple is decreased and the spectrum is shifted and dispersed to a higher frequency region.