Resampled pulse width modulation methods for high-bandwidth power electronic amplifiers

This work investigates modifications to the existing digital sampling methods for pulse width modulation of power electronic amplifiers so that faster and more accurate control can be achieved. It proposes resampled PWM as a generalisation of the existing methods and presents simulations and experiments that demonstrate its superior performance. Power hardware in the loop experiments are also presented as a demonstration of an application which demands both high bandwidth and high amplifier power levels and which benefits from the improved controllable bandwidth of resampled PWM

FPGA implementation of an arbitrary resample rate, first order hold (FOH), pulse width modulator

This paper presents an FPGA implementation of an advanced pulse width modulator which combines a first order hold (FOH) with phase accumulator carrier pulse width modulation (PACPWM) for significantly reduced phase delay, and bandwidth extension in multilevel applications. The FOH block supports arbitrary resampling rates and operates in a single clock cycle for simple integration into multi-rate or asynchronous systems. The proposed modulator is validated experimentally, with performance matching that predicted for both FOH and zero order hold (ZOH). For PWM with 8 kHz carrier frequency and 50.4 kHz resampling frequency, a 15 degree phase delay advantage is demonstrated for FOH compared with ZOH, across the 5-10 kHz modulation band

Advanced resampling techniques for PWM amplifiers in real-time applications

Regularly sampled pulse width modulation (PWM) has been a mainstay of the power electronics community since the advent of digital controllers. In this form of PWM the modulating signal is sampled only at either the peaks and/or the troughs of the triangular carrier waveform, then held constant until the next sampling instant, which allows ample time for the calculation of switching instants. Unfortunately, it produces phase and amplitude distortion of the modulating signal that can be significant at low pulse numbers. In applications where the desired modulating signal is not known a priori, this phase delay can become a critical limitation. The analogue alternative to regular sampling is naturally sampled PWM, where the modulating signal is permitted to vary as a continuous waveform. This form of PWM does not apply any phase or amplitude distortion to the modulating signal. True natural sampling is, however, impossible to implement on the digital control platforms that are used in modern power electronics applications. In this paper, a type of hold circuit known as a First-Order Hold (FOH) circuit is used in conjunction with the technique known as resampled regular PWM to improve upon the limitations of regular sampling. It is found that this augmentation to the PWM strategy improves both the linearity and phase delay of the modulator as well as (for high pulse numbers) harmonic performance. The FOH circuit has an overshoot in its transfer function which should be avoidable if the modulating signal is sampled at a sufficiently high rate

The importance of non-uniform geoelectric fields in calculating GIC distributions

During the ascending phase of solar cycle 24 concern in the power industry regarding space weather has increased significantly. This is driving the development of software tools to estimate GIC distributions in power networks for a given uniform geoelectric field. Typically, geoelectric fields induced during space weather disturbances are spatially non-uniform. This paper shows that for accurate planning and development of mitigation strategies, GIC analysis software needs to allow for specification of non-uniform geoelectric fields. Further, the notion held by power utilities in mid and low-latitude locations that space weather does not pose any risk to their systems is questionable. In this paper a methodology is developed to estimate the distribution of GICs in a specified power network during a significant geomagnetic event at mid-latitudes

Advanced resampling techniques for PWM amplifiers in real-time applications

Regularly sampled pulse width modulation (PWM) has been a mainstay of the power electronics community since the advent of digital controllers. In this form of PWM the modulating signal is sampled only at either the peaks and/or the troughs of the triangular carrier waveform, then held constant until the next sampling instant, which allows ample time for the calculation of switching instants. Unfortunately, it produces phase and amplitude distortion of the modulating signal that can be significant at low pulse numbers. In applications where the desired modulating signal is not known a priori, this phase delay can become a critical limitation. The analogue alternative to regular sampling is naturally sampled PWM, where the modulating signal is permitted to vary as a continuous waveform. This form of PWM does not apply any phase or amplitude distortion to the modulating signal. True natural sampling is, however, impossible to implement on the digital control platforms that are used in modern power electronics applications. In this paper, a type of hold circuit known as a First-Order Hold (FOH) circuit is used in conjunction with the technique known as resampled regular PWM to improve upon the limitations of regular sampling. It is found that this augmentation to the PWM strategy improves both the linearity and phase delay of the modulator as well as (for high pulse numbers) harmonic performance. The FOH circuit has an overshoot in its transfer function which should be avoidable if the modulating signal is sampled at a sufficiently high rate