Loschi, Hermes
(2023)
Modulation algorithms of power electronic converters for shaping of conducted interference.
PhD thesis, University of Zielona Gora.
Abstract
Remarkably, over the last few decades, the electromagnetic interference within 9 to 150 kHz was especially accentuated since the switching frequency of power electronic converters is still limited to several kHz. Thus, bringing up the debate on regulation. From the point of view of the electromagnetic interference noise shape, two cases represent the extremes of possibilities among the various possible converter control algorithms: the deterministic and pseudo-random modulation.
Pseudo-random modulation has been considered a complementary methodology to achieve electromagnetic compatibility, jointly with the electromagnetic interference filters and improvements on the printed circuit board layouts. The pseudo-random modulation methodology has also been utilized as prior-art for the reduction of converter power losses while achieving a target control dynamics or system power density or cost, and/or to achieve a flattening of power efficiency curves as function of processed power, and to improve control dynamics in transient operations. Notwithstanding, the impact of pseudo-random modulation on measured conducted electromagnetic interference is still unclear for the low frequency range.
For instance, evaluating any electromagnetic interference noise spreading approach is not apparent once it depends on several pseudo-random modulation parameters, dwell time and resolution bandwidth. The conventional super-heterodyne frequency band stepping EMI test receiver defines the dwell time and the resolution bandwidth. For this reason, historically, pseudo-random modulations have been questioned and accused of being a fraudulent way of passing regulations. Nonetheless, research has been presented over the last decades to support the electromagnetic interference noise spreading approach in practical situations, e.g., with power line communication systems.
Thus, the research carried out and presented in this thesis, all in all, proposed pseudo-random modulation control algorithms with a random stream based on different methods. The National Instruments PXI with Field-Programmable Gate Array was used as a cyber-physical platform for fast prototyping. This engineering tool enables the necessary electromagnetic interference investigations. The detail Field-Programmable Gate Array implementation and benchmarking of each studied methods are given. Although pseudo-random modulation methods exist previously to this thesis work, the main novelty of the proposed developments lies in the identification and selection of the most suited random stream method for the problem at hand, and its necessary modification for implementation in a fixed-point processor. In this way demonstrating that it is possible to develop new, dedicated converter control algorithms that allow shaping the spectrum of disturbances to meet standardization or technical requirements.
Furthermore, once it has been found that the conventional EMC test based on frequency scanning might not be sufficient to evaluate pseudo-random modulated DC/DC converter appropriately. A methodology is proposed to control the switching rate of change of DC/DC converters using pseudo-random modulation, which can achieve a suitable EMI measurement, regardless if long dwell times are considered.
Therefore, the objectives of this thesis are related to the identification and realization of whether it is possible to develop new, dedicated converter control algorithms that allow shaping the spectrum of disturbances to meet standardization or technical requirements, based on:
Usage of National Instruments PXI with Field-Programmable Gate Array based control hardware with a fixed point processor as a cyber-physical fast prototyping platform enabling electromagnetic compatibility investigations of pseudo-random modulated converters;
EMC-friendly PWM technique: the identification and selection of the most suited random stream method, shaping the electromagnetic interference noise from the critical fault areas of the information and communications technology equipment (increasing the effectiveness of an already implemented EMI filter);
Description of a concept of the control algorithm for power electronic converters, enabling electromagnetic interference shaping, providing 30\% reduction of Frame Error Rate in Power Line Communication;
Case study showing possibility of development of new, dedicated converter control algorithms that allow shaping of the spectrum of disturbances to meet standardization or technical requirements as well as presentation of the system for flexible implementation and validation of developed concepts.
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