Advanced Optimal Modulation for Grid-Connected Converters
Rahmanpour, Shirin (2026)
Tampere University
2026
Tieto- ja sähkötekniikan tohtoriohjelma - Doctoral Programme in Computing and Electrical Engineering
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
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Väitöspäivä
2026-11-06
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-03-4762-8
https://urn.fi/URN:ISBN:978-952-03-4762-8
Tiivistelmä
This thesis focuses on optimal modulation strategies for grid-connected power converters with an LCL filter, aiming to achieve grid-friendly operation at low switching frequencies. The ongoing transition toward renewable generation and widespread electrification has made power electronic converters a key enabling technology for efficient and controllable energy conversion. However, their growing penetration introduces challenges related to power quality, particularly when operated at low switching frequencies to reduce switching losses and improve converter efficiency. Under such conditions, conventional modulation techniques do not achieve the desired performance.
Optimized pulse patterns (OPPs) provide a promising solution for improving the trade-off between harmonic performance and converter efficiency. However, conventional OPP formulations do not account for the intrinsic dynamics of higher-order power electronic systems, nor do they ensure compliance with power quality requirements, such as harmonic limits, under different operating conditions. This limits their applicability in grid-connected applications.
In this work, the OPP optimization problem is reformulated to incorporate the LCL filter dynamics, enabling direct shaping of current and voltage harmonics at the point of common coupling (PCC). In addition, to ensure grid-friendly operation, explicit constraints on individual harmonic components are imposed in accordance with relevant grid standards. By relaxing the symmetry properties typically enforced on pulse patterns, the proposed modulation scheme provides additional degrees of freedom for shaping harmonic spectra.
To address non-ideal grid conditions, the proposed OPP framework is further extended to account for harmonic disturbances from other converters connected at the PCC, enabling the computation of disturbance-aware, grid-friendly OPPs. Since exact knowledge of harmonic disturbances is rarely available in practice, a robust OPP formulation is also developed to ensure compliance with harmonic grid standards under partially known or entirely unknown disturbance profiles.
Numerical and experimental results validate the effectiveness of the proposed techniques. Specifically, unlike conventional modulation methods, the proposed OPPs ensure full compliance under ideal grid conditions and in the presence of disturbances with known or partially known characteristics. Even when the disturbance profile is completely unknown during offline computation, compliance is guaranteed provided that the disturbance amplitudes remain below 50% of the maximum allowable limits.
Optimized pulse patterns (OPPs) provide a promising solution for improving the trade-off between harmonic performance and converter efficiency. However, conventional OPP formulations do not account for the intrinsic dynamics of higher-order power electronic systems, nor do they ensure compliance with power quality requirements, such as harmonic limits, under different operating conditions. This limits their applicability in grid-connected applications.
In this work, the OPP optimization problem is reformulated to incorporate the LCL filter dynamics, enabling direct shaping of current and voltage harmonics at the point of common coupling (PCC). In addition, to ensure grid-friendly operation, explicit constraints on individual harmonic components are imposed in accordance with relevant grid standards. By relaxing the symmetry properties typically enforced on pulse patterns, the proposed modulation scheme provides additional degrees of freedom for shaping harmonic spectra.
To address non-ideal grid conditions, the proposed OPP framework is further extended to account for harmonic disturbances from other converters connected at the PCC, enabling the computation of disturbance-aware, grid-friendly OPPs. Since exact knowledge of harmonic disturbances is rarely available in practice, a robust OPP formulation is also developed to ensure compliance with harmonic grid standards under partially known or entirely unknown disturbance profiles.
Numerical and experimental results validate the effectiveness of the proposed techniques. Specifically, unlike conventional modulation methods, the proposed OPPs ensure full compliance under ideal grid conditions and in the presence of disturbances with known or partially known characteristics. Even when the disturbance profile is completely unknown during offline computation, compliance is guaranteed provided that the disturbance amplitudes remain below 50% of the maximum allowable limits.
Kokoelmat
- Väitöskirjat [5374]