Frequency response identification and control strategy improvement of lcl grid-connected voltage source inverter
File(s)
Author(s)
Aldarmon, Mohamed
Type
Thesis
Abstract
The rapid penetration of inverter-based renewables (IBRS) is expected to grow in the
future. A large number of power electronic converters will be installed in the power
system. Most IBRs are connected to the grid via LCL filters, which must be carefully
designed to avoid exciting their resonance.
The thesis focuses on the frequency response method for LCL filters’ true resonance
identification and characterising of the three-phase grid tie inverter. A tool based on
this method is presented to assess the inverter controller’s behaviour during operation
and their contribution to grid voltage regulation. Additionally, the thesis presented
several steps that guide the filter design process. Then, using the frequency method to
assess the designed filter. A grid-connected inverter resonance frequency is analysed to
demonstrate the simplicity and effectiveness of the developed tool. Damping methods
are presented, and their effectiveness is evaluated to empower the representation of the
tool’s outcomes.
Modern power networks contain microgrids in their structure, where generation and
demand are connected nearby. This concept promotes the topology of parallel inverters.
Thus, the research investigated the impact of the parallel inverters topology on
the resonance-impedance relationship; And the thesis accurately identified the resonance
frequency of inverters and the system (identical and non-identical) in a modular
arrangement, terminating the need for complex analytical analysis.
Finally, a new feedback active damping control structure is presented, solving the issues
of shifting resonance frequency as well as the need to redesign the inverter controller parameters
in case of changing operation conditions such as system upgrade. In addition,
the damping methods that can adapt, often require additional voltage or current sensors.
However, the proposed control structure presents an active damping method that
avoids this shortcoming and remains robust to wide variations of equivalent inductance
and capacitance. Comparison against prior techniques shows excellent performance.
future. A large number of power electronic converters will be installed in the power
system. Most IBRs are connected to the grid via LCL filters, which must be carefully
designed to avoid exciting their resonance.
The thesis focuses on the frequency response method for LCL filters’ true resonance
identification and characterising of the three-phase grid tie inverter. A tool based on
this method is presented to assess the inverter controller’s behaviour during operation
and their contribution to grid voltage regulation. Additionally, the thesis presented
several steps that guide the filter design process. Then, using the frequency method to
assess the designed filter. A grid-connected inverter resonance frequency is analysed to
demonstrate the simplicity and effectiveness of the developed tool. Damping methods
are presented, and their effectiveness is evaluated to empower the representation of the
tool’s outcomes.
Modern power networks contain microgrids in their structure, where generation and
demand are connected nearby. This concept promotes the topology of parallel inverters.
Thus, the research investigated the impact of the parallel inverters topology on
the resonance-impedance relationship; And the thesis accurately identified the resonance
frequency of inverters and the system (identical and non-identical) in a modular
arrangement, terminating the need for complex analytical analysis.
Finally, a new feedback active damping control structure is presented, solving the issues
of shifting resonance frequency as well as the need to redesign the inverter controller parameters
in case of changing operation conditions such as system upgrade. In addition,
the damping methods that can adapt, often require additional voltage or current sensors.
However, the proposed control structure presents an active damping method that
avoids this shortcoming and remains robust to wide variations of equivalent inductance
and capacitance. Comparison against prior techniques shows excellent performance.
Version
Open Access
Date Issued
2024-06-13
Date Awarded
2025-06-01
Copyright Statement
Attribution-Non Commercial-No Derivatives 4.0 International Licence (CC BY-NC-ND)
License URL
Advisor
Junyent-Ferré, Adrià
Publisher Department
Department of Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)