Tese
Conversores multiníveis modulares: contribuições ao estudo e ao desenvolvimento de sistemas de controle distribuídos
Fecha
2017-10-05Autor
Silva, Guilherme Sebastião da
Institución
Resumen
This doctoral thesis presents contributions to the study and development of distributed
control systems applied to the Modular Multilevel Converter (MMC) operating
with a high number of submodules (SMs), which is the most promising multilevel
converter topology, especially in high voltage and high power applications. Initially,
operating principle, main concepts and a power flow analysis are presented in order to
justify the proposal. Based on the MMC power flow analysis, a control system is proposed
to ensure the power balance between the dc voltage bus and the ac power grid,
the power processing distribution between the arms and the individual capacitor voltage
control, with the control of N–1 capacitor voltages. One of the main MMC implementation
challenges is to ensure the suitable control of SM floating capacitors with an
easily scalable control system with reduced communication complexity. Thus, a distributed
control structure using sliding mode observer approach is proposed to reduce
the data flowing among through between the SMs needed to implement the MMC control
system. With this concept, the sliding-mode observer approach consists of: (i) an
equivalent capacitor voltage observer in the continuous-time domain, which are discretized
for processor implementation; and (ii) an equivalent capacitor voltage observer in
the discrete-time domain. Regarding the equivalent observers, the design methodology
for continuous-time and the results for the discretized observer are presented. The design
methodology of the discrete-time equivalent capacitor voltage observer is shown in
discrete-time to guarantee the steady-state and the transient performances and the results
for the discrete observer are presented. The Lyapunov stability analysis is presented
for each observer. Finally, it is worth to emphasize that simulation and experimental
results are presented considering the observer and the control performances under
different operating conditions.