A Real-Time Estimator for Capacitor Voltages in the Flying Capacitor Multilevel Converter

This work presents a practical method for estimating the flying capacitor voltages in flying capacitor multilevel (FCML) converters in real-time via direct measurements of only the input voltage and switched node voltage. The proposed technique greatly simplifies the circuitry required to sense flying capacitor voltages. The estimator is designed to run under variable operating points and to be compatible with arbitrary modulation strategies, making it highly suitable for feedback control of the flying capacitor voltages. We analyze the observability under practical sampling constraints, and present a real-time implementation on a commercial digital signal processor.