Least-squares estimation of capacitor voltages in flying capacitor multilevel converters

Flying capacitor multi‐level converters use charged capacitors as a critical element. For proper operation, the capacitor voltages must be known and regulated. Direct measurement is straightforward, but when the number of required measurements is high, this is a complicated approach. This paper introduces an estimation method for n capacitor voltages. The scheme is based on a system of (n+1) equations, which is defined in a way that it incorporates information of the actual capacitor voltages and open‐loop estimates of the capacitor voltages. The solution of the system gives the best estimates of the capacitor voltages in the sense of least square errors. The method requires only output voltage and output current sensors and its computational burden is low, saving cost and design efforts, and simplifying the hardware system. The performance of the proposed scheme is evaluated experimentally in a 9‐level flying capacitor chopper, where the estimates are used by the voltage balancing strategy and by the output current controller.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Estimation of the capacitor voltages in flying capacitor multi‐level converters

Escalante

Erdmann

2021

“…At present, multilevel converters mainly include neutral-point clamped converter [3], flying capacitor converter [4], cascaded multilevel converter [5][6][7] and modular multilevel converter (MMC) [8][9][10][11][12][13][14]. The topologies of neutral-point clamped converter and flying capacitor converter become more complex with the increase of output levels, which brings difficulty to control and modulation, so they are not suitable for high-voltage and -power applications.…”

Section: Introductionmentioning

confidence: 99%

Capacitor voltage balancing and current control method of modular multilevel converter based on generalised averaging approach

Chang

2017

To solve the capacitor voltage balancing problem of modular multilevel converter (MMC) under carrier phase-shifted modulation, MMC is modelled by generalised averaging approach. The quantitative relation between the capacitor voltage of submodule and other operating parameters is derived, and the corresponding balancing method is proposed which can make each capacitor voltage to track the reference value. According to the average model of MMC, a current controller is designed, which is suited to the voltage balancing method and can decouple the active and reactive currents. The effectiveness of the voltage balancing method and the current control method is verified by simulation results.

“…In recent years, valuable research studies in the field of FCM power converters have focused on the analytical modelling of natural balancing of FC voltages [9,14,19,[21][22][23][24] or proposing enhanced modulation strategies [25][26][27][28] or improved hybrid topologies [7,[29][30][31][32][33][34][35][36][37][38][39], to prove their merit for high-power energy conversion arena.…”

Section: Introductionmentioning

confidence: 99%

Enhanced double flying capacitor multicell power converter controlled with a new switching pattern

Vahidinasab¹,

Sadigh²,

Corzine³

2015

This study proposes an enhanced topology for pulse-width-modulated double flying capacitor multicell (DFCM) converter controlled with a new switching pattern in order to reduce voltage diversity and stored energy of flying capacitor (FC) to augment converter's integrity and modularity. The proposed power converter is a hybrid topology realised by cascade connection of DFCM and cascaded H-bridge (CHB) converters while combining, employing, and featuring advantages of both converters. The dc voltage sources and also power switches forming CHB converters' structure in the proposed hybrid topology possess low voltage-ratings, hence imposing low additional costs and prices on DFCM converter whereas improving and enhancing output voltage power quality significantly by increasing the number of output voltage-levels and improving output voltage frequency spectrum. This progress results in reducing the bulky and costly FCs, their voltage ratings and stored energy. The FC voltages of DFCM topology in the proposed hybrid converter get stabilised naturally at their requisite voltage-levels because of the redundant charging/discharging states. First, experimental measurements of the three-cell-seven-level DFCM are provided. Afterward, simulation results and experimental observations of 15-level enhanced DFCM converter are presented to verify and validate the effectiveness and advantages of the proposed topology as well as its suggested control and modulation strategy.