Abstract
This paper suggests the application of an embedded real-time simulator (eRTS) in the context of voltage–sensorless control of a modular multilevel power converter (MMC). This eRTS acts as an observer and ensures digital redundancy in the case of any fault occurring among the capacitor voltage sensors of the MMC submodules. Hence, in such a faulty situation, the MMC controller switches from the measured voltages to their estimated counterparts. As for the digital implementation, to ensure a high level of integration of the overall control system, the Xilinx Zynq-7020 system-on-chip field programmable gate array (SoC-FPGA) device was used. The controller was implemented in the hardwired ARM Cortex-A9 processor, with a 100 µs time step. Regarding the time-sensitive blocks (PWM, eRTS and measurements filtering), a full hardware implementation was privileged, using the FPGA fabric. The execution time of these blocks was 710 ns with a 100 MHz system clock, and the synchronization with the analog to digital acquisition chain was made with a 5 µs time resolution. The whole proof-of-concept system was experimentally tested, including the time/area evaluation of the implemented designs and the experimental validation of the eRTS estimations in both healthy and faulty scenarios.
Highlights
In the course of the last decade, real-time simulators (RTS) have been under the focus of important research in almost all areas of electrical engineering
This paper presented the development of a voltage sensorless controller of an modular multilevel converters (MMC)
This controller integrates an embedded real-time simulator (eRTS) that acts as a redundant block that estimates all the capacitor voltages of the MMC submodules
Summary
In the course of the last decade, real-time simulators (RTS) have been under the focus of important research in almost all areas of electrical engineering. Recent application trends consist in deploying these RTS as digital twins that are embedded (embedded RTS—eRTS) within the control system to provide additional functionalities, such as estimations/observations, online diagnostics and health monitoring, or to be used in fault-tolerant and sensorless control [7–10] Based on these assets, a digital twin can be advantageously used in the area of power electronics and in the context of HVDC grids that integrate modular multilevel converters (MMC) [11–18]. To ensure a high execution rate, each submodule of the MMC is individually represented by a dedicated model, leading to a full parallel structure This algorithmic organization implies the use of a fast and a highly integrated digital device, where the overall sensorless controller is to be implemented. Conclusions, nomenclature and references are provided at the end of this paper
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