A Control System Architecture of Modular Multilevel Converter

Abstract

The invention relates to a control system architecture of a modular multilevel converter. The control system architecture is characterized in that a control system comprises a three-level control architecture and an external extended AD (access device), and the three-level control architecture comprises a master controller, an auxiliary controller and module controllers. A DSP (digital signal processor) of the master controller is used for realizing a master control function, sampling arm currents, sharing voltages among sub-modules and designing algorithms, an FPGA (field programmable gate array) of the auxiliary controller is used for preprocessing capacitances and the voltages of the sub-modules, implementing modulation strategies, controlling the external extended AD and diagnosing and processing faults, and an FPGA of each module controller is used for sampling the corresponding capacitance and the corresponding voltage, driving switch tubes, extending PWM (pulse width modulation) signals and processing dead zones. The control system architecture has the advantages that communication protocols of the auxiliary controller and the module controllers are optimized, so that the usage of optical fibers is reduced, the problem that module controllers need to be synchronized is solved, the complexity of the system is reduced, and the cost of the system is lowered.

Description

technical field [0001] The invention relates to a control system in the field of multilevel power electronic converters, in particular to a control system architecture of a modular multilevel converter. Background technique [0002] In the field of high voltage and high power, multilevel power electronic converters have been more and more widely used due to their unique advantages. Modular Multilevel Converter (MMC) is a new type of voltage source converter, which adopts a strict modular design structure, which reduces production costs in mass production; through the series connection of sub-modules, the converter The voltage level and power level are easy to expand; the multi-level output form of the converter reduces the harmonic content and total distortion rate of the output voltage, thereby reducing or even eliminating the large-capacity AC filter; each bridge arm sub-module does not It needs to be turned on at the same time, which reduces the change rate of the voltag...

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Problems solved by technology

The PWM function of this control architecture is directly realized by each module controller, and there is a synchronization problem between each module controller, which requires additional control, which increases the complexity of the system; when the auxiliary controller sends data to the module controller, it needs to send 2 frames Data (each frame consists of 11 bits, followed by start bit, 8 data bits, parity bit and stop bit), will cause a certain delay in the PWM signal, and the real-time performance will be reduced. The sub-module voltage equalization algorithm is controlled by the assistant Compared with the implementation by the main controller DSP, this method is more complicated

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