Simplified Model Predictive Control Method for Three-Phase Four-Leg Voltage Source Inverters

Abstract

A simplified model predictive control method is presented in this paper. This method is based on a future reference voltage vector for a three-phase four-leg voltage source inverter (VSI). Compared with the three-leg VSIs, the four-leg VSI increases the possible switching states from 8 to 16 owing to a fourth leg. Among the possible states, this should be considered in the model predictive control method for selecting an optimal state. The increased number of candidate switching states and the corresponding voltage vectors increase the calculation burden. The proposed technique can preselect 5 among the 16 possible voltage vectors produced by the three-phase four-leg voltage source inverters, based on the position of the future reference voltage vector. The discrete-time model of the future reference voltage vector is built to predict the future movement of the load currents, and its position is used to choose five preselected vectors at every sampling period. As a result, the proposed method can reduce calculation load by decreasing the candidate voltage vectors used in the cost function for the four-leg VSIs, while exhibiting the same performance as the conventional method. The effectiveness of the proposed method is demonstrated with simulation and experiment results.

Zero-Axis Virtual Synchronous Coordinate Based Current Control Strategy for Grid-Connected Inverter

“…According to (12), the zero-axis signal virtual mapping system is a linear system. The dynamic response, stability and other performance depend on the low pass filter cut-off frequency ω c and the phase locked loop output frequencyω.…”

“…According to (12), once the voltage frequency of the grid is determined, the performance of the virtual mapping system of zero-axis signal is only related to the low pass filter cut-off frequency ω c . In order to achieve faster dynamic response and better filtering effect, it is necessary to optimize the parameter.…”

“…With the characteristics of high DC voltage utilization and small DC voltage ripple, three-phase four-leg grid-connected inverters [12] are considered a common structure of SPC [13]. When the three-phase negative-and zero-sequence current signals are transformed into reference signals in the synchronous rotating coordinate frame, the reference signals in dq0-axis are all AC signals.…”

Optimal Selection among Various Three-Phase Four-Wire Back-to-Back (BTB) Converters with Comparative Analysis for Wave Energy Converters

“…Complexity increases in modulation (SVPWM) application [14][15][16][17][18]. Obviously, many studies have been conducted, and applicability is not impossible, but model-based current control is more advantageous for converters with special configurations because it can configure a simple and intuitive controller [19,20]. That is, even if complex control variables exist in an unusual topology, such as a four-wire converter, it may have the advantage of being easy to apply.…”