Mathematical model for transient calculation in a three-phase current inverter with two-stage switching
Based on the operator method, a mathematical model for the calculation of transients in a three-phase current inverter with two-stage switching is proposed. The model allows the calculation of transients when the input voltage of the inverter changes, when the load changes, and also when the input voltage and load change simultaneously. The calculated ratios underlying the model make it possible to carry out software implementation without involving large machine resources using standard material support, ensures the accuracy of the analysis within the capabilities of the machine, independent of the value of the time step, as is inherent in various digital models of electrical circuits. It is shown that in the schemes of three-phase converters, due to the topological symmetry in phases, the same equivalent circuit, as the type, turns out to be fair and can be used to analyze processes with the same combination of switched-on valves with different numbers. Therefore, operator equivalent circuits are compiled for certain combinations of numbers of valves turned on and are used to calculate the process at the necessary stage for all phases, that is, all elements of the circuit. To facilitate the programming and calculation procedure, a universal correspondence matrix is proposed. This matrix can be used to calculate three-phase autonomous current inverters (ACI) of the following topologies: parallel ACI, parallel-series ACI, series-parallel ACI, series ACI, ACI with shut-off valves and ACI with two-stage switching. It has been revealed that six types of equivalent circuits are the basis for calculating the transition process of ACI with TC, various combinations of which represent the development paths of transient processes at clock intervals.