In the conditions of increasing use of dynamic and nonlinear loads, it is important to construct systems with frequency converters that will be invariant to the maximum number of external perturbations. For an asynchronous electric drive, it is advisable to use a matrix frequency converter (MFC), among which the advantages are: free power transfer and power supply; lack of energy accumulation; the formation of curves input and output currents and voltages with a minimum contribution of higher harmonics. This article presents the use of a geometric approach to control the MFC. The geometric approach method for describing variables is promising in relation to the choice of a system of variable transducers, which determines the maximum number of control channels that is the greatest problem in developing invariant systems. According to the scheme of the selected MFC, the formation of a sinusoidal input current and output voltage using a geometric approach is described for the description of variables. In [1, 2, 3, 5] we present a geometric approach for describing the input and output parameters of various systems. In this case, [1, 3, 5] only the formation of the output voltage according to known shoulder voltages is considered. At the same time, the simultaneous formation of the voltage of the given frequency and the sinusoidal current of consumption is appropriate for the construction of the power supply of the asynchronous electric drive. To construct a control system by the geometric approach, the input values form a three dimensional space in which the vectors of these quantities are located, and their projections form a two-dimensional space of output quantities, while the dimensions of the input and output voltage voltages of the converter depend on the number of the arms of the converter. For the formation of sinusoidal input current and output voltage, a geometric approach is used to describe the variables in the three- shoulders MFC (Fig.1), where each key represents a set of two transistors and two diodes that are engaged in counter-parallel (Fig.2). For all possible logical switches of the keys a table is created, where the input voltage is selected for the output voltage, the voltage at the load phases and the phase currents are selected for the output values. The MFC works both on the high and on the lower frequency (Fig.4). In the three-dimensional space of input values, vectors of shoulder voltages are constructed. The vectors of the shoulder voltages of the MFR form a three-dimensional space of input quantities (shoulder voltages O2O1, O2K, O2L, O1O2, O1H, O1F), shown in Fig.3. Projections of these input values into two-dimensional quantities: stresses on loading phases (Ua, Ub, Uc) and input phase currents (ia, ib, ic). Thus, the system of vectors in Fig.3 illustrates that at the same time forming the voltage in the loading and syncope phase phases, in the independent system of vectors in a three dimensional space, at least one vector appears, depending on both output variables.
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Copyright (c) 2019 Антон Васильович Соіч, Дмитро Анатолійович Миколаєць (Автор)
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