Predictive Control of Power Converters and Electrical Drives

7.2 System Model

7.2.1 Matrix Converter Model

The power circuit of the MC is presented in Figure 7.1. It uses a set of bidirectional switches to directly connect the three-phase power supply to a three-phase load. This is a 3 × 3 MC. As shown in Figure 7.1, each bidirectional switch is composed of two power transistors with their parallel diodes in anti-series connection.

The MC is connected to the three-phase source through the input filter L_f, R_f, C_f. This filter has two main purposes:

1. To avoid the generation of overvoltages, produced by the short-circuit impedance of the power supply (not shown in the figure), due to the fast commutation of currents i_eu, i_ev, and i_ew.

2. To eliminate high-frequency harmonics in the input currents i_u, i_v, i_w.

Figure 7.1 Power circuit of the MC

In Figure 7.1 each bidirectional switch is associated with a variable defined as S_xy with x ∈ {u, v, w} and y ∈ {a, b, c}. The conduction state of each bidirectional switch is determined exclusively by the value of its control signal. S_xy is also known as the switching function for switch xy. S_xy = 1 implies that switch xy is on, closed, or conducting, while S_xy = 0 means that the switch is off, open, or in blocking state.

It must be mentioned that the load current must not be interrupted abruptly, because the inductive nature of the load will generate an important overvoltage that can destroy the ...