Introduction - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 9

i o

T 1 T 3 T 5 +

v a

~

L

i a

v b

~

v o

i b

v c

~ R

i c

-

T 2

T 4 T 6

(a) Topology

v o

v ab v ac v bc v ba v ca v cb v ab v ac v bc v ba v ca v cb v o

α = π /2

α = π/6

0 π/3 π 2π 3π 4π 0 π/3 π 2π 3π 4π

ωt/rad ωt/rad

(b) α = π/ 6 (c) α = π/ 2

Figure 1.8 Phase-controlled three-phase rectifier with a large inductive load

voltage and a high-quality input current at the same time, many techniques based on active
current control have been developed (Bollen 2000; Sankaran 2002). One option is to cascade a
boost converter at the output of a diode bridge rectifier, as shown in Figure 1.10(a). The boost
converter can be controlled to make the input current in phase with the input voltage while
regulating the output voltage, e.g. with the basic hysteresis control strategy shown in Figure
1.10(b). Although the load current is mainly of DC, the input current is sinusoidal and the

v ab v ac v bc v ba v ca v cb v o v ab v ac v bc v ba v ca v cb

α = 2 π /3 α = 5 π /6 v o

0 π/3 π 2π 3π 4π 0 π/3 π 2π 3π 4π

ωt/rad ωt/rad

(a) α =2 π/ 3 (b) α =5 π/ 6

Figure 1.9 Phase-controlled three-phase rectifier operated in the inversion mode when a negative DC
bus voltage is present