Research on single - phase bridge rectifier circuit based on

1 Introduction

Rectifier, especially single-phase bridge controllable rectifier circuit is the most important and most widely used circuit in power electronics technology. It is not only applied to general industry, but also widely used in transportation, power system, communication system, Energy systems and other areas. Therefore, it is of great practical significance to compare and analyze the relevant parameters of the single-phase bridge-type controllable rectifier circuit and the work of different loads. It is not only an important part of the theoretical study of power electronic circuits, but also the practicality of engineering practice Applications have predictions and guidance.

2 single - phase bridge half - controlled rectifier circuit

Figure 1 VT1 and VT2 trigger pulse phase difference between the 180 ° thyristor, VD1 and VD2 for the rectifier diode, composed of these four devices single-phase bridge semi-rectifier rectifier circuit. Resistance R and inductance L for the load, assuming that the inductance L is large enough, that is, ωL ≥ R, because the inductor current can not be mutated, the load current can be considered in the steady state of the work to maintain a constant value. Due to the characteristics of the bridge structure, as long as the thyristor conduction, the load is always coupled with the forward voltage, and the load current is always unidirectional flow, so the bridge half-controlled rectifier circuit can only work in the first quadrant, because ωL ≥ R, So the change of the load current id is small regardless of the value of the control angle α.

Figure 1 single-phase bridge half-controlled rectifier circuit principle

In u2 positive half weeks, the trigger angle α to the thyristor VT1 to impose a trigger pulse, u2 by VT1 and VD4 to the load power supply. U2 zero turn negative, because the inductor current does not flow through the transformer secondary winding, but by the VT1 and VD2 freewheeling. At this stage, if the device's on-state voltage drop is ignored, the load voltage drop ud does not appear negative. At time u2 negative half-firing angle α, VT2 and VD3 trigger conduction, while the reverse voltage to the VT1 and make it off, u2 by VT2 and VD3 to the load power supply. U2 zero change, VD4 conduction, VD3 off. VT1 and VD4 freewheeling, the load voltage drop ud becomes zero again.

According to the above analysis, the output load voltage can be obtained as follows:

(1)

The phase shift of the alpha angle is 180 °. The average output current is:

(2)

The current average of the current flowing through the thyristor is only half of the output DC average,

(3)

Current flowing through the thyristor RMS:

(4)

Single-phase bridge half-controlled rectifier circuit simulation model shown in Figure 2.

Figure 2 single-phase bridge half-controlled rectifier circuit simulation model

(1) with a purely resistive load condition

The corresponding parameters set: ① AC voltage source parameters U = 100V, f = 50Hz; ② thyristor parameters Rn = 0.001Ω, Lon = 0H, Vf = 0.8V, Rs = 10Ω, Cs = 250e-6F; ③ load parameters R = 10Ω, L = 0H, C = inf; ④ pulse generator trigger signal 1,2 the amplitude of 5V, the cycle is 0.02s (that is, the frequency of 50Hz), the pulse width of 2.

Set the initial phase of the trigger signal 1 to 0s (ie 0?) And the initial phase of the trigger signal 2 is 0.01s (ie 180?). The simulation result is shown in Fig. 3 (a); set the trigger signal 1 The phase is 0.0025s (ie 45?), The initial phase of the trigger signal 2 is 0.0125s (ie 225?), And the simulation results are shown in Fig. 3 (b).