[0013] The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention. The present invention will be described in detail below in conjunction with the accompanying drawings.
[0014] refer to figure 1 , the two-stage three-phase soft-switching converter circuit includes an AC side filter inductor L a , L b , L c; DC input side inductance L 1; Four groups of half-bridge arms; DC side capacitor C dc; and a group consisting of a parallel diode D 7 The auxiliary switch tube S 7 , Resonant inductance L r , clamp capacitor C c The auxiliary resonant branch formed by the auxiliary switching tube S 7 with clamp capacitor C c After series connection and resonant inductance L r Parallel connection; each set of half-bridge arms is composed of two series-connected fully-controlled main switch tubes containing anti-parallel diodes, and the upper and lower main switch tubes of the first bridge arm and their anti-parallel diodes are respectively S 8 , S 9 and D 8 、D 9 , the upper and lower main switching tubes and their anti-parallel diodes of the second bridge arm are respectively S 1 , S 4 and D 1 、D 4 , the upper and lower main switching tubes and their anti-parallel diodes of the third bridge arm are respectively S 3 , S 6 and D 3 、D 6 , the upper and lower main switching tubes and their anti-parallel diodes of the fourth bridge arm are respectively S 5 , S 2 and D 5 、D 2 , the upper and lower ends of the four groups of bridge arms are connected in parallel to form a positive and negative common bus; the positive common bus and the DC side capacitor C dc The above-mentioned auxiliary resonant branch is connected between them; the midpoint of the first bridge arm is connected to the inductor L 1 end of the L 1 The other end of the DC source is connected to the positive end of the input DC source, and the negative end of the DC source is connected to the negative common bus; the midpoints of the second bridge arm, the third bridge arm, and the fourth bridge arm are respectively connected to L a , L b , L c , L a , L b , L c The other ends of each are connected to the three-phase power grid; each switching tube S 1 ~S 6 , S 8 ~S 9 and S 7 A resonant capacitor C is connected in parallel with the collector and the emitter 1 ~C 6 、C 8 ~C 9 and C 7.
[0015] For the two-stage three-phase soft-switching converter circuit, according to the three-phase output current i a i b i c phase situation, the working area is divided into six areas, such as figure 2 As shown, while the input current i 1 There are also two cases of greater than zero and less than zero. The following three-phase current i a i b i c is in region 1, and the input current i 1 is greater than zero as an example, analyze the working process of the circuit working in one switching cycle.
[0016] Since in region 1, i 1 i a greater than zero, i b i c is less than zero, in one switching period, there are four diodes commutating to the main switching tube, which are respectively D 8 to S 9 commutation, D 4 to S 1 commutation, D 3 to S 6 commutation, D 5 to S 2 commutation, in this switching cycle, the pulse control sequence of the switching tube is as follows: image 3 As shown, the converter has 14 working states in total. Figure 4-17 is the working equivalent circuit of one switching cycle in this area, and the main voltage and current waveforms during operation are as follows Figure 18 As shown, the voltage and current reference direction of the circuit is as figure 1 shown. The working process of the circuit in other intervals is similar to this.
[0017] The specific stages are analyzed as follows:
[0018] Stage one (t 0 ~t 1 ):
[0019] like Figure 4 As shown, the diode D on the first bridge arm 8 , the second leg lower tube diode D 4 , the upper tube diode D of the third bridge arm 3 , the diode D of the upper tube of the fourth bridge arm 5 Both conduct, by the resonant inductance L r , clamp capacitor C c , auxiliary switch S 7 The auxiliary circuit composed of the clamping capacitor C c The voltage across both ends is U Cc , the resonant inductor current rises linearly;
[0020] Stage two (t 1 ~t 2 ):
[0021] like Figure 5 shown, at t 1 Time auxiliary switch S 7 turn off, the resonant inductance L r Make the main switch S 9 , S 1 , S 6 , S 2 The shunt capacitor C 9 、C 1 、C 6 、C 2 discharge while enabling the auxiliary switch S 7 The shunt capacitor C 7 charging, the resonant inductance L r current i Lr resonance drops, at t 2 moment, the main switch S 9 , S 1 , S 6 , S 2 The shunt capacitor C 9 、C 1 、C 6 、C 2 The voltage resonates to zero and the phase ends;
[0022] Stage three (t 2 ~t 3 ):
[0023] like Image 6 shown, at t 2 after time D 9 、D 1 、D 6 、D 2 will turn on, the C 9 、C 1 、C 6 、C 2 The voltage on the clamp is zero, available at t 2 Always open S 9 , S 1 , S 6 , S 2 , can achieve S 9 , S 1 , S 6 , S 2 of zero voltage turn-on, at t 3 moment, D 9 、D 1 、D 6 、D 2 The current drops to zero and the phase ends.
[0024] Stage four (t 3 ~t 4 ):
[0025] like Figure 7 shown in D 9 、D 1 、D 6 、D 2 After shutting down, the circuit enters the commutation stage, and the current i 1 by diode D 8 To the switch tube S 9 commutation, current i a by diode D 4 To the switch tube S 1 commutation, current i b by diode D 3 To the switch tube S 6 commutation, current i c by diode D 5 To the switch tube S 2 commutation. During this phase the voltage across the resonant inductor Lr is clamped at V dc , the resonant inductor current i Lr Decreases linearly at t 4 At time , the commutation of the above four bridge arms ends, and this stage ends. where V dc is the voltage across the DC bus capacitor.
[0026] Stage five (t 4 ~t 5 ):
[0027] like Figure 8 shown, at t 4 time later i Lr keep falling, C 7 Start to discharge, C 8 、C 4 、C 3 、C 5 Start charging, the circuit enters the second resonance, at t 5 moment C 7 The voltage on resonates to zero and the phase ends.
[0028] Stage six (t 5 ~t 6 ):
[0029] like Figure 9 shown, t 5 time later, D 7 will turn on, the C 7 The voltage on the clamp is zero, for the auxiliary tube S 7 The zero voltage turn-on provides conditions that can be obtained at t 5 time to s 7 Send the turn-on signal to make it realize zero voltage turn-on, when S 9 at t 6 This phase ends when the moment is turned off.
[0030] Stage seven (t 6 ~t 7 ):
[0031] like Figure 10 Shown, S 9 at t 6 After the time is turned off, the upper and lower main switch tubes of the first bridge arm start to commutate, C 9 Start charging, C 8 start discharging, at t 7 moment, C 9 The voltage on the rises to U Cc +V dc , C 8 The voltage on drops to zero and the phase ends.
[0032] Stage eight (t 7 ~t 8 ):
[0033] like Figure 11 As shown, the commutation is completed in the first bridge arm, D 8 After freewheeling conduction, S 8 open, at this stage S 8 , S 1 , S 6 , S 2 Keep the on state, the resonant inductor current rises linearly, at t 8 Moment S 6 shutdown, the phase ends.
[0034] Stage nine (t 8 ~t 9 ):
[0035] like Figure 12 Shown, S 6 at t 8 After the time is turned off, the third bridge arm starts to commutate, C 6 Start charging, C 3 start discharging, at t 9 moment, C 6 The voltage on the rises to U Cc +V dc , C 3 The voltage on drops to zero and the phase ends.
[0036] Stage ten (t 9 ~t 10 ):
[0037] like Figure 13 As shown, the commutation is completed in the third bridge arm, D 3 After freewheeling conduction, S 3 open, at this stage S 8 , S 1 , S 3 , S 2 Keep the on state, the resonant inductor current rises linearly, at t 10 Moment S 2 shutdown, the phase ends.
[0038] Phase Eleven (t 10 ~t 11 ):
[0039] like Figure 14 Shown, S 2 at t 10 After the time is turned off, the fourth bridge arm starts to commutate, C 2 Start charging, C 5 start discharging, at t 11 moment, C 2 The voltage on the rises to U Cc +V dc , C 5 The voltage on drops to zero and the phase ends.
[0040] Phase twelve (t 11 ~t 12 ):
[0041] like Figure 15 As shown, the commutation is completed in the fourth bridge arm, D 5 After freewheeling conduction, S 5 open, at this stage S 8 , S 1 , S 3 , S 5 Keep the on state, the resonant inductor current rises linearly, at t 12 Moment S 1 shutdown, the phase ends.
[0042] Stage thirteen (t 12 ~t 13 ):
[0043] like Figure 16 Shown, S 1 at t 12 After the time is turned off, the second bridge arm starts to commutate, C 1 Start charging, C 4 start discharging, at t 13 moment, C 1 The voltage on the rises to U Cc +V dc , C 4 The voltage on drops to zero and the phase ends.
[0044] Stage fourteen (t 13 ~t 14 ):
[0045]The commutation is completed in the second bridge arm, D 4 After freewheeling conduction, S 4 open, at this stage S 8 , S 4 , S 3 , S 5 Keep the open state, the resonant inductor current decreases linearly, and this stage is the same as stage one.
