CN106059312A - Z-source DC converter and control method thereof - Google Patents

Abstract

The invention discloses a Z-source DC converter and a control method thereof. The Z-source DC converter comprises an inverter bridge, a resonant tank, a transformer and a rectifier bridge, wherein the inverter bridge is electrically connected with a DC power supply via a Z-source impedance network and is used for converting DC signals to AC signals and outputting the AC signals to the transformer; the resonant tank is serially connected between the inverter bridge and the primary side of the transformer and is used for adding resonant signals to the AC signals outputted by the inverter bridge when the inverter bridge is in a shoot-through state and outputting the AC signals with the resonant signals added to the rectifier bridge via the transformer; and the rectifier bridge is electrically connected with the secondary side of the transformer and is used for carrying out rectification processing on the AC signals with the resonant signals added and outputting the DC signals after rectification to a load. The problem of high switch loss of the Z-source converter in the prior art is solved, the switch loss is reduced, and the safety and the reliability of the Z-source DC converter are improved.

Description

A kind of Z source DC converter and control method thereof

Technical field

The present embodiments relate to Power Electronic Technique, particularly relate to a kind of Z source DC converter and control method thereof.

Background technology

Main converter circuit, by introducing an impedance network, is coupled by Z source DC converter with power supply or load.Just Property due to impedance network so that same changer has boosting and buck functionality simultaneously, output voltage range increases, Meet photovoltaic cell group grid-connected time requirement, there is preferable promotion prospect.

At present, the research contents to Z source DC converter mainly includes operation principle and the modulation plan of Z source DC converter The aspects such as the application of summary, the modeling of Z source DC converter and control and Z source DC converter.Due to, Z source DC converter energy Enough provide conventional voltage source and the unexistent stepping functions of current-source convertor, it is possible to adapt to input voltage width range Occasion.Being applied in grid-connected power generation system, compare traditional two-stage type changed power, its main circuit saving one is active Device, circuit structure is succinct.

But, Z source DC converter power in running, when switching frequency improves constantly, in the unit interval Element switch number of times increases relatively, opens and turns off brought switching loss and electromagnetic interference increases therewith, causes Z source direct current The switching loss of changer breaker in middle pipe is higher, and switching loss height becomes its wide variety of key factor of restriction.

Summary of the invention

The present invention provides a kind of Z source DC converter and control method thereof, to reduce the switch damage of Z source DC converter Consumption, improves the safety and reliability of Z source DC converter.

First aspect, embodiments provides a kind of Z source DC converter, including: inverter bridge, resonant slots, transformation Device and rectifier bridge；

Described inverter bridge is electrically connected with DC source by Z source impedance network, for direct current signal is converted into exchange letter Number, output AC signal is to transformator；

Described resonant slots is series between described inverter bridge and the former limit of described transformator, straight-through for being in inverter bridge During state, the AC signal additional resonance signal exported for described inverter bridge, after transformator output additional resonance signal AC signal is to rectifier bridge；

Described rectifier bridge electrically connects with the secondary of transformator, for the AC signal after additional resonance signal is carried out rectification Processing, the direct current signal after output rectification is to load.

Further, described resonant slots includes resonant inductance and resonant capacitance；

Described resonant inductance is series between described inverter bridge and described transformator, and, described resonant capacitance is connected in parallel on The former limit of described transformator.

Further, it is in series with between described DC source and Z source impedance network for preventing Z source impedance network electric current from returning The element of stream.

Further, also include that DC filtering inductance, described DC filtering inductance are series at described rectifier bridge and load Between, the dash current in the direct current signal suppressing output extremely described load.

Second aspect, the embodiment of the present invention additionally provides the control method of a kind of Z source DC converter, including above-mentioned first The Z source DC converter of aspect, its control method includes:

According to the drive pulse signal of inverter bridge, determine the Z source direct current that a switch periods each mode of operation interior is corresponding The equivalent circuit of changer, calculates current parameters and the voltage parameter of resonant slots according to described equivalent circuit；

Current parameters according to described resonant slots and voltage parameter, determine the straight-through pulse signal of Z source DC converter The straight-through time；

Adjust the drive pulse signal of described inverter bridge according to the described straight-through time, make the rising of described drive pulse signal Edge and trailing edge are respectively positioned in the range of the described straight-through time, to realize the Sofe Switch of described inverter bridge.

Further, described current parameters is the current value i of resonant inductance_Ls, and, described voltage parameter is resonant capacitance Magnitude of voltage V_Cp。

Further, according to current parameters and the voltage parameter of described resonant slots, the straight-through arteries and veins of Z source DC converter is determined Rush the straight-through time of signal, including:

Magnitude of voltage V according to resonant capacitance_CpRelational expression and the current value i of resonant inductance_LsRelational expression, determine that Z source is straight The phase-plane diagram of current converter；

The persistent period relational expression of each mode of operation in a switch periods is determined according to described phase-plane diagram；

Determine that no-voltage is opened and the time range of zero-current switching according to described persistent period relational expression, by described zero electricity Press off the straight-through time opening the time sum with zero-current switching as straight-through pulse signal.

Further, determine that no-voltage is opened and the time range of zero-current switching according to described persistent period relational expression, Including:

Average voltage according to a switch periods interior resonance inductance is zero, and, magnitude of voltage V_CpA switch periods First half and the opposite polarity of latter half, solve described persistent period relational expression, obtain no-voltage opening time scope With zero-current switching time range.

Further, also include:

The initial time of described zero-current switching time is current value i_LsEqual to inverter bridge DC bus current i_pnTime Carve.

The present invention, by series resonance groove between inverter bridge and the former limit of transformator, is in pass-through state in inverter bridge Time, resonant slots starts resonance, the AC signal additional resonance signal exported for described inverter bridge, additional humorous by transformator output The AC signal after signal that shakes is to rectifier bridge, thus is load supplying by rectifier bridge, use no-voltage to open inverter bridge and Zero-current switching mode, solves the problem that in prior art, Z source converter switching loss is high, reduces switching loss, improve Z The safety and reliability of source DC converter.

Accompanying drawing explanation

Fig. 1 is the circuit theory diagrams of the Z source DC converter in the embodiment of the present invention one；

Fig. 2 is the generation schematic diagram of the drive pulse signal of the Z source DC converter in the embodiment of the present invention one；

Fig. 3 is the operation principle oscillogram of the Z source DC converter in the embodiment of the present invention one；

Fig. 4 a is the Z source DC converting that the duty of the pattern one of a switch periods in the embodiment of the present invention one is corresponding The circuit theory diagrams of device；

Fig. 4 b is the Z source DC converting that the duty of the pattern two of a switch periods in the embodiment of the present invention one is corresponding The circuit theory diagrams of device；

Fig. 4 c is the Z source DC converting that the duty of the pattern three of a switch periods in the embodiment of the present invention one is corresponding The circuit theory diagrams of device；

Fig. 4 d is the Z source DC converting that the duty of the pattern four of a switch periods in the embodiment of the present invention one is corresponding The circuit theory diagrams of device；

Fig. 4 e is the Z source DC converting that the duty of the pattern five of a switch periods in the embodiment of the present invention one is corresponding The circuit theory diagrams of device；

Fig. 4 f is the Z source DC converting that the duty of the pattern six of a switch periods in the embodiment of the present invention one is corresponding The circuit theory diagrams of device；

Fig. 5 a be the pattern one of a switch periods in the embodiment of the present invention one corresponding with the duty of pattern two etc. Effect circuit diagram；

Fig. 5 b is the equivalent circuit diagram that the duty of the pattern three of a switch periods in the embodiment of the present invention one is corresponding；

Fig. 5 c is the equivalent circuit diagram that the duty of the pattern four of a switch periods in the embodiment of the present invention one is corresponding；

Fig. 5 d be the pattern five of a switch periods in the embodiment of the present invention one corresponding with the duty of pattern six etc. Effect circuit diagram；

Fig. 6 is the phase-plane diagram of the Z source DC converter in the embodiment of the present invention one；

Fig. 7 is the flow chart of the control method of Z source DC converter in the embodiment of the present invention two.

Detailed description of the invention

The present invention is described in further detail with embodiment below in conjunction with the accompanying drawings.It is understood that this place is retouched The specific embodiment stated is used only for explaining the present invention, rather than limitation of the invention.It also should be noted that, in order to just Part related to the present invention is illustrate only rather than entire infrastructure in description, accompanying drawing.

Embodiment one

The circuit theory diagrams of the Z source DC converter that Fig. 1 provides for the embodiment of the present invention one, the present embodiment is applicable to defeated Go out the situation of the bigger photovoltaic power generation grid-connecting of scope range of the fluctuation of voltage, specifically include: inverter bridge 110, resonant slots 120, transformator and Rectifier bridge 130.

Described inverter bridge 110 is electrically connected with DC source by Z source impedance network, for direct current signal is converted into exchange Signal, output AC signal is to transformator.Described resonant slots 120 is series at the former limit of described inverter bridge 110 and described transformator Between, it is used for when inverter bridge 110 is in pass-through state, the AC signal additional resonance signal exported for described inverter bridge 110, By the AC signal after transformator output additional resonance signal to rectifier bridge 130.Described rectifier bridge 130 and the secondary of transformator Electrical connection, for the AC signal after additional resonance signal carries out rectification process, the direct current signal after output rectification is to load.

Wherein, DC source can be photovoltaic cell.It is in series with for preventing between described DC source and Z source impedance network The only element of Z source impedance network current reflux.Such as, using diode D as the element preventing Z source impedance network current reflux. Photovoltaic cell exports direct current signal to Z source impedance network by diode D.

Z source impedance network includes inductance and the electric capacity (L being connected in parallel on photovoltaic cell outfan with X-shaped₁, L₂, C₁, C₂), and will Z source impedance network is designed as symmetrical network.

Inverter bridge 110 includes that switching tube, described switching tube can be insulated gate bipolar transistor (being called for short IGBT).Inversion The connected mode of bridge 110 can be to be connected to two IGBT (S on upper and lower brachium pontis₁、S₂、S₃、S₄).On each IGBT All inverse parallels have fly-wheel diode, and corresponding relation is insulated gate bipolar transistor S₁Corresponding sustained diode₁, insulated gate bipolar Transistor npn npn S₂Corresponding sustained diode₂, insulated gate bipolar transistor S₃Corresponding sustained diode₃, and, insulated gate is double Bipolar transistor S₄Corresponding sustained diode₄。

Resonant slots 120 includes resonant inductance L_sWith resonant capacitance C_p, described resonant inductance L_sIt is series at described inverter bridge 110 And between described transformator, and, described resonant capacitance C_pIt is connected in parallel on the former limit of described transformator.Wherein, transformator is isolation Transformator T.

The secondary of isolating transformer T is in series with rectifier bridge 130, and the upper and lower brachium pontis of described rectifier bridge 130 connects two respectively Diode (M₁, M₂, M₃, M₄).On the basis of technique scheme, also include DC filtering inductance L_f, described DC filtering electricity Sense L_fIt is series between described rectifier bridge 130 and load, the impact electricity in the direct current signal suppressing output extremely described load Stream.

The embodiment of the present invention, by series resonance groove between inverter bridge and the former limit of transformator, is in straight-through in inverter bridge During state, resonant slots starts resonance, the AC signal additional resonance signal exported for described inverter bridge, is exported attached by transformator Add the AC signal after resonance signal to rectifier bridge, thus be load supplying by rectifier bridge, use no-voltage to open inverter bridge Open and zero-current switching mode, solve the problem that in prior art, Z source converter switching loss is high, reduce switching loss, carry The high safety and reliability of Z source DC converter.

On the basis of technique scheme, the inductance (L of Z source impedance network₁、L₂) and DC filtering inductance L_fThe most long-range Resonant inductance L in resonant slots 120_sValue, and the inductance (C of Z source impedance network₁、C₂) it is much larger than the humorous of resonant slots 120 Shake electric capacity C_pValue.Therefore, inductance and the electric capacity of Z source impedance network can be equivalent to current source (I respectively_L1、I_L2、I_Lf) and Voltage source (V_C1、V_C2).Due to the symmetry of Z source impedance network, and, flow through the electric current of electric capacity of Z source impedance network at one Meansigma methods in switch periods is zero, can obtain:

V_C=V_C1=V_C2 (1)

I_L=I_L1=I_L2=I_i (2)

I_Lf=I_out (3)

Wherein, V_C1、V_C2It is respectively the first electric capacity C of Z source impedance network₁With the second electric capacity C₂Voltage.I_L1、I_L2Respectively For flowing through the first inductance L of Z source impedance network₁With the second inductance L₂Electric current.I_LfFor flowing through DC filtering inductance L_fElectric current.I_i And I_outIt is respectively DC source and load-side electric current meansigma methods in a switch periods.The electric current of transformer primary side is one Positive and negative square wave alternately, if setting square wave amplitude as I_T, transformer voltage ratio is n, then primary side current of transformer i_TCan be expressed as:

$i_T=\left\{\begin{array}{cc}{I}_T={\mathrm{nI}}_{Lf}={\mathrm{nI}}_{out}& v_{CP}\&GreaterEqual;0\\ -I_T=-{\mathrm{nI}}_{Lf}=-{\mathrm{nI}}_{out}& v_{CP}<0\end{array}\right.---\left(4\right)$

Fig. 2 is the generation schematic diagram of the drive pulse signal of the Z source DC converter in the embodiment of the present invention one.Will load On voltage V_oInput to switching tube driving module, by comparing voltage V_oWith preset reference voltage V_orefObtain voltage deviation Δ V_o.By voltage deviation Δ V_oInput voltage controlled oscillator, processes output switch frequency f through voltage controlled oscillator_s, by switching frequency f_sDefeated Enter pulse-modulator, process output switch pipe S by pulse-modulator₁To S₄Drive pulse signal v_GS1～v_GS4.And then, logical On and off in Guan Yi switch periods of overdrive pulse Signal-controlled switch.Thus, detection obtains a switch week Switching tube (S is flowed through in phase₁～S₄) electric current i_S1～i_S4, flow through the electric current i of diode D_D, flow through resonant inductance L_SElectric current i_LS, flow through inverter bridge DC bus current i_pn, and flow through the electric current i of transformer primary side_T.Additionally, also detection obtains one and opens Inverter bridge output voltage v in the cycle of pass_acWith resonant capacitance C_pOn voltageI.e. obtain the Z source DC converter shown in Fig. 3 Operation principle oscillogram.

As it is shown on figure 3, a switch periods can be divided into 12 mode of operations, due to front 6 operational modules and rear 6 works The working condition of operation mode is similar to, and analyzes front 6 mode of operations in detail below.

1) mode of operation 1 (t₀～t₁Stage)

Under the duty of mode of operation 1 correspondence, the circuit theory diagrams of Z source DC converter are as shown in fig. 4 a.Wherein, open Close pipe S₁To S₄It is in conducting state.As it is shown on figure 3, at t₀Moment i_LS<i_pn, therefore, sustained diode₂And D₃Turn off, electricity The stream change of current is to switching tube S₂And S₃, now inverter bridge is in pass-through state, and diode D turns off, the first electric capacity of Z source impedance network C₁With the second electric capacity C₂Give the first inductance L respectively₁With the second inductance L₂Constant-voltage charge, resonant inductance L_SWith resonant capacitance C_pStart humorous Shake.Diode M in transformer secondary side, in rectifier bridge₂、M₃Conducting powering load.Now, Z source DC converter is in work The equivalent circuit diagram of pattern 1 as shown in Figure 5 a, can obtain:

v_L(t)=V_C (5)

$\left\{\begin{array}{c}-C_p\frac{{\mathrm{dv}}_{Cp}\left(t\right)}{dt}+i_{L_s}\left(t\right)=-I_T\\ L_s\frac{{\mathrm{di}}_{L_s}\left(t\right)}{dt}=-v_{C_p}\left(t\right)\end{array}\right.---\left(6\right)$

Assuming thatCan obtain:

$\left\{\begin{array}{c}{v}_{C_p}\left(t\right)=-(I_m+I_T)Z_r{\mathrm{cos\&omega;}}_{r}t\\ i_{L_s}\left(t\right)=(I_m+I_T){\mathrm{sin\&omega;}}_{r}t-I_T\end{array}\right.---\left(7\right)$

Wherein,

ω_rFor the angular frequency of resonant slots,

Z_rFor the characteristic impedance of resonant slots,

2) mode of operation 2 (t₁～t₂Stage)

Under the duty of mode of operation 2 correspondence, the circuit theory diagrams of Z source DC converter are as shown in Figure 4 b.At t₁Time Carve, resonant inductance electric current i_LSWith inverter bridge input current i_PnEqual, and by i_LS<i_pnTo i_LS>i_pnChange.Now, switching tube S₂ And S₃Turn off, current commutation to diode D₂And D₃, inverter bridge is still in pass-through state.Diode D turns off, Z source impedance network First electric capacity C₁With the second electric capacity C₂Give the first inductance L respectively₁With the second inductance L₂Constant-voltage charge, resonant inductance L_SAnd resonant capacitance C_pStart resonance.Diode M in transformer secondary side, in rectifier bridge₂、M₃Conducting powering load.Now, Z source DC converting Device mode of operation 2 equivalent circuit diagram as shown in Figure 5 a,WithExpression formula identical with mode of operation 1.

3) mode of operation 3 (t₂～t₃Stage)

Under the duty of mode of operation 3 correspondence, the circuit theory diagrams of Z source DC converter are as illustrated in fig. 4 c.At t₂Time Carve, resonant inductance electric current i_LSReach maximum；Resonant capacitor voltageAnd byToChange；Transformation Device electric current turns negative number to positive number.Now, diode M in rectifier bridge₂And M₃Turn off, M₁And M₄Conducting.Switching tube S₁And S₄Conducting, switching tube S₂And S₃Turn off, current commutation to diode D₂And D₃, inverter bridge is still in pass-through state.Diode D turns off, Z source impedance network The first electric capacity C₁With the second electric capacity C₂Give the first inductance L respectively₁With the second inductance L₂Constant-voltage charge, resonant inductance L_SWith resonance electricity Hold C_pStart resonance.Diode M in transformer secondary side, in rectifier bridge₁、M₄Conducting powering load.Now, Z source direct current becomes Parallel operation mode of operation 3 equivalent circuit diagram as shown in Figure 5 b, can obtain:

v_L(t)=V_C (11)

$\left\{\begin{array}{c}-C_p\frac{{\mathrm{dv}}_{Cp}\left(t\right)}{dt}+i_{L_s}\left(t\right)=I_T\\ L_s\frac{{\mathrm{di}}_{L_s}\left(t\right)}{dt}=-v_{C_p}\left(t\right)\end{array}\right.---\left(6\right)$

Obtained by formula (12):

$\left\{\begin{array}{c}{v}_{C_p}\left(t\right)=(I_m-I_T)Z_r{\mathrm{sin\&omega;}}_r(t-t_2)\\ i_{L_s}\left(t\right)=(I_m-I_T){\mathrm{cos\&omega;}}_r(t-t_2)+I_T\end{array}\right.---\left(13\right)$

Wherein, I_m、ω_rAnd Z_rRelational expression see formula (8) to (10), here is omitted.

4) mode of operation 4 (t₃～t₄Stage)

Under the duty of mode of operation 4 correspondence, the circuit theory diagrams of Z source DC converter are as shown in figure 4d.At t₃Time Carve, resonant inductance electric current i_LSEqual to inverter bridge input current i_Pn, and t₃I in the previous mode of operation in moment_LS>i_pn.Now, D₂And D₃Turning off, inverter bridge is in non-pass-through state, and inverter bridge DC bus-bar voltageNow, Diode D turns off, the first electric capacity C of Z source impedance network₁With the second electric capacity C₂Give the first inductance L respectively₁With the second inductance L₂Permanent Pressure charging, resonant inductance L_SWith resonant capacitance C_pStart resonance.Diode M in transformer secondary side, in rectifier bridge₁、M₄Conducting Powering load.Now, Z source DC converter mode of operation 4 equivalent circuit diagram as shown in Figure 5 c, can obtain:

$v_L\left(t\right)=V_C-v_{ac}\left(t\right)=V_C-v_{C_p}\left(t\right)---\left(14\right)$

$\left\{\begin{array}{c}{v}_{C_p}\left(t\right)=v_{C_p}\left(t_3\right)+\frac{2I_L-I_T}{C_p}(t-t_3)\\ i_{L_s}\left(t\right)=i_{L_s}\left(t_3\right)\end{array}\right.---\left(15\right)$

5) mode of operation 5 (t₄～t₅Stage)

Under the duty of mode of operation 5 correspondence, the circuit theory diagrams of Z source DC converter are as shown in fig 4e.At t₄Time Carve,i_D> 0, diode D turns on, and DC source is the first electric capacity C₁With the second electric capacity C₂Charging. Now, Z source DC converter mode of operation 5 equivalent circuit diagram as fig 5d, can obtain:

v_L(t)=V_i-V_C (16)

$\left\{\begin{array}{c}-C_p\frac{{\mathrm{dv}}_{Cp}\left(t\right)}{dt}+i_{L_s}\left(t\right)=I_T\\ L_s\frac{{\mathrm{di}}_{L_s}\left(t\right)}{dt}=2V_C-V_i-v_{C_p}\left(t\right)\end{array}\right.---\left(17\right)$

Can be obtained by formula (17):

$\left\{\begin{array}{c}{v}_{C_p}\left(t\right)=2V_C-V_i+(2I_L-I_T)Z_r{\mathrm{sin\&omega;}}_r(t-t_4)\\ i_{L_s}\left(t\right)=(2I_L-I_T){\mathrm{cos\&omega;}}_r(t-t_4)+I_T\end{array}\right.---\left(18\right)$

Wherein, ω_rAnd Z_rRelational expression see formula (9) and (10), here is omitted.

6) mode of operation 6 (t₅～t₆Stage)

Under the duty of mode of operation 6 correspondence, the circuit theory diagrams of Z source DC converter are as shown in fig. 4f.At t₅Time Carve, resonant inductance electric current i_LS=0, and by i_LS> 0 to i_LS< 0 change.Now, switching tube S₁And S₄Turning off, current commutation is to afterflow Diode D₁And D₄, diode D turns on, and DC source is the first electric capacity C₁With the second electric capacity C₂Charging.Now, Z source DC converting Device mode of operation 6 equivalent circuit diagram as fig 5d,WithExpression formula similar with mode of operation 5.

Mode of operation 7 to mode of operation 12 and mode of operation 1 to mode of operation 6 are the relation of phase-inversion symmetric, by Working mould Formula 1 to mode of operation 6WithRelational expression, it is possible to obtain mode of operation 7 to mode of operation 12 aboutWithRelational expression.According in a switch periodsWithRelational expression, determine that Z source direct current becomes The phase-plane diagram of parallel operation.As shown in Figure 6, phase-plane diagram withFor abscissa,For vertical coordinate.Holding of each mode of operation The continuous time is as follows:

$T_{01}=t_1-t_0=\frac{1}{{\mathrm{\&omega;}}_r}(arcsin\frac{2I_L+I_T}{I_m+I_T}-arcsin\frac{2I_0+I_T}{I_m+I_T})---\left(19\right)$

$T_{12}=t_2-t_1=\frac{1}{{\mathrm{\&omega;}}_r}arccos\frac{2I_L+I_T}{I_m+I_T}---\left(20\right)$

$T_{23}=t_3-t_2=\frac{1}{{\mathrm{\&omega;}}_r}arccos\frac{2I_L-I_T}{I_m-I_T}---\left(21\right)$

$T_{34}=t_4-t_3=\frac{C_P(2V_C-V_i-Z_r\sqrt{{(I_m-I_T)}^2-{(2I_L-I_T)}^2})}{2I_L-I_T}---\left(22\right)$

$T_{46}=t_6-t_4=\frac{1}{{\mathrm{\&omega;}}_r}(\mathrm{\&pi;}+arccos\frac{I_0+I_T}{2I_L-I_T})---\left(23\right)$

Assuming that T_sFor switch periods, can obtain:

T₀₁+T₁₂+T₂₃+T₃₄+T₄₆=T_s/2 (24)

Owing in Z source impedance network middle in a switch periods, the average voltage of inductance is zero, can obtain:

$\begin{array}{c}{V}_L={\&Integral;}_{t_0}^{t_{12}}{v}_L\left(t\right)dt=2{\&Integral;}_{t_0}^{t_6}{v}_L\left(t\right)dt\\ =\frac{\{T_{03}{V}_C+T_{34}\&lsqb;V_C-\left(v_{C_p}\right(t_3)+v_{C_p}\left(t_4\right))\&rsqb;/2+T_{46}(V_i-V_c)\}}{T_s/2}=0\end{array}---\left(25\right)$

Wherein,

$v_{C_p}\left(t_4\right)=2V_c-V_i---\left(27\right)$

Due in a switch periods, the mode of operation (mode of operation 1 to mode of operation 6) of first half and latter half Operational module (mode of operation 7 to mode of operation 12) phase-inversion symmetric, have By the phase plane of Fig. 6 Figure understands:

$2V_C-V_i-Z_r\sqrt{{(2I_L-I_T)}^2-{(I_0+I_T)}^2}=Z_r\sqrt{{(I_m+I_T)}^2-{(I_0+I_T)}^2}---\left(28\right)$

Assuming that circuit parameter and duty determine, i.e. transformer voltage ratio n, resonant slots angular frequency_r, resonant slots characteristic resistance Anti-Z_r, input voltage V_i, input current I_i, output electric current I_outWith switch periods T_sKnown.By (2) formula, (4) formula, (19)～ (23) formula and (26)～(27) substitution (24) formula, (25) formula and (28) formula obtain (V_c, I_m, I₀).Again by (V_c, I_m, I₀) substitute into (19)～(21) formula, no-voltage opening time T is obtained₀₁With zero-current switching time T₁₃.By the described no-voltage opening time and zero The time sum of switch off current is as the straight-through time of straight-through pulse signal.Make inverter bridge DC bus-bar voltage v_pnIn the straight-through time Value be zero, thus obtain straight-through pulse signal.By straight-through pulse signal input to switching tube drive module, according to described directly Strobe signal adjusts the drive pulse signal of switching tube, makes the rising edge of described drive pulse signal and trailing edge be respectively positioned on institute State in the range of the straight-through time, to realize the Sofe Switch of described inverter bridge.

Embodiment two

Fig. 7 is the flow chart of the control method of Z source DC converter in the embodiment of the present invention two.The technical side of the present embodiment Case is for controlling the Z source DC converter of above-described embodiment, it is achieved the Sofe Switch of described Z source DC converter, specifically include as Lower step:

Step 210, drive pulse signal according to inverter bridge, in determining a switch periods, each mode of operation is corresponding The equivalent circuit of Z source DC converter, calculates current parameters and the voltage parameter of resonant slots according to described equivalent circuit.

Wherein, the drive pulse signal of inverter bridge can be driven module output by the switching tube of above-described embodiment.Drive arteries and veins The generation process rushing signal is shown in above-described embodiment, and here is omitted.Controller obtains the drive pulse signal of inverter bridge, and examines Switching tube (S is flowed through in surveying a switch periods₁～S₄) electric current i_S1～i_S4, flow through the electric current i of diode D_D, flow through resonance electricity Sense L_SElectric current i_LS, flow through inverter bridge DC bus current i_pn, and flow through the electric current i of transformer primary side_T.Additionally, also detect Obtain inverter bridge output voltage v in a switch periods_acWith resonant capacitance C_pOn voltageAccording to foregoing circuit parameter and Mode of operation, obtains Z source DC converter equivalent circuit of each mode of operation in a switch periods, equivalent circuit with state Embodiment is identical, and here is omitted.Current parameters and the voltage parameter of resonant slots is calculated according to described equivalent circuit.It is preferably The current value i of the resonant inductance of resonant slots is calculated according to described equivalent circuit_Ls, and, the magnitude of voltage V of resonant capacitance_Cp.Specifically Computational methods are shown in above-described embodiment, and here is omitted.

Step 220, according to the current parameters of described resonant slots and voltage parameter, determine the straight-through arteries and veins of Z source DC converter Rush the straight-through time of signal.

Wherein, the described straight-through time is inverter bridge DC bus-bar voltage v_pnIt it is the time of zero.Voltage according to resonant capacitance Value V_CpRelational expression and the current value i of resonant inductance_LsRelational expression, determine the phase-plane diagram of Z source DC converter.According to institute State phase-plane diagram and determine the persistent period relational expression of a switch periods each mode of operation interior.According to described persistent period relation Formula determines that no-voltage is opened and the time range of zero-current switching, such as, and average according to a switch periods interior resonance inductance Voltage is zero, and, magnitude of voltage V_CpAt first half and the opposite polarity of latter half of a switch periods, solve described in hold Continuous time history form, obtains no-voltage opening time scope and zero-current switching time range.Described no-voltage is opened and zero The time sum of switch off current is as the straight-through time of straight-through pulse signal.

Step 230, according to the described straight-through time adjust described inverter bridge drive pulse signal, make described driving pulse believe Number rising edge and trailing edge be respectively positioned in the range of the described straight-through time, to realize the Sofe Switch of described inverter bridge.

The embodiment of the present invention, by calculating the current parameters of the resonant slots that each mode of operation is corresponding in a switch periods And voltage parameter；Thus, determine the straight-through time of the straight-through pulse signal of Z source DC converter；Adjust further according to the straight-through time The drive pulse signal of described inverter bridge, makes the rising edge of described drive pulse signal and trailing edge be respectively positioned on the described straight-through time In the range of, to realize the Sofe Switch of described inverter bridge.The embodiment of the present invention solves Z source converter switching loss in prior art High problem, reduces switching loss, improves the safety and reliability of Z source DC converter.

On the basis of technique scheme, the initial time of described zero-current switching time is current value i_LsEqual to inversion Bridge DC bus current i_pnMoment.Further, at current value i_LsNot less than inverter bridge DC bus current i_pnTime, it is achieved inversion Bridge zero-current switching.

Note, above are only presently preferred embodiments of the present invention and institute's application technology principle.It will be appreciated by those skilled in the art that The invention is not restricted to specific embodiment described here, can carry out for a person skilled in the art various obvious change, Readjust and substitute without departing from protection scope of the present invention.Therefore, although by above example, the present invention is carried out It is described in further detail, but the present invention is not limited only to above example, without departing from the inventive concept, also Other Equivalent embodiments more can be included, and the scope of the present invention is determined by scope of the appended claims.

Claims (9)

1. a Z source DC converter, it is characterised in that including: inverter bridge, resonant slots, transformator and rectifier bridge；

Described inverter bridge is electrically connected with DC source by Z source impedance network, for direct current signal is converted into AC signal, defeated Go out AC signal to transformator；

Described resonant slots is series between described inverter bridge and the former limit of described transformator, for being in pass-through state in inverter bridge Time, the AC signal additional resonance signal exported for described inverter bridge, by the exchange after transformator output additional resonance signal Signal is to rectifier bridge；

Described rectifier bridge electrically connects with the secondary of transformator, for carrying out the AC signal after additional resonance signal at rectification Reason, the direct current signal after output rectification is to load.

Z source the most according to claim 1 DC converter, it is characterised in that described resonant slots includes that resonant inductance is harmonious Shake electric capacity；

Described resonant inductance is series between described inverter bridge and described transformator, and, described resonant capacitance is connected in parallel on described The former limit of transformator.

Z source the most according to claim 1 DC converter, it is characterised in that described DC source and Z source impedance network it Between be in series with the element for preventing Z source impedance network current reflux.

Z source the most according to claim 1 DC converter, it is characterised in that also include DC filtering inductance, described direct current Filter inductance is series between described rectifier bridge and load, the impact electricity in the direct current signal suppressing output extremely described load Stream.

5. the control method of a Z source DC converter, it is characterised in that include that the arbitrary described Z source of Claims 1-4 is straight Current converter, its control method includes:

According to the drive pulse signal of inverter bridge, determine the Z source DC converting that a switch periods each mode of operation interior is corresponding The equivalent circuit of device, calculates current parameters and the voltage parameter of resonant slots according to described equivalent circuit；

Current parameters according to described resonant slots and voltage parameter, determine straight-through pulse signal straight-through of Z source DC converter Time；

According to the described straight-through time adjust described inverter bridge drive pulse signal, make described drive pulse signal rising edge and Trailing edge is respectively positioned in the range of the described straight-through time, to realize the Sofe Switch of described inverter bridge.

The control method of Z source the most according to claim 5 DC converter, it is characterised in that including:

Described current parameters is the current value i of resonant inductance_Ls, and, described voltage parameter is the magnitude of voltage V of resonant capacitance_Cp。

The control method of Z source the most according to claim 6 DC converter, it is characterised in that according to described resonant slots Current parameters and voltage parameter, determine the straight-through time of the straight-through pulse signal of Z source DC converter, including:

Magnitude of voltage V according to resonant capacitance_CpRelational expression and the current value i of resonant inductance_LsRelational expression, determine that Z source direct current becomes The phase-plane diagram of parallel operation；

The persistent period relational expression of each mode of operation in a switch periods is determined according to described phase-plane diagram；

Determine that no-voltage is opened and the time range of zero-current switching according to described persistent period relational expression, described no-voltage is opened Open the straight-through time as straight-through pulse signal of the time sum with zero-current switching.

The control method of Z source the most according to claim 7 DC converter, it is characterised in that according to the described persistent period Relational expression determines that no-voltage is opened and the time range of zero-current switching, including:

Average voltage according to a switch periods interior resonance inductance is zero, and, magnitude of voltage V_CpBefore a switch periods Half part and the opposite polarity of latter half, solve described persistent period relational expression, obtain no-voltage opening time scope and zero Current-off time scope.

The control method of Z source the most according to claim 8 DC converter, it is characterised in that also include:

The initial time of described zero-current switching time is current value i_LsEqual to inverter bridge DC bus current i_pnMoment.