CN102709940A - Design method of energy storage quasi-Z source single-phase photovoltaic power generation system - Google Patents

Abstract

The invention discloses a design method of an energy storage quasi-Z source single-phase photovoltaic power generation system. The method comprises the steps of design of the voltage and the capacity of an energy storage battery, which are required by the system, selection of a photovoltaic battery module, design of inductance and capacitor parameters of a quasi-Z source network, design of voltage and current grades of an H-bridge inverter, design of a Z-source network diode, calculation of loss of a quasi-Z source inverter and the like. The design method is based on the voltage and power requirements of a user, application of the photovoltaic power generation system and the local climatic characteristics. According to the designed energy storage quasi-Z source single-phase photovoltaic power generation system, the requirement on the 1:2 wide range variation of the voltage of a photovoltaic battery can be met; no matter how the voltage of the photovoltaic battery changes, the system can output a voltage required by a load; and the energy storage quasi-Z source single-phase photovoltaic power generation system is suitable for the requirement for completing voltage rising/reduction, inversion and energy storage by the single-stage power conversion. The invention provides a simple, convenient, effective and rapid method for designing and implementing the energy storage quasi-Z source single-phase photovoltaic power generation system.

Description

The method for designing of the single-phase photovoltaic generating system in a kind of accumulation energy type standard-Z source

Technical field

The present invention relates to the photovoltaic power generation technology field, relate in particular to the method for designing of the single-phase photovoltaic generating system in a kind of accumulation energy type standard-Z source.

Background technology

Photovoltaic generation is desirable sustainable energy, and in its development and use process, power inverter/inverter is essential.But generally speaking, the amplitude of variation of photovoltaic cell output voltage can reach 2 times, uses traditional single-stage inverter structure, will cause the multiplication of inverter design capacity.If adopt two-stage structure, the DC/DC converter of introducing will increase expense, lower efficiency.For this reason; Researcher's new technology that begins one's study; Adopt Z-source and standard-Z source inventer to overcome these problems,, realize the twin-stage mapping function that tradition is made up of DC/DC and inverter because it is with the form of single-stage power conversion; Can not increase the inverter capacity, and compatible in field of photovoltaic power generation and legacy system.

On the other hand, photovoltaic generation power is very strong to illumination and temperature dependency, because illumination and variations in temperature are variable, the voltage and the power wide variety of photovoltaic cell output directly are incorporated into the power networks or independently-powered meeting causes negative effect to electrical network or load.So, except traditional independent photovoltaic generating system is used the scheme of energy-storage battery, in the parallel networking type solar electricity generation system, also adopt the energy-storage battery technology in recent years, with the buffer memory energy, stabilize the power that is incorporated into the power networks.General commonly used method is through two-way DC/DC converter energy-storage battery to be connected to DC side, and the power of realizing being incorporated into the power networks is stabilized function, but the extra cover DC/DC converter that increased, and has increased the cost of system.In order to overcome this problem, patent of invention [application number 201010234868.X, single-stage buck accumulation energy type photovoltaic grid-connected generating control system] with wherein electric capacity is parallelly connected always, has realized single-stage power conversion completion lifting/voltage reducing, inversion and energy storage with energy-storage battery.In this system, energy-storage battery is directly parallel on the electric capacity, need not to increase additional apparatus, and is economical and practical.But, so far, there is not document how to introduce as yet and respectively measures parameter in the design system, such as, energy-storage battery voltage, capacity, photovoltaic cell electric pressure, modulation index, each electric capacity, inductance, power switch losses analysis etc.For an accumulation energy type photovoltaic grid-connected generating control system, these Determination of Parameters are most important.

Summary of the invention

In order to overcome the above problems; The invention discloses the method for designing of the single-phase photovoltaic generating system in a kind of accumulation energy type standard-Z source, the single-phase photovoltaic generating system in said accumulation energy type standard-Z source comprises: energy-storage battery, H bridge inverter, standard-Z source network diode, first electrochemical capacitor, second electrochemical capacitor, first inductance, second inductance, LC filter, photovoltaic cell, electrical network and partial load; Said LC filter comprises output inductor and output filter capacitor composition; And the negative pole of said second electrochemical capacitor links to each other with the anode of said standard-Z source network diode, and the positive pole of the positive pole of said second electrochemical capacitor and said H bridge inverter connects; The negative electrode of said standard-Z source network diode links to each other with said second inductance with said first electrochemical capacitor is anodal simultaneously; It is anodal that the other end of said second inductance is connected in said H bridge inverter; The negative pole of said first electrochemical capacitor links to each other with the negative pole of said H bridge inverter; One end of said first inductance links to each other with the positive pole of said photovoltaic cell; The other end of said first inductance links to each other with the negative pole of said second electrochemical capacitor; Be connected to the grid behind the output process LC filter of said H bridge inverter, or the local load of supplying power; Said energy-storage battery cross-over connection is in the said first electrochemical capacitor two ends, and the positive pole of said energy-storage battery is connected in the positive pole of first electrochemical capacitor; Based on user's voltage and power requirement, photovoltaic generating system purposes, and local climate characteristics; This method comprises needed energy-storage battery voltage of system and capacity parameter design; Photovoltaic battery module is chosen, standard-Z source network inductance, capacitance parameter design, H bridge inverter voltage, current class design; Z-source network diode design, standard-Z source inventer loss calculating etc.

Further, as a kind of preferred, said H bridge inverter voltage, current class design comprise the steps:

Step 1 according to the load voltage or the place's line voltage that is incorporated into the power networks, is calculated the voltage magnitude v of single-phase inverter output _Al;

Step 2, setting photovoltaic cell operating voltage excursion is 1:2, and maximum photovoltaic cell voltage is V _In=v _Al, minimum is V _In=v _Al/ 2, accordingly, when photovoltaic cell voltage is maximum, inverter modulation index M=1, straight-through duty ratio D=0, the DC bus-bar voltage peak value is V _PN=v _Al, photovoltaic cell voltage hour, straight-through duty ratio D=1/3, inverter modulation index M=2/3, DC bus-bar voltage peak value are V _PN=1.5*v _Al

Further, as a kind of preferred, said electric capacity, inductance parameters design comprise:

Step 3 is calculated capacitor C ₁Voltage and batteries in parallel connection voltage V _C1=V _B=v _Al

Step 4 is calculated the DC bus-bar voltage peak value and is V to the maximum _PN=1.5 * v _Al

Step 5 is calculated capacitor C ₂Voltage max is V _C2=0.5 * v _Al

Step 6, maximum straight-through duty ratio D=1/3.

Further, as a kind of preferred, said photovoltaic battery module is chosen and is comprised:

Step 7 is according to the load or the power P that is incorporated into the power networks _o, consider that maximum power occurs in the maximum voltage place, the photovoltaic cell electric current does

Step 8, when the energy-storage battery discharge occurred in the photovoltaic power deficiency, according to above-mentioned design, the minimum operating voltage of photovoltaic cell was v _Al/ 2, k/one when providing electric current to be maximum power during the photovoltaic cell lowest power when setting the minimum intensity of illumination of permission work; Then to export P _oDuring power, it is P that battery need provide power _B=P _o-0.5 * v _Al* iL ₁/ k, then battery current is I _B=P _B/ V _BInductance L then ₂Electric current be i _L2=i _L1+ i _B

Further, as a kind of preferred, said energy-storage battery voltage and capacity parameter design comprise:

Step 9 is confirmed the capacity of storage battery, and the applied statistics data according to the local climate characteristics, in conjunction with the purposes of institute's design system, are confirmed the capacity of storage battery; If the photovoltaic system that requires set meter is under the sunshine condition of somewhere, except local load/electrical network was given in power supply, every day was also on average with P _xPower charged the battery x hour, for night all the time according to the time use, and the each depth of discharge of battery is y%, then needing battery capacity is [P _x* x/v _Al]/(1-y%) (Ah).

Further, as a kind of preferred, said photovoltaic battery module is chosen and is comprised:

Step 10 is confirmed photovoltaic battery module and quantity thereof, and selected photovoltaic battery module according to the local climate characteristics, is confirmed the maximum working voltage v in this module maximum power point _PvWith maximum operating currenbt i _Pv, then photovoltaic cell quantity can be calculated as Round numbers gets n,

Round numbers gets m, and photovoltaic battery module quantity is m*n.

Further, as a kind of preferred, said electric capacity, inductance parameters design comprise:

Step 11, capacitor C ₂Design, system adopts constant straight-through zero vector modulator approach, and then the ripple frequency of capacitance voltage is 2f on the Quasi-Z network _sDuring stable state, the initial value of capacitance voltage and final value equate in the one-period; Be example when straight-through, Quasi-Z network capacitance C ₂The ripple Δ V of voltage _C2For

Wherein,

-i _L1=i _C2, f _sBe carrier frequency, so have If the ripple of given capacitance voltage is Δ V _C2≤α V _C2, then have

For suppressing two frequency multiplication mains ripples, the electric capacity that needs does

In the formula, ε is that two frequency multiplication mains ripples account for V _PNRatio, f is load or line voltage frequency, then since capacitor C greater than And capacitor C ₁Parallelly connected with battery, so capacitor C ₂Be designed to $C_2=\frac{P_o}{4\mathrm{\π\; f}{V}_{\mathrm{PN}}^2\mathrm{\ϵ}};$

Step 12, capacitor C ₁Design, system adopts constant straight-through zero vector modulator approach, and then the ripple frequency of capacitance voltage is 2f on the Quasi-Z network _sDuring stable state, the initial value of capacitance voltage equates with final value in the one-period, is example when leading directly to, Quasi-Z network capacitance C ₁The ripple Δ V of voltage _C1For

Wherein,

i _C1=i _B-i _L2, f _sBe carrier frequency, so have

If the ripple of given capacitance voltage is Δ V _C1≤α V _C1, then have $C_1\≥(i_B-i_{L2})\frac{D}{2f_s\mathrm{\α}{V}_{C1}};$

Step 13, inductance L ₂Design, during stable state, the initial value of one-period internal inductance electric current and final value equate.Be example when straight-through, the ripple Δ i of Quasi-Z network inductive current _L2For

Wherein,

v _L2=V _C1So, have

If the ripple of given inductive current is Δ i _L2≤bi _L2, then have

Step 14, the design of inductance L 1, during stable state, the initial value of one-period internal inductance electric current and final value equate, is example when straight-through, the ripple Δ i of Quasi-Z network inductive current _L1For

Wherein,

V _In+ V _C2=v _L1So, have

If the ripple of given inductive current is Δ i _L1≤bi _L1, then have

Step 15; The parameter of diode in the Quasi-Z network, the diode in the Quasi-Z network are born back-pressure and are turn-offed under pass-through state, conducting under non-pass-through state; Therefore, can design this diode according to its electric current that flows through under the voltage at its two ends under the pass-through state and the non-pass-through state; To bear back-pressure be V to diode under the pass-through state _PN, the electric current through diode under the non-pass-through state is i _D≤i _L1+ i _C2=i _L1+ i _L2-i _d, at traditional zero vector in the time, i _d=0 o'clock, this moment diode to flow through maximum current be i _D=i _L1+ i _L2

Step 16, the parameter of power device of inverter is according to the load or the power P that is incorporated into the power networks _oAnd the load or the place's line voltage that is incorporated into the power networks, the computational load current effective value

The DC bus-bar voltage peak value V that calculates according to step 4 _PNThe load current effective value that gets with aforementioned calculation is as the voltage and current parameter of choosing of power device of inverter.

Further, as a kind of preferred, said standard-Z source inventer loss is calculated and is comprised:

Step 17, the single-phase photovoltaic DC-to-AC converter loss evaluation in accumulation energy type standard-Z source has 4 IGBT and inverse parallel diode thereof, a Z-source network diode, its loss can be calculated respectively according to device;

1) loss evaluation of 4 IGBT and inverse parallel diode thereof, this part loss loss and the straight-through loss that causes under can the branch traditional sense, the loss under the traditional sense comprises switching loss and conduction loss, and switching loss does

$P_{\mathrm{SW}}=\frac{4}{\mathrm{\π}}{f}_s\·(E_{\mathrm{ON},I}+E_{\mathrm{OFF},I}+E_{\mathrm{OFF},D})\·\frac{V_{\mathrm{PN}}}{V_{\mathrm{Ref}}}\·\frac{i_L}{i_{\mathrm{Ref}}},$ In the formula, E _{ON, I}, E _{Off, I}, E _{OFF, D}Be respectively power device at voltage V _RefAnd current i _RefThe time turn-on consumption, turn-off power loss and diode reverse recovery loss of energy, can obtain from the device handbook; i _LBe load current peak value, i _L=1.414*i _a, f _sBe switching frequency; For the conduction loss of each IGBT under the traditional sense, calculate according to formula

$P_{\mathrm{CV},I}=\frac{V_{\mathrm{CE},0}{i}_L}{2\mathrm{\π}}(1+\frac{\mathrm{\πM}}{4}-D)+\frac{r_{\mathrm{CE}}{i}_L^2}{2\mathrm{\π}}(\frac{\mathrm{\π}}{4}+\frac{2M}{3}-\frac{\mathrm{\πD}}{4})$

$P_{\mathrm{CV},D}=\frac{V_{F,0}\·i_L}{2\mathrm{\π}}(1-\frac{\mathrm{\π\; M}}{4}-D)+\frac{r_F\·i_L^2}{2\mathrm{\π}}(\frac{\mathrm{\π}}{4}-\frac{2M}{3}-\frac{\mathrm{\π\; D}}{4}),$ In the formula, V _CE0, V _{F, 0}Saturation voltage drop and conduction voltage drop for IGBT and diode; r _CE, r _FConducting resistance for IGBT and diode; M and D are respectively modulation index and straight-through duty ratio, and then the conduction loss of 4 IGBT and diode thereof is P _CV=4* (P _{CV, I}+ P _{CV, D}), for the straight-through loss that causes, only need to calculate switching loss and conduction loss from IGBT, promptly switching loss does $P_{\mathrm{SW},\mathrm{SH}}=4f_s\·(E_{\mathrm{ON},I}+E_{\mathrm{OFF},I})\·\frac{V_{\mathrm{PN}}}{V_{\mathrm{Ref}}}\·\frac{i_{L1}}{i_{\mathrm{Ref}}},$ Conduction loss does $P_{\mathrm{CV},\mathrm{SH}}=4*(V_{\mathrm{CE},0}{i}_{L1}D+r_{\mathrm{CE}}{i}_{L1}^{2}D+\frac{r_{\mathrm{CE}}{i}_L^{2}D}{8})$

2) loss of Z-source network diode, the Z-Source network diode current flow loss of each module does $P_{\mathrm{CV},D}=V_{\mathrm{DF},0}[{2i}_{L1}(1-D)-\frac{{\mathrm{Mi}}_L}{2})+r_{\mathrm{DF}}\frac{1-D}{2}[{8i}_{L1}^2+i_L^2]-r_{\mathrm{DF}}\frac{8(1-D)}{\mathrm{\π}}{i}_L{i}_{L1},$ In the formula, V _{DF, 0}Conduction voltage drop for Z-source network diode; r _DFBe the conducting resistance of Z-source network diode, its reverse recovery loss does

In the formula, E _RecFor Z-source network diode at I _FMAnd V _RThe time the reverse recovery loss energy; Total losses are P _SW+ P _CV+ P _{SW, SH}+ P _{CV, SH}+ P _{CV, D}+ P _{CV, DR}, through loss estimation, can compare alternative devices, as the optimised devices person's of choosing condition.

Through the inventive method, can design the single-phase photovoltaic generating system in accumulation energy type standard-Z source easy, effectively, quickly.

Description of drawings

When combining accompanying drawing to consider; Through with reference to following detailed, can more completely understand the present invention better and learn wherein many attendant advantages easily, but accompanying drawing described herein is used to provide further understanding of the present invention; Constitute a part of the present invention; Illustrative examples of the present invention and explanation thereof are used to explain the present invention, do not constitute to improper qualification of the present invention, wherein:

Fig. 1 is the structural representation of the single-phase photovoltaic inversion device in accumulation energy type standard-Z source;

Fig. 2 is the method for designing of the single-phase photovoltaic generating system in this accumulation energy type standard-Z source.

Embodiment

Followingly embodiments of the invention are described with reference to Fig. 1-2.

For make above-mentioned purpose, feature and advantage can be more obviously understandable, below in conjunction with accompanying drawing and embodiment the present invention done further detailed explanation.

The method for designing embodiment of the single-phase photovoltaic power generation control system in accumulation energy type standard-Z source.

As shown in Figure 1, the single-phase photovoltaic inversion device in accumulation energy type standard-Z source involved in the present invention comprises: energy-storage battery, H bridge inverter, standard-Z source network diode, the first electrochemical capacitor C 1, the second electrochemical capacitor C2, first inductance L 1, second inductance L 2, LC filter, photovoltaic cell, electrical network and partial load; Said LC filter comprises output inductor L _fWith output filter capacitor C _fForm; And the negative pole of the said second electrochemical capacitor C2 links to each other with the anode of said standard-Z source network diode, and the positive pole of the positive pole of the said second electrochemical capacitor C2 and said H bridge inverter connects; The negative electrode of said standard-Z source network diode links to each other with said second inductance L 2 with the said first electrochemical capacitor C1 is anodal simultaneously; It is anodal that the other end of said second inductance L 2 is connected in said H bridge inverter; The negative pole of the said first electrochemical capacitor C1 links to each other with the negative pole of said H bridge inverter; One end of said first inductance L 1 links to each other with the positive pole of said photovoltaic cell; The other end of said first inductance L 1 links to each other with the negative pole of the said second electrochemical capacitor C2; Be connected to the grid behind the output process LC filter of said H bridge inverter, or the local load of supplying power; Said energy-storage battery cross-over connection is in the said first electrochemical capacitor C 1 two ends, and the positive pole of said energy-storage battery is connected in the positive pole of the first electrochemical capacitor C1.

As shown in Figure 2, the method for designing of the single-phase photovoltaic generating system in a kind of accumulation energy type standard-Z source comprises:

S1, know user's voltage and power requirement, photovoltaic generating system purposes, and local climate characteristics;

S2, energy-storage battery voltage and capacity parameter design;

S3, photovoltaic battery module are chosen;

S4, standard-Z source network inductance, capacitance parameter design;

S5, H bridge inverter voltage, current class design;

S6, Z-source network diode design;

S7, standard-Z source inventer loss are calculated.

Embodiment

Purpose is single-phase photovoltaic power generation control system in accumulation energy type standard-Z source of design, and the phase voltage of load/electrical network is 120V, and power is 1700W.Then can confirm according to step:

Step 1 is calculated single-phase voltage amplitude v _Al=120 * 1.414=170V;

Step 2 is set photovoltaic cell operating voltage excursion 1:2, and maximum photovoltaic cell voltage is 170V, and minimum is 85V.Accordingly, when photovoltaic cell voltage is maximum, inverter modulation index M=1, straight-through duty ratio D=0, the DC bus-bar voltage peak value does

V _PN=170

Photovoltaic cell voltage hour, V _In=85V, straight-through duty ratio D=1/3, inverter modulation index M=2/3, the DC bus-bar voltage peak value does

V _PN=85*3=255V

Step 3, design capacitance C ₁Voltage and batteries in parallel connection voltage

V _C1=V _B=v _al＝170 V

Step 4 is calculated the DC bus-bar voltage peak value and is to the maximum

V _PN=170+85=255 V

Step 5 is calculated capacitor C ₂Voltage max does

V _C2=85 V

Step 6, maximum straight-through duty ratio D=1/3;

Step 7 is according to the load or the power P that is incorporated into the power networks _O, consider that maximum power occurs in the maximum voltage place, the photovoltaic cell component electric current does

$i_{L1}=\frac{P_o}{V_{\mathrm{in}}}=\frac{P_o}{v_{\mathrm{al}}}=\frac{1700}{170}=10A$

Step 8, energy-storage battery discharge occur in photovoltaic power when not enough, and according to above-mentioned design, the minimum operating voltage of photovoltaic cell is 85V, (the illumination 1000W/m during such as maximum of 1/3rd when providing electric current to be maximum power when setting minimum photovoltaic power ², hour 200W/m ²).In the time of then will exporting 1700W power, battery need provide power to do

P _B=1700-85×10/3=1416.7W

Then battery current does

i _B=P _B/V _B=8.3A

Inductance L then ₂Electric current

i _L2=i _L1+i _B=8.3+3.3=11.6 A

Step 9 is confirmed the capacity of storage battery

The applied statistics data according to the local climate characteristics, in conjunction with the purposes of institute's design system, are confirmed the capacity of storage battery.Such as, the photovoltaic system that requires to be designed is under the sunshine condition of somewhere, except local load/electrical network was given in power supply, also on average charged the battery 4 hours with the power of 1000W every day, for night all the time according to the time use, and the each depth of discharge of battery is y%.Then need battery capacity to do

[1000*4/170]/(1-y%)=23.5/(1-y%)Ah

Step 10 is confirmed photovoltaic battery module and quantity thereof

Suppose that certain photovoltaic battery panel is at S=1000W/m ², during T=25 °, maximum power point voltage v _Pv=42.4V, the maximum power point current i _Pv=5A.Along with the cell panel temperature rises, its maximum power point voltage descends, and considers the working range of 1:2, and then minimum is v _Pv=21.2V.

Then, photovoltaic cell quantity can be calculated as

$n=\frac{v_{\mathrm{al}}}{v_{\mathrm{pv}}}=\frac{170}{42.4}=4,$ $m=\frac{10}{5}=2$

This photovoltaic battery module quantity is m * n=8.

Step 11, capacitor C ₂Design

System adopts constant straight-through zero vector modulator approach, and then the ripple frequency of capacitance voltage is 2f on the Quasi-Z network _s

During stable state, the initial value of capacitance voltage and final value equate in the one-period.Be example when straight-through, Quasi-Z network capacitance C ₂The ripple Δ V of voltage _C2For

${\mathrm{\ΔV}}_{C2}=i_{C2}\frac{\mathrm{\Δt}}{C_2}$

Wherein, -i _L1=i _C2, f _sBe carrier frequency, so have

$C_2=i_{L1}\frac{D}{2f_s\mathrm{\Δ}{V}_{C2}}$

If the ripple of given capacitance voltage does

ΔV _C2≤αV _C2

Then have

$C_2\≥i_{L1}\frac{D}{{2f}_s\mathrm{\α}{V}_{C2}}$

If set α=1%, carrier frequency f _s=10kHz, then

$C_2\≥10\×\frac{1/3}{2\×10000\×0.01\×85}=196\mathrm{\μF}$

For single phase system, there is the pulsation of two frequencys multiplication.For Fig. 1 system, capacitor C ₁With the energy-storage battery parallel connection, and then and capacitor C ₂Series connection.For suppressing the pulsation of two frequencys multiplication, the total capacitance that needs does

$C=\frac{P_o}{4\mathrm{\πf}{V}_{\mathrm{PN}}\mathrm{\Δ}{V}_{\mathrm{PN}}}=\frac{P_0}{4\mathrm{\πf}{V}_{\mathrm{PN}}^2\mathrm{\ϵ}}$

In the formula, ε is that two frequency multiplication mains ripples account for V _PNRatio, Δ V _PN=ε V _PN, f is load or line voltage frequency.Set two frequency multiplication mains ripples than being ε=1%, f=50Hz, V _PN=255V, P _PV=1700W, then

$C=\frac{1700}{4\mathrm{\π}\×50\×{255}^2\×1\%}=4.16\mathrm{mF}$

Because capacitor C ₁Parallelly connected with energy-storage battery, can it be regarded as infinitely great electric capacity during design.So, capacitor C ₂Be 4.16mF.

Step 12, capacitor C ₁Design

System adopts constant straight-through zero vector modulator approach, and then the ripple frequency of capacitance voltage is 2f on the Quasi-Z network _s

During stable state, the initial value of capacitance voltage and final value equate in the one-period.Be example when straight-through, Quasi-Z network capacitance C ₁The ripple Δ V of voltage _C1For

$\mathrm{\Δ}{V}_{C1}=i_{C1}\frac{\mathrm{\Δt}}{C1}$

Wherein,

i _C1=i _B-i _L2, f _sBe carrier frequency, so have

$C_1=(i_B-i_{L2})\frac{D}{2f_s\mathrm{\Δ}{V}_{C1}}$

If the ripple of given capacitance voltage does

ΔV _C1≤αV _C1，

Then have

$C_1\≥(i_B-i_{L2})\frac{D}{{2f}_s\mathrm{\α}{V}_{C1}}$

Set other parameters as above, and I _B-I _L2=-I _L1=-10A, then

$C_1\×10\×\frac{1/3}{2\×10000\×0.01\×170}=98\mathrm{\μF}$

Step 13, inductance L ₂Design

During stable state, the initial value of one-period internal inductance electric current and final value equate.Be example when straight-through, the ripple Δ i of Quasi-Z network inductive current _L2For

$\mathrm{\Δ}{i}_{L2}=v_{L2}\frac{\mathrm{\Δt}}{L_2}$

Wherein, v _L2=V _C1So, have

$L_2=V_{C1}\frac{D}{{2f}_s\mathrm{\Δ}{i}_{L2}}$

If the ripple of given inductive current does

Δi _L2≤bi _L2

Then have

$L_2\≥V_{C1}\frac{D}{2f_{s}b{i}_{L2}}$

Set b=20%, i _L2=11.6A then

$L_1\≥170\×\frac{1/3}{2\×10000\×0.2\×11.6}=1.22\mathrm{mH}$

Step 14, inductance L ₁Design

During stable state, the initial value of one-period internal inductance electric current and final value equate.Be example when straight-through, the ripple Δ i of Quasi-Z network inductive current _L1For

${\mathrm{\Δi}}_{L1}=v_{L1}\frac{\mathrm{\Δt}}{L_1}$

Wherein,

V _In+ V _C2=v _L1So, have

$L_1=(V_{\mathrm{in}}+V_{C2})\frac{D}{2f_s\mathrm{\Δ}{i}_{L1}}$

If the ripple of given inductive current does

Δi _L1≤bi _L1

Then have

$L_1\≥(V_{\mathrm{in}}+V_{C2})\frac{D}{2f_{s}b{i}_{L1}}$

V _In=85V, current i _L1=10A, then

$L_1\≥(85+85)\×\frac{1/3}{2\×10000\×0.2\×10}=1.42\mathrm{mH}$

Step 15, the parameter of diode in the Quasi-Z network

Diode in the Quasi-Z network bears back-pressure and turn-offs under pass-through state, conducting under non-pass-through state.Therefore, can design this diode according to its electric current that flows through under the voltage at its two ends under the pass-through state and the non-pass-through state.

Diode bears back-pressure and is V to the maximum under the pass-through state _PN=255V.

Electric current through diode under the non-pass-through state does

i _D≤i _L1+i _C2=i _L1+i _L2-i _d

At traditional zero vector in the time, i _d=0 o'clock, diode flow through maximum current and did this moment

i _D=i _L1+i _L2=20 A

Step 16, the parameter of power device of inverter

According to the load or the power P that is incorporated into the power networks _oAnd the load or the place's line voltage that is incorporated into the power networks, the computational load current effective value

$i_a=\frac{\sqrt{2}{P}_o}{v_{\mathrm{al}}}=\frac{\sqrt{2}\×1700}{170}=14.1A$

The DC bus-bar voltage peak value V that calculates according to step 4 _PNThe load current effective value that gets with aforementioned calculation is as the voltage and current parameter of choosing of power device of inverter.

Step 17, the photovoltaic DC-to-AC converter loss evaluation of accumulation energy type standard-Z source

For circuit shown in Figure 1,4 IGBT (and inverse parallel diode) are arranged, a Z-source network diode, its loss can be calculated respectively according to device.

1) loss evaluation of 4 IGBT (and inverse parallel diode)

The loss and the straight-through loss that cause of this part loss under can the branch traditional sense.Loss under the traditional sense comprises switching loss and conduction loss, and switching loss does

$P_{\mathrm{SW}}=\frac{4}{\mathrm{\π}}{f}_s\·(E_{\mathrm{ON},I}+E_{\mathrm{OFF},I}+E_{\mathrm{OFF},D})\·\frac{V_{\mathrm{PN}}}{V_{\mathrm{ref}}}\·\frac{i_L}{i_{\mathrm{ref}}}$

In the formula, E _{ON, I}, E _{Off, I}, E _{OFF, D}Be respectively power device at voltage V _RefAnd current i _RefThe time turn-on consumption, turn-off power loss and diode reverse recovery loss of energy; i _LBe load current peak value, i _L=i _a* 1.414A, f _sBe switching frequency.According to voltage, the current parameters that step 4 and 16 calculates, choosing IGBT module SGH30N60RUFD is the inverter power switch, calculates its loss.According to device data are provided, at V _Ref=300V, i _RefDuring=30A, the switching loss energy during conducting is E _{ON, I}=0.919mJ/P, the switching loss energy during shutoff is E _{Off, I}=0.814mJ/P, oppositely recovering the switching loss energy is E _{OFF, D}=0.067mJ/P.i _L=14.1*1.414=19.94A, V _PN=255V, f _s=10kHz then calculates P _SW=12.9W.

For the conduction loss of each IGBT under the traditional sense, calculate according to formula

$P_{\mathrm{CV},I}=\frac{V_{\mathrm{CE},0}{i}_L}{2\mathrm{\π}}\·{\∫}_0^{\mathrm{\π}}\sin \mathrm{\ωt}\·(\frac{1+M\left(t\right)}{2}-\frac{D}{2})\·\mathrm{d\ωt}+\frac{r_{\mathrm{CE}}{i}_L^2}{2\mathrm{\π}}\·{\∫}_0^{\mathrm{\π}}{\sin }^2\mathrm{\ωt}\·(\frac{1+M\left(t\right)}{2}-\frac{D}{2})\·\mathrm{d\ωt}$

$=\frac{V_{\mathrm{CE},0}{i}_L}{2\mathrm{\π}}(1+\frac{\mathrm{\πM}}{4}-D)+\frac{r_{\mathrm{CE}}{i}_L^2}{2\mathrm{\π}}(\frac{\mathrm{\π}}{4}+\frac{2M}{3}-\frac{\mathrm{\πD}}{4})$

$P_{\mathrm{CV},D}=\frac{V_{F,0}{\·i}_L}{2\mathrm{\π}}\·{\∫}_0^{\mathrm{\π}}\sin \mathrm{\ωt}\·(\frac{1-M\left(t\right)}{2}-\frac{D}{2})\·\mathrm{d\ωt}+\frac{r_F{\·i}_L^2}{2\mathrm{\π}}\·{\∫}_0^{\mathrm{\π}}{\sin }^2\mathrm{\ωt}\·(\frac{1-M\left(t\right)}{2}-\frac{D}{2})\·\mathrm{d\ωt}$

$=\frac{V_{F,0}\·i_L}{2\mathrm{\π}}(1-\frac{\mathrm{\πM}}{4}-D)+\frac{r_F\·i_L^2}{2\mathrm{\π}}(\frac{\mathrm{\π}}{4}-\frac{2M}{3}-\frac{\mathrm{\πD}}{4})$

In the formula, V _CE0, V _{F, 0}Saturation voltage drop and conduction voltage drop for IGBT and diode; r _CE, r _FBe respectively the conducting resistance of IGBT and diode; M and D are respectively modulation index and straight-through duty ratio.Because V _CE0=2.2V, V _{F, 0}=1.3V, r _CE=0.02 Ω, r _F=0.01 Ω, M=2/3, D=1/3, then the conduction loss of 4 IGBT and diode thereof does

P _CV=4*(P _CV，I+P _CV，D)=45.8W

For the straight-through loss that causes, only need to calculate switching loss and conduction loss from IGBT, promptly switching loss does

$P_{\mathrm{SW},\mathrm{SH}}=4f_s\·(E_{\mathrm{ON},I}+E_{\mathrm{OFF},I})\·\frac{V_{\mathrm{PN}}}{V_{\mathrm{ref}}}\·\frac{i_{L1}}{i_{\mathrm{ref}}}=19.6W$

Conduction loss does

$P_{\mathrm{CV},\mathrm{SH}}=4*(V_{\mathrm{CE},0}{i}_{L1}D+r_{\mathrm{CE}}{i}_{L1}^{2}D+\frac{r_{\mathrm{CE}}{i}_L^{2}D}{8})=6.2W$

2) loss of Z-source network diode

The Z-Source network diode current flow loss of each module does

$P_{\mathrm{CV},D}=V_{\mathrm{DF},0}[{2i}_{L1}(1-D)-\frac{{\mathrm{Mi}}_L}{2})+r_{\mathrm{DF}}\frac{1-D}{2}[{8i}_{L1}^2+i_L^2]-r_{\mathrm{DF}}\frac{8(1-D)}{\mathrm{\π}}{i}_L{i}_{L1}$

Its reverse recovery loss does

$P_{\mathrm{CV},\mathrm{DR}}=\frac{2E_{\mathrm{rec}}{V}_{\mathrm{PN}}({\mathrm{\πi}}_{L1}-i_L)}{\mathrm{\π}{I}_{\mathrm{FM}}{V}_R}2f_s$

According to the diode parameters that step 15 calculates, choosing APT40DQ60B is Z-source network diode, at I _FM=30A, V _RReverse recovery loss energy E during=600V _Rec=0.06mJ/P, V _PN=255V, V _DF0=1.7V.P then _{CV, D}=14.7W, P _{CV, DR}=0.124W.

Total losses are P _SW+ P _CV+ P _{SW, SH}+ P _{CV, SH}+ P _{CV, D}+ P _{CV, DR}=118.2W.

Through loss estimation, can compare alternative devices, one of condition of selecting as optimised devices.

From the foregoing description, can find out, can design the major parameter of accumulation energy type standard-Z source photovoltaic generating system according to the present invention effectively.Institute's designed system is when photovoltaic cell voltage is low, and circuit boosts, and satisfies load request; When photovoltaic cell voltage is higher, need not boost, can meet the demands; At night, energy-storage battery can directly provide energy to load.Whole system realizes having the simplest structure, lower expense with the single-stage power circuit.And system is applicable to that independent photovoltaic generates electricity, and also is applicable to grid-connected photovoltaic power generation.

As stated, embodiments of the invention have been carried out explanation at length, but as long as not breaking away from inventive point of the present invention and effect in fact can have a lot of distortion, this will be readily apparent to persons skilled in the art.Therefore, such variation also all is included within protection scope of the present invention.

Claims (8)

1. the method for designing of the single-phase photovoltaic generating system in accumulation energy type standard-Z source, the single-phase photovoltaic generating system in accumulation energy type standard-Z source comprises: energy-storage battery, H bridge inverter, standard-Z source network diode, first electrochemical capacitor, second electrochemical capacitor, first inductance, second inductance, LC filter, photovoltaic cell, electrical network and partial load; Said LC filter comprises output inductor and output filter capacitor composition; And the negative pole of said second electrochemical capacitor links to each other with the anode of said standard-Z source network diode, and the positive pole of the positive pole of said second electrochemical capacitor and said H bridge inverter connects; The negative electrode of said standard-Z source network diode links to each other with said second inductance with said first electrochemical capacitor is anodal simultaneously; It is anodal that the other end of said second inductance is connected in said H bridge inverter; The negative pole of said first electrochemical capacitor links to each other with the negative pole of said H bridge inverter; One end of said first inductance links to each other with the positive pole of said photovoltaic cell; The other end of said first inductance links to each other with the negative pole of said second electrochemical capacitor; Be connected to the grid behind the output process LC filter of said H bridge inverter, or the local load of supplying power; Said energy-storage battery cross-over connection is in the said first electrochemical capacitor two ends, and the positive pole of said energy-storage battery is connected in the positive pole of first electrochemical capacitor;

It is characterized in that, based on user's voltage and power requirement, the photovoltaic generating system purposes; And the local climate characteristics, this method comprises needed energy-storage battery voltage of system and capacity parameter design, photovoltaic battery module is chosen; Standard-Z source network inductance, capacitance parameter design; H bridge inverter voltage, current class design, Z-source network diode design, the loss of standard-Z source inventer is calculated.

2. the method for designing of the single-phase photovoltaic generating system in a kind of according to claim 1 accumulation energy type standard-Z source is characterized in that, said H bridge inverter voltage, current class design comprise the steps:

Step 1 according to the load voltage or the place's line voltage that is incorporated into the power networks, is calculated the voltage magnitude v of single-phase inverter output _Al;

Step 2, setting photovoltaic cell operating voltage excursion is 1: 2, and maximum photovoltaic cell voltage is V _In=v _Al, minimum is V _In=v _Al/ 2, accordingly, when photovoltaic cell voltage is maximum, inverter modulation index M=1, straight-through duty ratio D=0, the DC bus-bar voltage peak value is V _PN=v _Al, photovoltaic cell voltage hour, straight-through duty ratio D=1/3, inverter modulation index M=2/3, DC bus-bar voltage peak value are V _PN=1.5*val.

3. the method for designing of the single-phase photovoltaic generating system in a kind of according to claim 1 accumulation energy type standard-Z source is characterized in that, said capacitor and inductor parameter designing comprises:

Step 3 is calculated capacitor C ₁Voltage and batteries in parallel connection voltage V _C1=V _B=v _Al

Step 4 is calculated the DC bus-bar voltage peak value and is V to the maximum _PN=1.5 * v _Al

Step 5 is calculated capacitor C ₂Voltage max is V _C2=0.5 * v _Al

Step 6, maximum straight-through duty ratio D=1/3.

4. the method for designing of the single-phase photovoltaic generating system in a kind of according to claim 1 accumulation energy type standard-Z source is characterized in that said photovoltaic battery module is chosen and comprised:

Step 7 is according to the load or the power P that is incorporated into the power networks _o, consider that maximum power occurs in the maximum voltage place, the photovoltaic cell electric current does

Step 8, when the energy-storage battery discharge occurred in the photovoltaic power deficiency, according to above-mentioned design, the minimum operating voltage of photovoltaic cell was v _Al/ 2, k/one when providing electric current to be maximum power during the photovoltaic cell lowest power when setting the minimum intensity of illumination of permission work; Then to export P _oDuring power, it is P that battery need provide power _B=P _o-0.5 * v _Al* i _L1/ k, then battery current is I _B=P _B/ V _BInductance L then ₂Electric current be i _L2=i _L1+ i _B

5. the method for designing of the single-phase photovoltaic generating system in a kind of according to claim 1 accumulation energy type standard-Z source is characterized in that, said energy-storage battery voltage and capacity parameter design comprise:

Step 9 is confirmed the capacity of storage battery, and the applied statistics data according to the local climate characteristics, in conjunction with the purposes of institute's design system, are confirmed the capacity of storage battery; If the photovoltaic system that requires set meter is under the sunshine condition of somewhere, except local load/electrical network was given in power supply, every day was also on average with P _xPower charged the battery x hour, for night all the time according to the time use, and the each depth of discharge of battery is y%, then needing battery capacity is [P _x* x/v _Al]/(1-y%) (Ah).

6. the method for designing of the single-phase photovoltaic generating system in a kind of according to claim 1 accumulation energy type standard-Z source is characterized in that said photovoltaic battery module is chosen and comprised:

Step 10 is confirmed photovoltaic battery module and quantity thereof, and selected photovoltaic battery module according to the local climate characteristics, is confirmed the maximum working voltage v in this module maximum power point _PvWith maximum operating currenbt i _Pv, then photovoltaic cell quantity can be calculated as

Round numbers gets n,

Round

Several m, photovoltaic battery module quantity is m*n.

7. the method for designing of the single-phase photovoltaic generating system in a kind of according to claim 1 accumulation energy type standard-Z source is characterized in that, said capacitor and inductor parameter designing comprises:

Step 11, capacitor C ₂Design, system adopts constant straight-through zero vector modulator approach, and then the ripple frequency of capacitance voltage is 2f on the Quasi-Z network _sDuring stable state, the initial value of capacitance voltage and final value equate in the one-period; Be example when straight-through, Quasi-Z network capacitance C ₂The ripple Δ V of voltage _C2For

Wherein, -i _L1=i _C2, f _sBe carrier frequency, so have If the ripple of given capacitance voltage is Δ V _C2≤α V _C2, then have

For suppressing two frequency multiplication mains ripples, the electric capacity that needs does In the formula, ε is that two frequency multiplication mains ripples account for V _PNRatio, f is load or line voltage frequency, then since capacitor C greater than

And capacitor C ₁Parallelly connected with battery, so capacitor C ₂Be designed to

Step 12, capacitor C ₁Design, system adopts constant straight-through zero vector modulator approach, and then the ripple frequency of capacitance voltage is 2f on the Quasi-Z network _sDuring stable state, the initial value of capacitance voltage equates with final value in the one-period, is example when leading directly to, Quasi-Z network capacitance C ₁The ripple Δ V of voltage _C1For

Wherein,

i _C1=i _B-i _L2f _sBe carrier frequency, so have

If the ripple of given capacitance voltage is Δ V _C1≤α V _C1, then have $C_1\≥(i_B-i_{L2})\frac{D}{2f_s\mathrm{\α}{V}_{C1}};$

Step 13, inductance L ₂Design, during stable state, the initial value of one-period internal inductance electric current and final value equate.Be example when straight-through, the ripple Δ i of Quasi-Z network inductive current _L2For

Wherein,

v _L2=V _C1So, have

If the ripple of given inductive current is Δ i _L2≤bi _L2, then have

Step 14, inductance L ₁Design, during stable state, the initial value of one-period internal inductance electric current and final value equate, is example when straight-through, the ripple Δ i of Quasi-Z network inductive current _L1For

Wherein,

V _In+ V _C2=v _L1So, have

If the ripple of given inductive current is Δ i _L1≤bi _L1, then have

Step 15; The parameter of diode in the Quasi-Z network, the diode in the Quasi-Z network are born back-pressure and are turn-offed under pass-through state, conducting under non-pass-through state; Therefore, can design this diode according to its electric current that flows through under the voltage at its two ends under the pass-through state and the non-pass-through state; To bear back-pressure be V to diode under the pass-through state _PN, the electric current through diode under the non-pass-through state is i _D≤i _L1+ i _C2=i _L1+ i _L2-i _d, at traditional zero vector in the time, i _d=0 o'clock, this moment diode to flow through maximum current be i _D=i _L1+ i _L2

Step 16, the parameter of power device of inverter is according to the load or the power P that is incorporated into the power networks _oAnd the load or the place's line voltage that is incorporated into the power networks, the computational load current effective value The DC bus-bar voltage peak value V that calculates according to step 4 _PNThe load current effective value that gets with aforementioned calculation is as the voltage and current parameter of choosing of power device of inverter.

8. the method for designing of the single-phase photovoltaic generating system in a kind of according to claim 1 accumulation energy type standard-Z source is characterized in that, said standard-Z source inventer loss is calculated and comprised:

Step 17, the single-phase photovoltaic DC-to-AC converter loss evaluation in accumulation energy type standard-Z source has 4 IGBT and inverse parallel diode thereof, a Z-source network diode, its loss can be calculated respectively according to device;

1) loss evaluation of 4 IGBT and inverse parallel diode thereof, this part loss loss and the straight-through loss that causes under can the branch traditional sense, the loss under the traditional sense comprises switching loss and conduction loss, and switching loss does $P_{\mathrm{SW}}=\frac{4}{\mathrm{\π}}{f}_s\·(E_{\mathrm{ON},I}+E_{\mathrm{OFF},I}+E_{\mathrm{OFF},D})\·\frac{V_{\mathrm{PN}}}{V_{\mathrm{Ref}}}\·\frac{i_L}{i_{\mathrm{Ref}}},$ In the formula, E _{ON, I}, E _{Off, I}, E _{OFF, D}Be respectively power device at voltage V _RefAnd current i _RefThe time turn-on consumption, turn-off power loss and diode reverse recovery loss of energy, can obtain from the device handbook; i _LBe load current peak value, i _L=1.414*i _a, f _sBe switching frequency; For the conduction loss of each IGBT under the traditional sense, calculate according to formula

$P_{\mathrm{CV},I}=\frac{V_{\mathrm{CE},0}{i}_L}{2\mathrm{\π}}(1+\frac{\mathrm{\πM}}{4}-D)+\frac{r_{\mathrm{CE}}{i}^{2}L}{2\mathrm{\π}}(\frac{\mathrm{\π}}{4}+\frac{2M}{3}-\frac{\mathrm{\πD}}{4})$

$P_{\mathrm{CV},D}=\frac{V_{F,0}\·i_L}{2\mathrm{\π}}(1-\frac{\mathrm{\π\; M}}{4}-D)+\frac{r_F\·i_L^2}{2\mathrm{\π}}(\frac{\mathrm{\π}}{4}-\frac{2M}{3}-\frac{\mathrm{\π\; D}}{4}),$ In the formula, V _CE0, V _{F, 0}Saturation voltage drop and conduction voltage drop for IGBT and diode; r _CE, r _FConducting resistance for IGBT and diode; M and D are respectively modulation index and straight-through duty ratio, and then the conduction loss of 4 IGBT and diode thereof is P _CV=4* (P _{CV, I}+ P _{CV, D}), for the straight-through loss that causes, only need to calculate switching loss and conduction loss from IGBT, promptly switching loss does $P_{\mathrm{SW},\mathrm{SH}}=4f_s\·(E_{\mathrm{ON},I}+E_{\mathrm{OFF},I})\·\frac{V_{\mathrm{PN}}}{V_{\mathrm{Ref}}}\·\frac{i_{L1}}{i_{\mathrm{Ref}}},$ Conduction loss does $P_{\mathrm{CV},\mathrm{SH}}=4*(V_{\mathrm{CE},0}{i}_{L1}D+r_{\mathrm{CE}}{i}_{L1}^{2}D+\frac{r_{\mathrm{CE}}{i}_L^{2}D}{8})$

2) loss of Z-source network diode, the Z-Source network diode current flow loss of each module does $P_{\mathrm{CV},D}=V_{\mathrm{DF},0}[{2i}_{L1}(1-D)-\frac{{\mathrm{Mi}}_L}{2})+r_{\mathrm{DF}}\frac{1-D}{2}[{8i}_{L1}^2+i_L^2]-r_{\mathrm{DF}}\frac{8(1-D)}{\mathrm{\π}}{i}_L{i}_{L1},$ In the formula, V _{DF, 0}Conduction voltage drop for Z-source network diode; r _DFBe the conducting resistance of Z-source network diode, its reverse recovery loss does

In the formula, E _RecFor Z-source network diode at I _FMAnd V _RThe time the reverse recovery loss energy; Total losses are P _SW+ P _CV+ P _{SW, SH}+ P _{CV, SH}+ P _{CV, D}+ P _{CV, DR}, through loss estimation, can compare alternative devices, as the optimised devices person's of choosing condition.

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