CN205753448U - A kind of grid-connected photovoltaic system - Google Patents

Abstract

The utility model discloses a kind of grid-connected photovoltaic system, be made up of photovoltaic array, Boost circuit, modified model Z source network, PWM inverter bridge, filter inductance, power distribution network six part.Boost circuit is followed the tracks of in order to realize photovoltaic array Maximum Power Output.Modified model Z source network, on the basis of the inversion network of traditional Z source, increases by 1 active switching devices and inductance, constitutes an equivalent Boost circuit in conjunction with the input diode in traditional Z source impedance network in prime, to improve boost capability；Simultaneously because the addition of inductance, start-up course limits inrush current, and ensure that the continuous of PWM inverter bridge input current.This system starting process is mild, and the quality of power supply is good, system effectiveness is high in output.

Description

A kind of grid-connected photovoltaic system

Technical field

This utility model relates to a kind of grid-connected photovoltaic system, belongs to distributed power generation and intelligent grid field.

Background technology

The utilization of solar energy is to alleviate the global energy important channel with problem of environmental pollution in short supply, and photovoltaic generation is exactly near One of focus studied over Nian.Use the most ripe electric electronic current change technology can convert solar energy into electric energy, Jin Ershi Existing voltage transformation controls with power.

Z-source inverter has with the impedance network of its uniqueness can realize DC side boosting inverter, allow inverter leg work Make in the advantages such as pass-through state, it is therefore not necessary in the control signal insert Dead Time improve inverter output the quality of power supply and The stability of system, is particularly well-suited to that the voltage of the sent electric energy of renewable energy system is low and the big feature that fluctuates, tool Have broad application prospects.But Z-source inverter also has certain limitation: 1, sensitizing factor is less, and boost capability extremely has Limit；2, input current is interrupted, and DC voltage utilization rate is low；3, initial start stage easily causes impedance network inductance capacitance resonance, thus Serious startup is caused to impact.

Summary of the invention

The technical problems to be solved in the utility model is: for the deficiencies in the prior art, has invented a kind of grid-connected Electricity system, by photovoltaic array, Boost circuit, modified model Z source network, PWM inverter bridge, filter inductance, power distribution network six part Composition.Boost circuit realizes photovoltaic array Maximum Power Output and follows the tracks of.Modified model Z source network is in traditional Z source inversion network On the basis of, increase by 1 active switching devices and inductance, in conjunction with the input diode in traditional Z source impedance network at prime structure Become an equivalent Boost circuit, to improve boost capability；Simultaneously because the addition of inductance, start-up course limits startup punching Hit electric current, and ensure that the continuous of PWM inverter bridge input current.This system starting process is mild, and the output quality of power supply is good, system Efficiency is high.

The technical solution of the utility model is: a kind of grid-connected photovoltaic system, rises piezoelectricity including photovoltaic array, Boost Road, modified model Z source network, PWM inverter bridge, filter inductance, power distribution network；Photovoltaic array, Boost circuit, modified model Z source net Network, PWM inverter bridge, filter inductance, power distribution network are sequentially connected with, and the direct current energy of photovoltaic array output is for conversion into AC energy also Enter power distribution network；Boost circuit includes photovoltaic side storage capacitor C₀, Boost boost inductance L₀, Boost circuit derailing switch Part S₀, Boost circuit diode VD₀, DC side storage capacitor C_d；Modified model Z source network includes inductance L_b, switching device S_b And anti-paralleled diode VD_b, diode VD_in, inductance L₁And L₂, electric capacity C₁And C₂；PWM inverter bridge is by four switching device S₁~ S₄And respective anti-paralleled diode VD₁～VD₄Composition；Photovoltaic array and photovoltaic side storage capacitor C₀It is connected in parallel, photovoltaic battle array Row output cathode and Boost boost inductance L₀It is connected, Boost boost inductance L₀The other end and Boost circuit switching device S₀ Colelctor electrode, Boost circuit diode VD₀Anode be connected, Boost circuit diode VD₀Negative electrode and DC side Storage capacitor C_dOne end, inductance L_bOne end be connected, inductance L_bThe other end and switching device S_bColelctor electrode, inverse parallel two Pole pipe VD_bNegative electrode, diode VD_inAnode be connected, diode VD_inNegative electrode and inductance L₁One end, electric capacity C₁One end It is connected, inductance L₁The other end and electric capacity C₂One end, switching device S₁Colelctor electrode, anti-paralleled diode VD₁Negative electrode, open Close device S₃Colelctor electrode, anti-paralleled diode VD₃Negative electrode be connected, electric capacity C₂The other end and inductance L₂One end, derailing switch Part S_bEmitter stage, anti-paralleled diode VD_bAnode, DC side storage capacitor C_dThe other end, Boost circuit switch Device S₀Emitter stage, photovoltaic array output negative pole be connected, electric capacity C₁The other end and inductance L₂The other end, switching device S₂ Emitter stage, anti-paralleled diode VD₂Anode, switching device S₄Emitter stage, anti-paralleled diode VD₃Anode be connected；Open Close device S₁Emitter stage and anti-paralleled diode VD₁Anode, switching device S₂Colelctor electrode, anti-paralleled diode VD₂The moon The most connected, this node is designated as A point；Switching device S₃Emitter stage and anti-paralleled diode VD₃Anode, switching device S₄Collection Electrode, anti-paralleled diode VD₄Negative electrode be connected, this node is designated as B point；Filter inductance L_fAn end be connected to A point, the other end with Power distribution network is connected, and the opposite side of power distribution network is connected to B point.

The beneficial effects of the utility model are: 1, without inserting people's Dead Time raising inverter output electricity in the control signal Can quality and the stability of system；2, boost capability is relatively strong, is particularly well-suited to the sent electric energy of renewable energy system Voltage is low and the big feature that fluctuates；3, PWM inverter bridge input current is continuous current；4, system starting process is mild, output electricity Quality is good, system effectiveness is high for energy.

Accompanying drawing explanation

Fig. 1 is this utility model structural representation.

Fig. 2 is this utility model equivalent circuit diagram under non-pass-through state.

Fig. 3 is this utility model equivalent circuit diagram under pass-through state.

Detailed description of the invention

Below in conjunction with Figure of description, the technical solution of the utility model is further elaborated, but is not limited to this.

As it is shown in figure 1, a kind of grid-connected photovoltaic system structural representation, including photovoltaic array, Boost circuit, Modified model Z source network, PWM inverter bridge, filter inductance, power distribution network；Photovoltaic array, Boost circuit, modified model Z source network, PWM inverter bridge, filter inductance, power distribution network are sequentially connected with, and the direct current energy of photovoltaic array output is for conversion into AC energy and is incorporated to Power distribution network；Boost circuit includes photovoltaic side storage capacitor C₀, Boost boost inductance L₀, Boost circuit switching device S₀, Boost circuit diode VD₀, DC side storage capacitor C_d；Modified model Z source network includes inductance L_b, switching device S_bAnd Its anti-paralleled diode VD_b, diode VD_in, inductance L₁And L₂, electric capacity C₁And C₂；PWM inverter bridge is by four switching device S₁～S₄ And respective anti-paralleled diode VD₁～VD₄Composition；Photovoltaic array and photovoltaic side storage capacitor C₀It is connected in parallel, photovoltaic array Output cathode and Boost boost inductance L₀It is connected, Boost boost inductance L₀The other end and Boost circuit switching device S₀'s Colelctor electrode, Boost circuit diode VD₀Anode be connected, Boost circuit diode VD₀Negative electrode and DC side store up Can electric capacity C_dOne end, inductance L_bOne end be connected, inductance L_bThe other end and switching device S_bColelctor electrode, inverse parallel two pole Pipe VD_bNegative electrode, diode VD_inAnode be connected, diode VD_inNegative electrode and inductance L₁One end, electric capacity C₁One end phase Even, inductance L₁The other end and electric capacity C₂One end, switching device S₁Colelctor electrode, anti-paralleled diode VD₁Negative electrode, switch Device S₃Colelctor electrode, anti-paralleled diode VD₃Negative electrode be connected, electric capacity C₂The other end and inductance L₂One end, switching device S_bEmitter stage, anti-paralleled diode VD_bAnode, DC side storage capacitor C_dThe other end, Boost circuit derailing switch Part S₀Emitter stage, photovoltaic array output negative pole be connected, electric capacity C₁The other end and inductance L₂The other end, switching device S₂'s Emitter stage, anti-paralleled diode VD₂Anode, switching device S₄Emitter stage, anti-paralleled diode VD₃Anode be connected；Switch Device S₁Emitter stage and anti-paralleled diode VD₁Anode, switching device S₂Colelctor electrode, anti-paralleled diode VD₂Negative electrode Being connected, this node is designated as A point；Switching device S₃Emitter stage and anti-paralleled diode VD₃Anode, switching device S₄Current collection Pole, anti-paralleled diode VD₄Negative electrode be connected, this node is designated as B point；Filter inductance L_fAn end be connected to A point, the other end with join Electrical network is connected, and the opposite side of power distribution network is connected to B point.

Boost circuit realizes photovoltaic array Maximum Power Output and follows the tracks of.Modified model Z source network is in the inversion of traditional Z source On the basis of network, increase by 1 active switching devices and inductance, in conjunction with the input diode in Conventional impedance network at prime structure Become an equivalent Boost circuit, to improve boost capability；Simultaneously because the addition of inductance, start-up course limits startup punching Hit electric current, and ensure that the continuous of PWM inverter bridge input current.

To simplify the analysis, hypothesis below is done: 1, device is ideal operation state；2, photovoltaic array, Boost circuit It is equivalent to a direct voltage source E.

On the basis of above-mentioned hypothesis, equivalent circuit diagram of the present utility model as shown in Figures 2 and 3: Fig. 2 show non-straight This utility model equivalent circuit diagram under logical state, Fig. 3 show this utility model equivalent circuit diagram under pass-through state.

When modified model Z source network works in effective status and 0 traditional state, the now input electricity of PWM inverter bridge Stream is by grid-connected current control, and therefore, PWM inverter bridge can be with a current source equivalence, and its two ends input voltage is referred to as direct-current chain Voltage, is designated as u_dc, therefore, effective status and 0 traditional state being referred to as non-pass-through state, equivalent circuit is as shown in Figure 2.Inductance L₁、L₂With electric capacity C₁、C₂Being respectively provided with identical inductance value L and capacitance C, impedance network is symmetrical, has following relation formula I to become Vertical:

$\left\{\begin{array}{c}{u}_{C1}=u_{C2}=u_C\\ u_{L1}=u_{L2}=u_L\end{array}\right.---\left(I\right)$

In formula I, u_C1、u_C2、u_L1、u_L2It is respectively electric capacity C₁, electric capacity C₂, inductance L₁, inductance L₂Both end voltage.

Under non-pass-through state, switching device S_bTurn off, diode VD_inConducting, now inductance L₁On voltage be:

u_L=u_C-u_dc (Ⅱ)。

Inductance L_bOn voltage be:

u_Lb=E-u_C-u_L (Ⅲ)。

Can be obtained by formula II and formula III:

u_Lb=E-2u_C+u_dc (Ⅳ)。

The state simultaneously turned on when two switching devices of the same brachium pontis of PWM inverter bridge is referred to as pass-through state, now PWM Inverter bridge can be with a short-circuit line equivalence, DC-link voltage u_dcIt is 0, as shown in Figure 3.Now Guan Bi switching device S_b, force two Pole pipe D_inTurn off, now inductance L₁On voltage be:

u_L=u_C (Ⅴ)。

Inductance L_bOn voltage be:

u_Lb=E (VI).

Volt-second equilibrium relation according to inductance, i.e. switch periods T_sIn, the meansigma methods of the voltage at inductance two ends is 0, therefore, the straight-through dutycycle of order is D₀, then the persistent period of effective status is (1-D₀)T_s, and the time of pass-through state is D₀T_s, in conjunction with formula II～formula VI, the DC-link voltage u of modified model Z source grid-connected inverter can be obtained_dcAnd Z source network electric capacity Voltage u_CAnd the relation between DC side input voltage E:

$\left\{\begin{array}{c}{u}_{dc}=\frac{1}{(1-2D_0)(1-D_0)}E\\ u_c=(1-D_0)u_{dc}=\frac{1}{1-2D_0}E\end{array}\right.---\left(VII\right).$

In definition this utility model, the sensitizing factor of modified model Z source network is B ', then have:

$B^{\′}=\frac{1}{(1-2D_0)(1-D_0)}---\left(VIII\right).$

The sensitizing factor of traditional Z source network is B=1/ (1-2D₀), by its compared with formula (VIII) visible, modified model Z source net Network improves a lot in boost capability relative to traditional Z source network, and for identical distribution voltage on line side, modified model Z source Network can be by straight-through dutycycle D₀Control in less scope, to reduce the switch stress of inverter switch device, it is ensured that good The good output quality of power supply.

Claims (1)

1. a grid-connected photovoltaic system, it is characterised in that include photovoltaic array, Boost circuit, modified model Z source net Network, PWM inverter bridge, filter inductance, power distribution network；Photovoltaic array, Boost circuit, modified model Z source network, PWM inverter bridge, Filter inductance, power distribution network are sequentially connected with, and the direct current energy of photovoltaic array output is for conversion into AC energy and is incorporated to power distribution network； Boost circuit includes photovoltaic side storage capacitor C₀, Boost boost inductance L₀, Boost circuit switching device S₀、 Boost circuit diode VD₀, DC side storage capacitor C_d；Modified model Z source network includes inductance L_b, switching device S_bAnd Anti-paralleled diode VD_b, diode VD_in, inductance L₁And L₂, electric capacity C₁And C₂；PWM inverter bridge is by four switching device S₁～S₄And Its respective anti-paralleled diode VD₁～VD₄Composition；Photovoltaic array and photovoltaic side storage capacitor C₀Being connected in parallel, photovoltaic array is defeated Go out positive pole and Boost boost inductance L₀It is connected, Boost boost inductance L₀The other end and Boost circuit switching device S₀Collection Electrode, Boost circuit diode VD₀Anode be connected, Boost circuit diode VD₀Negative electrode and DC side energy storage Electric capacity C_dOne end, inductance L_bOne end be connected, inductance L_bThe other end and switching device S_bColelctor electrode, anti-paralleled diode VD_bNegative electrode, diode VD_inAnode be connected, diode VD_inNegative electrode and inductance L₁One end, electric capacity C₁One end be connected, Inductance L₁The other end and electric capacity C₂One end, switching device S₁Colelctor electrode, anti-paralleled diode VD₁Negative electrode, switching device S₃Colelctor electrode, anti-paralleled diode VD₃Negative electrode be connected, electric capacity C₂The other end and inductance L₂One end, switching device S_b's Emitter stage, anti-paralleled diode VD_bAnode, DC side storage capacitor C_dThe other end, Boost circuit switching device S₀ Emitter stage, photovoltaic array output negative pole be connected, electric capacity C₁The other end and inductance L₂The other end, switching device S₂Transmitting Pole, anti-paralleled diode VD₂Anode, switching device S₄Emitter stage, anti-paralleled diode VD₃Anode be connected；Switching device S₁Emitter stage and anti-paralleled diode VD₁Anode, switching device S₂Colelctor electrode, anti-paralleled diode VD₂Negative electrode phase Even, this node is designated as A point；Switching device S₃Emitter stage and anti-paralleled diode VD₃Anode, switching device S₄Colelctor electrode, Anti-paralleled diode VD₄Negative electrode be connected, this node is designated as B point；Filter inductance L_fAn end be connected to A point, the other end and power distribution network Being connected, the opposite side of power distribution network is connected to B point.