CN203734527U - Two-phase alternating phase shifting Buck controller of photovoltaic off-grid system - Google Patents

Abstract

The utility model relates to a two-phase alternating phase shifting Buck controller of a photovoltaic off-grid system. The controller is characterized by including a first Buck circuit and a second Buck circuit. The first Buck circuit and the second Buck circuit are interleaved. A power switch is capable of realizing higher-frequency output at a lower switching frequency and under a condition that a total output current is identical, circuit total output current ripple waves can be reduced and an EMC performance can be improved. At the same time, the frequency of current ripple wave output is doubled so that the frequency of ripple wave current is multiplied and inductor design requirements are reduced; and capacity selection of filtering capacitors is reduced correspondingly and thus circuit dynamic responses is improved on the whole.

Description

The staggered phase shift Buck of a kind of photovoltaic off-grid system two controller

Technical field

The utility model relates to new forms of energy field of photovoltaic power generation, is specifically related to the controller circuitry of photovoltaic system.

Background technology

Photovoltaic industry relies on solar energy to clean and inexhaustible advantage, makes solar power generation in following energy resource consumption, occupy very important position, utilizes efficiently solar energy by the emphasis that is Future New Energy Source technological development always.At photovoltaic, in net electricity generation system, solar photovoltaic controller is the key component of whole system, and the controller for solar that performance is good can improve the utilance of solar cell and the reliability of photovoltaic system.But along with continuing to increase of the integrated scale of electronic system, require output current and the power of power supply increasing, system works frequency improve constantly the continuous reduction with operating voltage, require the ripple of power supply more and more less, the use of single DC/DC converter can not meet the demands, occur at present DC/DC converter to improve power grade by Multiphase Parallel technology and device parallel connection etc., thereby improved system overall efficiency.But device joint conference make circuit layout complicated, there is dynamic current equalizing, the equal flow problem of stable state simultaneously.By contrast, two-phase or multiphase DC/DC converter in parallel is more preponderated, and input current is shared on each phase road, reduces the current stress of power device.

Summary of the invention

For meeting continuing to increase of the integrated scale of electronic system with single Buck circuit in photovoltaic off-grid system middle controller circuit, require output current and the power of power supply increasing, system works frequency improve constantly the continuous reduction with operating voltage, require the more and more less grade of the ripple specification requirement of power supply, the utility model is by the following technical solutions: a kind of by the Buck circuit application of two-phase crisscross parallel in the control circuit of middle low power photovoltaic off-grid system, it is characterized in that: include a Buck circuit and the 2nd Buck circuit, a described Buck circuit is connected with the 2nd Buck circuit crisscross parallel.

As a kind of improvement, a kind of by the Buck circuit application of two-phase crisscross parallel in the control circuit of middle low power photovoltaic off-grid system, it is characterized in that: a Buck circuit includes the first Support Capacitor C1 and the first continued flow tube D1, the 2nd Buck circuit includes output capacitance C2 and the second continued flow tube D2, the positive pole of the first Support Capacitor C1 is connected with the input of first-phase Buck branch road, the negative pole of the first Support Capacitor C1 is connected with the first continued flow tube D1 anode of first-phase Buck branch road, wherein the input of second-phase Buck branch road is attempted by the input of first-phase Buck branch road, the second continued flow tube D2 anode of second-phase Buck branch road is connected with the negative pole of the first Support Capacitor C1, the positive pole of output capacitance C2 is connected with the output of the 2nd Buck circuit, the negative pole of output capacitance C2 is connected with the negative pole of the first Support Capacitor C1.

The utility model adopts above technical scheme to have the following advantages: Buck circuit itself has advantages of that device is few, simple, cost is low, MPPT controls also relatively simple, but output ripple current is larger, if by two-phase crisscross parallel Buck circuit application in photovoltaic off-grid system, can greatly reduce output ripple current, thereby improve photovoltaic system output current quality; In the situation that total output current size is constant, can reduce to a certain extent carrier frequency, total current ripple frequency is significantly improved, the electric current that power tube in each branch road bears is half of total current size, conduction loss and the switching loss of power device are reduced simultaneously, thermal design requires to decrease, and is conducive to the reduction of circuit cumulative volume and cost; If the ripple frequency fs of branch road inductive current, the total output current ripple frequency of circuit 2fs, two branch road inductive current ripple partial offsets, output total current ripple peak-to-peak value significantly reduces, reduce the requirement of branch road inductor design, meanwhile, corresponding output voltage ripple reduces, the requirement of output filter capacitor reduces, thereby improves system dynamic responding speed; Input voltage stable make MPPT constantly tracing property strengthen, MPPT controller output voltage is more stable, improves MPPT controller and follows the tracks of efficiency, entire system efficiency gets a promotion.

Here use two Buck circuit feature of using staggered phase shift in parallel, the benefit of using is like this to realize high-frequency output voltage with lower switching frequency, and need the inductance of use and electric capacity less, conveniently realize Miniaturization Design, the stable MPPT that improved of input voltage follows the tracks of efficiency, the utilance of raising system to solar energy constantly in addition.

Accompanying drawing explanation

Accompanying drawing 1 is the concise and to the point system block diagram of a kind of embodiment of the utility model;

Accompanying drawing 2 is that the utility model is for the wave simulation figure of power switch control impuls in system and two branch road inductive currents and output total current;

Accompanying drawing 3 is that the utility model carries out for staggered circuit the system block diagram that MPPT controls.

Embodiment

Below in conjunction with the drawings and specific embodiments, the utility model is further described.

This practical content concrete scheme is: as shown in Figure 1, the output current of photovoltaic module PV is by after DC filter filtering, by the two-phase Buck circuit of crisscross parallel, be converted into galvanic current and press, then accumulators charges after DC filter.Include a Buck circuit and the 2nd Buck circuit, a described Buck circuit is connected with the 2nd Buck circuit crisscross parallel.More excellent embodiment, the one Buck circuit includes the first Support Capacitor C1 and the first continued flow tube D1, the 2nd Buck circuit includes output capacitance C2 and the second continued flow tube D2, the positive pole of the first Support Capacitor C1 is connected with the input of first-phase Buck branch road, the negative pole of the first Support Capacitor C1 is connected with the first continued flow tube D1 anode of first-phase Buck branch road, wherein the input of second-phase Buck branch road is attempted by the input of first-phase Buck branch road, the second continued flow tube D2 anode of second-phase Buck branch road is connected with the negative pole of the first Support Capacitor C1, the positive pole of output capacitance C2 is connected with the output of the 2nd Buck circuit, the negative pole of output capacitance C2 is connected with the negative pole of the first Support Capacitor C1.Output capacitance C2 connects and can prevent the sudden change of electric current with inductance, supports output voltage stabilization, and output current is continuous.After DC filter filtering, be connected with storage battery again.The staggered phase shifting control of first-phase and second-phase wherein, when phase shift 180 is spent, output ripple is minimum, and output capacitance capacity is minimum.In the control design of staggered phase shift BUCK circuit, the design of the staggered trigger impulse of each branch road is wanted rationally, and according to mentioning in data of literatures, if the impulsive synchronization of two branch roads, whole converter property class is like single inverter; If the pulse of each branch road is separate and pulse frequency is incomplete same, between branch road, input and output current ripples randomness is eliminated.For eliminating to greatest extent current ripples, can make 2 branch roads of converter be operated under same frequency, staggered 180 ° of switch controlling signal in branch road, reduced so to a great extent current ripples, whole converter output ripple frequency becomes 2 times of single inverters simultaneously, is conducive to reduce the selection requirement of outputting inductance and electric capacity.

As shown in Figure 1, by input voltage V _in, electric current I _in, output voltage V _out, electric current I _outdeng sampling, after protective circuit, by A/D, change corresponding signal through MPPT control algolithm, obtain the best operating point of photovoltaic array work.

Take below and analyze the size that the running status of one-period is example calculating output ripple electric current.

As shown in Figure 2, after the high level arrival of trigger impulse 1, power tube T1 conducting, power tube T2 becomes cut-off state with continued flow tube D1, and inductance L 2 is by continued flow tube D2 afterflow, and now the energy linearity in inductance L 1 rises, after the high level of pulse 1 finishes, the energy in inductance L 1 reaches peak-peak.Prime Support Capacitor C1 and rear class Support Capacitor C2 are respectively discharge condition and charged state.This stage meets such relation:

U _L1＝U _C1-U _C2， $\frac{{\mathrm{di}}_{L1}}{\mathrm{dt}}=\frac{U_{C1}-U_{C2}}{L_1}=\frac{U_{C1}(1-D)}{L_1}$

In like manner: $\frac{{\mathrm{di}}_{L2}}{\mathrm{dt}}=-\frac{U_{C2}}{L_2}=-\frac{{\mathrm{DU}}_{C1}}{L_2},(L_1=L_2=L)$

The output ripple electric current of two branch roads is: ${i_1}^{\′}=\frac{U_{C1}(1-D)D}{L_1*f},{i_2}^{\′}=-\frac{D^2{U}_{C1}}{f*L_2}$

Before the high level of trigger impulse 1 finishes to arrive afterwards the high level of pulse 2, power tube T1 and power tube T2 are in cut-off state, inductance L 1 and inductance L 2 are respectively by continued flow tube D1 and continued flow tube D2 afterflow, energy on inductance is all linear decline state, rear class Support Capacitor C2 is in discharge condition, and the electric current in inductance L 2 reaches minimum peak.This stage meets relation:

$L_1=\frac{{\mathrm{di}}_{L1}}{\mathrm{dt}}=L_2\frac{{\mathrm{di}}_{L2}}{\mathrm{dt}}=-U_{C2}=-{\mathrm{DU}}_{C1}$

The output ripple electric current of two branch roads is:

After the high level of pulse 2 arrives, power tube T2 conducting, power tube T1 and continued flow tube D2 are cut-off state, and the energy linearity in inductance L 2 rises, and inductance L 1 continues afterflow by continued flow tube D1, and after pulse 2 high level finish, the energy in inductance L 2 reaches peak-peak.This stage meets relation:

$\frac{{\mathrm{di}}_{L1}}{\mathrm{dt}}=-\frac{U_{C2}}{L_1}=-\frac{{\mathrm{DU}}_{C1}}{L_1},\frac{{\mathrm{di}}_{L2}}{\mathrm{dt}}=\frac{U_{C1}-U_{C2}}{L_2}=\frac{(1-D)U_{C1}}{L_2}$

The output ripple electric current of two branch roads is:

After pulse 2 high level finish, power tube T1 and power tube T2 are in off state, and inductance L 1 and inductance L 2 release energy by continued flow tube D1 and continued flow tube D2, and the electric current in inductance L 1 reaches minimum peak, and rear class Support Capacitor C2 is in discharge condition.The state of power switch is with the same, so satisfied condition of this stage is the same with [014].

As shown in Figure 3, by the output voltage V of the current photovoltaic array of sampling _inand current value I _in, through calculating present output power value P _pv, by MPPT control algolithm, obtain the best operating point U of photovoltaic array work _ref, the PWM ripple generating after regulating by PI is adjusted the duty ratio of staggered phase-shift circuit, thereby obtains corresponding system output voltage.Too high for preventing exporting DC bus-bar voltage, set a higher limit U _dc-max, the comparison difference in magnitude of higher limit and current DC bus-bar voltage sampled value, after PI regulates, is exported the duty ratio that a reciprocal regulated quantity regulates staggered phase-shift circuit, thereby reaches the object that suppresses DC bus-bar voltage.

Claims (2)

1. the staggered phase shift Buck of photovoltaic off-grid system two controller, is characterized in that: include a Buck circuit and the 2nd Buck circuit, a described Buck circuit is connected with the 2nd Buck circuit crisscross parallel.

2. the staggered phase shift Buck of a kind of photovoltaic off-grid system two according to claim 1 controller, it is characterized in that: a Buck circuit includes the first Support Capacitor (C1) and the first continued flow tube (D1), the 2nd Buck circuit includes output capacitance (C2) and the second continued flow tube (D2), the positive pole of the first Support Capacitor (C1) is connected with the input of first-phase Buck branch road, the negative pole of the first Support Capacitor (C1) is connected with the first continued flow tube (D1) anode of first-phase Buck branch road, wherein the input of second-phase Buck branch road is attempted by the input of first-phase Buck branch road, the second continued flow tube (D2) anode of second-phase Buck branch road is connected with the negative pole of the first Support Capacitor (C1), the positive pole of output capacitance (C2) is connected with the output of the 2nd Buck circuit, the negative pole of output capacitance (C2) is connected with the negative pole of the first Support Capacitor (C1).