CN102856928A

CN102856928A - Inverter

Info

Publication number: CN102856928A
Application number: CN2012103656954A
Authority: CN
Inventors: 张颖
Original assignee: BEIJING JINGYI RENEWABLE ENERGY ENGINEERING CO LTD
Current assignee: BEIJING JINGYI RENEWABLE ENERGY ENGINEERING CO LTD
Priority date: 2012-09-27
Filing date: 2012-09-27
Publication date: 2013-01-02
Anticipated expiration: 2032-09-27
Also published as: CN102856928B

Abstract

The invention relates to an inverter which comprises a circuit system and a control system. The circuit system comprises a solar cell panel and a power grid output. A direct current switch, a BOOST boosted circuit, a single phase full bridge circuit and a grid-tied filter are sequentially arranged between the solar cell panel and the power grid output. The control system comprises a digital signal processor (DSP) control platform, the DSP control platform is connected with a protection module, a sampling and conditioning module, a passage zero comparison module and a level switch module, and the level switch module is connected with an input/output (I/O) information module, a driving module and a power amplifier module. The inverter has the advantages of being based on the DSP control platform, using modes of topology, modulation and the like, and having high efficiency, light weight, small size and the like in actual use. The highest efficiency reaches to 97.51%. Simultaneously, the inverter can control and track grid-tied voltage phase without dead beat, and achieves unity power factor grid-tied. Grid-tied current has good harmonic characteristics, and full load total harmonic distortion (THD) is 1.57%.

Description

A kind of inverter

Technical field

The present invention relates to electronic technology field, relate in particular to a kind of inverter.

Background technology

Along with the development of photovoltaic technology, and network electric energy quality and most important two indexs of these two photovoltaic combining inverters of efficient also become present technical difficult point and emphasis.Inverter on the market mainly is divided into isolated form and two kinds of photovoltaic DC-to-AC converters of non-isolation type now, including transformer in the isolated form inverter makes and does not have direct electrical communication between cell panel and the electrical network, guaranteed user's safety, but transformer brings the loss of efficient, general isolated form inverter efficiency is than non-isolated inverter low 1.5% or more, thus the inverter of non-isolation be after the main flow in market.

The photovoltaic DC-to-AC converter of non-isolation will solve the over the ground problem of common mode leakage current, and two kinds of approach are arranged, and a kind of is to use the bipolarity modulation system on the full-bridge basis, a kind ofly is with the unipolarity modulation system but needs in addition that other devices of increase limit the common mode leakage current.So the former generally adopts latter's technology owing to can reduce and network electric energy quality is used lessly.Solution on the market is now: 1, add by-pass switch in the direct current point of incoming cables of full bridge inverter, such as two kinds in H5, H6 circuit; 2, add continuous current circuit in the interchange outlet of full bridge inverter, such as the HERIC circuit; 3, adopt modified model NPC topological structure.

Although these technology can both solve the over the ground problem of common mode leakage current, but

method

1,2 all need to increase new power switch pipe on the basis of full-bridge, strengthened the difficulty of main circuit design and control, all work under the high frequency state with stylish switching tube, increase to a certain extent loss, lost the odds for effectiveness that adopts the unipolarity modulation to bring.Method 3 shortcomings are that the direct voltage input requirements is the twice of H bridge, and linear modulationra is low, need to improve the magnitude of voltage of bus, have increased the requirement of withstand voltage of dc-link capacitance and prime booster circuit.

Summary of the invention

The object of the present invention is to provide a kind of inverter, improve conversion efficiency to reach, improve the quality of power supply that is incorporated into the power networks, guarantee simultaneously lightweight, the characteristics such as volume is little of inverter.

Purpose of the present invention is achieved through the following technical solutions:

A kind of inverter, comprise Circuits System and control system, described Circuits System comprises solar panel and electrical network output, is provided with successively dc switch, BOOST booster circuit, single-phase full bridge circuit and the filter that is incorporated into the power networks between described solar panel and the electrical network output; Described control system comprises the DSP(Digital Signal Processing) the control platform; described DSP control platform is connected with protection module, sampling conditioning module, zero passage comparison module and level switch module, and described level switch module is connected with I/O information module, driver module and power amplifier module.

Further, be provided with successively lightning protection device and electromagnetic interface filter between described solar panel and dc switch; Described being incorporated into the power networks is provided with electromagnetic interface filter and lightning protection device between filter and the electrical network output successively.

Further, described DSP control platform is connected with communicating circuit, and described communicating circuit is connected with host computer with liquid crystal indicator.Be provided with AD sampling module, EPWM(enhancement mode pulse width modulator in the described DSP control platform) module, GPIO control module, serial communication modular, clock PLL(phase-locked loop) module and TZ drive lockout module.

Further, described DSP control platform is connected with auxiliary power circuit.

Beneficial effect of the present invention is: the present invention is based on DSP control platform, adopted the modes such as topology and modulation, have in actual use the advantages such as efficient is high, lightweight, volume is little, peak efficiency reaches 97.51%; Can dead beat control follow the tracks of the voltage-phase that is incorporated into the power networks simultaneously, realize that unity power factor is incorporated into the power networks, grid-connected current has outstanding harmonic characterisitic, and fully loaded THD is 1.57%.

Description of drawings

Fig. 1 is the circuit structure diagram of a kind of inverter in the embodiment of the invention;

Fig. 2 is the system construction drawing of a kind of inverter in the embodiment of the invention;

Fig. 3 is the global topological circuit structural representation of a kind of inverter in the embodiment of the invention;

Fig. 4 is the simple and easy unipolarity modulation principle figure of a kind of inverter in the embodiment of the invention.

Embodiment

The described a kind of inverter of the embodiment of the invention, comprise Circuits System and control system, described Circuits System comprises solar panel and electrical network output, is provided with successively dc switch, BOOST booster circuit, single-phase full bridge circuit and the filter that is incorporated into the power networks between described solar panel and the electrical network output; Described control system comprises DSP control platform, and described DSP control platform is connected with protection module, sampling conditioning module, zero passage comparison module and level switch module, and described level switch module is connected with I/O information module, driver module and power amplifier module.

Further, described DSP control platform is connected with communicating circuit, and described communicating circuit is connected with host computer with liquid crystal indicator.Be provided with AD sampling module, EPWM module, GPIO control module, serial communication modular, clock PLL module and TZ in the described DSP control platform and drive lockout module; Described DSP control platform is provided with auxiliary power circuit.

During implementation, the structure of whole inverter as depicted in figs. 1 and 2.The voltage of solar panel passes through first dc switch, laggard lightning protection component and electromagnetic interface filter, and this structure avoids extraneous fortuitous event to occur the normal operation of system is brought danger, has improved the safety and reliability of product.Major loop adopts the two-stage type topological structure, to enlarge the scope of cell panel input voltage.The prime booster circuit adopts traditional Boost circuit, the cell panel input voltage is increased to the high voltage that satisfies the inverter requirement, finish simultaneously the tracking to the cell panel maximum power point, rear class single-phase full bridge circuit is that alternating voltage realizes that unity power factor generates electricity by way of merging two or more grid systems with the direct voltage inversion.The ability of resisting external interference in order to improve the quality of power supply that is incorporated into the power networks and raising system before alternating current feeds electrical network, also will be carried out two stage filter and lightning protection and process.Do not comprise isolation transformer component in the whole inverter, make system can obtain higher efficient performance.

The flyback power supply structure is adopted in the power supply of system.The signal of transducer collection is through delivering to AD mouth and the I/O mouth of DSP control platform behind the modulate circuit; DSP control platform carries out analog-to-digital conversion to the sampling of analog quantity; result according to conversion protects judgement; carry out simultaneously closed loop calculating, the MPPT maximum power point tracking calculating of two-stage circuit according to the result, send PWM to module and drive signal.Native system has the functions such as man-machine interface serial communication, and the touch-screen control interface of hommization is user-friendly.

Consider from the angle that energy utilizes, if interrupted situation appears in the electric current of inductance in the BOOST circuit, then the inevitable for some time energy of cell panel is utilized, so circuit design should avoid occurring the situation of discontinuous current as far as possible, inductance value is chosen can not be too little.If ignore the dead resistance of inductance and electric capacity, when PWM ripple duty ratio was excessive, continuation increase duty ratio output voltage can not raise and can reduce on the contrary, and this is because the parasitic parameter of circuit causes.In side circuit is used, should limit the maximum pulse width of PWM ripple.The restriction maximum pulse width is 0.75 in the native system.

Combining inverter all adopts direct Current Control Technology, makes grid-connected current be in the feedback closed loop state, can obtain more preferably stable state accuracy and dynamic responding speed, and can reduce the susceptibility that electric current changes parameter, strengthens the interference rejection ability of system.Typical control method comprises Current Control based on the PI controller, hysteresis current control, the control of ratio resonance, internal model control, predicted current control theory etc.

As shown in Figure 3, the topological structure of inverter adopts traditional full bridge structure, and modulator approach adopts simple and easy unipolarity modulator approach.The switching tube state of tradition unipolarity modulation system, positive half period at modulating wave, all the time conducting of switching tube S1, S3, S4 replace break-make, and in fact S3 only under non-resistive load, PWM ripple fundametal compoment and electric current just need to be opened afterflow in the anti-phase zone, and all the other times are finished afterflow by anti-paralleled diode D3.The power factor that is incorporated into the power networks of at present relevant criterion requirement little power single phase combining inverter is 1 as far as possible, be that the load of combining inverter can be considered filter inductance and connects with pure resistive load, and relative resistive load, the impact of filter inductance is very little, so in photovoltaic combining inverter is used, can further the unipolarity modulation system be reduced to simple and easy unipolarity pattern, namely at the positive half period of modulating wave, all the time conducting of switching tube S1, S2, S3 turn-offs all the time, S4 is with PWM ripple mode break-make, at the negative half-cycle of modulating wave, all the time conducting of switching tube S3, S1, S4 turn-offs all the time, S2 is with PWM ripple mode break-make, as shown in Figure 4.

Like this, compare with traditional unipolarity modulation system, although in fact the switch motion that reduces can't bring the lifting on the efficient, but in actual applications, the former must need to add the dead band because two switching tubes of a brachium pontis replace break-make, grid-connected current is brought adverse effect, and can not need to add PWM ripple dead band under the modulation of simple and easy unipolarity, brachium pontis mid point output voltage has been reduced under normal circumstances because the harmonic wave that bring in the dead band.

Traditional implementation method is that S1 ~ S4 adopts IGBT, and four IGBT need action once in each switch periods, the loss of such power is larger, what native system adopted is that S1, S3 adopt IGBT, and S2 and S4 adopt coolMOS to replace IGBT, and S1 and S3 keep each switch periods action once, and S2 and S4 only need each sinusoidal cycles action once, greatly reduce like this loss of power device, thereby improved the conversion efficiency of whole system.

Native system inversion side adopts the typical control structure of ring control in busbar voltage outer shroud, the grid-connected current, wherein outer voltage adopts pi regulator, current inner loop is theoretical based on the dead beat Current Control, and whole controller only has a pi regulator, and parameter tuning is fairly simple.It is constant or realization MPPT control that the outer shroud voltage control makes the electrochemical capacitor DC bus-bar voltage; Interior circular current control guarantees the output quality of power supply.

The control core of inverter is based on the minimum system plate of the floating type digital signal processor TMS320F28335 of TI company, and the advantages such as its high accuracy, low-power consumption, high integration peripheral hardware provide assurance for the control performance that improves whole system.Native system adopts 12 high-precision A/D, has effectively improved the sampling precision of system.For in time protection, data processing provide reliable basis.Have the intelligent communication control system, can control by the unit touch-screen, also can control by remote detection.

Although below only described the specific embodiment of the present invention example, it will be understood by those of skill in the art that these only illustrate, protection scope of the present invention is limited by appended claims.Those skilled in the art can make various changes or modifications to these execution modes under the prerequisite that does not deviate from principle of the present invention and essence, but these changes or modification all fall into protection scope of the present invention.

Claims

1. inverter, comprise Circuits System and control system, it is characterized in that: described Circuits System comprises solar panel and electrical network output, is provided with successively dc switch, BOOST booster circuit, single-phase full bridge circuit and the filter that is incorporated into the power networks between described solar panel and the electrical network output; Described control system comprises DSP control platform, and described DSP control platform is connected with protection module, sampling conditioning module, zero passage comparison module and level switch module, and described level switch module is connected with I/O information module, driver module and power amplifier module.

2. a kind of inverter according to claim 1 is characterized in that: be provided with successively lightning protection device and electromagnetic interface filter between described solar panel and dc switch; Described being incorporated into the power networks is provided with electromagnetic interface filter and lightning protection device between filter and the electrical network output successively.

3. a kind of inverter according to claim 2 is characterized in that: described DSP control platform is connected with communicating circuit, and described communicating circuit is connected with host computer with liquid crystal indicator.

4. a kind of inverter according to claim 3 is characterized in that: be provided with AD sampling module, EPWM module, GPIO control module, serial communication modular, clock PLL module and TZ in the described DSP control platform and drive lockout module.

5. a kind of inverter according to claim 4 is characterized in that: described DSP control platform is connected with auxiliary power circuit.