CN103001310A - Photovoltaic power generation and urban power grid parallel power supply switching device - Google Patents
Photovoltaic power generation and urban power grid parallel power supply switching device Download PDFInfo
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- CN103001310A CN103001310A CN2012104792570A CN201210479257A CN103001310A CN 103001310 A CN103001310 A CN 103001310A CN 2012104792570 A CN2012104792570 A CN 2012104792570A CN 201210479257 A CN201210479257 A CN 201210479257A CN 103001310 A CN103001310 A CN 103001310A
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Abstract
The invention relates to a photovoltaic power generation and urban power grid parallel power supply switching device which solves the problems of the existing device that the existing device is complex in structure, high in cost and poor in backflow-prevention performance during parallel power supply and a photovoltaic power supply cannot output the maximum power constantly. The photovoltaic power generation and urban power grid parallel power supply switching device comprises an alternating-current switching unit, a power supply unit, a control unit, a driving circuit, a sampling regulation unit and the like. The alternating-current switching unit is subjected to logic switching control by aid of the pulse width modulation strategy and the digital signal processor (DSP) software phase lock technology. The photovoltaic power generation and urban power grid parallel power supply switching device provides good guarantee for achievement of backflow-free photovoltaic power generation and urban power grid parallel power supply.
Description
Technical field:
The present invention is with relevant with city's net parallel powering switching device shifter without the photovoltaic generation in the adverse current photovoltaic generating system.
Technical background:
Existing photovoltaic power generation grid-connecting system can be divided into two classes, and a class is contracurrent system, and a class is without contracurrent system.Contracurrent system just refers to electric power that solar battery produces except supplying with AC load, and unnecessary electric power feeds back to electrical network.When solar cell can not satisfy the load needs, directly by mains supply.And just refer to when the energy output of photovoltaic system is less than or equal to the power consumption of load that without contracurrent system inadequate electric weight is provided by electrical network.
Existing without the adverse current photovoltaic generating system in, owing to there is not good switch-control strategy to make photo-voltaic power supply prevent its adverse current can be with city's net parallel powering the time, so cause it to switch difficulty, operability is not high, and circuit is complicated, cost is high, thus use less so that the photovoltaic electric energy is not used more effectively.
Summary of the invention:
It is a kind of simple in structure that the purpose of patent of the present invention is to provide, cost is low, photo-voltaic power supply and city's net switch reliable, when powering simultaneously, both can prevent adverse current, photo-voltaic power supply is Maximum Power Output all the time, and the photo-voltaic power supply output voltage can be pressed together frequently photovoltaic generation and city's net parallel powering switching device shifter of homophase with urban network electricity.
The present invention is achieved in that
Photovoltaic generation and city's net parallel powering switching device shifter is characterized in that load passes through the first switch unit and be connected with photo-voltaic power supply, are connected with city's net by the second switch unit.The first switch unit is formed with the 1st, 2 diode D1, D2 reverse parallel connection respectively by the 1st, 2 igbt Q1, Q2, and the Q1 negative terminal links to each other with the Q2 negative terminal, and Q1, Q2 anode link to each other with photo-voltaic power supply, load respectively.The second switch unit is formed with the 3rd, 4 diode D3, D4 reverse parallel connection respectively by the 3rd, 4 igbt Q3, Q4, and the Q3 negative terminal links to each other with the Q4 negative terminal, and Q3, Q4 anode link to each other with load, city's net respectively.The grid of Q1 ~ Q4 links to each other with the first driver element, and the first driver element is connected with control unit.Photo-voltaic power supply output voltage, line voltage, load current pass through 1,2, No. 3 circuit sampling of sampling conditioning unit to control unit.
Photo-voltaic power supply is connected to form successively by photovoltaic array, pressure unit, inversion unit.Form reduction voltage circuit by the 5th igbt VQ5, the 9th diode D10, inductance L 1.The grid of VQ5 is connected to the 3rd driver element, and the 3rd driver element is connected to control unit.Sampling capacitance C1 both end voltage through sampling conditioning unit No. 4 circuit samplings to control unit.Inversion unit is comprised of with 5-8 diode D5 ~ D8 reverse parallel connection respectively 6-9 igbt VQ1 ~ VQ4.The negative terminal of VQ1 is connected with the anode of VQ2, and is connected with the first output, and the negative terminal of VQ3 is connected with the anode of VQ4, and is connected with the second output, and output is connected respectively to the first switch unit and load after inductance, resistance filtering and transformer boost.The negative terminal of the anode of VQ1, VQ3 and VQ2 and VQ4 connects the output of pressure unit.The grid of VQ1 ~ VQ4 pipe all is connected with the second driver element, and the second driver element is linked control unit again.
Photo-voltaic power supply output L, N are connected to 1,2 mouthful of terminals P 1 of sampling conditioning unit No. 1 circuit, be connected to resistance and the 1st amplifier U1, the output of the 1st amplifier U1 meets the 1st voltage follower U2, and the output of U2 is connected to control unit behind resistance and the first clamp circuit.City net output L1, N1 are connected to 1,2 mouthful of terminals P 2 of No. 2 circuit of sampling conditioning unit, be connected to resistance and the 2nd amplifier U3, the output one road of U3 is to the 2nd voltage follower U4, and the output of U4 is connected to control unit through resistance and the second clamp circuit.Another road output of the 2nd amplifier U3 is connected to control unit through zero-crossing comparator U5 and filter circuit.After the current Hall transducer of load current by sampling conditioning unit No. 3 circuit was connected to the modulate circuit that resistance, electric capacity and the 3rd amplifier U6 form, the zero level comparison circuit that forms through feedback amplifier U7 and diode was connected to control unit.The output of sampling capacitance C1 both end voltage is connected to resistance and the 4th amplifier U8 through 1,2 mouthful of No. 4 circuit terminal P3, and the output of the 4th amplifier U8 meets the 3rd voltage follower U9, and the output of U9 is connected to control unit behind resistance and the 3rd clamp circuit.
The power switching method is as follows:
(1) No. 1 circuit sampling photo-voltaic power supply of sampling conditioning unit output voltage waveforms, sample the respectively waveform of line voltage and load current of No. 2 circuit and No. 3 circuit, catch their zero crossing constantly, control unit calculates their frequency and phase difference value more constantly according to this, output regulation signal is to the second driver element, drive inversion unit, make the photo-voltaic power supply output voltage consistent with frequency and the phase place of line voltage.No. 4 circuit sampling capacitor C 1 both end voltage, control unit is adjusted duty ratio by calculating, and makes the photovoltaic array Maximum Power Output.
(2) when photo-voltaic power supply power output during more than or equal to default bearing power, judge that namely the photo-voltaic power supply power supply is normal, the control unit output signal is to the positive and negative half period in turn conducting of the first drive unit drives the first switch unit according to sinusoidal ac, at this moment, the second switch unit is closed, and is only powered to the load by photo-voltaic power supply.
(3) when photo-voltaic power supply power output during less than default bearing power, judge that namely the photo-voltaic power supply power supply is undesired, the control unit output signal drives first, second switch unit conducting to the first driver element, this moment photo-voltaic power supply and city's net parallel powering.
(4) detect the photo-voltaic power supply power supply and whether recover normal, if do not recover, then repeating step (3) if recover normal, then turns step (5).
(5) control unit is caught the difference of their frequency of zero crossing calculating of line voltage and load current by sampling conditioning unit 2, No. 3 circuit, output signal is to the second driver element, regulate the output of inversion unit, make the frequency of photo-voltaic power supply output voltage and line voltage consistent with phase place, at this moment, still by photo-voltaic power supply and city's net parallel powering.
(6) control unit is regulated the duty ratio output of line voltage gradually by the first driver element, and when being adjusted to zero, the first driver element is closed the second switch unit, and photo-voltaic power supply powers to the load through the first switch unit of conducting.
In the above-mentioned steps (1); when control unit captures the rising edge of a pulse of line voltage and load current, produce and interrupt; protect first the interrupt spot; namely preserve the value of related register; judge that again this interruption is that if the first capturing unit, namely interrupting constantly is the zero crossing of line voltage by the first capturing unit or the generation of the second capturing unit of control unit; this value of catching is deposited in the self-defining array, and this value of catching deducts the last time and catches the cycle that is worth line voltage.If the second capturing unit, namely interrupting constantly is the zero crossing of load current, this value of catching is deposited in self-defining another array, this value of catching deducts the last time and catches the cycle that is worth load current, the absolute value that compares the cycle difference of line voltage and load current | F|, if | F|=0, be that both frequencies are identical, do not adjust, if | F|〉0, then the period register of control unit inside is adjusted, if the cycle of load current greater than the cycle of line voltage, then reduces the value of period register, if the cycle of load current is less than the cycle of line voltage, then increase the value of period register, until the cycle of load current equals the cycle of line voltage, namely both frequencies are identical.
When the frequency of load current and line voltage is identical, calculate phase difference Ph by the value of catching, when capturing voltage zero-crossing point of power grid, utilize phase bit pointer P
IndexRecord k step signal processed.In allowed band, if within scope, then pointer does not adjust the value of judging phase difference.If not in allowed band, by current phase place pointer value and line voltage frequency, obtain step value λ, make forward or backward step value of phase bit pointer, realize that it crosses the zero phase value convergence to inversion. so just can realize that load current is consistent with the phase place of civil power, just can realize that also load current frequency and phase place are to the tracking of line voltage.
Photo-voltaic power supply is mainly realized 3 functions as main power source among the present invention: inversion, maximal power tracing and output current are phase-locked.Wherein inversion adopts the SPWM modulation to realize.On MPPT maximum power point tracking, adopt the fixed voltage method so that photo-voltaic power supply always works in maximum power point.The software phlase locking mode of the phase-locked employing controller DSP of output current realizes.Photo-voltaic power supply is by sampling unit Real-Time Monitoring urban network electricity source situation and load output situation, so that photo-voltaic power supply output voltage and urban network electricity are pressed with the frequency homophase and be operated on the maximum power point in the course of the work.When the normal band of photo-voltaic power supply carries, DSP output two-way complementary drive signal PWM1, PWM2, control fast full control Q1, the Q2 action of the first switch unit, and according to the in turn conducting of positive-negative half-cycle of sinusoidal ac, Q2 closes in voltage positive half period Q1 conducting, and Q1 closes in the Q2 conducting of voltage negative half period.
City's net is power supply in support, when the photo-voltaic power supply power output is not enough, by control unit output control signal, so that full control switching device switches according to the assigned switch logical action fast.Detailed process is for when photo-voltaic power supply power output during less than the load power demand, DSP exports four the road and drives signal PWM1, PWM2, PWM3, PWM4, control the action of the first switch unit and the second switch unit, when Q1 is conducting state, allow the Q4 conducting so that city's net power supply is pressed because photovoltaic electric forces down in urban network electricity, this moment, D2 can end, the photo-voltaic power supply output current is zero, provides electric current by city's net for load.When Q4 closes, the D2 conducting, photo-voltaic power supply continues power supply, and wherein the ON time of Q4 is determined by the pulse duration of corresponding PWM4.If voltage is in negative half-cycle, similar with positive half period, Q2 still keeps conducting state, allows the Q3 conducting so that city's net is powered, and this moment, D1 can end, and the photo-voltaic power supply output current is zero, provides electric current by city's net for load.When Q3 closes, the D1 conducting, photo-voltaic power supply continues power supply.Wherein the ON time of Q3 is determined by the pulse duration of corresponding PWM3.
The invention has the advantages that:
1, the designed switch circuit units of the present invention cooperates the switch control logic realization without photovoltaic generation and city's net parallel powering of adverse current, and simple in structure, cost is low, and photo-voltaic power supply and city's net switch reliable.
2, among the present invention in the situation of photo-voltaic power supply electricity shortage with city's net parallel powering, the power output of photo-voltaic power supply does not pollute city's net only for not flowing to city's net with load when taking full advantage of solar energy and city net.
3, the present invention is when the photo-voltaic power supply electricity shortage, the control of switching device has been adopted the control strategy of pulse width modulation, it is required that this strategy can export to satisfy the power of load by the duty ratio that in good time adjustment urban network electricity is pressed, and guarantee that the photo-voltaic power supply power output is maximum power.
4, the software phlase locking loop technique based on DSP of the present invention's employing, phase-locked precision is higher, has realized that well photo-voltaic power supply output voltage and line voltage are with the frequency homophase.
Description of drawings:
Fig. 1 is main circuit block diagram of the present invention.
Fig. 2 is the photo-voltaic power supply circuit theory diagrams.
Fig. 3 is sampling modulate circuit schematic diagram.
Fig. 4 is power switching flow chart of the present invention.
Fig. 5 is frequency adjustment flow chart of the present invention.
Fig. 6 is phase adjusted flow chart of the present invention.
Embodiment
Hardware cell of the present invention is as follows:
1. interchange switch unit: diode D1, D2, D3, the D4 of reverse parallel connection form main circuit of the present invention with it by 4 igbt Q1, Q2, Q3, Q4 and four.Wherein Q1 and D1 reverse parallel connection in the first switch unit, Q2 and D2 reverse parallel connection.The Q1 negative terminal links to each other with the Q2 negative terminal, and the Q1 anode then is connected respectively photo-voltaic power supply and load with the Q2 anode.Q3 and D3 reverse parallel connection in the second switch unit, Q4 and D4 reverse parallel connection.The Q3 negative terminal links to each other with the Q4 negative terminal, and the Q3 anode then is connected respectively load and city's net with the Q4 anode.Meanwhile, the grid of four igbts all is connected to the first driver element, and the first driver element is connected to control unit DSP(digital signal processor) on.4 road PWM(pulse width modulation waves by control unit) power amplification of output and driver element is carried out break-make control to 4 pipes.
2. power subsystem: this unit is comprised of two parts, and one is the photo-voltaic power supply in main circuit left side, and another then is the urban network electricity source on main circuit right side.Wherein the circuit structure of photo-voltaic power supply as shown in Figure 2.Photovoltaic array changes into electric energy with solar energy, the reduction voltage circuit that is formed by switching tube VQ5, diode D10 and inductance L 1, the grid of VQ5 is connected to the 3rd driver element, driver element is linked control unit again, sampling capacitance C1 both end voltage is passed to control unit after the sampling conditioning, realize the maximal power tracing of solar energy, make it guarantee in which kind of situation, all to be maximum power output.The inverter circuit that is comprised of igbt VQ1, VQ2, VQ3, VQ4 is finished from direct current to the inversion that exchanges, output voltage U through inductance L 2 and resistance R 1 filtering and after boosting
PvSimultaneously, the grid of four igbts also all is connected to the second driver element, and the second driver element is connected on the control unit DSP, by 4 road SPWM output of control unit and the power amplification of driver element 4 pipes is driven.Introduce from the main circuit right side in the urban network electricity source, output voltage U
Grid
3.
Control unit: that control unit adopts among the present invention is TMS320F2812 in the DSP of the TI company series.DSP finishes all signal controlling in whole switching device shifter, realizes simultaneously that sampling, signal rising edge are caught, the output of PWM ripple and SPWM ripple.
4.
Driver element: that first, second driver element adopts among the present invention is integrated package M57962L, and that the 3rd driver element adopts is device IR2110.
5.
The sampling conditioning unit: sample modulate circuit as shown in Figure 3, because the port input range of DSP is 0～3.3V, so need to change AC signal into its port receptible voltage range with modulate circuit.Wherein No. 1 circuit is the photovoltaic voltage sample, voltage U
PVIntroduce from 1, No. 2 interface of terminals P 1, by R2, R5 step-down, the step-down ratio is
R3, R4 then play the effect of balancing circuitry, because the R6 resistance equates with R7, so voltage is behind amplifier, magnitude of voltage 1/2nd behind the lifting 3.3V is sent into the voltage follower of rear end, the clamp circuit that forms by resistance with by electric capacity, voltage stabilizing didoe again in 3.3V, is connected to limiting voltage at last DSP and samples.No. 2 circuit are that line voltage sampling and zero passage are caught, voltage U grid is by resistance and the step-down of amplifier ratio, voltage after the step-down divides makes two-way, one the tunnel is connected to DSP through voltage follower samples, and another road is connected to DSP after by zero-crossing comparator and filter circuit elimination High-frequency Interference and catches.Sampling and zero passage that No. 3 circuit are load current are caught, and adopt the current Hall transducer access load circuit of model GCT220A, current signal are sent into the modulate circuit that is comprised of resistance, electric capacity and amplifier.By R17, R18 current signal is converted to voltage signal, capacitor C 10, C12 filtering clutter.It is two voltage comparators of LM324N that amplifier is selected model, after D5, D6 voltage stabilizing, sends into DSP through exporting pulse wave signal after feedback amplification and the zero level, and DSP can obtain zero cross signal by detecting rising edge and trailing edge.No. 4 circuit is capacitor C 1 both end voltage sample circuit, and is roughly the same with No. 1 circuit, therefore repeats no more.
Concrete software unit is as follows:
1.
The AD sampling: the function of A/D converter ADC module is converted into digital quantity for controller with analog quantity exactly.The ADC module of TMS320F2812 inside is the A/D converter of 12 bit resolutions, has 16 sampling channels, is divided into two groups: one group is ADCINA0 ~ ADCINA7, and another group is ADCINB0 ~ ADCINB7.By sampling modulate circuit as shown in Figure 3, photovoltaic voltage and urban network electricity corrugating and capacitor C 1 both end voltage are sampled the DSP port, become digital signal through sampling channel ADCINA0, ADCINA1 and ADCINB0, its magnitude of voltage is stored in the corresponding register of DSP, and with photovoltaic voltage, urban network electricity that each obtains in cycle press, the capacitance voltage sampled value is stored in self-defining array Sample1[], Sample2[] and Sample3[] in.
2. catch: 6 capturing unit CAP1 ~ CAP6 are arranged among the TMS320F2812, and effect is the variation of catching level on the pin, and moment of changing of recording level.Use two capturing unit CAP1 and CAP2 among the present invention, it is effective all to be set to detect rising edge.Because the capturing unit input signal is square-wave signal, therefore the interval between two adjacent rising edges is one-period just, simultaneously moment of occuring of rising edge be exactly sampled signal from negative to positive zero crossing, thereby realize the zero passage of line voltage and output current is caught.
3.PWM output: the PWM control technology is exactly the technology that the width of paired pulses is modulated, and namely obtains equivalently required waveform by the width of a series of pulses is modulated.Modulate be exactly change the duty ratio pulse-width of pulse, in a string desirable pulse period sequence (such as square wave), total the ratio in the duration of positive pulse and pulse cycle is duty ratio just.The impulse wave that produces by the modulation of PWM technology is the PWM ripple, and pulse duration changes by sinusoidal rule and the PWM waveform of sinusoidal wave equivalence just is called the SPWM ripple.In whole photovoltaic generation and city's net parallel powering switching device shifter, one has the output of five road PWM ripples and the output of four road SPWM ripples, wherein the break-make of four igbts of Q1 ~ Q4 in four road PWM1 ~ PWM4 control main circuit four the tunnel is exported the break-make that SPWM1 ~ SPWM4 then control four igbts of VQ1 ~ VQ4 in the photo-voltaic power supply in addition.The break-make of VQ5 in another road PWM5 control photo-voltaic power supply.Wherein the output of PWM1, PWM2 is by finishing to period register assignment T1PR with to comparing register assignment T1CMPR among the DSP.T1PR=TCLK/f wherein
Pv-1, T1CMPR=T1PR+1-d
1(T1PR+1), (TCLK is input clock frequency 37.5MHz, f
PvThe photo-voltaic power supply output voltage frequency, d
1Be duty ratio 0.5).And the output of PWM3, PWM4 is finished by the period register assignment T2PR among the DSP and comparand register T2CMPR assignment.T2PR=TCLK/f
Grid-1, T2CMPR=T2PR+1-d
2(T2PR+1) (TCLK is input clock frequency 37.5MHz, f
GridBe the line voltage frequency, its duty ratio d
2=U/U
Grid, U=U
Grid-U
Pv, wherein
Be the line voltage effective value,
Be photo-voltaic power supply output voltage effective value).In the situation that the photo-voltaic power supply power supply is only arranged, only has PWM1, PWM2 output.When detecting photo-voltaic power supply power output deficiency, enter interrupt service routine, finish the output of PWM3, PWM4.And four road SPWM ripples adopt the SPWM pulse modulation technology of carrier wave ratio N=400 to control the break-make of igbt VQ1 ~ VQ4 in addition.Wherein carrier frequency is 20kHz, and the input clock frequency of DSP is 37.5MHz.At first the DSP calculated off-line goes out the sine value of 400 points, according to sinusoidal pointer P
IndexAt sine table sin_table[P
Index], the sine table size is selected duty ratio for the position in n=400 and is revised the value of comparand register T3CMPR and comparand register T4CMPR, the SPWM ripple that produces 4 road band dead bands drives VQ1 ~ VQ4 pipe, and the value of period register T3PR and period register T4PR is as can be known simultaneously: 50 us/(2 * 26.7 ns)=936.Because simultaneously conducting of the upper and lower bridge arm of the inversion unit that VQ1 ~ VQ4 forms, and power switch pipe close time expand ratio to open time expand long, cause that for fear of simultaneously conducting of upper and lower bridge arm short circuit burns out components and parts, in programming, add dead band control time 1.6us.On maximal power tracing, because the corresponding voltage U of the maximum power point of photovoltaic array
MAnd exist approximate linear relationship, U between the open circuit voltage Uoc of photovoltaic array
M≈ k1Uoc, k1 are that the proportionality constant value is that 0.75, Uoc can by photovoltaic array and load are disconnected recording, can calculate voltage U corresponding to maximum power point like this
M, regulate the break-make of VQ5 so that output voltage is roughly U
MGet final product.The PWM5 output duty cycle is
Impulse waveform so that the reduction voltage circuit output voltage is roughly U
MU
C1Voltage for sampling capacitance C1 two ends.
Below in conjunction with accompanying drawing and example, the present invention is elaborated.The implementation case that this place is described is used for explaining the present invention, is not intended to limit the present invention.
Fig. 1 is main circuit block diagram of the present invention
Comprise two switch units in the main circuit, annexation as shown in Figure 1.Entirely control fast switching device in the example and adopt insulated gate bipolar transistor IGBT, each switch unit is comprised of two IGBT and two anti-paralleled diodes.Take the first switch unit as example, the emitter of Q1 is connected to the emitter of Q2 when linking to each other with diode D2 is anodal, and the collector electrode of Q1 links to each other with diode D1 negative pole, and the gate pole of Q1 links to each other with control unit, sends signal by control unit and controls.The emitter of Q2 is connected to the emitter of Q1 when linking to each other with diode D2 is anodal, the collector electrode of Q2 links to each other with diode D2 negative pole, and the gate pole of Q2 links to each other with control unit.The first switch unit is implemented to switch to photo-voltaic power supply in photo-voltaic power supply one side.The second switch unit is implemented to switch to the urban network electricity source in urban network electricity source one side.When photo-voltaic power supply was worked, the Q1 of the first switch unit, Q2 grid received conducting and drive signal.Driving signal PWM1, PWM2 is provided by the first driver element shown in Fig. 1, and purpose is the turn-on and turn-off of control switch unit IGBT.When work simultaneously in photo-voltaic power supply and urban network electricity source, the Q1 of first, second switch unit, Q2, Q3, Q4 gate pole all receive the driving signal, and driving signal PWM1, PWM2, PWM3, PWM4 is provided by the first driver element.
Setting as shown in Figure 1 the photo-voltaic power supply power supply end that links to each other with the first switch unit is L, and an end that links to each other with load is N.The end that the urban network electricity source links to each other with the second switch unit is L1, and the end that links to each other with load is N1.The A point is the load current test point among the figure.
Fig. 2 is the photo-voltaic power supply circuit theory diagrams
Direct current energy sends from photovoltaic array, be converted into AC energy output through reduction voltage circuit and inversion unit, control unit is by the igbt VQ5 of the 3rd driver element connection photo-voltaic power supply, and the break-make of adjusting VQ5 by the duty ratio of setting by control program makes it be operated in maximum power point.Control unit is adjusted frequency and the phase place of photo-voltaic power supply output voltage by the inversion unit of the second driver element connection photo-voltaic power supply by control program simultaneously.Detailed process is: control unit output sets the sinusoidal pulse width modulation signal SPWM of phase place, frequency information, export the drive circuit of the inverter circuit unit of photo-voltaic power supply to, switching device insulated gate bipolar transistor npn npn VQ1, VQ2, VQ3, the VQ4 of photo-voltaic power supply the second drive unit drives inverter circuit unit carry out switch motion according to the sinusoidal pulse width modulation signal, output inversion waveform is through photo-voltaic power supply resistance R 2, inductance L 1 filter circuit filtering and be connected to first and second output L, the N of photo-voltaic power supply after boosting.
Fig. 3 is sampling modulate circuit schematic diagram
Wherein the first via is the photovoltaic voltage sample, and voltage U pv introduces from 1, No. 2 interface of terminals P 1, and by R2 ~ R5 and R11 step-down, by R2, R5 step-down, the step-down ratio is
R3, R4 then play the effect of balancing circuitry, because the R6 resistance equates with R7, so voltage is behind amplifier, magnitude of voltage 1/2nd behind the lifting 3.3V is sent into the voltage follower of rear end, in 3.3V, sample by 174 pins that are connected at last DSP with limiting voltage for the clamp circuit that forms by resistance with by electric capacity, voltage stabilizing didoe again.The second the tunnel is line voltage sampling and zero passage capture circuit, voltage U grid is by resistance and the step-down of amplifier ratio, voltage after the step-down divides makes two-way, one tunnel 2 pins that are connected to DSP through voltage follower are sampled, and another road is connected to 106 pins of DSP after by zero-crossing comparator and filter circuit elimination High-frequency Interference and catches.Third Road is sampling and the zero passage capture circuit of load current, adopts the current Hall transducer access load circuit of model GCT220A, load current signal is sent into the modulate circuit that is comprised of resistance, electric capacity and amplifier.By R17, R18 current signal is converted to voltage signal, capacitor C 10, C12 filtering clutter.It is two voltage comparators of LM324N that amplifier is selected model.D5, D6 voltage stabilizing are exported 107 pins that pulse wave signal is sent into DSP more afterwards through the feedback amplification and with zero level, and DSP can obtain zero cross signal by detecting rising edge and trailing edge.The four the tunnel is capacitor C 1 both end voltage sample circuit, roughly the same with No. 1 circuit, sends into 173 pins of DSP after the sampling conditioning.
Fig. 4 is power switching flow chart of the present invention
Step 1: follow the tracks of grid voltage waveform, it is phase-locked to start numeral
Sampling unit real-time sampling photo-voltaic power supply voltage, load current, line voltage and capacitor C 1 both end voltage waveform, capturing unit is caught load current and voltage zero-crossing point of power grid.The break-make of control unit control VQ5 makes photo-voltaic power supply work in maximum power point.Simultaneously, when the capturing unit of control unit inside captures zero crossing, digital phase-locked startup.Because the phase-locked target of numeral is to make photovoltaic voltage and line voltage with the frequency homophase, because follow current is comparatively easy, so allow load current go to follow the tracks of the variation of line voltage.The phase-locked employing of output current DSP software phlase locking mode realizes.The load current frequency is to realize by adjusting the triangular carrier frequency that produces SPWM, if power frequency is less than mains frequency, then should reduce to occur the value of the relevant timer period register of SPWM signal, thereby realize that by improving the triangular carrier frequency load current is identical with the line voltage frequency, vice versa.The load current phase place is to realize by adjusting the moment that produces first some generation in the sinusoidal wave centrifugal pump of SPWM signal, when capturing the zero crossing of line voltage, adjusts immediately the pointer of sinusoidal wave centrifugal pump in the corresponding comparand register and adjusts phase place.The phase-locked design of numeral is among the present invention: at first use the two-way capturing unit to catch respectively frequency and the phase place of calculating line voltage and load current, regulate step value and bit pointer mutually in the algorithm according to result of calculation, thereby realize that load current is to the tracking of frequency and the phase place of line voltage.
At first adjust frequency, when capturing rising edge generation interruption, enter interrupt service routine, keep the scene intact first, judge that again interrupt source is CAP1 or CAP2.If CAP1, then the moment of explanation generation interruption is the zero crossing of line voltage.The value Uzero that the register CAPFIFO of control unit inside is caught deposits in the self-defining array, deducts the last value of catching U(N-1 again) zero, both differences just in time are the cycle T of line voltage
GridIf CAP2, then the moment of explanation generation interruption is the zero crossing of load current.The value Izero that CAPFIFO is caught deposits self-defining another array in, deducts the last value of catching I(N-1 again) zero, both differences just in time are the cycle T of load current
LoadThen take the cycle T of current line voltage
GridWith present load current cycle T
LoadMake comparisons, if both without difference, then do not adjust; If error is arranged, then period register T1PR is done corresponding the adjustment.If T
LoadLess than T
Grid, then increase the value in the T1PR, if T
LoadGreater than T
Grid, then reduce the value in the T1PR.Adjust to when identical with the line voltage frequency when the load current frequency, carry out the phase place adjustment.Utilize Uzero to deduct Izero and obtain phase difference Ph, because the phase bit pointer
Be 16 unsigned int variable, then the phase bit pointer of k step signal processed
Finger is
,
, N is carrier wave ratio, N=400, n are 16.Then the phase resolution of pointer is 2 pi/2s
16=9.6 * 10
-5(rad), the sinusoidal phase pointer of modulation signal is 1 step value at the increment in each sampling period
By current phase place pointer value and line voltage frequency, obtain step value λ, if phase difference Ph then is judged as roughly homophase less than 2 ° or greater than 358 °, pointer remains unchanged, if Ph greater than 2 ° less than 180 ° of pointers then
Reduce by a λ, if Ph greater than 180 ° less than 358 °, pointer then
Increase a λ so that it crosses the zero phase value convergence to inversion. so just can realize that load current is consistent with the phase place of civil power. just can realize that also load current frequency and phase place are to the tracking of line voltage.
Because program adopts the meter reading method. can there be certain phase error. theoretic maximum phase error is 9.6 * 10
-5(rad). this error is quite little, and digital phase-locked precision is higher, phase-locked finishing, load current is successfully followed the tracks of frequency and the phase place of line voltage, carry out step 2.
Whether step 2: it is unusual to detect the photo-voltaic power supply state
When photo-voltaic power supply power output during more than or equal to load, if the square-wave signal of i.e. photo-voltaic power supply voltage sample and zero cross detection circuit input within a cycle value in the Sample1 10 times more than or equal to setting sine table sin_table[P
Index] (sin_table[i]=V*|sin (i*360
o/ N) |, V=300, N=400) value, judge that then the photo-voltaic power supply power supply is normal, the first switch unit of its mains side is controlled switching device Q1, Q2 fast entirely according to the in turn conducting of positive-negative half-cycle of sinusoidal ac, namely exporting PWM ripple duty ratio is 0.5, and Q2 closes in voltage positive half period Q1 conducting, and Q1 closes in the Q2 conducting of voltage negative half period.Utilize simultaneously fast anti-paralleled diode realization afterflow and the buffering of full control switching device, device is carried out over-voltage over-current protection, reduce the switching loss of device.The second switch unit of civil power side fast full control switching device Q3, Q4 keep closed condition, city's net is power output not, only by photo-voltaic power supply to load supplying, simultaneously, load current real-time tracking line voltage frequency and phase place.
When photo-voltaic power supply power output during less than the load power demand, be not more than sine value in the sin_table of setting for 10 times if square-wave signal value in the Sample1 within a cycle of i.e. photo-voltaic power supply voltage sampling circuit input is continuous, judge the photo-voltaic power supply electricity shortage, then turn step 3.
Step 3:DSP control driver element is so that photo-voltaic power supply and electrical network parallel powering
1. sampling photovoltaic voltage waveform, if voltage is in positive half period, PWM1 exports effective high level, Q1 is conducting state, start the 2nd timer of DSP this moment and enable to export PWM4 and allow the Q4 conducting so that city's net power supply is pressed because photovoltaic electric forces down in urban network electricity, this moment, D2 can end, the photo-voltaic power supply output current is zero, and electric current brings out to send out through Q4, D3 and load from city net L1 and forms whole current circuit.When Q4 closes, the D2 conducting, photo-voltaic power supply continues power supply, and electric current brings out to send out through Q1, D2 and load from photo-voltaic power supply L and forms the loop.Wherein the ON time of Q4 is determined by the pulse duration of corresponding PWM4.
2. sampling photovoltaic voltage waveform, if voltage is in negative half-cycle, Q1 and Q3 have turn-offed, similar with positive half period, PWM2 exports effective high level, and Q2 still keeps conducting state, and the 2nd timer by starting DSP also enables to export PWM3 and allows the Q3 conducting so that city's net power supply, this moment D1 can to end the photo-voltaic power supply output current be zero, electric current flows out from city's net N1 end and forms whole current circuit by load, Q3 and D4.When Q3 closes, the D1 conducting, photo-voltaic power supply continues power supply, and electric current brings out to send out from photo-voltaic power supply N and forms whole current circuit through overload, Q2 and D1.Wherein the ON time of Q3 is determined by the pulse duration of corresponding PWM3.
So when the duty ratio that changes PWM3, PWM4 is namely revised the value of comparand register T2CMPR, just can change the power output of city's net.Again owing to entirely control fast the reverse cut-off characteristics of switching device and diode, can not form current path between city's net and the photo-voltaic power supply, can only be to setting load supplying, guaranteed that electric current can be from the photo-voltaic power supply adverse current to the urban network electricity source, just enough change the power output of city's net by regulating duty ratio, the break-make by control VQ5 makes photo-voltaic power supply work in maximum power point simultaneously.
Step 4: detect the photo-voltaic power supply state and whether recover normal
Sampling photovoltaic voltage waveform, if the square-wave signal of photo-voltaic power supply voltage sample and zero cross detection circuit input within a cycle value in the Sample1 10 times more than or equal to the sine value of setting in the sin_table, it is normal then to be judged to be the photo-voltaic power supply recovering state, turns step 5.
Step 5: again follow the tracks of line voltage, it is phase-locked to start numeral
Sampling photovoltaic supply voltage, load current and line voltage, capturing unit capture photovoltaic supply voltage and voltage zero-crossing point of power grid.When capturing zero crossing, digital phase-locked startup.Detailed process does not repeat them here with step 1.Phase-locked finishing, load current are successfully followed the tracks of frequency and the phase place of line voltage, turn step 6.
Electric network source is adjusted in step 6:DSP control and main circuit disconnects
When returning to, can normally be with when carrying photo-voltaic power supply, be still this moment by photo-voltaic power supply and city's net while powering load, so gradually duty ratio d2 is adjusted to zero by DSP, namely constantly reduce the value of comparand register T2CMPR, when being reduced to zero, the PWM3 of DSP, PWM4 mouth are no longer exported effective high level, and Q3, Q4 then can automatically shut down, and city's net is power output no longer.Q1 and Q2 are still according to the in turn conducting of positive-negative half-cycle of sinusoidal ac.
Fig. 5 and Fig. 6 are frequency adjustment flow chart of the present invention and phase adjusted flow chart, and detailed process has detailed description in step 1.
Claims (5)
1. photovoltaic generation and city's net parallel powering switching device shifter, it is characterized in that load passes through the first switch unit and be connected with photo-voltaic power supply, be connected with city's net by the second switch unit, the first switch unit is by the 1st, the 2nd igbt Q1, Q2 is respectively with the 1st, the 2nd diode D1, the D2 reverse parallel connection forms, the Q1 negative terminal links to each other with the Q2 negative terminal, Q1, the Q2 anode respectively with photo-voltaic power supply, load links to each other, the second switch unit is by the 3rd, the 4th igbt Q3, Q4 is respectively with the 3rd, the 4th diode D3, the D4 reverse parallel connection forms, the Q3 negative terminal links to each other with the Q4 negative terminal, Q3, the Q4 anode respectively with load, city's net links to each other, the grid of Q1 ~ Q4 links to each other with the first driver element, the first driver element is connected with control unit, the photo-voltaic power supply output voltage, line voltage, load current is by 1 of the sampling conditioning unit, 2, No. 3 circuit samplings are to control unit
Photo-voltaic power supply is by photovoltaic array, pressure unit, inversion unit connects to form successively, by the 5th igbt VQ5, the 9th diode D10, inductance L 1 forms reduction voltage circuit, the grid of VQ5 is connected to the 3rd driver element, the 3rd driver element is connected to control unit, sampling capacitance C1 both end voltage through sampling conditioning unit No. 4 circuit samplings to control unit, inversion unit is comprised of with 5-8 diode D5 ~ D8 reverse parallel connection respectively 6-9 igbt VQ1 ~ VQ4, the negative terminal of VQ1 is connected with the anode of VQ2, and be connected with the first output, the negative terminal of VQ3 is connected with the anode of VQ4, and be connected with the second output, first, two outputs are through inductance, after boosting, resistance filtering and transformer be connected respectively to the first switch unit and load, VQ1, the negative terminal of the anode of VQ3 and VQ2 and VQ4 connects the output of pressure unit, the grid of VQ1 ~ VQ4 pipe all is connected with the second driver element, and the second driver element is linked control unit again.
2. device according to claim 1 is characterized in that photo-voltaic power supply output L, N be connected to sampling conditioning unit No. 1 circuit terminals P 11,2 mouthfuls, be connected to resistance and the 1st amplifier U1, the output of the 1st amplifier U1 meets the 1st voltage follower U2, the output of U2 is connected to control unit behind resistance and the first clamp circuit, city net output L1, N1 be connected to the sampling conditioning unit No. 2 circuit terminals P 21,2 mouthfuls, be connected to resistance and the 2nd amplifier U3, the output one road of U3 is to the 2nd voltage follower U4, the output of U4 is connected to control unit through resistance and the second clamp circuit, another road output of the 2nd amplifier U3 is connected to control unit through zero-crossing comparator U5 and filter circuit, load current is connected to resistance by the current Hall transducer of No. 3 circuit of sampling conditioning unit, behind the modulate circuit that electric capacity and the 3rd amplifier U6 form, zero level comparison circuit through feedback amplifier U7 and diode composition is connected to control unit, the output of sampling capacitance C1 both end voltage is through 1 of No. 4 circuit terminal P3,2 mouthfuls, be connected to resistance and the 4th amplifier U8, the output of the 4th amplifier U8 meets the 3rd voltage follower U9, and the output of U9 is connected to control unit behind resistance and the 3rd clamp circuit.
3. device according to claim 1 is characterized in that the power switching method is as follows:
(1) No. 1 circuit sampling photo-voltaic power supply of sampling conditioning unit output voltage waveforms, sample the respectively waveform of line voltage and load current of No. 2 circuit and No. 3 circuit, catch their zero crossing constantly, control unit calculates their frequency and phase difference value more constantly according to this, output regulation signal is to the second driver element, drive inversion unit, make the photo-voltaic power supply output voltage consistent with frequency and the phase place of line voltage, No. 4 circuit sampling capacitor C 1 both end voltage, control unit is adjusted duty ratio by calculating, and makes the photovoltaic array Maximum Power Output;
(2) when photo-voltaic power supply power output during more than or equal to default bearing power, judge that namely the photo-voltaic power supply power supply is normal, the control unit output signal is to the positive and negative half period in turn conducting of the first drive unit drives the first switch unit according to sinusoidal ac, at this moment, the second switch unit is closed, and is only powered to the load by photo-voltaic power supply;
(3) when photo-voltaic power supply power output during less than default bearing power, judge that namely the photo-voltaic power supply power supply is undesired, the control unit output signal drives first, second switch unit conducting to the first driver element, this moment photo-voltaic power supply and city's net parallel powering;
(4) detect the photo-voltaic power supply power supply and whether recover normal, if do not recover, then repeating step (3) if recover normal, then turns step (5);
(5) control unit is caught the difference of their frequency of zero crossing calculating of line voltage and load current by sampling conditioning unit 2, No. 3 circuit, output signal is to the second driver element, regulate the output of inversion unit, make the frequency of photo-voltaic power supply output voltage and line voltage consistent with phase place, at this moment, still by photo-voltaic power supply and city's net parallel powering;
(6) control unit is regulated the duty ratio output of line voltage gradually by the first driver element, and when being adjusted to zero, the first driver element is closed the second switch unit, and photo-voltaic power supply powers to the load through the first switch unit of conducting.
4. device according to claim 3; it is characterized in that in the step (1); when control unit captures the rising edge of a pulse of line voltage and load current, produce and interrupt; protect first the interrupt spot; namely preserve the value of related register; judge that again this interruption is the first capturing unit or the generation of the second capturing unit by control unit; if the first capturing unit; namely interrupting constantly is the zero crossing of line voltage; this value of catching is deposited in the self-defining array; this value of catching deducts the last time and catches the cycle that is worth line voltage; if the second capturing unit; namely interrupting constantly is the zero crossing of load current; this value of catching is deposited in self-defining another array; this value of catching deducts the last time and catches the cycle that is worth load current; the absolute value that compares the cycle difference of line voltage and load current | F|; if | F|=0; be that both frequencies are identical; do not adjust; if | F|〉0; then the period register of control unit inside is adjusted; if the cycle of load current is greater than the cycle of line voltage; then reduce the value of period register; if the cycle of load current is less than the cycle of line voltage; then increase the value of period register, until the cycle of load current equals the cycle of line voltage, namely both frequencies are identical.
5. device according to claim 4 when it is characterized in that frequency when load current and line voltage is identical, calculates phase difference Ph by the value of catching, and utilizes the phase bit pointer when capturing voltage zero-crossing point of power grid
Record k step signal processed, judge that the value of phase difference is whether in allowed band, if within scope, then pointer does not adjust, if not in allowed band, by current phase place pointer value and line voltage frequency, obtain step value λ, make forward or backward step value of phase bit pointer, realize that it crosses the zero phase value convergence to inversion, so just can realize that load current is consistent with the phase place of civil power, just can realize that also load current frequency and phase place are to the tracking of line voltage.
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