CN103208939B - Photovoltaic micro-inverter based on secondary-side reference current reconstruction, control system and control method - Google Patents
Photovoltaic micro-inverter based on secondary-side reference current reconstruction, control system and control method Download PDFInfo
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Abstract
The invention discloses a photovoltaic micro-inverter based on secondary-side reference current reconstruction, a control system and a control method. A topological structure of a staggered flyback laser photovoltaic micro-inverter based on the secondary-side reference current reconstruction is adopted. The control system comprises the staggered flyback laser photovoltaic micro-inverter based on the secondary-side reference current reconstruction, a direct current voltage and current sampling module, a driving circuit, a secondary-side pulse current sampling module, an alternating current sampling and phase locking module and a signal processing unit. The control method is an indirect control method approximate to grid-connected current direct control, primary-side reference current based on the secondary-side reference current reconstruction is adopted to control connection and disconnection of a primary-side switching tube of a flyback converter, and the control method effectively avoids the problem of slow control response, low tracking accuracy and the like in a direct control method, can guarantee same frequency and same phase of output current and public power grid voltage, reduces total harmonic distortion of grid-connected current substantially, and improves output power quality.
Description
Technical field
The present invention relates to based on the photovoltaic micro-inverter of secondary side reference electric current reconstructing, control system and method.
Background technology
The continuous growth of world energy sources demand makes the utilization of regenerative resource, especially photovoltaic generation, is subject to increasing favor just gradually.In recent years, the accepting extensively and further investigate the practicality that further enhancing photovoltaic generating system of photovoltaic building integration system and micro-grid system, simultaneously, also the sight of people be attracted on micro-inverter, namely single photovoltaic module and inverter integrate and are directly fed to alternating current to utility network.Relative to traditional centralized photovoltaic combining inverter, micro-inverter have monolithic element MPPT maximum power point tracking, low dc voltage, expansion flexibly, the advantage such as plug and play.To electrical network inject high-quality same frequency homophase simple sinusoidal alternating current, photovoltaic module carried out to efficient MPPT maximum power point tracking and realizes efficient, high performance-price ratio and high reliability is the target that photovoltaic micro-inverter is pursued.
At present, the topology built based on anti exciting converter and converter bridge is considered to the optimal solution of micro-inverter.Because when anti exciting converter is operated in current continuity conduction mode on the one hand, the peak current that switching tube bears is lower, thus allows to use the power device of more low current quota, the incomplete degaussing of transformer on the other hand, contribute to reducing magnetic hysteresis loss, entire system efficiency is higher.Also can adopt high frequency modulated technology simultaneously, the impact of high frequency transformer volume can be reduced to a certain extent.
In existing technology, in order to ensure that AC module injects high-quality homophase simple sinusoidal alternating current to electrical network, main employing grid-connected current directly controls and indirectly controls primary current two kinds of control methods.In the direct control mode of grid-connected current, maximum power point tracking device goes out grid-connected current amplitude according to the state computation of photovoltaic module, single-phase phase-locked loop method is utilized to calculate grid phase, the two is multiplied as grid-connected current reference value, sampling grid-connected current carries out FEEDBACK CONTROL, realizes grid-connected current with certain precision track reference value.But anti exciting converter controls the right side half s plane zero point existed to the transfer function of output current under continuous conduction mode, not only limit system bandwidth, and have impact on controller to the tracking performance exporting grid-connected current.And indirectly control in primary current control program, primary current uses opened loop control to output grid-connected current, by to the control realization of primary current to the control of grid-connected current, thus fundamentally stopping the directly actuated defect of grid-connected current, but the control structure of two inner ring not only increases the complexity of control system, consume more controller resource, and be unfavorable for system stability.
Summary of the invention
The invention provides based on the photovoltaic micro-inverter of secondary side reference electric current reconstructing, control system and method, its object is to, by based on secondary side reference electric current reconstructing former limit reference current, using secondary current as control objectives, reduce total harmonic distortion to a certain extent, improve the quality of power supply.
Based on the photovoltaic micro-inverter of secondary side reference electric current reconstructing, comprise DC bus capacitor C
pV(301), crisscross parallel circuit of reversed excitation (302), H converter bridge (303) and output filter (304);
DC bus capacitor C
pVin parallel with photovoltaic cell; For cushioning DC side secondary ripple wave power;
Crisscross parallel circuit of reversed excitation comprises the first transformer T1, the second transformer T2, power MOSFET tube S
pV1, S
pV2, and Power Diode Pumped D
rect1and D
rect2; Output current wave for realizing grid-connected micro-inverter controls and maximum power of photovoltaic cell point is followed the tracks of;
Output filter comprises filter capacitor C
gridwith filter inductance L
grid;
H converter bridge comprises thyristor S
ac1, S
ac2with MOSFET pipe Q
ac1, Q
ac2, S
ac1and Q
ac1form forward change of current brachium pontis, S
ac1negative pole and filter inductance L
gridone end is connected, filter inductance L
gridthe other end and Q
ac1d pole be connected with electrical network; S
ac2and Q
ac2form negative sense change of current brachium pontis, Q
ac2d pole and filter inductance L
gridone end be connected, filter inductance L
gridthe other end and S
ac2negative pole be connected with electrical network; S
ac1and S
ac2positive pole and D
rect1negative pole connect, Q
ac1and Q
ac2s extremely all connect with the second end of the first transformer T1 and the second transformer T2 vice-side winding;
S
ac1negative pole and Q
ac1d pole connect the input side of output filter, S
ac2negative pole and Q
ac2d pole connect the input side of output filter, the outlet side of output filter and electrical network G
gridconnect;
First reverse block-type power switch S
pV1s pole connect the negative pole of photovoltaic cell, the first reverse block-type power switch S
pV1d pole connect the positive pole of photovoltaic cell by the former limit of the first transformer T1; Second reverse block-type power switch S
pV2s pole connect the negative pole of photovoltaic cell, the second reverse block-type power switch S
pV2d pole connect the positive pole of photovoltaic cell by the former limit of the second transformer T2;
First termination D of the vice-side winding of the first transformer T1
rect1positive pole, D
rect1negative pole meet S
ac1and S
ac2positive pole; First termination D of the vice-side winding of the second transformer T2
rect2positive pole, D
rect2negative pole and D
rect1negative pole be connected;
MOSFET pipe Q
ac1and Q
ac2s pole and the second end of the first transformer T1 and the second transformer T2 vice-side winding be shorted together;
C
gridbe connected to S
ac1negative pole and S
ac2negative pole between;
L
grida termination S
ac1negative pole, L
gridthe other end and S
ac2negative pole be linked in electrical network.
Based on the photovoltaic micro-inverter control system of secondary side reference electric current reconstructing, comprise the described photovoltaic micro-inverter based on secondary side reference electric current reconstructing, also comprise direct voltage and current sample module, drive circuit, secondary pulse current sampling module, AC sampling and phase-locked module and signal processing unit;
The input of described direct voltage sampling module connects with the positive pole of described photovoltaic cell and negative pole respectively, and output is connected with signal processing unit; For gathering the voltage of photovoltaic cell;
AC sampling and phase-locked module and described electrical network connect;
For detecting the amplitude of utility grid voltage, calculate utility network phase angle, wherein V
gridvoltage magnitude after being processed by AC sampling and phase-locked module;
Former edge-impulse current sample module is all connected with the first end of the first transformer with the former limit winding of the second transformer;
For detecting high frequency transformer primary current;
2 outputs of drive circuit respectively with power switch tube S
pV1and S
pV2g extremely connected;
For providing to former limit winding switching tube the drive singal opened or turn off;
Signal processing unit comprises MPPT controller, former limit reference current reconstructor, state machine, equalizing controller and grid-connected current controller;
Former limit reference current reconstructor and described direct voltage and current sample module and AC sampling and phase-locked module all connect;
Secondary side reference current amplitude for providing according to photovoltaic module output voltage, utility grid voltage amplitude and phase angle and MPPT maximum power point tracking device reconstructs former limit reference current.
Based on the photovoltaic micro-inverter control method of secondary side reference electric current reconstructing, the photovoltaic micro-inverter control system based on secondary current reconstruct described in employing, based on the photovoltaic micro-inverter control method of secondary current reconstruct, with secondary current amplitude for control objectives, with secondary side reference electric current reconstructing former limit reference current, by controlling the high frequency of former limit switching tube, namely calculated the main control quantity D of switching tube duty ratio by grid-connected current peak value, superpose after the additional controlled quentity controlled variable Δ D obtained by equalizing controller through modulator output pulse signal control S
pV1and S
pV2break-make, secondary current is remained
realize the control to grid-connected current in the grid-connected micro-inverter of interleaving inverse excitation.
Described control method concrete steps are as follows:
Step 1: utilize direct voltage and current sample module to detect photovoltaic cell output voltage V at each control cycle
pv, utilize AC sampling and phase-locked module to detect utility grid voltage amplitude v
g;
Step 2: adopt single-phase phase-locked loop to calculate current electric grid voltage-phase angle θ;
The phase-locked loop pll of grid-connected micro-inverter have employed the zero passage detection to line voltage, detects current electric grid voltage-phase angle θ (θ=ω t);
Step 3: initialization counter A is 0,1 is added to MPPT counter A, then MPPT counter A is judged, if MPPT counter A reaches set point M, then the MPPT execution cycle arrives, and carries out MPPT control, MPPT and Maximum Power Point Tracking is MPPT maximum power point tracking, perform step 4, otherwise, perform step 5;
In described step 3, MPPT controller performs frequency is 1 ~ 10Hz, in conjunction with the controller dominant frequency selected, utilizes controller dominant frequency to obtain value P divided by the operation execution frequency of MPPT controller, the count value M of setting MPPT counter, M=1/P;
Step 4: utilize MPPT maximum power point tracking method to calculate secondary side reference current amplitude
MPPT maximum power point tracking method: being with the average output voltage of photovoltaic cell and average output current for input, is its output with reference to grid-connected current peak value;
Step 5: former limit reference current reconstructor is based on secondary side reference electric current reconstructing former limit reference current
Wherein,
for the secondary side reference current amplitude that MPPT maximum power point tracking device calculates, v
gfor utility grid voltage amplitude, V
pvfor photovoltaic module output voltage, ω is the angular frequency of utility grid voltage,
be the first transformer and the second transformer secondary winding to the turn ratio of former limit winding, t=kT is the time that a kth control cycle is corresponding, and T=1/f, f are the frequency of grid-connected current closed-loop control;
Step 6: former limit reference current reconstructor reconstructs former limit reference current according to the method described above
the first transformer obtained in conjunction with former edge-impulse current sample module samples and the primary current detected value i of the second transformation
pv1and i
pv2carry out close loop negative feedback control, obtain the main control quantity D of switching tube duty ratio, superposition current-sharing adds controlled quentity controlled variable Δ D control MOSFETS after modulation
pV1and S
pV2break-make;
Step 7: differentiate grid-connected current direction according to grid phase angle ω t, control the thyristor S in forward and negative sense change of current brachium pontis with this
ac1and S
ac2and MOSFET Q
ac1and Q
ac2break-make;
ω t ∈ [0o, 180 °) time, open S
ac1, Q
ac1, close S
ac2, Q
ac2; ω t ∈ [180 °, 360 °) time, open S
ac2, Q
ac2, close S
ac1, Q
ac1.
In described step 7 grid-connected current discriminating direction and rate-determining steps as follows:
Step 1: if grid phase angle θ enters zero passage interval [α, β], closes power switch S
pV1and S
pV2and the drive singal of thyristor in the change of current brachium pontis of current conducting, and enter the state waited for and be switched to another group brachium pontis conducting;
Step 2: whether detection of grid exists voltage zero-crossing signal, if there is voltage zero-crossing signal, closes the MOSFET pipe in the change of current brachium pontis of current conducting;
Step 3: if grid phase angle has left zero passage interval [α, β], then enter step 4; Otherwise directly exit grid-connected current direction controlling;
Step 4: whether be in first, second quadrant to grid-connected current state and judge, is if so, then switched to the 3rd, fourth quadrant by current grid-connected current; Otherwise, grid-connected current is switched to first, second quadrant.
Described zero passage interval [α, β] arrange according to the switch performance of selected commutated thyristor, wherein, α depends on the turn off delay time of grid-connected current fall time and selected thyristor, set α to ensure grid-connected current drop to zero after the current thyristor energy reliable turn-off having opened change of current brachium pontis before electrical network zero passage, arrange with reference to the turn off delay time in the thyristor databook selected, thyristor turn off delay time standard extends 5% ~ 10%; β depends on that the reverse blocking of selected thyristor recovers the sensitivity of time delay and hardware zero passage detection, the change of current brachium pontis being about to open after set β will ensure the reliable zero passage of electrical network can be open-minded safely, arrange recovery time with reference to the forward blocking in the thyristor databook selected, thyristor forward blocking standard recovery time extends 5% ~ 10%.
The power of described photovoltaic micro-inverter is 100-200W.
Beneficial effect
The invention provides the photovoltaic micro-inverter based on secondary side reference electric current reconstructing, control system and method, adopt the topological structure based on secondary side reference electric current reconstructing photovoltaic micro-inverter, control system comprises the photovoltaic micro-inverter based on secondary side reference electric current reconstructing, direct voltage and current sample module, drive circuit, secondary pulse current sampling module, AC sampling and phase-locked module and signal processing unit, the control method that the present invention proposes is a kind of closer to the directly actuated method for indirectly controlling of grid-connected current, the former limit reference current based on secondary side reference electric current reconstructing is adopted to control the break-make of anti exciting converter former limit switching tube, both effectively prevent control response in direct control method blunt, the problems such as tracking accuracy is not high, also can ensure that output current and utility grid voltage are with frequency homophase, significantly reduce the total harmonic distortion of grid-connected current, improve and export the quality of power supply.
Accompanying drawing explanation
Fig. 1 is Control system architecture figure of the present invention;
Fig. 2 is the control block diagram of control method of the present invention;
Fig. 3 is control method flow chart of the present invention;
Fig. 4 is the primary current waveform of example of the present invention actual measurement after sampling circuit samples conditioning;
Fig. 5 is example of the present invention actual measurement line voltage, grid-connected current and output instantaneous power waveform;
Embodiment
Below in conjunction with accompanying drawing, the present invention is further illustrated.
As shown in Figure 1, for the structure chart of the photovoltaic micro-inverter control system based on secondary side reference electric current reconstructing of the present invention, comprise based on the photovoltaic micro-inverter (300) of secondary side reference electric current reconstructing, direct voltage and current sample module, drive circuit, secondary pulse current sampling module, AC sampling and phase-locked module and signal processing unit;
Photovoltaic micro-inverter (300) based on secondary side reference electric current reconstructing comprises DC bus capacitor C
pV(301), crisscross parallel circuit of reversed excitation (302), H converter bridge (303) and output filter (304):
DC bus capacitor C
pV(301), be connected in parallel with photovoltaic cell; For cushioning DC side secondary ripple wave power;
Crisscross parallel circuit of reversed excitation (302), comprises the first transformer T1 and the second transformer T2, power MOSFET tube S
pV1, S
pV2, and Power Diode Pumped D
rect1and D
rect2; Output current wave for realizing grid-connected micro-inverter controls and maximum power of photovoltaic cell point is followed the tracks of;
Output filter (304), comprises filter capacitor C
gridwith filter inductance L
grid;
H converter bridge comprises thyristor S
ac1, S
ac2with MOSFET pipe Q
ac1, Q
ac2, S
ac1and Q
ac1form forward change of current brachium pontis, S
ac1negative pole and filter inductance L
gridone end is connected, filter inductance L
gridthe other end and Q
ac1d pole be connected with electrical network; S
ac2and Q
ac2form negative sense change of current brachium pontis, Q
ac2d pole and filter inductance L
gridone end be connected, filter inductance L
gridthe other end and S
ac2negative pole be connected with electrical network; S
ac1and S
ac2positive pole and D
rect1negative pole connect, Q
ac1and Q
ac2s extremely all connect with the second end of the first transformer T1 and the second transformer T2 vice-side winding;
First reverse block-type power switch S
pV1s pole connect the negative pole of photovoltaic cell, the first reverse block-type power switch S
pV1d pole connect the positive pole of photovoltaic cell by the former limit of the first transformer T1; Second reverse block-type power switch S
pV2s pole connect the negative pole of photovoltaic cell, the second reverse block-type power switch S
pV2d pole connect the positive pole of photovoltaic cell by the former limit of the second transformer T2;
First termination D of the vice-side winding of the first transformer T1
rect1positive pole, D
rect1negative pole meet S
ac1and S
ac2positive pole; First termination D of the vice-side winding of the second transformer T2
rect2positive pole, D
rect2negative pole and D
rect1negative pole be connected;
MOSFET pipe Q
ac1and Q
ac2s pole and the second end of the first transformer T1 and the second transformer T2 vice-side winding be shorted together;
C
gridbe connected to S
ac1negative pole and S
ac2negative pole between;
L
grida termination S
ac1negative pole, L
gridthe other end and S
ac2negative pole be linked in electrical network.
The input of described direct voltage sampling module connects with the positive pole of described photovoltaic cell and negative pole respectively, and for gathering the voltage of photovoltaic cell, output is connected with signal processing unit;
AC sampling and phase-locked module, and described electrical network connects; Detect the amplitude of utility grid voltage, calculate utility network phase angle, wherein, V
gvoltage magnitude after being processed by AC sampling and phase-locked module;
Former edge-impulse current sample module is all connected with the first end of the first transformer with the former limit winding of the second transformer; Detect high frequency transformer primary current;
Two outputs of drive circuit respectively with power switch tube S
pV1and S
pV2g extremely connected; For providing to former limit winding switching tube the drive singal opened or turn off;
Signal processing unit comprises MPPT controller, former limit reference current reconstructor, state machine, equalizing controller and grid-connected current controller.
Former limit reference current reconstructor, all connects with described direct voltage and current sample module and AC sampling and phase-locked module; Secondary side reference current amplitude for providing according to photovoltaic module output voltage, utility grid voltage amplitude and phase angle and MPPT maximum power point tracking device reconstructs former limit reference current.
As shown in Figures 2 and 3, be control method block diagram of the present invention and flow chart.
Based on the photovoltaic micro-inverter control method of secondary side reference electric current reconstructing, adopt the control system based on the photovoltaic micro-inverter of secondary side reference electric current reconstructing, based on the photovoltaic micro-inverter control method of secondary side reference electric current reconstructing, with secondary current amplitude for control objectives, with secondary side reference electric current reconstructing former limit reference current, by controlling the high frequency of former limit switching tube, namely calculated the main control quantity D of switching tube duty ratio by grid-connected current peak value, superpose after the additional controlled quentity controlled variable Δ D obtained by equalizing controller through modulator output pulse signal control S
pV1and S
pV2break-make, secondary current is remained
realize the control to grid-connected current in the grid-connected micro-inverter of interleaving inverse excitation.
Described control method concrete steps are as follows:
Step 1: utilize direct voltage and current sample module to detect photovoltaic cell output voltage V at each control cycle
pv, utilize AC sampling and phase-locked module to detect utility grid voltage amplitude v
g;
Step 2: adopt single-phase phase-locked loop to calculate current electric grid voltage-phase angle θ;
The phase-locked loop pll of grid-connected Miniature inverter have employed the zero passage detection to line voltage, detects current electric grid voltage-phase angle θ (θ=ω t);
Step 3: initialization counter A is 0,1 is added to MPPT counter A, then MPPT counter A is judged, if MPPT counter A reaches set point M, then the MPPT execution cycle arrives, and carries out MPPT control, MPPT and Maximum Power Point Tracking is MPPT maximum power point tracking, perform step 4, otherwise, perform step 5;
In described step 3, MPPT controller performs frequency is 1 ~ 10Hz, in conjunction with the controller dominant frequency selected, utilizes controller dominant frequency to obtain value P divided by the operation execution frequency of MPPT controller, the count value M of setting MPPT counter, M=1/P;
Step 4: utilize MPPT maximum power point tracking method to calculate secondary side reference current amplitude
MPPT maximum power point tracking method: be with the average output voltage of photovoltaic cell and average output current for input, be its output with reference to grid-connected current peak value, there is the function of following the tracks of maximum power of photovoltaic cell point;
Step 5: former limit reference current reconstructor is based on secondary side reference electric current reconstructing former limit reference current
Wherein,
for the secondary side reference current amplitude that MPPT maximum power point tracking device calculates, v
gfor utility grid voltage amplitude, V
pvfor photovoltaic module output voltage, ω is the angular frequency of utility grid voltage,
be the first transformer and the second transformer secondary winding to the turn ratio of former limit winding, t=kT is the time that a kth control cycle is corresponding, and T=1/f, f are the frequency of grid-connected current closed-loop control;
Step 6: former limit reference current reconstructor reconstructs former limit reference current according to the method described above
the first transformer obtained in conjunction with former edge-impulse current sample module samples and the primary current detected value i of the second transformation
pv1and i
pv2carry out close loop negative feedback control, obtain the main control quantity D of switching tube duty ratio, superposition current-sharing adds controlled quentity controlled variable Δ D control MOSFETS after modulation
pV1and S
pV2break-make;
Step 7: differentiate grid-connected current direction according to grid phase angle ω t, control the thyristor S in forward and negative sense change of current brachium pontis with this
ac1and S
ac2and MOSFET Q
ac1and Q
ac2break-make.
ω t ∈ [0 °, 180 °) time, open S
ac1, Q
ac1, close S
ac2, Q
ac2; ω t ∈ [180 °, 360 °) time, open S
ac2, Q
ac2, close S
ac1, Q
ac1.As, grid-connected current is timing, S
ac1namely turn off at 110 °, Q
ac1turn off 170 ° time.
In described step 7 grid-connected current discriminating direction and rate-determining steps as follows:
Step 1: if grid phase angle θ enters zero passage interval [α, β], closes power switch S
pV1and S
pV2and the drive singal of thyristor in the change of current brachium pontis of current conducting, and enter the state waited for and be switched to another group brachium pontis conducting;
Step 2: whether detection of grid exists voltage zero-crossing signal, if there is voltage zero-crossing signal, closes the MOSFET in the change of current brachium pontis of current conducting;
Step 3: if grid phase angle has left zero passage interval [α, β], then enter step 4; Otherwise directly exit grid-connected current direction controlling;
Step 4: whether be in first, second quadrant to grid-connected current state and judge, is if so, then switched to the 3rd, fourth quadrant by current grid-connected current; Otherwise, grid-connected current is switched to first, second quadrant.
Described zero passage interval [α, β] arrange according to the switch performance of selected commutated thyristor, wherein, α depends on the turn off delay time of grid-connected current fall time and selected thyristor, set α to ensure grid-connected current drop to zero after the current thyristor energy reliable turn-off having opened change of current brachium pontis before electrical network zero passage, arrange with reference to the turn off delay time in the thyristor databook selected, thyristor turn off delay time standard extends 5% ~ 10%; β depends on that the reverse blocking of selected thyristor recovers the sensitivity of time delay and hardware zero passage detection, the change of current brachium pontis being about to open after set β will ensure the reliable zero passage of electrical network can be open-minded safely, arrange recovery time with reference to the forward blocking in the thyristor databook selected, thyristor forward blocking standard recovery time extends 5% ~ 10%.
As shown in Figure 4, the control system model for building based on the present invention carries out surveying the primary current waveform after sample circuit conditioning.Two parts are divided in figure, the top that Part I figure is in figure is divided into overall waveform figure, the Part II figure bottom be in figure is divided into the partial enlarged drawing of position in the Part I figure of cursor place, amplify 400 times, abscissa is time (ms), ordinate is voltage (V), in Part II figure, 10.0us refers to every large lattice 10us on horizontal scale, thus every large lattice 4.00ms in Part I figure, namely the 100us that in Part I figure, the signal of 40ms intercepts wherein is altogether carried out details display by Part II figure.Upper and lower two figure are the displays under Different time scales of same signal; 500mV refers to that the signal of passage 3 every lattice in vertical dimension represent 500mV (therefore the about 1.6V of signal in figure).125M time/stopwatch shows the sampling rate that oscilloscope is current, 5M: represent that oscilloscope is altogether sampled with the speed of 125M/ second the data point of 5M size under current time scale, in control system model, anti exciting converter design runs under continuous current mode, to reducing primary current peak value, reduce the current stress of switching tube; The incomplete degaussing of high frequency transformer, is conducive to reducing magnetic hysteresis loss, elevator system overall efficiency.Limit, figure Central Plains current waveform envelope line is coincide with the former limit reference current drawn by secondary side reference electric current reconstructing, proves that the control method adopted is correctly effective.
As shown in Figure 5, for carrying out actual measurement line voltage, grid-connected current and output instantaneous power based on control system of the present invention.In figure, 100V represents that the utility network of channel oscilloscope 1 is with the display of 100V/ lattice, and " ~ " represents it is exchange; 500mA represents that the grid-connected current of channel oscilloscope 4 is with the display of 500mA/ lattice, and " ~ " represents it is exchange; Pac=vgrid × igrid, figure is just shown as M=passage 1 × passage 4,100W and represents that instantaneous power pac shows with 100W/ lattice; The average 165W of M: refer to average to instantaneous power pac, current grid-connected power output is 165W.Actual measurement line voltage effective value is 231V, and given secondary current reference current peak value is 1A, exports instantaneous power and exports average power fluctuation to double line voltage frequency and to double.As can be seen from the figure, grid-connected current and the basic same homophase frequently of line voltage, measured power factor reaches 0.998, current waveform is totally sinusoidal waveform, percent harmonic distortion 3.66%, meets Specifications, has absolutely proved the validity of control method used in the present invention.
In example of the present invention, the converter bridge be made up of two thyristors and two MOSFET contributes to the convenient realization of hardware overcurrent protection.Be aided with the sampling of grid-connected current hardware and protective circuit; when grid-connected current exceeds certain value extremely; trigger hardware current foldback circuit; turn off two MOSFET in H converter bridge brachium pontis; realize the disconnection of inverter and utility network; and sending hardware over-current signal, other corresponding measure taked by " notice " controller.
With preferred embodiments openly as above, but it does not limit the present invention in the present invention.The scope that protection scope of the present invention defines with the claims in the present invention is as the criterion.Any those skilled in the art, not departing from scope of the present invention, can make suitable variation and amendment.
Claims (4)
1. based on the photovoltaic micro-inverter control method of secondary side reference electric current reconstructing, it is characterized in that, adopt a kind of photovoltaic micro-inverter control system based on secondary current reconstruct, this system comprises a kind of micro-inverter based on secondary side reference electric current reconstructing, also comprises direct voltage and current sample module, drive circuit, secondary pulse current sampling module, AC sampling and phase-locked module and signal processing unit;
The input of described direct voltage sampling module connects with the positive pole of described photovoltaic cell and negative pole respectively, and output is connected with signal processing unit;
AC sampling and phase-locked module and electrical network connect;
Former edge-impulse current sample module is all connected with the first end of the first transformer with the former limit winding of the second transformer;
2 outputs of drive circuit respectively with power MOSFET tube S
pV1with power MOSFET tube S
pV2g extremely connected;
Signal processing unit comprises MPPT controller, former limit reference current reconstructor, state machine, equalizing controller and grid-connected current controller;
Former limit reference current reconstructor and described direct voltage and current sample module and AC sampling and phase-locked module all connect;
Wherein, the photovoltaic micro-inverter based on secondary side reference electric current reconstructing in this system, comprises DC bus capacitor C
pV(301), crisscross parallel circuit of reversed excitation (302), H converter bridge (303) and output filter (304);
DC bus capacitor C
pVin parallel with photovoltaic cell; For cushioning DC side secondary ripple wave power;
Crisscross parallel circuit of reversed excitation comprises the first transformer T1, the second transformer T2, power MOSFET tube S
pV1, power MOSFET tube S
pV2, and Power Diode Pumped D
rect1with Power Diode Pumped D
rect2;
Output filter comprises filter capacitor C
gridwith filter inductance L
grid;
H converter bridge comprises thyristor S
ac1, thyristor S
ac2with MOSFET pipe Q
ac1, MOSFET pipe Q
ac2, thyristor S
ac1with MOSFET pipe Q
ac1form forward change of current brachium pontis, thyristor S
ac1negative pole and filter inductance L
gridone end is connected, filter inductance L
gridthe other end and MOSFET pipe Q
ac1d pole be connected with electrical network; Thyristor S
ac2with MOSFET pipe Q
ac2form negative sense change of current brachium pontis, MOSFET pipe Q
ac2d pole and filter inductance L
gridone end be connected, filter inductance L
gridthe other end and thyristor S
ac2negative pole be connected with electrical network; Thyristor S
ac1positive pole and thyristor S
ac2positive pole all with Power Diode Pumped D
rect1negative pole connect, MOSFET pipe Q
ac1s pole and MOSFET pipe Q
ac2s extremely all connect with the second end of the first transformer T1 vice-side winding and the second end of the second transformer T2 vice-side winding;
Thyristor S
ac1negative pole and MOSFET pipe Q
ac1d pole connect the input side of output filter, thyristor S
ac2negative pole and MOSFET pipe Q
ac2d pole connect the input side of output filter, the outlet side of output filter and electrical network G
gridconnect;
Power MOSFET tube S
pV1s pole connect the negative pole of photovoltaic cell, power MOSFET tube S
pV1d pole connect the positive pole of photovoltaic cell by the former limit of the first transformer T1; Power MOSFET tube S
pV2s pole connect the negative pole of photovoltaic cell, power MOSFET tube S
pV2d pole connect the positive pole of photovoltaic cell by the former limit of the second transformer T2;
First termination Power Diode Pumped D of the vice-side winding of the first transformer T1
rect1positive pole, Power Diode Pumped D
rect1negative pole meet thyristor S
ac1with thyristor S
ac2positive pole; First termination Power Diode Pumped D of the vice-side winding of the second transformer T2
rect2positive pole, Power Diode Pumped D
rect2negative pole and Power Diode Pumped D
rect1negative pole be connected;
MOSFET pipe Q
ac1with MOSFET pipe Q
ac2s pole and the second end of the first transformer T1 and the second transformer T2 vice-side winding be shorted together;
Filter capacitor C
gridbe connected to thyristor S
ac1negative pole and thyristor S
ac2negative pole between;
Filter inductance L
grida termination thyristor S
ac1negative pole, L
gridthe other end and thyristor S
ac2negative pole be linked in electrical network;
With secondary current amplitude for control objectives, with secondary side reference electric current reconstructing former limit reference current, by controlling the high frequency of former limit switching tube, namely calculated the main control quantity D of switching tube duty ratio by grid-connected current peak value, after superposing the additional controlled quentity controlled variable Δ D obtained by equalizing controller, control power MOSFET tube S through modulator output pulse signal
pV1with power MOSFET tube S
pV2break-make, secondary current is remained
realize the control to grid-connected current in the grid-connected micro-inverter of interleaving inverse excitation.
2. the photovoltaic micro-inverter control method based on secondary side reference electric current reconstructing according to claim 1, is characterized in that, described control method concrete steps are as follows:
Step 1: utilize direct voltage and current sample module to detect photovoltaic cell output voltage V at each control cycle
pv, utilize AC sampling and phase-locked module to detect utility grid voltage amplitude v
g;
Step 2: adopt single-phase phase-locked loop to calculate current electric grid voltage-phase angle θ;
Step 3: initialization counter A is 0,1 is added to MPPT counter A, then MPPT counter A is judged, if MPPT counter A reaches set point M, then the MPPT execution cycle arrives, and carries out MPPT control, MPPT and Maximum Power Point Tracking is MPPT maximum power point tracking, perform step 4, otherwise, perform step 5;
In described step 3, MPPT controller performs frequency is 1 ~ 10Hz, in conjunction with the controller dominant frequency selected, utilizes controller dominant frequency to obtain value P divided by the operation execution frequency of MPPT controller, the count value M of setting MPPT counter, M=1/P;
Step 4: utilize MPPT maximum power point tracking method to calculate secondary side reference current amplitude
MPPT maximum power point tracking method: being with the average output voltage of photovoltaic cell and average output current for input, is its output with reference to grid-connected current peak value;
Step 5: former limit reference current reconstructor is based on secondary side reference electric current reconstructing former limit reference current
Wherein,
for the secondary side reference current amplitude that MPPT maximum power point tracking device calculates, v
gfor utility grid voltage amplitude, V
pvfor photovoltaic module output voltage, ω is the angular frequency of utility grid voltage,
be the first transformer and the second transformer secondary winding to the turn ratio of former limit winding, t=kT is the time that a kth control cycle is corresponding, and T=1/f, f are the frequency of grid-connected current closed-loop control;
Step 6: former limit reference current reconstructor reconstructs former limit reference current according to the method described above
the first transformer obtained in conjunction with former edge-impulse current sample module samples and the primary current detected value i of the second transformation
pv1and i
pv2carry out close loop negative feedback control, obtain the main control quantity D of switching tube duty ratio, superposition current-sharing adds controlled quentity controlled variable Δ D and control power MOSFET tube S after modulation
pV1with power MOSFET tube S
pV2break-make;
Step 7: differentiate grid-connected current direction according to grid phase angle ω t, control the thyristor S in forward and negative sense change of current brachium pontis with this
ac1with thyristor S
ac2and MOSFET pipe Q
ac1with MOSFET pipe Q
ac2break-make;
ω t ∈ [0 °, 180 °) time, open thyristor S
ac1, MOSFET pipe Q
ac1, close thyristor S
ac2, MOSFET pipe Q
ac2; ω t ∈ [180 °, 360 °) time, open thyristor S
ac2, MOSFET pipe Q
ac2, close thyristor S
ac1, MOSFET pipe Q
ac1.
3. the photovoltaic micro-inverter control method based on secondary side reference electric current reconstructing according to claim 2, is characterized in that, in described step 7 grid-connected current discriminating direction and rate-determining steps as follows:
Step 1: if grid phase angle θ enters zero passage interval [α, β], closes power MOSFET tube S
pV1with power MOSFET tube S
pV2and the drive singal of thyristor in the change of current brachium pontis of current conducting, and enter the state waited for and be switched to another group brachium pontis conducting;
Step 2: whether detection of grid exists voltage zero-crossing signal, if there is voltage zero-crossing signal, closes the MOSFET pipe in the change of current brachium pontis of current conducting;
Step 3: if grid phase angle has left zero passage interval [α, β], then enter step 4; Otherwise directly exit grid-connected current direction controlling;
Step 4: whether be in first, second quadrant to grid-connected current state and judge, is if so, then switched to the 3rd, fourth quadrant by current grid-connected current; Otherwise, grid-connected current is switched to first, second quadrant.
4. the photovoltaic micro-inverter control method based on secondary side reference electric current reconstructing according to claim 3, it is characterized in that, described zero passage interval [α, β] arrange according to the switch performance of selected commutated thyristor, wherein, α depends on the turn off delay time of grid-connected current fall time and selected thyristor, set α to ensure grid-connected current drop to zero after the current thyristor energy reliable turn-off having opened change of current brachium pontis before electrical network zero passage, arrange with reference to the turn off delay time in the thyristor databook selected, thyristor turn off delay time standard extends 5% ~ 10%, β depends on that the reverse blocking of selected thyristor recovers the sensitivity of time delay and hardware zero passage detection, the change of current brachium pontis being about to open after set β will ensure the reliable zero passage of electrical network can be open-minded safely, arrange recovery time with reference to the forward blocking in the thyristor databook selected, thyristor forward blocking standard recovery time extends 5% ~ 10%.
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| CN103516306B (en) * | 2013-08-28 | 2016-03-09 | 浙江工业大学 | A kind of be applicable to photovoltaic array can present formula MPPT interface circuit |
| CN103516307B (en) * | 2013-08-28 | 2015-11-25 | 浙江工业大学 | What be applicable to photovoltaic array can present formula MPPT interface circuit |
| CN103647453B (en) * | 2013-12-13 | 2017-01-11 | 中南大学 | CCM-based micro inverter and control method thereof |
| CN103840764B (en) * | 2014-02-26 | 2016-09-21 | 国家电网公司 | A kind of MPPT control device and method of photovoltaic generation |
| CN104065274A (en) * | 2014-07-10 | 2014-09-24 | 航天长峰朝阳电源有限公司 | Integrated interleaved flyback redundant parallel DC/DC power module |
| CN104796022B (en) * | 2015-05-08 | 2017-10-17 | 阳光电源股份有限公司 | A kind of electricity generation system and its control method |
| CN105610185A (en) * | 2015-12-15 | 2016-05-25 | 国网山东泗水县供电公司 | Intelligent grid connection control method for photovoltaic grid-connected inverter |
| CN106058927B (en) * | 2016-06-27 | 2020-07-17 | 扬州大学 | Photovoltaic grid-connected micro-inverter maximum power point rapid algorithm based on peak current |
| CN107919800B (en) * | 2016-10-08 | 2020-05-26 | 亚力电机股份有限公司 | Boost type zero ripple DC converter |
| CN106300430B (en) * | 2016-10-26 | 2019-01-11 | 中国能源建设集团广东火电工程有限公司 | A kind of miniature photovoltaic grid-connected inverter and its grid-connected control method |
| CN107706945A (en) * | 2017-12-04 | 2018-02-16 | 河南城建学院 | A kind of system for suppressing inverter parallel system disturbance |
| CN109856444B (en) * | 2019-01-25 | 2020-07-07 | 同济大学 | Current transformer direct-current voltage detection system and method based on current switch harmonic waves |
| CN110808686B (en) * | 2019-10-31 | 2021-07-20 | 北京建筑大学 | Auxiliary converter, single-phase rectifier and control method of single-phase rectifier |
| CN116599511A (en) * | 2023-05-23 | 2023-08-15 | 小米汽车科技有限公司 | Power device switching speed control method and device and electric driving system |
| CN116937953B (en) * | 2023-09-18 | 2023-12-15 | 锦浪科技股份有限公司 | Micro inverter zero crossing control method |
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| CN102074968B (en) * | 2009-11-19 | 2013-01-30 | 上海岩芯电子科技有限公司 | Photovoltaic miniature grid-connected inverter control device and control method thereof |
| CN101784149B (en) * | 2010-02-10 | 2012-12-26 | 无锡睿阳微电子科技有限公司 | Feedforward control circuit for stable load |
| CN102801179A (en) * | 2011-05-26 | 2012-11-28 | 武汉金天新能源科技有限公司 | Photovoltaic grid-connected micro-inverter system |
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