CN203103983U - Hybrid-clamping type three-level three-phase four-wire photovoltaic system based on 3D-SPWM - Google Patents
Hybrid-clamping type three-level three-phase four-wire photovoltaic system based on 3D-SPWM Download PDFInfo
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- CN203103983U CN203103983U CN2012207506025U CN201220750602U CN203103983U CN 203103983 U CN203103983 U CN 203103983U CN 2012207506025 U CN2012207506025 U CN 2012207506025U CN 201220750602 U CN201220750602 U CN 201220750602U CN 203103983 U CN203103983 U CN 203103983U
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Abstract
The utility model relates to a hybrid-clamping type three-level three-phase four-wire photovoltaic system based on 3D-SPWM. The three-level three-phase four-wire photovoltaic system adopts a 3D-SPWM control mode, effectively reduces system leakage current, guarantees neutral point potential balance, guarantees balance of output three-phase voltage when the photovoltaic system is in an independent operation state and guarantees balance of three-phase grid connected current when the photovoltaic system is in a grid connected operation state. In addition, neutral current can be effectively reduced by controlling zero-sequence component. The photovoltaic system comprises three-phase bridge arms connected in parallel. Each bridge arm comprises four IGBTs connected in series, a neutral point of each phase bridge arm is connected with a corresponding resistor through a filter, and the resistors are grounded. A pair of capacitors C1 and C2 in series connection is connected with an input terminal of each bridge arm in parallel, and the capacitors C1 and C2 are connected with an acquisition photovoltaic array. A pair of diodes is connected between a first IGBT and a fourth IGBT in each bridge arm in series. Neutral points of the capacitors C1 and C2 are grounded. In addition, clamped capacitors Cxi are connected on each pair of diodes in parallel, wherein i is equal to a, b and c. Each IGBT is controlled by a control circuit adopting the 3D-SPWM mode to balance the neutral point potential.
Description
Technical field
The utility model relates to a kind of combination clamping formula three level three-phase four-line system photovoltaic systems based on 3D-SPWM.
Background technology
Three-level inverter has withstand voltage height, and switch stress is little, and characteristics such as output waveform quality height have very widely in the high-power occasion to be used.Along with developing rapidly of photovoltaic industry, three level so that more multi-electrical level inverter be applied among the photovoltaic generating system gradually.But for the conventional diode clamp type tri-level inversion system of non-isolation, problems such as the balance of its midpoint potential, system's leakage current and anti-threephase load imbalance are difficult to be well solved simultaneously.And for the non-isolation three level photovoltaic inversion systems of cascade, because it needs multichannel independent current source (generally be independently photovoltaic battery panel), all have parasitic capacitance between each road independent photovoltaic cell panel and the earth like this, the inhibition of system's leakage current becomes complicated more and difficult like this.In addition, for cascade three level photovoltaic systems, because each road battery modules all has its own MPPT to control the easy like this imbalance that causes the three-phase grid electric current, therefore needing increases extra control algolithm, and this has greatly reduced the reliable rows and the real-time of system.
Three-phase four-wire system conventional diode clamp type inverter has obtained in fields such as active power filtering, special power supplies using widely, the three-level inverter of this kind structure needs complicated 3D-SVPWM control algolithm, also to consider the midpoint potential equilibrium problem, can cause system's control complexity to increase like this, have a strong impact on system reliability.Moreover, there is document to point out that 3D-SVPWM and 3D-SPWM are normalizings in the three-phase four-wire system, promptly both do not have any difference from control performance index aspect.The complexity of 3D-SVPWM control is apparently higher than 3D-SPWM, but for three-phase four-wire system diode-clamped inverter, the control of its midpoint potential need be analyzed the influence of each vector alignment current potential, and 3D-SPWM is then because the relatively poor balance of its control midpoint potential that makes of flexibility becomes difficult.Therefore, for the inverter of this class formation, can only adopt 3D-SVPWM just can get a desired effect.In a word, the control of three-phase four-wire system conventional diode clamp type inverter is too complicated, realizes difficulty.
The utility model content
In order to address the above problem, the utility model proposes a kind of based on 3D-SPWM combination clamping formula three level three-phase four-line system photovoltaic systems.Its adopts 3D-SPWM control mode, not only can effectively reduce system's leakage current, guarantees the midpoint potential balance, and the balance of three-phase grid electric current when the balance of output three-phase voltage and assurance are incorporated into the power networks can guarantee the photovoltaic system independent operating time.In addition, can effectively reduce current in middle wire by control to zero-sequence component.
For achieving the above object, the utility model adopts following technical scheme:
A kind of based on 3D-SPWM combination clamping formula three level three-phase four-line system photovoltaic systems, it comprises three-phase brachium pontis in parallel, and each brachium pontis comprises the IGBT pipe of four series connection, and the mid point of each phase brachium pontis is connected with the corresponding resistor load through filter, each ohmic load ground connection; Be parallel with a pair of capacitor C 1, the capacitor C 2 of series connection at each brachium pontis input of parallel connection, capacitor C 1, capacitor C 2 and gather photovoltaic array and be connected; In each brachium pontis, be connected in series pair of diodes between IGBT pipe and the 4th IGBT pipe, the neutral earthing of described capacitor C 1, capacitor C 2, simultaneously each to diode on clamping capacitance Cxi also in parallel, i=a wherein, b, c; Described each IGBT pipe adopts the 3D-SPWM mode to control the balance midpoint potential by control circuit.
Described filter adopts LC filter circuit, electric capacity common end grounding wherein.
Described control circuit comprises modulate circuit, sample circuit, control circuit and the drive circuit that connects successively, modulate circuit is gathered direct voltage Vdc, the direct current Idc of photovoltaic array and three-phase voltage Va, Vb, Vc and three-phase current signal ia, ib, the ic of filter output, three-phase voltage Va, Vb, Vc also send into phase lock circuitry, phase lock circuitry is connected with control circuit, and control circuit also is provided with protective circuit; Drive circuit output PWM controls opening and turn-offing of corresponding IGBT pipe in each phase brachium pontis.
Described control circuit adopts the FPGA module, when being incorporated into the power networks pattern, the phase information of the line voltage that three-phase grid current i a, ib, ic and the phase lock circuitry that sampling obtains obtains is carried out coordinate transform, be three-dimensional rotation coordinate system d-q-0 promptly, and then obtain that the d axle of three-phase grid electric current is meritorious, the q axle is idle, 0 zero-sequence component by three phase static a-b-c coordinate system transformation; The set-point i of zero-sequence current component
0* be 0, this given component and the actual zero-sequence component that obtains compare after the controlled amount V of pi regulator
0The specified rate i of idle component
q* also be 0, this specified rate and the actual idle component that obtains compare after the controlled amount V of pi regulator
qThe given i of real component
d* by the given and actual bus voltage comparison of direct voltage after controlled amount V behind the pi regulator
d, and the given output that derives from the MPPT algorithm of direct voltage; V
0, V
q, V
dThrough obtain the modulation voltage under the three phase static coordinate system through the coordinate inverse transformation, produce the three-phase voltage signal V of output again
A-m, V
B-m, V
C-mTo drive circuit, the drive circuit output pwm signal.
Described direct voltage is not less than 600V, if specified rate is lower than 600V, then forcing specified rate is 600V.
Described control circuit adopts the FPGA module, when independent operating, and the instantaneous phase voltage V that sampling obtains
a, V
b, V
cTransform to three-dimensional rotation coordinate system d-q-0 by three phase static coordinate system a-b-c, thereby obtain actual amount V
d, V
q, V
0The set-point of zero sequence voltage component should be 0, this specified rate V
0* compare with actual amount after the controlled amount V of pi regulator
0_ inv; Q axle specified rate Vq* is 0, and this specified rate and actual amount compare after the controlled amount V of pi regulator
q_ inv; For d axle component, make the specified rate V of d axle component
d*=1, perunit value, base value are 220V, and this specified rate and actual amount comparison are after the controlled amount V of pi regulator
d_ inv; Three controlled quentity controlled variables process coordinate inverse transformations that will obtain at last obtain the modulation voltage under the three phase static coordinate system, and this modulation voltage is sent to drive circuit and generates pwm signal.
The utility model is owing to be the three-phase four-wire system structure, in order to obtain good control effect, system need control to guarantee the height balance of three-phase voltage the zero-sequence component of three-phase output voltage during independent operating, and system need control guaranteeing the height balance of three-phase grid electric current the zero-sequence component of three-phase grid electric current when being incorporated into the power networks, and effectively reduces system's current in middle wire.
The beneficial effects of the utility model are: for the three-phase four-wire system structure, just can guarantee that system has less leakage current as long as can guarantee the balance of midpoint potential, the relevant derivation of equation provides in next part.For common diode-clamped three-phase and four-line structure, the control of midpoint potential is very complicated, is difficult to guarantee its reliable balance, so the leakage current of system is wayward.For combination clamping type three-phase four-wire system structure, because discharging and recharging between dc bus capacitor and clamping capacitance and the load circuit can effectively guarantee the balance of DC side midpoint potential, thereby the system that guaranteed has very little leakage current.This system is not only applicable to photovoltaic generating system, also is applicable to the design of UPS.
Description of drawings
Fig. 1 is the utility model system construction drawing;
Fig. 2 is SPWM modulating wave, carrier waveform;
Fig. 3 a, 3b are three-phase four-wire system inversion part-structure and clamping capacitance charge circuit thereof;
Fig. 3 c, 3d, 3e are three-phase four-wire system inversion part-structure and clamping capacitance discharge loop thereof;
Fig. 4 is system's leakage current analysis chart;
Fig. 5 is the time control block diagram that is incorporated into the power networks;
Fig. 6 is time control block diagram for independent operating;
Fig. 7 is 2D-SPWM and the 3D-SPWM influence (independent, laod unbalance degree 20%) to the output voltage degree of unbalance;
Fig. 8 a is 2D-SPWM and the 3D-SPWM influence (being incorporated into the power networks) to the grid-connected current degree of unbalance;
Fig. 8 b is the influence (being incorporated into the power networks) of 2D-SPWM and 3D-SPWM alignment current potential;
Fig. 8 c is the influence (being incorporated into the power networks) of 2D-SPWM and 3D-SPWM center line electric current;
Fig. 8 d is 2D-SPWM and the 3D-SPWM influence (being incorporated into the power networks) to leakage current;
Fig. 9 a is the experimental waveform figure of midpoint potential;
Fig. 9 b is clamping capacitance voltage experimental waveform figure;
Fig. 9 c is filtering front voltage experimental waveform figure;
Fig. 9 d is phase voltage experimental waveform figure (laod unbalance degree 20%) after the filtering.
Embodiment
Below in conjunction with accompanying drawing and embodiment the utility model is described further.
Fig. 1 is a system construction drawing, and main circuit is a combination clamping type three-level inverter, and the DC side mid point directly directly links to each other with photovoltaic battery array, and filter is the LC filter circuit.System's output links to each other with three phase network with load, and the common port n of three phase network links to each other with load common port, filter capacitor common port and DC side mid point.
For the three-phase four-wire system structure,,, then can cause filter capacitor common port output current i owing to comprise a large amount of triple-frequency harmonics in the final modulation waveform if adopt the 2D-SVPWM control mode
CExcessive (surpassing 10A), imbalance appears in load during at this moment as if independent operating, and then i_n is bigger, can make that so total current in middle wire i_nc is excessive, and then cause center line to cross the thermal impact system safety easily.Adopt the 2D-SPWM control mode, because modulation waveform be strict sine wave, the filter capacitor common port is just exported and can not contained triple harmonic current like this, will make i like this
CLess (less than 2A).But when system's independent operating, the degree of unbalance of output voltage is than nearly 1 times of the height under the 3D-SPWM control under the 2D-SPWM control; When system was incorporated into the power networks, the 2D-SPWM control mode not only can cause three-phase grid current imbalance degree higher (about 3%) but also can make i_n (can reach more than the 4A) bigger than normal, and then can make total current in middle wire i_nc bigger.And the 3D-SPWM control mode that native system adopts can address the above problem well by the effective control to zero-sequence component.It is the same with the control effect of 3D-SPWM in three-phase four-wire system that pertinent literature provides 3D-SVPWM, and promptly this moment, dual mode was a normalizing.For combination clamping type tri-level inversion system, 3D-SPWM is more suitable.
Signal conditioning circuit is nursed one's health the coherent signal that Hall element records, and obtains the analog signal that sample circuit can receive.The sampling of AD converter is controlled by FPGA with conversion, is digital quantity with conditioned analog signal conversion.The processing of digital signal and coordinate transform, PI control, protection, phase-locked and 3D-SPWM control, PWM produce by FPGA and realize, the final pwm signal that generates is given drive circuit and gone to control opening and turn-offing of IGBT pipe.
Fig. 2 is SPWM modulating wave, carrier waveform, and Fig. 3 a, Fig. 3 b are three-phase four-wire system inversion part-structure and clamping capacitance charge circuit; Fig. 3 b, Fig. 3 c, Fig. 3 d and Fig. 3 e are three-phase four-wire system inversion part-structure and clamping capacitance discharge loop.Concrete control mode is as follows:
Modulating wave is a three-phase sine-wave, promptly
u
ra=sinωT
u
rb=sin(ωT-120°)
u
rc=sin(ωt-240°)
Carrier wave is for differing 180 ° triangular wave, as shown in Figure 2 on phase place.
With a is example mutually, and the on off sequence generating mode is as follows:
(1) if Ura〉CA1 and Ura CA2, then the switch vector (Va1, Va2, Va3, Va4)=(1,1,0,0)-vector P.
(2) if Ura＜CA1 and Ura＜CA2, then the switch vector (Va1, Va2, Va3, Va4)=(0,0,1,1)-vector N.
(3) if Ura〉CA1 and Ura＜CA2, then the switch vector (Va1, Va2, Va3, Va4)=(1,0,1,0)-zero vector O1.
(4) if Ura＜CA1 and Ura〉CA2, then the switch vector (Va1, Va2, Va3, Va4)=(0,1,0,1)-zero vector O2.
(increase c) makes the obtain manner of its zero level be different from the diode-clamped three-level inverter to clamping capacitance Cxi for i=a, b.The balance of midpoint potential mainly realizes by discharging and recharging of dc bus capacitor and clamping capacitance for three-phase system.The discharge loop of three-phase system clamping capacitance and single phase system have bigger difference in addition, and this part emphasis is analyzed the discharge loop of clamping capacitance, and have summed up two conclusions:.
1, clamping capacitance charge circuit
At different vector state situations, Cxa is an example with a phase clamping capacitance, and its charge condition such as Fig. 3 a are shown in the 3b.
Vector P: at this moment, Va1, Va2 conducting, Va3, Va4 turn-off, if the voltage of Cxa is lower than Ud/2, then C1 will charge to Cxa according to Fig. 3 a overstriking show circuit.
Zero vector O2: at this moment, Va2, Va4 conducting, Va1, Va3 turn-off, if the voltage of Cxa is lower than Ud/2, then C2 charges Fig. 3 b overstriking show circuit to Cxa.
Zero vector O1: at this moment, Va1, Va3 conducting, Va2, Va4 turn-off, if the voltage of Cxa is lower than Ud/2, then C1 charges Fig. 3 a overstriking show circuit to Cxa.
Vector N: at this moment, Va3, Va4 conducting, Va1, Va2 turn-off, if the voltage of Cxa is lower than Ud/2, then C2 will charge to Cxa according to Fig. 3 b overstriking show circuit.
2, clamping capacitance discharge loop
For single phase system, under N and the O1 state, clamping capacitance does not have discharge loop.Discharge loop is than single phase system complexity under the three-phase system situation, and for each phase, clamping capacitance all has more discharge loop to make it by load circuit unnecessary tele-release be fallen in the short period of time.Pertinent literature does not provide analysis meticulously to the clamping capacitance discharge loop of three-phase system.Fig. 3 c, 3d, 3e have provided the partial discharge loop of combination clamping three-phase and four-line three-level inverter clamping capacitance respectively.
To be example with Cxa carried out detailed mark to the discharge loop of clamping capacitance to the utility model.With on off state PPN, (O2) PN, (O1) PN, NPN are that example analyzes to the discharge loop of Cxa that (wherein the meaning of PPN is at a time, and a phasor1 P works; B phasor1 N works; C phasor1 N works.Similar, (O1) meaning of PN is at a time, a phase zero vector O1 works; B phasor1 P works; C phasor1 N works), be generalized to more on off states according to this.
When the voltage of Cxa was higher than Ud/2, the discharge loop of these four kinds of states as shown in Figure 3.
PPN, (O2) PN:Cxa will discharge along Fig. 3 c overstriking show circuit and Fig. 3 d overstriking show circuit.
(O1) PN, NPN:Cxa will discharge along Fig. 3 d overstriking show circuit and Fig. 3 e overstriking show circuit.
Can obtain as drawing a conclusion by above analysis:
(1) when a is on off state P or O2 mutually, exist on off state N can realize the discharge of Cxa in b, the c two-phase;
(2) when a is on off state N or O1 mutually, as long as exist on off state P can realize the discharge of Cxa among the b, c two-phase.
The control method that satisfies top two conditions can be so that Cxa be discharged and recharged fast, thereby can keep the balance of midpoint potential and clamping capacitance.By analyzing as can be known, phase-shifting carrier wave SPWM control mode meets two conditions that preamble is analyzed, and promptly can guarantee the balance of midpoint potential.
Fig. 4 is system's leakage current analysis chart.According to the foundation of the leakage current model of mentioning in the pertinent literature, the utility model has been set up the leakage current model of combination clamping formula three-phase four-wire system photovoltaic system, as shown in Figure 3.Wherein the leakage inductance of each phase is respectively L1, L2, L3, center line leakage inductance L
n, below earlier the common-mode voltage of each phase is analyzed:
For a phase, common-mode voltage V
Cma=(V
AN+ V
ON)/2+ ((L
n-L
1)/2 (L
1+ L
n)) (V
AN-V
ON);
For the b phase, common-mode voltage V
Cmb=(V
BN+ V
ON)/2+ ((L
n-L
2)/2 (L
2+ L
n)) (V
BN-V
ON);
For the c phase, common-mode voltage V
Cmc=(V
CN+ V
ON)/2+ ((L
n-L
3)/2 (L
3+ L
n)) (V
CN-V
ON);
Desirable three-phase balanced system, L
1=L
2=L
3=L, L
n=0;
The common-mode voltage V that system is total
Tcm=(V
Cma+ V
Cmb+ V
Cmc)/3;
The above analysis can obtain V
Tcm=V
ON/ 2, therefore as long as guarantee that the balance of DC side midpoint potential just can be so that system's common-mode voltage maintains V
DcAbout/2, ideally common-mode voltage equals V
Dc/ 2, this moment the leakage current i of system
Ik=CdV
Tcm/ dt=0, and in conjunction with the analysis that discharges and recharges of last minute electric capacity adopts the 3D-SPWM mode can be than the balance that is easier to realize midpoint potential, so the utility model can effectively suppress the leakage current of system, considers L in the actual conditions certainly
nBe generally and approach zero non-zero number, and the leakage inductance of three-phase system can be strict equates, so the leakage current of real system is non-vanishing, but can effectively be suppressed in the small range.
Control block diagram when Fig. 5 is incorporated into the power networks for system.The phase information of the line voltage that three-phase grid current i a, ib, ic and the PLL circuit that sampling obtains obtains is carried out coordinate transform, be three-dimensional rotation coordinate system d-q-0 promptly, and then obtain d axle (gaining merit), q axle (idle), 0 (zero sequence) component of three-phase grid electric current by three phase static a-b-c coordinate system transformation.For the control of zero-sequence current component, for the degree of balance that improves grid-connected current and effectively reduce current in middle wire, the set-point i of zero-sequence current component
0* be 0, this given component and the actual zero-sequence component that obtains compare after the controlled amount V of pi regulator
0In order to realize that unity power factor is incorporated into the power networks, the specified rate i of idle component
q* also be 0, this specified rate and the actual idle component that obtains compare after the controlled amount V of pi regulator
qThe given i of real component
d/ 2 by the given and actual bus voltage comparison of direct voltage after obtain behind the pi regulator, and the given output that derives from the MPPT algorithm of direct voltage, for the stage photovoltaic single grid-connected system, MPPT control has many methods, here just give unnecessary details no longer one by one, what adopt in the utility model is the conductance increment method.It should be noted that for three-phase system,,, then may cause system normally to be incorporated into the power networks, so-called direct voltage collapse that Here it is if specified rate is lower than 600V for its direct voltage that reliably is incorporated into the power networks is not less than 600V.In order to address this problem, can increase a link, promptly forcing specified rate when direct voltage during less than 600V is 600V, thereby can guarantee that direct voltage does not collapse, this is to be output as cost with the actual maximum power of sacrificing this time certainly.Relevant simulation waveform and analysis thereof will provide later.
Control block diagram when Fig. 6 is system's independent operating.During the system independent operating, need to guarantee output three-phase 220V symmetrical alternating current voltage.The instantaneous phase voltage V that sampling obtains
An, V
Bn, V
CnTransform to three-dimensional rotation coordinate system d-q-0 by three phase static coordinate system a-b-c, thereby obtain actual amount V
d, V
q, V
0For the control of residual voltage, owing to need to guarantee the height balance of three-phase output voltage, thus the set-point of zero sequence voltage component should be 0, this specified rate V
0* compare with actual amount after the controlled amount V of pi regulator
0_ inv.For q axle component, owing to do not relate to the control of idle component during the system independent operating, so q axle specified rate Vq* is 0, and this specified rate and actual amount compare after the controlled amount V of pi regulator
q_ inv.For d axle component,, make the specified rate V of d axle component in order to make that the output phase voltage is 220V
d*=1 (perunit value, base value are 220V), this specified rate and actual amount comparison are after the controlled amount V of pi regulator
d_ inv.Three controlled quentity controlled variables process coordinate inverse transformations that will obtain at last obtain the modulation voltage under the three phase static coordinate system, and this modulation voltage is sent to the PWM generation module and generates the PWM waveform.Relevant emulation and experimental result thereof will provide later.
Fig. 7 is 2D-SPWM and the 3D-SPWM influence (independent, laod unbalance degree 20%) to the output voltage degree of unbalance.Scheme as can be seen thus, under 2D-SPWM control, the degree of unbalance (being about 0.55%) of three-phase output phase voltage is than nearly one times of degree of unbalance (the being about 0.3%) height under the 3D-SPWM control.Therefore, by simulation result as can be seen, D S PWM control mode can better suppress the imbalance of three-phase output voltage when system's independent operating.
When system's independent operating, 3D-SPWM can control effect in every respect preferably, and general effect is more quite a lot of than 2D-SPWM control mode.When system is in when being incorporated into the power networks, the advantage of 3D-SPWM control mode is more obvious, compares analysis below in conjunction with relevant simulation waveform.
Fig. 8 a is 2D-SPWM and the 3D-SPWM influence (being incorporated into the power networks) to the grid-connected current degree of unbalance, system at 0.2s constantly, the photovoltaic battery array power output reduces suddenly.From 0-0.2s constantly, after system stability was incorporated into the power networks, for the 2D-SPWM mode, the degree of unbalance of grid-connected current can reach 1%, and under the 3D-SPWM mode, the degree of unbalance of grid-connected current is less than 0.15%; 0.2s after, after system stability was incorporated into the power networks, for the 2D-SPWM mode, the degree of unbalance of grid-connected current can reach 3.5%, and adopted the 3D-SPWM mode, the degree of unbalance less than 0.25% of grid-connected current.Therefore, for the control of the grid-connected current degree of balance, 3D-SPWM has obvious advantages.
Fig. 8 b is the influence (being incorporated into the power networks) of 2D-SPWM and 3D-SPWM alignment current potential, and system is in the 0.2s moment, and the photovoltaic battery array power output reduces suddenly.As can be seen from the figure, the control effect of 3D-SPWM control mode alignment current potential is than good many of 2D-SPWM control mode, almost not fluctuation, and midpoint potential has the fluctuation of certain limit under the 2D-SPWM mode.
Fig. 8 c is the influence (being incorporated into the power networks) of 2D-SPWM and 3D-SPWM center line electric current, and system is in the 0.2s moment, and the photovoltaic battery array power output reduces suddenly.Filter capacitor common port output current i
CSize is equal substantially under these two kinds of control modes, can maintain below the 1.7A, no longer too much discusses here.But for current i _ n, under the 2D-SPWM control mode, its effective value can reach 3.5A, and under the 3D-SPWM control mode, its effective value can remain on about 0.4A, is significantly less than the former.
Fig. 8 d is 2D-SPWM and the 3D-SPWM influence (being incorporated into the power networks) to leakage current.Two kinds of control modes almost do not have difference to the peak value influence of leakage current, and the system that can well guarantee has very little leakage current.
Fig. 9 a is the experimental waveform figure of midpoint potential.This waveform is for loading on the waveform of (independent operating) under 20% degree of unbalance, and by waveform as can be seen, when the DC side total voltage was suddenlyd change, the voltage on dc bus capacitor C1, the C2 can equivalently synchronously change, and promptly its midpoint potential can well keep balance.
Fig. 9 b is clamping capacitance voltage experimental waveform figure.By waveform as can be seen, when dc voltage suddenlyd change, clamping capacitance CXa, CXb, CXc can successfully discharge and recharge to V
Dc/ 2.
Fig. 9 c is filtering front voltage experimental waveform figure.By waveform as can be seen, filtering front voltage presents+V
Dc/ 2,0 ,-V
Dc/ 2 three kinds of level.
Fig. 9 d is phase voltage experimental waveform figure (laod unbalance degree 20%) after the filtering.If three-phase three-wire system, laod unbalance can cause the serious imbalance of output voltage, after the employing three-phase four-wire system mode, can effectively suppress imbalance of three-phase voltage, guarantee other index conformance with standard simultaneously.
Claims (3)
1. one kind based on 3D-SPWM combination clamping formula three level three-phase four-line system photovoltaic systems, and it comprises three-phase brachium pontis in parallel, and each brachium pontis comprises the IGBT pipe of four series connection, and the mid point of each phase brachium pontis is connected with corresponding resistor through filter, each grounding through resistance; Be parallel with a pair of capacitor C 1, the capacitor C 2 of series connection at each brachium pontis input of parallel connection, capacitor C 1, capacitor C 2 and gather photovoltaic array and be connected; In each brachium pontis, be connected in series pair of diodes between IGBT pipe and the 4th IGBT pipe, it is characterized in that, the neutral earthing of described capacitor C 1, capacitor C 2, simultaneously each to diode on clamping capacitance Cxi also in parallel, i=a wherein, b, c; Described each IGBT pipe adopts the 3D-SPWM mode to control the balance midpoint potential by control circuit.
2. as claimed in claim 1 based on 3D-SPWM combination clamping formula three level three-phase four-line system photovoltaic systems, it is characterized in that during the system independent operating, described filter adopts the LC filter circuit, when being incorporated into the power networks, system adopts LCL filter circuit, capacity earth wherein.
3. as claimed in claim 1 based on 3D-SPWM combination clamping formula three level three-phase four-line system photovoltaic systems, it is characterized in that, described control circuit comprises modulate circuit, sample circuit, control circuit and the drive circuit that connects successively, modulate circuit is gathered direct voltage Vdc, the direct current Idc of photovoltaic array and three-phase voltage Va, Vb, Vc and three-phase current signal ia, ib, the ic of filter output, three-phase voltage Va, Vb, Vc also send into phase lock circuitry, phase lock circuitry is connected with control circuit, and control circuit also is provided with protective circuit; Drive circuit output PWM controls opening and turn-offing of corresponding IGBT pipe in each phase brachium pontis.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2012207506025U CN203103983U (en) | 2012-12-31 | 2012-12-31 | Hybrid-clamping type three-level three-phase four-wire photovoltaic system based on 3D-SPWM |
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| CN2012207506025U CN203103983U (en) | 2012-12-31 | 2012-12-31 | Hybrid-clamping type three-level three-phase four-wire photovoltaic system based on 3D-SPWM |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103023070A (en) * | 2012-12-31 | 2013-04-03 | 山东大学 | Hybrid-clamped three-electric-level three-phase four-wired photovoltaic system based on 3D-SPWM (three-dimensional sinusoidal pulse width modulation) |
| CN105553309A (en) * | 2015-12-28 | 2016-05-04 | 许继集团有限公司 | T-type three-level inverter and midpoint balance control method thereof |
| CN106532731A (en) * | 2016-04-13 | 2017-03-22 | 国船电气（武汉）有限公司 | DSVG double-loop control method |
| CN116207789A (en) * | 2023-05-06 | 2023-06-02 | 锦浪科技股份有限公司 | PID effect suppression method based on zero sequence |
-
2012
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103023070A (en) * | 2012-12-31 | 2013-04-03 | 山东大学 | Hybrid-clamped three-electric-level three-phase four-wired photovoltaic system based on 3D-SPWM (three-dimensional sinusoidal pulse width modulation) |
| CN103023070B (en) * | 2012-12-31 | 2014-12-10 | 山东大学 | Hybrid-clamped three-electric-level three-phase four-wired photovoltaic system based on 3D-SPWM (three-dimensional sinusoidal pulse width modulation) |
| CN105553309A (en) * | 2015-12-28 | 2016-05-04 | 许继集团有限公司 | T-type three-level inverter and midpoint balance control method thereof |
| CN106532731A (en) * | 2016-04-13 | 2017-03-22 | 国船电气（武汉）有限公司 | DSVG double-loop control method |
| CN116207789A (en) * | 2023-05-06 | 2023-06-02 | 锦浪科技股份有限公司 | PID effect suppression method based on zero sequence |
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