CN103095163A - High order position difference energy storage photovoltaic inverter - Google Patents
High order position difference energy storage photovoltaic inverter Download PDFInfo
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- CN103095163A CN103095163A CN2011103726134A CN201110372613A CN103095163A CN 103095163 A CN103095163 A CN 103095163A CN 2011103726134 A CN2011103726134 A CN 2011103726134A CN 201110372613 A CN201110372613 A CN 201110372613A CN 103095163 A CN103095163 A CN 103095163A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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Abstract
The invention discloses a high order position difference energy storage photovoltaic inverter, and belongs to the field of photovoltaic power generation. Direct current (DC) generated by a photovoltaic system is converted to power frequency alternating current (AC). Most front level large capacity energy storage filtering is adopted for direct power difference of input DC and AC by a traditional photovoltaic inverter. The method is adopted in small or micro photovoltaic inverting with low voltage input, and due to the fact that front level energy storage capacity is required to be large in capacity, only an electrolytic capacitor is adopted currently. The electrolytic capacitor has the disadvantages of being narrow in working temperature range, short in service life, and the like. The structure of a constant power transfer pushing up circuit and a high order position difference energy storage capacitor is adopted, and the problems are solved. A low frequency energy storage electrolytic capacitor which is of low voltage and small fluctuation and located at the front end is omitted, and therefore the control temperature range of the inverter is greatly widened, and the service life of the inverter is greatly prolonged.
Description
Technical field
The invention belongs to the field of photovoltaic power generation in new forms of energy, is to realize that the direct current that photovoltaic sends becomes alternating current, i.e. a kind of technology in inversion.
Background technology
In current photovoltaic power generation technology, inverter is one of core link, and its reliability and life-span are most important.The life-span of now general photovoltaic battery panel reached more than 20 years, but current inverter accomplishes that the life-span of so growing is more difficult or cost is too high.In inverter, especially in small-sized and Miniature inverter, the weakest link in life-span is alminium electrolytic condenser, and the life-span of alminium electrolytic condenser is being below 10000 hours under 105 degrees centigrade, and the every reduction by 10 of temperature is spent the life-span and doubled.But because inverter is power conversion apparatus, energy consumption is arranged self, energy consumption causes temperature to rise, and temperature rises and causes the lost of life.So reduce temperature, just need to raise the efficiency or increase heat radiation.But bring up to a certain degree when efficient, further raise the efficiency, cost increases exponentially, must adopt expensive device and some complicated circuits (such as soft switch circuit etc.).If increase heat radiation, will increase fan or water-cooled etc.These have increased again cost and the complexity of product greatly.Why will that use alminium electrolytic condenser? reason is as follows:
The PV characteristic of photovoltaic cell has caused, and only has when system and just can send maximum electricity during at specific electrical voltage point, and the PV characteristic is with reference to figure 4.So in order to send maximum electricity, the input service voltage constant of inverter to be operated in maximum power point voltage proper, what photovoltaic can continue like this generates electricity according to maximum power.But photovoltaic DC-to-AC converter output is the power frequency electricity, and the power of output is with the twice power frequency fluctuation, with reference to figure 2, Fig. 3, Fig. 4.Photovoltaic DC-to-AC converter is from transient state, and input power is the metastable (P in Fig. 4
pv), power output is with the twice power frequency fluctuation (P in Fig. 4
out), so the energy-storage travelling wave tube that absorbs and discharge with the twice power frequency must be arranged in inverter.P in Fig. 4
pvThe dash area of bottom is the energy that in inverter, energy-storage travelling wave tube absorbs, P
pvThe dash area on top is the energy that in inverter, energy-storage travelling wave tube discharges.Fig. 2 is conventional photovoltaic inverter rough schematic view, wherein C
inIt is storage capacitor.The twice power frequency energy-storage travelling wave tube of the photovoltaic DC-to-AC converter that occurs now is all the capacitor C with prime
inComplete.The energy storage of electric capacity is C*U
2/ 2, in the situation that electric capacity is constant, energy stores by the variation of voltage and discharges.So guarantee that PV works near fixing electrical voltage point, send maximum electricity, just must guarantee that the photovoltaic voltage fluctuation is very little, i.e. storage capacitor C
inVoltage fluctuation very little.Storage capacitor C
inLearn through derivation and experiment:
C
in≈ K * P
pv/ (V
pv* Δ V
in) formula 1
In following formula, K is a constant relevant to output frequency, K ≈ 0.0032 when output frequency is 50hz.
Fluctuation voltage (the Δ V in Fig. 1
in) less, photovoltaic efficiency is higher, but learns according to formula 1, and this requires storage capacitor C
inLarger; V
pvLess, also require storage capacitor larger.Such as, the optimum operating voltage of a photovoltaic module is 25V, power output is 200W, requires photovoltaic voltage fluctuation Δ V
inLess than 1V, the input side storage capacitor that connects its little inverter is: 200/ (314 * 25 * 1) ≈ 25.6mF.25.6mF electric capacity, only have pot electrochemical capacitor proper with present industrial level.Here it is current photovoltaic DC-to-AC converter why, especially small-sized and miniature photovoltaic DC-to-AC converter (because input voltage is low), general aluminium electrochemical capacitor.Because the electric capacity of so large capacity other types is too expensive.
Owing to having adopted aluminium electroloysis, cause the operating temperature range of inverter limited, the life-span is not easy to guarantee, and has increased many costs in order to solve hot problem.
Summary of the invention
The invention solves the problems referred to above, the method for employing is to raise circuit and a high potential difference storage capacitor C in the inverter prime with a permanent power delivery voltage
mReplace the original storage capacitor C that is positioned at prime
inBe that whole inverter is comprised of three parts: permanent power delivery voltage raises circuit, high potential difference storage capacitor and DC/AC circuit.When stable state, permanent power delivery voltage raises circuit and with high-frequency switch circuit, the electric energy that photovoltaic sends is pushed to the high potential difference energy storage capacitor C that is positioned at the centre with power constant in power frequency period
mWith the rear class inverter circuit.With reference to figure 5 and Fig. 6.Permanent power delivery voltage raises the generated output that power that circuit pushes is photovoltaic, it is the average power of inverter industrial frequency AC output, here so-called permanent power is not absolute invariable, just in power frequency period, not with power frequency or twice power frequency fluctuation, compare with the transient state power output of inverter is relatively constantly (to please refer to Fig. 7, P
tBe the through-put power of permanent power delivery circuit, P
outTransient state power output for inverter); But from for a long time, yes changes with the average output power of inverter for it.High potential difference storage capacitor C
mWith the output-power fluctuation than the higher voltage of photovoltaic output voltage and voltage fluctuation buffering industrial frequency AC, with reference to the C of the high potential difference storage capacitor in figure 6
mVoltage V
mWaveform.Raise the barrier of circuit due to persevering power delivery voltage, high potential difference storage capacitor C
mVoltage fluctuation Δ V
mDo not affect photovoltaic generation voltage, just do not affect the generating efficiency of photovoltaic, so C yet
mLarger voltage fluctuation Δ V can be arranged
mC why
mBeing referred to as high potential difference electric capacity is because its current potential V
mThan photovoltaic voltage V
pvHeight, and potential difference Δ V
mAlso can be very large.In order to store and stabilize the power fluctuation of inverter industrial frequency AC output, C
mThe appearance value select and C
inSimilar:
C
m≈ K * P
pv/ (V
m* Δ V
m) formula 2
Identical in K and formula 1 in following formula, when the inverter output frequency is 50hz, K ≈ 0.0032.
Relatively formula 1 and formula 2, just can learn: due to V
m, Δ V
mThan V
in, Δ V
inCan be much larger, so C
mJust can compare C
mLittle a lot.Realize so same accumulation of energy, adopt technology of the present invention just can adopt the little a lot of electric capacity of appearance value later.Because capacitance is little, just can avoid having used electrochemical capacitor, adopt long-life thin-film capacitor just passable.
It is just permanent power in constant situations such as service conditions, power frequency loads that certain so-called permanent power delivery voltage raises circuit, is that the power fluctuation of suitable inverter power frequency output in power frequency period is constant.Be to have high-frequency switch circuit to realize because permanent power delivery voltage raises circuit, from high frequency be, also may fluctuate, very small frequency is very high for the amplitude of fluctuation in real time, sees that from power frequency just approximate is constant.Here so-called high frequency refers to the frequency that 10KHz is above.
The spitting image of the two-layer configuration of conventional photovoltaic inversion, with reference to figure 5 and Fig. 8, but their essence is different on the frame structure in the present invention.The difference that permanent power voltage in the present invention raises the photovoltaic DC-to-AC converter of circuit and traditional two-layer configuration is:
1. the permanent power delivery voltage in the present invention raises the power that circuit transmits to rear class, when environment and power frequency load do not change, is constant to the power of carrying in power frequency period; And the DC/DC that boosts in the photovoltaic DC-to-AC converter of traditional two-layer configuration observes in power frequency period, to rear class transmission be identical with the inverter power output, be with the frequency fluctuation of twice power frequency.With reference to figure 7 and Fig. 9,
2. to observe in the power frequency period be that power to the rear class delivered constant is purpose to the control strategy that raises circuit of the permanent power delivery voltage in the present invention; And the control strategy of the DC/DC that boosts in the photovoltaic DC-to-AC converter of traditional two-layer configuration to observe in the power frequency period be to be purpose for rear class provides the voltage of quite stable
3. the energy snubber of the twice power frequency fluctuation of the inverter power output in the present invention is to be raised the rear class capacitor C of circuit by permanent power voltage
mVoltage fluctuation realize; And the photovoltaic DC-to-AC converter of traditional two-layer configuration, the twice power frequency fluctuation of stabilizing the inverter power output is by the C that is positioned at prime
inVoltage fluctuation realizes
Beneficial effect of the present invention is mainly greatly to have dwindled the storage capacitor capacity requirement of stabilizing the inverter power output pulsation, thereby has avoided short, thermally sensitive electrochemical capacitor in useful life.Owing to not needing to have used electrochemical capacitor, so overcome the conventional photovoltaic inverter, the life and reliability bottleneck of miniature, the low profile photovoltaic inverter of low-voltage input has especially improved life-span and the operating temperature range of photovoltaic DC-to-AC converter greatly.In addition, due to the storage capacitor of the two frequencys multiplication fluctuations of stabilizing power output from moving on to foremost the middle part of inverter, and it is that firm power is pushed to the generated output of photovoltaic on the high potential difference storage capacitor that permanent power delivery voltage raises circuit, thereby greatly reduced the fluctuation of photovoltaic Voltage-output, can more efficiently complete the maximum power point generating of photovoltaic cell, improve the generating efficiency of photovoltaic.
Description of drawings
This specification has 11 accompanying drawings:
Fig. 1, the power voltage characteristic of photovoltaic generation;
Fig. 2, conventional photovoltaic inverter schematic diagram;
Fig. 3, conventional photovoltaic contravarianter voltage current curve;
Fig. 4, conventional photovoltaic inverter power voltage curve;
Fig. 5, photovoltaic DC-to-AC converter principle schematic of the present invention
Fig. 6, photovoltaic DC-to-AC converter voltage-current curve of the present invention;
Fig. 7, photovoltaic DC-to-AC converter power voltage curve of the present invention;
Fig. 8, the photovoltaic DC-to-AC converter block diagram of traditional two-layer configuration;
Fig. 9, the photovoltaic DC-to-AC converter power voltage curve of traditional two-layer configuration;
Figure 10, photovoltaic DC-to-AC converter embodiment schematic diagram of the present invention;
Figure 11, photovoltaic DC-to-AC converter embodiment schematic diagram of the present invention;
Embodiment
Figure 10 uses principle of the present invention to realize the example of a little inverter of output 50Hz/220V.Here analyze stable situation: under certain temperature and sunshine, the maximum power point operating voltage of photovoltaic module output is 25V, and electric current is 8A, and generated output is 200W.In Figure 10, permanent power delivery voltage raises the class boost circuit that circuit adopts the nothing isolation, the C in figure
iBe high frequency energy storage capacitor, C
mElectricity is low frequency high potential difference energy storage capacitor, and Q1 is high frequency MOSFE switch.C
iBe the high frequency energy storage capacitor, it raises circuit medium-high frequency power fluctuation and uses in order to stabilize permanent power delivery voltage, and because operating frequency is very high, the time of each energy storage is very short, so energy storage capacity is little, so capacity requirement is also little.If in this example, switching frequency is 100KHz, 200 watts of permanent power delivery, operating voltage 25V, the photovoltaic voltage fluctuation allows 0.5V, C
iFor capacity be that 10uF is just enough.Even, if L1 selects the larger C of inductance value
iAlso can.In Figure 10, control circuit does not draw.Control circuit is constantly adjusted frequency and the duty ratio of Q1 switching signal, guarantee through-put power by this part circuit constant be the average output power of inverter.Figure 11 is the electric current and voltage of some key signals in this example, because the low frequency energy storage capacitor has moved on to middle rank from prime, so the electric current and voltage that sends of photovoltaic is stable in power frequency period, and high potential difference energy storage capacitor C
mVoltage fluctuate between 120V～160V with the frequency of twice power frequency.
In Figure 10, permanent power voltage raises circuit and has adopted class boost topology without isolation, can certainly adopt as required non-isolation or with other topological structures of high-frequency isolation, such as CUK, SEPIC, instead swashs topology, normal shock, recommends, the topological circuit such as bridge-type.Here adopt simple non-isolation boost just for principle of the present invention is described.The class boost circuit here, different from the prime boost occupation mode of traditional two-layer configuration photovoltaic DC-to-AC converter, traditional two-layer configuration photovoltaic DC-to-AC converter prime boost is in order to improve the V higher than the ac output voltage peak value to rear class
Out-peakBurning voltage, the low frequency accumulation of energy of whole inverter or at foremost C
inTo be pushed to high potential difference storage capacitor C for the electricity that photovoltaic is sent with firm power and the permanent power voltage here raises the class boost circuit of circuit
mOn, the low frequency accumulation of energy of whole inverter is to be positioned at the C in stage casing
m
Known to preamble, if adopt conventional photovoltaic inverter structure (as Fig. 2, Fig. 8), if within requiring the 1V of shake of photovoltaic output voltage, according to formula 1, the input side energy storage capacitor will be at least 25.5mF.If the photovoltaic DC-to-AC converter that adopts principle of the present invention to realize, the low frequency energy storage capacitor has been transferred to the rear class C that permanent power delivery voltage raises circuit
mUpper, if design C here
mVoltage fluctuation be size in Figure 11, according to formula 2, high potential difference storage capacitor C
mThe appearance value be 0.23mF.0.23mF compare 25.6mF little two orders of magnitude.According to current industry ability, the both economical capacitance of realizing 25.5mF only has alminium electrolytic condenser proper, realizes that the electric capacity of so large capacitance other types is just too expensive.If but realized the electric capacity of 0.23mF, operating temperature range is wide, the life-span is long thin-film capacitor just could be adopted.
Claims (3)
1. high potential difference energy storage photovoltaic DC-to-AC converter, it is the product that a kind of direct current that photovoltaic is sent converts industrial-frequency alternating current to, it is characterized in that it is comprised of the DC/AC translation circuit that permanent power delivery voltage raises circuit, high potential difference storage capacitor and rear class, when systematic steady state, permanent power delivery voltage raises circuit the electric energy that photovoltaic sends is pushed to rear class with high-frequency switch circuit with constant power, and the voltage of high potential difference storage capacitor is stabilized the power fluctuation in power frequency period of inverter power frequency output with the frequency fluctuation of twice power frequency.
2. high potential difference energy storage photovoltaic DC-to-AC converter as claimed in claim 1 is characterized in that the difference between DC stabilization power that interchange power output and photovoltaic with the twice power frequency fluctuation send is mainly to be stabilized with the voltage fluctuation of the frequency of twice power frequency by the high potential difference storage capacitor that is positioned at the middle part, and namely the low frequency storage capacitor of whole inverter is positioned at the middle part of inverter.
3. high potential difference energy storage photovoltaic DC-to-AC converter as claimed in claim 1 is characterized in that the HF switch control strategy that wherein permanent power delivery voltage raises circuit is take relatively constant power delivery as main purpose, is not to think that it is main purpose that rear class provides a relatively high burning voltage.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011103726134A CN103095163A (en) | 2011-11-04 | 2011-11-04 | High order position difference energy storage photovoltaic inverter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011103726134A CN103095163A (en) | 2011-11-04 | 2011-11-04 | High order position difference energy storage photovoltaic inverter |
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| CN103095163A true CN103095163A (en) | 2013-05-08 |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003009398A (en) * | 2001-06-19 | 2003-01-10 | Sanyo Electric Co Ltd | Control method of system interconnection power generation system and the system interconnection power generation system |
| CN1929276A (en) * | 2006-08-09 | 2007-03-14 | 哈尔滨工业大学 | Soft switch back exciting converter used for solar energy photovoltaic generation incorporate in power network |
| CN101599710A (en) * | 2009-07-24 | 2009-12-09 | 南京航空航天大学 | Monopole inverter capable of boosting voltage |
| CN101630903A (en) * | 2008-07-18 | 2010-01-20 | 全汉企业股份有限公司 | Power supply for improving capacitance recession |
-
2011
- 2011-11-04 CN CN2011103726134A patent/CN103095163A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003009398A (en) * | 2001-06-19 | 2003-01-10 | Sanyo Electric Co Ltd | Control method of system interconnection power generation system and the system interconnection power generation system |
| CN1929276A (en) * | 2006-08-09 | 2007-03-14 | 哈尔滨工业大学 | Soft switch back exciting converter used for solar energy photovoltaic generation incorporate in power network |
| CN101630903A (en) * | 2008-07-18 | 2010-01-20 | 全汉企业股份有限公司 | Power supply for improving capacitance recession |
| CN101599710A (en) * | 2009-07-24 | 2009-12-09 | 南京航空航天大学 | Monopole inverter capable of boosting voltage |
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Address after: 201114, Shanghai, Minhang District, Pujiang, Zhenjiang Road, No. 999, 5 odd floor Park, 1 floor Applicant after: Fengzhi (Shanghai) New Energy Technology Co., Ltd. Address before: 201112, No. 7, Urarie Chise business park, No. 1188, Union Road, Shanghai, Minhang District, A303 Applicant before: Fengzhi (Shanghai) New Energy Technology Co., Ltd. |
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Application publication date: 20130508 |