CN102136810B - Pulse frequency modulation and quasi-resonant modulation dual-mode micro grid inverter control method - Google Patents
Pulse frequency modulation and quasi-resonant modulation dual-mode micro grid inverter control method Download PDFInfo
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- CN102136810B CN102136810B CN 201010275942 CN201010275942A CN102136810B CN 102136810 B CN102136810 B CN 102136810B CN 201010275942 CN201010275942 CN 201010275942 CN 201010275942 A CN201010275942 A CN 201010275942A CN 102136810 B CN102136810 B CN 102136810B
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Abstract
The invention relates to a pulse frequency modulation and quasi-resonant modulation dual-mode micro grid inverter control method. In a flyback micro inverter, the part close to a voltage zero crossing point of a power grid is controlled by a pulse frequency modulation mode to avoid over-high switching frequency when in quasi-resonant control mode, namely, the opening time Ton of an MOS (metal oxide semiconductor) pipe is maintained the same, and the switching frequency Ts is adjusted to guarantee the current of the grid to be sine wave; and when the voltage of the power grid is higher, the flyback inverter is controlled by the quasi-resonant mode, so that the primary side MOS pipe of the flyback inverter to be in a ZVS (zero voltage switch) state so as to reduce consumption of the system.
Description
Technical field
The present invention relates to the micro grid inverter control method of a kind of pulse frequency modulated and the double mode modulation of quasi-resonance, belong to the technical field of generation of electricity by new energy control system.
Background technology
Miniature photovoltaic grid-connected inverter is installed the Miniature inverter of integrated various protections and control function at the every photovoltaic module back side; directly be connected to the grid some equal modules formation in parallel with electrical network grid-connected photovoltaic system after by Miniature inverter transformation of electrical energy being become alternating current.Than traditional centralized grid-connected photovoltaic system, each module of miniature photovoltaic grid-connected inverter is carried out MPPT maximum power point tracking, can reduce the power loss that assembly does not mate or local shade causes, and improves the efficient of system.
Many topology and corresponding control strategies thereof for miniature photovoltaic grid-connected inverter are in the news, and wherein back exciting converter only needs three switching devices, and is simple in structure, with low cost, is better than other topological structures (as shown in Figure 2).When back exciting converter is applied to miniature photovoltaic parallel in system at present, in order to improve system effectiveness, usually make back exciting converter be operated in quasi-resonant mode, namely when the drain electrode of the former limit of circuit of reversed excitation metal-oxide-semiconductor and the voltage U of source electrode
DsResonance is to zero or open metal-oxide-semiconductor during minimum point, the leakage inductance energy that is stored in like this in the metal-oxide-semiconductor " flows back to " input capacitance, and the while metal-oxide-semiconductor can be operated in no-voltage and open under (Zero Voltage Switching, ZVS) state, switching loss significantly reduces, and system effectiveness significantly improves.But the shortcoming of quasi-resonant mode is that the metal-oxide-semiconductor switching frequency will be very high when line voltage during near zero-crossing point, and this will cause switching loss significantly to rise, and affect entire system efficient, therefore should not adopt the quasi-resonance control method at the electrical network near zero-crossing point.
Summary of the invention
The present invention relates to the micro grid inverter control method of a kind of pulse frequency modulated and the double mode modulation of quasi-resonance, in the flyback type miniature inverter, too high switching frequency appears for fear of electrical network near zero-crossing point quasi-resonant mode, the present invention adopts the pulse frequency modulated pattern, namely keeps the service time T of metal-oxide-semiconductor
OnFixing, by by-pass cock frequency T
s, guarantee to reduce switching frequency under the prerequisite of inverter output sinusoidal current; When line voltage is higher, still use quasi-resonant mode control flyback transformer, make the former limit metal-oxide-semiconductor of flyback transformer be operated in the ZVS state, to reduce system loss.
According to the inventive concept of appeal, the present invention adopts following technical proposals;
The micro grid inverter control method of a kind of pulse frequency modulated and the double mode modulation of quasi-resonance, its control step is as follows:
(1) phase-locked loop is followed the tracks of and to be obtained electrical network angle θ, and sampling line voltage amplitude is higher than the threshold voltage U of setting when the line voltage amplitude
SetThe time, execution in step (2); Otherwise execution in step (3);
(2) control of operation quasi-resonant mode judges whether this cycle is last switch periods of quasi-resonant mode, if it is records the ON time T of last switch periods
Const, switch periods T '
sWith current electrical network angle θ ', computed duty cycle d '=T
Const/ T '
sOtherwise return step (1);
(3) circuit of reversed excitation enters the control of pulse frequency modulated pattern, switch periods when calculating the pulse frequency modulated pattern
Control ON time T
On=T
Const, switch periods is T
s
Threshold voltage U in above-mentioned a kind of pulse frequency modulated and the micro grid inverter control method of the double mode modulation of quasi-resonance, described step (1)
SetA predefined voltage, can be according to the magnitude of voltage U of efficient the best of experimental selection
SetIf the line voltage peak value is U
m, then work as the electrical network angle when [α, π-α] and [π+α, 2 π-α] scope is interior, line voltage is higher than U
SetWhen electrical network angle line voltage in [α, α] and [π-°, π+α] scope the time is lower than U
Set, α=arcsin (U wherein
Set/ U
m).
Above-mentioned a kind of pulse frequency modulated and the micro grid inverter control method of the double mode modulation of quasi-resonance, the method of quasi-resonant mode control is in the described step (1): have no progeny when switching tube closes, energy in the flyback transformer magnetic core discharges to electrical network by the secondary winding, when the electric current of secondary inductance is zero, former limit inductance L
pWith metal-oxide-semiconductor parasitic capacitance C
rBeginning resonance is because the effect U of resonance
DsWaveform concussion appears, at U
DsVoltage resonance to the moment of minimum point open metal-oxide-semiconductor and can realize ZVS, reduce the turn-on consumption of metal-oxide-semiconductor.
Above-mentioned a kind of pulse frequency modulated and the micro grid inverter control method of the double mode modulation of quasi-resonance, when carrying out mode conversion in the described step (3), in order to guarantee that grid-connected current can not suddenly change, should keep the service time of pulse frequency modulated consistent with last switch periods of switch periods and quasi-resonant mode; Grid-connected current when guaranteeing quasi-resonant mode keeps service time T for sinusoidal
OnConstant, the by-pass cock cycle
When line voltage was very low, for example in the 300us at zero passage place scope, the driving that should block former limit metal-oxide-semiconductor reduced zero passage place's grid-connected current wave distortion.
The present invention has following remarkable advantage: the algorithm that the present invention relates to can solve anti-swash combining inverter under quasi-resonant mode control when near the too high problem of the switching frequency line voltage zero passage, near the line voltage zero passage, use the pulse frequency modulated mode controlling mode, with the ON time T of switch
OnFixing, the by-pass cock cycle T
s, make grid-connected current under the pulse frequency modulated state, still keep sinusoidal.
Description of drawings
Fig. 1 is pulse frequency modulated of the present invention and the double mode control flow chart of quasi-resonance.
Fig. 2 is photovoltaic miniature grid-connected inverter control device structured flowchart of the present invention.
Fig. 3 is pulse frequency modulated of the present invention and the double mode schematic diagram of quasi-resonance.
Fig. 4 is the present invention's circuit of reversed excitation waveform under quasi-resonant mode.
Fig. 5 is the drive waveforms of the present invention's grid voltage waveform and former limit metal-oxide-semiconductor under the pulse frequency modulated pattern.
Embodiment
Referring to Fig. 1, the micro grid inverter control method of a kind of pulse frequency modulated and the double mode modulation of quasi-resonance, the control step is as follows:
1. phase-locked loop is followed the tracks of and to be obtained electrical network angle θ, and sampling line voltage amplitude is higher than the threshold voltage U of setting when the line voltage amplitude
SetThe time, execution in step is 2.; Otherwise execution in step 3.;
2. move quasi-resonant mode control, judge whether this cycle is last switch periods of quasi-resonant mode, if it is records the ON time T of last switch periods
Const, cycle T '
sWith current electrical network angle θ ', computed duty cycle d '=T
Const/ T '
sOtherwise return step 1.;
3. circuit of reversed excitation enters the control of pulse frequency modulated pattern, in order to guarantee the output current of inverter under the PFM pattern for sinusoidal, control T
sSo that:
Wherein θ ' is last cycle phase-locked loop electrical network angle of quasi-resonant mode, T '
sSwitch periods for last cycle of quasi-resonant mode; Control ON time T
On=T
Const, switch periods is T
s
The micro grid inverter control method of above-mentioned pulse frequency modulated and the double mode modulation of quasi-resonance, threshold voltage U
SetA predefined voltage, can be according to the threshold value of efficient the best of experimental selection.If the line voltage peak value is U
m, when the electrical network angle in [α, π-°] and [π+α, 2 π-α] scope the time, line voltage is higher than U
SetWhen the electrical network angle was in [α, α] and [π-α, π+α] scope, line voltage was lower than U
Set, α=arcsin (U wherein
Set/ U
m).
The micro grid inverter control method of above-mentioned pulse frequency modulated and the double mode modulation of quasi-resonance, the method for quasi-resonant mode control is: have no progeny U when switching tube closes
DsVoltage rises, and the energy in the flyback transformer magnetic core discharges to electrical network by the secondary winding, when the electric current of secondary inductance is zero, and former limit inductance L
pWith metal-oxide-semiconductor parasitic capacitance C
rBeginning resonance, harmonic period
Because the effect U of resonance
DsWaveform concussion appears.After being down to zero from the secondary inductance electric current through T
r=T
sAfter/2, U
DsVoltage with resonance to minimum point, open metal-oxide-semiconductor can realize ZVS this moment, reduces the turn-on consumption of metal-oxide-semiconductor.Concrete waveform as shown in Figure 3, U among Fig. 3
DsRepresent the drain electrode of former limit metal-oxide-semiconductor and the voltage between source electrode, U
gRepresent the driving signal of metal-oxide-semiconductor, I
pRepresent the primary current of flyback transformer, I
sRepresent the secondary current of flyback transformer.
The micro grid inverter control method of above-mentioned pulse frequency modulated and the double mode modulation of quasi-resonance, when control model becomes pulse frequency modulated from quasi-resonance, can saltus step for the grid-connected current that guarantees to export, need to guarantee that the duty cycle of switching under two states is consistent.Therefore first switch periods when entering pulse frequency modulated should keep the service time in this cycle consistent with last switch periods of switch periods and quasi-resonant mode.In the control range of pulse frequency modulated, keep service time not become T '
On, according to formula (1) by-pass cock cycle T
sAt one-period T '
sRemain unchanged with sin θ ', the electrical network angle θ according to current tables look-up and tries to achieve
Value, can calculate easily switch periods T under the pulse frequency modulated pattern
sWhen line voltage was very low, for example in the 300us at zero passage place scope, the driving that should block former limit metal-oxide-semiconductor can reduce the grid-connected current wave distortion at zero passage place like this.Drive waveforms under the PFM pattern as shown in Figure 4.Among Fig. 4, U
GridRepresent the line voltage at zero passage place, U
gRepresent the driving signal of metal-oxide-semiconductor, because the time range of pulse frequency modulated pattern is generally less than 1ms, line voltage during this period of time is approximately straight line.
Should be understood that; concerning the those of ordinary skill in field, place of the present invention; can be equal to accordingly according to technical scheme of the present invention and design thereof and change or replace, and all these changes or replacement, all should belong to the protection range of claims of the present invention.
The principle that mains frequency of the present invention detects is summarized as follows:
In the control range of pulse frequency modulated pattern for the electric current that guarantees to export for sinusoidal, so requirement
Wherein k is a certain constant.
In last switch periods of quasi-resonant mode:
Therefore
With formula (4) substitution formula (2)
If make the ON time T under the pulse frequency modulated pattern
On=T '
On, then derive formula (1).
Claims (4)
1. the micro grid inverter control method of a pulse frequency modulated and the double mode modulation of quasi-resonance, it is as follows to it is characterized in that controlling step:
(1) phase-locked loop is followed the tracks of and to be obtained electrical network angle θ, and sampling line voltage amplitude is higher than the threshold voltage U of setting when the line voltage amplitude
SetThe time, execution in step (2); Otherwise execution in step (3);
(2) control of operation quasi-resonant mode judges whether this cycle is last switch periods of quasi-resonant mode, if it is records the ON time T of last switch periods
Const, switch periods T '
sWith current electrical network angle θ ', computed duty cycle d '=T
Const/ T '
sOtherwise return step (1);
(3) circuit of reversed excitation enters the control of pulse frequency modulated pattern, switch periods when calculating the pulse frequency modulated pattern
Control ON time T
On=T
Const, switch periods is T
s, ON time T
Const, switch periods T '
sWith current electrical network angle θ '.
2. the micro grid inverter control method of a kind of pulse frequency modulated according to claim 1 and the double mode modulation of quasi-resonance is characterized in that, threshold voltage U in the described step (1)
SetA predefined voltage, can be according to magnitude of voltage U of experimental selection
SetIf the line voltage peak value is U
m, then work as the electrical network angle when [α, π-α] and [π+α, 2 π-α] scope is interior, line voltage is higher than U
SetWhen electrical network angle line voltage when [α, α] and [π-α, π+α] scope is interior is lower than U
Set, α=arcsin (U wherein
Set/ U
m).
3. the micro grid inverter control method of a kind of pulse frequency modulated according to claim 1 and the double mode modulation of quasi-resonance, it is characterized in that, the method of quasi-resonant mode control is in the described step (2): have no progeny when switching tube closes, energy in the flyback transformer magnetic core discharges to electrical network by the secondary winding, when the electric current of secondary inductance is zero, former limit inductance L
pWith metal-oxide-semiconductor parasitic capacitance C
rBeginning resonance is because the effect U of resonance
DsWaveform concussion appears, at U
DsVoltage resonance to the moment of minimum point open metal-oxide-semiconductor and can realize that no-voltage is open-minded, reduce the turn-on consumption of metal-oxide-semiconductor.
4. the micro grid inverter control method of a kind of pulse frequency modulated according to claim 1 and the double mode modulation of quasi-resonance, it is characterized in that, when carrying out mode conversion in the described step (3), in order to guarantee that grid-connected current can not suddenly change, should keep the service time of pulse frequency modulated consistent with last switch periods of switch periods and quasi-resonant mode; Grid-connected current when guaranteeing quasi-resonant mode is for sinusoidal, control ON time T
OnConstant, the by-pass cock cycle
When line voltage in the 300us at zero passage place scope, the driving that should block former limit metal-oxide-semiconductor reduces zero passage place's grid-connected current wave distortion.
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| CN102594180B (en) * | 2012-01-21 | 2014-05-21 | 浙江昱能科技有限公司 | Control method for switch tube of photovoltaic grid-connected staggered shunt-wound flyback inverter |
| CN102751742B (en) * | 2012-07-25 | 2014-03-26 | 漳州科华技术有限责任公司 | Method for improving grid-connected performance by variable switching frequency |
| CN103391010B (en) * | 2013-07-25 | 2015-10-21 | 深圳市明微电子股份有限公司 | A kind of Switching Power Supply driving chip and switch power source driving circuit |
| TWI703792B (en) * | 2018-08-27 | 2020-09-01 | 飛宏科技股份有限公司 | Modulation method for inverter ac waveform |
| CN112701924B (en) * | 2020-12-28 | 2022-07-08 | 昂宝电子（上海）有限公司 | Apparatus and method for valley lock in quasi-resonant switching power supplies |
| CN114900027B (en) * | 2022-07-14 | 2022-11-15 | 阳光电源股份有限公司 | Converter and wave-sealing control method thereof |
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|---|---|---|---|---|
| EP0346860A1 (en) * | 1988-06-14 | 1989-12-20 | Kabushiki Kaisha Toshiba | Electromagnetic cooker including load control |
| CN101710718A (en) * | 2009-12-03 | 2010-05-19 | 天津理工大学 | Working method of grid-connected photovoltaic power generation system |
| CN101714763A (en) * | 2009-09-03 | 2010-05-26 | 周德佳 | High-efficiency stable multifunctional single-stage photovoltaic single-phase grid-connected control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000004589A (en) * | 1998-06-12 | 2000-01-07 | Futaba Corp | Resonance-type dc-to-ac converter |
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|---|---|---|---|---|
| EP0346860A1 (en) * | 1988-06-14 | 1989-12-20 | Kabushiki Kaisha Toshiba | Electromagnetic cooker including load control |
| CN101714763A (en) * | 2009-09-03 | 2010-05-26 | 周德佳 | High-efficiency stable multifunctional single-stage photovoltaic single-phase grid-connected control method |
| CN101710718A (en) * | 2009-12-03 | 2010-05-19 | 天津理工大学 | Working method of grid-connected photovoltaic power generation system |
Non-Patent Citations (3)
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| JP特开2000-4589A 2000.01.07 |
| 史丽萍等.谐振过渡软开关单相PWM并网逆变器.《电源技术》.2010,第34卷(第1期),63-65. |
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