WO2016168999A1 - 一种微型光伏逆变器及其控制方法 - Google Patents

一种微型光伏逆变器及其控制方法 Download PDF

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Publication number
WO2016168999A1
WO2016168999A1 PCT/CN2015/077156 CN2015077156W WO2016168999A1 WO 2016168999 A1 WO2016168999 A1 WO 2016168999A1 CN 2015077156 W CN2015077156 W CN 2015077156W WO 2016168999 A1 WO2016168999 A1 WO 2016168999A1
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Prior art keywords
converter
mode
resonant
voltage
inverter
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PCT/CN2015/077156
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English (en)
French (fr)
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柳萌
刘宝其
崔开涌
薛丽英
胡兵
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阳光电源股份有限公司
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Priority to PCT/CN2015/077156 priority Critical patent/WO2016168999A1/zh
Publication of WO2016168999A1 publication Critical patent/WO2016168999A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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

Definitions

  • the present application relates to the field of power electronics technology, and more particularly to a miniature photovoltaic inverter and a control method thereof.
  • the existing micro-photovoltaic inverter generally adopts a two-stage structure of flyback + power frequency commutation, but the voltage stress of the switch tube is relatively large due to the low utilization rate of the front stage flyback transformer and the large current shutdown, which is inevitable.
  • the resulting flyback transformer is inefficient and bulky, which in turn affects the overall efficiency of the system and the volume of the product, hindering the development of the product.
  • the present application provides a miniature photovoltaic inverter and a control method thereof to improve overall system efficiency and reduce product volume.
  • a miniature photovoltaic inverter control method is applied to a miniature photovoltaic inverter adopting a three-stage topology, including a DC/DC converter of a front stage, a resonant converter of an intermediate stage, and a DC/AC converter of a subsequent stage.
  • the method includes:
  • the mode 1 is entered, and the DC/AC converter is started to stabilize the inverter bus voltage when the inverter bus voltage reaches the target value.
  • the PV voltage reaches the photovoltaic power generation
  • the switching frequency of the resonant converter still does not reach the resonant frequency
  • the current switching frequency of the resonant converter is maintained unchanged, and then enters mode 3; if the switching frequency of the resonant converter When the resonant frequency is reached, the PV voltage still does not reach the predicted point of the maximum power of photovoltaic power generation, then enter mode 4;
  • the resonant converter When it is judged that there is no voltage shock on the inverter bus, the resonant converter is fixed to the resonant frequency to start, and the DC/DC converter is started to perform the voltage transformation work, and the voltage of the inverter bus is reached.
  • the target value is activated to activate the DC/AC converter to stabilize the inverter bus voltage, and then enter mode 2;
  • the maximum power point tracking of the photovoltaic power generation is performed in real time, the resonant frequency of the resonant converter is fixed at the resonant frequency, and the inverter bus voltage does not deviate from the modulation range as a target state, and the reasonable adjustment is performed.
  • the working mode of the micro photovoltaic inverter is performed in real time, the resonant frequency of the resonant converter is fixed at the resonant frequency, and the inverter bus voltage does not deviate from the modulation range as a target state, and the reasonable adjustment is performed.
  • mode 1 is: the DC/DC converter is directly connected, and the resonant converter is slowed down;
  • Mode 2 is: the DC/DC converter is directly connected, the resonant converter is fixed at a resonant frequency, and the DC/AC converter is connected in a double loop and performs maximum power point tracking of photovoltaic power generation;
  • Mode 3 is: the DC/DC converter is directly connected, the resonant converter is down-converted and performs maximum power point tracking of photovoltaic power generation, and the DC/AC converter is dual-loop connected to the grid;
  • Mode 4 is: the DC/DC converter performs photovoltaic power generation maximum power point tracking, the resonant converter is fixed at a resonant frequency, and the DC/AC converter is dual-loop connected to the grid.
  • the real-time photovoltaic power generation maximum power point tracking, the resonant converter constant frequency at the resonant frequency, and the inverter bus voltage do not deviate from the modulation range as a target state, and the working mode of the micro photovoltaic inverter is reasonably adjusted.
  • V dcmin represents the minimum inverter bus voltage that satisfies the modulation
  • V dcmax represents the maximum inverter bus voltage that satisfies the modulation
  • A represents the boost ratio of the resonant converter.
  • micro photovoltaic inverter control method further includes:
  • mode 1 mode 2, mode 3 or mode 4 when it is detected that the PV power is lower than the preset value, the Burst mode is entered, and the original working mode is not switched until the PV power is not lower than the preset value.
  • the resonant converter in the Burst mode, is fixed-frequency and operates at a resonant frequency open-loop; the DC/DC converter performs a maximum power point tracking of the photovoltaic power generation when the PV voltage is lower than the first threshold, in the PV voltage The bypass is higher than the second threshold; the DC/AC converter adopts a grid-connected current single-loop control strategy; wherein the second threshold is greater than or equal to the first threshold.
  • a miniature photovoltaic inverter comprising a cascade circuit and a system controller, wherein:
  • the cascode circuit includes a DC/DC converter of a front stage, a resonant converter of an intermediate stage, and a DC/AC converter of a subsequent stage;
  • the system controller is connected to the cascade circuit for determining whether there is a voltage impact on the inverter bus; when it is judged that there is a voltage shock on the inverter bus, the mode 1 is entered, and the inverter bus voltage reaches the target value.
  • the DC/AC converter is activated to stabilize the inverter bus voltage.
  • the switching frequency of the resonant converter still does not reach the resonant frequency, and the The current switching frequency of the resonant converter is unchanged, and then enters mode 3; if the switching frequency of the resonant converter reaches the resonant frequency, and the PV voltage still does not reach the estimated point of the maximum power of photovoltaic power generation, it enters mode 4;
  • the resonant converter is fixed to the resonant frequency to start, and the DC/DC converter is started to perform the voltage transformation work, and the inverter is to be turned on when the inverter bus voltage reaches the target value.
  • the DC/AC converter is used to stabilize the inverter bus voltage, and then enters mode 2; and after the micro-photovoltaic inverter enters a steady state, the photovoltaic power generation is performed in real time. Power point tracking, fixed frequency resonant converter in the resonant frequency, and mode of operation without departing from the bus voltage of the inverter modulation range of the target state, a reasonable adjustment of the micro PV inverter;
  • mode 1 is: the DC/DC converter is directly connected, and the resonant converter is slowed down;
  • Mode 2 is: the DC/DC converter is directly connected, the resonant converter is fixed at a resonant frequency, and the DC/AC converter is connected in a double loop and performs maximum power point tracking of photovoltaic power generation;
  • Mode 3 is: the DC/DC converter is directly connected, the resonant converter is down-converted and performs maximum power point tracking of photovoltaic power generation, and the DC/AC converter is dual-loop connected to the grid;
  • Mode 4 is: the DC/DC converter performs photovoltaic power generation maximum power point tracking, the resonant converter is fixed at a resonant frequency, and the DC/AC converter is dual-loop connected to the grid.
  • mode 3 when the switching frequency of the resonant converter drops to a resonant frequency, it switches to mode 2; in mode 4, entry mode when V dcmin / A ⁇ PV voltage ⁇ V dcmax / a 2; in mode 2, mode 3 when entering PV voltage> V dcmax / a, 4 access control mode when the PV voltage ⁇ V dcmin / a Device
  • V dcmin represents the minimum inverter bus voltage that satisfies the modulation
  • V dcmax represents the maximum inverter bus voltage that satisfies the modulation
  • A represents the boost ratio of the resonant converter.
  • the system controller is in mode 1, mode 2, mode 3 or mode 4, and is checked.
  • the Burst mode is entered, and the controller is switched back to the original working mode until the PV power is not lower than the preset value.
  • the DC/DC converter is a Boost circuit, a Buck circuit or a Buck-Boost circuit.
  • the resonant bridge arm of the resonant converter can select a full bridge or a half bridge, and the resonant cavity can be selected from an LC, LLC or LCC structure.
  • the DC/AC converter is a five-level inverter topology.
  • the present application uses a resonant converter instead of a flyback transformer, firstly obtained from both volume and efficiency, and the DC/DC converter and the DC/AC converter are There is also a large optimization space in terms of efficiency and volume, so that an optimized DC/DC converter and DC/AC converter are used together with the resonant converter to form an efficient, small-volume three-stage topology micro-PV inverter.
  • the present application hierarchically controls the three-level topology structure to ensure that the system startup has basically no impact, stable steady state operation, and can maximize the utilization of photovoltaic energy.
  • FIG. 1a-1b are flowcharts of a micro photovoltaic inverter control method disclosed in an embodiment of the present application
  • FIG. 2 is a schematic diagram of a three-level topology structure of a miniature photovoltaic inverter disclosed in an embodiment of the present application;
  • FIG. 3 is a schematic structural diagram of a miniature photovoltaic inverter disclosed in an embodiment of the present application.
  • the embodiment of the present application discloses a micro photovoltaic inverter control method, which is applied to a micro-photovoltaic inverter adopting a three-level topology, and the three-level topology structure is as shown in FIG. 2, including the pre-stage.
  • the DC/DC converter 101, the intermediate stage resonant converter 102 and the subsequent stage DC/AC converter 103 are used to improve the overall efficiency of the system and reduce the product volume; the method includes two parts: startup logic and stable operation logic.
  • the startup logic includes:
  • Step S101 determining whether there is a voltage impact on the inverter bus of the micro photovoltaic inverter, if there is a voltage impact, proceeds to step S102; otherwise, proceeds to step S107;
  • Step S102 Enter mode 1, and start the DC/AC converter 103 to stabilize the inverter bus voltage V dc when the inverter bus voltage V dc reaches the target value; the target value of V dc is generally set to satisfy the modulation of the grid voltage.
  • Step S103 determining whether the PV voltage reaches the estimated point V mppt of the maximum power of photovoltaic power generation, if yes, proceeds to step S104; otherwise, proceeds to step S105;
  • Step S104 The current switching frequency f 102 of the resonant converter 102 is maintained unchanged, and then enters mode 3, and the current start logic control ends.
  • Step S105 determining whether the switching frequency f 102 of the resonant converter 102 reaches the resonant frequency f s , if yes, proceeds to step S106; otherwise, proceeds to return to step S103;
  • Step S106 Enter mode 4, and the current startup logic control ends.
  • Step S107 The resonant converter 102 is frequency-controlled to the resonant frequency fs to start, and the DC/DC converter 101 is started to perform the voltage transformation operation.
  • the inverter bus voltage V dc reaches the target value
  • the DC/AC converter 103 is activated to stabilize the inverse.
  • the bus voltage V dc is changed, and then enters mode 2, and the logic control is terminated this time.
  • the stable operation logic is: after the micro photovoltaic inverter enters a steady state, the photovoltaic power generation maximum power point tracking is performed in real time, the resonant converter 102 is fixed at a resonant frequency, and the inverter bus voltage V dc is not separated from the modulation.
  • the range is used as the target state to properly adjust the operating mode of the micro-PV inverter. Referring to FIG. 1b, the specific includes:
  • mode 2 when the PV voltage > satisfies the modulated maximum inverter bus voltage V dcmax / the boost ratio A of the resonant converter 102, enters mode 3; when the PV voltage ⁇ satisfies the modulated minimum inverter bus voltage V dcmin / When the boosting ratio of the resonant converter 102 is A, the mode 4 is entered.
  • mode 1 is: the DC/DC converter 101 is directly connected, and the resonant converter 102 is slowed down;
  • Mode 2 DC/DC converter 101 is through, resonant converter 102 is fixed at a resonant frequency, DC/AC converter 103 is dual-loop connected to the grid and performs maximum power point tracking of photovoltaic power generation; wherein, the so-called DC/AC converter 103 double loop Grid-connected, refers to the double closed-loop strategy of the inverter bus voltage outer loop and the inverter inductor current inner loop;
  • Mode 3 DC/DC converter 101 is through, the resonant converter 102 is down-converted and performs maximum power point tracking of photovoltaic power generation, and the DC/AC converter 103 is dual-loop connected;
  • Mode 4 is: DC/DC converter 101 performs maximum power point tracking of photovoltaic power generation, resonant converter 102 is fixed at a resonant frequency, and DC/AC converter 103 is dual-loop connected.
  • micro photovoltaic inverter control method shown in FIGS. 1a-1b and the micro photovoltaic inverter to which the method is applied will be described in detail below.
  • the micro-photovoltaic inverter adopts a three-stage topology: 1) The front stage: the DC/DC converter 101 can perform maximum power point tracking of photovoltaic power generation in a wide input voltage range, thereby improving the energy conversion efficiency of the photovoltaic panel.
  • the DC/DC converter 101 has a large optimization space in terms of efficiency and volume. There are also many high-efficiency, small-volume existing products available on the market.
  • the resonant converter 102 has many advantages, such as low noise, low stress, use of fewer components and only less switching losses, etc., matching the switching frequency f 102 of the resonant converter 102 with After the relationship of the resonant frequency f s , the circuit can realize ZVS (Zero Voltage Switching) or ZCS (Zero Current Switching) characteristics, optimization of circuit components and EMI (Electro-Magnetic Interference). The features are very advantageous.
  • the DC/AC converter 103 also has a large optimization space in terms of efficiency and volume, such as the existing five-level inverter topology, which has high efficiency, small output harmonics, small required inductance, and can be reduced. Small size.
  • the present embodiment uses the resonant converter 102 instead of the flyback transformer, firstly gaining both volume and efficiency, and the DC/DC converter 101 and the DC/AC converter 103 are in efficiency and volume.
  • the DC/DC converter 101 and the DC/AC converter 103 are in efficiency and volume.
  • this embodiment hierarchically controls the three-level topology structure in stages, ensuring that the system startup is basically shock-free, stable in steady state operation, and can maximize the utilization of photovoltaic energy.
  • the specific description is as follows:
  • the three-stage topology of the micro-photovoltaic inverter is analyzed. It can be seen that the AC side of the DC/AC converter 103 is directly connected to the power grid, and the power of the grid directly passes through the rectifier bridge inside the DC/AC converter 103 after power-on.
  • the busbar capacitor is charged to cause the inverter bus voltage V dc to rise to the unregulated rectification voltage of the grid.
  • the input end of the DC/DC converter 101 is directly connected to the photovoltaic panel, and the output capacitor of the DC/DC converter 101 is charged, so that the output voltage of the DC/DC converter 101 rises directly to the voltage across the photovoltaic panel, also called PV. Voltage.
  • the boosting ratio of the resonant converter 102 the gain of the resonant converter 102 * the transformer ratio, when the voltage of the PV voltage is boosted by the resonant converter 102 and output to the inverter bus is higher than the unregulated rectified voltage of the grid, Impact on the inverter bus.
  • the resonant converter 102 has a gain-adjustable characteristic, that is, the switching frequency f 102 of the resonant converter 102 is equal to the resonant frequency f s when the gain is maximum, and the gain is smaller than the resonant frequency f s , and the resonant voltage is directly passed to mitigate the PV voltage.
  • the device 102 boosts the impact on the inverter bus, and the gain adjustment of the resonant converter 102 can be performed as follows:
  • the V dc is fixed, if the resonant converter 102 continues to frequency down, the PV voltage will be lowered, and the maximum is far away.
  • the power point is not conducive to maximizing the utilization of photovoltaic energy, so the current switching frequency f 102 is maintained unchanged; after that, entering mode 3, the switching frequency f 102 of the resonant converter 102 is reduced to the maximum while utilizing the photovoltaic energy.
  • the DC/AC converter 103 is activated to stabilize the inverter bus voltage V dc , if the switching frequency f 102 of the resonant converter 102 has dropped to the resonance frequency f s , the PV voltage is still higher than The estimated point V mppt of the maximum power of the photovoltaic panel maintains the current switching frequency f 102 of the resonant converter 102 unchanged, and then enters mode 4. Because: when the switching frequency of the resonant converter 102 reaches the resonant frequency, the gain is already maximum. If the PV voltage is still greater than V mppt , the DC voltage converter 101 needs to be used to disturb the PV voltage to V mppt to achieve maximum Use photovoltaic energy.
  • the resonant converter 102 is fixed to the resonance frequency f s to start, and the DC/DC converter 101 is started to perform the voltage transformation work, and the inverter bus voltage V dc is reached.
  • the present embodiment is based on the advantages of the system hardware topology itself, and through the coordinated control of the system, the overall efficiency of the system is improved, and the product volume is reduced, thereby effectively solving the problems existing in the prior art.
  • the micro photovoltaic inverter control method further comprises: entering the Burst mode when the PV power is lower than a preset value in any working mode until the PV power is not lower than the preset value. Switching back to the original working mode; wherein the Burst mode is a mode in which the energy is small and needs to be accumulated, and the output is re-output after reaching a certain value.
  • Burst mode is also an important working mode of the micro-PV inverter.
  • the power of the photovoltaic panel is low (such as less than 10% of the rated power)
  • the DC/AC converter 103 is still working, then the output Too small a current will introduce a large amount of reactive power, which is not only inefficient for the system but also detracts from the service life of the device.
  • the resonant converter 102 is fixed-frequency at the resonant frequency f s open-loop operation, using the inverter bus capacitor to store energy; when the PV voltage is lower than the first threshold, the photovoltaic is performed by the DC/DC converter 101 The maximum power point of the power generation is tracked; when the PV voltage is higher than the second threshold, the DC/DC converter 101 is bypassed, and the energy is transmitted from the resonant converter 102 to the inverter bus capacitor.
  • the DC/AC converter 103 adopts a grid-connected current single-loop control strategy, and the PV energy charges the inverter bus capacitor through N power frequency cycles to reach the DC/AC converter 103 startup condition and then transmits the energy through the DC/AC converter 103. To the grid.
  • the micro photovoltaic inverter control method disclosed in this embodiment is preferably a hysteresis comparison method when performing logical judgment.
  • the value of the second threshold is preferably greater than the first threshold to avoid the DC/DC converter 101 frequently switching the operating state at the critical point.
  • an embodiment of the present application discloses a micro-photovoltaic inverter to improve overall system efficiency and reduce product volume, including: cascade circuit 100 and system controller 200;
  • the cascade circuit 100 includes a DC/DC converter 101 of the preceding stage, a resonant converter 102 of the intermediate stage, and a DC/AC converter 103 of the subsequent stage;
  • the system controller 200 is connected to the cascade circuit 100 for sampling the cascade circuit 100 and performing corresponding control. Specifically, it is used to determine whether there is a voltage impact on the inverter bus; when it is determined that the inverter bus exists When the voltage is impacted, enter mode 1, and start the DC/AC converter 103 to stabilize the inverter bus voltage V dc when the inverter bus voltage V dc reaches the target value.
  • mode 1 is: the DC/DC converter 101 is directly connected, and the resonant converter 102 is slowed down;
  • Mode 2 DC/DC converter 101 is through, resonant converter 102 is fixed at a resonant frequency, DC/AC converter 103 is dual-loop connected to the grid and performs maximum power point tracking of photovoltaic power generation; wherein, the so-called DC/AC converter 103 double loop Grid-connected, refers to the double closed-loop strategy of the inverter bus voltage outer loop and the inverter inductor current inner loop;
  • Mode 3 DC/DC converter 101 is through, the resonant converter 102 is down-converted and performs maximum power point tracking of photovoltaic power generation, and the DC/AC converter 103 is dual-loop connected;
  • Mode 4 is: DC/DC converter 101 performs maximum power point tracking of photovoltaic power generation, resonant converter 102 is fixed at a resonant frequency, and DC/AC converter 103 is dual-loop connected.
  • the system controller 200 switches to mode 2; in mode 4, when When V dcmin /A ⁇ PV voltage ⁇ V dcmax /A, enter mode 2; in mode 2, when PV voltage >V dcmax /A, enter mode 3; when PV voltage ⁇ V dcmin /A, enter mode 4 Controller
  • V dcmin represents the minimum inverter bus voltage that satisfies the modulation
  • V dcmax represents the maximum inverter bus voltage that satisfies the modulation
  • A represents the boost ratio of the resonant converter 102.
  • the system controller 200 can also enter the Burst mode when the PV power is lower than the preset value in the mode 1, the mode 2, the mode 3 or the mode 4 until the PV power is not lower than the preset. The value is switched back to the controller of the original working mode.
  • the DC/DC converter 101 can select a Boost circuit, a Buck circuit or a Buck-Boost circuit; the resonant bridge of the resonant converter 102 can select a full bridge or a half bridge, and the resonant cavity can be selected from LC, LLC, LCC or other types.
  • the DC/AC converter 103 is preferably a high efficiency, small volume multi-level inverter topology, such as a five-level inverter topology.
  • the number of phases and the number of levels of the cascade circuit 100 can be adjusted according to actual needs, supporting multiple PV inputs and multi-phase grid output.
  • the present application replaces the flyback transformer with a resonant converter, firstly gaining both volume and efficiency, and the efficiency and volume of the DC/DC converter and the DC/AC converter.

Abstract

一种微型光伏逆变器及其控制方法，该方法包括：判断逆变母线上是否存在电压冲击；若存在，进入模式1并在逆变母线电压达到目标值时启动DC/AC变换器，此时：若PV电压达到光伏发电最大功率的预估点时，谐振变换器的开关频率仍未达到谐振频率，则维持当前开关频率不变，进入模式3；若达到谐振频率时未达到预估点，进入模式4；若不存在冲击，将谐振变换器定频到谐振频率启动，启动DC/DC和DC/AC变换器，之后进入模式2；在微型光伏逆变器进入稳态后，以实时进行光伏发电最大功率点跟踪、谐振变换器定频在谐振频率、逆变母线电压不脱离调制范围作为目标状态，调节逆变器的工作模式；以提高系统整体效率、降低产品体积。

Description

一种微型光伏逆变器及其控制方法 技术领域
本申请涉及电力电子技术领域，更具体地说，涉及一种微型光伏逆变器及其控制方法。
背景技术
现有的微型光伏逆变器一般采用反激+工频换向的两级结构，但由于前级反激变压器利用率比较低、且大电流关断等造成开关管电压应力较大，不可避免的导致反激变压器效率低下且体积较大，进而影响了系统整体效率和产品体积，阻碍了产品的发展。
发明内容
有鉴于此，本申请提供一种微型光伏逆变器及其控制方法，以提高系统整体效率、降低产品体积。
一种微型光伏逆变器控制方法，应用于采用三级拓扑结构的微型光伏逆变器，包括前级的DC/DC变换器、中间级的谐振变换器和后级的DC/AC变换器，所述方法包括：
判断逆变母线上是否存在电压冲击；
当判断得到逆变母线上存在电压冲击时，进入模式1，并在逆变母线电压达到目标值时启动所述DC/AC变换器以稳定逆变母线电压，此时：若是PV电压达到光伏发电最大功率的预估点时，所述谐振变换器的开关频率仍未达到谐振频率，则维持所述谐振变换器当前的开关频率不变，之后进入模式3；若是所述谐振变换器的开关频率达到谐振频率时，PV电压仍未达到光伏发电最大功率的预估点，则进入模式4；
在判断得到逆变母线上不存在电压冲击时，将所述谐振变换器定频到谐振频率启动，同时启动所述DC/DC变换器进行变压工作，待逆变母线电压达到 目标值时启动所述DC/AC变换器以稳定逆变母线电压，之后进入模式2；
在所述微型光伏逆变器进入稳态后，以实时进行光伏发电最大功率点跟踪、所述谐振变换器定频在谐振频率，以及逆变母线电压不脱离调制范围作为目标状态，合理调节所述微型光伏逆变器的工作模式；
其中，模式1为：所述DC/DC变换器直通，所述谐振变换器降频缓起；
模式2为：所述DC/DC变换器直通，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网并进行光伏发电最大功率点跟踪；
模式3为：所述DC/DC变换器直通，所述谐振变换器降频并进行光伏发电最大功率点跟踪，所述DC/AC变换器双环并网；
模式4为：所述DC/DC变换器进行光伏发电最大功率点跟踪，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网。
其中，所述以实时进行光伏发电最大功率点跟踪、所述谐振变换器定频在谐振频率，以及逆变母线电压不脱离调制范围作为目标状态，合理调节所述微型光伏逆变器的工作模式，包括：
在模式3下：当所述谐振变换器的开关频率降至谐振频率时，切换为模式2；
在模式4下：当Vdcmin/A≤PV电压≤Vdcmax/A时，进入模式2；
在模式2下：当PV电压>Vdcmax/A时，进入模式3；当PV电压<Vdcmin/A时，进入模式4；
其中，Vdcmin表示满足调制的最小逆变母线电压；Vdcmax表示满足调制的最大逆变母线电压；A表示所述谐振变换器的升压比。
可选地，所述微型光伏逆变器控制方法，还包括：
在模式1、模式2、模式3或模式4下，当检测到PV功率低于预设值时，进入Burst模式，直至PV功率不低于所述预设值时才切换回原工作模式。
其中，在所述Burst模式下，所述谐振变换器定频在谐振频率开环工作；所述DC/DC变换器在PV电压低于第一阈值时进行光伏发电最大功率点跟踪，在PV电压高于第二阈值时旁路；所述DC/AC变换器采用并网电流单环控制策略；其中，所述第二阈值大于或等于所述第一阈值。
一种微型光伏逆变器，包括级联电路和系统控制器，其中：
所述级联电路包括前级的DC/DC变换器、中间级的谐振变换器以及后级的DC/AC变换器；
所述系统控制器与所述级联电路相连，用于判断逆变母线上是否存在电压冲击；当判断得到逆变母线上存在电压冲击时，进入模式1，并在逆变母线电压达到目标值时启动所述DC/AC变换器以稳定逆变母线电压，此时：若是PV电压达到光伏发电最大功率的预估点时，所述谐振变换器的开关频率仍未达到谐振频率，则维持所述谐振变换器当前的开关频率不变，之后进入模式3；若是所述谐振变换器的开关频率达到谐振频率时，PV电压仍未达到光伏发电最大功率的预估点，则进入模式4；在判断得到逆变母线上不存在电压冲击时，将所述谐振变换器定频到谐振频率启动，同时启动所述DC/DC变换器进行变压工作，待逆变母线电压达到目标值时启动所述DC/AC变换器以稳定逆变母线电压，之后进入模式2；以及在所述微型光伏逆变器进入稳态后，以实时进行光伏发电最大功率点跟踪、所述谐振变换器定频在谐振频率，以及逆变母线电压不脱离调制范围为目标状态，合理调节所述微型光伏逆变器的工作模式；
其中，模式1为：所述DC/DC变换器直通，所述谐振变换器降频缓起；
模式2为：所述DC/DC变换器直通，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网并进行光伏发电最大功率点跟踪；
模式3为：所述DC/DC变换器直通，所述谐振变换器降频并进行光伏发电最大功率点跟踪，所述DC/AC变换器双环并网；
模式4为：所述DC/DC变换器进行光伏发电最大功率点跟踪，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网。
其中，所述系统控制器为在所述微型光伏逆变器进入稳态后，在模式3下，当所述谐振变换器的开关频率降至谐振频率时切换为模式2；在模式4下，当Vdcmin/A≤PV电压≤Vdcmax/A时进入模式2；在模式2下，当PV电压>Vdcmax/A时进入模式3，当PV电压<Vdcmin/A时进入模式4的控制器；
其中，Vdcmin表示满足调制的最小逆变母线电压；Vdcmax表示满足调制的最大逆变母线电压；A表示所述谐振变换器的升压比。
可选地，所述系统控制器为在模式1、模式2、模式3或模式4下，当检 测到PV功率低于预设值时，进入Burst模式，直至PV功率不低于所述预设值时才切换回原工作模式的控制器。
其中，所述DC/DC变换器为Boost电路、Buck电路或Buck-Boost电路。
其中，所述谐振变换器的谐振桥臂可选择全桥或半桥，其谐振腔可选择LC、LLC或LCC结构。
其中，所述DC/AC变换器为五电平逆变拓扑。
从上述的技术方案可以看出，在硬件结构上，本申请使用谐振变换器取代了反激变压器，首先从体积和效率上都获得了提升，而且DC/DC变换器和DC/AC变换器在效率和体积上也都有很大的优化空间，从而通过选用优化的DC/DC变换器和DC/AC变换器，与谐振变换器一起构成高效、小体积的三级拓扑结构微型光伏逆变器，非常有利于产品的发展；在软件控制上，本申请对所述三级拓扑结构分级分阶段控制，保证了系统启动基本无冲击、稳态运行稳定，且能够最大化利用光伏能量。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据提供的附图获得其他的附图。
图1a-1b为本申请实施例公开的一种微型光伏逆变器控制方法流程图；
图2为本申请实施例公开的一种微型光伏逆变器的三级拓扑结构示意图；
图3为本申请实施例公开的一种微型光伏逆变器结构示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造 性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
参见图1a-1b，本申请实施例公开了一种微型光伏逆变器控制方法，应用于采用三级拓扑结构的微型光伏逆变器，其三级拓扑结构如图2所示，包括前级的DC/DC变换器101、中间级的谐振变换器102和后级的DC/AC变换器103，以提高系统整体效率、降低产品体积；所述方法包括启动逻辑和稳定运行逻辑两部分。
参见图1a，所述启动逻辑包括：
步骤S101：判断所述微型光伏逆变器的逆变母线上是否存在电压冲击，若存在电压冲击，进入步骤S102；否则，进入步骤S107；
步骤S102：进入模式1，并在逆变母线电压Vdc达到目标值时启动DC/AC变换器103以稳定逆变母线电压Vdc；Vdc的目标值一般设定为电网电压对应的满足调制的最小逆变母线电压Vdcmin，即以Vdc＝Vdcmin作为DC/AC变换器103的启动条件；
步骤S103：判断PV电压是否达到光伏发电最大功率的预估点Vmppt，若达到，进入步骤S104；否则，进入步骤S105；
步骤S104：维持谐振变换器102当前的开关频率f102不变，之后进入模式3，本次启动逻辑控制结束。
步骤S105：判断谐振变换器102的开关频率f102是否达到谐振频率fs，若达到，进入步骤S106；否则，进入返回步骤S103；
步骤S106：进入模式4，本次启动逻辑控制结束。
步骤S107：将谐振变换器102定频到谐振频率fs启动，同时启动DC/DC变换器101进行变压工作，待逆变母线电压Vdc达到目标值时启动DC/AC变换器103以稳定逆变母线电压Vdc，之后进入模式2，本次启动逻辑控制结束。
所述稳定运行逻辑为：在所述微型光伏逆变器进入稳态后，以实时进行光伏发电最大功率点跟踪、谐振变换器102定频在谐振频率，以及逆变母线电压Vdc不脱离调制范围作为目标状态，来合理调节微型光伏逆变器的工作模式。参见图1b，其具体包括：
在模式3下，当开关频率f102降至谐振频率fs时，切换为模式2；
在模式4下，当满足调制的最小逆变母线电压Vdcmin/谐振变换器102的升压比A≤PV电压≤满足调制的最大逆变母线电压Vdcmax/谐振变换器102的升压比A时，进入模式2；
在模式2下，当PV电压>满足调制的最大逆变母线电压Vdcmax/谐振变换器102的升压比A时，进入模式3；当PV电压<满足调制的最小逆变母线电压Vdcmin/谐振变换器102的升压比A时，进入模式4。
其中，模式1为：DC/DC变换器101直通，谐振变换器102降频缓起；
模式2为：DC/DC变换器101直通，谐振变换器102定频在谐振频率，DC/AC变换器103双环并网并进行光伏发电最大功率点跟踪；其中，所谓DC/AC变换器103双环并网，是指逆变母线电压外环和逆变电感电流内环的双闭环策略；
模式3为：DC/DC变换器101直通，谐振变换器102降频并进行光伏发电最大功率点跟踪，DC/AC变换器103双环并网；
模式4为：DC/DC变换器101进行光伏发电最大功率点跟踪，谐振变换器102定频在谐振频率，DC/AC变换器103双环并网。
为了更清楚的描述本实施例所述的技术方案，下面，对图1a-1b所示的微型光伏逆变器控制方法以及该方法所适用的微型光伏逆变器进行详述。
所述微型光伏逆变器采用三级拓扑结构：1)前级：DC/DC变换器101可以在宽输入电压范围内进行光伏发电最大功率点跟踪，提高光伏电池板的能量转换效率。DC/DC变换器101在效率和体积上都有很大的优化空间。且市面上也有很多高效、小体积的现有产品可供选择。2)中间级：谐振变换器102采用全桥/半桥与变压器结合的谐振变换拓扑，可实时调节变压比，满足逆变母线电压需求。相较于反激变换器，谐振变换器102具有诸多优点，如低噪声、低应力、使用较少元器件且仅有较少的开关损耗等，匹配好谐振变换器102的开关频率f102与谐振频率fs的关系后，电路可实现ZVS(Zero Voltage Switching，零电压开关)或ZCS(Zero Current Switching，零电流开关)特性，对电路元件的优化和EMI(Electro-Magnetic Interference，电磁干扰)特性非常有利。3)后级：DC/AC变换器103用于将传递来的直流能量转化为交流能 量输出。DC/AC变换器103在效率和体积上同样具有很大的优化空间，如现有的五电平逆变拓扑结构，该逆变拓扑效率高，输出谐波小，需要的电感小，可以减小体积。
可见，在硬件结构上，本实施例使用谐振变换器102取代了反激变压器，首先从体积和效率上都获得了提升，而且DC/DC变换器101和DC/AC变换器103在效率和体积上也都有很大的优化空间，从而构成了微型光伏逆变器高效、小体积的三级拓扑结构，非常有利于产品的发展。
在软件控制上，本实施例对该三级拓扑结构分级分阶段控制，保证了系统启动基本无冲击、稳态运行稳定，且能够最大化利用光伏能量。具体描述如下：
分析所述微型光伏逆变器的三级拓扑结构，可知：DC/AC变换器103的交流侧直接连接电网，上电后电网能量直接经过后级DC/AC变换器103内部的整流桥给逆变母线电容充电，使逆变母线电压Vdc上升到电网的不控整流电压。DC/DC变换器101的输入端直接连接光伏电池板，给DC/DC变换器101的输出电容充电，使DC/DC变换器101的输出电压直接上升至光伏电池板两端电压，又称PV电压。
谐振变换器102的升压比＝谐振变换器102的增益*变压器变比，当PV电压经谐振变换器102升压后输出到逆变母线上的电压高于电网的不控整流电压时，会对逆变母线造成冲击。由于谐振变换器102具有增益可调的特性，即，谐振变换器102的开关频率f102等于谐振频率fs时增益最大，大于谐振频率fs则增益变小，为缓解PV电压直接通过谐振变换器102升压对逆变母线造成的冲击，可对谐振变换器102进行增益调节，具体做法如下：
1)若PV电压＞电网的不控整流电压/谐振变换器102的升压比，说明逆变母线上将会出现电压冲击，应当进入模式1，因为：降频会使谐振变换器102增益增大，使谐振变换器102的输出电压随之抬高，进而降低PV电压直接通过谐振变换器102升压后对逆变母线造成的冲击。
在模式1执行过程中，需实时判断DC/AC变换器103是否满足启动条件，若满足，则启动DC/AC变换器103以稳定逆变母线电压Vdc。在此基础上，若PV电压达到光伏发电最大功率的预估点Vmppt，而谐振变换器102的开关频 率f102仍未降至谐振频率fs，则维持谐振变换器102当前的开关频率f102不变，之后进入模式3，因为：降频会使谐振变换器102的升压比变化，在Vdc固定的情况下，若谐振变换器102继续降频必然使PV电压变低，远离最大功率点，不利于最大化利用光伏能量，故维持当前开关频率f102不变；之后，进入模式3，在保证最大化利用光伏能量的前提下，使谐振变换器102的开关频率f102降至谐振频率fs，从而达到PV电压＝Vmppt、且f102＝fs这一最理想的状态。
或者，在模式1正在执行且已启动DC/AC变换器103稳定逆变母线电压Vdc的基础上，若谐振变换器102开关频率f102已降至谐振频率fs，而PV电压仍高于光伏电池板最大功率的预估点Vmppt，则维持谐振变换器102当前的开关频率f102不变，之后再进入模式4。因为：谐振变换器102的开关频率达到谐振频率时增益已然最大，此时如果PV电压仍大于Vmppt，则需要通过DC/DC变换器101来扰动PV电压使其降至Vmppt，以实现最大化利用光伏能量。
2)在确认逆变母线上不会出现电压冲击时，将谐振变换器102定频到谐振频率fs启动，同时启动DC/DC变换器101进行变压工作，待逆变母线电压Vdc达到目标值时启动DC/AC变换器103以稳定逆变母线电压Vdc，之后进入模式2，从而达到PV电压＝Vmppt、且f102＝fs这一最理想的状态。
在稳态运行阶段，具体描述如下：
1)在模式3下：当f102＝fs时，切换为模式2，以保证增益最大化；
2)在模式4下：当Vdcmin/A≤PV电压≤Vdcmax/A时，进入模式2，通过扰动Vdc使光伏电池板工作在最大功率点，以实现最大化利用光伏能量；
3)在模式2下：当PV电压>Vdcmax/A时，进入模式3，通过扰动开关频率f102使逆变母线电压落回可调制范围；当PV电压<Vdcmin/A时，进入模式4，通过DC/DC变换器101扰动PV电压，使光伏电池板工作在最大功率点，逆变母线电压Vdc则维持Vdcmin不变。
至此，可以看出，本实施例基于系统硬件拓扑本身的优势，通过对系统的协调控制，提高了系统整体效率、降低了产品体积，从而有效解决了现有技术存在的问题。
作为优选，所述微型光伏逆变器控制方法还包括：在任一工作模式下，当检测到PV功率低于预设值时，进入Burst模式，直至PV功率不低于所述预设值时才切换回原工作模式；其中，所述Burst模式为能量较小需进行累积，累积达到一定值后再次输出的模式。
Burst模式也是所述微型光伏逆变器的一种重要工作模式，当光伏电池板的功率较低时(比如低于额定功率的10％)，如果DC/AC变换器103仍工作，那么由于输出电流过小会引入大量无功，对系统来说不仅效率降低而且有损器件的使用寿命。
具体的，在Burst模式下，谐振变换器102定频在谐振频率fs开环工作，利用逆变母线电容存储能量；当PV电压低于第一阈值时，由DC/DC变换器101进行光伏发电最大功率点跟踪；当PV电压高于第二阈值时，DC/DC变换器101旁路，由谐振变换器102将能量传输给逆变母线电容。DC/AC变换器103采用并网电流单环控制策略，PV能量经过N个工频周期给逆变母线电容充电，达到DC/AC变换器103启动条件后经过DC/AC变换器103经能量传输至电网。
最后需要说明的是，本实施例所公开的微型光伏逆变器控制方法在进行逻辑判断时，优选滞环比较方法。例如，在Burst模式下，所述第二阈值的取值优选大于所述第一阈值，以避免DC/DC变换器101在临界点处频繁切换工作状态。
参见图3，本申请实施例公开了一种微型光伏逆变器，以提高系统整体效率、降低产品体积，包括：级联电路100和系统控制器200；
其中，级联电路100包括前级的DC/DC变换器101、中间级的谐振变换器102和后级的DC/AC变换器103；
系统控制器200与级联电路100相连，用于对级联电路100进行采样，并进行相应的控制，具体的，用于判断逆变母线上是否存在电压冲击；当判断得到逆变母线上存在电压冲击时，进入模式1，并在逆变母线电压Vdc达到目标值时启动DC/AC变换器103以稳定逆变母线电压Vdc，此时：若是PV电压达 到光伏发电最大功率的预估点时，谐振变换器102的开关频率f102仍未达到谐振频率fs，则维持谐振变换器102当前的开关频率f102不变，之后进入模式3；若是谐振变换器102的开关频率f102达到谐振频率fs时，PV电压仍未达到光伏发电最大功率的预估点，则进入模式4；在判断得到逆变母线上不存在电压冲击时，将谐振变换器102定频到谐振频率fs启动，同时启动DC/DC变换器101进行变压工作，待逆变母线电压Vdc达到目标值时启动DC/AC变换器101以稳定逆变母线电压Vdc，之后进入模式2；以及在所述微型光伏逆变器进入稳态后，以实时进行光伏发电最大功率点跟踪、谐振变换器102定频在谐振频率，以及逆变母线电压不脱离调制范围为目标状态，合理调节所述微型光伏逆变器的工作模式；
其中，模式1为：DC/DC变换器101直通，谐振变换器102降频缓起；
模式2为：DC/DC变换器101直通，谐振变换器102定频在谐振频率，DC/AC变换器103双环并网并进行光伏发电最大功率点跟踪；其中，所谓DC/AC变换器103双环并网，是指逆变母线电压外环和逆变电感电流内环的双闭环策略；
模式3为：DC/DC变换器101直通，谐振变换器102降频并进行光伏发电最大功率点跟踪，DC/AC变换器103双环并网；
模式4为：DC/DC变换器101进行光伏发电最大功率点跟踪，谐振变换器102定频在谐振频率，DC/AC变换器103双环并网。
其中，系统控制器200为在所述微型光伏逆变器进入稳态后，在模式3下，当谐振变换器102的开关频率降至谐振频率时，切换为模式2；在模式4下，当Vdcmin/A≤PV电压≤Vdcmax/A时，进入模式2；在模式2下，当PV电压>Vdcmax/A时，进入模式3；当PV电压<Vdcmin/A时，进入模式4的控制器；
其中，Vdcmin表示满足调制的最小逆变母线电压；Vdcmax表示满足调制的最大逆变母线电压；A表示谐振变换器102的升压比。
作为优选，系统控制器200也可以为在模式1、模式2、模式3或模式4下，当检测到PV功率低于预设值时，进入Burst模式，直至PV功率不低于所述预设值时才切换回原工作模式的控制器。
其中，DC/DC变换器101可选择Boost电路、Buck电路或Buck-Boost电路；谐振变换器102的谐振桥臂可选择全桥或半桥，谐振腔可选择LC、LLC、LCC或者其它类型的结构；DC/AC变换器103优选高效、小体积的多电平逆变拓扑，如五电平逆变拓扑等。级联电路100的相数、电平数可根据实际需要进行调整，支持多路PV输入，多相电网输出。
综上所述，在硬件结构上，本申请使用谐振变换器取代了反激变压器，首先从体积和效率上都获得了提升，而且DC/DC变换器和DC/AC变换器在效率和体积上也都有很大的优化空间，从而通过选用优化的DC/DC变换器和DC/AC变换器，与谐振变换器一起构成高效、小体积的三级拓扑结构微型光伏逆变器，非常有利于产品的发展；在软件控制上，本申请对所述三级拓扑结构分级分阶段控制，保证了系统启动基本无冲击、稳态运行稳定，且能够最大化利用光伏能量。
本说明书中各个实施例采用递进的方式描述，每个实施例重点说明的都是与其他实施例的不同之处，各个实施例之间相同相似部分互相参见即可。对于实施例公开的微型光伏逆变器而言，由于其与实施例公开的方法相对应，所以描述的比较简单，相关之处参见方法部分说明即可。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本申请。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本申请实施例的精神或范围的情况下，在其它实施例中实现。因此，本申请实施例将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (10)

  1. 一种微型光伏逆变器控制方法，其特征在于，应用于采用三级拓扑结构的微型光伏逆变器，包括前级的DC/DC变换器、中间级的谐振变换器和后级的DC/AC变换器，所述方法包括：
    判断逆变母线上是否存在电压冲击；
    当判断得到逆变母线上存在电压冲击时，进入模式1，并在逆变母线电压达到目标值时启动所述DC/AC变换器以稳定逆变母线电压，此时：若是PV电压达到光伏发电最大功率的预估点时，所述谐振变换器的开关频率仍未达到谐振频率，则维持所述谐振变换器当前的开关频率不变，之后进入模式3；若是所述谐振变换器的开关频率达到谐振频率时，PV电压仍未达到光伏发电最大功率的预估点，则进入模式4；
    在判断得到逆变母线上不存在电压冲击时，将所述谐振变换器定频到谐振频率启动，同时启动所述DC/DC变换器进行变压工作，待逆变母线电压达到目标值时启动所述DC/AC变换器以稳定逆变母线电压，之后进入模式2；
    在所述微型光伏逆变器进入稳态后，以实时进行光伏发电最大功率点跟踪、所述谐振变换器定频在谐振频率，以及逆变母线电压不脱离调制范围作为目标状态，合理调节所述微型光伏逆变器的工作模式；
    其中，模式1为：所述DC/DC变换器直通，所述谐振变换器降频缓起；
    模式2为：所述DC/DC变换器直通，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网并进行光伏发电最大功率点跟踪；
    模式3为：所述DC/DC变换器直通，所述谐振变换器降频并进行光伏发电最大功率点跟踪，所述DC/AC变换器双环并网；
    模式4为：所述DC/DC变换器进行光伏发电最大功率点跟踪，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网。
  2. 根据权利要求1所述的方法，其特征在于，所述以实时进行光伏发电最大功率点跟踪、所述谐振变换器定频在谐振频率，以及逆变母线电压不脱离调制范围作为目标状态，合理调节所述微型光伏逆变器的工作模式，包括：
    在模式3下：当所述谐振变换器的开关频率降至谐振频率时，切换为模式 2；
    在模式4下：当Vdcmin/A≤PV电压≤Vdcmax/A时，进入模式2；
    在模式2下：当PV电压>Vdcmax/A时，进入模式3；当PV电压<Vdcmin/A时，进入模式4；
    其中，Vdcmin表示满足调制的最小逆变母线电压；Vdcmax表示满足调制的最大逆变母线电压；A表示所述谐振变换器的升压比。
  3. 根据权利要求1或2所述的方法，其特征在于，还包括：
    在模式1、模式2、模式3或模式4下，当检测到PV功率低于预设值时，进入Burst模式，直至PV功率不低于所述预设值时才切换回原工作模式。
  4. 根据权利要求3所述的方法，其特征在于，在所述Burst模式下，所述谐振变换器定频在谐振频率开环工作；所述DC/DC变换器在PV电压低于第一阈值时进行光伏发电最大功率点跟踪，在PV电压高于第二阈值时旁路；所述DC/AC变换器采用并网电流单环控制策略；其中，所述第二阈值大于或等于所述第一阈值。
  5. 一种微型光伏逆变器，其特征在于，包括级联电路和系统控制器，其中：
    所述级联电路包括前级的DC/DC变换器、中间级的谐振变换器以及后级的DC/AC变换器；
    所述系统控制器与所述级联电路相连，用于判断逆变母线上是否存在电压冲击；当判断得到逆变母线上存在电压冲击时，进入模式1，并在逆变母线电压达到目标值时启动所述DC/AC变换器以稳定逆变母线电压，此时：若是PV电压达到光伏发电最大功率的预估点时，所述谐振变换器的开关频率仍未达到谐振频率，则维持所述谐振变换器当前的开关频率不变，之后进入模式3；若是所述谐振变换器的开关频率达到谐振频率时，PV电压仍未达到光伏发电最大功率的预估点，则进入模式4；在判断得到逆变母线上不存在电压冲击时，将所述谐振变换器定频到谐振频率启动，同时启动所述DC/DC变换器进行变压工作，待逆变母线电压达到目标值时启动所述DC/AC变换器以稳定逆变母线电压，之后进入模式2；以及在所述微型光伏逆变器进入稳态后，以实时进行光伏发电最大功率点跟踪、所述谐振变换器定频在谐振频率，以及逆变母线 电压不脱离调制范围为目标状态，合理调节所述微型光伏逆变器的工作模式；
    其中，模式1为：所述DC/DC变换器直通，所述谐振变换器降频缓起；
    模式2为：所述DC/DC变换器直通，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网并进行光伏发电最大功率点跟踪；
    模式3为：所述DC/DC变换器直通，所述谐振变换器降频并进行光伏发电最大功率点跟踪，所述DC/AC变换器双环并网；
    模式4为：所述DC/DC变换器进行光伏发电最大功率点跟踪，所述谐振变换器定频在谐振频率，所述DC/AC变换器双环并网。
  6. 根据权利要求5所述的微型光伏逆变器，其特征在于，所述系统控制器为在所述微型光伏逆变器进入稳态后，在模式3下，当所述谐振变换器的开关频率降至谐振频率时切换为模式2；在模式4下，当Vdcmin/A≤PV电压≤Vdcmax/A时进入模式2；在模式2下，当PV电压>Vdcmax/A时进入模式3，当PV电压<Vdcmin/A时进入模式4的控制器；
    其中，Vdcmin表示满足调制的最小逆变母线电压；Vdcmax表示满足调制的最大逆变母线电压；A表示所述谐振变换器的升压比。
  7. 根据权利要求5或6所述的微型光伏逆变器，其特征在于，所述系统控制器为在模式1、模式2、模式3或模式4下，当检测到PV功率低于预设值时，进入Burst模式，直至PV功率不低于所述预设值时才切换回原工作模式的控制器。
  8. 根据权利要求5所述的微型光伏逆变器，其特征在于，所述DC/DC变换器为Boost电路、Buck电路或Buck-Boost电路。
  9. 根据权利要求5所述的微型光伏逆变器，其特征在于，所述谐振变换器的谐振桥臂可选择全桥或半桥，其谐振腔可选择LC、LLC或LCC结构。
  10. 根据权利要求5所述的微型光伏逆变器，其特征在于，所述DC/AC变换器为五电平逆变拓扑。
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CN113890337A (zh) * 2021-08-25 2022-01-04 杭州中恒电气股份有限公司 光伏直流变换器输出电压控制方法、电子装置及存储介质
CN113890337B (zh) * 2021-08-25 2024-04-30 杭州中恒电气股份有限公司 光伏直流变换器输出电压控制方法、电子装置及存储介质
CN117452078A (zh) * 2023-12-26 2024-01-26 锦浪科技股份有限公司 一种母线电解电容的容值衰减预测方法及光伏系统
CN117452078B (zh) * 2023-12-26 2024-04-05 锦浪科技股份有限公司 一种母线电解电容的容值衰减预测方法及光伏系统
CN117811092A (zh) * 2024-02-29 2024-04-02 锦浪科技股份有限公司 一种基于无线通讯的光伏优化器系统的启动方法
CN117811092B (zh) * 2024-02-29 2024-05-14 锦浪科技股份有限公司 一种基于无线通讯的光伏优化器系统的启动方法

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