WO2012167691A1 - 逆变装置及应用其的太阳能光伏并网系统 - Google Patents

逆变装置及应用其的太阳能光伏并网系统 Download PDF

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Publication number
WO2012167691A1
WO2012167691A1 PCT/CN2012/075848 CN2012075848W WO2012167691A1 WO 2012167691 A1 WO2012167691 A1 WO 2012167691A1 CN 2012075848 W CN2012075848 W CN 2012075848W WO 2012167691 A1 WO2012167691 A1 WO 2012167691A1
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Prior art keywords
voltage
power
inverter
power switch
diode
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PCT/CN2012/075848
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English (en)
French (fr)
Inventor
李泉
Original Assignee
华为技术有限公司
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Publication date
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to AU2012266985A priority Critical patent/AU2012266985B2/en
Priority to EP12796096.1A priority patent/EP2611023A4/en
Publication of WO2012167691A1 publication Critical patent/WO2012167691A1/zh

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Classifications

    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/5388—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with asymmetrical configuration of switches
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • 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
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • 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
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters
    • 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 invention relates to the field of solar photovoltaic power generation technologies, and in particular, to an inverter device and a solar photovoltaic grid-connected system using the same. Background technique
  • the inverter device is a bridge connecting solar photovoltaic power generation with the power grid. It is one of the necessary equipments in the solar photovoltaic power generation grid-connected system, and is used to convert the direct current generated on the solar battery into the alternating current required by the power grid.
  • Fig. 1 shows the structure of a solar photovoltaic power generation grid-connected system used in the prior art.
  • the system includes: a solar panel 11, an inverter 12, a filter circuit 13, a main control unit 14, and a power grid 15.
  • the inverter device 12 includes: a bridge inverter 16 and a booster circuit 17.
  • the bridge inverter 16 shown in Fig. 1 is a two-level three-phase inverter bridge comprising three bridge arms (bridge arm A, bridge arm B and bridge arm C), each of which has the same structure.
  • bridge arm A the power switch tube T is connected in series with the power switch tube T', and the diode D is connected in parallel with the power switch tube T, the diode D' is connected in parallel with the power switch tube T', and the source of the power switch tube T is used for outputting the AC voltage. / current.
  • the AC voltage/current output from the three bridge arms is filtered by the filter circuit and integrated into the grid.
  • the boosting circuit 17 boosts the voltage of the solar panel 11 to provide the bus X with DC power required for the normal operation of the bridge inverter 16 to prevent the voltage of the solar panel 11 from being too low.
  • the transformer 16 does not operate normally, wherein the bus X is a line that supplies a DC voltage to the inverter 16.
  • the main control device 14 is configured to provide a trigger pulse signal to the bridge inverter 16 to control the bridge inverter 16 to output the converted three-phase AC power.
  • the output AC voltage peak value must be smaller than the input DC voltage amplitude, and the input DC voltage.
  • the voltage is provided by the boost circuit, so the output voltage and operating range of the inverter are determined by the DC voltage provided by the boost circuit. Therefore, the power consumption of the boosting circuit in the energy consumption of the entire system is relatively high, and the efficiency of the entire system (the ratio of the output power of the system to the input power) is difficult to increase.
  • Embodiments of the present invention provide an inverter device and a solar photovoltaic grid-connected system using the same, which can significantly reduce the energy consumption of the booster circuit and the switching loss of the inverter under the premise of ensuring normal operation of the inverter.
  • An inverter device includes: a bridge inverter and a booster circuit, the bridge inverter includes at least one bridge arm, and the at least one bridge arm includes: first to third power switch tubes and a first The first diode and the first power switch tube form a supplementary branch, wherein the first diode is forwardly connected in series with the source and drain of the first power switch tube; a current input end of the supplementary branch is electrically connected to a voltage output end of the boosting circuit; a drain of the second power switch tube is electrically connected to a voltage output end of the boosting circuit; and the second power switch a source of the tube, a drain of the third power switch, a current output of the supplemental branch, and an AC output; the AC output is configured to output an AC voltage/current to the grid; a source of the three-power switch is electrically connected to a cathode of the DC power source; a positive pole of the DC power source is electrically connected to a voltage input end of the booster circuit; and the booster circuit is configured to have
  • a solar photovoltaic grid-connected system comprising a solar panel, the above-mentioned inverter device, a filter circuit, a main control device and a power grid; the inverter device is configured to pass the DC power supply provided by the solar panel through the main control The control of the device is converted to an AC power source and the AC power source is delivered to the power grid by filtering of a filter circuit connected between the inverter device and the power grid.
  • the booster circuit and the DC power source can directly directly to the inverter device.
  • the inverter provides DC power, which enables the inverter to operate in a three-level inverter mode, which not only reduces the energy consumption of the booster circuit, but also reduces the switching loss of the inverter, thereby applying the inverter device.
  • it comes to solar photovoltaic grid-connected systems, it can significantly improve the efficiency of the entire system.
  • FIG. 1 is a structural block diagram of a solar photovoltaic power generation grid-connected system used in the prior art
  • FIG. 2 is a circuit diagram of an inverter device according to Embodiment 1 of the present invention
  • 3A is a circuit diagram of a boost circuit in the prior art
  • FIG. 3B is a circuit diagram showing the addition of a bypass unit in the boost circuit shown in FIG. 3A;
  • FIG. 4A to FIG. 4C are point-to-AC voltage output points on the bridge arms of the first embodiment of the present invention at the capacitors C1 and C2; Improvement scheme between circuits;
  • FIG. 5 to FIG. 8 are circuit diagrams of a modified inverter device according to Example 1 of the present invention
  • 9 is a circuit diagram in which the booster circuit, the bypass unit, and the switch unit of FIG. 7 are replaced with specific circuits;
  • FIG. 10 is a block diagram of a solar photovoltaic grid-connected system according to Embodiment 2 of the present invention. Specific form
  • the embodiment provides an inverter device for converting DC power into AC power to provide AC power for loads such as power grids and motors.
  • the inverter device has the following structure.
  • the inverter device includes: a bridge inverter 21 and a booster circuit 22, wherein the bridge inverter includes at least one bridge arm, and the bridge inverter shown in FIG. 2 has three bridge arms, each bridge The arms have the same structure and can output three-phase AC power.
  • the number of bridge arms is not limited thereto, and the number of bridge arms can be increased or decreased according to the demand of the load to obtain the number of phases of the increased or decreased AC power.
  • the structure of the at least one bridge arm will be described below by taking the bridge arm 23 in the broken line frame as an example.
  • the bridge arm 23 includes: first to third power switching tubes (T21, ⁇ 22, and ⁇ 23) and a first diode D21.
  • the first diode D21 and the first power switch T21 form a supplementary branch, wherein the first diode D21 is connected in series with the source and drain of the first power switch T21, that is, As shown in FIG. 2, the source of the first power switch T21 is electrically connected to the anode of the first diode D21 (may also be that the drain of the first power switch is electrically connected to the cathode of the first diode)
  • the current input of the supplemental branch is electrically connected to the voltage output of the booster circuit.
  • the drain of the second power switch T22 is electrically connected to the voltage output of the boost circuit 22
  • the source of the second power switch T22, the drain of the third power switch T23, the current output of the supplemental branch, and the AC output VA are electrically connected; the third power switch
  • the source of T23 is electrically connected to the cathode of the DC power source; the anode of the DC power source is electrically connected to the voltage input terminal of the booster circuit 22.
  • the AC output VA is used to output an AC voltage/current to a power grid (not shown).
  • the boosting circuit 22 is configured to prevent the voltage Vh outputted by the voltage output terminal of the boosting circuit 22 when the voltage Vi of the DC power source is less than the voltage required for the normal operation of the bridge inverter 21 Less than the voltage required for the bridge inverter to operate normally.
  • the first to third power switching transistors may be Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) or insulated gate bipolar transistors (Insulated). Gate Bipolar Transistor, referred to as: IGBT), or Integrated Gate Commutated Thyristors (IGCT), or other controllable switches.
  • IGBT Metal-Oxide-Semiconductor Field-Effect Transistors
  • IGCT Integrated Gate Commutated Thyristors
  • a reverse current path can be provided when the reverse voltage is applied between the drain and the source of the MOSFET.
  • the diode can be reversely connected in parallel between the drain and the source of the MOSFET. To provide a more reliable reverse current path.
  • the second diode D22 is connected in anti-parallel with the source and drain of the first power switching transistor T21;
  • the diode D23 is in anti-parallel with the source and drain of the second power switch T22;
  • the fourth diode D24 is connected in anti-parallel with the source and drain of the third power switch T23.
  • the first diode is connected in series with the source and the drain of the first power switch, and may include the following two connection modes.
  • the anode of the first diode is electrically connected to the source of the first power switch tube (as shown in FIG. 2).
  • the drain of the first power switch T21 and the second diode D22 The cathode is electrically connected; the source of the first power switch T21, the anode of the second diode D22, and the anode of the first diode D21 are electrically connected.
  • the cathode of the first diode is electrically connected to the cathode of the second diode (as shown in Figure 4C).
  • the drain of the first power switch T21, the cathode of the second diode D22, and the cathode of the first diode D21 are electrically connected; the source of the first power switch T21 and the second diode D22
  • the anode is electrically connected.
  • the first diode D21 functions to prevent the first power switch tube T21 connected in series from being subjected to back pressure
  • the position of the first diode D21 is connected to the first as shown in FIG.
  • the source of the power switch T21 or the drain of the first power switch T21 as shown in FIG. 4C can perform the above functions.
  • the booster circuit 22 When the above-mentioned inverter device is used, if the voltage Vi of the DC power source is lower than the voltage required for the normal operation of the bridge inverter 21, the booster circuit 22 operates so that the voltage Vh outputted from the voltage output terminal of the booster circuit 22 is not less than
  • the bridge inverter 21 operates at a voltage required for normal operation, so that the bridge inverter 21 can obtain not only the DC power of the voltage Vi from the DC power source but also the DC power of the voltage Vh from the booster circuit 22.
  • the output potential of the bridge inverter 21 has three levels, that is, Vh, Vi, and 0, so that the bridge inverter 21 Works in a three-level inverter mode.
  • the boost circuit 22 Since the bridge inverter 21 outputs the Vh level (the power switch tube whose drain is electrically connected to the voltage output terminal of the booster circuit, for example, when the second power switch transistor T22 is turned on), the boost circuit 22 is required. When the output power is supplied and the other levels are output, the bridge inverter 21 still directly supplies the output power from the DC power source, so that the power consumption of the booster circuit 22 can be greatly reduced.
  • the voltage Vi of the DC power source is smaller than the voltage required for the bridge inverter 21 to operate normally. At the time, since the bridge inverter 21 operates in the three-level inverter mode, there are advantages such as low switching loss and small output inductor ripple.
  • the DC power source can supply power to the bridge inverter 21, and the boost circuit 22 can be
  • the boost circuit 22 that operates, does not work, is in either of the following two states.
  • the booster circuit 22 is in an open state, and the voltage input terminal and the voltage output terminal are disconnected, and no voltage is output.
  • the booster circuit 22 is in a short-circuit state, the voltage input terminal and the voltage output terminal are short-circuited, and the output voltage Vh is equal to the voltage Vi of the DC power source.
  • the external control circuit can not apply a control pulse to the second power switch tube T22, so that the bridge inverter 21 only supplies the direct current voltage of the voltage Vi to the DC voltage, that is, the bridge inverter
  • the device 21 operates in a two-level inverter mode.
  • Vh is equal to the voltage Vi of the DC power source.
  • the bridge inverter 21 can be placed in any one of the following three operating states.
  • the bridge inverters 21 all operate in a two-level inverter mode.
  • the booster circuit 22 may specifically be a boost circuit (see Fig. 3A), or other circuits having a DC voltage boost function known to those skilled in the art.
  • the boost circuit shown in FIG. 3A includes: an inductor L, a power switch tube T, a diode D, and a capacitor (when the circuit is not operating, that is, when the power switch tube is turned off, the output voltage Vin is equal to the input voltage Vout, which is equivalent to The voltage output is shorted to the voltage input.
  • the voltage input terminal when the voltage is not working, the voltage input terminal is disconnected from the voltage output terminal. If it is required to obtain the same voltage as the voltage input terminal at its voltage output terminal, it can be at the voltage input terminal and voltage of the booster circuit. Parallel connection of a bypass unit between the output terminals for powering the DC power supply When the voltage is not less than the voltage required for the normal operation of the bridge inverter, the voltage input terminal and the voltage output terminal of the booster circuit are short-circuited.
  • FIG. 3B is a structure in which a bypass unit is provided in the boost circuit shown in FIG. 3A, and the same portion of FIG. 3B as that of FIG. 3A has the same reference numeral as that of FIG. 3A, and is connected in parallel with the voltage input terminal and voltage of the boost circuit.
  • the diode D' between the output terminals can be used as a bypass unit.
  • the anode of the diode D' is electrically connected to the voltage input terminal, and the cathode is electrically connected to the voltage output terminal.
  • the bypass unit can also be other than the DC power supply voltage.
  • a circuit or device that shorts the voltage input terminal of the booster circuit to the voltage output terminal such as a transistor, a relay, or a contactor, when the voltage required for the normal operation of the bridge inverter is normal.
  • the booster circuit 22 When the voltage required for normal operation is not working, the booster circuit 22 does not operate. Since the booster circuit 22 does not operate, of course, no power is consumed, thereby reducing the power consumption of the inverter device.
  • the boost circuit 22 is always in the working state, taking the boost circuit shown in FIG. 3A as an example, when the circuit is operated, when the external control circuit controls the power switch tube T to be turned on, the inductor L starts to store energy, and at this time, the capacitor is used.
  • the output voltage V0Ut is supplied to the load, and then the control circuit controls the power switch tube T to turn off, the inductor L releases energy, and charges the capacitor C, so that the output voltage Vout rises.
  • the control circuit controls the power switch tube T to turn off, the inductor L releases energy, and charges the capacitor C, so that the output voltage Vout rises.
  • the voltage of the bus A of the bridge inverter 21 is increased by the operation of the booster circuit 22.
  • the switching loss of the bridge inverter 21 is increased compared to the case where the boosting circuit 22 is not working, but since the Vh>Vi of the boosting circuit 22, the bridge inverter 21 operates at the three powers.
  • the power consumption of the booster circuit and the switching loss of the inverter provided in this embodiment are relatively low compared to the prior art.
  • a fourth power switch tube T24 (shown in FIG. 4A) may be disposed in the bridge arm, and the source and drain of the fourth power switch tube T24 are opposite to the first diode D21.
  • the drain of the fourth power switch T24 is electrically connected to the cathode of the first diode D21, and the source is electrically connected to the anode of the first diode D21, so that when the bridge inverter 21 outputs the Vi level
  • the inductor current in the bridge inverter 21 has a bidirectional channel, so that the bridge inverter 21 can still use the Vi power through the freewheeling of the fourth power switch tube T24 during the negative half cycle of the inverter and the reactive output.
  • the flatness helps to reduce the switching loss of the bridge inverter 21 under the working condition and can reduce the output inductor ripple.
  • FIG. 4A, FIG. 4B and FIG. 4C are diagrams showing an improvement of the circuit between the positive pole of the DC power source and the AC voltage output point of one of the bridge arms (bridge arms 23) of the bridge inverter 21 shown in FIG. 2, FIG. 4A, FIG. 4B and FIG. 4C, the same portions as those of FIG. 2 follow the reference numerals of FIG. 2, and the fourth power switch tube T24 connected in parallel across the first diode D21 in FIG. 4A is the inductor current in the bridge inverter. A freewheeling path is provided.
  • the freewheeling path can also be provided for the inductor current in the bridge inverter through the circuit shown in Figure 4B.
  • a freewheeling branch (circuit in the dotted line) may be connected in parallel to the supplementary branch formed by the first power switch T21, the first diode D21 and the second diode D22.
  • the freewheeling branch includes a fifth power switch transistor 25 and a fifth diode D25; a source of the fifth power switch transistor 25 is electrically connected to a current input terminal of the supplemental branch; and the fifth power switch transistor 25 The drain is electrically connected to the cathode of the fifth diode D25; the anode of the fifth diode D25 is electrically connected to the current output of the supplemental branch.
  • the fourth and fifth power switch tubes may be MOSFETs, IGBTs, or IGCTs, or other controllable switches.
  • a diode the sixth diode D26 in FIG. 4B
  • Reverse current through when the reverse voltage is applied between the poles Road Since the drain and source of the MOSFET form a parasitic diode, a reverse current path can be provided when the reverse voltage is applied between the drain and the source of the MOSFET.
  • the diode can be reversely connected in parallel between the drain and the source of the MOSFET. To provide a more reliable reverse current path.
  • FIG. 4C The structure of another freewheeling path is as shown in FIG. 4C, which is similar to the structure of FIG. 4A, except that the cathode of the first diode D21 is electrically connected to the drain of the first power switch T21, so that The fourth power switch tube T24 of the freewheeling is interchanged with the position of the first power switch tube T21.
  • the first diode D21 can be electrically connected to the drain of the first power switch T21 by a cathode, or can be electrically connected to the source of the first power switch T21 by an anode.
  • the protection of the first power switch tube T21 by a diode D21 can function as a freewheeling.
  • the structure of the freewheeling path is not limited to the above three types, and may be another circuit capable of freewheeling the inductor current in the inverter known to those skilled in the art.
  • the inverter device may have the structure shown in Fig. 5, and the same portions as those of Fig. 2 in Fig. 5 are denoted by the same reference numerals as those in Fig. 2.
  • the inverter device shown in FIG. 5 is different from the inverter device shown in FIG.
  • a bypass unit X is connected in parallel between a voltage input terminal and a voltage output terminal of the boosting circuit; a first capacitor C1 is added, a second capacitor C2 and a switch unit K, wherein one end of the first capacitor C1 is electrically connected to a voltage output end of the booster circuit 22; the other end of the first capacitor C1, an output end of the switch unit ⁇ , and One end of the second capacitor C2 is electrically connected; the input end of the switch unit ⁇ is electrically connected to the voltage input end of the booster circuit 22; the other end of the second capacitor C2 is electrically connected to the negative pole of the DC power source connection.
  • the switch unit ⁇ is configured to: when the voltage Vi of the DC power source is less than a voltage required for the normal operation of the bridge inverter 21, the drain of the first power switch tube T21 and the DC power source The positive electrode is electrically connected; otherwise, the electrical connection between the drain of the first power switch T21 and the positive terminal of the DC power source is disconnected.
  • the switching unit K can be specifically a transistor such as a MOSFET, an IGBT, a thyristor, a reverse blocking IGBT having a reverse blocking capability, or a common IGBT and a diode
  • the series combination, or other controllable transistors, etc., the switching unit ⁇ can also be realized by mechanical switches such as contactors and relays.
  • the bypass unit X is configured to short-circuit the voltage input terminal and the voltage output terminal of the booster circuit 22 when the voltage Vi of the DC power source is not less than the voltage required for the normal operation of the bridge inverter 21, so that the voltage output terminal The output voltage Vh is equal to Vi.
  • the bypass unit X may be the diode shown in Fig. 3B or other circuit configuration.
  • the inverter unit shown in FIG. 5 can save the bypass unit X.
  • the boost circuit is operated by an external control circuit to make the output voltage Vh. Not less than the voltage required for the normal operation of the bridge inverter 21, and the switch unit K is controlled by an external control circuit to electrically connect the drain of the first power switch tube with the positive electrode of the DC power source, and then the second capacitor C2 The voltage is equal to the voltage Vi of the DC power source, so that the bridge inverter 21 can obtain not only the DC power of the voltage Vi from the DC power source but also the DC power of the voltage Vh from the booster circuit 22.
  • the output potential of the bridge inverter 21 has three levels, that is, Vh, Vi, and 0, so that the bridge inverter 21 Works in a three-level inverter mode.
  • the boost circuit 22 Since the bridge inverter 21 outputs the Vh level (the power switch tube whose drain is electrically connected to the voltage output terminal of the booster circuit, for example, when the second power switch transistor T22 is turned on), the boost circuit 22 is required. When the output power is supplied and the other levels are output, the inverter circuit still directly supplies the output power from the DC power source, so the power consumption of the booster circuit 22 can be greatly reduced.
  • the switching unit K is controlled by an external control circuit to make the drain and DC power of the first power switch tube The electrical connection between the positive poles is disconnected, while the control boost voltage is not working, and the bypass device is turned on, then Vh is equal to Vi. At this time, the first capacitor C1 and the second capacitor C2 divide Vh to make the bridge inverter 21 operate according to the conventional T-symmetric three-level inverter mode.
  • the inverter device shown in FIG. 5 since the booster circuit and the DC power source can directly supply DC power to the inverter at the same time when the voltage of the DC power source is low, the inverter operates in the three-level inverter mode. Not only can reduce the energy consumption of the booster circuit, but also reduce the switching loss of the inverter. In addition, when the voltage of the DC power source is high, not only the booster circuit does not consume power, but also the inverter can still operate in the three-level inverter mode due to the voltage division of the capacitor, compared to the inverter shown in FIG. The device can further reduce the energy consumption of the inverter device, so that when the inverter device is applied to the solar photovoltaic grid-connected system, the efficiency of the entire system can be significantly improved.
  • the improvement scheme shown in FIG. 4A to FIG. 4C can also be used to provide a freewheeling path for the inductor current in the bridge inverter 21 to reduce the bridge inverter 21.
  • the inductor ripple is output, and the switching loss is further reduced.
  • the specific circuit is shown in FIG. 6 to FIG. 8. The same portions as those in FIG. 5 and FIG. 4A to FIG. 4C in FIG. 6 to FIG. 8 are used in FIG. 5 and FIG. 4A to FIG. Reference mark.
  • the booster circuit and the bypass unit in FIG. 7 are replaced by the circuit shown in FIG. 3B, and the switching unit in FIG. 7 is replaced with the power switch tube Tk, and the circuit diagram shown in FIG. 9 is formed.
  • the same portions as those of Fig. 7 follow the reference numerals in Fig. 7.
  • the embodiment provides a solar photovoltaic grid-connected system.
  • the system includes: a solar panel 101, an inverter device 102 provided in Embodiment 1, a filter circuit 103, a main control device 104, and a power grid 105.
  • the inverter device 102 is configured to convert the DC power supply provided by the solar panel 101 into AC power through the control of the main control device 10, and is connected between the inverter device 102 and the power grid 105. Filtering of the filter circuit 103, the AC power source It is delivered to the grid 105.
  • the specific circuit structure and working principle of the inverter device 102 have been described in detail in Embodiment 1, and details are not described herein again.
  • the efficiency of the solar photovoltaic grid-connected system can be significantly improved.

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Abstract

一种逆变装置以及太阳能光伏并网系统，该逆变装置包括升压电路（22）和桥式逆变器（21），桥式逆变器包括一补充支路，该补充支路包括第一功率开关管（T21）及第一二极管（D21），第一二极管（D21）和第一功率开关管（T21）的源漏极正向串联，补充支路的电流输入端与升压电路的电压输出端电连接，补充支路的电流输出端与交流输出端（VA）电连接。在直流电源电压（Vi）较低时，升压电路和直流电源可同时向逆变电路提供直流电能，使逆变器以三电平方式工作，提高系统的效率。

Description

逆变装置及应用其的太阳能光伏并网系统
技术领域 本发明涉及太阳能光伏发电技术领域， 尤其涉及逆变装置及应用其的 太阳能光伏并网系统。 背景技术
随着常规能源枯竭、 环境问题日益严重， 太阳能光伏发电作为一项新 兴清洁能源产业， 发展十分迅速， 每年以 30%的增幅增长。
逆变装置是太阳能光伏发电与电网连接的桥梁， 是太阳能光伏发电并 网系统中必备的设备之一， 用于将太阳能电池上产生的直流电转换为电网 所需的交流电。
图 1示出了现有技术使用的太阳能光伏发电并网系统的结构。 该系统包 括： 太阳能电池板 11、 逆变装置 12、 滤波电路 13、 主控装置 14及电网 15。 其中， 逆变装置 12包括： 桥式逆变器 16及升压电路 17。
图 1所示的桥式逆变器 16为二电平三相逆变桥， 包括三个桥臂（桥臂 A、 桥臂 B及桥臂 C) ， 每个桥臂具有相同的结构。 桥臂 A中： 功率开关管 T与功 率开关管 T' 串联， 且二极管 D与功率开关管 T并联， 二极管 D' 与功率开关 管 T' 并联， 功率开关管 T的源极用于输出交流电压 /电流。 三个桥臂输出的 交流电压 /电流经滤波电路滤波后并入电网。
升压电路 17将太阳能电池板 11的电压提升后，为母线 X提供桥式逆变器 16正常工作时所需电压的直流电能， 用于防止太阳能电池板 11的电压过低 时， 桥式逆变器 16无法正常工作， 其中， 母线 X是为逆变器 16提供直流电压 的线路。 主控装置 14用于向桥式逆变器 16提供触发脉冲信号， 以控制桥式 逆变器 16输出变换后的三相交流电能。 在使用上述太阳能光伏发电并网系统进行发电的过程中， 由于二电平 三相逆变器具有降压控制功能， 其输出的交流电压峰值必须小于输入其的 直流电压幅值， 而输入的直流电压由升压电路来提供， 因此， 逆变器的输 出电压和工作范围由升压电路所提供的直流电压来决定。 从而， 使得整个 系统的能耗中升压电路能耗占的比例较高， 导致整个系统的效率 （系统的 输出功率与输入功率之比） 难以提高。
另外， 在太阳能电池板的电压较高时， 由于升压电路的存在， 使得逆 变器的母线电压升高， 从而使得逆变器的开关损耗增加， 导致整个系统的 效率进一步降低。 发明内容
本发明的实施例提供一种逆变装置及应用其的太阳能光伏并网系统， 能在保证逆变器正常工作的前提下， 显著减小升压电路的能耗及逆变器的 开关损耗。
为达到上述目的， 本发明的实施例采用如下技术方案：
一种逆变装置， 包括： 桥式逆变器及升压电路， 所述桥式逆变器包括 至少一个桥臂， 所述至少一个桥臂包括： 第一至第三功率开关管及第一二 极管； 所述第一二极管及所述第一功率开关管构成补充支路， 其中， 所述 第一二极管与所述第一功率开关管的源漏极正向串联； 所述补充支路的电 流输入端与所述升压电路的电压输出端电连接； 所述第二功率开关管的漏 极与所述升压电路的电压输出端电连接； 所述第二功率开关管的源极、 所 述第三功率开关管的漏极、 所述补充支路的电流输出端及交流输出端电连 接； 所述交流输出端用于向电网输出交流电压 /电流； 所述第三功率开关管 的源极与直流电源的负极电连接； 所述直流电源的正极与所述升压电路的 电压输入端电连接； 所述升压电路， 用于在所述直流电源的电压小于所述 桥式逆变器正常工作所需的电压时， 使所述升压电路的电压输出端输出的 电压不小于所述桥式逆变器正常工作所需的电压。
一种太阳能光伏并网系统， 包括太阳能电池板、 上述的逆变装置、 滤 波电路、 主控装置及电网； 所述逆变装置用于将所述太阳能电池板提供的 直流电源通过所述主控装置的控制转换为交流电源， 并通过连接在所述逆 变装置及所述电网之间的滤波电路的滤波， 将所述交流电源输送至所述电 网。
本发明实施例提供的逆变装置及应用其的太阳能光伏并网系统中， 由 于在给逆变装置供电的直流电源的电压较低时， 升压电路和直流电源可以 同时直接向该逆变装置中的逆变器提供直流电能， 使得逆变器工作在三电 平逆变方式， 不仅能降低升压电路的能耗， 还能降低逆变器的开关损耗， 从而在将该逆变装置应用到太阳能光伏并网系统中时， 能显著提高整个系 统的效率。 附图说明
为了更清楚地说明本发明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发明的一些实施例， 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， 还可以根据这些附图获得其他的附 图。
图 1为现有技术使用的太阳能光伏发电并网系统的结构框图； 图 2为本发明实施例 1提供的一种逆变装置的电路图；
图 3 A为现有技术中 boost电路的电路图；
图 3B为在图 3A所示的 boost电路中增加了旁路单元的电路图； 图 4A〜图 4C为本发明实施例 1中一个桥臂上的、 位于电容 C1和 C2 中点至交流电压输出点之间电路的改进方案；
图 5〜图 8为本发明实例 1提供的变形的逆变装置电路图； 图 9为将图 7中的升压电路、 旁路单元及开关单元用具体电路替换后 的电路图；
图 10为本发明实施例 2提供的太阳能光伏并网系统的方框图。 具体实 式
下面将结合本发明实施例中的附图， 对本发明实施例中的技术方 案进行清楚、 完整地描述， 显然， 所描述的实施例仅仅是本发明一部分实 施例， 而不是全部的实施例。 基于本发明中的实施例， 本领域普通技术人 员在没有作出创造性劳动的前提下所获得的所有其他实施例， 都属于本发 明保护的范围。
实施例 1
本实施例提供一种逆变装置， 用于将直流电能转换为交流电能， 以便 为电网、 电机等负载提供交流电能。 如图 2所示， 该逆变装置具有如下结 构。
逆变装置包括： 桥式逆变器 21及升压电路 22， 其中， 所述桥式逆变器 包括至少一个桥臂， 图 2示出的桥式逆变器具有三个桥臂， 每个桥臂具有 相同的结构， 能输出三相交流电能， 当然桥臂的个数并不限于此， 可根据 负载的需求增加或减少桥臂的个数， 以获得增加或减少的交流电能的相数。 下面以图中虚线框中的桥臂 23为例， 介绍所述至少一个桥臂的结构。
桥臂 23包括： 第一至第三功率开关管（T21、 Τ22及 Τ23 )及第一二极 管 D21。 所述第一二极管 D21及所述第一功率开关管 T21构成补充支路， 其中，所述第一二极管 D21与所述第一功率开关管 T21的源漏极正向串联， 即如图 2所示第一功率开关管 T21的源极与所述第一二极管 D21的阳极电 连接 （也可以是第一功率开关管的漏极与第一二极管的阴极电连接）； 所述 补充支路的电流输入端与所述升压电路的电压输出端电连接。
所述第二功率开关管 T22的漏极与所述升压电路 22的电压输出端电连 接； 所述第二功率开关管 T22的源极、 所述第三功率开关管 T23的漏极、 所述补充支路的电流输出端及交流输出端 VA电连接；所述第三功率开关管 T23的源极与直流电源的负极电连接；所述直流电源的正极与所述升压电路 22的电压输入端电连接。
所述交流输出端 VA用于向电网 （图中未示出） 输出交流电压 /电流。 所述升压电路 22，用于在所述直流电源的电压 Vi小于所述桥式逆变器 21 正常工作所需的电压时， 使所述升压电路 22 的电压输出端输出的电压 Vh不小于所述桥式逆变器正常工作所需的电压。
上述逆变装置中， 第一至第三功率开关管可以是金属氧化物场效应晶 体管（ Metal-Oxide-Semiconductor Field-Effect Transistor,简称为： MOSFET )， 也可以是绝缘栅双极型晶体管 （Insulated Gate Bipolar Transistor, 简称为： IGBT),或者为集成门极换流晶闸管（Intergrated Gate Commutated Thyristors， 简称为： IGCT) , 或者为其它可控开关管。 当第一至第三功率开关管采用 IGBT或 IGCT时， 优选在第一至第三功率开关管的源漏极反向并联一个二 极管， 以在功率开关管的漏极与源极间承受反向电压时提供反向电流通路。 由于 MOSFET的漏极与源极形成有寄生二极管，可在 MOSFET的漏极与源 极间承受反向电压时提供反向电流通路， 当然也可以在 MOSFET的漏极与 源极间反向并联二极管， 以提供更加可靠的反向电流通路。
图 2示出了第一至第三功率开关管的源漏极分别与二极管反向并联的 情形： 第二二极管 D22与第一功率开关管 T21的源漏极反向并联； 第三二 极管 D23与第二功率开关管 T22的源漏极反向并联； 第四二极管 D24与第 三功率开关管 T23的源漏极反向并联。
上述逆变装置中， 所述第一二极管与所述第一功率开关管的源漏极正 向串联， 可以包括以下两种连接方式。
1、第一二极管的阳极与第一功率开关管的的源极电连接 (如图 2所示）。 相应地， 参见图 2， 第一功率开关管 T21的漏极与第二二极管 D22的 阴极电连接； 第一功率开关管 T21的源极、 第二二极管 D22的阳极及第一 二极管 D21的阳极电连接。
2、 第一二极管的阴极与第二二极管的阴极电连接 （如图 4C所示）。 相应地， 第一功率开关管 T21的漏极、 第二二极管 D22的阴极及第一 二极管 D21的阴极电连接； 第一功率开关管 T21的源极与第二二极管 D22 的阳极电连接。
图 2中， 由于第一二极管 D21的作用是防止与其相串联的第一功率开 关管 T21承受反压， 因此， 不管第一二极管 D21的位置是如图 2所示连接 在第一功率开关管 T21 的源极， 还是如图 4C连接在第一功率开关管 T21 的漏极， 都可以起到上述作用。
在使用上述逆变装置时， 如果直流电源的电压 Vi小于桥式逆变器 21 正常工作所需的电压， 则升压电路 22工作， 使升压电路 22的电压输出端 输出的电压 Vh不小于桥式逆变器 21正常工作所需的电压， 从而使得桥式 逆变器 21不仅从直流电源获得电压为 Vi的直流电能， 还能从升压电路 22 获得电压为 Vh的直流电能。 此时， 通过外部的控制电路给桥式逆变器 21 施加控制脉冲， 则桥式逆变器 21的输出电位会存在 3个电平， 即 Vh、 Vi 及 0， 使得桥式逆变器 21按照三电平逆变方式工作。
由于仅当桥式逆变器 21输出 Vh电平时 （漏极与升压电路的电压输出 端电连接的功率开关管， 如第二功率开关管 T22导通时）， 才需要由升压电 路 22提供输出功率， 输出其它电平时， 桥式逆变器 21仍然由直流电源直 接提供输出功率， 因此能大大降低升压电路 22的能耗。 实验证明， 当需要 向负载提供 30KW的交流电能时， 如果用传统的仅由升压电路提供直流电 能的逆变装置， 则升压电路需要提供超过 30KW的直流电能， 而如果用本 实施例提供的逆变装置， 则升压电路只需要提供 5KW左右的直流电能， 其 余的直流电能都由直流电源来提供。
另外， 在直流电源的电压 Vi小于桥式逆变器 21正常工作所需的电压 时， 由于桥式逆变器 21工作于三电平逆变方式， 因此存在开关损耗低、 输 出电感纹波小等优点。
当直流电源的电压 Vi不小于 （即大于或等于） 桥式逆变器 21正常工 作所需的电压时， 可以由直流电源向桥式逆变器 21提供电能， 此时升压电 路 22可以不工作，不工作的升压电路 22处于以下两种状态中的任意一种。
1、 升压电路 22处于断路状态， 电压输入端及电压输出端断开， 不输 出电压。
2、 升压电路 22处于短路状态， 电压输入端及电压输出端短接， 输出 电压 Vh等于直流电源的电压 Vi。
当升压电路 22断路时， 可使外部的控制电路不给第二功率开关管 T22 施加控制脉冲， 使得桥式逆变器 21仅由直流电压提供电压为 Vi的直流电 會^ 即桥式逆变器 21工作在二电平逆变方式。
当升压电路 22短路时， Vh等于直流电源的电压 Vi， 通过改变控制脉 冲的控制逻辑，可使得桥式逆变器 21处于以下三种工作状态中的任意一种， 这三种工作状态中桥式逆变器 21都以二电平逆变方式工作。
1、 所有的功率开关管都工作；
2、 除第二功率开关管 T22外的所有的功率开关管都工作；
3、 除第一功率开关管 T21外的所有的功率开关管都工作。
所述的升压电路 22具体可以是 boost电路 （参见图 3A) , 也可以是本 领域技术人员所知的其它具有直流电压升压功能的电路。
图 3A所示的 boost电路包括： 电感 L、 功率开关管 T、 二极管 D及电 容( 。 该电路不工作时， 即功率开关管 Τ关断时， 输出电压 Vin与输入电 压相等 Vout, 相当于将电压输出端与电压输入端短接。
对于有些升压电路， 其不工作时， 电压输入端会与电压输出端断开， 如果需要在其电压输出端获得与电压输入端相同的电压时， 可以在升压电 路的电压输入端与电压输出端间并联一个旁路单元， 用于在直流电源的电 压不小于桥式逆变器正常工作所需的电压时， 将升压电路的电压输入端及 电压输出端短接。
图 3B为在图 3A所示的 boost电路中设置旁路单元的结构，图 3B中的、 与图 3A相同的部分具有与图 3A相同的附图标记， 并联在 boost电路的电 压输入端与电压输出端之间的二极管 D' 可作为旁路单元， 二极管 D' 的 阳极与电压输入端电连接， 阴极与电压输出端电连接， 当然， 旁路单元也 可以为其它能在直流电源电压不小于桥式逆变器正常工作所需的电压时， 将升压电路的电压输入端与电压输出端短接的电路或器件， 如晶体管、 继 电器， 或者接触器等开关器件。
以上描述了当直流电源的电压 Vi不小于 （即大于或等于） 桥式逆变器
21正常工作所需的电压时， 升压电路 22不工作的情况， 由于升压电路 22 不工作， 当然不会消耗电能， 因此降低了逆变装置的能耗。
如果使升压电路 22始终处于工作状态，以图 3A所示的 boost电路为例， 该电路工作时， 外部的控制电路控制功率开关管 T导通时， 电感 L开始储 存能量， 此时由电容向负载提供输出电压 V0Ut， 随后控制电路控制功率开 关管 T关断， 电感 L释放能量， 给电容 C充电， 使得输出电压 Vout升高。 通过控制功率开关管 T的开关频率， 可控制输出电压 Vout的大小。 则当直 流电源的电压 Vi不小于 （即大于或等于） 桥式逆变器 21正常工作所需的 电压时， 桥式逆变器 21的母线 A的电压会因升压电路 22的工作而提高， 会使得桥式逆变器 21 的开关损耗相比于升压电路 22不工作的情况有所增 力口，但由于升压电路 22的 Vh>Vi，桥式逆变器 21工作于三电平逆变状态， 本实施例提供的升压电路的能耗及逆变器的开关损耗相比于现有技术还是 比较低的。
本实施例中， 由于在直流电源的电压较低时， 升压电路和直流电源可 以同时直接向逆变器提供直流电能， 使得逆变器工作在三电平逆变方式， 不仅能降低升压电路的能耗， 还能降低逆变器的开关损耗， 从而在将该逆 变装置应用到太阳能光伏并网系统中时， 能显著提高整个系统的效率。 上述的逆变装置中，还可以在桥臂中设置一个第四功率开关管 T24 (如 图 4A所示）， 该第四功率开关管 T24的源漏极与第一二极管 D21的反向并 联， 即第四功率开关管 T24的漏极与第一二极管 D21的阴极电连接,源极与 第一二极管 D21的阳极电连接， 使得当桥式逆变器 21输出 Vi电平时， 桥 式逆变器 21 中的电感电流存在双向通道， 这样桥式逆变器 21在逆变负半 周时及无功输出时，通过第四功率开关管 T24的续流，仍然可使用 Vi电平， 有助于降低该工作状况下的桥式逆变器 21的开关损耗， 并能减小输出电感 纹波。
图 4A、 图 4B及图 4C为图 2所示的桥式逆变器 21的一个桥臂 （桥臂 23 ) 中直流电源正极与交流电压输出点之间的电路的改进方案， 图 4A、 图 4B及图 4C中的、与图 2相同的部分沿用了图 2的附图标记， 图 4A中并联 在第一二极管 D21两端的第四功率开关管 T24为桥式逆变器中电感电流提 供了续流通路。
当然，还可以通过图 4B所示的电路为桥式逆变器中电感电流提供续流 通路。如图 4B所示， 可以在由第一功率开关管 T21、 第一二极管 D21及第 二二极管 D22构成的补充支路旁并联一条续流支路（虚线框中的电路）， 该 续流支路包括第五功率开关管 Τ25及第五二极管 D25; 所述第五功率开关 管 Τ25 的源极与补充支路的电流输入端电连接； 所述第五功率开关管 Τ25 的漏极与所述第五二极管 D25的阴极电连接； 所述第五二极管 D25的阳极 与补充支路的电流输出端电连接。
上述第四及第五功率开关管可以 MOSFET, 也可以是 IGBT, 或者为 IGCT, 或是其它可控开关管。 当第五功率开关管 T25采用 IGBT或 IGCT 时， 优选在其源漏极反向并联一个二极管 （图 4B中的第六二极管 D26) , 以在第五功率开关管 T25 的漏极与源极间承受反向电压时提供反向电流通 路。由于 MOSFET的漏极与源极形成有寄生二极管，可在 MOSFET的漏极 与源极间承受反向电压时提供反向电流通路， 当然也可以在 MOSFET的漏 极与源极间反向并联二极管， 以提供更加可靠的反向电流通路。
另一种续流通路的结构如图 4C所示， 该结构与图 4A的结构类似， 不 同之处在于第一二极管 D21的阴极与第一功率开关管 T21的漏极电连接， 使得起续流作用的第四功率开关管 T24与第一功率开关管 T21的位置互换。 前面已经描述过:第一二极管 D21既可以以阴极电连接第一功率开关管 T21 的漏极， 也可以以阳极电连接第一功率开关管 T21 的源极， 任何位置都不 会影响第一二极管 D21对第一功率开关管 T21 的保护作用。 因此， 图 4C 所示的电路结构一样能起到续流的作用。
续流通路的结构并不限于上述三种， 也可以是本领域技术人员所知的 其它能续流逆变器中电感电流的电路。 逆变装置还可以具有图 5所示的结构， 图 5中的、 与图 2相同的部分 采用与图 2相同的附图标记。 图 5所示的逆变装置与图 2所示的逆变装置 的不同之处在于： 升压电路的电压输入端与电压输出端之间并联了旁路单 元 X； 增加了第一电容 Cl、 第二电容 C2及开关单元 K， 所述第一电容 C1 的一端与所述升压电路 22的电压输出端电连接； 所述第一电容 C1的另一 端、所述开关单元 Κ的输出端及所述第二电容 C2的一端电连接；所述开关 单元 Κ的输入端与所述升压电路 22的电压输入端电连接； 所述第二电容 C2的另一端与所述直流电源的负极电连接。
其中，开关单元 Κ用于在所述直流电源的电压 Vi小于所述桥式逆变器 21正常工作所需的电压时， 将所述第一功率开关管 T21的漏极与所述直流 电源的正极电连接； 否则使所述第一功率开关管 T21 的漏极与所述直流电 源的正极之间的电连接断开。开关单元 K可以具体为晶体管，如 M0SFET、 IGBT、 晶闸管、 具备反向阻断能力的逆阻型 IGBT、 或普通 IGBT与二极管 的串联组合、 或其他可控晶体管等， 开关单元 κ也可为接触器、 继电器等 机械开关来实现。
旁路单元 X用于在直流电源的电压 Vi不小于所述桥式逆变器 21正常 工作所需的电压时， 将升压电路 22的电压输入端及电压输出端短接， 使电 压输出端输出的电压 Vh等于 Vi。 旁路单元 X可以为图 3B所示的二极管， 也可以是其它电路结构。
如果升压电路 22能在直流电源的电压 Vi不小于所述桥式逆变器 21正 常工作所需的电压时， 将电压输入端及电压输出端短接（例如图 3A所示的 boost电路在不工作时， Vh=Vi)， 则图 5所示的逆变装置可以省去旁路单元 X。
在使用图 5所示的逆变装置时， 当直流电源的电压 Vi小于桥式逆变器 21 正常工作所需的电压， 则通过外部的控制电路使升压电路开始工作， 以 使输出电压 Vh不小于桥式逆变器 21正常工作所需的电压， 同时， 通过外 部的控制电路控制开关单元 K, 使第一功率开关管的漏极与直流电源的正 极电连接，则第二电容 C2上的电压等于直流电源的电压 Vi，从而使得桥式 逆变器 21不仅能从直流电源获得电压为 Vi的直流电能， 还能从升压电路 22获得电压为 Vh的直流电能。 此时， 通过外部的控制电路给桥式逆变器 21施加控制脉冲， 则桥式逆变器 21的输出电位会存在 3个电平， 即 Vh、 Vi及 0， 使得桥式逆变器 21按照三电平逆变方式工作。
由于仅当桥式逆变器 21输出 Vh电平时 （漏极与升压电路的电压输出 端电连接的功率开关管， 如第二功率开关管 T22导通时）， 才需要由升压电 路 22提供输出功率， 输出其它电平时， 逆变电路仍然由直流电源直接提供 输出功率， 因此能大大降低升压电路 22的能耗。
另外， 在直流电源的电压 Vi小于桥式逆变器 21正常工作所需的电压 时， 由于桥式逆变器 21工作于三电平逆变方式， 因此存在开关损耗低、 输 出电感纹波小等优点。 当直流电源的电压 Vi不小于 （即大于或等于） 桥式逆变器 21正常工 作所需的电压时， 通过外部的控制电路控制开关单元 K, 使第一功率开关 管的漏极与直流电源的正极之间的电连接断开， 同时控制升压电压不工作， 旁路设备开通工作， 则 Vh等于 Vi。 此时， 第一电容 C1及第二电容 C2对 Vh分压使桥式逆变器 21按照传统的 T型对称三电平逆变方式工作。
图 5所示的逆变装置中， 由于在直流电源的电压较低时， 升压电路和 直流电源可以同时直接向逆变器提供直流电能， 使得逆变器工作在三电平 逆变方式， 不仅能降低升压电路的能耗， 还能降低逆变器的开关损耗。 另 外， 在直流电源的电压较高时， 不仅升压电路不消耗电能， 且由于电容的 分压，逆变器仍然能工作在三电平逆变方式，相比于图 2所示的逆变装置， 能进一步降低逆变装置的能耗， 从而在将该逆变装置应用到太阳能光伏并 网系统中时， 能显著提高整个系统的效率。
图 5所示的逆变装置中， 也可以采用图 4A〜图 4C所示的改进方案， 为桥式逆变器 21 中的电感电流提供续流通路， 以减小桥式逆变器 21 的输 出电感纹波， 并进一步降低开关损耗， 具体的电路参见图 6〜图 8， 图 6〜 图 8中与图 5及图 4A〜图 4C相同的部分沿用了图 5及图 4A〜图 4C中的 附图标记。
另外， 将图 7中的升压电路、 旁路单元用图 3B所示的电路替换， 且将 图 7中的开关单元用功率开关管 Tk替换后， 形成图 9所示的电路图， 图 9 中与图 7相同的部分沿用了图 7中的附图标记。
实施例 2
本实施例提供一种太阳能光伏并网系统， 如图 10所示， 该系统包括： 太阳能电池板 101、 实施例 1提供的逆变装置 102、 滤波电路 103、 主控装 置 104及电网 105。该逆变装置 102用于将所述太阳能电池板 101提供的直 流电源通过所述主控装置 10的控制转换为交流电源， 并通过连接在所述逆 变装置 102及所述电网 105之间的滤波电路 103的滤波， 将所述交流电源 输送至所述电网 105。该逆变装置 102的具体电路结构及工作原理已在实施 例 1中做了详细说明， 在此不再赘述。
本实施例中， 由于采用了实施例 1 提供的逆变装置， 可使太阳能光伏 并网系统效率获得显著的提升。
以上所述， 仅为本发明的具体实施方式， 但本发明的保护范围并不局 限于此， 任何熟悉本技术领域的技术人员在本发明揭露的技术范围内， 可 轻易想到的变化或替换， 都应涵盖在本发明的保护范围之内。 因此， 本发 明的保护范围应以所述权利要求的保护范围为准。

Claims

权利要求
1、 一种逆变装置， 包括： 桥式逆变器及升压电路， 其特征在于， 所述 桥式逆变器包括至少一个桥臂， 所述至少一个桥臂包括： 第一至第三功率 开关管及第一二极管；
所述第一二极管及所述第一功率开关管构成补充支路， 其中， 所述第 一二极管与所述第一功率开关管的源漏极正向串联； 所述补充支路的电流 输入端与所述升压电路的电压输出端电连接；
所述第二功率开关管的漏极与所述升压电路的电压输出端电连接； 所 述第二功率开关管的源极、 所述第三功率开关管的漏极、 所述补充支路的 电流输出端及交流输出端电连接； 所述交流输出端用于向电网输出交流电 压 /电流；
所述第三功率开关管的源极与直流电源的负极电连接； 所述直流电源 的正极与所述升压电路的电压输入端电连接；
所述升压电路， 用于在所述直流电源的电压小于所述桥式逆变器正常 工作所需的电压时， 使所述升压电路的电压输出端输出的电压不小于所述 桥式逆变器正常工作所需的电压。
2、 根据权利要求 1所述的逆变装置， 其特征在于， 还包括： 第二至第 四二极管， 所述第二二极管与所述第一功率开关管的源漏极反向并联； 所 述第三二极管与所述第二功率开关管的源漏极反向并联； 所述第四二极管 与所述第三功率开关管的源漏极反向并联。
3、 根据权利要求 1或 2所述的逆变装置， 其特征在于， 所述至少一个 桥臂还包括第四功率开关管；
所述第四功率开关管的源漏极与所述第一二极管反向并联。
4、 根据权利要求 1或 2所述的逆变装置， 其特征在于， 所述至少一个 桥臂还包括第五功率开关管及第五二极管；
所述第五功率开关管的源极与所述补充支路的电流输入端电连接； 所 述第五功率开关管的漏极与所述第五二极管的阴极电连接； 所述第五二 ¾ 管的阳极与所述补充支路的电流输出端电连接。
5、 根据权利要求 4所述的逆变装置， 其特征在于， 还包括： 第六二 ¾ 管， 所述第六二极管与所述第五功率开关管的源漏极反向并联。
6、 根据权利要求 2所述的逆变装置， 其特征在于， 所述升压电路还月 于： 在所述直流电源的电压不小于所述桥式逆变器正常工作所需的电压时 将所述电压输入端及所述电压输出端短接。
7、 根据权利要求 2所述的逆变装置， 其特征在于， 还包括与所述升 电路并联的旁路单元；
所述旁路单元， 用于在所述直流电源的电压不小于所述桥式逆变器 常工作所需的电压时， 将所述升压电路的所述电压输入端及所述电压输 端短接。
8、 根据权利要求 6或 7所述的逆变装置， 其特征在于， 还包括： 第 电容、 第二电容及开关单元；
所述第一电容的一端与所述升压电路的电压输出端电连接； 所述第 电容的另一端、 所述开关单元的输出端及所述第二电容的一端电连接； 所述开关单元的输入端与所述升压电路的电压输入端电连接； 所述第二电容的另一端与所述直流电源的负极电连接；
所述开关单元用于在所述直流电源的电压小于所述桥式逆变器正常 作所需的电压时， 将所述第一功率开关管的漏极与所述直流电源的正极 连接； 否则使所述第一功率开关管的漏极与所述直流电源的正极之间的 连接断开。
9、 根据权利要求 7所述的逆变装置， 其特征在于， 所述旁路单元为第 七二极管， 所述第七二极管的阳极与所述升压电路的电压输入端电连接； 所述第七二极管的阴极与所述升压电路的电压输出端电连接。
10、 一种太阳能光伏并网系统， 其特征在于， 包括： 太阳能电池板、 权利要求 1〜3任一项所述的逆变装置、 滤波电路、 主控装置及电网； 所述逆变装置用于将所述太阳能电池板提供的直流电源通过所述主控 装置的控制转换为交流电源， 并通过连接在所述逆变装置及所述电网之间 的滤波电路的滤波， 将所述交流电源输送至所述电网。
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