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CN-116015087-B - Step-down auxiliary split source inverter

CN116015087BCN 116015087 BCN116015087 BCN 116015087BCN-116015087-B

Abstract

A buck-assisted split source inverter includes a DC link having two voltage rails, at least two pairs of switches connected in series, a first connection point and a second connection point for receiving voltage terminals of a fuel cell, one of the two voltage rails forming the first connection point, a switching component and an inductor connected in series, having a first end formed by the terminals of the switching component and a second end formed by the terminals of the inductor, the first end forming the second connection point for receiving voltage terminals of the fuel cell. The inverter further comprises at least two first diodes, a second diode having a first terminal and a second terminal, wherein the switching member is adapted to be controlled to be conductive when any one of the lower switches connected to the voltage rails forming the first connection point is controlled to be conductive.

Inventors

  • Ahmed Abdul Hakim
  • Cicero portillone
  • Abel hadiu

Assignees

  • ABB瑞士股份有限公司

Dates

Publication Date
20260512
Application Date
20221021
Priority Date
20211022

Claims (8)

  1. 1. A buck-assisted split source inverter comprising: A DC link having two voltage rails; At least two pairs of series connected switches, wherein anti-parallel diodes are connected between the voltage rails of the DC link, the series connected switches having a lower switch connected to one of the two voltage rails, the center points of the series connected switches forming the phase output of the inverter; A first connection point and a second connection point for receiving a voltage terminal of a fuel cell, one of the two voltage rails forming the first connection point; a switching component and an inductor connected in series, having a first end formed by a terminal of the switching component and a second end formed by a terminal of the inductor, the first end forming a second connection point for receiving a voltage terminal of the fuel cell; At least two first diodes having one of their corresponding terminals connected together and to the series-connected second end of the switching component and the inductor, and the other terminals of the at least two first diodes connected to separate phase outputs of the inverter, and A second diode having a first terminal and a second terminal, the first terminal being connected to a point between the switching component and the inductor, and the second terminal being connected to a voltage rail forming the first connection point, the polarity of the second diode corresponding to the polarity of the at least two first diodes such that a current path is formed through the second diode and the at least two first diodes, Wherein the switching means is adapted to be controlled to be on when any one of the lower switches connected to a voltage rail forming the first connection point is controlled to be on.
  2. 2. The buck-assisted split source inverter of claim 1, wherein the first connection point is formed by a negative voltage rail of the DC link, anodes of the at least two first diodes are connected together, and anodes of the second diodes are connected to the negative voltage rail of the DC link.
  3. 3. The buck-assisted split source inverter of claim 1, wherein the first connection point is formed by a positive voltage rail of the DC link, the cathodes of the at least two first diodes are connected together, and the cathode of the second diode is connected to the positive voltage rail of the DC link.
  4. 4. A buck-assisted split source inverter according to claim 1,2 or 3 wherein the switching means is adapted to be controlled to be on when any one of the switches connected to the voltage rail forming the first connection point is controlled to be on and when a control signal is active.
  5. 5. A buck-assisted splitting source inverter according to any of claims 1 to 3, wherein the DC link of the buck-assisted splitting source inverter comprises a capacitor connected between the voltage rails of the DC link.
  6. 6. A buck-assisted splitting source inverter according to any of claims 1 to 3, wherein the DC link of the buck-assisted splitting source inverter comprises a battery connected between the voltage rails of the DC link.
  7. 7. The buck-assisted split source inverter of any of claims 1-3, wherein the buck-assisted split source inverter comprises a boost converter connected to the DC link, the boost converter receiving power from a battery or supercapacitor.
  8. 8. The buck-assisted split source inverter of claim 7, wherein the DC link comprises a battery connected between voltage rails of the DC link, wherein the battery is connected to an output of the boost converter.

Description

Step-down auxiliary split source inverter Technical Field The present invention relates to an inverter, and particularly to a split source inverter having a fuel cell as an energy source. Background Integration of Low Voltage (LV) energy sources such as Photovoltaic (PV) and Fuel Cells (FC) into ac power grids has been the subject of research in the past few years. In addition to this, integration of these energy sources with Medium Voltage (MV) grids is receiving higher attention because of the advantages seen behind MV integration at higher power levels. PV applications typically stack solar panels to achieve voltages up to 1.5kV, however, this is not the case for FCs that still have a limitation of output voltage, with the highest voltage range seen in the market being 400 v-700 v. Thus, integration of FC to LV or MV power grids requires the use of a boost DC-DC converter and inverter to connect the FC to the AC power grid, where a high boost converter or transformer is necessary for the MV power grid. Typically, FC systems require two power conditioning stages, where a DC-DC converter is used before a DC-AC converter to achieve the correct voltage level for LV or MV AC grid integration as shown in fig. 1. In addition, an isolation or step-up transformer may be used. Another approach is to use a single stage solution, such as a Split Source Inverter (SSI) as shown in fig. 2, where boost capability is integrated in the inverting operation. The integrated solution uses inverter switches with additional diodes connected to a common inductor to achieve the boost characteristic, i.e. it avoids the use of additional active switches and gate drive circuits. The operation of SSI is described in volume 31, stage 11, pages 7451-7461, month 2016, 11 of A.Abdelhakim, P.Mattavelli and G.Spiazzi"Three-Phase Split-Source Inverter(SSI):Analysis and Modulation"IEEE Transactions on Power Electronics,. The inverter uses at least one of the lower semiconductor switches to charge the input inductor, while when all upper switches are on, only one state is used to discharge the inductor on the inverter dc link. The operation of the three-phase SSI does not require any special pulses to be generated for its basic operation or modifications to the standard modulation scheme of the Voltage Source Inverter (VSI). Thus, the same modulation scheme of VSI can be applied to SSI. When employing SSI topologies with a voltage source such as a fuel cell, it is important that the utilization of the available voltage is as high as possible. Disclosure of Invention It is an object of the present invention to provide a buck-assisted split source converter that alleviates the above-mentioned drawbacks related to voltage utilization. The object of the present invention is achieved by an inverter circuit according to an embodiment of the present invention. According to an embodiment of the present invention, a buck-assisted split source inverter is provided. The buck-assist split source inverter includes a DC link having two voltage rails, at least two pairs of series-connected switches, wherein anti-parallel diodes are connected between the voltage rails of the DC link, a center point of the series-connected switches forming a phase output of the inverter, a first connection point and a second connection point for receiving voltage terminals of the fuel cell, one of the two voltage rails forming a first connection point, a series-connected switching component and an inductor having a first end formed by terminals of the switching component and a second end formed by terminals of the inductor, the first end forming a second connection point for receiving voltage terminals of the fuel cell, at least two first diodes having one of their corresponding terminals connected together and to the series-connected second end of the switching component and the inductor, and other terminals of the at least two first diodes connected to separate phase outputs of the inverter, and a second diode having a first terminal and a second terminal, the first terminal being connected to a point between the switching component and the inductor, and the second terminal being formed by a polarity of at least two first diodes being adapted to be turned on when the first connection point of the first terminal and the first terminal is formed by the first diode and the first connection rail is turned on. According to an embodiment of the invention, the first connection point is formed by a negative voltage rail of the DC link, the anodes of the at least two first diodes are connected together, and the anode of the second diode is connected to the negative voltage rail of the DC link. According to an embodiment of the invention, the first connection point is formed by a positive voltage rail of the DC link, the cathodes of the at least two first diodes are connected together, and the cathode of the second diode is connected to the positive voltage rail of the DC link. Accor