Inverter for grounded direct current source, more specifically for a photovoltaic generator

• US 20090034304A1
• Filed: 07/10/2008
• Published: 02/05/2009
• Est. Priority Date: 08/04/2007
• Status: Active Grant

• Current Assignee: SMA Solar Technology AG
• Original Assignee: SMA Solar Technology AG
• Inventors: Zacharias, Peter, Mallwitz, Regine, Engel, Bernd
• Granted Patent: US 8,023,288 B2
• Time in Patent Office: Days
• US Class Current: 363/71
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 7/05 Capacitor coupled rectifiers
• CPC Class Codes: Y02B 70/10 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
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

An inverter (1) for a grounded direct voltage source, in particular for a photovoltaic generator (2), a battery or a fuel cell, for converting the direct voltage into an alternative voltage with a DC-DC converter (3) and a pulse inverter that is supplied by said DC-DC converter (3), said DC-DC converter (3) being configured to be an oscillating circuit inverter and comprising a series resonant oscillating circuit, said DC-DC converter (3), which is configured to be an oscillating circuit inverter, being configured to be a series-compensated oscillating circuit inverter with a choke (L1) and a series-mounted capacitor array consisting of two or several oscillating circuit capacitors, a rectifier bridge branch including 2 diodes (D3, D4; D5, D6, . . . ), being connected to each of the partial oscillating circuit capacitors, said rectifier bridge branch being connected with its positive or its negative pole to output side intermediate circuit capacitors which are preferably connected in series so that said DC-DC converter (3) delivers at least two bipolar output voltages and is combined with the pulse inverter (4) with a divided voltage intermediate circuit that is supplied from the oscillating circuit inverter.

Claims

1. An inverter (1) for a grounded direct voltage source, in particular for a photovoltaic generator (2), a battery or a fuel cell, for converting the direct voltage into an alternative voltage with a DC-DC converter (3) and a pulse inverter that is supplied by said DC-DC converter (3), said DC-DC converter (3) being configured to be an oscillating circuit inverter and comprising a series resonant oscillating circuit, characterized in that said DC-DC converter (3), which is configured to be an oscillating circuit inverter, is configured to be a series-compensated oscillating circuit inverter with a choke (L1) and a series-mounted capacitor array consisting of two or several oscillating circuit capacitors, that a rectifier bridge branch including 2 diodes (D3, D4;

D5, D6, . . . ), is connected to each of the partial oscillating circuit capacitors, said rectifier bridge branch being connected with its positive or its negative pole to output side intermediate circuit capacitors which are preferably connected in series so that said DC-DC converter (3) delivers at least two bipolar output voltages and is combined with the pulse inverter (4) with a divided voltage intermediate circuit that is supplied from the oscillating circuit inverter.

2. The inverter as set forth in claim 1, characterized in that the associated parallel oscillating circuit capacitors (C1, C2) have the same capacitance.

3. The inverter as set forth in claim 1, characterized in that several voltage levels having the same polarity may be provided by at least four oscillating circuit capacitors (C1, C2, C5, C6).

4. The inverter as set forth in claim 1, characterized in that two series-connected capacitors (C3, C4) are mounted parallel to the direct voltage source (2) on the DC intermediate circuit, a grounding point lying optionally either between the capacitors (C3, C4) or at a positive pole of the source, the capacitor (C3) lying at the positive pole being bridged or lying at a negative pole of the source, in which case it is the capacitor (C4) lying at the negative pole that is bridged.

5. The inverter as set forth in claim 1, characterized in that the DC-DC converter (3) comprises two series-connected semi-conducting switching elements (S1, S2) that are connected parallel to the direct voltage source, the oscillating circuit consisting of the choke (L1) and the capacitor array being connected to the connection point of the semi-conductor switching elements (S1, S2) for a positive and negative output current to flow through alternate switching of the semi-conductor switching elements (S1, S2).

6. The inverter as set forth in claim 5, characterized in that the semi-conductor switching elements (S1, S2), which are connected to the oscillating circuit, are switched alternately at high frequency, only one of the two semi-conductor switching elements (S1, S2) being always clocked at high frequency both at positive and at negative output current.

7. The inverter as set forth in claim 6, characterized in that the pulse inverter includes a bridge circuit with at least two active semi-conductor switches so that, together with the semi-conductor switches connected to the oscillating circuit, four active switches in all are provided and that the switches of the bridge circuit modulate the output current of the inverter (1) for feeding into the grid and that the switches of the oscillating circuit control the intermediate circuit voltage.

8. The inverter as set forth in claim 2, characterized in that several voltage levels having the same polarity may be provided by at least four oscillating circuit capacitors (C1, C2, C5, C6).