Method for setting switching times, in particular idle times, of an inverter based on detected power, and inverter

• US 7,733,679 B2
• Filed: 10/29/2004
• Issued: 06/08/2010
• Est. Priority Date: 10/31/2003
• Status: Active Grant

• Current Assignee: Fronius International GmbH (G&K Privatstiftung)
• Original Assignee: Fronius International GmbH (G&K Privatstiftung)
• Inventors: Bittmann, Clemens, Luger, Andreas
• Primary Examiner(s): BEHM, HARRY RAYMOND
• Application Number:
  US10/577,336
• Publication Number:
  US 20070030717A1
• Time in Patent Office: 2,048 Days
• Field of Search: 363/98, 363/41, 363/21.03, 363/56.04, 363/132, 323/906
• US Class Current: 363/98
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A method for an inverter, for inputting power output by a direct current voltage source in an alternating current voltage network chops the direct current voltage source by a bridge inverter by alternate switching of parallel-mounted and series-mounted circuit elements, in the form of a pulse width modulation, and the chopped power is transmitted via a transformer which is connected between the series-mounted elements. The transmitted power is then rectified and input in the alternating current voltage network via a down-converter transformer. In order to adapt the inverter to the power supplied, the switching times of the circuit elements of the bridge inverter are controlled or regulated. In order to provide a simple way of enhancing performance, the power output by the direct current voltage source is detected in particular on a cyclic or permanent basis and the switching times of the circuit elements of the bridge inverter, in particular the idle times and/or the interval duration and or the frequency for pulse width modulation, for switching the circuit elements are adjusted based on the detected power of the direct current voltage source.

Claims

1. A solar inverter for feeding current produced by a d.c. voltage source into an a.c. voltage grid, said d.c. voltage source being formed by a solar module, said inverter comprising a bridge inverter, a transformer having a primary winding, a rectifier, a buck chopper including a full bridge and an output filter;

wherein a control device is provided for controlling the parameters of the inverter;

wherein a device for detecting the current produced by the d.c. voltage source and flowing over the primary winding of the transformer is provided, which device is connected to the control device; and

wherein the bridge inverter is designed for adapting a dead time for the switching elements as a function of the mean value of the current detected flowing over the primary winding of the transformer by selecting the dead time from a table with correspondingly stored data for the most varying mean values, the dead time representing a time of the switching elements for switching over from one switching element to a further switching element connected in series of the bridge inverter, thereby ensuring that parasitic capacitances stored in the switching elements of the bridge inverter can be completely recharged and no excessively long switching pauses can occur at the same time.

2. A method for a solar inverter for feeding current produced by a d.c. voltage source formed by a solar module into an a.c. voltage grid comprising the steps of:

(a) chopping the current produced by the d.c. voltage source in a form of a pulse width modulation by a bridge inverter by alternate switching of switching elements connected in parallel and connected in series;

(b) transmitting the current chopped via a transformer connected between the switching elements that are connected in series, the transformer having a primary winding; and

(c) rectifying the current transmitted and feeding the current into the a.c. voltage grid via a buck chopper;

wherein, for a power adaptation, the switching times of the switching elements of the bridge inverter are controlled, or regulated;

wherein the current produced by the d.c. voltage source is detected from current flowing over the primary winding of the transformer continuously or at cyclical intervals, and

wherein a dead time of the switching elements of the bridge inverter is set as a function of the mean value of the detected current of the d.c. voltage source flowing over the primary winding of the transformer by selecting the dead time from a table with correspondingly stored data for the most varying mean values, the dead time representing a time of the switching elements for switching over from one switching element to a further switching element connected in series of the bridge inverter, thereby ensuring that parasitic capacitances stored in the switching elements of the bridge inverter can be completely recharged and no excessively long switching pauses can occur at the same time.

3. The method according to claim 2, wherein a period duration or a frequency for the pulse width modulation for switching over the switching elements of the bridge inverter is set as a function of the current detected.

4. The method according to claim 2, wherein the switching times of the switching elements of the bridge inverter are evaluated as a function of the current detected and set automatically.

5. The method according to claim 2, wherein the switching elements are activated at appropriately set points of time.