Inverter circuit and method of operation
First Claim
1. A method of operating an inverter for converting direct current (DC) to alternating current (AC) comprising:
- (a) measuring input DC voltage to the inverter;
(b) measuring input DC current to the inverter;
(c) measuring output AC voltage from the inverter;
(d) measuring output AC current; and
(e) determining solar insolation.
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Abstract
An inverter includes a first switch to disconnect an output of the inverter from any device connected thereto; a second switch to disconnect and connect an input of the inverter from direct current fed to the inverter; a discharge device to discharge any residual charge on a large capacitor; a voltage sensor to measure input DC voltage to the inverter; a current sensor to measure input DC current to the inverter; and a data recorder to provide a current voltage trace to provide a current-voltage curve tracer to provide current-voltage curve data that may then be used to calibrate a maximum power point tracker or alternatively sense array shading.
371 Citations
17 Claims
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1. A method of operating an inverter for converting direct current (DC) to alternating current (AC) comprising:
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(a) measuring input DC voltage to the inverter;
(b) measuring input DC current to the inverter;
(c) measuring output AC voltage from the inverter;
(d) measuring output AC current; and
(e) determining solar insolation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 17)
(a) operating the inverter at a maximum power point;
(b) calculating, from the input DC voltage and the input DC current, input power to the inverter; and
(c) calculating, from the input power to the inverter, a solar insolation value.
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3. The method of claim 2 further comprising:
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(a) calculating output power from the inverter; and
(b) calculating operating efficiency of the inverter.
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4. The method of claim 1 further comprising calculating harmonic distortion of an output signal of the inverter.
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5. The method of claim 1 further comprising:
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(a) determining the maximum power point of the inverter;
(b) determining the temperature of a solar cell; and
(c) calculating solar insolation.
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6. The method of claim 1 further comprising:
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(a) storing a plurality of maximum power point data for a plurality of respective current-voltage curves;
(b) determining temperature of the solar cell to provide temperature data; and
(c) determining a solar insolation value from the determined temperature data and a selected one of the plurality of maximum power point data.
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7. The method of claim 1 further comprising:
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(a) storing a plurality of maximum power point data for a plurality of respective current-voltage curves;
(b) determining insolation with a sensor; and
(c) obtaining a cell temperature from the insolation and a selected one of the plurality of maximum power point data.
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8. The method of claim 1 further comprising:
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(a) measuring wind speed about a photovoltaic power system to which the inverter is coupled;
(b) measuring ambient temperature about the photovoltaic power system; and
(c) measuring module temperature of the inverter.
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17. The method of claim 1, wherein the inverter is coupled to a PV module and the method further comprises measuring temperature of the PV module.
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9. A method for measuring parameters of a photovoltaic array by operating an inverter having an input and an output, the method comprising:
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(a) disconnecting the output of the inverter from any device connected thereto;
(b) disconnecting the input of the inverter from a direct current fed to the inverter;
(c) discharging residual charge on a capacitor;
(d) connecting the input of the direct current across a capacitor;
(e) measuring input DC voltage to the inverter;
(f) measuring input DC current to the inverter; and
providing current voltage data indicative of the parameters of the photovoltaic array.- View Dependent Claims (10, 11, 12)
(a) repeating the steps of;
(i) disconnecting an output of the inverter from any device connected thereto;
(ii) disconnecting an input of the direct current fed to the inverter;
(iii) discharging any residual charge on a large fully discharged capacitor;
(iv) connecting the input of the direct current across a large fully discharged capacitor;
(v) measuring input DC voltage to the inverter;
(vi) measuring input DC current to the inverter; and
(vii) calculating a current voltage trace to provide a current-voltage curve tracer; and
(b) comparing current measurements with prior measurements to deduce solar array degradation.
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11. The method of claim 9 further comprising:
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(a) repeating the steps of;
(i) disconnecting an output of the inverter from any device connected thereto;
(ii) disconnecting an input of the direct current fed to the inverter;
(iii) discharging any residual charge on a capacitor;
(iv) connecting the input of the direct current across a capacitor;
(v) measuring input DC voltage to the inverter;
(vi) measuring input DC current to the inverter; and
(vii) providing a current voltage trace to provide a current-voltage curve tracer; and
(b) comparing current measurements with known measurements to ensure proper insolation measurements.
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12. The method of claim 9 further comprising:
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(a) repeating the steps of;
(i) disconnecting an output of the inverter from any device connected thereto;
(ii) disconnecting an input of the direct current fed to the inverter;
(iii) discharging any residual charge on a capacitor;
(iv) connecting the input of the direct current across a capacitor;
(v) measuring input DC voltage to the inverter;
(vi) measuring input DC current to the inverter; and
(vii) providing a current voltage trace to provide a current-voltage curve tracer; and
(b) comparing current measurements with known measurements and calibrating a maximum power point tracker using current measurements.
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13. An inverter comprising:
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(a) a first switch coupled between an output of the inverter and a device connected to the output of the inverter, said first switch;
(b) a second switch for disconnecting an input of the direct current fed to the inverter;
(c) a discharge circuit coupled to a capacitor;
(d) means for connecting the input of the direct current across the large fully discharged capacitor;
(e) a voltage sensor coupled to the input of the inverter, said voltage sensor for measuring input DC voltage to the inverter; and
(f) a current sensor coupled to the input of said inverter, said current sensor for measuring input DC current to the inverter. - View Dependent Claims (14, 15, 16)
(a) means for comparing current measurements with known measurements to ensure proper insolation measurements.
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16. The inverter of claim 13 further comprising a comparator for comparing current measurements with known measurements and calibrating a maximum power point tracker using up to date measurements.
Specification