Current Waveform Construction to Generate AC Power with Low Harmonic Distortion from Localized Energy Sources
First Claim
1. A method of shaping a current waveform for supply to a transformer primary winding, the method comprising:
- constructing a current waveform that comprises a sequence of current signals of alternating polarity, the constructed waveform having a period corresponding to a fundamental frequency, wherein each current signal is formed within one-half of one period by performing steps comprising;
(i) turning on a switch corresponding to a polarity of the current signal being constructed;
(ii) increasing a current supplied from an output node from substantially zero to a first current level by discharging a capacitance until the voltage on the capacitance substantially matches a voltage of a first voltage source;
i) increasing the current from the first current level to a second current level by connecting the output node substantially directly to the voltage source;
(iv) turning off the switch once; and
,(v) decreasing the current to substantially zero by directing the current that continues to flow after the switch turns off to recharge the capacitance.supplying the constructed waveform to a first winding of a transformer.
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Accused Products
Abstract
Methods and apparatus to provide low harmonic distortion AC power for distribution by converting energy from natural or renewable sources into electrical form, and constructing a current waveform on a primary winding of a transformer by recapturing inductive energy previously stored in the transformer so as to transform the converted electrical energy into substantially sinusoidal AC voltage at a secondary winding of the transformer. For example, AC power may be supplied to a utility power grid from raw electrical energy from renewable energy sources (e.g., solar cells). An inverter may construct the primary winding current waveform using two unidirectional switches. On each half cycle, one of the switches first applies energy previously recaptured from primary winding inductance, and then applies the raw energy to the transformer primary winding at the utility power grid frequency. Accordingly, the constructed primary winding current may exhibit substantially improved total harmonic distortion.
74 Citations
13 Claims
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1. A method of shaping a current waveform for supply to a transformer primary winding, the method comprising:
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constructing a current waveform that comprises a sequence of current signals of alternating polarity, the constructed waveform having a period corresponding to a fundamental frequency, wherein each current signal is formed within one-half of one period by performing steps comprising; (i) turning on a switch corresponding to a polarity of the current signal being constructed; (ii) increasing a current supplied from an output node from substantially zero to a first current level by discharging a capacitance until the voltage on the capacitance substantially matches a voltage of a first voltage source; i) increasing the current from the first current level to a second current level by connecting the output node substantially directly to the voltage source; (iv) turning off the switch once; and
,(v) decreasing the current to substantially zero by directing the current that continues to flow after the switch turns off to recharge the capacitance. supplying the constructed waveform to a first winding of a transformer. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for generating high quality alternating current (AC) electrical power for supply to a high voltage electic power distribution network, the system comprising:
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an energy collection node to convert a naturally-occuring form of energy to electrical energy; an energy processing module that converts the converted electrical energy to an alternating current signal having energy at a fundamental frequency and at least one harmonic of the fundamental frequency; a transformer comprising; (i) a first winding that receives the alternating current signal; (ii) a second winding that outputs AC power by delivering the power in the form of a substantially sinusoidal voltage signal; (iii) a third winding; and a harmonic suppression module coupled to the third winding and responsive to the alternating current in the first winding, and further configured to substantially offset the energy coupled from the first winding to the second winding at the at least one harmonic frequency. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification