Independent load sharing of AC power systems connected in parallel
First Claim
1. A parallel redundant power system comprising at least two power systems connected in parallel so as to provide AC power to a load via a common power connection, at least one of said power systems comprising:
- means for generating an AC output voltage from a DC input power source;
means for sampling one of a DC input voltage from the DC input power source and said AC output voltage from said AC output voltage generating means to provide power level samples;
means for determining the AC output power of said AC output voltage generating means from the power level samples; and
means for providing a control signal to said AC output voltage generating means to control the AC output phase and output frequency of said AC output voltage from said AC output voltage generating means based on the output power level of the AC output voltage generating means and a derivative of the output power level of the AC output voltage generating means so as to affect load sharing in a manner proportional to a unit power rating of said power system with other power systems to which the power system is connected in parallel without requiring inter-unit signaling between the power systems.
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Accused Products
Abstract
A parallel redundant power supply system which does not use any inter-unit signaling is obtained by using the AC output power level of a power system to coordinate load sharing. The necessary information for load sharing is derived solely from each power system'"'"'s output power level in such a manner that the output of a power system is inherently phase locked to the output of other power systems to which it is connected in parallel. Each parallel connected power system designed in accordance with the invention includes means for generating an AC output voltage from a DC input power source, means for sampling either a DC input voltage from the DC input power source or the AC output voltage from the AC output voltage generating means to provide power level samples, and means for determining the AC output power of the AC output voltage generating means from the power level samples. A control signal is then generated and provided to the AC output voltage generating means to control the AC output phase and output frequency of the AC output voltage from the AC output voltage generating means based on the output power level of the AC output voltage generating means and a derivative of the output power level of the AC output voltage generating means so as to affect load sharing in a manner proportional to a unit power rating of the power system with other power systems to which the power system is connected in parallel without requiring inter-unit signaling between the power systems. Generally, the control signal is determined by integrating the derivative of the output power level of the AC output voltage generating means as determined from the power level samples.
167 Citations
25 Claims
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1. A parallel redundant power system comprising at least two power systems connected in parallel so as to provide AC power to a load via a common power connection, at least one of said power systems comprising:
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means for generating an AC output voltage from a DC input power source; means for sampling one of a DC input voltage from the DC input power source and said AC output voltage from said AC output voltage generating means to provide power level samples; means for determining the AC output power of said AC output voltage generating means from the power level samples; and means for providing a control signal to said AC output voltage generating means to control the AC output phase and output frequency of said AC output voltage from said AC output voltage generating means based on the output power level of the AC output voltage generating means and a derivative of the output power level of the AC output voltage generating means so as to affect load sharing in a manner proportional to a unit power rating of said power system with other power systems to which the power system is connected in parallel without requiring inter-unit signaling between the power systems. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of providing independent load sharing amongst at least two power systems connected in parallel so as to provide AC power from an AC power generating means of each power system to a load via a common power connection, comprising the steps of:
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generating an AC output voltage from a DC input power source; sampling one of a DC input voltage from the DC input power source and said AC output voltage from said AC power generating means to provide power level samples; determining the AC output power of said AC power generating means from the power level samples; and providing a control signal to said AC power generating means to control the AC output phase and output frequency of said AC output voltage from said AC power generating means based on the output power level of the AC power generating means and a derivative of the output power level of the AC power generating means so as to affect load sharing in a manner proportional to a unit power rating of said power system with other power systems to which the power system is connected in parallel without requiring inter-unit signaling between the power systems. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method of providing independent load sharing amongst at least two DC to AC inverters connected in parallel so as to provide AC power from a DC to AC inverter of each power system to a load via a common power connection, comprising the steps of:
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generating an AC output voltage from a DC input power source; sampling one of a DC input voltage from the DC input power source and said AC output voltage from said DC to AC inverter to provide power level samples; determining a derivative of an input power level to said DC to AC inverter to generate a control signal and from said power level samples and providing said control signal to said DC to AC inverter so as to stabilize a load share operation with other DC to AC inverters to which said DC to AC inverter is connected in parallel; and using a DC input power level to said DC to AC inverter to control an AC output voltage phase angle so that the AC output voltage phase is synchronized to said other DC to AC inverters to which said DC to AC inverter is connected in parallel, while simultaneously adjusting said AC output voltage frequency toward one of a fixed frequency and a frequency of an alternate power source.
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Specification