Ballard Power Systems Corporation

Continental Automotive Systems Us, Inc.

Siemens Vdo Automotive Corporation

Anil Tuladhar

Duo Deng

Kerry Eden Grand

Kenneth James Farkas

Kent Michael Harmon

Vijay Bhavaraju

Cycle error correction is performed in an electronic power system to compensate for a difference between an AC grid side frequency and an AC load side frequency. The electronic power system can comprise an electronic power inverter, such as one usable with an uninterruptible power supply. Cycles of signals indicative of the AC grid power and the AC load power are counted and compared to obtain a cycle error value. If the cycle error value exceeds a first value to indicate that AC load side frequency is too high or too low, then compensation is performed to change the AC load side frequency to be closer to the AC grid side frequency. If the cycle error value falls below a second value to indicate that the AC grid side frequency and AC load side frequency are sufficiently close to one another, then the compensation is deactivated.

Method and apparatus for cycle error correction for a power converter device, such as an electronic power inverter

An electrical power converter system adjusts a wakeup voltage periodically, to permit earlier connection and/or operation, to increase performance. The electrical power converter system selects between a mathematically adjusted wakeup voltage based on at least one previous period, and a table derived wakeup voltage that takes into account historical information. The electrical power converter system is particularly suited to applications with periodicity such as solar based photovoltaic power generation.

Method and apparatus for adjusting wakeup time in electrical power converter systems and transformer isolation

Cycle error correction is performed in an electronic power system to compensate for a difference between an AC grid side frequency and an AC load side frequency. The electronic power system includes an electronic power inverter, such as one usable with an uninterruptible power supply. Cycles of signals indicative of the AC grid power and the AC load power are counted and compared to obtain a cycle error value. If the cycle error value exceeds a first value to indicate that AC load side frequency is too high or too low, then compensation is performed to change the AC load side frequency to be closer to the AC grid side frequency. If the cycle error value falls below a second value to indicate that the AC grid side frequency and AC load side frequency are sufficiently close to one another, then the compensation is deactivated.

The maximum power point (MPP) of a photovoltaic array that can be coupled to power inverter is determined. A capacitor on a DC-bus side of the inverter is used as a load from which I-V characteristics of the photovoltaic array can be generated. The photovoltaic array is connected to the capacitor, which has been previously discharged by a bleed down resistor. Short circuit current, open circuit voltage, and values of current and voltage as the capacitor charges are determined and used to generate I-V characteristics of the photovoltaic array. From the I-V characteristics, the MPP can be calculated.

Method and apparatus for determining a maximum power point of photovoltaic cells

A power system employs an outer voltage feedback loop and an inner current feedback loop to control a power converter, such as a DC to AC inverter for transferring electrical power between a power source, for example a photovoltaic array, and a load, for example a power grid. The outer loop accommodates variations in the output of the power source, for example accommodating anomalies in IV characteristics such as IV droop characteristic associated with photovoltaic cells. The outer loop may employ a first control regime or a second control regime, for example, dependent on whether a DC bus voltage or power is smaller than a value corresponding to measurement resolution or expected noise.

Method and apparatus for tracking maximum power point for inverters, for example, in photovoltaic applications

Devices and methods for detecting islanding operation of a static power source involve injection of a non-harmonic error on the phase angle of the static power source in regular steps to introduce a very small intentional phase shift for the output voltage of the static power source in every voltage cycle which is corrected in each cycle in synchronization with the grid voltage in normal operation of the grid. In abnormal operation of a grid loss, this intentional small phase shift or error causes an intentional small frequency drift in each voltage cycle that continues in one cycle after another cycle. When the intentional frequency drift is over a preset level, a detection circuit starts to isolate the static power source from the grid to prevent islanding operation.

Devices and methods for detecting islanding operation of a static power source

Techniques for determining root mean square (RMS) values of a signal for controlling operation of grid-linked converters, such as DC-to-AC inverters, via squaring the signal, sampling the squared signal n times during a cycle period to obtain n samples, summing the first n&#x2212;1 samples to obtain a first value, multiplying the first value by a sampling time and a frequency of the signal to obtain a second value, determining a compensation factor, adding the compensation factor to the second value to obtain a third value, and determining a square root of the third value to obtain a RMS result.

Method for determining RMS values for grid-linked converters

A device and method for detecting islanding of a grid connected inverter makes use of an injected white noise as a perturbing force on the output voltage of the inverter. The white noise is injected at least once in every cycle and can be generated at different rates in implementation. On loss of the grid, a frequency drift of the output voltage is detected and a positive feedback is activated that accelerates the drift.

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Dearborn Heights, MI, United States of America

Anil Tuladhar