Abstract: A transformerless parallel active rectifier system includes N multiphase common mode inductors directly connected to a shared multiphase AC input with no intervening transformer, and N active rectifiers coupled to respective ones of the N multiphase common mode inductors and having respective DC outputs coupled to a shared DC bus, where N is an integer greater than 1. The N active rectifiers have ground current regulators and are synchronized to provide DPWM switching control signals synchronized to one another to regulate their respective ground currents and concurrently regulate the shared DC bus voltage.

Abstract: For Direct Current (DC) bus voltage control, a method generates a q-axis reference current from a DC voltage error that includes a DC voltage input modified by a DC bus voltage in a closed outer loop. The method further generates a d-axis reference current from the DC voltage error, wherein the second-order harmonic in the d-axis reference current is delayed from that in q-axis reference current by 90 degrees. The method generates a q-axis current from the q-axis reference current. The method generates a d-axis current from the d-axis reference current. The second-order harmonic in d-axis current is offset from the second-order harmonic in q-axis current by 90 degrees. The method controls the DC bus voltage of a voltage control plant to mitigate a second-order harmonic in the DC bus voltage with the second-order harmonics in the q-axis current and the d-axis current.

Abstract: For Direct Current (DC) bus voltage control, a method generates a q-axis reference current from a DC voltage error that includes a DC voltage input modified by a DC bus voltage in a closed outer loop. The method further generates a d-axis reference current from the DC voltage error, wherein the second-order harmonic in the d-axis reference current is delayed from that in q-axis reference current by 90 degrees. The method generates a q-axis current from the q-axis reference current. The method generates a d-axis current from the d-axis reference current. The second-order harmonic in d-axis current is offset from the second-order harmonic in q-axis current by 90 degrees. The method controls the DC bus voltage of a voltage control plant to mitigate a second-order harmonic in the DC bus voltage with the second-order harmonics in the q-axis current and the d-axis current.

Abstract: A component includes an adaptive estimator. A converter includes a switching rectifier connected to an LCL filter with a converter inductor, a capacitor, and grid inductor connected to a voltage source through a conductor with unknown inductance. Current of the converter inductor is input to the adaptive estimator which includes an ideal LCL filter model that generates, using a simple filter, a desired dynamic behavior of the converter and LCL filter and a disturbance compensator. An LCL steady-state (“SS”) compensation models a steady-state effect of the LCL filter and conductor. Output of the adaptive estimator is subtracted from output of the LCL SS compensation to form a disturbance estimate, which is summed with a feedback loop output of the converter to form a voltage control signal that controls switching of the switching rectifier. The voltage control signal is summed with the disturbance estimate and is input to the adaptive estimator.

Abstract: A system may include a power converter and a control system communicatively coupled to the power converter. The control system may determine a first DC voltage associated with the DC bus based on one or more DC external capacitance values that correspond to one or more loads coupled to the power converter. The control system may also determine a second DC voltage associated with the DC bus based on a capacitance of a system in which the power converter operates. The control system may also determine a third DC voltage associated with the DC bus based on the first DC voltage and the second DC voltage and adjust an operation of the power converter based on the third DC voltage.

Abstract: A system may include a power converter and a control system communicatively coupled to the power converter. The control system may determine a first DC voltage associated with the DC bus based on one or more DC external capacitance values that correspond to one or more loads coupled to the power converter. The control system may also determine a second DC voltage associated with the DC bus based on a capacitance of a system in which the power converter operates. The control system may also determine a third DC voltage associated with the DC bus based on the first DC voltage and the second DC voltage and adjust an operation of the power converter based on the third DC voltage.

Abstract: A system may include a power converter and a control system communicatively coupled to the power converter. The control system may determine a first DC voltage associated with the DC bus based on one or more DC external capacitance values that correspond to one or more loads coupled to the power converter. The control system may also determine a second DC voltage associated with the DC bus based on a capacitance of a system in which the power converter operates. The control system may also determine a third DC voltage associated with the DC bus based on the first DC voltage and the second DC voltage and adjust an operation of the power converter based on the third DC voltage.

Abstract: System, apparatus and methods are provided for identifying a phase loss condition in a motor drive. In one example, a power conversion system includes an active rectifier, a switching inverter, and a controller. The controller is operative to generate rectifier switching control signals to operate the rectifier, measure AC input voltage signals and determine grid current signals. If the rectifier circuit is not in a switching mode, the controller identifies a suspected AC input phase loss condition if two of the AC input voltage signals are in phase with one another. If the rectifier is in the switching mode, the controller identifies a suspected AC input phase loss condition if the absolute value of the sum of two of the grid current signals is less than a predetermined non-zero threshold.

Abstract: Disclosed examples include power conversion systems, computer readable mediums and methods for mitigating input filter resonance, in which a controller operates an active front end (AFE) rectifier in a first mode to turn a single rectifier switching device on and off and measures a filter voltage or current signal while all of the rectifier switches are off. The controller determines a resonant frequency based on a transient response of the measured voltage or current signal, and selectively adjusts a rectifier control parameter to mitigate filter resonance based on the resonant frequency.

Abstract: Power conversion systems and methods are provided for ride through of abnormal grid conditions or disturbances, in which a system rectifier is operated in a first mode to regulate a DC voltage of an intermediate DC circuit, an inverter is operated in the first mode to convert DC power from the intermediate DC circuit to provide AC output power to drive a load. In response to detecting an abnormal grid condition, the system changes to a second mode in which the rectifier is turned off and the inverter regulates the DC voltage of the intermediate DC circuit using power from the load.

Abstract: Disclosed examples include power conversion systems, computer readable mediums and methods for mitigating input filter resonance, in which a controller operates an active front end (AFE) rectifier in a first mode to turn a single rectifier switching device on and off and measures a filter voltage or current signal while all of the rectifier switches are off. The controller determines a resonant frequency based on a transient response of the measured voltage or current signal, and selectively adjusts a rectifier control parameter to mitigate filter resonance based on the resonant frequency.

Abstract: Power conversion systems and methods are provided for ride through of abnormal grid conditions or disturbances, in which a system rectifier is operated in a first mode to regulate a DC voltage of an intermediate DC circuit, an inverter is operated in the first mode to convert DC power from the intermediate DC circuit to provide AC output power to drive a load. In response to detecting an abnormal grid condition, the system changes to a second mode in which the rectifier is turned off and the inverter regulates the DC voltage of the intermediate DC circuit using power from the load.

Abstract: System, apparatus and methods are provided for identifying a phase loss condition in a motor drive. In one example, a power conversion system includes an active rectifier, a switching inverter, and a controller. The controller is operative to generate rectifier switching control signals to operate the rectifier, measure AC input voltage signals and determine grid current signals. If the rectifier circuit is not in a switching mode, the controller identifies a suspected AC input phase loss condition if two of the AC input voltage signals are in phase with one another. If the rectifier is in the switching mode, the controller identifies a suspected AC input phase loss condition if the absolute value of the sum of two of the grid current signals is less than a predetermined non-zero threshold.

Abstract: Impedance detection methods and systems are presented for automatic computation of an electrical component impedance value at one or more specific frequencies of interest using quadrature voltage and current values generated by quadrature tracking filters based on sensed or measured voltage and current signals or values and a base frequency input.

Abstract: Described herein are methods, systems, and apparatuses for determining sag in a signal. In one example, a method of tracking sag in a signal includes, when in an initial state, monitoring for when the signal transitions to a sag state based at least on an output of a tracking filter. In response to the signal transitioning to the sag state, increasing a bandwidth of the tracking filter and, when in the sag state, monitoring for when the signal transitions to a recovering state. The method further includes, in response to the signal transitioning to the recovering state, decreasing the bandwidth of the tracking filter.

Abstract: Methods and apparatus are presented for unintentional islanding detection for grid tie converters in which the phase angle disturbance is introduced by modification of grid side converter switching control signals and a mismatch of reactive power between generation and the grid load is formed upon the occurrence of unintentional islanding, where the applied phase disturbance is determined according to two pre-defined curves to form an equivalent positive feedback at different frequencies to prevent the converter from forming an island at a new stable frequency after the grid is disconnected.

Abstract: Present embodiments relate to a method for synchronizing an electric grid. The method includes receiving a phase voltage of the electric grid. The method further includes determining one or more disturbance frequencies in the phase voltage via a plurality of sequential tracking filters, wherein each of the plurality of tracking filters corresponds to a harmonic of the received phase voltage. The method further includes removing the disturbance frequencies components sequentially to produce a minimally distorted frequency, and performing a PLL operation on the clean frequency to determine a phase angle of the frequency.

Abstract: Present embodiments relate to a method for synchronizing an electric grid. The method includes receiving a phase voltage of the electric grid. The method further includes determining one or more disturbance frequencies in the phase voltage via a plurality of sequential tracking filters, wherein each of the plurality of tracking filters corresponds to a harmonic of the received phase voltage. The method further includes removing the disturbance frequencies components sequentially to produce a minimally distorted frequency, and performing a PLL operation on the clean frequency to determine a phase angle of the frequency.

Abstract: A phase angle detector with a PLL, a power converter, and a method for reducing offsets in an input signal, in which an adaptive offset processor selectively removes a DC offset component from the input signal to generate a modified signal including a fundamental frequency component and higher order harmonics of the input signal with the DC offset component removed, and the PLL provides a phase angle signal at least partially according to the modified signal.

Abstract: A double fed induction generator (DFIG) converter, methods and computer readable mediums are presented in which rotor side current spikes are attenuated by selectively activating at least one series damping circuit to conduct current through a series damping circuit resistance coupled in series between one or more DFIG rotor leads and a grid side converter in response to a grid fault occurrence or a grid fault clearance, and selectively bypassing the series damping circuit resistance after activating the series damping circuit.