Abstract: A DC monitoring system is configured to measure and analyze VFD (Variable Frequency Drive) operational characteristics. The VFD is configured to receive three-phase input power from a standardized source and to provide variable frequency three-phase output power to a three-phase motor. In some applications, the VFD and motor operate at a medium voltage. The VFD can include multiple inverter modules consisting of a DC section and switching section, also referred to as a multiple bus configuration. The DC monitoring system includes a measurement module coupled to each DC bus of the VFD, a data communication network, and a PQube monitoring device for transmitting data signals corresponding to voltage values of the VFD DC bus obtained in a medium voltage compartment to a low voltage compartment for processing and analysis. Processing of the data signals enables comparative and predictive analysis to determine early warning for possible capacitance failure in the VFD.

Abstract: A DC monitoring system is configured to measure and analyze VFD (Variable Frequency Drive) operational characteristics. The VFD is configured to receive three-phase input power from a standardized source and to provide variable frequency three-phase output power to a three-phase motor. In some applications, the VFD and motor operate at a medium voltage. The VFD can include multiple inverter modules consisting of a DC section and switching section, also referred to as a multiple bus configuration. The DC monitoring system includes a measurement module coupled to each DC bus of the VFD, a data communication network, and a PQube monitoring device for transmitting data signals corresponding to voltage values of the VFD DC bus obtained in a medium voltage compartment to a low voltage compartment for processing and analysis. Processing of the data signals enables comparative and predictive analysis to determine early warning for possible capacitance failure in the VFD.

Abstract: A system measures the stability of a live a.c. power distribution grid, without disrupting sensitive loads on that grid. The system applies repetitive time-synchronized loads to create current pulses, and resulting voltage instabilities, on the grid. The current pulses are sized to ensure that the resulting voltage instabilities are too small to affect the sensitive loads. Time-synchronized voltage measurement devices record the voltage instabilities. The time synchronization, and the repetitive nature of the current pulses, allow the voltage instabilities caused by the current pulses to be extracted from the larger background voltage variations.

Abstract: A method and apparatus for detecting cyber attacks on remotely-operable elements of an alternating current distribution grid. Two state estimates of the distribution grid are prepared, one of which uses micro-synchrophasors. A difference between the two state estimates indicates a possible cyber attack.

Abstract: A method and apparatus are provided for capturing voltage phase angle data on an alternating current power grid. The method includes periodically making a voltage phase angle measurement at each of a plurality of locations on the alternating current power grid relative to a timing reference signal (e.g., a GPS timing signal) that is available at each location. For each of the locations, the voltage phase angle measurements are stored locally at the location. A trigger event is selected that will be simultaneously detectable at two or more of the locations. The method includes monitoring for the trigger event at each of the plurality of locations. In response to detecting the trigger event at one or more of the locations, a select amount of pre-trigger and post-trigger measurements are transmitted over a data communications network to a pre-designated destination from each location at which the trigger event was detected.

Abstract: A means and method for measuring precise voltage phasors on medium-voltage alternating current (AC) distribution grids, using existing distribution transformers as voltage sensors. The errors introduced by the distribution transformers are minimized by taking into account the transformer's vector impedance, combined with measuring the transformer secondary current phasor. The invention includes a means and a method of measuring the distribution transformer's vector impedance.

Abstract: A voltage sag generator for alternating current power systems intentionally creates power quality disturbances. The sag generator combines different switching technologies to optimize power dissipation and transition performance.

Abstract: A voltage sag generator for alternating current power systems intentionally creates power quality disturbances. The sag generator has a switch-mode impedance between its input and its output. Varying the duty-cycle of the switch-mode impedance causes voltage sags.