Abstract: An active current injection device is used to generate and inject fundamental and non-fundamental frequency current components onto an AC power line. A current pump control circuit receives an input signal which is representative of the line voltage of the power line. In response, the current pump control circuit generates a control signal which is used to generate a current component at the fundamental frequency which lags the line voltage by approximately 90 degrees. This fundamental frequency current component is transmitted through an impedance to the power line, thereby causing a voltage drop at the fundamental frequency across the impedance which is within a selected range about the line voltage. In one embodiment, this selected range is equal to approximately 25 to approximately 150 percent of the line voltage. Also, a damping control circuit receives an input signal which is representative of the line voltage of the power line.

Abstract: An active current injection device is used to generate and inject fundamental and non-fundamental frequency current components onto an AC power line. A current pump control circuit receives an input signal which is representative of the line voltage of the power line. In response, the current pump control circuit generates a control signal which is used to generate a current component at the fundamental frequency which lags the line voltage by approximately 90 degrees. This fundamental frequency current component is transmitted through an impedance to the power line, thereby causing a voltage drop at the fundamental frequency across the impedance which is within a selected range about the line voltage. In one embodiment, this selected range is equal to approximately 25 to approximately 150 percent of the line voltage. Also, a damping control circuit receives an input signal which is representative of the line voltage of the power line.

Abstract: An AC power line is monitored for currents and voltages at non-fundamental frequencies (including harmonics). A controlled active filter injects compensating current into the AC power line. The injected compensating current is responsive to both the sensed non-fundamental frequency current and to the sensed non-fundamental frequency voltage residing on the power line. In one embodiment, the controlled active filter comprises a transconductance amplifier which obtains its operating power from a controlled flow of power from the AC power line being monitored.