A control module controls impedance injection units (IIUs) to form multiple connection configurations in sequence. Each connection configuration has one IIU, or multiple IIUs in series, parallel or combination of series and parallel. The connection configurations of IIUs are coupled to a high-voltage transmission line. The control module and the IIUs generate rectangular impedance injection waveforms. When the waveforms are combined and injected to the high-voltage transmission line, this produces a pseudo-sinusoidal waveform.

A control module controls impedance injection units (IIUs) to form multiple connection configurations in sequence. Each connection configuration has one IIU, or multiple IIUs in series, parallel or combination of series and parallel. The connection configurations of IIUs are coupled to a high-voltage transmission line. The control module and the IIUs generate rectangular impedance injection waveforms. When the waveforms are combined and injected to the high-voltage transmission line, this produces a pseudo-sinusoidal waveform.

A control module controls impedance injection units (IIUs) to form multiple connection configurations in sequence. Each connection configuration has one IIU, or multiple IIUs in series, parallel or combination of series and parallel. The connection configurations of IIUs are coupled to a high-voltage transmission line. The control module and the IIUs generate rectangular impedance injection waveforms. When the waveforms are combined and injected to the high-voltage transmission line, this produces a pseudo-sinusoidal waveform.

This invention describes a means of statically controlling the negative and zero sequence couplings of an overhead line with unequal spacing between phases and describes a means of controlling either the negative sequence coupling or the zero sequence coupling, which may be advantageous for some power system applications. In particular, this invention describes a means of reducing either the negative sequence coupling or the zero sequence coupling to a value approaching zero, thereby reducing the negative sequence or zero sequence induced voltage resulting from balanced current flows.

This invention describes a means of statically controlling the negative and zero sequence couplings of an overhead line with unequal spacing between phases and describes a means of controlling either the negative sequence coupling or the zero sequence coupling, which may be advantageous for some power system applications. In particular, this invention describes a means of reducing either the negative sequence coupling or the zero sequence coupling to a value approaching zero, thereby reducing the negative sequence or zero sequence induced voltage resulting from balanced current flows.

A power quality compensation system has the functions of controlling the bus voltage and the current peak value. A first instruction current under control of a first peak current processing unit is lower than or equal to a first current threshold value. A second peak current processing unit outputs a second PWM driving signal according to a sampled current and a second current threshold value. A third peak current processing unit outputs a third PWM driving signal according to the sampled current and a third current threshold value. A conversion unit is operated according to the PWM driving signals. Moreover, the first current threshold value is adjusted in real time according to the comparing result of the sample current and the first current threshold value and the comparing result of the real DC bus voltage and the reference DC bus voltage.

A power quality compensation system has the functions of controlling the bus voltage and the current peak value. A first instruction current under control of a first peak current processing unit is lower than or equal to a first current threshold value. A second peak current processing unit outputs a second PWM driving signal according to a sampled current and a second current threshold value. A third peak current processing unit outputs a third PWM driving signal according to the sampled current and a third current threshold value. A conversion unit is operated according to the PWM driving signals. Moreover, the first current threshold value is adjusted in real time according to the comparing result of the sample current and the first current threshold value and the comparing result of the real DC bus voltage and the reference DC bus voltage.

A power quality compensation system has the functions of controlling the bus voltage and the current peak value. A first instruction current under control of a first peak current processing unit is lower than or equal to a first current threshold value. A second peak current processing unit outputs a second PWM driving signal according to a sampled current and a second current threshold value. A third peak current processing unit outputs a third PWM driving signal according to the sampled current and a third current threshold value. A conversion unit is operated according to the PWM driving signals. Moreover, the first current threshold value is adjusted in real time according to the comparing result of the sample current and the first current threshold value and the comparing result of the real DC bus voltage and the reference DC bus voltage.

A power quality compensation system has the functions of controlling the bus voltage and the current peak value. A first instruction current under control of a first peak current processing unit is lower than or equal to a first current threshold value. A second peak current processing unit outputs a second PWM driving signal according to a sampled current and a second current threshold value. A third peak current processing unit outputs a third PWM driving signal according to the sampled current and a third current threshold value. A conversion unit is operated according to the PWM driving signals. Moreover, the first current threshold value is adjusted in real time according to the comparing result of the sample current and the first current threshold value and the comparing result of the real DC bus voltage and the reference DC bus voltage.

An impedance injection unit (IIU) system is coupled to a high-voltage (HV) transmission line. The IIUs are activated in sequences of activation in successive time periods. This injects an impedance waveform onto the HV transmission line. The ordering of IIUs in the sequences of activation is repeatedly changed in successive time periods. This equalizes electrical stress across the IIUs used, leading to overall improvement in IIU system lifetimes.