Abstract: A converter circuit is provided. The converter circuit includes a capacitor module, bridge arms, a voltage measuring module and an open-circuit detection module. Each bridge arm is connected to the capacitor module in parallel and includes an upper arm and a lower bridge arm connected at a middle point. The voltage measuring module measures voltage differences between each two bridge arms. The open-circuit detection module transmits test impulse signals to the bridge arms to activate at least one upper-conducted bridge arm and at least one lower-conducted bridge arm. The open-circuit detection module retrieves the voltage differences of each pair of the upper-conducted and lower-conducted bridge arms to make comparison with a reference value to determine an operation state thereof, and makes comparison of the operation state determined according to the different groups of test impulse signals to determine whether the upper and the lower bridge arms are actually open circuit.

Abstract: A method for detecting a short circuit fault in a multi-level inverter circuit is provided. The multi-level inverter circuit includes a plurality of single phase branches each including of switches. The method includes steps outlined below. At least one detecting pulse sequence is transmitted to the switches of each of the single phase branches. Whether a conducting path is formed in any of the single phase branches is determined according to the detecting pulse sequence. When the conducting loop is formed, respective position of one or more malfunctioned switch in the single phase branches is located according to a path of the conducting loop. A short-circuit detection device and a three-phase three-level inverter circuit are also disclosed herein.

Abstract: A five-level converting device includes an AC terminal, a bus capacitor module having a positive terminal, a negative terminal and a neutral terminal, a first switch module and a second switch module. The first switch module includes a bidirectional switching circuit, and the bidirectional switching circuit includes two first switching units reversely connected in series. The second switch module includes two second switching units, two third switching units, two fourth switching units, and two fifth switching units. The two second switching units are cascaded and connected to the two fourth switching units in parallel. The third, the fourth and the fifth switching units are cascaded and are connected to the bus capacitor module in parallel. Two different connection points of the first switch module are connected to the third switching units and fifth switching units through two flying capacitor modules respectively.

Abstract: A voltage sampling system is provided. The voltage sampling system includes a voltage sampling device, two optic-fiber transmission lines and a control device. The voltage sampling device includes a voltage-dividing resistor module, a common mode rejection circuit and an analog-to-digital converter. The voltage-dividing resistor module generates a first and a second divided voltages according to a voltage source. The common mode rejection circuit receives the first and the second divided voltages to perform a common-mode noise rejecting process to generate an output voltage. The analog-to-digital converter converts the output voltage to generate a digital data signal. The two optic-fiber transmission lines transmit the digital data signal and a clock signal respectively. The control device receives the digital data signal from the analog-to-digital converter and the clock signal to perform a digital data processing.

Abstract: A five-level converting device includes a first switch module, a second switch module and a third switch modules each connects to a neutral point, a positive terminal and a negative terminal of a bus capacitor module. A first switch module includes a plurality of bidirectional switching circuits cascaded to each other, and each bidirectional switching circuit includes two first switching units reversely connected in series. Second switch module includes a plurality of second switching units connected in series. Third switch module includes a plurality of third switching units connected in series. A first flying capacitor unit is connected across the first switching module and a second switch module, and a second flying capacitor unit is connected across the first switching module and a third switching module. The first flying capacitor unit and the second flying capacitor unit are connected to different connection points between the first switch units respectively.

Abstract: A voltage sampling system is provided. The voltage sampling system includes a first and a second input paths and a signal-processing module. The first input path includes a first input voltage-dividing resistor unit, a second input voltage-dividing resistor unit and a first DC voltage-dividing resistor unit to generate a first input divided voltage and a first DC bias voltage to further generate a first sampled voltage signal according to a first input voltage and a DC voltage source. The second input path includes a third input voltage-dividing resistor unit, a fourth input voltage-dividing resistor unit and a second DC voltage-dividing resistor unit to generate a second input divided voltage and a second DC bias voltage to further generate a second sampled voltage signal according to a second input voltage and the DC voltage source. The signal-processing module receives the first and the second sampled voltage signals to perform signal processing.

Abstract: A five-level converting device includes a first switch module, a second switch module and a third switch modules each connects to a neutral point, a positive terminal and a negative terminal of a bus capacitor module. A first switch module includes a plurality of bidirectional switching circuits cascaded to each other, and each bidirectional switching circuit includes two first switching units reversely connected in series. Second switch module includes a plurality of second switching units connected in series. Third switch module includes a plurality of third switching units connected in series. A first flying capacitor unit is connected across the first switching module and a second switch module, and a second flying capacitor unit is connected across the first switching module and a third switching module. The first flying capacitor unit and the second flying capacitor unit are connected to different connection points between the first switch units respectively.

Abstract: A five-level converting device includes an AC terminal, a bus capacitor module having a positive terminal, a negative terminal and a neutral terminal, a first switch module and a second switch module. The first switch module includes a bidirectional switching circuit, and the bidirectional switching circuit includes two first switching units reversely connected in series. The second switch module includes two second switching units, two third switching units, two fourth switching units, and two fifth switching units. The two second switching units are cascaded and connected to the two fourth switching units in parallel. The third, the fourth and the fifth switching units are cascaded and are connected to the bus capacitor module in parallel. Two different connection points of the first switch module are connected to the third switching units and fifth switching units through two flying capacitor modules respectively.

Abstract: A mid-voltage variable-frequency driving system and a total harmonic distortion compensation control method are provided in this invention. The mid-voltage variable-frequency driving system includes a total harmonic distortion compensation unit. The total harmonic distortion compensation unit is used to perform an optimal adjustment on a reactive component reference value of a grid-side phase current, such that a harmonic component of the grid-side phase current may be reduced and a power factor of a three-phase switch-mode rectifier module within the mid-voltage variable-frequency driving system may be maintained.

Abstract: A voltage sampling system is provided. The voltage sampling system includes a voltage sampling device, two optic-fiber transmission lines and a control device. The voltage sampling device includes a voltage-dividing resistor module, a common mode rejection circuit and an analog-to-digital converter. The voltage-dividing resistor module generates a first and a second divided voltages according to a voltage source. The common mode rejection circuit receives the first and the second divided voltages to perform a common-mode noise rejecting process to generate an output voltage. The analog-to-digital converter converts the output voltage to generate a digital data signal. The two optic-fiber transmission lines transmit the digital data signal and a clock signal respectively. The control device receives the digital data signal from the analog-to-digital converter and the clock signal to perform a digital data processing.

Abstract: A voltage sampling system is provided. The voltage sampling system includes a first and a second input paths and a signal-processing module. The first input path includes a first input voltage-dividing resistor unit, a second input voltage-dividing resistor unit and a first DC voltage-dividing resistor unit to generate a first input divided voltage and a first DC bias voltage to further generate a first sampled voltage signal according to a first input voltage and a DC voltage source. The second input path includes a third input voltage-dividing resistor unit, a fourth input voltage-dividing resistor unit and a second DC voltage-dividing resistor unit to generate a second input divided voltage and a second DC bias voltage to further generate a second sampled voltage signal according to a second input voltage and the DC voltage source. The signal-processing module receives the first and the second sampled voltage signals to perform signal processing.

Abstract: A converter circuit is provided. The converter circuit includes a capacitor module, bridge arms, a voltage measuring module and an open-circuit detection module. Each bridge arm is connected to the capacitor module in parallel and includes an upper arm and a lower bridge arm connected at a middle point. The voltage measuring module measures voltage differences between each two bridge arms. The open-circuit detection module transmits test impulse signals to the bridge arms to activate at least one upper-conducted bridge arm and at least one lower-conducted bridge arm. The open-circuit detection module retrieves the voltage differences of each pair of the upper-conducted and lower-conducted bridge arms to make comparison with a reference value to determine an operation state thereof, and makes comparison of the operation state determined according to the different groups of test impulse signals to determine whether the upper and the lower bridge arms are actually open circuit.

Abstract: A method for detecting a short circuit fault in a multi-level inverter circuit is provided. The multi-level inverter circuit includes a plurality of single phase branches each including of switches. The method includes steps outlined below. At least one detecting pulse sequence is transmitted to the switches of each of the single phase branches. Whether a conducting path is formed in any of the single phase branches is determined according to the detecting pulse sequence. When the conducting loop is formed, respective position of one or more malfunctioned switch in the single phase branches is located according to a path of the conducting loop. A short-circuit detection device and a three-phase three-level inverter circuit are also disclosed herein.

Abstract: The present invention provides a medium voltage variable frequency driving system, including a three-phase switch-mode rectification module, a multilevel inverter and a high-capacity capacitor module. The three-phase switch-mode rectification module is coupled with a three-phase electrical grid, for converting an AC voltage input with a fixed operating frequency on the three-phase electrical grid into a DC voltage. The multilevel inverter is used for converting the DC voltage into an AC voltage with a required variable frequency, so as to drive an induction motor. The high-capacity capacitor module is coupled between the three-phase switch-mode rectification module and the multilevel inverter, for temporarily storing the DC voltage. In the present invention, a three-phase switch-mode rectification technology is used at the front-end rectifier, and a diode-clamped three-level inverter is adapted correspondingly at the rear-end inverter.

Abstract: A mid-voltage variable-frequency driving system and a total harmonic distortion compensation control method are provided in this invention. The mid-voltage variable-frequency driving system includes a total harmonic distortion compensation unit. The total harmonic distortion compensation unit is used to perform an optimal adjustment on a reactive component reference value of a grid-side phase current, such that a harmonic component of the grid-side phase current may be reduced and a power factor of a three-phase switch-mode rectifier module within the mid-voltage variable-frequency driving system may be maintained.

Abstract: The present invention provides a medium voltage variable frequency driving system, including a three-phase switch-mode rectification module, a multilevel inverter and a high-capacity capacitor module. The three-phase switch-mode rectification module is coupled with a three-phase electrical grid, for converting an AC voltage input with a fixed operating frequency on the three-phase electrical grid into a DC voltage. The multilevel inverter is used for converting the DC voltage into an AC voltage with a required variable frequency, so as to drive an induction motor. The high-capacity capacitor module is coupled between the three-phase switch-mode rectification module and the multilevel inverter, for temporarily storing the DC voltage. In the present invention, a three-phase switch-mode rectification technology is used at the front-end rectifier, and a diode-clamped three-level inverter is adapted correspondingly at the rear-end inverter.