Abstract: A method for determining phase angle in phase shift transformer for medium voltage inverter is disclosed, the method including selecting an arbitrary phase shift angle and phase angle relative to a unit power cell of the first stage, determining a phase angle displacement in consideration of the phase shift angle and the number of unit power cells connected to each phase of a motor, determining a phase angle of the unit power cell at the second stage using a phase angle of the unit power cell at the first stage, and adjusting a phase angle when the determined phase angle of the unit power cell at the second stage exceeds a predetermined phase angle.

Abstract: An apparatus for estimating a parameter of an induction motor is provided. The estimating apparatus receives an output from a current controller and d and q-axis currents in a synchronous reference frame applied to an induction motor, calculates an error of rotor resistance, and obtains a difference between the rotor resistance and nominal rotor resistance.

Abstract: A cascaded H-bridge inverter capable of operating in bypass mode is disclosed where a bypass function can be performed through control of power switch, instead of allowing each unit power cell forming a cascaded H-bridge inverter to use a separate bypass switch, and a cell driver controls each power switch in a freewheeling mode to allow a current inputted to any output terminal to flow other output terminals when bypass function is to be performed for relevant unit power cell, whereby a stable operation can be performed even if there is no bypass switch at each unit power cell, and a cost saving can be accomplished, because an additional bypass switch such as a MC (Magnetic Controller) is not used.

Abstract: An apparatus for estimating a parameter of an induction motor is provided. The estimating apparatus receives an output from a current controller and d and q-axis currents in a synchronous reference frame applied to an induction motor, calculates an error of rotor resistance, and obtains a difference between the rotor resistance and nominal rotor resistance to calculate stator resistance therefrom.

Abstract: An apparatus for controlling an induction motor is provided, the apparatus generates generating a d-axis current command and a q-axis current command of a torque command, estimating speed of a rotor of the motor, and correcting the d-axis and q-axis current commands by using the estimated speed, to enhances the rotor speed and position estimation performance by increasing the slip frequency.

Abstract: An apparatus for estimating capacitance of a DC link capacitor in an inverter is provided. The apparatus for estimating capacitance of a DC link capacitor selects a unit power cell in which capacitance of a DC link capacitor is to be estimated, from unit power cells, and estimates capacitance of the DC link capacitor by correcting a reference voltage that controls a plurality of unit power cells.

Abstract: A control apparatus for regenerative medium voltage inverter is disclosed. The control apparatus controls a switching of a PWM converter unit by generating a voltage compensating a power difference between an input and an output of the PWM converter unit.

Abstract: An apparatus for controlling an induction machine is disclosed, wherein a magnitude of a current outputted to the induction machine to an inverter is determined by the apparatus to determine a voltage amount that compensates the command voltage in response to the magnitude of the current, and a voltage compensation amount is added to a command voltage determined from a voltage-frequency relationship according to a relevant voltage compensation amount to output a final command voltage.

Abstract: A phase compensation apparatus in an inverter output voltage in a system is provided, whereby performance of an inverter can be enhanced by compensating a time delay of measured voltage of inverter output voltage detection unit.

Abstract: An apparatus for restarting a medium voltage inverter is disclosed, wherein the inverter changes a voltage or a frequency outputted to a motor in response to an input voltage of the motor and a rotor speed of the motor and a predetermined voltage-frequency ratio.

Abstract: An inverter device may include a converter unit configured to receive single phase AC power to output DC power; a capacitor unit configured to absorb the DC power; an inverter unit configured to synthesize the absorbed DC power to output the drive power of a load; and a converter controller configured to control the converter unit based on the AC power and the output DC power of the converter unit, wherein the converter controller includes a converter gate signal generator configured to control a plurality of gates contained in the converter unit; and an input line harmonic voltage generator configured to output converter additional power having a predetermined multiple of the frequency of the fundamental frequency component of the AC power with the same size as that of the fundamental frequency component of the AC power to an adder connected to the input side of the converter gate signal generator.

Abstract: The disclosure relates to an electric power conversion apparatus, and capable of determining a minimum output voltage of a boost converter based on a voltage of the grid, and comparing the minimum output voltage of the converter with an input voltage of the converter, and controlling the operation of the converter based on the comparison result, thereby reducing the unnecessary operation and switching loss of the converter, the electric power conversion apparatus according to the invention comprises a converter; and a control unit configured to detect a grid voltage to determine a minimum output voltage of the converter based on the grid voltage, and control the operation of the converter based on an input voltage of the converter and the determined minimum output voltage.

Abstract: A method for determining phase angle in phase shift transformer for medium voltage inverter is disclosed, the method including selecting an arbitrary phase shift angle and phase angle relative to a unit power cell of the first stage, determining a phase angle displacement in consideration of the phase shift angle and the number of unit power cells connected to each phase of a motor, determining a phase angle of the unit power cell at the second stage using a phase angle of the unit power cell at the first stage, and adjusting a phase angle when the determined phase angle of the unit power cell at the second stage exceeds a predetermined phase angle.

Abstract: A multi-level medium-voltage inverter that receives three-phase power and outputs a three-phase voltage to a three-phase motor, includes: a plurality of unit power cells connected in series to output a single phase voltage, individual unit power cells each having a phase voltage forming a single level to configure multiple levels; and a module-type phase shift transformer configured to convert the three-phase power and applying the converted power to three unit power cells constituting one level, wherein the module-type phase shift transformer includes a plurality of modules.

Abstract: An apparatus for determining start of electric machine is disclosed wherein a frequency of a 3-phase current inputted from a motor is estimated to determine whether the motor has started using a difference between the estimated frequency and a frequency of output voltage of inverter configured to drive the motor.

Abstract: A multi-level inverter includes: a rectifying unit to rectify received a three-phase voltage; a smoothing unit to receive the rectified voltage and provide the rectified voltage as voltages having different levels to first to third different nodes; and an inverter unit including a plurality of switch units to transfer the voltages having three levels provided from the smoothing unit, wherein the inverter unit includes a first switch unit provided between the first node and a first output terminal, a second switch unit provided between the second node and the first output terminal, a third switch unit provided between the third node and the first output terminal, a fourth switch unit provided between the first node and a second output terminal, a fifth switch unit provided between the second node and the second output terminal, and a sixth switch unit provided between the third node and the second output terminal.

Abstract: A multilevel inverter having a configuration adequate to enhance efficiency while reducing conduction loss is disclosed, the multilevel inverter including a rectifier, a smoothing unit and an inverter unit, wherein the inverter unit includes a first switch unit interposed between the first node and a first output terminal, second switch units interposed between the second node and the first output terminal, a third switch unit interposed between the third node and the first output terminal, a fourth switch unit interposed between the first node and a second output terminal, fifth switch units interposed between the second node and the second output terminal and a sixth switch unit interposed between the third node and the second output terminal.

Abstract: A multilevel inverter having an efficient structure is provided, the multilevel inverter including a modularized phase-shift transformer including a plurality of modules to provide a phase shifted voltage by receiving a 3-phase input voltage, a plurality of first group unit power cells configured to provide an output voltage of predetermined phase, a plurality of second group unit power cells configured to provide an output voltage of predetermined phase, a plurality of third group unit power cells configured to provide an output voltage of predetermined phase. One of the first group unit power cells, one of the second group unit power cells and one of the third group unit power cells are paired to provide an output voltage of same phase.

Abstract: A sensor-less vector control apparatus for induction motor enhanced in performance of sensor-less vector control by estimating changes in parameters in real time is provided, the apparatus including a current controller, a first phase converting unit, a second phase converting unit, a rotor speed and position estimator configured to measure a rotor speed of a rotor and a rotor flux using an output value of the first phase converting unit and to estimate a rotor position using the output value, and a stator resistance and angle error estimator configured to calculate a stator resistance and an angle error of the induction motor by receiving d, q axis current commands on the synchronous reference frame inputted from the current controller and d, q voltages on the synchronous reference frame outputted from the current controller, and to provide the stator resistance to the rotor speed and position estimator.

Abstract: Provided is an energy storage system including: a battery device that is configured from multiple battery unit modules; and a power converting system that is configured to be connected to the battery device and that converts electric power that is applied between an electric power system and the battery device, in which the battery device includes multiple switches, each of which establishes a connection between each of the battery unit modules and the power converting system.