Abstract: A grid voltage phase detector includes: a d-q transformation unit for receiving a three-phase signal and producing a signal on d axis and a signal on q axis; a phase signal producing unit for producing a signal for phase synchronization of grid voltage from the signal on d axis and the signal on q axis; and a PR filtering unit, with a first filter having no change in magnitude and phase at a rated frequency, a second filter introducing 90° phase lead at a rated frequency, a third filter introducing 90° phase lag, and a fourth filter having no change in magnitude and phase at a rated frequency, for removing unbalanced components and harmonic components from the signal on d axis and the signal on q axis produced by the d-q transformation unit and providing the signals to the phase signal producing unit.

Abstract: A method for determining a scheme for converting power in every power conversion control period and converting power according to the determined scheme may comprise the steps of: calculating average power in a transformer inductor at the time of power conversion according to an SPWM scheme in a control period; calculating average power in the transformer inductor at the time of power conversion according to a DPWM scheme in a control period; and converting power according to a scheme by means of which the calculated average power of the transformer inductor is greater. Here, in the step of calculating the average power in the transformer inductor at the time of power conversion according to the DPWM scheme, it is possible to select a DPWM scheme with the maximum duty in a step-up or step-down condition given in the control period.

Abstract: Provided are a device and method for SoC balance control for a delta structure semiconductor transformer-based energy storage device, for operating a charging and discharging time of a system by controlling balance of battery SoC of a PCS connected by a delta connection so as to prevent overdischarging and overcharging of a specific battery, controlling a zero-phase-sequence component of the delta connection to balance the battery SoC for each phase, and controlling balance of an individual battery SoC. The device for SoC balance control for a delta structure semiconductor transformer-based energy storage device of the present invention is composed of an SoC balance control device that controls charging and discharging of a battery such that, in a PCS that performs charging and discharging from three-phase AC power, an A-phase, a B-phase, and a C-phase PCS connected by a delta connection, and the battery SoC of the PCS, are balanced.

Abstract: The present invention relates to a composite charging system and method capable of producing charging power for an electric vehicle by utilizing hydrogen energy supplied to a hydrogen vehicle, and compositely connecting hydrogen energy with a power system to efficiently perform charging of the electric vehicle, and more flexibly coping with the use of energy. The composite charging system according to the present invention comprises: a hydrogen charger which charges hydrogen into a vehicle; a hydrogen power supply system which generates and supplies power on the basis of hydrogen; a system power supply system which supplies power from a power system; an electric charger which charges the electric vehicle; and a battery power supply system which stores power supplied from the hydrogen power supply system and the system power supply system, and supplies the stored power to the electric charger.

Abstract: Proposed is a method for accurately predicting an overcurrent flowing inside an isolated bidirectional DC-DC converter even without using a current sensor on primary and secondary sides of a transformer. In the converter according to the present disclosure, an average value of the inductor current is calculated after deriving inflection point current values by respectively modeling a current waveform for an inductor current of the transformer. A secondary side output current average value is calculated by comparing the calculated average value of the inductor current with a secondary side capacitor current average value of the converter at no load. Next, an error between the secondary side output current average value and an actually measured secondary side output current is calculated, and the inflection point current values of the current waveform are updated using a gain for reducing the error through PI control, whereby the overcurrent may be predicted.

Abstract: A power facility for remote control includes: an analog sensing value reception unit that collects an internal analog sensing value of the power facility; a digital conversion unit that converts the analog sensing value into digital information; and a communication unit that transmits the digital information to an external remote control device by using one optical path. Therefore, by allowing a plurality of analog sensing values from the power facility to be transmitted to the remote control device by using one optical path, transmission efficiency can be increased, and by converting a plurality of analog sensing values of the power facility into digital information and transmitting the digital information with an asynchronous frame, the plurality of analog sensing values can be efficiently transmitted through one optical path without a separate synchronous signal.

Abstract: A grid voltage phase detector includes: a d-q transformation unit for receiving a three-phase signal and producing a signal on d axis and a signal on q axis; a phase signal producing unit for producing a signal for phase synchronization of grid voltage from the signal on d axis and the signal on q axis; and a PR filtering unit, with a first filter having no change in magnitude and phase at a rated frequency, a second filter introducing 90° phase lead at a rated frequency, a third filter introducing 90° phase lag, and a fourth filter having no change in magnitude and phase at a rated frequency, for removing unbalanced components and harmonic components from the signal on d axis and the signal on q axis produced by the d-q transformation unit and providing the signals to the phase signal producing unit.

Abstract: A method for determining a scheme for converting power in every power conversion control period and converting power according to the determined scheme may comprise the steps of: calculating average power in a transformer inductor at the time of power conversion according to an SPWM scheme in a control period; calculating average power in the transformer inductor at the time of power conversion according to a DPWM scheme in a control period; and converting power according to a scheme by means of which the calculated average power of the transformer inductor is greater. Here, in the step of calculating the average power in the transformer inductor at the time of power conversion according to the DPWM scheme, it is possible to select a DPWM scheme with the maximum duty in a step-up or step-down condition given in the control period.

Abstract: Provided is a switching control method for an isolated bidirectional DC-DC converter, wherein the isolated bidirectional DC-DC converter connected between a DC grid system and a battery uses multiple switching controls together depending on a voltage of the battery, thereby facilitating high efficiency control. In the isolated bidirectional DC-DC converter according to the present invention, switching of a first switching unit and a second switching unit is controlled to control the flow of power by changing the bidirectional DC-DC voltage between the DC grid system and the battery, and the first and the second switching unit are switched using PSM switching control, SPWM switching control, and DPWM switching control together depending on a voltage with which the battery is charged and load capacity, thereby enhancing efficiency of the system.

Abstract: Provided is a switching control method for an isolated bidirectional DC-DC converter, wherein the isolated bidirectional DC-DC converter connected between a DC grid system and a battery uses multiple switching controls together depending on a voltage of the battery, thereby facilitating high efficiency control. In the isolated bidirectional DC-DC converter according to the present invention, switching of a first switching unit and a second switching unit is controlled to control the flow of power by changing the bidirectional DC-DC voltage between the DC grid system and the battery, and the first and the second switching unit are switched using PSM switching control, SPWM switching control, and DPWM switching control together depending on a voltage with which the battery is charged and load capacity, thereby enhancing efficiency of the system.