Jin-Hyuk Park

Adaptive output voltage tracking controller for uncertain DC/DC boost converter

ABSTRACT This paper presents a cascade output voltage control strategy for an uncertain DC/DC boost converter adopting an adaptive current controller in its inner loop. Considering the non-linearity, load uncertainties and parameter uncertainties of the converter, the proposed controller is designed following the conventional cascade voltage controller design method. The proposed method makes the following three contributions. First, a coordinate transformation is introduced for the inner loop, enabling avoidance of the singularity problem caused by the estimates of uncertain parameters. Second, a slight modification to the adaptation law is performed to guarantee closed-loop stability in the presence of the time-varying component of the load current. Third, the outer-loop controller is devised such that its performance can be adjusted without any parameter information. The closed-loop performance is demonstrated through simulations and experiments using the DSP28335 with a 3 kW DC/DC boost converter.

Predictive Control Algorithm Including Conduction-Mode Detection for PFC Converter

This paper proposes a predictive control algorithm that includes conduction-mode detection for power factor correction (PFC) converter. In PFC converters, the line current is usually distorted because of the characteristics of the proportional-integral (PI) current controller. To improve the quality of the current, the PI current controller requires additional circuits or algorithms. However, because of the optimal duty cycle determined by estimating the next-state current in both the continuous-conduction mode and the discontinuous-conduction mode, the proposed predictive control method has a fast dynamic response and accuracy compared to the PI current-control method. Moreover, the proposed algorithm can detect the conduction mode without any additional circuitry or mode-detection algorithm using the characteristic of the optimal duty cycle calculated by the predictive control. These advantages of the proposed algorithm improve the quality of the line current for PFC converters. We verify the proposed method by performing experiment using a 1.5-kW PFC converter.

Second order harmonics reduction technique using model predictive control for household energy storage systems

This paper proposes an output current ripple reduction algorithm using model-based predictive control (MPC) for an energy storage system (ESS). In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The MPC predicts the output current of next state from a converter model. The optimal duty is determined by minimizing the error between the reference and the predicted current. Due to the calculated optimal duty, the dynamic response is fast. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation with the 3 kW ESS model.

Scheme to Improve the Line Current Distortion of PFC Using a Predictive Control Algorithm

This paper presents a scheme to improve the line current distortion of power factor corrector (PFC) topology at the zero crossing point using a predictive control algorithm in both the continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The line current in single-phase PFC topology is distorted at the zero crossing point of the input AC voltage because of the characteristic of the general proportional integral (PI) current controller. This distortion degrades the line current quality, such as the total harmonic distortion (THD) and the power factor (PF). Given the optimal duty cycle calculated by estimating the next state current in both the CCM and DCM, the proposed predictive control algorithm has a fast dynamic response and accuracy unlike the conventional PI current control method. These advantages of the proposed algorithm lower the line current distortion of PFC topology. The proposed method is verified through PSIM simulations and experimental results with 1.5 kW bridgeless PFC (BLPFC) topology.

Power Loss Analysis of EV Fast Charger with Wide Charging Voltage Range for High Efficiency Operation

Power losses of a 1-stage DC-DC converter and 2-stage DC-DC converter are compared in this paper. A phase-shift full-bridge DC-DC converter is considered as 1-stage topology. This topology has disadvantages in the stress of rectifier diodes because of the resonance between the leakage inductor of the transformer and the junction capacitor of the rectifier diode. 2-stage topology is composed of an LLC resonant full-bridge DC-DC converter and buck converter. The LLC resonant full-bridge DC-DC converter does not need an RC snubber circuit of the rectifier diode. However, there is the drawback that the switching loss of the buck converter is large due to the hard switching operation. To reduce the switching loss of the buck converter, SiC MOSFET is used. This paper analyzes and compares power losses of two topologies considering temperature condition. The validity of the power loss analysis and calculation is verified by a PSIM simulation model.

Improved DPWM scheme for improvement of grid current quality in a large-scale grid-connected inverter system with a LCL-filter

This paper proposes an improved discontinuous PWM (DPWM) method in a grid-connected inverter system. When the conventional 60° DPWM is used in the switching method, the output voltage of the inverter has many harmonics compared to the continuous PWM (CPWM) switching method. In large-scale system, a LCL-filter cannot sufficiency reduce the harmonics of the inverter output voltage. If these harmonics and the resonance frequency band caused by a grid-connected LCL-filter are overlapped, the grid current oscillates. To solve this problem, the proposed method continuously changes the discontinuous modulation signal by injecting triangular wave to modulation signal. The proposed algorithm can reduce the harmonics of inverter output voltage. The proposed DPWM is verified from PSIM simulation with a 600-kW 2-level grid-connected inverter system.

An improved DPWM method for reduction of resonant problem in the inverter

This paper proposes an improved discontinuous PWM (DPWM) algorithm. The modulation signal of the conventional DPWM changes discontinuously and has many harmonic components. If these harmonics components and the resonant frequency band by a grid-connected LCL-filter are overlapped, the grid current oscillates. To solve this problem, the proposed method uses the 6-th harmonic injection technique to the modulation signal. As the proposed method is used, the modulation signal changes smoothly and the harmonic components is sufficiently reduced. The proposed DPWM method is verified from the PSIM simulation with a 10 kW photovoltaic (PV) power conditioning system (PCS).

An optimal control method of clamp switch for ZVS bi-directional DC-DC converter

This paper proposes an optimal control method of clamp switch for ZVS bi-directional DC-DC converter. The bidirectional DC-DC converter using the clamp switch can achieve zero voltage switching (ZVS) operation. In this topology, the clamp switch separates the inductor current from input and output voltage and maintains minimum current for ZVS operation. The separation of the inductor current can reduce the inductor current ripple and the power loss of the power devices. Therefore, it is important to the optimal control method of clamp switch to improve the system efficiency. This paper proposes the optimal clamp switch control method using micro controller unit (MCU) without the additional circuit. The proposed control is verified from PSIM simulations using 1-kW ZVS bi-directional DC-DC converter system.

Robust optimal output voltage tracking algorithm for interleaved N-phase DC/DC boost converter with performance recovery property

ABSTRACT This article suggests a cascade output voltage regulation algorithm for an N-phase interleaved DC/DC boost converter based on reference dynamics. The proposed algorithm has two advantages. The first is to guarantee the performance recovery property using the reference dynamics in the presence of a model-plant mismatch, and the second is to present a systematic procedure determining the stabilising control gains by solving an optimisation problem. The closed-loop performance of the proposed method is evaluated through simulations and experiments using a 3-kW four-phase interleaved DC/DC boost converter where the proposed method is compared with the feedback linearising method.

Model-based Optimal Control Algorithm for the Clamp Switch of Zero-Voltage Switching DC-DC Converter

This paper proposes a model-based optimal control algorithm for the clamp switch of a zero-voltage switching (ZVS) bidirectional DC–DC converter. The bidirectional DC–DC converter (BDC) can accomplish the ZVS operation using the clamp switch. The minimum current for the ZVS operation is maintained, and the inductor current is separated from the input and output voltages by the clamp switch in this topology. The clamp switch can decrease the inductor current ripple, switching loss, and conduction loss of the system. Therefore, the optimal control of the clamp switch is significant to improve the efficiency of the system. This paper proposes a model-based optimal control algorithm using phase shift in a micro-controller unit. The proposed control algorithm is demonstrated by the results of PSIM simulations and an experiment conducted in a 1-kW ZVS BDC system.