• Journal of Electrical Engineering and Technology
• /
• v.11 no.3
• /
• pp.629-638
• /
• 2016

This paper proposes a State-of-Charge (SOC) balancing control of Battery Power Modules (BPMs) for a modularized battery for Electric Vehicles (EVs) without additional balancing circuits. The BPMs are substituted with the single converter in EVs located between the battery and the inverter. The BPM is composed of a two-phase interleaved boost converter with battery modules. The discharge current of each battery module can be controlled individually by using the BPM to achieve a balanced state as well as increased utilization of the battery capacity. Also, an SOC balancing method is proposed to reduce the equalization time, which satisfies the regulation of a constant DC-link voltage and a demand of the output power. The proposed system and the SOC balancing method are verified through simulation and experiment.

• Journal of Electrical Engineering and Technology
• /
• v.9 no.5
• /
• pp.1471-1481
• /
• 2014

This paper presents the new power dissipation model of individual switching device in a high-level modular multilevel converter (MMC), which can be mostly used in voltage sourced converter (VSC) based high-voltage direct current (HVDC) system and flexible AC transmission system (FACTS). Also, the voltage balancing method based on sorting algorithm is newly proposed to advance the MMC functionalities by effectively adjusting switching variations of the sub-module (SM). The proposed power dissipation model does not fully calculate the average power dissipation for numerous switching devices in an arm module. Instead, it estimates the power dissipation of every switching element based on the inherent operational principle of SM in MMC. In other words, the power dissipation is computed in every single switching event by using the polynomial curve fitting model with minimum computational efforts and high accuracy, which are required to manage the large number of SMs. After estimating the value of power dissipation, the thermal condition of every switching element is considered in the case of external disturbance. Then, the arm modeling for high-level MMC and its control scheme is implemented with the electromagnetic transient simulation program. Finally, the case study for applying to the MMC based HVDC system is carried out to select the appropriate insulated-gate bipolar transistor (IGBT) module in a steady-state, as well as to estimate the proper thermal condition of every switching element in a transient state.

• Proceedings of the KIPE Conference
• /
• 2007.07a
• /
• pp.256-258
• /
• 2007

A charge equalization converter with parallel-connected primary windings of transformers is proposed in digest. The proposed work effectively balance the voltage among Lithium-Ion battery cells despite each battery cell has low voltage gap compared with its SOC. The principle of the proposed work is that the equalizing energy from all battery strings moves to the lowest voltage battery through the isolated dc/dc converter controlled by the corresponding bi-directional switch. In this digest, a prototype of four Lithium-Ion battery cells is optimally designed and implemented, and experimental results show that the proposed method has excellent cell balancing performance.

• Proceedings of the KIPE Conference
• /
• 2008.06a
• /
• pp.535-537
• /
• 2008

This paper proposes a modularized two-stage charge equalization converter for a series-connected lithium-ion battery string. In this paper, the series-connected battery sting is modularized into M modules, and each module has K cells in series. With this modularization, low voltage stress on the electronic devices can be achieved. A two-stage dc-dc converter with cell selection switches is employed. The first stage dc-dc converter steps down the high bus voltage to about 10 V. The second stage dc-dc converter integrated with selection switches equalizes the cell voltages. A prototype for 88 lithium-ion battery cells is optimally designed and implemented. Experimental results verify that the proposed equalization method has good cell balancing performance showing low voltage stress, small size, and low cost.

• Journal of Power Electronics
• /
• v.17 no.6
• /
• pp.1490-1499
• /
• 2017

The modular multilevel converter (MMC) is generally considered to be a promising topology for medium-voltage and high-voltage applications. However, in order to apply it to high-power applications, a huge number of switching devices is essential. The numerous switching devices lead to considerable switching losses, high cost and a larger heat sink for each of the switching device. In order to reduce the switching losses of a MMC, this paper analyzes the performance of the conventional discontinuous pulse-width modulation (DPWM) method and its efficiency. In addition, it proposes a modified novel DPWM method for advanced switching losses reduction. The novel DPWM scheme includes an additional rotation method for voltage-balancing and power distribution among sub modules (SMs). Simulation and experimental results verify the effectiveness and performance of the proposed modulation method in terms of its switching losses reduction capability.

• Journal of Power Electronics
• /
• v.19 no.4
• /
• pp.934-943
• /
• 2019

A current balance problem exists in multi-phase LLC converters due to the resonant parameter tolerance. This paper presents a current balancing method for interleaved three-phase half bridge LLC converters. This method regulates the phase shift angle of the driving signals between the three phases based on a converter with a floating Y-connection. The floating midpoint voltage has different influences on each phase current and makes the three-phase current balance performance better than midpoint non-floating systems. Phase shift control between modules can further regulate the midpoint voltage. Then three phase current sharing is realized without adding extra components. The current distributions in a midpoint non-floating system and a midpoint floating system are compared. Then the principle and implementation of the proposed control strategy are analyzed in detail. A 3kW prototype is built to verify the validity and feasibility of the proposed method.