Laxman Maharjan

State-of-Charge (SOC)-Balancing Control of a Battery Energy Storage System Based on a Cascade PWM Converter

Renewable energy sources such as wind turbine generators and photovoltaics produce fluctuating electric power. The fluctuating power can be compensated by installing an energy storage system in the vicinity of these sources. This paper describes a 6.6-kV battery energy storage system based on a cascade pulsewidth-modulation (PWM) converter with focus on a control method for state-of-charge (SOC) balancing of the battery units. A 200-V, 10-kW, 3.6-kWh (13-MJ) laboratory system combining a cascade PWM converter with nine nickel metal hydride (NiMH) battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed balancing control.

A Transformerless Energy Storage System Based on a Cascade Multilevel PWM Converter With Star Configuration

This paper describes a transformerless energy storage system based on a cascade multilevel pulsewidth modulation converter with star configuration. The system is intended for power leveling of renewable energy sources, as well as for improving power quality and reliability of a power distribution system. This paper pays attention to active-power control and voltage-balancing control that are indispensable for proper operation of the energy storage system. A 200-V 10-kW 8.8-kJ downscaled laboratory system is designed, constructed, and tested, replacing electric double-layer capacitors with large-capacity electrolytic capacitors. Experimental results obtained from the laboratory system verify the viability and effectiveness of the 6.6-kV energy storage system.

Active-Power Control of Individual Converter Cells for a Battery Energy Storage System Based on a Multilevel Cascade PWM Converter

The battery energy storage system is an essential enabling device of the smart grid, because it helps grid connection of massive renewable energy resources. This paper has a brief discussion on a battery energy storage system based on a multilevel cascade pulsewidth-modulated (PWM) converter for its practical use. The active-power control of individual converter cells is presented to make it possible to charge and discharge the battery units at different power levels while producing a three-phase balanced line-to-line voltage. This results in the maximum utilization of battery energy even when the power-handling capabilities of the battery units differ. Experimental results obtained from a 200-V, 10-kW, 3.6-kWh battery energy storage system verify the effectiveness of the presented active-power control.

Fault-Tolerant Operation of a Battery-Energy-Storage System Based on a Multilevel Cascade PWM Converter With Star Configuration

This paper focuses on fault-tolerant control for a battery-energy-storage system based on a multilevel cascade pulsewidth-modulation (PWM) converter with star configuration. During the occurrence of a single-converter-cell or single-battery-unit fault, the fault-tolerant control enables continuous operation and maintains state-of-charge balancing of the remaining healthy battery units. This enhances both system reliability and availability. A 200-V, 10-kW, 3.6-kW·h laboratory system combining a three-phase cascade PWM converter with nine nickel-metal-hydride battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed fault-tolerant control.

A transformerless battery energy storage system based on a multilevel cascade PWM converter

Renewable energy sources such as wind turbine generators and photovoltaics produce a fluctuating electric power. A battery energy storage system (BESS) should be installed in the vicinity of these sources. The fluctuating power is compensated by appropriately controlling an active power stored in the battery. This paper describes a feasible circuit configuration of a 6.6-kV transformerless battery energy storage system based on a multilevel cascade PWM (pulse-width-modulation) converter, with focus on a control method for active power and SOC (state-of- charge) balancing. A 200-V, 10-kW, 3.6-kWh (13-MJ) laboratory system combining a multilevel cascade PWM converter with nine NiMH (nickel metal hydride) battery units is designed, constructed, and tested to verify the viability and effectiveness of the 6.6-kV system.

A Transformerless Energy Storage System Based on a Cascade PWM Converter with Star-Configuration

This paper describes a 6.6-kV transformerless energy storage system based on a cascade PWM converter with star-configuration. The system is intended to make a power system reliable and efficient, and to improve power quality in power systems. The paper pays attention to active-power control and voltage-balancing control that are indispensable for proper operation of the energy storage system. A 200-V, 10-kW, 8.8-kJ down-scaled laboratory system is designed, constructed, and tested replacing EDLCs (electric double layer capacitors) with large-capacity electrolytic capacitors. Experimental results obtained from the laboratory system verify the viability and effectiveness of the 6.6-kV system.

A battery energy storage system based on a multilevel cascade PWM converter

This paper describes a 6.6-kV battery energy storage system based on a multilevel cascade PWM (pulse-width-modulation) converter with star configuration. It discusses design concepts with and without a line-frequency transformer for grid connection. The control system consists of SOC(state-of-charge)-balancing control and fault-tolerant control. The former is indispensable for effective utilization of battery energy while the latter is required for maintaining continuous operation during a converter-cell or battery-unit fault. A 200-V, 10-kW, 3.6-kWh laboratory system combining a three-phase cascade PWM converter with nine NiMH (Nickel-metal-hydride) battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed control system.

Discussions on a battery energy storage system based on a cascade PWM converter with star configuration

This paper makes discussions on a battery energy storage system based on a multilevel cascade pulsewidth-modulated (PWM) converter for its practical use. Briefly discussed are several considerations including state-of-charge (SOC) balancing of multiple battery units, and fault tolerance of the system. An active-power control of individual converter cells is presented to make the multiple battery units charged or discharged at different power levels, producing a three-phase balanced line-to-line voltage. Experimental results obtained from a 200-V, 10-kW, 3.6-kWh battery energy storage system verify its effectiveness.