Three-Level DC Converter for Balancing DC 800-V Voltage

Abstract

This paper studies a three-level dc converter for balancing the dc input voltage, which has a similar topology with the conventional three-level dc converter. It can easily build a neutral line for changing a dc voltage source into two dc voltage-level sources. A control strategy of conducting time extension of partial switch devices is also presented for achieving three-level states of each power switch. The operating principle of the converter is analyzed in detail based on the presented control strategy. The small-signal model and the effects of the proposed control strategy are also driven. Finally, a prototype is fabricated and tested in the lab and the experimental results verify the converter to achieve three-level characteristics and to have a good ability of balancing the input voltage.

Three‐level dual‐buck voltage balancer with active output voltagesbalancing

“…The renewable resource generations based on DC grids, such as wind energy, photovoltaic generation and hybrid energy [12][13][14][15][16][17][18][19][20][21][22][23], are driven by the energy crisis and environmental pollution. Then, they can directly supply super high-quality electric power to consumers and have more attraction compared with the conventional AC power grids.…”

“…However, the aforementioned methods for balancing the input voltage of three-level topologies are not suitable for DC grids, because these methods only focus on three-level topologies themselves. Hence, from a viewpoint of DC power transmitting systems, it is a better way that a neutral line is independently built on substation side by a voltage balancer or DC redistributor [18][19][20][21][22][23]. So that the input voltage (u in ) can be split into two output voltage sources (u out1 and u out2 ).…”

“…Where the two sources may meet (u out = u out2 = u out1 ) and customers may have options to flexibly choose three voltage levels: u out , −u out and 2u out . Thus, the DC system has higher reliability, flexibility, and power quality [18][19][20][21][22][23]. Meanwhile, the neutral line connected with ground is particularly need for domestic and office devices from the view of the security of the persons.…”

“…The voltage balancer has two-level half-bridge balancer [19][20][21] and three-level half-bridge balancer [22]. Though the three-level half-bridge balancer can decrease the voltage stresses of power devices, the half-bridge topology may suffer from an inherent and potential shoot-through risk.…”

“…At last, the experimental results verify the theoretical analysis. Compared with the three-level halfbridge balancer [22], the proposed topology and control strategy are more complicated, but it does not have the inherent and potential shoot-through problem and a reactive circulating current.…”