Non-isolated Single Phase Research Articles

一种低漏电流六开关单相全桥并网逆变拓扑

针对非隔离型单相光伏并网逆变器中的漏电流问题，提出一种改进型低漏电流六开关单相全桥逆变器拓扑，通过在直流侧母线电压中点处增加开关管，并改进该拓扑的开关驱动信号，改变共模电流回路。分析了功率传输过程中改进拓扑结构的并网电流在正半周期和负半周期的流通路径及共模电压水平，对改进拓扑增加的两支开关管和二极管全桥在续流阶段的工作机制进行了详细分析。对比分析了Heric拓扑与改进拓扑的电压、电流及对漏电流抑制的有效性。仿真表明改进拓扑的漏电流远低于Heric拓扑，验证了提出的改进拓扑结构在抑制漏电流方面的有效性。 Focusing on the leakage current problem of non-isolated single-phase photovoltaic grid connected inverter, an improved H6 single-phase full bridge inverter with low leakage current was proposed. The switch is added at the voltage midpoint of DC bus and the drive signal of topology is improved to change the current loop of common mode. The topology of grid current flow path and common mode voltage level in the positive and negative half cycle were analyzed during the power transmission process, and working mechanism of the improved topology was explored in detail. Moreover, voltage and current of Heric topology with improved topology were compared and the effectiveness of leakage current suppression was analyzed as well. Simulation results show that the leakage current of improved topology will be much lower than that of Heric topology, and the effectiveness of proposed improved topology in suppressing leakage currents was validated.

A Nonisolated Single-Phase UPS Topology With 110-V/220-V Input–Output Voltage Ratings

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A circuit configuration of a single-phase nonisolated online uninterruptible power supply (UPS) with 110-V/220-V input–output voltage ratings is proposed, allowing the bypass operation without a transformer even if the input voltage is different from the output voltage. The converter consists of an ac–dc/dc–dc three-level boost converter combined with a double half-bridge inverter. In this type of configuration size, cost and efficiency are improved due to the reduced number of switches and batteries, and also, no low-frequency isolation transformer is required to realize bypass operation because of the common neutral connection. Both stages of the proposed circuit operate at high frequency by using a passive nondissipative snubber circuit in the boost converter and insulated-gate bipolar-transistor switches in the double half-bridge inverter, with low conduction losses, low tail current, and low switching losses. Principle of operation and experimental results for a 2.6-kVA prototype are presented to demonstrate the UPS performance. </para>

A Non-isolated Single Phase Ups Topology With 110v/220v Input Output Voltage Ratings

A circuit configuration of a single phase non-isolated on-line uninterruptible power supply (UPS) with 110V/220V input output voltage ratings is proposed, allowing the bypass operation without a transformer even if the input voltage is different of the output voltage. The converter consists of an AC-DC/DC-DC three level boost converter combined with a double half bridge inverter. In this type of configuration size, cost and efficiency are improved due to reduced number of switches and batteries, as well as no low frequency isolation transformer is required to realize bypass operation because of the common neutral connection. Both stages of the proposed circuit operate in high frequency, using a passive non-dissipative snubber circuit in the boost converter and IGBTs switches in the double half bridge inverter, with low conduction losses, low tail current and low switching losses. Principle of operation and experimental results for a 2.6kVA prototype are presented to demonstrate UPS performance.