Neng Zhang

A Single-Switch Quadratic Buck–Boost Converter With Continuous Input Port Current and Continuous Output Port Current

A single-switch quadratic buck–boost converter with continuous input port current and continuous output port current is proposed in this paper. Compared with the traditional buck-boost converter, the proposed converter can obtain a wider range of the voltage conversion ratio with the same duty cycle. Moreover, the proposed converter can operate with continuous input port current and continuous output port current compared to the existing counterparts with inherently discontinuous input port current and discontinuous output port current. The operating principle and steady-state performance of the proposed converter under continuous inductor current mode is analyzed in detail. Then, the comparison between the proposed converter and the existing quadratic buck–boost converters has been conducted to demonstrate the unique features of the proposed one. Finally, experimental results from a prototype built in the lab are recorded to verify the effectiveness and validity of the proposed quadratic buck–boost converter.

A four-port DC-DC converter to integrate energy storage system and solar PV to supply the grid and local load demand

In this paper, a four-port DC-DC converter is proposed for applications in a grid-connected integrated solar PV and energy storage system. The four ports of the converter are one input source, one bidirectional port, and two output ports. The bidirectional port can be used to integrate the energy storage system to the solar PV generation system, while the two outputs provide the flexibility to supply either two loads or a single load. The detailed analysis and two applications of the four-port DC-DC converter are given in this paper. All of the theoretical analyses are verified by the simulation results.

A Δ-Y Hybrid Impedance Network Boost Converter With Reduced Input Current Ripple

This letter is to present a Δ-Y hybrid impedance network based boost converter with reduced input current ripple. Comparing to the existing impedance network based boost converters to enhance the output port characteristic, i.e., voltage conversion ratio, of the traditional boost converter (TBC), the proposed converter applies the impedance network to improve its input port performance, i.e., the input current ripple issue. The proposed Δ-Y hybrid impedance network consists of the TBCs main inductor, an additional coupled inductor, and an additional resonant inductor and capacitor pair. Although the peak currents flowing through the diode and the switch are higher in comparison to the TBC, the proposed converter can remain TBCs voltage conversion feature and effectively reduce the input current ripple and the average current of the main inductor with the application of the Δ-Y hybrid impedance network. The operating principle of the proposed converter is explained and the principle of current ripple reduction is analyzed in detail. Experimental results from a prototype are carried out to validate the effectiveness of the proposed converter.

Systematic Derivation of Dead-Zone Elimination Strategies for the Noninverting Synchronous Buck–Boost Converter

The noninverting synchronous buck-boost converter is preferable to operate in buck and boost operating modes to obtain a high operating efficiency. However, the dead zone, which degrades the performance of the converter, will occur when the converter shifts from buck operating mode to boost operating mode or vice versa. Therefore, the origin of the dead zone is derived in this paper by analyzing the relationship between the voltage conversion ratio and the duty cycles of the switches. Based on this, a series of three-mode and four-mode modulation schemes are systematically derived to completely eliminate the dead zone. The ripple and average value of the inductor current under different modulation schemes are investigated to evaluate the performance of these modulation schemes. To demonstrate the effectiveness of the proposed modulation schemes, two implementations of a four-mode modulation scheme are presented and experimentally tested as the examples for all modulation schemes. Experimental results correspond well with the theoretical analysis in both implementations over the entire input voltage range.

An energy storage integrated dual-input PV system with distributed maximum power point tracking

This paper proposes an energy storage unit integrated dual input PV system with distributed maximum power point tracking (MPPT). Through applying a symmetrical configuration, the proposed PV system has a single stage structure to implement voltage boosting and inversion, which contributes to the advantages such as compact size and high power conversion efficiency. The design of the control strategy is relative easy due to the inherently decoupled connection among all ports of the system. Moreover, the intermittent nature of the solar power can be handled well by the integrated energy storage unit. The configuration and operation principle of the proposed PV system is explained and the design of the control strategy is derived in this paper. MATLAB/SIMULINK simulation results are used to verify the performance of the proposed PV system and the accordingly designed control strategy.

Analysis of the non-inverting buck-boost converter with four-mode control method

It is generally preferred for the non-inverting buck-boost converter to operate in buck mode when the input voltage is higher than the output voltage and in boost mode vice versa to improve the efficiency. However, the performance of the converter would be degraded under this operating scheme when the input voltage approaches to the output voltage due to the occurrence of the dead-zone. The four-mode control method is a potential solution to eliminate the dead-zone issue. This paper is to analyze the operating principle and the performance of the converter with four-mode control method. A prototype with 16.8V output voltage is tested in the laboratory. Analytical and experimental results show that the converter can obtain high efficiency, fast load and input voltage transient response in the entire input voltage range with the four-mode control method.

Design and control of a boost inverter based multi-input converter

By utilizing an inherently symmetrical differential structure, several boost DC/DC converters can be used to construct a multi input DC/DC or DC/AC converter. The use of integral state feedback based pole placement control strategy has been reported in the literature to control this type of converter. However, this control method is based on the small signal model of the circuit and highly dependent on the circuit operating point and the parameters of the components. In this paper, a control strategy based on the average model of the circuit is proposed for an integrated multi-input converter. The proposed control strategy can deal with the varying operating points, disturbances of the input voltage and varying load conditions. The design of the parameters in the circuit and the compensators in the control loop are discussed. Simulation results demonstrate the effectiveness of the proposed control strategy.

A buck-boost converter based multi-input DC-DC/AC converter

The buck-boost inverter can be easily used to construct a multi-input converter due to its inherent symmetrical and extendable differential structure. This paper proposed a multi-input converter derived from the buck-boost inverter to interface different input sources. When two pure DC voltages are chosen as the references for the two output capacitor voltages, the proposed converter will operate in DC-DC mode. When two dc-biased sinusoidal voltages with 180° phase shift are chosen as the references, the proposed converter will operate in DC-AC mode. Compared to the boost inverter based multi-input converters, an advantage is that the output voltages of the capacitors are not limited to be larger than the input voltages. A control strategy based on the average model of the circuit is proposed for the proposed converter. Single current control loops are designed for the buck-boost converters that used for interfacing the input sources and controlling the input power. Voltage-current double control loops are designed for the buck-boost converters that used for forming the buck-boost inverter and interfacing the energy storage system. The proposed control strategy can deal well with the varying operating points and the disturbances of the input voltage and load conditions. Simulation results are worked out to verify the effectiveness and validity of the proposed converter and its control strategy.

A novel topology for integration of solar PV and energy storage system

This paper proposes a compact topology for an integrated PV and energy storage system based on three boost converters and one bidirectional buck-boost converter. One of the boost converters is used for MPPT control, and the other two boost converters are used to implement a boost inverter that can generate sinusoidal waveform. A bidirectional buck-boost converter, to charge and discharge the energy storage system to balance the power gap between the PV panels and the load, is also integrated in the topology. A control strategy is developed to balance the supply and load demand. Simulation results validate the performance of the proposed topology and control strategy.