Evaluation of gaseous concentrations, bacterial diversity and microbial quantity in different layers of deep litter system

Li, Jing,Wang, Jingyu,Wang, Fujin,Wang, Aiguo,Yan, Peishi Asian Australasian Association of Animal Productio 2017 Animal Bioscience Vol.30 No.2

Objective: An experiment was conducted to investigate the environment of the deep litter system and provided theoretical basis for production. Methods: The bedding samples were obtained from a pig breeding farm and series measurements associated with gases concentrations and the bacterial diversity as well as the quantity of Escherichia coli, Lactobacilli, Methanogens were performed in this paper. Results: The concentrations of $CO_2$, $CH_4$, and $NH_3$ in the deep litter system increased with the increasing of depth while the $N_2O$ concentrations increased fiercely from the 0 cm to the -10 cm depth but then decreased beneath the -10 cm depth. Meanwhile, the Shannon index, the dominance index as well as the evenness index at the -20 cm layer was significantly different from the other layers (p<0.05). On the other hand, the quantity of Escherichia coli reached the highest value at the surface beddings and there was a significant drop at the -20 cm layer with the increasing depth. The Lactobacilli numbers increased with the depth from 0 cm to -15 cm and then decreased significantly under the -20 cm depth. The expression of Methanogens reached its largest value at the depth of -35 cm. Conclusion: The upper layers (0 cm to -5 cm) of this system were aerobic, the middle layers (-10 cm to -20 cm) were micro-aerobic, while that the bottom layers (below -20 cm depth) were anaerobic. In addition, from a standpoint of increasing the nitrification pathway and inhibiting the denitrification pathway, it should be advised that the deep litter system should be kept aerobic.

Performance Improvement in Single-Phase Electric Spring Control

Wang, Qingsong,Zuo, Wujian,Cheng, Ming,Deng, Fujin,Buja, Giuseppe The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.3

Two objectives can be pursued simultaneously with the ${\delta}$ control of a single-phase electric spring (ES). These objectives are the stabilization of the voltage across the critical load (CL) of a power system, and the achievement of a specific functionality similar to the pure compensation of reactive power or the correction of the power factor. However, existing control systems implementing the ${\delta}$ control do not cope with non-ideal operating conditions, such as line voltage distortions, and exhibit a somewhat sluggish regulation of the CL voltage. In an effort to improve both the steady-state and transient performances of an ES power system, this paper proposes implementing the ${\delta}$ control by means of a control system built up on the repetitive control and assisted by state feedback with pole assignment. This paper starts by analyzing the dynamics of an ES power system in terms of its poles and zeros. After that, a reduced second-order model of the dynamics is formulated to avoid a notch filter in the pole assignment. A repetitive control for an ES power system is then designed to meet the two above mentioned objectives. Experimental tests carried out on a laboratory setup demonstrate the effectiveness of the proposed control system in significantly improving the ES power system performance, while reaching the two objectives. In particular, the tests outline the large mitigation of harmonics in the CL voltage under line voltage distortions and its fast stabilization action.

A Dynamic Power Distribution Strategy for Large-scale Cascaded Photovoltaic Systems

Wang, Kangan,Wu, Xiaojie,Deng, Fujin,Liu, Feng The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

The cascaded H-bridge (CHB) multilevel converter is a promising topology for large-scale photovoltaic (PV) systems. The output voltage over-modulation derived by the inter-module active power imbalance is one of the key issues for CHB PV systems. This paper proposed a dynamic power distribution strategy to eliminate the over-modulation in a CHB PV system by suitably redistributing the reactive power among the inverter modules of the CHB PV system. The proposed strategy can effectively extend the operating region of the CHB PV system with a simple control algorithm and easy implementation. Simulation and experimental results carried out on a seven-level CHB grid-connected PV system are shown to validate the proposed strategy.

Performance Improvement in Single-Phase Electric Spring Control

Qingsong Wang,Wujian Zuo,Ming Cheng,Fujin Deng,Giuseppe Buja 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.3

Two objectives can be pursued simultaneously with the δ control of a single-phase electric spring (ES). These objectives are the stabilization of the voltage across the critical load (CL) of a power system, and the achievement of a specific functionality similar to the pure compensation of reactive power or the correction of the power factor. However, existing control systems implementing the δ control do not cope with non-ideal operating conditions, such as line voltage distortions, and exhibit a somewhat sluggish regulation of the CL voltage. In an effort to improve both the steady-state and transient performances of an ES power system, this paper proposes implementing the δ control by means of a control system built up on the repetitive control and assisted by state feedback with pole assignment. This paper starts by analyzing the dynamics of an ES power system in terms of its poles and zeros. After that, a reduced second-order model of the dynamics is formulated to avoid a notch filter in the pole assignment. A repetitive control for an ES power system is then designed to meet the two above mentioned objectives. Experimental tests carried out on a laboratory setup demonstrate the effectiveness of the proposed control system in significantly improving the ES power system performance, while reaching the two objectives. In particular, the tests outline the large mitigation of harmonics in the CL voltage under line voltage distortions and its fast stabilization action.

A Dynamic Power Distribution Strategy for Large-scale Cascaded Photovoltaic Systems

Kangan Wang,Xiaojie Wu,Fujin Deng,Feng Liu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

The cascaded H-bridge (CHB) multilevel converter is a promising topology for large-scale photovoltaic (PV) systems. The output voltage over-modulation derived by the inter-module active power imbalance is one of the key issues for CHB PV systems. This paper proposed a dynamic power distribution strategy to eliminate the over-modulation in a CHB PV system by suitably redistributing the reactive power among the inverter modules of the CHB PV system. The proposed strategy can effectively extend the operating region of the CHB PV system with a simple control algorithm and easy implementation. Simulation and experimental results carried out on a seven-level CHB grid-connected PV system are shown to validate the proposed strategy.

Improved Control Strategy for T-type Isolated DC/DC Converters

Dong Liu,Fujin Deng,Yanbo Wang,Zhe Chen 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4

T-type isolated DC/DC converters have recently attracted attention due to their numerous advantages, including few components, low cost, and symmetrical operation of transformers. This study proposes an improved control strategy for increasing the efficiency of T-type isolated DC/DC converters. Under the proposed strategy, the primary circulating current flows through the auxiliary switches (metal–oxide–semiconductor field-effect transistors) instead of their body diodes in free-wheeling periods. Such feature can reduce conduction losses, thereby improving the efficiency of T-type isolated DC/DC converters. The operation principles and performances of T-type isolated DC/DC converters under the proposed control strategy are analyzed in detail and verified through the simulation and experimental results.

Improved Control Strategy for T-type Isolated DC/DC Converters

Liu, Dong,Deng, Fujin,Wang, Yanbo,Chen, Zhe The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4

T-type isolated DC/DC converters have recently attracted attention due to their numerous advantages, including few components, low cost, and symmetrical operation of transformers. This study proposes an improved control strategy for increasing the efficiency of T-type isolated DC/DC converters. Under the proposed strategy, the primary circulating current flows through the auxiliary switches (metal-oxide-semiconductor field-effect transistors) instead of their body diodes in free-wheeling periods. Such feature can reduce conduction losses, thereby improving the efficiency of T-type isolated DC/DC converters. The operation principles and performances of T-type isolated DC/DC converters under the proposed control strategy are analyzed in detail and verified through the simulation and experimental results.

Energy Management System Applied in DC Electric Springs

Daojun Zha,Qingsong Wang,Ming Cheng,Fujin Deng 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Recently, a novel topology of DC electric spring (DCES) was proposed for household application to solve the voltage stability and power quality issues caused by renewable energy source (RES) in DC micorgrids. The novel DCES consists of a DC/DC three port converter (TPC) and energy storage system. The input port of TPC is connected to RES, and a non-critical load (NCL) and a critical load (CL) locate at other two separate ports. The energy storage system paralleled with DC bus where the CL locates, and composed of bi-directional buck-boost converter (BBC) and battery system, is mainly used to ensure the voltage stability and power quality of the CL. This paper proposes an energy management system (EMS) for the novel DCES. The EMS controls the operating mode transition of the BBC, and changes the operating status of the battery system, and realizes multiple charging and/or discharging mechanism. Therefore, the EMS can ensure the voltage stability of CL, maintain the state of charge (SOC) of battery within a reasonable range, extend the battery life and ensure the safe and reliable operation of energy storage system.

New Strategy for Eliminating Zero-sequence Circulating Current between Parallel Operating Three-level NPC Voltage Source Inverters

Li, Kai,Dong, Zhenhua,Wang, Xiaodong,Peng, Chao,Deng, Fujin,Guerrero, Josep,Vasquez, Juan The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.

New Strategy for Eliminating Zero-sequence Circulating Current between Parallel Operating Three-level NPC Voltage Source Inverters

Kai Li,Zhenhua Dong,Xiaodong Wang,Chao Peng,Fujin Deng,Josep M. Guerrero,Juan Vasquez 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.