Liu Jianzheng

Bio: Liu Jianzheng is an academic researcher from Tsinghua University. The author has contributed to research in topics: Maximum power point tracking & Photovoltaic system. The author has an hindex of 7, co-authored 11 publications receiving 445 citations.

A Single-Stage Three-Phase Grid-Connected Photovoltaic System With Modified MPPT Method and Reactive Power Compensation

Abstract: Single-stage grid-connected photovoltaic (PV) systems have advantages such as simple topology, high efficiency, etc. However, since all the control objectives such as the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current need to be considered simultaneously, the complexity of the control scheme is much increased. This paper presents the implementation of a single-stage three-phase grid-connected PV system. In addition to realize the aforementioned control objectives, the proposed control can also remarkably improve the stability of the MPPT method with a modified incremental conductance MPPT method. The reactive power compensation for local load is also realized, so as to alleviate grid burden. A DSP is employed to implement the proposed MPPT controller and reactive power compensation unit. Simulation and experimental results show the high stability and high efficiency of this single-stage three-phase grid-connected PV system.

Comparison of three PWM strategies-SPWM, SVPWM & one-cycle control

Abstract: Sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) are the most popular modulation strategies applied to variable frequency and adjusting speed systems, and there are diverges in comparing the merits and demerits of their own Also there is another modulation strategy called one-cycle control This paper gathers the three strategies and does some comparisons through simulation based on a simulation tool-PSIM, and has drawn some profitable conclusions

Modified MPPT strategy applied in single-stage grid-connected photovoltaic system

Abstract: Single-stage grid-connected photovoltaic (PV) system has advantages such as simple topology, low cost, etc. However, since this kind of system has only one stage of power conversion, all the control objectives need to be considered simultaneously, such as maximum power point tracking (MPPT), synchronization with the utility voltage and harmonics reduction for output current, so that the complexity of control scheme is much increased. This paper presents a modified MPPT strategy, which can remarkably improve the stability of the single-stage grid-connected PV system during rapidly changing process of light intensity, besides realizing the control objectives above. Comparing it with traditional constant-step MPPT strategy, this paper illustrates the improvement of the novel strategy based on PSIM simulation platform. A 300 Wp grid-connected PV system is also established in laboratory to verify the stability of this modified MPPT strategy, in which DSP (TMS320F2407) is employed to implement the proposed MPPT controller. Simulation and experimental results show the high stability and high efficiency of this modified strategy applied in single-stage grid-connected PV system

Intelligent controller for photovoltaic lighting systems

Abstract: Photovoltaic lighting systems have problems such as low efficiency, instabilities, short battery life, etc. To solve these problems, this paper presents a costeffective and intelligent controller for photovoltaic lighting systems using a cheap MCU 89C51. The proposed energy management controller effectively enhances the system performance. The controller uses the maximum power point tracking (MPPT) scheme with precise control over the battery charge. The intelligent management system enables stable and efficient system operation. Test results verified the analysis.

Implementation of a stand-alone photovoltaic lighting system with maximum power point tracking and high pressure sodium lamp

Abstract: This paper presents a high-efficiency stand-alone photovoltaic (PV) lighting system which can provide functional illumination based on high-pressure sodium (HPS) lamp HPS lamp in the system works at very high efficiency with specially designed ballast and ignitor In order to provide a steady-state operating environment for HPS lamp, a DC-DC converter and a DC-AC inverter are also implemented A high frequency also remarkably reduces the size and the operating noise of the ballast Maximum power point tracking (MPPT) technique is also implemented in this system Experimental results will show the performances of the photovoltaic lighting system

A review on solar energy use in industries

Abstract: Presently, solar energy conversion is widely used to generate heat and produce electricity A comparative study on the world energy consumption released by International Energy Agency (IEA) shows that in 2050, solar array installations will supply around 45% of energy demand in the world It was found that solar thermal is getting remarkable popularity in industrial applications Solar thermal is an alternative to generate electricity, process chemicals or even space heating It can be used in food, non-metallic, textile, building, chemical or even business related industries On the other hand, solar electricity is wildly applied in telecommunication, agricultural, water desalination and building industry to operate lights, pumps, engines, fans, refrigerators and water heaters It is very important to apply solar energy for a wide variety of applications and provide energy solutions by modifying the energy proportion, improving energy stability, increasing energy sustainability, conversion reduction and hence enhance the system efficiency The present work aimed to study the solar energy systems utilization in industrial applications and looked into the industrial applications which are more compatible to be integrated with solar energy systems

Reliability Issues in Photovoltaic Power Processing Systems

Abstract: Power processing systems will be a key factor of future photovoltaic (PV) applications. They will play a central role in transferring, to the load and/or to the grid, the electric power produced by the high-efficiency PV cells of the next generation. In order to come up the expectations related to the use of solar energy for producing electrical energy, such systems must ensure high efficiency, modularity, and, particularly, high reliability. The goal of this paper is to provide an overview of the open problems related to PV power processing systems and to focus the attention of researchers and industries on present and future challenges in this field.

A review of maximum power point tracking techniques of PV system for uniform insolation and partial shading condition

Abstract: This paper presents a review on the state-of-the-art maximum power point tracking (MPPT) techniques for PV power system applications. The main techniques that will be deliberated are the Perturb and Observe, Incremental Conductance and Hill Climbing. The coverage will also encompass their variations and adaptive forms. In addition, the more recent MPPT approaches using soft computing methods such as Fuzzy Logic Control, Artificial Neural Network and Evolutionary Algorithms are included. Whilst the paper provides as thorough treatment of MPPT at normal (uniform) insolation, its focus will be on the applications of the abovementioned techniques during partial shading conditions. It is envisaged that this review work will be a source of valuable information for PV professionals to keep abreast with the latest progress in this area, as well as for new researchers to get started on MPPT.

A Single-Stage Three-Phase Grid-Connected Photovoltaic System With Modified MPPT Method and Reactive Power Compensation

Abstract: Single-stage grid-connected photovoltaic (PV) systems have advantages such as simple topology, high efficiency, etc. However, since all the control objectives such as the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current need to be considered simultaneously, the complexity of the control scheme is much increased. This paper presents the implementation of a single-stage three-phase grid-connected PV system. In addition to realize the aforementioned control objectives, the proposed control can also remarkably improve the stability of the MPPT method with a modified incremental conductance MPPT method. The reactive power compensation for local load is also realized, so as to alleviate grid burden. A DSP is employed to implement the proposed MPPT controller and reactive power compensation unit. Simulation and experimental results show the high stability and high efficiency of this single-stage three-phase grid-connected PV system.

A Control Methodology and Characterization of Dynamics for a Photovoltaic (PV) System Interfaced With a Distribution Network

Abstract: This paper proposes a control strategy for a single-stage, three-phase, photovoltaic (PV) system that is connected to a distribution network. The control is based on an inner current-control loop and an outer DC-link voltage regulator. The current-control mechanism decouples the PV system dynamics from those of the network and the loads. The DC-link voltage-control scheme enables control and maximization of the real power output. Proper feedforward actions are proposed for the current-control loop to make its dynamics independent of those of the rest of the system. Further, a feedforward compensation mechanism is proposed for the DC-link voltage-control loop, to make the PV system dynamics immune to the PV array nonlinear characteristic. This, in turn, permits the design and optimization of the PV system controllers for a wide range of operating conditions. A modal/sensitivity analysis is also conducted on a linearized model of the overall system, to characterize dynamic properties of the system, to evaluate robustness of the controllers, and to identify the nature of interactions between the PV system and the network/loads. The results of the modal analysis confirm that under the proposed control strategy, dynamics of the PV system are decoupled from those of the distribution network and, therefore, the PV system does not destabilize the distribution network. It is also shown that the PV system dynamics are not influenced by those of the network (i.e., the PV system maintains its stability and dynamic properties despite major variations in the line length, line X/R ratio, load type, and load distance from the PV system).