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Liu X.,Nanjing Southeast University | Zheng J.,Nanjing Southeast University | Zheng J.,Laboratory of Electrical Equipment and Automation in Suzhou | You J.,Nanjing Southeast University | And 3 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

A topology of switched-inductor Quasi-Z source inverter is proposed, which reserves the advantages of traditional Quasi-Z source inverter, enhances the boost ability under same shoot-through ratio. It achieves higher boost ability with smaller shoot-through ratio, which makes the setting range of modulation factor larger and improves the output voltage quality and the system stability. It adopts modified SVPWM control and the simulative and experimental results show its higher boost ability.


Wang C.,Nanjing Southeast University | Wang C.,Laboratory of Electrical Equipment and Automation in Suzhou | Zheng J.,Nanjing Southeast University | Zheng J.,Laboratory of Electrical Equipment and Automation in Suzhou | And 6 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

The gird-connection control with fixed frequency current-hysteresis is proposed for Z-source three-phase photovoltaic power system. The complex plane is divided into six sectors based on grid voltage space vectors to realize the decoupling control of line currents. The fixed frequency control is realized by the periodic comparison of line current with a fixed times, which avoids the problem of conducting time interposition. It runs with unity power factor, quick response, high accuracy, less switching times and simpler digital implementation. Compared with the traditional hysteresis control, it has less control error and better anti-interference ability. Its feasibility is proved by simulation and experiment.


Zheng J.,Nanjing Southeast University | Zheng J.,Laboratory of Electrical Equipment and Automation in Suzhou | Wang J.,Nanjing Southeast University | Wang J.,Laboratory of Electrical Equipment and Automation in Suzhou | And 3 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

A hysteresis current control based on voltage space vector is proposed, which obtains three groups of current error vector by importing the phase current error to the hysteresis comparator and outputs the optimal voltage space by determining the distribution of current error vector and reference voltage vector. Therefore, the current error is limited in the hysteresis width. It can efficiently eliminate the interference and restrict the current error under a lower switching frequency. A fully digital control system based on DSP-FPGA is designed, with quicker current response, better current tracking performance and enhanced system stability. Simulative and experimental results verify the correctness of the given control strategy.


Liu B.,Nanjing Southeast University | Liu B.,Laboratory of Electrical Equipment and Automation in Suzhou | Mei J.,Nanjing Southeast University | Mei J.,Laboratory of Electrical Equipment and Automation in Suzhou | And 4 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2013

With the grid-connected resistive SFCL(Superconducting Fault Current Limiter) as the research object, its impact on the wiring mode of grounding impedance relay is studied in detail and a new wiring mode is proposed. With PSCAD/EMTDC simulation software, a power system model is built and the grounding fault is set at different positions of line, based on which, the cooperation of SFCL with distance protection in new wiring mode is simulated. The simulative results show that, the relay measures the impedance with much lower error in new wiring mode and locates the fault point correctly. Therefore, SFCL can work in with the line distance protection properly.


Zheng J.-Y.,Nanjing Southeast University | Zheng J.-Y.,Laboratory of Electrical Equipment and Automation in Suzhou | Huang J.-J.,Nanjing Southeast University | Huang J.-J.,Laboratory of Electrical Equipment and Automation in Suzhou | And 6 more authors.
Dianji yu Kongzhi Xuebao/Electric Machines and Control | Year: 2010

In Z source based photovoltaic grid-connected system for the control of Z source, the shoot through time must be added in the control algorithm. A new kind of control algorithm based on fixed-frequency current hysteresis used in photovoltaic (PV)grid-connected system based on Z-source converter is presented in this paper. This algorithm comprehended benefits of direct current control, such as quick dynamic response, high tracking precision, high stability, ect. Overcoming the disadvantages such as high switch loss and difficulties of filter design which were caused by not fixed switch frequency. With the control of the algorithm, through the effect of Z source Boost, grid current was increased significantly, and there was no impact on grid current, when DC voltage was changed in some range, and the PV grid-connected system can track grid voltage effectively, so that grid current and grid voltage can be kept synchronous. Both comparison with the traditional hysteresis control by simulation and grid connected experiment proved the feasibility of the algorithm.


You J.,Nanjing Southeast University | You J.,Laboratory of Electrical Equipment and Automation in Suzhou | Huang J.,Nanjing Southeast University | Huang J.,Laboratory of Electrical Equipment and Automation in Suzhou | And 4 more authors.
Taiyangneng Xuebao/Acta Energiae Solaris Sinica | Year: 2011

Z-source based PV grid-connected systems, using hysteresis control in three-phase full-bridge circuit, inserting straight through time synchronously, was studied. By summarizing control features of both hysteresis and Z topology control, a fixed-frequency grid connected control strategy used in three-phase Z-source based PV systems was proposed. This control strategy was good at fast response, high accuracy, high stability, etc. Grid voltage was tracked effectively. Using fixed-frequency control, filter circuits was easy to be designed. According to the characteristics of full-bridge, straight through time was successfully inserted, it was easy to be controlled by DSP. Because of the independent control of each phase, the reference current can be set independently. For PV systems, fluctuation of DC side voltage within a certain range was allowed. With the control of the algorithm, through the effect of Z Source Boost, Grid current was increased significantly. Both comparison with the traditional hysteresis control by simulation and grid connected experiment proved the feasibility of the algorithm.

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