Papers by Keyword: PV Inverter

Abstract: Renewable energy are usually connected to the power grid through an inverter. As the penetration level of such inverter-based distribution generation resources increases, PCC point harmonics become an important concern for grid stability and power quality. In this paper, the PCC-point harmonics in a parallel-inverter-based photovoltaic station were measured and some significant characteristics of such harmonics were presented. These harmonics are stationary; the voltage and current waveforms are lower frequency, power correlation and inter-harmonic. And these harmonics are 3-phase symmetric and contain 3^rd and 6^th harmonic components. The transitions of the PCC harmonic occurrence and vanishing are instantaneous. The analysis indicates that the PCC harmonics are not produced by the resonances related to the linearities of PV inverters but the inverter nonlinearities are the primary reasons. The strategy to eliminate the PCC point harmonics are proposed in this study.

Abstract: With more and more photovoltaic systems connected to the grid, a strategy for grid-connection control is proposed. The topology of PV inverter and photovoltaic inverter and the active and reactive power decoupling control of photovoltaic system are analyzed. The feasibility and effectiveness of the strategy for grid-connection control is verified by simulation and experiment by the case on the RTDS.

Abstract: The active and reactive power decoupling control of photovoltaic system is analyzed in this paper. The DC-DC and DC-AC two level photovoltaic inverter model are built on the RTDS. A new type LVRT control strategy about photovoltaic system is proposed. In the symmetrical grid drop fault case, photovoltaic system output reactive power to support the grid voltage recovering and save reactive power equipment. The feasibility and effectiveness of the control strategy is verified by simulation and experiment on the RTDS.

Abstract: The control strategy based on predictive current is proposed to solve problems that destruct stable operation of grid-connected photovoltaic system during asymmetrical fall. A mathematical model of PV inverter is established to calculate current instruction; a method of tracking based on predictive current is proposed to reduce the fluctuations of 2 times frequency. In the meantime, PV inverter provides reactive power to support voltage recovery according to the depth of grid voltage sags and realize LVRT. The result also shows that the proposed control strategy can reduce wave of DC voltage and provide reactive power to support voltage recovery.

Abstract: The PV system generation changes with insolation rapidly and randomly ,and the change of power-flow increase the flicker severity in grid. The IEC standards 61400-21 provides recommended test method for wind turbines. In this paper, a model including virtual grid and flickermeter is developed. The testing and simulation procedure for PV inverter is proposed and finally, the test result is demonstrated.

Abstract: Switching converters and photovoltaic panels are nonlinear models, but existing PV inverter control methods are mostly based on the linearization control methods. The traditional linear methods are often difficult to eliminate static errors and the dynamic responses are not very satisfactory. In this paper, on the basis of nonlinear methods to control the switching converter, a mathematical model of discrete rotating coordinate system is given and an inverse optimal control method for single-phase grid-connected inverter control is proposed at the same time. This method achieved independent power control purposes due to implementing active and reactive power decomposition; and it is easier to use a microcontroller digital implementation for the discrete method. Simulation results show that this method can eliminate the static errors, and have a good dynamic response.

Abstract: A novel method for optimum vector PWM (OVPWM) control of three-phase grid-connected photovoltaic inverter was described. The control vector and its corresponding action duration composed of the PWM sequences generated by optimum vector PWM strategy. A Differential Evolution (DE) algorithm was applied to determine the action duration of the output voltage vector based on conventional vector PWM (CVPWM). The Matlab-based model of three-phase grid-connected photovoltaic generation system was established. Comparative analysis proving superiority of the OVPWM technique over the CVPWM, and the results of the simulation confirmed the feasibility and advantage of proposed OVPWM strategy.

Abstract: This paper puts forward the unique design, through the research by solar panels, battery, the converter and photovoltaic power generation system composed by switch electrical, and according to the characteristics of solar panels and batteries, the actual situation and the requirements of a stable system, the battery charging and discharging control, etc. Then this paper further researched control strategies of the two kinds of operating mode of electric power grid and battery from nets, designed a converter of rated power 50 kW used for light storage complementary power generation system and light storage complementary test platform. Using the test platform to do the storage battery charging and discharging experiments and away from the grid experiments, the final experiment results show that the hardware design and the control strategy in this paper are proposed correctness and effectiveness.

Abstract: The output power of single-phase PV inverter is AC and the input power is DC，so there exists fluctuations in the power transmission. Generally, the fluctuations can be removed by using coupling capacitors. However, the voltage fluctuations of coupling capacitors will result in corresponding input power fluctuations, and will affect the maximum power tracking of the system. In this paper, the power transfer process is analysised, and a theoretical derivation to voltage fluctuations of the generatrix capacitor and the impact on the input currents is designed.The corresponding correction control algorithm of subdivision control is developed according to its characteristics. The feasibility of the solution is verified by the 3KW experimental prototype.

Abstract: Equivalent sized (4.5 mm2 die area), 1200 V, 4H-SiC, vertical trench Junction Field Effect Transistors (JFETs) were characterized in terms of DC and switching performance. The 100 mΩ Enhancement-Mode (EM) JFET was found to have natural advantages in safe operation being normally-off, whereas the Depletion-Mode (DM) JFET was found to have advantages with ~ twice as high saturation current, less on-resistance (85 mΩ) and no gate current required in the on-state. The JFETs were found to both have radically less (five to ten times) switching energies than corresponding 1200 V Si transistors, with the DM JFET and EM JFET having EON and EOFF of only 115 µJ and 173 µJ, respectively when tested at half-rated voltage (600 V) and 12 A.