Research On Digital Photovoltaic Array Emulator Based On DSP

Solar energy is an important part of humanity energy in the future. The photovoltaic power generation systems have broad prospects for development due to non-polluting emissions, high reliability, resistance to severe weather conditions and other advantages. In the study of photovoltaic technology, the photovoltaic array emulators can simulate the work of solar cells under various conditions indoors, which can reduce the development time and cost effectively.Based on introduction of the research background and current situations in solar energy utilization, this paper firstly introduces the principles and characteristics of analog and digital photovoltaic array emulators, and summarizes the current status and development trends of domestic and foreign emulators. Then the principle, output characteristics, as well as light and temperature characteristics of solar cells are expounded. And this paper selects a high precision solar project mathematical model, so it can simulate the output characteristics under different irradiation and temperature.Through researching main circuit topology of several common photovoltaic array emulators, the essay proposes a main circuit topology based on a single-phase PWM rectifier and a buck circuit. Afterwards the working process of two kinds of circuit is analyzed in detail and the method of how to calculate the filter parameters of main circuit is described.Next introduce the control strategy of emulator system, the single-phase PWM rectifier adopts double closed loop control strategy. In order to eliminate the influence of control delay in deadbeat current control, this paper proposes an improved deadbeat current predictive control algorithm, deduces the discrete transfer function of improved algorithm, and analyzes the influence of inductance parameter and sample time on control system’s stability and dynamic performance. And total harmonic distortion (THD) of the grid current is analyzed. The control method of buck circuit is sampling the voltage across the load and calculating reference current of the load. On the basis of solar project mathematical model, look-up table method and calculation method are combined to generate the output characteristic curve.A small power photovoltaic emulator experiment platform is built based on DSP TMS320F28335as the core control chip. The platform is divided into three parts, power circuit, control circuit and LabVIEW interactive system. The essay introduces the key circuit design of each part, and then described the program flow of control algorithm and the LabVIEW communication. Single-phase PWM rectifier and photovoltaic array emulator experiments are performed on this platform, the simulation and experimental results show validity of the topology and the control strategy which are proposed in this paper. And the photovoltaic emulator has good dynamic and static performance, and its output characteristic is consistent with the actual.