The mismatch effect of photovoltaic (PV) arrays due to different illumination intensity has a significant impact on the output characteristics and output power of PV arrays, which is crucial to understand the output characteristics of PV arrays and optimize the array configuration in order to improve the value of the maximum power point. This paper illustrates the short-circuit current mismatch of series circuits, and the open-circuit voltage mismatch of parallel circuits and proposes corresponding solutions for each mismatch phenomenon. The output characteristics of multi-stage series PV arrays and multi-stage parallel PV arrays under complex illumination are analyzed by using the peak point approximation calculation method, and the distribution law of peak voltage points as well as the I-V (Current-Voltage) characteristic equation of each operating section are proposed. On this basis, the output characteristics of 3 x 3 centralized PV arrays are analyzed and verified by simulation. By comparing series and parallel PV arrays with the same condition, as well as several groups of centralized PV arrays with the same topology and different types of illumination distribution, this paper proposes a configuration optimization method for PV arrays. Matlab/Simulink simulation results confirm that the output power of parallel arrays is greater than that of series arrays under the same configuration and illuminationt distribution type, and the peak point is less than that of series arrays under the same configuration and lighting conditions; while in centralized PV arrays, the fewer series modules are shaded, the greater the output power and the less the peak point.

Coordinate Measurement Machines (CMMs) have been extensively used in inspecting mechanical parts with higher accuracy. In order to enhance the efficiency and precision of the measurement of aviation engine blades, a sampling method of profile measurement of aviation engine blade based on the firefly algorithm is researched. Then, by comparing with the equal arc-length sampling algorithm (EAS) and the equi-parametric sampling algorithm (EPS) in one simulation, the proposed sampling algorithm shows its better sampling quality than the other two algorithms. Finally, the effectiveness of the algorithm is verified by an experimental example of blade profile. Both simulated and experimental results show that the method proposed in this paper can ensure the measurement accuracy by measuring a smaller number of points.