In this thesis, a vibrational energy harvester is provided. The proposed model is an array with radial arrangement to increase the amount of energy produced by the system and reduce the sensitivity to the excitation direction. The model is an array with assumptions of nonlinear system and multiple frequency. The array includes four piezoelectric cantilevers with ferromagnetic substrates and permanent magnet that is on a spring in the middle of array. Middle magnet causes nonlinear behavior in the harvester. Mathematical model is developed to simulate the electromechanical behavior of the harvester. Interaction betweens the middle magnetic and the cantilever is taken into account in simulation. Differential equations that governs the electromechanichal behavior of the system was obtained from Lagrange equation that is solved numerically. With numerical simulations electromechanical behavior in different excitation domains for harmonic and random excitation with linear and nonlinear behaviors of the system is studied. The behavior of the system is also investigated in linear and nonlinear modes, in the absence and presence of middle magnet and spring, respectively. Two kind of cantilever, one of them without tip mass and the other with tip mass is used to harvest energy from multiple frequencies. The output voltage, power and cantilever tip displacement were obtained. The results have shown that the amount of voltage obtained from the beam having a tip mass is greater than that of the beam without the tip mass. The power of the system is approximately equal in both harmonic and random excitation with linear and nonlinear behavior of the system. Results were compared with the test in similar models and satisfactory results were obtained. Multi-frequency energy harvesters increased bandwidth of the received energy. Keywords: Piezoelectric; Nonlinear multi-frequency converter; energy harvesting; broadband vibration