A Control Strategy of Depressing the Voltage Spike During Soft-Switch Based on the Method of PI in Photovoltaic Converte
For the problem of voltage spike which is caused by the MOSFET, and the issue of Variable calculation complex, given in the fly-back photovoltaic converter system (hereinafter abbreviated as PV). A new physical circuit of soft-switch control strategy is p
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Abstract. For the problem of voltage spike which is caused by the MOSFET, and the issue of Variable calculation complex, given in the fly-back photovoltaic converter system (hereinafter abbreviated as PV). A new physical circuit of soft-switch control strategy is proposed which based on PI controller with the algorithm of variable power step to suppress the voltage spike value. According to the theoretical analysis, in this paper, the output voltage of DC part is equal to the input voltage of photovoltaic array and the reflected voltage of secondary side by clamping the voltage of clamped capacitor. The output voltage value from PI controller is used to recovery the leak inductance energy which will help the converter for working on the maximum power point(MPP) steadily. The new design can absorb the leak inductance energy and suppress the voltage spike efficiently. In this paper, for solve the traditional problem, we correct the formula of soft-switch by the method of maximum power point tracking (MPPT) algorithm. The new soft-switch algorithm formula can simplify the demand of physical circuit design through the method of variable power step. Keywords: Solar energy Fly-back converter PI controller Voltage spike Soft-switch
1 Introduction DC/DC conversion is an important part in photovoltaic converter system [1, 2, 6] (PV). It principle is that transform the continuous DC voltage to the intermittent DC voltage by high frequency MOSFEET. The aim is to making converter work under the boundary current mode (BCM) [3]. But the energy loss, which caused by the MOSFET will sharply reduce the inverter efficiency, especially in the high frequency converter system [7]. According to the theory, the soft-switch algorithm can reduce the energy loss to zero [3]. Traditionally, such as mentioned in the Ref. [3], there are multiple variables in the calculation formula of soft-switch complex variable, which will make hardware system more stringent. In Ref. [8], the author has implemented a soft-switch DC/DC converter, which can realize soft switch in the range of load, and diode zero current turn off. But the voltage spike that generate from the leak inductance energy and the MOSFET have not be suppressed, which will bring significant energy loss in the process of switch. In this paper, we design a new regulation circuit to recovery the © Springer International Publishing Switzerland 2016 D.-S. Huang and K.-H. Jo (Eds.): ICIC 2016, Part II, LNCS 9772, pp. 161–169, 2016. DOI: 10.1007/978-3-319-42294-7_13
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H. Xu and N. Li
leak inductance energy by the PI controller with the algorithm of variable power step to suppress the voltage spike value. The algorithm combined with the algorithm of MPPT [4, 5] to simplify hardware circuit topology. Compared with others, the algorithms which mentioned in this paper, can improve the efficiency of the conversion better. According to the algorithm of MPPT, we modify the complex calculation variables in the theoretical formula.
2 The Control Strategy of Voltage Spike Depress Based on PI
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