Multifunction converter based on Lyapunov function used in a photovoltaic system

Abstract

Abstract:The development of distributed generations (DGs) is essential to help solve energy crises and improve the reliability of electricity supplies. However, the involvement of a DG in a grid along with an increase of the nonlinear load will reduce the power quality. To solve this problem, we want the converter used in the DG to work flexibly, intelligently, and more accurately. To contribute to the improvement of quality of the DG, this paper proposes a multifunction converter (MFC) model. With the proposed model, the photovoltaic generator, which can be operated at harmonic suppression, and the power injection are more flexible than in the conventional controller used in DG. The controller of the MFC, which is designed based on the Lyapunov function, always ensures the stability of the system. Simulations and experimental results are presented to validate the correctness and effectiveness of the proposed model.

A generalized design method for multifunction converters used in a photovoltaic system

“…As mentioned in [22], to simplify the calculation, capacitor C f can be ignored. The resultant equivalent singlephase circuit of the PVG is shown in Figure 2, in which …”

“…Using the proposed method, the PVG controller can flexibly switch between HAS and POI modes, as achieved in [22], and can operate accurately and efficiently, even under varying system parameters. The controller of the proposed model is designed based on a combination of the Lyapunov technique and the generalized algorithm for determining the optimal values of the stability bound.…”

“…The inside of the circuit diagram of the load current's calculation block, using the SDFT technique, is expressed in detail in [22]. The output of this block yields the load fundamental current i LF dq , the load harmonic current i LH dq , and the total harmonic distortion (THD) of the load current.…”

“…is defined as a switching state function, in which u s is the switching function of the IGBT bridge (as presented in [22]). Eqs.…”

“…To do this, the controller of the DG must be flexible and intelligent. In [22], a multifunction converter (MFC) model for photovoltaic systems was proposed. In this model, a PVG can automatically or manually switch control between the 2 modes of working (POI mode or HAS mode) depending on the status of the utility grid, the weather conditions, and the requirements of the operator.…”