This paper presents a complete approach for switched reluctance generator (SRG) in variable wind energy conversion systems. Two forms of direct power control (DPC) and a commutative system that allows SRG performance at a wide range of speed variations are proposed. Thus, more mechanical energy can be captured in wind generation. In the proposed structure, the SRG operates in a self-excited mode using a common dc bus system of a voltage source inverter connected to an electrical grid. DPCs are proposed by hysteresis of the SRG phase current for low-speed operation (DPC-LS) and by a single pulse of current for high-speed operation (DPC-HS). The low-pass filter employed to obtain the average power generated may slow down the response of the control system of the DPC applied to SRG. To improve the system performance, sliding mode controllers in DPCs were used. For operation throughout a wide speed range, the DPC-LS and DPC-HS controls should be joined. Therefore, a commutative system with smooth transition between DPC modes is proposed. Finally, simulations and experimental tests were conducted to verify the behavior of the proposed arrangement. The results confirmed correct operation of the proposed system.

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This paper presents a power management strategy (PMS) to control the power flow in a DC microgrid operating in the grid-connected mode. The microgrid model is composed of the AC utility grid interfaced with a voltage source inverter operating as a grid-forming converter (VSC), an energy storage system (ESS) formed by a battery bank and a bidirectional DC-DC converter operating as a grid-supporting unit, a distributed generation acting as a grid-feeding unit, and the customer loads with strict voltage regulation. The power management technique applies a virtual inertia concept together with a state of charge-based management function to regulate the charging and discharging process of the battery bank according to the DC microgrid power flow. Thus, high-rate peaks of power are avoided, which improves the ESS life cycle. With the proposed PMS, an autonomous power flow is achieved inside the DC microgrid, while the AC utility grid focuses exclusively upon forming the DC bus and processing the surplus or shortage of power. In addition, the proposed strategy simplifies the communication link between the grid inverter and the ESS, since the VSC power is the sole information exchanged. The experimental results show that the proposed PMS is reliable, leading to high ESS performance and power flow control within the DC microgrid, without degrading the DC bus voltage.

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