Abstract
Passivity-based nonlinear control for an isolated microgrid system is proposed in this paper. The microgrid consists of a photovoltaic array and a battery energy storage connected to a point of common converters, supplying a constant power load. The purpose of this control strategy is to maintain the output direct current voltage in its reference value under load variations, improving battery interaction. The system is represented by its state space averaged model and the proposed controller is designed using the interconnection and damping assignment strategy, which allows obtaining controller parameters while ensuring the closed-loop system stability. The unknown constant power load is estimated using an observer based on the energy function of the system. The behavior of the proposed control strategy is validated with simulation and experimental results.
Highlights
Direct current (DC) microgrids (MGs) are being increasingly used in conjunction with the classic electric power system to meet energy demand problems [1,2]
Based on the described problem, this paper proposes a controller based on IDAPBC to regulate the DC-link voltage on a MG when a constant power loads (CPLs) is connected to it
It can be seen that both controllers allow regulating the mean value of the DC-link voltage, but the proportional integral (PI) controller presents a greater overshoot and oscillations when it is adjusted for the same convergence speed as the interconnection and damping assignment (IDA)-Passivity-based control (PBC)
Summary
Direct current (DC) microgrids (MGs) are being increasingly used in conjunction with the classic electric power system to meet energy demand problems [1,2]. Some types of loads connected on the DC link can produce a negativeimpedance effect, generating system instability and loss of regulation on the feeder system [3,17,18] Other effects such as high stress and temperature rise in power converter elements may occur, reducing its performance and lifetime [19]. LBatiBat = −u2vdc − rBatiBat + vBat. where vdc is the DC-link voltage; u1 and u2 are the control signals of UC and BC; Cdc is the DC-link capacitance; LPV and LBat are the inductances between the energy sources and the converters, with resistances rPV and rBat, which represent the internal resistance of each inductor and the losses in the power converters; vPV, vBat, iPV, and iBat are the voltages and currents in the PV array and in the battery bank, respectively; RL is the load resistance; and PCPL is the power of the CPL.
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