Abstract
The photovoltaic DC microgrid has strong nonlinearity and time variation. Therefore, traditional dual closed-loop control strategy of voltage and current based on PI controller cannot effectively restrain the fluctuation and impact of DC bus voltage when the dynamic response of the system is improved. Under this situation, in this paper, the fuzzy-PI dual-mode controller is designed to upgrade the traditional dual closed-loop control, taking voltage outer ring into consideration, which is adopted to achieve good transient performance while the bus voltage deviation is large. While the bus voltage deviation is small, the PI controller is utilized for good steady-state performance. Hence, simulation and experimental results show that the fuzzy-PI dual-mode controller has the same advantages with both fuzzy control and PI control; in other words, it has the features of speedy response, low overshoot, good robustness, and strong anti-interference under different working conditions.
Highlights
In terms of the photovoltaic DC microgrid system, the bus voltage is the only standard to measure the systematic security and stability [1, 2]
Compensation is made through energy storage device (ESD) that is incorporated into the DC bus through the bidirectional DC/DC converter (BDC) [4]. e micropower source is able to supply energy and the load can store energy, relying on the amount of the bus voltage, so as to strengthen the systematic robustness [5,6,7,8,9,10]
In order to effectively cope with the contradiction of the dual closed-loop control based on the PI in improving the steady accuracy and dynamic performance of the system, this paper proposes a PI controller that the fuzzy-PI dualmode controller replaces the voltage outer ring with combining the advantages of the fuzzy controller and PI controller
Summary
In terms of the photovoltaic DC microgrid system, the bus voltage is the only standard to measure the systematic security and stability [1, 2]. Is traditional control fails to effectively restrain the large fluctuation and impact of the DC bus voltage while improving the systematic dynamic response According to this problem, a great number of scholars introduce the method of feedforward control into the traditional dual closed-loop control [13, 14]. Zhi-Lin et al, taking the fluctuation problem of the DC bus caused by the mismatch between output power and load consumption of renewable energy for the DC microgrid into consideration, raised the control method of power feedforward compensation based on the classical dual closed-loop control to lead power disturbance into controller through the feedforward channel, so as to restrain the fluctuation of the bus voltage and reinforce systematic stability [19]. The dynamic equation for the DC bus is
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