Abstract
This paper deals with a battery energy storage system (BESS) in only one of its multiple operating modes, that is when the BESS is charging the battery bank and with the focus on the control scheme design for the BESS input stage, which is a three-phase LCL-filter PWM rectifier. The rectifier's main requirements comprise output voltage regulation, power factor control, and low input current harmonic distortion, even in the presence of input voltage variations. Typically, these objectives are modeled by using a dq model with its corresponding two-loop controller architecture, including an outer voltage loop and a current internal loop. This paper outlines an alternative approach to tackle the problem by using not only an input–output map linearization controller, with the aim of a single-loop current control, but also by avoiding the dq modeling. In this case, the voltage is indirectly controlled by computing the current references based on the converter power balance. The mathematical model of the three-phase LCL-filter PWM rectifier is defined based on the delta connection of the filter, which accomplishes the requirements of a 100 kW BESS module. Extensive simulation results are included to confirm the performance of the proposed closed-loop control in practical applications.
Highlights
The three-phase PWM voltage source rectifiers are broadly used in several industrial applications, such as battery energy storage systems (BESSs), which have been firmly increasing in installed power worldwide since 2015 [1,2,3,4]
We have proposed the use of a single current loop to solve the input current tracking problem and a current reference generator based on the ac–dc power balance to indirectly regulate the dc bus voltage of a three-phase LCL PWM rectifier, avoiding the abc–dq–abc transformations
Due to the fact of considering the delta-connected LCL filter for control purposes, the first three reference derivatives must be included, and this means that the control must be parametrized
Summary
The three-phase PWM voltage source rectifiers are broadly used in several industrial applications, such as battery energy storage systems (BESSs), which have been firmly increasing in installed power worldwide since 2015 [1,2,3,4]. As a starting background, a BESS must work in current and voltage control modes either for discharging energy to the grid or charging the battery bank [2]. To reduce high-frequency harmonic contents, according to the international standards such as IEEE519 and IEC 1000-3-2, the PWM rectifier is connected to the grid through an LCL filter for medium power applications. This type of filter leads to better mitigation of switching harmonics with lower inductances and allows compliance with the voltage and current control modes when the converter delivers energy to the grid [9,10,11,12]
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