Universal Current-Mode Control Schemes to Charge Li-Ion Batteries Under DC/PV Source

Abstract

A pair of universal current mode control schemes for charging a Li-ion battery for mobile applications are discussed in this paper. The peak-current mode control schemes, based on a single control loop, is universal because it is designed with a single-stage buck charger for both a conventional wall adapter dc source as well as a solar photovoltaic (PV) module of comparable specifications. The charging schemes remove the need for an extra MPPT (maximum power point tracking) power converter stage. This control scheme is non-linear and incorporates all possible scenarios: mode of operation of a battery, current charging rate and power characteristic of input source. The algorithm uses need-based MPPT and ensures minimal battery discharge, and also uses minimum number of sense variables in the circuit. The methods differ in the way MPPT is implemented: perturb and observe (P&O) and fractional open circuit voltage. Simulation results demonstrating battery charge profile, validity of the algorithm under varying insolation conditions and platform workloads are presented, along with a discussion of the trade-offs of the two methods. Proof-of-concept hardware results are also provided.

Control of a Charger/Discharger DC/DC Converter with Improved Disturbance Rejection for Bus Regulation

“…Another important application in which batteries are extensively used is the construction of stand-alone renewable power systems, which are common solutions for remote energy generation and urban/distributed energy systems for pollution reduction [13,14]. A common structure of such power systems based on renewable generators and batteries is presented in Figure 1 [15][16][17][18][19][20][21][22]. Such an architecture has a renewable energy source as the main energy generator, e.g., photovoltaic modules or fuel cell, interacting with a unidirectional DC/DC converter that is responsible for optimizing the source operating conditions.…”

“…The charger/discharger converter is controlled to regulate the DC bus voltage within safe limits and simultaneously impose a given energy flow between the battery and the DC bus. Due to safety implications for the source and load, there are many research papers focused on regulating the DC bus voltage using charger/discharger converters: some of them are based on linear control [16,[23][24][25][26], others are based on intelligent control [13,[27][28][29][30][31][32], and others are based on non-linear control strategies [15,[17][18][19][20][21][22]. In particular, sliding-mode controllers (SMCs) have been widely used for this application to ensure global stability, robustness to parameter tolerances, higher bandwidth compared with classical linear controllers [17,22,33], and reduced implementation cost and complexity compared with intelligent controllers [31,34].…”

Parameter-Independent Control for Battery Chargers Based on Virtual Impedance Emulation

“…As shown in the figure, the maximum battery voltage reaches 54.60 V, well above the maximum voltage, and the duration of the overvoltage is very long (the voltage remains 3.1 s over 54.1 V), which contributes to fast battery aging. In order to compensate the wide resistance range, some authors have proposed non-linear control schemes [25], [29], [30], [36]. Although they do improve the robustness against parameter variations, these controls are either much more complex or are unable to maintain a constant switching frequency.…”

“…During CC mode, I * bat,CC is selected and the outer loop is thus deactivated. Then, during CV mode, I * bat,CV is selected and reduced below I * bat,CC in order to control the battery voltage [26]- [30]. Excluding low power applications, the cascaded solution is preferred since the battery current is always controlled.…”

“…Whereas the dynamic variability is reduced, this method presents low noise immunity and implies variable switching frequency. In [29] and [30], an adaptive control is proposed to be robust against battery resistance variation. The problem of this method is that a complex algorithm is required to estimate the resistance value.…”