SOC Balancing and Power Distribution Strategies Considering Different Capacities of Energy Storage

doi:10.12204/j.issn.1000-7229.2023.06.002

Abstract

Abstract:

Isolated DC microgrids should be equipped with energy storage systems consisting of distributed energy storage units. To extend the service life of the energy storage system, the latter should keep the charge state of distributed energy storage units (DESUs) in a balanced state; however, in practice, there may be differences in the capacity of DESUs and mismatch in line resistance, which seriously affect the balancing effect of state of charge (SOC). To address this issue, this study proposes an improved sag control strategy, which enhances the discrimination of the sag coefficient to SOC variations by nesting exponential functions with power functions, thus improving the equalization effect of the SOC. Next, by defining and equalizing the power state factor, the output power of DESUs is proportionally distributed according to their capacity. To reduce the communication pressure, this study adopts a sparse communication network to convey the required information of each DESUs, i.e., the global average value is estimated by applying the dynamic consistency algorithm. Finally, a simulation model built on MATLAB/Simulink verifies the effectiveness of the proposed strategy.

Key words: DC microgrid, distributed energy storage units(DESUs), state of charge(SOC), power distribution, dynamic consensus algorithm

CLC Number:

TM712

DAI Guanggui, HE Jin, ZHANG Bojia. SOC Balancing and Power Distribution Strategies Considering Different Capacities of Energy Storage[J]. ELECTRIC POWER CONSTRUCTION, 2023, 44(6): 12-22.

Figures/Tables 13

Fig.1 Typical structure diagram of isolated DC microgrid

Fig.2 Equivalent model of DC microgrid with two DESUs

Fig.3 R d i ?surface graph with different values of S O C i, p and n

Fig.4 The change curve of R d i ?on es,α and β

Fig.5 Communication topology of DESUs

Fig.6 Overall control block diagram of DESUs

Table 1 System simulation parameters

Fig.7 Waveform of each variable under the control strategy strategy proposed in the literature[26] (charging)

Fig.8 Variable variation waveform under the proposed strategy (charging)

Fig.9 Waveform of each variable under the control strategy strategy proposed in the literature[26] (discharging)

Fig.10 Variable variation waveform under the proposed strategy (discharging)

Fig.11 Control results under load changes

Fig.12 Control results under PV output power variation

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