Stability Analysis of Paralleled Boost DC/DC Voltage-Source Interfaced System with Constant Power Load

doi:10.12204/j.issn.1000-7229.2023.03.013

Abstract

Abstract:

Aiming at the stability problem of source-load cascade system with constant power load in paralleled Boost DC/DC converter in DC network, the stability of the paralleled Boost DC/DC converters and the load capacity with constant power load are analyzed by eigenvalue method and impedance ratio method. The correctness of the theoretical analysis is verified by the time-domain simulation method, and the advantages and disadvantages of V-I and I-V droop control for the load power sharing are systematically compared in this paper. For multiple paralleled Boost DC/DC converters with resistance load, the stability region of controller parameters does not change with the increase of the number of paralleled units. The decrease of virtual impedance in V-I droop system, or the increase of virtual impedance in I-V droop system will lead to the deterioration of system stability. For multiple paralleled Boost DC/DC converters with constant power load, the change of the load capacity of the system is consistent with the stability. With the same virtual impedance, the load capacity of multiple paralleled V-I droop system is greater than that of I-V droop system. This paper provides general design rules for two types of droop control in practical engineering applications of parallel Boost DC/DC converters.

Key words: DC distribution system, boost DC/DC converter, stability analysis, V-I/I-V droop control, constant power load

CLC Number:

TM712

XIAO Zhaoxia, LI Pan, ZHU Hongchi, ZHANG Shirong, CAO Jianing. Stability Analysis of Paralleled Boost DC/DC Voltage-Source Interfaced System with Constant Power Load[J]. ELECTRIC POWER CONSTRUCTION, 2023, 44(3): 122-137.

Figures/Tables 24

Fig.1 Topology of DC microgrid with storages

Fig.2 Transfer function for voltage-controlled Buck converter

Fig.3 The influence of voltage-loop controller parameters on CPL input impedance

Table 1 Eigenvalues of λ1 and λ2 when number of converters changes with the droop coefficient

Fig.4 Root locus of main eigenvalue when the controller parameters of N converters in parallel change

Fig.5 DC-bus voltage when the parameters changes with multi-converter

Fig.6 Root locus of main eigenvalue when the controller parameters of N converters in parallel change

Fig.7 DC-bus voltage when the parameters change with multi-converter

Fig.8 Stability margin changes with the virtual impedance using V-I or I-V droop control

Fig.9 Simplified circuit diagram of DC microgrid model

Table 2 Comparison of load capacity with V-I/I-V droop control

Fig.10 Bode diagram and Nyquist diagram of input and output impedance of a single converter based on droop control

Fig.11 The bus voltage fluctuation when a single converter changes P*

Fig.12 Bode diagram and Nyquist diagram of parallel input and output impedance of two converters based on droop control

Fig.13 The bus voltage fluctuation when two converters are connected in parallel to changes P*

Fig.14 Bode diagram and Nyquist diagram of parallel input and output impedance of ten converters based on droop control

Fig.15 The bus voltage fluctuation when ten converters are connected in parallel to change P*

Fig.16 HIL platform

Fig.17 HIL test results of droop control with resistive load

Fig.18 HIL test results of droop control with CPL

Table 3 Comparison of V-I/I-V droop control applied in paralleled boost DC/DC converters

Fig.A1 Two droop control schemes for paralleled boost DC/DC converter

Table B1 Cascaded system and its controller parameters

Table B2 Hardware circuit parameters of HIL experimental platform

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