Fig.1

Distributed propulsion DC microgrid system architecture of fuel cell UAV

Fig.2

Characteristics of constant-power loads

Fig.3

Block diagram of the Boost converter droop control small signal

Fig.4

Block diagram of the droop control of an equivalent bidirectional DC/DC converter

Fig.5

Inverter open-loop system

Fig.6

Simplified model of constant power load system

Fig.7

Cascade system model with virtual resistance and capacitance control

Fig.8

Simulation of DC bus voltage for small signal stability

Fig.9

Simulation of small signal stability with active damping

Fig.10

Simplified diagram of the large signal model

Fig.11

Constant power load power demand profile of fuel cell UAV

Table 1

Large signal stability parameters of the system

Fig.12

Three-dimensional plot of variation of P1*(i,v) and ∂P1*(i,v)/∂t with voltage and current

Fig.13

Three-dimensional plot of variation of P2*(i,v) and ∂P2*(i,v)/∂t with voltage and current

Fig.14

Pole distribution of constant power load model

Fig.15

Simplified diagram of the large signal model of the system with the addition of supercapacitors

Fig.16

Increasing the asymptotic stabilization domain of the supercapacitor

Fig.17

Simulated waveform of large signal stability

Fig.18

Fuel cell efficiency curve

Table 2

Rule-based energy management strategies

Fig.19

The constant power load does not exceed the stable boundary condition

Fig.20

The constant power load power exceeds the stable boundary conditions

Fig.21

Simulation curve of the system with active damping

Fig.22

Simulation curves of incorporating supercapacitor system

Fig.23

System efficiency comparison chart

Fig.24

Semi-physical platform architecture of fuel cell UAV DC microgrid system

Fig.25

Diagram of Typhoon-HIL 604 interface with RT-LAB 5700 semi-physical platform

Fig.26

Semi-physical experimental simulation results of load power in the stable domain

Fig.27

Semi-physical experimental results with active damping method added

Fig.28

Semi-physical experimental simulation results after adding supercapacitors