Delay discounting refers to the decline in the value of a payoff as the objective delay to its fulfillment increases. Recent research on delay discounting has examined its relationship with time and risk perceptions through correlational studies. Manipulated experiments were conducted in the current research to further investigate the causal links among the relevant variables. Experiment 1 revealed causal influences of objective delay on both risk perception and delay discounting as well as a positive correlation between risk perception and delay discounting. By manipulating risk perception, Experiment 2 demonstrated further a causal impact of risk perception on delay discounting. Experiment 3 manipulated time perception and provided further evidence for causal pathways from time perception to risk perception and delay discounting. Overall, the results verified a causal chain from objective delay to delay discounting through time and risk perceptions in support of the implicit-risk hypothesis regarding delay discounting.
The virtual synchronous generator (VSG), which emulates the essential behavior of the conventional synchronous generator, has attracted great attention. This paper proposes to analyze the harmonic resonance characteristics in VSG using the state-space model. The analysis is based on a full-order state-space small-signal model that fully considers the dynamic of the inner loops and the VSG-based outer power control loop. Participation analysis is used to point out the contributions of different states to the eigenvalues. Moreover, eigenvalue locus and singular value decomposition (SVD) are applied together to evaluate the impact of the inner loop parameters on the harmonic resonance characteristics around the LCL filter resonance frequency. The analysis indicates that the harmonic resonance instability is mainly caused by decreasing the proportional gains of the current loop and the voltage loop. Finally, extensive numerical simulation and experimental results are given to verify the validity of the theoretical analysis. Both the simulation and experimental results indicate that the voltage of the common coupling point is unstable after decreasing the proportional gains of the current and voltage controllers. As Kpc decreases from 5 to 0.4 or Kpv decreases from 0.6 to 0.2, the harmonic distortion factor (HDF) around the LCL filter resonance frequency increases. Furthermore, the consistency of simulation results, experimental results, and the theoretical analysis results is validated.
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