Quantum Key Distribution for Virtual Power Plant Communication: A Lightweight Key-Aware Scheduler with Provable Stability

TL;DR

The paper tackles the problem of securing high-frequency VPP communications under scarce, stochastic QKD key generation. It introduces a key-aware priority-quota framework that budgets keys across traffic classes using forecast-driven quotas, a weighted DRR arbiter, an emergency reserve, and graceful degradation via OTP/AES switching and down-sampling. The approach is analyzed with a Lyapunov drift-plus-penalty framework, establishing strong stability and an $O(1/V)$ performance gap, and is validated on reproducible IEEE 33-/123-bus VPP testbeds under normal, degraded, and outage regimes. Results show significant tail-latency reductions, lower passive timeouts, higher key efficiency, and improved power-tracking reliability, with robust behavior under regime changes and scalable performance as the system grows.

Abstract

Virtual power plants (VPPs) are becoming a cornerstone of future grids, aggregating distributed PV, wind, storage, and flexible loads for market participation and real-time balancing. As operations move to minute-- and second--level feedback, communication security shifts from a compliance item to an operational constraint: latency, reliability, and confidentiality jointly determine whether dispatch, protection, and settlement signals arrive on time. Conventional PKI and key-rotation schemes struggle with cross-domain, high-frequency messaging and face long-term quantum threats. Quantum key distribution (QKD) offers information-theoretic key freshness, but its key yield is scarce and stochastic, often misaligned with bursty VPP traffic. This paper proposes a key-aware priority and quota framework that treats quantum keys as first-class scheduling resources. The design combines (i) forecast-driven long-term quotas and short-term tokens, (ii) key-aware deficit-round-robin arbitration, (iii) a preemptive emergency key reserve, and (iv) graceful degradation via encryption-mode switching and controlled down-sampling for non-critical traffic. A drift-plus-penalty analysis establishes strong stability under average supply--demand balance with quantifiable bounds on backlog and tail latency, providing interpretable operating guarantees. We build a reproducible testbed on IEEE 33- and 123-bus VPP systems and evaluate normal, degraded, and outage regimes with industry-consistent message classes and TTLs. Against FIFO, fixed-priority, and static-quota baselines, the proposed scheme consistently reduces tail delay and passive timeouts for critical messages, improves per-bit key utility, and enhances power-tracking reliability during key scarcity and regime switches.

Figures (12)

• Figure 1: Overall P99 end-to-end delay across classes and methods (mean $\pm$ 95% CI). For visual comparability, Prot delays are converted from ms to seconds.
• Figure 2: Left: total discard rate per method with passive timeouts (bottom) and active drops (top). Right: key efficiency measured as successful critical messages per key bit.
• Figure 3: Representative 12-minute window showing key generation $G(t)$, inventories $K(t)$, emergency reserves $R_{\text{emg}}(t)$, and served protection packets $S(t)$ (scaled) for our method vs. a priority baseline. Regime shifts (normal $\rightarrow$ degraded $\rightarrow$ short outages) illustrate resilience and reserve behavior.
• Figure 4: P99 end-to-end delay across key-generation regimes (Normal, Degraded, Outage) and methods; median markers shown inside each violin.
• Figure 5: Total discard rate across regimes and methods, decomposed internally (violin width reflects sample density across seeds).