3.1. Integration of Predicted Data and DRL State Space
To fully exploit the predictive capability of the LSTM-LSSVM-CC model, this section proposes a Dynamic Spatiotemporal Fusion (DSTF) method, which organically integrates the predicted future power demand sequence with the real-time vehicle states into the state space of the DRL algorithm, thereby enabling the agent to make anticipatory and informed control decisions.
The implementation logic and technical details of this fusion process are divided into three main steps.
Traditional DRL state spaces rely solely on the current vehicle states (such as
and power demand). In contrast, the proposed method introduces predicted power demand sequences and historical residual information to construct a multi-dimensional composite state vector, defined as:
In this framework, the prediction sequence represents the output of LSTM-LSSVM-CC for the next k steps (e.g., = 5), capturing short-term power demand trends. The historical residual refers to the error between the actual and predicted power over the past m steps (), reflecting the model’s recent reliability.
Experimental results demonstrate that the DRL strategy achieves optimal balance between energy efficiency and stability when
= 5 (5 s prediction window) and
= 3 (3-step residual backtracking) (
Figure 2).
As illustrated in
Figure 2, when k = 5, the system achieves optimal equilibrium between hydrogen consumption efficiency (lowest on the left axis) and
stability (lowest on the right axis). Increasing the m value enhances stability (the triangular marker shifts closer to the bottom of the right axis), but results in a slight increase in hydrogen consumption. When k = 7, performance degrades, indicating that an excessively long prediction window causes model overfitting.
- 2.
Dynamic Confidence Weight Allocation
The reliability of the predicted data varies dynamically with driving conditions; therefore, confidence weights are introduced to adaptively adjust their influence on the state space.
The confidence coefficient is calculated as follows:
When the confidence weight
∈ [0, 1] is set, the larger the residual fluctuation (indicating unreliable predictions), the smaller
becomes. Then, the state vector is corrected by introducing a weight attenuation factor into the prediction sequence to suppress interference from low-confidence predictions.
As shown in the formula, denotes the equivalent predicted power value after safety boundary correction. when the prediction error is significant (e.g., < 0.3), the predicted value becomes an inertial extension of the current value, preventing erroneous predictions from misleading the DRL strategy.
- 3.
Data Standardization and Feature Engineering
To eliminate dimensionality differences and enhance DRL training efficiency, the state vector undergoes hierarchical normalization. The current state battery is linearly mapped to [0, 1], with the target range (40–80%) corresponding to [0.4, 0.8]. is standardized using Z-score, based on the historical data mean and standard deviation .
The predicted value is independently normalized at each step, with the dynamic benchmark being the current power demand, as shown in the formula.
where
denotes the system’s rated power to prevent the denominator from becoming too small. The historical residuals are standardized using a sliding window, with the window length matching the residual backtracking step size m.
Taking the CLTC-P operating condition as an example, the DRL strategy performance before and after state space expansion is compared, as detailed in
Table 2.
The state-space fusion reduces hydrogen consumption by 8.1%, minimizes fluctuations by 25.3%, and enhances dynamic response speed by 56.3%. This section demonstrates the effectiveness and engineering feasibility of predictive data and DRL state-space fusion through theoretical analysis and simulation validation, laying the foundation for subsequent multi-objective optimization design.
3.2. Multi-Objective Optimization Design
In the field of multi-objective optimization, the goals of economic efficiency, durability, and dynamic performance often exhibit significant conflicts and nonlinear coupling characteristics. To achieve optimal energy management for fuel cell hybrid power systems (FCHPS), this paper proposes a Dynamic Hierarchical Adaptive Multi-Objective Framework (DHAMOF). By integrating prediction information with Deep Reinforcement Learning (DRL) through a collaborative mechanism, this framework constructs hierarchically weighted reward functions and dynamic constraint conditions, enabling the energy management strategy to adaptively balance multi-objective priorities under varying operating conditions.
The core concept of DHAMOF lies in leveraging the predictive guidance provided by future data to achieve dynamic decoupling and rebalancing of optimization objectives, thereby overcoming the limitations of conventional fixed-weight strategies.
In multi-objective optimization problems, Pareto Optimality serves as the fundamental criterion for evaluating solution quality. However, the real-time control requirements of fuel cell hybrid systems demand that the control policy rapidly converge to a feasible near-optimal solution, rather than exhaustively exploring the entire Pareto frontier. To this end, the DHAMOF framework adopts a strategy that combines the weighted-sum method with prediction-driven dynamic constraints, transforming the multi-objective optimization problem into a dynamic single-objective optimization formulation. The mathematical representation is expressed as:
In the formula: is the dynamic weight coefficient, which depends on the predicted power sequence and the real-time state with being the reward function for each sub-objective and representing the constraint based on predicted data.
The advantage of this modeling method is that it not only retains the computational efficiency of the weighted sum method, but also enhances the time-varying nature of the constraints through predictive information, thus better meeting the requirements of actual working conditions.
Based on the core optimization objectives of the fuel cell hybrid system, the following sub-reward functions and their dynamic coupling mechanisms are defined.
- (1)
Hydrogen minimization
In the formula, denotes the instantaneous hydrogen consumption rate of the fuel cell, while represents the maximum allowable hydrogen consumption. indicates the optimal power point (approximately 70% of rated power) for fuel cell efficiency, driving its operation within the high-efficiency range. When the predicted power demand remains stable (), increasing the weight of enhances economic performance.
- (2)
Power tracking accuracy
The formula directly penalizes deviations between actual output and required power to ensure real-time power response. In rapid acceleration scenarios (), the system prioritizes supercapacitor activation to meet high-frequency demands by adjusting the γ parameter.
- (3)
Durability Objective: Battery Life Protection
The exponential term in the formula forces the battery State of Charge () to remain near the midpoint (60%), thereby slowing down battery aging. The linear term suppresses high-current charging and discharging (with as the maximum allowable current). When the consistently deviates from the safe range (e.g., >80% or <40% for more than 5 min), it triggers the time-varying increment of .
To address the time-varying nature of operating conditions, the DHAMOF framework dynamically adjusts the weight coefficients
of each sub-objective based on predicted data, as detailed in
Table 3.
In
Table 3, the economic weight is adjusted adaptively according to the forecast volatility as shown in the formula:
Here, denotes the base value of the economic weight, while represents the standard deviation of the predicted power sequence , which characterizes the volatility of future power demand.
The dynamic weight surges during power fluctuations, with the specific variation as shown in the formula:
where
denotes the base value of the dynamic weight.
: The power variation rate between adjacent prediction steps (
), indicating the magnitude of power demand fluctuations. The
function, a hyperbolic tangent function with an output range of (−1, 1), is employed to mitigate the impact of abrupt changes.
The dynamic adjustment rule for the durability weight is based on the following key parameters:
- (a)
Battery deviation: | − 0.6| (absolute value of deviation from the 60% midpoint of );
- (b)
Charge and discharge current: || (absolute value of the battery’s instantaneous current)
- (c)
Trigger time threshold: cumulative time during which the battery remains outside the safe range (e.g., < 40% for 300 s)
Its dynamic adjustment formula:
where
represents the durability base value weight, κ
1 and κ
2 are the gain coefficients for
deviation and current penalty, and
denotes the time threshold for triggering compensation (e.g.,
= 300 s).
- (d)
Prediction-driven constraint design
To enhance the strategy’s foresight, dynamic constraints are imposed based on predicted power demand sequences: the fuel cell power limit, with specific settings as shown in the formula:
Ensure the fuel cell output covers future demand with a 20% margin. The charge–discharge current constraints are given by the following formula.
The current limit is relaxed dynamically according to the forecast of future demand to avoid short-time overload.
Table 4 compares the performance of the DHAMOF framework with fixed-weight strategies under the CLTC-P and WLTP hybrid driving cycle.
The dynamic weight adjustment and predictive constraints significantly improve the overall performance of the strategy, especially under high dynamic conditions, where the fuel cell efficiency and battery life protection are optimized simultaneously.
From a control theory perspective, the DHAMOF framework fundamentally constructs an approximate analytical solution space for time-varying multi-objective optimization problems. By incorporating predictive data, the system captures implicit characteristics of future operating conditions within extended state space dimensions, transforming traditional static optimization into a dynamic game process. This mechanism mirrors human drivers’ decision-making: experienced drivers not only respond to current road conditions but also preemptively adjust throttle and braking strategies by anticipating road surface undulations and traffic signal changes, achieving optimal balance between fuel efficiency and driving comfort. Within this framework, the predictive model serves as the agent’s “pre-sensor,” while DRL simulates the brain’s “decision center.” Through adaptive weight adjustment mechanism, both components work in close coordination to achieve global optimization. Notably, although the DHAMOF framework demonstrates significant simulation advantages, its engineering implementation still faces real-time challenges in onboard computing units. Future research could explore edge-cloud collaborative architectures, transferring high-load predictive model computations to the cloud while retaining DRL’s real-time decision-making capabilities in onboard terminals, thereby achieving optimal performance trade-offs under limited resources.
3.3. Real-Time Control and Dynamic Adjustment
To achieve real-time energy management in fuel cell hybrid systems, this paper proposes a predictive-driven dynamic closed-loop control architecture. By deeply integrating DRL strategies with online prediction model updates, it establishes a “perception-decision-correction” real-time control loop. The architecture ensures system stability and efficiency under complex operating conditions through dynamic priority adjustment, rolling optimization, and residual compensation. The following sections elaborate on three key aspects: control flow, dynamic parameter correction, and real-time performance assurance.
Real-time control consists of two core modules (
Figure 3): feedforward prediction compensation and feedback dynamic correction, forming a closed-loop optimization system. The feedforward module predicts future power demand using LSTM-LSSVM-CC to generate initial power allocation commands. The feedback module continuously adjusts prediction errors by incorporating real-time operational data (e.g.,
, fuel efficiency) and modifies DRL policy actions accordingly. The high-speed control loop (50 ms cycle) executes DRL actions and power allocation, while the low-speed update loop (1 s cycle) performs real-time updates to prediction model weights and DRL policy parameters.
To mitigate the cumulative effect of prediction errors on DRL strategies, a window-rolling optimization method is proposed. The initial action a(t) is generated from the current prediction sequence {
, …,
}, and the local optimization problem is recalculated at each
time step (t = 0.5) using the latest prediction data. The detailed process is illustrated in the formula.
Then perform incremental correction on the initial motion:
λ is the smoothing factor, which inhibits the frequent action jump.
To compensate for the prediction residual
, the compensation signal
is constructed. Here, the proportional gain
targets the fast-response instantaneous residual, while the integral gain
eliminates the steady-state residual. This compensation signal is directly superimposed onto the DRL output action to form the final power command:
The DRL strategy handles global optimization, while the compensation module focuses on local error correction to prevent frequent policy adjustments due to prediction errors, thereby enhancing system stability. To avoid compensation overshoot and adapt to varying operating conditions, a dynamic gain mechanism is introduced, as shown in the following equation:
In such cases, when predicting high volatility (), reduce to suppress high-frequency noise interference; when the residual accumulation is large (), reduce to avoid integration saturation.