The event-based model predictive control (MPC) problem for discrete-time non-linear control systems with external disturbances is studied. Two triggering conditions are designed based on whether the system state is within the terminal region or not. The first one is triggered outside the terminal region when the difference between the actual system state trajectory and the corresponding optimal state trajectory violates a relative threshold, while the second one is triggered inside the terminal region if the difference between the actual system state trajectory and the predicted nominal state trajectory violates a desired relative threshold. The feasibility analysis and stability analysis are given in detail. Sufficient conditions for feasibility relating to the triggering threshold and disturbance bound are obtained. Sufficient conditions for stability of the event-based control system referring to system parameters, triggering threshold and disturbance bound are given. Besides, the upper bound of the state trajectory is obtained and a robust invariant set that the system state will enter in finite time is given. Finally, simulation examples are given to validate the effectiveness of the proposed method.
This paper introduces a new MMC topology, in which each phase leg consists of four arms. Two of the arms consists of cascaded connected submodules and are just like single phase leg in traditional MMC topology. Another two arms are formed by series switches such as high voltage IGBT, which are only activated when the ac voltage changes polarity. And then three phase legs are series connected in vertical direction to support the DC bus voltage. The major advantage of proposed topology are as follows: (1) The total number of required submodules are reduced to 1/3 compared with traditional MMC topology. (2) The energy ripple in each arm is calculated to be smaller than the traditional 3-phase MMC. Therefore, the total capacitor size can be reduced. A detailed 20 MW simulation has been conducted and the related results of proposed topology have been presented. What's more, The SM prototype and preliminary experiments are also demonstrated and analyzed.
This work focuses on the joint design of the event-triggered mechanism and disturbance observer (DOB) in the receding horizon control (RHC) framework for linear systems in the presence of slowly varying disturbance. The state difference between the current system state and the state from the present triggering time instant is used to develop an event-triggered mechanism. To mitigate the effects of disturbances, a DOB is presented using the latest received state measurement by the controller. A constrained optimal control problem (OCP) of the robust RHC is defined at each time instant, in which the modified tightened sets are imposed to satisfy the control and state constraints. A composite controller combining an RHCbased controller with a disturbance-related controller is proposed to stabilize the controlled system. Theoretical analysis of the feasibility of the OCP and closed-loop system stability are elaborated in detail, respectively. A simulation example is provided to demonstrate the proposed control strategy's effectiveness.
In this experiment, response surface methodology was used to study the preparation of malic acid calcium salt from bovine bones assisted by ultrasonication. The results showed that the optimum conditions for ultrasound-assisted preparation of calcium malate from bovine bone were as follows: solid-liquid ratio 1:15, solid-acid ratio 1:1.5, ultrasonic power 200 W, ultrasonic temperature 35°C, and ultrasonication time 17 min. The efficiency of calcium recovery was 66.16%, and the purity was 92.54%. After three ultrasonic treatments of 17 min each, the calcium malate conversion rate of bovine bone reached 95.73%. Animal experiments showed that feeding bovine bone-derived calcium malate significantly increased alkaline phosphatase (ALP) activity and bone calcium content, reduced tartrate-resistant acid phosphatase (TRAP) activity, and maintained the balance of serum calcium and phosphorus. These results indicated that the ultrasonic method effectively ionized calcium in bovine bone, which provides a reference point for the industrial production of calcium products with bovine bone as the raw material.
This work develops a disturbance rejection model predictive control (MPC) algorithm for discrete-time linear systems with bounded disturbances. A disturbance observer is designed to estimate the unknown matched disturbances with bounded incremental constraint. A tube-based MPC algorithm is presented to handle the system constraints. A composite controller is presented to stabilize the systems, including a MPC controller to drive the system state into the neighborhood of the origin, and a disturbance estimation-dependent controller to compensate for the effect of external disturbances. The feasibility of the disturbance rejection MPC is analyzed, and the stability of the system can be guaranteed. Simulation results show the effectiveness of the proposed methods.
$LLC$ and $CLLC$ resonant converters are good candidates for the isolated dc–dc stage in electric vehicle (EV) onboard chargers (OBCs) due to their capability of achieving zero-voltage-switching (ZVS) at full load range. The synchronous rectifier (SR) is usually utilized to reduce the conduction loss and improve the system efficiency compared with the conventional diode bridge rectifier. In this article, a high-dv/dt-immune, fine-controlled, and parameter-adaptive gate driving scheme is presented for GaN-based SR in EV OBCs. A novel self-driven SR drain-to-source voltage sensing circuit is proposed. The circuit provides a low-impedance bypassing path for the displacement current induced by the high dv/dt, which addresses the overvoltage and oscillation issues for the controller input. The detailed operating principles and the design considerations of the novel sensing circuit are discussed as well. Moreover, the adaptive SR ON-time tuning algorithm is implemented, which avoids the influence from the loop stray inductance and the propagation delay in the path and reaches the SR zero-current turn-off moment with fine accuracy. A 3.3-kW, 500-kHz $CLLC$ resonant converter prototype is built to validate the proposed SR gate driving scheme. With the employment of the proposed gate driving scheme, the SR almost achieves zero-current turn-off for the whole operating frequency range. The prototype demonstrates the peak efficiency of 97.6% and the power density of 130 W/in 3 .
In this article, event-triggered model predictive control (EMPC) of continuous-time nonlinear systems with bounded disturbances is studied. Two novel event-triggered control schemes are proposed. In the first strategy, an event-triggering condition, designed based on the state error between the actual system state and the optimal one, with an absolute threshold is considered. In the second strategy, an event-triggering condition with a mixed threshold is designed to further save the computational resources. The minimal interevent times of both event-triggered control schemes are obtained to avoid the Zeno behavior. Sufficient conditions of recursive feasibility for these two triggering strategies, which refer to the prediction horizon, the triggering level, and the disturbance bound, are obtained, respectively. Input-to-state practical stability (ISpS) of both event-triggered control systems is established without requiring the system state entering the terminal set in finite time, respectively. Finally, the numerical simulation shows the effectiveness of the proposed methods.
This paper proposes a novel multilevel topology “Modular-Isolated-Multilevel-Converter” which achieves almost zero low frequency capacitor voltage fluctuation. It inherits the structure of MMC but replaces the half bridge module by the newly proposed Isolated Half-Bridge (IHB). The fundamental and 2nd order harmonic frequency current originally in the MMC module capacitor have been eliminated through connecting the secondary sides of the IHB at the same level of the three phases together. The elimination is due to that the 1st and 2nd order components in the arm current are 120° phase shifted in three phases. Therefore, the module capacitance is reduced by more than 10 times since it only carries switching frequency ripple. Moreover, the arm inductance can also be significantly reduced since the 2nd order harmonic current disappears. The topology is specifically suitable for variable frequency drive application, because its capacitance and inductance are not affected by the output frequency. The challenges of zero frequency start-up when MMC is adopted for VSD can be addressed here. In the paper, the operation principle of the proposed MIMC is fully analyzed and the mathematical model is built. Moreover, a methodology of capacitor sizing and arm inductor design for general MMC topology is proposed. The detailed design considerations for MIMC are also discussed and presented. The plant modeling and control strategy have been proposed for MIMC. A 55-kW simulation is carried out to verify the theoretical analysis. And a 6-kW downscaled hardware prototype is also developed to demonstrate the benefits of the new topology over the traditional MMC.
Pulse power supply is an important field of high-frequency power electronics. In advanced applications, such as ultrasonic sensors, Lidar waves, and laser generators, the voltage supply with high amplitude and high frequency is required to achieve sufficient technical performance. Meanwhile, the high power quality is pursued in some sensor applications to obtain better performance. This article develops a ±1000-V/1.5-MHz LCC resonant pulse inverter for electromagnetic acoustic transducer. First, the LCC filter is optimized to achieve the goals of low total harmonics distortion (THD), small gain variation, and zero-voltage soft-switching (ZVS) in a wide load range. The design guideline of LCC filter for nonresistive load conditions is proposed, and the design considerations for burst mode converters are summarized. Second, the startup and ending transients occur repetitively, which is a common problem for burst mode converters. The proposed precharging and damping strategy solves this transient problem. Moreover, by analyzing the circuit state equations, this strategy provides a general method for eliminating transients of resonant converters. Next, the signal receiving circuit uses depletion mode MOSFETs to attenuate the high transmitting load voltage while amplifying microvolt receiving signals. Finally, the experimental results under four worst case conditions validate the LCC filter design. A control experiment with or without the proposed transient mitigation method has been conducted to verify the effectiveness of the proposed strategy.
In this paper, input-to-state stability (ISS) properties of perturbed systems with event-triggered receding horizon control (RHC) schemes are studied. Two event-triggered control schemes, which are the event-triggered quasi-infinite RHC (EQRHC) and the event-triggered dual-mode RHC (EDRHC) strategies, respectively, are considered. In the EQRHC scheme, an optimal control problem (OCP) should be considered at triggering time and the event is triggered if the error between the actual system state and the optimal system state violating a threshold. While in the EDRHC strategy, an OCP is only solved outside the terminal region and a local control law will be used inside the terminal region. The corresponding event condition is redesigned based on if the system state enters the terminal region or not. The event-triggering condition outside the terminal region is the same with that of the EQRHC scheme and the event-triggering condition inside the terminal region is proposed based on the difference between the actual system state and the predictive system state. Sufficient conditions of feasibility are proposed and ISS properties of both event-triggered control schemes are studied, respectively. At last, numerical simulations show the validity of the proposed methods.
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