Publications

In recent years, Finite Control Set Model Predictive Control (FCS-MPC) has been widely used in power converters due to its advantages of fast dynamic response, no regulator and multi-constraint control. However, due to traversing all possible voltage vectors, the computational burden of traditional FCS-MPC is relatively heavy. In order to reduce the computational complexity of FCS-MPC strategy in rolling optimization, a simplified control method based on support vector machine ( SVM ) is proposed in this paper. The SVM model is trained by collecting the input and output data of the controller during the steady-state operation of the system, and the mapping relationship between the system state and the optimal vector is established. In the control process, SVM is used to quickly predict the optimal vector and construct a candidate vector set, thereby reducing the search space and performing optimization. The simulation model of three-phase two-level LCL grid-connected inverter is built in MATLAB / SIMULINK. The simulation results show that the consistency rate of this method with full vector search is 98 % in steady state, which significantly reduces the computational burden and improves the control efficiency.

One of the advantages of finite control set model predictive control (FCS-MPC) is that it allows for the consideration of multiple constraints simultaneously, thereby facilitating the achievement of multi-objective control. The configuration of weighting factors (WFs) in its cost function is the key to ensuring a balance between various control objectives and achieving optimal performance. However, there is a paucity of mature theoretical guidance to determine these WFs, which usually depends on experience or trial and error. This has the consequence of leading to a cumbersome debugging process and difficulty in obtaining optimal control effects. The paper proposes a strategy for the design of WFs, based on the particle swarm optimisation algorithm (PSO) and the radial basis function neural network algorithm (RBFNN). This strategy is intended to develop a set of scientific and systematic design processes for the selection of WFs. To verify the effectiveness of the proposed method, a three-phase LCL grid-connected inverter is selected as the control object, and a large number of simulations and experiments are carried out.

This paper proposes a single-stage single-inductor Buck-Boost inverter (SIBBI) with leakage current suppression capability. By controlling the DC-side electrolytic capacitor voltage to remain balanced, common-mode leakage current can be eliminated. Compared to traditional half-bridge Buck-Boost inverters, the SIBBI uses only one inductor for energy regulation, thereby improving the utilisation rate of the inductor during both positive and negative half-cycles, reducing losses and costs, and further enhancing power density. The SIBBI employs a multi-modal control algorithm based on dead-beat control (DBC), ensuring that only one switch is in the high-frequency state at any given time, thereby reducing switching losses. Additionally, when the capacitance of the electrolytic capacitor decreases, the SIBBI can operate in pure Buck-Boost mode, thereby extending the lifespan of the electrolytic capacitor. This makes it suitable for photovoltaic inverter applications.

For the renewable energy sources whose outputs vary continuously, a Z-source current-type inverter has been proposed as a possible buck-boost alternative for grid-interfacing. With a unique X-shaped LC network connected between its dc power source and inverter topology, Z-source current-type inverter is however expected to suffer from compounded resonant complications in addition to those associated with its second-order output filter. To improve its damping performance, this paper proposes the careful integration of Posicast or three-step compensators before the inverter pulse-width modulator for damping triggered resonant oscillations. In total, two compensators are needed for wave-shaping the inverter boost factor and modulation ratio, and they can conveniently be implemented using first-in first-out stacks and embedded timers of modern digital signal processors widely used in motion control applications. Both techniques are found to damp resonance of ac filter well, but for cases of transiting from current-buck to boost state, three-step technique is less effective due to the sudden intermediate discharging interval introduced by its non-monotonic stepping (unlike the monotonic stepping of Posicast damping). These findings have been confirmed both in simulations and experiments using an implemented laboratory prototype.

The transition to renewable energy is crucial in addressing climate change, yet the intermittent availability of wind and solar power presents challenges to energy reliability. To overcome this, effective energy storage solutions are essential for stabilizing and scaling energy supply. Power-to-X (P2X) technologies have emerged as a key strategy for converting surplus renewable electricity into storable energy carriers, with hydrogen production through electrolysis being a prominent approach. By splitting water into hydrogen and oxygen, excess renewable energy can be efficiently stored and later utilized as a clean and versatile fuel. Solid Oxide Electrolysis Cells (SOECs) offer a highly efficient pathway for large-scale hydrogen production in P2X systems. However, widespread deployment is hindered by challenges such as material degradation, thermal instability, and high operational costs. Operating SOECs under elevated pressure has been identified as an effective method to enhance performance, reduce capital expenditures (CAPEX), and improve hydrogen output. This study introduces a novel high-pressure SOEC setup, integrating nickel/yttria-stabilized zirconia (YSZ) cathodes, YSZ electrolytes, and lanthanum strontium cobaltite (LSC) air electrodes. The system operates in a controlled gas environment, with precise pressure regulation maintained via Equilibar back-pressure regulators. To ensure system stability, pressure is gradually increased at a rate of 0.5–1 bar per hour. Electrochemical performance is assessed through open-circuit voltage (OCV) measurements, current-voltage (I/V) curves, and electrochemical impedance spectroscopy (EIS). A novel AC:DC cycling strategy has been developed to enhance thermal and electrochemical stability under pressurized conditions. This method alternates between electrolysis and fuel cell modes, incorporating periodic reverse pulses to regulate thermal distribution and mitigate nickel migration—a primary cause of SOEC degradation. The optimization of the AC:DC cycling profile is currently under investigation, with switching frequencies ranging from 30 Hz to 0.91 Hz. Experimental results reveal a slight voltage drop and a notable increase in cell impedance as frequency increases during electrolysis and fuel cell operations, respectively. At low frequencies, a significant voltage drop in fuel cell mode is observed, likely due to mass transfer limitations affecting hydrogen availability at the reaction site (electrode/electrolyte interface), leading to localized "starvation" of the cell. The findings suggest that operating at frequencies above 10 Hz improves system performance. At different cycling frequencies, local SOEC temperature variations along the gas flow direction play a crucial role. Higher frequencies lead to more uniform temperature distribution, increasing the overall average operating temperature and reducing thermal gradients. When the cycling frequency exceeds 10 Hz, both the average operating temperature and the maximum temperature gradient stabilize, as shorter cycle durations prevent significant gas composition fluctuations. At the lowest tested frequency (0.91 Hz), gas composition and temperature undergo considerable variations within each cycle, influencing overall system stability. By maintaining a thermoneutral balance, this cycling strategy promotes system stability and mitigates stress-induced degradation. Long-term testing exceeding 600 hours is currently underway, comparing DC-only and AC:DC cycling modes. Post-mortem analysis is being conducted to evaluate degradation mechanisms and material stability. Preliminary results indicate enhanced charge and mass transfer, increased hydrogen production efficiency, and reduced degradation under pressurized conditions. These findings demonstrate the feasibility of integrating high-pressure SOEC operation with dynamic cycling for large-scale hydrogen production. The advancements presented in this study contribute to the development of more durable and cost-effective electrolysis technologies, supporting the transition to sustainable hydrogen production and green energy solutions on a global scale.

Hybrid AC/DC microgrids with distributed energy storage (DS) improve power reliability in remote areas. Existing power management methods either focus on steady-state power sharing or transient inertia support, but rarely combine both. They also often ignore frequency and voltage deviations caused by droop control, which can harm sensitive loads. To overcome these issues, this paper proposes a full-time-scale (FTS) power management strategy that unifies transient inertia sharing and steady-state power allocation through a novel dynamic concatenator. It also introduces autonomous frequency/voltage restoration to eliminate steady-state deviations in each subgrid. Additionally, a global equivalent circuit model (GECM) is developed to simplify system analysis and design. Experiments confirm that the approach maintains nominal frequency and voltage in steady state while enabling seamless transition between transient inertia support and proportional power sharing across all time scales.

The lifetime of a high-speed Integrated Motor Drive (IMD) is highly dependent on its power converter, where power devices are the most prone to failures. This paper studies the reliability of SiC-MOSFET-based high-speed IMDs, highlighting its critical role in determining the overall lifetime of the system. The proposed reliability model estimates the End of Life (EoL) of power devices by analyzing the junction temperature, which is influenced by the load conditions based on the applied mission profile. The applied mission profile, which covers all operating conditions and a wide speed range, including maximum torque per ampere and field weakening strategies, is translated into the motor current and voltage. Then, the power losses of power devices and electrical motor are obtained through three-phase currents and voltages and applied to the thermal model of the IMD. In addition to the self-thermal effect of power devices, the mutual thermal effect of the electrical motor must be considered in the IMD's thermal model. To handle a long mission profile, the average loss model is adopted instead of using a heavy simulation. The proposed reliability model can help in designing heatsink and electrical motor cooling methods, contributing to enhanced thermal management in order to meet the lifetime requirements of specific applications for IMDs.

In this paper, a common ground three-terminal rectifier with active power decoupling ability is proposed. The proposed topology establishes a direct connection between the AC and DC ground, thereby suppressing common mode leakage currents and eliminating the demand for an isolation transformer. Additionally, the active power decoupling function enables the double line frequency ripple power to be absorbed by the decoupling circuit, significantly reducing the DC-link capacitance, which in turn enhances the power density and operational lifespan of the converter. Moreover, compared to existing decoupling topologies, the proposed design imposes lower voltage stress on the decoupling components, reducing the performance requirements for these devices. Finally, the feasibility of the proposed AC/DC converter is validated through simulation studies.