Search Results (47)

Leakage current is a prevalent issue in non-isolated photovoltaic (PV) energy storage inverter systems, which not only induces additional power losses but also poses potential safety hazards and degrades system operational efficiency. To address this critical problem, this paper proposes an improved three-phase four-leg PV energy storage inverter topology integrated with independent split capacitors, based on the traditional three-level topology. First, an in-depth analysis of the leakage current generation mechanism is conducted, focusing on the impacts of common-mode voltage fluctuations and parasitic capacitance on leakage current paths. By establishing an equivalent mathematical model, a systematic comparative analysis is performed between the proposed topology and the traditional topology regarding key performance indicators, including leakage current suppression capability, DC-side neutral point potential stability, and power quality. Notably, the improved topology requires no additional control strategy design; under the same carrier modulation strategy and parameter configuration as the traditional topology, it can stably constrain the DC-side neutral point potential to fluctuate within an acceptable range. Experimental results demonstrate that the proposed topology reduces the peak leakage current to within 200 mA while maintaining the total harmonic distortion (THD) of the load-side current at a low level. These performance metrics comply with the relevant national and industry power quality standards for PV grid-connected systems, endowing the topology with high engineering practical value. Full article

This paper employs a four-leg inverter topology to mitigate the high cost and zero-sequence current suppression challenges associated with dual-inverter open-winding permanent magnet synchronous motor (OW-PMSM) systems. Building on this topology, an improved current hysteresis control strategy incorporating a switching-state lookup table is proposed to suppress switching frequency fluctuations and current ripple. The developed system maintains high DC-link utilization and low cost while addressing the modulation complexity of conventional vector control and the switching frequency instability inherent in traditional hysteresis control. The study establishes a mathematical model of the OW-PMSM, analyzes the voltage vector distribution of the four-leg inverter, and designs an enhanced hysteresis control algorithm. By utilizing a predefined switching table to regulate switching logic in real time, the strategy achieves fixed switching frequency and effective harmonic suppression while preserving the fast-response characteristics of conventional hysteresis control. The experimental results demonstrate that the proposed control strategy achieves superior performance, effectively suppressing current ripple and providing ample stability margin, thereby validating its feasibility and effectiveness for practical engineering applications. Full article

This paper proposes a nonlinear control strategy for a microgrid, comprising a PV generator, wind turbine, battery, solid oxide fuel cell (SOFC), electrolyzer, and a three-phase four-leg voltage source inverter (VSI) with an LC filter. The microgrid is designed to supply unbalanced AC loads while maintaining high power quality. To address chattering and enhance control precision, a super-twisting algorithm (STA) is integrated, outperforming traditional PI, IP, and classical SMC methods. The four-leg VSI enables independent control of each phase using a dual-loop strategy (inner voltage, outer current loop). Stability is ensured through Lyapunov-based analysis. Scalar PWM is used for inverter switching. The battery, SOFC, and electrolyzer are controlled using integral backstepping, while the SOFC and electrolyzer also use Lyapunov-based voltage control. A hybrid integral backstepping–STA strategy enhances PV performance; the wind turbine is managed via integral backstepping for power tracking. The system achieves voltage and current THD below 0.40%. An energy management algorithm maintains power balance under variable generation and load conditions. Simulation results confirm the control scheme’s robustness, stability, and dynamic performance. Full article

Dynamic voltage restores (DVRs) are usually used to mitigate the effect of voltage sag and guarantee sufficient power supply for sensitive loads. However, three-phase voltage cannot be compensated to the desired balance voltage under unbalanced three-phase loads by traditional DVRs with a three-phase, three-leg inverter. To address this problem, a three-phase, four-leg inverter-based DVR is first introduced in this paper, and then the state space model in its continuous form and discrete form are established, respectively. A two-step predictive method is proposed for the prediction of the output voltage in each switching state by the established voltage prediction model. Finite-control-set model predictive control (MPC) is developed to be used in the three-phase, four-leg inverter-based DVR. Its dynamic response is effectively improved by the proposed MPC method under various voltage sag conditions. The proposed DVR control strategy is validated via MATLAB/Simulink-R2022b simulations, which demonstrate its effectiveness in voltage compensation under various sag conditions. Full article

Virtual synchronous generator (VSG) control has positive effects on the stability of microgrids. In practical power systems, both single-phase loads and three-phase unbalanced loads are present. The four-leg inverter is an alternative solution for the power supply of unbalanced loads and grid connections. The traditional VSG control strategy still faces challenges when using a four-leg inverter to provide a symmetrical voltage and stable frequency in the load power supply and pre-synchronization. This paper proposes a VSG-based control strategy along with a pre-synchronization method for four-leg inverters. An improved VSG control strategy is put forward for four-leg inverters. The improved virtual impedance control and power calculation methods are integrated into the control loop to suppress the voltage asymmetry and frequency ripples. Building on the improved VSG control strategy, a pre-synchronization control approach is proposed to minimize the amplitude and phase angle discrepancies between the inverter output voltage and the power grid voltage. In addition, an optimized design method for control parameters is presented to improve VSG dynamic performance. A hardware prototype of the four-leg inverter is built; the results show that the voltage unbalance ratio can be reduced by 89%, and the response time can be shortened by 50%. Full article

This paper presents the design of a disturbance observer-based controller that regulates the output voltage of three-phase four-leg voltage source inverters (VSIs) deployed for grid-forming operation in Renewable Energy-based Distributed Generation (REDG) Systems. The primary objective of the controller is to provide a symmetric and sinusoidal voltage at the output of the VSI when supplying highly unbalanced and nonlinear loads. The controller employs the feedback linearization (FL) technique and incorporates a disturbance observer (DO) to address a range of disturbances that include oscillations resulting from unbalanced loads, harmonics generated by nonlinear loads, and non-oscillatory disturbances. Notably, the controller adopts a direct control scheme without the need for nested current control loops and does not use any transformation frames. Simulation studies and experimental investigations were conducted to assess the controller’s performance under various load conditions, including both linear and nonlinear types, as well as load transients. The findings demonstrate the controller’s capability to accurately track references while complying with the IEEE power quality standards for the tested conditions. Full article

The classical four-level nested neutral point-clamped (4L NNPC) inverter-leg is a hybrid of the flying-capacitor and diode-clamped 4L-inverter-leg configurations. Though uniform reduced voltage stress (1/3 of input voltage) on constituting switches is evident in the 4L NNPC inverter-leg, trails of the drawbacks of the diode-clamping concept still exist. With the significantly rated off-the-shelf IGBT switch modules (6.5 kV, 1200 A), chances of deployment of the newly evolved Four-Level Nested T-Type inverter (4L NTTI) in certain applications is high. Compared with the classical 4L NNPC inverter, 4L NTTI involves a smaller number of power switches and low conduction losses. However, in 4L NTTI, two of the six active switches have a blocking voltage rating of 2/3 of the input voltage. Considering this limiting topological feature in 4L NTTI, a six-switch inverter-leg for the four-level active neutral point-clamped (4L ANNPC) inverter is presented in this paper. In the proposed 4L ANNPC inverter-leg, only one switch has a voltage stress of 2/3 of the input voltage. This ameliorated voltage stress translates to low-cost and -loss inverter implementation. The operational characteristics and competitiveness of the 4L ANNPC inverter are analyzed in detail and demonstrated with a prototype. Full article

The surge in demand for eco-friendly transportation and electric vehicle (EV) charging infrastructure necessitates innovative solutions. This study proposed a novel approach to charging slow-moving vehicles, prioritizing efficiency and minimizing output pulsation. Central to the research is the development of a receiver-side power-regulated constant charging system, focusing on power regulation and maintaining consistent charging parameters. This system integrates a receiver-side pulse density-modulated active bridge rectifier, dynamically adjusting driving pulse density to regulate delivered power. Additionally, a receiver-side reconfigurable compensation network ensures constant current and voltage delivery to the charging device, eliminating the need for an additional D.C.-D.C. converter. A 3.3 kW charging structure employing a multi-leg inverter topology and energizing four ground-side transmitter pads exemplifies the proposed approach. The vertical air gap of charging pads is 150 mm, and the system achieves a maximal efficiency of 93.4%. This innovative strategy holds significant promise for advancing sustainable transportation infrastructure and meeting the evolving demands of the EV market. Full article

In order to meet the necessities of steady and protected operation of a permanent magnet synchronous motor (PMSM) in electromechanical pressure gadget aviation beneath complicated working conditions, a three-phase four-arm inverter fuzzy self-disturbance suppression management (Fuzzy-ADRC) approach for PMSM is proposed to suppress the motor torque pulsation beneath complicated working conditions. Firstly, the defects of the common inverter are analyzed, the three-phase four-bridge inverter is changed via the standard three-phase three-bridge inverter, and the present-day harmonic suppression’s overall performance of the three-phase four-bridge inverter is modeled, analyzed, and verified. Secondly, the ADRC and fuzzy management approach is analyzed, the Kalman filter is delivered into the motor pace loop management to enhance the overall performance of ADRC, and then the fuzzy manipulate and ADRC are blended to similarly enhance the torque ripple suppression’s overall performance of the everlasting magnet synchronous motor. Finally, the proposed three-phase four-arm inverter and fuzzy-ADRC approach are combined, and contrasted with the normal three-phase three-arm inverter and ADRC method. The simulation consequences exhibit that the proposed manipulation technique can efficiently suppress the torque ripple of everlasting magnet synchronous motor and has robust reliability. Full article

This study proposes an unbalanced current compensation method based on a four-leg inverter using an artificial neural network (ANN) under unbalanced load conditions. Distribution systems exhibit rapid load variations, and conventional filter-based control methods suffer from the drawback of requiring an extended time period to reach a steady state. To address this problem, an ANN is applied to calculate the unbalanced current reference and enhance dynamic performance. Additionally, because of the periodic incorrect output inherent in the ANN, applying it to a proportional–integral controller would result in an error being directly reflected in the current reference. In the aforementioned problem, an ANN is applied to the dq0 coordinate system current controller to compensate for the periodic incorrect output in the current reference calculation. The proposed ANN-based unbalanced current compensation method is validated through PSIM simulations and experiments. Full article

Bipedal robots have long been a focal point of robotics research with an unwavering emphasis on platform stability. Achieving stability necessitates meticulous design considerations at every stage, encompassing resilience against environmental disturbances and the inevitable wear associated with various tasks. In pursuit of these objectives, here, the bipedal L04 Robot is introduced. The L04 Robot employs a groundbreaking approach by compactly enclosing the hip joints in all directions and employing a coupled joint design. This innovative approach allows the robot to attain the traditional 6 degrees of freedom in the hip joint while using only four motors. This design not only enhances energy efficiency and battery life but also safeguards all vulnerable motor reducers. Moreover, the double-slider leg design enables the robot to simulate knee bending and leg height adjustment through leg extension. This simulation can be mathematically modeled as a linear inverted pendulum (LIP), rendering the L04 Robot a versatile platform for research into bipedal robot motion control. A dynamic analysis of the bipedal robot based on this structural innovation is conducted accordingly. The design of motion control laws for forward, backward, and lateral movements are also presented. Both simulation and physical experiments corroborate the excellent bipedal walking performance, affirming the stability and superior walking capabilities of the L04 Robot. Full article

The use of renewable energy sources (RES) such as wind and solar power is increasing rapidly to meet growing electricity demand. However, the intermittent nature of RES poses a challenge to grid stability. Energy storage (ES) technologies offer a solution by adding flexibility to the system. With the emergence of distributed energy resources (DERs) and the transition to prosumer-based electricity systems, energy management systems (EMSs) have become crucial to coordinate the operation of different devices and optimize system efficiency and functionality. This paper presents an EMS for a residential photovoltaic (PV) and battery system that addresses two different functionalities: energy cost minimization, and self-consumption maximization. The proposed EMS takes into account the operational requirements of the devices and their lower-level controllers. A genetic algorithm (GA) is used to solve the optimization problems, ensuring a desired State of Charge (SOC) at the end of the day based on the next day forecast, without discretizing the SOC transitions allowing a continuous search space. The importance of adhering to the manufacturer’s operating specification to avoid premature battery degradation is highlighted, and a comparative analysis is performed with a simple tariff-driven solution, evaluating total cost, energy exchange, and peak power. Tests are carried out in a detailed model, where Power Electronics Converters (PECs) and their local controllers are considered together with the EMS. Full article

This paper presents a comparative review of three different widely used power inverters, namely the conventional six-switch inverter; the reduced switch count four-switch inverter; and the eight-switch inverter. The later inverter can be reconfigured as a neutral-point diode-clamped inverter at the failure of one inverter leg. The three power inverters are compared and discussed with respect to cost, complexity, losses, common mode voltage, and control techniques. The paper is intended to serve as a guide regarding selecting the appropriate inverter for each specific application. Simulation results are presented to demonstrate the performance of the three power inverters, followed by a comprehensive comparison between the three power inverters. Full article

In this paper, a fault tolerant control method is proposed for a permeant magnet synchronous motor (PMSM) servo drive system with four leg inverters to cope with the open phase fault. As one of common faults in the motor drive system, the open phase fault will degrade the control performance and efficiency. Even serious damage is caused in some extreme cases. Hence, it is meaningful to realize the fault tolerance of the drive system with open phase fault. The proposed method includes three parts: a torque-producing current calculator, phase voltage determination and voltage distributor. The torque-producing current calculator is designed by taking the third harmonic flux into consideration to calculate the torque-producing current. In the phase voltage determination, it is proved that the third harmonic flux has no influence on the line voltage equation. For healthy operation and fault operation, the voltage requirements in remaining healthy phases are determined based on the line voltages. Finally, two voltage distributors are designed to distributor the phase voltages into remaining inverter leg. The main difference of two voltage distributors is the polarity of two remaining voltage. Compared to the conventional method, the proposed method can reduce the torque ripple under a postfault condition. In addition, the controller structure will not be changed under a pre-fault and postfault condition. The proposed method has been validated by simulated results and experimental results. Full article

Three-phase four-wire voltage inverters are commonly used in energy complexes based on distributed generation sources (solar panels, wind power plants, hydrogen fuel cells) and accumulator batteries. They allow to power loads, including single-phase ones, which require neutral point connection. In these cases, phase voltage formed by spatial pulse-width modulation (PWM) methods considerably differs from sinusoidal waves and has high total harmonic distortions of voltage and current curves. This article is devoted to research into the authors’ control method of a three-phase four-wire inverter, allowing for the rectification of the form of phase voltage supplying the load when applying the most common PWM (SVPWM, DPWMMIN, DPWMMAX, GDPWM) methods. The description of the method and its research results by simulation modeling and test bench are presented in the article. The simulation modeling was carried out by the developed Simulink-model of the three-phase four-wire inverter and its control system. The modeling results showed that the method application ensures sinusoidal voltage form when applying any PWM method. At this, THD_U was reduced from 21.56% to 4.39%, while THD_I was reduced from 21.16% to 1.69%. Experimental tests were carried out by a test bench featuring an uninterruptible power supply source. The authors researched the inverter operation as a component of the test bench under the control of the proposed method to form neutral point voltage. The experimental test results coincided with the simulation modeling results. Full article