An Extended Lyapunov-Function-Based Control Strategy for Single-Phase UPS Inverters

This study introduces an innovative disturbance observer to tackle external disturbances and model uncertainties, along with a control strategy based on Lyapunov functions, ensuring global asymptotic stability for a single-phase multilevel inverter for UPS applications. The stability analysis of the proposed method is presented, based on two theorems. The first Theorem guarantees presents a disturbance observer, provides a bounded estimation error for the unknown disturbance, in the single-phase UPS inverter (UPSI). The bounded estimation is then used in designing an observer-based robust controller in the second Theorem, which ensures the convergence of tracking error to a small neighborhood of the origin. The numerical and practical results indicate that the developed control scheme ensures global stability and leads to the desired sinusoidal voltage with an almost low THD. Meanwhile, almost zero steady-state error in the output voltage (OV), and robust dynamic performance under uncertainties and disturbances are attained.

Design concept of FPGA based hardware controller is proposed with basic modules for the development of power electronics applications. Also an autonomous decentralized control system for single phase UPS inverter with FPGA based hardware controller using software CPU core is described. Progress of FPGA technology makes it possible to include the software macro CPU core into the FPGA chip, a high flexibility can be realized for the construction of the control processor in power electronics application. But the basic modules for power electronics application are not enough in the environment of FPGA development platform. In this paper, several modules are presented for power electronics applications, and also proposed an autonomous distributed control system for single phase UPS inverter with FPGA based hardware controller using CPU core. The advantages of FPGA based hardware control system are discussed.

In this paper, a modified Lyapunov function based control strategy that assures global stability is proposed for single phase cascaded H bridge multilevel converter feeding nonlinear loads. The Lyapunov function is formed from the energy stored in the inductor and capacitor. The Lyapunov function based control strategy proposed in the literature for the single phase converter assures global stability with only output voltage and current control. But the DC link voltages of the multilevel inverter fluctuate due to the disturbances in the input and output side. Hence the Lyapunov function based control strategy is modified by including a DC link voltage control is proposed for the multilevel inverter. Detailed analysis has been conducted to verify the effectiveness of the proposed system and is compared with the conventional control strategies. A fast dynamic response and lower distortion in output voltage is obtained with the proposed strategy compared to the conventional control strategies. Simulation and experimental results from a laboratory scale prototype is demonstrated to assess the performance of the suggested control scheme.

It is common practice to measure the instantaneous load current for realizing current trajectory control for UPS inverters. A recent paper describes an interesting sliding control mode scheme for 1-ph inverters with an LC filter in which the A.C. load current needs to be monitored. A modification to the scheme is presented in this paper which enables sliding mode control by monitoring the instantaneous D.C. line current and the load voltage. A simple observer can estimate the load current. The use of the observer helps in overcoming the problem of high voltage swings experienced by current sensors and errors due to common mode signals.

Sequences having the minimum peak aperiodic autocorrelation sidelobe level one (1) are called Barker Sequences. Such sequences have been used in numerous real-world applications such as channel estimation, radar and spread spectrum communication etc. Unfortunately, the longest known biphase and quadriphase Barker sequences are of lengths 13 and 15 respectively. In this paper Modified Simulated Annealing Algorithm (MSAA) is used to design thirty-two phase sequences, which have good autocorrelation properties. Some of the synthesized results are presented here. The properties of the sequences up to length 24 have Barker properties which were not reported in literature earlier. The sequences of lengths from 4 to 289 have autocorrelation properties better than Frank codes. The synthesized 32-phase sequence sets are promising for practical application to radar and spread spectrum communication systems.

This paper deals with the robust output voltage tracking problem with prescribed performance for single-phase voltage source uninterruptible power supply inverters. We construct two linear internal models to reproduce the steady-state information, based on which we transform our problem into the robust stabilization problem with prescribed performance of an augmented system. Then, we incorporate a novel error transformation into the existing framework for the robust output regulation problem to design a stabilization controller, based on which we synthesize our control law to make the tracking error converge to zero asymptotically while always satisfying the prescribed performance.

Performance evaluation of isolated three-phase voltage source inverter with LC filter adopting different MPC methods under various types of load

This paper proposes new and simple control method for a stand-alone doubly fed induction generator (DFIG) connected to unbalanced and nonlinear loads. This type of load causes harmonic distortion in the stator current and voltage. To solve this problem, a novel control method is proposed in the load side converter (LSC). In this method, instantaneous active and reactive power theory in stationary [α-β] frame is used. Unlike other control strategies, which needs to extract and compensate each harmonic or unbalanced component individually, in this paper, all harmonics and unbalanced components are injected by LSC. Finally, stator voltage becomes sinusoidal with very fast dynamic response. The performance of the DFIG feeding nonlinear and unbalanced loads is evaluated for steady state and dynamic conditions, using MATLAB/Simulink.

This paper proposes a control strategy for single-phase PWM boost-type inverters. The idea in this strategy is to have feedforward and feedback terms in the control variable. It is shown that the output voltage follows its reference without any error when there is a perfect match between estimated and actual filter capacitance. However, there exists a steady-state error in the output voltage due to the mismatch between estimated and actual filter capacitance. It is shown that this error can be minimized considerably if the controller gain is chosen as large as possible. The feasibility and the performance of the proposed control strategy has been tested and verified by simulations and experiments under linear and nonlinear loads.

The output of the three-phase inverter should have fewer harmonics, differential-free control, and fast dynamic response. In this paper, the off-grid voltage control of the three-phase inverter is proposed that provides excellent steady-state and dynamic performance of the output voltage. State feedback and complex variable resonant controllers are used to achieve zero steady-state control of the output voltage based on the state-space model. Feedforward links of load current and reference are added to the control structure. The feedforward gain is designed according to the principle of closed-loop zero and dominant pole pair elimination, so that the feedforward link can greatly speed up the dynamic process when the load and reference change abruptly and improve the response speed of the output voltage. Simulink simulation results show that the output voltage of the proposed inverter control method tracks the voltage reference without steady-state errors, and has a fast dynamic response.

Alternative energy systems (AES) are becoming popular for small scale power generation. Designing the converters which transform the DC power into AC is the main development area of AES. Conventional single-phase voltage source inverter (VSI) uses buck topology which gives lower average output voltage than the input DC voltage. However, where the output voltage requirement is larger than the input DC voltage, such as uninterruptible power supply, fuel cell (FC) and photovoltaic systems, boost inverters are used. The boost inverter applied in this study consists of two boost DC-DC converters, which provides sinusoidal AC voltage output. The key drawback of the inverter lies in its control structure. In this paper, a dual loop control method is applied to ensure pure sinusoidal output voltage with fast dynamic response and low input current ripple. The input voltage of the inverter is assumed to be stable at 48 V considering commercially available FC voltage and the output voltage is regulated at 110 Vrms. In this article, the operating principle, mathematical modelling, analysis and control strategy of the boost inverter is presented. The proposed control strategy is verified with simulation using MATLAB/Simulink®. Simulation results show that the output voltage is 110 Vrms pure sinusoidal and the input current has low ripples.

This paper proposes a new three-phase inverter [11] for voltage generation. The control of the proposed inverter is based on circuit-level decoupling instead of d/q conversion; it is implemented by appropriate rotary logic circuitry in combination with control-core and dual-loop feedback compensator. Control-core can be implemented by One-Cycle Controller (OCC) and Pulse-Width Modulation (PWM) controller. Dual-loop feedback compensator is implemented with switching component of Ic as feedback variable. Superior performance such as low THD, fast dynamic response, as well as low switching loss has been demonstrated. Yet the implementation is simple and flexible. The proposed concept is supported by simulation and experimental results from a 1kW prototype. The prototype is tested under all loading conditions, i.e. no load, full load and non-linear load. With OCC control-core, it has the strength of full rejection of input voltage perturbations as well as the ability to track abrupt reference change. With dual-loop compensator, it can achieve satisfactory output voltage regulation at low switching frequency.

This article addresses the predefined-time optimal motion control problem of an autonomous surface vehicle (ASV) with disturbances under dynamic self-triggered frameworks via reinforcement learning (RL). Initially, to eliminate the influence of disturbance on the ASV, a predefined-time second-order integral sliding mode control (SOISM) strategy is formulated by establishing a novel integral sliding mode (ISM) function and a terminal sliding mode function. Subsequently, a predefined-time approximate optimal motion (AOM) control strategy is further developed to ensure the ASV maintains a stable state. Furthermore, a single critic network is used to obtain an approximate solution of the Hamilton-Jacobi-Bellman (HJB) equation. The above two strategies are established under the dynamic self-triggered framework, which relies on the current information to predict the next updating time, effectively reducing the computational and communication burden while avoiding the continuous monitoring of the ASV state. In the theoretical analysis, the main challenges lie in the design of Lyapunov functions and triggered conditions to ensure the stability of the sliding mode dynamics and the disturbed ASV. By applying the Lyapunov stability principle and designing two novel Lyapunov functions and triggered conditions that both contain dynamic variables, we demonstrate that the developed control strategies can ensure the stability within the specified time frame. Ultimately, simulation results verify the efficacy of the proposed motion control approach.

Malaria remains one of the most life-threatening infectious diseases worldwide, causing hundreds of thousands of deaths annually, particularly among children and pregnant women in tropical and subtropical regions. To better understand its complex transmission dynamics, this study develops and analyzes both deterministic and stochastic mathematical models of malaria based on systems of differential equations. The main objective of this research is to study the stability of both the deterministic and stochastic malaria models analytically and numerically using the Lyapunov function, the Euler method, and the Euler–Maruyama method. For the deterministic model, the disease-free and endemic equilibrium points are derived, and their local and global stability are investigated. Numerical simulations are conducted using the mentioned numerical methods to demonstrate the dynamic behavior of the system. The stochastic extension of the model incorporates random perturbations to represent environmental and demographic fluctuations that influence disease spread. The analytical and numerical results reveal that stochastic effects significantly influence malaria dynamics, potentially reducing disease persistence and stabilizing the system under certain conditions. These findings provide deeper insights into malaria transmission mechanisms and contribute to the development of more effective and evidence-based control strategies.

The buck-boost DC-AC inverter generates an alternating output voltage as the differential voltage of two DC-DC individual buck-boost converters that are driven with two 180/spl deg/ phase-shifted DC-biased sinusoidal references. The peak value of the inverter alternating output voltage does not depend on the direct input voltage. In addition, an advantage over the Boost DC-AC inverter is that the output voltages of both Buck-Boost converters are also independent of the direct input voltage. The difficulty of the topology lies in the control of both buck-boost DC-DC converters as they are required to work with variable operating-points. A double-loop control strategy is proposed for the buck-boost DC-DC converter with a new inner control loop for the inductor current and also a new outer control loop for the output voltage. These control schemes include different compensations that make possible a fast and accurate control of both converters with variable operating points. With these compensations, the controllers are easy to design, implement and develop. Furthermore, feedforward loops are included to increase the robustness of the inverter to external disturbances in both the input voltage and output load. The proposed control strategy is designed and implemented on a prototype 1.5 kW buck-boost DC-AC inverter. The control strategy is validated by means of both simulation and experimental tests. The results show that the proposed strategy achieves a robust, reliable and accurate control of the inverter even in hard situations such as nonlinear loads, sudden load changes and transient short circuits.