Optimum Trajectory Switching Control for Series-Parallel Resonant Converter

The series-parallel resonant converter (SPRC) is known to have combined merits of the series resonant converter (SRC) and PRC. However, the SPRC has a three-element LCC structure with complex transient dynamics, and without control of the resonant circuit's dynamics, the converter's closed-loop bandwidth to switching-frequency ratio will be much reduced compared to that of pulsewidth-modulation (PWM) converters. This paper presents the optimal trajectory enabling any SPRC's steady state be achieved within one cycle. Dynamics using the state-plane analysis is presented, and the optimal state trajectory for transients is derived. Experimental results with comparison to frequency control show much reduced resonant circuit response time for step changes in output voltage. This improved resonant circuit control allows subsequent current and voltage-loop controls of the SPRC to be treated as that of a conventional PWM voltage source     

A Novel Robust Control Method for the Series–Parallel Resonant Converter

A novel robust control method for the series–parallel resonant converter (SPRC), which moves the inverter switching point to switch in advance or with lag w.r.t. the rectifier commutation point (RCP), thereby varying the converter gain around the load-independent point, is presented. The converter gain is derived using a novel analytical tool that combines state-plane analysis and superposition with added RCP constraint. Unlike traditional fundamental harmonic analysis , the exact gain and frequency expressions for the SPRC at the load-independent point and its neighborhood are obtained with this method. The proposed gain adjustment technique is combined with feedback to form a simple resonant converter controller. This control method is shown to be highly robust to resonant tank parameter uncertainty and circuit/switching delay. It also significantly simplifies the resonant converter controller's design.      

Sampled-data modeling and digital control of resonant converters

A sampled-data model to describe the dynamics of large signals and of small perturbations away from a cyclic steady state is developed. Associated transfer functions are obtained. The application of the model is illustrated by correlating the analysis with simulation results obtained for a series resonant DC/DC power converter. A discrete-time microprocessor-based controller, designed using the aforementioned dynamic model, has been built and tested using a simulation for a series-resonant DC/DC converter set up on the Massachusetts Institute of Technology Parity Simulator. The control methods implemented are state feedback and periodic output feedback, each designed to achieve a specified set of closed-loop poles. The controller has been implemented using the Parity Simulator generalized controller. Results of the closed-loop response showed an improvement over the open-loop response. In addition, the effect of the microprocessor computation delay on the closed-loop dynamics of the converter is investigated     

High-frequency high-order parallel resonant converter

A novel approach to the analysis of design of a high-order high-frequency LCC-type capacitive coupled parallel resonant converter (PRC-LCC) operated in the continuous-conduction mode is presented. The presence of an additional capacitor in series with the inductance of the conventional PRC results in a converter with more desirable control characteristics. It is shown that, at switching frequencies lower than the resonant frequency, the gain of the LCC-type converter is lower than the grain of the conventional PRC. This facilitates the converter design with a lower turn-ratio transformer and therefore allows for a higher operating frequency. The complete state-plane diagram of the LCC-type converter, from which a set of steady-state characteristic curves is plotted, is given. Various design curves for component value selections and device ratings are given. A design example with computer simulation results is presented     

Smart Internet of Things (IOT) System for Performance Improvement of Dual Bridge LLC Resonant Converter by Using Sophisticated Distribution Control Method (SDC)

A resonant converter is a kind of electric power converter that contains a system of inductors and capacitors called a resonant tank, tuned to resonate at a particular frequency in this work recommends a better-quality dual bridge LLC resonant converter with a novel controller technique. The resonant converters include the serial or parallel connections of inductors and capacitors to activate the switch to realize the Zero Current Switching (ZCS) and Zero Volt Switching (ZVS) under resonance conditions. The resonant effects are switching sufferers, turning strain and electromagnetic interference problems the switching resonant converter controls the output voltage through changing frequency and generally can be sub classified in ZCS converter and ZVS converter. This scheme had combined wireless monitoring for dual bridge LLC resonant converter for dc distribution applications based on sophisticated distribution controller (SDC) through the internet of things and embedded structure access and other mechanisms. The consequence of our exhibition demonstrates that the framework can monitor and store the manipulate data from the converter. Thus, the wireless monitoring functions are realized in real-time. This converter permits both forward and reverses power exchange between the source and the load, to keep up the output voltage consistent, regardless of load and line unsettling influences, it is important to work the converter as a closed loop system. The proposed SDC based dual bridge resonant converter has validated through simulation in Matlab Simulink environment. A hardware setup is also developed to validate the simulation. General 97% effectiveness accomplished at full load condition in light of the dual bridge resonant converter.     

一种双极性电流源型功率谐振直流变换器

介绍了一种双极性电流源型谐振直流变换器，该变换器综合了串联谐振变换器和并联谐振变换器的优点，并且克服了各自的缺陷。文章运用经典交流分析法，推导了电流传输增益，同时分析了断续工作模式下的各种开关状态，得出相应的等效电路，并利用仿真结果验证了所做的理论分析。     

Multiple converter performance and active filtering

The application of active power filtering to power systems in limited by the low switching rate of available high power inverter switches. In this paper, parallel and series connection of multiple voltage source inverter bridges are examined to increase their effective switching rate. The analysis of the inverter voltage spectrum for double edge modulation shows the modulation desired for the separate bridges in open loop. Intuitively “i” bridges in series or parallel increases the effective switch rate by a factor “i”. However the modulation process for each power converter maintains its pattern for its switching period T which gives a roll off at high frequencies and reduces effective bandwidth. The experimental system of two 10 kVA voltage source inverters demonstrated how the closed loop control strategies for the active filter can be applied for multiple bridges implementing periodic optimized error sawtooth feedback control. The double bridge closed loop system showed that the lowest switch frequency terms were double that of the separate bridges. The higher frequency switching lines that should have been cancelled in theory were still discernible due to the finite precision of the edge timing     

Robust High Bandwidth Discrete-Time Predictive Current Control with Predictive Internal Model—A Unified Approach for Voltage-Source PWM Converters

This paper presents a robust high bandwidth discrete-time predictive current control scheme for voltage-source pulsewidth-modulated (VS-PWM) converters. First, to achieve high bandwidth current control characteristics, a digital predictive current controller with delay compensation is adopted. The compensation method utilizes a current observer with an adaptive internal model for system uncertainties. The predictive nature of both the current observer and the internal model forces the delays elements to be equivalently placed outside the closed loop system. Second, to ensure perfect tracking of the output current in the presence of uncertainties and providing means for attenuating low- and high- frequency system disturbances, the frequency modes of the disturbances to be eliminated should be included in the stable closed loop system. Toward this, an adaptive internal model for the estimated uncertainty dynamics is proposed. To cope with the high bandwidth property of the lump of uncertainties in VS-PWM converter applications, the disturbance slowly varying assumption is relaxed in the proposed controller. The relaxation is achieved by adopting a curbing sliding-mode-based feedback gain vector within the internal model observation system. Comparative evaluation tests were carried out on a grid-connected VS-PWM converter and a direct drive permanent magnet synchronous motor (DD-PMSM) drive system to demonstrate the validity and effectiveness of the proposed control scheme at different operating conditions.     

Small signal analysis of the LCC-type parallel resonant converterusing discrete time domain modeling

Discrete state-space modeling of the LCC-type parallel resonant power converter is presented. Using these large signal equations, small signal modeling of the power converter is obtained. Multiple loops have been used for the closed loop operation. State variable feedback control has been integrated with the linear small signal state-space model and the associated control aspects are studied. The small signal state-space model has been used to study the small signal behavior of the power converter for open loop and closed loop operation for parameters like control to output transfer function, audio-susceptibility and output impedance. Key theoretical results have been experimentally verified     

Operation of the LCC-type parallel resonant converter as a lowharmonic rectifier

A single-phase high-frequency transformer isolated single-stage AC-to-DC controlled rectifier with low line current harmonic distortion using a variable-frequency controlled LCC-type (or series-parallel) resonant power converter (SPRC) is presented. A simple analysis and design procedure is used for designing the converter for low line current harmonic distortion and high power factor operation. The converter performance characteristics have been verified with SPICE3 simulations (without active control) and experimental prototype SPRC (rated at 150 W, with and without active control) for variation in load as well as line voltage. When operated with active current shaping, this converter operates in zero-voltage-switching mode for the complete range, maintaining power factor close to unity with low line current distortion and low peak current compared to the parallel resonant converter     

Implementation of a neural controller for the series resonantconverter

A neural controller implementing an energy feedback control law is proposed as an alternative to classic control of resonant converters. The properties of the energy feedback control, and particularly the optimal trajectory control law, are analyzed. As a result, the state space is considered to be divided into two subspaces, that correspond to different states of the switches in the converter. An analog neural network learns to classify these two classes by means of a learning algorithm. A simple electronic implementation of this controller is proposed and applied to a series resonant converter (SRC). Results based on prototype measurements show a good improvement in the SRC response versus classical control methods based on the linearization of the state variable equations around a working point and confirm the validity of the neural approach     

Closed loop low-velocity regulation of hybrid stepping motorsamidst torque disturbances

To regulate the velocity of hybrid stepper motor motion control systems, a control law which exploits the nonlinear dynamics to create an analog positional control in conjunction with a traditional linear control is introduced. This nonlinear approach allows a much coarser position sensor to be used, including position estimates based on back EMF measurements. The form of the control law admits the use of a wide variety of compensators, whereas earlier laws use only velocity damping compensation. Two specific compensators, i.e., velocity damping and integral control are analyzed in detail, then compared to each other and to open loop microstepping control. It is shown that velocity damping allows the design of the eigenvalues of the closed loop system and provides a linear system approach about a specified operating point. Unfortunately, this operating point includes the value of external DC torque (drag) present, so the closed loop dynamics cannot be guaranteed amidst steady state torque fluctuations. Integral feedback (within a PID controller) improves upon velocity damping by not only allowing the design of the closed loop eigenvalues, but also by completely linearizing the system regardless of external DC torque values. Furthermore, the integral feedback produces zero steady state position error (as expected from linear control theory) and significantly decreases the tendency of the motor to lose step. Experimental results validate the analyses     

Self-sustained oscillating resonant converters operating above theresonant frequency

This paper presents a new control technique for resonant converters. Unlike conventional variable frequency control which externally imposes the switching frequency, the proposed scheme is based on controlling the displacement angle between one of the resonant circuit variables, typically the current through the resonant inductor, and the voltage at the output of the inverter. As a result, zero-voltage switching (ZVS) can be ensured over a wide operating range. The proposed control technique cam be applied for series, parallel, and series-parallel resonant converters. As an example, the static characteristics and dynamic model of a series-parallel resonant converter with the proposed controller are derived and the system behaviour is investigated in detail. Experimental results are given to demonstrate the operation of resonant converters with the proposed controller and to validate the analysis     

A Novel Control Method for Piezoelectric-Transformer Based Power Supplies Assuring Zero-Voltage-Switching Operation

In this paper, a new control strategy that allows zero-voltage-switching (ZVS) operation of power converters using piezoelectric transformers (PTs) is proposed. The control circuit operates in a closed loop by measuring the phase between the PTs resonant current and the switching pattern and adjusting the switching frequency to the optimum value so that ZVS operation is assured. An innovative nonlinear regulator based on an analog multiplexer is presented. The regulator automatically swaps the signs of the sensed signal and the reference signal to allow generation of the adequate control action. A laboratory prototype for a 6 W resonant inverter was tested; obtained experimental results are also shown.     

基于LM5117P的降压型直流开关稳压电源设计

降压型直流开关稳压电源是一种单向DC-DC变换器,实现稳定直流降压功能.本系统采用同步降压控制器LM5117P作为电路控制核心,以同步Buck电路作为降压主电路,通过闭环回路反馈设计以及芯片本身的精准采样,将输入电压16V降为5V恒压输出.     

Nonlinear Current Control of Single-Phase PFC Converters

A set of new nonlinear current control methods are presented for single-phase power factor corrected ac-dc converters. These control methods combine input current feedforward with partial feedback based on the switch current to achieve sinusoidal input current and unity input power factor. They overcome the limitations of conventional linear (average) current control in terms of control bandwidth and sensitivity to noise, resulting in high-performance input current control which can meet the most stringent harmonic current limits required by variable-frequency airborne power systems. The control methods are also ideally suited for integrated mixed-signal implementation, requiring an analog current controller which is very simple, much less sensitive to noise than conventional linear feedback control, and independent of converter and control design parameters; and a digital controller which operates with a sampling frequency much lower than the switching frequency. Detailed development of the control methods is presented along with their stability analysis and circuit implementation. A prototype converter and its operation are also presented to validate the analysis and to demonstrate the performance of the control methods.     

Buck converter small-signal models and dynamics: comparison ofquasi-resonant and pulsewidth modulated switches

The generalized canonical model obtained from extended state-space averaging is used as a design tool for the evaluation of the buck converter dynamics in different switching schemes. Designs are given at a specified constant conversion ratio and load for the pulse width modulated, zero current, zero voltage, and nonlinear resonant switch full- and half-wave converters. The small signal equivalent circuit model is discussed, and the feedback effects introduced by resonant switching on line and control transfer functions are evaluated. The small signal transfer functions of half-wave converters are heavily load-current dependent, and exhibit significant damping at light loads, which can result in two real poles in the converter response instead of a complex conjugate pair. This damping effect is evaluated over the entire normalized load current range for the linear and nonlinear zero-current switching converters. Simple approximate expressions are given for the real poles. Experimental verification of the half-wave analysis is presented, and the effects of converter efficiency on model accuracy are discussed     

Decentralized nonlinear adaptive control of an HVAC system

This paper presents a new decentralized nonlinear adaptive controller (DNAC) for a heating, ventilating, and air conditioning (HVAC) system capable of maintaining comfortable conditions under varying thermal loads. In this scheme, an HVAC system is considered to be two subsystems and controlled independently. The interactions between the two subsystems are treated as deterministic types of uncertain disturbances and their magnitudes are supposed to be bounded by absolute value. The decentralized nonlinear adaptive controller (DNAC) consists of an inner loop and an outer loop. The inner loop is a single-input fuzzy logic controller (FLC), which is used as the feedback controller to overcome random instant disturbances. The outer loop is a Fourier integral-based control, which is used as the frequency-domain adaptive compensator to overcome steady, lasting uncertain disturbances. The global DNAC controller ensures that the system output vector tracks a desired trajectory vector within the system bandwidth and that the tracking error vector converges uniformly to a zero vector. The simulated experimental results on the HVAC system show that the performance is dramatically improved.     

Digital Current Control of a Voltage Source Converter With Active Damping of LCL Resonance

Inductance–capacitor–inductance (LCL)-filters installed at converter outputs offer higher harmonic attenuation than L-filters, but careful design is required to damp LCL resonance, which can cause poorly damped oscillations and even instability. A new topology is presented for a discrete-time current controller which damps this resonance, combining deadbeat current control with optimal state-feedback pole assignment. By separating the state feedback gains into deadbeat and damping feedback loops, transient overcurrent protection is realizable while preserving the desired pole locations. Moreover, the controller is shown to be robust to parameter uncertainty in the grid inductance. Experimental tests verify that fast well-damped transient response and overcurrent protection is possible at low switching frequencies relative to the resonant frequency.     

Loss calculations in transistorized parallel resonant convertersoperating above resonance

The optimum operating point under certain constraints for a parallel resonant converter (PRC) operating above resonance is obtained. A systematic way to calculate losses in a PRC operating above resonance is presented and illustrated for bipolar and MOS power transistor switches. Experimental results obtained with prototype converters employing the above devices are given to support the theory. Both theory and experiments show that MOSFETs are better switching devices at a power level of about 1 kW