Load Resonant Frequency Research Articles

POWER SUPPLIES BASED FULL-BRIDGE LLC RESONANT CONVERTER PERFORMANCE FOR IH APPLICATIONS

This paper describes the analysis and performance of a full-bridge LLC resonant converter based on power supplies for IH applications. The analysis contains five components: half bridge inverter, resonant tank, high frequency transformer, rectifier and coil. The switching bridge generates a square waveform to excite the LLC resonant tank, which will produce a resonant sinusoidal current which is transferred to the secondary of the converter through a high-frequency transformer. As it scales the voltage up or down according to the output requirements. The load represented by the equivalent circuit of the coil and work-piece is fed by the current transformed by the rectifiers. Considering that load parameters and resonant frequency vary greatly in all phases of system operation, this paper provides improved knowledge of output power control for high temperature applications. The validity of the analyzed converter parameters had been simulated and tested using MATLAB-SIMULINK software. The results of testing demonstrated that the proposed scheme and assembly has good efficiency, and it is well suited for magnetic induction heating systems

An improved active islanding detection method for grid-connected solar inverters with a wide range of load conditions and reactive power

Islanding occurs when a utility-interactive distributed generator (DG) is disconnected from the utility grid and continues to supply power to local loads. This condition has several consequences including damage to the equipment and personnel safety risks. Therefore, it is required by utility interconnection standards for the DG to stop energizing local loads in the case of islanding. In this paper, an active islanding detection method (IDM) based on injecting a disturbance into the phase-locked loop (PLL) of a grid-connected photovoltaic (PV) inverter and monitoring the harmonic components of the point of common coupling (PCC) is proposed. A modified Goertzel algorithm is utilized to detect the injected harmonic which is effective for a wide range of load conditions in terms of load quality factor, resonant frequency, and reactive power. The simulation results in MATLAB/Simulink show that the proposed technique is fast with minimum side effects on power quality features such as output current total harmonic distortion (THD). This method is implemented on a single phase 5 kW grid-tied PV inverter and is tested experimentally. The experimental results verify that the proposed technique is fast with zero non-detection zone (NDZ) which is effective for a variety of load conditions.

A self-oscillating series-none inductive power transfer system using a matrix converter

Power density and conversion efficiency are two critical parameters of inductive power transfer (IPT) systems. These parameters are related to the number of components in the power conversion circuit as well as its modulation method. The combination of Midpoint Matrix Converter and pulse-density modulation (PDM) has a potential to improve these parameters, due to a low number of semiconductor switches utilization as well as constant efficiency at the maximum output and partial load operations . In this context, this paper analyzes the performance of a three-phase to single-phase Midpoint Matrix Converter using a Free-wheeling Switch (MMCFS) and the PDM in a high coupling factor series-none IPT application. This converter utilizes on–off control to manage power transfer, which automatically tracks the load resonant frequency. Dynamic and steady-state mathematical equations were derived to represent the converter and the IPT system characteristics. These equations show a relationship between the link efficiency, the link gain, the damping ratio and the coupling factor. A kick-start method and a multistep switching strategy were developed to start and operate the converter, respectively. Additionally, a 150 W MMCFS-based IPT prototype was built to verify the improvement, which demonstrated an efficiency of around 80% at the maximum output and partial load operations.

Efficiency Considerations of LLC Resonant Converter for Induction Heating Application

Due to the high efficiency, high power density and low EMI provided by the LLc resonant converter, it has been widely used by researchers in many fields such as induction heating (IH). This converter is based on a resonant circuit consisting of a capacitor (Cr) and two inductors Lr, Lm operating in wide output load regulating ranges for the purpose of achieving good efficiency for very high power systems using a high operating frequency. This paper aims to present a half-bridge LLC resonant converter based on power supplies for IH applications. The analysis contains five components: half bridge inverter, resonant tank, high frequency transformer, rectifier and coil. The switching bridge generates a square waveform to excite the LLC resonant tank, which will produce a resonant sinusoidal current which is transferred to the secondary of the converter through a high-frequency transformer. as it scales the voltage up or down according to the output requirements. The load represented by the equivalent circuit of the coil and work-piece is fed by the current transformed by the rectifiers. This paper provides an improved knowledge of the control of the output power for high-temperature applications through numerical simulation Considering that the load parameters and resonant frequency vary substantially throughout the system operation. The results of testing demonstrated that the proposed scheme and assembly has good efficiency, and it is well suited for magnetic induction heating systems.

The invention relates to an intermediate frequency power supply fast start and digital phase locked loop control technology

Intermediate frequency induction heating is widely used because of its low energy consumption and high thermal efficiency, but the speed of traditional intermediate frequency power supply is slow and its frequency tracking accuracy is limited. In order to maintain the resonant state of the load during the working process of the induction heating power supply and realize the automatic frequency tracking control during the working process. The frequency tracking of the 40kW intermediate frequency power supply is researched, and a method of combining the resonant frequency automatic identification algorithm and the digital phase locked loop frequency tracking control method is proposed. MATLAB simulation and experiment show that the system based on this control method can save the time of searching the load resonance frequency in the initial stage of the power supply, improve the frequency tracking speed, accelerate the dynamic response speed of the system, avoid the failure of frequency lock, and play the role of fast and stable startup.

Automatic Calculation Method of Load Resonant Frequency of Photovoltaic Power Supply

The resonance phenomenon of photovoltaic power supply load makes the output voltage of grid-connected photovoltaic power supply system difficult to keep stable, which brings trouble to power supply. Therefore, it is necessary to study the automatic calculation method of load resonance frequency of photovoltaic power supply, so as to detect the load resonance frequency of photovoltaic power supply in real time, thereby ensuring the normal operation of photovoltaic power supply system. The load resonance frequency of photovoltaic power supply is divided into steady-state load resonance frequency and dynamic load resonance frequency. The mathematical model of load resonant circuit of photovoltaic power supply is established by calculating algorithm of load resonant frequency of photovoltaic power supply in steady state, and load resonant frequency of photovoltaic power supply in steady state is calculated. The resonance detection algorithm based on wavelet transform and Hilbert-Huang transform is used to analyze and calculate the load resonance frequency after detecting the resonance signal of photovoltaic power system. The experimental results show that the resonant frequency of photovoltaic power supply load calculated by this method is not much different from the actual resonant frequency of photovoltaic power supply load, and the error range is between-0.30% and 0.49%. Therefore, this method can keep the load resonance frequency of the photovoltaic power supply the same as the RF transmission resonance frequency, and can ensure the normal operation of the photovoltaic power supply.

Measurement of quartz crystal unit parameters based on the precise derivation of zero phase frequency

It is usually considered that the resonance frequency of quartz crystal resonator is only related to dynamic inductance L 1 and dynamic capacitance C 1, and load resonance frequency has connection with L 1, C 1 and static capacitance C 0. Hence, the dynamic resistance cannot be measured by frequency. The deduction show that all the frequencies relates to L 1, C 1, C 0 and dynamic resistance R 1. Then, a method for measuring the total equivalent parameters of quartz crystal resonator based on zero phase frequency is proposed in this Letter. The simulation results of advanced design system (ADS) verify the validity of this proposal in theory. After that, the phase-frequency-curves of a quartz crystal resonator with 10 and 5 MHz are measured, which can obtain equivalent parameters of through data processing. The results show that this method has calculated parameters essentially in agreement with nominal parameters. This method does not have reciprocating debugging process, and the test process is simple as well. In addition, the approximate calculation is not used in this method, and it could be widely extent to the field of sensors, such as quartz crystal microbalance sensors, temperature sensors and so on.

Low frequency wireless power transfer using modified parallel resonance matching at a complex load

Series resonant and strong coupling structures under an impedance matching (IM) condition of wireless power transfer (WPT) have been widely studied. These operate under an optimal resistive load and high resonant frequency of greater than 1 MHz. However, the optimal parameters (particular values) limit the design. The common loads are complex and the high frequency RF sources used are usually inefficient. This paper presents a modified parallel resonant (PR) structure that can operate at a low frequency of 15 kHz without an optimal parameter under an IM condition with a complex load. The calculated and experimental efficiencies for a 5 cm transfer distance were 71.2 % at 15 kHz and 68% at 17 kHz, respectively. Hence, a modified two-coil PR structure can be operated at a low frequency with high efficiency.

The Application of Phase-Locked Loop Frequency Tracking in the Intelligence-Type Induction Heating Power Supply

As the induction heating power was working, its load resonant frequency constantly changes. In order to improve the efficiency of power supply, it requires that the inverter output frequency can follow changes in natural frequency of the load, namely the frequency tracking control. Aiming at the deficiency of the frequency tracking control system, this paper presents a method that the phase locked loop (PLL) tracking system works on real-time control of the output frequency of the power supply,and introduces a phase locked mathematical model which fits the inverter power supply, and offers a simulated analysis by using PSPICE. Through experiments, the system proves to be good at frequency tracking.

Modal and Wind Vibration Analysis about Steel Chimney Outer Wall with a Spiral Guide Plate Based on Workbench

This paper analysis a steel chimney outer wall with a spiral guide plate. Through calculation the steel chimney structure modal, self-vibration and wind vibration frequency verify this steel chimney can reduce the wind load impact on the chimney and flange connection. Achieve a method of improved the strength of chimney structure. The chimney under wind load resonant frequency band is reduced effectively and obtained a more stable exterior structure, offered basis for steel chimney transform in wind vibration problem.

Study on Topology Design of Wireless Power Transfer for Electric Vehicle Based on Magnetic Resonance Coupling

Wireless power transfer (WPT) is required for the diffusion of Electric Vehicle (EV) because it makes possible the process of automatically charging EV. Magnetic resonance coupling is a new technology for WPT, which can transfer a large amount of energy with high efficiency in middle distance. In this paper the topology design of WPT for EV by using this technology is investigated. Through theoretical analysis we obtain expressions of optimal efficiency with different topologies based on equivalent circuits and define a condition criterion, which is related with load resistance, transmission distance, resonance frequency and coil size. According to the condition criterion we can design the appropriate topology easily to guarantee optimal transmission efficiency. Finally, simulations and experiments show that the defined condition criterion has high sensitivity and the proposed method of designing topology is effective and feasible.

A Method of Single Phase High Frequency Inverter Based on Tracking Control to Load Resonant Frequency

In this paper, we propose a new control method of the inverter frequency and the inverter output power with load resonant frequency adjusting phase shift inverter. The proposed control method is applicable to stet the phase-shift inverter with only one output current sensor. When the proposed method is employed, the fundamental waveform signal of inverter output voltage is obtained because the output voltage of a phase-shift inverter is a pulse waveform. Unity power factor and a high efficiency are achieved by adopting the proposed method involving the tracking control of load resonant frequency. In the proposed method, the fundamental waveform signal of inverter output voltage coincides with the detected inverter output current waveform. Moreover, as the inverter output power is regulated by controlling the phase angle of inverter leg in this proposed method, soft-switching control can be realized. In study, the validity of the proposed method is confirmed on the basis of experimental results.

A malfunction problem and its solution in load-resonant inverters

Load-resonant inverters drive their loads at the load's resonant frequency. The frequency control unit of this type of inverter may be implemented simply by using phase-locked loop-based tuning circuits. However, a problem is detected that may arise randomly in this type of frequency control scheme. When this problem occurs, the inverter's frequency jumps to a value unrelated to the load-resonant frequency and sticks there. Following the analysis of the underlying cause of the problem, it is understood that the problem is caused by the two-valued characteristic of a phase frequency detector. A correction circuit is presented in this paper. When the proposed correction circuit was incorporated into the existing tuning circuitry, the problem was eliminated in the experiments. This shows not only that the correction circuit works well but also that the mechanism of the malfunction was diagnosed accurately.

Phase detector for tuning circuit of resonant inverters

The tuning circuit in a resonant inverter determines the inverter frequency and makes it track the load resonant frequency. Current phase detectors have some serious drawbacks for this application. A new phase detector circuit is presented which can overcome these drawbacks.

Practical evaluations of a ZVS-PFM quasi load-resonant high-frequency inverter using a new generation IGBT for an induction-heated cooking appliance

This paper presents an efficient and compact type quasi load-resonant high-frequency inverter using a new generation IGBT and its specially-designed intelligent driver IC for induction-heated cooking appliances that can operate under a ZVS-PFM power regulation scheme. The generic voltage-fed and current-fed circuit topologies of single-ended quasi load-resonant inverters for consumer and home appliances are proposed and systematically classified on the basis of the topological circuit configuration methods. The advanced IGBT, designed for the application-specific soft-switching, and its intelligent driver IC, including a multi-functional control circuit, are introduced for a new electromagnetic induction-heating rice cooker and cooking stove. A self-excited ZVS quasi load-resonant high-frequency inverter using a new IGBT, which is composed of a working coil-linked inductionheated pan and vessel loads, is evaluated from an experimental point of view. This feasible voltage-fed quasi load-resonant frequency conversion system, with a highpower factor correction and sine wave line current shaping functions, is actually implemented and incorporates a high-frequency IGBT with reduced saturation voltage characteristics. The promising high-power density and energy-saving induction-heated cooker, as a home-power electronic appliance, is demonstrated (Hirota et al. 1995).

Resonant-current phasor shifting control-based voltage-fed high-frequency inverter with load resonant frequency tracking scheme and performance analysis.

Resonant-current phasor shifting control-based voltage-fed high-frequency inverter with load resonant frequency tracking scheme and performance analysis.

Broad-Band Coupling to High-Q Resonant Loads

Broad-band coupling between a resistive source and a resonant load is considered for coupling networks consisting of a uniform transmission line of impedance Z/sub I/ and length equal to a quarter wavelength at the load resonant frequency. An approximate analysis is used to show that either maximally flat or ripple insertion loss frequency response can be obtained by proper choice of Z/sub I/, and the 3-dB bandwidth obtained in either case is always greater than 1/Q. Depending on the ratio of load and source resistances, the bandwidth may be greater than 1 octave. Network design curves for maximally flat operation with a variety of load parameters are computed without approximation. The design of lumped element approximations for the transmission line network is also described.