Double bridge resonant DC link converter with variable input and output frequency

In cement mill application, the different equipments are used to grind the solid clinker from the furnace into the fine powder. Further, in a cement mill drives, different motors are used with frequency and voltage converters. Besides, the frequency of produced electricity is 50 Hz in India, which is not useful in many applications. Many drives need the variable frequency than the constant frequency such as cement mills drives. Therefore, it is required to get the variable frequency and variable voltage for proper operation of the cement mills. The cycloconverters are widely used for this purpose, as it is not possible to change a number of poles during the operating condition. The cycloconverter output voltage and frequency can be changed uninterruptedly using a fuzzy logic based control circuit. In this chapter, the fuzzy logic controller is used to control the output of the converter. This work shows how to get variable voltage and frequency to control the cement mill drives with the help of a fuzzy-based controller. Hence, an idea of controlling the cement mill drives with the fuzzy controller has been given in the chapter so the complete system is made in such a manner that it is efficient and reliable. Further, results show the effectiveness of the proposed scheme.

In this paper, a single-phase to three-phase converter is proposed to provide variable output voltage and frequency. The proposed topology employs only six IGBT switches, which form the front-end rectifier and the output inverter for the one step conversion from single-phase supply to output three-phase supply. The front-end rectifier permits bidirectional power flow and provides excellent regulation against fluctuations in source voltage. Moreover, it incorporates active input current shaping feature. An easy method to implement control strategy is proposed. This control strategy ensures nearly unity input power factor with sinusoidal input current over the operating range. Based on sensorless vector control technique, the proposed converter is used for the speed control of the three-phase induction motor. A low cost motor drive can be achieved using the proposed converter and control technique. Simulation and experimental results are carried out to analyse and explore the characteristics of the low cost drive system.

Nowadays, variable frequency AC generation system is widely used on more electric aircraft because of their advantages of simple structure, high power density, and high reliability. However, a variable frequency system has a wide range of operating speeds and frequencies, and its exciter field is designed to be highly saturated at low speed. Under the condition of a saturated exciter field at high speed, the generator can produce a very high voltage, which will cause damage to aircraft utilization equipment, leading to catastrophic failures. Therefore, to protect the safety of the aircraft, transient voltage regulation performance and voltage protection design are critical in the system design of variable frequency AC generation. This paper focuses on the design of voltage regulation and protection of variable frequency electrical power systems that can meet airworthiness requirements.

the high voltage variable frequency system has complicated structure and high power density. It comprises industrial frequency AC, DC and variable frequency AC. All of these bring new challenges to the system's protection and stability control. This paper considered the protection strategy in two aspects: device-level protection and system-level protection. Through improving the circuit structure and configuring microcomputer protection system, the paper designed a complete protection strategy for NPC three-level variable frequency drive system. The protection covered the fault of rectifier input, DC link, inverter output and the induction motor. The paper also analyzed the cooperation of protective trip and pulse blocking, which intending to restrain the feedback energy, and validated the feasibility of setting an output breaker to cut the feedback.

Medium-voltage cyclo-converter drives are commonly used for low-speed salient pole synchronous motors in mines. Cyclo-converters give very reliable, efficient and simple solution because they use rugged thyristor devices. Generally, the mines are located at remote locations and the availability factor is very important to minimize Business Interruption loss. However, a cyclo-converter drive has the drawback of generation of sub-harmonics and inter-harmonics along with high-order harmonics. These harmonics are harmful to transformers and weak supply networks and may cause saturation and instabilities. The sub-harmonic frequencies are a function of output frequency and change with output frequency. To mitigate these frequencies, huge passive filters are employed. If the output frequency is fixed, the filter designs are relatively simple but with the variable frequency it becomes complicated. For operational requirements in a mill, on-load output frequency trimming is required. This creates additional problems in terms of MVA sizing of equipment and the requirement of additional filter banks. This paper simulates the fixing and trimming of operating speed of medium-voltage cyclo-converter driven, low-speed, salient pole synchronous motor and brings out issues related to equipment sizing, harmonic mitigation, etc.KeywordsMV driveSynchronous motorCyclo-converter

A novel variable-speed, constant-frequency (VSCF) 400 Hz aircraft generating system has been developed using an actively clamped resonant DC link converter. The design approach used to select the best configuration for the resonant converter power stage is described, including techniques for choosing power component values to meet key governing performance specifications. Interactions between the various converter components are discussed, suggesting approaches for selecting values which must meet multiple and sometimes conflicting system performance criteria. Verification is provided using a combination of simulation results and test data from a 60 kVA laboratory breadboard system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper proposes a novel three-phase nine-switch AC/AC converter topology. This converter features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost. The operating principle of the converter is elaborated, its modulation schemes are discussed, and experimental results from a 5 kVA prototype system are provided.

A novel three-phase PWM rectifier-inverter topology (Fig. 2) for UPS applications is proposed in this paper. The topology uses only nine IGBT devices for AC/AC conversion through a quasi d.c. link circuit. This converter topology features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost. The operating principle of the converter is elaborated and a dedicated space vector modulation scheme is presented. The performance of the proposed converter is verified by experiments on a 5 kVA prototyping UPS system.

This paper presents a zero-voltage-switching (ZVS) three-level DC/DC resonant converter for high-power distributed power systems. The paper first addresses the operation of the converter at a fixed frequency, which is achieved by applying phase-shift control between the primary and the secondary sides of the transformer. Next, the operation of the converter at variable frequency is presented. In both operating modes, the converter can achieve ZVS operation in the entire load range by using the magnetizing inductance of the transformer. In addition, the converter can operate with wide input voltage variations without penalizing the efficiency. As a result, the converter is suitable for applications in which high efficiency and high power density are required. The principle of operation for the converter is analyzed and verified on a 2.75 kW, 745 kHz experimental prototype.

This paper describes a novel 10 kW (10 kV, 1 A) high voltage capacitor charger which has the combined advantage both series loaded resonant inverter and ZVS full-bridge PWM inverter. Series loaded resonant inverter has a wide ZV or ZC switching range regardless of load condition. However it can generate audible noise at light load condition and requires careful filter design because it should be controlled by variable frequency. On the other hand, ZVS full-bridge PWM inverter can be controlled by phase delay of each switching signal with fixed switching frequency, but when it is working at light load condition, efficiency will be decrease because of loosing soft switching condition. The proposed charger has the same structure like series resonant inverter, and controlled at fixed frequency by way of phase shifted PWM. The operational principle of proposed charger and soft switching mechanism is analyzed. The developed charger is verified to have higher efficiency at light load condition and higher power density by way of simulation and experiments. Developed charger and 10 kV IGBT stack based solid state pulsed power modulator was combined and tested with various load conditions. The experimental results verified that the proposed charger can be used effectively for high voltage pulsed power modulator which requires the various kinds of load condition with respect to the applications.

Fishtail divertor (FTD), a new divertor concept, is a significant research object of EAST tokamak divertor system. Considering the requirement of sinusoidal current precision and stable output with variable frequency (10-3800Hz) and adjustable amplitude (0-5000A) in complex and arguable electromagnetic environment, a resonant frequency feedback control strategy is proposed for FTD magnet coil power supply. The equivalent mathematical model of the FTD coil PS and control process is set up. Through detailed theoretical analysis and simulation, the conclusion of performance optimization based on control strategy is obtained. At the work of frequency feedback control strategy, the power supply can promptly identify the resonant network frequency deviation caused by the interference of electromagnetic environment on the equivalent load characteristics within 1.5S, and actively correct the excitation voltage frequency, so as to ensure the accuracy of the FTD magnet coil current. Finally, the correctness of the design is verified through experimental tests.

Single stage AC/DC converters based on series-parallel resonant circuit and operating above the resonance frequency provide high input power factor. However, with conventional variable frequency control, zero voltage switching may be lost in some operating conditions. In this paper two control techniques for resonant converter operating above resonance frequency are compared. These control techniques ensure zero voltage switching in all operating points allowing operation at high frequencies. A design procedure is suggested for the selection of resonant circuit parameters. Finally experimental results from a 500 W power factor corrected AC/DC power supply are given to verify the predicted results.

This paper presents a steady-state comparison of two methods that generate an orthogonal voltage system for a single-phase Phase-Locked Loop (PLL) structure: a widely accepted one based on a Second Order Generalized Integrator (SOGI) and a new one based on a All-Pass Filter (APF) with Lattice structure. Both methods are very attractive because of their simple digital implementation, low computational load and good performance under harmonically distorted grid conditions and variable frequency, so they are a good alternative to other known methods. The paper derives and analyzes the full state space models of the two methods.It is shown that these two methods are equivalent in the most common operation conditions of distributed energy resources, although the APF structure is clearly better than the SOGI one because it maintains its orthogonal generation ability for any higher notch frequencies and any lower sampling frequencies. The comparative analysis were validated by simulation with MATLAB/Simulink and experimental results using a fixed-point DSP.

A SOGI-based adaptive controller design for second-harmonic currents suppression of variable frequency loads in DC buildings

The article provides a detailed overview of the history, development and applications of frequency converters, with particular emphasis on their use in the oil and gas industry. It traces the evolution of frequency converters from their inception in the late 19th and early 20th centuries to their modern applications, which use microprocessors and digital signal processing to precisely control the output frequency. In the oil and gas industry, frequency converters are critical to efficient and accurate induction heating of pipelines. They convert a fixed frequency and voltage power supply into a variable frequency and variable voltage output, controlling the speed of the induction motors used in the heating process. The article also covers the design and modeling of frequency converters, discussing the process of characterizing them, creating mathematical models, and using modeling software tools such as MatLab. It presents equations for inductive energy, capacitor energy, resonance conditions and power factor, which are necessary in the mathematical modeling of frequency converters. The article concludes by highlighting the impact of frequency converters on the efficiency and economics of induction heating systems. It emphasizes the need for careful design and modeling to ensure optimal performance and safety.