Kapil Jha

High-Quality Sine Wave Generation Using a Differential Boost Inverter at Higher Operating Frequency

Buck-converter-based topologies are used to generate high-frequency sinusoidal outputs. Buck-based inversion circuits such as voltage source inverters or class-D amplifiers have inherent control-to-output linearity in large-signal sense. However, in these topologies, the instantaneous output is always smaller than the dc-input during linear modulation. A differential boost inverter (DBI) is a boost-based topology that is used to generate a sinusoidal output. In DBI, the instantaneous output can be higher or lower than the dc-input voltage. DBI exhibits nonlinear control-to-output behavior in large-signal dynamic sense. Therefore, generating a high-frequency sinusoidal output using this topology is a challenge. The issues associated with a DBI for high-frequency sine wave generation are characterized in this paper. Conventional linear and nonlinear control techniques fail to produce a high-quality sine wave output at higher operating frequency. A nonlinear feedback linearization technique is proposed, which forces the output to be linear with respect to the reference even at higher operating frequency. This leads to a high-frequency high-quality sine wave generation using a DBI. The proposed modulator is verified using a laboratory prototype to generate a sine wave up to 2 kHz. A triangular wave of 100-Hz frequency is also generated by the proposed technique. Superior dynamic responses of a dynamic linearizing modulator controlled DBI for a step change in frequency, load current, input voltage, and reference are also experimentally verified.

Boost-Amplifier-Based Power-Hardware-in-the-Loop Simulator

Power-hardware-in-the-loop (PHIL) simulations are used to test power hardware with the help of computer-based real-time simulations. Generally, buck-based power amplifiers that have good dynamic performance are used to construct a PHIL simulator because of their linear large signal control-to-output characteristics. However, their output voltage peak is limited to the applied dc input in the linear region of modulation. In this paper, a differential boost converter (DBC)-based power amplifier is proposed for PHIL simulations, which does not suffer from the aforementioned limitations of a buck-based amplifier. A conventional DBC exhibits highly nonlinear control-to-output behavior. A feedback linearization technique is used to linearize the DBC in a large signal and dynamic sense, which makes it suitable for PHIL applications. Using this power amplifier and a MATLAB/Simulink toolbox for real-time simulations, the PHIL simulator is constructed. Experimental results under various operating conditions of source voltages, such as unipolar, bipolar, transients in frequency, and the dc step, and various load conditions, such as reactive, nonlinear, and transient faults, are provided to confirm the effmicacy of the proposed PHIL simulator.

A dynamic linearizing modulator based boost inverter

Differential Boost Inverter (DBI) can generate an amplified bipolar output voltage from a DC-input in a single power stage. However, traditional contol techinque limits a DBIs power bandwidth. Dynamic linearizing modulation (DLM) was used to lineazie an uni-polar boost converter to improve its power bandwidth. In this paper, DLM principle is applied to DBI topology to construct a variable amplitude, and frequency source. Implementation aspects, analysis, and operational challenges of this realization are presented. An experimental prototype was used to realize a variable amplitude and frequency source based on the proposed concept. An output of 62.4 V (peak-to-peak), 100 Hz sine wave was generated from a 20 V DC-input. The technique is also extended to generate a 200 Hz, and 500 Hz sine wave outputs.

Large-signal linearization of a boost converter

Various methods to linearize the large-signal control-to-output behavior of a boost converter are discussed. Most of the previously reported linearizing techniques are not suitable when the reference input amplitude or operating frequency is large. In this paper, a dynamic linearizing modulator (DLM) for the boost converter is proposed, which transforms the open-loop converter into a linear amplifier with an operating frequency as high as one-fifth of the switching frequency. The modulator generates the duty by comparing the non-linear part of a boost converter dynamic equation with a sine wave reference voltage on a cycle-to-cycle basis. The technique exhibits superior audio-susceptibility due to the feed-forward of input voltage. The formulation, implementation, and verification of this technique are discussed. Experimental results show that the output voltage is able to track a large-signal reference input upto one-fifth the switching frequency.

Boost-based power amplifier for power-hardware-in-the-loop simulations

Power-hardware-in-the-loop (PHIL) simulation technique allows part of the simulation circuit to be realized using a physical hardware. It has a real-time software component and a hardware component which work like one unit. A power amplifier is one of the most fundamental interface blocks in a PHIL simulation. It converts a low power signals received from the software simulator to a high power signal. This high power signal drives the hardware component of the simulation and is called hardware under test (HUT). Generally, power amplifiers are constructed using buck based topology due to their large signal linear control-to-output characteristics. However, their major drawback is that the output voltage amplitude is always smaller than the applied dc-input in linear modulation region. In this paper, a boost converter based topology known as differential boost inverter (DBI), which does not suffer from the aforementioned limitations of a buck based amplifier, is used as power amplifier for PHIL simulations. However, the DBI exhibits non-linear control-to-output characteristic and cannot be used for PHIL simulations as such. A feedback linearization technique known as dynamic linearizing modulator is used to linearize the control-to-output behavior of a DBI. Experimental result verifies that the proposed power amplifier exhibits superior dynamic performance and it is used in PHIL simulations for various power HUTs.

An inductor current sensing technique for digital controllers

This paper explains a current sensing technique suitable for digital controller implementation. The technique uses only one analog comparator to estimate the DC as well as ripple of the inductor current of a regulated DC-DC converter. For systems where input voltage variation is anticipated, a low speed ADC can be used to take care of the variation in input voltage for inductor current estimation. The proposed technique is experimentally demonstrated for buck and boost converters and can be easily extended for other converters. A lab prototype proves the operation of the sensing technique using a DSP (TMS-F28335) based digital voltage mode control. The verification of the proposed method to implement hysteretic current mode control using PSPICE simulation is also provided to validate its effectiveness.

Design aspects of a power hardware in loop simulator

Power hardware in loop (PHIL) is a simulation technique which allows testing of a power hardware under test (HUT) under various operating conditions. Using PHIL simulations, the behavior of power HUT can be examined when it is integrated to the system without building the complete system. In this paper, various design aspects to construct a PHIL simulator are described. Details of necessary system components such as real time simulator, interface algorithm, power amplifier, interface card, and sensors are provided. MATLAB/SIMULINK based real time simulation platform is used to implement the PHIL simulator. Bidirectional power amplifier having excellent dynamic performance is constructed to realize the PHIL simulator. Working methodology and various implementation aspects of the simulator are discussed. Validity, efficacy, and stability of the PHIL simulator are confirmed using experimental results.

Improving the large signal gain of dynamic linearizing modulator controlled boost converter

A traditional Boost Inverter generates output more than the applied DC-input. However, boost converter exhibits highly nonlinear control to output response. A Dynamic linearizing modulator (DLM) was used to control a boost converter which improves the large signal linearity of the converter at higher operating frequency. The DLM controlled boost converter has a conversion ratio which is highly dependent on the design of the modulator. These design limitations are described in this paper. Methods to overcome these limitations are proposed. Based on these proposals, an improved control strategy is validated using simulation and experiments.