Frequency-modulated Output Research Articles

Optimal Allocation of Primary Frequency Modulation Capacity of Battery Energy Storage Based on Antlion Algorithm

Currently, the integration of new energy sources into the power system poses a significant challenge to frequency stability. To address the issue of capacity sizing when utilizing storage battery systems to assist the power grid in frequency control, a capacity optimal allocation model is proposed for the primary frequency regulation of energy storage. Due to the requirement of a large number of actual parameters for the optimal allocation model, a simulation model of energy storage capacity is constructed based on the characteristics of primary frequency control to provide the necessary parameters. Subsequently, the primary frequency modulation output model of energy storage is established by considering the basic action output, the action in the frequency modulation dead zone, and a certain capacity margin. The antlion algorithm is employed to solve the capacity optimal allocation model. Finally, three groups of experiments are designed and compared to demonstrate the effectiveness of the proposed method in setting the capacity margin, which can increase profit to a certain extent.

Asynchronous Upconversion Sampling of Frequency Modulated Combs

AbstractIn recent years, optical frequency combs with a frequency modulated output have attracted considerable attention. While first observed decades ago in externally modulated lasers, a whole class of semiconductor lasers has since been identified to spontaneously enter such a regime of self frequency modulation. However, the temporal properties of these sources could so far only be measured indirectly via phase‐resolved frequency domain measurements. In this work, an asynchronous optical sampling technique which operates directly in time domain is demonstrated. On the basis of a mid‐infrared quantum cascade laser frequency comb, both its instantaneous intensity and optical frequency are measured. The results confirm a quasi‐constant intensity output alongside a close to linear frequency chirp, in accordance with phase‐resolved spectral measurements. Contrary to previous works, stable phase‐locking is achieved in a regime of positive intracavity dispersion resulting in an inversion of the observed frequency modulation.

Research on optimization strategy of grid frequency modulation based on doubly-fed wind turbines

Abstract The increasing global energy and environmental problems are encouraging to the development and utilization of renewable and clean energy in various countries. Wind power is one of the major source in large-scale renewable energy applications. However, the frequency regulation becomes a critical issue while the technology is spreading. Research on the frequency modulation (FM) technology of wind turbines and its control strategy for future power grids become significant. The paper proposes a novel coordinated frequency control strategy with the synchronous generator to solve the unmatched state between the output power of the doubly-fed wind turbines (doubly-fed induction generators) and the grid frequency, combined with the frequency response characteristics of the synchronous generator. The FM coordination strategy is formulated by the modulation coefficient from current wind speed and operation mode of each wind turbine. By coordinating the FM output of the doubly-fed wind turbine and the synchronous generator within the allowable range of frequency deviation, it will achieve the dual goal of reducing the frequency regulation pressure of the synchronous generator and indirectly reducing the abandoned wind volume of the wind turbine. The simulation is carried out on the MATLAB/SIMULINK platform. The results show that the presenting variable coefficient frequency modulation strategy could significant smooth the wind power fluctuation, and allow the reserve power of the doubly-fed wind turbine can fully engaged in frequency modulation which will reduces the frequency modulation pressure of the synchronous generator in the system.

Frequency modulated free electron laser.

It is shown that the output frequency of a free electron laser may be modulated to generate a series of modes that span a bandwidth of at least an order of magnitude greater than the normal FEL bandwidth. This new method of frequency modulated FEL operation has close analogies to frequency modulation in conventional cavity lasers. The FM-FEL is analysed and described in the linear regime by a summation over the exponentially amplified frequency modes. Simulations using a 3D, broad bandwidth, numerical code also demonstrate FM-FEL operation for parameters typical of FEL facilities currently under construction. Harmonic bunching methods are used to seed the FM-FEL modes to generate a temporally correlated frequency modulated output over a large bandwidth. This new, FM-FEL mode of operation scales well for X-ray generation, offering users a significantly new form of high-power, short wavelength FEL output.

Coordinated control strategy for improving the two drops of the wind storage combined system

In the power system with high permeability wind power, due to wind power fluctuation, the operation of large-scale wind power grid connected to the system brings challenges to the frequency stability of the system. When the doubly fed wind power generation unit does not reserve spare capacity to participate in the system frequency regulation, the system frequency will produce two drops in different degrees when the wind power exits frequency modulation and enters the speed recovery stage. To solve this problem, based on the complementary advantages of wind turbines and energy storage systems in power transmission and frequency modulation, a wind storage combined frequency modulation strategy based on sectional control is proposed in this paper. Based on the TOP wind power frequency modulation strategy, the wind power output reference value is determined according to the linear relationship between the output and the speed of the wind turbine, and the auxiliary wind power load reduction is controlled when the wind power exits frequency modulation into the speed recovery stage, so that the wind turbine is recovered to run at the optimal speed. Then, according to the system frequency and the wind turbine operation state, set the energy storage system frequency modulation output. Energy storage output active support is triggered during wind speed recovery. And then when the system frequency to return to the normal operating frequency range, reduce energy storage output or to exit frequency modulation. The simulation results verify the effectiveness of the proposed method.

High Quality Factor Resonant MEMS Accelerometer With Continuous Thermal Compensation

We report a new silicon Microelectromechanical systems (MEMS) accelerometer based on differential frequency modulation (FM) with experimentally demonstrated thermal compensation over a dynamic temperature environment and $\mu g$ -level Allan deviation of bias. The sensor architecture is based on resonant frequency tracking in a vacuum packaged silicon-on-insulator (SOI) tuning fork oscillator. To address drift over temperature, the MEMS sensor die incorporates two identical tuning forks with opposing axes of sensitivity. Demodulation of the differential FM output from the two simultaneously operated oscillators eliminates common mode errors and provides an FM output with continuous thermal compensation. The first SOI prototype with quality factor of 350000 was built and characterized over a temperature range between 30 °C and 75 °C. Temperature characterization of the FM accelerometer showed less than a 0.5% scale-factor change throughout a temperature range from 30 °C to 75 °C, without any external compensation. This is enabled by an inherently differential frequency output, which cancels common-mode influences, such as those due to temperature. Allan deviation of the differential FM accelerometer revealed a bias instability of $6\,\, \mu \text{g}$ at 20 s, along with an elimination of any temperature drift due to increases in averaging time. After comparing the measured bias instability with the designed linear range of 20 g, the sensor demonstrates a wide dynamic range of 130 dB. A second design iteration of the FM accelerometer, vacuum-sealed with getter material, was created to maximize $Q$ -factor, and thereby frequency resolution. A $Q$ -factor of 2.4 million was experimentally demonstrated, with a time constant of >20 min.

Laser frequency stabilisation by the Pound — Drever — Hall method using an acousto-optic phase modulator operating in the pure Raman — Nath diffraction regime

Frequency stabilisation of diode laser radiation has been implemented by the Pound — Drever — Hall method using a new acousto-optic phase modulator, operating in the pure Raman — Nath diffraction regime. It is experimentally shown that, as in the case of saturated-absorption spectroscopy in atomic vapour, the spatial divergence of the frequency-modulated output spectrum of this modulator does not interfere with obtaining error signals by means of heterodyne frequency-modulationspectroscopy with a frequency discriminator based on a high-Q Fabry — Perot cavity with finesse of several tens of thousands.

Continual in-plane displacement measurement with temporal wavelet transform speckle pattern interferometry

A heterodyne temporal speckle pattern interferometer that measures the in-plane displacement dynamically has been built. The object is displaced in its plane continuously and the frequency-modulated output signals with a carrier frequency are recorded by a CCD camera. The displacement information is extracted with wavelet transform technique. Preliminary experiments have been performed with such interferometer. The respective measurement results recovered from wavelet transform and Fourier transform are compared.

Assessing FM transparency, FM/HA ratio with digital aids

The advantages of frequency modulation (FM) systems are well recognized.' In an ideal situation, an FM system that is connected to a hearing aid (HA) maintains the frequency-output characteristics of the hearing aid and enhances the signal-to-noise ratio (SNR) of the listening environment. That said, a clinician who works with FM and hearing aids must evaluate if the addition of the FM results in the optimal use of the FM-HA combination. Specifically, the clinician must verify that: (1) the electroacoustics of FM and HA meet specifications (i.e., sufficiently broad bandwidth, no evidence of distortion, etc); (2) the coupling of the FM does not change the frequency response of the hearing aid in the various FM receiver positions (such as HA, FM, FM+HA) for the same stimulus input (i.e., transparency); and (3) the ratio of the FM output to the hearing aid output, when used in the FM+HA mode, is favorable. This last verification goal is also known as the SNR advantage of the FM in the FM+HA mode. h is i mportant for clinicians working with these two devices to know how to determine the FM/HA ratio and, when necessary, to adjust the sensitivity of the devices to achieve the optimal ratio. The implicit expectation is that the FM+HA mode will increase wearer satisfaction. Clinicians have sought to standardize the verification of FM systems when used with hearing aids. However, with the advent of digital signal processing (DSP) hearing aids, the parameters and protocols previously used to verify FMs and HAs may be inadequate. Digital processing can interact with the type and duration of the stimulus used, resulting in equivocal results. Furthermore, the type of FM system used, as well as the hearing aid analyzer used to measure transparency and FM/HA ratio, may affect the outcome of the verification. Kuk and Keenan evaluated the impact of stimulus duration and stimulus type on the reliability and validity of verification. 2 Integrating their findings, we will present in this article a three-step protocol for measuring both the transparency and the FM/HA ratio in one measurement session. Specifically, we will describe the protocol, provide

A fiber-optic current sensor with frequency-codified output for high-voltage systems

The authors present a frequency-output fiber-optic current sensor for high-power systems. The sensor exploits the magnetostriction of the ferromagnetic core of a standard current transformer, which is interrogated by a length of single-mode fiber coiled onto it and a Mach-Zehnder interferometer. The deformation of the core due to the magnetic field generated by the current produces a frequency-modulated output signal. The current is obtained from the frequency features of the optical signal, and so the sensor avoids certain shortcomings of other fiber optic current sensors such as light power fluctuations, phase drift, and polarization sensitivity.

Telemetry system for monitoring anterior cruciate ligament graft forces in vivo.

Quantifying changes in the tension of an anterior cruciate ligament (ACL) graft in vivo during rehabilitative exercises is useful for developing the optimum rehabilitation for patients who have had reconstructive surgery. The purpose of the work reported is to design, build and test a telemetry system that can measure the in vivo ACL graft tension post-operatively. A commercially available fixation device is modified to sense the graft tension, house electronic components, transmit an output signal and pass the power generating signal. A transcutaneous inductive link is used to power the implanted telemetry electronics. The current difference technique is used to measure changes in two resistance strain gauges that monitor shear strain developed on the femoral fixation device by the ACL graft. This current regulates a frequency-modulated output signal that is transmitted using a new technique. Harnessing the ionic and volume conduction properties of the body fluids, the new technique involves injecting current subcutaneously into the tissue and then sensing the potential developed on the skin by surface electrodes. The waveform shape, amount of charge injected, charge density and current density are regulated to avoid tissue damage, pain and unwanted muscular stimulation. A signal conditioning board detects and converts the output to an analogue voltage for collection by a computer data-acquisition system. A performance evaluation demonstrates that the telemetry system either meets or exceeds all of the criteria necessary for the application.

A silicon thermocapacitive flow sensor with frequency modulated output

A silicon thermocapacitive gas-flow sensor with frequency modulated output where the shift in the oscillation frequency is related to the gas-flow velocity has been developed. The sensing module, which is fabricated using a MOS-compatible process combined with EDP groove etching, is a capacitor. The dielectric material of the capacitor is r.f.-sputtered SrTiO 3, the large dielectric constant of which is also temperature dependent. Together with an external 555 IC, the oscillator frequency at zero flow velocity and 250 mW of heater power is 8.7 kHz. The sensitivity is 118 Hz (ms −1) −1 in the linear region, wuth 250 mW of heater power.

Binary rate modulation, its application and stability in control systems

This paper describes a set of piecewise constant waveforms which, when used as the method of dispatch of power to a first-order system, offers distinct advantages over other piecewise constant signal methods. The waveforms are similar to those which are produced by binary rate multipliers and the technique is called ‘Binary Rate Modulation’. The stability of the resulting discrete closed loop system is investigated using a circle criterion adaptation, applied to a multiple nonlinearity, with a multiple pulse output in each nonlinearity and by a proposed ultimate linear technique. The gains for asymptotic stability and limit cycling are found from the techniques. Results in accordance with the predicted values are obtained from observed system responses. The two stability techniques can be easily applied to systems using pulse width or pulse frequency modulation output drives to first-order systems.

Optical detection of ultrasound with a microchip laser

A novel optical ultrasonic detector that relies on frequency modulation of a microchip laser is proposed and demonstrated. When the laser is placed in a time-varying acoustic field, the microchip laser cavity length is periodically modulated, creating a frequency-modulated optical output in which the frequency shift is linearly proportional to the acoustic-wave amplitude. With a confocal Fabry-Perot slope filter and a Nd:YAG microchip laser operating at 1.06 microm, a detector response of 7.5 MHz/kPa was measured at an acoustic frequency of 7.75 MHz. A one-dimensional acoustic model is developed to explain the observed detector performance.

Application of transducers with frequency-modulated outputs in measuring, monitoring, and control systems

The development of transducers with frequency-modulated output signals in Russia and abroad is discussed. Certain characteristics of domestic transducers and their manufacturers (designers) are mentioned.

Passive FM locking and pulse generation from 980-nm strained-quantum-well Fabry-Perot lasers

Multiple-order passive frequency modulation (FM) locking in 980-nm lasers has been measured using autocorrelation and optical spectra. Optical fiber dispersion provided a simple means of converting the coherent FM output to an amplitude modulation (AM) pulse train at multiples of the laser round-trip frequency. We have produced such pulses at frequencies of up to 233 GHz from a single source with no external modulation. Extension of this technique should be possible with 1550-nm lasers. >

Fiber-Optic Hydrophone using a Zeeman Laser

Heterodyne fiber-optic hydrophone systems of the single fiber type and the Mach-Zehnder type using a transverse Zeeman laser were studied. The carrier frequency obtained from the optical beat of two orthogonally polarized laser lights of different frequencies was 488 kHz and a S/N ratio of 60 dB was obtained. The frequency shift caused by underwater sound was evaluated by the spectrum analysis of the frequency modulated output signal. The ratio of the optical frequency shift per meter of the fiber to the sound pressure of 6 kHz was 9.95×10-6 Hz/µPa·m for the single fiber scheme and 1.46×10-3 Hz/µPa·m for the Mach-Zehnder scheme.

Capabilities and limits of silicon pressure sensors

The pressure sensors currently available or that will be marketed in the near future pertain to the categories of capacitive and piezoresistive sensors. The basis of capacitive pressure sensors is a thin single-crystalline or polycrystalline silicon diaphragm. From a metrological point of view, these sensors are characterized by a high pressure sensitivity and a markedly low temperature sensitivity. They can operate up to temperatures of about 300 °C and remain almost free of hysteresis. On the other hand, they are non-linear, but their behaviour is fully determined by their normalized response. Piezoresistive sensors consist of silicon diaphragms on which strain—stress gauges are either deposited or implanted. The diaphragm acts as a stress amplifier. These sensors exhibit a linear response to low levels of stress. The monocrystalline silicon gauges are characterized by a pressure sensitivity two or three times greater than that of laser-recrystallized polysilicon gauges. The major problem encountered with piezoresistive sensors is their high temperature sensitivity, which has to be reduced by means of resistor compensation networks. The sensors with gauges diffused or implanted in the diaphragm should be able to operate up to 200 °C, whereas deposited gauges extend the temperature range up to 300 °C. The comparison of normalized responses indicates that the sensitivity to pressure of piezoresistive sensors is less than that of capacitive sensors. Among the other varieties of silicon pressure sensors, MOST gauge sensors as well as resonant sensors offer the advantage of giving a frequency-modulated output.

Rotary Encoder Using Amorphous Star-Shaped Core Field Sensor

The authors describe a magnetic rotary encoder consisting of a ring-shaped multi-pole magnet and amorphous magnetic core multivibrator sensors positioned radially around the magnet. The frequency-modulated output is sinusoidal, with a distortion of less than 1% when operating at 50 kHz; the encoder is impervious to mechanical disturbances, and can be used at relatively high temperatures.

Frequency-modulation detection of particle diffusion from heterodyne quasi-elastic light scattering

The Brownian/diffusive motion of micrometer-sized, suspended particles has been observed by using heterodyne light scattering with frequency-modulation (FM) detection and signal processing. The FM output is linear in the coherent velocity of the particles, with the random diffusive velocity component giving rise to background noise in the FM output. Experimental measurements of polystyrene latex spheres in water corroborate the predicted result for the signal-to-noise ratio. The noise component of the FM output was found to be independent of the particle number and, within the instrumental bandwidth, to be flat. Good quantitative agreement between the predicted and measured noise backgrounds was obtained for particle diameters from 0.5 to 50 μm.