Showing papers on "Dynamic demand published in 1998"

Regression Models for Behavioral Power Estimation

Abstract: Behavioral power estimation is required to help the designer in making important architectural choices. In this work we propose an accurate and general behavioral power modeling approach especially suited for synthesis-based design ows making use of a library of hard macros implementing behavioral operators. Power dissipation models are pre-characterized and back-annotated in a preliminary step. Accurate information on the power dissipation of the used macros can then be collected during behavioral simu- lation of the synthesized circuit. Our characterization and modeling methodology is based on the theory of linear regression. Optimal linear power models are obtained with methods of least squares fitting and their generalization to a recursive procedure called tree regression. The regression models can be used for pattern-based dynamic power simulation and for probabilistic static power estimation as well. Our behavioral simulator is integrated within PPP, a multilevel simulation engine for power estimation fully compatible with Verilog XL.

Protection from voltage dips with the dynamic voltage restorer

Abstract: Dynamic Power Limited (DPL) is a 50/50 joint venture between Rolls-Royce and Scottish Power. The Company provides a range of power quality enhancement systems, known collectively as “Custom Power”. These systems, based on technology developed by Westinghouse, are designed to protect users from disruptions to their operations which result from power supply disturbances. A Custom Power device provides “wide area” power quality protection: that is to say a single device can protect all of a plant's critical loads, rather than protecting a single load like a UPS product. The Custom Power products are appropriate for large energy users which are particularly sensitive to the quality of electricity supply (e.g. chemical manufacturers, paper mills, semiconductor factories, automotive factories) and to the electric utilities supplying these users. The processes employed by these industries are becoming increasingly sophisticated and in many instances this has resulted in plants becoming more susceptible to production losses resulting from imperfections in supply quality. Although the UK enjoys very high levels of power quality, a typical industrial user might experience between 10 and 50 power quality-related disturbances in a year. No utility can guarantee that its supply will be free of such disturbances since they are caused by events outside its control. (6 pages)

Dynamic power allocation system and method for multi-beam satellite amplifiers

Abstract: The new signal amplifiers dynamically adjust based on the signal's power level. When used on multi-beam satellites, increased signal power indicates an increase in traffic on the channel. The power level of the input signal is sensed and converted to a DC signal, which is applied to a control terminal of a power supply that regulates DC power supplied to the amplifier. During periods of increased traffic, an increase in system power is allocated to the channel. By monitoring traffic on a plurality of channels, available onboard power is allocated based upon the relative channel requirements. The sensed power of multiple channels is summed and scaled to determine the power requirement of the channel relative to the other channels. A command voltage received from a ground station may be switched in place of the summed voltage to allow amplification levels to be controlled from the ground station.

A new full adder cell for low-power applications

Abstract: A new low power CMOS 1-bit full adder cell is presented. It is based on recent design of XOR and XNOR gates, and pass-transistors, it has 17 transistors. This cell has been compared to two widely used efficient adder cells; the transmission function full adder cell (16 transistors) and the low power adder cell (14 transistors). The new cell has no short circuit power and lower dynamic power (than the other adder cells), because of less number and magnitude of circuit capacitances. It consumes 10% to 15% less power than the other two cells. A comparative analysis (using Magic and Hspice) for 8-bit ripple carry and carry select adders shows that the adders based on the new cell can save up to 25% of power consumption.

Separation and extraction of short-circuit power consumption in digital CMOS VLSI circuits

Abstract: In this paper, we present a new technique which indirectly separates and extracts the total short-circuit power consumption of digital CMOS circuits. We avoid a direct encounter with the complex behavior of the short-circuit currents. Instead, we separate the dynamic power consumption from the total power and extract the total short-circuit power. The technique is based on two facts: first, the short-circuit power consumption disappears at a V/sub dd/ close to V/sub T/ and, secondly, the total capacitance depends on supply voltage in a sufficiently weak way in standard CMOS circuits. Hence, the total effective capacitance can be estimated at a low V/sub dd/. To avoid reducing V/sub dd/ below the specified forbidden level, a polynomial is used to estimate the power versus supply voltage down to V/sub T/ based on a small voltage sweep over the allowed supply voltage levels. The result shows good accuracy for the short-circuit current ranges of interest.

Low power fractional pulse generation in frequency tracking multi-band fractional-N phase lock loop

Abstract: Multi-band fractional-N PLL synthesizers with built-in spurious sideband compensation, which tracks the VCO output, tend to consume large amounts of power (as much as 10 times) due to the RF operation of the compensation circuitry This patent introduces a dynamic power approach where the compensation circuitry is biased only during the fractional portion of the cycle This technique provides the advantages of fractional-N synthesizers with spur suppression, such as higher speed and lower phase noise with ultra low power dissipation

Load-frequency control service in a deregulated environment

Abstract: In a deregulated environment, independent generators and utility generators may or may not participate in the load frequency control of the system. For the purpose of evaluating the performance of such a system, a flexible method has been developed and implemented. The method assumes that load frequency control is performed by an ISO based on parameters defined by the participating generating units. The participating units comprise utility generators and independent power producers. The utilities define the units which will be under load frequency control, while the independent power producers may or may not participate in the load frequency control. For all the units which participate in the load frequency control, the generator owner defines: (a) generation limits, (b) rate of change and (c) economic participation factor. This information is transmitted to the ISO. This scheme allows the utilities to economically dispatch their own system, while at the same time permitting the ISO to control the interconnected system operation.

Dynamic power supply current testing of CMOS SRAMs

Abstract: We describe the design and implementation of a dynamic power supply current sensor which is used to detect SRAM-specific faults such as disturb faults as well as logic cell faults. The sensor detects disturb faults by detecting abnormal levels of the power supply current. The sensor is embedded in the SRAM and offers on-chip detectability of faults.

Inclusion of price dependent load models in the optimal power flow

Abstract: The authors investigate the inclusion of price-dependent loads into the traditional optimal power flow algorithm. The development of the model will be based on the solution of the OPF using an objective function for maximization of social welfare. The paper shows that a traditional OFF algorithm that minimizes supplier costs can be modified to solve the social welfare maximization problem by including price-dependent load models. This modification to the standard OPF is intuitive and very simple. They show this modified OPF formulation facilitates simulation of a spot market for electricity. While the development in the paper accounts for both real and reactive power supply and consumption, the examples in the paper concentrate on real power markets. The algorithm is demonstrated on a range of practical examples, including several small systems, and on a system with over a hundred buses. The impact of such price dependent loads on congestion and bus marginal costs is highlighted.

Full dynamic power bipolar device models for circuit simulation

Abstract: Accurate physics-based circuit-oriented power bipolar device models are feasible on a regional basis thanks to an analogue solution to the ambipolar diffusion equation. Several models have been proposed in this way to describe the operating characteristics of PIN diodes, bipolar transistors, GTO thyristors and IGBTs, with satisfactorily results. In this paper, the modeling approach is extended with a view to achieving a coherent simulation of power circuits involving several interacting semiconductor switches.

Vector compaction for efficient simulation-based power estimation [CMOS design]

Abstract: Low power digital CMOS circuit design requires accurate power estimation. To achieve the accuracy of dynamic power estimation and the speed of static estimation methods, one approach is to generate a compact, representative vector set with similar switching behaviour to the original larger vector set. In this paper, we present an algorithm based on fractal concepts to generate a compacted vector that allows fast, accurate power estimation through simulation. The fractal approach exploits the correlation in the toggle distribution of the circuit's internal nodes for compaction of the input vector set. Experiments on ISCAS85 benchmark circuits with a vector set size of 4000, resulted in a compaction of 65.57/spl times/ (max) and 38.14/spl times/ (avg) with power estimation error of 2.40% (max) and 2.06% (avg). Also, experiments with different vector set sizes up to 100,000 were also carried out.

Power flow studies of a regional grid with inter-state tie-line constraints

Abstract: This paper aims to present a methodology to conduct load flow studies of a multi-area power system with constraints on power settings/power limits on the tie lines linking different areas. Two algorithms are proposed and implemented on test systems including a typical regional grid of an Indian power system. The results of the studies are reported and analyzed.

SRAM test using on-chip dynamic power supply current sensor

Abstract: We present an overview of power supply current testing of SRAMs and propose a test method to improve the CMOS SRAM test efficiency by using on-chip dynamic power supply current sensors. It is shown that the test method provides full observability of cell switching and allows for a significant reduction in test time. The test length is O(n) including coupling faults.

Time-suboptimal analysis and control of fast three-phase active filter acting in one sixth of period

Abstract: The paper presents a dynamic power active parallel filter for the VAr and higher harmonics compensation of symmetrical nonharmonic/nonlinear loads. The new original thought, which has been used, is the creation of a complex vector of investigated quantities and its decomposition into real- and imaginary components. The acquisition and control circuitry of the filter can then handle fast dynamic changes of load using a discrete Fourier harmonic analysis in the complex domain. The analysis should be completed within one sixth of the period for a three-phase power system (from acquired data of previous sixth), due to six-side symmetry of complex vector. The compensator response to the actual state of the load is then very fast.

Techniques of active load's current or/and power computing for dynamic compensation of three-phase symmetrical system

Abstract: The paper deals with computing techniques of both active current and power, and their DSP implementation for dynamic compensation of three-phase symmetrical system. The dynamic power active filter using this techniques is determinated for the VAr and higher harmonics compensation of symmetrical nonharmonic/nonlinear loads. The new original concept, which has been used, is the creation of a complex vector of investigated quantities and its hardware decomposition into real- and imaginary components using Clarke orthogonal transform. The analysis can be completed within one sixth of the period for three-phase system (from acquired data of previous sixth), due to six-side symmetry of complex vector. The compensator response to the actual state of the load is then very fast. Discrete Fourier transform and/or numeric solution of active power computation are used for generating new reference data for each successive sixth of the period. The computation-mainly integration can be done by either fast digital signal processor or mixed (analog) signal unit. Simulation experiments in DesignLab environment are presented at the end of the paper.

Stochastic assessment of power supplied to intermittent loads

Abstract: This paper presents a direct probabilistic method for network power assessment. The random variations of power drawn by cyclic intermittent loads are often caused by their nondeterministic switching as well as their different operating characteristics. The basic problem is to find the net value of the required power which depends on the number of loads in operation. Consequently, a more realistic information on the power consumption may be obtained by taking into account the time varying conditions of an electrical installation and then assess its power requirement. Predicting the harmonic emission of polluting loads could be another application of the proposed method.

On the integrated power control and cell-site selection problems of a cellular DS/CDMA system employing multi-user receivers

Abstract: For a cellular CDMA system, we suppose that a promising receiver structure, the ideal multi-user detection, will eliminate the mutual interference between users within the same cell. In this case, the interference patterns are different from the conventional CDMA system, thus different power control problems occurred. Moreover, the out-cell interference which accounts for half of the total interference within the system is still a critical factor affecting the system capacity, and is out of the control of multi-user detection at the current time. So there must be a dynamic power balancing between users that are not in the same cell in order to guarantee the maximum system capacity. This paper initially deals with the power control problems of a multi-user receiver CDMA system. Based upon the system model established in this paper, the optimum power balancing algorithms firstly allocate power to different cells and ultimately the power is allocated to users within the cell to meet their communication requirements. The decentralized algorithm that combines power control and cell-site selection is also proposed. Combining power control and multi-user receiver will increase the system capacity dramatically, meanwhile, reducing the transmitter power.