Electric Spring Research Articles

Electric Springs—A New Smart Grid Technology

The scientific principle of “mechanical springs” was described by the British physicist Robert Hooke in the 1660's. Since then, there has not been any further development of the Hooke's law in the electric regime. In this paper, this technological gap is filled by the development of “electric springs.” The scientific principle, the operating modes, the limitations, and the practical realization of the electric springs are reported. It is discovered that such novel concept has huge potential in stabilizing future power systems with substantial penetration of intermittent renewable energy sources. This concept has been successfully demonstrated in a practical power system setup fed by an ac power source with a fluctuating wind energy source. The electric spring is found to be effective in regulating the mains voltage despite the fluctuation caused by the intermittent nature of wind power. Electric appliances with the electric springs embedded can be turned into a new generation of smart loads, which have their power demand following the power generation profile. It is envisaged that electric springs, when distributed over the power grid, will offer a new form of power system stability solution that is independent of information and communication technology.

Motion of a three-degree-of-freedom gyro with an electric spring and with zero angular momentum

We consider the motion of a three-degree-of-freedom gyro with an electric spring and with zero angular momentum mounted on a fixed base. The gimbal rotation angles are constrained by an elastic ring that is attached to the base and confines a rod attached to the internal gimbal. The equations of motion of the gyro are supplemented with equations allowing for the delay in the response of the gyro feedback circuit. By numerical integration we find a steady-state mode of the gyro motion, in which the rod alternately slides along the ring and moves in the interior of the ring. This motion can be used to check the gyro performance after launching a spacecraft to a near-Earth orbit by comparing the gyro motions in ground tests and on the orbit.

The Role of Climate Forecasts in Western U.S. Power Planning

Abstract The benefits of potential electric power transfers between the Pacific Northwest (PNW) and California (CA) are evaluated using a linked set of hydrologic, reservoir, and power demand simulation models for the Columbia River and the Sacramento–San Joaquin reservoir systems. The models provide a framework for evaluating climate-related variations and long-range predictability of regional electric power demand, hydropower production, and the benefits of potential electric power transfers between the PNW and CA. The period of analysis is 1917–2002. The study results show that hydropower production and regional electric power demands in the PNW and CA are out of phase seasonally but that hydropower productions in the PNW and CA have strongly covaried on an annual basis in recent decades. Winter electric power demand and spring and annual hydropower production in the PNW are related to both El Niño–Southern Oscillation (ENSO) and the Pacific decadal oscillation (PDO) through variations in winter climate. Summer power demand in CA is related primarily to variations in the PDO in spring. Hydropower production in CA, despite recent covariation with the PNW, is not strongly related to ENSO variability overall. Primarily because of strong variations in supply in the PNW, potential hydropower transfers between the PNW and CA in spring and summer are shown to be correlated to ENSO and PDO, and the conditional probability distributions of these transfers are therefore predictable with long lead times. Such electric power transfers are estimated to have potential average annual benefits of $136 and $79 million for CA and the PNW, respectively, at the year-2000 regional demand level. These benefits are on average 11%–27% larger during cold ENSO/PDO events and are 16%–30% lower during warm ENSO/PDO events. Power transfers from the PNW to CA and hydropower production in CA are comparable in magnitude, on average.

Haptic Display With an Interface Device Capable of Continuous-Time Impedance Display Within a Sampling Period

Stability of a haptic interface is an important issue in virtual reality because an operator directly touches haptic interface devices. Stability is influenced by the sampling period and the discrete-time property of the control system. For decreasing the sampling system influence, this paper proposes a haptic device with an analog circuit which is placed between the computer and the haptic device. The circuit functions as springs and dampers. The control system can specify stiffness, damping coefficients, and their equilibrium. Since the impedance generated by the electric spring and damper can work continuously within the sampling period, it is effective for making the system more stable. We also develop a control method for displaying a static virtual object with the proposed device. Further, we discuss the effects of the proposed approach analytically, using passivity analysis for a 1-degree-of-freedom display system. Finally, some experimental results in a two-dimensional virtual environment are presented.

Electric spring modeling for a comb actuator deformed by the footing effect in deep reactive ion etching

We present a model to explain the electric spring effect of a silicon comb actuator deformed by the footing effect in the deep reactive ion etching process. A deformed comb actuator generally has L-shaped comb electrodes and these mean that the actuator shows undesired nonlinear characteristics under differential driving conditions. According to the model, the resonant frequency is estimated to increase as the bias voltage increases, and the static displacement curve shows an ‘S’ shape. A test comb-drive actuator has been fabricated by the silicon-on-glass process to verify the validity of our modeling. Static and dynamic responses of the fabricated microactuator have been measured for the various bias voltages. The measured resonant frequency of the actuator increases from 93 to 128 Hz when the bias voltage increases from 1 to 5 V. The nonlinearity of static displacement increases as the bias voltage increases. The measured static displacements for the same fixed control voltage of 0.5 V are 1.6, 3.2, 4 and 4.6 μm, respectively, when the bias voltage is 1, 2, 3 and 4 V. The incremental displacement for each bias voltage change is 1.6 μm for 1–2 V, 0.8 μm for 2–3 V, and 0.6 μm for 3–4 V. The increasing rate of measured displacement becomes lower as the bias voltage increases due to the electric spring effect.