Abstract: A balancing control strategy that allows the voltage differences among the DC link capacitors of the generalized n-level power converter to be minimized is presented. The case n=3 is treated, but the technique can be generalized to larger n values. The balancing algorithm does not achieve correct voltage sharing of the capacitors under all operating conditions, but it provides a great improvement. This strategy appears to be very promising in single-phase applications, for which nonredundant switching configurations do not affect the capacitor voltage balance. >

Abstract: Disclosed is a power system for use with a computer, the power system having incorporated in it circuitry for automatically varying the supply voltage output to the computer system based upon the magnitude of the current being supplied to the computer by the power system. Also included in the computer system is a variable frequency clock circuit, the frequency of which changes based upon the supply voltage produced by the power system. This permits, during computer system operation where low voltage and low clock speeds will be sufficient to provide the performance needed, achievement of a power saving since both the voltage and frequency at which the system operates is reduced, thereby markedly reducing the power consumption.

Abstract: A digital solid state electric power usage meter for determining power usage by a load attached to an electric power network. The meter has a current sensor coupled to each phase of the electric power network for sensing current in each phase, a voltage divider coupled to each phase of the power network for detecting the voltage level on each phase, an analog to digital (A/D) converter coupled to the current sensors and voltage dividers receiving signals from the current sensors related to the current in each phase and signals from the voltage dividers related to the voltage on each phase. The A/D converter samples the current and voltage related signals at predetermined times at a rate which insures that samples of the current and voltage related signals do not repeat for a large number of cycles of the network frequency or never repeat and which rate is at least twice as fast as the rate of change of the current and voltage related signals and converts the samples to digital signals representing the voltage levels and current at the predetermined times. A processor calculates instantaneous values of power at the predetermined times from the digital signals and a memory accumulates the instantaneous values so as to form a value representative of electric power usage by the load attached to the network.

Abstract: The stages of a voltage collapse in a power system are described. Circuit and system techniques for analyzing voltage collapse that relate it to the changing number of solutions for the power-flow equations, due to slow changes in system parameters are presented. It is shown that to fully analyze voltage collapse for small- and large-disturbance cases, the essential dynamic mechanisms are considered. Several algorithms developed to detect how close a system is to voltage collapse are discussed. A voltage-collapse scenario based on the interaction among dynamic mechanisms is outlined. >

Abstract: Controlling a customer voltage and VAR flow in a power transmission and distribution system includes measuring first voltages in a power line directed to a first location related to customers. Both the customer voltage and the VAR flow for the network is determined in relation to the number of capacitors associated with the first location which are switched in or out of the network. The measured voltages are communicated to a voltage control. Voltage deviations of the measured first voltage are determined relative to a predetermined voltage range intended to be present at the first locations. Switching the capacitor means into or out of the network is determined by the voltage control in accordance with a voltage rise table. A VAR flow controller is responsive to the voltage at the first locations, the effect of the VAR generation by the capacitors and the change of VAR generation by the capacitor. A decrease in voltage at the customers saves energy use. A decrease in the VAR generated upstream of the customer results in greater efficiency of energy generation.

Abstract: A power inverter formed by several transformers having their secondary windings wired in series and their primary windings connected to respective switching bridges. The turns ratios of each of the primary windings vary from each other by a factor of 3 to provide good voltage resolution over a wide dynamic range. The switching bridges are controlled by a decoder and timing circuit which is, in turn, controlled by a microprocessor. The microprocessor closes the switches in the switching bridges in up to 27 different combinations to produce 27 different output voltages, thereby generating a relatively accurate replica of a sine wave. Voltage regulation is accomplished by sampling the A.C. voltage, comparing the magnitude of the A.C. voltage to a reference voltage, and adjusting the selection of output voltage values so that the A.C. voltage matches the reference voltage. The switching bridge may also be controlled to convert an A.C. voltage applied to the transformer secondaries to a D.C. voltage for battery charging purposes.

Abstract: An electric power system for large marine vehicles in which one or more AC generators are shared as the ship's propulsion power source and the ship's electrical service power source. The voltage from the AC generator(s) is rectified to a reduced DC voltage such that voltage transients in the propulsor motor do not reflect into the ship service power system. Silicon controlled rectifier (SCR) bridges are utilized to convert the generator's AC voltage into a reduced DC voltage. As a supplement for emergency power, a rechargeable battery is included to provide power for propulsion and ship service.

Abstract: An electronic control arrangement for controlling the power applied to an electrical load, in which the electronic control includes in its memory a predetermined power control parameter look-up table associated with each of a plurality of potentially applicable voltage ranges. Each table contains the appropriate control parameters for controlling the load when the associated one of the input voltage ranges is applied to the load. The control, in response to an input signal identifying the voltage to be applied, selects the control parameters from the look-up table associated with the identified voltage. This signal may be generated by voltage sensing circuitry which monitors the supply voltage, or by a manually adjustable circuit which enables presetting for a particular supply voltage.

Abstract: For promoting the application of electroluminescent (EL) devices, a thin-plate-typ DC-AC converter is required. For this purpose, a novel type of power supply that uses switched capacitor (SC) transformers is presented. This power supply generates on AC voltage of more than 100 V with several hundred hertz by using two types of SC transformers. This scheme has the following advantages: (1) it operates on a low battery voltage, (2) it realizes a very large transformer ratio, (3) it is capable of realization in an IC form as a thin plate type power supply that is capable of being unified onto the back of an EL device, and (4) it generates a sinusoidal voltage in a novel way by selection of voltages. The circuit configurations, operations, and basic experimental results are presented. >

Abstract: A digital voltage protection circuit (138) and a phase monitor circuit (154, 160, 162, 168) disconnect AC-powered user equipment (22,182) from the AC power supply (141) whenever the AC power line voltage is outside a predetermined operating voltage window and when any two phases of the power supply (141) are separated by more than a predetermined phase angle. The user equipment (182) is automatically reconnected to the power supply (141) only after the power line voltage and phase remain continuously within operating range for a predetermined delay period. The voltage monitor (138) contains a digital comparator (18) that uses integrated circuit digital logic thresholds as reference voltages for setting upper and lower voltage window limits. The controller protects the user equipment from both over-voltage and under-voltage (brownout) conditions and from phase errors.

Abstract: This dissertation deals with voltage stability simulations, including dynamic load models, on-load tap-changer control system dynamics and generator reactive power output capacity limits. The simulations are based on sequential solving of ordinary load flow cases augmented with dynamic models. A dynamic load model, that describes load areas including many home heating appliances, is derived from field measurements. The most impressive result is the power recovery, in the range of minutes, due to the thermostat controlled radiators in the system, after a voltage reduction. It is proved in the dissertation that for voltage stability studies electrical heating cannot be seen as constant impedance. The influence of tap-changer control system dynamics is demonstrated for cascaded tap-changers on different voltage levels, and principles for tap-changer settings are discussed. Both the maximum power transfer capability and the load device power consumption are affected by the tap-changer actions. Generator stator and rotor current limiter models are used in order to take into account the rapidly decreasing reactive power output capability at lower voltages. The load dynamics and tap-changer control system dynamics, as well as generator reactive limits, have a significant impact on the voltage collapse, stability margins, power transfer limits and other criteria related to the voltage stability phenomenon.

Abstract: An approach to interfacing renewable energy sources such as photovoltaic, wind-electric, and small hydroplants with three-phase utility systems is presented. By modulating the DC-link currents and then reinjecting the modulating currents on the AC side, distortion in the line currents can be reduced to be within the allowable limits. Other advantages include the capability to provide electrical isolation by means of high-frequency transformers and the potential for an overall low cost. With the presently available semiconductor switches such as insulated-gate bipolar transistors (IGBTs) and gate turn-off thyristors (GTOs), this approach can be used in a very wide range of voltage and power ratings in interfacing nearly all power electronics equipment to three-phase utility systems. >

Abstract: The ‘distortion power’ DB, also termed ‘deformation power’, is one of the fundamental power quantities in circuits with nonsinusoidal voltages and currents, and power properties of such circuits are often specified in terms of this power. Unfortunately, it was introduced to the power theory of nonsinusoidal circuits because of substantial misinterpretation of these properties. The notion of ‘distortion power’ and its relation to the waveforms distortion is the main subject of this paper. It is shown that the necessary condition for the lack of waveforms distortion is in the contradiction to such a condition for the ‘distortion power’ zero value. Therefore, its value is not a measure of the waveforms distortion effect on the source apparent power S. Thus, this power should not be used in the apparent power equation of the source. Also it is shown that the quantity termed an ‘active distortion power’ has a misleading name and was identified earlier as a scattered power.

Abstract: A regulated power supply provides a regulated supply voltage at a preselected level under normal operating conditions. When power demands of the circuitry driven by the supply requires a higher voltage, the supply adapts to supply such a higher voltage. Such a supply can be used with automotive electronic circuitry, and can supply voltages up to approximately the voltage available on an automobile battery when such higher power demands occur. The higher supply voltages remain regulated, and return to normal levels when the extra power requirement is removed.

Abstract: An internal power voltage generating circuit of a semiconductor memory device may be constructed with a voltage sensing circuit (100) and a reference voltage controller (300) providing an internal power voltage int. VCC of a given reference voltage amplitude Vref and an external power voltage amplitude ext. VCC. Thus, when a high voltage over an operating voltage of a chip is applied to a pad (10) of the chip, the internal power voltage is raised to the level of the external power voltage. Therefore, when stress is added to the chip during a "burn-in-test", the defective chip is easily detected. Consequently, the reliability of those semiconductor memory devices subjected to post-manufacturing testing can be improved.

Abstract: A digital-to-analog (D/A) converter characterized by a decoder which decodes a multi-bit digital input into a plurality of cell activation signals; a converter comprising a number of current cells which can be individually activated by respective cell activation signals; a bias generator which develops a bias voltage for the current cells; and a compensator which compensates the bias voltage to reduce the effects of voltage variations in the power supply. The compensator includes a variation detector coupled to the power supply and develops an error signal when the power supply voltage fluctuates. A variation compensator is responsive to the error signal and is operative to stabilize the bias level. The method of the present invention includes the steps of developing a bias voltage from a power supply, sensing voltage variations in the power supply, and compensating the bias voltage to counteract the effects of the voltage variations.

Abstract: A method and apparatus for controlling a fire pump motor for use in a building having a water supply for a fire protection system, a power line, and a pressure sensor. The pressure sensor detects a high or low system water pressure with respect to a reference water pressure. A voltage controller is coupled between the power line and the fire pump motor for controlling the voltage from the power line to the fire pump motor, responsive to indications from the pressure sensor. The voltage controller increases the voltage to the fire pump motor to full voltage and runs the fire pump motor at full voltage for a minimum run time and until high pressure is indicated. The voltage controller then decreases the voltage to the fire pump motor from full voltage to a predetermined voltage level. The voltage controller holds the voltage to the fire pump at the predetermined voltage level for a first preset period of time. The voltage controller thereafter decreases the voltage to the fire pump motor from the predetermined voltage level to zero. The voltage is increased any time low pressure is indicated. The voltage is subsequently decreased from full voltage, held at the predetermined level, and decreased to zero when high pressure is indicated.

Abstract: A device to produce alternating electric current of high frequency for power consumers such as fluorescent lamps, which includes the means of supplying a DC voltage nearly twice the size of the peak voltage of the alternating voltage input--with negligible loss of power--to the remainder of the circuit and thus reducing the intrinsic power consumption of the device as well as making it possible to supply the said power consumer such as the fluorescent lamp with a higher start voltage as well as a higher voltage in operation.

Abstract: In order to control a voltage using e.g. a tap transformer (5000), the difference V between the actual voltage (V) and a reference voltage (110) is obtained (120) and integrated over time (130). That integral is then modified by at least one parameter generated by fuzzy logic (3000) from control conditions of the voltage. In this way the fuzzy logic (3000) may find the optimum control strategy which keeps the actual voltage closest to the reference voltage without an excessive number of tap position changes. The reference voltage (110) may vary with time, and therefore the control of the voltage with time may be evaluated (2000), and the control conditions varied accordingly, e.g. by fuzzy logic so that the control arrangement can exhibit learning. Normally, the integral is modified by such that ∫ΔVdt ≧ B when B is the parameter determined by the fuzzy logic (3000), but other control strategies may be used. The present invention is also applicable to control of reactive power.

Abstract: An AC system having, for example, a voltage source, an inductance and a load has connected thereto an apparatus for controlling the phase and amplitude of the voltage of the system. The instantaneous current and voltage in the AC electrical system are measured and power measurements derived therefrom. The power measurements may be instantaneous real and imaginary power, instantaneous active and reactive power, or active and reactive power averaged over less than one cycle. The power measurements are then used to derive phase related control values, on the basis of which control signals are generated to a converter. The action of the converter in accordance with the control signals thus controls the amplitude and phase of the voltage. By use of power measurements, it is not necessary to measure the phase of the voltage of the AC system.

Abstract: An RF generator is provided with an analog feedback circuit (24, 26, 28) in combination with a digital levelling assist circuit (32) to compensate for non-linearities in the power metering circuit (20,22) that measures the RF output energy. The digital leveling assist circuit has a digitizer (36,38) with inputs coupled to receive the measured power voltage supplied from the power metering circuit (20,22) and a power demand voltage. The digitizer has outputs that provide digital representations of the measured power voltage and the power demand voltage to a digital control element (34) that derives a digital correction factor based on these digital representations. A d/a converter (42) coupled to the digital control element provides a correction voltage corresponding to this digital correction factor, and this is furnished to a summing circuit (26,28) that combines the correction voltage with the power demand voltage and with a control voltage that is supplied by the analog feedback circuit (24). The leveling assist circuit increases the accuracy of control of the RF output power with respect to the power demand voltage, without sacrificing the speed of the analog feedback circuit.

Abstract: In a fuse programmable voltage generator providing an optimal internal voltage VCCINT, a counter outputs various values to a voltage down comparator to output corresponding internal voltages VCCINT until a desired voltage is obtained. Once the desired internal voltage VCCINT is determined, the counter is disabled and a fuse circuit is configured to substantially maintain the output of the desired internal voltage VCCINT.

Abstract: A system and method for coordinating shunt reactance switching in a system with a transformer having a primary voltage and a secondary voltage for supplying low voltage power to a load. Voltage and power meters are provided for measuring the primary voltage and the reactive power flowing to the load. A programmable logic controller receives as one set of inputs measurements of primary voltage and reactive power flowing to the load, and as another set of inputs, predetermined ranges establishing high and low limits for the primary voltage and the reactive power. Based on these inputs, the programmable logic controller connects or disconnects at least one shunt reactance to maintain the load voltage substantially constant.

Abstract: First, second, and third power supply lines are separate from each other. A power supply circuit receives electric power from the first power supply line, and generates a given power supply voltage from the received electric power and outputs the generated power supply voltage to the third power supply line. An electronic circuit is connected to the third power supply line to be activated by the power supply voltage. The electronic circuit has an input section for receiving an input signal from the second power supply line. A protective circuit provided in the electronic circuit leaks a current from the input section of the electronic circuit toward the third power supply line when a voltage of the input signal exceeds the power supply voltage. A reference voltage generating device serves to generate a first reference voltage in the presence of the electric power fed from the first power supply line to the power supply circuit, and serves to generate a second reference voltage in the absence of the electric power fed from the first power supply line to the power supply circuit. The second reference voltage is lower than the first reference voltage. A voltage limiting device being responsive to the first and second reference voltages serves to limit a voltage of the third power supply line to below a level approximately equal to the first or second reference voltage.

Abstract: The authors propose two types of switching voltage regulators with improved input power factor using new diode rectifier topology, based on the dither effect. These regulators can achieve over 99% input power factor using simple circuitry and a simple control method. These regulators are distinguished by the absence of rush current during the start up, which can be achieved by control of the switching devices. The basic operation of the dither rectifiers and a comparison between the two switching regulator circuits are presented. Experimental results confirmed over 99.2% power factor and 78% efficiency. >

Abstract: PURPOSE:To prevent the operating voltage from being largely apart from a maximum power point by dispensing with control of the maximum power pint and keeping the operating voltage in an unchanged state if generated power is changed by the change of the solar radiation quantity while judging the change cause of the generated power. CONSTITUTION:A measuring device 4 measures the power generated by a solar battery 1 and stores the measured values in a memory device 5. A control circuit 3 decides whether the generated power is changed by the change of the operating voltage or the change of the solar radiation quantity. When the change of the solar radiation quantity is performed, a power converter 2 is instructed to dispense with tracking control of the maximum power point, and the maximum power point tracking control is performed only when the solar radiation is stable. That is, all the measured values of the measurement value W1 set before the change of the operating voltage, the measurement value W2 set after the change of the operating voltage, and the measurement value W3 set when the changed operating voltage before the change is restored are stored and then compared with each other. Then the operating voltage before the change is kept when W1 W2 and W2>W3 are satisfied respectively.

Abstract: The authors propose a method to regulate a single-phase AC source by using a series-connected auxiliary voltage source. A voltage source inverter, connected in series with the AC supply through a transformer, is used to compensate the input voltage variations in order to achieve a regulated load voltage. Input power factor improvement can also be obtained, when operating with reactive load, by phase-shifting the compensating voltage with respect to the input voltage. The total kVA rating for the system is a fraction of the load total power, and is determined by the maximum allowable line voltage variation. The use of a series connection together with a high-performance modulation technique results in a fast dynamic response and a small-size filter. A high-quality output is readily achieved. The authors describe the proposed method, implementation principles, design equations, and a design example. Simulated and experimental results confirm the concept and feasibility of the proposed system. >

Abstract: The characteristics of a power system that have become of increased importance because of interconnection are discussed. They are: very small damping of disturbances; the need for more voltage support; much more complexity in design, operation, control, protection, and analysis; and much more pervasive and numerous controls. Some new problems introduced by interconnection are examined. They are: the appearance of spontaneous tie-line power oscillations under certain line loading conditions; the appearance of voltage instability with resulting voltage collapse; and widespread blackouts. >