A load management and control apparatus comprising a control unit in which system voltage and a power flow state are measured to make an arithmetic decision by using the resultant variations in voltage and reactive power so as to estimate system reactance, and the estimated system reactance is used to carry out control operation while establishing unique relationship between tap changing operation of the transformer and connection or disconnection of the reactive power supply unit in the receiving side sub-station so as to set voltage and power factor of the receiving side of power system in desired ranges, whereby in a receiving end side substation, it is possible to prevent frequent tap changing operation of the transformer, and adjust system voltage not only to reduce the voltage deviation but also to provide integrated and reasonable management of the reactive power.

Load management and control apparatus

PROBLEM TO BE SOLVED: To provide a system for evaluating the quality of electric power which infers the causes for generation of higher harmonics based on electric physical quantities, such as current and voltage of consumers receiving power supply. SOLUTION: This system for evaluating quality of electric power 1A is equipped with harmonic component calculation means 8 for calculating the harmonic components of the measured electrical physical quantity 6 per each measuring place, based on the electric physical quantity 6 that includes at least either one of current and voltage measured on at least one or more places of electric power system, and harmonic components agreement calculation means 10, which cross-checks the harmonic component calculated by the harmonic components calculation means 8, with the data of harmonic component generator DB15 which resulted from association of the harmonic component generator itself with harmonic component of this generator, to calculate the agreement level between the harmonic components calculated by the harmonic component calculation means 8 and the harmonic components of the harmonic component generator DB15 data. COPYRIGHT: (C)2008,JPO&INPIT

System for evaluating quality of electric power

PURPOSE:To improve the compensation performance of an apparatus in such manner that a three-phase PWM converter generates only a harmonic voltage and an exciting current necessary for maintaining a parallel resonance is caused to flow from the three-phase PWM converter. CONSTITUTION:A first reactor 32 and a resonance circuit 3 composed of a capacitor 31 and parallel-resonating with a power supply frequency are connected in series with each phase of a three-phase AC power supply 1 for supplying a load 2 such as thyristorized Leonard apparatus with power, an AC reactor 4 is connected in series with each phase of the side opposite to the power supply side of the resonance circuit 3, and a three-phase PWM converter 5 is connected with the side opposite to the resonance circuit 3 side of this AC reactor 4. Further, this PWM converter 5 generates only a harmonic voltage. Therefore, a harmonic current canceling the harmonic current of the load 2 and the basic exciting current circulating through the parallel resonance circuit 3 and power supply 1 flows to the PWM converter 5. As a result, it is possible to cause an exciting current necessary for maintaining a parallel resonance to flow when the PWM converter 5 is used as a harmonic voltage source.

Active resonant filter

PROBLEM TO BE SOLVED: To provide a harmonic wave estimation device, harmonic wave estimation method and harmonic wave estimation program that easily estimate a state of a harmonic wave of a power distribution system.SOLUTION: A harmonic voltage estimation formula generation unit 13 is configured to generate a harmonic estimation formula including a state variable for obtaining an estimation value of a harmonic voltage in each user on the basis of a generation rate of the harmonic current to be connected to a power distribution line and per power consumption in the user, a distribution model of the harmonic current generated in each user, a harmonic group having the harmonic current generated from the user classified, a sent-out harmonic voltage of the power distribution line, a sent-out harmonic current of the power distribution line, impedance in the power distribution line, a capacitance of a load of each user, and a capacitance of a power-factor improvement capacitor in each user. A harmonic estimation unit 14 is configured to calculate an estimation value of the harmonic voltage in each user using a least square method on the basis of the formula generated by the harmonic voltage estimation formula generation unit 13.

Harmonic wave estimation device, harmonic wave estimation method and harmonic wave estimation program

PURPOSE:To keep system voltage stable by controlling the voltage and reactive power of a system within the limits of a blind sector provided in and around a set target value with the primary side bus voltage and secondary side bus voltage of a controlled transformer as control variables CONSTITUTION:With the primary side and secondary side bus voltage of a controlled transformer 6 as control variables the voltage and reactive power of a power system is controlled within the limits of a blind sector 4 provided in and around the set target value Consequently, a control vector 5 of each voltage regulator on a V-V plane with the primary side bus voltage V1 on the vertical line and the secondary side bus voltage V2 on the horizontal line will face the direction of a point of intersection 3 of a rectangular coordinate axis, so that the primary side and secondary side bus voltage V1 and V2 deviated from the blind sector 4 by system disturbance can be converged effectively

Method of controlling voltage and reactive power

PURPOSE:To ensure the following even to the frequent actions carried out to the variation of the system conditions and the load by selecting a controller after deciding whether are deviation between the system voltage and the reactive voltage which is generated by the variation of the back voltage at the system side. CONSTITUTION:Both the system voltage and the reactive power of systems 1-3 are measured by a CPU76 via input signal converters 71-75 of a voltage-reactive power controller 7. The CPU76 identifies the initial value from said measured value as well as the system reactance from the initial value and its variation. Then the CPU76 decides whether the deviation between the system voltage and the reactive power which is due to the variation of the system back voltage satisfies a specific function relation decided by the prescribed system voltage, the blind sector width of the reactive power and reactance respectively. Based on this decision, the CPU76 selects a tap switch 41 or a breaker 51 for shunt reactor and a breaker 61 for static capacitor via output signal converters 77-79. These controllers are sequentially operated.

Voltage-reactive power control system

Distribution system harmonic control system

Power system control system

PURPOSE: To perform desired higher harmonic suppression reliably by regulating/ controlling the rate of higher harmonic component in a current flowing from the load side to the power system side while checking the conditions on the power system side and the load side. CONSTITUTION: A power supply 7 employing semiconductor elements, connected with a branch line 3 from a branch point 4, receives an output from a metering/ management control circuit 5A and feeds power to a corresponding load. A branch line load 8 is fed with power from the power supply 7 employing semiconductor elements. The metering/management circuit 5A measures the values of voltage and current, containing higher harmonic components, in the power system based on the outputs from a voltage detector 40 and current detectors 41, 42 and controls the power supply 7 as required. By such arrangement, higher harmonic component can considerably be reduced in the power system. COPYRIGHT: (C)1991,JPO&Japio

Hiroshi Suzuki

Papers

Voltage-reactive power control system

Distribution system harmonic control system

Power system control system

Higher harmonic suppressing system