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39 results about "Unbalanced line" patented technology

In electrical engineering, an unbalanced line is a transmission line, often coaxial cable, whose conductors have unequal impedances with respect to ground; as opposed to a balanced line. Microstrip and single-wire lines are also unbalanced lines.

Comprehensive evaluation method for line loss level of low-voltage transformer area

A comprehensive evaluation method for the line loss level of a low-voltage transformer area comprises the steps as follows: equivalent resistance of distribution lines in the low-voltage transformer area is calculated respectively; the line loss rate and head end average load current of a low-voltage circuit are measured; a load curve characteristic coefficient and a three-phase unbalanced line loss correction coefficient are calculated respectively; the theoretic line loss rate in the low-voltage transformer area is calculated, and the measured line loss rate and the theoretic line loss rate are compared, so that the management line loss level in the low-voltage transformer area is judged; and the like, wherein the head end average load current, the load curve characteristic coefficient, the three-phase unbalanced line loss correction coefficient and the like are calculated along with a calculation method of the theoretic line loss of the to-be-calculated low-voltage transformer area after a simultaneous equation set is established. According to the method, the parameters and a management line loss evaluation threshold can be accurately calculated, and comprehensive evaluation of the line loss level of the low-voltage transformer area can be accurately completed further; and particularly, when electricity stealing and leakage conditions occur, the method can accurately judge the line loss level, and misjudgments are avoided.
Owner:STATE GRID CHONGQING ELECTRIC POWER +1

Three-phase imbalance adjustment control method, three-phase imbalance adjustment control device and three-phase imbalance adjustment system

The invention relates to a three-phase imbalance adjustment control method, a three-phase imbalance adjustment control device and a three-phase imbalance adjustment system. The actual value of three-phase imbalance is obtained according to the current of the maximum current phase and the current of the minimum current phase in currents of three phases collected, and is sent to an outer voltage loop. Then, the difference between the actual value of three-phase imbalance and a given value of three-phase imbalance is calculated. Through voltage and current closed-loop control and positive / negative-sequence dq / abc coordinate transformation, total modulating wave for making active power compensation from the maximum current phase to the minimum current phase is generated, and a control signal for adjusting the active power is generated after modulation. According to the invention, the electric energy of the three phases is redistributed according to the load demand, electric energy can be switched fast between unbalanced lines, and three-phase imbalance at the output side of a power distribution transformer can be adjusted quickly and smoothly. Moreover, the loss of power distribution lines can be reduced effectively, the output power of power distribution transformers and the safety operation ability of the power distribution system are improved, and the quality of power supply to users is improved.
Owner:TIANJIN PINGGAO INTELLIGENT ELECTRIC +2

Control method for photovoltaic power generation and power grid three-phase balance

A control method for photovoltaic power generation and power grid three-phase balance is implemented by a measurement and control device and a power grid treatment device and comprises the steps of 1,judging a power flow direction of a power grid according to a power read by the measurement and control device, wherein power is supplied to a load from the power grid when the power is positive, andthe power is fed to the power grid by photovoltaic power generation when the power is negative; 2, performing average value calculation on the read three-phase power grid by the measurement and control device; 3, judging a phase circuit with maximum power supplied from the power grid to the load or maximum power fed to the power grid by photovoltaic power generation when the three-phase power isunbalanced; 4, calculating a power allocation coefficient of each power grid treatment device in the three-phase unbalanced line; 5, calculating a power allocation value of each power grid treatment device in the three-phase unbalanced line; and 6, controlling the corresponding power grid treatment devices to output or absorb the power by the measurement and control device according to the power allocation value of the power grid treatment device. By the control method, the purpose of three-phase power balance of the power grid is achieved.
Owner:INST OF ELECTRICAL ENG CHINESE ACAD OF SCI +1

Energy-saving device based on low-voltage line load balance

The invention discloses an energy-saving device based on low-voltage line load balance. The energy-saving device comprises a low-voltage master control switch, wherein the first end of the low-voltage master control switch is connected with the secondary side of a transformer, a primary side of the transformer is used for being connected with the power grid power supply end, the second end of the low-voltage master control switch is connected into a low-voltage bus, a multiple balance power distribution lines are further connected onto the low-voltage bus and are series circuits formed by sequentially connecting a wire outlet switch and N sectioned switches, the wire outlet switch is connected into the low-voltage bus, and the tail ends between every two balance power distribution lines are connected through an interconnection switch and form a low-voltage loop. The low-voltage master control switch and the wire outlet switch on each low-voltage master control switch are connected with a load balance controller through an independent communication channel, and the N sectioned switches on each balance power distribution line are connected with the load balance controller through an independent communication channel. The line heavy load or overload problem caused by unbalanced line load is solved, and the whole line outage caused by faults or overhauling is avoided.
Owner:STATE GRID CORP OF CHINA +2

Three-phase voltage unbalance degree determination method and device for wind power collection area

The invention provides a three-phase voltage unbalance degree determination method and device for a wind power collection area. The method comprises the steps of determining a three-phase impedance matrix of an unbalanced line according to line parameters of the wind power collection area; establishing an equivalent model according to power grid parameters and a topological structure of the wind power collection area, and determining three-phase voltage and three-phase current of an equivalent node in the equivalent model; determining a positive sequence voltage and a negative sequence voltageof an equivalent node of the wind power collection area according to the three-phase impedance matrix, the three-phase voltage of the equivalent node and the three-phase current; and determining thethree-phase voltage unbalance degree of the wind power collection region according to the determined positive sequence voltage and negative sequence voltage of the equivalent node of the wind power collection region. By utilizing the method, the key factors influencing the three-phase voltage imbalance of the wind power plant can be simply and clearly analyzed, and the method has important guidingsignificance for exploring the voltage imbalance mechanism of a large-scale wind power collection region.
Owner:ELECTRIC POWER RES INST STATE GRID JIBEI ELECTRIC POWER COMPANY +3
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