Distribution transformer negative-sequence current control device and method
A technology for distribution transformers and negative sequence currents, applied in harmonic reduction devices and AC networks to reduce harmonics/ripples, etc., can solve the problems of large impact on filtering performance and bulky volume, and achieve the goal of reducing negative sequence currents Effect
Inactive Publication Date: 2014-04-02
CHONGQING UNIV
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However, SVC itself is also a harmonic source, and the harmonic order changes with the load. Installing a filtering branch for each harmonic will cause the entire device to be bulky, and the filtering performance is greatly affected by system parameters, so it is inevitable There is a possibility of series and parallel resonance with the grid equivalent impedance
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[0022] The present invention will be further described below with reference to the accompanying drawings.
[0023] see figure 1 A distribution transformer negative-sequence current control device includes two parts, an active filter and a dynamic full-capacitance reactive power compensator, so that the control effect is the best. Active filters and dynamic full capacitive reactive power compensators can also be used separately when managing negative sequence currents. Wherein the active filter includes a harmonic detection unit 1, a PWM trigger pulse generation circuit unit 2 and a PWM inverter main circuit unit 3, and the harmonic detection unit 1 collects the voltage and current transformers into the three-phase The voltage, current and neutral current signals are processed to obtain the harmonic current, and then the harmonic current is input to the PWM trigger pulse generation circuit unit 2 for current control and generates a PWM trigger pulse, and the PWM trigger pulse ...
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The invention relates to a distribution transformer negative-sequence current control device and method. The device comprises an active power filter and a dynamic reactive power compensator; the method comprises the steps of obtaining three phase current of a secondary edge and current in middle wire of a distribution transformer by a harmonic detection unit, obtaining harmonic current through separation, generating PWM (Pulse Width Modulation) pulse control signals by the harmonic current through passing through a PWM trigger pulse generating circuit unit, triggering the switch-on of a thyristor in a PWM inverter main circuit unit to produce harmonic compensation current, thus eliminating the harmonic current and reducing negative-sequence current caused by the harmonic current; collecting three phase voltage, the three phase current and the current in middle wire by the dynamic reactive power compensator in a real-time dynamic way through a data collection unit, calculating interphase and phase-to-earth reactive compensation by a central information processor unit, and dynamically switching capacitor banks, thus reducing negative-sequence current caused by the unbalance of three phase fundamental current. The device is simple in control, easy to implement, and capable of effectively reducing the harm of the negative-sequence current and facilitating productization.
Description
technical field [0001] The invention relates to the field of three-phase unbalanced current control of distribution transformers, in particular to the realization of a negative sequence current control method caused by harmonic wave and fundamental wave unbalanced current. Background technique [0002] With the rapid development of the national economy and production technology, the load conditions in the power system are becoming increasingly diverse and complex, and the three-phase loads in the power grid are in an unbalanced state for a long time, which will generate large negative sequence currents, especially some dynamic loads. The use of non-linear unbalanced loads (such as electric arc furnaces, electrified railways, electric welding machines, etc.) will also have high negative sequence and harmonic (voltage and current) levels in their nearby grids. Under the combined effect of negative sequence and harmonics, it will cause the relay protection and automatic device ...
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IPC IPC(8): H02J3/01
CPCY02E40/40
Inventor 张占龙郭民怿张家铭周鹏罗晨
Owner CHONGQING UNIV