A stray current active absorption device

Abstract

The present invention discloses a stray current active absorption device, which relates to the field of pipeline cathodic protection. The stray current active absorption device includes a four-quadrant converter unit, a battery, an energy regulation unit, and a control processing unit, and has both reverse compensation and active absorption functions. The microprocessor controls the device to work in different modes by analyzing the pipe-to-ground potential at the current position and the demand for reverse compensation / active absorption. The present invention suppresses the outflow / inflow of stray current from the damaged point of the pipeline, thereby suppressing pipeline corrosion caused by positive pipe-to-ground potential or pipeline hydrogen embrittlement caused by negative pipe-to-ground potential, thereby solving the technical problem of pipeline DC stray current interference caused by rail transit.

Claims

1. A stray current active absorption device, characterized in that, it includes a four-quadrant converter unit, and the four-quadrant converter unit includes a full-bridge circuit and a bi-directional flyback converter connected in sequence; the input side of the bi-directional flyback converter is connected to a storage battery; the negative output of the full-bridge circuit is connected to an auxiliary anode in a cathodic protection station, and the positive output of the full-bridge circuit is connected to a buried pipeline; by controlling the working mode of the full-bridge circuit, reverse compensation or active absorption of stray current is carried out, and the specific implementation process includes: Sampling tube ground potential U p ; When the tube ground potential U p >T1, the full-bridge circuit is controlled to operate in the first quadrant mode or the second quadrant mode to reversely compensate or actively absorb the stray current; When the tube ground potential U p When <T2, the full-bridge circuit is controlled to operate in the third quadrant mode or the fourth quadrant mode to reversely compensate or actively absorb the stray current; When T2≤U p When ≤T1, there is no stray current interference, and the full-bridge circuit stops working; wherein, the first quadrant mode means that the output current flows from the positive output of the full-bridge circuit to the negative output, the output voltage of the full-bridge circuit is positive, the voltage of the positive output is positive, and the voltage of the negative output is negative; the second quadrant mode means that the output current flows from the positive output of the full-bridge circuit to the negative output, the output voltage of the full-bridge circuit is negative, the voltage of the positive output is negative, and the voltage of the negative output is positive; the third quadrant mode means that the output current flows from the negative output of the full-bridge circuit to the positive output, the output voltage of the full-bridge circuit is negative, the voltage of the positive output is negative, and the voltage of the negative output is positive; the fourth quadrant mode means that the output current flows from the negative output of the full-bridge circuit to the positive output, the output voltage of the full-bridge circuit is positive, the voltage of the positive output is positive, and the voltage of the negative output is negative; T1 is the first voltage threshold, and T2 is the second voltage threshold; The four-quadrant converter unit includes a first switch tube S 1 , transformer, second switch tube S 2 , the first capacitor C 1 , a first LC filter, a full bridge circuit and a second LC filter; a first switch tube S 1 Connected to the primary side of the transformer; the second switch tube S 2 With the first capacitor C 1 After being connected in series, it is connected to the secondary side of the transformer; the first LC filter and the first capacitor C 1 Parallel connection; capacitor C in the first LC filter 2 In parallel with the full-bridge circuit, the second LC filter is connected to the midpoint of the bridge arm of the full-bridge circuit.

2. The stray current active absorption device according to claim 1, characterized in that, the storage battery is connected to a boost chopper converter; the boost chopper converter is connected to a photovoltaic unit.

3. The stray current active absorption device according to claim 1, characterized in that, the full-bridge circuit is connected to an LC filter; wherein, one end of the inductor of the LC filter is connected between two switching tubes of the first bridge arm of the full-bridge circuit, and the other end is connected to the buried pipeline; one end of the capacitor of the LC filter is connected between the inductor and the buried pipeline, and the other end is connected to the auxiliary anode and is connected between two switching tubes of the second bridge arm of the full-bridge circuit.

4. The stray current active absorption device according to claim 2, characterized in that, the positive and negative electrodes of the storage battery are connected to a controllable switch and a discharge resistor to form a loop.

5. The stray current active absorption device according to claim 4, characterized in that, when the SOC of the storage battery < 0.85, the boost chopper converter charges the storage battery, and the controllable switch remains open; when 0.85 ≤ SOC ≤ 0.95, the boost chopper converter stops charging the storage battery, and the controllable switch remains open; when 0.95 < SOC, the boost chopper converter stops charging the storage battery, the controllable switch closes, and the storage battery discharges through the discharge resistor.

6. The stray current active absorption device according to any one of claims 1 to 5, characterized in that, The duty cycle D of the switch tube in the full bridge circuit 1 The calculation formula is: D 1 =k pI (I ABref -k·I AB )+k iI ∫(I ABref -k·I AB )dt; Among them, k pI , k iI Respectively represent the proportional coefficient and integral coefficient of the PI controller; in the first quadrant mode and the second quadrant mode, k = 1; in the third quadrant mode and the fourth quadrant mode, k = -1; I AB Indicates the actual value of the full-bridge circuit output current; in the first quadrant mode and the third quadrant mode, I ABref =k pU (k·(U ABref -U AB ))+k iU ∫(k·(U ABref -U AB ))dt,k pU , k iU Respectively represent the proportional coefficient and integral coefficient of the voltage loop PI controller, U ABref Output voltage command value for the full-bridge circuit.

7. The stray current active absorption device according to any one of claims 1 to 5, characterized in that, The driving signal acquisition process of the bidirectional flyback converter includes: 2 After PWM modulation, the driving signal of the bidirectional flyback converter is obtained; wherein, D 2 =K p (YOU busref -YOU bus )+K i ∫(You busref -YOU bus )dt; U busref is the output voltage command value of the bidirectional flyback converter; U bus is the output voltage feedback value of the bidirectional flyback converter; K p , K i They represent the proportional coefficient and integral coefficient of the PI controller respectively.

8. The stray current active absorption device according to any one of claims 1 to 5, characterized in that, The SOC calculation formula of the battery is as follows: Among them, SOC 0 is the initial state value of the battery SOC, η is the battery discharge efficiency, I 1 is the battery discharge current, Q N is the rated capacity of the battery.

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