A negative sequence and harmonic current detection and compensation device and method for traction substation

Abstract

The present invention provides a negative sequence and harmonic current detection and compensation device and method for a traction substation, and relates to the field of DSP automatic control technology. The system includes a current detection module, a central controller module, an IGBT isolation drive module, a battery pack, and an inverter module; the central controller containing the DSP TMS320F28335 is used as the main control module, and the bus current of the traction substation is measured and monitored by the current detection device, and the detection result is sent to the DSP for data processing, and then the drive trigger signals of the two inverters are generated, and the harmonics and negative sequence currents of the traction substation are comprehensively compensated respectively. The current comprehensive compensation device can reduce the negative sequence and harmonic currents injected into the power grid by the traction substation, improve the utilization rate of the transformer capacity, reduce the line loss, and effectively reduce the malfunction of the protection device. The safety, reliability and economy of the power system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of DSP automatic control, and in particular to a negative sequence and harmonic current detection and compensation device and method for a traction substation. Background Art

[0002] my country's electrified railways are developing rapidly. The normal operation of electrified railways is closely related to the safety and reliability of the traction power supply network. Due to the special three-phase-two-phase connection form of the traction transformer and the power supply for high-power single-phase loads, the three-phase current is seriously unbalanced and negative sequence current flows into the power grid. In addition, with the large-scale operation of AC-DC electric locomotives and AC-DC-AC electric locomotives, the harmonic content generated by the electronic rectifier circuit is very high, which seriously affects the power quality of the power grid and will have a serious impact on the power supply network, electric locomotives, and surrounding enterprises, households, etc. The power safety has a serious impact. Therefore, it is particularly necessary and important to study the detection and compensation technology of negative sequence and harmonic currents in electrified railways and take effective measures to control them. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a negative sequence and harmonic current detection and compensation device and method for a traction substation, which can improve the power quality of the power grid and ensure the stable operation of the power grid after large-scale electrified railways are connected to the grid.

[0004] On the one hand, a negative sequence and harmonic current detection and compensation device for a traction substation includes a current detection module, a DSP central controller module, an IGBT isolation drive module, a battery pack, an inverter 1, and an inverter 2.

[0005] The input end of the current detection module is connected to the primary side line of the traction transformer, and the output end is connected to the input end of the DSP central controller module;

[0006] The output end of the DSP central controller module is connected to the input end of the IGBT isolation drive module;

[0007] The IGBT isolation drive module is connected to the trigger pulse receiving end of the inverter 1 and the inverter 2; the battery pack is connected to the input end of the inverter 1 and the inverter 2.

[0008] The DSP central controller comprises a first PWM controller, a second PWM controller, a third PWM controller, a fourth PWM controller, a fifth PWM controller, a sixth PWM controller, a seventh PWM controller, an eighth PWM controller, a ninth PWM controller, a tenth PWM controller, an eleventh PWM controller, a twelfth PWM controller, a DC power supply, and an A / D converter; a VCC pin of the DSP central controller is connected to the DC power supply, and a first PWM pin, a second PWM pin, a third PWM pin, a fourth PWM pin, a fifth PWM pin, a sixth PWM pin, a seventh PWM pin, an eighth PWM pin, a ninth PWM pin, a tenth PWM pin, an eleventh PWM pin, and a twelfth PWM pin of the DSP central controller are connected to the first PWM controller, the second PWM controller, the third PWM pin, the fourth PWM pin, the fifth PWM pin, the sixth PWM pin, the seventh PWM pin, the eighth PWM pin, the ninth PWM pin, the tenth PWM pin, the eleventh PWM pin, and the ... The input ends of the WM controller, the fourth PWM controller, the fifth PWM controller, the sixth PWM controller, the seventh PWM controller, the eighth PWM controller, the ninth PWM controller, the tenth PWM controller, the eleventh PWM controller and the twelfth PWM controller are connected; the output ends of the first PWM controller, the second PWM controller, the third PWM controller, the fourth PWM controller, the fifth PWM controller, the sixth PWM controller, the seventh PWM controller, the eighth PWM controller, the ninth PWM controller, the tenth PWM controller, the eleventh PWM controller and the twelfth PWM controller are respectively connected to the input end of the IGBT isolation drive module; the input end of the current detection module is connected to the primary side line of the traction transformer and the output end is connected to the input end of the A / D converter; the output end of the A / D converter is connected to the DSP central controller

[0009] The inverter 1 includes a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, a fifth power switch tube, a sixth power switch tube, a first voltage regulator tube, a second voltage regulator tube, a third voltage regulator tube, a fourth voltage regulator tube, a fifth voltage regulator tube, a sixth voltage regulator tube, a first bridge arm inductor, a second bridge arm inductor, a third bridge arm inductor, a buffer circuit RC1, a buffer circuit RC2, a buffer circuit RC3, a buffer circuit RC4, a buffer circuit RC5, and a buffer circuit RC6; the inverter 2 includes a seventh power switch tube, an eighth power switch tube, a ninth power switch tube, a tenth power switch tube, an eleventh power switch tube, a twelfth power switch tube, a seventh voltage regulator tube, an eighth voltage regulator tube, a ninth voltage regulator tube, a tenth voltage regulator tube, an eleventh voltage regulator tube, a twelfth voltage regulator tube, a fourth bridge arm inductor, a fifth bridge arm inductor, a sixth bridge arm inductor, a buffer circuit RC7, a buffer circuit RC8, a buffer circuit RC9, a buffer circuit RC10, a buffer circuit RC11, and a buffer circuit RC12. The first voltage regulator tube and the buffer circuit RC1 are connected in parallel between the emitter and collector of the first power switch tube, the second voltage regulator tube and the buffer circuit RC2 are connected in parallel between the emitter and collector of the second power switch tube, the third voltage regulator tube and the buffer circuit RC3 are connected in parallel between the emitter and collector of the third power switch tube, the fourth voltage regulator tube and the buffer circuit RC4 are connected in parallel between the emitter and collector of the fourth power switch tube, the fifth voltage regulator tube and the buffer circuit RC5 are connected in parallel between the emitter and collector of the fifth power switch tube, the sixth voltage regulator tube and the buffer circuit RC6 are connected in parallel between the emitter and collector of the sixth power switch tube, the seventh voltage regulator tube and the buffer circuit RC7 are connected in parallel between the emitter and collector of the seventh power switch tube, the eighth voltage regulator tube and the buffer circuit RC8 are connected in parallel between the emitter and collector of the eighth power switch tube, and the ninth voltage regulator tube and the buffer circuit RC9 are connected in parallel between the emitter and collector of the ninth power switch tube. The tenth voltage regulator tube and the buffer circuit RC10 are connected in parallel between the emitter and the collector of the tenth power switch tube, the eleventh voltage regulator tube and the buffer circuit RC11 are connected in parallel between the emitter and the collector of the eleventh power switch tube, and the twelfth voltage regulator tube and the buffer circuit RC12 are connected in parallel between the emitter and the collector of the twelfth power switch tube; the first bridge arm inductor is connected between the first power switch tube and the A-phase busbar on the primary side of the traction transformer, the second bridge arm inductor is connected between the third power switch tube and the B-phase busbar on the primary side of the traction transformer, the third bridge arm inductor is connected between the fifth power switch tube and the C-phase busbar on the primary side of the traction transformer, the fourth bridge arm inductor is connected between the seventh power switch tube and the A-phase busbar on the primary side of the traction transformer, the fifth bridge arm inductor is connected between the ninth power switch tube and the B-phase busbar on the primary side of the traction transformer, and the sixth bridge arm inductor is connected between the eleventh power switch tube and the C-phase busbar on the primary side of the traction transformer.

[0010] On the other hand, the present invention provides a method for detecting and compensating negative sequence and harmonic currents of a traction transformer, which is implemented by a current compensation device controller as described above, and comprises the following steps:

[0011] Step 1: Inverter 1 detects the primary current of the traction transformer through the current detection module, converts it through the A / D converter, and performs symmetrical component method calculation internally through the programming of the DSP central controller;

[0012] Step 2: Process the calculated result in the DSP central controller as a reference value for compensating negative sequence current;

[0013] Step 3: Compare the current reference value with the output current of inverter 1. If the inverter output current exceeds the preset reference current hysteresis band, the upper bridge arm fully-controlled devices of each corresponding bridge arm of inverter 1 circuit are turned off, and the lower bridge arm fully-controlled devices are turned on. If the inverter output current is lower than the preset reference current hysteresis band, the upper bridge arm fully-controlled devices of each corresponding bridge arm of inverter 1 circuit are turned on, and the lower bridge arm fully-controlled devices are turned off.

[0014] Step 4: Inverter 2 detects the three-phase line current through the current detection device, converts it through the A / D converter, and performs symmetrical component method calculation internally through the programming of the DSP central controller;

[0015] Step 5: The calculated positive sequence current signal is transformed from three-phase static to two-phase static current iα and iβ through coordinate transformation; then iα and iβ are transformed into active current ip and reactive current iq through instantaneous reactive power theory. At this time, the current with high-order harmonic content in the positive sequence component is filtered out to obtain the fundamental component of the line positive sequence current. Then ip and iq are inversely transformed into two-phase static iα 1 , iβ 1 , and then transformed into three-phase static currents ia, ib, ic as subtrahends to be subtracted from the positive sequence current calculated by the symmetrical component method, and the calculated result is processed in the DSP central controller to output the three-phase current signal as the reference value for compensating the positive sequence harmonic current;

[0016] Step 6: Compare the current reference value with the output current of inverter 2. If the inverter output current exceeds the preset reference current hysteresis band, the upper bridge arm fully-controlled devices of each corresponding bridge arm of inverter 2 are turned off, and the lower bridge arm fully-controlled devices are turned on. If the inverter output current is lower than the preset reference current hysteresis band, the upper bridge arm fully-controlled devices of each corresponding bridge arm of inverter 2 are turned on, and the lower bridge arm fully-controlled devices are turned off.

[0017] The beneficial effects of adopting the above technical solution are:

[0018] The present invention provides a negative sequence and harmonic current detection and compensation device and method for a traction substation. Due to the rapid development of electrified railways and the special wiring form of traction transformers, when the traction substation supplies power to the electric railway, negative sequence current and harmonic current will be detected on the primary side of the traction transformer, and flow into the power grid to affect the power quality of the power grid. Therefore, the above control strategy is designed to comprehensively compensate for the negative sequence and harmonic current on the primary side of the traction transformer to improve the power quality of the power grid, thereby further improving the reliability and stability of the power grid that supplies power to it. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a structural diagram of a current comprehensive compensation controller for a traction substation according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of a central controller according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of an IGBT isolation drive signal circuit according to an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of a current detection module according to an embodiment of the present invention;

[0023] Figure 5 1 is a circuit schematic diagram of inverter 1 and inverter 2 according to an embodiment of the present invention;

[0024] Figure 6 This is a flow chart of the current comprehensive compensation control method according to an embodiment of the present invention.

[0025] Figure 7 This is a waveform diagram of the primary current of the traction transformer before and after the comprehensive compensation device is used in the embodiment of the present invention.

[0026] in, Figure 7 (a)-Three-phase current waveform before comprehensive compensation, Figure 7 (b)-Three-phase current waveform after comprehensive compensation. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0028] On the one hand, a negative sequence and harmonic current detection and compensation device for a traction substation, such as Figure 1 As shown, it includes a current detection module, a DSP central controller module, an IGBT isolation drive module, a battery pack, an inverter 1, and an inverter 2.

[0029] The current detection module is as follows Figure 4As shown, the input end is connected to the primary side line of the traction transformer, and the output end is connected to the input end of the central controller;

[0030] The output end of the central controller is connected to the input end of the IGBT isolation drive module;

[0031] The IGBT isolation drive module is as follows Figure 3 As shown, it is connected to the trigger pulse receiving end of the inverter; the battery pack is connected to the input end of the inverter;

[0032] The DSP central controller is as follows Figure 2 As shown, it includes a first PWM controller, a second PWM controller, a third PWM controller, a fourth PWM controller, a fifth PWM controller, a sixth PWM controller, a seventh PWM controller, an eighth PWM controller, a ninth PWM controller, a tenth PWM controller, an eleventh PWM controller, a twelfth PWM controller, a DC power supply, and an A / D converter; the VCC pin of the DSP central controller is connected to the DC power supply, and the first PWM pin, the second PWM pin, the third PWM pin, the fourth PWM pin, the fifth PWM pin, the sixth PWM pin, the seventh PWM pin, the eighth PWM pin, the ninth PWM pin, the tenth PWM pin, the eleventh PWM pin, and the twelfth PWM pin of the DSP central controller are respectively connected to the first PWM controller, the second PWM controller, the third PWM controller The input ends of the first PWM controller, the second PWM controller, the third PWM controller, the fourth PWM controller, the fifth PWM controller, the sixth PWM controller, the seventh PWM controller, the eighth PWM controller, the ninth PWM controller, the tenth PWM controller, the eleventh PWM controller and the twelfth PWM controller are connected to the input end of the IGBT isolation drive module respectively; the input end of the current detection module is connected to the primary side line of the traction transformer and the output end is connected to the input end of the A / D converter; the output end of the A / D converter is connected to the DSP central controller

[0033] The inverter 1 and the inverter 2 are as follows Figure 5As shown, the inverter 1 includes a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, a fifth power switch tube, a sixth power switch tube, a first voltage regulator tube, a second voltage regulator tube, a third voltage regulator tube, a fourth voltage regulator tube, a fifth voltage regulator tube, a sixth voltage regulator tube, a first bridge arm inductor, a second bridge arm inductor, a third bridge arm inductor, a buffer circuit RC1, a buffer circuit RC2, a buffer circuit RC3, a buffer circuit RC4, a buffer circuit RC5, and a buffer circuit RC6; the inverter 2 includes a seventh power switch tube, an eighth power switch tube, a ninth power switch tube, a tenth power switch tube, an eleventh power switch tube, a twelfth power switch tube, a seventh voltage regulator tube, an eighth voltage regulator tube, a ninth voltage regulator tube, a tenth voltage regulator tube, an eleventh voltage regulator tube, a twelfth voltage regulator tube, a fourth bridge arm inductor, a fifth bridge arm inductor, a sixth bridge arm inductor, a buffer circuit RC7, a buffer circuit RC8, a buffer circuit RC9, a buffer circuit RC10, a buffer circuit RC11, and a buffer circuit RC12. The first voltage regulator tube and the buffer circuit RC1 are connected in parallel between the emitter and collector of the first power switch tube, the second voltage regulator tube and the buffer circuit RC2 are connected in parallel between the emitter and collector of the second power switch tube, the third voltage regulator tube and the buffer circuit RC3 are connected in parallel between the emitter and collector of the third power switch tube, the fourth voltage regulator tube and the buffer circuit RC4 are connected in parallel between the emitter and collector of the fourth power switch tube, the fifth voltage regulator tube and the buffer circuit RC5 are connected in parallel between the emitter and collector of the fifth power switch tube, the sixth voltage regulator tube and the buffer circuit RC6 are connected in parallel between the emitter and collector of the sixth power switch tube, the seventh voltage regulator tube and the buffer circuit RC7 are connected in parallel between the emitter and collector of the seventh power switch tube, the eighth voltage regulator tube and the buffer circuit RC8 are connected in parallel between the emitter and collector of the eighth power switch tube, and the ninth voltage regulator tube and the buffer circuit RC9 are connected in parallel between the emitter and collector of the ninth power switch tube. The tenth voltage regulator tube and the buffer circuit RC10 are connected in parallel between the emitter and the collector of the tenth power switch tube, the eleventh voltage regulator tube and the buffer circuit RC11 are connected in parallel between the emitter and the collector of the eleventh power switch tube, and the twelfth voltage regulator tube and the buffer circuit RC12 are connected in parallel between the emitter and the collector of the twelfth power switch tube; the first bridge arm inductor is connected between the first power switch tube and the A-phase busbar on the primary side of the traction transformer, the second bridge arm inductor is connected between the third power switch tube and the B-phase busbar on the primary side of the traction transformer, the third bridge arm inductor is connected between the fifth power switch tube and the C-phase busbar on the primary side of the traction transformer, the fourth bridge arm inductor is connected between the seventh power switch tube and the A-phase busbar on the primary side of the traction transformer, the fifth bridge arm inductor is connected between the ninth power switch tube and the B-phase busbar on the primary side of the traction transformer, and the sixth bridge arm inductor is connected between the eleventh power switch tube and the C-phase busbar on the primary side of the traction transformer.

[0034] On the other hand, the present invention provides a method for detecting and compensating negative sequence and harmonic currents of a traction transformer, which is implemented by a current compensation device controller as described above. Figure 6 As shown, the following steps are included:

[0035] Step 1: Attach Figure 1 The middle inverter 1 detects the primary current of the traction transformer through the current detection module, converts it through the A / D converter, and performs symmetrical component method calculation internally through the programming of the DSP central controller;

[0036] Step 2: Process the calculated result in the DSP central controller as a reference value for compensating negative sequence current;

[0037] Step 3: Compare the current reference value with the Figure 1 If the inverter output current exceeds the preset reference current hysteresis band, the Figure 1 In the inverter 1 circuit, the upper bridge arm fully controlled device of each corresponding bridge arm is turned off, and the lower bridge arm fully controlled device is turned on. If the inverter output current is lower than the preset reference current hysteresis band, the attached Figure 1 The upper bridge arm fully-controlled devices of each corresponding bridge arm of the middle inverter 1 are turned on, and the lower bridge arm fully-controlled devices are turned off.

[0038] Step 4: Attach Figure 1 The middle inverter 2 detects the three-phase line current through the current detection device, converts it through the A / D converter, and performs symmetrical component method calculation internally through the programming of the DSP central controller;

[0039] Step 5: The calculated positive sequence current signal is transformed from three-phase static to two-phase static current iα and iβ through coordinate transformation; then iα and iβ are transformed into active current ip and reactive current iq through instantaneous reactive power theory. At this time, the current with high-order harmonic content in the positive sequence component is filtered out to obtain the fundamental component of the line positive sequence current. Then ip and iq are inversely transformed into two-phase static iα 1 , iβ 1 , and then transformed into three-phase static currents ia, ib, ic as subtrahends to be subtracted from the positive sequence current calculated by the symmetrical component method, and the calculated result is processed in the DSP central controller to output the three-phase current signal as the reference value for compensating the positive sequence harmonic current;

[0040] Step 6: Compare the current reference value with the Figure 1 If the inverter output current exceeds the preset reference current hysteresis band, the Figure 1 The upper bridge arm fully controlled devices of each corresponding bridge arm of the middle inverter 2 are turned off, and the lower bridge arm fully controlled devices are turned on. If the inverter output current is lower than the preset reference current hysteresis band, the attached Figure 1 The upper bridge arm fully-controlled devices of each corresponding bridge arm of the middle inverter 2 are turned on, and the lower bridge arm fully-controlled devices are turned off.

[0041] The waveforms of the three-phase current on the primary side of the traction transformer before and after the compensation device is used in the embodiment of the present invention are as follows: Figure 7 As shown, it can be seen intuitively from the waveform diagram that after comprehensive compensation, the asymmetry of the current is greatly reduced, approaching three-phase symmetry, and the compensation device has a good compensation effect on the negative sequence and harmonic current.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A negative sequence and harmonic current detection and compensation device for a traction substation, characterized in that: include: Current detection module, DSP central controller module, IGBT isolation drive module, battery pack, inverter 1, inverter 2; The input end of the current detection module is connected to the primary side line of the traction transformer, and the output end is connected to the input end of the DSP central controller module; The output end of the DSP central controller module is connected to the input end of the IGBT isolation drive module; The IGBT isolation drive module is connected to the trigger pulse receiving end of inverter 1 and inverter 2; the battery pack is connected to the input end of inverter 1 and inverter 2; The DSP central controller comprises a first PWM controller, a second PWM controller, a third PWM controller, a fourth PWM controller, a fifth PWM controller, a sixth PWM controller, a seventh PWM controller, an eighth PWM controller, a ninth PWM controller, a tenth PWM controller, an eleventh PWM controller, a twelfth PWM controller, a DC power supply, and an A / D converter; a VCC pin of the DSP central controller is connected to the DC power supply, and a first PWM pin, a second PWM pin, a third PWM pin, a fourth PWM pin, a fifth PWM pin, a sixth PWM pin, a seventh PWM pin, an eighth PWM pin, a ninth PWM pin, a tenth PWM pin, an eleventh PWM pin, and a twelfth PWM pin of the DSP central controller are connected to the first PWM controller, the second PWM controller, the third PWM controller, the fourth PWM pin, the fifth PWM pin, the sixth PWM pin, the seventh PWM pin, the eighth PWM pin, the ninth PWM pin, the tenth PWM pin, the eleventh PWM pin, and the twelfth PWM pin of the DSP central controller are connected to the first PWM controller, the second PWM controller, the third PWM controller, the The input ends of the first PWM controller, the second PWM controller, the third PWM controller, the fourth PWM controller, the fifth PWM controller, the sixth PWM controller, the seventh PWM controller, the eighth PWM controller, the ninth PWM controller, the tenth PWM controller, the eleventh PWM controller and the twelfth PWM controller are connected; the output ends of the first PWM controller, the second PWM controller, the third PWM controller, the fourth PWM controller, the fifth PWM controller, the sixth PWM controller, the seventh PWM controller, the eighth PWM controller, the ninth PWM controller, the tenth PWM controller, the eleventh PWM controller and the twelfth PWM controller are respectively connected to the input end of the IGBT isolation drive module; the input end of the current detection module is connected to the primary side line of the traction transformer and the output end is connected to the input end of the A / D converter; the output end of the A / D converter is connected to the DSP central controller; The inverter 1 includes a first power switch tube, a second power switch tube, a third power switch tube, a fourth power switch tube, a fifth power switch tube, a sixth power switch tube, a first voltage regulator tube, a second voltage regulator tube, a third voltage regulator tube, a fourth voltage regulator tube, a fifth voltage regulator tube, a sixth voltage regulator tube, a first bridge arm inductor, a second bridge arm inductor, a third bridge arm inductor, a buffer circuit RC1, a buffer circuit RC2, a buffer circuit RC3, a buffer circuit RC4, a buffer circuit RC5, and a buffer circuit RC6; The inverter 2 includes a seventh power switch tube, an eighth power switch tube, a ninth power switch tube, a tenth power switch tube, an eleventh power switch tube, a twelfth power switch tube, a seventh voltage regulator tube, an eighth voltage regulator tube, a ninth voltage regulator tube, a tenth voltage regulator tube, an eleventh voltage regulator tube, a twelfth voltage regulator tube, a fourth bridge arm inductor, a fifth bridge arm inductor, a sixth bridge arm inductor, a buffer circuit RC7, a buffer circuit RC8, a buffer circuit RC9, a buffer circuit RC10, a buffer circuit RC11, and a buffer circuit RC12; The first voltage regulator tube and the buffer circuit RC1 are connected in parallel between the emitter and collector of the first power switch tube, the second voltage regulator tube and the buffer circuit RC2 are connected in parallel between the emitter and collector of the second power switch tube, the third voltage regulator tube and the buffer circuit RC3 are connected in parallel between the emitter and collector of the third power switch tube, the fourth voltage regulator tube and the buffer circuit RC4 are connected in parallel between the emitter and collector of the fourth power switch tube, the fifth voltage regulator tube and the buffer circuit RC5 are connected in parallel between the emitter and collector of the fifth power switch tube, the sixth voltage regulator tube and the buffer circuit RC6 are connected in parallel between the emitter and collector of the sixth power switch tube, the seventh voltage regulator tube and the buffer circuit RC7 are connected in parallel between the emitter and collector of the seventh power switch tube, the eighth voltage regulator tube and the buffer circuit RC8 are connected in parallel between the emitter and collector of the eighth power switch tube, and the ninth voltage regulator tube and the buffer circuit RC9 are connected in parallel between the emitter and collector of the ninth power switch tube. The tenth voltage regulator tube and the buffer circuit RC10 are connected in parallel between the emitter and the collector of the tenth power switch tube, the eleventh voltage regulator tube and the buffer circuit RC11 are connected in parallel between the emitter and the collector of the eleventh power switch tube, and the twelfth voltage regulator tube and the buffer circuit RC12 are connected in parallel between the emitter and the collector of the twelfth power switch tube; the first bridge arm reactor is connected between the first power switch tube and the A-phase busbar on the primary side of the traction transformer, the second bridge arm reactor is connected between the third power switch tube and the B-phase busbar on the primary side of the traction transformer, the third bridge arm reactor is connected between the fifth power switch tube and the C-phase busbar on the primary side of the traction transformer, the fourth bridge arm reactor is connected between the seventh power switch tube and the A-phase busbar on the primary side of the traction transformer, the fifth bridge arm reactor is connected between the ninth power switch tube and the B-phase busbar on the primary side of the traction transformer, and the sixth bridge arm reactor is connected between the eleventh power switch tube and the C-phase busbar on the primary side of the traction transformer; The negative sequence and harmonic current detection and compensation device of a traction substation is used to implement a traction transformer negative sequence and harmonic current detection and compensation method, comprising the following steps: Step 1: Inverter 1 detects the primary current of the traction transformer through the current detection module, converts it through the A / D converter, and performs symmetrical component method calculation internally through the programming of the DSP central controller; Step 2: Process the calculated result in the DSP central controller as a reference value for compensating negative sequence current; Step 3: Compare the current reference value with the output current of the inverter 1. If the output current of the inverter exceeds the preset reference current hysteresis band, the upper bridge arm fully-controlled device of each corresponding bridge arm of the inverter 1 circuit is turned off, and the lower bridge arm fully-controlled device is turned on. If the output current of the inverter is lower than the preset reference current hysteresis band, the upper bridge arm fully-controlled device of each corresponding bridge arm of the inverter 1 circuit is turned on, and the lower bridge arm fully-controlled device is turned off. Step 4: Inverter 2 detects the three-phase line current through the current detection device, converts it through the A / D converter, and performs symmetrical component method calculation internally through the programming of the DSP central controller; Step 5: The calculated positive sequence current signal is transformed from three-phase static current to two-phase static current iα, iβ through coordinate transformation; then iα, iβ are transformed into active current ip, reactive current iq through instantaneous reactive power theory, at this time, the current with high-order harmonic content in the positive sequence component is filtered out to obtain the fundamental component of the line positive sequence current, and then ip, iq are inversely transformed into two-phase static iα1, iβ1, and then transformed into three-phase static current ia, ib, ic as subtrahends to be subtracted from the positive sequence current calculated by the symmetrical component method, and the calculated result is processed in the DSP central controller to output the three-phase current signal as the reference value for compensating the positive sequence harmonic current; Step 6: Compare the current reference value with the output current of inverter 2. If the inverter output current exceeds the preset reference current hysteresis band, the upper bridge arm fully-controlled devices of each corresponding bridge arm of inverter 2 are turned off, and the lower bridge arm fully-controlled devices are turned on. If the inverter output current is lower than the preset reference current hysteresis band, the upper bridge arm fully-controlled devices of each corresponding bridge arm of inverter 2 are turned on, and the lower bridge arm fully-controlled devices are turned off.

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