A metro energy feedback system and ice melting energy feedback method with direct current ice melting function

Abstract

The application discloses a metro energy feedback system with a direct current ice melting function, which comprises a medium voltage looped network, a contact network, a running rail and positive and negative bus lines, and further comprises a metro rectifying module and a metro energy feedback module; the metro rectifying module is connected with the positive and negative bus lines; the positive bus line is connected with the contact network, and the negative bus line is connected with the running rail; the metro energy feedback module is connected with the positive bus line, the negative bus line, the running rail and the medium voltage looped network respectively; the metro energy feedback module is further connected with the contact network through a circuit breaker QF, and the contact network is connected with the running rail through a remote short-circuit switch K4. The application further discloses an ice melting energy feedback method of the metro energy feedback system with the direct current ice melting function. The application has both the direct current ice melting function and the metro regenerative energy feedback function, and the two functions are controlled by switches to realize time-sharing multiplexing, so that the efficient utilization of equipment is realized, and the performance cost ratio is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transportation, in particular to a metro energy feedback system with direct current ice melting function and an ice melting energy feedback method. BACKGROUND

[0002] Metro is a way for citizens to travel daily, and has many advantages, so it has developed rapidly. Metro is also facing some problems while developing rapidly. Problem one, how to recycle the regenerative braking energy of metro, which plays an important role in reducing energy consumption, suppressing catenary voltage fluctuation and improving the stability of power supply system. The main metro regenerative braking energy utilization technologies at present mainly include energy storage type and energy feedback type. The energy feedback type energy absorption device directly feeds the regenerative electric energy to the alternating current power grid for reuse. Compared with the energy storage type energy absorption device, it does not need to configure a large number of energy storage elements, and is mature in technology, easy to maintain and repair, which is the inevitable trend of future development of metro related technologies. The energy feedback type energy absorption device adopts IGBT and other power electronic devices to constitute a high-power three-phase converter. The direct current side of the converter is connected with the direct current bus in the traction substation. When the metro braking produces regenerative braking energy and raises the voltage of the direct current catenary, the energy feedback device will convert the regenerative braking energy that cannot be absorbed by the adjacent car into three-phase alternating current through the converter, transmit it to the low-voltage side of the energy feedback transformer, and feed it back to the medium-voltage ring network for use by other system loads in the metro. When the metro traction causes the direct current network voltage to drop, the energy of the medium-voltage ring network will be transmitted to the direct current bus end through the rectification of the converter, so as to achieve the effect of energy saving and voltage stabilization. Problem two, when the metro vehicle adopts overhead catenary power supply, the influence of rain, snow and ice weather on the catenary is particularly prominent. The catenary is an important power supply facility for metro traction. When the catenary surface is covered with ice, it will seriously affect the normal current collection of the pantograph and reduce the reliability of metro power supply, thereby threatening the safety of train operation. Small-scale line icing can be removed by artificial or mechanical methods (such as knocking with a wooden hammer), high-pressure steam ice melting, etc., but for large-scale and long-distance lines, such methods are inefficient and have poor ice melting effect. Therefore, it is of great economic and social significance to install advanced and reliable ice melting devices in the traction substation to safely and quickly remove the ice on a large range of catenaries. From the current technical level at home and abroad, direct current ice melting technology is the most mature and feasible ice melting method, and its basic principle is to use the heat generated by the direct current passing through the wire to melt the ice layer.

[0003] The existing metro energy feedback device adopts NPC three-level inverter circuit in structure, and in addition to the functions of converting the excess regenerative braking energy into AC power and feeding the AC power to the medium voltage looped network for reuse and rectifying the power of the medium voltage looped network and outputting the power to the DC bus to provide traction energy for the train, the device can also compensate the reactive power of the AC medium voltage power grid. A DC deicing device with a reactive power compensation function (SVG) is also particularly attractive, which has the functions of reactive power compensation and DC deicing, is easy to switch, is economical and effective, and mostly adopts half-bridge type, full-bridge type and hybrid MMC topological structure.

[0004] The existing metro energy feedback device and DC deicing device have relatively single functions. For example, the metro energy feedback device only has the functions of recycling the metro regenerative braking energy and stabilizing the DC catenary voltage, the DC deicing device only has the deicing function and is only used when the catenary is iced, and has a long idle time. If the traction substation needs the above two functions, two sets of devices must be configured, the device occupies a large area, and the cost of purchasing the device is high. SUMMARY

[0005] The purpose of the present application is to provide a metro energy feedback system and deicing energy feedback method with DC deicing function, which has the functions of DC deicing and metro regenerative energy feedback, and the two functions are time-shared and multiplexed through switch control, realizes efficient use of the device, and improves the performance-price ratio.

[0006] A metro energy feedback system with DC deicing function, comprising a medium voltage looped network, a catenary, a running rail and positive and negative buses, further comprising:

[0007] A metro rectifier module, which reduces the voltage of the introduced city power grid AC power, and then outputs stable DC power through efficient rectification and voltage regulation technology to meet the power supply demand of high-power and long-distance metro lines;

[0008] A metro energy feedback module, which on the one hand transmits the regenerative braking electric energy to the medium voltage looped network for use by other devices after conversion and voltage increase, and on the other hand, when the DC network voltage drops, transmits the electric energy from the medium voltage looped network to the DC bus after voltage reduction and rectification to ensure that the DC catenary voltage returns to the normal value;

[0009] The metro rectifier module is connected with the positive and negative buses; the positive bus is connected with the catenary, and the negative bus is connected with the running rail;

[0010] The metro energy feedback module is connected with the positive bus, the negative bus, the running rail and the medium voltage looped network respectively;

[0011] The metro energy feedback module is further connected with the catenary through a circuit breaker QF, and the catenary and the running rail are connected through a remote short-circuit switch K4.

[0012] Further, the subway energy feedback module comprises a switch cabinet K1, a disconnector cabinet K2, a converter cabinet, a contactor KM, an energy feedback transformer and a switch cabinet K3.

[0013] The converter cabinet is connected with the switch cabinet K1 and the negative bus through the disconnector cabinet K2, and the switch cabinet K1 is further connected with the positive bus.

[0014] The converter cabinet is further connected with one end of the energy feedback transformer through the contactor KM, and the other end of the energy feedback transformer is connected with a medium voltage looped network through the switch cabinet K3.

[0015] Further, the subway energy feedback module adopts a three-phase active neutral point clamped three-level topology structure, comprising three bridge arms, namely a bridge arm A, a bridge arm B and a bridge arm C, and further comprising an inductor L1, an inductor L2, an inductor L3, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4 and a capacitor C5.

[0016] In the bridge arm A, the collector of the power switch tube Q3 is connected with a DC+ point, the emitter of the power switch tube Q3 and the collector of the power switch tube Q4 are connected, the emitter of the power switch tube Q4 and the collector of the power switch tube Q5 are connected with an a1 point, the emitter of the power switch tube Q5 and the collector of the power switch tube Q6 are connected, the emitter of the power switch tube Q6 is connected with a DC- point, the midpoint of the power switch tube Q3 and the power switch tube Q4 is connected with the collector of the power switch tube Q1, the emitter of the power switch tube Q1 and the collector of the power switch tube Q2 are connected with an a2 point, and the a2 point is connected with the midpoint O of the bus capacitor C1 and the bus capacitor C2, the midpoint of the power switch tube Q5 and the power switch tube Q6 is connected with the emitter of the power switch tube Q2, one end of the capacitor C1 is connected with the DC+ point, and the other end is connected with the neutral point O, one end of the capacitor C2 is connected with the DC- point, and the other end is connected with the neutral point O, the bridge arm A, the bridge arm B and the bridge arm C have the same structure, all the power switch tubes are reversely connected with a diode in parallel, the anode of each diode is connected with the emitter of the power switch tube, and the cathode of each diode is connected with the collector of the power switch tube.

[0017] In the bridge arm B, the connection point a1 is b1 compared with the bridge arm A, and in the bridge arm C, the connection point a1 is c1 compared with the bridge arm A.

[0018] One end of the inductor L1 is connected with the a1 point in the bridge arm A, and the other end is connected with one end of the capacitor C5 and the contactor KM, one end of the inductor L2 is connected with the b1 point in the bridge arm B, and the other end is connected with one end of the capacitor C4 and the contactor KM, one end of the inductor L3 is connected with the c1 point in the bridge arm C, and the other end is connected with one end of the capacitor C3 and the contactor KM, and the other ends of the capacitor C1, the capacitor C2 and the capacitor C3 are connected with one point.

[0019] Further, the metro rectification module comprises a step-down transformer, a rectification unit and a plurality of switches;

[0020] One end of the step-down transformer is connected with the medium-voltage looped network, and the other end is connected with one end of the rectification unit; the other end of the rectification unit is connected with positive and negative busbars respectively; the positive busbar is connected with the catenary, and the negative busbar is connected with the running rail.

[0021] An ice-melting energy feedback method of a metro energy feedback system with a direct-current ice-melting function comprises the following steps:

[0022] When the contactor KM is closed and the circuit breaker QF is opened, the system starts the metro energy feedback mode; the regenerative braking electric energy is converted into three-phase alternating current through the conversion of the conversion cabinet, and then the three-phase alternating current is filtered, boosted to 35KV through the energy feedback transformer and transmitted to the 35KV medium-voltage looped network for use by other devices, until the direct-current catenary voltage returns to the normal value, and the energy feedback is automatically stopped; when the metro traction causes the direct-current network voltage to drop, the 35KV medium-voltage looped network transmits electric energy to the high-voltage side of the energy feedback transformer, and the electric energy is output as 1500V direct current to the direct-current busbar through the rectification of the energy feedback transformer and the conversion cabinet, until the direct-current catenary voltage returns to the normal value, and the energy supply is automatically stopped.

[0023] When the circuit breaker QF is closed and the contactor KM is opened, the device starts the direct-current ice-melting mode; the conversion cabinet outputs direct current to the catenary, and the switch K4 is in the closed state, so that the output direct current forms a loop between the catenary and the running rail, and the direct current flowing through the catenary generates Joule heat to melt the ice.

[0024] The circuit topology of the present application realizes two function modes, which can solve the problem of utilization of metro regenerative braking energy, achieve the effects of energy saving and voltage stabilization, increase the utilization rate of equipment and improve the economy. The metro energy feedback device with the direct-current ice-melting function has the characteristics of convenience, speediness and high efficiency. In normal times, the device is used as a metro energy feedback device, and in the case of catenary icing in extreme environment, the device can also be used as a direct-current ice-melting device to play a significant role in preventing the pantograph from being in poor contact with the catenary and causing the metro to lose power.

[0025] The two modes of the present application do not need to be performed at the same time, so two switches need to be arranged at the output side to control the selection of the modes, and the switching is convenient, simple and efficient.

[0026] The active neutral point clamped three-level circuit adopted in the converter cabinet has many advantages. Compared with the two-level circuit, the voltage stress of each switch tube is only half of the DC bus voltage, and under the same voltage level of the DC bus, a switch tube with a smaller voltage level can be selected; due to the significant reduction of dv / dt in the switching process of each switch tube, the system electromagnetic interference is improved. Compared with the neutral point clamped (NPC) three-level circuit, the problem of uneven heat distribution is solved by replacing the clamping diode with a switch tube. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 For the system topology of the present application Figure 1 ;

[0028] Figure 2 is a schematic diagram of the metro energy feedback module circuit of the present application;

[0029] Figure 3 is a circuit diagram of one phase under the direct current ice melting mode of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the prior known technology. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments.

[0031] As shown in Figure 1 , a metro energy feedback system with direct current ice melting function includes a medium voltage ring network, a catenary, a running rail, and positive and negative buses, and further includes: a metro rectifier module, which reduces the voltage of the introduced urban power grid alternating current, and then outputs stable direct current through high-efficiency rectification and voltage regulation technology, to meet the power supply demand of a high-power and long-distance metro line. The metro rectifier module includes a step-down transformer, a rectifier unit, and a plurality of switches; one end of the step-down transformer is connected with the medium voltage ring network, and the other end is connected with one end of the rectifier unit; the other end of the rectifier unit is connected with the positive and negative buses respectively; the positive bus is connected with the catenary respectively, and the negative bus is connected with the running rail.

[0032] As shown in Figure 1 , the metro system introduces medium voltage 35KV alternating current from the urban power grid, and the introduced alternating current is reduced in voltage by the step-down transformer of the traction substation, and then input to the rectifier unit, to output stable 1500V direct current through high-efficiency rectification and voltage regulation technology, to meet the power supply demand of a high-power and long-distance metro line. The positive power supply on the output side of the rectifier unit is connected with the positive bus, and the positive bus is connected with the catenary and the running rail through switches K5, K6, K7 and K8. The negative power supply on the output side of the rectifier unit is connected with the negative bus, and the voltage level of the positive bus is 1500V direct current. The positive and negative buses are connected with the catenary and the running rail through switches K5, K6, K7 and K8.

[0033] The subway energy feedback module is connected with the positive bus and the negative bus, and is connected with the running rail and the medium voltage loop network.

[0034] The subway energy feedback module comprises a switch cabinet K1, an isolation switch cabinet K2, a converter cabinet, a contactor KM, an energy feedback transformer and a switch cabinet K3.

[0035] As shown in the figure, the subway energy feedback module adopts a three-phase active neutral point clamped three-level topology structure, and outputs or inputs three-phase alternating current. Figure 2

[0036] The structure comprises three bridge arms, namely a bridge arm A, a bridge arm B and a bridge arm C, and further comprises inductors L1, L2 and L3, capacitors C1, C2, C3, C4 and C5.

[0037] In the bridge arm A, the collector of the power switch tube Q3 is connected with the DC+ point, the emitter of the power switch tube Q3 and the collector of the power switch tube Q4 are connected, the emitter of the power switch tube Q4 and the collector of the power switch tube Q5 are connected with the a1 point, the emitter of the power switch tube Q5 and the collector of the power switch tube Q6 are connected, the emitter of the power switch tube Q6 is connected with the DC- point, the midpoint of the power switch tube Q3 and the power switch tube Q4 is connected with the collector of the power switch tube Q1, the emitter of the power switch tube Q1 and the collector of the power switch tube Q2 are connected with the a2 point, and the a2 point is connected with the midpoint O of the bus capacitor C1 and the bus capacitor C2, the midpoint of the power switch tube Q5 and the power switch tube Q6 is connected with the emitter of the power switch tube Q2, one end of the capacitor C1 is connected with the DC+ point, and the other end is connected with the neutral point O, one end of the capacitor C2 is connected with the DC- point, and the other end is connected with the neutral point O, the bridge arm A, the bridge arm B and the bridge arm C have the same structure, all the power switch tubes are reversely connected with a diode, the anode of each diode is connected with the emitter of the power switch tube, and the cathode of each diode is connected with the collector of the power switch tube.

[0038] ​In the bridge arm B, the connection point a1 is b1 relative to the connection point a1 in the bridge arm A; in the bridge arm C, the connection point a1 is c1 relative to the connection point a1 in the bridge arm A.

[0039] One end of the inductor L1 is connected to the point a1 in the bridge arm A, and the other end is connected to one end of the capacitor C5 and the contactor KM; one end of the inductor L2 is connected to the point b1 in the bridge arm B, and the other end is connected to one end of the capacitor C4 and the contactor KM; one end of the inductor L3 is connected to the point c1 in the bridge arm C, and the other end is connected to one end of the capacitor C3 and the contactor KM, and the other ends of the capacitors C1, C2 and C3 are all connected to one point.

[0040] The metro energy feedback module is installed in the traction substation. The input end of the converter cabinet is connected to the positive bus, the input end is connected to the negative bus and the running rail, and the line is controlled by the 1500V switch cabinet K1. The on-off of the line is controlled by the disconnector cabinet K2. The converter cabinet has two outputs. One output is three-phase alternating current, which is controlled by the contactor KM and the on-off of the low-voltage side of the energy feedback transformer, and the on-off of the high-voltage side of the energy feedback transformer and the 35KV medium-voltage ring network is controlled by the 35KV switch cabinet K3. The other output is direct current, which is controlled by the circuit breaker QF and the on-off of the contact net, and the running rail and the contact net are controlled by the switch K4. When KM is closed and QF is opened, the device starts the metro energy feedback mode. In this mode, when the metro braking generates regenerative braking energy and raises the voltage of the direct current contact net, the regenerative braking energy that cannot be absorbed by the adjacent car is converted into three-phase alternating current by the converter cabinet, filtered, boosted to 35KV by the energy feedback transformer, and transmitted to the 35KV medium-voltage ring network for use by other equipment, until the voltage of the direct current contact net returns to the normal value, and the energy feedback is automatically stopped. When the metro traction causes the voltage of the direct current net to drop, the 35KV medium-voltage ring network transmits energy to the high-voltage side of the energy feedback transformer, which is reduced by the energy feedback transformer and rectified by the converter cabinet, and outputs 1500V direct current to the direct current bus, until the voltage of the direct current contact net returns to the normal value, and the energy supply is automatically stopped. When QF is closed and KM is opened, the device starts the direct current deicing mode. In this mode, the converter cabinet outputs direct current to the contact net, and the contact net and the running rail are short-circuited by a switch K4. The switch K4 is in a closed state in the direct current deicing mode, and the output direct current forms a loop between the contact net and the running rail. The direct current flows through the contact net to generate Joule heat, which melts the ice.

[0041] Figure 3The circuit diagram of one phase in three-phase DC output in DC de-icing mode. The circuit is actually one phase of three-phase active neutral point clamped (ANPC) three-level circuit, in series with an inductor and in parallel with a capacitor, forming a buck DC / DC circuit. There are three such bridge arms in the converter cabinet, forming a three-way buck DC / DC circuit, and the output DC of the parallel output is connected to the catenary. The catenary and the far end of the running rail are short-circuited by closing the switch K4, forming a current loop, which melts the ice on the catenary. The size of the de-icing current is adjusted by the three-way buck DC / DC.

[0042] The circuit topology in the converter cabinet realizes two functions in time division multiplexing. In metro energy feedback DC / AC mode, the converter cabinet outputs three-phase AC power, which is boosted by the energy feedback transformer to transmit power to the 35KV medium voltage ring network or in AC / DC mode, the 35KV medium voltage ring network reversely transmits power to the converter cabinet outputting 1500V DC to the DC bus. In DC de-icing DC / DC mode, the converter cabinet outputs DC power, which forms a current loop between the upper and lower catenaries or between the catenary and the running rail, generating heat to melt the ice on the catenary. In DC de-icing DC / DC mode, the running rail and the catenary can be de-iced at the same time, increasing the adhesion coefficient of the running rail and preventing the metro vehicle from slipping. The present application uses a three-phase active neutral point clamped three-level circuit to realize three-way DC output by switching the control mode.

[0043] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A metro energy feedback system with direct current ice melting function, comprising a medium voltage looped network, a catenary, a running rail, and positive and negative busbars, characterized in that, Also include: The subway rectifier module, the introduced city power supply AC voltage is reduced, and then through the high efficiency rectification and voltage regulation technology output stable DC power, meet the power supply demand of high power, long distance subway line; The subway energy feedback module, on the one hand, the regenerative braking power is transmitted to the medium voltage ring network after conversion and voltage rise for other equipment, on the other hand, when the DC network voltage drops, the medium voltage ring network transmission power is output to the DC bus after voltage reduction and rectification, to ensure that the DC catenary voltage returns to the normal value; The subway rectifier module is connected with the positive and negative bus; the positive bus is connected with the catenary, and the negative bus is connected with the running rail; The subway energy feedback module is connected with the positive bus, the negative bus, the running rail and the medium voltage ring network respectively; The subway energy feedback module is also connected with the catenary through the circuit breaker QF, and the catenary is connected with the running rail through the remote short circuit switch K4; The subway energy feedback module includes switch cabinet K1, disconnecting switch cabinet K2, converter cabinet, contactor KM, energy feedback transformer and switch cabinet K3; The converter cabinet is connected with the switch cabinet K1 and the negative bus through the disconnecting switch cabinet K2, and the switch cabinet K1 is also connected with the positive bus; The converter cabinet is also connected with one end of the energy feedback transformer through the contactor KM, and the other end of the energy feedback transformer is connected with the medium voltage ring network through the switch cabinet K3.

2. The metro energy feeding system with DC de-icing function according to claim 1, characterized in that, The subway energy feedback module adopts three-phase active neutral point clamped three-level topology structure, including three bridge arms, namely bridge arm A, bridge arm B and bridge arm C; it also includes inductance L1, inductance L2, inductance L3, capacitor C1, capacitor C2, capacitor C3, capacitor C4 and capacitor C5; In bridge arm A, the collector of power switch tube Q3 is connected with DC+ point, the emitter of power switch tube Q3 and the collector of power switch tube Q4 are connected, the emitter of power switch tube Q4 and the collector of power switch tube Q5 are connected with a1 point, the emitter of power switch tube Q5 and the collector of power switch tube Q6 are connected, the emitter of power switch tube Q6 is connected with DC- point, the midpoint of power switch tube Q3 and power switch tube Q4 is connected with the collector of power switch tube Q1; the emitter of power switch tube Q1 and the collector of power switch tube Q2 are connected with a2 point, and a2 point is connected with the midpoint O of bus capacitor C1 and bus capacitor C2; the midpoint of power switch tube Q5 and power switch tube Q6 is connected with the emitter of power switch tube Q2; one end of capacitor C1 is connected with DC+ point, and the other end is connected with neutral point O point; one end of capacitor C2 is connected with DC- point, and the other end is connected with neutral point O point; bridge arm A, bridge arm B and bridge arm C have the same structure; all power switch tubes are reversely connected with a diode, and the anode of each diode is connected with the emitter of power switch tube, and the cathode of each diode is connected with the collector of power switch tube; In bridge arm B, the connection point a1 is b1 compared with bridge arm A; in bridge arm C, the connection point a1 is c1 compared with bridge arm A; One end of the inductor L1 is connected with a1 point in the bridge arm A, the other end is connected with one end of the capacitor C5 and the contactor KM; one end of the inductor L2 is connected with b1 point in the bridge arm B, the other end is connected with one end of the capacitor C4 and the contactor KM; one end of the inductor L3 is connected with c1 point in the bridge arm C, the other end is connected with one end of the capacitor C3 and the contactor KM, the other ends of the capacitor C1, the capacitor C2 and the capacitor C3 are connected to one point.

3. The metro energy feeding system with DC de-icing function according to claim 1, characterized in that, The subway rectification module comprises a step-down transformer, a rectification unit and a plurality of switches; One end of the step-down transformer is connected with a medium voltage looped network, the other end is connected with one end of the rectification unit; the other end of the rectification unit is connected with a positive bus and a negative bus respectively; the positive bus is connected with a catenary, and the negative bus is connected with a running rail.

4. The ice-melting energy feeding method of the metro energy feeding system with the DC ice-melting function according to claim 2, characterized in that, The method comprises the following steps: When the contactor KM is closed and the circuit breaker QF is opened, the system starts the subway energy feedback mode; the regenerative braking electric energy is converted into three-phase alternating current through the rectification cabinet, and then the three-phase alternating current is filtered, boosted to 35KV through the energy feedback transformer and transmitted to the 35KV medium voltage looped network for use by other equipment, until the DC catenary voltage returns to the normal value, the energy feedback is automatically stopped; when the subway traction causes the DC network voltage to drop, the 35KV medium voltage looped network transmits electric energy to the high voltage side of the energy feedback transformer, and the electric energy is rectified through the energy feedback transformer and the rectification cabinet, and then 1500V DC power is output to the DC bus, until the DC catenary voltage returns to the normal value, the energy supply is automatically stopped. When the circuit breaker QF is closed and the contactor KM is opened, the device starts the DC deicing mode; the rectification cabinet outputs DC power to the catenary, and the switch K4 is in the closed state, so that the output DC power forms a loop between the catenary and the running rail, the DC current flows through the catenary to generate Joule heat, thereby achieving the effect of melting ice.

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