A method for ground energy storage of regenerative braking energy on long and steep slopes

Abstract

The present invention relates to the field of energy storage technology, and in particular to a method for ground energy storage of regenerative braking energy on a long and steep slope. When a train is traveling on a downhill slope on a long and steep slope, a supercapacitor energy storage device is controlled to be charged to absorb the regenerative braking energy generated by the train, thereby reducing the contact network voltage and restoring the contact network voltage to a normal range. When the train is traveling on an uphill slope on the long and steep slope, the supercapacitor energy storage device is controlled to release electric energy and increase the contact voltage, thereby restoring the contact network voltage to a normal range. This ensures that the regenerative braking of the train will not fail, and improves the safety of train operation and the utilization rate of regenerative braking energy.

Description

Technical Field

[0001] The invention relates to the technical field of energy storage, and in particular to a method for ground energy storage of regenerative braking energy on a long and steep slope. Background Art

[0002] As the high-speed railway network continues to expand in the western region, where the terrain is undulating and complex, it is inevitable that more and more routes with long and steep slopes will appear.

[0003] When high-speed trains are going downhill on long and steep slopes, air brakes cannot keep the trains running at a constant speed. Therefore, regenerative braking will be frequently used, and the regenerative braking energy generated will be sent back to the traction power grid, which will cause the contact network voltage to rise significantly, resulting in excessive voltage in the power supply arm. When the voltage exceeds the normal range, the train regenerative braking will fail, seriously affecting the train's operational safety. At the same time, the running EMU trains contain certain high-order harmonics, which can easily cause high-order harmonic resonance in the traction power supply system, causing a decline in power supply quality and affecting the safety of power supply equipment. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a method for ground energy storage of regenerative braking energy on long and steep slopes, which is intended to solve the problem of failure of train regenerative braking and deterioration of power supply quality when a train is running on a long and steep slope.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A method for ground energy storage of regenerative braking energy on a long and steep slope comprises the following steps:

[0007] Establish a supercapacitor energy storage device, connect the bidirectional DC / DC converter of the supercapacitor energy storage device to the DC side of the converter, and connect the AC side of the converter to the end of the power supply arm and the track;

[0008] When the EMU train performs regenerative braking, the regenerative braking energy passes through the converter to step down the contact network voltage, and the stepped-down voltage is rectified to obtain a stable DC voltage. The DC voltage is then stepped down by a bidirectional DC / DC converter, and finally the stepped-down energy is input into the supercapacitor bank of the supercapacitor energy storage device for storage.

[0009] When there is an EMU train in traction state in the power supply arm, the supercapacitor energy storage device releases electrical energy.

[0010] Through the above technical solution of the present invention, when the train is running in the traction stage, the contact network will provide electricity to the train, and when the train is running in the braking stage, the braking energy will be fed back to the contact network. When the train is running on a long slope downhill, in order to maintain a uniform speed, braking measures need to be taken, which will generate a large amount of regenerative braking energy, so that the contact network voltage is high and exceeds the normal range. At this time, the energy storage device is charged to absorb the regenerative braking energy generated by the train, thereby reducing the contact network voltage, so that the contact network voltage is restored to the normal range; when the train is running on a long slope uphill, in order to maintain a uniform speed, the traction power needs to be increased, so that the contact network voltage is reduced and below the normal range. At this time, the supercapacitor energy storage device releases electric energy, increases the contact network voltage, and restores the contact network voltage to the normal range; therefore, a series of problems caused by a significant increase in the contact network voltage can be avoided.

[0011] Preferably, the converter steps down the voltage at a voltage ratio of 25:1, and steps down the AC voltage of 25kV / 50Hz of the power grid to 1000V / 50Hz.

[0012] Preferably, the bidirectional DC / DC converter reduces the DC voltage to 2000V.

[0013] Furthermore, it is characterized in that the bidirectional DC / DC converter includes a boost mode and a buck mode. When the train goes downhill on a long slope, the bidirectional DC / DC converter is in the buck mode; when the train goes uphill on a long slope, the bidirectional DC / DC converter is in the boost mode.

[0014] Through the above two working modes of the bidirectional DC / DC converter, the charging and discharging of the supercapacitor energy storage device is realized by relying on the change of current while keeping the voltage polarity unchanged.

[0015] Furthermore, it also includes obtaining the voltage of the contact network, adjusting the charging and discharging state of the supercapacitor energy storage device based on the obtained contact network voltage, charging the supercapacitor energy storage device when the contact network voltage is greater than a threshold, and discharging the supercapacitor energy storage device when the contact network voltage is less than a threshold.

[0016] Furthermore, the steps for obtaining the electric grid voltage are as follows:

[0017] The voltage of the electric contact grid is divided by a voltage divider, and the divided voltage is sent to a high-precision voltage sensor through a four-layer shielded cable, and a voltage signal is obtained based on the high-precision voltage sensor;

[0018] The signal conditioner divides the voltage signal obtained by the high-precision voltage sensor, performs analog filtering on the divided voltage signal, and converts the analog signal into a digital signal;

[0019] The voltage signal converted into a digital signal is sent to the overhead line voltage detection data processing workstation for digital filtering to obtain the real-time voltage value of the overhead line, and the real-time voltage value of the overhead line is sent to the controller of the bidirectional DC / DC converter; the controller of the bidirectional DC / DC converter compares the real-time voltage value of the overhead line with the set threshold value, and controls the working mode of the DC / DC converter based on the comparison result.

[0020] Furthermore, the control steps of the controller of the bidirectional DC / DC converter are as follows:

[0021] Get the contact network voltage U gd and feeder current I k The working condition of the supercapacitor energy storage device is judged. The supercapacitor bank of the supercapacitor energy storage device is charged with constant power. The charging power P is proportional to the actual voltage U of the DC side obtained by sampling. d The result of the quotient is sent to the PI regulator, and the PI regulator outputs the result of the quotient as the expected current value of the supercapacitor current Current Expected Value Then compare with the actual current value I l The difference is sent to the PI regulator and limited, and then PWM modulation is performed to obtain the pulse signal for controlling the switch.

[0022] Based on the above technical solution, it is effectively avoided that the charging current or voltage is too large to damage the energy storage device when charging and discharging the ground energy storage system of regenerative braking energy on long slopes; and based on the above technical solution, the stability of the contact network voltage is maintained.

[0023] Furthermore, when the supercapacitor group is charged and discharged, the charge and discharge efficiency is improved by reducing the equivalent internal resistance of the supercapacitor group or increasing the charge and discharge voltage ratio of the supercapacitor group.

[0024] The beneficial effects of the present invention include:

[0025] Through the present invention, when a train is traveling down a long slope, the supercapacitor energy storage device is controlled to charge and absorb the regenerative braking energy generated by the train, thereby reducing the contact network voltage and restoring the contact network voltage to a normal range; when the train is traveling up a long slope, the supercapacitor energy storage device is controlled to release electric energy and increase the contact voltage and restore the contact network voltage to a normal range; thereby ensuring that the regenerative braking of the train will not fail, and improving the safety of train operation and the utilization rate of regenerative braking energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The regenerative braking energy ground energy storage system structure of the present invention;

[0027] Figure 2 is a schematic diagram of an equalizing circuit of the present invention;

[0028] Figure 3 It is a schematic diagram of the principle of the contact network real-time voltage detection device of the present invention;

[0029] Figure 4 This is a control principle block diagram of the DC / DC controller of the present invention. DETAILED DESCRIPTION

[0030] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application usually described and shown in the drawings here can be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0031] The following is combined with Figure 1 and attached Figure 4 The present invention is further described in detail:

[0032] A method for ground energy storage of regenerative braking energy on a long and steep slope comprises the following steps:

[0033] See attached Figure 1 , establish a supercapacitor energy storage device, connect the bidirectional DC / DC converter of the supercapacitor energy storage device to the DC side of the converter, and connect the AC side of the converter to the end of the power supply arm and the track;

[0034] When the EMU train performs regenerative braking, the regenerative braking energy passes through the converter to step down the contact network voltage, and the stepped-down voltage is rectified to obtain a stable DC voltage. The DC voltage is then stepped down by a bidirectional DC / DC converter, and finally the stepped-down energy is input into the supercapacitor bank of the supercapacitor energy storage device for storage.

[0035] When there is an EMU train in traction state in the power supply arm, the supercapacitor energy storage device releases electrical energy.

[0036] Through the above technical solution of the present invention, when the train is running in the traction stage, the contact network will provide electricity to the train, and when the train is running in the braking stage, the braking energy will be fed back to the contact network. When the train is running on a long slope downhill, in order to maintain a uniform speed, braking measures need to be taken, which will generate a large amount of regenerative braking energy, so that the contact network voltage is high and exceeds the normal range. At this time, the energy storage device is charged to absorb the regenerative braking energy generated by the train, thereby reducing the contact network voltage, so that the contact network voltage is restored to the normal range; when the train is running on a long slope uphill, in order to maintain a uniform speed, the traction power needs to be increased, so that the contact network voltage is reduced and below the normal range. At this time, the supercapacitor energy storage device releases electric energy, increases the contact network voltage, and restores the contact network voltage to the normal range; therefore, a series of problems caused by a significant increase in the contact network voltage can be avoided.

[0037] The converter steps down the voltage at a voltage ratio of 25:1, and steps down the AC voltage of 25 kV / 50 Hz of the power grid to 1000 V / 50 Hz.

[0038] The bidirectional DC / DC converter reduces the DC voltage to 2000V.

[0039] The bidirectional DC / DC converter includes a boost mode and a buck mode. When the train goes downhill on a long slope, the bidirectional DC / DC converter is in the buck mode; when the train goes uphill on a long slope, the bidirectional DC / DC converter is in the boost mode.

[0040] Through the above two working modes of the bidirectional DC / DC converter, the charging and discharging of the supercapacitor energy storage device is realized by relying on the change of current while keeping the voltage polarity unchanged.

[0041] See attached Figure 3 In this embodiment, it also includes obtaining the voltage of the contact network, adjusting the charging and discharging state of the supercapacitor energy storage device based on the obtained contact network voltage, charging the supercapacitor energy storage device when the contact network voltage is greater than a threshold, and discharging the supercapacitor energy storage device when the contact network voltage is less than a threshold.

[0042] The steps for obtaining the electric grid voltage are as follows:

[0043] The voltage of the electric contact grid is divided by a voltage divider, and the divided voltage is sent to a high-precision voltage sensor through a four-layer shielded cable, and a voltage signal is obtained based on the high-precision voltage sensor;

[0044] The signal conditioner divides the voltage signal obtained by the high-precision voltage sensor, performs analog filtering on the divided voltage signal, and converts the analog signal into a digital signal;

[0045] The voltage signal converted into a digital signal is sent to the overhead line voltage detection data processing workstation for digital filtering to obtain the real-time voltage value of the overhead line, and the real-time voltage value of the overhead line is sent to the controller of the bidirectional DC / DC converter; the controller of the bidirectional DC / DC converter compares the real-time voltage value of the overhead line with the set threshold value, and controls the working mode of the DC / DC converter based on the comparison result.

[0046] See attached Figure 4 , the control steps of the controller of the bidirectional DC / DC converter are as follows:

[0047] Get the contact network voltage U gd and feeder current I k The working condition of the supercapacitor energy storage device is judged. The supercapacitor bank of the supercapacitor energy storage device is charged with constant power. The charging power P is proportional to the actual voltage U of the DC side obtained by sampling. d The result of the quotient is sent to the PI regulator, and the PI regulator outputs the result of the quotient as the expected current value of the supercapacitor current Current Expected Value Then compare with the actual current value I l The difference is sent to the PI regulator and limited, and then PWM modulation is performed to obtain the pulse signal for controlling the switch.

[0048] Based on the above technical solution, it is effectively avoided that the charging current or voltage is too large to damage the energy storage device when charging and discharging the ground energy storage system of regenerative braking energy on long slopes; and based on the above technical solution, the stability of the contact network voltage is maintained.

[0049] When the supercapacitor group is charged and discharged, the charge and discharge efficiency is improved by reducing the equivalent internal resistance of the supercapacitor group or increasing the charge and discharge voltage ratio of the supercapacitor group.

[0050] The supercapacitor group of the present invention is firstly formed by connecting a plurality of supercapacitors in series to form a supercapacitor unit, and then connecting a plurality of supercapacitor units in parallel to form the supercapacitor group.

[0051] There are two problems with the supercapacitor group formed by the above series-parallel connection: First, the voltage of each supercapacitor cell in the supercapacitor group is different, which leads to a decrease in the energy storage rate of the supercapacitor group; second, due to production process problems, the capacitance of each supercapacitor cell will have a certain deviation, so that when the supercapacitor group is charged, the voltage of each supercapacitor cell is not uniform. When the voltage at both ends of some supercapacitor cells exceeds the rated voltage, the supercapacitor cells will be instantly broken down. If the above two problems are not handled, the life of the supercapacitor group will be greatly reduced, and even cause explosion accidents.

[0052] So Figure 2 As shown, the input and output voltages are controlled by a voltage balancing circuit connected in parallel at both ends of the supercapacitor. When the voltage at the end of the supercapacitor reaches the maximum withstand voltage, an instantaneous increase in current will pass through the supercapacitor, thereby reducing the voltage to ensure that the supercapacitor always works within the rated voltage range. When designing a voltage balancing circuit, the larger the value of the voltage divider resistor in the circuit, the smaller the energy consumption generated by the voltage divider resistor.

[0053] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A method for ground energy storage of regenerative braking energy on long and steep slopes, It is characterized in that The following steps are involved: Establish a supercapacitor energy storage device, connect the bidirectional DC / DC converter of the supercapacitor energy storage device to the DC side of the converter, and connect the AC side of the converter to the end of the power supply arm and the track; When the EMU train performs regenerative braking, the regenerative braking energy passes through the converter to step down the contact network voltage, and the stepped-down voltage is rectified to obtain a stable DC voltage. The DC voltage is then stepped down by a bidirectional DC / DC converter, and finally the stepped-down energy is input into the supercapacitor bank of the supercapacitor energy storage device for storage. When there is an EMU train in traction state in the power supply arm, the supercapacitor energy storage device releases electrical energy; The method also includes obtaining a voltage of the contact network, adjusting a charge and discharge state of the supercapacitor energy storage device based on the obtained contact network voltage, charging the supercapacitor energy storage device when the contact network voltage is greater than a threshold value, and discharging the supercapacitor energy storage device when the contact network voltage is less than the threshold value; The steps for obtaining the contact network voltage are as follows: The contact network voltage is divided by a voltage divider, and the divided voltage is sent to a high-precision voltage sensor through a four-layer shielded cable, and a voltage signal is obtained based on the high-precision voltage sensor; The signal conditioner divides the voltage signal obtained by the high-precision voltage sensor, performs analog filtering on the divided voltage signal, and converts the analog signal into a digital signal; The control steps of the controller of the bidirectional DC / DC converter are as follows: Get the voltage of the contact network and feeder current The working condition of the supercapacitor energy storage device is judged. The supercapacitor bank of the supercapacitor energy storage device is charged with constant power. The charging power P is proportional to the actual voltage on the DC side obtained by sampling. The result of the quotient is sent to the PI regulator, and the PI regulator outputs the result of the quotient as the expected current value of the supercapacitor current , current expected value Then compare with the actual current value The difference is sent to the PI regulator and limited, and then PWM modulation is performed to obtain the pulse signal for controlling the switch.

2. A method for ground energy storage of regenerative braking energy on a long slope according to claim 1, It is characterized in that The converter steps down the voltage at a voltage ratio of 25:1, and steps down the AC voltage of 25 kV / 50 Hz of the power grid to 1000 V / 50 Hz.

3. A method for ground energy storage of regenerative braking energy on a long and steep slope according to claim 1, It is characterized in that The bidirectional DC / DC converter reduces the DC voltage to 2000V.

4. A method for ground energy storage of regenerative braking energy on a long slope according to claim 1, It is characterized in that The bidirectional DC / DC converter includes a boost mode and a buck mode. When the train goes downhill on a long slope, the bidirectional DC / DC converter is in the buck mode; when the train goes uphill on a long slope, the bidirectional DC / DC converter is in the boost mode.

5. The method for ground energy storage of regenerative braking energy on a long slope according to claim 1, It is characterized in that The step of obtaining the contact network voltage also includes: The voltage signal converted into a digital signal is sent to the overhead line voltage detection data processing workstation for digital filtering to obtain the real-time voltage value of the overhead line, and the real-time voltage value of the overhead line is sent to the controller of the bidirectional DC / DC converter; the controller of the bidirectional DC / DC converter compares the real-time voltage value of the overhead line with the set threshold value, and controls the working mode of the DC / DC converter based on the comparison result.

6. A method for ground energy storage of regenerative braking energy on a long and steep slope according to claim 1, It is characterized in that When the supercapacitor group is charged and discharged, the charge and discharge efficiency is improved by reducing the equivalent internal resistance of the supercapacitor group or increasing the charge and discharge voltage ratio of the supercapacitor group.

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