CN109004673B - Direct-current voltage detection and control method for subway regenerative energy feedback device - Google Patents

Direct-current voltage detection and control method for subway regenerative energy feedback device Download PDF

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CN109004673B
CN109004673B CN201810895656.2A CN201810895656A CN109004673B CN 109004673 B CN109004673 B CN 109004673B CN 201810895656 A CN201810895656 A CN 201810895656A CN 109004673 B CN109004673 B CN 109004673B
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voltage
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direct current
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feedback device
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胡磊磊
李锦�
仇志凌
陈蕾
张明
芮国强
葛文海
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Nanjing Apaitek Technology Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract

The invention relates to a direct-current voltage detection and control method of a regenerative energy feedback device of a subway. A voltage detection and protection method is provided for solving the disturbance problem existing in a direct current traction network. Disturbance time superposed in a direct current network system in a subway power supply system is generally microsecond, and when interference occurs, the disturbance time superposed in the direct current network system can be effectively filtered by adopting the method, so that error protection of equipment is prevented; when the direct current power grid has real overvoltage or undervoltage faults, the protection time does not exceed 1ms, and the response time requirement of the system is completely met. Aiming at the problem of low circulation or response speed caused by alternating voltage fluctuation, a control method of direct voltage starting threshold and control self-adaption is provided. The method is simple to implement, so that the problem of circulation or over-slow response speed caused by alternating current network pressure fluctuation is effectively solved.

Description

Direct-current voltage detection and control method for subway regenerative energy feedback device
Technical Field
The invention relates to the technical field of power electronics and automatic detection and control, in particular to a direct-current voltage detection and control method of a subway regenerative energy feedback device.
Background
The ground-based subway regenerative braking energy inversion feedback device (hereinafter referred to as energy feedback device) is installed in a traction voltage reduction hybrid substation of a subway station, and when a subway vehicle enters the station, mechanical energy generated during subway braking can be converted into alternating current electric energy and fed back to a power grid for being used by a station load or other traction vehicles, so that the aim of recycling regenerative braking energy is fulfilled. When the device works in a rectification mode, the device can be matched with a traction rectifier set to provide energy for a direct current side at the same time, the output of the traction rectifier set can be reduced, and the reliability of a power supply system of the subway vehicle is improved.
The subway power supply system needs to ensure high reliability, the direct current end of the energy feeder is connected with a direct current traction network, the alternating current end of the energy feeder is connected with a medium-voltage power grid of alternating current 35kV (10kV), wherein the direct current traction network voltage is obtained by the medium-voltage alternating current power grid through a rectifier unit, and therefore a high requirement is provided for the control stability of the energy feeder. In order to improve the stability and steady-state accuracy of the energy-fed device, a double closed-loop control strategy of combining a voltage outer loop with a current inner loop is generally adopted. The direct current side voltage is detected in real time, when the voltage exceeds a starting threshold value of equipment due to energy during braking, a closed-loop control mode is started, the direct current voltage is controlled at a target value, energy flows in two directions, and the energy feedback or traction rectification function is achieved.
In the above-mentioned dual closed-loop control strategy, the method for detecting and controlling the dc-side grid voltage becomes more critical. But the rapidity and accuracy of the detection algorithm. The speed of a detection algorithm can influence the response speed of a closed-loop system, and if only instantaneous value detection is adopted for protection, equipment can often misreport direct current overvoltage or undervoltage faults to cause misoperation of the device due to the fact that the subway power supply system has large interference and burrs; the detection of the effective value can ensure the accuracy of the detection, but the response speed can become slow, and the rapidity of the device tracking is influenced.
The control of the dc side voltage, the current control method is basically to directly sample the dc incoming line voltage and compare it with the threshold value of the starting voltage of the energy feeding device, and once the threshold value is set, the threshold value will remain unchanged during operation. If the braking energy exceeds the braking energy, the equipment starts to perform inversion feedback (or traction rectification), and the process of inversion feedback (or traction rectification) is stopped when the braking (or traction) energy is gradually reduced to zero. When the alternating current network voltage is higher or lower, the direct current side network voltage can change correspondingly, so that under the condition of fixing the starting voltage threshold, when the alternating current network voltage is too high, the no-load voltage of the direct current side diode rectifier unit can exceed the starting voltage threshold, a circulation current is generated between the diode rectifier unit and the energy feedback device, and the loss of equipment is increased; when the ac network voltage is too low, the response speed of feedback is too slow under the condition that the start threshold is fixed.
Disclosure of Invention
1. The technical problem to be solved is as follows:
in order to solve the technical problems, the method provides a direct-current voltage detection and control method of a subway regeneration energy feedback device. The method effectively eliminates misjudgment caused by burrs, interference and the like by detecting and protecting the direct-current side voltage of the energy feedback device, and ensures the rapidity and the accuracy of detection; the method also provides a method for dynamically adjusting the direct current starting voltage threshold value of the energy feeding device and simultaneously determining the direct current voltage reference value, can solve the problem that the circulating current or the response speed possibly generated by overhigh or overlow voltage of the alternating current side becomes slow, and ensures the reliability of the operation of equipment.
2. The technical scheme is as follows:
a direct-current voltage detection and control method for a regenerative energy feedback device of a subway is characterized by comprising the following steps: the method comprises the following steps: detecting and protecting the direct-current side voltage of the energy feedback device; the method specifically comprises the following steps:
1.1 DC Voltage sensor device to subway renewable energy feedback device DC side with preset sampling frequency fNCollecting a voltage value, wherein the collected direct current voltage instantaneous value is Vdc; and inputting the collected direct current voltage instantaneous value Vdc into the controller through the AD sampling unit.
1.2 the controller will receive the voltage instantaneous value Vdc and the preset overvoltage protection value VOVUndervoltage protection value VLVA real-time comparison is performed. If the instantaneous value Vdc of the DC voltage is detected to be greater than the overvoltage protection value VOVAt the moment, the voltage on the direct current side of the subway regenerative energy feedback device has the possibility of overvoltage; step 1.3 is performed. If the instantaneous value Vdc of the direct current voltage is detected to be less than the preset undervoltage protection value VLVAt the moment, the voltage on the direct current side of the subway regenerative energy feedback device has the possibility of undervoltage; step 1.4 is performed.
1.3 from the moment of detecting possible overvoltage, sampling the voltage on the direct current side of the subway regenerative energy feedback device for N times, and comparing the result of each sampling with the overvoltage protection value VOVComparing; if the sampling value is greater than the overvoltage protection value VOVJudging that the device really has overvoltage faults; if notThe sample value is greater than the overvoltage protection value VOVIf so, judging that no overvoltage fault exists, resetting the count value, judging that interference occurs, and continuing normal operation of the equipment.
1.4 from the moment of detecting possible undervoltage, sampling the voltage at the direct current side of the subway regenerative energy feedback device for N times, and comparing the sampling result and the undervoltage protection value VLVComparing; if the sampling value is less than the preset undervoltage protection value VLVJudging that the device really has an undervoltage fault; if no sampling value is less than the preset undervoltage protection value VLVIf so, judging that no undervoltage fault exists, resetting the count value, judging that interference occurs, and continuing normal operation of the equipment. Wherein the N value is selected and the sampling frequency fNCorrelation, satisfying the relationship:
Figure BDA0001758076090000021
step two: dynamically adjusting the direct current starting voltage threshold value and determining a direct current voltage reference value; the specific process comprises the following steps:
2.1 collecting the DC side voltage of the energy feedback device, and presetting the initial value V of the starting voltage threshold according to the collected resultth0At this time, the rated value U of the AC side grid voltage is correspondedSN。
2.2, acquiring three-phase voltages Usa, Usb and Usc at an alternating current end of the subway regenerative energy feedback device in real time by using a voltage sensor, and inputting the three-phase voltages Usa, Usb and Usc into a controller through AD conversion; the controller calculates the effective value U of the three-phase AC network voltagearms、Ubrms、UcrmsAnd calculating the average value of the effective values of the three-phase alternating current grid voltage: usav ═ (Uarms + Ubrms + Ucrms)/3.
2.3 define the dc voltage regulation coefficient Kus ═ Usav/USN。
2.4 real-time value V defining the threshold of the starting voltageth：Vth＝VthoKu s, reference value of dc voltage control: vref is Vth- Δ v; wherein, Δ v is overshoot, has a voltage of tens of volts, is a positive value in the inversion feedback mode, and is a negative value in the rectification mode.
3. Has the advantages that:
(1) the method provides a voltage detection and protection method aiming at the disturbance problem existing in the direct current traction network. Because the disturbance time superposed in a direct current network system in a subway power supply system is generally microsecond, when interference occurs, the invention can effectively filter the interference superposed in the direct current network, thereby preventing the error protection of equipment; when the direct current power grid has real overvoltage or undervoltage faults, the protection time does not exceed 1ms, so that the response time requirement of the system is completely met, and the stable operation of the device is ensured.
(2) The method provides a direct-current voltage starting threshold value and control self-adaptive control method aiming at the problem of low circulation or response speed caused by alternating-current voltage fluctuation. The method is simple to implement, and can dynamically adjust the direct current starting voltage threshold value and the reference value in real time, so that the problem of circulation current or over-slow response speed caused by alternating current network voltage fluctuation is effectively avoided.
Drawings
FIG. 1 is a flow chart of DC side voltage detection and protection in the present invention;
fig. 2 is a control flow chart of the dynamic adjustment and determination of the dc start voltage threshold value according to the present invention.
Detailed Description
The method is described in detail below with reference to the accompanying drawings.
Fig. 1 shows a flow chart of detecting and protecting the dc side voltage in the present invention, which shows that the dc side voltage of the feedable device is detected and protected; the method specifically comprises the following steps: 1.1 DC Voltage sensor device to subway renewable energy feedback device DC side with preset sampling frequency fNCollecting a voltage value, wherein the collected direct current voltage instantaneous value is Vdc; and inputting the collected direct current voltage instantaneous value Vdc into the controller through the AD sampling unit. 1.2 the controller will receive the voltage instantaneous value Vdc and the preset overvoltage protection value VOVUndervoltage protection value VLVA real-time comparison is performed. If the instantaneous value Vdc of the DC voltage is detected to be greater than the overvoltage protection value VOVAt the moment, the voltage on the direct current side of the subway regenerative energy feedback device has the possibility of overvoltage; step 1.3 is performed. If the instantaneous value Vdc of the direct current voltage is detected to be less than the preset undervoltage protection value VLVAt the moment, the voltage on the direct current side of the subway regenerative energy feedback device has the possibility of undervoltage; step 1.4 is performed. 1.3 from the moment of detecting possible overvoltage, sampling the voltage on the direct current side of the subway regenerative energy feedback device for N times, and comparing the result of each sampling with the overvoltage protection value VOVComparing; if the sampling value is greater than the overvoltage protection value VOVJudging that the device really has overvoltage faults; if no sampling value is greater than the overvoltage protection value VOVIf so, judging that no overvoltage fault exists, resetting the count value, judging that interference occurs, and continuing normal operation of the equipment. 1.4 from the moment of detecting possible undervoltage, sampling the voltage at the direct current side of the subway regenerative energy feedback device for N times, and comparing the sampling result and the undervoltage protection value VLVComparing; if the sampling value is less than the preset undervoltage protection value VLVJudging that the device really has an undervoltage fault; if no sampling value is less than the preset undervoltage protection value VLVIf so, judging that the undervoltage fault does not exist, resetting the count value, judging that the interference occurs, and continuing normal operation of the equipment; wherein the N value is selected and the sampling frequency fNCorrelation, satisfying the relationship:
Figure BDA0001758076090000041
in the process, the direct-current voltage sensor collects the direct-current voltage instantaneous value Vdc in real time, the direct-current voltage instantaneous value Vdc is sent to the AD sampling unit of the controller, and the direct-current voltage is sampled at the sampling frequency fNSampling in real time and comparing with overvoltage protection value VOVUndervoltage protection value VLVComparing in real time, if no overvoltage or undervoltage fault exists, the device operates normally; when detecting that a direct current overvoltage or undervoltage fault occurs at a certain moment, timing from the moment, continuously sampling for N times, and comparing and judging whether overvoltage or undervoltage occurs or not in each sampling. If an overvoltage or undervoltage signal still exists after the judgment, the fault is judged to be really happened,the device will immediately block the pulse and perform a shutdown action. If the fault signal disappears after the judgment, the count value is cleared, and the device keeps normal operation and is not influenced.
Fig. 2 is a control flow chart for dynamically adjusting the dc start voltage threshold and determining the dc voltage reference value, which includes the following steps: 2.1 collecting the DC side voltage of the energy feedback device, and presetting the initial value V of the starting voltage threshold according to the collected resultth0At this time, the rated value U of the AC side grid voltage is correspondedSN。
2.2, acquiring three-phase voltages Usa, Usb and Usc at an alternating current end of the subway regenerative energy feedback device in real time by using a voltage sensor, and inputting the three-phase voltages Usa, Usb and Usc into a controller through AD conversion; the controller calculates the effective value U of the three-phase AC network voltagearms、Ubrms、UcrmsAnd calculating the average value of the effective values of the three-phase alternating current grid voltage: usav ═ (Uarms + Ubrms + Ucrms)/3.
2.3 define the dc voltage regulation coefficient Kus ═ Usav/USN。
2.4 real-time value V defining the threshold of the starting voltageth：Vth＝VthoKu s, reference value of dc voltage control: vref is Vth- Δ v; wherein, Δ v is overshoot, has a voltage of tens of volts, is a positive value in the inversion feedback mode, and is a negative value in the rectification mode.
In the above process, according to the DC voltage sampling value, setting the initial value V of the starting voltage thresholdth0According to instantaneous values Usa, Usb and Usc of the AC power grid obtained by real-time sampling, the three-phase voltage is subjected to AD conversion and then is sent to a controller unit, and an effective value U of the three-phase AC power grid voltage is calculatedarms、Ubrms、UcrmsAnd calculating the average value Uav of the effective values of the three-phase alternating current network voltage as (Uarms + Ubrms + Ucrms)/3. Corresponding to AC side network voltage rated value USNCalculating the DC voltage regulation coefficient Kus ═ Uav/USN. The initial value V of the adjustment coefficient and the starting voltage thresholdth0Multiplying the two to obtain a real-time value of the starting voltage threshold: vth＝VthoKu s. Straight barThe galvanic voltage loop adopts proportional integral control (PI control), certain overshoot is realized during control, and the overshoot is recorded as delta v. The reference value of the dc voltage is Vref-Vth- Δ v, where Δ v is typically several tens of volts (overshoot is a positive value in the inverter feedback mode and a negative value in the rectifier mode).
By the detection control method, the device can effectively avoid pulse interference on a direct current side power grid in the normal operation process, and meanwhile, the device can respond to real voltage faults in time, so that the operation reliability of the device is maintained. Meanwhile, a direct-current voltage adjustment coefficient K is obtained by monitoring the real-time fluctuation condition of the alternating-current side network voltageusThe adjustment coefficient is added into a direct current voltage starting threshold value and a reference value, so that negative effects of alternating current side network voltage fluctuation on direct current loop control can be effectively avoided, and long-term, reliable and stable operation of the energy feedback system is guaranteed.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (1)

1. A direct-current voltage detection and control method for a regenerative energy feedback device of a subway is characterized by comprising the following steps:
the method comprises the following steps: detecting and protecting the direct-current side voltage of the energy feedback device; the method specifically comprises the following steps:
1.1 DC Voltage sensor device to subway renewable energy feedback device DC side with preset sampling frequency fNCollecting a voltage value, wherein the collected direct current voltage instantaneous value is Vdc; inputting the collected direct current voltage instantaneous value Vdc into a controller through an AD sampling unit;
1.2 the controller will receive the voltage instantaneous value Vdc and the preset overvoltage protection value VOVUndervoltage protection value VLVPerforming real-time comparison;
if the instantaneous value Vdc of the DC voltage is detected to be greater than the overvoltage protection value VOVAt the moment, the voltage on the direct current side of the subway regenerative energy feedback device has the possibility of overvoltage; step 1.3 is carried out;
if the instantaneous value Vdc of the direct current voltage is detected to be less than the preset undervoltage protection value VLVAt the moment, the voltage on the direct current side of the subway regenerative energy feedback device has the possibility of undervoltage; step 1.4 is carried out;
1.3 from the moment of detecting possible overvoltage, sampling the voltage on the direct current side of the subway regenerative energy feedback device for N times, and comparing the result of each sampling with the overvoltage protection value VOVComparing; if the sampling value is greater than the overvoltage protection value VOVJudging that the device really has overvoltage faults; if no sampling value is greater than the overvoltage protection value VOVIf so, judging that no overvoltage fault exists, resetting the count value, judging that interference occurs, and continuing normal operation of the equipment;
1.4 from the moment of detecting possible undervoltage, sampling the voltage at the direct current side of the subway regenerative energy feedback device for N times, and comparing the sampling result and the undervoltage protection value VLVComparing; if the sampling value is less than the preset undervoltage protection value VLVJudging that the device really has an undervoltage fault; if no sampling value is less than the preset undervoltage protection value VLVIf so, judging that the undervoltage fault does not exist, resetting the count value, judging that the interference occurs, and continuing normal operation of the equipment;
wherein the N value is selected and the sampling frequency fNCorrelation, satisfying the relationship:
Figure FDA0003165106990000011
step two: dynamically adjusting the direct current starting voltage threshold value and determining a direct current voltage reference value; the specific process comprises the following steps:
2.1 collecting the DC side voltage of the energy feedback device, and presetting the initial value V of the starting voltage threshold according to the collected resultth0At this time, the rated value U of the AC side grid voltage is correspondedSN；
2.2 real-time acquisition of subway regenerative energy by voltage sensorThree-phase voltages Usa, Usb and Usc at the alternating current end of the feed device are input into the controller through AD conversion; the controller calculates the effective value U of the three-phase AC network voltagearms、Ubrms、UcrmsAnd calculating the average value of the effective values of the three-phase alternating current grid voltage: usav ═ (Uarms + Ubrms + Ucrms)/3;
2.3 define the dc voltage regulation coefficient Kus ═ Usav/USN；
2.4 real-time value V defining the threshold of the starting voltageth：Vth＝Vtho*Kus，
Reference value of the dc voltage control: vref is Vth- Δ v; wherein, Δ v is overshoot, has a voltage of tens of volts, is a positive value in the inversion feedback mode, and is a negative value in the rectification mode.
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