Intelligent energy storage measurement and control device and method for direct current traction

Abstract

The application discloses a kind of intelligent energy storage measurement and control device and method of direct current traction, and the device is set on the primary side or secondary side of rectifier transformer AC current detection unit and AC line voltage detection unit, and voltage sensor and current sensor are set on DC bus and DC feeder, and by the measurement unit connection energy storage device control interface.The measurement unit calculates the active power of rectifier unit AC side or the equivalent active current converted to DC side, and corrects no-load loss according to the detection position, and identifies traction, regeneration and no-load condition accordingly;When traction, control energy storage discharge according to the difference between feeder current and equivalent active current, when regeneration, control energy storage charging according to feeder current, and when feeder current is zero, set zero to charge and discharge command.The application does not use DC bus voltage threshold as condition criterion, which can avoid the risk of energy storage device refusal and misoperation, improve the utilization rate of regenerated energy, and avoid the risk of train electric brake failure.

Description

Technical Field

[0001] This application belongs to the field of DC traction power supply and energy storage control technology for rail transit, specifically relating to an intelligent energy storage measurement and control device and method for DC traction substations that uses the active power on the AC side of the rectifier unit to identify the operating conditions and controls the charging and discharging of the energy storage device accordingly. Background Technology

[0002] Urban rail transit trains frequently start and stop. During regenerative braking, the traction motor converts kinetic energy into electrical energy. The DC traction power supply system, using diode rectifier units, only allows electrical energy to flow from the AC grid to the DC traction grid; it cannot feed residual regenerative energy back to the AC grid. When a nearby traction train cannot absorb regenerative energy in time, the DC bus voltage rises. When it reaches a certain value, the rectifier unit shuts down, and the remaining energy is consumed by the braking resistor or by the train switching to mechanical (air) braking. This not only wastes energy but also increases the burden on tunnel cooling and environmental control systems.

[0003] One existing approach to recovering regenerative electrical energy is to connect an energy storage device to the DC traction substation and switch charging and discharging based on whether the DC bus voltage exceeds an activation threshold. While simple and easy to understand, this method has significant drawbacks: an excessively high threshold may cause the energy storage device to fail to activate, meaning it cannot charge in time, wasting energy and creating a risk of train electric brake failure, forcing the train to switch to mechanical braking. Conversely, an excessively low threshold may misinterpret traction voltage fluctuations as regenerative conditions, leading to false charging, circulating current, or additional losses. Another approach is to activate an energy feedback device based on a voltage threshold, but this also suffers from the problems of feedback device failure and false activation. Yet another approach involves using a test resistor on the DC side for operating condition identification, but the test element incurs additional losses, and under conditions of high DC current and wide measurement range, it is difficult to simultaneously achieve both measurement accuracy and economy, affecting practicality.

[0004] Therefore, it is necessary to establish a measurement and control link that does not use DC voltage threshold as the operating condition criterion, and to accurately identify traction, regeneration and no-load operating conditions by utilizing the physical characteristics of unidirectional energy transmission of diode rectifier units, and to perform charging and discharging control of energy storage devices consistent with the operating conditions. Summary of the Invention

[0005] The technical problem this application aims to solve is: addressing the issue that existing DC traction substation energy storage devices, which rely on voltage threshold control, are prone to failure to operate or malfunction. This application provides an intelligent energy storage measurement and control device and method that uses the active power on the AC side of the rectifier unit to characterize the rectification status, thereby identifying traction, regeneration, and no-load operating conditions. This method completes the identification of traction, regeneration, and no-load operating conditions without setting a DC test resistor, and enables the energy storage device to charge during regeneration and discharge during traction, achieving optimal energy saving and preventing train electric brake failure.

[0006] This application provides one or more embodiments of an intelligent energy storage monitoring and control device for a DC traction substation. The DC traction substation includes a three-phase high-voltage bus HB, a rectifier transformer TT1, a rectifier unit REC, an energy storage device SE, a DC bus DB, and a DC feeder F. The primary side of the rectifier transformer TT1 is connected to the three-phase high-voltage bus HB, and the secondary side is connected to the AC side of the rectifier unit REC. The DC side of the rectifier unit REC and the energy storage device SE are respectively connected to the DC bus DB, and the DC feeder F is connected to the overhead contact line. The intelligent energy storage monitoring and control device includes an AC current detection unit, an AC line voltage detection unit, a DC bus voltage sensor DYH, a DC feeder current sensor HCS, and a calculation unit MC. The AC current detection unit and the AC line voltage detection unit are located on the same side of the primary or secondary side of the rectifier transformer TT1. The DC bus voltage sensor DYH and the DC feeder current sensor HCS respectively acquire the DC bus voltage and the DC feeder current. Each detection signal is input to the calculation unit MC, which calculates the active power P on the AC side of the rectifier unit REC. rec or equivalent active current I rec According to the active power P rec or equivalent active current I rec It identifies traction, regenerative, and no-load operating conditions, and controls the energy storage device SE to charge or discharge through the control interface P.

[0007] In some embodiments, the rated voltage U of the DC bus DB N The voltage is 750 V or 1500 V, enabling the device to be adapted to common urban rail transit DC traction power supply systems.

[0008] In some embodiments, the energy storage device SE includes a bidirectional DC / DC converter and an energy storage unit SC, and the control interface P is connected to the control terminal of the bidirectional DC / DC converter.

[0009] In some embodiments, the AC current detection unit includes a first current transformer LH1, a second current transformer LH2, and a third current transformer LH3, with the three current transformers respectively installed on the same three-phase line on the primary or secondary side of the rectifier transformer TT1; the AC line voltage detection unit includes a first voltage transformer YH1 and a second voltage transformer YH2, with the two voltage transformers respectively connected across two sets of different phase-to-phase lines on the same side as the AC current detection unit.

[0010] One or more embodiments of this application also provide a smart energy storage measurement and control method for DC traction substations. The measurement unit MC acquires the three-phase current detected by the AC current detection unit, the AC line voltage detected by the AC line voltage detection unit, and the DC bus voltage U. DB and DC feeder current I D ; Calculate the active power P on the AC side of the rectifier unit REC based on the three-phase current and AC line voltage.rec And based on the active power P rec and DC bus voltage U DB The equivalent active current I converted to the DC side is obtained. rec Depending on whether the AC current detection unit is located on the primary or secondary side of the rectifier transformer TT1, the active power P is... rec or equivalent active current I rec No-load loss correction is performed, and the traction, regenerative or no-load conditions are identified based on whether the rectifier unit REC outputs active power to the DC bus DB. In the traction condition, a discharge control command is output, in the regenerative condition, a charging control command is output, and in the no-load condition, both the charging current command and the discharge current command are set to zero.

[0011] In some embodiments, when the AC current detection unit is located on the secondary side of the rectifier transformer TT1, if the P of the rectifier unit REC... rec Greater than zero or I rec If the value is greater than zero, meaning the rectifier unit REC is in rectification mode, then the DC bus DB is determined to be in traction mode; if the P value of the rectifier unit REC is greater than zero, then the DC bus DB is determined to be in traction mode. rec equal to zero or I rec If the value is zero, meaning the rectifier unit REC is in the off state, then the DC bus DB is determined to be in regenerative or no-load condition. When the AC current detection unit is located on the primary side of the rectifier transformer TT1, the no-load active power loss P0 of the rectifier transformer TT1 and its corresponding equivalent no-load active current I0 are obtained in advance; if the value of P0 in the rectifier unit REC is zero, it indicates that the DC bus DB is in regenerative or no-load condition. rec Greater than P0 or I rec If the value is greater than I0, meaning the rectifier unit REC is in rectification mode, then the DC bus DB is determined to be in traction mode; if the P value of the rectifier unit REC is greater than I0, then the DC bus DB is determined to be in traction mode. rec Less than P0 or I rec If the value is less than I0, meaning the rectifier unit REC is in the off state, then the DC bus DB is determined to be in regeneration or no-load operation.

[0012] In some embodiments, under traction conditions, the calculation unit MC calculates the traction current I of the DC feeder. D Equivalent active current I rec The discharge current command is determined by the allowable discharge current of the energy storage device SE, causing the discharge current I of the energy storage device SE to... dis =I D -I rec And not greater than the maximum allowable discharge current of the energy storage device SE.

[0013] In some embodiments, under regenerative operation, the measurement unit MC issues a charging current command, causing the charging current I of the energy storage device SE to... ch =I D And not greater than the maximum allowable charging current of the energy storage device SE; where, ID =0 corresponds to no-load operating condition.

[0014] In some embodiments, the calculation unit MC calculates based on the DC bus voltage U. DB Charging current I ch and discharge current I dis Accumulated charging energy E cha and discharge electrical energy E dis Daily and monthly reports are generated; at the same time, the DC bus voltage change curves under traction, regenerative and no-load conditions are recorded respectively, and the DC bus voltage change curves are compared with the preset voltage threshold and the operation records when voltage threshold control is used.

[0015] The beneficial effects of this application are as follows:

[0016] 1. Utilizing the inherent characteristic that diode rectifier units can only transfer active power from the AC side to the DC side, the active power or equivalent active current on the AC side is used to characterize whether the rectifier unit is in rectification mode. Based on this, traction operation or regeneration and no-load operation can be identified, and the DC bus voltage threshold is no longer used as the operating condition criterion, thus avoiding the risk of energy storage devices failing to operate or operating erroneously.

[0017] 2. In traction conditions, press I dis =I D -I rec Determine the discharge current, and apply it according to I during regeneration. ch =I D The charging current is determined and constrained by the maximum allowable discharge current and the maximum allowable charging current of the energy storage device, so that the direction of operation and the magnitude of the current of the energy storage device are matched with the energy flow on site.

[0018] 3. The AC current detection unit and the AC line voltage detection unit can be set on the primary or secondary side of the rectifier transformer; when detecting on the primary side, the rectification status is judged by correcting the no-load active power loss, and when detecting on the secondary side, the judgment is made directly based on the AC input active power of the rectifier unit, which can take into account both new projects and the renovation of existing DC traction substations.

[0019] 4. No test resistor needs to be connected in parallel on the DC side, which avoids additional losses in the test branch.

[0020] 5. By accumulating charging and discharging energy and recording DC bus voltage curves under different operating conditions, traceable operation evaluation data can be generated, providing a basis for energy-saving effect assessment and control parameter verification.

[0021] The working principle of the technical solution in this application is as follows:

[0022] The diode rectifier unit REC of the DC traction substation can only send electrical energy from the AC side to the DC side: When the train is traction, the AC power is sent to the DC bus DB through the rectifier transformer TT1 and the rectifier unit REC, and then supplied to the train through the DC feeder; when the train is regenerative braking, the regenerated power returns to the DC bus DB along the DC feeder, but cannot be sent back to the AC side through the diode rectifier unit REC. It can only be absorbed by the traction train in the same direction. The remaining part should be sent to the energy storage device SE for storage, and the energy should be released to the DC bus DB when the train needs power for traction.

[0023] To accurately determine the current operating condition, the calculation unit MC uses the three-phase current and line voltage on the AC side to calculate the active power of the rectifier unit REC. This determines whether the rectifier unit REC is drawing energy from the AC system and supplying power to the DC bus DB, i.e., whether it is in traction mode or non-traction (regenerative or no-load) mode. When the AC detection quantity is taken from the primary side of the rectifier transformer TT1, the calculation unit MC corrects for the transformer's no-load loss. When it is taken from the secondary side, it directly reflects the AC input active power of the rectifier unit REC.

[0024] The calculation unit MC forms a closed loop for operating condition identification and charge / discharge control based on the above detection results. When the rectifier unit REC outputs active power to the DC bus DB, the system is in traction mode, and the calculation unit MC calculates based on I... dis =I D -I rec Determine the discharge current command and ensure that the discharge current does not exceed the maximum allowable discharge current of the energy storage device SE; when the rectifier unit REC no longer outputs active power, the system is in regenerative or no-load condition, and the calculation unit MC calculates the DC feeder current I. D Determine the energy state. Under regenerative operation, the measurement unit MC calculates based on I. ch =I D Generate a charging current command and ensure that the charging current does not exceed the maximum allowable charging current of the energy storage device SE; when I D When the value is 0, corresponding to the no-load condition, the calculation unit MC sets both the charging current command and the discharging current command to zero. Therefore, the direction and magnitude of the energy storage device SE's operation correspond to the actual energy flow within the DC traction substation. Attached Figure Description

[0025] Figure 1 A schematic diagram of the overall structure of the intelligent energy storage and control device for DC traction substation when the AC current detection unit is set on the primary side of rectifier transformer TT1.

[0026] Figure 2 A schematic diagram of the overall structure of the intelligent energy storage measurement and control device for DC traction substation when the AC current detection unit is set on the secondary side of rectifier transformer TT1. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings. The described embodiments are used to explain this application, not to limit its scope of protection; where there is no technical conflict, technical features in different embodiments can be combined with each other.

[0028] One specific embodiment of this application provides an intelligent energy storage monitoring and control device for a DC traction substation, such as... Figure 1 or Figure 2 As shown in the diagram, the DC traction substation includes a three-phase high-voltage busbar HB, a rectifier transformer TT1, a diode rectifier unit REC, an energy storage device SE, a DC busbar DB, and a DC feeder F. The primary side of the rectifier transformer TT1 draws power from the three-phase high-voltage busbar HB, and the secondary side is connected to the AC side of the rectifier unit REC. The DC side of the rectifier unit REC and the energy storage device SE are respectively connected to the DC busbar DB. The DC feeder F is led out from the DC busbar DB and connected to the contact wire or the third rail, with the rail serving as the traction return current channel. The connections in the diagram are used to illustrate the power and signal paths and do not limit the specific number of switches, isolation devices, protection devices, and measuring terminals.

[0029] The intelligent energy storage monitoring and control device includes an AC current detection unit, an AC line voltage detection unit, a DC bus voltage sensor DYH, a DC feeder current sensor HCS, and a calculation unit MC. In this embodiment, the AC current detection unit includes a first current transformer LH1, a second current transformer LH2, and a third current transformer LH3. These three current transformers are respectively mounted or connected in series with phases A, B, and C on the same detection side, and are used to output sampling signals proportional to the three-phase AC current. The AC line voltage detection unit includes a first voltage transformer YH1 and a second voltage transformer YH2, which are respectively connected across two sets of different phase-to-phase lines on the same side as the AC current detection unit, and are used to obtain the line voltages of the two lines. The calculation unit MC can reconstruct the three-phase phase voltages based on the two line voltages, or it can directly use a three-phase power algorithm suitable for the combination of line voltage and line current.

[0030] Here, "same detection side" means that all three current transformers and the AC line voltage detection unit are located on the primary side of rectifier transformer TT1, or all on the secondary side of rectifier transformer TT1. Each AC current and AC line voltage should correspond to the same electrical side and use the same transformation ratio and phase sequence. If the current is taken from the primary side and the voltage from the secondary side, or if the phase sequence and polarity are inconsistent, it will introduce phase angle errors and affect the sign of the active power. Therefore, during wiring verification, the polarity, phase sequence, transformation ratio, and channel mapping relationship of the transformers should be checked.

[0031] A DC bus voltage sensor DYH is connected in parallel between the positive and negative terminals of the DC bus DB to measure the DC bus voltage U. DBThe DC feeder current sensor HCS is installed on the DC feeder F to measure the feeder current I. D .

[0032] The outputs of the three current transformers in the AC current detection unit, the two voltage transformers in the AC line voltage detection unit, the DC bus voltage sensor DYH, and the DC feeder current sensor HCS are respectively connected to the input of the calculation unit MC. The calculation unit MC can be implemented by an industrial controller, digital signal processor, programmable logic controller, embedded controller, or a combination control platform composed of the above devices, and has functions such as synchronous sampling, digital filtering, coordinate transformation, active power calculation, status judgment, limiting, hysteresis, delay, data storage, and communication.

[0033] The device scheme in this application comprehensively includes three links in terms of connection: AC-side active power detection, DC-side voltage and current detection, and energy storage control output. AC-side active power detection is used to determine whether the rectifier unit (REC) is drawing energy from the AC system and supplying power to the DC bus (DB); DC feeder current detection is used to determine whether the DC bus (DB) is currently absorbing or supplying electrical energy; and DC bus voltage detection is used for power conversion, energy accumulation, over-limit protection, and operation recording. These three types of information perform different functions, avoiding the inference of energy flow solely based on the DC bus voltage (threshold).

[0034] In one specific embodiment, the rated voltage U of the DC bus DB N The rated voltage is 750 V or 1500 V. This rated voltage is used to configure the range of the DC bus voltage sensor DYH, the withstand voltage level of the bidirectional DC / DC converter, and the series-parallel structure of the energy storage unit SC, and is not equivalent to the charge / discharge action threshold. For both 750 V and 1500 V systems, the calculation unit MC can store the corresponding allowable operating voltage range, insulation monitoring interlock values, and DC / DC converter protection parameters, respectively. The core of operating condition identification remains the rectified active power, which does not change due to different rated voltages used in the line.

[0035] In one specific embodiment, the energy storage device SE completely comprises a bidirectional DC / DC converter, an energy storage unit SC, and a control interface P. One side of the bidirectional DC / DC converter is connected to the DC bus DB, and the other side is connected to the energy storage unit SC. It can transfer energy from the DC bus to the energy storage unit SC during charging and transfer energy from the energy storage unit SC to the DC bus DB during discharging. The energy storage unit SC can be a DC interface unit corresponding to a supercapacitor, electrochemical battery, flywheel energy storage, or a combination thereof. The control interface P receives mode commands and current or power inputs from the measurement unit MC and feeds back readiness, fault, state of charge, allowable charging current, and allowable discharging current to the measurement unit MC.

[0036] When the first voltage transformer YH1 and the second voltage transformer YH2 constitute an AC line voltage detection unit, they can detect U respectively. AB and U BC In a three-phase three-wire system, the line voltage of the third phase can be obtained based on vector relationships. If a digital measuring device capable of providing synchronous three-phase voltage is available on-site, it can replace two independent voltage transformers. Regardless of the method used, the AC line voltage and three-phase current measurements should be synchronous enough to calculate the active power, and the sampling time deviation should preferably be less than the allowable phase angle error within one control cycle.

[0037] One specific embodiment of this application also provides an intelligent energy storage measurement and control method for DC traction substations. The method includes the following steps: S1, the measurement unit MC acquires the three-phase current detected by the AC current detection unit, the AC line voltage detected by the AC line voltage detection unit, and the DC bus voltage U. DB and DC feeder current I D S2, Calculate the active power P on the AC side of the rectifier unit REC based on the three-phase current and AC line voltage. rec And based on the active power P rec and DC bus voltage U DB The equivalent active current I converted to the DC side is obtained. rec S3, depending on the location of the AC current detection unit on the primary or secondary side of the rectifier transformer TT1, the active power P... rec or equivalent active current I rec Perform no-load loss correction and determine whether the rectifier unit REC outputs active power to the DC bus DB to identify traction, regenerative or no-load conditions; S4, output discharge control command in traction condition, output charging control command in regenerative condition, and set both charging current command and discharge current command to zero in no-load condition.

[0038] The instantaneous power method can be used to calculate P in the measurement unit MC. rec The reconstructed three-phase phase voltage u a u b u c and three-phase current i a i b i c For example, instantaneous active power can be expressed as p=u a ·i a +u b ·i b +u c ·i c P can be obtained by performing low-pass filtering or moving average on p for one or more fundamental periods. rec The three-phase voltage and current can also be transformed into a stationary or synchronously rotating coordinate system, and P can be calculated through the active axis components.rec The calculation methods may differ, but the direction information of active power should be preserved, and the influence of rectifier harmonics, commutation gaps, and sampling noise on the state determination should be suppressed.

[0039] To make the AC-side active power and DC feeder current have comparable dimensions, it can be based on I rec =P rec / U DB The equivalent active current I converted to the DC side is obtained. rec U DB Use the average DC bus voltage within the same sampling window; when U DB When the reading is below the effective lower limit of measurement or the sensor is invalid, the calculation unit MC does not perform division conversion, but maintains a safe state and reports a measurement fault. If the controller directly uses P... rec If used as a criterion, there is no need to perform current conversion, and I0 can be set equivalently in terms of power.

[0040] P rec This indicates the active power flowing into the rectifier transformer or rectifier unit at the AC detection location. rec This represents the equivalent active current calculated based on the DC bus voltage, not the effective value of any single phase current, nor a value obtained simply by adding the amplitudes of the three-phase currents. Using this interpretation, I... rec Both the DC feeder current and the energy storage charging and discharging current can be compared at the boundary according to the DC side current caliber, avoiding direct calculation of currents at different voltage levels or on different sides.

[0041] In one specific implementation, when the AC current detection unit is located on the secondary side of the rectifier transformer TT1, if P rec Greater than zero or I rec If the value is greater than zero, meaning the rectifier unit REC is in rectification mode, then the DC bus DB is determined to be in traction mode; if P rec equal to zero or I rec If the value is zero, meaning the rectifier unit REC is in the off state, then the DC bus DB is determined to be in regeneration or no-load operation.

[0042] In another specific embodiment, when the AC current detection unit is located on the primary side of the rectifier transformer TT1, the no-load active power loss P0 of the rectifier transformer TT1 is obtained in advance, and then I0 = P0 / U DB The corresponding equivalent no-load active current I0 is obtained; if P rec Greater than P0 or I rec If I is greater than I0, meaning the rectifier unit REC is in rectification mode, then the DC bus DB is determined to be in traction mode; if P rec Less than P0 or I recIf the value is less than I0, meaning the rectifier unit REC is in the off state, then the DC bus DB is determined to be in regenerative or no-load condition. During engineering implementation, a tolerance range can be set around P0 or I0 based on measurement errors to avoid frequent switching caused by critical sampling values.

[0043] The no-load active power loss P0 can be determined using transformer factory test values, field no-load test values, or values ​​identified from operating data. During field identification, multiple samples of the primary-side active power can be taken and statistically stable values ​​obtained when it is confirmed that the DC feeder has no traction or regenerative current, the energy storage device SE is locked, and the rectifier unit REC is not carrying a DC load. P0 can be corrected for different zones based on transformer temperature and AC line voltage, but the correction should not change its meaning as representing "the baseline active power when the primary side exists but the secondary side has no traction output."

[0044] In one specific implementation, the complete discharge control scheme under traction conditions is as follows: the calculation unit MC confirms that the rectifier unit REC is in rectification state, and obtains the DC feeder traction current I. D Equivalent active current I rec And the allowable discharge current of the energy storage device SE, according to I dis =I D -I rec Determine the discharge current command and ensure that the discharge current does not exceed the maximum permissible discharge current of the energy storage device SE. rec The equivalent active current converted to the DC side is used as a quantity for calculating the discharge current, rather than being directly subtracted from the phase current on different voltage sides.

[0045] In one specific implementation, the complete charging control scheme under regenerative operation is as follows: After the calculation unit MC confirms that the rectifier unit REC is not outputting active power and the DC feeder current is in a regenerative state, it issues a charging current command, according to I... ch =I D Determine the charging current, ensuring it does not exceed the maximum permissible charging current of the energy storage device SE. If I D As I decreases, the charging current command also decreases; when I... D When the value is 0, corresponding to the no-load condition, the charging current command drops to zero.

[0046] in I D When the maximum allowable charging current of the energy storage device SE is not reached, the charging current I ch Follow me D Change; when I DWhen the equipment reaches its maximum allowable limit, the charging current is constrained by the maximum allowable charging current of the energy storage device (SE). For DC traction substations with multiple feeders or multiple parallel energy storage devices, the sum of the regenerative currents of each feeder can be used as the basis for the absorbable current, and the charging instructions are allocated according to the allowable charging capacity of each energy storage device. If the energy storage unit is close to its maximum state of charge, exceeds the temperature limit, or the DC-DC converter is limited, the charging instructions are reduced; the regenerative energy not absorbed by the energy storage device is still handled by the traction vehicle, the adjacent traction substation, or the existing protection device according to the original coordination relationship.

[0047] The complete control scheme under no-load conditions is as follows: when the rectifier unit REC does not output identifiable active power and the DC feeder current I... D When I = 0, the calculation unit MC sets both the charging current command and the discharging current command to zero. In engineering implementation, the current amplitude detected by the DC feeder current sensor HCS within the zero current tolerance band can be considered as I... D =0. Under no-load conditions, it does not actively charge or discharge even when the DC bus voltage is at the high or low end of the allowable range, thus avoiding ineffective energy circulation between the rectifier unit, energy storage device, and line in order to maintain a certain fixed voltage value.

[0048] DC bus voltage U DB In this method, it is not a criterion for action in traction, regeneration, and no-load conditions, but it still serves as a safety protection and operational constraint function. When U DB When the charging voltage exceeds the allowable charging voltage of the energy storage device, falls below the allowable discharging voltage, or the sensor malfunctions, the calculation unit MC should override the normal operating condition command and execute current limiting, interlocking, or shutdown. Overvoltage, undervoltage, overcurrent, insulation, and temperature protection implemented by hardware protection devices are not eliminated by adopting this method; intelligent identification control and hardware protection form a hierarchical relationship.

[0049] In one specific implementation, the measurement unit MC fully performs charge / discharge energy statistics and voltage curve recording. During charging, according to U DB with I ch The product of these two components is integrated over the sampling period to obtain the charging energy E. cha During discharge, according to U DB with I dis The product integral yields the discharge energy E. dis Statistics can be summarized by day, month, train time period, or traction substation, and the number of charge / discharge cycles, duration, peak power, average power, and energy conversion efficiency should be recorded. In cases where DC-DC converter losses exist, measurements can be taken separately at the DC bus side and the energy storage unit side to distinguish between recovered energy and actual stored energy.

[0050] The measurement unit MC is marked with traction, regeneration, and no-load operating conditions respectively, and records U under each corresponding operating condition. DBThe curve shows the change in voltage. Comparing the curve with a preset voltage threshold allows evaluation of whether the bus voltage remains within the allowable range when this threshold is not used as the primary operating condition criterion. Comparing the charging and discharging energy and the highest bus voltage of this method with existing voltage threshold control records reveals the failure and maloperation situations of existing voltage threshold methods, and quantifies the accuracy of identification and the effectiveness of regenerative energy utilization. Statistical analysis and comparison are not involved in necessary real-time protection; therefore, short-term interruptions in data storage or communication should not disrupt basic charging and discharging control.

[0051] Figure 1 This illustration shows an implementation where the detection unit is located on the primary side of the rectifier transformer TT1. Three current transformers LH1 to LH3 and two voltage transformers YH1 and YH2 are positioned on the primary side, and the measured P... rec This includes the no-load active power loss of the rectifier transformer. During commissioning, P0 is first obtained under conditions of no traction, no regeneration, and energy storage lockout. Then, during operation, the active power exceeding P0 and its tolerance is considered to be related to the rectifier output. This arrangement is suitable for projects where there are already metering transformers on the primary side and the goal is to reduce the addition of new high-voltage equipment on the secondary side.

[0052] Figure 2 This illustration shows an implementation where the detection unit is located on the secondary side of the rectifier transformer TT1. Three current transformers LH1 to LH3 and two voltage transformers YH1 and YH2 are positioned on the secondary side, and the measured P... rec This arrangement more directly reflects the AC input active power of the rectifier unit, eliminating the need to deduct the primary-side no-load loss of the rectifier transformer from the measured value. It is suitable for projects where the secondary side has installation space or existing digital measurement equipment. Both the primary and secondary schemes use the same feeder current direction criteria, charging / discharging boundaries, and data recording logic.

[0053] Before commissioning the equipment, the following checks should be performed sequentially: channel verification, no-load reference verification, traction condition verification, and regenerative condition verification. Channel verification confirms the turns ratio, polarity, phase sequence, and timestamp of the three-phase current, line voltage, DC bus voltage, and feeder current. No-load reference verification confirms zero active power tolerance or P0 and I0. Traction condition verification confirms that the rectified active power and the feeder current in the traction direction are simultaneously established. Regenerative condition verification confirms that the rectified active power returns to the non-rectified range and the feeder current reverses. Automatic charging and discharging should not be directly activated if any sign contradiction occurs at any step.

[0054] The measurement unit MC can also be configured to determine measurement reliability. This includes conditions such as severe three-phase current imbalance, AC line voltage phase loss, and P... recWhen the DC-side power fails to meet the allowable error for an extended period, or when the DC bus voltage sensor and the internal voltage measurement of the DC-DC converter deviate significantly, the corresponding channel will be marked as invalid. When a measurement is invalid, the controller can lock the energy storage device, maintain zero-power standby, or switch to a degraded control mode as determined by a safety assessment. It will also record the original sampling data before and after the fault, facilitating maintenance personnel in identifying transformer, sensor, wiring, or communication faults.

[0055] For traction substations with multiple rectifier units connected in parallel, each rectifier unit can be equipped with an AC-side detection channel, and the active power of each unit can be summed to obtain the total rectified active power of the traction substation. Alternatively, a detection unit can be installed at the common AC incoming line where the total active power and no-load loss can be distinguished. When multiple units start and stop, P0 should be updated according to the actual number of rectifier transformers in operation. Energy storage control is still based on whether the total rectified active power exceeds the corresponding no-load reference and the direction of the combined power of the DC feeder.

[0056] Communication timeout and command verification can be set between the measurement unit MC and the energy storage device SE. When the control interface P uses communication mode, the control frame can include mode, setpoint, timestamp, incrementing sequence number, and verification information; the energy storage device feeds back the actual current, DC side voltage, state of charge, temperature, available power, and fault codes. If communication fails to update within the preset time, the sequence number is abnormal, or the setpoint and feedback value deviate too much for an extended period, the energy storage device will exit charging and discharging according to the preset slope, the measurement unit MC will record the fault and stop accumulating the charging and discharging energy during the invalid period.

[0057] Operating parameters can be saved separately by traction substation, rectifier unit combination, and time period. Parameters must include at least the transformer ratio, sensor zero point, P0 or I0, upper and lower limits of each tolerance band, hysteresis width, duration of judgment, charge / discharge slope, and allowable energy storage current. Parameter modifications should be subject to access control and version logging. After modification, a range check should be performed before the changes take effect in the zero-power state of the energy storage device. This prevents unverified parameters from directly altering the operating condition boundaries during train operation.

[0058] Daily and monthly reports can each provide E cha E dis Charge-discharge ratio, cumulative duration of regeneration operation, cumulative duration of traction discharge, maximum and minimum U DB The report includes the number of operating condition switching times and the number of abnormal lockout times. To evaluate energy-saving benefits, the energy stored for discharge can be analyzed in conjunction with the energy stored for charging, auxiliary losses, and energy storage attenuation costs under a unified metering boundary. The report does not change the real-time control logic; its purpose is to correlate the operating condition identification results, energy flow, and bus voltage performance, providing a basis for parameter verification and maintenance.

[0059] The aforementioned devices and methods can be used for both new DC traction substations and the retrofitting of existing lines. When retrofitting existing lines, AC transformers, DC bus voltage sensors, and feeder current sensors that meet accuracy, bandwidth, and isolation requirements can be reused, and connected to energy storage devices via a newly added calculation unit MC and control interface P. In this application, "connection" includes direct electrical connection, connection via sampling and conditioning circuit, connection via isolation module, and communication connection via fieldbus or network transmission of measured values ​​and control commands; "output charging control command or discharging control command" includes both output discrete mode quantities and output continuous current or power commands; "rectification state" refers to the state in which the diode rectifier unit obtains active power from the AC side and supplies power to the DC bus, and it is not required that there be no commutation pulsation at every instantaneous sampling point.

[0060] Without departing from the technical concept of this application, the AC line voltage detection unit can be a voltage transformer, an isolated voltage sensor, or a digital measuring device capable of providing synchronous AC line voltage data; the calculation unit MC and the energy storage device controller can be set separately or integrated into the same control device; the type, capacity, and series-parallel connection method of the energy storage unit SC can be determined according to the line regeneration power, duration, and economy.

[0061] Throughout the control process, the measurement unit (MC) filters measurement noise and short-term fluctuations through tolerance bands, hysteresis intervals, and continuous decision time, preventing the energy storage device (SE) from frequently switching near operating condition boundaries. When DC bus overvoltage, undervoltage, energy storage state exceeding limits, measurement anomalies, or equipment failures occur, safety protection and interlocking conditions take precedence over normal charging and discharging control. Simultaneously, the measurement unit (MC) records the DC bus voltage, charging and discharging current, and accumulated energy under different operating conditions, generating corresponding operating data. This allows operating condition identification, energy storage control, safety protection, and operational evaluation to constitute a complete working process.

[0062] The above embodiments describe the device connection, parameter meanings, operating condition criteria, charge / discharge boundaries, data statistics, and engineering extensions. For those skilled in the art, equivalent substitutions, conventional parameter adjustments, or combinations made without departing from the principles of this application are all included within the scope of the technical concept of this application.

Claims

1. A smart energy storage and control device for a DC traction substation, the DC traction substation comprising a three-phase high-voltage busbar HB, a rectifier transformer TT1, a rectifier unit REC, an energy storage device SE, a DC busbar DB, and a DC feeder F. The primary side of the rectifier transformer TT1 is connected to the three-phase high-voltage bus HB, the secondary side of the rectifier transformer TT1 is connected to the AC side of the rectifier unit REC, the DC side of the rectifier unit REC and the energy storage device SE are respectively connected to the DC bus DB, and the DC feeder F is connected to the contact network. The characteristic of this design is that... The intelligent energy storage monitoring and control device includes an AC current detection unit, an AC line voltage detection unit, a DC bus voltage sensor DYH, a DC feeder current sensor HCS, and a calculation unit MC. The AC current detection unit is installed on the same side of the three-phase line of the primary or secondary side of the rectifier transformer TT1; the AC line voltage detection unit is connected across two sets of different phase lines on the same side as the AC current detection unit. The DC bus voltage sensor DYH is installed on the DC bus DB, and the DC feeder current sensor HCS is installed on the DC feeder between the DC bus DB and the DC traction network. The output terminals of the AC current detection unit, the AC line voltage detection unit, the DC bus voltage sensor DYH, and the DC feeder current sensor HCS are respectively connected to the input terminal of the calculation unit MC, and the output terminal of the calculation unit MC is connected to the control interface P of the energy storage device SE. The calculation unit MC is used to calculate the active power P based on the current and voltage on the AC side of the rectifier unit REC. rec Or the equivalent active current I converted to the DC side rec According to the active power P rec or equivalent active current I rec It identifies traction, regeneration, and no-load conditions and outputs charging or discharging control commands to the control interface P.

2. The intelligent energy storage and control device for DC traction substations according to claim 1, characterized in that, The rated voltage U of the DC bus DB N It is 750 V or 1500 V.

3. The intelligent energy storage and control device for DC traction substations according to claim 1, characterized in that, The energy storage device SE includes a bidirectional DC / DC converter and an energy storage unit SC, and the control interface P is connected to the control terminal of the bidirectional DC / DC converter.

4. The intelligent energy storage and control device for DC traction substations according to claim 1, characterized in that, The AC current detection unit includes a first current transformer LH1, a second current transformer LH2, and a third current transformer LH3; the first current transformer LH1, the second current transformer LH2, and the third current transformer LH3 are respectively installed on the same three-phase line on the primary or secondary side of the rectifier transformer TT1; the AC line voltage detection unit includes a first voltage transformer YH1 and a second voltage transformer YH2; the first voltage transformer YH1 and the second voltage transformer YH2 are respectively connected across two sets of different phase lines on the same side as the AC current detection unit.

5. A smart energy storage measurement and control method for a DC traction substation, applied to a DC traction substation equipped with a rectifier transformer TT1, a diode rectifier unit REC, an energy storage device SE, a DC bus DB, an AC current detection unit, an AC line voltage detection unit, a DC bus voltage sensor DYH, a DC feeder current sensor HCS, and a calculation unit MC. Its features are, Includes the following steps: S1: The calculation unit MC acquires the three-phase current detected by the AC current detection unit, the AC line voltage detected by the AC line voltage detection unit, and the DC bus voltage U detected by the DC bus voltage sensor DYH. DB And the DC feeder current I detected by the DC feeder current sensor HCS D ; S2: The calculation unit MC calculates the active power P on the AC side of the rectifier unit REC based on the three-phase current and AC line voltage. rec And according to the active power P rec and DC bus voltage U DB The equivalent active current I converted to the DC side is obtained. rec ; S3: The calculation unit MC calculates the active power P based on the location of the AC current detection unit on the primary or secondary side of the rectifier transformer TT1. rec or equivalent active current I rec Perform no-load loss correction and determine whether the rectifier unit REC outputs active power to the DC bus DB to identify traction operation, regenerative operation or no-load operation; S4: In traction mode, output discharge control command to the energy storage device SE; in regeneration mode, output charging control command to the energy storage device SE; in no-load mode, set both charging current command and discharging current command of the energy storage device SE to zero.

6. The intelligent energy storage measurement and control method for DC traction substations according to claim 5, characterized in that, When the AC current detection unit is located on the secondary side of the rectifier transformer TT1, if the P of the rectifier unit REC... rec Greater than zero or I rec If the value is greater than zero, meaning the rectifier unit REC is in rectification mode, then the DC bus DB is determined to be in traction mode. If the P value of the rectifier unit REC is greater than zero... rec equal to zero or I rec If the value is zero, meaning the rectifier unit REC is in the off state, then the DC bus DB is determined to be in regeneration or no-load operation. When the AC current detection unit is located on the primary side of the rectifier transformer TT1, it pre-obtains the no-load active power loss P0 of the rectifier transformer TT1 and its corresponding equivalent no-load active current I0. If the P of the rectifier unit REC... rec Greater than P0 or I rec If I0 is greater than 0, meaning the rectifier unit REC is in rectification mode, then the DC bus DB is determined to be in traction mode. If the P value of the rectifier unit REC is greater than 0, then the DC bus DB is determined to be in traction mode. rec Less than P0 or I rec If the value is less than I0, meaning the rectifier unit REC is in a closed state, then the DC bus DB is determined to be in regeneration or no-load operation.

7. The intelligent energy storage measurement and control method for DC traction substations according to claim 5, characterized in that, Under traction conditions, the calculation unit MC calculates the traction current I of the DC feeder. D The equivalent active current I rec The discharge current command is determined based on the allowable discharge current of the energy storage device SE, causing the discharge current I of the energy storage device SE to... dis =I D - I rec And it shall not exceed the maximum allowable discharge current of the energy storage device SE.

8. The intelligent energy storage measurement and control method for DC traction substations according to claim 5, characterized in that, Under regeneration conditions, the calculation unit MC issues a charging current command, causing the charging current I of the energy storage device SE to... ch =I D And not greater than the maximum allowable charging current of the energy storage device SE, where I D =0, corresponding to no-load condition.

9. The intelligent energy storage measurement and control method for DC traction substations according to claim 5, characterized in that, The calculation unit MC is based on the DC bus voltage U DB Charging current I ch and discharge current I dis Accumulated charging energy E cha and discharge electrical energy E dis Daily and monthly reports are generated, and the DC bus voltage variation curves under traction, regenerative and no-load conditions are recorded respectively. The DC bus voltage variation curves are compared with the preset voltage threshold and the operation records when voltage threshold control is used.

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