Full-through flexible traction substation and energy management method thereof

Abstract

The invention discloses a full-through flexible traction substation and an energy management method thereof. The substation comprises a circuit breaker, a three-phase-single-phase converter, a filter circuit and an isolation transformer, the three-phase-single-phase converter comprises a three-phase input side, a single-phase output side and a filter circuit; each of the three-phase input side and the single-phase output side comprises an upper bridge arm unit, a lower bridge arm unit and a bridge arm inductor arranged between the upper bridge arm unit and the lower bridge arm unit; and the upper bridge arm unit and the lower bridge arm unit both adopt a modularized multi-level topological structure comprising a plurality of half-bridge sub-modules connected in series. The traction substation is designed according to the module multi-level topological structure, the problems that in the prior art, the occupied area is large, and noise pollution is large are solved, the multi-level topological structure can be expanded and designed according to the capacity requirement of the substation, and the power supply efficiency of the traction substation is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of traction power supply, and in particular to a fully-through flexible traction substation and an energy management method thereof. Background Art

[0002] At present, the existing traction substation uses traditional traction transformers to realize three-phase-two-phase power supply, and uses electric phase separation devices to realize zone power supply. In the prior art, the traditional traction transformer will generate noise pollution when working, and the zone power supply is realized by the electric phase separation device, and the actual power supply efficiency is not high. In addition, the capacity between the two substations cannot be used as backup for each other, so each substation needs to prepare a backup transformer, resulting in a certain capacity waste and low transformer utilization.

[0003] With the development of power electronics technology, through-type traction substations with power electronics equipment such as modular multilevel converters as core equipment can achieve adjustable and controllable voltage amplitude, phase, and frequency between different power supply arms and between different substations, thereby eliminating the phase separation within and between traction substations and improving the speed and load capacity of trains. At the same time, it can also solve energy quality problems such as reactive power, negative sequence and harmonics, and facilitate access to new energy and energy storage devices.

[0004] The existing traction substation with traditional traction transformer as the core is replaced by a through-type flexible traction substation based on modular multi-level converter. Due to the particularity of railway system trains as single-phase loads and the different working conditions of trains such as traction, braking, and inertia, the source-load relationship between the train and the traction substation will change continuously. Moreover, as the train moves in real time, the impedance of the load end will also change continuously. Therefore, in order to give full play to the advantages of flexible controllability of power electronic converters and access to new energy and energy storage, it is also necessary to study an energy management method suitable for fully through-type flexible traction substations with efficient energy utilization. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a fully-through flexible traction substation and an energy management method thereof.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0007] In a first aspect, a fully through flexible traction substation is provided, which includes a circuit breaker, a three-phase-single-phase converter, a filter circuit and an isolation transformer;

[0008] The three-phase-single-phase converter includes a three-phase input side, a single-phase output side and a filter circuit; the three-phase input side is connected to the three phases of the three-phase power grid through a circuit breaker, the single-phase output side is connected to the primary side of the isolation transformer through the filter circuit, and the secondary side of the isolation transformer is connected to the traction grid and the grounding rail through a circuit breaker;

[0009] The three-phase input side and the single-phase output side both include an upper bridge arm unit, a lower bridge arm unit, and a bridge arm inductor arranged between the upper bridge arm unit and the lower bridge arm unit; the upper bridge arm unit and the lower bridge arm unit both adopt a modular multi-level topology structure including multiple series-connected half-bridge sub-modules.

[0010] Furthermore, each half-bridge sub-module includes a first IGBT semiconductor switch, a second IGBT semiconductor switch, a support capacitor and a bypass switch; the first IGBT semiconductor switch and the second IGBT semiconductor switch are connected in series, the support capacitor and the bypass switch are connected in parallel with the first IGBT semiconductor switch and the second IGBT semiconductor switch, the anode side of the second IGBT semiconductor switch serves as the input side of the half-bridge sub-module, and the cathode side of the second IGBT semiconductor switch serves as the output side of the half-bridge sub-module.

[0011] Furthermore, the three-phase-to-single-phase converter is also provided with a control module for current inner loop control and power outer loop control and a modulation module for half-bridge sub-module modulation; the input of the control module is the electrical quantity parameter of the three-phase-to-single-phase converter, the output of the control module is the instantaneous value of the modulation wave, the input of the modulation module is the instantaneous value of the modulation wave output by the control module, and the output of the modulation module is the on and off signal of the IGBT semiconductor switch.

[0012] Furthermore, the control process of the control module is specifically as follows: obtaining the electrical quantity parameters of the three-phase-single-phase converter, constructing a mathematical model of the three-phase-single-phase converter in a three-phase rotating coordinate system based on the electrical quantity parameters of the three-phase-single-phase converter, converting it into a mathematical model of the three-phase-single-phase converter in a two-phase rotating coordinate system through Park transformation, and based on the mathematical model of the three-phase-single-phase converter in the two-phase rotating coordinate system, using a PI controller to design a current inner loop controller and a power outer loop controller to output the instantaneous value of the modulation wave.

[0013] Furthermore, the expression of the current inner loop controller is:

[0014]

[0015] Where: i vn (n=d,q) represents the three-phase grid-side input current in the two-phase rotating dq coordinate system in the frequency domain, d represents the d-axis in the dq coordinate system, q represents the q-axis in the dq coordinate system, s represents the complex frequency domain, u diffn(n=d,q) represents the common mode voltage of the upper and lower bridge arms of the three phases in the two-phase rotation dq coordinate system in the frequency domain, L is the inductance of the converter bridge arm, u sn (n=d,q) represents the three-phase grid-side input voltage in the two-phase rotating dq coordinate system, represents the reference current at the output side of the three-phase rectifier in the two-phase rotating dq coordinate system in the frequency domain, k p1 , k i1 , k p2 , k i2 is the proportional-integral coefficient of the PI controller, and ω is the angular frequency of the railway system.

[0016] Furthermore, the expression of the power outer loop controller is:

[0017]

[0018] Where: i vn (n=d,q) represents the three-phase grid-side input current in the two-phase rotating dq coordinate system in the frequency domain, d represents the d-axis in the dq coordinate system, q represents the q-axis in the dq coordinate system, s represents the complex frequency domain, Represents the given reference active power, Represents the given reference reactive power, P s Indicates active power, Q s Represents reactive power, U sm Indicates the effective value of the three-phase grid-side input voltage, i* vn (n=d,q) represents the reference current at the output side of the three-phase rectifier in the two-phase rotating dq coordinate system in the frequency domain, k p3 , k i3 , k p4 , k i4 is the proportional-integral coefficient of the PI controller.

[0019] Furthermore, the modulation process of the modulation module is specifically as follows: based on the instantaneous value of the modulation wave, the number of half-bridge sub-modules respectively put into use in the upper and lower bridge arms is calculated; according to the number of half-bridge sub-modules respectively put into use in the upper and lower bridge arms, the current current direction and the capacitance voltage of all half-bridge sub-modules, the nearest level approximation modulation strategy is used to determine the half-bridge sub-modules that need to be put into use, and the on and off signals of the IGBT semiconductor switch are generated to perform half-bridge sub-module modulation.

[0020] Furthermore, the expression for calculating the number of half-bridge sub-modules respectively put into the upper and lower bridge arms based on the instantaneous value of the modulation wave is:

[0021]

[0022] Where: n down Indicates the number of half-bridge submodules in the upper bridge arm, n upIndicates the number of half-bridge submodules in the lower bridge arm, n indicates the number of half-bridge submodules in each bridge arm, u refj (j=a,b,c) represents the instantaneous value of the modulation wave, a represents the a-axis in the abc coordinate system, b represents the b-axis in the abc coordinate system, c represents the c-axis in the abc coordinate system, Uc represents the average value of the capacitor voltage of the half-bridge submodule, and the round() function is a rounding function, which means taking the nearest integer.

[0023] In a second aspect, an energy management method applied to the above-mentioned fully-through flexible traction substation is provided, which comprises the following steps:

[0024] S1. Obtaining the energy flow model of the railway system based on the fully connected flexible traction substation;

[0025] S2. Based on the railway system energy flow model, setting the train in traction state to the first energy management mode, setting the train in braking state to the second energy management mode, and setting the train in non-operating state to the third energy management mode;

[0026] S3. Based on the first energy management mode, the second energy management mode and the third energy management mode, energy management is performed on the fully-through flexible traction substation.

[0027] Further, in step S2, the first energy management mode includes working condition 1, working condition 2, working condition 3 and working condition 4; the second energy management mode includes working condition 5, working condition 6, working condition 7 and working condition 8; the third energy management mode includes working condition 9; all working conditions are based on the management of the full-through flexible traction substation for energy transmission;

[0028] Working condition 1: The photovoltaic port and energy storage port are locked; energy is provided to the train load and station load through the three-phase grid port;

[0029] Working condition 2: The photovoltaic port is locked and the energy storage port is opened; the sum of the train operating power and the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 2-1, and energy is provided to the train load and the station load through the energy storage port in working condition 2-1; the sum of the train operating power and the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 2-2, and energy is provided to the train load and the station load through the energy storage port and the three-phase grid port in working condition 2-2;

[0030] Working condition 3: The energy storage port is locked and the photovoltaic port is opened; the photovoltaic power is greater than the sum of the train running power and the station load power, which is determined as working condition 3-1. In working condition 3-1, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is returned to the three-phase grid; the photovoltaic power is less than the sum of the train running power and the station load power, which is determined as working condition 3-2. In working condition 3-2, energy is provided to the train load and the station load through the photovoltaic port, and the difference energy is provided to the train load and the station load through the three-phase grid port;

[0031] Working condition 4: The photovoltaic port and the energy storage port are turned on; the photovoltaic port power is greater than the sum of the train running power and the station load power, and the sum of the photovoltaic port power minus the train running power and the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 4-1. In working condition 4-1, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is stored in the energy storage port; the photovoltaic port power is greater than the sum of the train running power and the station load power, and the sum of the photovoltaic port power minus the train running power and the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 4-2. In working condition 4-2, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is first stored in the energy storage port. After the energy storage port is fully charged, the excess energy of the photovoltaic port is stored in the energy storage port. The remaining energy is stored in the three-phase grid port; the photovoltaic port power is less than the sum of the train running power and the station load power, and the sum of the train running power and the station load power minus the photovoltaic port power is less than the maximum discharge power of the energy storage port, which is determined as operating condition 4-3. In operating condition 4-3, energy is provided to the train load and the station load through the photovoltaic port, and the difference energy is provided to the train load and the station load through the energy storage port; the photovoltaic port power is less than the sum of the train running power and the station load power, and the sum of the train running power and the station load power minus the photovoltaic port power is greater than the maximum discharge power of the energy storage port, which is determined as operating condition 4-4. In operating condition 4-4, energy is first provided to the train load and the station load through the photovoltaic port and the energy storage port, and then the difference energy is provided to the train load and the station load through the three-phase grid port;

[0032] Working condition 5: The photovoltaic port and the energy storage port are locked; the regenerative braking power is greater than the station load power, which is determined as working condition 5-1, and in working condition 5-1, the excess energy is returned to the three-phase grid port; the regenerative braking power is less than the station load power, which is determined as working condition 5-2, and in working condition 5-2, the difference energy is provided to the station load through the three-phase grid port;

[0033] Working condition 6: The photovoltaic port is locked and the energy storage port is opened; the regenerative braking power is less than the station load power, and the difference power required by the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 6-1. In working condition 6-1, the difference power is provided to the station load through the energy storage port; the regenerative braking power is less than the station load power, and the difference power required by the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 6-2. In working condition 6-2, the energy storage port is operated at maximum power discharge, and the three-phase grid port is operated at the difference power required by the station load power; the regenerative braking power is greater than the station load power, and the excess power of the railway system is less than the maximum charging power of the energy storage port, which is determined as working condition 6-3. In working condition 6-3, the excess regenerative braking energy is absorbed through the energy storage port; the regenerative braking power is greater than the station load power, and the excess power of the railway system is greater than the maximum charging power of the energy storage port, which is determined as working condition 6-4. In working condition 6-4, after the energy storage port is charged at maximum power, the remaining energy is returned to the three-phase grid;

[0034] Working condition 7: The photovoltaic port is turned on and the energy storage port is locked; the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, which is determined as working condition 7-1. In working condition 7-1, the remaining energy is returned to the three-phase grid port; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, which is determined as working condition 7-2. In working condition 7-2, the difference power required by the station load is used to supply energy through the three-phase grid port;

[0035] Working condition 8: Both the photovoltaic port and the energy storage port are turned on; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, and the difference power required by the railway system is less than or equal to the maximum discharge power of the energy storage port, which is determined as working condition 8-1. In working condition 8-1, the difference power required by the station load is supplied through the energy storage port; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, and the difference power required by the railway system is greater than the maximum discharge power of the energy storage port, which is determined as working condition 8-2. In working condition 8-2, the energy storage port is first discharged at maximum power, and then discharged through the three-phase grid port. Supply the difference power required by the station load; when the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, and the excess power in the railway system is less than the maximum charging power of the energy storage port, it is determined as working condition 8-3, and in working condition 8-3, the energy storage port is charged with the excess power of the railway system; when the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, and the excess power in the railway system is greater than the maximum charging power of the energy storage port, it is determined as working condition 8-4, and in working condition 8-4, the energy storage port is first charged with the maximum power, and then the remaining power of the railway system is returned to the three-phase power grid;

[0036] Working condition 9: The photovoltaic port is locked; the energy storage port is charged through the three-phase grid port. When the energy storage device is ≥80%, the energy storage port is locked.

[0037] The present invention has the following beneficial effects:

[0038] (1) The present invention solves the problems of large floor space and high noise pollution in the prior art by designing a traction substation according to a modular multi-level topology structure, and can also expand the design of the multi-level topology structure according to the substation capacity requirements, thereby improving the power supply efficiency of the traction substation;

[0039] (2) The present invention can adjust the amplitude and phase of the traction network voltage at any time by setting a control module and a modulation module in the three-phase-single-phase converter, thereby eliminating the electrical phase separation within and between traction substations, thereby improving the train running speed and load capacity;

[0040] (3) The present invention sets a bypass switch in the half-bridge submodule and connects the output of the half-bridge submodule in parallel with the bypass switch. When a half-bridge submodule fails to work, the present invention can bypass the half-bridge submodule by closing the bypass switch, and the remaining half-bridge submodules jointly output a single-phase voltage, thereby improving the reliability of the railway system power supply;

[0041] (4) The present invention obtains an energy flow model of the railway system based on a fully-through flexible traction substation, and then sets the train in the traction state to the first energy management mode, the train in the braking state to the second energy management mode, and the train in the non-running state to the third energy management mode based on the energy flow model of the railway system, so as to perform energy management on the fully-through flexible traction substation and realize the maximum efficient utilization of energy among the three-phase power grid, photovoltaic energy, energy storage and train braking energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the structure of a fully-through flexible traction substation;

[0043] Figure 2 A specific control block diagram of the three-phase to single-phase converter provided by the present invention;

[0044] Figure 3 A specific modulation block diagram of the three-phase to single-phase converter provided by the present invention;

[0045] Figure 4 It is a schematic diagram of the self-healing reconstruction of the three-phase-single-phase converter of the through-type flexible traction substation of the present invention;

[0046] Figure 5 Schematic diagram of energy flow under different working conditions in the present invention. DETAILED DESCRIPTION

[0047] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0048] like Figure 1 As shown, a fully through flexible traction substation includes a circuit breaker, a three-phase-single-phase converter, a filter circuit and an isolation transformer; the three-phase-single-phase converter includes a three-phase input side, a single-phase output side and a filter circuit; the three-phase input side is respectively connected to the circuit breaker QF 1 , QF 2 , QF 3 Then it is connected to the A phase, B phase and C phase of the three-phase power grid. The single-phase output side is connected to the primary side of the isolation transformer after passing through the filter circuit. The inductor L t and capacitor C f The circuit is a filter circuit. The secondary side of the isolation transformer is connected through the circuit breaker QF 4 , QF 5 The three-phase input side and the single-phase output side both include an upper bridge arm unit, a lower bridge arm unit, and a bridge arm inductor L arranged between the upper bridge arm unit and the lower bridge arm unit. 0 , the bridge arm inductance L in the three-phase to single-phase converter 0 The parameters are the same; both the upper bridge arm unit and the lower bridge arm unit adopt a modular multi-level topology structure including a plurality of series-connected half-bridge sub-modules SM1 to SMn.

[0049] In an optional embodiment of the present invention, the half-bridge submodules each include a first IGBT semiconductor switch S1, a second IGBT semiconductor switch S2, a support capacitor C and a bypass switch T; the first IGBT semiconductor switch and the second IGBT semiconductor switch are connected in series, the support capacitor and the bypass switch are both connected in parallel with the first IGBT semiconductor switch and the second IGBT semiconductor switch, the anode side of the second IGBT semiconductor switch serves as the input side of the half-bridge submodule, and the cathode side of the second IGBT semiconductor switch serves as the output side of the half-bridge submodule. The parameters of the support capacitor C in the three-phase-single-phase converter are the same.

[0050] In an optional embodiment of the present invention, the three-phase-single-phase converter is also provided with a control module for current inner loop control and power outer loop control and a modulation module for half-bridge sub-module modulation; the input of the control module is the electrical quantity parameter of the three-phase-single-phase converter, the output of the control module is the instantaneous value of the modulation wave, the input of the modulation module is the instantaneous value of the modulation wave output by the control module, and the output of the modulation module is the on and off signal of the IGBT semiconductor switch.

[0051] The control process of the control module is specifically as follows: obtaining the electrical quantity parameters of the three-phase-single-phase converter, constructing a mathematical model of the three-phase-single-phase converter in a three-phase rotating coordinate system based on the electrical quantity parameters of the three-phase-single-phase converter, converting it into a mathematical model of the three-phase-single-phase converter in a two-phase rotating coordinate system through Park transformation, and based on the mathematical model of the three-phase-single-phase converter in a two-phase rotating coordinate system, using a PI controller to design a current inner loop controller and a power outer loop controller to output the instantaneous value of the modulation wave, as shown in the following figure. Figure 2 As shown:

[0052] The present invention obtains the electrical quantity parameters of the three-phase to single-phase converter by first locking u through a phase-locked loop PLL vj (j=a,b,c) phase ωt, then i vj (j=a,b,c) is converted from the three-phase rotating abc coordinate system to the two-phase rotating dq coordinate system i vn (n=d,q), and then according to the expression of the current inner loop controller and the expression of the power outer loop controller, we can get u diffn (n=d,q), and finally by rotating the two phases u in the dq coordinate system diffn (n=d,q) is converted to u in the three-phase rotating abc coordinate system refj (j=a,b,c) to complete the current inner loop control and power outer loop control. vj (j=a,b,c) represents the grid-side voltage in the three-phase rotating abc coordinate system, i vj (j=a,b,c) represents the grid-side current in the three-phase rotating abc coordinate system, i vn (n=d,q) represents the grid-side current in the two-phase rotating dq coordinate system, u diffn (n=d,q) represents the common mode voltage of the upper and lower bridge arms of the three phases in the two-phase rotating dq coordinate system, u refj (j=a, b, c) represents the instantaneous value of the modulation wave in the three-phase rotating abc coordinate system.

[0053] The mathematical model of the three-phase-single-phase converter constructed by the present invention in the three-phase rotating coordinate system is expressed as follows:

[0054]

[0055] Where: i vj (j=a,b,c) represents the input current on the three-phase grid side, a represents the a-axis in the abc coordinate system, b represents the b-axis in the abc coordinate system, c represents the c-axis in the abc coordinate system, u diffj (j=a, b, c) represents the common mode voltage of the upper and lower bridge arms of the three phases, R represents the equivalent bridge arm loss resistance, L represents the converter bridge arm inductance, usj (j=a,b,c) represents the three-phase grid-side input voltage, Represents the time derivative of a variable.

[0056] The present invention converts the mathematical model of the three-phase-single-phase converter in the three-phase rotating coordinate system into the mathematical model of the three-phase-single-phase converter in the two-phase rotating coordinate system through Park transformation, and the expression is:

[0057]

[0058] Where: i vn (n=d,q) represents the three-phase grid-side input current in the two-phase rotating dq coordinate system, u diffn (n=d,q) represents the common mode voltage of the upper and lower bridge arms of the three phases in the two-phase rotating dq coordinate system, R represents the equivalent bridge arm loss resistance, L represents the converter bridge arm inductance, u sn (n=d,q) represents the three-phase grid-side input voltage in the two-phase rotating dq coordinate system, represents the time derivative of the variable and ω represents the angular frequency of the AC railway system.

[0059] The expression of the current inner loop controller is:

[0060]

[0061] Where: i vn (n=d,q) represents the three-phase grid-side input current in the two-phase rotating dq coordinate system in the frequency domain, d represents the d-axis in the dq coordinate system, q represents the q-axis in the dq coordinate system, s represents the complex frequency domain, u diffn (n=d,q) represents the common mode voltage of the upper and lower bridge arms of the three phases in the two-phase rotation dq coordinate system in the frequency domain, L is the inductance of the converter bridge arm, u sn (n=d,q) represents the three-phase grid-side input voltage in the two-phase rotating dq coordinate system, represents the reference current at the output side of the three-phase rectifier in the two-phase rotating dq coordinate system in the frequency domain, k p1 , k i1 , k p2 , k i2 is the proportional-integral coefficient of the PI controller, and ω is the angular frequency of the AC railway system.

[0062] The expression of the power outer loop controller is:

[0063]

[0064] Where: i vn(n=d,q) represents the three-phase grid-side input current in the two-phase rotating dq coordinate system in the frequency domain, d represents the d-axis in the dq coordinate system, q represents the q-axis in the dq coordinate system, s represents the complex frequency domain, Indicates the given reference active power, Q * s Represents the given reference reactive power, P s Indicates active power, Q s Represents reactive power, U sm Indicates the effective value of the three-phase grid-side input voltage, i* vn (n=d,q) represents the reference current at the output side of the three-phase rectifier in the two-phase rotating dq coordinate system in the frequency domain, k p3 , k i3 , k p4 , k i4 is the proportional-integral coefficient of the PI controller.

[0065] The modulation process of the modulation module is as follows: based on the instantaneous value of the modulation wave, the number of half-bridge sub-modules put into the upper and lower bridge arms is calculated respectively; according to the number of half-bridge sub-modules put into the upper and lower bridge arms respectively, the current current direction and the capacitance voltage of all half-bridge sub-modules, the nearest level approximation modulation strategy is used to determine the half-bridge sub-modules that need to be put into use, and the on and off signals of the IGBT semiconductor switch are generated to modulate the half-bridge sub-modules. Figure 3 As shown:

[0066] The present invention adopts the nearest level approximation modulation strategy to determine the half-bridge sub-modules that need to be invested according to the number of half-bridge sub-modules invested in the upper and lower bridge arms respectively, the current current direction and the capacitor voltage magnitudes of all the half-bridge sub-modules, so as to perform half-bridge sub-module modulation. The specific process is as follows: the modulation wave within one cycle needs to go through nine different time periods of t0-t1, t1-t2, t2-t3, t3-t4, t4-t5, t5-t6, t6-t7, t7-t8 and t8-t9. It can be seen from the figure that when the modulation wave is 0, the upper and lower bridge arms respectively invest the same number of half-bridge sub-modules. As the modulation wave increases positively from 0, the number of half-bridge sub-modules invested in the lower bridge arm of the phase gradually increases. In order to ensure the stability of the output DC side, the number of half-bridge sub-modules invested in the upper bridge arm will be reduced accordingly. The total number of half-bridge sub-modules invested in the upper and lower bridge arms is 0. The number of modules put into operation remains unchanged. When the modulation wave reaches the peak value, all the half-bridge sub-modules of the upper bridge arm are withdrawn, and all the half-bridge sub-modules of the lower bridge arm are put into operation. As the modulation wave decreases, the half-bridge sub-modules of the upper bridge arm are gradually put into operation, and the half-bridge sub-modules of the lower bridge arm are gradually withdrawn. When the modulation wave reaches 0 again, the number of half-bridge sub-modules put into operation in the upper and lower bridge arms respectively returns to the same, and the previous process of putting into operation and withdrawing is repeated, and finally the effect of the port output level approaching the modulation wave is achieved; for example, if two half-bridge sub-modules are put into operation in a certain phase upper bridge arm at a certain moment, the current direction at this time is from the power grid to all the half-bridge sub-modules, that is, if the half-bridge sub-module is put into operation, it is in a charging state. According to the capacitor voltage of all the half-bridge sub-modules, the two half-bridge sub-modules with the smallest voltage are selected to be put into operation, so that the voltage between each half-bridge sub-module is kept balanced.

[0067] Combination Figure 4 It can be seen that the output capacitor of each half-bridge submodule is connected in parallel with the bypass switch. When a half-bridge submodule fails to work, the half-bridge submodule can be bypassed by closing the bypass switch, and the remaining half-bridge submodules jointly output a single-phase 27.5kV / 50Hz voltage, thereby improving the reliability of the railway system power supply. In summary, the present invention can convert the three-phase voltage into a single-phase controllable voltage (27.5kV) during the control and modulation process, and can adjust the amplitude and phase of the traction network voltage at any time, thereby realizing the elimination of electrical phase separation within and between traction substations, and improving the train running speed and load capacity.

[0068] The expression for calculating the number of half-bridge sub-modules respectively put into the upper and lower bridge arms based on the instantaneous value of the modulation wave is:

[0069]

[0070] Where: n down Indicates the number of half-bridge submodules in the upper bridge arm, n up Indicates the number of half-bridge submodules in the lower bridge arm, n indicates the number of half-bridge submodules in each bridge arm, u refj(j=a,b,c) represents the instantaneous value of the modulation wave, a represents the a-axis in the abc coordinate system, b represents the b-axis in the abc coordinate system, c represents the c-axis in the abc coordinate system, Uc represents the average value of the capacitor voltage of the half-bridge submodule, and the round() function is a rounding function, which means taking the nearest integer.

[0071] The expression for obtaining the instantaneous value of the modulation wave in the present invention is:

[0072]

[0073] Where: u refj (j=a, b, c) represents the instantaneous value of the modulation wave in the three-phase rotating abc coordinate system, t represents time, and ω represents the angular frequency of the AC railway system.

[0074] An energy management method applied to the above-mentioned fully-through flexible traction substation includes steps S1-S3, which are specifically as follows:

[0075] S1. Obtain the energy flow model of the railway system based on the fully-through flexible traction substation.

[0076] In an optional embodiment of the present invention, the expression of the railway system energy flow model obtained by the present invention based on the fully-through flexible traction substation is:

[0077] P L +P G +P BA +P PV +P T =0

[0078] Where: P L Indicates the station load power, P G Indicates the power of the three-phase power grid port, P BA Represents the energy storage port power, P PV Indicates the photovoltaic port power, P T Indicates the train operating power.

[0079] S2. Based on the energy flow model of the railway system, the train is set to the first energy management mode when it is in traction state, the train is set to the second energy management mode when it is in braking state, and the train is set to the third energy management mode when it is not in operation.

[0080] In an optional embodiment of the present invention, the first energy management mode includes operating conditions 1, 2, 3 and 4; the second energy management mode includes operating conditions 5, 6, 7 and 8; and the third energy management mode includes operating condition 9. Figure 5 As shown, Figure 5It is a schematic diagram of energy flow under different working conditions. All working conditions are based on the management of the fully-through flexible traction substation for energy transmission.

[0081] Working condition 1: The photovoltaic port and energy storage port are locked; energy is provided to the train load and station load through the three-phase grid port.

[0082] Working condition 2: The PV port is locked and the energy storage port is opened; the sum of the train operating power and the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 2-1, and in working condition 2-1, energy is provided to the train load and the station load through the energy storage port; the sum of the train operating power and the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 2-2, and energy is provided to the train load and the station load through the energy storage port and the three-phase grid port in working condition 2-2.

[0083] Working condition 3: the energy storage port is locked and the photovoltaic port is opened; the photovoltaic power is greater than the sum of the train operating power and the station load power, which is determined as working condition 3-1. In working condition 3-1, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is returned to the three-phase grid; the photovoltaic power is less than the sum of the train operating power and the station load power, which is determined as working condition 3-2. In working condition 3-2, energy is provided to the train load and the station load through the photovoltaic port, and the difference energy is provided to the train load and the station load through the three-phase grid port.

[0084] Working condition 4: The photovoltaic port and the energy storage port are turned on; the photovoltaic port power is greater than the sum of the train running power and the station load power, and the sum of the photovoltaic port power minus the train running power and the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 4-1. In working condition 4-1, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is stored in the energy storage port; the photovoltaic port power is greater than the sum of the train running power and the station load power, and the sum of the photovoltaic port power minus the train running power and the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 4-2. In working condition 4-2, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is first stored in the energy storage port. After the energy storage port is fully charged, the excess energy of the photovoltaic port is stored in the energy storage port. The surplus energy is stored in the three-phase grid port; the photovoltaic port power is less than the sum of the train running power and the station load power, and the sum of the train running power and the station load power minus the photovoltaic port power is less than the maximum discharge power of the energy storage port, which is determined as operating condition 4-3. In operating condition 4-3, energy is provided to the train load and the station load through the photovoltaic port, and the difference energy is provided to the train load and the station load through the energy storage port; the photovoltaic port power is less than the sum of the train running power and the station load power, and the sum of the train running power and the station load power minus the photovoltaic port power is greater than the maximum discharge power of the energy storage port, which is determined as operating condition 4-4. In operating condition 4-4, energy is first provided to the train load and the station load through the photovoltaic port and the energy storage port, and then the difference energy is provided to the train load and the station load through the three-phase grid port.

[0085] Working condition 5: The photovoltaic port and the energy storage port are locked; the regenerative braking power is greater than the station load power, which is determined as working condition 5-1, and in working condition 5-1, the excess energy is returned to the three-phase grid port; the regenerative braking power is less than the station load power, which is determined as working condition 5-2, and in working condition 5-2, the difference energy is provided to the station load through the three-phase grid port.

[0086] Specifically, the regenerative braking power is the same as the train operating power.

[0087] Working condition 6: The photovoltaic port is locked and the energy storage port is opened; the regenerative braking power is less than the station load power, and the difference power required by the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 6-1. In working condition 6-1, the difference power is provided to the station load through the energy storage port; the regenerative braking power is less than the station load power, and the difference power required by the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 6-2. In working condition 6-2, the energy storage port is operated at maximum power discharge, and the three-phase grid port is operated at the difference power required by the station load power; the regenerative braking power is greater than the station load power, and the excess power of the railway system is less than the maximum charging power of the energy storage port, which is determined as working condition 6-3. In working condition 6-3, the excess regenerative braking energy is absorbed through the energy storage port; the regenerative braking power is greater than the station load power, and the excess power of the railway system is greater than the maximum charging power of the energy storage port, which is determined as working condition 6-4. In working condition 6-4, after the energy storage port is charged at maximum power, the remaining energy is returned to the three-phase grid.

[0088] Operating condition 7: The photovoltaic port is turned on and the energy storage port is locked; the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, which is determined as operating condition 7-1. In operating condition 7-1, the remaining energy is returned to the three-phase grid port; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, which is determined as operating condition 7-2. In operating condition 7-2, energy is supplied through the three-phase grid port with the difference power required by the station load.

[0089] Working condition 8: Both the photovoltaic port and the energy storage port are turned on; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, and the difference power required by the railway system is less than or equal to the maximum discharge power of the energy storage port, which is determined as working condition 8-1. In working condition 8-1, the difference power required by the station load is supplied through the energy storage port; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, and the difference power required by the railway system is greater than the maximum discharge power of the energy storage port, which is determined as working condition 8-2. In working condition 8-2, the energy storage port is first discharged at maximum power, and then discharged through the three-phase grid port. Supply the difference power required by the station load; when the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, and the excess power in the railway system is less than the maximum charging power of the energy storage port, it is determined as operating condition 8-3, and in operating condition 8-3, the energy storage port is charged with the excess power of the railway system; when the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, and the excess power in the railway system is greater than the maximum charging power of the energy storage port, it is determined as operating condition 8-4, and in operating condition 8-4, the energy storage port is first charged with the maximum power, and then the remaining power of the railway system is returned to the three-phase grid.

[0090] Working condition 9: The photovoltaic port is locked; the energy storage port is charged through the three-phase grid port. When the energy storage device is ≥80%, the energy storage port is locked.

[0091] S3. Based on the first energy management mode, the second energy management mode and the third energy management mode, energy management is performed on the fully-through flexible traction substation.

[0092] In an optional embodiment of the present invention, the present invention performs energy management on the fully-through flexible traction substation based on the first energy management mode, the second energy management mode and the third energy management mode, performs energy transfer based on the management of the fully-through flexible traction substation, and realizes the maximum efficient utilization of energy among the three-phase power grid, photovoltaic energy, energy storage and train braking energy.

[0093] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0094] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0095] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0096] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0097] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A fully through flexible traction substation, characterized in that: It includes circuit breaker, three-phase-single-phase converter, filter circuit and isolation transformer; The three-phase-single-phase converter includes a three-phase input side, a single-phase output side and a filter circuit; the three-phase input side is connected to the three phases of the three-phase power grid through a circuit breaker, the single-phase output side is connected to the primary side of the isolation transformer through the filter circuit, and the secondary side of the isolation transformer is connected to the traction grid and the grounding rail through a circuit breaker; The three-phase input side and the single-phase output side both include an upper bridge arm unit, a lower bridge arm unit, and a bridge arm inductor arranged between the upper bridge arm unit and the lower bridge arm unit; the upper bridge arm unit and the lower bridge arm unit both adopt a modular multi-level topology structure including multiple series-connected half-bridge sub-modules.

2. The fully through flexible traction substation according to claim 1 is characterized in that: The half-bridge sub-modules each include a first IGBT semiconductor switch, a second IGBT semiconductor switch, a support capacitor and a bypass switch; the first IGBT semiconductor switch and the second IGBT semiconductor switch are connected in series, the support capacitor and the bypass switch are connected in parallel with the first IGBT semiconductor switch and the second IGBT semiconductor switch, the anode side of the second IGBT semiconductor switch serves as the input side of the half-bridge sub-module, and the cathode side of the second IGBT semiconductor switch serves as the output side of the half-bridge sub-module.

3. The fully through flexible traction substation according to claim 1 is characterized in that: The three-phase-to-single-phase converter is also provided with a control module for current inner loop control and power outer loop control and a modulation module for half-bridge sub-module modulation; the input of the control module is the electrical quantity parameter of the three-phase-to-single-phase converter, the output of the control module is the instantaneous value of the modulation wave, the input of the modulation module is the instantaneous value of the modulation wave output by the control module, and the output of the modulation module is the on and off signal of the IGBT semiconductor switch.

4. The fully through flexible traction substation according to claim 3 is characterized in that: The control process of the control module is specifically as follows: obtaining the electrical quantity parameters of the three-phase-single-phase converter, constructing a mathematical model of the three-phase-single-phase converter in a three-phase rotating coordinate system based on the electrical quantity parameters of the three-phase-single-phase converter, converting it into a mathematical model of the three-phase-single-phase converter in a two-phase rotating coordinate system through Park transformation, and based on the mathematical model of the three-phase-single-phase converter in the two-phase rotating coordinate system, using a PI controller to design a current inner loop controller and a power outer loop controller to output the instantaneous value of the modulation wave.

5. The fully through flexible traction substation according to claim 4 is characterized in that: The expression of the current inner loop controller is: Where: i vn (n=d,q) represents the three-phase grid-side input current in the two-phase rotating dq coordinate system in the frequency domain, d represents the d-axis in the dq coordinate system, q represents the q-axis in the dq coordinate system, s represents the complex frequency domain, u diffn (n=d,q) represents the common mode voltage of the upper and lower bridge arms of the three phases in the two-phase rotation dq coordinate system in the frequency domain, L is the bridge arm inductance of the converter, u sn (n=d,q) represents the three-phase grid-side input voltage in the two-phase rotating dq coordinate system, represents the reference current at the output side of the three-phase rectifier in the two-phase rotating dq coordinate system in the frequency domain, k p1 , k i1 , k p2 , k i2 is the proportional-integral coefficient of the PI controller, and ω is the angular frequency of the railway system.

6. The fully through flexible traction substation according to claim 4 is characterized in that: The expression of the power outer loop controller is: Where: i vn (n=d,q) represents the three-phase grid-side input current in the two-phase rotating dq coordinate system in the frequency domain, d represents the d-axis in the dq coordinate system, q represents the q-axis in the dq coordinate system, s represents the complex frequency domain, Represents the given reference active power, Represents the given reference reactive power, P s Indicates active power, Q s Represents reactive power, U sm Indicates the effective value of the three-phase grid-side input voltage, i* vn (n=d,q) represents the reference current at the output side of the three-phase rectifier in the two-phase rotating dq coordinate system in the frequency domain, k p3 , k i3 , k p4 , k i4 is the proportional-integral coefficient of the PI controller.

7. The fully through flexible traction substation according to claim 3 is characterized in that: The modulation process of the modulation module is specifically as follows: based on the instantaneous value of the modulation wave output by the control module, the number of half-bridge sub-modules put into use in the upper and lower bridge arms is calculated respectively; according to the number of half-bridge sub-modules put into use in the upper and lower bridge arms respectively, the current current direction and the capacitance voltage of all half-bridge sub-modules, the nearest level approximation modulation strategy is used to determine the half-bridge sub-module that needs to be put into use, and the on and off signals of the IGBT semiconductor switch are generated to perform half-bridge sub-module modulation.

8. The fully through flexible traction substation according to claim 7 is characterized in that: The expression for calculating the number of half-bridge sub-modules put into the upper and lower bridge arms respectively based on the instantaneous value of the modulation wave is: Where: n down Indicates the number of half-bridge submodules in the upper bridge arm, n up Indicates the number of half-bridge submodules in the lower bridge arm, n indicates the number of half-bridge submodules in each bridge arm, u refj (j=a,b,c) represents the instantaneous value of the modulation wave, a represents the a-axis in the abc coordinate system, b represents the b-axis in the abc coordinate system, c represents the c-axis in the abc coordinate system, Uc represents the average value of the capacitor voltage of the half-bridge submodule, and the round() function is a rounding function, which means taking the nearest integer.

9. An energy management method applied to the fully-through flexible traction substation according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Obtaining the energy flow model of the railway system based on the fully connected flexible traction substation; S2. Based on the railway system energy flow model, setting the train in traction state to the first energy management mode, setting the train in braking state to the second energy management mode, and setting the train in non-operating state to the third energy management mode; S3. Based on the first energy management mode, the second energy management mode and the third energy management mode, energy management is performed on the fully-through flexible traction substation.

10. The energy management method of the fully-through flexible traction substation according to claim 9 is characterized in that: In step S2, the first energy management mode includes working condition 1, working condition 2, working condition 3 and working condition 4; the second energy management mode includes working condition 5, working condition 6, working condition 7 and working condition 8; the third energy management mode includes working condition 9; all working conditions are based on the management of the full-through flexible traction substation for energy transmission; Working condition 1: The photovoltaic port and energy storage port are locked; energy is provided to the train load and station load through the three-phase grid port; Working condition 2: The photovoltaic port is locked and the energy storage port is opened; the sum of the train operating power and the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 2-1, and energy is provided to the train load and the station load through the energy storage port in working condition 2-1; the sum of the train operating power and the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 2-2, and energy is provided to the train load and the station load through the energy storage port and the three-phase grid port in working condition 2-2; Working condition 3: The energy storage port is locked and the photovoltaic port is opened; the photovoltaic power is greater than the sum of the train running power and the station load power, which is determined as working condition 3-1. In working condition 3-1, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is returned to the three-phase grid; the photovoltaic power is less than the sum of the train running power and the station load power, which is determined as working condition 3-2. In working condition 3-2, energy is provided to the train load and the station load through the photovoltaic port, and the difference energy is provided to the train load and the station load through the three-phase grid port; Working condition 4: The photovoltaic port and the energy storage port are turned on; the photovoltaic port power is greater than the sum of the train running power and the station load power, and the sum of the photovoltaic port power minus the train running power and the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 4-1. In working condition 4-1, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is stored in the energy storage port; the photovoltaic port power is greater than the sum of the train running power and the station load power, and the sum of the photovoltaic port power minus the train running power and the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 4-2. In working condition 4-2, energy is provided to the train load and the station load through the photovoltaic port, and the excess energy of the photovoltaic port is first stored in the energy storage port. After the energy storage port is fully charged, the excess energy of the photovoltaic port is stored in the energy storage port. The remaining energy is stored in the three-phase grid port; the photovoltaic port power is less than the sum of the train running power and the station load power, and the sum of the train running power and the station load power minus the photovoltaic port power is less than the maximum discharge power of the energy storage port, which is determined as operating condition 4-3. In operating condition 4-3, energy is provided to the train load and the station load through the photovoltaic port, and the difference energy is provided to the train load and the station load through the energy storage port; the photovoltaic port power is less than the sum of the train running power and the station load power, and the sum of the train running power and the station load power minus the photovoltaic port power is greater than the maximum discharge power of the energy storage port, which is determined as operating condition 4-4. In operating condition 4-4, energy is first provided to the train load and the station load through the photovoltaic port and the energy storage port, and then the difference energy is provided to the train load and the station load through the three-phase grid port; Working condition 5: The photovoltaic port and the energy storage port are locked; the regenerative braking power is greater than the station load power, which is determined as working condition 5-1, and in working condition 5-1, the excess energy is returned to the three-phase grid port; the regenerative braking power is less than the station load power, which is determined as working condition 5-2, and in working condition 5-2, the difference energy is provided to the station load through the three-phase grid port; Working condition 6: The photovoltaic port is locked and the energy storage port is opened; the regenerative braking power is less than the station load power, and the difference power required by the station load power is less than the maximum discharge power of the energy storage port, which is determined as working condition 6-1. In working condition 6-1, the difference power is provided to the station load through the energy storage port; the regenerative braking power is less than the station load power, and the difference power required by the station load power is greater than the maximum discharge power of the energy storage port, which is determined as working condition 6-2. In working condition 6-2, the energy storage port is operated at maximum power discharge, and the three-phase grid port is operated at the difference power required by the station load power; the regenerative braking power is greater than the station load power, and the excess power of the railway system is less than the maximum charging power of the energy storage port, which is determined as working condition 6-3. In working condition 6-3, the excess regenerative braking energy is absorbed through the energy storage port; the regenerative braking power is greater than the station load power, and the excess power of the railway system is greater than the maximum charging power of the energy storage port, which is determined as working condition 6-4. In working condition 6-4, after the energy storage port is charged at maximum power, the remaining energy is returned to the three-phase grid; Working condition 7: The photovoltaic port is turned on and the energy storage port is locked; the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, which is determined as working condition 7-1. In working condition 7-1, the remaining energy is returned to the three-phase grid port; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, which is determined as working condition 7-2. In working condition 7-2, the difference power required by the station load is used to supply energy through the three-phase grid port; Working condition 8: Both the photovoltaic port and the energy storage port are turned on; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, and the difference power required by the railway system is less than or equal to the maximum discharge power of the energy storage port, which is determined as working condition 8-1. In working condition 8-1, the difference power required by the station load is supplied through the energy storage port; the sum of the regenerative braking power and the photovoltaic power is less than the station load power, and the difference power required by the railway system is greater than the maximum discharge power of the energy storage port, which is determined as working condition 8-2. In working condition 8-2, the energy storage port is first discharged at maximum power, and then discharged through the three-phase grid port. Supply the difference power required by the station load; when the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, and the excess power in the railway system is less than the maximum charging power of the energy storage port, it is determined as working condition 8-3, and in working condition 8-3, the energy storage port is charged with the excess power of the railway system; when the sum of the regenerative braking power and the photovoltaic power is greater than the station load power, and the excess power in the railway system is greater than the maximum charging power of the energy storage port, it is determined as working condition 8-4, and in working condition 8-4, the energy storage port is first charged with the maximum power, and then the remaining power of the railway system is returned to the three-phase power grid; Working condition 9: The photovoltaic port is locked; the energy storage port is charged through the three-phase grid port. When the energy storage device is ≥80%, the energy storage port is locked.

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