Energy storage type direct coupling DC transformer and control method

Abstract

The application provides an energy storage type direct coupling DC transformer and a control method, which comprises a chain module 1 and a chain module 2; the chain module 1 comprises a plurality of single-polarity full-bridge sub-modules connected in series; the chain module 2 comprises a plurality of energy storage type half-bridge sub-modules connected in parallel; each energy storage type half-bridge sub-module comprises a half-bridge type unit and an energy storage type unit connected in parallel, the direct coupling DC transformer is constructed by using the single-polarity full-bridge type sub-module and the energy storage type half-bridge sub-module, the isolation of short-circuit fault current can be realized, the uninterrupted power supply under high-voltage short-circuit fault and the peak load shifting and valley fill in the power supply process under normal operation can be realized through the energy storage type sub-module, the reliability of power supply is improved, and the probability of power failure of low-voltage side users is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of direct current power transmission, and particularly relates to a direct coupling type direct current transformer with energy storage and a control method. BACKGROUND

[0002] The development of the direct current power grid is still limited by the lag of key equipment such as a direct current breaker and a direct current transformer. The direct current transformer is of great significance for connecting different direct current lines to form the direct current power grid. Compared with the traditional alternating current power grid, it can be found that there are multiple different voltage levels in the alternating current power grid, in which a higher voltage level is used for long-distance power transmission, and a lower voltage level is used for power distribution and power consumption. Similarly, in the direct current power grid, in order to reduce transmission loss, a higher direct current voltage level needs to be used from a power generation center to a load center, and a lower voltage level needs to be used in the power distribution network and the user side. Therefore, the application occasions all put forward the demand for a high-voltage DC-DC transformer for the direct current power transmission system. At the same time, many power generation devices, such as wind turbines, large photovoltaic power stations and bioenergy power stations, need to be equipped with additional DC / AC inverters to be connected to the power grid for effective use. This scheme not only causes a large amount of loss, but also brings potential threats such as stability to the traditional alternating current power system due to the parallel connection of a large number of inverters. If a direct current power grid is used, the DC / AC inversion link can be omitted, the conversion loss can be reduced, and the operation efficiency can be improved. Similarly, at the load side, a large number of electronic devices, data centers and variable frequency devices all need direct current power supply or a direct current link. Therefore, the direct current power grid means that these loads do not need rectifier devices, the converter cost is saved, and the operation efficiency is improved. The implementation of these applications also depends on the connection of the high-voltage DC-DC transformer.

[0003] The direct current power grid is a "low-inertia" system. If a direct current fault occurs, a large short-circuit current may be generated, and the entire direct current power grid will be affected instantaneously. The response time requirement of the protection system is very high. The traditional alternating current system protection methods, such as overcurrent protection, distance protection and differential protection, are not suitable for being directly applied to the direct current power grid. Moreover, the direct current power grid is large in scale, complex in structure, various in operation mode and large in number of devices. The protection method of cutting off the entire direct current system from the alternating current side cannot be simply used in the two-end direct current power transmission system. At the same time, in the direct current power transmission and distribution system, it is difficult to develop a large-capacity direct current breaker. In order to effectively prevent the rapid spread of the direct current fault, the direct current transformer is usually required to have a fault protection and isolation function to prevent the fault from being transmitted to endanger the normal power supply system. For sensitive loads of the direct current power consumption, such as data centers, semiconductor enterprises and high-end manufacturing enterprises, the DC-DC transformer not only needs to have the function of blocking the direct current fault current, but also needs to have the function of uninterrupted power supply to improve the reliability of power supply for the load.

[0004] At present, the existing direct coupling type DC transformer based on half-bridge sub-modules has high utilization rate of modules and low investment cost, but when a high-voltage side short-circuit fault occurs, the half-bridge sub-modules cannot cut off the fault short-circuit current by locking the converter, and at the same time, the low-voltage DC side loses power supply and the load is powered off, which seriously affects the reliability of the system. Therefore, how to make the direct coupling type DC transformer have the fault current isolation function, and at the same time realize the uninterrupted power supply of the load when the high-voltage side fault current is isolated is a problem to be solved by those skilled in the art. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the present application provides an energy storage type direct coupling type DC transformer, comprising:

[0006] a chain module 1 and a chain module 2;

[0007] The positive electrode of the chain module 1 is connected with the positive electrode of the high-voltage side DC power supply;

[0008] The positive electrode of the chain module 2 is connected with the negative electrode of the chain module 1 and the positive electrode of the low-voltage side DC power supply respectively; the negative electrode of the chain module 2 is connected with the negative electrode of the high-voltage side DC power supply and the negative electrode of the low-voltage side DC power supply respectively;

[0009] The chain module 1 comprises a plurality of single-polarity full-bridge sub-modules connected in series; the chain module 2 comprises a plurality of energy storage type half-bridge sub-modules connected in parallel; each energy storage type half-bridge sub-module comprises a half-bridge type unit and an energy storage type unit connected in parallel.

[0010] Preferably, the number of single-polarity full-bridge type sub-modules and the number of energy storage type half-bridge sub-modules are configured in a ratio determined by the transformation ratio of the DC transformer.

[0011] Preferably, the energy storage type unit comprises:

[0012] a first power switch sub-unit, a second power switch sub-unit, a third filter inductor, a resistor and an energy storage battery;

[0013] The positive electrode of the energy storage battery is connected with the positive electrode of the second power switch sub-unit in sequence through the resistor and the third filter inductor;

[0014] The negative electrode of the second power switch sub-unit is connected with the negative electrode of the energy storage battery and the negative electrode of the half-bridge type unit respectively;

[0015] The positive electrode of the first power switch sub-unit is connected with the positive electrode of the half-bridge type unit; the negative electrode of the first power switch sub-unit is connected with the positive electrode of the second power switch sub-unit.

[0016] Preferably, the DC transformer further comprises a first filter inductor and a second filter inductor;

[0017] The first filter inductance is connected in series between the positive pole of the high-voltage side DC power supply and the positive pole of the chain module 1.

[0018] The second filter inductance is connected in series between the positive pole of the low-voltage side DC power supply and the positive pole of the chain module 2.

[0019] Based on the same inventive concept, the application also provides a control method of the energy storage type directly coupled DC transformer, comprising:

[0020] obtaining an output voltage control signal and a protection control signal of the DC transformer;

[0021] adjusting the working states of the unipolar full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 based on the output voltage control signal and the protection control signal of the DC transformer, so as to realize the output voltage control and the protection control of the DC transformer;

[0022] The working states of the unipolar full-bridge sub-modules include: being put into operation, being bypassed and being locked out.

[0023] The working states of the energy storage type half-bridge sub-modules include: being put into energy storage charging, being put into energy storage discharging, being bypassed and being locked out.

[0024] Preferably, adjusting the working states of the unipolar full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 based on the output voltage control signal and the protection control signal of the DC transformer, so as to realize the output voltage control and the protection control of the DC transformer, comprises:

[0025] When the system is normally running, the unipolar full-bridge sub-modules in the chain module 1 are controlled to switch between the put-into-operation state and the bypassed state, and the energy storage type half-bridge sub-modules in the chain module 2 are controlled to switch between the put-into-energy storage charging state, the put-into-energy storage discharging state and the bypassed state based on the output voltage control signal of the DC transformer, so as to realize the output voltage control of the DC transformer.

[0026] When a short-circuit fault occurs, the unipolar full-bridge sub-modules in the chain module 1 and / or the energy storage type half-bridge sub-modules in the chain module 2 are controlled to be locked out based on the protection control signal, so as to realize the protection control of the DC transformer.

[0027] Preferably, when the system is normally running, the unipolar full-bridge sub-modules in the chain module 1 are controlled to switch between the put-into-operation state and the bypassed state, and the energy storage type half-bridge sub-modules in the chain module 2 are controlled to switch between the put-into-energy storage charging state, the put-into-energy storage discharging state and the bypassed state based on the output voltage control signal of the DC transformer, so as to realize the output voltage control of the DC transformer, comprising:

[0028] determining the number of the single-polarity full-bridge sub-modules in the chain module 1 and the energy-storage half-bridge sub-modules in the chain module 2 to be put into based on the output voltage control signal of the DC transformer;

[0029] determining whether the single-polarity full-bridge sub-modules in the chain module 1 and the energy-storage half-bridge sub-modules in the chain module 2 are in the put-in state or in the bypass state based on the number;

[0030] determining whether the energy-storage half-bridge sub-modules in the chain module 2 in the put-in state are in the put-in energy-storage charging state or in the put-in energy-storage discharging state based on the output voltage control signal of the DC transformer;

[0031] generating a pulse signal to control the single-polarity full-bridge sub-modules in the chain module 1 to switch between the put-in state and the bypass state and to control the energy-storage half-bridge sub-modules in the chain module 2 to switch between the put-in energy-storage charging state, the put-in energy-storage discharging state and the bypass state to realize the output voltage control of the DC transformer based on the working states of the single-polarity full-bridge sub-modules in the chain module 1 and the energy-storage half-bridge sub-modules in the chain module 2.

[0032] Preferably, the calculation formula of the number is as follows:

[0033]

[0034] wherein, n down is the number of the energy-storage half-bridge sub-modules in the chain module 2 to be put into, n up is the number of the single-polarity full-bridge sub-modules in the chain module 1 to be put into, round is the rounding function, and u s is the output voltage control signal of the DC transformer.

[0035] Preferably, determining whether the single-polarity full-bridge sub-modules in the chain module 1 and the energy-storage half-bridge sub-modules in the chain module 2 are in the put-in state or in the bypass state based on the number comprises:

[0036] determining whether the number of the single-polarity full-bridge sub-modules in the chain module 1 and the energy-storage half-bridge sub-modules in the chain module 2 needs to be adjusted: if not, the working states of the single-polarity full-bridge sub-modules in the chain module 1 and the energy-storage half-bridge sub-modules in the chain module 2 do not change; if yes, determining the current state of the chain module: if the current of the chain module is greater than zero, determining the working states of the n down sub-modules with smaller capacitor voltages in each chain module to be in the put-in state and the working states of the remaining sub-modules to be in the bypass state based on the sorting state of the capacitor voltages of all the sub-modules in each chain module; if the current of the chain module is less than zero, determining the working states of the n upThe working state of the sub-module is an input state, and the working state of the rest of the sub-modules is a bypass state.

[0037] Preferably, based on the output voltage control signal of the DC transformer, it is determined whether the energy storage type half-bridge sub-module in the input state in the chain module 2 works in the input energy storage charging state or the input energy storage discharging state, comprising:

[0038] Based on the output voltage control signal of the DC transformer, it is determined whether the output voltage of the DC transformer meets the load power demand: if the load power demand cannot be met, it is determined that the energy storage type half-bridge sub-module in the input state in the chain module 2 works in the input energy storage discharging state; if the load power demand can be met, it is determined that the energy storage type half-bridge sub-module in the input state in the chain module 2 works in the input energy storage charging state.

[0039] In the input energy storage discharging state, the first power switch sub-unit of each energy storage type unit in the energy storage type half-bridge sub-module is closed and the switch of the second power switch sub-unit is turned on, and the energy storage type unit is discharged.

[0040] In the input energy storage charging state, the first power switch sub-unit of each energy storage type unit in the energy storage type half-bridge sub-module is turned on and the switch of the second power switch sub-unit is closed, and the energy storage type unit is charged.

[0041] Preferably, when a short circuit fault occurs, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 and / or the energy storage type half-bridge sub-module in the chain module 2 are controlled to be locked, realizing protection control of the DC transformer, comprising:

[0042] When a high-voltage side short circuit fault occurs, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 is controlled to be locked, realizing isolation of the short circuit fault.

[0043] When a low-voltage side short circuit fault and a bipolar short circuit fault occur, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 and the energy storage type half-bridge sub-module in the chain module 2 are controlled to be locked, realizing isolation of the short circuit fault.

[0044] Compared with the closest prior art, the present application has the following beneficial effects:

[0045] The application provides a kind of energy storage type direct coupling DC transformer and control method, comprising: chain module 1 and chain module 2;The positive pole of chain module 1 is connected with the positive pole of high voltage side DC power supply;The positive pole of chain module 2 is connected with the negative pole of chain module 1 and the positive pole of low voltage side DC power supply respectively;The negative pole of chain module 2 is connected with the negative pole of high voltage side DC power supply and the negative pole of low voltage side DC power supply respectively;Chain module 1 includes a plurality of single polarity full-bridge sub-modules in series;Chain module 2 includes a plurality of energy storage type half-bridge sub-modules in parallel;Each energy storage type half-bridge sub-module includes a half-bridge type unit and an energy storage type unit in parallel, the application adopts single polarity full-bridge type sub-module and energy storage type half-bridge sub-module to construct direct coupling DC transformer, that is, short-circuit fault current can be isolated, at the same time, energy storage type sub-module can be used to realize uninterrupted power supply under high voltage short-circuit fault and peak clipping under power supply process in normal operation, improve the reliability of power supply and reduce the probability of low voltage side user power failure. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 A topological structure diagram of the energy storage type direct coupling DC transformer provided by the application is provided.

[0047] Figure 2 A control method schematic diagram of the energy storage type direct coupling DC transformer provided by the application is provided.

[0048] Figure 3 A topological structure diagram of the energy storage type direct coupling DC transformer provided in the embodiment of the application is provided.

[0049] Figure 4 A single polarity full-bridge type sub-module topological structure diagram provided in the embodiment of the application is provided.

[0050] Figure 5 An energy storage type half-bridge type sub-module topological structure diagram provided in the embodiment of the application is provided.

[0051] Figure 6 A schematic diagram of capacitor voltage equalization control based on recent level approximation modulation provided in the embodiment of the application is provided.

[0052] Figure 7 A running schematic diagram of energy storage type sub-module in charging state provided in the embodiment of the application is provided.

[0053] Figure 8 A running schematic diagram of energy storage type sub-module in discharging state provided in the embodiment of the application is provided. DETAILED DESCRIPTION

[0054] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings.

[0055] Embodiment 1:

[0056] The energy storage type direct-coupled DC transformer provided by the embodiment of the present application comprises: Figure 1

[0057] a chain module 1 and a chain module 2;

[0058] The positive pole of the chain module 1 is connected with the positive pole of the high-voltage side DC power supply.

[0059] The positive pole of the chain module 2 is connected with the negative pole of the chain module 1 and the positive pole of the low-voltage side DC power supply respectively; and the negative pole of the chain module 2 is connected with the negative pole of the high-voltage side DC power supply and the negative pole of the low-voltage side DC power supply respectively.

[0060] The chain module 1 comprises a plurality of single-polarity full-bridge sub-modules connected in series; the chain module 2 comprises a plurality of energy storage type half-bridge sub-modules connected in parallel; each energy storage type half-bridge sub-module comprises a half-bridge type unit and an energy storage type unit connected in parallel.

[0061] The configuration ratio of the number m of single-polarity full-bridge type sub-modules and the number n of energy storage type half-bridge sub-modules is determined by the transformation ratio of the DC transformer.

[0062] Embodiment 2:

[0063] The energy storage type direct-coupled DC transformer provided by the embodiment of the present application comprises: Figure 3

[0064] a chain module 1, a chain module 2, a first filter inductor L a and a second filter inductor L f .

[0065] The positive pole of the chain module 1 is connected with the positive pole of the high-voltage side DC power supply through the first filter inductor L a .

[0066] The positive pole of the high-voltage side DC power supply is connected with the positive pole of the chain module 1 and the negative pole of the chain module 2 through the second filter inductor L f .

[0067] The positive pole of the chain module 2 is connected with the negative pole of the chain module 1; and the negative pole of the chain module 2 is connected with the negative pole of the high-voltage side DC power supply and the negative pole of the low-voltage side DC power supply respectively.

[0068] The chain module 1 comprises a plurality of single-polarity full-bridge type sub-modules connected in series, and the topology structure of the single-polarity full-bridge type sub-module is as shown in Figure 4 ; the chain module 2 comprises a plurality of energy storage type half-bridge sub-modules connected in parallel, and the topology structure of the energy storage type half-bridge sub-module is as shown in Figure 5 ​​As shown in the figure, each energy storage type half-bridge sub-module includes a half-bridge type unit and an energy storage type unit in parallel.

[0069] The energy storage type unit in the energy storage type half-bridge sub-module includes:

[0070] The first power switch sub-unit, the second power switch sub-unit, the third filter inductor, the resistor and the energy storage battery.

[0071] The positive electrode of the energy storage battery is connected with the positive electrode of the second power switch sub-unit through the resistor and the third filter inductor in sequence.

[0072] The negative electrode of the second power switch sub-unit is connected with the negative electrode of the energy storage battery and the negative electrode of the half-bridge type unit respectively.

[0073] The positive electrode of the first power switch sub-unit is connected with the positive electrode of the half-bridge type unit, and the negative electrode of the first power switch sub-unit is connected with the positive electrode of the second power switch sub-unit.

[0074] The converter is used for connecting a high-voltage side DC voltage source Udc1 and a low-voltage side DC voltage source Udc2 with different voltage levels, wherein Udc1 is greater than Udc2.

[0075] Embodiment 3

[0076] The embodiment of the application discloses a control method of an energy storage type direct coupling DC transformer, as shown in the figure, including: Figure 2 As shown in the figure, including:

[0077] S1 obtains an output voltage control signal and a protection control signal of the DC transformer;

[0078] S2 adjusts the working state of the unipolar full-bridge sub-module in the chain module 1 and the energy storage type half-bridge sub-module in the chain module 2 based on the output voltage control signal and the protection control signal of the DC transformer, so as to realize the output voltage control and the protection control of the DC transformer;

[0079] The working state of the unipolar full-bridge sub-module includes: putting in, bypassing and locking.

[0080] The working state of the energy storage type half-bridge sub-module includes: putting in energy storage charging, putting in energy storage discharging, bypassing and locking.

[0081] The output voltage control signal is generated by voltage closed-loop control, including:

[0082] The output voltage control signal is generated by voltage closed-loop control, including:

[0083] The actual output voltage udc2 of the DC transformer is subtracted from the output voltage given value Uref and input into a PI regulator to obtain a given value of duty cycle d, and an output voltage control signal is generated based on the regulated duty cycle d. The output voltage of the DC transformer is controlled, and at this time the output voltage udc2 is not a voltage source, so a filter capacitor Cf needs to be connected in parallel on the udc2 side.

[0084] Based on the output voltage control signal of the DC transformer and the protection control signal, the working states of the unipolar full-bridge sub-modules in chain module 1 and the energy storage type half-bridge sub-modules in chain module 2 are adjusted to realize DC transformer output voltage control and protection control, including:

[0085] When the system is running normally, based on the output voltage control signal of the DC transformer, the unipolar full-bridge sub-modules in chain module 1 are controlled to switch between the input and bypass working states, and the energy storage type half-bridge sub-modules in chain module 2 are controlled to switch between the input energy storage charging, input energy storage discharging, and bypass working states to realize DC transformer output voltage control.

[0086] When a short circuit fault occurs, based on the protection control signal, the unipolar full-bridge sub-modules in chain module 1 and / or the energy storage type half-bridge sub-modules in chain module 2 are controlled to be locked out to realize protection control of the DC transformer.

[0087] Specifically, when the system is running normally, based on the output voltage control signal of the DC transformer, the unipolar full-bridge sub-modules in chain module 1 are controlled to switch between the input and bypass working states, and the energy storage type half-bridge sub-modules in chain module 2 are controlled to switch between the input energy storage charging, input energy storage discharging, and bypass working states to realize DC transformer output voltage control, including:

[0088] Based on the output voltage control signal of the DC transformer, the number of unipolar full-bridge sub-modules in chain module 1 and energy storage type half-bridge sub-modules in chain module 2 that are input is determined;

[0089] Based on the number of inputs, it is determined whether the unipolar full-bridge sub-modules in chain module 1 and the energy storage type half-bridge sub-modules in chain module 2 are working in the input state or the bypass state;

[0090] Based on the output voltage control signal of the DC transformer, it is determined whether the energy storage type half-bridge sub-modules in chain module 2 that are in the input state are working in the input energy storage charging state or the input energy storage discharging state;

[0091] Based on the working states of the unipolar full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2, corresponding trigger pulses are obtained to control the unipolar full-bridge sub-modules in the chain module 1 to switch between the input and bypass working states, and to control the energy storage type half-bridge sub-modules in the chain module 2 to switch between the input energy storage charging, input energy storage discharging and bypass working states. The strategy selects appropriate sub-module inputs, suppresses the fluctuation of the module capacitor voltage, can quickly balance the voltage between the modules, and simultaneously realizes the output control of the DC transformer.

[0092] Specifically, the calculation formulae of the input number of the unipolar full-bridge sub-modules in the chain module 1 and the input number of the energy storage type half-bridge sub-modules in the chain module 2 are as follows:

[0093]

[0094] In the formula, n down is the number of the energy storage type half-bridge sub-modules in the chain module 2 that should be input, n up is the number of the unipolar full-bridge sub-modules in the chain module 1 that should be input, round is the rounding function, u s is the output voltage control signal of the DC transformer, 0≤n down ≤n, 0≤n up ≤n.

[0095] Specifically, based on the input number, it is determined whether the unipolar full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 work in the input state or the bypass state, as shown in the following table: Figure 6

[0096] It is judged whether the input number of the unipolar full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 needs to be adjusted: if not, the working states of the unipolar full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 do not change; if yes, it is judged whether the current state of the chain module: if the current of the chain module is greater than zero, based on the real-time acquisition of the unordered module voltage of each sub-module, the capacitor voltages of all the sub-modules are sorted by the sorting algorithm to obtain an ordered voltage sequence, based on the sorting state of the capacitor voltages of all the sub-modules in each chain module, the working state of n down sub-modules with smaller capacitor voltages in each sub-module is determined to be the input state, and the working state of the remaining sub-modules is the bypass state; if the current of the chain module is less than zero, based on the real-time acquisition of the unordered module voltage of each sub-module, the capacitor voltages of all the sub-modules are sorted by the sorting algorithm to obtain an ordered voltage sequence, based on the sorting state of the capacitor voltages of all the sub-modules in each chain module, the working state of n up ​The working state of the sub-module is in the input state, and the working state of the remaining sub-modules is in the bypass state.

[0097] Specifically, based on the output voltage control signal of the DC transformer, it is determined whether the energy storage type half-bridge sub-module in the input state in the chain module 2 works in the input energy storage charging state or the input energy storage discharging state, including:

[0098] Based on the output voltage control signal of the DC transformer, it is determined whether the output voltage of the DC transformer meets the load power demand: if the load power demand cannot be met, it is determined that the energy storage type half-bridge sub-module in the input state in the chain module 2 works in the input energy storage discharging state; if the load power demand can be met, it is determined that the energy storage type half-bridge sub-module in the input state in the chain module 2 works in the input energy storage charging state.

[0099] In the input energy storage discharging state, the first power switch sub-unit switch Sw3 of each energy storage type unit in the energy storage type half-bridge sub-module is locked and the switch Sw4 of the second power switch sub-unit is turned on, and the energy storage type unit is discharged, as shown in detail in Figure 7 ;

[0100] In the input energy storage charging state, the first power switch sub-unit switch Sw3 of each energy storage type unit in the energy storage type half-bridge sub-module is turned on and the switch Sw4 of the second power switch sub-unit is locked, and the energy storage type unit is charged, as shown in detail in Figure 8 .

[0101] Specifically, when a short circuit fault occurs, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 and / or the energy storage type half-bridge sub-module in the chain module 2 are controlled to be locked, realizing the protection control of the DC transformer, including:

[0102] When a high-voltage side short circuit fault occurs, based on the protection control signal, the IGBT switches S1, S2 and S3 in the unipolar full-bridge sub-module in the chain module 1 are closed, and the unipolar full-bridge sub-module enters the locked working state, realizing the fault isolation of the high-voltage DC side through the capacitor voltage Uc of each sub-module in the chain module 1.

[0103] When a low-voltage side short circuit fault and a bipolar short circuit fault occur, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 and the energy storage type half-bridge sub-module in the chain module 2 are controlled to be locked, realizing the fault isolation of the low-voltage DC side through the capacitor voltage Uc of each sub-module in the chain module 1 and the chain module 2.

[0104] Specifically, the uninterrupted power supply strategy includes:

[0105] When a short circuit fault occurs in the high-voltage side DC side, the voltage discharge loop of the low-voltage DC side is prevented from discharging through the blocking module 1; at the same time, the energy storage type unit of the starting module 2 is started, so that the energy storage type unit works in the charging and discharging state of the DC / DC, and the voltage of the low-voltage DC side is maintained in the form of a voltage source, so that the switching process of the whole system realizes uninterrupted power supply of the low-voltage DC side.

[0106] Those skilled in the art will appreciate that embodiments of the application can be provided as methods, systems, or computer program products. Accordingly, the application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer-readable program code.

[0107] The application is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as combinations of flows and / or blocks in the flowcharts and / or block diagrams, 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 apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that implements the functions specified in one or more flows and / or blocks.

[0108] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction apparatus, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that implements the functions specified in one or more flows and / or blocks.

[0109] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable data processing apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that implements the functions specified in one or more flows and / or blocks.

[0110] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit the protection scope thereof, and although the present application has been described in detail with reference to the above examples, it should be understood by those skilled in the art that the specific embodiments of the present application can be changed, modified or replaced equivalently by those skilled in the art after reading the present application, but these changes, modifications or equivalent replacements are all within the protection scope of the claims of the present application.

Claims

1. An energy storage type direct-coupled DC voltage transformer, characterized by, Comprise: Chain module 1 and chain module 2; The positive pole of the chain module 1 is connected with the positive pole of the high-voltage side DC power supply; The positive pole of the chain module 2 is connected with the negative pole of the chain module 1 and the positive pole of the low-voltage side DC power supply respectively; The negative pole of the chain module 2 is connected with the negative pole of the high-voltage side DC power supply and the negative pole of the low-voltage side DC power supply respectively; The chain module 1 comprises a plurality of single-polarity full-bridge sub-modules connected in series; The chain module 2 comprises a plurality of energy storage type half-bridge sub-modules connected in series; Each energy storage type half-bridge sub-module comprises a half-bridge type unit and an energy storage type unit connected in series; Wherein, the energy storage type unit comprises: A first power switch sub-unit, a second power switch sub-unit, a third filter inductor, a resistor and an energy storage battery; The positive pole of the energy storage battery is connected with the positive pole of the second power switch sub-unit through the resistor and the third filter inductor in sequence; The negative pole of the second power switch sub-unit is connected with the negative pole of the energy storage battery and the negative pole of the half-bridge type unit respectively; The positive pole of the first power switch sub-unit is connected with the positive pole of the half-bridge type unit; The negative pole of the first power switch sub-unit is connected with the positive pole of the second power switch sub-unit.

2. The dc-dc converter of claim 1, wherein The number of single-polarity full-bridge type sub-modules and the number of energy storage type half-bridge sub-modules are configured in a ratio determined by the voltage conversion ratio of the DC transformer.

3. The dc-dc converter of claim 1, wherein Further comprise: A first filter inductor and a second filter inductor; The first filter inductor is connected in series between the positive pole of the high-voltage side DC power supply and the positive pole of the chain module 1; The second filter inductor is connected in series between the positive pole of the low-voltage side DC power supply and the positive pole of the chain module 2.

4. A control method of an energy storage type direct coupling DC voltage transformer, characterized by, Comprise: Obtaining the output voltage control signal and the protection control signal of the DC transformer; Based on the output voltage control signal and the protection control signal of the DC transformer, the working states of the single-polarity full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 are adjusted to realize the output voltage control and the protection control of the DC transformer; The working state of the single-polarity full-bridge sub-module comprises: putting in, bypassing and locking out; The working state of the energy storage type half-bridge sub-module comprises: putting in energy storage charging, putting in energy storage discharging, bypassing and locking out; Wherein, the energy storage type half-bridge sub-module comprises an energy storage type unit; The energy storage type unit comprises: A first power switch sub-unit, a second power switch sub-unit, a third filter inductor, a resistor and an energy storage battery; The positive pole of the energy storage battery is connected with the positive pole of the second power switch sub-unit through the resistor and the third filter inductor in sequence; The negative pole of the second power switch sub-unit is connected with the negative pole of the energy storage battery and the negative pole of the half-bridge type unit respectively; The positive pole of the first power switch sub-unit is connected with the positive pole of the half-bridge type unit; The negative pole of the first power switch sub-unit is connected with the positive pole of the second power switch sub-unit.

5. The method of claim 4, wherein, The output voltage control signal and the protection control signal of the DC transformer, the working states of the single-polarity full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 are adjusted based on the output voltage control signal and the protection control signal of the DC transformer to realize the output voltage control and the protection control of the DC transformer, comprising: When the system is in normal operation, based on the output voltage control signal of the DC transformer, the single-polarity full-bridge sub-modules in the chain module 1 are controlled to switch between the input and bypass states, and the energy storage type half-bridge sub-modules in the chain module 2 are controlled to switch among the input energy storage charging state, the input energy storage discharging state and the bypass state, so as to realize the output voltage control of the DC transformer. When a short circuit fault occurs, based on the protection control signal, the single-polarity full-bridge sub-modules in the chain module 1 and / or the energy storage type half-bridge sub-modules in the chain module 2 are controlled to be locked, so as to realize the protection control of the DC transformer.

6. The method of claim 5, wherein, When the system is in normal operation, based on the output voltage control signal of the DC transformer, the single-polarity full-bridge sub-modules in the chain module 1 are controlled to switch between the input and bypass states, and the energy storage type half-bridge sub-modules in the chain module 2 are controlled to switch among the input energy storage charging state, the input energy storage discharging state and the bypass state, so as to realize the output voltage control of the DC transformer. Based on the output voltage control signal of the DC transformer, the number of the single-polarity full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 is determined. Based on the number, it is determined whether the single-polarity full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 work in the input state or the bypass state. Based on the output voltage control signal of the DC transformer, it is determined whether the energy storage type half-bridge sub-modules in the chain module 2 in the input state work in the input energy storage charging state or the input energy storage discharging state. Based on the working states of the single-polarity full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2, a pulse signal is generated to control the single-polarity full-bridge sub-modules in the chain module 1 to switch between the input and bypass states, and to control the energy storage type half-bridge sub-modules in the chain module 2 to switch among the input energy storage charging state, the input energy storage discharging state and the bypass state, so as to realize the output voltage control of the DC transformer.

7. The method of claim 6, wherein, The calculation formula of the number is as follows: In the formula, n down is the number of energy storage type half-bridge submodules to be put into the chain module 2, n up is the number of unipolar full-bridge submodules to be put into the chain module 1, round is the rounding function, and u s is the output voltage control signal of the DC transformer.

8. The method of claim 6, wherein, Based on the number, it is determined whether the single-polarity full-bridge sub-modules in the chain module 1 and the energy storage type half-bridge sub-modules in the chain module 2 work in the input state or the bypass state. determining whether the number of single-polarity full-bridge sub-modules in the chain module 1 and the number of energy-storage half-bridge sub-modules in the chain module 2 need to be adjusted: if not, the working states of the single-polarity full-bridge sub-modules in the chain module 1 and the energy-storage half-bridge sub-modules in the chain module 2 remain unchanged; if yes, determining the current state of the chain module: if the current of the chain module is greater than zero, based on the sorting state of the capacitor voltages of all the sub-modules in each chain module, determining the working states of the sub-modules in the chain module: the working states of n down sub-modules with smaller capacitor voltages are the input states, and the working states of the remaining sub-modules are the bypass states; if the current of the chain module is less than zero, based on the sorting state of the capacitor voltages of all the sub-modules in each chain module, determining the working states of the sub-modules in the chain module: the working states of n up sub-modules with greater capacitor voltages are the input states, and the working states of the remaining sub-modules are the bypass states.

9. The method of claim 6, wherein, Based on the output voltage control signal of the DC transformer, it is determined whether the energy storage type half-bridge sub-modules in the chain module 2 in the input state work in the input energy storage charging state or the input energy storage discharging state. Based on the output voltage control signal of the DC transformer, it is determined whether the output voltage of the DC transformer meets the load power demand: if the load power demand cannot be met, it is determined that the energy storage type half-bridge sub-modules in the chain module 2 in the input state work in the input energy storage discharging state; if the load power demand can be met, it is determined that the energy storage type half-bridge sub-modules in the chain module 2 in the input state work in the input energy storage charging state. In the input energy storage discharging state, the first power switch sub-unit of each energy storage unit in the energy storage type half-bridge sub-module is locked and the switch of the second power switch sub-unit is turned on, and the energy storage unit is discharged. In the input energy storage charging state, the first power switch subunit switch of each energy storage type unit in the energy storage type half-bridge sub-module is turned on and the second power switch subunit switch is locked, and the energy storage type unit is charged.

10. The method of claim 5, wherein, When a short circuit fault occurs, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 and / or the energy storage type half-bridge sub-module in the chain module 2 are controlled to be locked, realizing protection control of the DC transformer, comprising: When a high-voltage side short circuit fault occurs, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 is controlled to be locked, realizing isolation of the short circuit fault; When a low-voltage side short circuit fault and a bipolar short circuit fault occur, based on the protection control signal, the unipolar full-bridge sub-module in the chain module 1 and the energy storage type half-bridge sub-module in the chain module 2 are controlled to be locked, realizing isolation of the short circuit fault.

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