CN109103873B - High-capacity direct-current energy storage device with direct-current DVR - Google Patents
High-capacity direct-current energy storage device with direct-current DVR Download PDFInfo
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- CN109103873B CN109103873B CN201811286581.4A CN201811286581A CN109103873B CN 109103873 B CN109103873 B CN 109103873B CN 201811286581 A CN201811286581 A CN 201811286581A CN 109103873 B CN109103873 B CN 109103873B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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Abstract
The invention provides a high-capacity direct-current energy storage device with a direct-current DVR, and belongs to the technical field of power energy storage and direct-current conversion. According to the device, a lithium battery or a super capacitor is used as an energy storage unit, a mode of combining a main energy storage module and a compensation energy storage module is adopted, when the voltage of a direct current bus is reduced to be lower than a reference value, the energy stored in the compensation energy storage module is output to be direct current voltage meeting system requirements under the action of a direct current DVR (digital video recorder), so that the voltage drop caused by the internal resistance of the main energy storage module, the line impedance and the energy release to a load side is compensated, the voltage of the bus is kept stable at the reference value, and the power is continuously supplied to the load side.
Description
Technical Field
The invention relates to a high-capacity direct-current energy storage device with a direct-current DVR, and belongs to the technical field of power energy storage and direct-current conversion.
Background
Lithium ion batteries generally use lithium metal oxides, such as lithium iron phosphate, lithium manganate, ternary, etc., as the positive electrode material and graphite as the negative electrode material. Lithium batteries are widely used in various military and civil fields such as energy storage systems of water power, firepower, wind energy, solar energy and the like, uninterruptible power supplies of communication equipment, electric tools, electric vehicles, military equipment, aerospace and the like. It has the following advantages: small volume, light weight and high energy density which can reach 460 to 600 Wh/Kg; the service life is long, and generally can reach more than 6 years; the rated voltage is high, the voltage of a single battery is 3.2V or 3.7V, and the voltage is equivalent to that of 3 nickel-metal hydride batteries which are connected in series; the lithium iron phosphate battery has high discharge rate capability, wherein the discharge rate of the lithium iron phosphate battery for the electric automobile can reach dozens of C, and the lithium iron phosphate battery can be used for instantaneous large-current charging and discharging occasions; the self-discharge rate is low and can not exceed 1 percent per month; the method is green and environment-friendly, and does not contain harmful heavy metal elements and substances such as lead, mercury and the like in the processes of production, use and scrapping. Due to the advantages, the lithium ion battery is very suitable for being applied to electric power energy storage occasions with high energy density requirements and limited volume.
The super capacitor, also called farad capacitor, is widely used in new energy fields such as electric hybrid bus, crane, rail traffic energy recovery and the like at present, and obtains super capacity by utilizing an electric double layer structure composed of an activated carbon porous electrode and an electrolyte. It has the following advantages: the charging speed is high, and the charging time can reach more than 95% of the rated capacity after 10 seconds to 10 minutes; the service life of the ring is long, the number of times of deep charge-discharge cycle use can reach 1-50 ten thousand, and no memory effect exists; the large-current discharge capacity is super strong, the energy conversion efficiency is high, the process loss is small, and the large-current energy circulation efficiency is more than or equal to 90 percent; the power density is high and can reach 300-5000W/KG, which is 5-10 times of that of the battery; the raw materials of the product are pollution-free in the processes of composition, production, use, storage and disassembly, and the product is an ideal green and environment-friendly power supply; the charging and discharging circuit is simple, a charging circuit like a rechargeable battery is not needed, the safety coefficient is high, and the maintenance is avoided after long-term use; the ultra-low temperature has good characteristics, and the temperature range is wide from minus 40 ℃ to plus 70 ℃. Due to the advantages, the super capacitor is very suitable for being applied to electric occasions with high requirements on charge and discharge power.
A dynamic voltage regulator DVR is an electric energy quality control device based on a user electric power technology, which utilizes a power electronic technology and a modern control theory to effectively solve the electric energy quality problems of voltage drop, harmonic pollution, power supply interruption and the like. However, at present, most research and application of DVRs are focused on ac occasions, and it is difficult to find similar documents or application examples in dc occasions, especially in large-capacity dc energy storage occasions.
As a power supply device of a high-power motor driving system, maintaining the constant voltage of a direct-current bus is an important guarantee for ensuring stable operation of clicking and system stability. If the energy storage scheme of pure batteries or pure capacitors is adopted, the number of required batteries or capacitors is huge due to the application of the energy storage scheme to high-voltage and high-current occasions, and the problems of large bus voltage drop, uncontrolled operation process and the like exist. At present, a mode of additionally installing a direct current converter at a front stage is generally adopted to carry out bus voltage stabilization control, but in a high-capacity application occasion, the selection of key devices, such as inductors and switching devices, in the direct current converter becomes very difficult, and the contradiction between the performance, the volume and the weight of the converter is difficult to take into account.
Aiming at the large-capacity electric energy storage occasion, an energy storage scheme which can make the number of required energy storage units as small as possible and make the power of a direct current converter as small as possible is urgently needed, so that the volume, the weight and the cost of the energy storage scheme are controlled, the power density of the whole system is ensured, and the stable and controllable bus voltage can be realized.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a high-capacity direct-current energy storage device with a direct-current DVR dynamic voltage regulator. The method is characterized in that a lithium battery or a super capacitor is used as an energy storage unit, a mode of combining a main energy storage module and a compensation energy storage module is adopted, when the voltage of a direct current bus is reduced to be lower than a reference value, the energy stored in the compensation energy storage module is output to be direct current voltage meeting system requirements under the action of a direct current DVR (digital video recorder), so that the internal resistance of the main energy storage module, the voltage drop caused by line impedance and energy release to a load side are compensated, the voltage of the bus is kept stable at the reference value, and power is continuously supplied to the load side. The invention adopts the following specific technical scheme:
a high-capacity direct-current energy storage device with a direct-current DVR (digital video recorder) comprises a main energy storage module 1, a DVR compensator 2, a compensation energy storage module 3, a fly-wheel diode 4, a filter capacitor 5, an energy storage management system 6, an energy storage management system II 7, a charging device I8, a charging device II 9, a control unit 10, a direct-current voltage sampling unit 11, a direct-current sampling unit 12 and an isolation driving unit 13; the main energy storage module 1 is connected with the DVR compensator 2 in series; the DVR compensator 2 is connected with a freewheeling diode 4 in parallel; the charging ends of the main energy storage module 1 and the compensation energy storage module 3 are respectively connected with the power supply ends of a first charging device 8 and a second charging device 9; the operation index control ends of the main energy storage module 1 and the compensation energy storage module 3 are respectively connected with the monitoring control ends of the energy storage management system I6 and the energy storage management system II 7; the terminal voltage signal end of the main energy storage module 1 and the output voltage end of the DVR compensator 2 are connected with the sampling end of the direct current voltage sampling unit 11; the sampling digital signal output end of the direct current voltage sampling unit 11 is connected with the voltage sampling digital signal input end of the control unit 10; the output current end of the DVR compensator 2 is connected with the sampling end of the direct current sampling unit 12; the sampling digital signal output end of the direct current sampling unit 12 is connected with the current sampling digital signal input end of the control unit 10; the signal output end of the control unit 10 is connected with the signal input end of the isolation driving unit 13; and the signal output end of the isolation driving unit 13 is connected with a switching tube in the DVR compensator 2.
The main energy storage module 1, the DVR compensator 2, the compensation energy storage module 3, the freewheeling diode 4, the filter capacitor 5, the energy storage management system I6, the energy storage management system II 7, the charging device I8 and the charging device II 9 form a main topology of the direct current energy storage device; the DVR compensator 2 is connected with the freewheeling diode 4 in parallel and then connected with the main energy storage module 1 in series, so that when the DVR works, the output current is the same as the bus current and changes according to the requirement of a load side. The energy storage management system I6 and the energy storage management system II 7 respectively monitor and control voltage, current, temperature and the like of the main energy storage module 1 and the compensation energy storage module 3; the first charging device 8 and the second charging device 9 are used for charging the main energy storage module 1 and the compensation energy storage module 3 during the operation interval of the energy storage system so as to ensure the energy required by the next operation of the system. The direct current voltage sampling unit 11 samples the voltage at the end of the main energy storage module 1 and the output voltage of the DVR compensator 2, the output side is connected with the control unit 10, the collected voltage analog quantity is converted into digital quantity through analog-to-digital conversion, and the digital quantity is sent to the control unit 10 for processing. Similarly, the dc current sampling unit 12 detects and samples the output current of the DVR, and is connected to the control unit 10. The input end of the isolation driving unit 13 is connected with the control unit 10, and the output end is connected with a switching tube in the DVR compensator 2.
Furthermore, the main energy storage module and the compensation energy storage module 3 use a lithium battery cell or a super capacitor module as a basic energy storage unit; the lithium battery monomer or the super capacitor module forms the main energy storage module and the compensation energy storage module 3 in a series-parallel connection mode, if the energy storage unit is a lithium battery, the energy storage management system is a battery management system, and if the energy storage unit is a super capacitor, the energy storage management system is a super capacitor management system.
Further, the selection process of the serial-parallel connection number of the lithium battery or the super capacitor module is as follows:
the method comprises the following steps: calculating to obtain the serial number M1 and the parallel number N1 of the main energy storage module according to the serial number model and the parallel number model of the main energy storage module, wherein the serial number model and the parallel number model of the main energy storage module are respectively as follows:
M1＝ceil(Udcmax/Ur_es1) (1)
N1＝ceil(Idcmax/Ir_es1) (2)
wherein Udcmax is the maximum value of bus voltage, Idcmax is the maximum value of bus current, UrThe battery module in the main energy storage module is a _es1, Ir _ es1 is rated voltage and rated current of a single or super capacitor module, the serial number of the main energy storage module is M1, the parallel number of the main energy storage module is N1, the serial number of the compensation energy storage module is M2, the parallel number of the compensation energy storage module is N2, and ceil is an upward integer function;
step two: the maximum value of the output current of the compensation energy storage module is Idcmax 1+0.5 × P%, the serial number M2 and the parallel number N2 of the compensation energy storage module are obtained through calculation according to the serial number model and the parallel number model of the main energy storage module, and the serial number model and the parallel number model of the main energy storage module are respectively as follows:
N2＝ceil[Idcmax(1+0.5*P％)/Ir_es2] (3)
M2＝ceil[UBuckmax(1+A％)/Ur_es2] (4)
the compensation energy storage module comprises a battery module, a monomer or super capacitor module, Ur _ es2 and Ir _ es2, wherein the battery module, the monomer or super capacitor module and the monomer or super capacitor module are compensated, P% is an inductive current ripple rate, and the value range of P is 10-40; the A% is used for compensating the voltage drop of the energy storage module in the estimated discharging process when Buck works, and the voltage drop of different energy storage units in different running states is different;
step three: if the preliminarily selected M2 is not enough to meet the time from 0 to t2, the bus voltage is stabilized at a reference value Uref, the serial number M2 is proved not to meet the requirement, the M2 is made to be M2+1, and the serial number meeting the voltage stabilization requirement is upwards searched until the M2 meeting the requirement is found; if M2 selected preliminarily enables the energy storage system to realize voltage stabilization, the serial number M2 is proved to meet the requirement, M2 is made to be M2-1, the minimum serial number meeting the requirement is searched downwards until M2 just cannot meet the requirement, then M2+1 at the moment is the serial number just meeting the requirement, and the purposes of reducing the number of required energy storage modules as much as possible, reducing the system volume, reducing the cost and improving the power density can be achieved.
Further, the working modes of the large-capacity direct-current energy storage device with the direct-current DVR are as follows: when the high-capacity direct-current energy storage device starts to operate, the compensation energy storage module 3 and the DVR compensator 2 do not work, the main energy storage module 1 works independently to provide energy for a load, and the freewheeling diode 4 plays a freewheeling role; then the high-capacity direct-current energy storage device carries out the judgment of an enabling link, and when the judgment result is that the bus voltage is reduced to the voltage stabilizing value of the device, the compensation energy storage module 3 and the DVR compensator 2 start to work and output compensation voltage; the compensation energy storage module 3 provides compensation energy for the DVR compensator 2 until the current running time reaches the high-capacity direct current energy storage device to complete a complete discharging process; the main energy storage module 1 and the compensation energy storage module 3 wait for charging and prepare for the next work.
Further, the specific process of the enabling link judgment is as follows:
when UES1<Uref, which indicates that the bus voltage begins to drop below Uref, the DVR should run immediately and compensate the voltage drop, and the output of the enabling link is 1; when UES1>UrefIndicates that the bus voltage is still higher than UrefAnd the DVR does not work, the output of the enabling link is 0, and in the running process of the high-capacity direct current energy storage device, the enabling link is judged in real time until the one-time complete discharging process of the energy storage device is finished.
Further, the control unit 10 adopts a control mode of a bus voltage outer ring and a DVR output current inner ring double closed loop, and the specific process of the bus voltage outer ring and the DVR output current inner ring double closed loop control is as follows:
the bus voltage stable value U of the high-capacity direct current energy storage devicerefThe method comprises the steps that the sum of the voltage of a main energy storage module 1 and the output voltage of a DVR compensator 2 is obtained by sampling as the reference quantity of a voltage outer ring, the sum is used as the feedback quantity of the voltage outer ring according to the judgment result obtained by judging an enabling link, the reference quantity of the voltage outer ring and the feedback quantity of the voltage outer ring are multiplied to be used as input signals, the input signals are sent to a voltage regulator in a control unit 10 to be subjected to PI regulation processing, the output of the voltage regulator is used as the reference quantity of the current inner ring, the output current of the DVR obtained by sampling is used as the feedback quantity of the current, the difference between the reference quantity of the current and the feedback quantity of the current is used as the input signals of a current regulator in the control unit 10, the output result of the current regulator after PU regulation is the.
The invention has the beneficial effects that:
the high-capacity direct-current energy storage device with the direct-current DVR greatly reduces the number of basic energy storage units, simultaneously greatly reduces the power of a direct-current converter, and compared with the direct-current energy storage device in the prior art, the number of the basic energy storage units of the high-capacity direct-current energy storage device is reduced by 50%, the power of the direct-current converter is reduced by 80% under the same battery capacity, and further the volume, the weight and the cost of the high-capacity direct-current energy storage device are reduced. Meanwhile, the high-capacity direct-current energy storage device with the direct-current DVR not only ensures the power density of the whole energy storage system, but also realizes the stability and controllability of the bus voltage.
Drawings
Fig. 1 is a block diagram of a large-capacity dc energy storage device with a dc DVR.
Fig. 2 is four main circuit topologies of the dc energy storage device of the embodiment, wherein, (a) the battery plus capacitor main circuit diagram; (b) a battery and a battery main circuit diagram; (c) a capacitor and capacitor main circuit diagram; (d) capacitance plus battery main circuit diagram.
FIG. 3 is a diagram illustrating a related DC voltage waveform according to an embodiment.
Fig. 4 is a flow chart of selecting the number of the energy storage modules connected in series and in parallel according to the embodiment.
Fig. 5 is a schematic diagram of closed-loop control of the dc energy storage device according to the embodiment.
Fig. 6 is a flowchart illustrating an embodiment of determining an operating mode of an energy storage device.
1, a main energy storage module; 2, a DVR compensator; 3, compensating the energy storage module; 4, a freewheeling diode; 5, a filter capacitor; 6, the energy storage management system is uniform; 7, an energy storage management system II; 8, a first charging device; 9, a second charging device; 10, a control unit; 11, a direct current voltage sampling unit; 12, a direct current sampling unit; 13, isolating the drive unit
Detailed description of the invention
The present invention will be further described with reference to the following specific examples, but the present invention is not limited to these examples.
Example 1:
in this embodiment, a large-capacity dc energy storage device with a dc DVR is provided, as shown in fig. 1, the device includes a main energy storage module 1, a DVR compensator 2, a compensation energy storage module 3, a freewheeling diode 4, a filter capacitor 5, an energy storage management system 6, an energy storage management system two 7, a charging device one 8, a charging device two 9, a control unit 10, a dc voltage sampling unit 11, a dc current sampling unit 12, and an isolation driving unit 13; the main energy storage module 1 is connected with the DVR compensator 2 in series; the DVR compensator 2 is connected with a freewheeling diode 4 in parallel; the charging ends of the main energy storage module 1 and the compensation energy storage module 3 are respectively connected with the power supply ends of a first charging device 8 and a second charging device 9; the operation index control ends of the main energy storage module 1 and the compensation energy storage module 3 are respectively connected with the monitoring control ends of the energy storage management system I6 and the energy storage management system II 7; the terminal voltage signal end of the main energy storage module 1 and the output voltage end of the DVR compensator 2 are connected with the sampling end of the direct current voltage sampling unit 11; the sampling digital signal output end of the direct current voltage sampling unit 11 is connected with the voltage sampling digital signal input end of the control unit 10; the output current end of the DVR compensator 2 is connected with the sampling end of the direct current sampling unit 12; the sampling digital signal output end of the direct current sampling unit 12 is connected with the current sampling digital signal input end of the control unit 10; the signal output end of the control unit 10 is connected with the signal input end of the isolation driving unit 13; and the signal output end of the isolation driving unit 13 is connected with a switching tube in the DVR compensator 2.
The main energy storage module 1 adopts a lithium battery with high discharge rate as an energy storage unit, the compensation energy storage module 3 adopts a super capacitor module as an energy storage unit, and a lithium battery monomer or the super capacitor module is properly combined in series and parallel according to the maximum bus voltage value, the maximum bus current value and the energy requirement of the energy storage system so as to meet the high-capacity application requirement of the system. The DVR compensator 2 is connected with the freewheeling diode 4 in parallel and then connected with the main energy storage module 1 in series, so that when the DVR works, the output current is the same as the bus current and changes according to the requirement of a load side. The energy storage management system I6 and the energy storage management system II 7 respectively monitor and control voltage, current, temperature and the like of the main energy storage module 1 and the compensation energy storage module 3, on one hand, man-machine interaction is convenient, on the other hand, voltage balance among the energy storage modules is guaranteed, and the system stability and the service life of the energy storage unit are prolonged. The first charging device 8 and the second charging device 9 are used for charging the main energy storage module 1 and the compensation energy storage module 3 during the intermittent operation period of the energy storage system so as to ensure the energy required by the next operation of the system. The direct current voltage sampling unit 11 samples the voltage at the end of the main energy storage module 1 and the output voltage of the DVR compensator 2, the output side is connected with the control unit 10, the collected voltage analog quantity is converted into digital quantity through analog-to-digital conversion, and the digital quantity is sent to the control unit 10 for processing. Similarly, the dc current sampling unit 12 detects and samples the output current of the DVR, and is connected to the control unit 10. The isolation driving circuit 14 can effectively suppress external interference and ensure the completeness and accuracy of driving pulse, and the input end of the isolation driving circuit is connected with the control unit 10, and the output end of the isolation driving circuit is connected with a switching tube in the DVR compensator 2.
Example 2
The embodiment provides a large-capacity direct-current energy storage device with a direct-current DVR, and the device comprises a main energy storage module 1, a DVR compensator 2, a compensation energy storage module 3, a freewheeling diode 4, a filter capacitor 5, an energy storage management system 6, an energy storage management system II 7, a charging device I8, a charging device II 9, a control unit 10, a direct-current voltage sampling unit 11, a direct-current sampling unit 12 and an isolation driving unit 13. The DVR compensator 2 is implemented by a DCDC converter, and includes common forms such as Buck, Boost, Buck-Boost, and the like, and the main circuit of the high-capacity dc energy storage device having the dc DVR in this embodiment has four forms in total, as shown in fig. 2.
The Buck circuit consists of a switching tube, a freewheeling diode, a filter inductor, a filter capacitor and the like. Common switching devices include an IGBT and a power MOSFET, and although the MOSFET has low conduction voltage drop and high switching frequency, the voltage resistance and the rated current value are low, and the application requirements of high-capacity power energy storage occasions cannot be met, so that the IGBT is selected as the switching device in the embodiment. The relevant voltage waveform of the energy storage power supply system is shown in fig. 3 schematically, in the time of 0-t 1, the conduction voltage drop of the freewheeling diode D1 is ignored, the bus voltage is equal to the terminal voltage of the main energy storage module, the bus voltage rapidly drops along with the high-power discharge, and the bus voltage is reduced to the regulated voltage value U required by the system design at the moment of t1reAnd f, the compensation energy storage module starts to release energy at the moment, and outputs direct current voltage UDVR through Buck chopping of the Buck circuit so as to compensate for voltage drop caused by self internal resistance, line impedance and energy release to a load of the main energy storage module and dynamically maintain the bus voltage at UrefAnd finishing a complete discharging process of the energy storage device until the time t2 is finished. In the time from t1 to t2, the bus voltage is equal to the sum of the voltage of the main energy storage module terminal and the Buck output voltage UDVR, the diode D1 is cut off due to the back pressure, the Buck output is connected with the main energy storage module in series, so the Buck output current, namely the inductive current, is the same as the bus current,the period variation trend is affected by the load side demand. During the working process of the Buck circuit, the input voltage of the Buck circuit, namely the terminal voltage of the compensation energy storage module, is continuously reduced due to discharging, and is lowest at the moment t2, but is not lower than the U at the moment due to the topological constraint of BuckBuck. And Buck input current is in a chopping mode due to high-frequency switching action of a switching tube T, the compensation energy storage module discharges in the switching-on period of the switching tube, the Buck input current is the same as the output current, the inductor is in the charging process, the inductor current gradually rises, and in the switching-off period of the switching tube, the compensation energy storage module is opened, the filter inductor discharges to the output side together with the filter capacitor, and the filter inductor current gradually falls after flowing through a diode D2. Therefore, the output current of the compensation energy storage module has the same peak value as the inductive current, and if the ripple rate of the inductive current is P% and the maximum value of the bus current is Idcmax, the peak value of the output current of the compensation energy storage module is Idcmax 1+0.5 × P%.
Example 3
The embodiment provides a large-capacity direct-current energy storage device with a direct-current DVR, and the device comprises a main energy storage module 1, a DVR compensator 2, a compensation energy storage module 3, a freewheeling diode 4, a filter capacitor 5, an energy storage management system 6, an energy storage management system II 7, a charging device I8, a charging device II 9, a control unit 10, a direct-current voltage sampling unit 11, a direct-current sampling unit 12 and an isolation driving unit 13. The main energy storage module and the compensation energy storage module 3 use a lithium battery monomer or a super capacitor module as a basic energy storage unit; the lithium battery monomer or the super capacitor module forms the main energy storage module and the compensation energy storage module 3 in a series-parallel connection mode, if the energy storage unit is a lithium battery, the energy storage management system is a battery management system, and if the energy storage unit is a super capacitor, the energy storage management system is a super capacitor management system.
The selection process of the series-parallel connection quantity of the lithium battery or the super capacitor module is as follows:
the method comprises the following steps: calculating to obtain the serial number M1 and the parallel number N1 of the main energy storage module according to the serial number model and the parallel number model of the main energy storage module, wherein the serial number model and the parallel number model of the main energy storage module are respectively as follows:
M1＝ceil(Udcmax/Ur_es1) (1)
N1＝ceil(Idcmax/Ir_es1) (2)
the system comprises a main energy storage module, a compensation energy storage module and a control module, wherein Udcmax is the maximum value of bus voltage, Idcmax is the maximum value of bus current, Ur _ es1 and Ir _ es1 are battery modules in the main energy storage module, rated voltage and rated current of a single or super capacitor module, the series number of the main energy storage module is M1, the parallel number is N1, the series number of the compensation energy storage module is M2, the parallel number is N2, and ceil is an upward integer function;
step two: the maximum value of the output current of the compensation energy storage module is Idcmax 1+0.5 × P%, the serial number M2 and the parallel number N2 of the compensation energy storage module are obtained through calculation according to the serial number model and the parallel number model of the main energy storage module, and the serial number model and the parallel number model of the main energy storage module are respectively as follows:
N2＝ceil[Idcmax(1+0.5*P％)/Ir_es2] (3)
M2＝ceil[UBuckmax(1+A％)/Ur_es2] (4)
the compensation energy storage module comprises a battery module, a monomer or super capacitor module, Ur _ es2 and Ir _ es2, wherein the battery module, the monomer or super capacitor module and the monomer or super capacitor module are compensated, P% is an inductive current ripple rate, and the value range of P is 10-40; the A% is used for compensating the voltage drop of the energy storage module in the estimated discharging process when Buck works, and the voltage drop of different energy storage units in different running states is different;
step three: if the preliminarily selected M2 is not enough to meet the time from 0 to t2, the bus voltage is stabilized at a reference value Uref, the serial number M2 is proved not to meet the requirement, the M2 is made to be M2+1, and the serial number meeting the voltage stabilization requirement is upwards searched until the M2 meeting the requirement is found; if M2 selected preliminarily enables the energy storage system to realize voltage stabilization, the serial number M2 is proved to meet the requirement, M2 is made to be M2-1, the minimum serial number meeting the requirement is searched downwards until M2 just cannot meet the requirement, then M2+1 at the moment is the serial number just meeting the requirement, and the purposes of reducing the number of required energy storage modules as much as possible, reducing the system volume, reducing the cost and improving the power density can be achieved.
Thus, the selection of the serial number M1, the parallel number N1 of the main energy storage module and the serial number M2 and the parallel number N2 of the compensation energy storage module is completed.
Example 4
The embodiment provides a large-capacity direct-current energy storage device with a direct-current DVR, and the device comprises a main energy storage module 1, a DVR compensator 2, a compensation energy storage module 3, a freewheeling diode 4, a filter capacitor 5, an energy storage management system 6, an energy storage management system II 7, a charging device I8, a charging device II 9, a control unit 10, a direct-current voltage sampling unit 11, a direct-current sampling unit 12 and an isolation driving unit 13. The control unit 10 adopts a double closed-loop control mode of a bus voltage outer loop and a DVR output current inner loop, wherein the voltage outer loop and the current inner loop respectively use bus voltage and inductive current as control quantities, the closed-loop control principle applied in the embodiment is shown in FIG. 5, a main circuit adopting a battery module as main energy storage and compensation energy storage is taken as an example, and the other three topologies are the same. Specifically, the voltage at the end of the main energy storage module and the voltage output by the DVR compensator are respectively processed by a direct current voltage sampling circuit and low-pass filtering to filter high-frequency harmonics in a voltage signal to obtain UES1 and UDVR, the inductive current is processed by a direct current sampling circuit and low-pass filtering to filter high-frequency harmonics in a current signal to obtain IL, wherein the filtering comprises analog filtering of a hardware circuit and digital filtering in a software program, and both the software and the hardware filtering are used in the embodiment. The UES1, UDVR and IL are then fed to the controller for processing.
First, the UES1 go through the DVR enabling link to determine whether the DVR is working, and determine what working mode the energy storage device is in, and the determination process is shown in fig. 6. When UES1< Uref indicates that the bus voltage begins to drop below Uref, the DVR immediately runs and compensates the voltage drop, and the output of an enabling link is 1; when the UES1> Uref, indicating that the bus voltage is still higher than Uref, DVR does not work, and the output of the enabling link is 0. The enabling link needs to be judged in real time until the energy storage device finishes a complete discharging process. In the present example, the voltage and current regulator is realized by a proportional integral PI regulator, the proportional P part realizes the quick tracking of the feedback quantity to the reference quantity, and the integral part I ensures that the feedback quantity has no static difference with the reference quantity in a steady state. And taking Uref as an ideal reference quantity of a voltage outer ring, taking the sum of UES1 and UDVR as an actual feedback quantity of bus voltage, multiplying the difference between the UES1 and the UDVR by an output result of an enabling link, taking the multiplied result as an input signal, and sending the input signal to a voltage PI regulator for processing, wherein the regulator is provided with an amplitude limiting link, and the upper and lower output limits of the regulator are respectively the maximum value and the minimum value of inductive current, namely Idcmax and 0. The output of the voltage regulator is used as the reference quantity of the current inner loop, the sampled IL is used as the feedback quantity of the current inner loop, the two are subjected to difference and sent to the current PI regulator for processing, the output is a duty ratio signal, the regulator is provided with an amplitude limiting link, and the upper limit and the lower limit of the regulator are respectively the maximum value and the minimum value of the duty ratio, namely 1 and 0. The duty ratio output by the current regulator is compared with the triangular carrier to obtain a PWM signal, and the Buck circuit and the whole energy storage device are controlled by driving the switching tube to act through the isolation driving circuit. Therefore, the closed-loop control of the high-capacity direct-current energy storage device with the direct-current DVR is completed.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (5)
1. A high-capacity direct-current energy storage device with a direct-current DVR (digital video recorder) is characterized by comprising a main energy storage module (1), a DVR compensator (2), a compensation energy storage module (3), a freewheeling diode (4), a filter capacitor (5), an energy storage management system (6), an energy storage management system II (7), a charging device I (8), a charging device II (9), a control unit (10), a direct-current voltage sampling unit (11), a direct-current sampling unit (12) and an isolation driving unit (13); the main energy storage module (1) is connected with the DVR compensator (2) in series; the DVR compensator (2) is connected with the freewheeling diode (4) in parallel; the charging ends of the main energy storage module (1) and the compensation energy storage module (3) are respectively connected with the power supply ends of a first charging device (8) and a second charging device (9); the operation index control ends of the main energy storage module (1) and the compensation energy storage module (3) are respectively connected with the monitoring control ends of the energy storage management system I (6) and the energy storage management system II (7); the terminal voltage signal end of the main energy storage module (1) and the output voltage end of the DVR compensator (2) are connected with the sampling end of the direct current voltage sampling unit (11); the sampling digital signal output end of the direct-current voltage sampling unit (11) is connected with the voltage sampling digital signal input end of the control unit (10); the output current end of the DVR compensator (2) is connected with the sampling end of the direct current sampling unit (12); the sampling digital signal output end of the direct current sampling unit (12) is connected with the current sampling digital signal input end of the control unit (10); the signal output end of the control unit (10) is connected with the signal input end of the isolation driving unit (13); the signal output end of the isolation driving unit (13) is connected with a switching tube in the DVR compensator (2);
the selection process of the series-parallel connection quantity of the lithium battery or the super capacitor module comprises the following steps:
the method comprises the following steps: calculating to obtain the serial number M1 and the parallel number N1 of the main energy storage module according to the serial number model and the parallel number model of the main energy storage module, wherein the serial number model and the parallel number model of the main energy storage module are respectively as follows:
M1＝ceil(Udcmax/Ur_es1) (1)
N1＝ceil(Idcmax/Ir_es1) (2)
wherein, UdcmaxIs the maximum value of the bus voltage, IdcmaxIs the maximum value of the bus current, Ur_es1，Ir_es1The series number of the main energy storage module is M1, the parallel number of the main energy storage module is N1, the series number of the compensation energy storage module is M2, the parallel number of the compensation energy storage module is N2, and ceil () is an upward integer function;
step two: the maximum value of the output current of the compensation energy storage module is Idcmax(1+ 0.5) P%), calculating the serial number M2 and the parallel number N2 of the compensation energy storage modules according to the serial number model of the compensation energy storage modules and the parallel number model of the main energy storage modules, wherein the serial number model of the compensation energy storage modules and the parallel number model of the main energy storage modules areThe number models of the modules connected in parallel are respectively as follows:
N2＝ceil[Idcmax(1+0.5*P％)/Ir_es2] (3)
M2＝ceil[UBuckmax(1+A％)/Ur_es2] (4)
wherein, Ur_es2，Ir_es2In order to compensate the rated voltage and the rated current of a battery module, a single body or a super capacitor module in the energy storage module, P% is the ripple rate of the inductive current, and the value range of P is 10-40; the A% is used for compensating the voltage drop of the energy storage module in the estimated discharging process when Buck works, and the voltage drop of different energy storage units in different running states is different;
step three: if the preliminarily selected M2 is not enough to meet the time from 0 to t2, the bus voltage is stabilized at the reference value UrefIf the serial number M2 does not meet the requirement, making M2 equal to M2+1, and upwards searching the serial number meeting the voltage stabilization requirement until M2 meeting the requirement is found; if the initially selected M2 enables the energy storage system to realize voltage stabilization, it is proved that the serial number M2 meets the requirement, and M2 is made to be M2-1, the minimum serial number meeting the requirement is searched downwards until M2 just cannot meet the requirement, and then (M2+1) at this time is the serial number just meeting the requirement.
2. The high-capacity direct-current energy storage device with the direct-current DVR according to claim 1 is characterized in that the main energy storage module and the compensation energy storage module (3) use a lithium battery cell or a super capacitor module as a basic energy storage unit; the lithium battery single body or the super capacitor module forms the main energy storage module and the compensation energy storage module (3) in a series-parallel connection mode.
3. The high-capacity direct-current energy storage device with the direct-current DVR according to claim 1, characterized in that the working mode of the high-capacity direct-current energy storage device with the direct-current DVR is as follows: when the high-capacity direct-current energy storage device starts to operate, the compensation energy storage module (3) and the DVR compensator (2) do not work, the main energy storage module (1) works independently to provide energy for a load, and the freewheeling diode (4) plays a freewheeling role; then the high-capacity direct-current energy storage device carries out energy-carrying link judgment, when the bus voltage is reduced to the voltage-stabilizing value of the device according to the judgment result, the compensation energy storage module (3) and the DVR compensator (2) start to work and output compensation voltage; the compensation energy storage module (3) provides compensation energy for the DVR compensator (2) until the current running time reaches the high-capacity direct current energy storage device to complete a complete discharging process; the main energy storage module (1) and the compensation energy storage module (3) wait for charging and prepare for the next work.
4. The high-capacity direct-current energy storage device with the direct-current DVR according to claim 3, characterized in that the specific process of the enabling link judgment is as follows:
when U is turnedES1<UrefIndicating that the bus voltage begins to drop to UrefIf the voltage drops, the DVR is operated immediately and compensates the voltage drops, and the output of an enabling link is 1; when U is turnedES1>UrefIndicates that the bus voltage is still higher than UrefAnd the DVR does not work, the output of the enabling link is 0, and in the running process of the high-capacity direct current energy storage device, the enabling link is judged in real time until the one-time complete discharging process of the energy storage device is finished.
5. The high-capacity direct-current energy storage device with the direct-current DVR according to claim 1, characterized in that the control unit (10) adopts a control mode of a bus voltage outer ring and a DVR output current inner ring double closed loop, and the specific process of the bus voltage outer ring and the DVR output current inner ring double closed loop control is as follows:
the bus voltage stable value U of the high-capacity direct current energy storage devicerefThe method comprises the steps that the sum of the voltage of a main energy storage module (1) and the output voltage of a DVR compensator (2) obtained by sampling is taken as the feedback quantity of a voltage outer ring as the reference quantity of the voltage outer ring, the judgment result obtained by judging the enabling link is combined, the reference quantity of the voltage outer ring and the feedback quantity of the voltage outer ring are multiplied to be taken as input signals, the input signals are sent to a voltage regulator in a control unit (10) to carry out PI regulation processing, the output of the voltage regulator is taken as the reference quantity of the current inner ring, the output current of the DVR obtained by sampling is taken as the feedback quantity of the currentAnd taking the difference between the current reference quantity and the current feedback quantity as an input signal of a current regulator in the control unit (10), wherein the output result of the current regulator after PU regulation is the duty ratio, and the PWM driving signal of the DVR compensator can be obtained after the duty ratio is compared with the carrier wave.
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