CN112769121A - Direct current bus energy absorption and feedback system structure and control method - Google Patents

Direct current bus energy absorption and feedback system structure and control method Download PDF

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Publication number
CN112769121A
CN112769121A CN202110068957.XA CN202110068957A CN112769121A CN 112769121 A CN112769121 A CN 112769121A CN 202110068957 A CN202110068957 A CN 202110068957A CN 112769121 A CN112769121 A CN 112769121A
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converter
bidirectional
energy storage
storage unit
bus
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国海峰
孙力
刘青山
赵克
段建东
王帅
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; 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
    • H02J1/10—Parallel operation of DC sources
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60M—POWER SUPPLY LINES, AND DEVICES ALONG RAILS, FOR ELECTRICALLY- PROPELLED VEHICLES
    • B60M3/00—Feeding power to supply lines in contact with collector on vehicles; Arrangements for consuming regenerative power
    • B60M3/06—Arrangements for consuming regenerative power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; 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
    • H02J1/10—Parallel operation of DC sources
    • H02J1/102—Parallel operation of DC sources being switching converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or discharging batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other DC sources, e.g. providing buffering
    • H02J7/345—Parallel operation in networks using both storage and other DC sources, e.g. providing buffering using capacitors as storage or buffering devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of DC power input into DC power output
    • H02M3/02—Conversion of DC power input into DC power output without intermediate conversion into AC
    • H02M3/04—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters
    • H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of DC power input into DC power output
    • H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
    • H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
    • H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
    • H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33584—Bidirectional converters

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

本发明公开了一种直流母线能量吸收与回馈系统结构及控制方法，将双向DC/DC变换器输出与储能单元串联在一起，实现直流母线和储能单元之间的能量流动。它包括输入开关保险单元，主储能单元，双向DC/DC1变换器1，辅助储能单元，双向DC/DC2变换器2，控制单元，滤波电容C1、C2、L1。直流母线正极（Ubus+）通过输入开关保险单元连接主储能单元正极，主储能单元负极连接双向DC/DC1变换器1的A+极，双向DC/DC1变换器1的A‑极接参考地。滤波电容C2并联到双向DC/DC变换器1的A+极和A‑极两端。双向DC/DC1变换器1的B+极接辅助储能单元正极，双向DC/DC变换器2的D‑极接参考地。滤波电容C1并联到双向DC/DC变换器2的D+极和D‑极两端。

Figure 202110068957

The invention discloses a structure and a control method of a DC bus energy absorption and feedback system. The bidirectional DC/DC converter output and the energy storage unit are connected in series to realize the energy flow between the DC bus and the energy storage unit. It includes input switch fuse unit, main energy storage unit, bidirectional DC/DC1 converter 1, auxiliary energy storage unit, bidirectional DC/DC2 converter 2, control unit, filter capacitors C1, C2, L1. The positive pole of the DC bus (Ubus+) is connected to the positive pole of the main energy storage unit through the input switch fuse unit, the negative pole of the main energy storage unit is connected to the A+ pole of the bidirectional DC/DC1 converter 1, and the A- pole of the bidirectional DC/DC1 converter 1 is connected to the reference ground. The filter capacitor C2 is connected in parallel to both ends of the A+ pole and the A‑ pole of the bidirectional DC/DC converter 1 . The B+ pole of the bidirectional DC/DC1 converter 1 is connected to the positive pole of the auxiliary energy storage unit, and the D- pole of the bidirectional DC/DC converter 2 is connected to the reference ground. The filter capacitor C1 is connected in parallel to both ends of the D+ pole and the D- pole of the bidirectional DC/DC converter 2 .

Figure 202110068957

Description

Direct current bus energy absorption and feedback system structure and control method
Technical Field
The invention relates to the technical field of energy absorption and feedback, in particular to a direct current bus energy absorption and feedback system structure and a control method.
Background
In various energy storage application fields, energy storage elements of the energy storage device are mostly super capacitors or lithium batteries, and in order to realize bidirectional flow of energy of an energy storage unit, a bidirectional DCDC converter needs to be configured. For example, in the energy storage of the direct current microgrid, when the voltage of the direct current bus rises, the super capacitor is charged through the bidirectional DC/DC converter, and the redundant energy on the direct current bus is transferred to the super capacitor. When the voltage of the direct current bus is reduced, the energy of the super capacitor is output to the direct current bus through the bidirectional DC/DC converter so as to maintain the stability of the voltage of the direct current bus. In such applications, the conventional technical process is shown in fig. 2. The energy of the output of the direct current bus is transferred to the energy storage module after passing through the DC/DC converter, the conversion power borne by the DC/DC converter is all the power transferred by the direct current bus (P1 = U1I 1), and the DC/DC converter generally adopts a BUCK/BOOST BUCK-BOOST circuit structure. Since the DC bus voltage is high (several hundred V) and the power released needs to be absorbed up to megawatts, the DC/DC converter converts power very much. In practical application, the switching frequency of the DC/DC converter can only be about 2kHz, and the DC/DC converter is large in size and high in price. A novel bidirectional energy storage conversion structure is provided, the power of a DC/DC converter is reduced, the switching frequency is improved, and the overall efficiency of a system is improved, so that the bidirectional energy storage conversion structure is one of key technologies in the field of energy storage conversion.
Disclosure of Invention
The present invention is directed to a bootstrap series DC/DC circuit and converter, which overcome the shortcomings of the prior art. The technical scheme adopted by the invention is as follows: a bootstrap series DC/DC converter structure is constructed, so that the energy of a direct current bus is controlled to be transferred to an energy storage module (a super capacitor or a battery) by using smaller conversion power, and the energy of the energy storage module is fed back to the bus.
The structural block diagram is shown in fig. 1, and the bidirectional DC/DC1 converter comprises an input switch fuse unit, a main energy storage electric unit, a bidirectional DC/DC1 converter 1, an auxiliary energy storage unit, a bidirectional DC/DC2 converter 2, a control unit, filter capacitors C1, C2 and L1.
The input switch fuse unit plays roles of overcurrent protection and switch isolation. The main energy storage unit and the auxiliary energy storage unit can be composed of super capacitors or lithium batteries. The bidirectional DC/DC converter 1 and the bidirectional DC/DC2 converter 2 are in a non-isolation structure (such as a BUCK/BOOST structure) or an isolation structure (such as a double H bridge DC/DC converter structure). The control unit realizes the control of the bidirectional DC/DC converter 1 and the bidirectional DC/DC2 converter 2 and adopts control strategies such as PWM control, LLC control, full-bridge phase-shift control and the like.
The positive pole (Ubus +) of the direct current bus is connected with the positive pole of the main energy storage unit through the input switch fuse unit, the negative pole of the main energy storage unit is connected with the A + pole of the bidirectional DC/DC1 converter 1, and the A-pole of the bidirectional DC/DC1 converter 1 is connected with the ground reference.
The filter capacitor C2 is connected in parallel across the a + pole and the a-pole of the bidirectional DC/DC converter 1.
The B + pole of the bidirectional DC/DC1 converter 1 is connected with the anode of the auxiliary energy storage unit, and the B-pole of the bidirectional DC/DC converter 1 and the cathode of the auxiliary energy storage unit are connected with the ground.
The C + pole of the bidirectional DC/DC converter 2 is connected with the anode of the auxiliary energy storage unit, and the B-pole of the bidirectional DC/DC converter 2 is connected with the reference ground.
The D + electrode of the bidirectional DC/DC converter 2 is connected with one end of an inductor L1, and the other end of the inductor L1 is connected with the anode of the main energy storage unit. The D-pole of the bidirectional DC/DC converter 2 is connected to the ground.
The filter capacitor C1 is connected in parallel across the D + pole and the D-pole of the bidirectional DC/DC converter 2.
In the direct current bus energy absorption and feedback system structure and the control method, when the direct current bus energy needs to be absorbed, the direct current bus voltage Ubus, the main energy storage unit voltage U1, the bidirectional DC/DC converter 1A + and the A-terminal voltage U2 need to meet the condition that Ubus is more than or equal to (U1+ U2).
When the voltage Ubus of the direct current bus rises and reaches a set value, the energy absorption starts.
In the direct current bus energy absorption and feedback system structure and the control method, the control unit acquires the voltage of Ubus, U1, U2 and U3, controls the bidirectional DC/DC converter 1, adjusts the current magnitude of I1 (flows out of the direct current bus), limits the voltage of the direct current bus to a certain maximum value, and realizes that the excess energy on the direct current bus is absorbed and stored in the main energy storage unit and the auxiliary energy storage unit.
In the direct current bus energy absorption and feedback system structure and the control method, when the stored energy needs to be fed back, the direct current bus voltage Ubus, the main energy storage voltage U1, the voltage U2 of the A + and A-ends of the bidirectional DC/DC converter 1 need to meet the requirement that (U1+ U2) is more than or equal to Ubus.
When the voltage Ubus of the direct current bus is reduced and falls to a set value, the feedback energy begins.
In the direct current bus energy absorption and feedback system structure and the control method, the control unit acquires the voltage of Ubus, U1, U2 and U3, controls the DC/DC converter 1, adjusts the current magnitude of I1 (flowing to the direct current bus), limits the voltage of the direct current bus to a certain minimum value, and realizes that the energy in the main energy storage unit and the auxiliary energy storage unit is fed back to the direct current bus.
In the direct current bus energy absorption and feedback system structure and the control method thereof, the auxiliary energy storage unit is an energy provider and an energy absorber of the bidirectional DC/DC converter 1, and the energy of the auxiliary energy storage unit and the energy of the main energy storage unit should keep a proper proportional relation. Energy exchange between the auxiliary energy storage unit and the direct current bus is formed through the bidirectional DC/DC converter 2. When the energy of the auxiliary energy storage unit is too high, the redundant energy is sent to the direct current bus, and when the energy of the auxiliary energy storage unit is too low, the energy is obtained from the direct current bus. By such control, the energy of the auxiliary energy storage unit is ensured to be at a proper level.
In the direct current bus energy absorption and feedback system structure and the control method, the flow between the direct current bus energy and the energy storage unit is realized by controlling the output current of the bidirectional DC/DC converter 1.
The voltage U2= Ubus-U1 at the bidirectional DC/DC converter 1 (neglecting the internal resistance voltage drop of the DC bus and the main energy storage unit), so that the conversion power of the bidirectional DC/DC converter 1 is only PDC = I1 (Ubus-U1), which is greatly reduced compared with the converter power of the classical scheme (PDC = I1).
In particular, the PDC is small, i.e., a large power output is controlled and regulated by a small power conversion, when U1 is similar to Ubus.
In the direct current bus energy absorption and feedback system structure and the control method, the control circuit acquires the voltage of Ubus, the voltage of U1 and the voltage of U2, and the energy storage and feedback are realized by the control modes of the voltage outer ring (stable Ubus, Uinmax is more than or equal to Uinmin) and the current inner ring (I1 current is constant and controllable).
In the direct current bus energy absorption and feedback system structure and the control method, when energy is absorbed, the input energy of the bidirectional DC/DC converter 1 converter comes from the direct current bus, and the output energy is stored in the auxiliary energy storage unit. When the energy is absorbed, the main energy storage unit and the auxiliary energy storage unit both perform energy storage work.
In the direct current bus energy absorption and feedback system structure and the control method, when energy is fed back, the input energy of the bidirectional DC/DC converter 1 comes from the auxiliary energy storage unit, the output energy (I1) is fed back to the direct current bus through the main energy storage unit, and when the energy is fed back, the main energy storage unit and the auxiliary energy storage unit release energy to work.
In the direct current bus energy absorption and feedback system structure and the control method, the bidirectional DC/DC converter 2 solves the problem of matching the capacity of the auxiliary energy storage unit with the capacity of the main energy storage unit.
In practical application, the energy of the increased DC bus voltage needs the main energy storage unit and the auxiliary energy storage unit to absorb and store together, and the energy storage unit has the maximum storage capacity, so that the storage capacities of the main energy storage unit and the auxiliary energy storage unit have a proper proportional relationship. To prevent this proper scaling during operation, the bi-directional DC/DC converter 2 is necessary.
Particularly, the capacity of the auxiliary energy storage unit is too low, and the energy of the main energy storage unit cannot be maximally fed back to the direct current bus during energy feedback, so that the absorbed energy is insufficient during reabsorption. At this time, the bidirectional DC/DC converter 2 charges the auxiliary energy storage unit.
Particularly, the capacity of the auxiliary energy storage unit is too high, and the energy absorbed by the auxiliary energy storage unit is limited, which results in insufficient energy absorbed by the main energy storage unit. At this point, the bidirectional DC/DC converter 2 discharges the auxiliary energy storage unit (energy is sent to the DC bus).
In particular, the bidirectional DC/DC converter 2 only undertakes the capacity matching work of the auxiliary energy storage unit and the main energy storage unit, and the conversion power is small. About 20% of the bidirectional DC/DC converter 1.
In the direct current bus energy absorption and feedback system structure and the control method, the bidirectional DC/DC converter 1 and the bidirectional DC/DC converter 2 can be formed by connecting n groups of DC/DC converters with the same structure in series or in parallel, so that power expansion is realized. After series connection or parallel connection, each group of DC/DC converters can adopt current-sharing and voltage-sharing control modes such as staggered parallel connection, master-slave mode, droop control and the like.
The invention has the beneficial effects that: through the proposal, the problem that the overall efficiency of the system is not high due to high power and low switching frequency of the DC/DC converter is solved, and the system structure chart is proposed:
on one hand, the output of the bidirectional DC/DC converter 1 is connected with the main energy storage unit in series, and the energy flow between the direct current bus and the energy storage unit is realized by adjusting the output current of the bidirectional DC/DC converter 1. The difference between the voltage of the direct current bus and the voltage of the energy storage unit is within a certain reasonable range (20-30%), and the bidirectional DC/DC converter 1 only needs to output the difference voltage. Therefore, the conversion power of the bidirectional DC/DC converter is greatly reduced compared with a general full-power structural mode, and the conversion power is 20-30% of that of a classical structure. The manufacturing cost of the product is reduced, and the overall efficiency of the system is improved;
on the other hand, since the bidirectional DC/DC converter 1 is powered down and the output voltage is lowered, the power device selection range is widened. The switching frequency of the converter can be greatly increased to reach more than 20 kHz. The volume of the DC/DC converter is reduced.
Drawings
Fig. 1 is a structural diagram of a dc bus energy absorption and feedback system according to the present invention;
FIG. 2 is a diagram of a conventional classical energy absorption feedback structure;
fig. 3 is a structural diagram of a dc bus energy absorption and feedback system in embodiment 1;
FIG. 4 shows an energy absorption circuit model (VT 1 operation) of example 1;
FIG. 5 shows an energy feedback circuit model (VT 2 operation) of example 1;
FIG. 6 is a circuit model of the auxiliary energy storage unit energy increasing circuit (VT 3 operation) in embodiment 1;
FIG. 7 is a circuit model of the auxiliary energy storage unit energy reduction circuit (VT 4 operation) in embodiment 1;
fig. 8 is a structural diagram of a dc bus energy absorption and feedback system in embodiment 2;
FIG. 9 is a model of an energy absorption circuit (BUCK mode) of embodiment 2;
FIG. 10 is a model of an energy absorption circuit (BOOST mode) of example 2;
FIG. 11 shows an energy feedback circuit model (BUCK mode) of example 2;
fig. 12 is an energy feedback circuit model (BOOST mode) of example 2.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
Example one
This embodiment 1 provides a dc bus energy absorption and feedback system structure and a control method. As shown in fig. 3.
The bidirectional DC/DC1 converter comprises an input switch fuse unit, a main energy storage unit, a bidirectional DC/DC1 converter 1, an auxiliary energy storage unit, a bidirectional DC/DC2 converter 2, a control unit and filter capacitors C1, C2 and L1. The input switch fuse unit plays roles of overcurrent protection and switch isolation. The main energy storage unit and the auxiliary energy storage unit can be composed of super capacitors or lithium batteries. The bidirectional DC/DC converter 1 is of a BUCK/BOOST structure, and the bidirectional DC/DC2 converter 2 is of a BOOST/BUCK structure. The control unit realizes the control of the bidirectional DC/DC converter 1 and the bidirectional DC/DC2 converter 2 and adopts a PWM control strategy.
The positive pole (Ubus +) of the direct current bus is connected with the positive pole of the main energy storage unit through the input switch fuse unit, the negative pole of the main energy storage unit is connected with the A + pole of the bidirectional DC/DC1 converter 1, and the A-pole of the bidirectional DC/DC1 converter 1 is connected with the ground reference.
The filter capacitor C2 is connected in parallel across the a + pole and the a-pole of the bidirectional DC/DC converter 1.
The B + pole of the bidirectional DC/DC1 converter 1 is connected with the anode of the auxiliary energy storage unit, and the B-pole of the bidirectional DC/DC converter 1 and the cathode of the auxiliary energy storage unit are connected with the ground.
The C + pole of the bidirectional DC/DC converter 2 is connected with the anode of the auxiliary energy storage unit, and the B-pole of the bidirectional DC/DC converter 2 is connected with the reference ground.
The D + electrode of the bidirectional DC/DC converter 2 is connected with one end of an inductor L1, and the other end of the inductor L1 is connected with the anode of the main energy storage unit. The D-pole of the bidirectional DC/DC converter 2 is connected to the ground.
The bidirectional DC/DC converter 1 is composed of VT1, VT2, and L2. The collector of VT1 is connected to A + terminal, the emitter of VT1 is connected to VT2 collector and L2, the other end of L2 is connected to B + terminal, and the emitter of VT2 is connected to ground.
The bidirectional DC/DC converter 2 is composed of VT3, VT4 and L3. VT3 is connected with collector L1 and C1, VT3 emitter is connected with collector VT4 and L3, L3 is connected with C + end, and VT4 emitter is connected with ground.
The filter capacitor C1 is connected in parallel across the D + pole and the D-pole of the bidirectional DC/DC converter 2.
The switch device is an IGBT or an MOSFET, and a diode is arranged inside the switch device.
In the energy absorption and feedback system structure of the DC bus and the control method according to embodiment 1 of the present invention, energy flow between the DC bus and the energy storage unit is realized by controlling the current I1 at the a + end of the DC/DC converter 1.
In particular, Ubus ≧ U1+ U3 when the DC bus voltage is too high. The control unit collects voltages of Ubus, U1, U2 and U3, controls the bidirectional DC/DC converter 1 to work in a BUCK mode, controls VT1 to work in a PMW control mode, adjusts the magnitude of I1 current (marked as a negative value according to figure 3), absorbs and stores redundant energy on the direct current bus in the main energy storage unit and the auxiliary energy storage unit, and limits the voltage of the direct current bus on a certain maximum value.
When VT1 is turned on, the circuit model is shown in FIG. 4. The direct current bus current returns to the direct current bus through the switch fuse unit, the main energy storage unit, the VT1, the L2 and the auxiliary energy storage unit. When VT1 is turned off, the inductive current freewheels through the auxiliary energy storage unit and the diode inside VT 2.
Specifically, when the direct current bus is too low, the bidirectional DC/DC converter 1 is controlled to operate in a BOOST mode, the VT2 operates in a PMW control mode, the magnitude of the I1 current (marked as positive according to fig. 3) is adjusted, the energy in the main energy storage unit and the auxiliary energy storage unit is fed back to the direct current bus, and the direct current bus voltage Ubus is limited to a certain minimum value.
When VT2 is turned on, the circuit model is shown in FIG. 5. The energy of the auxiliary energy storage unit flows out through L2 and VT2, and the inductive current is increased. When the VT2 is turned off, the inductive current is fed back to the dc bus through the VT1 internal diode, the main energy storage unit, and the switch fuse unit.
In the structure and the control method of the direct current bus energy absorption and feedback system described in embodiment 1 of the present invention, voltages of each part of the system need to satisfy: (U1+ U3) < Ubusmin, and the main energy storage unit and the auxiliary energy storage unit are prevented from uncontrolled energy feedback to the direct current bus.
In the structure and the control method of the energy absorption and feedback system for the DC bus according to embodiment 1 of the present invention, an energy exchange between the auxiliary energy storage unit and the DC bus is formed through the bidirectional DC/DC converter 2.
In particular, when the energy of the auxiliary energy storage unit is too low, the bidirectional DC/DC converter 2 operates in a BUCK mode, and the VT3 operates in a PMW control mode to transfer the DC bus energy to the auxiliary energy storage unit to keep the U3 stable.
When VT3 is turned on, the circuit model is shown in FIG. 6. The direct current bus current returns to the direct current bus through the switch fuse unit, the L1, the VT3, the L3 and the auxiliary energy storage unit. When the VT3 is turned off, the current in the inductor L3 flows through the auxiliary energy storage unit and the internal diode of the VT 4.
In particular, when the energy of the auxiliary energy storage unit is too high, the bidirectional DC/DC converter 2 operates in BOOST mode, and the VT4 operates in PMW control mode, so as to feed the excess energy of the auxiliary energy storage unit back to the DC bus, thereby keeping the U3 stable.
When VT4 is turned on, the circuit model is shown in FIG. 7. The energy of the auxiliary energy storage unit flows out through L3 and VT4, and the inductive current is increased. When the VT4 is turned off, the inductor L3 current is fed back to the dc bus through the VT3 internal diode, the L1, and the switch fuse unit.
In the structure and the control method of the direct current bus energy absorption and feedback system according to embodiment 1 of the present invention, the bidirectional DC/DC converter 1 and the bidirectional DC/DC converter 2 may be implemented by connecting n sets of DC/DC converters having the same structure in parallel, so as to implement power expansion.
After parallel connection, each group of DC/DC converters can adopt current sharing control modes such as staggered parallel connection, master-slave mode, droop control and the like.
In the structure and the control method of the energy absorption and feedback system for the DC bus according to embodiment 1 of the present invention, the voltage between a + and a-of the bidirectional DC/DC converter 1 is U2= Ubus-U1 (neglecting the internal resistance voltage drop of the DC bus and the main energy storage unit), so that the conversion power of the DC/DC converter 1 is only PDC = I1 (Ubus-U1), which is greatly reduced compared with the converter power (P = I1 Ubus) in the classical scheme. I.e. a large power output is controlled and regulated by a small power conversion.
Specifically, for a 1500V rail transit traction network system, Ubusmax =1800V and Ubusmin =1350V are set. The upper limit of the control voltage is 1700V. Therefore, the voltage of the main energy storage unit is 1300V, and the voltage of the auxiliary energy storage unit is 500V. Bidirectional DC/DC converter 1 power Pdc = (1700) -1300 × I1=400 × I1. Whereas the classical solution Pdc1=1700 × I1. The power of the bidirectional DC/DC converter 1 is only 24% of the power of the converter in the classical technical scheme.
Example two
This embodiment 2 provides a dc bus energy absorption and feedback system structure and a control method. As shown in fig. 8.
The bidirectional DC/DC1 converter comprises an input switch fuse unit, a main energy storage unit, a bidirectional DC/DC1 converter 1, an auxiliary energy storage unit, a bidirectional DC/DC2 converter 2, a control unit and filter capacitors C1, C2 and L1.
The input switch fuse unit plays roles of overcurrent protection and switch isolation. The main energy storage unit and the auxiliary energy storage unit can be composed of super capacitors or lithium batteries. The bidirectional DC/DC converter 1 is of a BOOST/BUCK structure, and the bidirectional DC/DC2 converter 2 is of a BOOST/BUCK structure. The control unit realizes the control of the bidirectional DC/DC converter 1 and the bidirectional DC/DC2 converter 2 and adopts a PWM control strategy.
The positive pole (Ubus +) of the direct current bus is connected with the positive pole of the main energy storage unit through the input switch fuse unit, the negative pole of the main energy storage unit is connected with the A + pole of the bidirectional DC/DC1 converter 1, and the A-pole of the bidirectional DC/DC1 converter 1 is connected with the ground reference.
The filter capacitor C2 is connected in parallel across the a + pole and the a-pole of the bidirectional DC/DC converter 1.
The B + pole of the bidirectional DC/DC1 converter 1 is connected with the anode of the auxiliary energy storage unit, and the B-pole of the bidirectional DC/DC converter 1 and the cathode of the auxiliary energy storage unit are connected with the ground.
The C + pole of the bidirectional DC/DC converter 2 is connected with the anode of the auxiliary energy storage unit, and the B-pole of the bidirectional DC/DC converter 2 is connected with the reference ground.
The D + electrode of the bidirectional DC/DC converter 2 is connected with one end of an inductor L1, and the other end of the inductor L1 is connected with the anode of the main energy storage unit. The D-pole of the bidirectional DC/DC converter 2 is connected to the ground.
The filter capacitor C1 is connected in parallel across the D + pole and the D-pole of the bidirectional DC/DC converter 2.
The bidirectional DC/DC converter 1 consists of VT1-VT4 and L2. The VT1 collector is connected to the A + terminal, the VT1 emitter is connected to the VT2 collector, and then to the L2, the VT2 emitter is connected to the reference ground (A-terminal). The VT3 collector is connected to the B + terminal, the VT3 emitter is connected to the VT4 collector and then to the other end of L2, and the VT4 emitter is connected to the reference ground (B-terminal).
The bidirectional DC/DC converter 2 is composed of VT5, VT6 and L3. VT5 is connected with collector L1 and C1, VT5 emitter is connected with collector VT6 and L3, L3 is connected with C + end, and VT6 emitter is connected with ground.
In the energy absorption and feedback system structure of the DC bus and the control method according to embodiment 2 of the present invention, energy flow between the DC bus and the energy storage unit is realized by controlling the current I1 at the a + end of the DC/DC converter 1.
Particularly, when the voltage of the direct current bus is too high, the control unit collects the voltages of Ubus, U1, U2 and U3, controls the bidirectional DC/DC converter 1 to work in a BUCK or BOOST mode, and controls VT1 or VT4 to work in a PMW control mode, so that the magnitude of I1 current (marked as a negative value according to figure 3) is adjusted, the excess energy on the direct current bus is absorbed and stored in the main energy storage unit and the auxiliary energy storage unit, and the voltage of the direct current bus Ubus is limited to a certain maximum value.
(Ubus-U1) > U3, the bidirectional DC/DC converter 1 operates in BUCK mode. When the VT1 works, the circuit model is as shown in fig. 9, the VT1 is turned on, and the dc bus returns to the dc bus via the switch fuse unit, the main energy storage unit, the VT1, the L2, the internal diode of the VT3, and the auxiliary energy storage unit. When the VT1 is turned off, the current in the inductor L2 flows through the internal diode of the VT3, the auxiliary energy storage unit, and the internal diode of the VT 2.
(Ubus-U1) < U3, the bidirectional DC/DC converter 1 operates in BOOST mode. The VT4 works (VT 1 long pass), the circuit model is as shown in fig. 10, VT4 is turned on, and the dc bus returns to the dc bus through the switch fuse unit, the main energy storage unit, VT1, L2, VT 4. When the VT4 is turned off, the direct current bus current returns to the direct current bus through the switch fuse unit, the main energy storage unit, the VT1, the L2, the diode inside the VT3 and the auxiliary energy storage unit.
Specifically, when the direct current bus is too low, the bidirectional DC/DC converter 1 is controlled to operate in a BOOST or BUCK mode, and the VT2 or VT3 operates in a PMW control mode, so as to adjust the magnitude of the I1 current (which is marked as a positive value according to fig. 3), and feed the energy in the main energy storage unit and the auxiliary energy storage unit back to the direct current bus, and the voltage Ubus of the direct current bus is limited to a certain minimum value.
(Ubus-U1) < U3, the bidirectional DC/DC converter 1 operates in BUCK mode. When the VT3 works, the circuit model is as shown in fig. 11, the VT3 is turned on, and the current of the auxiliary energy storage unit is fed back to the dc bus through the VT3, the L2, the internal diode of the VT1, and the switch fuse unit. When the VT3 is turned off, the current in the inductor L2 flows through the internal diode of the VT1, the main energy storage unit, the switch fuse unit and the internal diode of the VT 4.
(Ubus-U1) > U3, the bidirectional DC/DC converter 1 operates in BOOST mode. The VT2 works (VT 3 long pass), the circuit model is as shown in FIG. 12, VT2 is conducted, the energy of the auxiliary energy storage unit is released through VT3, L2 and VT2, and L2 stores energy. When the VT2 is turned off, the energy of the auxiliary energy storage unit is fed back to the dc bus through the internal diodes of VT3, L2, VT1, the main energy storage unit, and the switch fuse unit.
In the structure and the control method of the energy absorption and feedback system for the DC bus according to embodiment 2 of the present invention, an energy exchange between the auxiliary energy storage unit and the DC bus is formed through the bidirectional DC/DC converter 2.
In particular, when the energy of the auxiliary energy storage unit is too high, the bidirectional DC/DC converter 2 operates in BOOST mode, and the VT6 operates in PMW control mode, so as to feed the excess energy of the auxiliary energy storage unit back to the DC bus, thereby keeping the U3 stable.
In particular, when the energy of the auxiliary energy storage unit is too low, the bidirectional DC/DC converter 2 operates in a BUCK mode, and the VT5 operates in a PMW control mode to transfer the DC bus energy to the auxiliary energy storage unit to keep the U3 stable.
In the structure and the control method of the direct current bus energy absorption and feedback system according to embodiment 2 of the present invention, the bidirectional DC/DC converter 1 and the bidirectional DC/DC converter 2 may be implemented by connecting n sets of DC/DC converters having the same structure in parallel, so as to implement power expansion.
After parallel connection, each group of DC/DC converters can adopt current sharing control modes such as staggered parallel connection, master-slave mode, droop control and the like.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (10)

1.一种直流母线能量吸收与回馈系统结构，其特征在于，所述结构包括输入开关保险单元，主储能电单元，双向DC/DC变换器1，辅助储能单元，双向DC/DC2变换器2，控制单元，滤波电容C1、C2以及L1；1. A DC bus energy absorption and feedback system structure, is characterized in that, described structure comprises input switch insurance unit, main energy storage power unit, bidirectional DC/DC converter 1, auxiliary energy storage unit, bidirectional DC/DC2 conversion Device 2, control unit, filter capacitors C1, C2 and L1; 所述的双向DC/DC变换器1的A+和A-端与所述的主储能电单元串联；The A+ and A- terminals of the bidirectional DC/DC converter 1 are connected in series with the main energy storage unit; 所述的双向DC/DC变换器1的B+和B-端与所述的辅助储能电单元并联；The B+ and B- terminals of the bidirectional DC/DC converter 1 are connected in parallel with the auxiliary energy storage unit; 所述的双向DC/DC变换器2的C+和C-端与所述的辅助储能电单元并联；The C+ and C- terminals of the bidirectional DC/DC converter 2 are connected in parallel with the auxiliary energy storage unit; 所述的双向DC/DC变换器2的D+通过L1与主储能电单元正极相连；The D+ of the bidirectional DC/DC converter 2 is connected to the positive pole of the main energy storage unit through L1; 所述的双向DC/DC变换器2的D-接参考地。The D- of the bidirectional DC/DC converter 2 is connected to the reference ground. 2.根据权利要求1所述的一种直流母线能量吸收与回馈系统结构，其特征在于，所述的双向DC/DC变换器1为非隔离结构或隔离结构。2 . The structure of a DC bus energy absorption and feedback system according to claim 1 , wherein the bidirectional DC/DC converter 1 is a non-isolated structure or an isolated structure. 3 . 3.根据权利要求1所述的一种直流母线能量吸收与回馈系统结构，其特征在于，所述的双向DC/DC变换器1为BUCK/BOOST变换器结构，当储能系统吸收直流母线能量时为BUCK降压结构，储能系统回馈能量时为BOOST升压结构。3. a kind of direct current bus energy absorption and feedback system structure according to claim 1 is characterized in that, described bidirectional DC/DC converter 1 is BUCK/BOOST converter structure, when energy storage system absorbs direct current bus energy When it is a BUCK step-down structure, when the energy storage system feeds back energy, it is a BOOST boost structure. 4.根据权利要求1所述的一种直流母线能量吸收与回馈系统结构，其特征在于，所述的双向DC/DC变换器1为BOOST/BUCK变换器结构，当储能系统吸收直流母线能量时为BOOST升压结构，储能系统回馈能量时为BUCK降压结构。4. a kind of direct current bus energy absorption and feedback system structure according to claim 1, is characterized in that, described bidirectional DC/DC converter 1 is BOOST/BUCK converter structure, when energy storage system absorbs direct current bus energy When the energy storage system is feeding back energy, it is a BOOST boost structure, and when the energy storage system feeds back energy, it is a BUCK step-down structure. 5.根据权利要求1所述的一种直流母线能量吸收与回馈系统结构，其特征在于，所述的双向DC/DC变换器1为BOOST/BUCK升降压变换器结构，即储能系统吸收直流母线能量时，当U2＞U3时，双向DC/DC变换器1工作在BUCK状态下；当U2＜U3时，双向DC/DC变换器1工作在BOOST状态下；5. The structure of a DC bus energy absorption and feedback system according to claim 1, wherein the bidirectional DC/DC converter 1 is a boost/buck converter structure, that is, the energy storage system absorbs When the DC bus energy is present, when U2>U3, the bidirectional DC/DC converter 1 works in the BUCK state; when U2<U3, the bidirectional DC/DC converter 1 works in the BOOST state; 储能系统回馈能量时,当U2＜U3时，双向DC/DC变换器1工作在BUCK状态下，当U2＞U3时，双向DC/DC变换器1工作在BOOST状态下。When the energy storage system feeds back energy, when U2<U3, the bidirectional DC/DC converter 1 works in the BUCK state, and when U2>U3, the bidirectional DC/DC converter 1 works in the BOOST state. 6.根据权利要求1所述的一种直流母线能量吸收与回馈系统结构，其特征在于，所述的控制单元实现对双向DC/DC变换器1的A+端电流I1控制。6 . The structure of a DC bus energy absorption and feedback system according to claim 1 , wherein the control unit controls the current I1 of the A+ terminal of the bidirectional DC/DC converter 1 . 7 . 7.根据权利要求1所述的一种直流母线能量吸收与回馈系统结构，其特征在于，所述的控制单元用于对双向DC/DC变换器2的C+端和C-端电压控制。7 . The structure of a DC bus energy absorption and feedback system according to claim 1 , wherein the control unit is used to control the voltage of the C+ terminal and the C- terminal of the bidirectional DC/DC converter 2 . 8 . 8.根据权利要求1所述的一种直流母线能量吸收与回馈系统结构，其特征在于，所述的双向DC/DC变换器1和双向DC/DC变换器2以n组相同结构的DC/DC变换器并联，用于功率扩展。8. The structure of a DC bus energy absorption and feedback system according to claim 1, wherein the bidirectional DC/DC converter 1 and the bidirectional DC/DC converter 2 are composed of n groups of DC/DC converters with the same structure. DC converters are connected in parallel for power expansion. 9.根据权利要求1-8中任一所述的一种直流母线能量吸收与回馈系统结构的控制方法，其特征在于，当所述的双向DC/DC变换器1为BUCK/BOOST变换器结构时，主储能单元及辅助储能单元电压取值原则：（U1+U3）＜Ubusmin，其中，双向DC/DC变换器1为BOOST/BUCK变换器结构时，主储能单元及辅助储能单元电压取值原则：U1＜Ubusmin，（U1+U3）＞Ubusmax。9. according to the control method of a kind of DC bus energy absorption and feedback system structure described in any one of claim 1-8, it is characterized in that, when described bidirectional DC/DC converter 1 is BUCK/BOOST converter structure When the voltage of the main energy storage unit and the auxiliary energy storage unit is selected, the principle of voltage value: (U1+U3)<Ubusmin, in which, when the bidirectional DC/DC converter 1 is a BOOST/BUCK converter structure, the main energy storage unit and the auxiliary energy storage unit Unit voltage value principle: U1 < Ubusmin, (U1 + U3) > Ubusmax. 10.根据权利要求9所述的一种直流母线能量吸收与回馈系统结构的控制方法，其特征在于，当所述的双向DC/DC变换器1为BOOST/BUCK升降压变换器结构时，U1＜Ubusmin，其中，U1为主储能单元电压，U3为辅助储能单元电压，Ubusmin和Ubusmax分别为直流母线工作时最小电压和最大电压。10. The control method of a DC bus energy absorption and feedback system structure according to claim 9, characterized in that, when the bidirectional DC/DC converter 1 is a BOOST/BUCK buck-boost converter structure, U1<Ubusmin, where U1 is the voltage of the main energy storage unit, U3 is the voltage of the auxiliary energy storage unit, and Ubusmin and Ubusmax are the minimum and maximum voltages when the DC bus is working, respectively.
CN202110068957.XA 2021-01-19 2021-01-19 Direct current bus energy absorption and feedback system structure and control method Pending CN112769121A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114188932A (en) * 2021-10-25 2022-03-15 广西电网有限责任公司玉林供电局 Intelligent bus coupler applied to station direct-current power supply system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114188932A (en) * 2021-10-25 2022-03-15 广西电网有限责任公司玉林供电局 Intelligent bus coupler applied to station direct-current power supply system

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Application publication date: 20210507