CN108767863B - Power regulation and control strategy of two-subarea power distribution system with DAB converter as node - Google Patents

Power regulation and control strategy of two-subarea power distribution system with DAB converter as node Download PDF

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CN108767863B
CN108767863B CN201810663209.4A CN201810663209A CN108767863B CN 108767863 B CN108767863 B CN 108767863B CN 201810663209 A CN201810663209 A CN 201810663209A CN 108767863 B CN108767863 B CN 108767863B
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voltage
distribution
power
current
control signal
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CN108767863A (en
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游江
廖梦岩
邓梦露
李晓旭
王西贝
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Harbin Engineering University
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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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • H02J3/383—
    • H02J3/386—
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

Abstract

The invention provides a power regulation strategy of a two-subarea power distribution system by taking a DAB converter as a node, and a current signal of a current loop A is obtained through a droop control module A
Figure DDA0001707185860000011
With the actual current signal iADifference is made to obtain deviation ieAObtaining a control signal via a current controller
Figure DDA0001707185860000012
Setting a voltage threshold u in the voltage loop A for the distribution sub-zone BTHBAs a given signal, with the DC bus voltage u of the distribution bay BBDifference deviation ueAObtaining control signals via a voltage controller
Figure DDA0001707185860000013
Will be provided with
Figure DDA0001707185860000014
And
Figure DDA0001707185860000015
drive pulse phase shift angle of power distribution partition A-side full-bridge converter with minimum value
Figure DDA0001707185860000016
Side B is the same as side a. The free smooth switching and flexible adjustment of the electric energy transmission direction and size between the two power distribution subareas are realized, the power distribution subareas of the output power of the DAB converter cannot enable the voltage of a direct current bus of the power distribution subareas to be lower than an allowed minimum operation voltage threshold value due to overlarge output power, and the power distribution subareas of the input power cannot be higher than an allowed maximum operation voltage threshold value due to the overlarge absorbed power.

Description

Power regulation and control strategy of two-subarea power distribution system with DAB converter as node
Technical Field
The invention belongs to the technical field of power electronics, and particularly relates to a power regulation and control strategy of a two-subarea power distribution system with a DAB converter as a node.
Background
In a power distribution system taking a DAB converter as a regulation node, two ports of the DAB converter are expanded into two isolated power distribution subareas. The two power distribution subareas can be connected with a plurality of photovoltaic solar power generation devices, wind power generation devices and the like, and at the same time, under the influence of weather and environmental factors, the power of the power which can be output by each power generation device in the power distribution subareas can have larger difference, the condition that the power generated by a power supply cannot meet the power required by the load of the power supply can occur, and the voltage of a direct current bus of the power distribution subarea can be reduced at the moment. Meanwhile, when the electric energy in a certain power distribution partition cannot meet the power required by the load due to the increase of the load, the bus voltage also falls, and the operation of the system is influenced. Therefore, the relative stability of the direct current bus voltage in the power distribution subareas on two sides of the DAB converter is kept through an effective control means, and the relative stability is limited to be more than the lowest stable operation voltage threshold value so as to reliably supply the load in the power distribution subareas and enable the two power distribution subareas to mutually support each other, which is significant for improving the fault tolerance performance, the continuous power supply capability and the reliability of the two power distribution subareas.
Disclosure of Invention
The invention aims to provide a power regulation strategy of a two-subarea power distribution system by taking a DAB converter as a node
The purpose of the invention is realized as follows:
a power regulation and control strategy of a two-subarea power distribution system with a DAB converter as a node comprises the following specific implementation steps:
step 1, initializing the system to enable the first current controller G dcA0, second current controller G dcB0, first voltage controller G dvA0, second voltage controller G dvB0, first phase control signal
Figure GDA0002888545080000011
Second phase controlSignal
Figure GDA0002888545080000012
Third phase control signal
Figure GDA0002888545080000013
A fourth phase control signal
Figure GDA0002888545080000014
Step 2, detecting by a first voltage sensor VSA to obtain a first direct current bus voltage uAObtaining a first current through the first voltage droop control module A
Figure GDA0002888545080000015
Obtaining a second DC bus voltage u by a second voltage sensor VSBBObtaining a second current through a second voltage droop control module B
Figure GDA0002888545080000016
Step 3, measuring a third current i through the first current sensor CSAAAnd obtaining a first deviation amount
Figure GDA0002888545080000017
Then passes through a first current controller GdcATo obtain a first phase control signal
Figure GDA0002888545080000018
Fourth current i measured by second current sensor CSBBAnd obtaining a second deviation amount
Figure GDA0002888545080000019
Then through a second current controller GdcBIs operated to obtain a second phase control signal
Figure GDA00028885450800000110
Step 4, setting a second voltage threshold uTHBAnd a secondDC bus voltage value uBThird deviation u obtained by differenceeAInput the first voltage controller GdvATo obtain a third phase control signal
Figure GDA0002888545080000021
A first voltage threshold u to be setTHAAnd a first DC bus voltage value uAFourth deviation u obtained by differenceeBInput a second voltage controller GdvBTo obtain a fourth phase control signal
Figure GDA0002888545080000022
Step 5, controlling the first phase of the first phase control signal for the power distribution subarea A
Figure GDA0002888545080000023
And a third phase control signal
Figure GDA0002888545080000024
Sending to the link of finding small value minATaking the small one as the first phase shift angle control signal of the distribution subarea A full-bridge converter
Figure GDA0002888545080000025
Namely have
Figure GDA0002888545080000026
Figure GDA0002888545080000027
Second phase control signal to be used for distribution partition B
Figure GDA0002888545080000028
And a fourth phase control signal
Figure GDA0002888545080000029
Sending to the link of finding small value minBAnd taking the small one as a second phase shift angle control signal of the distribution partition B full-bridge converter
Figure GDA00028885450800000210
Namely have
Figure GDA00028885450800000211
Step 6, the first phase shifting angle control signal is transmitted
Figure GDA00028885450800000212
The phase-shift control signal is used as the phase-shift control signal of the full-bridge converter carrier of the distribution subarea A, the signal with the amplitude of one half of the carrier period is used as the modulation signal for PWM modulation, the pulse signal used for driving the switching tube of the full-bridge converter of the distribution subarea A is obtained, and the second phase-shift angle control signal
Figure GDA00028885450800000213
The phase-shift control signal is used as a phase-shift control signal of a full-bridge converter carrier of the distribution subarea B, and a signal with the amplitude of one half of the carrier period is used as a modulation signal for PWM modulation to obtain a pulse signal for driving a switching tube of the full-bridge converter of the distribution subarea B;
and 7, repeatedly executing the steps 2 to 6 under the condition that a stop instruction is not obtained, otherwise, exiting the running state.
The first current in step 2
Figure GDA00028885450800000214
And a second current
Figure GDA00028885450800000215
Can be obtained by the following formula,
Figure GDA00028885450800000216
Figure GDA00028885450800000217
KDAis the droop coefficient, K, of the first voltage droop control module ADBFor the second voltage droop controlDroop coefficient for module B.
The first current controller G in the step 1dcAA second current controller GdcBA first voltage controller GdvAA second voltage controller GdvBAre all PI regulators.
The invention has the beneficial effects that:
compared with the traditional mode of realizing electric energy transmission by closing a manual switch or an automatic switch, the electric energy transmission device can realize free and smooth switching and flexible adjustment of the electric energy transmission direction and size between two power distribution sub-areas; when power is transmitted between two power distribution subareas on two sides of the DAB converter, the direct-current bus voltage of the power distribution subarea outputting the power is not lower than the allowed minimum operation voltage threshold value due to the fact that the output power is too large, and the power distribution subarea inputting the power is not higher than the allowed maximum operation voltage threshold value due to the fact that the absorbed power is too large.
Drawings
Fig. 1 is a flow chart of two isolated power distribution with a DAB converter as a regulation node.
Fig. 2 is a topology structure diagram of two isolated power distribution partitions using a DAB converter as a regulation node.
Fig. 3 is a characteristic graph of the voltage droop control.
Fig. 4 is a graph of voltage waveforms simulated for two power distribution partitions.
Fig. 5 is a graph of simulated power waveforms for two power distribution partitions.
The specific implementation mode is as follows:
the invention is further described with reference to the accompanying drawings in which:
example 1
The two power distribution subareas use a DAB converter as an electric energy regulation node, the topological structure of the DAB converter is shown by a dotted line in the figure, two sides of a high Frequency transformer HFT (high Frequency transformer) are respectively connected with a full-bridge converter, the duty ratio of all switching tubes of the full-bridge converter is 0.5, the full-bridge converter is in a complementary conduction mode with an upper switching tube and a lower switching tube of a bridge arm, in the patent, the phase shift angle between the bridge arms A1 and A2 in the figure is fixed to be 180 degrees, and the phase shift angle between the bridge arms B1 and B2 in the figure is also fixed to be 1 degree80 degrees. The operating principle of the DAB-converter itself is well established and will not be described in detail here. Two direct current power distribution partitions are arranged on two sides of the DAB converter and are respectively marked as a power distribution partition A and a power distribution partition B. Taking distribution partition A as an example, power supply PS is connected in the partitionA(e.g. power supply provided by photovoltaic or wind power generation, etc.) and a load (shown as concentrated load R)ARepresentation). The configuration of the power distribution partition B is similar to that of the power distribution partition A, and the description is omitted. The current sensors CSA and CSB in fig. 2 are used to measure the current i in the distribution section a and the distribution section B, respectivelyAAnd iBThe voltage sensors VSA and VSB are respectively used for measuring the DC bus voltage u of the distribution subarea A and the distribution subarea BAAnd uB。
Because in the control strategy designed by the patent, the relation between the power distribution partition A and the power distribution partition B is equivalent. The adopted control strategy is completely consistent with the structure of the control system, and the control algorithms aiming at the power distribution subarea A and the power distribution subarea B are parallel.
The specific implementation steps are as follows:
step 1, initializing the system to enable the first current controller G dcA0, second current controller G dcB0, first voltage controller G dvA0, second voltage controller G dvB0, first phase control signal
Figure GDA0002888545080000031
Second phase control signal
Figure GDA0002888545080000032
Third phase control signal
Figure GDA0002888545080000033
A fourth phase control signal
Figure GDA0002888545080000034
Step 2, detecting through a first voltage sensor VSA to obtain a first direct current bus voltage uAObtaining the first voltage droop control module AA current
Figure GDA0002888545080000035
Obtaining a second DC bus voltage u by a second voltage sensor VSBBObtaining a second current through a second voltage droop control module B
Figure GDA0002888545080000036
Step 3, measuring a third current i through the first current sensor CSAAAnd obtaining a first deviation amount
Figure GDA0002888545080000037
Then passes through a first current controller GdcATo obtain a first phase control signal
Figure GDA0002888545080000038
Fourth current i measured by second current sensor CSBBAnd obtaining a second deviation amount
Figure GDA0002888545080000039
Then through a second current controller GdcBIs operated to obtain a second phase control signal
Figure GDA00028885450800000310
Step 4, setting a second voltage threshold uTHBAnd a second DC bus voltage value uBThird deviation u obtained by differenceeAInput the first voltage controller GdvATo obtain a third phase control signal
Figure GDA0002888545080000041
A first voltage threshold u to be setTHAAnd a first DC bus voltage value uAFourth deviation u obtained by differenceeBInput a second voltage controller GdvBTo obtain a fourth phase control signal
Figure GDA0002888545080000042
Step 5, controlling the first phase of the first phase control signal for the power distribution subarea A
Figure GDA0002888545080000043
And a third phase control signal
Figure GDA0002888545080000044
Sending to the link of finding small value minATaking the small one as the first phase shift angle control signal of the distribution subarea A full-bridge converter
Figure GDA0002888545080000045
Namely have
Figure GDA0002888545080000046
Figure GDA0002888545080000047
Second phase control signal to be used for distribution partition B
Figure GDA0002888545080000048
And a fourth phase control signal
Figure GDA0002888545080000049
Sending to the link of finding small value minBAnd taking the small one as a second phase shift angle control signal of the distribution partition B full-bridge converter
Figure GDA00028885450800000410
Namely have
Figure GDA00028885450800000411
Step 6, the first phase shifting angle control signal is transmitted
Figure GDA00028885450800000412
The phase-shift control signal is used as the phase-shift control signal of the full-bridge converter carrier of the distribution subarea A, and the signal with the amplitude of one half of the carrier period is used as the modulation signal for PWM modulation to obtain the pulse for driving the switching tube of the full-bridge converter of the distribution subarea ARush signal, second phase shift angle control signal
Figure GDA00028885450800000413
The phase-shift control signal is used as a phase-shift control signal of a full-bridge converter carrier of the distribution subarea B, and a signal with the amplitude of one half of the carrier period is used as a modulation signal for PWM modulation to obtain a pulse signal for driving a switching tube of the full-bridge converter of the distribution subarea B;
and 7, repeatedly executing the steps 2 to 6 under the condition that a stop instruction is not obtained, otherwise, exiting the running state.
The first current in step 2
Figure GDA00028885450800000414
And a second current
Figure GDA00028885450800000415
Can be obtained by the following formula,
Figure GDA00028885450800000416
Figure GDA00028885450800000417
KDAis the droop coefficient, K, of the first voltage droop control module ADBFor the droop coefficient of the second voltage droop control module B, K can be set according to the requirement of the system on the voltage precisionDAAnd KDBValue of (A), KDAThe smaller the value of (A) is, the smaller the slope of the line (and K)DA2Correspondingly), the smaller the amount of change in voltage, the higher the accuracy of control of the voltage at a given change in current. Conversely, the lower the accuracy of the voltage control.
The first current controller G in the step 1dcAA second current controller GdcBA first voltage controller GdvAA second voltage controller GdvBAre all PI regulators.
According to the principle of DAB convertersWhen distribution partition A transfers power to distribution partition B, it transfers power PACan be expressed as:
Figure GDA00028885450800000418
when distribution partition B transfers power to distribution partition A, the transferred power PBComprises the following steps:
Figure GDA00028885450800000419
wherein L isABComprises the following steps:
Figure GDA0002888545080000051
suppose that distribution partition A is delivering power to distribution partition B, distribution partition A is flowing current iAHas an average value of IA,When the distribution subarea B transmits power to the distribution subarea A, the current i of the distribution subarea BBHas an average value of IB. Then
Figure GDA0002888545080000052
Figure GDA0002888545080000053
The average current in the two formulas is at the steady-state working point by partial differentiation
Figure GDA0002888545080000054
And (3) carrying out small signal linearization processing to obtain the small signal disturbance quantity of the average current of the two power distribution subareas respectively:
Figure GDA0002888545080000055
Figure GDA0002888545080000056
from the above equation, there is a coupling between the two average current disturbances. When distribution partition A transfers power to distribution partition B, if
Figure GDA0002888545080000057
When the distribution partition B transfers energy to the distribution partition A, if
Figure GDA0002888545080000058
Under this condition, the current iAAnd iBThe small signal disturbance quantity expression of the average value is as follows:
Figure GDA0002888545080000059
Figure GDA00028885450800000510
from the above formula, see
Figure GDA00028885450800000511
And
Figure GDA00028885450800000512
under the decoupling condition of (2), the current average values of the distribution subarea A and the distribution subarea B are respectively controlled only by the phase shift angle of the full-bridge converter of the respective distribution subarea
Figure GDA00028885450800000513
And
Figure GDA00028885450800000514
under the control strategy provided by the patent, the condition for realizing the power distribution partition current decoupling control can be automatically obtained when the steady state is achieved.
When distribution subarea A is distributedWhen the electric subarea B transmits power, i is determinedA>0, correspondingly have
Figure GDA00028885450800000515
Are present. Since this current set signal is given by the droop control module A, u is derivedA>uTHAThat is, when the distribution sub-area A transfers power to the distribution sub-area B, the DC bus voltage is not lower than the set threshold uTHA. Therefore, the condition that the DC bus voltage of the distribution subarea A of the output power is lower than the lowest operation threshold u because the power required by the distribution subarea B of the input power is overlarge is avoidedTHA。
On the other hand, if initially, the DC bus voltage of distribution partition B is lower than its threshold voltage uTHBAnd the power distribution subarea A transfers power to the power distribution subarea B with larger input power, and in an extreme case, the power distribution subarea A transfers redundant power to the power distribution subarea B until the direct-current bus voltage u of the power distribution subarea AADown to slightly above uTHA. This may cause the voltage of distribution bay B to rise even above the maximum voltage value allowed for its operation. Thus, it is necessary to add a voltage control loop A to the DC bus voltage u in the distribution sub-area BBRises to a threshold voltage uTHBTime, voltage controller GdvADesaturation enters a state of linear regulation. At this time, the current controller GdcAWill enter into saturation operation state, and will be subjected to small loop segment taking for minAThen, the phase shift angle of distribution zone B will be
Figure GDA0002888545080000061
Thereby limiting the DC bus voltage of the distribution partition B to a threshold voltage uTHBPower distribution partition a will no longer transmit more power to power distribution partition B.
The process of transmitting power from the power distribution partition B to the power distribution partition a is similar to the above analysis, and is not described again.
Operating mode of a power distribution system formed by DAB
(1) Mode of operation 1-no power transfer between power distribution bays
When two are matchedWhen the voltage of the direct current bus of the electric subareas is larger than the set threshold voltage, i.e. uA>uTHA，uB>uTHBDeviation amount ueBAnd ueAWill all be less than 0 and pass through respective voltage regulators GdvBAnd GdvAAfter the integral operation in (1), outputting a phase shift angle signal
Figure GDA0002888545080000062
Will be at the lowest limiting value of 0, i.e.
Figure GDA0002888545080000063
At this time, the current controller GdcAAnd GdcBWill be in saturation state, and will have after taking small operation
Figure GDA0002888545080000064
So that no power is transferred between the two power distribution bays.
(2) Mode of operation 2-distribution zone a transfers power to distribution zone B
When the DC bus voltage u of the distribution subarea AA>uTHAAnd the DC bus voltage u of the distribution sub-area BB<uTHBThen (c) is performed. (u)THA-uA) Difference u ofeBLess than 0, the difference passing through a voltage regulator GdvBAfter the integral operation in (1), obtaining an output
Figure GDA0002888545080000065
Will be at the lowest clipping value of 0. And with voltage uBWill generate a negative current set signal with an absolute value gradually decreasing to 0
Figure GDA0002888545080000066
Difference i ofeBIncreasing from near 0 to always greater than 0, current regulator GdvBThe output of the linear regulation state gradually enters an upper amplitude limiting saturation state, and finally the upper amplitude limiting saturation state is obtained after small operation
Figure GDA0002888545080000067
Thereby ensuringAnd (4) realizing a decoupling condition.
If the power transmitted from the distribution subarea A to the distribution subarea B can be used for converting the direct-current bus voltage u of the distribution subarea BBIs raised to a threshold value uTHBThen voltage regulator GdvAA state of linear regulation will be entered. At this time, the droop control module A generates a current setting signal
Figure GDA0002888545080000068
Will always be greater than the actual current signal iAThus having ieA>0, thereby making the current controller GdcAThe upper amplitude limiting saturation state is always kept, and the small operation is carried out to obtain the upper amplitude limiting saturation state
Figure GDA0002888545080000069
If the power transmitted from the distribution subarea A to the distribution subarea B cannot convert the direct-current bus voltage u of the distribution subarea BBIs raised to a threshold value uTHB(other measures may be taken depending on the actual situation and are not discussed in this patent), but u is always presentB<uTHBVoltage controller GdvAWill be in upper limit amplitude saturation state, current controller GdcAGenerated by the droop control module A to be tracked
Figure GDA00028885450800000610
And in the linear regulation state, the linear regulation state is obtained by small calculation
Figure GDA00028885450800000611
(3) Working mode 3-distribution zone B transfers power to distribution zone a
This operation mode is similar to operation mode 2 and will not be described again.
Example 2
The invention belongs to the technical field of power electronics, and particularly relates to a control strategy for realizing automatic coordinated power transmission of two isolated subarea power distribution systems by taking a DAB converter as a regulation node.
In a power distribution system taking a DAB converter as a regulation node, two ports of the DAB converter are expanded into two isolated power distribution subareas. The two power distribution subareas can be connected with a plurality of photovoltaic solar power generation devices, wind power generation devices and the like, and at the same time, under the influence of weather and environmental factors, the power of the power which can be output by each power generation device in the power distribution subareas can have larger difference, the condition that the power generated by a power supply cannot meet the power required by the load of the power supply can occur, and the voltage of a direct current bus of the power distribution subarea can be reduced at the moment. Meanwhile, when the electric energy in a certain power distribution partition cannot meet the power required by the load due to the increase of the load, the bus voltage also falls, and the operation of the system is influenced. Therefore, the relative stability of the direct current bus voltage in the power distribution subareas on two sides of the DAB converter is kept through an effective control means, and the relative stability is limited to be more than the lowest stable operation voltage threshold value so as to reliably supply the load in the power distribution subareas and enable the two power distribution subareas to mutually support each other, which is significant for improving the fault tolerance performance, the continuous power supply capability and the reliability of the two power distribution subareas.
The invention aims to provide a power automatic control strategy for realizing a two-isolation subarea power distribution system by taking a DAB converter as a regulation node, which mainly contributes to and is characterized in that:
a system-level control strategy for realizing mutual power transmission between two isolated power distribution partitions at two sides of a DAB converter is designed, and the control strategy can realize the following steps:
(1) compared with the traditional mode of realizing electric energy transmission by closing a manual switch or an automatic switch, the electric energy transmission device can realize free and smooth switching and flexible adjustment of the electric energy transmission direction and size between two power distribution sub-areas;
(2) when power is transmitted between two power distribution subareas on two sides of the DAB converter, the direct-current bus voltage of the power distribution subarea outputting the power is not lower than the allowed minimum operation voltage threshold value due to the fact that the output power is too large, and the power distribution subarea inputting the power is not higher than the allowed maximum operation voltage threshold value due to the fact that the absorbed power is too large.
The object of the invention is achieved by combining with the attached figure 2:
as shown in fig. 2, two power distribution sub-zones use a DAB converter as a node for electric energy regulation, a topology structure of the DAB converter is shown by a dotted line in the figure, two sides of a high Frequency transformer hft (high Frequency transformer) are respectively connected with a full-bridge converter, duty ratios of all switching tubes of the full-bridge converter are 0.5, and the two switching tubes on the same bridge arm are in complementary conduction modes, in the patent, a phase shift angle between a bridge arm a1 and a2 in the figure is fixed to be 180 °, and a phase shift angle between a bridge arm B1 and a bridge arm B2 in the figure is also fixed to be 180 °. The operating principle of the DAB-converter itself is well established and will not be described in detail here. Two direct current power distribution partitions are arranged on two sides of the DAB converter and are respectively marked as a power distribution partition A and a power distribution partition B. Taking distribution partition A as an example, power supply PS is connected in the partitionA(e.g. power supply provided by photovoltaic or wind power generation, etc.) and a load (shown as concentrated load R)ARepresentation). The configuration of the power distribution partition B is similar to that of the power distribution partition A, and the description is omitted. The current sensors CSA and CSB in fig. 2 are used to measure the current i in the distribution section a and the distribution section B, respectivelyAAnd iBThe voltage sensors VSA and VSB are respectively used for measuring the DC bus voltage u of the distribution subarea A and the distribution subarea BAAnd uB。
Because in the control strategy designed by the patent, the relation between the power distribution partition A and the power distribution partition B is equivalent. The adopted control strategy is completely consistent with the structure of the control system, and the control algorithms aiming at the power distribution subarea A and the power distribution subarea B are parallel. The proposed control strategy is therefore explained below using the power distribution partition a as an example.
Setting the lowest voltage threshold value allowed by the power distribution subarea A as uTHA(distribution partition B is uTHB). DC bus voltage u of power distribution partition A obtained by sampling in droop control module AAAnd a set voltage threshold uTHADifference between the values and droop control coefficient KDAMultiplying to obtain a current given signal of the current loop A
Figure GDA0002888545080000081
The signal is compared with the actual current signal iADifference is made to obtain deviation ieAAt ieAThrough a current controller GdcAAfter operation, the control signal is obtained through amplitude limiting processing
Figure GDA0002888545080000082
Voltage threshold u set for distribution sub-area B in voltage loop ATHBAs a given signal and with the dc bus voltage u of the actual distribution bay BBPerforming difference to obtain deviation ueAA deviation amount ueAInput voltage controller GdvAThe obtained result is processed by amplitude limiting to obtain control signal
Figure GDA0002888545080000083
Will be provided with
Figure GDA0002888545080000084
And
Figure GDA0002888545080000085
by taking small ring segments of minAAfter (x, y) is subjected to small calculation, the full-bridge converter on the side of the distribution subarea A is obtained (namely, the switching tube S1A-S4AConstructed full bridge) of the drive pulse phase shift angle
Figure GDA0002888545080000086
Controller G used in the control block diagram of FIG. 2dvAAnd GdvB，GdcAAnd GdcBAre all PI regulators.
The control algorithm of the power distribution partition B is consistent with that of the power distribution partition A, and the detailed description is omitted here. The full-bridge converter (i.e. the switch tube S) at the side of the distribution partition B can be obtained1B-S4BConstructed full bridge) of the drive pulse phase shift angle
Figure GDA0002888545080000087
With reference to fig. 2, the execution flow of the control strategy for implementing automatic power regulation of the two-isolated-partition power distribution system by using the DAB converter as a regulation node in the patent is described as follows:
(1) firstly, at the initial stage of system power-on, the software and hardware initialization work related to system control is carried out, in which the important work is to set the current controller G in the programdcA、GdcBAnd a voltage controller GdvA、GdvBOutput of
Figure GDA0002888545080000088
And
Figure GDA0002888545080000089
Figure GDA00028885450800000810
is 0.
(2) Respectively obtaining direct current bus voltage values u of two distribution subareas by using voltage sensors VSA and VSBAAnd uBThen, according to the voltage droop control modules A and B, a current instruction signal is obtained
Figure GDA00028885450800000811
And
Figure GDA00028885450800000812
wherein KDAAnd KDBIs the voltage droop coefficient.
(3) Two voltage droop control modules respectively generate current instructions
Figure GDA00028885450800000813
And
Figure GDA00028885450800000814
the direct currents i are respectively sent into the respective full-bridge converters by the current sensors CSA and CSB and two power distribution subareas measured by the current sensors CSA and CSBAAnd iBMaking a difference to obtain a deviation ieAAnd ieB. Deviation amount ieAAnd ieBRespectively sent to a current controller GdcAAnd GdcBPerforming operation to obtain a group for twoControl signals for power distribution bays
Figure GDA00028885450800000815
And
Figure GDA00028885450800000816
(4) will be voltage threshold uTHBAnd uTHARespectively serving as command signals of a voltage ring A and a voltage ring B in the two power distribution subareas, and respectively measuring the command signals and the voltage rings by using voltage sensors VSA and VSB to obtain direct current bus voltage values u of the two power distribution subareasBAnd uAMaking a difference to obtain a deviation ueAAnd ueB. The deviation ueAAnd ueBRespectively input voltage controller GdvAAnd GdvBPerforming operation to obtain another set of control signals for two power distribution subareas
Figure GDA0002888545080000091
And
Figure GDA0002888545080000092
(5) two control signals to be used for distribution partition A
Figure GDA0002888545080000093
And
Figure GDA0002888545080000094
sending to the link of finding small value minATaking the small one as the phase shift angle control signal of the A full bridge converter of the power distribution subarea
Figure GDA0002888545080000095
Namely have
Figure GDA0002888545080000096
Two control signals to be used for distribution partition B
Figure GDA0002888545080000097
And
Figure GDA0002888545080000098
sending to the link of finding small value minBTaking the small one as the phase shift angle control signal of the B full bridge converter in the power distribution subarea
Figure GDA0002888545080000099
Namely have
Figure GDA00028885450800000910
(6) Respectively control the phase shift angle
Figure GDA00028885450800000911
And the phase-shifted control signals are used as phase-shifted control signals of the full-bridge converter carriers corresponding to the power distribution subareas A and B, and signals with the amplitude of one half of the carrier period are used as modulation signals for PWM modulation, so that pulse signals respectively used for driving switching tubes of the full-bridge converter with the two power distribution subareas are finally obtained.
(7) And (4) repeatedly executing the steps (2) to (6) under the condition that a stop instruction is not obtained, and otherwise, exiting the running state.
1. Description of droop control module for generating current command signal
The droop control module a and the droop control module B in fig. 1 are used for generating current command signals of the voltage ring a and the voltage ring B, and expressions of the two modules are respectively:
Figure GDA00028885450800000912
Figure GDA00028885450800000913
k in the formulae (1) and (2)DAAnd KDBThe droop coefficients of the two droop control modules are respectively. K can be set according to the requirement of the system on voltage precisionDAAnd KDBThe value of (c). With K in droop control module ADAFor example, as shown in FIG. 2, KDANumerical value ofThe smaller the slope of the line (vs. K)DA2Correspondingly), the smaller the amount of change in voltage, the higher the accuracy of control of the voltage at a given change in current. Conversely, the lower the accuracy of the voltage control.
Description of power transfer decoupling in 2 DAB converters
According to the principle of the DAB converter, the power P transmitted by the distribution subarea A when the distribution subarea A transmits the power to the distribution subarea B can be obtainedACan be expressed as:
Figure GDA00028885450800000914
when distribution partition B transfers power to distribution partition A, the transferred power PBComprises the following steps:
Figure GDA00028885450800000915
in formulae (3) and (4), LABComprises the following steps:
Figure GDA0002888545080000101
suppose that distribution partition A is delivering power to distribution partition B, distribution partition A is flowing current iAHas an average value of IA,When the distribution subarea B transmits power to the distribution subarea A, the current i of the distribution subarea BBHas an average value of IB. Then the results are obtained from (3) and (4)
Figure GDA0002888545080000102
Figure GDA0002888545080000103
By partial differentiation, the average current in equations (6) and (7) is taken to be at the steady-state operating point
Figure GDA0002888545080000104
And (3) carrying out small signal linearization processing to obtain the small signal disturbance quantity of the average current of the two power distribution subareas respectively:
Figure GDA0002888545080000105
Figure GDA0002888545080000106
as can be seen from equations (8) and (9), there is a coupling between the two average current disturbance amounts. When distribution partition A transfers power to distribution partition B, if
Figure GDA0002888545080000107
When the distribution partition B transfers energy to the distribution partition A, if
Figure GDA0002888545080000108
Under this condition, the current iAAnd iBThe expression of the small signal disturbance amount of the average value is shown in (10) and (11):
Figure GDA0002888545080000109
Figure GDA00028885450800001010
as can be seen from (10) and (11), in
Figure GDA00028885450800001011
And
Figure GDA00028885450800001012
under the decoupling condition of (2), the current average values of the distribution subarea A and the distribution subarea B are respectively controlled only by the phase shift angle of the full-bridge converter of the respective distribution subarea
Figure GDA00028885450800001013
And
Figure GDA00028885450800001014
under the control strategy provided by the patent, the condition for realizing the power distribution partition current decoupling control can be automatically obtained when the steady state is achieved.
Implementation of direct current bus voltage limitation in 3-distribution partition
Referring to fig. 1, a power distribution partition a is illustrated as an example. When the distribution subarea A transfers power to the distribution subarea B, i is determinedA>0, correspondingly have
Figure GDA00028885450800001015
Are present. Since this current set signal is given by the droop control module A, u is derivedA>uTHAThat is, when the distribution sub-area A transfers power to the distribution sub-area B, the DC bus voltage is not lower than the set threshold uTHA. Therefore, the condition that the DC bus voltage of the distribution subarea A of the output power is lower than the lowest operation threshold u because the power required by the distribution subarea B of the input power is overlarge is avoidedTHA。
On the other hand, if initially, the DC bus voltage of distribution partition B is lower than its threshold voltage uTHBAnd the power distribution subarea A transfers power to the power distribution subarea B with larger input power, and in an extreme case, the power distribution subarea A transfers redundant power to the power distribution subarea B until the direct-current bus voltage u of the power distribution subarea AADown to slightly above uTHA. This may cause the voltage of distribution bay B to rise even above the maximum voltage value allowed for its operation. Thus, it is necessary to add a voltage control loop A to the DC bus voltage u in the distribution sub-area BBRises to a threshold voltage uTHBTime, voltage controller GdvADesaturation enters a state of linear regulation. At this time, the current controller GdcAWill enter into saturation operation state, and will be subjected to small loop segment taking for minAThen, the phase shift angle of distribution zone B will be
Figure GDA00028885450800001110
Thereby limiting the DC bus voltage of the distribution partition B to a threshold voltage uTHBPower distribution partition a will no longer transmit more power to power distribution partition B.
The process of transmitting power from the power distribution partition B to the power distribution partition a is similar to the above analysis, and is not described again.
Operating mode of a power distribution system comprising 4 DAB
(1) Mode of operation 1-no power transfer between power distribution bays
When the direct current bus voltage of the two power distribution subareas is greater than the set threshold voltage, namely uA>uTHA，uB>uTHBDeviation amount ueBAnd ueAWill all be less than 0 and pass through respective voltage regulators GdvBAnd GdvAAfter the integral operation in (1), outputting a phase shift angle signal
Figure GDA0002888545080000111
Will be at the lowest limiting value of 0, i.e.
Figure GDA0002888545080000112
At this time, the current controller GdcAAnd GdcBWill be in saturation state, and will have after taking small operation
Figure GDA0002888545080000113
So that no power is transferred between the two power distribution bays.
(2) Mode of operation 2-distribution zone a transfers power to distribution zone B
When the DC bus voltage u of the distribution subarea AA>uTHAAnd the DC bus voltage u of the distribution sub-area BB<uTHBThen (c) is performed. (u)THA-uA) Difference u ofeBLess than 0, the difference passing through a voltage regulator GdvBAfter the integral operation in (1), obtaining an output
Figure GDA0002888545080000114
Will be at the lowest clipping value of 0. And with voltage uBWill generate a negative current set signal with an absolute value gradually decreasing to 0
Figure GDA0002888545080000115
Difference i ofeBIncreasing from near 0 to always greater than 0, current regulator GdvBThe output of the linear regulation state gradually enters an upper amplitude limiting saturation state, and finally the upper amplitude limiting saturation state is obtained after small operation
Figure GDA0002888545080000116
Thereby ensuring that the decoupling condition is achieved.
If the power transmitted from the distribution subarea A to the distribution subarea B can be used for converting the direct-current bus voltage u of the distribution subarea BBIs raised to a threshold value uTHBThen voltage regulator GdvAA state of linear regulation will be entered. At this time, the droop control module A generates a current setting signal
Figure GDA0002888545080000117
Will always be greater than the actual current signal iAThus having ieA>0, thereby making the current controller GdcAThe upper amplitude limiting saturation state is always kept, and the small operation is carried out to obtain the upper amplitude limiting saturation state
Figure GDA0002888545080000118
If the power transmitted from the distribution subarea A to the distribution subarea B cannot convert the direct-current bus voltage u of the distribution subarea BBIs raised to a threshold value uTHB(other measures may be taken depending on the actual situation and are not discussed in this patent), but u is always presentB<uTHBVoltage controller GdvAWill be in upper limit amplitude saturation state, current controller GdcAGenerated by the droop control module A to be tracked
Figure GDA0002888545080000119
And in the linear regulation state, the linear regulation state is obtained by small calculation
Figure GDA0002888545080000121
(3) Working mode 3-distribution zone B transfers power to distribution zone a
This operation mode is similar to operation mode 2 and will not be described again.
(VI) simulation results
By adopting the method disclosed by the patent, the direct-current bus voltage threshold values of the power distribution partition 1 and the power distribution partition 2 are respectively set as follows according to the input power of the system: u. ofTHA＝180V，u THB160V; concentrated load R of two distribution partitionsA＝RB10 Ω. Power supply PS of power distribution partition AAThe output power is 4120W when 0-1.2 s and 2700W when 1.2-2 s; power supply PS of power distribution partition BBThe output power is 3100W for 0-0.6 s, 2100W for 0.6-1.2 s, and 3100W for 1.2-2 s. Obtaining the DC bus voltage waveform u of two distribution subareas through simulationA、uBAnd power P of two power distribution subareas respectively transmitted to the opposite sideA、PBAs shown in fig. 4 and 5, respectively.

Claims (3)

1. A power regulation strategy of a two-zone power distribution system with a DAB converter as a node is characterized by comprising the following specific implementation steps:
step 1, initializing the system to enable the first current controller GdcAOutput of (2)
Figure FDA0002888545070000011
Second current controller GdcBOutput of (2)
Figure FDA0002888545070000012
First voltage controller GdvAOutput of (2)
Figure FDA0002888545070000013
Second voltage controller GdvBOutput of (2)
Figure FDA0002888545070000014
Setting zero;
step 2, detecting by a first voltage sensor VSA to obtain a first direct current bus voltage uAObtaining a first current through the first voltage droop control module A
Figure FDA0002888545070000015
Obtaining a second DC bus voltage u by a second voltage sensor VSBBObtaining a second current through a second voltage droop control module B
Figure FDA0002888545070000016
Step 3, measuring a third current i through the first current sensor CSAAAnd obtaining a first deviation amount
Figure FDA0002888545070000017
Then passes through a first current controller GdcATo obtain a first phase control signal
Figure FDA0002888545070000018
Fourth current i measured by second current sensor CSBBAnd obtaining a second deviation amount
Figure FDA0002888545070000019
Then through a second current controller GdcBIs operated to obtain a second phase control signal
Figure FDA00028885450700000110
Step 4, setting a second voltage threshold uTHBAnd a second DC bus voltage value uBThird deviation u obtained by differenceeAInput the first voltage controller GdvATo obtain a third phase control signal
Figure FDA00028885450700000111
A first voltage threshold to be setuTHAAnd a first DC bus voltage value uAFourth deviation u obtained by differenceeBInput a second voltage controller GdvBTo obtain a fourth phase control signal
Figure FDA00028885450700000112
Step 5, controlling the first phase of the first phase control signal for the power distribution subarea A
Figure FDA00028885450700000113
And a third phase control signal
Figure FDA00028885450700000114
Sending to the link of finding small value minATaking the small one as the first phase shift angle control signal of the distribution subarea A full-bridge converter
Figure FDA00028885450700000115
Second phase control signal to be used for distribution partition B
Figure FDA00028885450700000116
And a fourth phase control signal
Figure FDA00028885450700000117
Sending to the link of finding small value minBAnd taking the small one as a second phase shift angle control signal of the distribution partition B full-bridge converter
Figure FDA00028885450700000118
Step 6, the first phase shifting angle control signal is transmitted
Figure FDA00028885450700000119
The phase-shift control signal is used as the phase-shift control signal of the full-bridge converter carrier of the distribution subarea A, and the signal with the amplitude of one half of the carrier period is used as the modulation signal for PWM modulation to obtain the signal for driving the switching tube of the full-bridge converter of the distribution subarea APulse signal, second phase-shift angle control signal
Figure FDA00028885450700000120
The phase-shift control signal is used as a phase-shift control signal of a full-bridge converter carrier of the distribution subarea B, and a signal with the amplitude of one half of the carrier period is used as a modulation signal for PWM modulation to obtain a pulse signal for driving a switching tube of the full-bridge converter of the distribution subarea B;
and 7, repeatedly executing the steps 2 to 6 under the condition that a stop instruction is not obtained, otherwise, exiting the running state.
2. A two-zone power distribution system power regulation strategy with a DAB converter as a node as claimed in claim 1, wherein: the first current in step 2
Figure FDA00028885450700000121
And a second current
Figure FDA00028885450700000122
Can be obtained by the following formula,
Figure FDA00028885450700000123
Figure FDA00028885450700000124
KDAis the droop coefficient, K, of the first voltage droop control module ADBIs the droop coefficient of the second voltage droop control module B.
3. A two-zone power distribution system power regulation strategy with a DAB converter as a node as claimed in claim 1, wherein: first current controller G in step 1dcAA second current controller GdcBA first voltage controller GdvAThe second electricityPressure controller GdvBAre all PI regulators.
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