CN116632806B - SOC (system on chip) quick equalization strategy without sagging control of direct-current micro-grid energy storage system - Google Patents
SOC (system on chip) quick equalization strategy without sagging control of direct-current micro-grid energy storage system Download PDFInfo
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- CN116632806B CN116632806B CN202310648306.7A CN202310648306A CN116632806B CN 116632806 B CN116632806 B CN 116632806B CN 202310648306 A CN202310648306 A CN 202310648306A CN 116632806 B CN116632806 B CN 116632806B
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- 238000004146 energy storage Methods 0.000 title claims abstract description 85
- 238000007665 sagging Methods 0.000 title description 3
- 238000004891 communication Methods 0.000 claims abstract description 12
- 230000007704 transition Effects 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims description 11
- 238000005070 sampling Methods 0.000 claims description 6
- 230000001133 acceleration Effects 0.000 claims description 4
- 238000004364 calculation method Methods 0.000 claims description 3
- 230000006698 induction Effects 0.000 claims description 3
- 238000010586 diagram Methods 0.000 description 8
- 230000007547 defect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/14—Balancing the load in a network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J1/00—Circuit arrangements for dc mains or dc distribution networks
- H02J1/10—Parallel operation of dc sources
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- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention discloses an SOC rapid equalization strategy without droop control for a direct-current micro-grid energy storage system, which mainly comprises a communication module, a current equalization module, a voltage compensation module, an SOC equalization module and a voltage and current double closed loop module. In the communication module, each energy storage unit only performs point-to-point communication with the adjacent node, and the average value of the SOC and the virtual state variable of the energy storage system can be obtained without a central controller; in the current sharing module, by introducing a transition factor, the output current is accurately distributed in proportion to the capacity of the energy storage unit; in the voltage compensation module, the sag of the bus voltage is effectively compensated, and the bus voltage is controlled to be near a rated value; in the SOC equalization module, the current closed-loop control of the energy storage unit is directly influenced by the SOC, so that the output current is further dynamically changed, and the SOC is rapidly equalized.
Description
Technical Field
The invention relates to the field of direct-current micro-grid energy storage systems, in particular to an SOC (system on chip) rapid equalization strategy for no droop control of a direct-current micro-grid energy storage system
Background
With the rapid development of renewable energy sources, micro-grid technology has received a great deal of attention. Compared with an alternating-current micro-grid, the direct-current micro-grid does not need to consider the problems of phase synchronization, reactive compensation, harmonic suppression and the like, and can be compatible with direct-current power sources such as photovoltaics, fuel cells and the like. Because the renewable energy source power generation unit in the direct current micro-grid has randomness and volatility, the system power fluctuation is stabilized by mainly relying on the energy storage system, and the system stability is improved. In order to avoid the failure of the whole energy storage system caused by single-point faults of a power grid, a plurality of energy storage units are required to be connected in parallel to form a distributed energy storage system, when the plurality of energy storage units are used in parallel, the difference of Charge States (SOC) can cause the overdischarge or deep charging of part of the energy storage units, the service life of the distributed energy storage units is shortened, meanwhile, sagging control is used as a common current equalizing method in a direct-current micro-grid, and due to the characteristics of the current equalizing method, the defect that the accurate power distribution and the voltage drop of a bus cannot be simultaneously considered, the output current of the energy storage units needs to be regulated through the capacity and the SOC of the energy storage units, and the accurate distribution of the output current of the energy storage units in proportion to the capacity, the SOC equalization and the voltage drop of the bus are ensured to be in an allowable range.
Disclosure of Invention
In order to achieve the above purpose, the technical scheme provided by the invention is as follows:
1) The two energy storage units pass through the corresponding converters and the line impedance R linei Parallel connected to the DC bus to supply the load R load Supplying power to the induction current i at the starting point of each sampling period Li Output current i oi Output voltage u oi State of charge SOC of energy storage unit i Sampling is carried out respectively;
2) In the communication module, each energy storage unit only needs to exchange information with the adjacent energy storage unit, and the state of charge (SOC) of each energy storage unit in the energy storage system can be obtained without a central controller i And a virtual state variable y i And then the dynamic consistency algorithm is utilized to obtain the charge state average value SOC of the energy storage system avg And virtual state variable average y avg ；
3) In the current equalizing module, the output current i oi Divided by the maximum rated current i of the energy storage unit max Dividing by the capacity coefficient k of the energy storage unit i Obtaining an intermediate coefficient n i Subtracting the intermediate coefficient n from the coefficient 1 i Obtaining the transition factor m i ；
4) In the voltage compensation module, the transition factor m i Multiplying by output voltage u oi Obtaining the virtual state variable y i Then the dynamic consistency algorithm is utilized to obtain the average value y of the virtual state variable avg Reusing virtual state variable average y avg Divided by the transition factor m i Obtaining a process voltage u zi Reuse of reference voltage u ref Subtracting the process voltage u zi Obtaining voltage compensation quantity delta u through an integrator i ；
5) In the SOC balancing module and the voltage-current double closed-loop module, the voltage compensation quantity delta u obtained in the voltage compensation module is calculated i Directly to the reference voltage u ref Subtracting the output voltage u of the energy storage unit oi Then pass through a voltage outer loop PI controller G V (s) obtaining a current inner loop reference current I ai And then I is carried out ai Equalizing current I with SOC bi After addition the inductor current i is subtracted Li The obtained result passes through a current inner loop PI controller G I (s) obtaining a driving voltage u si And then drive the voltage u si Comparing with the triangular carrier wave to obtain PWM modulation signal, wherein the SOC balances the current I bi The specific calculation process is as follows:
SOC (state of charge) of local energy storage unit i Subtracting the energy storage system state of charge average value SOC obtained in the communication module avg Multiplying byObtaining the equalization coefficient q i Wherein ρ is an acceleration factor, ε is an accurate factor, and the equalization coefficient q is calculated i Multiplying the absolute value of the current loop reference current I ai Obtaining SOC balance current I bi SOC equalizes current I bi The expression of (2) is:
compared with the prior art, the principle and the advantages of the scheme are as follows:
the invention discloses an SOC rapid equalization strategy without droop control for a direct-current micro-grid energy storage system, which mainly comprises a communication module, a current equalization module, a voltage compensation module, an SOC equalization module and a voltage and current double closed loop module. In the communication module, each energy storage unit only performs point-to-point communication with the adjacent node, and the average value of the SOC and the virtual state variable of the energy storage system can be obtained without a central controller; in the current sharing module, by introducing a transition factor, the output current is accurately distributed in proportion to the capacity of the energy storage unit; in the voltage compensation module, the sag of the bus voltage is effectively compensated, and the bus voltage is controlled to be near a rated value; in the SOC equalization module, the current closed-loop control of the energy storage unit is directly influenced by the SOC, so that the output current is further dynamically changed, and the SOC is rapidly equalized.
Drawings
FIG. 1 is a main circuit diagram of a DC micro-grid energy storage system according to an embodiment of the present invention;
fig. 2 is a control block diagram of an SOC fast equalization strategy without droop control for a dc micro-grid energy storage system in an embodiment of the present invention;
FIG. 3 is a diagram showing an SOC waveform of the energy storage unit according to an embodiment of the present invention;
FIG. 4 is a graph showing a waveform of the output current of the DC side of the energy storage unit according to the embodiment of the present invention;
fig. 5 is a waveform diagram of a bus voltage of the energy storage system according to an embodiment of the present invention.
Detailed Description
The invention is further illustrated by the following examples:
FIG. 1 is a main circuit diagram of a DC micro-grid energy storage system consisting of two energy storage units connected in parallel via DC-DC converters, DESU 1 For the first energy storage unit, u o1 For outputting voltage i to DC side of first energy storage unit o1 For the direct current side of the first energy storage unit, R line1 Corresponding to the first energy storage unitThe line impedance of the two energy storage units is 0.4Ω and 0.5Ω, R load Is the load resistance.
Fig. 2 is a control block diagram of a SOC fast equalization strategy for droop-free control of a dc micro-grid energy storage system, comprising the steps of:
1) The two energy storage units pass through the corresponding converters and the line impedance R linei Parallel connected to the DC bus to supply the load R load Supplying power to the induction current i at the starting point of each sampling period Li Output current i oi Output voltage u oi State of charge SOC of energy storage unit i Sampling is carried out respectively;
2) In the communication module, each energy storage unit only needs to exchange information with the adjacent energy storage unit, and the state of charge (SOC) of each energy storage unit in the energy storage system can be obtained without a central controller i And a virtual state variable y i And then the dynamic consistency algorithm is utilized to obtain the charge state average value SOC of the energy storage system avg And virtual state variable average y avg ；
3) In the current equalizing module, the output current i oi Divided by the maximum rated current i of the energy storage unit max Dividing by the capacity coefficient k of the energy storage unit i Obtaining an intermediate coefficient n i Subtracting the intermediate coefficient n from the coefficient 1 i Obtaining the transition factor m i ；
4) In the voltage compensation module, the transition factor m i Multiplying by output voltage u oi Obtaining the virtual state variable y i Then the dynamic consistency algorithm is utilized to obtain the average value y of the virtual state variable avg Reusing virtual state variable average y avg Divided by the transition factor m i Obtaining a process voltage u zi Reuse of reference voltage u ref Subtracting the process voltage u zi Obtaining voltage compensation quantity delta u through an integrator i ；
5) In the SOC balancing module and the voltage-current double closed-loop module, the voltage compensation quantity delta u obtained in the voltage compensation module is calculated i Directly to the reference voltage u ref Subtracting the output power of the energy storage unitPressing u oi Then pass through a voltage outer loop PI controller G V (s) obtaining a current inner loop reference current I ai And then I is carried out ai Equalizing current I with SOC bi After addition the inductor current i is subtracted Li The obtained result passes through a current inner loop PI controller G I (s) obtaining a driving voltage u si And then drive the voltage u si Comparing with the triangular carrier wave to obtain PWM modulation signal, wherein the SOC balances the current I bi The specific calculation process is as follows:
SOC (state of charge) of local energy storage unit i Subtracting the energy storage system state of charge average value SOC obtained in the communication module avg Multiplying byObtaining the equalization coefficient q i Wherein ρ is an acceleration factor, ε is an accurate factor, and the equalization coefficient q is calculated i Multiplying the absolute value of the current loop reference current I ai Obtaining SOC balance current I bi SOC equalizes current I bi The expression of (2) is:
FIG. 3 is a waveform diagram of the SOC of the energy storage unit, the distributed energy storage system operating in discharge mode, initial SOC 1 、SOC 2 90% and 87% respectively, and when the SOC is higher than the average value, the SOC balances the current I bi > 0, to make the DC side output current i oi The discharging speed of the energy storage unit is increased, and the SOC of the energy storage unit with larger SOC is reduced more rapidly; when SOC is lower than average, and vice versa; eventually, SOC equalization was achieved at 1.04 seconds.
FIG. 4 is a graph showing the DC side output current of the energy storage units, wherein the capacity ratio of the two energy storage units is 3:2, and therefore the capacity coefficients are selected to be k respectively 1 ＝3、k 2 In discharge mode, because of the capacity coefficient k =2 i After the equalization of the two energy storage units SOC, the output currents of the two energy storage units are respectively 12A and 8A,the purpose of accurate distribution in proportion to the capacity of the energy storage unit is achieved.
FIG. 5 is a waveform diagram of the bus voltage of the energy storage system, which can ensure that the bus voltage is controlled near the reference value 400V when the system is stable due to the existence of the voltage compensation module; although the bus voltage does not reach around 400V before SOC equalization, SOC can achieve equalization at 1.04 seconds, and therefore this is acceptable; bus voltage fluctuation caused by SOC equalization is also within an allowable range.
The above embodiments are only preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, so variations in shape and principles of the present invention should be covered.
Claims (2)
1. The SOC rapid equalization strategy without droop control of the direct-current micro-grid energy storage system is characterized by comprising the following steps:
1) The two energy storage units pass through the corresponding converters and the line impedance R linei Parallel connected to the DC bus to supply the load R load Supplying power to the induction current i at the starting point of each sampling period Li Output current i oi Output voltage u oi State of charge SOC of energy storage unit i Sampling is carried out respectively;
2) In the communication module, each energy storage unit only needs to exchange information with the adjacent energy storage unit, and the state of charge (SOC) of each energy storage unit in the energy storage system can be obtained without a central controller i And a virtual state variable y i And then the dynamic consistency algorithm is utilized to obtain the charge state average value SOC of the energy storage system avg And virtual state variable average y avg ；
3) In the current equalizing module, the output current i oi Divided by the maximum rated current i of the energy storage unit max Dividing by the capacity coefficient k of the energy storage unit i Obtaining an intermediate coefficient n i Subtracting the intermediate coefficient n from the coefficient 1 i Obtaining the transition factor m i ；
4) In the voltage compensation module, the transition is performedFactor m i Multiplying by output voltage u oi Obtaining the virtual state variable y i Then the dynamic consistency algorithm is utilized to obtain the average value y of the virtual state variable avg Reusing virtual state variable average y avg Divided by the transition factor m i Obtaining a process voltage u zi Reuse of reference voltage u ref Subtracting the process voltage u zi Obtaining voltage compensation quantity delta u through an integrator i ；
5) In the SOC balancing module and the voltage-current double closed-loop module, the voltage compensation quantity delta u obtained in the voltage compensation module is calculated i Directly to the reference voltage u ref Subtracting the output voltage u of the energy storage unit oi Then pass through a voltage outer loop PI controller G V (s) obtaining a current inner loop reference current I ai And then I is carried out ai Equalizing current I with SOC bi After addition the inductor current i is subtracted Li The obtained result passes through a current inner loop PI controller G I (s) obtaining a driving voltage u si And then drive the voltage u si Comparing with the triangular carrier wave to obtain PWM modulation signal, wherein the SOC balances the current I bi The specific calculation process is as follows:
SOC (state of charge) of local energy storage unit i Subtracting the energy storage system state of charge average value SOC obtained in the communication module avg Multiplying byObtaining the equalization coefficient q i Wherein ρ is an acceleration factor, ε is an accurate factor, and the equalization coefficient q is calculated i Multiplying the absolute value of the current loop reference current I ai Obtaining SOC balance current I bi SOC equalizes current I bi The expression of (2) is:
2. the SOC rapid equalization strategy without droop control for a dc micro-grid energy storage system of claim 1, wherein the acceleration factor ρ in step 5) has a value range of 0.6< ρ <1.2 and the equalization accuracy factor ε has a value range of 0.001< ε <0.01.
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| CN111987713A (en) * | 2020-08-05 | 2020-11-24 | 安徽工程大学 | Direct-current micro-grid improved droop control method based on charge state balance |
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