CN110525264B - Control system and control method for improving operation reliability of parallel charging pile - Google Patents
Control system and control method for improving operation reliability of parallel charging pile Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
- B60L53/60—Monitoring or controlling charging stations
- B60L53/62—Monitoring or controlling charging stations in response to charging parameters, e.g. current, voltage or electrical charge
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
- B60L53/60—Monitoring or controlling charging stations
- B60L53/67—Controlling two or more charging stations
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/7072—Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/10—Technologies relating to charging of electric vehicles
- Y02T90/12—Electric charging stations
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/10—Technologies relating to charging of electric vehicles
- Y02T90/16—Information or communication technologies improving the operation of electric vehicles
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Abstract
The invention provides a control system and a control method for improving the running reliability of parallel charging piles, which comprises the following steps: recording an input voltage current effective value and an output voltage current effective value of the AC-DC converter once every set time threshold, and calculating input active power, reactive power, output active power and power loss to form a two-dimensional function table taking the input active power and the reactive power as independent variables and the power loss as dependent variables; fitting the discrete data to obtain a functional relation between the loss of the charging pile and input active power and input reactive power; defining an overall reliability control objective function of the charging pile, and forming an optimization model by the reliability objective function and a constraint equation; solving an optimization model to obtain input active power, input reactive power and output power of each charging pile; and judging the working state of the charging pile and adjusting according to the state of the charging pile by combining input active power and reactive power to ensure the stability of junction temperature.
Description
Technical Field
The invention relates to the technical field of charging pile design, in particular to a control system and a control method for improving the operation reliability of parallel charging piles.
Background
With the continuous development of electric drive technology and battery energy storage technology, the number of electric automobiles is continuously increased. The construction of filling electric pile plays important effect in promoting electric automobile development process, and current fills electric pile and designs according to the requirement of small-size charging load such as family car, also can leave certain surplus when satisfying small-size charging load charging power requirement. When the large-scale electric pile that fills uses when filling electric pile to small-size load, just can't satisfy charging power's demand, it needs to consume a large amount of time to accomplish to charge. Recently, a multi-power-section parallel charging technology is provided by a patent, so that an idle charging pile can be effectively utilized, the requirement of a low-power charging load can be met, and the requirement of a high-power charging load can also be met. The basic idea is that the parallel charging system is formed by the parallel charging system and the adjacent charging piles, and at most 3 charging piles can supply power for the charging load at the same time for the high-power charging load, so that the utilization rate of the charging piles is improved, and the charging power requirement of the high-power charging load is also improved.
The electric vehicle charging pile is a conversion device of electric energy and a generating device of heat loss. As is known in the art, a charging pile is unique from a conventional power device in that an internal power switch device is used, and high-frequency on/off of the power switch device is the most basic element for the charging pile to realize a charging function. On one hand, due to the non-ideal conducting characteristic and the on/off characteristic of the power device, heat loss is generated by high-frequency operation of the power device, internal junction temperature rises, and the junction temperature of the power device fluctuates irregularly due to the power fluctuation characteristic when the power of the charging pile changes along with the charging mode. Studies have shown that excessive junction temperatures and severe junction temperature fluctuations are the main causes of damage to semiconductor devices. According to international authority statistics, nearly 40% of inverter faults are caused by damage of power devices, and are mostly unrepairable serious faults, so that the maintenance cost is extremely high. Therefore, the reliability of the switching device in the charging pile is improved, and the important means for prolonging the service life of the charging pile is provided. However, before the parallel charging mode of the charging pile occurs, the charging pile can only be in a charging state and a standby state, and the output power difference between the charging pile and the standby state is huge, so that the junction temperature difference is huge, the junction temperature is severely fluctuated, and the operation reliability of the charging pile is seriously threatened. In the future, charging piles are not only important devices in power systems, but also the most basic facilities of national daily life, and the operation reliability is very important. Along with filling the appearance of electric pile parallel charging mode, fill electric pile and change to the cluster traffic direction by the independent operation, the control flexibility ratio of filling electric pile in parallel will be far higher than single and fill electric pile, this also provides the condition for promoting the parallel electric pile reliability of filling. However, the control structure and the control process of the existing parallel charging pile are mostly from the viewpoint of completing the charging task, and there is no control structure and control method for the reliability of the charging pile.
Disclosure of Invention
Aiming at the problems that the existing control structure and process of the parallel charging pile mostly start from the viewpoint of completing the charging task, and a control structure and a control method aiming at the reliability of the charging pile do not exist, the invention provides a control system and a control method for improving the operation reliability of the parallel charging pile.
The technical scheme of the invention is as follows:
on one hand, the technical scheme of the invention provides a control system for improving the running reliability of a parallel charging pile, which comprises a multi-power-section parallel charging subsystem; the multi-power-section parallel charging subsystem comprises a plurality of charging piles, a controller is arranged in each charging pile, and adjacent charging piles are connected through a communication device;
the controller comprises a loss and active and reactive function relationship updating unit, a reliability control model generating unit, a reliability control parameter solving unit and a control unit;
the loss and active and reactive function relationship updating unit is used for receiving voltage and current information in the operation process of each charging pile and updating the loss and active and reactive function relationship in real time;
the reliability control model generating unit is used for generating a control model of the reliability of the charging pile according to the relation between the loss and the active and reactive functions;
the reliability control parameter solving unit is used for calculating input active power, reactive power and output power of each charging pile in the next control period according to the received charging pile reliability control model;
and the control unit is used for judging the working state of the charging pile and adjusting according to the state of the charging pile by combining input active power and reactive power to ensure the stability of junction temperature.
Further, an AC-DC converter in the charging pile is used for detecting input voltage and current and outputting voltage and current;
and the AC-DC converter is also used for finishing active and reactive output according to the active and reactive instructions.
Further, the loss and active and reactive function relationship updating unit is used for defining input active and reactive power of the charging pile, output power of the charging pile and charging power required by the electric automobile;
the loss and active and reactive function relation updating unit is used for recording the input voltage and current effective values and the output voltage and current effective values of the AC-DC converter once every set time threshold value, and calculating the input active power, the reactive power, the output active power and the power loss to form a two-dimensional function table which takes the input active power and the reactive power as independent variables and the power loss as dependent variables;
in order to avoid the increase of the data record quantity along with the increase of time, the newly recorded data can cover the original data, the loss and active and reactive functional relation updating unit utilizes a multivariate least square method to fit the discrete data, and the functional relation between the loss of the charging pile and the input active power and the input reactive power is obtained.
Further, the reliability control model generating unit is configured to define a power loss difference between two times of sampling, where the power loss difference represents a difference between a power loss calculated by the current sampling and a power loss calculated last time;
and the reliability control model generating unit is also used for defining an overall reliability control objective function of the charging pile and an optimization model consisting of the reliability objective function and a constraint equation.
Furthermore, the number of the charging piles is three;
a loss and active and reactive function relationship updating unit for defining the input active and reactive power P of the three charging piles M,in 、Q M,in (M =1,2,3), output power P of charging pile M,out Charging power P required by electric vehicle EV ；
A loss and active and reactive function relationship updating unit for updating the time threshold t set every time record Recording the input voltage and current effective values and the output voltage and current effective values of the AC-DC converter once, and calculating the input active power P M,in Reactive power Q M,in And output active power P M,out Power loss P M,loss ，P M,loss ＝P M,in -P M,out Form a to input active power P M,in And reactive power Q M,in As an independent variable, power loss P M,loss A two-dimensional function table as a dependent variable;
the loss and active and reactive function relation updating unit utilizes a multivariable least square method to fit discrete data to obtain chargeFunctional relation P between electric pile loss and input active power and input reactive power M,loss ＝f(P M,in ,Q M,in )。
Further, a reliability control model generating unit for defining the power loss difference Δ P of two samplings M,loss It represents the difference between the power loss calculated by this sampling and the power loss calculated last time:
ΔP M,loss (P M,in (k),Q M,in (k))＝P M,loss (P M,in (k),Q M,in (k))-P M,loss (P M,in (k-1),Q M,in (k-1)) wherein k represents the current sampling number, k-1 represents the last sampling number, and P M,in (k)、Q M,in (k) To await a quantity, P M,in (k-1)、Q M,in (k-1) is a known amount;
the reliability control model generating unit is also used for defining an overall reliability control objective function of the charging pile and an optimization model consisting of the reliability objective function and a constraint equation;
the objective function is:
the optimization model is as follows:
s.t-P M,in,max ≤P M,in (k)≤P M,in,max
-Q M,in,max ≤Q M,in (k)≤Q M,in,max
wherein, P M,in,max 、Q M,in,max 、S M,max Show respectively and fill electric pile active power, reactive power, apparent power's maximum value.
Further, the control unit is used for judging that when the charging pile is in a charging state, loss is controlled by distributing active power, and therefore the purpose of controlling junction temperature is achieved;
the control unit is used for judging that when the charging pile does not work and the output ends of the charging piles are connected in parallel, active circulation current is added between the charging piles connected in parallel, so that the charging piles are guaranteed to have power loss all the time, and the stability of junction temperature is further guaranteed;
and the control unit is used for judging that when the charging pile does not work and the output ends are not connected in parallel, adding reactive circulation between the inverters, and ensuring the loss of a switching device by using the reactive circulation so as to ensure the stability of junction temperature.
On the other hand, the technical scheme of the invention provides a control method for improving the running reliability of parallel charging piles, which comprises the following steps:
recording an input voltage current effective value and an output voltage current effective value of the AC-DC converter once every set time threshold, and calculating input active power, reactive power, output active power and power loss to form a two-dimensional function table taking the input active power and the reactive power as independent variables and the power loss as dependent variables;
fitting the discrete data to obtain a functional relation between the loss of the charging pile and input active power and input reactive power;
defining an overall reliability control objective function of the charging pile, and forming an optimization model by the reliability objective function and a constraint equation;
solving an optimization model to obtain input active power, input reactive power and output power of each charging pile;
and judging the working state of the charging pile and adjusting according to the state of the charging pile by combining input active power and reactive power to ensure the stability of junction temperature.
Further, every t record Recording once AC-DC convertersInput voltage current effective value and output voltage current effective value, and calculating input active power P M,in And reactive power Q M,in And output active power P M,out Power loss P M,loss ，P M,loss ＝P M,in -P M,out Form a group P M,in 、Q M,in Is an independent variable, P loss A two-dimensional function table as a dependent variable;
fitting the discrete data by using a multivariable least square method to obtain a functional relation P between the loss of the charging pile and the input active power and the input reactive power M,loss ＝f(P M,in ,Q M,in )；
Calculating the difference value between the power loss and the power loss calculated last time:
ΔP M,loss (P M,in (k),Q M,in (k))＝P M,loss (P M,in (k),Q M,in (k))-P M,loss (P M,in (k-1),Q M,in (k-1))
the overall reliability control objective function of the charging pile is defined as follows:
forming an optimization model by a reliability objective function and a constraint equation;
s.t-P M,in,max ≤P M,in (k)≤P M,in,max
-Q M,in,max ≤Q M,in (k)≤Q M,in,max
wherein, P M,in,max 、Q M,in,max 、S M,max Respectively representing the maximum values of active power, reactive power and apparent power of the charging pile;
and solving the optimization model by using a particle swarm algorithm to obtain the input active power, the input reactive power and the output power of each charging pile.
Further, the step of judging the working state of the charging pile and adjusting according to the state of the charging pile by combining input active power and reactive power to ensure the stability of junction temperature specifically comprises:
when the charging pile is in a charging state, loss is controlled by distributing active power, and the purpose of controlling junction temperature is further achieved;
when the charging pile does not work and the output ends of the charging piles are connected in parallel, active circulation current is added between the charging piles connected in parallel, so that the charging piles are guaranteed to have power loss all the time, and the stability of junction temperature is further guaranteed;
when the charging pile does not work and the output ends are not connected in parallel, reactive circulation current is added between the inverters, loss of the switching device is guaranteed by the reactive circulation current, and therefore stability of junction temperature is guaranteed. On the basis of the existing parallel charging piles, a switching device junction temperature online extraction unit and a reliability online evaluation unit are added to evaluate the current reliability of each charging pile. And adding a junction temperature control strategy alternative set and a control objective function into the main control unit, and preferably selecting a junction temperature control strategy and a regulation and control parameter according to the acquired charging pile reliability information so as to greatly reduce the junction temperature fluctuation of the charging piles and improve the operation reliability of the parallel charging piles.
According to the technical scheme, the invention has the following advantages: on the basis of not increasing the hardware structure, through the electric pile input active power of rational planning, input reactive power, output active power, when not influencing normal charging, show to reduce the junction temperature fluctuation of filling semiconductor device in the electric pile, promote the operational reliability who fills electric pile, from the charging station operation economic nature perspective, the improvement class of filling electric pile reliability can promote the normal service life who fills electric pile greatly to increase the income of charging station.
In addition, the invention has reliable design principle, simple structure and very wide application prospect.
Therefore, compared with the prior art, the invention has prominent substantive features and remarkable progress, and the beneficial effects of the implementation are also obvious.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
Fig. 1 and 2 are control structure diagrams for improving the operation reliability of the parallel charging pile;
FIG. 3 is a flow chart of the work for improving the operational reliability of the parallel charging piles;
fig. 4 is an effect diagram of improving the operational reliability of the parallel charging pile.
Detailed Description
In order to make those skilled in the art better understand the technical solutions of the present invention, 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. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
As shown in fig. 1 and 2, the technical solution of the present invention provides a control system for improving the operational reliability of a parallel charging pile, which includes a multi-power-stage parallel charging subsystem; the multi-power-section parallel charging subsystem comprises a plurality of charging piles, a controller is arranged in each charging pile, and adjacent charging piles are connected through a communication device; the AC-DC converter in the charging pile is used for detecting input voltage and current and outputting voltage and current; and the AC-DC converter is also used for finishing active and reactive outputs according to the active and reactive instructions, and the specific implementation mode is common knowledge in the industry. The power circuit structure of the AC-DC converter is determined according to the power grade of the charging pile, and the power circuit structure is common knowledge in the industry. The communication device is used for transmitting sampling signals and control signals required by reliability control between adjacent charging piles and between the charging pile and the electric automobile. The specific hardware structure and the underlying driver are common knowledge in the art. The connection device between the charging piles can be closed or opened in response to a command, and the specific principle thereof is common knowledge in the art.
The controller comprises a loss and active and reactive function relationship updating unit, a reliability control model generating unit, a reliability control parameter solving unit and a control unit;
the loss and active and reactive function relationship updating unit receives voltage and current information in the operation process of each charging pile and updates the loss and active and reactive function relationship in real time; a reliability control model generating unit generates a control model aiming at the reliability of the three parallel charging piles according to the relation between loss and active and reactive functions; and the reliability control parameter solving unit calculates the input active power and reactive power control unit of each charging pile in the next control period according to the received pile reliability control model, and is used for judging the working state of the charging pile and adjusting according to the state of the charging pile by combining the input active power and reactive power to ensure the stability of junction temperature.
In the loss and active and reactive function relationship updating unit, input active and reactive powers of the three charging piles are defined to be P respectively M,in 、Q M,in (M =1,2, 3), the output power of the three charging piles is P M,out The charging power required by the electric automobile is P EV . Controller in charging pile every t record Recording the output voltage and current effective values of the AC-DC converter once and calculating the input active power P M,in Reactive power Q M,in And output active power P M,out . The controller calculatesPower loss P M,loss ，P M,loss ＝P M,in -P M,out Taking an integer number of output powers and storing the power loss in the controller at a location corresponding to the output power, corresponds to forming a P-th power M,in ,Q M,in Is an independent variable, P loss Is a two-dimensional function table of dependent variables. The process does not need to be carried out independently, and only the record is needed to be carried out in the charging process of the electric automobile. The loss characteristic of the charging pile slightly changes along with the increase of the service life, so the function of calculating the power loss is operated all the time. In order to avoid the increase of the data record quantity along with the increase of time, the newly recorded data can cover the original data, and the multivariate least square method is utilized to fit the discrete data to obtain the functional relation P between the loss of the charging pile and the input active power and the input idle power M,loss ＝f(P M,in ,Q M,in ). The specific calculation process of the multivariate least squares method is common knowledge.
In the reliability control model generating unit, the power loss difference of two sampling is defined as delta P M,loss It represents the difference between the power loss calculated by this sampling and the power loss calculated last time:
ΔP M,loss (P M,in (k),Q M,in (k))＝P M,loss (P M,in (k),Q M,in (k))-P M,loss (P M,in (k-1),Q M,in (k-1))
wherein k represents the sampling sequence number of this time, and k-1 represents the sampling sequence number of the last time. P is M,in (k)、Q M,in (k) As a quantity to be sought, P M,in (k-1)、Q M,in (k-1) is a known amount.
Further, the overall reliability control objective functions of the three charging piles are defined as follows. Since reliability is closely related to junction temperature fluctuations, reducing junction temperature fluctuations can improve reliability. Defining an objective function for improving reliability as follows:
the optimization model consisting of the reliability objective function and the constraint equation is as follows:
s.t-P M,in,max ≤P M,in (k)≤P M,in,max
-Q M,in,max ≤Q M,in (k)≤Q M,in,max
wherein, P M,in,max 、Q M,in,max 、S M,max Show respectively and fill electric pile active power, reactive power, apparent power's maximum value.
In this embodiment, when the charging pile is in a charging state, loss is controlled by distributing active power, so as to achieve the purpose of controlling junction temperature; when the charging pile does not work and the output ends of the charging pile are connected in parallel, namely S1 and S2 are closed, active circulation current is added between the charging piles connected in parallel, so that the charging pile is guaranteed to have power loss all the time, and the stability of junction temperature is further guaranteed; when the charging pile does not work and the output ends are not connected in parallel, namely S1 and S2 are disconnected, reactive circulation current is added between the inverters, loss of the switching device is guaranteed by the reactive circulation current, and then stability of junction temperature is guaranteed.
Example two
As shown in fig. 3, the multi-power-stage charging method based on optimal efficiency according to the embodiment of the present invention includes the following steps:
controller in charging pile every t record Recording the effective values of the output voltage and the output current of the AC-DC converter once, and calculating the input active power P M,in And reactive power Q M,in And output active power P M,out . ControllerCalculating the power loss P M,loss ，P M,loss ＝P M,in -P M,out Taking an integer number of output powers and storing the power loss in the controller at a location corresponding to the output power, corresponds to forming a P-th power M,in ,Q M,in Is an independent variable, P loss Is a two-dimensional function table of dependent variables.
Fitting the discrete data by using a multivariable least square method to obtain a functional relation P between the loss of the charging pile and the input active power and the input reactive power M,loss ＝f(P M,in ,Q M,in )。
Difference between the calculated power loss and the last calculated power loss:
ΔP M,loss (P M,in (k),Q M,in (k))＝P M,loss (P M,in (k),Q M,in (k))-P M,loss (P M,in (k-1),Q M,in (k-1))
the following optimization model is composed of a reliability objective function and a constraint equation:
s.t-P M,in,max ≤P M,in (k)≤P M,in,max
-Q M,in,max ≤Q M,in (k)≤Q M,in,max
solving the optimization model by using a particle swarm algorithm to obtain input active power, input reactive power and output power of each charging pile;
when the charging pile is in a charging state, loss is controlled by distributing active power, and the purpose of controlling junction temperature is further achieved; when the charging pile does not work and the output ends of the charging pile are connected in parallel, namely S1 and S2 are closed, active circulation current is added between the charging piles connected in parallel, so that the charging pile is guaranteed to have power loss all the time, and the stability of junction temperature is further guaranteed; when the charging pile does not work and the output ends are not connected in parallel, namely S1 and S2 are disconnected, reactive circulation is added between the inverters, loss of a switching device is guaranteed by the reactive circulation, and therefore stability of junction temperature is guaranteed. By reasonably planning the input active power, the input reactive power and the output active power of the charging pile, junction temperature fluctuation of a semiconductor device in the charging pile is obviously reduced and the operation reliability of the charging pile is improved without influencing normal charging, as shown in fig. 4.
Although the present invention has been described in detail by referring to the drawings in connection with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (4)
1. A control system for improving the running reliability of a parallel charging pile is characterized by comprising a multi-power-section parallel charging subsystem; the multi-power-section parallel charging subsystem comprises a plurality of charging piles, a controller is arranged in each charging pile, and adjacent charging piles are connected through a communication device;
the controller comprises a loss and active and reactive function relationship updating unit, a reliability control model generating unit, a reliability control parameter solving unit and a control unit;
the loss and active and reactive function relationship updating unit is used for receiving voltage and current information in the operation process of each charging pile and updating the loss and active and reactive function relationship in real time;
the reliability control model generating unit is used for generating a control model of the reliability of the charging pile according to the relation between the loss and the active and reactive functions;
the reliability control parameter solving unit is used for calculating input active power, reactive power and output power of each charging pile in the next control period according to the received charging pile reliability control model;
the control unit is used for judging the working state of the charging pile and adjusting according to the state of the charging pile by combining input active power and reactive power to ensure the stability of junction temperature;
the AC-DC converter in the charging pile is used for detecting input voltage and current and outputting voltage and current;
the AC-DC converter is also used for finishing active and reactive output according to the active and reactive instructions;
the loss and active and reactive function relationship updating unit is used for defining input active and reactive power of the charging pile, output power of the charging pile and charging power required by the electric automobile;
the loss and active and reactive function relation updating unit is used for recording the input voltage and current effective values and the output voltage and current effective values of the AC-DC converter once every set time threshold value, calculating input active power, reactive power, output active power and power loss, and forming a two-dimensional function table which takes the input active power and reactive power as independent variables and the power loss as dependent variables;
the loss and active and reactive function relation updating unit is used for fitting the discrete data by using a multivariate least square method to obtain the function relation between the loss of the charging pile and input active power and input reactive power;
a reliability control model generating unit, configured to define a power loss difference between two times of sampling, where the power loss difference represents a power loss difference between a power loss calculated by the current sampling and a power loss calculated last time;
the reliability control model generating unit is also used for defining an overall reliability control objective function of the charging pile and an optimization model consisting of the reliability objective function and a constraint equation;
the number of the charging piles is three;
a loss and active and reactive function relationship updating unit for defining the input active and reactive power P of the three charging piles M,in 、Q M,in (M =1,2,3), output power P of charging pile M,out Charging power P required by electric vehicle EV ；
A loss and active and reactive function relationship updating unit for updating the time threshold t set every other record Recording the input voltage and current effective values and the output voltage and current effective values of the AC-DC converter once, and calculating the input active power P M,in Reactive power Q M,in And output active power P M,out Power loss P M,loss， P M,loss ＝P M,in -P M,out Form a to input active power P M,in Reactive power Q M,in As an independent variable, power loss P M,loss A two-dimensional function table as a dependent variable;
a loss and active and reactive function relationship updating unit which utilizes a multivariate least square method to fit the discrete data to obtain a function relationship P between the loss of the charging pile and the input active power and the input reactive power M,loss ＝f(P M,in ,Q M,in )；
A reliability control model generation unit for defining power loss difference DeltaP of two sampling M,loss It represents the difference between the power loss calculated by this sampling and the power loss calculated last time:
ΔP M,loss (P M,in (k),Q M,in (k))＝P M,loss (P M,in (k),Q M,in (k))-P M,loss (P M,in (k-1),Q M,in (k-1))
wherein k represents the sampling sequence number of this time, k-1 represents the sampling sequence number of the last time, P M,in (k)、Q M,in (k) To await a quantity, P M,in (k-1)、Q M,in (k-1) is a known amount;
the reliability control model generating unit is also used for defining an overall reliability control objective function of the charging pile and an optimization model consisting of the reliability objective function and a constraint equation;
the objective function is:
the optimization model is as follows:
s.t-P M,in,max ≤P M,in (k)≤P M,in,max
-Q M,in,max ≤Q M,in (k)≤Q M,in,max
wherein, P M,in,max 、Q M,in,max 、S M,max Show respectively and fill electric pile active power, reactive power, apparent power's maximum value.
2. The control system for improving the operational reliability of the parallel charging piles according to claim 1,
the control unit is used for judging that when the charging pile is in a charging state, loss is controlled by distributing active power, and the purpose of controlling junction temperature is further achieved;
the control unit is used for judging that when the charging pile does not work and the output ends of the charging piles are connected in parallel, active circulation current is added between the charging piles connected in parallel, so that the charging piles are guaranteed to have power loss all the time, and the stability of junction temperature is further guaranteed;
and the control unit is used for judging that when the charging pile does not work and the output ends are not connected in parallel, adding reactive circulation between the inverters, and ensuring the loss of a switching device by using the reactive circulation so as to ensure the stability of junction temperature.
3. A control method for improving the operation reliability of a parallel charging pile is characterized by comprising the following steps:
recording an input voltage current effective value and an output voltage current effective value of the AC-DC converter once every set time threshold, and calculating input active power, reactive power, output active power and power loss to form a two-dimensional function table taking the input active power and the reactive power as independent variables and the power loss as dependent variables;
fitting the discrete data to obtain a functional relation between the loss of the charging pile and input active power and input reactive power;
defining an overall reliability control objective function of the charging pile, and forming an optimization model by the reliability objective function and a constraint equation;
solving the optimization model to obtain the input active power, the input reactive power and the output power of each charging pile;
judging the working state of the charging pile and adjusting according to the state of the charging pile by combining input active power and reactive power to ensure the stability of junction temperature;
every t record Recording the input voltage and current effective values and the output voltage and current effective values of the AC-DC converter once, and calculating the input active power P M,in Reactive power Q M,in And output active power P M,out Power loss P M,loss ，P M,loss ＝P M,in -P M,out Form a group P M,in 、Q M,in Is an independent variable, P loss A two-dimensional function table as a dependent variable;
fitting the discrete data by using a multivariate least square method to obtain a functional relation P between the loss of the charging pile and the input active power and the input reactive power M,loss ＝f(P M,in ,Q M,in )；
Calculating the difference value between the power loss and the power loss calculated last time:
ΔP M,loss (P M,in (k),Q M,in (k))＝P M,loss (P M,in (k),Q M,in (k))-P M,loss (P M,in (k-1),Q M,in (k-1))
the overall reliability control objective function of the charging pile is defined as follows:
forming an optimization model by a reliability objective function and a constraint equation;
s.t-P M,in,max ≤P M,in (k)≤P M,in,max
-Q M,in,max ≤Q M,in (k)≤Q M,in,max
wherein, P M,in,max 、Q M,in,max 、S M,max Respectively representing the maximum values of the active power, the reactive power and the apparent power of the charging pile;
and solving the optimization model by using a particle swarm algorithm to obtain the input active power, the input reactive power and the output power of each charging pile.
4. The control method for improving the operation reliability of the parallel charging piles according to claim 3, wherein the step of judging the working state of the charging piles and adjusting the working state according to the state of the charging piles in combination with input active power and reactive power to ensure the stability of junction temperature specifically comprises the following steps:
when the charging pile is in a charging state, loss is controlled by distributing active power, and the purpose of controlling junction temperature is further achieved;
when the charging pile does not work and the output ends of the charging piles are connected in parallel, active circulation current is added between the charging piles connected in parallel, so that the charging piles are guaranteed to have power loss all the time, and the stability of junction temperature is further guaranteed;
when the charging pile does not work and the output ends are not connected in parallel, reactive circulation is added between the inverters, loss of the switching device is guaranteed by the reactive circulation, and therefore stability of junction temperature is guaranteed.
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