NL2024252A - A charge-discharge control method for an electric vehicle based on virtual inertia - Google Patents

A charge-discharge control method for an electric vehicle based on virtual inertia Download PDF

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Publication number
NL2024252A
NL2024252A NL2024252A NL2024252A NL2024252A NL 2024252 A NL2024252 A NL 2024252A NL 2024252 A NL2024252 A NL 2024252A NL 2024252 A NL2024252 A NL 2024252A NL 2024252 A NL2024252 A NL 2024252A
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charge
electric vehicle
virtual inertia
discharge control
constant
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NL2024252A
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Dutch (nl)
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NL2024252B1 (en
Inventor
Peng Ke
Wei Zhiyu
Chen Jiajia
Jiao Ticao
Lu Maozeng
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Univ Shandong Technology
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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
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • H02J3/322—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means the battery being on-board an electric or hybrid vehicle, e.g. vehicle to grid arrangements [V2G], power aggregation, use of the battery for network load balancing, coordinated or cooperative battery charging
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/00714—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery charging or discharging current
    • 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
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage
    • 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
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries
    • 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
    • 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
    • Y02T90/14—Plug-in electric vehicles
    • 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
    • Y02T90/167—Systems integrating technologies related to power network operation and communication or information technologies for supporting the interoperability of electric or hybrid vehicles, i.e. smartgrids as interface for battery charging of electric vehicles [EV] or hybrid vehicles [HEV]
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S30/00—Systems supporting specific end-user applications in the sector of transportation
    • Y04S30/10—Systems supporting the interoperability of electric or hybrid vehicles
    • Y04S30/12—Remote or cooperative charging

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)

Abstract

Disclosed herewith a charge-discharge control method for an electric vehicle based on virtual inertia, comprising steps of: obtaining an input signal; comparing the input signal with a reference value and then outputting a difference value; performing proportional integral on the difference value by a PI controller, which is in parallel connection with a virtual inertia compensation function for introducing a virtual inertia as supplement; and outputting a modulated signal.

Description

A CHARGE-DISCHARGE CONTROL METHOD FORAN ELECTRIC VEHICLE BASED ON VIRTUAL INERTIA
Technical Field
The present invention relates to the technical field of charge-discharge control for electric vehicles, in particular to a charge-discharge control method for an electric vehicle based on virtual inertia.
Technical Background
DC power distribution system is the new development direction for future urban power distribution system. With the increasing popularity of electric vehicles, they will have a major impact on the stability of DC distribution network. As the charge-discharge technology for electric vehicles has been continuously developing, there are more and more charge-discharge modes for electric vehicles. At present, conventional charge methods for electric vehicle batteries in the DC distribution network include a constant current charge mode, a constant power charge mode, a constant voltage charge mode, and a constant current and constant voltage charge mode. Among others, for the constant current charge mode, the constant power charge mode and the constant voltage charge mode, the charging current, the charging power and the charging voltage should be kept constant during respective charging procedures. The constant current and constant voltage charge mode combines two charge modes of constant current charge and of constant voltage charge together. As shown in Fig. 1, the charging current is kept constant in a first stage, and the charging voltage is kept constant in a second stage. When the charging current is reduced to the minimum value, or an external charging termination command is received, the electric vehicle battery is no longer charged.
-1 The conventional discharge modes for electric vehicle batteries include a constant current discharge mode and a constant power discharge mode. When the constant current discharge mode is adopted in an electric vehicle, constant current discharging output is maintained, and the voltage across the battery is detected always. When the voltage across the battery is less than a system threshold, or an electric SOC state value is less than a system set value, the electric vehicle battery is no longer discharged. When the constant power discharge mode is adopted in an electric vehicle, the discharging power P is kept constant. Since the voltage of the battery continues to decrease during the discharging procedure, the current will be increased always during the constant power discharging procedure. When the voltage across the battery is less than the system threshold, or the electric SOC state value is less than the system set value, the electric vehicle battery is no longer discharged.
With the increasing load of the DC distribution network, some disturbances will inevitably occur. The conventional charge-discharge control methods for electric vehicles generally use conventional power control, such as constant current control, constant voltage control, and constant power control. The conventional control structure is simple and easy to implement, and is able to meet charging requirements of batteries. However, its control effect is less satisfactory. Negative damping characteristic of the constant power control will degrade the stability of the system. Moreover, although the damping of the constant voltage control is in a critical state, and the damping of the constant current control is theoretically greater than zero, which means it per se does not excite instability phenomenon, the constant voltage and constant current control systems both have a certain dynamic response characteristics, and thus different control parameters will also affect the stability of the system. When the structure of the DC power distribution system is relatively complex, the power quality may fail to meet the requirements.
Summary of the Invention
-2 In order to solve the above-mentioned problems, the present invention aims to provide a charge-discharge control method for an electric vehicle based on virtual inertia, which can further improve the system’s inertia compared with the conventional control of conventional charge-discharge modes.
The present invention proposes a charge-discharge control method for an electric vehicle based on virtual inertia, comprising introducing a virtual inertia in a procedure of charge-discharge control for the electric vehicle as compensation for DC components.
As a possible implement mode of the present embodiment, the charge-discharge control method for an electric vehicle comprises steps of: obtaining an input signal; comparing the input signal with a reference value and then outputting a difference value; performing proportional integral on the difference value by a PI controller, which is in parallel connection with a virtual inertia compensation function for introducing a virtual inertia as supplement; and outputting a modulated signal.
As a possible implement mode of the present embodiment, the procedure of charge-discharge control for the electric vehicle includes: a constant current charge-discharge control procedure, a constant power charge-discharge control procedure, or a constant voltage charge-discharge control procedure.
As a possible implement mode of the present embodiment, the constant current charge-discharge control procedure comprises steps of: taking a DC current input into the electric vehicle as input signal z; comparing the input signal i with its reference value z'ref to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an inner loop current control cycle, and simultaneously introducing a virtual inertia Gc by the virtual inertia compensation function, which is in parallel connection with the PI controller acting as the inner loop current control cycle, for compensation; and outputting a modulated signal Pm of a chopper of the electric vehicle.
-3 As a possible implement mode of the present embodiment, the constant current charge-discharge control procedure includes a constant current charge control procedure and a constant current discharge control procedure.
As a possible implement mode of the present embodiment, the constant power charge-discharge control procedure comprises steps of taking an active power input into the electric vehicle as input signal P; comparing the input signal P with its reference value Pref to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an outer loop power control cycle, and simultaneously introducing a virtual inertia Gc by the virtual inertia compensation function, which is in parallel connection with the PI controller acting as the outer loop power control cycle, for compensation; outputting a DC current reference value zrcf of a current inner loop; taking a DC current input into the electric vehicle as input signal i; comparing the input signal i with the DC current reference value zref of the current inner loop to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an inner loop current control cycle; and outputting a modulated signal Pm of a chopper of the electric vehicle.
As a possible implement mode of the present embodiment, the constant power charge-discharge control procedure includes a constant power charge control procedure and a constant power discharge control procedure.
As a possible implement mode of the present embodiment, the constant voltage charge-discharge control procedure comprises steps of taking a DC voltage at the electric vehicle as input signal Uac; comparing the input signal Ude with its reference value ί/dcref to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an outer loop DC voltage control cycle, and simultaneously introducing a virtual inertia Gc by the virtual inertia compensation function, which is in parallel connection with the PI controller acting as the outer loop DC voltage control cycle, for compensation; outputting a DC current reference value 7ref of a current inner loop; taking a DC current input into the electric vehicle as input signal comparing the input signal i with the DC current reference value zref of the current inner loop to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an inner loop current control cycle; and -4 outputting a modulated signal Pm of a chopper of the electric vehicle.
As a possible implement mode of the present embodiment, the constant voltage charge-discharge control procedure includes a constant voltage charge control procedure and a constant voltage discharge control procedure.
As a possible implement mode of the present embodiment, the compensation function for the virtual inertia Gc is as follows:
=------Kc+sHc wherein Kc is damping parameter, Hc is inertia time constant, and v is Laplacian operator.
The embodiment of the present invention can generate the following technical effect.
According to the technical solution of the embodiment of the present invention, a virtual inertia is introduced during the charge-discharge control procedure for the electric vehicle as compensation for DC components. Since the virtual inertia control provides a large damping and a high inertia, the DC bus voltage oscillation will be gradually attenuated to be stable under the virtual inertia charge-discharge mode. Therefore, it can provide stronger damping compared to the conventional control mode without introducing the virtual inertia, and effectively enhancing stability of the system. In this manner, the system’s inertia is further improved compared to the conventional control of the conventional charge-discharge mode, so that the voltage is prevented from changing too fast to maintain the grid stable when the DC distribution network is disturbed, and the further power quality requirements of other DC load users can be met.
With the virtual inertia introduced, the charge-discharge current in the steady state for the constant current mode according to the technical solution of the embodiment of the present invention can remain unchanged, the charge-discharge active power in the steady state for the constant power mode can remain unchanged, and the charge-discharge voltage in the steady state for the constant voltage mode can
- 5 remain unchanged. Therefore, the system has greater inertia and is more stable.
Brief Description of the Drawings
Fig. 1 schematically shows the conventional constant current and constant voltage charge mode;
Fig. 2 is a flow chart of a charge-discharge control method for an electric vehicle based on virtual inertia according to an exemplary embodiment of the present invention;
Fig. 3 is a block diagram of the configuration of constant current control for electric vehicle based on virtual inertia;
Fig. 4 is a block diagram of the configuration of constant voltage control for electric vehicle based on virtual inertia;
Fig. 5 is a block diagram of the configuration of constant power control for electric vehicle based on virtual inertia;
Fig. 6 is a circuit diagram of a simulation example of a DC power distribution system, including an electric vehicle, according to the present invention;
Fig. 7 is a simulation diagram of a DC bus voltage during constant current charge with virtual inertia;
Fig. 8 is a simulation diagram of a DC bus voltage during constant voltage charge with virtual inertia;
Fig. 9 is a simulation diagram of a DC bus voltage during constant power charge with virtual inertia;
Fig. 10 is a simulation diagram of a DC bus voltage during constant current
-6 discharge with virtual inertia; and
Fig. 11 is a simulation diagram of a DC bus voltage during constant power discharge with virtual inertia.
Detailed Description of the Invention
The present invention will be described in further detail with reference to preferred embodiments in combination with the accompanying drawings.
In order to clearly illustrate the technical features of the present solution, the present invention will be described in detail below through specific embodiments and the accompanying drawings. The following content provides many different embodiments or examples for implementing different structures of the present invention. In order to simplify the description of the present invention, the components and configurations of specific examples are described below. Moreover, in the present invention reference numerals and/or letters can be repeatedly used in different examples. This repetition is for the purpose of simplicity and clarity, and is not a reflection in the relationship between various embodiments and/or configurations discussed. It should be noted that the components illustrated in the drawings are not necessarily drawn to scale. The known components, processing techniques and procedures are not described here in order to avoid limiting the present invention unnecessarily.
According to an embodiment of the present invention, a charge-discharge control method for an electric vehicle based on virtual inertia is provided, wherein a virtual inertia is introduced during the charge-discharge control procedure for the electric vehicle as compensation for DC components. Negative damping characteristic of the constant power control will degrade the stability of the system. Moreover, although the damping of the constant voltage control is in a critical state, and the damping of the constant current control is theoretically greater than zero, which means it per se does not excite instability phenomenon, the constant voltage and constant current control systems both have a certain dynamic response characteristics, and thus
-7 different control parameters will also affect the stability of the system. The present invention can, without changing other control parameters, increase the system inertia by introducing a virtual inertia as a link in the outer loop control, thereby achieving the purpose of enhancing the stability of the DC power distribution system.
Fig. 2 is a flow chart of a charge-discharge control method for an electric vehicle based on virtual inertia according to an exemplary embodiment of the present invention. As shown in Fig. 2, the charge-discharge control method for an electric vehicle based on virtual inertia according to the embodiment of the present invention includes steps of: obtaining an input signal; comparing the input signal with a reference value to output a difference value; performing proportional integral on the difference value by a PI controller, which is in parallel connection with a virtual inertia compensation function for introducing a virtual inertia as supplement; and outputting a modulated signal.
In a possible implementation mode, the charge-discharge control procedure for an electric vehicle includes: a constant current charge-discharge control procedure, a constant power charge-discharge control procedure, or a constant voltage charge-discharge control procedure.
In a possible implementation mode, the constant current charge-discharge control procedure including steps of: taking a DC current input into the electric vehicle as an input signal /; comparing the input signal i with its reference value zrcf to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an inner loop current control cycle, and simultaneously introducing a virtual inertia Gc by the virtual inertia compensation function, which is in parallel connection with the PI controller acting as the inner loop current control cycle, for compensation; and outputting a modulated signal Pm of a chopper of the electric vehicle.
In a possible implementation mode, the constant current charge-discharge control procedure includes a constant current charge control procedure and a constant current discharge control procedure.
-8In a possible implementation mode, the constant power charge-discharge control procedure includes steps of: taking an active power input into the electric vehicle as an input signal P\ comparing the input signal P with its reference value ΡΚΐ to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an outer loop power control cycle, and simultaneously introducing a virtual inertia Gc by the virtual inertia compensation function, which is in parallel connection with the PI controller acting as the outer loop power control cycle, for compensation; outputting a DC current reference value zref of a current inner loop; taking a DC current input into the electric vehicle as an input signal z; comparing the input signal i with the DC current reference value zref of the current inner loop to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an inner loop current control cycle; and outputting a modulated signal Pm of a chopper of the electric vehicle.
In a possible implementation mode, the constant power charge-discharge control procedure includes a constant power charge control procedure and a constant power discharge control procedure.
In a possible implementation mode, the constant voltage charge-discharge control procedure includes steps of: taking a DC voltage at the electric vehicle as an input signal GdC; comparing the input signal U<j.c with its reference value U<jCK{ to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an outer loop DC voltage control cycle, and simultaneously introducing a virtual inertia Gc by the virtual inertia compensation function, which is in parallel connection with the PI controller acting as the outer loop DC voltage control cycle, for compensation; outputting a DC current reference value zref of a current inner loop; taking a DC current input into the electric vehicle as an input signal z; comparing the input signal i with the DC current reference value zref of the current inner loop to obtain a difference value; performing proportional integral on the difference value by a PI controller acting as an inner loop current control cycle; and outputting a modulated signal Pm of a chopper of the electric vehicle.
In a possible implementation mode, the constant voltage charge-discharge control procedure includes a constant voltage charge control procedure and a constant -9voltage discharge control procedure.
In a possible implementation mode, the compensation function for the virtual inertia Gc is as follows:
G -----Kc+sHc wherein Kc is damping parameter, Hc is inertia time constant, and 5 is Laplacian operator.
As the load on the DC distribution network increases, it is inevitable that some disturbance will occur. In order to further improve the system’s inertia on the basis of the conventional control of the conventional charge-discharge mode, that is, the voltage is prevented from changing too fast to maintain the grid stable when the DC distribution network is disturbed, and at the same time increase the system’s stability, the present invention introduces a virtual inertia compensation function in the outer loop of the conventional control as compensation for DC components, thereby increasing the inertia of the system. The adopted virtual inertia compensation function is:
Gc.=----ï---Kc+sHe
In order to further verify the technical solution of the present invention, wherein the virtual inertia control of the present invention is based on conventional controls, the following will describe the constant current and constant power charge-discharge strategies for an electric vehicle based on the virtual inertia, and the constant voltage charge strategy for an electric vehicle based on the virtual inertia.
1. Constant current charge-discharge strategy for an electric vehicle based on virtual inertia
According to the constant current charge-discharge strategy for an electric vehicle, the charge-discharge current for the electric vehicle can be kept unchanged. After the virtual inertia is introduced, the stability of the system must be enhanced while the charge-discharge current are kept unchanged. Fig. 3 is a block diagram of the configuration of the constant current control for an electric vehicle based on
- io virtual inertia. In Fig. 3, i and zref are the DC current signal of the current inner loop and its reference value respectively, Fm is the chopper's modulated signal, Kp\+K\/s is the PI controller arranged as a link in the current inner loop of control, and Xpi and K\t are respectively the proportional coefficient and the integral coefficient of the PI controller of the current inner loop.
In the conventional constant current control, the DC current input into the electric vehicle is taken as the input signal z, which is compared with its reference value zref to obtain a difference value. Then, the difference value is subjected to the proportional integral cycle Xpi+Xj/s, and finally the modulated signal Pm of the electric vehicle’s chopper is output. The virtual inertia Gc is introduced in the form of a virtual inertia compensation function in parallel connection with the PI controller Kpi+K}i/s. Since the measured value is still the DC current input into the electric vehicle, the charge-discharge current can be kept constant during the charge-discharge procedure.
2. Constant power charge-discharge strategy for an electric vehicle based on virtual inertia
According to the constant power charge-discharge strategy for an electric vehicle, the charge-discharge power for the electric vehicle can be kept unchanged. After the virtual inertia is introduced, the stability of the system must be enhanced while the charge-discharge power are kept unchanged. Fig. 4 is a block diagram of the configuration of the constant power control for an electric vehicle based on virtual inertia. In Fig. 4, P and PKi are the active power signal of the power outer loop and its reference value respectively, XpP+A'iP/s is the PI controller arranged as a link in the power outer loop of control, and A’pp and A'jp are respectively the proportional coefficient and the integral coefficient of the PI controller of the active power outer loop. Other variants have the same meaning as those in Fig. 3 respectively.
In the conventional constant power control, the active power input into the electric vehicle is taken as the input signal P, which is compared with its reference value Pref to obtain a difference value. Then, the difference value is subjected to the power outer loop proportional integral link Kpp+Kip/s, and a DC current reference
- π value z'ref of the current inner loop is output. After a conventional current inner loop control, a modulated signal Pm of the electric vehicle’s chopper is output. The virtual inertia Gc is introduced in the form of a virtual inertia compensation function in parallel connection with the power outer loop PI controller Fpp+A',p/s. Since the measured value is still the active power input into the electric vehicle, the charge-discharge power can be kept constant during the charge-discharge procedure.
3. Constant voltage discharge strategy for an electric vehicle based on virtual inertia
According to the constant voltage discharge strategy for an electric vehicle, the discharging voltage for the electric vehicle can be kept unchanged. After the virtual inertia is introduced, the stability of the system must be enhanced while the discharging voltage is kept unchanged. Fig. 5 is a block diagram of the configuration of the constant power voltage control for an electric vehicle based on virtual inertia. In Fig. 5, I/dc and L/dcref are the voltage signal of the DC voltage outer loop and its reference value respectively, ^pv+AiV/s is the PI controller arranged as link in the DC voltage outer loop of control, and and are respectively the proportional coefficient and the integral coefficient of the PI controller of the DC voltage outer loop. Other variants have the same meaning as those in Fig. 3 respectively.
In the conventional constant voltage control, the DC voltage at the electric vehicle is taken as the input signal Ude, which is compared with its reference value I/dcref to obtain a difference value. Then, the difference value is subjected to the DC voltage outer loop proportional integral link K^+K^/s, and a DC current reference value /ref of the current inner loop is output. After a conventional current inner loop control, a modulated signal Pm of the electric vehicle’s chopper is output. The virtual inertia Gc is introduced in the form of a virtual inertia compensation function in parallel connection with the DC voltage outer loop PI controller XpV+Xjv/s. Since the measured value is still the DC voltage at the electric vehicle, the charge-discharge voltage can be kept constant during the charge-discharge procedure.
4. Simulation Verification
- 12 In order to compare the stability of the system before and after the introduction of the virtual inertia compensation function, and verify the effectiveness of the present invention, a simulation example of a typical DC power distribution system including an electric vehicle is provided by means of simulation software. As shown in Fig. 6, in the example, the AC voltage is 0.22kV, and the rated voltage of the common DC bus is 0.4kV.
Since the DC voltage is an important index for evaluating the stability of the DC power distribution system, the common DC bus is selected as the index for evaluating the stability of the system. The stability of the system before and after the introduction of the virtual inertia compensation function is verified.
1) Charging simulation verification
The DC bus voltage waveforms of the constant current, the constant voltage, and the constant power charge modes and those of corresponding modes based on virtual inertia are respectively shown in Fig. 7, Fig. 8 and Fig. 9.
It can be seen from Fig. 7, Fig. 8 and Fig. 9 that the DC bus voltage oscillates and diverges under three conventional charge modes, and thus the system is unstable. Since the virtual inertia control provides high damping and large inertia, the DC bus voltage oscillation of the charge modes based on virtual inertia is gradually attenuated to become stable.
2) Discharging simulation verification
The DC bus voltage waveforms of the constant current and the constant voltage discharge modes and those of corresponding modes based on virtual inertia are respectively shown in Fig. 10 and Fig. 11.
It can be seen from Fig. 10 and Fig. 11 that the DC bus voltage oscillates and diverges under two conventional discharge modes, and thus the system is unstable. Since the virtual inertia control provides high damping and large inertia, the DC bus voltage oscillation of the discharge modes based on virtual inertia is gradually
- 13 attenuated to become stable.
Upon comprehensive analysis of the above simulation verifications, it can be found that the control modes proposed by the present invention by introducing virtual inertia in conventional control modes has stronger damping capacity than the conventional control modes, and can effectively improve stability of the system.
For a DC power distribution system including an electric vehicle, the present invention proposes a charge-discharge control mode for the electric vehicle based on virtual inertia, which enables, without changing the electrical parameters and other control parameters of the DC power distribution network, the inertia of the DC power distribution system including the electric vehicle is further increased and the stability thereof is enhanced, so as to further meet the power quality requirements of other DC load users. Compared with the prior arts, the present invention has the following advantages.
1. In the constant current mode, the charge-discharge current in the steady state can remain unchanged after the introduction of the virtual inertia. Therefore, the system has greater inertia and is more stable.
2. In the constant power mode, the charge-discharge active power in the steady state can remain unchanged after the introduction of the virtual inertia. Therefore, the system has greater inertia and is more stable.
3. In the constant voltage mode, the charge-discharge voltage in the steady state can remain unchanged after the introduction of the virtual inertia. Therefore, the system has greater inertia and is more stable.
The above description of specific embodiments of the present invention has been described with reference to the accompanying drawings, but is not intended to limit the scope of the invention. Other different forms of modifications or variations may be made by those skilled in the art in light of the above description. There is no need and no way to exhaust all of the implementation modes. On the basis of the technical solutions of the present invention, various modifications or variations that can be
- 14 made by those skilled in the art without any creative effort are still within the scope of the present invention.

Claims (10)

CONCLUSIESCONCLUSIONS 1. Een oplading-ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid, omvattende het introduceren van een virtuele traagheid in een opladingontladingsbesturingsprocedure voor het elektrische voertuig als compensatie voor gelijkstroom (DC) componenten.A charge-discharge control method for a virtual inertia-based electric vehicle, comprising introducing a virtual inertia into a electric-vehicle discharge-discharge control procedure as compensation for direct current (DC) components. 2. De oplading-ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 1, waarbij de werkwijze stappen omvat van:The charge-discharge control method for a virtual inertia electric vehicle according to claim 1, wherein the method comprises steps of: het verkrijgen van een invoersignaal;obtaining an input signal; het vergelijken van het ingangssignaal met een referentiewaarde en vervolgens het uitvoeren van een verschilwaarde;comparing the input signal with a reference value and then outputting a difference value; het uitvoeren van een proportionele integraal op de verschilwaarde door een Pl-regelaar, die parallel verbonden is met een virtuele traagheidscompensatiefunctie voor het introduceren van een virtuele traagheid als supplement; en het uitvoeren van een gemoduleerd signaal.performing a proportional integral to the difference value by a P1 controller, which is connected in parallel with a virtual inertia compensation function for introducing a virtual inertia as a supplement; and outputting a modulated signal. 3. De oplading-ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 2, waarbij de oplading-ontladingsbesturingsprocedure voor het elektrische voertuig omvat: een constante stroom opladingontladingsbesturingsprocedure, een constante vermogen opladingontladingsbesturingsprocedure, of een constante spanning opladingontladingsbesturingsprocedure.The charge-discharge control method for a virtual inertia electric vehicle according to claim 2, wherein the electric-vehicle discharge discharge control procedure comprises: a constant current charge discharge control procedure, a constant power charge discharge control procedure, or a constant voltage charge discharge control procedure. 4. De oplading- ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 3, waarbij de constante-stroom opladingontladingsbesturingsprocedure stappen omvat van:The charge-discharge control method for a virtual inertia electric vehicle according to claim 3, wherein the constant-current charge discharge control procedure comprises steps of: het nemen van een gelijkstroominvoer in het elektrische voertuig als invoersignaal /;taking a direct current input into the electric vehicle as an input signal /; het vergelijken van het ingangssignaal / met zijn referentiewaarde /ref om een verschilwaarde te verkrijgen;comparing the input signal / with its reference value / ref to obtain a difference value; het uitvoeren van een proportionele integraal op de verschilwaarde door een Pl-controller die werkt als een binnenlusstroombesturingscyclus, en tegelijkertijd een virtuele traagheid Gc introduceert door de virtuele traagheidcompensatiefunctie, die parallel verbonden is met de Pl-controller die werkt als de binnenlusstroombesturingscyclus, voor compensatie; en het uitvoeren van een gemoduleerd signaal Pm van een chopper van het elektrische voertuig.performing a proportional integral to the difference value by a P1 controller that acts as an indoor loop current control cycle, and at the same time introduces a virtual inertia G c through the virtual inertia compensation function, which is connected in parallel to the P1 controller that acts as the indoor loop current control cycle, for compensation ; and outputting a modulated signal P m from a chopper of the electric vehicle. 5. De oplading- ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 4, waarbij de constante stroom opladingontladingsbesturingsprocedure een constante stroom opladingsbesturingsprocedure en een constante stroom ontladingsbesturingsprocedure omvat.The charge-discharge control method for a virtual inertia electric vehicle according to claim 4, wherein the constant current charge discharge control procedure comprises a constant current charge control procedure and a constant current discharge control procedure. 6. De oplading- ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 3, waarbij de constante vermogen opladingontladingsbesturingsprocedure stappen omvat van:The charge-discharge control method for a virtual inertia electric vehicle according to claim 3, wherein the constant power charge discharge control procedure comprises steps of: het nemen van een actieve vermogensinvoer in het elektrische voertuig als invoersignaal P; het vergelijken van het ingangssignaal P met zijn referentiewaarde Pref om een verschilwaarde te verkrijgen;taking an active power input to the electric vehicle as the input signal P; comparing the input signal P with its reference value Pref to obtain a difference value; het uitvoeren van een proportionele integraal op de verschilwaarde door een Pl-controller die werkt als een binnenlusstroombesturingscyclus, en tegelijkertijd een virtuele traagheid Gc introduceert door de virtuele traagheidcompensatiefunctie, die parallel verbonden is met de Pl-controller die werkt als de binnenlusstroombesturingscyclus, voor compensatie;performing a proportional integral to the difference value by a P1 controller that acts as an indoor loop current control cycle, and at the same time introduces a virtual inertia G c through the virtual inertia compensation function, which is connected in parallel to the P1 controller that acts as the indoor loop current control cycle, for compensation ; het uitvoeren van een gelijkstroomreferentiewaarde iret van een binnenlusstroom;performing a direct current reference value i t a re binnenlusstroom; het nemen van een gelijkstroominvoer in het elektrische voertuig als invoersignaal /;taking a direct current input into the electric vehicle as an input signal /; het vergelijken van het ingangssignaal / met de gelijkstroomreferentiewaarde /ref van de binnenlusstroom om een verschilwaarde te verkrijgen;comparing the input signal / with the DC reference value / ref of the inner loop current to obtain a difference value; het uitvoeren van een proportionele integraal op de verschilwaarde door een Pl-regelaar die werkt als een binnenlusstroombesturingscyclus; en het uitvoeren van een gemoduleerd signaal Pm van een chopper van het elektrische voertuig.outputting a proportional integral to the difference value by a P1 controller operating as an indoor loop current control cycle; and outputting a modulated signal P m from a chopper of the electric vehicle. 7. De oplading- ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 6, waarbij de constante vermogensoplading-ontlading besturingsprocedure een constante vermogen opladingsbesturingsprocedure en een constante vermogen ontladingsbesturingsprocedure omvat.The charge-discharge control method for a virtual inertia-based electric vehicle according to claim 6, wherein the constant power charge-discharge control procedure comprises a constant power charge control procedure and a constant power discharge control procedure. 8. De oplading- ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 3, waarbij de constante-spanning opladingontladingsbesturingsprocedure stappen omvat van:The charge-discharge control method for a virtual inertia electric vehicle according to claim 3, wherein the constant-voltage charge discharge control procedure comprises steps of: het nemen van een gelijkspanning op het elektrische voertuig als ingangssignaal Udc\ het vergelijken van het ingangssignaal Uac met zijn referentiewaarde Udcref om een verschilwaarde te verkrijgen;taking a direct voltage on the electric vehicle as the input signal Udc, comparing the input signal Uac with its reference value Udcref to obtain a difference value; het uitvoeren van een proportionele integraal op de verschilwaarde door een Pl-controller die werkt als een buitenlus gelijkstroom-spanningsbesturingscyclus, en tegelijkertijd een virtuele traagheid Gc introduceert door de virtuele traagheidcompensatiefunctie, die parallel verbonden is met de Pl-controller die werkt als de buitenlus gelijkstroomspanningsbesturingscyclus, ter compensatie;performing a proportional integral to the difference value by a P1 controller operating as an outer loop DC voltage control cycle, and at the same time introducing a virtual inertia G c through the virtual inertia compensation function, which is connected in parallel to the P1 controller operating as the outer loop DC voltage control cycle, for compensation; het uitvoeren van een gelijkstroomreferentiewaarde /ref van een binnenlusstroom;outputting a DC reference value / ref of an inner loop current; het nemen van een gelijkstroominvoer in het elektrische voertuig als invoersignaal /;taking a direct current input into the electric vehicle as an input signal /; het vergelijken van het ingangssignaal / met de gelijkstroomreferentiewaarde /ref van de binnenlusstroom om een verschilwaarde te verkrijgen;comparing the input signal / with the DC reference value / ref of the inner loop current to obtain a difference value; het uitvoeren van een proportionele integraal op de verschilwaarde door een Pl-regelaar die werkt als een binnenlusstroombesturingscyclus; en het uitvoeren van een gemoduleerd signaal Pm van een chopper van het elektrische voertuig.outputting a proportional integral to the difference value by a P1 controller operating as an indoor loop current control cycle; and outputting a modulated signal P m from a chopper of the electric vehicle. 9. De oplading- ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens conclusie 8, waarbij de constante-spanning opladingontladingsbesturingsprocedure een constante-spanning opladingsbesturingsprocedure en een constante spanning ontladingsbesturingsprocedure omvat.The charge-discharge control method for a virtual inertia electric vehicle according to claim 8, wherein the constant-voltage charge-discharge control procedure comprises a constant-voltage charge control procedure and a constant-voltage discharge control procedure. 10. De oplading- ontladingsbesturingswerkwijze voor een elektrisch voertuig op basis van virtuele traagheid volgens een van de conclusies 1 tot 9, waarbij de compensatiefunctie voor de virtuele traagheid Gc als volgt is:10. The oplading- discharge control method for an electric vehicle on the basis of a virtual inertia according to any one of claims 1 to 9, wherein the compensation function for the virtual inertia G c is as follows: G. =----ï---waarin Kc de dempingsparameter is, Hc de traagheidstijdconstante is en s de Laplaciaanse operator is.G. = ---- ï --- where K c is the damping parameter, H c is the inertia time constant and s is the Laplacian operator.
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