CN110957751A - Bidirectional wireless charging system for high-power electric automobile and power distribution method thereof - Google Patents
Bidirectional wireless charging system for high-power electric automobile and power distribution method thereof Download PDFInfo
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- CN110957751A CN110957751A CN201911212540.5A CN201911212540A CN110957751A CN 110957751 A CN110957751 A CN 110957751A CN 201911212540 A CN201911212540 A CN 201911212540A CN 110957751 A CN110957751 A CN 110957751A
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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
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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
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/30—Circuit arrangements or systems for wireless supply or distribution of electric power using light, e.g. lasers
Abstract
The invention relates to a bidirectional wireless charging system for a high-power electric automobile and a power distribution method thereof. The system comprises a ground end and a vehicle-mounted end, wherein the ground end comprises a PWM (pulse-width modulation) rectification module, a DC/DC (direct current/direct current) module, a high-frequency inversion module, a ground end control module and a ground end resonant coupling module, and the vehicle-mounted end comprises a vehicle-mounted end resonant coupling module, a PWM (pulse-width modulation) module, a battery management module and a vehicle-mounted end control module. Through the arrangement, the bidirectional operation of the wireless charging system of the electric automobile can be realized, and the power distribution can be quickly realized.
Description
Technical Field
The invention relates to the field of wireless charging and control thereof, in particular to a bidirectional wireless charging system for a high-power electric vehicle and a power distribution method thereof.
Background
The existing wireless charging circuit of the electric automobile is a low-power unidirectional charging circuit, and the circuit realizes low-power wireless energy transmission to the electric automobile through a power grid, but the circuit has the following defects that 1, the power level is low, the circuit is only suitable for charging a single electric automobile, and the charging time is long; 2. when the existing electric automobile is charged wirelessly, the electric automobile can only be charged in one direction through a power grid, and the reason that the existing electric automobile wireless charging circuit can only realize single-phase operation and cannot feed back energy to the power grid is solved. 3. The existing wireless charging system for the electric automobile is not designed for power distribution when multiple electric automobiles are charged simultaneously, and the simultaneous efficient charging of multiple electric automobiles cannot be met.
Therefore, in order to improve the wireless charging power level, realize the simultaneous operation of wireless charging of multiple electric vehicles, and realize the bidirectional operation of the wireless charging system, the existing wireless charging system for electric vehicles needs to be improved.
Disclosure of Invention
The invention aims to provide a high-power electric vehicle bidirectional wireless charging system and a power distribution method thereof, which can realize bidirectional operation of the electric vehicle wireless charging system and rapid power distribution.
In order to achieve the purpose, the invention provides the following scheme:
a high-power electric automobile bidirectional wireless charging system comprises a ground end and a vehicle-mounted end, wherein the ground end comprises a PWM (pulse-width modulation) rectification module, a DC/DC (direct current/direct current) module, a high-frequency inversion module, a ground end control module and a ground end resonant coupling module, the PWM rectification module is used for converting a power frequency point of a power grid into direct current, the PWM rectification module is connected with the DC/DC module, the DC/DC module is used for reducing the voltage of the direct current and converting the direct current into adjustable voltage, the high-frequency inversion module is connected with the DC/DC module, and the high-frequency inversion module is used for converting the output direct current adjustable voltage of the DC/DC module into a square wave power supply; the ground control module is respectively connected with the PWM rectification module, the DC/DC module and the high-frequency inversion module, and is used for adjusting the operation direction and the output power of the PWM rectification module, the DC/DC module and the high-frequency inversion module according to charging information; the ground end resonant coupling module is connected with the high-frequency inversion module;
the vehicle-mounted end comprises a vehicle-mounted end resonant coupling module, a PWM module, a battery management module and a vehicle-mounted end control module, and the vehicle-mounted end resonant coupling module is arranged corresponding to the ground end resonant coupling module; the PWM module is connected with the vehicle-mounted end resonant coupling module, the PWM module is used for converting high-frequency electric energy of the vehicle-mounted end resonant coupling module into direct-current electric energy, the PWM module is connected with the battery management module, the battery management module is used for controlling the direct-current electric energy output by the PWM module to charge the power battery pack of the electric automobile and collecting voltage and SOC of the power battery pack of the electric automobile, and the vehicle-mounted end control module is respectively connected with the vehicle-mounted end resonant coupling module, the PWM module and the battery management module.
Optionally, the vehicle-mounted terminal further includes an optical fiber transmitting module in signal connection with the vehicle-mounted terminal control module; the ground terminal comprises an optical fiber receiving module in signal connection with the ground terminal control module, the optical fiber receiving module is used for being matched with the optical fiber transmitting module to receive charging information of the battery management system module, and the charging information comprises battery residual capacity, charging current and PWM pulse width information in the battery management system module.
Optionally, the vehicle-mounted end resonant coupling module is installed below a chassis of the electric vehicle; the ground end resonant coupling module is installed in a ground charging area.
Optionally, magnetic sheets are laid below the ground end resonant coupling module and above the vehicle-mounted end resonant coupling module.
A power distribution method for charging an electric vehicle by a power grid comprises the following steps:
obtaining rated power and load power of a wireless charging system of the high-power bidirectional electric automobile;
judging whether the rated power is larger than the load power or not to obtain a first judgment result;
if the first judgment result shows that the rated power is larger than the load power, acquiring the charging power of the power battery of the electric automobile;
determining a power result according to the charging power and a discrimination factor of whether the electric automobile is in a charging state;
judging whether the electric automobile corresponding to the charging power is in a normal charging state or not according to the power result to obtain a second judgment result;
if the second judgment result shows that the electric automobile corresponding to the charging power is in a normal charging state, acquiring the charging power of the wireless charging system of the high-power bidirectional electric automobile;
obtaining a charging power difference according to the power result and the charging power of the high-power bidirectional electric automobile wireless charging system;
determining initial distribution power according to the charging power difference and a power given correction parameter;
correcting the initial distribution power by adopting a power correction algorithm to obtain corrected distribution power;
obtaining a given current reference value of the corresponding bidirectional DC/DC converter according to the corrected distributed power and the corresponding battery voltage;
sampling the given current reference value to obtain an inductance current value;
obtaining a PWM control signal according to the inductance current value;
determining charging control according to the PWM control signal;
if the second judgment result indicates that the electric vehicle corresponding to the charging power is not in a normal charging state, returning to 'acquiring the charging power of the power battery of the electric vehicle';
and if the first judgment result shows that the rated power is less than or equal to the load power, charging according to the rated power of the battery.
Optionally, before determining the initial distribution power according to the charging power difference and the power given correction parameter, the method further includes:
by the formula
Determining a given power correction parameter;
wherein, ξiSetting a correction variable m for the power of the ith electric vehicleiThe coefficient, SOC, for determining whether the ith electric vehicle is in a charging stateiThe state of charge of the power battery of the ith electric automobile.
Optionally, the modifying the initial allocated power by using a power modification algorithm to obtain a modified allocated power specifically includes:
first, judging whether the initial distribution power is larger than or equal to
Wherein P iseRated charging power for each electric vehicle; if yes, let yi＝mi·P e1,/3, i ═ 1,2,. cndot, N; otherwise, let yi＝xi,i＝1,2,...,N；
The second step is that: giving an initial value p which is 0, and entering the next step if p is less than or equal to 1; otherwise output yi(i ═ 1,2,. N), the correction process ends;
the third step: judgment of yi≤PeAnd/3, if yes, outputting y without correcting the poweri(i ═ 1,2,. N), the correction process ends; otherwise, entering the next step;
the fourth step: if yi＞PeLet variable fi0(i ═ 1,2, …, N); otherwise, let variable fi＝1(i＝1,2,…,N)；
The fifth step: will yiIs given by ziSubstituting the parameters into the following formula to calculate to obtain a corrected power value;
and a sixth step: and returning to the second step when p is p + 1.
A power distribution method for feeding energy back to a power grid by an electric automobile comprises the following steps:
obtaining rated power and load power of a wireless charging system of the high-power bidirectional electric automobile;
judging whether the rated power is larger than the load power or not to obtain a first judgment result;
if the first judgment result shows that the rated power is larger than the load power, acquiring a reference value of the direct-current bus voltage;
obtaining a current set value according to the reference value of the direct current bus voltage;
acquiring the charge state and the compensation coefficient of the power battery of the electric automobile;
determining a current given correction parameter according to the state of charge and the compensation coefficient;
obtaining a control target value of each phase current according to the current set value and the current set correction parameter;
sampling the control target value of each phase current to obtain feedback of each phase current value;
feeding back the phase values of the currents of all the phases, and performing phase shifting to obtain a PWM control signal of a ground control end;
and if the first judgment result shows that the rated power is less than or equal to the load power, charging according to the rated power of the battery.
Optionally, the determining a current given correction parameter according to the state of charge and the compensation coefficient specifically includes:
using a formula according to the state of charge and the compensation coefficient
Determining a current given correction parameter;
wherein A is a current given correction parameter, SOCiThe charge state of the power battery of the ith electric automobile is V, a compensation coefficient is v, and v is min { SOC ═ i1,SOC2,...,SOCi,...,SOCN}。
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention aims to provide a high-power electric vehicle bidirectional wireless charging system and a power distribution method thereof, overcomes the defect that the conventional electric vehicle wireless charging system can only operate in a unidirectional low power mode, and can realize simultaneous charging of a plurality of electric vehicles. And a grid-connected feedback power distribution control strategy based on the power of the state of charge is provided based on the state of charge of each electric automobile, and the power distribution rate is obviously accelerated by changing the current correction parameter. Meanwhile, a charging power distribution control strategy based on the power of the state of charge is provided in combination with the wireless charging requirement of the electric automobile, and power distribution is rapidly realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a schematic diagram of a bidirectional wireless charging system of a high-power electric vehicle according to the present invention;
FIG. 2 is a schematic diagram of a bidirectional wireless charging system for a high-power electric vehicle according to the present invention;
FIG. 3 is a schematic diagram of the multi-way multiple interleaved parallel DC/DC module of the present invention;
FIG. 4 is a flow chart of a power distribution method for charging an electric vehicle by a power grid according to the present invention;
FIG. 5 is a diagram of a state of charge power distribution for an electric vehicle based on power to the power of a power;
FIG. 6 is a flow chart of a power distribution method for feeding back energy to a power grid by an electric vehicle according to the present invention;
fig. 7 is a structural diagram of electric vehicle grid-connected feedback power distribution based on the power of the state of charge.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
The invention aims to provide a high-power electric vehicle bidirectional wireless charging system and a power distribution method thereof, which can realize bidirectional operation of the electric vehicle wireless charging system and rapid power distribution.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic diagram of a component module of a bidirectional wireless charging system of a high-power electric vehicle. Fig. 2 is a schematic diagram of a bidirectional wireless charging system for a high-power electric vehicle according to the invention. As shown in fig. 1, a bidirectional wireless charging system for a high-power electric vehicle comprises a ground end and a vehicle-mounted end, wherein the ground end comprises a PWM rectification module 1, a DC/DC module 2, a high-frequency inversion module 3, a ground end control module 4 and a ground end resonant coupling module 5, the PWM rectification module 1 is used for converting a power frequency point of a power grid into direct current, the PWM rectification module 1 is connected with the DC/DC module 2, the DC/DC module 2 is used for reducing the voltage of the direct current and converting the direct current into adjustable voltage, the high-frequency inversion module 3 is connected with the DC/DC module 2, and the high-frequency inversion module 3 is used for converting the output direct current adjustable voltage of the DC/DC module 2 into a square wave power supply; the ground control module 4 is respectively connected with the PWM rectification module 1, the DC/DC module 2 and the high-frequency inversion module 3, and the ground control module 4 is used for adjusting the running direction and the output power of the PWM rectification module 1, the multi-directional multi-staggered parallel connection DC/DC module 2 and the high-frequency inversion module 3 according to the charging information; the ground end resonant coupling module 5 is connected with the high-frequency inversion module 3;
the vehicle-mounted end comprises a vehicle-mounted end resonant coupling module 6, a PWM module 7, a battery management module 8 and a vehicle-mounted end control module 9, wherein the vehicle-mounted end resonant coupling module 6 is arranged corresponding to the ground end resonant coupling module 5; PWM module 7 is connected with on-vehicle end resonant coupling module 6, PWM module 7 is used for converting the high frequency electric energy of on-vehicle end resonant coupling module into direct current electric energy, PWM module 7 and battery management module 8 are connected, battery management module 8 is used for controlling the direct current electric energy of PWM module 7 output in order to charge for electric automobile power battery group, and gather electric automobile power battery group voltage and state of charge SOC, on-vehicle end control module 9 respectively with on-vehicle end resonant coupling module 6, PWM module 7 and battery management module 8 are connected. The vehicle-mounted end control module 9 is responsible for communicating with the battery management module 8, the vehicle-mounted end resonant coupling module 6 and the PWM module 7, and the purpose of controlling the output power of the vehicle-mounted end is achieved by acquiring the voltage and current information of the modules.
The vehicle-mounted end also comprises an optical fiber transmitting module in signal connection with the vehicle-mounted end control module 9; the ground end comprises an optical fiber receiving module in signal connection with the ground end control module 4, the optical fiber receiving module is used in cooperation with the optical fiber transmitting module to receive charging information of the battery management system module, and the charging information comprises battery residual capacity, charging current and PWM pulse width information in the battery management system module.
The vehicle-mounted end resonant coupling module 6 is arranged below a chassis of the electric automobile; the ground-side resonant coupling module 5 is installed in a ground charging area.
Magnetic sheets are laid below the ground end resonant coupling module 5 and above the vehicle-mounted end resonant coupling module 6.
The PWM rectification module 1 comprises a first gate pole pulse circuit, and the ground end control module 4 sends a PWM pulse signal to a power device gate pole in the first gate pole pulse circuit.
The DC/DC module 2 comprises a second gate pulse circuit; the ground control module 4 sends a PWM pulse signal to a power device gate pole in a second gate pole pulse circuit, and the DC/DC module 2 adopts a multi-way multi-interleaving parallel DC/DC module.
The ground control module 4 comprises an AD sampling unit for collecting input voltage, output voltage, input current and output current of the PWM rectification module 1, and the ground control module 4 comprises an AD sampling unit for collecting input voltage, output voltage, input current and output current of the multi-directional multiple interleaved parallel DC/DC module.
The PWM rectification module 1 adopts a three-phase full-bridge topology, and the topology structure has the advantages of realizing four-quadrant operation and having the functions of converting alternating current of a power frequency power grid into direct current and converting the direct current into alternating current of the power frequency power grid. When a high-power bidirectional electric vehicle wireless charging system charges an electric vehicle, the PWM rectifier module 1 is in a rectification state, and when the high-power bidirectional electric vehicle wireless charging system feeds energy back to a power grid, the PWM rectifier module 1 is in an inversion state. The output voltage regulation of the PWN rectifier module is realized by the ground control module 4. The PWM rectifier module 1 can select proper power devices according to the required power requirement to meet different charging situations.
Fig. 3 is a schematic diagram of the multi-directional multiple interleaved parallel DC/DC module composition of the present invention, which has the advantages of small current ripple factor and large capacity, and when a high-power bidirectional wireless charging system for electric vehicles is used, the multi-directional multiple interleaved parallel DC/DC module is equivalent to a BUCK circuit, and performs a voltage reduction process on the DC power generated by the PWM rectifier module 1 to generate a DC voltage source with adjustable amplitude, and the DC voltage source with adjustable amplitude supplies power to the ground-side high-frequency inverter module 3, and the output power of the high-frequency inverter module 3 can be adjusted by the amplitude of the DC voltage output by the regulator. When a high-power bidirectional wireless charging system of an electric vehicle feeds energy back to a power grid, the multi-directional multi-interleaved parallel DC/DC module is equivalent to a BOOST circuit, and the control of the adjustable direct-current voltage is realized through the ground control module 4.
The ground control module 4 is constructed by adopting an ALTERA hurricane IV FPGA series chip and a DSP28335 chip, the ground controller has strong functions, the ground control module 4 has an input signal capturing function and can demodulate the acquired optical fiber signals, so that the input and output voltage and current information of the PWM rectification module 1 and the multidirectional multiple staggered parallel DC/DC module can be acquired, and the adjustment target value required by the modules can be calculated.
The ground control module 4 has an AD sampling function, and the function can perform AD sampling on input voltage, output voltage, input current and output current of the multi-directional multiple interleaved parallel DC/DC module; the ground control module 4 generates two groups of control signals according to the acquired information and the ground control power target value, and respectively adjusts the PWM rectification module 1 and the multi-directional multiple interleaved parallel DC/DC module, so that the output power of the ground just meets the power requirement of the vehicle-mounted end without causing power waste.
Fig. 4 is a flow chart of a power distribution method for charging an electric vehicle by a power grid according to the present invention. As shown in fig. 4, a power distribution method for charging an electric vehicle by a power grid includes:
step 101: obtaining rated power and load power of a wireless charging system of the high-power bidirectional electric automobile;
step 102: judging whether the rated power is larger than the load power or not to obtain a first judgment result;
step 103: if the first judgment result shows that the rated power is larger than the load power, acquiring the charging power of the power battery of the electric automobile;
step 104: determining a power result according to the charging power and a discrimination factor of whether the electric automobile is in a charging state; wherein the discrimination factor passes miRepresents:
step 105: judging whether the electric automobile corresponding to the charging power is in a normal charging state or not according to the power result to obtain a second judgment result;
step 106: if the second judgment result shows that the electric automobile corresponding to the charging power is in a normal charging state, acquiring the charging power of the wireless charging system of the high-power bidirectional electric automobile;
step 107: obtaining a charging power difference according to the power result and the charging power of the high-power bidirectional electric automobile wireless charging system;
step 108: determining initial distribution power according to the charging power difference and a power given correction parameter;
step 109: correcting the initial distribution power by adopting a power correction algorithm to obtain corrected distribution power;
step 110: obtaining a given current reference value of the corresponding bidirectional DC/DC converter according to the corrected distributed power and the corresponding battery voltage;
step 111: sampling the given current reference value to obtain an inductance current value;
step 112: obtaining a PWM control signal according to the inductance current value;
step 113: determining charging control according to the PWM control signal;
if the second judgment result indicates that the electric vehicle corresponding to the charging power is not in a normal charging state, returning to 'acquiring the charging power of the power battery of the electric vehicle';
step 114: and if the first judgment result shows that the rated power is less than or equal to the load power, charging according to the rated power of the battery.
Before step 108, further comprising:
by the formula
Determining a given power correction parameter;
wherein, ξiSetting a correction variable m for the power of the ith electric vehicleiThe coefficient, SOC, for determining whether the ith electric vehicle is in a charging stateiThe state of charge of the power battery of the ith electric automobile.
The electric vehicle power battery in the charging state belongs to the load end, and is not required to maintain the direct current bus voltage. Therefore, it is necessary to redesign the power distribution control strategy under the charging state according to the characteristics of the charging process of the electric vehicle and the requirement of two-stage charging of the storage battery. The invention provides a charging power distribution control strategy based on the power of the state of charge, and fig. 5 is a structural diagram of the charging power distribution of an electric vehicle based on the power of the state of charge.
The high-power bidirectional electric vehicle wireless charging system is characterized in that n electric vehicles are charged, the charging power of the electric vehicle power battery obtained by calculation in the electric vehicle is multiplied by the judging coefficient of whether the electric vehicle is in the charging state or not after passing through the low-pass filter, and the result obtained by multiplication can judge whether a certain electric vehicle is in the normal charging state or not and the charging power P of the high-power bidirectional electric vehicle wireless charging systemCAnd (4) performing difference making, multiplying the result by the power given correction parameter to obtain initial distribution power, and performing a power correction algorithm on the initial distribution power to obtain corrected distribution power. Corrected distributed power and power battery voltage U in electric automobileb1The given current reference value of the bidirectional DC/DC converter can be obtained by the phase division, the sampled inductance current value is fed back, the error of the inductance current value is subjected to duty ratio signal by a current loop PI controller, and finally the PWM control signal of the converter is obtained by a phase shifting link, so that the charging control of the wireless charging system of the high-power bidirectional electric automobile is realized.
According to the charging power P of the wireless charging system of the high-power bidirectional electric automobileCRated power P of wireless charging system of whole high-power bidirectional electric automobileEAs a result of the comparison, the power distribution control in the charging state can be divided into two modes:
1.PC≥PE
when P is presentC≥PEIn the process, each electric automobile works under the rated power and is charged according to the rated power of the electric automobile, and the power cannot be distributed according to the charge state of a power battery in each electric automobile.
2.PC＜PE
When P is presentC＜PEIn time, the wireless charging system of the high-power bidirectional electric automobile can distribute the charging power of each electric automobile according to the charge state of the power battery of the electric automobile, but the charging power P distributed by some electric automobilesi(i.e., initially allocated power) may exceed its rated power, where PiIs expressed as
In order to enable the charging power distributed by each electric vehicle not to exceed the rated power of the electric vehicle on the premise that the total charging power of the wireless charging system is not changed, step 109 provides a power correction algorithm, which specifically comprises:
first, judging whether the initial distribution power is larger than or equal to
Wherein P iseRated charging power for each electric vehicle; if yes, let yi＝mi·P e1,/3, i ═ 1,2,. cndot, N; otherwise, let yi＝xi,i＝1,2,...,N；
The second step is that: giving an initial value p which is 0, and entering the next step if p is less than or equal to 1; otherwise output yi(i ═ 1,2,. N), the correction process ends;
the third step: judgment of yi≤PeAnd/3, if yes, outputting y without correcting the poweri(i ═ 1,2,. N), the correction process ends; otherwise, entering the next step;
the fourth step: if yi＞PeLet variable fi0(i ═ 1,2, …, N); otherwise, let variable fi＝1(i＝1,2,…,N)；
The fifth step: will yiIs given by ziSubstituting the parameters into the following formula to calculate to obtain a corrected power value;
and a sixth step: and returning to the second step when p is p + 1.
And the corrected power value is used as an input variable of the converter control system, so that the charging control of each electric automobile is realized. When the state of charge of the power battery of the electric automobile reaches a limit value, the electric automobile enters a charging mode, the electric automobile exits a power distribution mode at the moment, and the rest modules continue to operate in the power distribution mode.
In order to enable the wireless charging system of the high-power bidirectional electric automobile to work in a normal running state during charging, the method limits some parameters of power distribution control in the charging state.
1. Limitation of power battery SOC of each rechargeable electric vehicle: when SOC is reachedi<0.9, the electric automobile works in a charging mode; when SOC is reachediAnd when the power distribution mode is larger than or equal to 0.9, the electric automobile exits the power distribution working mode.
2. Equalizing rate: the value of the power n is related to the rate at which the output power of each electric automobile finally tends to be consistent. The larger n, the faster the rate tends to be uniform, and the smaller n, the slower the rate tends to be uniform. The selection of n is required depending on the power distribution rate requirement of the energy storage system.
Taking the fact that i electric vehicles are connected in parallel in the system as an example, the influence of power correction on a control system is not considered temporarily, and the relation of charging power of i modules is deduced: current control target value of converter 1:
current control target value of converter i:
according to miThe expression of (1) is:
m1＝m2＝...＝mi＝1
if the SOC of the i modules is in the normal working range, the terminal voltages of the power batteries in the i electric vehicles are approximately equal, so that the terminal voltages can be approximately considered as
ub1＝ub2＝...＝ubi
Charging power of power battery in electric automobile 1
P1＝3i1ref·ub1
Charging power of storage battery in energy storage module i
Pi＝3iiref·ubi
P1And PiThe relationship of (A) is as follows:
according to the formula, when the high-power bidirectional wireless electric automobile charging system works in a charging state, the charging power of the electric automobile is in an inverse proportion relation with the n-th power of the charge state of the power battery, so that the electric automobile with a large charge state is small in charging power, the electric automobile with a small charge state is large in charging power, power distribution is achieved at a high speed, and the charging power of each energy storage module tends to be equal.
Fig. 6 is a flow chart of a power distribution method for feeding back energy to a power grid by an electric vehicle according to the present invention. As shown in fig. 6, a power distribution method for feeding back energy to a power grid by an electric vehicle includes:
step 201: obtaining rated power and load power of a wireless charging system of the high-power bidirectional electric automobile;
step 202: judging whether the rated power is larger than the load power or not to obtain a first judgment result;
step 203: if the first judgment result shows that the rated power is larger than the load power, acquiring a reference value of the direct-current bus voltage;
step 204: obtaining a current set value according to the reference value of the direct current bus voltage;
step 205: acquiring the charge state and the compensation coefficient of the power battery of the electric automobile;
step 206: determining a current given correction parameter according to the state of charge and the compensation coefficient, wherein the method specifically comprises the following steps:
using a formula according to the state of charge and the compensation coefficient
DeterminingSetting a correction parameter by current; wherein A is a current given correction parameter, SOCiThe charge state of the power battery of the ith electric automobile is V, a compensation coefficient is v, and v is min { SOC ═ i1,SOC2,...,SOCi,...,SOCN}。
Step 207: obtaining a control target value of each phase current according to the current set value and the current set correction parameter;
step 208: sampling the control target value of each phase current to obtain feedback of each phase current value;
step 209: feeding back the phase values of the currents of all the phases, and performing phase shifting to obtain a PWM control signal of a ground control end;
step 210: and if the first judgment result shows that the rated power is less than or equal to the load power, charging according to the rated power of the battery.
When the wireless charging system of the high-power bidirectional electric automobile is in an energy feedback state to a power grid, feedback power needs to be reasonably distributed according to the charge states of power batteries in all the electric automobiles, so that the charge states of the power batteries in all the electric automobiles tend to be consistent. In the process of feeding back energy, the application provides a power distribution method for feeding back energy to a power grid by an electric automobile, and the distribution method is a discharge power distribution method based on the power of a state of charge.
In the wireless charging system of the high-power bidirectional electric automobile, each electric automobile has its own rated feedback power, so that the rated power of each electric automobile needs to be considered in the power distribution process of the feedback state. According to load power PLRated power P of wireless charging system of high-power bidirectional electric automobileEAccording to the comparison result, the power distribution control under the feedback state to the power grid can be divided into two modes:
1.PL≥PE
when P is presentL≥PEIn the meantime, the wireless charging system of the high-power bidirectional electric automobile cannot completely meet the load requirement, all the electric automobiles work under the rated power at the moment, and all the electric automobiles work according to the rated power of the electric automobilesEnergy is fed back to the power grid, and power cannot be distributed according to the charge states of the power batteries of the electric automobiles.
2.PL＜PE
When P is presentL＜PEIn time, the wireless charging system of the high-power bidirectional electric automobile can meet the load requirement, but feedback power P distributed by a certain electric automobileiMay exceed its own rated power, where PiThe expression of (a) is:
in order to prevent the feedback power distributed by a certain electric automobile from exceeding the rated power of the electric automobile, the application is in the specification iLrefAfter multiplying the current given correction parameter, adding an amplitude limiting link, wherein the amplitude limiting value is as follows:
Iimin＝0，i＝1,2,...,N
Iiminthe minimum amplitude limit value of the ith electric automobile; i isimaxThe maximum amplitude of the ith electric automobile is obtained; peiThe minimum amplitude limit value of the ith electric automobile; u shapebiIs the terminal voltage of the power battery in the ith electric automobile.
By setting the amplitude limit value, the power distribution of the system to the power grid under the state of feeding back the power can be realized on the premise that the total feedback power of the high-power bidirectional electric vehicle wireless charging system is unchanged and the power distributed by each electric vehicle does not exceed the rated power of the system.
In order to enable the wireless charging system of the high-power bidirectional electric automobile to work in a normal running state during discharging, the method limits some parameters for power distribution control in a state of feeding back energy to a power grid:
(1) limiting the maximum feedback power of each electric automobile: as can be seen from the two working modes of the power distribution control, the feedback power of each electric automobile must not exceed the rated feedback power, i.e. the feedback power of each electric automobile must not exceed the rated feedback power of each electric automobile
Pdi＝Ped，i＝1,2,...,N
Wherein, PdiThe discharge power distributed to the ith electric vehicle; pedAnd distributing rated discharge power for the electric automobile blocks.
(2) Limitation of the SOC of the electric vehicle in each electric vehicle: each electric automobile power battery in the high-power bidirectional electric automobile wireless charging system has a safe SOC working range, and the power battery can stably work only if the SOC is in the safe range, so that the service life of the power battery is shortened and the high-power bidirectional electric automobile wireless charging system cannot stably work if the SOC exceeds the safe range. When the wireless charging system of the high-power bidirectional electric automobile works in a power grid feedback state, if the SOC of a power battery module exceeds a safety range, the electric automobile is cut off from the wireless charging system of the high-power bidirectional electric automobile, and other modules continue to perform power distribution control. When the wireless charging system of the high-power bidirectional electric automobile works in a feedback state to a power grid, the SOC safety range of the power battery is as follows:
SOCi≥0.15，i＝1,2,...,N
SOCithe state of charge of the power battery of the ith electric automobile.
(3) Limitation of equalization rate: the value of the power n is related to the rate at which the output power of each electric automobile finally tends to be consistent. The larger n, the faster the rate tends to be uniform, and the smaller n, the slower the rate tends to be uniform. The selection of n is required to be determined according to the requirement of the distribution rate of the wireless charging system of the high-power bidirectional electric automobile.
The direct current side of the high-power bidirectional electric automobile wireless charging system is connected with N electric automobiles in parallel. Given DC bus voltage reference value udcrefSampling direct current bus voltage feedback through a ground end control module, and obtaining an initial current given value i through an error of the direct current bus voltage feedback through a voltage loop PI controllerLref. SOC (state of charge) of power battery of ith electric vehicleiThe nth power of the current is divided by the nth power of the coefficient v to obtain a current given correction parameter,where v is the DC bus voltage compensation coefficient, whose value is min { SOC1,SOC2,...,SOCi,...,SOCNAnd the function is to maintain the voltage of the direct current bus stable and prevent the direct current bus from falling. i.e. iLrefThe control target value of each phase current multiplied by the current given correction parameter is added with an amplitude limiting link in order to ensure that the feedback power of each electric automobile does not exceed the rated power limit. The control target value of each phase output current is fed back through each phase current value obtained by sampling, each phase duty ratio signal is obtained after the control target value passes through a current loop PI controller, the PWM control signal of each ground control end is obtained through a phase shifting link, and finally the reasonable distribution of the load power among each electric automobile is realized, and fig. 7 is a grid-connected feedback power distribution structure diagram of the electric automobile based on the power of the state of charge.
The application N electric automobile jointly to electric wire netting repay energy, do not consider power amplitude limiting to control system's influence temporarily, deduce to electric wire netting under the repayment state N electric automobile's of counter current output's relation:
current control target value of the electric vehicle 1:
wherein k isdp1，kdi1And the parameters of a voltage loop PI controller in the control system of the electric automobile 1.
Current control target value of electric vehicle N:
wherein k isdpN，kdiNAnd the parameters of a voltage loop PI controller in the N control system of the electric automobile are obtained.
Output power of power battery in electric vehicle 1:
P1＝3iiref·ub1
output power of storage battery in electric automobile N
PN＝3iNref·ubN
The simultaneous above formula can yield:
from the above formula, when the wireless charging system of the high-power bidirectional electric vehicle works to feed back energy to the power grid, the power generated by the power battery of each electric vehicle is in direct proportion to the N power of the state of charge, the electric vehicle with a large state of charge generates larger power, the electric vehicle with a small state of charge generates smaller power, and when the states of charge of the power batteries in the N electric vehicles tend to be consistent, the electric vehicles are discharged with the same power.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (9)
1. The bidirectional wireless charging system of the high-power electric automobile is characterized by comprising a ground end and a vehicle-mounted end, wherein the ground end comprises a PWM (pulse-width modulation) rectifying module, a DC/DC (direct current/direct current) module, a high-frequency inverting module, a ground end control module and a ground end resonant coupling module, the PWM rectifying module is used for converting a power frequency point of a power grid into direct current, the PWM rectifying module is connected with the DC/DC module, the DC/DC module is used for reducing the voltage of the direct current and converting the direct current into adjustable voltage, the high-frequency inverting module is connected with the DC/DC module, and the high-frequency inverting module is used for converting the output direct current adjustable voltage of the DC/DC module into a square wave power; the ground control module is respectively connected with the PWM rectification module, the DC/DC module and the high-frequency inversion module, and is used for adjusting the operation direction and the output power of the PWM rectification module, the DC/DC module and the high-frequency inversion module according to charging information; the ground end resonant coupling module is connected with the high-frequency inversion module;
the vehicle-mounted end comprises a vehicle-mounted end resonant coupling module, a PWM module, a battery management module and a vehicle-mounted end control module, and the vehicle-mounted end resonant coupling module is arranged corresponding to the ground end resonant coupling module; the PWM module is connected with the vehicle-mounted end resonant coupling module, the PWM module is used for converting high-frequency electric energy of the vehicle-mounted end resonant coupling module into direct-current electric energy, the PWM module is connected with the battery management module, the battery management module is used for controlling the direct-current electric energy output by the PWM module to charge the power battery pack of the electric automobile and collecting voltage and SOC of the power battery pack of the electric automobile, and the vehicle-mounted end control module is respectively connected with the vehicle-mounted end resonant coupling module, the PWM module and the battery management module.
2. The bidirectional wireless charging system for the high-power electric automobile according to claim 1, wherein the vehicle-mounted terminal further comprises an optical fiber transmitting module in signal connection with a vehicle-mounted terminal control module; the ground terminal comprises an optical fiber receiving module in signal connection with the ground terminal control module, the optical fiber receiving module is used for being matched with the optical fiber transmitting module to receive charging information of the battery management system module, and the charging information comprises battery residual capacity, charging current and PWM pulse width information in the battery management system module.
3. The bidirectional wireless charging system for the high-power electric automobile according to claim 1, wherein the vehicle-mounted end resonant coupling module is installed below a chassis of the electric automobile; the ground end resonant coupling module is installed in a ground charging area.
4. The bidirectional wireless charging system for the high-power electric vehicle as claimed in claim 1, wherein magnetic sheets are laid below the ground-end resonant coupling module and above the vehicle-mounted-end resonant coupling module.
5. A power distribution method for charging an electric vehicle from a power grid is applied to the high-power electric vehicle bidirectional wireless charging system of any one of claims 1 to 4, and the method comprises the following steps:
obtaining rated power and load power of a wireless charging system of the high-power bidirectional electric automobile;
judging whether the rated power is larger than the load power or not to obtain a first judgment result;
if the first judgment result shows that the rated power is larger than the load power, acquiring the charging power of the power battery of the electric automobile;
determining a power result according to the charging power and a discrimination factor of whether the electric automobile is in a charging state;
judging whether the electric automobile corresponding to the charging power is in a normal charging state or not according to the power result to obtain a second judgment result;
if the second judgment result shows that the electric automobile corresponding to the charging power is in a normal charging state, acquiring the charging power of the wireless charging system of the high-power bidirectional electric automobile;
obtaining a charging power difference according to the power result and the charging power of the high-power bidirectional electric automobile wireless charging system;
determining initial distribution power according to the charging power difference and a power given correction parameter;
correcting the initial distribution power by adopting a power correction algorithm to obtain corrected distribution power;
obtaining a given current reference value of the corresponding bidirectional DC/DC converter according to the corrected distributed power and the corresponding battery voltage;
sampling the given current reference value to obtain an inductance current value;
obtaining a PWM control signal according to the inductance current value;
determining charging control according to the PWM control signal;
if the second judgment result indicates that the electric vehicle corresponding to the charging power is not in a normal charging state, returning to 'acquiring the charging power of the power battery of the electric vehicle';
and if the first judgment result shows that the rated power is less than or equal to the load power, charging according to the rated power of the battery.
6. The method for distributing power to charge electric vehicles through power grid according to claim 1, wherein before determining the initial distribution power according to the charging power difference and the given correction parameter, the method further comprises:
by the formula
Determining a given power correction parameter;
wherein, ξiSetting a correction variable m for the power of the ith electric vehicleiThe coefficient, SOC, for determining whether the ith electric vehicle is in a charging stateiThe state of charge of the power battery of the ith electric automobile.
7. The power distribution method for charging an electric vehicle by using a power grid according to claim 1, wherein the step of correcting the initial distributed power by using a power correction algorithm to obtain a corrected distributed power specifically comprises:
first, judging whether the initial distribution power is larger than or equal to
Wherein P iseRated charging power for each electric vehicle; if yes, let yi＝mi·Pe1,/3, i ═ 1,2,. cndot, N; otherwise, let yi＝xi,i＝1,2,...,N；
The second step is that: to giveSetting the initial value p as 0, and entering the next step if p is less than or equal to 1; otherwise output yi(i ═ 1,2,. N), the correction process ends;
the third step: judgment of yi≤PeAnd/3, if yes, outputting y without correcting the poweri(i ═ 1,2,. N), the correction process ends; otherwise, entering the next step;
the fourth step: if yi＞PeLet variable fi0(i ═ 1,2, …, N); otherwise, let variable fi＝1(i＝1,2,…,N)；
The fifth step: will yiIs given by ziSubstituting the parameters into the following formula to calculate to obtain a corrected power value;
and a sixth step: and returning to the second step when p is p + 1.
8. A power distribution method for feeding energy back to a power grid by an electric automobile is characterized by comprising the following steps:
obtaining rated power and load power of a wireless charging system of the high-power bidirectional electric automobile;
judging whether the rated power is larger than the load power or not to obtain a first judgment result;
if the first judgment result shows that the rated power is larger than the load power, acquiring a reference value of the direct-current bus voltage;
obtaining a current set value according to the reference value of the direct current bus voltage;
acquiring the charge state and the compensation coefficient of the power battery of the electric automobile;
determining a current given correction parameter according to the state of charge and the compensation coefficient;
obtaining a control target value of each phase current according to the current set value and the current set correction parameter;
sampling the control target value of each phase current to obtain feedback of each phase current value;
feeding back the phase values of the currents of all the phases, and performing phase shifting to obtain a PWM control signal of a ground control end;
and if the first judgment result shows that the rated power is less than or equal to the load power, charging according to the rated power of the battery.
9. The method of claim 8, wherein the determining a current setting correction parameter according to the state of charge and the compensation factor comprises:
using a formula according to the state of charge and the compensation coefficient
Determining a current given correction parameter;
wherein A is a current given correction parameter, SOCiThe charge state of the power battery of the ith electric automobile is V, a compensation coefficient is v, and v is min { SOC ═ i1,SOC2,...,SOCi,...,SOCN}。
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