CN111668865B - Hierarchical control method and related device for echelon utilization energy storage system - Google Patents
Hierarchical control method and related device for echelon utilization energy storage system Download PDFInfo
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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
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0063—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with circuits adapted for supplying loads from the battery
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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
- 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
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Abstract
The application discloses a hierarchical control method and a related device for a echelon utilization energy storage system, wherein the method comprises the following steps: acquiring the instruction power of a power grid, battery parameters of each battery power module and first access current of a DC-DC converter accessing to the power grid, wherein the battery parameters comprise: SOH parameters and SOC parameters; calculating a second access current corresponding to each battery power module according to the instruction power and each battery parameter; based on the first access current and each second access current, the duty ratio of a DC-DC converter in each battery power module is adjusted according to a droop control strategy and a current closed-loop control strategy so as to realize the control of each battery power module, and the technical problem that the existing energy storage system formed by retired power batteries is difficult to realize in a power grid is solved.
Description
Technical Field
The present application relates to the field of energy storage application technologies, and in particular, to a hierarchical control method and related apparatus for a echelon utilization energy storage system.
Background
With the rapid development of the new energy automobile industry, the new energy automobile has an important meaning for relieving energy and environmental pressure, and meanwhile, a series of problems caused by a power battery in the new energy automobile also attract extensive attention, wherein the disposal problem after the power battery is retired is particularly obvious. The recycling of the retired power battery is a relatively healthy and environment-friendly disposal mode. The retired power battery can be used in an energy storage system after re-detection, analysis management and grouping pairing, is particularly suitable for a small-scale dispersed energy storage system, can solve the problem of power fluctuation caused by intermittent energy power generation, and achieves the purpose of providing stable output power for a power grid.
However, due to the fact that the retired power batteries are different in retired state, namely inconsistency exists among the retired power batteries, the short plate effect of the battery pack in the energy storage system is obvious, and the performance of the battery pack is poor. Therefore, the use of energy storage systems consisting of retired power cells in the grid has also been difficult to achieve.
Disclosure of Invention
The application provides a hierarchical control method and a related device for a echelon utilization energy storage system, and the method can be used for the energy storage system formed by retired power batteries in a power grid.
In view of the above, a first aspect of the present application provides a hierarchical control method for a echelon utilization energy storage system, where the echelon utilization energy storage system includes: a retired power battery system and a plurality of DC-DC converters; the low-voltage side of the DC-DC converter is connected to a power grid, and the high-voltage side of the DC-DC converter is connected with the decommissioned power battery system; the decommissioning power battery system comprises: a plurality of battery modules formed by retired power batteries; the single DC-DC converter is connected with the single battery module to form a single battery power module;
the hierarchical control method comprises the following steps:
acquiring the instruction power of the power grid, the battery parameters of each battery power module and the first access current of the DC-DC converter accessing the power grid, wherein the battery parameters comprise: SOH parameters and SOC parameters;
calculating second access current corresponding to each battery power module according to the instruction power and each battery parameter;
and adjusting the duty ratio of the DC-DC converter in each battery power module according to a droop control strategy and a current closed-loop control strategy on the basis of the first access current and each second access current so as to realize the control of each battery power module.
Optionally, the obtaining the battery parameters of each battery power module specifically includes:
establishing a state space model corresponding to each battery power module by using a battery SOC parameter and a battery internal resistance r in each battery power module as state variables, terminal voltage as an observed quantity and current as an input quantity through an ampere-hour integration method, wherein the state space model is;
Vo(k)=E+I(k)r(k)+K+ε
in the formula, QmaxFor the rated capacity of the battery, SOC (k +1) is the state of charge of the battery power module at the moment k +1, SOC (k) is the state of charge of the battery power module at the moment k, I (k) is the actual current of the battery in the battery power module at the moment k, delta T is discrete time, omega1For process noise, r (k +1) is the internal battery resistance of the battery power module at the time k +1, and r (k) is the internal battery resistance of the battery power module at the time k, ω2Is process noise, Vo(k) The battery terminal voltage at time k, E the battery open circuit voltage,k is the correction error of the battery model, and epsilon is the measurement noise;
let x be [ SOC, r]TSolving the state space model through an unscented Kalman filtering algorithm to obtain battery SOC parameters and battery internal resistance r corresponding to each battery power module;
calculating the SOH parameter corresponding to each battery power module according to the internal battery resistance r in each battery power module based on a first formula, wherein the first formula is as follows:
in the formula, rnewIs the internal resistance r of the battery in the battery power module when the battery leaves the factoryEOLIs the internal resistance at the end of the battery life in the battery power module.
Optionally, calculating, according to the instruction power and each of the battery parameters, a second access current corresponding to each of the battery power modules specifically includes:
based on a power calculation formula, acquiring operating power corresponding to each battery power module according to each battery parameter and the instruction power;
and calculating second access current corresponding to each battery power module according to the running power and the voltage of the battery power module.
Optionally, the power calculation formula is:
n is the number of battery power modules, Pi *For operating power, SOH, of the battery power module iiSOH parameter, SOC, for a battery power module iiIs the SOC parameter, P, of the battery power module iegIs the commanded power.
The present application provides in a second aspect a hierarchical control apparatus for a echelon utilization energy storage system, the echelon utilization energy storage system including: a retired power battery system and a plurality of DC-DC converters; the low-voltage side of the DC-DC converter is connected to a power grid, and the high-voltage side of the DC-DC converter is connected with the decommissioned power battery system; the decommissioning power battery system comprises: a plurality of battery modules formed by retired power batteries; the single DC-DC converter is connected with the single battery module to form a single battery power module;
the hierarchical control apparatus includes:
an obtaining unit, configured to obtain an instruction power of the power grid, a battery parameter of each battery power module, and a first access current of the DC-DC converter accessing the power grid, where the battery parameter includes: SOH parameters and SOC parameters;
the calculating unit is used for calculating second access current corresponding to each battery power module according to the instruction power and each battery parameter;
and the adjusting unit is used for adjusting the duty ratio of the DC-DC converter in each battery power module according to a droop control strategy and a current closed-loop control strategy on the basis of the first access current and each second access current so as to realize control over each battery power module.
Optionally, the obtaining the battery parameters of each battery power module specifically includes:
establishing a state space model corresponding to each battery power module by using an SOC parameter of a battery in each battery power module and an internal resistance r of the battery as state variables, terminal voltage as an observed quantity and current as an input quantity through an ampere-hour integration method, wherein the state space model is;
Vo(k)=E+I(k)r(k)+K+ε
in the formula, QmaxFor the rated capacity of the battery, SOC (k +1) is the state of charge of the battery power module at the moment k +1, SOC (k) is the state of charge of the battery power module at the moment k, I (k) is the actual current of the battery in the battery power module at the moment k, delta T is discrete time, omega1For process noise, r (k +1) is the internal battery resistance of the battery power module at the time k +1, and r (k) is the internal battery resistance of the battery power module at the time k, ω2Is process noise, Vo(k) The voltage of the battery terminal at the moment K, E is the open-circuit voltage of the battery, K is the correction error of the battery model, and epsilon is the measurement noise;
let x be [ SOC, r]TSolving the state space model through an unscented Kalman filtering algorithm to obtain battery SOC parameters and battery internal resistance r corresponding to each battery power module;
calculating the SOH parameter corresponding to each battery power module according to the internal resistance r corresponding to each battery power module based on a first formula, wherein the first formula is as follows:
in the formula, rnewThe internal resistance r of the battery in the battery power module when the battery leaves factoryEOLIs the internal resistance at the end of the battery life in the battery power module.
Optionally, the computing unit specifically includes:
the obtaining subunit is configured to obtain, based on a power calculation formula, operating power corresponding to each battery power module according to each battery parameter and the instruction power;
and the calculating subunit is used for calculating second access current corresponding to each battery power module according to the operating power and the voltage of the battery power module.
Optionally, the power calculation formula is:
n is the number of battery power modules, Pi *For operating power, SOH, of the battery power module iiSOH parameter, SOC, for a battery power module iiIs the SOC parameter, P, of the battery power module iegIs the commanded power.
A third aspect of the present application provides a hierarchical control apparatus for a echelon utilization energy storage system, the apparatus comprising a processor and a memory; the memory is used for storing program codes and transmitting the program codes to the processor; the processor is configured to execute the hierarchical control method for echelon utilization of the energy storage system according to the instructions in the program code.
A fourth aspect of the present application provides a storage medium for storing program code for executing the hierarchical control method of a echelon utilization energy storage system according to the first aspect.
According to the technical scheme, the embodiment of the application has the following advantages:
the application provides a hierarchical control method for a echelon utilization energy storage system, which is used for acquiring instruction power of a power grid, battery parameters of each battery power module and first access current of a DC-DC converter accessed to the power grid, wherein the battery parameters comprise: SOH parameters and SOC parameters; calculating a second access current corresponding to each battery power module according to the instruction power and each battery parameter; and adjusting the duty ratio of the DC-DC converter in each battery power module according to a droop control strategy and a current closed-loop control strategy based on the first access current and each second access current so as to realize the control of each battery power module.
In the application, after the instruction power of the power grid, the battery parameters of each battery power module and the first access current of the DC-DC converter accessing the power grid are obtained, the second access current of each battery power module is calculated according to the instruction power of the power grid and the battery parameters, which is equivalent to performing power distribution on the instruction power of the power grid, so that the requirement on the consistency of the battery power modules is reduced, the batteries in the battery power modules simultaneously reach a charging cut-off state or a discharging cut-off state, the energy utilization rate is improved, then based on the first access current and the second access current, the duty ratio of the DC-DC converter in each battery power module is adjusted according to a droop control strategy and a current closed-loop control strategy so as to realize the control on each battery power module, and the charging and discharging currents of each battery power module are independently controlled according to the droop control strategy and the current closed-loop control strategy, the stable control of the whole retired power battery system is realized through a power distribution strategy, a droop control strategy and a current closed-loop control strategy, so that the technical problem that an energy storage system formed by retired power batteries is difficult to realize in the conventional power grid is solved.
Drawings
Fig. 1 is a schematic flowchart of a first embodiment of a hierarchical control method for echelon utilization of an energy storage system according to an embodiment of the present application;
FIG. 2 is a control block diagram of an echelon energy storage system in an embodiment of the present application;
FIG. 3 is a schematic overall structure diagram of an echelon energy storage topology in an embodiment of the present application;
FIG. 4 is a control block diagram of a single DC-DC converter in an embodiment of the present application;
FIG. 5 is a flowchart illustrating a second embodiment of a hierarchical control method for echelon utilization of an energy storage system according to an embodiment of the present disclosure;
FIG. 6 is a control diagram of a current command in an embodiment of the present application;
FIG. 7 is a waveform of charge/discharge transition in the embodiment of the present application;
FIG. 8 is a simulation of inter-module power distribution in an embodiment of the present application;
FIG. 9 is a bus voltage spike disturbance simulation waveform in an embodiment of the present application;
FIG. 10 is a waveform of bus voltage dip disturbance simulation in an embodiment of the present application;
fig. 11 is a simulation of instantaneous switching-out when a power module of battery No. 15 in the converter in the embodiment of the present application fails;
fig. 12 is a schematic structural diagram of a hierarchical control device for echelon utilization of an energy storage system according to an embodiment of the present application.
Detailed Description
The embodiment of the application provides a hierarchical control method and a related device for a echelon utilization energy storage system, and solves the technical problem that the existing energy storage system formed by retired power batteries is difficult to realize in a power grid.
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, 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 application.
Referring to fig. 1, a schematic flow chart of a first embodiment of a hierarchical control method for echelon utilization of an energy storage system in an embodiment of the present application includes:
The energy storage system in this embodiment includes: a retired power battery system and a plurality of DC-DC converters; the low-voltage side of the DC-DC converter is connected to a power grid, and the high-voltage side of the DC-DC converter is connected with a decommissioning power battery system; retired power battery system includes: a plurality of battery modules formed by retired power batteries; and the single DC-DC converter is connected with the single battery module to form a single battery power module.
It will be appreciated that the low side of the DC-DC converter may be connected directly to the DC grid or to the AC grid via a bi-directional DC-AC converter.
The plurality of DC-DC converters are connected in series to the power grid, so that the first access currents corresponding to the plurality of DC-DC converters are the same value, namely the current of the series inductor connected in series with the DC-DC converters.
The SOH parameter, i.e., the degree of battery aging, represents the state of health of the battery. The SOC parameter refers to the state of charge, also called the remaining charge.
And 102, calculating a second access current corresponding to each battery power module according to the instruction power and each battery parameter.
According to the instruction power of the power grid and the battery parameters representing the performance of each battery power module, the second access current of each battery power module accessed to the DC-DC converter based on the instruction power can be obtained, and the second access current is also the instruction current corresponding to each battery power module.
And 103, adjusting the duty ratio of the DC-DC converter in each battery power module according to a droop control strategy and a current closed-loop control strategy based on the first access current and each second access current so as to realize the control of each battery power module.
In this embodiment, the charging and discharging currents of the battery power modules are independently controlled according to the droop control strategy and the current closed-loop control strategy, and the control chart is shown in fig. 2, where in fig. 2, psgkPower allocated to the kth energy storage string, iHrFor the current command before secondary regulation, iHCurrent command for energy storage string, iLSInductor current for energy storage string, G1And(s) is a function corresponding to the PI link during secondary regulation, and PWM is a pulse width modulation link. As shown in the dashed box of fig. 3, the structure of the energy storage group string in this embodiment is shown.
Fig. 3 shows a control block diagram of a single DC-DC converter, which is composed of a droop link and a current control link. In FIG. 4, H(s) is the feedback loop transfer function, Gci(s) is a function corresponding to the PI link, a left-side dotted line frame is a droop control link, and the expression is as follows:
i=iHj-tejvoj=iHj-tejdjvgj;
wherein i is an intermediate variable, iHjFor a second supply current of the jth battery power module, tejIs the proportional coefficient, v, of the jth battery power module after per unitojIs the output voltage of the jth battery power module, djIs the duty cycle, v, of the jth battery power modulegjIs the input voltage of the jth battery power module, i.e., the battery power module battery side voltage.
The right dashed box is the circuit model, the corresponding circuit model function GL(s) is expressed as:
in the formula, voFor the total output voltage, s is the representation frequency domain and L is the inductance.
To establish overall system control, our small signal model assumes the following conditions:
firstly, the voltage change of the battery is ignored;
the voltages of all the batteries are consistent;
and thirdly, the feedback path delay is ignored.
The variable instructions of the whole control are as follows: second access current variation Δ iHjTotal output voltage variation Δ voInductance current variation (first access current variation) Δ iL。
Under this condition, an expression of the amount of current change can be obtained:
in the formula,. DELTA.djIs the amount of change in duty cycle.
When Δ vojWhen the system open-loop function g(s) is 0:
at this time, the system closed loop transfer function is:
when Δ iHjThe system closed loop transfer function is 0:
this makes it possible to obtain:
Δvo=djnvgj-vo。
the inductive current is also the first access current, the relation between the output voltage and the duty ratio is known, when the input current instruction changes or the output voltage changes, the output current of each battery power module is different, but because the output sides of the battery power modules are connected in series, in order to ensure the consistency of the output current, the duty ratio is adjusted by controlling the two links of droop control and power-on control, and then each battery power module outputs the same current, so that the stability is ensured.
In the embodiment, after the instruction power of the power grid, the battery parameters of each battery power module and the first access current of the DC-DC converter accessing the power grid are obtained, the second access current of each battery power module is calculated according to the instruction power of the power grid and the battery parameters, which is equivalent to performing power distribution on the instruction power of the power grid, so that the requirement on the consistency of the battery power modules is reduced, the batteries in the battery power modules simultaneously reach a charging cut-off state or a discharging cut-off state, so that the energy utilization rate is improved, then based on the first access current and the second access current, the duty ratio of the DC-DC converter in each battery power module is adjusted according to a droop control strategy and a current closed-loop control strategy so as to realize the control on each battery power module, and the charging and discharging currents of each battery power module are independently controlled according to the droop control strategy and the current closed-loop control strategy, the stable control of the whole retired power battery system is realized through a power distribution strategy, a droop control strategy and a current closed-loop control strategy, so that the technical problem that an energy storage system formed by retired power batteries is difficult to realize in the conventional power grid is solved.
The above is a first embodiment of a hierarchical control method for a echelon utilization energy storage system provided by the embodiment of the present application, and the following is a second embodiment of the hierarchical control method for the echelon utilization energy storage system provided by the embodiment of the present application.
Referring to fig. 5, a schematic flow chart of a second embodiment of a hierarchical control method for echelon utilization of an energy storage system in an embodiment of the present application includes:
and step 501, obtaining the instruction power of the power grid.
The state space model is;
Vo(k)=E+I(k)r(k)+K+ε
in the formula, QmaxFor the rated capacity of the battery, SOC (k +1) is the battery state of charge of the battery power module at the moment k +1, SOC (k) is the battery state of charge of the battery power module at the moment k, I (k) is the actual current of the battery in the battery power module at the moment k, Delta T is the discrete time, i.e. the time difference between the moment k +1 and the moment k, omega1For process noise, r (k +1) is the internal battery resistance of the battery power module at the time k + 1, and r (k) is the internal battery resistance of the battery power module at the time k, ω2Is process noise, Vo(k) The battery terminal voltage at time K, E the battery open-circuit voltage, K the correction error of the battery model, and E the measurement noise.
And 505, based on the first formula, calculating the SOH parameter corresponding to each battery power module according to the internal resistance r of each battery power module.
The first formula in this embodiment is:
in the formula, rnewIs the internal resistance r of the battery in the battery power module when the battery leaves the factoryEOLIs the internal resistance at the end of the battery life in the battery power module.
And step 506, acquiring the operating power corresponding to each battery power module according to each battery parameter and the instruction power based on the power calculation formula.
The power calculation formula in this embodiment is:
n is the number of battery power modules, Pi *For operating power, SOH, of the battery power module iiSOH parameter, SOC, for a battery power module iiIs the SOC parameter, P, of the battery power module iegIs the commanded power.
And 507, calculating second access current corresponding to each battery power module according to the running power and the voltage of the battery power module.
And step 508, based on the first access current and each second access current, adjusting the duty ratio of the DC-DC converter in each battery power module according to a droop control strategy and a current closed-loop control strategy so as to realize control over each battery power module.
In the embodiment, after the instruction power of the power grid, the battery parameters of each battery power module and the first access current of the DC-DC converter accessing the power grid are obtained, the second access current of each battery power module is calculated according to the instruction power of the power grid and the battery parameters, which is equivalent to performing power distribution on the instruction power of the power grid, so that the requirement on the consistency of the battery power modules is reduced, the batteries in the battery power modules simultaneously reach a charging cut-off state or a discharging cut-off state, so that the energy utilization rate is improved, then based on the first access current and the second access current, the duty ratio of the DC-DC converter in each battery power module is adjusted according to a droop control strategy and a current closed-loop control strategy so as to realize the control on each battery power module, and the charging and discharging currents of each battery power module are independently controlled according to the droop control strategy and the current closed-loop control strategy, the stable control of the whole retired power battery system is realized through a power distribution strategy, a droop control strategy and a current closed-loop control strategy, so that the technical problem that an energy storage system formed by retired power batteries is difficult to realize in the conventional power grid is solved.
In the above second embodiment of the hierarchical control method for a echelon utilization energy storage system provided in the embodiment of the present application, the hierarchical control method for a echelon utilization energy storage system provided in the embodiment of the present application is verified as follows:
the method shown is validated as follows:
the simulation experiment condition is that 15 battery power modules are adopted, the battery voltage of a single battery power module is 50V, the bus voltage is 600V, and the rated current of the flexible energy storage converter is 75A.
The function experiment of the flexible energy storage converter mainly comprises three parts of power instruction control, charge-discharge conversion, power distribution among modules and the like.
1) Power command control
The experimental conditions are as follows:
(1) the battery voltage of each battery power module is 50V, the bus voltage is 600V, and the power is distributed evenly;
(2) the power command control, i.e. the second access current change, selects 0A → 20A → -20A → 0A, and commands the interval time 0.05 s.
TABLE 1 Power instruction control simulation parameter Table
The experimental simulation result is shown in fig. 6, and analysis can obtain that in the cascaded half-bridge topology energy storage system, the output power of the cascaded side can stably change in real time along with the power instruction, and the control error is less than 1A.
2) Charge-discharge transition time
The experimental conditions are as follows:
(1) the battery voltage of each battery power module is 50V, the bus voltage is 600V, and the power is distributed evenly;
(2) the power command control, i.e. the second cut-in current (current control command in the figure) change, selects 75A → -75A, and the command interval time is 0.1 s.
Table 2 charge-discharge conversion simulation parameter table
The experimental simulation results are shown in fig. 7, and analysis can obtain:
firstly, in the simulation, discharging 75A is converted into charging 75A, the time is about 35ms and is less than the design index of 100 ms;
secondly, during conversion, the maximum value of current overshoot is about 25A, the overshoot time is about 70ms, and the current overshoot time needs to be set within a protection limit value.
3) Power distribution among battery power modules
The experimental conditions are as follows:
(1) the battery voltage of each battery power module is 50V, the bus voltage is 600V, and the power is distributed evenly;
(2) and (3) power distribution among the battery power modules, namely adjusting a given current parameter, selecting the first three battery power modules for power distribution, converting the power distribution from 1:1:1 to 11:10:9, and recovering the power distribution to 1:1:1, wherein the corresponding instruction can be realized by a per unit value method. When the power distribution instructions of the first three battery power modules are 11:10:9, the droop current parameters are given, and the formula is as follows:
in the formula iH1,iH2,iH3Command currents i of the battery power modules 1, 2, 3, respectivelyNRated current, v, output for the energy storage stringNTotal sum output for systemConstant voltage, vN1,vN2,vN3The nominal output voltage of the battery power module 1/2/3.
TABLE 3 simulation parameter table for power distribution among battery power modules
The simulation results are shown in fig. 8, and the analysis results are:
in simulation, the first three battery power modules work under power distribution of 1:1:1, the power is 800W, after the power is adjusted to 11:10:9 at 0.1s, the power is adjusted to 880W, 800W and 720W, and after the power distribution instruction is restored to 1:1:1, the power of the three battery power modules is equal and is 800W.
4) Stability experimental verification
Bus voltage disturbance
The experimental conditions are as follows:
(1) the battery voltage of each battery power module is 50V, the bus voltage is 600V, and the power is distributed evenly;
(2) bus voltage disturbance, sudden increase of 75V and sudden decrease of 75V simulation experiments.
Experiment one: in a bus voltage disturbance experiment I, the bus voltage is 600V, and the bus voltage is instantly increased by 75V.
TABLE 4 simulation parameter table for power distribution among battery power modules
Experiment two: and in a bus voltage disturbance experiment II, the bus voltage is 600V, and the bus voltage is instantly reduced by 75V.
TABLE 5 simulation parameter table for power distribution among battery power modules
The results of the experimental simulation are shown in fig. 9 and 10, and analysis can obtain:
firstly, when the voltage of a bus suddenly increases or drops, the output current value of a battery power module is changed due to the droop effect, the voltage is increased by 75V in simulation, the value is correspondingly reduced by 3.75A after the current is stabilized, the value is consistent with the droop parameter of the circuit design, and the current value can be restored to the given current value through the secondary regulation of a controller of the battery power module;
secondly, when the bus voltage suddenly changes, the output current of the battery power module is caused to overshoot in a short time, and the overshoot is not more than 3A under the experimental conditions given in the text.
5) Fault redundancy, module cut-in
The redundancy condition of the module in the flexible energy storage converter mainly comprises two conditions, one is serious faults of cascade side overcurrent, battery overcurrent, voltage overvoltage and the like, and the module needs to be quickly cut out even if the battery and the DC/DC are protected; and the other is that when the battery is actively and uniformly regulated, the battery needs to be bypassed, and does not participate in the situations of charging and discharging and the like any more, so that the battery is allowed to be cut out within a certain time.
Experiment: single module redundancy is allowed, and the impact on the operation of other modules is analyzed.
The experimental conditions are as follows:
(1) the battery voltage of each battery power module is 50V, the bus voltage is 600V, and the power is distributed evenly;
(2) and the No. 15 battery power module is in failure and is cut off instantly.
The simulation results are shown in fig. 11, and the analysis can obtain:
firstly, a single battery power module is cut out instantaneously, the discharge direction of inductive current is reduced, the descending depth is about 20A, then the current is readjusted to a similar steady-state current value, a new steady-state value can be obtained by calculation of droop parameters (the cut-out module voltage is borne by other 14 battery power modules, the working point moves along a droop curve, the output current is reduced), the descending depth of current is because the duty ratio of the module is limited by PI calculation and can not be suddenly changed, so that the voltage at the cascade side is smaller than the bus voltage, and the discharge direction of the inductive current is reduced;
the method can be obtained in simulation, after one battery power module is cut out, the inductive current ripple becomes large due to synchronous phase shifting of 15 battery power modules, the phase shifting phase of each battery power module is a fixed value, and after one battery power module is cut out, the voltage difference of the missing phase is large, so that the inductive current ripple is increased;
an embodiment of a hierarchical control apparatus for a gradient-based energy storage system according to an embodiment of the present application is shown in fig. 12.
The embodiment of the application provides a hierarchical controlling means who utilizes energy storage system echelon, echelon utilization energy storage system includes: a retired power battery system and a plurality of DC-DC converters; the low-voltage side of the DC-DC converter is connected to a power grid, and the high-voltage side of the DC-DC converter is connected with a decommissioning power battery system; retired power battery system includes: a plurality of battery modules formed by retired power batteries; the single DC-DC converter is connected with the single battery module to form a single battery power module;
the hierarchical control device includes:
the obtaining unit 1301 is configured to obtain an instruction power of a power grid, a battery parameter of each battery power module, and a first access current of the DC-DC converter accessing the power grid, where the battery parameter includes: SOH parameters and SOC parameters;
a calculating unit 1302, configured to calculate, according to the instruction power and each battery parameter, a second access current corresponding to each battery power module;
and an adjusting unit 1303, configured to adjust duty ratios of the DC-DC converters in the battery power modules according to the droop control strategy and the current closed-loop control strategy based on the first access current and the second access currents, so as to implement control on the battery power modules.
Further, the acquiring the battery parameters of each battery power module specifically includes:
establishing a state space model corresponding to each battery power module by using a battery SOC parameter and a battery internal resistance r in each battery power module as state variables, terminal voltage as an observed quantity and current as an input quantity through an ampere-hour integration method, wherein the state space model is as follows;
Vo(k)=E+I(k)r(k)+K+ε
in the formula, QmaxFor the rated capacity of the battery, SOC (k +1) is the state of charge of the battery power module at the moment k +1, SOC (k) is the state of charge of the battery power module at the moment k, I (k) is the actual current of the battery in the battery power module at the moment k, delta T is discrete time, omega1For process noise, r (k +1) is the internal battery resistance of the battery power module at the time k + 1, and r (k) is the internal battery resistance of the battery power module at the time k, ω2Is process noise, Vo(k) The voltage of the battery terminal at the moment K, E is the open-circuit voltage of the battery, K is the correction error of the battery model, and epsilon is the measurement noise;
let x be [ SOC, r]TSolving a state space model through an unscented Kalman filtering algorithm to obtain battery SOC parameters and battery internal resistance r corresponding to each battery power module;
based on a first formula, calculating the SOH parameter corresponding to each battery power module according to the internal resistance r of the battery in each battery power module, wherein the first formula is as follows:
in the formula, rnewIs the internal resistance r of the battery in the battery power module when the battery leaves the factoryEOLIs the internal resistance at the end of the battery life in the battery power module.
Further, the calculation unit specifically includes:
the obtaining subunit is used for obtaining the operating power corresponding to each battery power module according to each battery parameter and the instruction power based on the power calculation formula;
and the calculating subunit is used for calculating the second access current corresponding to each battery power module according to the operating power and the voltage of the battery power module.
Further, the power calculation formula is:
n is the number of battery power modules, Pi *For operating power, SOH, of the battery power module iiSOH parameter, SOC, for a battery power module iiIs the SOC parameter, P, of the battery power module iegIs the commanded power.
In the embodiment, after the instruction power of the power grid, the battery parameters of each battery power module and the first access current of the DC-DC converter accessing the power grid are obtained, the second access current of each battery power module is calculated according to the instruction power of the power grid and the battery parameters, which is equivalent to performing power distribution on the instruction power of the power grid, so that the requirement on the consistency of the battery power modules is reduced, the batteries in the battery power modules simultaneously reach a charging cut-off state or a discharging cut-off state, so that the energy utilization rate is improved, then based on the first access current and the second access current, the duty ratio of the DC-DC converter in each battery power module is adjusted according to a droop control strategy and a current closed-loop control strategy so as to realize the control on each battery power module, and the charging and discharging currents of each battery power module are independently controlled according to the droop control strategy and the current closed-loop control strategy, the stable control of the whole retired power battery system is realized through a power distribution strategy, a droop control strategy and a current closed-loop control strategy, so that the technical problem that an energy storage system formed by retired power batteries is difficult to realize in the conventional power grid is solved.
The embodiment of the application also provides hierarchical control equipment for the echelon utilization energy storage system, which comprises a processor and a memory; the memory is used for storing the program codes and transmitting the program codes to the processor; the processor is configured to execute the hierarchical control method for echelon utilization of the energy storage system according to the first embodiment or the second embodiment according to instructions in the program code.
The embodiment of the application further provides a storage medium, wherein the storage medium is used for storing a program code, and the program code is used for executing the hierarchical control method for the echelon utilization energy storage system in the first embodiment or the second embodiment.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (8)
1. A hierarchical control method for a echelon utilization energy storage system, the echelon utilization energy storage system comprising: a retired power battery system and a plurality of DC-DC converters; the high-voltage side of the DC-DC converter is connected to a power grid, and the low-voltage side of the DC-DC converter is connected with the decommissioned power battery system; the decommissioning power battery system comprises: a plurality of battery modules formed by retired power batteries; the single DC-DC converter is connected with the single battery module to form a single battery power module;
the hierarchical control method comprises the following steps:
acquiring the instruction power of the power grid, the battery parameters of each battery power module and the first access current of the DC-DC converter accessing the power grid, wherein the battery parameters comprise: SOH parameters and SOC parameters;
calculating second access current corresponding to each battery power module according to the instruction power and each battery parameter;
based on the first access current and each second access current, adjusting the duty ratio of the DC-DC converter in each battery power module according to a droop control strategy and a current closed-loop control strategy so as to realize the control of each battery power module;
the obtaining of the battery parameters of each battery power module specifically includes:
establishing a state space model corresponding to each battery power module by using a battery SOC parameter and a battery internal resistance r in each battery power module as state variables, terminal voltage as an observed quantity and current as an input quantity through an ampere-hour integration method, wherein the state space model is;
in the formula, QmaxFor the rated capacity of the battery, SOC (k +1) is the state of charge of the battery power module at the moment k +1, SOC (k) is the state of charge of the battery power module at the moment k, I (k) is the actual current of the battery in the battery power module at the moment k, delta T is discrete time, omega1For process noise, r (k +1) is the internal battery resistance of the battery power module at the time k +1, and r (k) is the internal battery resistance of the battery power module at the time k, ω2Is process noise, Vo(k) The voltage of the battery terminal at the moment K, E is the open-circuit voltage of the battery, K is the correction error of the battery model, and epsilon is the measurement noise;
let x be [ SOC, r]TSolving the state space model through an unscented Kalman filtering algorithm to obtain battery SOC parameters and battery internal resistance r corresponding to each battery power module;
calculating the SOH parameter corresponding to each battery power module according to the internal battery resistance r in each battery power module based on a first formula, wherein the first formula is as follows:
in the formula, rnewIs the internal resistance r of the battery in the battery power module when the battery leaves the factoryEOLIs the internal resistance at the end of the battery life in the battery power module.
2. The hierarchical control method for a echelon utilization energy storage system according to claim 1, wherein calculating the second access current corresponding to each battery power module according to the command power and each battery parameter specifically includes:
based on a power calculation formula, acquiring operating power corresponding to each battery power module according to each battery parameter and the instruction power;
and calculating second access current corresponding to each battery power module according to the running power and the voltage of the battery power module.
3. The hierarchical control method for a echelon utilization energy storage system according to claim 2, wherein the power calculation formula is:
n is the number of battery power modules, Pi *For operating power, SOH, of the battery power module iiSOH parameter, SOC, for a battery power module iiIs the SOC parameter, P, of the battery power module iegIs the commanded power.
4. A hierarchical control apparatus for a echelon utilization energy storage system, the echelon utilization energy storage system comprising: a retired power battery system and a plurality of DC-DC converters; the high-voltage side of the DC-DC converter is connected to a power grid, and the low-voltage side of the DC-DC converter is connected with the decommissioned power battery system; the decommissioning power battery system comprises: a plurality of battery modules formed by retired power batteries; the single DC-DC converter is connected with the single battery module to form a single battery power module;
the hierarchical control apparatus includes:
an obtaining unit, configured to obtain an instruction power of the power grid, a battery parameter of each battery power module, and a first access current of the DC-DC converter accessing the power grid, where the battery parameter includes: SOH parameters and SOC parameters;
the calculating unit is used for calculating second access current corresponding to each battery power module according to the instruction power and each battery parameter;
the adjusting unit is used for adjusting the duty ratio of the DC-DC converter in each battery power module according to a droop control strategy and a current closed-loop control strategy on the basis of the first access current and each second access current so as to realize control over each battery power module;
the obtaining of the battery parameters of each battery power module specifically includes:
establishing a state space model corresponding to each battery power module by using a battery SOC parameter and a battery internal resistance r in each battery power module as state variables, terminal voltage as an observed quantity and current as an input quantity through an ampere-hour integration method, wherein the state space model is;
in the formula, QmaxFor the rated capacity of the battery, SOC (k +1) is the state of charge of the battery power module at the moment k +1, SOC (k) is the state of charge of the battery power module at the moment k, I (k) is the actual current of the battery in the battery power module at the moment k, delta T is discrete time, omega1For process noise, r (k +1) is the internal battery resistance of the battery power module at the time k +1, and r (k) is the internal battery resistance of the battery power module at the time k, ω2Is process noise, Vo(k) The voltage of the battery terminal at the moment K, E is the open-circuit voltage of the battery, K is the correction error of the battery model, and epsilon is the measurement noise;
let x be [ SOC, r]TBy unscented Kalman Filter computationSolving the state space model to obtain battery SOC parameters and battery internal resistance r corresponding to each battery power module;
calculating the SOH parameter corresponding to each battery power module according to the internal battery resistance r in each battery power module based on a first formula, wherein the first formula is as follows:
in the formula, rnewIs the internal resistance r of the battery in the battery power module when the battery leaves the factoryEOLIs the internal resistance at the end of the battery life in the battery power module.
5. The hierarchical control device for a echelon utilization energy storage system according to claim 4, wherein the computing unit specifically includes:
the obtaining subunit is configured to obtain, based on a power calculation formula, operating power corresponding to each battery power module according to each battery parameter and the instruction power;
and the calculating subunit is used for calculating second access current corresponding to each battery power module according to the operating power and the voltage of the battery power module.
6. The hierarchical control apparatus for a echelon utilization energy storage system according to claim 5, wherein the power calculation formula is:
n is the number of battery power modules, Pi *For operating power, SOH, of the battery power module iiSOH parameter, SOC, for a battery power module iiIs the SOC parameter, P, of the battery power module iegIs the commanded power.
7. A hierarchical control apparatus for a echelon utilization energy storage system, the apparatus comprising a processor and a memory;
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the hierarchical control method for a echelon utilization energy storage system according to any one of claims 1 to 3 according to instructions in the program code.
8. A storage medium for storing a program code for executing the hierarchical control method of a echelon utilization energy storage system according to any one of claims 1 to 3.
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