Control method of fuzzy weighted controller for dual-channel battery charging and discharging circuit

Abstract

The present invention discloses a control method of a fuzzy weighted controller of a dual-channel battery charging and discharging circuit, including: 1) the bus voltage sampling signal output by the charging and discharging circuit and the bus voltage given signal are sent to a subtractor together, and the bus voltage error signal generated after the subtractor is sent to the bus voltage controller; 2) the battery pack discharge current reference signal and the battery pack voltage sampling signal of each channel are sent to the fuzzy weighted control law together, and the battery pack discharge current reference signal of each channel and the corresponding battery pack current sampling signal are sent to the subtractor together, and the battery pack current error signal of each channel is generated after the subtractor and sent to the corresponding current controller to generate the control signal of each channel; 3) the control signal of each channel is used as a modulation wave to compare with the carrier signal in the PWM modulator to generate a duty cycle signal, and then the switch tube in the charging and discharging circuit is controlled by the driving circuit. The present invention can give full play to the performance of different batteries and help to extend the service life of the battery.

Description

Technical Field

[0001] The present invention relates to, in particular to, a fuzzy weighted controller for a dual-channel battery charging and discharging circuit. Background Art

[0002] In order to achieve the comprehensive utilization of batteries with different performances in energy storage equipment, thereby reducing the cost of energy storage, batteries with similar performances are currently packaged together for use. However, due to different performances, multiple such battery packs are not suitable for direct parallel use. For this reason, it is necessary to install a battery pack equalizer between different battery packs to achieve voltage balance control of the two battery packs. However, this method is complex to control, increases the burden of the entire system operation, and increases the cost of the system due to the addition of an additional device, and reduces the reliability of the energy storage system. In view of this situation, independent power electronic circuits can be used to charge and discharge battery packs with different performances. However, when battery packs with different performances jointly form the DC bus voltage in the energy storage equipment through the discharge circuit, the discharge current of each battery pack needs to be allocated according to performance to ensure the life of the battery; and the size of the battery pack discharge current can usually be allocated by weighted method, that is, the discharge current of the high-voltage battery pack is greater than the discharge current of the low-voltage battery pack, but this method fails to fully consider the characteristics of the battery, such as changes in the internal resistance, which may lead to misjudgment of battery performance. To solve this problem, the state of charge (SOC) of the battery packs in different channels can be monitored. Common SOC estimation methods include the ampere-hour method, the open circuit voltage method, the neural network method, etc., and then the discharge current of each battery pack is allocated according to the size of the SOC. However, this increases the burden on the CPU and increases costs. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a control method of a fuzzy weighted controller for a dual-channel battery charging and discharging circuit, which can adaptively allocate the discharge current size of the battery packs in each channel by detecting the size and change rate of the battery pack voltage in the discharge condition.

[0004] The object of the present invention is achieved as follows: a control method of a fuzzy weighted controller of a dual-channel battery charging and discharging circuit, wherein the controller includes three links: a bus voltage controller, a fuzzy weighted control law, and a corresponding channel current controller, and specifically includes the following steps:

[0005] 1) The bus voltage sampling signal output by the charge and discharge circuit and the bus voltage given signal are sent to the subtractor together, and the bus voltage error signal generated after the subtractor is sent to the bus voltage controller, and the bus voltage controller outputs the battery pack discharge current reference signal;

[0006] 2) The battery pack discharge current reference signal and the battery pack voltage sampling signal of each channel are sent to the fuzzy weighted control law to obtain the battery pack discharge current reference signal of each channel. The battery pack discharge current reference signal of each channel and the corresponding battery pack current sampling signal are sent to the subtractor to generate the battery pack current error signal of each channel. The error signal is sent to the corresponding current controller to generate the control signal of each channel.

[0007] 3) The control signal of each channel is used as a modulation wave and compared with the carrier signal in the PWM modulator to generate a duty cycle signal, which is then controlled by the drive circuit to turn on and off the switch tube in the charging and discharging circuit.

[0008] As a further limitation of the present invention, the implementation of the fuzzy weighted control law specifically includes a fuzzy controller and a weighted law: the inter-channel battery pack voltage error obtained by subtracting the 1# channel battery pack voltage sampling signal from the 2# channel battery pack voltage sampling signal The error is sent to the fuzzy controller, and the change rate error of the battery pack voltage between channels is obtained by subtracting the change rate of the battery pack voltage of channel 1 from the change rate of the battery pack voltage of channel 2. The fuzzy controller outputs a weighted coefficient increment, and the weighted coefficient increment is used to obtain the weighted coefficient required for calculating the battery pack discharge current reference signal of each channel through the weighting law. The weighted coefficient is multiplied by the battery pack discharge current reference signal output by the bus voltage controller to obtain the battery pack discharge current reference signal of each channel.

[0009] As a further limitation of the present invention, the weighting law is implemented by the following formula:

[0010]

[0011] In the formula and They are the initial weighting coefficients of the battery pack discharge current reference signals of channel 1# and channel 2#, and They are the initial voltage sampling signals of the battery pack of channel 1# and channel 2# respectively;

[0012]

[0013] In the formula and They are the current weighting coefficients of the battery pack discharge current reference signals of channel 1# and channel 2#, and are the weighted coefficients of the last battery pack discharge current reference signals of channel 1# and channel 2#, respectively, and Δρ is the weighted coefficient increment output by the fuzzy controller.

[0014] As a further limitation of the present invention, the fuzzy control rule design method of the weighted coefficient increment specifically includes: if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive When the negative value is large, the weighting coefficient increment Δρ is 0; if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive When the battery pack voltage error between the two channels is positive, the weighting coefficient increment Δρ is positive; When the voltage change rate error of the battery pack between channels is positive If the negative value is small, the weighting coefficient increment Δρ takes a positive value; if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive If the battery pack voltage error between the two channels is positive, the weighting coefficient increment Δρ will be positive. When the voltage change rate error of the battery pack between channels is positive is 0, the weighting coefficient increment Δρ is positive; when the battery pack voltage error between the two channels When positive is small, it is 0, and when negative is large, it is small, and so on. Follow the above idea and make analogies.

[0015] As a further limitation of the present invention, the fuzzy weighted control law performs fuzzy weighted distribution on the battery pack discharge current reference signal output by the bus voltage controller according to the sampling signal of the battery pack voltage of each channel, and obtains the battery pack discharge current reference signal of the corresponding channel current controller. The control signal output by the corresponding channel current controller is used as the modulation signal of the PWM modulator. The pulse control signal generated by the PWM modulator is then used to control the on and off of the switch tube in the charging and discharging circuit after passing through the driving circuit, thereby realizing adaptive adjustment of the discharge current of the battery pack of each channel according to the battery performance and achieving bus voltage stability.

[0016] The present invention adopts the above technical solution, and compared with the prior art, the beneficial effects are as follows: according to the sampling value of the battery pack voltage of each channel in the charge and discharge circuit and its rate of change, a fuzzy weighted controller is used to calculate the battery pack discharge current reference signal required by each channel current controller, so that even if the battery pack voltages of each channel are inconsistent, the voltages of the battery packs of each channel can be balanced during the discharge process; when the battery pack voltages are equal, the method of the present invention actually distributes the discharge current according to the performance of each battery pack, thereby extending the battery life. The method of the present invention avoids the cost increase and reliability reduction caused by installing a battery pack equalizer between battery packs. It is only implemented through software programming on the basis of existing hardware, without additional cost, so it has high cost performance.

[0017] The method of the present invention can not only give full play to the performance of different battery packs, but also realize voltage equalization of two battery packs during discharge. The algorithm is realized through software programming, and there is no need to establish an accurate model of the battery or use a complex algorithm to accurately evaluate the remaining battery capacity before obtaining the discharge current of the battery pack in each channel. Instead, fuzzy reasoning is performed based on the battery pack voltage sampling signal of each channel. The weighting coefficient of each channel is corrected in real time through the weighting law, and the reference signal of the battery pack discharge current in the corresponding channel can be obtained. Therefore, the method is intelligent and highly reliable.

[0018] Other advantages and effects of the present invention will be described below.

[0019] The terms involved in the present invention include: PWM (Pulse-Width Modulation), SOC (State of Charge). BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the composition of the fuzzy weighted controller of the present invention.

[0021] Figure 2 A schematic diagram of the charging and discharging circuit system used in the present invention.

[0022] Figure 3 Schematic diagram of the implementation of the fuzzy weighted control law of the present invention.

[0023] Figure 4 A membership function curve diagram of the inter-channel battery pack voltage error and the inter-channel battery pack voltage change rate error of the present invention.

[0024] Figure 5 Membership function curve diagram of weighted coefficient increment of the present invention.

[0025] Figure 6 Schematic diagram of a dual-channel dual active bridge charging and discharging circuit in an embodiment of the present invention.

[0026] Figure 7 The present invention adopts the discharge simulation waveforms of batteries with different performances of the traditional weighted controller.

[0027] Figure 8 The present invention adopts the discharge simulation waveform of batteries with different performances using a fuzzy weighted controller.

[0028] Figure 1 Symbolic names in:

[0029]

[0030]

[0031] Figure 2 Symbolic names in:

[0032] Other Figure 1 Description of symbols.

[0033] Figure 3 Symbolic names in:

[0034]

[0035]

[0036] Other Figure 1 Description of symbols.

[0037] Figure 4 Symbolic names in:

[0038] NB Negative NS Negative small ZE zero PS Just small PB Zhengda

[0039] Figure 5 The symbol names in Figure 4

[0040] Figure 6 Symbolic names in:

[0041]

[0042] Figure 7 Symbolic names in:

[0043]

[0044] Other Figure 2 Description of symbols.

[0045] Figure 8 The symbol names in Figure 7 . DETAILED DESCRIPTION

[0046] like Figure 1 , Figure 2 As shown, the components of the present invention include: a bus voltage controller 1, a fuzzy weighted control law 2, and a corresponding channel current controller 3.

[0047] like Figure 1 As shown in FIG. 1 , the fuzzy weighted controller of the dual-channel battery charging and discharging circuit is composed of three parts: bus voltage controller 1, fuzzy weighted control law 2 and corresponding channel current controller 3. Figure 2 As shown, the bus voltage V output by the charge and discharge circuit 7 BUS The bus voltage sampling signal U obtained by the sampling and conditioning circuit 8 BUS With bus voltage given signal U BUS-refThe two signals are sent to the subtractor together, and the bus voltage error signal U is obtained after subtraction. BUS-err The bus voltage controller 1 outputs the battery pack discharge current reference signal i bat-ref ;Battery pack discharge current reference signal i bat-ref And the battery pack voltage sampling signal of each channel The fuzzy weighted control law 2 is sent together to obtain the battery pack discharge current reference signal of each channel. Battery pack discharge current reference signal for each channel and the corresponding battery pack current sampling signal The currents are sent to the subtractor together, and the subtractor generates the battery pack current error signal of each channel after subtraction. The corresponding current controller 3 is composed of the corresponding channel current controller of channel 1# and the corresponding channel current controller of channel 2#. The corresponding channel current controller of channel 1# and the corresponding channel current controller of channel 2# generate the control signal u of each channel respectively. (1) 、u (2) , each channel control signal u (1) 、u (2) As the modulation wave, it is compared with the carrier signal in the PWM modulator 5 to generate a pulse control signal v duty , and then outputs the driving signal v through the driving circuit 6 dr To control the on and off of the switch tube in the charge and discharge circuit 7.

[0048] The fuzzy weighted controller 4 of the dual-channel battery charging and discharging circuit 7 and the implementation method of the fuzzy weighted control law 2 are mainly composed of the fuzzy controller 9 and the weighted law 10: the battery voltage sampling signal of the 1# channel With 2# channel battery voltage sampling signal The battery pack voltage error between channels obtained by subtraction The fuzzy controller is sent to the battery voltage change rate of channel 1. The change rate of the battery voltage of channel 2# Subtract the error of the battery voltage change rate between channels The fuzzy controller 9 outputs a weighted coefficient increment Δρ, thereby forming a dual-input, single-output fuzzy controller; the weighted coefficient increment Δρ is obtained by the weighting law 10 to obtain the weighted coefficient required for calculating the reference signal of the battery pack discharge current of each channel. The weighting coefficient The bus voltage controller outputs a battery pack discharge current reference signal i bat-ref Multiply them to get the battery pack discharge current reference signal of each channel Battery pack discharge current reference signal for each channel The error signal of the current sampling signal of the corresponding channel The corresponding channel current controller 3 generates the modulation wave signal u of the corresponding channel (1) 、u (2) .

[0049] The weighting law 10 is implemented by the following formula:

[0050]

[0051] The initial weighting coefficient The calculation is as follows:

[0052]

[0053] In the formula and They are the initial weighting coefficients of the battery pack discharge current reference signals of channel 1# and channel 2#, and They are the initial voltage sampling signals of the battery pack of channel 1# and channel 2# respectively; and They are the current weighting coefficients of the battery pack discharge current reference signals of channel 1# and channel 2#, and are the weighted coefficients of the last battery pack discharge current reference signals of channel 1# and channel 2#, respectively, and Δρ is the weighted coefficient increment output by the fuzzy controller; the specific calculation is implemented by program code in the digital signal processor DSP.

[0054] like Figure 2 The proposed dual-channel battery charging and discharging circuit fuzzy weighted controller 4 can be used to control the sampling signal of the battery pack voltage of each channel according to the fuzzy weighted control law 2. The battery pack discharge current reference signal i output by the bus voltage controller 1 is bat-ref Perform fuzzy weighted allocation to obtain the battery pack discharge current reference signal of the corresponding channel current controller 3 The control signal u output by the corresponding channel current controller 3 (1) 、u (2) As the modulation signal of the PWM modulator 5, the pulse control signal v generated by the PWM modulator 5 duty , and then generates a driving signal v after passing through the driving circuit 6 dr , which is used to control the on and off of the switch tube in the charge and discharge circuit 7, so as to realize the adaptive adjustment of the discharge current of each channel battery pack according to the battery performance, and realize the bus voltage V BUS stability.

[0055] The design process of fuzzy weighted controller 4 is given below. Figure 3As shown, the fuzzy weighted controller 4 consists of two parts: a fuzzy controller 9 and a weighted law 10. The input quantity of the fuzzy controller 9 is the battery pack voltage error between channels. The voltage change rate error of the battery pack between channels The output of the fuzzy controller 9 is the weighting coefficient increment Δρ. The weighting law 10 iterates the weighting coefficient increment Δρ output by the fuzzy controller 9 and the previous weighting coefficient to obtain the weighting coefficient of the current battery pack discharge current reference signal of each channel. and The function of fuzzy weighted controller 2: according to the input and The size of is inferred by the fuzzy control rule table of the weighted coefficient increment Δρ, and combined with the weighted law as shown in formula (1), the weighted coefficient of the discharge current reference signal of the battery pack in the dual channels is obtained, so that the discharge current of the battery pack in the corresponding channel is controlled by the corresponding channel current controller; the control process of the actual fuzzy weighted controller is divided into two stages. The first stage is to make the battery pack voltages in the dual channels gradually tend to be equal when the battery pack voltages in each channel are inconsistent; the second stage is to adaptively distribute the discharge current of the battery pack in each channel according to the performance of the battery pack in each channel after the battery pack voltages in each channel tend to be equal.

[0056] like Figure 2 and Figure 3 As shown, by sampling the battery pack voltage of each channel, the sampling signal of the battery pack voltage of channel 1# is obtained. And the sampling signal of the battery pack voltage of channel 2# The battery pack voltage sampling signal of each channel The fuzzy controller firstly uses a subtractor to sample the voltage of the battery pack on channel 1. And 2# channel battery pack voltage sampling signal Subtract the two to get an input quantity of fuzzy controller 9 - the battery pack voltage error between channels Subtract the current 1# channel and 2# channel battery pack voltage sampling signals from the previous 1# channel and 2# channel battery pack voltage sampling signals to obtain the 1# channel and 2# channel battery pack voltage change rate. and Then the obtained battery pack voltage change rate of channel 1# is And the battery pack voltage change rate of channel 2# Subtract the voltage change rate error of the battery pack between channels to obtain another input quantity of the fuzzy controller 9

[0057] The fuzzy controller 9 mainly consists of three parts: fuzzification, fuzzy control reasoning and defuzzification. Fuzzification refers to the process of converting the input quantity from the precise quantity to the fuzzy quantity through the fuzzification method, and at the same time converting the domain of the fuzzy quantity into the corresponding fuzzy language set. (1,2) ,EC (1,2) To represent the actual input The fuzzy set of the fuzzy weighted controller input The basic domain of is {-4, 4}, its fuzzy domain is {-2, 2}, and the fuzzy language set is {NB (negative large), NS (negative small), ZO (zero), PS (positive small), PB (positive large)}. The basic domain of is {-2, 2}, its fuzzy domain is {-2, 2}, and the fuzzy language set is {NB (negative large), NS (negative small), ZO (zero), PS (positive small), PB (positive large)}. The input variable is converted from the basic domain to the fuzzy domain by quantizing the factors To achieve is defined as:

[0058]

[0059]

[0060] Among them, n and m are fuzzy domain values ​​(both are 2 here), is the maximum value of the basic domain (4 and 2 respectively).

[0061] Let P represent the fuzzy set of Δρ. The basic domain of the output Δρ of the fuzzy weighted controller 9 is {-0.5, 0.5}, its fuzzy domain is {-2, 2}, and the corresponding fuzzy language set is {NB (negative large), NS (negative small), ZO (zero), PS (positive small), PB (positive large)}. The fuzzy domain of the output can be converted from the fuzzy domain to the basic domain by the proportional factor K Δρ If K Δρ is defined as:

[0062]

[0063] Among them, l is the fuzzy domain value of the output (here it is taken as 2), Δρ xam is the maximum value of the basic domain (here it is 0.5).

[0064] By solving the scale factor and quantization factor in the above formula, the domain can be transformed by setting the scale factor and quantization factor. The quantization factor and scale factor can scale the input and output. Scaling factor K ΔρIt needs to be set according to the characteristics of the controlled object, and the settings of both also affect the gain of the entire loop.

[0065] After the definition of the fuzzy subsets of input and output is completed, its membership function needs to be determined. By introducing the quantization factor, the input can be transformed from the exact value to the fuzzy value, and E (1,2) ,EC (1,2) The membership assignment table of P is shown in Table 1. By introducing the proportional factor, the output can be transformed from fuzzy value to precise value, and the membership assignment table of P is obtained, as shown in Table 2. The input and output membership functions are both simple in shape and have strong real-time controllability. (1,2) ,EC (1,2) The membership function curve is as follows Figure 4 As shown, the membership function curve of the Δρ fuzzy set P is as follows Figure 5 The expression of the triangular membership function is as follows:

[0066]

[0067] Where x is the input variable, a, b, and c are the domain segmentation points of the membership function, and the function value represents the degree of membership of the fuzzy language value in the region.

[0068] Table 1 E (1,2) and EC (1,2) Membership assignment table

[0069]

[0070] Table 2 Membership degree assignment table of Δρ

[0071]

[0072] Fuzzy control reasoning is based on fuzzy control rules. Fuzzy control rules are formed by integrating the relationship between input and output in the fuzzy controller into multiple fuzzy control statements through fuzzy statements through the knowledge or experience of engineers. Fuzzy control rules are used as the criterion for fuzzy reasoning. Fuzzy reasoning is to infer the output that meets the actual needs based on the input according to the fuzzy control rules. The function of the fuzzy weighted controller 4 of the present invention is mainly divided into two stages. and After the size of is fuzzified, the weight coefficient of the battery pack discharge current reference signal in the dual channel is obtained by inferring the fuzzy control rule table of the weight coefficient increment Δρ and combining the weight law 10 as shown in formula (1): and Thus, the battery pack discharge current reference signal of the corresponding channel is obtained The discharge current of the battery pack of the corresponding channel is controlled by the corresponding channel current controller 3 .

[0073] The design method of the fuzzy control rule of the weighted coefficient increment Δρ, the design idea of ​​the control rule is as follows: if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive When the negative value is large, the weighting coefficient increment Δρ is 0; if the battery pack voltage error between the two channels is U e (1,2) When the voltage change rate error of the battery pack between channels is positive When the battery pack voltage error between the two channels is positive, the weighting coefficient increment Δρ is positive; When the voltage change rate error of the battery pack between channels is positive If the negative value is small, the weighting coefficient increment Δρ takes a positive value; if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive If the battery pack voltage error between the two channels is positive, the weighting coefficient increment Δρ will be positive. When the voltage change rate error of the battery pack between channels is positive If the battery pack voltage error between the two channels is When the battery pack voltage change rate error between channels is positive, When the negative value is large, the weighting coefficient increment Δρ takes a small negative value; if the battery pack voltage error between the two channels When the battery pack voltage change rate error between channels is positive, When the battery pack voltage error between the two channels is positive, the weighting coefficient increment Δρ is positive; When the battery pack voltage change rate error between channels is positive, If the negative hour, the weighting coefficient increment Δρ is 0; if the battery pack voltage error between the two channels When the battery pack voltage change rate error between channels is positive, If the positive value is small, the weighting coefficient increment Δρ takes a positive value; if the battery pack voltage error between the two channels When the battery pack voltage change rate error between channels is positive, If the battery pack voltage error between the two channels is When it is 0, and the voltage change rate error of the battery pack between channels When the negative value is large, the weighting coefficient increment Δρ takes a large negative value; if the battery pack voltage error between the two channels is When it is 0, and the voltage change rate error of the battery pack between channels When the battery pack voltage error between the two channels is positive, the weighting coefficient increment Δρ is positive; When it is 0, and the voltage change rate error of the battery pack between channels If the negative value is small, the weighting coefficient increment Δρ takes a small negative value; if the battery pack voltage error between the two channels When it is 0, and the voltage change rate error of the battery pack between channels If the positive value is small, the weighting coefficient increment Δρ takes a positive value; if the battery pack voltage error between the two channels When it is 0, and the voltage change rate error of the battery pack between channels If the battery pack voltage error between the two channels is When the negative voltage is large, and the voltage change rate error of the battery pack between channels When the negative value is large, the weighting coefficient increment Δρ takes a large negative value; if the battery pack voltage error between the two channels is When the negative voltage is large, and the voltage change rate error of the battery pack between channels When the weighting coefficient increment Δρ is positive, it is 0; if the battery pack voltage error between the two channels When the negative voltage is large, and the voltage change rate error of the battery pack between channels If the negative value is small, the weighting coefficient increment Δρ will be large; if the battery pack voltage error between the two channels When the negative voltage is large, and the voltage change rate error of the battery pack between channels If the positive value is small, the weighting coefficient increment Δρ will be small; if the battery pack voltage error between the two channels When the negative voltage is large, and the voltage change rate error of the battery pack between channels is 0, the weighted coefficient increment Δρ takes a large negative value; if the battery pack voltage error between the two channels Negative hours, and the voltage change rate error of the battery pack between channels When the negative value is large, the weighting coefficient increment Δρ takes a large negative value; if the battery pack voltage error between the two channels is Negative hours, and the voltage change rate error of the battery pack between channels When the positive value is large, the weighting coefficient increment Δρ takes a small negative value; if the battery pack voltage error between the two channels Negative hours, and the voltage change rate error of the battery pack between channels If the negative value is small, the weighting coefficient increment Δρ takes a small negative value; if the battery pack voltage error between the two channels Negative hours, and the voltage change rate error of the battery pack between channels If the positive hour is small, the weighting coefficient increment Δρ is 0; if the battery pack voltage error between the two channels Negative hours, and the voltage change rate error of the battery pack between channels If is 0, the weighting coefficient increment Δρ takes a small negative value;

[0074] It can be seen that if the inter-channel battery pack voltage error and the inter-channel battery pack voltage change rate error are both fuzzified with five-segment domain, there are 25 control rules as above; if the inter-channel battery pack voltage error and the inter-channel battery pack voltage change rate error are both fuzzified with seven-segment domain, 49 rules are obtained accordingly; if the inter-channel battery pack voltage error and the inter-channel battery pack voltage change rate error are both fuzzified with more segment domains, more control rules are obtained accordingly. Here, we can use the above five-segment domain fuzzification to obtain the fuzzy control rule table of the weighted coefficient increment Δρ as shown in Table 3.

[0075] The control rule table of the weighted coefficient increment Δρ shown in Table 3 takes into account the initial voltage of the battery pack and the performance of the battery in the two channels, and calculates the voltage error of the battery pack between channels in different regions. The voltage change rate error of the battery pack between channels Fuzzy reasoning is performed on Table 3, and then combined with the weighting law 10 as shown in formula (1), the discharge current reference signal of the battery pack suitable for each channel in the current system is obtained. and Required weighting factor and The designed fuzzy controller 9 and weighting law 10 constitute a fuzzy weighted control law 2, and without knowing the precise SOC of the battery, a reference signal of the battery pack discharge current in the channel can be realized according to the battery performance, thereby obtaining the rapidity and stability of the battery discharge system.

[0076] Table 3 Fuzzy control rules for weighted coefficient increment Δρ

[0077]

[0078] In the CPU, the fuzzy control rules can be formed by a series of "if-then" statements, and the reasoning process is expressed by statements to represent the control rules of Δρ, as follows:

[0079]

[0080] Each statement corresponds to a corresponding fuzzy relationship, which can be expressed as R1, R2, R3…, R 25 ,Right now:

[0081]

[0082] 25 fuzzy relations R1~R 25 The total fuzzy relation R of the control rule merged into Δρ is:

[0083]

[0084] According to the above fuzzy control rules, fuzzy reasoning can be performed to obtain the fuzzy set of output quantities. The fuzzy quantity in the fuzzy set reflects the relationship between the output language variable and its membership degree. The controlled object is controlled by precise quantity, so defuzzification is also required, which is the opposite of fuzzification. The defuzzification method here may as well use the weighted average method, that is, the elements of each fuzzy output quantity are weighted averaged, and then the proportional factor K is used. Δρ Thus, the accurate value Δρ is output, and we have:

[0085]

[0086] Among them, k is the number of quantization levels, x i is an element in the fuzzy domain of the output quantity, μ A (x i )dx is x i The corresponding membership degree of the input quantity in each fuzzy subset can be used to convert the output fuzzy quantity into the precise quantity of control through the above formula.

[0087] like Figure 3 As shown, by sampling the voltage of the battery pack in each channel, the battery pack voltage sampling signal of channel 1# is obtained. And the battery pack voltage sampling signal of channel 2# By inputting the weighted law as shown in formula (1), the current battery pack discharge current reference signal of each channel can be obtained. Required weighting factor The current weighting coefficient of each channel current The discharge reference current i output by bus voltage controller 1 bat-ref Multiplying them together will give the battery pack discharge current reference signal for each channel. The calculation formula is as follows:

[0088]

[0089] Through the above design process of the fuzzy weighted controller 4 of the present invention, it is known that the proposed method can reflect the performance of the battery according to the actual size of the voltage of the battery pack of each channel and its change during the discharge process, and thus obtain the weighting coefficient required for calculating the discharge current reference signal of the battery pack of each channel; the weighting coefficient is multiplied by the battery pack discharge current reference signal output by the bus voltage controller 1 to obtain the battery pack discharge current reference signal of each channel, and the corresponding channel current controller 3 controls the actual discharge current of each channel, thereby achieving the purpose of extending the battery life.

[0090] Fuzzy weighted controller 4 for dual-channel battery charging and discharging circuits, used in Figure 2The control system shown in the figure is characterized in that the fuzzy weighted control law 2 can convert the battery pack discharge current reference signal i output by the bus voltage controller 1 into a reference signal according to the sampling signal of the battery pack voltage of each channel. bat-ref Perform fuzzy weighted allocation to obtain the battery pack discharge current reference signal of the corresponding channel current controller 3 The control signal u output by the corresponding channel current controller 3 (1) 、u (2) As the modulation signal of the PWM modulator 5, the pulse control signal v generated by the PWM modulator 5 duty , and then generates a driving signal v after passing through the driving circuit 6 dr It is used to control the on and off of the switch tube in the charge and discharge circuit 7, so as to realize the discharge current of each channel battery pack according to the battery performance. The size can be adjusted adaptively to achieve bus voltage V BUS stability.

[0091] A specific embodiment of the present invention is as follows:

[0092] The content of the present invention is applied to a dual-channel dual active bridge circuit. Figure 2 shown, and Figure 2 The charge and discharge circuit 7 in the embodiment is composed of Figure 6 The dual-channel dual active bridge circuit shown is realized, Figure 6 The dual-channel dual-active bridge circuit is composed of a 1# dual-active bridge 11 and a 2# dual-active bridge 12. Figure 2 The system adopts full digital control, and the CPU adopts Hunan Jinxin's digital signal processor (DSP), model ADP32F035. Figure 2 The PWM modulator 5 and the fuzzy weighted controller 4 in the DSP are implemented by the DSP. The dual-channel dual active bridge main circuit mainly includes the 1# channel battery pack (1# channel battery pack voltage ), 2# channel battery pack (2# channel battery pack voltage ), bus capacitors C3 and C4 (bus voltage V BUS ), 16 power switch tubes Q1~Q8 and M1~M8, inductor L s1 and L s2 , 1# channel battery side capacitor C1, 2# channel battery side capacitor C2, DC blocking capacitor C b1 and C b2 、Transformer T r1 and T r2 Inductance L s1 =L s2 =2.3μH, capacitor C1=C2=88.6mF, C3=C4=1mF, DC blocking capacitor C b1 =C b2 =3.8μF, transformer Tr1 and T r2 The turns ratio is 1:8 (the number of turns of the battery side winding: the number of turns of the bus side winding). The voltage of the two battery packs in the dual channel and The range is 40V~60V, bus voltage V BUS Set at 400V, switching frequency f=40kHz. Figure 6 In the dual active bridge circuit, the low-voltage side switch tubes (Q1~Q4 and M1~M4) use Fairchild's FDA032N08 (75V / 165A), and the high-voltage side switch tubes (Q5~Q8 and M5~M8) use Fairchild's FCH072N60F (600V / 52A).

[0093] Battery pack voltage of channel 1# in the embodiment 2# channel battery pack voltage 1# channel battery pack discharge current 2# channel battery pack discharge current and bus voltage V BUS After the sampling and conditioning circuit 8, the battery pack voltage sampling signals are obtained respectively Battery pack discharge current sampling signal Bus voltage sampling signal U BUS These sampling signals are sent to the AD sampling port of ADP32F035; in the program, the bus voltage given value U BUS-ref And bus voltage sampling signal U BUS The error obtained by subtraction is sent to the bus voltage controller 1, where the bus voltage controller 1 adopts a digital PI algorithm to obtain the battery pack discharge current given value i bat-ref , and sent to fuzzy weighted control law 2, battery pack voltage sampling signal It is also sent to the fuzzy weighted control law 2, and then the fuzzy weighted control law 2 obtains the discharge current set value of the corresponding channel current controller 3 (the discharge current set value of the battery pack of channel 1# And the given value of the discharge current of the battery pack of channel 2# ), 1# channel battery pack discharge current given value And the given value of the discharge current of the battery pack of channel 2# Respectively with the 1# channel battery pack discharge current sampling signal And 2# channel battery pack discharge current sampling signal The error signal is obtained by subtracting and sent to the corresponding 1# channel battery pack current controller and 2# channel battery pack current controller. In the embodiment, the 1# channel battery pack current controller and the 2# channel battery pack current controller both adopt the digital PI algorithm, and the 1# channel battery pack current controller and the 2# channel battery pack current controller respectively output the 1# channel control signal u (1)and 2# channel control signal u (2) , and sent to PWM modulator 5, which outputs pulse control signal v duty (The dual active bridge circuit uses phase shift control to achieve this signal), and then outputs the drive signal v through the drive circuit 6 dr To control the on and off of the switch tubes Q1~Q8 and M1~M8 in the dual active bridge circuit.

[0094] The algorithm of the fuzzy weighted controller 4 of the present invention is implemented in the DSP through program code. In the fuzzy weighted controller 4, the current reference signal i output by the bus voltage controller 1 is used as the reference signal. bat-ref And the weighted coefficient obtained by fuzzy weighted control law 2 Multiply them respectively to get the corresponding 1# channel and 2# channel battery pack discharge current reference signal and According to the battery pack voltage of each channel and its change during the discharge process, the fuzzy weighted controller 4 realizes the discharge current based on the dual-channel dual active bridge circuit. and The size can be adjusted adaptively to achieve bus voltage V BUS stability.

[0095] The input of the fuzzy controller in the implementation example is The basic domains are {-1, 1} and {-0.2, 0.2}, and the corresponding quantization factors are As a result, the fuzzy domain is {-2, -1, 0, 1, 2}; the basic domain of the output Δρ of the fuzzy controller is {-0.5, 0.5}, and the proportional factor K Δρ =0.25, so the fuzzy domain is {-2, -1, 0, 1, 2}.

[0096] As shown in formula (2), the initial weighting law of the reference current of each channel can be calculated by the initial sampling signal of the battery pack voltage of each channel. The weighting coefficient required to calculate the reference signal of the discharge current of the battery pack of each channel can be obtained by continuous iteration of the weighting law of formula (1), and multiplied with the battery current reference signal to obtain the reference signal of the discharge current of the battery pack of each channel, as shown in formula (10).

[0097] According to the above parameters, a simulation model was built in the PSIM simulation software, and the control program was written using Visual Studio and a dynamic link library was generated. The battery discharge simulation experiment was carried out on the dual-channel dual active bridge circuit using the traditional weighted controller and the fuzzy weighted controller of the present invention respectively through PSIM and the dynamic link library. The simulation model simulated the 1# channel battery pack and the 2# channel battery pack with different performances. The performance of the 1# channel battery pack is better than that of the 2# channel battery pack, and the initial voltages are 58V and 60V respectively. The bus voltage given value in the program is 400V, and a 5kW load is configured for simulation. Figure 7 is the simulation waveform using the traditional weighted controller. Figure 8 The simulation waveforms of the fuzzy weighted controller of the present invention are shown in Figure 1. From top to bottom, they are the internal electromotive force (Ebat1 and Ebat2) of the 1# channel battery pack and the 2# channel battery pack, the terminal voltage ( and ), the discharge current of the 1# channel battery pack and the 2# channel battery pack ( and ), steady-state bus voltage (V BUS ).Depend on Figure 7 It can be seen that when the battery voltage is simulated for 0.035s, the traditional weighted controller fails to achieve voltage balancing of the two battery packs, and there is no obvious difference in the discharge current of the battery packs in the two channels. Figure 8 It can be seen that within the same simulation time, the fuzzy weighted controller of the present invention achieves voltage balance of the two battery packs at 0.032s, and has a significant discharge current difference compared with the traditional weighted controller, that is, the performance of the battery is fully utilized: the 1# channel battery pack has better performance than the 2# channel battery pack, although its initial voltage is lower, but when the simulation time is as long as 0.032s, its terminal voltage is achieved. and 2# channel battery pack terminal voltage The simulation results show that the fuzzy weighted controller of the present invention realizes two stages of control process (the first stage is to make the battery pack voltages in the two channels gradually equal when the battery pack voltages in the channels are inconsistent; the second stage is to adaptively distribute the discharge current of the battery packs in each channel according to the performance of the battery packs in each channel after the battery pack voltages in each channel are equal).

[0098] From the above description, it can be seen that the fuzzy weighted controller of the dual-channel battery charging and discharging circuit of the invention can reflect the performance of the battery according to the actual voltage and its change amount of each channel battery pack during the discharge process, and has the following advantages:

[0099] (1) By adopting the technology of the present invention, the reference signal of the discharge current of the battery pack of each channel can be obtained only based on the actual voltage of the battery pack of each channel and the voltage change during the discharge process through fuzzy control reasoning combined with the weighting law;

[0100] (2) The fuzzy weighted controller can evaluate the battery performance without knowing the precise battery SOC, and then decide the discharge current of each channel battery pack based on the battery performance, thereby saving costs, improving system reliability, and helping to extend the battery life;

[0101] (3) The technology of the present invention is not limited to application in dual-channel dual-active bridge main circuits, but can also be applied to other dual-channel or even multi-channel charging and discharging circuits to achieve adaptive allocation of discharge current reference signals for battery packs with different performances.

[0102] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A control method of a fuzzy weighted controller for a dual-channel battery charging and discharging circuit, wherein the controller includes three links: a bus voltage controller, a fuzzy weighted control law, and a corresponding channel current controller, and is characterized in that: The specific steps include: 1) The bus voltage sampling signal output by the charge and discharge circuit and the bus voltage given signal are sent to the subtractor together. The bus voltage error signal generated by the subtractor is sent to the bus voltage controller, and the bus voltage controller outputs the battery pack discharge current reference signal; 2) The battery pack discharge current reference signal and the battery pack voltage sampling signal of each channel are sent to the fuzzy weighted control law to obtain the battery pack discharge current reference signal of each channel. The battery pack discharge current reference signal of each channel and the corresponding battery pack current sampling signal are sent to the subtractor to generate the battery pack current error signal of each channel and send it to the corresponding current controller to generate the control signal of each channel; 3) The control signal of each channel is used as a modulation wave to compare with the carrier signal in the PWM modulator to generate a duty cycle signal, which is then controlled by the drive circuit to turn on and off the switch tube in the charge and discharge circuit; The implementation of the fuzzy weighted control law specifically includes a fuzzy controller and a weighted law: the inter-channel battery pack voltage error obtained by subtracting the 1# channel battery pack voltage sampling signal from the 2# channel battery pack voltage sampling signal The error is sent to the fuzzy controller, and the change rate error of the battery pack voltage between channels is obtained by subtracting the change rate of the battery pack voltage of channel 1 from the change rate of the battery pack voltage of channel 2. The fuzzy controller outputs a weighted coefficient increment, and the weighted coefficient increment is used to obtain the weighted coefficient required for calculating the battery pack discharge current reference signal of each channel through the weighted law. The weighted coefficient is multiplied by the battery pack discharge current reference signal output by the bus voltage controller to obtain the battery pack discharge current reference signal of each channel; The weighting law is implemented by the following formula: ； In the formula and They are the initial weighting coefficients of the battery pack discharge current reference signals of channel 1# and channel 2#, and They are the initial voltage sampling signals of the battery pack of channel 1# and channel 2# respectively; ； In the formula and They are the current weighting coefficients of the battery pack discharge current reference signals of channel 1# and channel 2#, and They are the weighting coefficients of the last battery pack discharge current reference signal of channel 1# and channel 2#, is the weighted coefficient increment output by the fuzzy controller.

2. The control method of the fuzzy weighted controller of the dual-channel battery charging and discharging circuit according to claim 1 is characterized in that: The fuzzy control rule design method of the weighted coefficient increment specifically includes: if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive When the negative is large, the weighting coefficient increment Take 0; if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive When positive, the weighting coefficient increment Take the larger positive value; if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive Negative hours, the weighting coefficient increment Take the smaller positive value; if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive When the positive hour is Take the larger positive value; if the battery pack voltage error between the two channels When the voltage change rate error of the battery pack between channels is positive is 0, the weighting coefficient increment Take the positive value; when the battery pack voltage error between the two channels When positive is small, it is 0, and when negative is large, it is small, and so on. Follow the above idea and make analogies.

3. The control method of the fuzzy weighted controller of the dual-channel battery charging and discharging circuit according to claim 1 is characterized in that: The fuzzy weighted control law performs fuzzy weighted distribution on the battery pack discharge current reference signal output by the bus voltage controller according to the sampling signal of the battery pack voltage of each channel, and obtains the battery pack discharge current reference signal of the corresponding channel current controller. The control signal output by the corresponding channel current controller is used as the modulation signal of the PWM modulator. The pulse control signal generated by the PWM modulator is then used to control the on and off of the switch tube in the charging and discharging circuit after passing through the driving circuit, thereby realizing adaptive adjustment of the discharge current of the battery pack of each channel according to the battery performance and achieving bus voltage stability.

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