Control method of multi-channel battery charging and discharging system

Abstract

The present invention provides a control method for a multi-channel battery charging and discharging system, comprising: determining a power-on sequence through DC / AC unit parameters, and determining the number and order of starting DC / AC units according to the power-on sequence; collecting current and voltage parameters on the input side of the DC / AC unit, calculating a bus voltage reference value according to the parameters, and calculating a modulation voltage; a DC / DC module collecting bus voltage and current parameters, determining an output mode that should be currently adopted, and collecting input battery voltage, and entering a corresponding mode for output according to a charging and discharging instruction and a current battery voltage. In the control method for a multi-channel battery charging and discharging system of the present invention, the DC / AC module determines the operating state of each channel by monitoring the relevant parameters of the voltage and current of each connected channel, so that the operating state can be regulated according to the actual situation of each channel, thereby realizing the management of multiple channels, and can control the channel to output in a corresponding manner according to the instruction.

Description

[Technical field]

[0001] The present invention relates to the technical field of battery testing, and in particular to a control method for a multi-channel battery charging and discharging system. [Background technology]

[0002] With the rise of electric vehicles, the demand for power batteries is gradually increasing. The demand for high-power battery charging and discharging test systems from major power battery manufacturers is also gradually increasing, so the power requirements for the power supply and load used in the test are also increasing. However, the output power of traditional battery charging and discharging equipment is limited. For high-voltage and high-current batteries, it can only work in a constant power mode, which cannot meet the full-power test requirements of constant voltage and constant current for batteries. Therefore, a battery charging and discharging system that can control the channel more accurately is needed. [Summary of the invention]

[0003] In order to solve the above problems existing in the prior art, the present invention proposes a control method for a multi-channel battery charging and discharging system. The system achieves capacity expansion by connecting multiple DC / AC units in parallel and then connecting multiple DC / DCs in parallel and then in series. At the same time, the system can adjust the output mode of the DC / AC module in real time according to instructions and current voltage and current parameters to meet different test requirements such as constant voltage and constant current of the battery.

[0004] A control method for a multi-channel battery charging and discharging system, comprising:

[0005] Determine a power-on sequence by using DC / AC unit parameters, and determine the number and order of starting the DC / AC units according to the power-on sequence;

[0006] Collecting current and voltage parameters at the input side of the DC / AC unit, calculating a bus voltage reference value according to the parameters, and calculating a modulation voltage through the bus voltage reference value;

[0007] The DC / DC module collects bus voltage and current parameters, determines the constant current and voltage limiting output mode that should be used, and collects the input battery voltage, and enters the corresponding mode for output according to the charge and discharge instructions and the current battery voltage.

[0008] Furthermore, the step of determining the power-on timing sequence by parameters includes:

[0009] Obtain the parallel parameters of the current DC / AC unit and compare them with the preset maximum parallel number;

[0010] If the comparison result is that the two are the same, then further check whether the current DC / AC unit meets the startup conditions. If not, stop running;

[0011] If the comparison result shows that the two are different, the current DC / AC unit is controlled to stop running.

[0012] Furthermore, the step of detecting whether the DC / AC unit meets the startup conditions includes:

[0013] The DC / AC unit enters the self-check state to detect whether the parameters obtained by the acquisition unit meet the power-on conditions. If so, the timer T is started;

[0014] The bus voltage output value is detected by the acquisition unit, and it is determined whether the bus voltage output value is greater than a preset startup voltage threshold. If it is determined that the bus voltage output value is greater than the startup voltage threshold, it is detected within a preset timer T whether the number of modules currently running in the DC / AC unit is equal to the maximum parallel number;

[0015] If the number of currently running modules is equal to the maximum parallel number, it is determined that the current DC / AC unit enters the running state.

[0016] Furthermore, the step of collecting the current and voltage parameters of the input side of the DC / AC unit, calculating the bus voltage reference value according to the parameters, and calculating the modulation voltage when the DC / AC module is started includes:

[0017] Acquire the current and voltage parameters of the input side through the acquisition unit, and calculate the bus voltage reference value according to the current and voltage parameters;

[0018] The current and voltage parameters of the input side are acquired through the acquisition unit, and the bus voltage reference value is calculated according to the current and voltage parameters, the modulation voltage is calculated through the bus voltage reference value, and the DC / AC module is controlled to connect to the grid and output at the bus voltage;

[0019] The control unit generates a PWM wave according to the modulation voltage, controls the DC / AC module to connect to the grid and outputs a bus voltage that is the same as the bus voltage reference value.

[0020] Furthermore, the step of collecting bus voltage and current parameters by the DC / DC module and determining the output mode to be currently adopted includes:

[0021] The DC / DC module collects the bus voltage value and compares it with the preset second startup voltage threshold. If the bus voltage value is less than the preset second startup voltage threshold, the control channel turns off the switch and stops running;

[0022] If the bus voltage value is greater than or equal to the preset second startup voltage threshold, the DC / DC module completes the soft start process according to the current battery voltage control channel;

[0023] The DC / DC module compares the current battery back-end voltage with the preset voltage lower limit; if the back-end voltage is greater than the preset voltage lower limit, the corresponding channel is controlled to enter the constant voltage and current limiting operation mode, otherwise the corresponding channel is controlled to enter the constant current and voltage limiting operation mode.

[0024] In the control method of the multi-channel battery charging and discharging system of the present invention, the control unit determines the operating state of each channel by monitoring the relevant parameters of the voltage and current of each module and each channel, so as to adjust the operating state according to the actual situation of each channel and realize the management of multiple channels. And according to the instruction, the control channel can output in a corresponding manner.

Brief Description of the Drawings

[0025] Figure 1 A schematic diagram of the system composition structure of a control method for a multi-channel battery charging and discharging system of the present invention;

[0026] Figure 2 FIG. 1 is a flow chart of the steps of a first embodiment of a control method for a multi-channel battery charging and discharging system of the present invention. [Specific implementation method]

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0028] It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings. In addition, the embodiments in this application and the features in the embodiments may be combined with each other without conflict.

[0029] The structural schematic diagram of the multi-channel battery charging and discharging system of the present invention is shown in FIG. Figure 1 , 4 DC / AC modules are connected in parallel on the AC side and the input side is connected to the grid through an industrial frequency isolation transformer, and the DC side is connected in parallel on the output side to form a DC / AC unit. The DC / AC unit is connected in series with a 4-channel DC / DC module converter to form a two-stage bidirectional charge and discharge test system, which receives control instructions from the intermediate computer through the communication bus.

[0030] Reference Figure 2 The first embodiment of the present invention provides a control method for a multi-channel battery charging and discharging system, comprising:

[0031] Step S10, determining a power-on sequence by using DC / AC unit parameters, and determining the number of DC / AC unit startups according to the power-on sequence;

[0032] Specifically, the power-on sequence is determined by calculation, and the power-on sequence and the number of DC / AC units that are finally started are determined based on the voltage, current, temperature and other parameters of the DC / AC module obtained by the acquisition unit, as well as the number of DC / AC units in parallel that the DC / AC module can support.

[0033] Step S20, collecting current and voltage parameters at the input side of the DC / AC unit, calculating a bus voltage reference value according to the parameters, and calculating output parameters of the DC / AC module.

[0034] Specifically, the DC / AC module collects input AC voltage and current, performs Park transformation based on the fundamental positive sequence components of voltage and current, and finally calculates the bus voltage reference value. The bus voltage reference value is compared with the preset thresholds of various voltage parameters to calculate the specific output parameters of the DC / AC module.

[0035] Step S30, controlling the output mode of the channel through bus voltage and current parameters.

[0036] Specifically, the bus voltage is compared with a preset startup voltage setting value, and whether the module is powered on, the state at startup, and the number of channels in operation are determined based on the comparison result.

[0037] The DC / AC module first needs to determine the power-on sequence of each DC / AC unit in the module. The DC / AC module obtains the maximum parallel number N that the currently connected DC / AC units can support. m , and then obtain the current number of DC / AC units in parallel N through polling c To ensure the accuracy of information, the polling times are set to 3N. m Then N c With N m When the comparison is performed and the current DC / AC parallel number is detected to be the maximum, a self-test is performed. The self-test is to collect the corresponding voltage, current, temperature and other related parameters through the acquisition unit to determine whether the current unit is faulty. The DC / AC module will send a power-on command to the DC / AC unit that has passed the self-test and start the power-on timer T1. Otherwise, it is determined that the current DC / AC unit does not meet the operating conditions.

[0038] The DC / AC unit that receives the power-on command first collects relevant parameters such as voltage, current, and temperature through the corresponding acquisition unit and performs self-checking. After the relevant parameters meet the power-on conditions, it then determines whether to enter the operating state based on the current DC / AC unit bus voltage and whether the number of parallel DC / AC units meets the conditions. If the current DC / AC unit does not meet the operating conditions, it stops running. In this way, the operating status and power-on sequence of each DC / AC unit in the DC / AC module can be determined.

[0039] After determining the power-on sequence, the final channel output mode needs to be determined by determining the output parameters. First, the bus voltage reference value needs to be calculated. In order to obtain a more accurate bus voltage reference value, the AC voltage and current on the input side need to be detected during calculation, and then the fundamental positive sequence components of the voltage and current are extracted. Then, the fundamental positive sequence components are transformed by Parker, and the result is calculated with the initial reference value of the bus voltage to obtain the bus voltage reference value. The formula is: U ref =U ref0 +k dp I' d .

[0040] After the bus voltage reference value is calculated, the current bus voltage output value is obtained through the acquisition unit, and the difference between the two is calculated to obtain the bus voltage error value. The bus voltage error value is compared with the preset first error threshold. If the current error value is large, the current bus voltage output value is obtained, the current output value is calculated, and the current instantaneous output power P is further calculated. bus The DC / AC module obtains the input AC voltage V through the acquisition unit. ab 、V bc 、V ca , according to V ab 、V bc 、V ca Calculate the current maximum AC voltage V max , through P and V, with the formula Calculate the current bus voltage outer loop integral feedforward value U Ifb , and then according to the formula Calculate the current bus voltage outer loop output value I * d The DC / AC module obtains the current bus voltage output value U through the data acquisition unit. bus , according to the bus voltage reference value U ref Design of voltage outer loop based on PI control and The electricity The output value of the outer pressure loop is used as the reference value of the active current component of the inner current loop. * q， formula The DC / AC module sets the current reactive power factor value Ф ref , calculate the reactive current component reference value I of the current inner loop * q . formula

[0041] The DC / AC module uses the active energy component of the current inner loop as reference I * d And the current reactive current component reference value I * q, and the current I a ,I b ,I c Perform DQ transformation to get I d ,I q Design the current inner loop based on PI control + real-time grid voltage positive sequence component feedforward, and its output is V md 、V mq The control unit generates a PWM wave according to the modulation voltage, and controls the DC / AC module to connect to the grid and output a bus voltage that is the same as the bus voltage reference value through the PWM wave. md 、V mq And perform DQ inverse transformation and then use the third harmonic injection method to obtain SVPWM to obtain the modulation voltage V ma 、V mb 、V mc Ultimately controls the output of the DC / AC module.

[0042] The control method of the multi-channel battery charging and discharging system of the present invention measures various parameters of the DC / AC module and compares and analyzes them with corresponding preset parameters, thereby judging the current operating environment of the DC / AC module. And according to the obtained comparison results, the operating state of the DC / AC module is adjusted, or the DC / AC unit in the DC / AC module is precisely controlled. Thus, the DC / AC module works in an output mode that meets the use requirements, including a constant current and constant voltage output mode.

[0043] Step S10 of determining the power-on sequence by using the DC / AC unit parameters includes:

[0044] Step S11, obtaining the current parallel parameters of the DC / AC modules and comparing them with the preset maximum parallel number.

[0045] Step S12: if the two are the same, then check whether the DC / AC module meets the startup conditions, if not, then stop running;

[0046] Step S13: if the two are different, stop the operation.

[0047] Specifically, the voltage, current, temperature and other operating parameters collected by the DC / AC module can determine whether the DC / AC module meets the conditions required for startup. The startup state of the DC / AC module is determined based on the comparison result between the connected parallel number and the preset parallel number.

[0048] In order to ensure the safe and efficient operation of the DC / AC module, it is necessary to perform detection before operation, including collecting data such as voltage, current, and temperature. The DC / AC module controls the corresponding DC / AC unit to start only after the startup conditions are met. The DC / AC module detects the current parallel number N1 of the current DC / AC unit and compares it with the preset maximum parallel number N2. If N1 is equal to N2 and the parameters meet the operation requirements, it is determined that the DC / AC unit meets the startup conditions and controls the DC / AC unit to start and run. By collecting the operating parameters of the DC / AC unit through the acquisition module, it can quickly and conveniently determine whether the current state of the DC / AC unit needs to be started.

[0049] Step S12, after the step of detecting whether the DC / AC unit meets the startup condition, includes:

[0050] Step S14, the DC / AC unit enters a self-check state to detect whether the parameters acquired by the acquisition unit meet the power-on conditions, and if so, starts the timer T;

[0051] Step S15, detecting whether the bus voltage output value is greater than the preset startup voltage threshold value, if so, entering the parallel operation state, and at the same time, whether the number of modules running within the time period set by the timer T is equal to the maximum parallel number;

[0052] Step S16: If the number of currently running modules is equal to the maximum parallel number, it is determined that the DC / AC enters the running state.

[0053] Specifically, in order to further determine the power-on sequence and normal operation of the DC / AC units in the DC / AC module, the DC / AC units that meet the startup conditions also need to determine whether to start running by detecting the bus voltage output value and whether the number of modules running within the set timer time is the maximum parallel number.

[0054] After the DC / AC unit meets the startup conditions, it first needs to detect the bus voltage output value and determine whether the bus voltage output value is greater than the preset startup voltage threshold. If the bus voltage output value is not greater than the startup voltage threshold, the current DC / AC unit is controlled to stop running. Then determine whether the number of modules currently entering the running state is the same as the maximum parallel number supported by the current DC / AC unit. If they are the same, the DC / AC unit is determined to enter the running state, thereby determining the power-on timing of each unit in the DC / AC module.

[0055] Furthermore, in step S20, the step of calculating the output parameters of the DC / AC module includes:

[0056] Step S21, obtaining the current and voltage parameters of the input side through the acquisition unit, and calculating the bus voltage reference value according to the current and voltage parameters, obtaining the modulation voltage through the bus voltage reference value, and controlling the DC / AC module to connect to the grid and output at the bus voltage;

[0057] Step S22: The control unit generates a PWM wave according to the modulation voltage to control the DC / AC module to connect to the grid and output a bus voltage that is the same as the bus voltage reference value.

[0058] Specifically, by measuring the bus point reference value, and then measuring and calculating the output voltage, output power and other parameters, the calculation of the bus voltage reference value requires measuring the AC voltage and current, and is calculated based on the fundamental positive sequence component and the Parker transformation (DQ transformation). After calculating the bus voltage reference value, the bus voltage reference value is used to calculate the filtered output voltage, instantaneous output power, and bus outer loop output value using the corresponding calculation formula. And the modulation voltage is finally obtained through the corresponding formula calculation, and the DC / AC module is controlled to output according to the modulation voltage.

[0059] The DC / AC module obtains the input AC side voltage V through the data acquisition unit ab 、V bc 、V ca , current I a ,I b ,I c The DC / AC module uses the following method to extract the fundamental positive sequence component V' of voltage and current when in operation: ab , V′ bc , V′ ca , I′ a , I′ b , I′ c . And the current fundamental positive sequence component V′ ab , V′ bc , V′ ca , I′ a , I′ b , I′ c Perform DQ transformation to obtain V′ d , V′ q , I′ d , I′ q The calculation formula is:

[0060] Where k is the gain coefficient; w is the input frequency value; s is the complex frequency.

[0061] The DC / AC module sets the initial reference value of the bus voltage according to the current setting U ref0 And the current AC input side current fundamental positive sequence active component I' dCalculate the bus voltage reference value U corresponding to the output current in the current operating state ref The formula is: U ref =U ref0 +k dp I' d .

[0062] Then the DC / AC module collects the current bus voltage output value U bus , calculate U ref with U bus The difference between the two gives the error value U err , and compares it with the preset first error threshold, and according to different results, uses different methods to calculate the current reactive current component reference value I * q .

[0063] If U err If the error is greater than the first error threshold, the DC / AC module obtains the current bus voltage and current output value U through the data acquisition unit. bus ,I bus According to the current bus voltage output value U bus , calculate the current bus voltage output value U bus The filtered output value U′ bus , according to the current bus voltage output value U′ bus ,I bus Calculate the current instantaneous output power P bus The DC / AC module obtains the input AC side voltage V through the data acquisition unit ab 、V bc 、V ca , according to the current V ab 、V bc 、V ca Calculate the current maximum AC voltage V max , the DC / AC module outputs power P according to the current instantaneous bus And the current maximum AC voltage V max , calculate the current bus voltage outer loop integral feedforward value U Ifb , according to the current bus voltage outer loop integral feedforward value U Ifb , calculate the current bus voltage outer loop output value I*d root as the current inner loop reference value. The calculation formula is:

[0064] Where W c is the cut-off frequency value; K P is the proportionality coefficient; K fb is the feedback coefficient; s is the complex frequency.

[0065] If U erris less than the first error threshold, the DC / AC module obtains the current bus voltage output value U through the data acquisition unit. bus , according to the bus voltage reference value U ref Design a voltage outer loop based on PI control and use the output value of the voltage outer loop as the reference value I*q of the active current component of the current inner loop. The DC / AC module sets the value Ф according to the current reactive power factor. ref , calculate the reactive current component reference value I*q of the current inner loop. The calculation formula is:

[0066]

[0067] The DC / AC module uses the current inner loop active power component reference I*d and the current reactive current component reference value I*q as well as the current current I a ,I b ,I c Perform DQ transformation to get I d ,I q Design the current inner loop based on PI control + real-time grid voltage positive sequence component feedforward, and its output is V md 、V mq According to the output V of the current loop md 、V mq And perform DQ inverse transformation and then use the third harmonic injection method to obtain SVPWM to obtain the modulation voltage V ma 、V mb 、V mc The modulation voltage is calculated by the bus voltage reference value, and the DC / AC module is controlled to connect to the grid and output the bus voltage. The control unit generates a PWM wave according to the modulation voltage, controls the DC / AC module to connect to the grid and output the bus voltage that is the same as the bus voltage reference value.

[0068] Further, in step S30, the DC / DC module collects bus voltage and current parameters, and the step of determining the output mode to be currently adopted includes:

[0069] Step S31, the DC / DC module collects the bus voltage value and compares it with the preset second startup voltage threshold. If the bus voltage value is less than the preset second startup voltage threshold, the control channel closes the switch and stops running;

[0070] Step S32, if the bus voltage value is greater than or equal to the preset second startup voltage threshold, the DC / DC module completes the soft start process according to the current battery voltage control channel;

[0071] In step S33, the DC / DC module compares the battery rear end voltage with a preset voltage lower limit; if the rear end voltage is greater than the preset voltage lower limit, the corresponding channel is controlled to enter a constant voltage and current limiting operation mode; otherwise, the corresponding channel is controlled to enter a constant current and voltage limiting operation mode.

[0072] Specifically, the opening and closing of the control switch is determined by the bus voltage and the calculated current parameters, and the changing state of the bus voltage reference value within the timer time. The opening and closing of the switch controls the size of the voltage at the back end of the switch, thereby determining whether the channel operates in constant voltage or constant current mode.

[0073] The input side bus voltage and current values ​​Ubus and Ibus are collected through the data acquisition unit. After receiving the channel power-on command, the module detects whether the bus voltage is greater than the preset second power-on voltage setting threshold. The detection process continues for the preset duration T2 until it is detected to be less than or the duration ends. If it is detected that the bus voltage is always greater than the second power-on voltage setting threshold within T2, the DC / DC module enters the power-on soft start state, otherwise the operation of the DC / DC module is stopped.

[0074] After entering the soft start state, the output channel current I is collected through the data acquisition unit bat , switch C front end voltage U bat1 And the voltage U behind the switch C bat2 When the voltage U bat1 The voltage U at the back end of switch C bat2 When the difference is less than the second error setting threshold, the control switch C is closed and the channel enters the running state. After the control DC / DC module receives the charge and discharge instruction, the charge and discharge test is performed on the channel that enters the running state. The microcontroller determines the rear end voltage U bat2 Less than the upper limit of the battery voltage or the voltage U at the back end of switch C bat2 When the voltage is greater than the lower limit of the battery voltage, the channel enters the constant voltage and current limiting operation mode, otherwise the channel enters the constant current and voltage limiting operation mode.

[0075] In the control method of the multi-channel battery charging and discharging system of the present invention, the control unit determines the operating state of each channel by monitoring the relevant parameters of the voltage and current of each module and each channel, so as to adjust the operating state according to the actual situation of each channel and realize the management of multiple channels. And according to the instruction, the control channel can output in a corresponding manner.

Claims

1. A control method for a multi-channel battery charging and discharging system, characterized in that: include: Determine the power-on sequence through the DC / AC unit parameters, and determine the number and order of starting the DC / AC units according to the power-on sequence; collect the current and voltage parameters at the input side of the DC / AC unit, calculate the bus voltage reference value according to the current and voltage parameters, and calculate the modulation voltage through the bus voltage reference value; The DC / DC module collects bus voltage and current parameters, determines the constant current and voltage limiting output mode that should be used currently, collects the input battery voltage, and enters the corresponding mode for output according to the charge and discharge instructions and the current battery voltage; the step of determining the power-on timing by the DC / AC unit parameters includes: obtaining the parallel parameters of the current DC / AC unit, and comparing it with the preset maximum parallel number; If the comparison result is that the two are the same, further detect whether the current DC / AC unit meets the startup condition, if not, stop running; if the comparison result is that the two are different, control the current DC / AC unit to stop running; the step of collecting the current and voltage parameters on the input side of the DC / AC unit, calculating the bus voltage reference value according to the parameters, and calculating the modulation voltage when the DC / AC module is started includes: Acquire the current and voltage parameters of the input side through the acquisition unit, and calculate the bus voltage reference value according to the current and voltage parameters; The current and voltage parameters of the input side are acquired through the acquisition unit, and the bus voltage reference value is calculated according to the current and voltage parameters, the modulation voltage is calculated through the bus voltage reference value, and the DC / AC module is controlled to connect to the grid and output at the bus voltage; The control unit generates a PWM wave according to the modulation voltage, controls the DC / AC module to connect to the grid and output a bus voltage that is the same as the bus voltage reference value; the DC / DC module collects bus voltage and current parameters, and the steps of determining the output mode that should be currently adopted include: The DC / DC module collects the bus voltage value and compares it with the preset second startup voltage threshold. If the bus voltage value is less than the preset second startup voltage threshold, the control channel turns off the switch and stops running; If the bus voltage value is greater than or equal to the preset second startup voltage threshold, the DC / DC module completes the soft start process according to the current battery voltage control channel; The DC / DC module compares the current battery back-end voltage with the preset voltage lower limit; if the back-end voltage is greater than the preset voltage lower limit, the corresponding channel is controlled to enter the constant voltage and current limiting operation mode, otherwise the corresponding channel is controlled to enter the constant current and voltage limiting operation mode.

2. The control method of the multi-channel battery charging and discharging system as claimed in claim 1, characterized in that: The step of detecting whether the DC / AC unit meets the startup conditions comprises: The DC / AC unit enters the self-check state to detect whether the parameters obtained by the acquisition unit meet the power-on conditions. If so, the timer T is started; The bus voltage output value is detected by the acquisition unit, and it is determined whether the bus voltage output value is greater than a preset startup voltage threshold. If it is determined that the bus voltage output value is greater than the startup voltage threshold, it is detected within a preset timer T whether the number of modules currently running in the DC / AC unit is equal to the maximum parallel number; If the number of currently running modules is equal to the maximum parallel number, it is determined that the current DC / AC unit enters the running state.

Images