CN117879032A - Control method and power supply device of bidirectional direct current converter - Google Patents
Control method and power supply device of bidirectional direct current converter Download PDFInfo
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Abstract
The application relates to a control method of a bidirectional direct current converter, which provides a new control strategy for the bidirectional direct current converter, under the condition that a battery module enters a power-preserving state, the bidirectional direct current converter is not closed, only the driving of the bidirectional direct current converter is stopped, under the condition that the power failure of a power grid is detected, and the bus voltage is abnormal, the situation that the inverter is not required to wait for communication transmission of a grid-connected switching off-network signal and restart the bidirectional direct current converter as in the related art, but the normal driving of the bidirectional direct current converter is quickly restored when the power failure is detected, so that the driving of the bidirectional direct current converter can be instantly opened, the direct current bus voltage is maintained through closed-loop control, the power failure of the power grid can be ensured, the inverter cannot be shut down due to overlong grid-connected switching off time, the load is in a state of running all the time, and the user experience is improved.
Description
Technical Field
The application belongs to the technical field of power electronics, and particularly relates to a control method of a bidirectional direct current converter, a power supply device and a computer readable storage medium.
Background
With the gradual maturity of lithium battery and photovoltaic module technology and the reduction of production cost, more and more families begin to install household photovoltaic energy storage systems, and after the systems are installed, certain electric charge can be saved for families, and short-term electric power support can be provided in areas with unstable power grids. The system stores photovoltaic energy through the energy storage equipment, a household uses the power grid to supply power when the power is used in a valley, and uses the energy storage equipment to supply power when the power is used in a peak, so that the power consumption peak is staggered, the power consumption in the actual region is more uniform in time for the power grid, the power consumption of the power grid in the peak period of the region, the capacity of a transformer and the maximum required power are reduced, the electricity price and the basic electricity price can be reduced simultaneously, the carbon emission is reduced, and the running efficiency of the power grid is improved.
The common household photovoltaic energy storage system needs to dispatch photovoltaic power when grid connection, on one hand, the battery is charged, and on the other hand, the household load is powered. When the power grid fails and the region fails, the power grid needs to be switched into an off-grid mode rapidly, and the energy of the energy storage equipment is utilized to support the household load to normally operate when the power grid fails. In order to cope with possible power failure risks, a State of Charge (SOC) is usually set in the household photovoltaic energy storage system, when the power grid is normal and the power quantity of the energy storage device is lower than the SOC, the energy storage device is not discharged any more, and if a power failure occurs, the remaining power quantity of the energy storage device can be discharged again for household use. Conventional household photovoltaic energy storage systems typically enter a power-conserving state when the power value of the energy storage device consumes a power-conserving power, so as to reserve the remaining power for the energy storage device to support subsequent self-starting of the photovoltaic off-grid system. However, as a certain time is needed for the energy storage device to enter off-grid discharge from the power-preserving state during grid connection, in the process from power failure of the power grid to restarting of the energy storage device, the household electric equipment can be automatically powered off due to power loss, and the use experience of the photovoltaic energy storage system is affected.
Disclosure of Invention
The invention aims to provide a control method, a power supply device and a computer readable storage medium of a bidirectional direct current converter, and aims to solve the problem that in the related art, a load is shut down and restarted in the process of switching grid connection to off-grid.
In a first aspect, embodiments of the present application provide a control method of a bidirectional dc converter, where the bidirectional dc converter includes a first end and a second end, the first end is used to connect to a battery module, the second end is used to connect to a dc bus of an inverter, and an ac end of the inverter is used to connect to a power grid and/or a load, and the control method includes:
when the inverter is in a grid-connected state and the electric quantity of the battery module is larger than a power-saving threshold value, the bidirectional direct current converter is controlled to work in a charging mode or a discharging mode according to a preset regulation strategy; the battery module is charged by the direct current bus through the bidirectional direct current converter in a charging mode, and the battery module is discharged to the direct current bus through the bidirectional direct current converter in a discharging mode;
stopping driving the bidirectional direct current converter to work under the condition that the electric quantity of the battery module is smaller than or equal to the electricity-keeping threshold value and the bidirectional direct current converter does not work in a charging mode;
And under the condition that the power failure of the power grid is detected, restoring to execute the preset regulation strategy to control the bidirectional direct current converter to work in a charging mode or a discharging mode.
In one embodiment, the controlling the bidirectional dc converter to operate in a charging mode or a discharging mode according to a preset regulation strategy further includes:
performing first amplitude limiting treatment on the initial given current to obtain a first given current; wherein the first given current causes the bi-directional dc converter to transfer power from the first end to the second end or causes the bi-directional dc converter to transfer power from the second end to the first end;
and generating a driving signal according to the first given current and the actual output current of the bidirectional direct current converter to drive the bidirectional direct current converter to work.
In one embodiment, the method further comprises:
under the condition that the electric quantity of the battery module is smaller than or equal to a power-keeping threshold value, performing second limiting treatment on the initial reference current to obtain a second given current; wherein the second given current causes the bi-directional dc converter to transfer power from the second end to the first end or causes the bi-directional dc converter to not transfer power from the first end to the second end;
And under the condition that the bidirectional converter works in a charging mode, generating a driving signal according to the second given current and the actual output current of the bidirectional direct current converter to drive the bidirectional direct current converter to work.
In one embodiment, when the electric quantity of the battery module is less than or equal to a power-keeping threshold and the bidirectional dc converter is not operated in the charging mode, stopping driving the bidirectional dc converter includes:
and stopping generating a driving signal to stop driving the bidirectional direct current converter to work under the condition that the electric quantity of the battery module is smaller than or equal to a power-keeping threshold value and the bidirectional direct current converter does not work in a charging mode.
In one embodiment, the method further comprises:
acquiring a given voltage;
and obtaining an initial reference current according to the given voltage and the actual output voltage.
In one embodiment, the method further comprises:
after the bidirectional DC converter is started, the given voltage is controlled to gradually increase from 0 to a target voltage.
In one embodiment, the obtaining the initial reference current from the given voltage and the output voltage includes:
Obtaining the output voltage of the bidirectional direct current converter;
and calculating according to the voltage difference between the output voltage and the given voltage to obtain an initial reference current.
In one embodiment, the generating a drive signal based on the first given current and an actual output current of the bi-directional dc converter includes:
acquiring the actual output current of the bidirectional direct current converter;
calculating to obtain a duty ratio according to the current difference between the actual output current and the first given current;
the drive signal is generated based on the duty cycle.
In a second aspect, an embodiment of the present application further provides a power supply device, including a bidirectional dc converter, a memory, a processor, and a computer program stored in the memory and executable on the processor, where the bidirectional dc converter includes a first end and a second end, the first end is used to connect to a battery module, the second end is used to connect to a dc bus of an inverter, an ac end of the inverter is used to connect to a power grid and/or a load, and the processor implements the steps of the control method of the bidirectional dc converter when executing the computer program.
In a third aspect, embodiments of the present application further provide a computer readable storage medium storing a computer program, where the computer program when executed by a controller may implement the steps of the control method of a bidirectional dc converter as described above.
Compared with the related art, the embodiment of the application has the beneficial effects that: according to the control method of the bidirectional direct current converter, a new control strategy is provided for the bidirectional direct current converter, under the condition that a battery module is kept powered, the bidirectional direct current converter is not closed, only the driving of the bidirectional direct current converter is stopped, when the power failure of a power grid is detected, under the condition that the bus voltage is abnormal, the situation that the inverter is required to wait for communication transmission of a grid-connected switching off-network signal and restart the bidirectional direct current converter in the related art is avoided, and the normal driving of the bidirectional direct current converter is immediately restored when the power failure of the power grid is detected, so that the driving of the bidirectional direct current converter can be instantly opened, the direct current bus voltage is maintained through closed-loop control, the inverter cannot be shut down due to overlong grid-connected switching off-network time in the power grid losing process, the load is in a state of running constantly, and the user experience is improved.
Drawings
Fig. 1 is a schematic structural diagram of a photovoltaic energy storage system according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a battery pack according to an embodiment of the present disclosure;
FIG. 3 is a flow chart of a control method of a bi-directional DC converter according to an embodiment of the present disclosure;
FIG. 4 is a flowchart of a control method of a bi-directional DC converter according to an embodiment of the present disclosure;
FIG. 5 is a control loop diagram of a control method of a bi-directional DC converter according to an embodiment of the present disclosure;
FIG. 6 is a flowchart of a control method of a bi-directional DC converter according to an embodiment of the present disclosure;
fig. 7 is a flowchart of a control method of a bidirectional dc converter according to an embodiment of the present application;
fig. 8 is a schematic block diagram of a control device of a bidirectional dc converter according to an embodiment of the present disclosure;
fig. 9 is a schematic structural diagram of a power supply device according to an embodiment of the present disclosure.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the present application and simplify description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be configured and operated in a particular orientation, and therefore should not be construed as limiting the present application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
As shown in fig. 1, a general household photovoltaic energy storage system is composed of a photovoltaic panel PV, an inverter INV, and one or more battery PACKs PACK1 to PACK3. The photovoltaic panel PV is connected to a PV input port of the inverter INV, one or more battery PACKs PACK 1-PACK 3 form energy storage equipment and are connected to a direct current bus of the inverter INV, and an alternating current end of the inverter INV is externally connected with a GRID and a LOAD. The data is communicated between the different devices through a CAN (Controller Area Network) bus.
The photovoltaic panel PV is mainly responsible for converting solar energy into electric energy, and is formed by connecting photovoltaic panel assemblies in series and parallel. The inverter INV integrates the functions of grid-connected photovoltaic power generation, energy storage and grid off, can overcome the defect of unstable output power caused by the change of external natural conditions of the photovoltaic panel PV, provides stable and pure current with small total harmonic distortion (Total Harmonic Distortion, THD) for a power grid/load, and improves the power quality of power supply to the power grid/load. The battery PACK is used as energy storage equipment, on one hand, the electric energy generated by the photovoltaic panel PV solar energy is stored, and on the other hand, the electric energy can be taken from a power grid for storage when the electricity price is lower.
The block diagram inside the PACK is shown in fig. 2, and the electric energy stored in the electric core is supplied to the inverter INV through the bidirectional direct current converter to be used by the LOAD, or fed to the GRID to earn benefits, or the electric energy provided by the photovoltaic panel PV and/or the electric energy of the low-price GRID is converted into the appropriate voltage and current to be stored in the electric core. Referring to fig. 1 and 2, the bi-directional dc converter includes a first end LV for connecting a battery module (e.g., a battery cell), and a second end HV for connecting to a dc bus of an inverter INV, an ac end of the inverter INV for connecting to a GRID and/or a LOAD.
In general, the total capacity of the battery PACK can be composed of normal electric quantity used normally and electric quantity which is not used in a grid-connected state, and the proportion of the electric quantity to the total capacity can be set by a user according to the self requirement.
When the GRID of the power GRID is normally connected (namely connected), when the conventional electric quantity of the energy storage equipment is exhausted and no energy is charged, the energy storage equipment enters a shutdown state, each control link of the bidirectional direct current converter in the battery PACK PACK is not calculated any more, the running data is cleared, the bidirectional direct current converter enters the shutdown state, and the battery PACK PACK enters a power-preserving mode. When the battery PACK is in a power-keeping state, the voltage of the direct current bus is not continuously discharged and maintained in a designed range, so when the power GRID is stopped to supply power (such as power GRID faults, disconnection from the power GRID and the like), the inverter INV cannot acquire energy from the power GRID and cannot acquire energy from the direct current bus to maintain LOAD operation, the system is stopped, the inverter INV waits for transmitting a power GRID fault switching off-network signal to the battery PACK through CAN bus communication, then the battery PACK is restarted, the voltage of the direct current bus is maintained in a normal operation range of the system again, and then the inverter INV is restarted to supply power to the LOAD, so that off-network switching is completed.
When the battery enters from GRID-connected power-preserving state to off-GRID discharging state, the bidirectional direct current converter is restarted from a shutdown state, enters soft start and then jumps to an operation state, so that a user can experience the situation that the LOAD is completely powered off from the power failure of the GRID until the LOAD resumes power supply by using the power-preserving electric quantity.
Referring to fig. 3, an embodiment of the present application provides a control method of a bidirectional dc converter, which includes:
step S110, when the inverter is in a grid-connected state and the electric quantity of the battery module is larger than the electricity-keeping threshold value, controlling the bidirectional direct current converter to work in a charging mode or a discharging mode according to a preset regulation strategy; the battery module is charged by the direct current bus through the bidirectional direct current converter in the charging mode, and is discharged by the bidirectional direct current converter in the discharging mode.
In one example, under a preset regulation strategy, in a normal GRID-connected operation process, under the condition that the electricity price of the GRID is high and the photovoltaic panel PV power is insufficient to support LOAD operation, the battery module actively bears the power consumption of the LOAD by utilizing conventional electric quantity, namely, in a discharging mode, the battery module discharges to a direct current bus through a bidirectional direct current converter so as to supply power to the LOAD through the inverter INV. And under the condition that the power price of the GRID is low, the photovoltaic panel PV power is insufficient to support the LOAD to operate, the power consumption of the LOAD can be borne by the GRID, and the battery module is charged. Alternatively, in case the photovoltaic panel PV power is more than the power required for LOAD operation, the excess power may be used to charge the battery module or to sell electricity by feeding the GRID through the inverter INV. In the charging mode, the power GRID electrically rectifies the alternating current of the power GRID through the inverter INV to output direct current to a direct current bus, or the photovoltaic panel PV outputs direct current to the direct current bus after MPPT (Maximum Power Point Tracking ) is performed through the inverter INV, and the direct current bus charges the battery module through the bidirectional direct current converter.
In one example, when the electric quantity of the battery module is greater than the electricity-keeping threshold, the preset regulation policy may be regarded as charge-discharge control of the battery module by the conventional bidirectional dc converter, which is not limited herein.
In step S120, when the electric quantity of the battery module is less than or equal to the power-keeping threshold and the bidirectional dc converter is not operating in the charging mode, the bidirectional dc converter is stopped.
When the inverter is in a GRID-connected state and the conventional electric quantity of the battery module is exhausted, the battery module does not output electric energy to supply power to a LOAD, and the residual electricity-keeping electric quantity is not discharged under the condition that the GRID is normal. Therefore, when the bidirectional DC converter is not in the charging mode, the bidirectional DC converter is stopped to be driven to work, so that the electricity-retaining quantity of the battery module is prevented from being consumed.
Wherein, stopping driving the bidirectional dc converter means stopping outputting a driving signal (e.g., PWM wave) to the bidirectional dc converter, and not completely closing the bidirectional dc converter, the loop control is still running, the internal relay is in a closed state, and the charge/discharge circuit is kept on, i.e., the battery module is in an active state. Therefore, only when the output of the drive signal to the bidirectional dc converter is stopped and the other modules of the battery module, such as the controller, remain in operation, the output of the drive signal to the bidirectional dc converter can immediately output power when the battery module needs to operate.
The two-way direct current converter is closed and the two-way direct current converter is stopped to be driven to work differently, and after the two-way direct current converter is closed, the battery module is already closed, so that after the GRID power fails, the energy storage equipment needs a certain starting time to restart the battery module, and therefore the LOAD can be automatically closed due to power supply loss, and the use experience of the photovoltaic energy storage system is affected.
And step S130, under the condition that the power failure of the power grid is detected, the preset regulation strategy is restored to be executed so as to control the bidirectional direct current converter to work in a charging mode or a discharging mode.
And when the GRID is abnormal, the electricity-retaining quantity is used for maintaining LOAD power supply. Because, when the GRID is normal, even if the battery module enters the power-keeping state, the battery module is not shut down, and only the bidirectional DC converter in the battery module is stopped to be driven to work. Therefore, when the GRID is abnormal, the energy storage device outputs the driving signal again to drive the bidirectional direct current converter to work, so that the battery module can immediately output power, and at the moment, the preset regulation strategy is restored to be executed to control the bidirectional direct current converter to work in a charging mode or a discharging mode. Therefore, when the photovoltaic PV power is insufficient and the GRID is abnormal, the automatic shutdown of the LOAD due to power supply loss can be avoided, and the use experience of the photovoltaic energy storage system is improved.
Referring to fig. 4, in one embodiment, step S110 further includes:
step S112, performing a first clipping process on the initial given current to obtain a first given current.
Wherein the first given current causes the bi-directional dc converter to transfer power from the first terminal LV to the second terminal HV, i.e. the battery module is in a charged state. Alternatively, the bi-directional dc converter is caused to transfer power from the second end HV to the first end LV, i.e. the battery module is in a discharged state.
When the GRID is normal, the inverter is in a GRID-connected state, and the battery module does not enter a power-saving state. Taking the scenes shown in fig. 2, 4 and 5 as an example, under a preset regulation strategy, an initial given current is output from a first PI (proportion integration, proportional integral) controller in a voltage control loop, and to ensure that the given current is within a reasonable range, a first limiter is used to perform a first limiting process on the initial given current to obtain a first given current i ref1 . The first clipping process may be configured according to the maximum/minimum charge/discharge current of the battery module and the maximum/minimum operation current of the bi-directional dc converter (ensuring higher conversion efficiency). For example, assuming that the charging current is positive and the discharging current is negative, the first given current i may be determined from the smaller absolute value of these current parameters ref1 Lower limit value of (2): ilmt, upper limit value: ilmt.
Step S114, a driving signal is generated to drive the bidirectional DC converter to operate according to the first given current and the actual output current of the bidirectional DC converter.
In one exampleIn which the actual output current i of the first end LV of the bi-directional dc converter is sampled samp As a feedback current, the actual output current i samp With a first given current i ref1 And comparing to obtain a current deviation value, calculating by the second PI controller according to the current deviation value to obtain an output duty ratio, obtaining a duty ratio which is finally effective after the duty ratio passes through the second amplitude limiter, and generating a PWM driving signal for driving the bidirectional DC converter by the PWM modulator based on the finally effective duty ratio. The bidirectional DC converter comprises the following steps: in the charging mode, the bidirectional DC converter takes electricity from the DC bus to charge the battery module, and in the discharging mode, takes electricity from the battery module and transmits the electricity to the DC bus.
It is understood that the value of the duty cycle determines the charge-discharge voltage of the battery module, and here, the parameter configuration of the second limiter may be set according to the maximum/minimum charge-discharge voltage of the battery pack. The second limiter is provided to limit the maximum/minimum duty ratio of the loop, and to ensure that the charge/discharge voltage of the battery module does not exceed the maximum/minimum charge/discharge voltage allowed by the battery module when the loop is controlled.
Referring to fig. 6, in one embodiment, the control method further includes:
step S210, under the condition that the electric quantity of the battery module is smaller than or equal to the electricity-keeping threshold value, performing second limiting processing on the initial reference current to obtain a second given current.
In connection with fig. 2, 5 and 6, after the GRID is normal, in order to prevent the bi-directional dc converter from drawing power from the battery module after the battery module enters the power-conserving state, a given current of the bi-directional dc converter (i.e., a second given current) may be set by a second clipping process such that the bi-directional dc converter transmits power from the second terminal HV to the first terminal LV, or such that the bi-directional dc converter does not transmit power from the first terminal LV to the second terminal HV, i.e., such that the bi-directional dc converter is allowed to charge the battery module without allowing the battery module to discharge.
Specifically, the initial reference current from the output of the first PI controller in the voltage control loop is changed from the first clipping process to the second clipping process, resulting in a second given currenti ref2 . Assuming that the charging current is positive and the discharging current is negative, the second clipping process is: the lower limit value is changed to 0. After the second clipping process, the second given current must be greater than or equal to 0, and then the second given current must not be a discharge current, thereby realizing that the bidirectional direct current converter is allowed to charge the battery module, but the battery module is not allowed to discharge.
It will be appreciated that at different stages different clipping processes may be achieved by modifying the parameters of the first clipper.
Step S220, in the case that the bidirectional converter is operated in the charging mode, generating a driving signal according to the second given current and the actual output current of the bidirectional dc converter to drive the bidirectional dc converter to operate.
In one example, the actual output current i of the first end LV of the bi-directional DC converter is sampled samp As a feedback current, the actual output current i samp With a second given current i ref2 And comparing to obtain a current deviation value, calculating by the second PI controller according to the current deviation value to obtain an output duty ratio, obtaining a duty ratio which is finally effective after the duty ratio passes through the second amplitude limiter, and generating a PWM driving signal for driving the bidirectional DC converter by the PWM modulator based on the finally effective duty ratio. The bidirectional DC converter comprises the following steps: in the charging mode, electricity is taken from the direct-current bus to charge the battery module.
It will be appreciated that the value of the duty cycle determines the charging voltage of the battery module, where the parameter configuration of the second limiter may be set in dependence on the maximum/minimum charging voltage of the battery pack. The second limiter is provided to limit the maximum/minimum duty ratio of the loop, and to ensure that the charging voltage of the battery module does not exceed the maximum/minimum charging voltage allowed by the battery module when the loop is controlled.
It will be appreciated that in this embodiment, the battery module is not allowed to discharge, but is actually outputting current i samp But there may be a discharge power of the battery module, which is slowly reduced from the power normally discharged in the non-power-conserving state to around 0 but may not be exactly equal to 0. If it isAt this time, the battery module is in a charging state (the power of the battery module is positive and the charging power is greater than the threshold for determining the charging state), and the battery module is waiting for the electric quantity of the battery module to be higher than the power-keeping threshold, and the power-keeping state is exited to step S112. If the battery module is in a discharge state at this time, step 120 is entered.
In one embodiment, step S120 includes: and under the condition that the electric quantity of the battery module is smaller than or equal to the electricity-keeping threshold value and the bidirectional direct current converter does not work in the charging mode, stopping generating a driving signal to stop driving the bidirectional direct current converter to work.
According to the above embodiment, in the case where the electric quantity of the battery module is equal to or less than the power retention threshold, the second given current iref2 is set, the lower limit value: 0, upper limit value: ilmt. In this case, the bidirectional dc converter is not allowed to discharge the battery module.
Thus, referring to fig. 4, in case the bi-directional dc converter is not operating in the charging mode, the current i is actually output samp Is 0, a second given current i ref2 And the duty ratio of the output calculated by the second PI controller is zero, so that the generation of the driving signal is stopped to stop driving the bidirectional direct current converter to work, and the battery module in the power-keeping state is prevented from being overdischarged when the GRID is normal.
Referring to fig. 7, in one embodiment, the control method further includes:
step S310, a given voltage is acquired.
Step S310, obtaining initial reference current according to the given voltage and the actual output voltage.
Referring to fig. 2, 5 and 7, no matter the battery module is in a power-on state or a power-off state, the voltage control loop needs to be executed under a preset regulation strategy.
In one example, a given voltage v of the voltage control loop ref For example the target output voltage of the second terminal HV of the bi-directional dc converter. Taking the circuit in fig. 2 as an example, when the bidirectional dc converter is in a boost state, the actual output voltage v of the second terminal HV of the bidirectional dc converter needs to be sampled samp As a feedback voltage, the voltage deviation amount is compared with a given voltage vref, and the first PI controller calculates an initial reference current according to the voltage deviation amount. The output voltage of the bidirectional direct current converter is obtained, and the initial reference current is obtained through calculation according to the voltage difference between the output voltage and the given voltage.
Thereafter, step S112 or step S210 is performed according to whether the battery module is in a power-on state, thereby achieving control of charge and discharge current of the battery module.
In one embodiment, the control method further includes: after the bi-directional DC converter is started, the given voltage is controlled to gradually increase from 0 to the target voltage.
In the starting process of the bidirectional direct current converter, in order to avoid large current impact on an input or output capacitor caused by abrupt change of voltage, the output voltage of the bidirectional direct current converter can be gradually increased from 0 to a target voltage, and soft starting of the bidirectional direct current converter is completed in the processes of reducing loss and reducing current impact.
In one embodiment, step S114 includes: acquiring the actual output current of the bidirectional direct current converter; calculating to obtain a duty ratio according to the current difference between the actual output current and the first given current; a drive signal is generated based on the duty cycle.
Referring to fig. 5, the actual output current i of the first end LV of the bidirectional dc converter is sampled samp As a feedback current, the actual output current i samp With a first given current i ref1 And comparing to obtain a current difference, calculating an output duty ratio by the second PI controller according to the current difference, obtaining a duty ratio which is finally effective after the duty ratio passes through the second limiter, and generating a PWM driving signal for driving the bidirectional direct current converter by the PWM modulator based on the finally effective duty ratio so as to control the bidirectional direct current converter to work.
The photovoltaic energy storage system enters a power-preserving state when the electric quantity value of the battery module consumes the power-preserving electric quantity so as to reserve the power-preserving electric quantity for the battery module to support off-GRID operation of the photovoltaic energy storage system, but because a certain time is required for the battery module to enter off-GRID discharge from the power-preserving state when the battery module is connected with the GRID, the LOAD can be automatically shut down due to power loss in the process from GRID power failure to restarting of the equipment. According to the embodiment of the application, by designing a new control strategy, when the battery module enters the power-preserving state, the battery module is not closed, only the driving signal of the bidirectional direct current converter is closed, when the condition that the power failure of the power GRID is detected, the inverter INV is not required to wait for communication transmission of GRID-connected switching off-GRID signals, the driving signal of the bidirectional direct current converter is instantly opened, the voltage of the direct current bus of the inverter INV is maintained through closed-loop control, the battery module and the inverter INV are not powered off in the power GRID losing process, the LOAD LOAD is in a state of running constantly, and the user experience is optimized.
Referring to fig. 8, an embodiment of the present application further provides a control device of a bidirectional dc converter, including:
the first parallel control module 101 is configured to control, according to a preset regulation policy, the bidirectional dc converter to operate in a charging mode or a discharging mode when the inverter is in a grid-connected state and the electric quantity of the battery module is greater than a power-saving threshold; the battery module is charged by the direct current bus through the bidirectional direct current converter in a charging mode, and the battery module is discharged to the direct current bus through the bidirectional direct current converter in a discharging mode;
The second grid-connected control module 102 is configured to stop driving the bidirectional dc converter to operate when the electric quantity of the battery module is less than or equal to the power-maintaining threshold and the bidirectional dc converter is not operating in the charging mode;
and the off-grid control module is used for recovering to execute the preset regulation strategy to control the bidirectional direct current converter to work in a charging mode or a discharging mode under the condition that the power failure of the power grid is detected.
In one embodiment, the first parallel control module 101 includes:
the limiting module is used for carrying out first limiting treatment on the initial given current to obtain a first given current; wherein the first given current causes the bi-directional dc converter to transfer power from the first end to the second end or causes the bi-directional dc converter to transfer power from the second end to the first end;
and the driving unit is used for generating a driving signal according to the first given current and the actual output current of the bidirectional direct current converter so as to drive the bidirectional direct current converter to work.
In one embodiment:
the amplitude limiting module is further used for performing second amplitude limiting processing on the initial reference current to obtain a second given current under the condition that the electric quantity of the battery module is smaller than or equal to an electricity keeping threshold value; wherein the second given current causes the bi-directional dc converter to transfer power from the second end to the first end or causes the bi-directional dc converter to not transfer power from the first end to the second end;
The driving unit is further configured to generate a driving signal to drive the bidirectional dc converter to operate according to the second given current and an actual output current of the bidirectional dc converter in a case where the bidirectional dc converter operates in a charging mode.
In one embodiment, the second grid-tie control module 102 is specifically configured to:
and stopping generating a driving signal to stop driving the bidirectional direct current converter to work under the condition that the electric quantity of the battery module is smaller than or equal to a power-keeping threshold value and the bidirectional direct current converter does not work in a charging mode.
In one embodiment, the control device further comprises:
the acquisition module is used for acquiring a given voltage;
and the calculation module is used for obtaining initial reference current according to the given voltage and the actual output voltage.
In one embodiment, the first parallel control module 101 and the first parallel control module 101 are further configured to: after the bidirectional DC converter is started, the given voltage is controlled to gradually increase from 0 to a target voltage.
In one embodiment, the computing module includes:
the first acquisition unit is used for acquiring the output voltage of the bidirectional direct current converter;
And the first calculation unit is used for calculating an initial reference current according to the voltage difference between the output voltage and the given voltage.
In one embodiment, the driving unit includes:
the second acquisition unit is used for acquiring the actual output current of the bidirectional direct current converter;
the second calculation unit is used for calculating a duty ratio according to the current difference between the actual output current and the first given current;
and the PWM modulation unit is used for generating the driving signal based on the duty ratio.
For a specific embodiment of the control device of the bidirectional dc converter and a description of related beneficial effects, please refer to a description of a specific embodiment of the control method of the bidirectional dc converter, which is not repeated herein.
Referring to fig. 1, 2 and 9, the embodiment of the present application further provides a power supply device 90, where the power supply device 90 includes a bidirectional dc converter 91, a memory 92, a processor 93, and a computer program 921 stored in the memory 92 and capable of running on the processor 93, the bidirectional dc converter 91 includes a first end LV and a second end HV, the first end LV is used for connecting a battery module (e.g., a battery core), the second end HV is used for connecting a dc bus of an inverter INV, an ac end of the inverter INV is used for connecting to a GRID and/or a LOAD, the bidirectional dc converter 91 is further connected to the processor 93, and the processor 93 implements the steps of the control method of the bidirectional dc converter when executing the computer program 921.
It will be appreciated that the power supply 90 may be a single power device, a battery pack having a battery module 901, or an energy storage device including a plurality of battery packs having battery modules 901.
It will be appreciated by those skilled in the art that fig. 9 is merely an example of the power supply 90 and is not meant to limit the power supply 90, and may include more or fewer components than shown, or may combine certain components, or may include different components, such as input-output devices, network access devices, etc.
The processor 93 may be a central processing unit (Central Processing Unit, CPU), and the processor 93 may also be other general purpose controllers, digital signal controllers (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), off-the-shelf programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. The general purpose controller may be a microcontroller or may be any conventional controller.
The memory 92 may in some embodiments be an internal storage unit of the power supply 90 or the energy storage device, such as a hard disk or a memory of the power supply 90 or the energy storage device. The memory 92 may also be an external storage device of the power supply apparatus 90 or the energy storage device in other embodiments, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card) or the like, which are provided on the power supply apparatus 90 or the energy storage device. Further, the memory 92 may also include both an internal storage unit of the power supply 90 or the energy storage device and an external storage device. The memory 92 is used to store an operating system, application programs, boot Loader (Boot Loader), data, and other programs, etc. The memory 92 may also be used to temporarily store data that has been output or is to be output.
The present embodiment also provides a computer-readable storage medium storing a computer program 921, which computer program 921, when executed by a processor 93, implements the steps of the respective method embodiments described above.
The present embodiments provide a computer program product which, when run on a computer, causes the computer to perform the steps of the various method embodiments described above.
The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. With such understanding, the present application implements all or part of the flow of the above-described method embodiments, and may be implemented by a computer program 921 for instructing relevant hardware, the computer program 921 being stored in a computer readable storage medium, the computer program 921, when executed by the processor 93, implementing the steps of the above-described method embodiments. The computer program 921 includes, among other things, computer program 921 code, which may be in source code form, object code form, executable file or some intermediate form, etc. The computer readable medium may include at least: any entity or device capable of carrying the computer program 921 code to a photographing device/terminal apparatus, a recording medium, a computer Memory 92, a ROM (Read-Only Memory 92), a RAM (Random Access Memory, random access Memory 92), a CD-ROM (Compact Disc Read-Only Memory), a magnetic tape, a floppy disk, an optical data storage device, and the like. The computer readable storage medium mentioned in the present application may be a non-volatile storage medium, in other words, a non-transitory storage medium.
It should be understood that all or part of the steps to implement the above-described embodiments may be implemented by software, hardware, firmware, or any combination thereof. When implemented in software, it may be implemented in whole or in part in the form of a computer program 921 product. The computer program 921 product includes one or more computer instructions. The computer instructions may be stored in the computer-readable storage medium described above.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and in part, not described or illustrated in any particular embodiment, reference is made to the related descriptions of other embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In the embodiments provided in the present application, it should be understood that the disclosed apparatus/electronic device and method may be implemented in other manners. For example, the apparatus/electronic device embodiments described above are merely illustrative, e.g., the division of modules or units is merely a logical functional division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection via interfaces, devices or units, which may be in electrical, mechanical or other forms.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; 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 scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (10)
1. A control method of a bidirectional dc converter, wherein the bidirectional dc converter comprises a first end for connecting a battery module and a second end for connecting to a dc bus of an inverter, and an ac end of the inverter for connecting to a power grid and/or a load, the control method comprising:
When the inverter is in a grid-connected state and the electric quantity of the battery module is larger than a power-saving threshold value, the bidirectional direct current converter is controlled to work in a charging mode or a discharging mode according to a preset regulation strategy; the battery module is charged by the direct current bus through the bidirectional direct current converter in a charging mode, and the battery module is discharged to the direct current bus through the bidirectional direct current converter in a discharging mode;
stopping driving the bidirectional direct current converter to work under the condition that the electric quantity of the battery module is smaller than or equal to the electricity-keeping threshold value and the bidirectional direct current converter does not work in a charging mode;
and under the condition that the power failure of the power grid is detected, restoring to execute the preset regulation strategy to control the bidirectional direct current converter to work in a charging mode or a discharging mode.
2. The control method according to claim 1, wherein the controlling the bidirectional dc converter to operate in the charging mode or the discharging mode according to the preset regulation strategy includes:
performing first amplitude limiting treatment on the initial given current to obtain a first given current; wherein the first given current causes the bi-directional dc converter to transfer power from the first end to the second end or causes the bi-directional dc converter to transfer power from the second end to the first end;
And generating a driving signal according to the first given current and the actual output current of the bidirectional direct current converter to drive the bidirectional direct current converter to work.
3. The control method according to claim 1, characterized in that the method further comprises:
under the condition that the electric quantity of the battery module is smaller than or equal to a power-keeping threshold value, performing second limiting treatment on the initial reference current to obtain a second given current; wherein the second given current causes the bi-directional dc converter to transfer power from the second end to the first end or causes the bi-directional dc converter to not transfer power from the first end to the second end;
and under the condition that the bidirectional converter works in a charging mode, generating a driving signal according to the second given current and the actual output current of the bidirectional direct current converter to drive the bidirectional direct current converter to work.
4. The control method according to claim 3, wherein the stopping driving the bidirectional dc converter in a case where the amount of electricity of the battery module is less than or equal to a power retention threshold and the bidirectional dc converter is not operated in the charging mode includes:
And stopping generating a driving signal to stop driving the bidirectional direct current converter to work under the condition that the electric quantity of the battery module is smaller than or equal to a power-keeping threshold value and the bidirectional direct current converter does not work in a charging mode.
5. The control method according to any one of claims 2 to 4, characterized in that the method further comprises:
acquiring a given voltage;
and obtaining an initial reference current according to the given voltage and the actual output voltage.
6. The control method according to claim 5, characterized in that the method further comprises:
after the bidirectional DC converter is started, the given voltage is controlled to gradually increase from 0 to a target voltage.
7. The control method of claim 5, wherein said deriving an initial reference current from said given voltage and output voltage comprises:
obtaining the output voltage of the bidirectional direct current converter;
and calculating according to the voltage difference between the output voltage and the given voltage to obtain an initial reference current.
8. The control method of claim 2, wherein the generating a drive signal based on the first given current and an actual output current of the bi-directional dc converter comprises:
Acquiring the actual output current of the bidirectional direct current converter;
calculating to obtain a duty ratio according to the current difference between the actual output current and the first given current;
the drive signal is generated based on the duty cycle.
9. A power supply device comprising a bi-directional dc converter, a memory, a processor and a computer program stored in the memory and executable on the processor, the bi-directional dc converter comprising a first end for connecting to a battery module and a second end for connecting to a dc bus of an inverter, an ac end of the inverter for connecting to a power grid and/or a load, the processor executing the computer program to implement the steps of the control method of the bi-directional dc converter according to any one of claims 1 to 8.
10. A computer readable storage medium, characterized in that the computer readable storage medium stores a computer program which, when executed by a controller, implements the steps of the method for controlling a bi-directional dc converter according to any one of claims 1 to 8.
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| CN202311794652.2A CN117879032A (en) | 2023-12-22 | 2023-12-22 | Control method and power supply device of bidirectional direct current converter |
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| CN202311794652.2A CN117879032A (en) | 2023-12-22 | 2023-12-22 | Control method and power supply device of bidirectional direct current converter |
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