CN114844076A - Grid-connected inversion control method for energy storage system and power grid control system - Google Patents
Grid-connected inversion control method for energy storage system and power grid control system Download PDFInfo
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- CN114844076A CN114844076A CN202110139647.2A CN202110139647A CN114844076A CN 114844076 A CN114844076 A CN 114844076A CN 202110139647 A CN202110139647 A CN 202110139647A CN 114844076 A CN114844076 A CN 114844076A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/48—Controlling the sharing of the in-phase component
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/50—Controlling the sharing of the out-of-phase component
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Abstract
The invention relates to a grid-connected inversion control method and a power grid control system of an energy storage system, wherein the control method comprises the following steps: acquiring the voltage and current of a power grid; judging the working mode of the energy storage system; when the working mode of the energy storage system is a non-operation mode, comparing the power grid voltage with a preset voltage, obtaining a first target reactive power according to a comparison result, and obtaining an inversion control signal according to the first target reactive power; when the working mode of the energy storage system is an operation mode, calculating the active power of the power grid according to the voltage of the power grid and the current of the power grid, comparing the active power of the power grid with a preset power value, obtaining a second target reactive power according to a comparison result, and obtaining an inversion control signal according to the second target reactive power and the target active power.
Description
Technical Field
The embodiment of the disclosure relates to the technical field of power grid control, and more particularly to a grid-connected inversion control method for an energy storage system and a power grid control system.
Background
A Power Conversion System (PCS) for battery energy storage is a unit for realizing Power interaction between an energy storage battery and a Power grid, and is a key component of the energy storage System, and the PCS System mainly has a function of charging and discharging the energy storage battery System in a grid-connected mode; and the active power and the reactive power of the bidirectional flow are regulated and controlled by controlling the active and reactive four-quadrant operation functions.
However, in the grid-connected operation process of the PCS system, a large amount of inductive loads often exist, so that reactive power is gradually increased, thereby causing continuous increase of power consumption, directly affecting the power supply quality of the power grid, and finally affecting the economic benefit of the power enterprise, and therefore, improvement on the PCS system and the control method of the power grid is needed.
Disclosure of Invention
An object of the disclosed embodiment is to provide a new technical solution of a grid-connected inversion control method for an energy storage system.
According to a first aspect of the disclosure, a grid-connected inversion control method for an energy storage system is provided, the method comprising:
acquiring the voltage and current of a power grid;
judging the working mode of the energy storage system;
when the working mode of the energy storage system is a non-operation mode, comparing the power grid voltage with a preset voltage, obtaining a first target reactive power according to a comparison result, and obtaining an inversion control signal according to the first target reactive power;
when the working mode of the energy storage system is an operation mode, calculating the active power of the power grid according to the voltage of the power grid and the current of the power grid, comparing the active power of the power grid with a preset power value, obtaining a second target reactive power according to a comparison result, and obtaining an inversion control signal according to the second target reactive power and the target active power.
Optionally, when the operating mode of the energy storage system is a non-operating mode, comparing the grid voltage with a preset voltage, obtaining a first target reactive power according to a comparison result, and obtaining an inverter control signal according to the first target reactive power, where the method includes:
the preset voltage includes: the voltage regulator comprises a first preset voltage, a second preset voltage, a third preset voltage and a fourth preset voltage, wherein the fourth preset voltage is greater than the third preset voltage, the third preset voltage is greater than the second preset voltage, and the second preset voltage is greater than the first preset voltage;
when the grid voltage is greater than the fourth preset voltage, the first target reactive power is a first power value;
when the power grid voltage is greater than the third preset voltage and less than or equal to a fourth preset voltage, the first target reactive power is a second power value;
when the power grid voltage is greater than the second preset voltage and less than or equal to a third preset voltage, the first target reactive power is a third power value;
and when the power grid voltage is greater than the first preset voltage and less than or equal to a second preset voltage, the first target reactive power is a fourth power value.
Optionally, the first power value is-Qmax, and Qmax is the maximum reactive power allowed to be output;
the second power value is Qmax (V3-V)/(V4-V3), V3 is a third preset voltage, V4 is a fourth preset voltage, V is the grid voltage, and Qmax is the maximum allowable output reactive power;
the third power value is Qmax (V2-V)/(V2-V1), V2 is a second preset voltage, V1 is a first preset voltage, and Qmax is the maximum allowed reactive power;
the fourth power value is Qmax, and Qmax is the maximum reactive power allowed to be output.
Optionally, the grid voltage is an average value of a plurality of grid voltages collected within a certain time period.
Optionally, when the operating mode of the energy storage system is an operating mode, calculating an active power of a power grid according to the voltage of the power grid and the current of the power grid, comparing the active power of the power grid with a preset power value, obtaining a second target reactive power according to a comparison result, and obtaining an inversion control signal according to the second target reactive power and the target active power, where the method includes:
the preset power values comprise a first preset power value, a second preset power value and a third preset power value, wherein the first preset power value is larger than the second preset power value, and the second preset power value is larger than the third preset power value;
when the active power of the power grid is larger than the first preset power value, the second target reactive power is a first target value;
when the active power of the power grid is larger than the second preset power value and smaller than the first preset power value, the second target reactive power is a second target value;
and when the active power of the power grid is greater than the third preset power value and less than a second preset power value, the second target reactive power is a third target value.
Optionally, the first target value is-Qmax, and Qmax is the maximum reactive power allowed to be output;
the second target value is Qmax (P2-P)/(P1-P2), Qmax is the maximum reactive power allowed to be output, P1 is a first preset power value, P2 is a second preset power value, and P is the active power of the power grid;
the third target value is Qmax, which is the maximum reactive power allowed to be output.
Optionally, obtaining an inversion control signal according to the first target reactive power includes:
carrying out park transformation on the power grid current to obtain a first current and a second current corresponding to the power grid current;
carrying out park transformation on the power grid voltage to obtain a first voltage and a second voltage corresponding to the power grid voltage;
obtaining a first target reactive current according to the first target reactive power;
carrying out proportional integral control on a difference value of the first target reactive current and the first current to obtain a first error signal, and adding the first error signal and a first voltage to obtain a first control quantity; performing proportional-integral control on the second current to obtain a second error signal, and adding the second error signal and the second voltage to obtain a second control quantity;
and carrying out park inverse transformation on the first control quantity and the second control quantity to obtain the inversion control signal.
Optionally, obtaining an inversion control signal according to the second target reactive power and the target active power, including:
acquiring a second target reactive current according to the second target reactive power;
obtaining a target active current according to the preset target active power;
performing park transformation on the power grid current to obtain a first current and a second current corresponding to the power grid current;
carrying out park transformation on the power grid voltage to obtain a first voltage and a second voltage corresponding to the power grid voltage;
carrying out proportional integral control on the difference value of the second target reactive current and the first current to obtain a first error signal, and adding the first error signal and a first voltage to obtain a first control quantity; performing proportional-integral control on a difference value of the target active current and the second current to obtain a second error signal, and adding the second error signal and the second voltage to obtain a second control quantity;
and carrying out park inverse transformation on the first control quantity and the second control quantity to obtain the target control signal, wherein the target control signal is a PWM duty ratio.
Optionally, the method further comprises:
and performing phase-locked control on the actual voltage of the power grid to obtain a phase-locked angle, and performing park transformation on the actual current and the actual voltage by using the phase-locked angle so as to enable the phase of the current and the voltage in the alternating current signal output by the inverter circuit to be the same as the phase of the actual voltage of the power grid.
According to a second aspect of the present disclosure, there is also provided a grid control system, the system comprising: a controller and a battery energy storage system, the battery energy storage system comprising a battery and an inverter circuit connected between the battery and a power grid, the controller comprising a memory for storing a computer program and a processor for performing the method of any of the first aspects under control of the computer program.
According to a third aspect of the present disclosure, there is provided a computer-readable storage medium, characterized in that the readable storage medium stores thereon a program or instructions which, when executed by a processor, implement the method of any one of the first aspects.
One beneficial effect of the disclosed embodiment is that the target current is obtained according to the running state of the energy storage system and the actual voltage and the actual current of the power grid; the system comprises a battery, an inverter circuit, a power grid control signal and a power grid control signal, wherein the inverter circuit is used for driving the power grid to run, the power grid control signal is used for controlling the power grid control signal, and the power grid control signal is used for controlling the power grid control signal.
Other features of embodiments of the present disclosure and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which is to be read in connection with the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the embodiments of the disclosure.
Fig. 1 is a schematic diagram of a component structure of a power grid control system according to an embodiment of the present disclosure;
FIG. 2 is a schematic flow diagram of a method of controlling a battery energy storage system according to one embodiment;
FIG. 3 is a schematic diagram of a method for controlling a battery energy storage system in the event that the energy storage system is not operational in an operational state, according to one embodiment;
fig. 4 is a control method of the battery energy storage system in a case where the operation state of the energy storage system is in operation according to an embodiment.
Detailed Description
Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
< System embodiment >
Fig. 1 is a schematic diagram of a configuration of a power grid control system to which an embodiment can be applied. As shown in fig. 1, the system includes a control module 107 and a battery energy storage system, the battery energy storage system includes a battery 100 and an inverter circuit 101 connected between the battery 100 and a power grid 103, and the system can be applied to a grid-connected operation scenario in which a power transmission line is connected to a power transmission grid in a power system.
In this embodiment, the control module 107 is configured to execute the method for controlling the battery energy storage System disclosed in this embodiment, for example, the control module 107 in this embodiment may be a digital signal processing chip of a Power Conversion System (PCS) or a Field-Programmable Gate Array (FPGA).
In this embodiment, the inverter circuit 101 may receive charging and discharging from the power grid, convert the ac signal provided by the power grid 103 into a dc signal and provide the dc signal to the battery 100, and charge the battery 100. The battery of the battery energy storage system is an energy storage battery, and can be used for storing electric energy of the direct current signal output by the inverter circuit 101 and providing electric energy for load equipment.
In this embodiment, the inverter circuit 101 is capable of performing bidirectional commutation between the battery and the grid, for example, receiving a control signal from the control module 107, converting the dc power on the battery side into ac power by the control signal, and inputting the ac power to the grid side. The dc side of the inverter circuit is connected to the battery via a dc contactor 104, and the ac side is connected to the grid via an ac contactor 105 and an ac breaker 106. The dc contactor 104 and the ac contactor 105 are used to control the on/off of current to control the on/off of a circuit, and the ac breaker 106 is used to break the circuit when the load on the circuit is excessive.
In this embodiment, the energy storage system may further include a filter 102 and a sampling circuit, and the inverter circuit 101 includes various power electronic devices, such as an Insulated Gate Bipolar Transistor (IGBT) and a DCAC ac/dc bidirectional conversion circuit. The filter 102 is used for filtering the ac output and filtering out harmonic components of the ac output. The sampling circuit can comprise a voltage transformer, a current transformer, a Hall sensor and a synchronous capture circuit. For example, the sampling circuit is connected to the battery voltage detection circuit and the current detection circuit through the dc side input, the ac side filter front and rear inverter voltage sampling circuit, the grid current sampling circuit, and the IO input/output signal circuit, all sampling signals and control signals collected by the sampling circuit are input to the control module 107 for control, and the control module outputs a modulation signal to drive the inverter circuit 101 to output a target current or a target voltage.
Referring to fig. 1, the sampling circuit includes a dc voltage sampling circuit, an ac voltage sampling circuit, an inverter voltage sampling circuit, and a grid voltage sampling circuit, and the dc voltage sampling circuit is used for collecting dc voltage at the battery side to the control module, so as to monitor whether the voltage at the battery side is normally and stably output; the alternating current sampling circuit and the inversion voltage sampling circuit are used for collecting current and voltage after inversion to the control module, so that whether the current and the voltage after inversion are consistent with target current and target voltage or not is monitored, and the control efficiency of the system is improved.
In this embodiment, the battery energy storage system further includes an interaction module 108, where the interaction module 108 is configured to perform interaction between a user and the battery energy storage system, and the user obtains all information of the battery energy storage system through the interaction module 108, and can control the system through the interaction module 108. For example, the interaction module 108 is configured to receive a control instruction input by a user, and send the control instruction to the control module 107, so that the control module 107 executes the control instruction; the control instruction comprises an instruction for controlling the generator set to start or stop;
the interaction module 108 is further configured to receive control information input by a user, and send the control information to the control module, so that the control module 107 executes the control method of the battery energy storage system disclosed in this embodiment according to the control information; wherein the control information includes at least one of a reference power, a preset voltage, and a target active power.
A skilled person can design a computer program according to the solution of the embodiments of the present disclosure. How the computer program controls the processor to operate is well known in the art and will not be described in detail here.
< method examples >
Fig. 2 is a flow chart illustrating a control method of a battery energy storage system according to an embodiment. The main implementation body of this embodiment is a power grid control system, for example, a control module in fig. 1.
As shown in fig. 2, the control method of the battery energy storage system of the present embodiment may include the following steps S210 to S240:
and step S210, acquiring the voltage and the current of the power grid.
In this embodiment, the operating state of the energy storage system includes the operating state and the non-operating state of the energy storage system, under the operating condition of the energy storage system, the power grid and the energy storage system are connected to each other, the power grid is charged and discharged by the energy storage system, the non-operating state of the system can be a standby state, a hot standby state or a dynamic monitoring state, considering that the power grid side can cause electric energy loss due to the increase of reactive power when the energy storage system is in operation and not in operation, the embodiment compensates the power grid from the operating state and the non-operating state of the energy storage system respectively, so as to improve the efficiency of the active power of the power grid side.
In this embodiment, the voltage and current of the power grid are actual voltage and current of the power grid, and the actual active power and reactive power of the power grid can be calculated according to the actual voltage and current of the power grid. The actual voltage and the actual current of the power grid may be obtained by a sampling circuit, for example, the power grid voltage sampling circuit and the power grid current sampling circuit in the above system embodiment.
And step S220, judging the working mode of the energy storage system.
The working modes of the energy storage system comprise a non-operation mode and an operation mode, the non-operation mode of the energy storage system is that the system is not in an off-grid state, the energy storage system is disconnected with a power grid at the moment, the operation mode of the energy storage system is that the system is in a grid-connected state, and the energy storage system is connected with the power grid at the moment. The working mode of the energy storage system can be judged according to the change condition of the voltage and the current through manual detection or through the change of the voltage and the current, and then the working mode of the energy storage system is obtained by automatically reporting the working state and the like.
In this embodiment, different control methods are adopted for different operating states of the energy storage system, and when the operating state of the energy storage system is in operation, the control method includes the following steps:
step S230, when the working mode of the energy storage system is a non-operation mode, comparing the grid voltage with a preset voltage, obtaining a first target reactive power according to a comparison result, and obtaining an inversion control signal according to the first target reactive power.
In this embodiment, because voltages at different circuit sampling points or different moments may be different, in order to improve control accuracy, the grid voltage in this embodiment is obtained by collecting actual voltages of a grid, calculating an average value of a plurality of grid voltages collected within a certain period of time, and then comparing the grid voltage with a preset voltage to determine a target reactive power.
Specifically, referring to fig. 3, the preset voltage includes a first preset voltage, a second preset voltage, a third preset voltage and a fourth preset voltage, wherein the fourth preset voltage is greater than the third preset voltage, the third preset voltage is greater than the second preset voltage, and the second preset voltage is greater than the first preset voltage.
When the voltage of the power grid is greater than the fourth preset voltage, the sign of the first target reactive power is negative, and the numerical value of the first target reactive power is a first power value;
when the voltage of the power grid is greater than a third preset voltage and less than or equal to a fourth preset voltage, the first target reactive power is a second power value;
when the voltage of the power grid is greater than the second preset voltage and less than or equal to a third preset voltage, the first target reactive power is a third power value;
when the voltage of the power grid is greater than a first preset voltage and less than or equal to a second preset voltage, the first target reactive power is a second power value;
the first power value may be set manually, for example, the first power value is set to a power value obtained through practice so that the system has the optimal operating efficiency, and may also be the maximum reactive power Qmax that the system allows to output. The maximum reactive power Qmax is the reactive power at which the active power efficiency of the system is lowest.
Therefore, in the case that the first power value Qm is Qmax, the calculation formula of the first target reactive power of the power grid in the embodiment is as follows:
wherein Qobj is a first target reactive power, Qmax is a maximum reactive power allowed to be output by the system, V4 is a fourth preset voltage, V3 is a third preset voltage, V2 is a second preset voltage, and V1 is a first preset voltage.
The first preset voltage, the second preset voltage, the third preset voltage and the fourth preset voltage of the above embodiments are respectively proportional to the rated voltage, for example, the values of V4, V3, V2 and V1 are respectively 1.3, 1.1, 0.8 and 0.6 of the rated voltage of the system, when the grid voltage is greater than the fourth preset voltage, the amplitude of the grid voltage is large, it is necessary to perform inductive reactive compensation on the grid, and the grid voltage is pulled down, but the reactive power allowed to be output cannot exceed the maximum reactive power allowed to be output by the system, therefore, in this embodiment, when the grid voltage is greater than the fourth preset voltage, the first target reactive power is-, when the grid voltage is less than the fourth preset voltage and greater than the third preset voltage, the first target reactive power is
The specific numerical value of the first target reactive power is determined by utilizing the difference value between the fourth preset voltage and the power grid voltage and the difference value between the fourth preset voltage and the third preset voltage, so that the linear relation between the voltage value and the first target reactive power can be better reflected, a better error control effect is achieved, and the control precision of the target reactive power is improved.
Similarly, when the grid voltage is smaller than the third preset voltage and larger than the second preset voltage, the amplitude of the grid voltage is larger, and the capacitive reactive compensation needs to be performed on the grid to raise the grid voltage. In this embodiment, when the grid voltage is greater than the second preset voltage and less than the third preset voltage, the first target reactive power is
And when the grid voltage is less than the second preset voltage and greater than the first preset voltage, the target reactive power is Qmax so as to raise the grid voltage.
In this embodiment, since the system has a large change in power relative to the load and a relatively stable voltage, resulting in a large current change range, the current is selected as the control variable in this embodiment, and the target reactive power is adjustedThe magnitude of the rate is calculated. Therefore, after the first target reactive power is determined, a first target reactive current needs to be determined, and the calculation formula of the first target reactive current is as follows:
the Iobj is a first target reactive current, the Qobj is a first target reactive power, and the V is an actual voltage of the power grid.
In this embodiment, after obtaining the first target reactive power and the first target reactive current, obtaining the inverter control signal according to the first target reactive power, specifically includes: carrying out park transformation on the power grid current to obtain a first current and a second current corresponding to the power grid current; carrying out park transformation on the power grid voltage to obtain a first voltage and a second voltage corresponding to the power grid voltage; obtaining a first target reactive current according to the first target reactive power; carrying out proportional integral control on a difference value of the first target reactive current and the first current to obtain a first error signal, and adding the first error signal and the first voltage to obtain a first control quantity; performing proportional-integral control on the second current to obtain a second error signal, and adding the second error signal and the second voltage to obtain a second control quantity; and performing park inverse transformation on the first control quantity and the second control quantity to obtain an inversion control signal.
For example, referring to fig. 3, a first target reactive current, a grid current and a grid voltage are used to obtain a target control signal, the grid current is park-transformed to obtain a first current I corresponding to the grid current q And a second current I d (ii) a Carrying out park transformation on the power grid voltage to obtain a first voltage u corresponding to the power grid voltage q And a second voltage u d For the first target reactive current and the first current I q Performing PI control on the difference value to obtain a first error signal, correcting the control quantity to be output according to the first error signal, and simultaneously correcting the first error signal and a first voltage u q Adding to obtain a first control quantity C q Thereby eliminating static difference, enabling output to be more stable and improving the response speed of the system; since the system is in a non-operating state, the system is in the operating stateThe input of work power may be zero, thus directly utilizing the second current I d And a second voltage u d Adding to obtain a second control quantity C d For the first control quantity C q And a second control quantity C d And carrying out park inverse transformation to obtain a target control signal, thereby obtaining the PWM duty ratio meeting the target.
In this embodiment, the principle of proportional-integral control is to form a control deviation according to a given value and an actual output value, linearly combine the proportion and the integral of the deviation to form a control quantity, control a controlled object, and control I of a three-phase current a ，I b ，I c Is three-phase data having a phase with a direction, and the control object of proportional integration is a specific value, so that the value of the three-phase current needs to be converted into a specific value without a direction in the present embodiment. The park transformation is a coordinate conversion mode and can convert the I of three-phase current a ，I b ，I c The projection of the current on the alpha axis and the beta axis is equivalent to the d axis and the q axis, so that the current on the stator is equivalent to the direct axis and the quadrature axis, wherein the d axis is the direct axis, and the q axis is the quadrature axis. Therefore, park transformation is adopted in the present embodiment to convert the three-phase current. Referring to fig. 4, in the present embodiment, the q-axis current and the corresponding first target reactive current are used for proportional-integral control, and the d-axis current and the corresponding target active current are used for proportional-integral control, that is, the q-axis current is used for regulating and controlling the reactive power of the power grid, and the d-axis current is used for regulating and controlling the active power of the power grid.
In this embodiment, when the first target reactive current and the grid current are subjected to PI control, phase-locking and park transformation are performed on the actual voltage, so as to achieve a feedforward control effect, and after regulation and control of the target current are completed, the output reactive power is closer to the target reactive power, and meanwhile, phase-locking control is performed on the actual voltage of the grid to obtain a phase-locking angle.
In this embodiment, when the operating state of the energy storage system is in operation, the control method includes the following steps:
step S240, when the working mode of the energy storage system is the running mode, calculating the active power of the power grid according to the voltage and the current of the power grid, comparing the active power of the power grid with a preset power value, obtaining a second target reactive power according to the comparison result, and obtaining an inversion control signal according to the second target reactive power and the target active power.
In one possible example, the grid active power may be calculated using a power formula P ═ Uabc ═ Iabc, where P is the grid active power, Uabc is the grid voltage, and Iabc is the grid current. And determining a second target reactive power of the power grid according to the size relation between the active power of the power grid and the preset power value. In the embodiment, as the system is in a grid-connected operation state, the voltage of the system is relatively stable, and the variation range of the current is relatively large relative to the variation of the load power, the current is also selected as the control variable, the second target reactive current of the power grid is determined according to the second target reactive power, and the system is controlled according to the second reactive current.
In this embodiment, in a grid-connected state, the active power of the power grid is much greater than the reactive power, and therefore, the magnitude of the second target reactive power is determined by using the active power of the power grid in this embodiment. Determining a second target reactive power of the power grid according to the size relation between the active power of the power grid and a preset power value, wherein the preset power value comprises a first preset power value, a second preset power value and a third preset power value, the first preset power value is larger than the second preset power value, and the second preset power value is larger than the third preset power value; when the active power of the power grid is larger than a first preset power value, the second target reactive power is a first target value; when the active power of the power grid is larger than a second preset power value and smaller than the first preset power value, the second target reactive power is a second target value; and when the active power of the power grid is greater than the third preset power value and less than the second preset power value, the second target reactive power is a third target value. The first target value, the second target value and the third target value can be set artificially according to the actual operation conditions of the energy storage system and the power grid.
In a possible embodiment, when the grid active power is greater than the first preset power value, the efficiency of the active power is higher, and when the reactive power is not greater than the maximum reactive power allowed to be output by the system, the system can still operate efficiently, but when the active power of the system is too high, the voltage on the grid side is caused to be higher, so that when the grid active power is greater than the first preset power value, the first target value is-Qmax, and Qmax is the maximum reactive power allowed to be output, so as to improve the grid voltage.
When the active power of the power grid is greater than the second preset power value and smaller than the first preset power value, a better error control effect is achieved by utilizing the difference value between the actual active power and the first preset power value and the difference value between the first preset power value and the second preset power value, so that the control precision of the target reactive power is improved, and therefore, the second target value is
Qmax is the maximum reactive power allowed to be output, P1 is a first preset power value, P2 is a second preset power value, and P is the active power of the power grid.
When the active power of the power grid is greater than the third preset power value and smaller than the second preset power value, the active power efficiency of the system is lower at this moment, and at this moment, the third target value can be Qmax, so as to offset the reactive power generated at the power grid side, and thus the active power efficiency of the system is improved, and Qmax is the maximum reactive power allowed to be output.
In this embodiment, the expression of the second target reactive power may be:
where Qobj is the second target reactive power, Qmax is the maximum reactive power allowed to be output by the system, P1 is the first preset power value, P2 is the second preset power value, P3 is the third preset power value, P is the actual active power, is the first target value,
qmax is a third target value.
The values of P1, 2, and 3 in the above expression of the target reactive power are respectively proportional to the rated power of the system, for example, the values of P1, 2, and 3 are respectively 60%, 30%, and 20% of the rated power of the system. When the actual active power is greater than 60% of the rated power, the efficiency of the active power is higher, and the reactive power at this time can still operate efficiently as long as the reactive power is not greater than the maximum reactive power allowed to be output by the system, but when the active power of the system is too high, the voltage on the side of the power grid is higher, so when the actual active power is greater than the first preset power value, the first target value may be negative Qmax, and when the target reactive power is negative Qmax, the voltage of the power grid is improved. When the actual active power is greater than 30% of the rated power and less than 60% of the rated power, the active power of the representative system is not high, and at this time, the system is still required to output a certain reactive power to regulate and control the reactive power generated at the power grid side
The difference value of the actual active power and the first preset power value and the difference value of the first preset power value and the second preset power value are utilized to have a better error control effect, so that the control precision of the target reactive power is improved, and therefore, the second target value is
At this time, the target reactive power is
When the actual active power is more than 20 of rated powerAnd% is less than 30% of the rated power, which indicates that the active power efficiency of the system is low at this time, the third target value may be Qmax, and the target reactive power is Qmax at this time, so as to offset the reactive power generated at the grid side, thereby improving the active power efficiency of the system.
In this embodiment, the current is used as a control variable, so after the second target reactive power is determined, the second target reactive current needs to be determined, and a calculation formula of the second target reactive current is as follows:
wherein Iq _ obj is a second target reactive current, Qobj is a second target reactive power, and Uabc is a grid voltage.
In this embodiment, since the system is in a grid-connected state, and an active current of the power grid needs to be obtained to control the system together with the second target reactive current, a target active current of the power grid needs to be obtained, and the target active current may be determined by obtaining a preset target active power and a target active voltage, for example, the preset target active power P sent by the client may be received Target And a target active voltage U Target Obtaining a target active current Id by using the target active power obj ＝ Target /U Target Wherein, U Target The target control signal can be obtained according to the second target reactive current, the target active current, the power grid current and the power grid voltage.
In this embodiment, the target active power and the target active voltage may be obtained through an interaction module, for example, the interaction module shown in fig. 1 is configured to receive control information input by a user, and send the control information to the control module.
In this embodiment, obtaining the inversion control signal according to the second target reactive power and the target active power includes: carrying out park transformation on the power grid current to obtain a first current and a second current corresponding to the power grid current; carrying out park transformation on the power grid voltage to obtain a first voltage and a second voltage corresponding to the power grid voltage; carrying out proportional integral control on a difference value of the target reactive current and the first current to obtain a first error signal, and adding the first error signal and the first voltage to obtain a first control quantity; performing proportional-integral control on a difference value of the target active current and the second current to obtain a second error signal, and adding the second error signal and the second voltage to obtain a second control quantity; and carrying out park inverse transformation on the first control quantity and the second control quantity to obtain a target control signal, wherein the target control signal is a PWM duty ratio.
In one possible example, referring to fig. 4, the park transformation is performed on the grid current to obtain a first current I corresponding to the grid current q And a second current I d (ii) a Carrying out park transformation on the power grid voltage Uabc to obtain a first voltage u corresponding to the power grid voltage q And a second voltage u d (ii) a For the second target reactive current and the first current I q Performing proportional-integral control on the difference value to obtain a first error signal, correcting the control quantity to be output according to the first error signal, and mixing the first error signal with a first voltage u q Adding to obtain a first control quantity C q Thereby eliminating static difference, enabling output to be more stable and improving the response speed of the system; to the target active current Id obj And a second current I d Performing proportional-integral control on the difference value to obtain a second error signal, correcting the control quantity to be output according to the second error signal, and connecting the second error signal and a second voltage u d Adding to obtain a second control quantity C d Thereby eliminating static difference and enabling output to be more stable; at this time, the first control quantity C q And a second control quantity C d Still, the three-phase signals are projected on the d and q axes, so the embodiment applies the first control quantity C q And a second control quantity C d Performing inverse park transformation to convert C d And C q And converting the three-phase PWM waves into three-phase PWM waves to obtain the three-phase duty ratio. Resulting in a target control signal, which may be a PWM duty cycle that meets a target condition. Wherein the second target reactive current and the first current I can be adjusted by the PI regulator q Performing proportional integral control by using the target reactive current and the secondA current I q The actual current difference is subjected to Proportional Integral (PI) control to obtain a first error signal.
In this embodiment, when PI control is performed on the first target reactive current and the target active current, phase-locking and park conversion are performed on the actual voltage, so that a feedforward control function is performed, and after regulation and control of the target current are completed, the output reactive power is closer to the target reactive power.
It should be noted that, when performing park transformation on the actual current and the actual voltage, the present embodiment performs phase-lock control on the actual voltage of the power grid to obtain a phase-lock angle, and performs park transformation on the actual current and the actual voltage by using the phase-lock angle to lock a projection angle of the actual current and the actual voltage during park transformation, that is, a phase angle between current and voltage in an ac signal output by the inverter circuit is the same as the phase-lock angle, so that a phase between current and voltage in the ac signal output by the inverter circuit is the same as a phase of the actual voltage of the power grid.
The phase-locked control in the embodiment can be realized by adopting a phase-locked loop, and the phase-locked loop mainly obtains the angle of the voltage of the power grid, so that the control current and the voltage in the system control are synchronous and consistent with the actual power grid.
In this embodiment, the target control signal may be a pulse width modulation PWM signal, and may be implemented by a module having a PWM signal output function, for example, the control module in fig. 1, which converts an analog signal into a PWM signal code required by a digital circuit.
In the present embodiment, the inverter circuit is configured to convert the dc power at the battery side into ac power, and as in the above system embodiment, the inverter circuit includes an inverter circuit, a filter, and a sampling circuit, and drives the inverter circuit by a PWM signal to generate an ac signal, where a current of the ac signal corresponds to a target current. The current in the ac signal may be consistent with the target current, or may have an error within an allowable range from the target current.
In the embodiment, when the system runs, the target reactive power is determined according to the actual power and the preset power value, the actual current of the power grid is controlled through the target active power and the target reactive power, and a target control signal is output; when the system does not operate, the target reactive power is determined according to the actual voltage and the preset voltage, the actual current of the power grid is controlled through the target reactive power, a target control signal is output, and the power grid voltage during operation and during non-operation can be respectively controlled according to the operation state of the energy storage system, so that the power grid stably operates and the efficiency of active power is improved.
The present invention may be a system, method and/or computer program product. The computer program product may include a computer-readable storage medium having computer-readable program instructions embodied therewith for causing a processor to implement various aspects of the present invention.
The computer readable storage medium may be a tangible device that can hold and store the instructions for use by the instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic memory device, a magnetic memory device, an optical memory device, an electromagnetic memory device, a semiconductor memory device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a Static Random Access Memory (SRAM), a portable compact disc read-only memory (CD-ROM), a Digital Versatile Disc (DVD), a memory stick, a floppy disk, a mechanical coding device, such as punch cards or in-groove projection structures having instructions stored thereon, and any suitable combination of the foregoing. Computer-readable storage media as used herein is not to be construed as transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission medium (e.g., optical pulses through a fiber optic cable), or electrical signals transmitted through electrical wires.
The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to a respective computing/processing device, or to an external computer or external storage device via a network, such as the internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. The network adapter card or network interface in each computing/processing device receives computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in the respective computing/processing device.
The computer program instructions for carrying out operations of the present invention may be assembler instructions, Instruction Set Architecture (ISA) instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, aspects of the present invention are implemented by personalizing an electronic circuit, such as a programmable logic circuit, a Field Programmable Gate Array (FPGA), or a Programmable Logic Array (PLA), with state information of computer-readable program instructions, which can execute the computer-readable program instructions.
Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer-readable program instructions.
These computer-readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer-readable program instructions may also be stored in a computer-readable storage medium that can direct a computer, programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer-readable medium storing the instructions comprises an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer, other programmable apparatus or other devices implement the functions/acts specified in the flowchart and/or block diagram block or blocks.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. It is well known to those skilled in the art that implementation by hardware, by software, and by a combination of software and hardware are equivalent.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. The scope of the invention is defined by the appended claims.
Claims (11)
1. A grid-connected inversion control method for an energy storage system is characterized by comprising the following steps:
acquiring the voltage and current of a power grid;
judging the working mode of the energy storage system;
when the working mode of the energy storage system is a non-operation mode, comparing the power grid voltage with a preset voltage, obtaining a first target reactive power according to a comparison result, and obtaining an inversion control signal according to the first target reactive power;
when the working mode of the energy storage system is an operation mode, calculating the active power of the power grid according to the voltage of the power grid and the current of the power grid, comparing the active power of the power grid with a preset power value, obtaining a second target reactive power according to a comparison result, and obtaining an inversion control signal according to the second target reactive power and the target active power.
2. The method according to claim 1, wherein when the operation mode of the energy storage system is a non-operation mode, the comparing the grid voltage with a preset voltage, obtaining a first target reactive power according to the comparison result, and obtaining an inverter control signal according to the first target reactive power comprises:
the preset voltage includes: the voltage regulator comprises a first preset voltage, a second preset voltage, a third preset voltage and a fourth preset voltage, wherein the fourth preset voltage is greater than the third preset voltage, the third preset voltage is greater than the second preset voltage, and the second preset voltage is greater than the first preset voltage;
when the grid voltage is greater than the fourth preset voltage, the first target reactive power is a first power value;
when the power grid voltage is greater than the third preset voltage and less than or equal to a fourth preset voltage, the first target reactive power is a second power value;
when the power grid voltage is greater than the second preset voltage and less than or equal to a third preset voltage, the first target reactive power is a third power value;
and when the power grid voltage is greater than the first preset voltage and less than or equal to a second preset voltage, the first target reactive power is a fourth power value.
3. The method of claim 2, wherein the first power value is-Qmax, Qmax being the maximum reactive power allowed to be output;
the second power value is Qmax (V3-V)/(V4-V3), V3 is a third preset voltage, V4 is a fourth preset voltage, V is the power grid voltage, and Qmax is the maximum allowable output reactive power;
the third power value is Qmax (V2-V)/(V2-V1), V2 is a second preset voltage, V1 is a first preset voltage, and Qmax is the maximum allowed reactive power;
the fourth power value is Qmax, and Qmax is the maximum reactive power allowed to be output.
4. The method of claim 2, wherein the grid voltage is an average of a plurality of the grid voltages collected over a period of time.
5. The method according to claim 1, wherein when the operating mode of the energy storage system is an operating mode, calculating a grid active power according to the grid voltage and the grid current, comparing the grid active power with a preset power value, obtaining a second target reactive power according to a comparison result, and obtaining an inverter control signal according to the second target reactive power and the target active power, the method includes:
the preset power values comprise a first preset power value, a second preset power value and a third preset power value, wherein the first preset power value is larger than the second preset power value, and the second preset power value is larger than the third preset power value;
when the active power of the power grid is larger than the first preset power value, the second target reactive power is a first target value;
when the active power of the power grid is larger than the second preset power value and smaller than the first preset power value, the second target reactive power is a second target value;
and when the active power of the power grid is greater than the third preset power value and less than a second preset power value, the second target reactive power is a third target value.
6. The method of claim 5,
the first target value is-Qmax, and Qmax is the maximum allowable output reactive power;
the second target value is Qmax (P2-P)/(P1-P2), Qmax is the maximum reactive power allowed to be output, P1 is a first preset power value, P2 is a second preset power value, and P is the active power of the power grid;
the third target value is Qmax, which is the maximum reactive power allowed to be output.
7. The method of claim 1, wherein deriving an inverter control signal based on the first target reactive power comprises:
carrying out park transformation on the power grid current to obtain a first current and a second current corresponding to the power grid current;
carrying out park transformation on the power grid voltage to obtain a first voltage and a second voltage corresponding to the power grid voltage;
obtaining a first target reactive current according to the first target reactive power;
carrying out proportional integral control on a difference value of the first target reactive current and the first current to obtain a first error signal, and adding the first error signal and a first voltage to obtain a first control quantity; performing proportional-integral control on the second current to obtain a second error signal, and adding the second error signal and the second voltage to obtain a second control quantity;
and carrying out park inverse transformation on the first control quantity and the second control quantity to obtain the inversion control signal.
8. The method of claim 1, wherein deriving the inverter control signal according to the second target reactive power and the target active power comprises:
acquiring a second target reactive current according to the second target reactive power;
obtaining a target active current according to the preset target active power;
carrying out park transformation on the power grid current to obtain a first current and a second current corresponding to the power grid current;
carrying out park transformation on the power grid voltage to obtain a first voltage and a second voltage corresponding to the power grid voltage;
carrying out proportional integral control on the difference value of the second target reactive current and the first current to obtain a first error signal, and adding the first error signal and a first voltage to obtain a first control quantity; performing proportional-integral control on a difference value of the target active current and the second current to obtain a second error signal, and adding the second error signal and the second voltage to obtain a second control quantity;
and carrying out park inverse transformation on the first control quantity and the second control quantity to obtain the target control signal, wherein the target control signal is a PWM duty ratio.
9. The method according to claim 7 or 8, characterized in that the method further comprises:
and performing phase-locked control on the actual voltage of the power grid to obtain a phase-locked angle, and performing park transformation on the actual current and the actual voltage by using the phase-locked angle so as to enable the phase of the current and the voltage in the alternating current signal output by the inverter circuit to be the same as the phase of the actual voltage of the power grid.
10. A grid control system, the system comprising: a controller and a battery energy storage system, the battery energy storage system comprising a battery and an inverter circuit connected between the battery and a power grid, the controller comprising a memory for storing a computer program and a processor for performing the method according to any of claims 1 to 9 under the control of the computer program.
11. A computer-readable storage medium, on which a program or instructions are stored, which when executed by a processor, implement the method of any one of claims 1 to 9.
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