A generator access control method for an energy storage power generation system

Abstract

The present application discloses a generator access control method for an energy storage power generation system, comprising the following steps: connecting the generator to the AC side of an energy storage converter via a control switch; when the energy storage converter is in an off-grid state, if the total power supply of the energy storage converter meets the load demand, the generator is disconnected from the load via the control switch, and the energy storage converter is now loaded alone; if the total power supply of the energy storage converter does not meet the load demand, the output power of the generator is judged; if the generator output power is not overloaded relative to the load demand, the control switch is closed so that the generator is loaded alone, and the energy storage converter is blocked; otherwise, the control switch is closed so that the energy storage converter and the generator are loaded together. The beneficial effects of the present application are: blocking the energy storage converter after the generator is connected to the system can prevent power from accumulating on the bus for a long time, thereby avoiding the risk of bus overvoltage.

Description

Technical Field

[0001] The present application relates to the technical field of inverters, and in particular to a generator access control method for an energy storage power generation system. Background Art

[0002] Energy storage power generation systems primarily include two main functions: power conversion and storage. Taking a photovoltaic power generation system as an example, the direct current (DC) generated by photovoltaic panels is first converted into alternating current (AC) for use by households, industries, and commercial equipment. When the power generated by photovoltaic panels exceeds immediate demand, the excess power is stored in a battery pack, typically a lithium-ion battery or a lead-acid battery. When sunlight is insufficient or power demand peaks, the power stored in the battery pack can be reconverted into AC power through an inverter to meet power demand. However, the layout of energy storage converters is generally fixed for a long time, while the load power demand gradually increases, which makes it difficult for the energy storage converter to meet the load power demand. Summary of the Invention

[0003] One of the objectives of the present application is to provide a generator access control method for an energy storage power generation system that can solve at least one of the defects in the above-mentioned background technology.

[0004] To achieve at least one of the above-mentioned purposes, the technical solution adopted in the present application is: a generator access control method for an energy storage power generation system, comprising the following steps: connecting the generator to the AC side of the energy storage converter through a control switch; when the energy storage converter is in an off-grid state, collecting the bus voltage and the SOC of the energy storage battery of the energy storage converter, and then calculating the total power supply of the energy storage converter; if the total power supply of the energy storage converter meets the load demand, the generator is disconnected from the load through the control switch, and the energy storage converter executes the off-grid control loop as a voltage source to carry the load alone; if the total power supply of the energy storage converter does not meet the load demand, the output power of the generator is judged; if the generator output power is not overloaded relative to the load demand, closing the control switch so that the generator carries the load alone as a voltage source, and the energy storage converter is blocked; otherwise, closing the control switch so that the energy storage converter executes the grid-connected control loop as a current source and the generator carries the load together as a voltage source.

[0005] Preferably, the connection between the generator and the load includes the following process: controlling the generator to start, and sampling the output voltage of the generator after the generator outputs normally, and then using it as the input of the off-grid control loop of the energy storage inverter; at the same time, sampling the output frequency of the generator, and then calculating the output angular velocity of the generator and assigning it to the phase-locked loop as input; after the energy storage inverter completes the phase locking of the generator output, closing the control switch to connect the generator to the system and the load, and at the same time the energy storage inverter performs wave blocking.

[0006] Preferably, the energy storage inverter includes a power generation unit and an energy storage battery, and the power generation unit and the energy storage battery are respectively connected in parallel to the DC / AC unit through a DC / DC unit and a bidirectional DC / DC unit; when the generator is loaded alone, the energy storage inverter is suitable for charging the energy storage battery through the power generation unit; when the energy storage battery is charged to a preset SOC, the energy storage inverter is suitable for releasing the wave and re-loading, at which time the control switch is disconnected and the generator is shut down.

[0007] Preferably, when the generator is loaded alone, the process of the power generation unit charging the energy storage battery is as follows: the DC / DC unit is released again, the bidirectional DC / DC unit executes the off-grid control loop, and the power generation unit charges the energy storage battery through the DC / DC unit and the bidirectional DC / DC unit. At this time, the DC / AC unit continues to keep the wave closed.

[0008] Preferably, the control process when the generator output power is overloaded relative to the load demand is as follows: the energy storage converter re-discharges and executes the grid-connected control loop; when executing the grid-connected control loop, the output voltage of the generator is sampled and used as the input of the phase-locked loop in the grid-connected control loop of the energy storage converter, and then the discharge power of the energy storage battery is controlled by the grid-connected control loop to be the difference between the load demand and the generator output power.

[0009] Preferably, the grid-connected control loop of the bidirectional DC / DC unit includes a battery current limiting loop, a battery current loop and a control signal generating module; the given value of the bus voltage is used as the input of the battery current limiting loop and the error calculation is performed on the sampled value of the bus voltage, and the calculation result is sent to the PI controller; the output of the PI controller is used as the limiting value of the given value in the battery current loop, and the error calculation is performed on the given value after limiting and the current sampling value of the energy storage battery, and the calculation result is sent to the PI controller; the PI controller outputs the duty cycle and sends it to the control signal generating module, which outputs the control signal corresponding to the bidirectional DC / DC unit; the off-grid control loop of the bidirectional DC / DC unit includes a bus voltage loop, a battery current loop and a control signal generating module; the given value of the bus voltage is used as the input of the bus voltage loop and the error calculation is performed on the bus voltage sampled value, and the calculation result is sent to the PI controller; the output of the PI controller is limited and used as the given value of the battery current loop, and the error calculation is performed on the current sampling value of the energy storage battery, and the calculation result is sent to the PI controller; the PI controller sends the output duty cycle to the control signal generating module, and outputs the control signal corresponding to the bidirectional DC / DC unit.

[0010] Preferably, the grid-connected control loop of the DC / AC unit includes a phase-locked loop, a bus voltage loop, an AC current loop, a dq conversion unit, and a control signal generation module; the grid voltage sampling value or the generator output voltage sampling value is used as the input of the phase-locked loop, and the corresponding phase and frequency are output; at the same time, the three-phase current and voltage on the AC side are converted into corresponding active value, reactive value and 0-sequence injection through the dq conversion unit; the given value of the bus voltage is used as the input of the bus voltage loop and the error calculation is performed with the bus voltage sampling value, and the calculation result is sent to the PI controller to output as the active given value of the AC current loop, and then the error calculation is performed with the converted current active value, and the calculation result is sent to the PI controller; the reactive given value of the AC current loop is calculated with the converted current reactive value, and the calculation result is sent to the PI controller; the converted voltage active value and voltage reactive value are respectively fed forward with the output result of the AC current loop; the two feedforward results and the 0-sequence injection are converted into a duty cycle through the dq conversion unit and sent to the control signal generation module, and the control signal corresponding to the DC / AC unit is output.

[0011] Preferably, the off-grid control loop of the DC / AC unit includes a phase-locked loop, a voltage setting generation module, an output voltage loop, an output current loop, a dq conversion unit, and a control signal generation module; the generator output voltage sampling value is used as the input of the phase-locked loop, and the corresponding phase and frequency are output; at the same time, the three-phase current and voltage on the AC side are converted into corresponding active value, reactive value and 0 sequence through the dq conversion unit; the voltage and frequency required to be output by the energy storage converter are input into the voltage setting generation module, and converted into the voltage active setting value and voltage reactive setting value corresponding to the output voltage loop; the output voltage loop calculates the error between the voltage active setting and the converted voltage active value, and the calculation result The output result of the PI controller is used as the active power given value of the output current loop, and the error is calculated with the current active value obtained by the transformation, and the calculation result is sent to the PI controller; at the same time, the output voltage loop calculates the error between the voltage reactive power given value and the voltage reactive power value obtained by the transformation, and the calculation result is sent to the PI controller; the output result of the PI controller is used as the reactive power given value of the output current loop, and the error is calculated with the current reactive power value obtained by the transformation, and the calculation result is sent to the PI controller; the output result of the output current loop and the 0-sequence injection are converted into a duty cycle through the dq conversion unit and sent to the control signal generation module to output the control signal corresponding to the DC / AC unit.

[0012] Preferably, the control switch adopts a selection switch, and the AC side of the energy storage inverter is connected to the generator and the power grid respectively through the control switch, and the load is connected between the output port of the energy storage inverter and the control switch; when the energy storage inverter supplies power to the load alone, the control switch remains disconnected from the generator; when the generator supplies power to the load, the control switch is closed to connect the generator to the AC side of the energy storage inverter.

[0013] Preferably, the load and the generator are both connected in parallel to the AC side of the energy storage inverter through a branch, and the control switch is set on the branch corresponding to the generator; when the energy storage inverter supplies power to the load alone, the control switch remains disconnected; when the generator supplies power to the load, the control switch is closed to connect the generator to the AC side of the energy storage inverter.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] After the generator is connected to the system, the energy storage converter is disabled to prevent prolonged power accumulation on the busbar and avoid the risk of busbar overvoltage. The generator can also be used as a voltage source to carry the load independently, or the energy storage converter can be used as a current source to carry the load together with the generator when the generator power is insufficient. This prevents the combined load of two voltage sources from causing uncontrollable output power of the energy storage converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the working process of this application.

[0017] Figure 2 This application is based on Figure 1 Schematic diagram of the working process shown.

[0018] Figure 3 This is a structural diagram of one example of the generator hardware connected to the energy storage power generation system in this application.

[0019] Figure 4 This is a structural diagram of another example of the generator hardware being connected to the energy storage power generation system in this application.

[0020] Figure 5 This is a schematic diagram of the working scenario judgment process of the energy storage power generation system of this application.

[0021] Figure 6 This is a schematic diagram of power distribution when the generator is alone and load-carrying in this application.

[0022] Figure 7 This is a schematic diagram of power distribution when the generator and energy storage converter are jointly loaded in this application.

[0023] Figure 8 Schematic diagram of the structure of the mode judgment loop in this application.

[0024] Figure 9 Schematic diagram of the control loop structure of the DC / DC unit in this application.

[0025] Figure 10 Schematic diagram of the control loop structure of the bidirectional DC / DC unit in this application.

[0026] Figure 11Schematic diagram of the control loop structure of the DC / AC unit in this application.

[0027] In the figure: power generation unit 101, DC / DC unit 102, DC / AC unit 103, bidirectional DC / DC unit 104, energy storage battery 105, load switch 106, grid-connected switch 107, electric meter 108, power grid 200, load 300, generator 401, control switch 402. DETAILED DESCRIPTION

[0028] Below, the present application is further described in conjunction with specific implementation methods. It should be noted that, in the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like are intended to mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0029] In the description of this application, it should be noted that for directional words, such as the terms "center", "horizontal", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and so on, indicating the orientation and position relationship are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of this application.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0031] In this application, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," and "fixed" should be understood in a broad sense. For example, they may refer to connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0032] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0033] The terms "comprises" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units expressly listed, but may include other steps or units not expressly listed or inherent to such process, method, product or apparatus.

[0034] One of the preferred embodiments of this application is as follows: Figures 1 to 4 As shown, a generator access control method for an energy storage power generation system includes the following steps: connecting the generator 401 to the AC side of the energy storage converter through the control switch 402, that is, first connecting the generator 401 to the energy storage power generation system through a hardware connection. When the energy storage converter is in an off-grid state, the bus voltage and the SOC of the energy storage battery 105 of the energy storage converter are collected, and then the total power supply of the energy storage converter is calculated. If the total power supply of the energy storage converter meets the needs of the load 300, the generator 401 is disconnected from the load 300 by controlling the switch 402. At this time, the energy storage converter executes the off-grid control loop as a voltage source to supply power to the load 300 to achieve independent load carrying. If the total power supply of the energy storage converter does not meet the demand of the load 300, it is necessary to judge the output power of the generator 401; if the output power of the generator 401 is not overloaded relative to the demand of the load 300, that is, the generator 401 will not be overloaded during operation, then the control switch 402 can be closed to connect the generator 401 to the load 300 to realize the independent load-carrying of the generator 401 as a voltage source, and the energy storage converter is blocked at this time; otherwise, the control switch 402 is closed to enable the energy storage converter to execute the grid-connected control loop as a current source and the generator 401 as a voltage source to simultaneously supply power to the load 300 to realize common load-carrying.

[0035] It is understood that after generator 401 is connected to the energy storage power generation system, disabling the energy storage converter can prevent prolonged accumulation of power on the bus and avoid the risk of bus overvoltage. Furthermore, by using generator 401 as a sole voltage source to carry the load, or by using the energy storage converter as a current source to carry the load together with generator 401 when generator 401 power is insufficient, it is possible to avoid uncontrollable output power of the energy storage converter caused by the combined load of the two voltage sources.

[0036] In order to facilitate the understanding of this embodiment, the structure of the energy storage power generation system can be described first. Figure 3 and Figure 4 As shown, the energy storage power generation system includes a power generation unit 101, a DC / DC unit 102, a DC / AC unit 103, a bidirectional DC / DC unit 104, an energy storage battery 105, a load switch 106, a grid-connected switch 107, and a load 300. The power generation unit 101 and the energy storage battery 105 are connected in parallel to the DC-side busbar of the DC / AC unit 103 via the corresponding DC / DC unit 102 and bidirectional DC / DC unit 104, respectively. Specifically, a three-level connection can be used, namely, connecting the positive busbar BUS+, the busbar midpoint BUSM, and the negative busbar BUS- on the DC side of the DC / AC unit 103, respectively. The AC side of the DC / AC unit 103 is connected to the load 300 via the load switch 106. Simultaneously, the AC side of the DC / AC unit 103 is also connected to the power grid 200 via the grid-connected switch 107. This allows the grid-connected switch 107 to be closed when the energy storage power generation system is grid-connected and opened when the energy storage power generation system is off-grid. Because the control loop for grid-connected operation requires the acquisition of the voltage of the grid 200, an electric meter 108 is installed on the connection side of the grid 200. This meter can acquire the voltage of the grid 200 and transmit it to the corresponding power devices via a communication protocol. The connection architecture between the power generation unit 101, DC / DC unit 102, DC / AC unit 103, bidirectional DC / DC unit 104, and energy storage battery 105 forms an energy storage converter.

[0037] It should be noted that there are various specific types of energy storage power generation systems, such as photovoltaic power generation systems and wind power generation systems. For ease of understanding, this application will use a photovoltaic power generation system as an example, in which the power generation unit 101 of the energy storage power generation system adopts a PV module. There are various specific ways to connect the hardware of the generator 401 to the above energy storage power generation system. For ease of understanding, the following will provide a detailed description using two specific examples.

[0038] Example 1: Figure 3As shown, a control switch 402 is further provided between the grid-connected switch 107 and the grid 200. The control switch 402 is a selector switch, so that the AC side of the energy storage converter is connected to the generator 401 and the grid 200 respectively through the control switch 402. When the energy storage converter is solely supplying power to the load 300, the control switch 402 can remain in the open state, so that the generator 401 is not connected to the AC side of the energy storage converter. When the generator 401 is solely supplying power to the load 300, the control switch 402 can be closed to the generator 401 position, so that the generator 401 is connected to the AC side of the energy storage converter.

[0039] Example 2: For example Figure 4 As shown, generator 401 is connected in parallel to the AC side of the energy storage converter via a branch circuit, and control switch 402 is provided in the branch circuit corresponding to generator 401. In this case, grid-connected switch 107 is located between the connection point of generator 401 and grid 200. When the energy storage converter is solely supplying power to load 300, control switch 402 remains open, so that generator 401 is not connected to the AC side of the energy storage converter. When generator 401 is supplying power to load 300, control switch 402 is closed to connect generator 401 to the AC side of the energy storage converter.

[0040] It is understood that both of the above examples can meet the requirements of this application, and those skilled in the art can make their own selection based on actual needs. To facilitate control of generator 401, control switch 402 can be a switch with remote control function, such as an ATS switch; or a generator 401 with remote start and stop control can be used.

[0041] It should be noted that the operating modes of conventional energy storage power generation systems are divided into grid-connected mode (MOD=0) and off-grid mode (MOD=1), depending on whether the grid 200 is connected. In grid-connected mode, the grid 200 can provide energy to the load 300 or the energy storage battery 105, while in off-grid mode, the energy storage inverter provides all the power required by the load 300. As can be seen from the foregoing, the units of the energy storage inverter that can supply power to the load 300 include the power generation unit 101 and the energy storage battery 105. That is, the energy storage inverter can supply power to the load 300 solely through the power generation unit 101, solely through the energy storage battery 105, or simultaneously through the power generation unit 101 and the energy storage battery 105. The technical solution of the present application is to connect the generator 401 to power the load 300 when the conventional energy storage power generation system cannot meet the needs of the load 300 through the energy storage inverter in the off-grid state. For ease of understanding, the specific working scenarios of the energy storage power generation system of this application in off-grid mode will be described in detail below.

[0042] like Figure 5 As shown, when the energy storage power generation system works in off-grid mode, the PV components give priority to providing power to the load 300, according to the bus voltage v bus and the SOC value of the energy storage battery 105 to determine the control instructions that the current system should execute. ref1 Indicates the upper threshold of bus voltage, v ref2 Indicates the lower limit threshold of bus voltage, SOC th1 Indicates the upper limit threshold of the SOC of the energy storage battery 105, SOC th2 Indicates the lower SOC threshold of the energy storage battery 105 .

[0043] Scenario 1: When the bus voltage v bus Greater than or equal to the upper threshold value v of the bus voltage ref1 When the output power of the PV module is P pv Greater than the load 300 required power P load If the SOC of the energy storage battery 105 is greater than or equal to the SOC upper limit threshold SOC th1 , indicating that the energy storage battery 105 is fully charged. Then the output power P of the PV module pv Load limit is performed, and the load limit value is equal to the required power P of the load 300 load .

[0044] Scenario 2: When the bus voltage v bus Greater than or equal to the upper threshold value v of the bus voltage ref1 When the output power of the PV module is P pv Greater than the load 300 required power P load If the SOC of the energy storage battery 105 is less than the SOC upper limit threshold SOC th1 , indicating that the energy storage battery 105 is not fully charged at this time, the PV module can charge the energy storage battery 105 through the bidirectional DC / DC unit 104, and the charging power P bat For (P pv -P load ) and P batmax The smaller value between the two; where P batmax Indicates the maximum charging power. At this time, the output power of the PV module P pv Equal to the required power P of the load 300 load Add the charging power P of the energy storage battery 105 bat ; That is, at this time the PV component is loaded and the energy storage battery 105 is charged.

[0045] Scenario 3: When the bus voltage v bus Less than or equal to the lower threshold value v of the bus voltage ref2 When the output power of the PV module is Ppv (at the maximum power point) is less than the required power P of the load 300 load If the SOC of the energy storage battery 105 is greater than the SOC lower limit threshold SOC th2 , the energy storage battery 105 can discharge the load 300 through the bidirectional DC / DC unit 104, and the discharge power P bat P load -P pv That is, at this time, the PV components and the energy storage battery 105 are loaded at the same time.

[0046] Scenario 4: When the bus voltage v bus Less than or equal to the lower threshold value v of the bus voltage ref2 When the output power of the PV module is P pv (at the maximum power point) is less than the required power P of the load 300 load If the SOC of the energy storage battery 105 is less than or equal to the SOC lower limit threshold SOC th2 , indicating that the energy storage battery 105 is insufficient and cannot guarantee the power supply of the load 300 for a long time; at this time, the system enters the generator mode (GENMOD), that is, the generator 401 is connected to the energy storage power generation system and supplies power to the load 300.

[0047] It should be noted that when the SOC of the energy storage battery 105 reaches the lower limit threshold SOC th2 When SOC is 0, the energy storage battery 105 should be able to provide power to the load 300 for a period of time. th2 The capacity of the energy storage battery 105 in the energy storage power generation system and the maximum output power P of the energy storage converter should be considered. invmax , the starting time of generator 401, phase lock time and other conditions are reasonably set. bus Between the upper threshold of bus voltage v ref1 With the lower threshold v ref2 Maintain the current control strategy.

[0048] It is understandable that, from the above analysis process, when the energy storage power generation system works in scene 1 or scene 2, due to changes in light or load 300 demand power P load The increase in the output power P of the PV module pv Less than the load 300 required power P load When the energy storage power generation system switches from scenario 1 or scenario 2 to scenario 3, the PV module and the energy storage battery 105 jointly provide power to the load 300. When the energy storage battery 105 is discharged to the SOC lower limit threshold SOC th2When the generator mode is switched from scene 3 to scene 4, the technical solution of the present application is mainly aimed at the process of switching from scene 3 to scene 4. For the convenience of understanding, the specific process of switching from scene 3 to scene 4 will be described in detail below.

[0049] Specifically, such as Figure 2 As shown, when the PV assembly and the energy storage battery 105 supply power to the load 300 at the same time, the energy storage converter can control the generator 401 to start. At this time, the power generation power P of the energy storage battery 105 bat = P load -P pv It should be noted that before the generator 401 is started, the energy storage converter needs to execute the off-grid control loop.

[0050] After the generator 401 outputs normally, the output voltage waveform of the energy storage converter needs to track the output voltage waveform of the generator 401. gena 、v genb 、v genc The sampling is performed as the input of the voltage setting generation module in the off-grid control loop of the DC / AC unit 103 in the energy storage converter; at the same time, the output frequency f of the generator 401 is gen Sampling is performed to calculate the output angular velocity ω of the generator 401 gen Assigned to the input ω of the phase-locked loop in the off-grid control loop of the DC / AC unit 103 ref .

[0051] After the energy storage converter has phase-locked the output of generator 401, it controls switch 104 to close, connecting generator 401 to the energy storage power generation system to power load 300. Simultaneously, the energy storage converter is blocked, specifically the DC / DC unit 102, bidirectional DC / DC unit 104, and DC / AC unit 103 within the converter. It is important to note that the switching time must be considered when blocking the energy storage converter to ensure a short interval between blocking the energy storage converter and connecting generator 401.

[0052] If the generator 401 is in a non-overloaded state, that is, the normal output power P of the generator 401 gen Less than the maximum output power P of generator 401 genmax , or the required power P of the load 300 load Less than or equal to the output power P of the generator 401 gen In simple terms, the output power of the generator 401 when it is working normally can meet the demand of the load 300. In order to meet the possible demand power P of the load 300 loadAt the same time, since the energy consumption of the generator 401 is relatively high, the access time of the generator 401 should be shortened as much as possible. When the generator 401 is alone with the load, the PV component as the power generation unit 101 can be used to charge the energy storage battery 105.

[0053] When the PV panels charge the energy storage battery 105, the DC side of the energy storage converter discharges the current. The control loop of the DC / DC unit 102 is activated, while the control loop of the bidirectional DC / DC unit 104 performs off-grid control. The PV panels then charge the energy storage battery 105 through the DC / DC unit 102 and the bidirectional DC / DC unit 104. During this time, the AC side of the energy storage converter remains blocked, disabling the corresponding control loop of the DC / AC unit 103. This prevents the operation of the generator 401 from affecting the charging of the energy storage battery 105.

[0054] When the energy storage battery 105 is charged to a preset SOC, that is, the SOC of the energy storage battery 105 is greater than the SOC upper limit threshold SOC th1 When the PV component stops charging the energy storage battery 105, the AC wave of the energy storage converter is released, so that the DC / AC unit 103 executes the off-grid control loop, and the energy storage converter supplies power to the load 300; when the energy storage converter outputs a stable current, the control switch 402 can be disconnected, the generator 401 is disconnected from the energy storage power generation system and shuts down normally.

[0055] If the generator 401 is in an overload state, that is, the power demand P of the load 300 is load Greater than the normal output power P of the generator 401 gen In simple terms, when generator 401 is operating normally, its output power cannot meet the needs of load 300. At this point, generator 401 will be overloaded. Prolonged overload operation of generator 401 is not permitted. At this point, the energy storage converter needs to be connected to achieve shared load sharing to prevent generator 401 from being overloaded for a long time.

[0056] Specifically, the energy storage converter re-discharges and executes the grid-connected control loop. When executing the grid-connected control loop, the output voltage v of the generator 401 is gena 、v genb 、v genc The sampling is performed and used as the input of the phase-locked loop in the grid-connected control loop of the DC / AC unit 103 in the energy storage converter, and then the discharge power of the energy storage battery 105 is controlled by the grid-connected control loop to be the difference between the load 300 demand and the output power of the generator 401, that is, the output power P of the energy storage converter at this time inv =P load -P genAt the same time, the output power of the PV module can be identified during this process. If the output power of the PV module P pv Not working at the maximum power point P pvmax , the PV component can now perform MPPT tracking and charge the energy storage battery 105.

[0057] In order to further facilitate the understanding of the operation of the generator 401 connected to the energy storage power generation system, the system power distribution in the generator mode will be described in detail below.

[0058] 1. A scenario in which the generator 401 supplies power to the load 300 alone.

[0059] like Figure 6 As shown, at time t1, the required power P of the load 300 is load Increase, the output power of the energy storage converter increases accordingly. At this time, the energy storage power generation system still executes the off-grid control loop (MOD=1).

[0060] At time t2, the output power of the PV module is P pv Less than the load's required power P load , and the SOC of the energy storage battery 105 drops to the SOC lower limit threshold SOC th2 At this time, the energy storage power generation system enters the generator mode, the energy storage converter controls the generator 401 to start, and the energy storage power generation system still executes the off-grid control loop (MOD=1).

[0061] At time t3, generator 401 is started, and the output voltage waveform of the energy storage converter tracks the output voltage waveform of generator 401. At time t4, the energy storage converter completes phase locking of the output voltage waveform of generator 401 and closes control switch 402, connecting generator 401 to the energy storage power generation system.

[0062] At time t5, switch 402 is closed, and generator 401 is connected to the energy storage power generation system. Since the energy storage inverter is now executing its off-grid control loop (MOD = 1), it acts as a voltage source. Generator 401 is also a voltage source, and the two voltage sources are connected in parallel, redistributing the power output to load 300. Therefore, at time t6, the energy storage inverter is switched off, and the power required by load 300 is fully provided by generator 401, preventing the simultaneous operation of two voltage sources from causing uncontrollable output power of the energy storage inverter. Simultaneously, the PV module charges the energy storage battery 105 via the DC / DC unit 102 and the bidirectional DC / DC unit 104.

[0063] At time t7, the SOC of the energy storage battery 105 reaches the SOC upper limit threshold SOC th1, the PV module stops charging the energy storage battery 105 and begins powering the load 300 through the DC / DC unit 102 and the DC / AC unit 103. At this point, the energy storage inverter executes the off-grid control loop (MOD=1), connecting the two voltage sources in parallel and redistributing the power output to the load 300. Therefore, the energy storage inverter needs to disconnect the control switch 402, disconnecting the generator 401 from the energy storage power generation system. This prevents the two voltage sources from operating simultaneously, causing uncontrollable output power of the energy storage inverter, while also reducing overall system energy consumption. At time t8, the disconnection of the control switch 402 is complete, disconnecting the generator 401 from the energy storage power generation system, and the power demand of the load 300 is now entirely provided by the energy storage inverter.

[0064] It should be noted that the SOC threshold for the PV module to charge the energy storage battery 105 in the generator mode may not be the SOC upper threshold SOC th1 , should be reasonably set according to the actual operating conditions. In the above case, generator 401 can always meet the power demand of load 300, and the energy storage converter is not required to provide power to load 300; therefore, the energy storage converter always executes the off-grid control loop (MOD=1).

[0065] 2. A scenario in which the generator 401 and the energy storage converter jointly supply power to the load 300.

[0066] like Figure 7 As shown, the energy storage power generation system enters the generator mode during the time period t1-t6, and the process is the same as Figure 6 The process when the generator 401 is loaded alone is the same, so it will not be repeated.

[0067] At time a, the required power P of load 401 load Increase, and the required power after the increase P load Greater than the maximum output power P of the generator 401 genmax , generator 401 is in overload state.

[0068] At time b, after receiving the overload information from generator 401, the energy storage converter activates the grid-connected control loop (MOD = 0). The energy storage converter acts as a current source to supply power to load 300, and its output power gradually increases during this process.

[0069] It should be noted that, regarding the reception of the overload information of the generator 401 , in addition to the energy storage converter directly obtaining the overload information of the generator 401 through communication, it is also possible to determine whether the generator 401 is overloaded by detecting the output power of the generator 401 .

[0070] At time c, the output power of the generator 401 decreases to the maximum output power P genmax, the output power of the energy storage converter stops increasing, and the excess power of the PV module can be used to charge the energy storage battery 105.

[0071] At time d, the SOC of the energy storage battery 105 reaches the SOC upper limit threshold SOC th1 , the PV panels stop charging the energy storage battery 105. The energy storage converter switches from the grid-connected control loop (MOD = 0) to the off-grid control loop (MOD = 1). The subsequent process is identical to that of generator 401 operating independently and will not be repeated here.

[0072] In this embodiment, the on-grid and off-grid control loops of the energy storage power generation system primarily refer to the on-grid and off-grid control loops corresponding to the DC / DC unit 102, DC / AC unit 103, and bidirectional DC / DC unit 104 in the energy storage converter. For ease of understanding, the specific operating processes of the on-grid and off-grid control loops of the DC / DC unit 102, DC / AC unit 103, and bidirectional DC / DC unit 104 are described in detail below.

[0073] It should be noted that the execution of the on-grid and off-grid control loops of the above-mentioned power units needs to be judged first through the mode judgment loop. Figure 8 As shown, the mode judgment loop is based on the collected SOC of the energy storage battery 105 and the output power P of the energy storage converter. inv , bus voltage v bus , grid voltage v ga 、v gb 、v gc The control mode of the energy storage power generation system is judged by the information, and then the mode selection signal MOD and the battery current given value i are output. bat * , bus voltage given value v bus * etc. for use in the subsequent on-grid and off-grid control process of power units.

[0074] At the same time, when the energy storage power generation system operates in grid-connected mode, the AC side terminal voltage of the energy storage converter will be determined by the power grid 200, so in grid-connected mode, the energy storage converter acts as a current source. When the energy storage power generation system operates in off-grid mode, the grid-connected switch 107 will be disconnected. At this time, the energy storage converter needs to stabilize the output voltage, so in off-grid mode, the energy storage converter acts as a voltage source. Of course, when the energy storage converter and the generator 401 are loaded at the same time, although the energy storage power generation system executes the grid-connected mode, the grid-connected switch 107 remains disconnected. At this time, the AC side terminal voltage of the energy storage converter will be determined by the generator 401, so in this grid-connected mode, the energy storage converter still acts as a current source.

[0075] 1. A control loop for the on-grid and off-grid control of the DC / DC unit 102 .

[0076] When the DC / DC unit 102 is operating, either the power generation unit 101 supplies power to the energy storage battery 105 or to the load 300. Therefore, regardless of whether the energy storage converter is in grid-connected or off-grid mode, the DC / DC unit 102 is performing MPPT tracking. Therefore, the control loop of the DC / DC unit 102 can also be referred to as a PV control loop.

[0077] like Figure 9 As shown in Figure 1, the PV control loop includes the MPPT calculation unit, the PV voltage outer loop, the PV current inner loop, and the control signal generation module. The output voltage v pv With the output current i pv The sampling value is used as the input of the MPPT calculation unit, and the MPPT calculation unit outputs v pv * As the given value of the PV voltage outer loop, it is related to the output voltage sampling value v of the PV component. pv The error calculation is performed and the calculation result is sent to the PI controller. The current given value i output by PI controller 1 pv * Do the limiting and determine the limiting value i according to the specific control strategy pv-max The size of the energy storage battery 105 is determined by the SOC of the energy storage battery 105 and the power P of the power grid 200. grid Limit the output current of PV modules to prevent excess power from being fed into the grid. The current setting value after limiting is i pv * As the input of the PV current inner loop, it is connected to the output current sampling value i of the PV module. pv Calculate the error and send the result to the PI controller. The PI controller outputs the duty cycle d pv The control signal generating module outputs the corresponding control signal PWM of the DC / DC unit 102. DC / DC .

[0078] 2. Grid-connected and off-grid control loop for the bidirectional DC / DC unit 104.

[0079] like Figure 10 As shown, when the energy storage converter is in grid-connected mode, that is, MOD=0, the grid-connected control loop of the bidirectional DC / DC unit 104 is called the grid-connected battery control loop, which includes the battery current limiting loop, the battery current loop and the control signal generation module. bus * As the input of the battery current limiting loop, it is connected to the sampling value of the bus voltage v bus The error calculation is performed and the calculation result is sent to the PI controller. The output of the PI controller is used as the current set value i in the battery current loop. bat* The current setting value after limiting is i bat * and the current sampling value i of the energy storage battery 105 bat Calculate the error and send the result to the PI controller. The PI controller outputs the duty cycle d bat The control signal generating module outputs the control signal PWM corresponding to the bidirectional DC / DC unit 105. bat .

[0080] When the energy storage converter is in off-grid mode, that is, MOD=1, the off-grid control loop of the bidirectional DC / DC unit 104 is called the off-grid battery control loop, which includes the bus voltage loop, the battery current loop and the control signal generation module. bus * As the input of the bus voltage loop, it is connected to the bus voltage sampling value v bus The error calculation is done and the calculation result is sent to the PI controller. The current given value i output by the PI controller bat * After limiting, it is used as the given value input of the battery current loop. bat * and the current sampling value i of the energy storage battery 105 bat Calculate the error and send the result to the PI controller. The PI controller outputs the duty cycle d bat The control signal generating module outputs the control signal PWM corresponding to the bidirectional DC / DC unit 104. bat .

[0081] 3. On-grid and off-grid control loop for the DC / AC unit 103.

[0082] like Figure 11 As shown, when the energy storage converter is in grid-connected mode, that is, MOD=0, the grid-connected control loop of the DC / AC unit 103 includes a phase-locked loop, a bus voltage loop, an AC current loop, a dq conversion unit, and a control signal generation module.

[0083] If the grid-connected mode of the energy storage converter is to connect to the grid 200, close the grid-connected switch 107, and the grid voltage v collected by the electric meter 108 is ga 、v gb 、v gc That is the AC side voltage v of the energy storage converter a 、v b 、v c , the voltage v a 、v b 、v cAs the input of the phase-locked loop, the grid voltage frequency ω is obtained after the phase-locked loop, and then the grid voltage frequency ω is integrated to obtain the phase θ g At the same time, the AC side three-phase current sampling value i collected by the electric meter 108 a 、i b 、i c Converted into i by dq conversion unit d 、i q , i0, grid voltage v ga 、v gb 、v gc Converted into V by dq conversion unit d 、v q , v0. Among them, i d and v d are the active values ​​of current and voltage respectively, i q and v q are the reactive values ​​of current and voltage respectively, i0 and v0 are injected as 0-sequence.

[0084] The given value of bus voltage v bus * As the input of the bus voltage loop, it is connected to the bus voltage sampling value v bus The error calculation is performed and the calculation result is sent to the PI controller. The output of the PI controller is used as the active power given value i of the AC current loop. d * , and the active current value i obtained by dq transformation d Do error calculation and send the result to PI controller to output voltage active value v d * The reactive power given value i of the AC current loop q * , and the current reactive value i obtained by dq transformation q Do error calculation and send the result to PI controller to output voltage reactive power given value v q * The voltage active value v obtained by dq transformation d and voltage reactive value v q The voltage active power given value v obtained by the AC current loop output is d * and voltage reactive power given value v q * Do feedforward. The two results after feedforward and 0 sequence injection are converted into duty cycle d through dq conversion unit DC / AC The control signal generating module outputs the control signal PWM corresponding to the DC / AC unit 103. DC / AC .

[0085] If the grid-connected mode of the energy storage converter is to realize the common load with the generator 401, then the grid-connected switch 107 is disconnected and the output voltage v of the generator 401 is gena 、v genb 、v genc The sampling is used as the input of the phase-locked loop, and the output frequency f of the generator 401 is obtained after the phase-locked loop. gen , and then calculate the output angular velocity ω of the generator 401 gen Assigned to the input of the phase-locked loop ω ref , and then integrate the frequency ω output by the phase-locked loop to obtain the corresponding phase θ g .

[0086] At the same time, the three-phase current sampling value i output by the energy storage converter a 、i b 、i c Converted into i by dq conversion unit d 、i q , i0, output three-phase voltage v a 、v b 、v c Converted into V by dq conversion unit d 、v q , v0. Among them, i d and v d are the active values ​​of current and voltage respectively, i q and v q i0 and v0 are the reactive values ​​of current and voltage respectively, and are injected as sequence 0. The subsequent control process is the same as the control process of connecting to the power grid 200, so it will not be repeated here.

[0087] When the energy storage converter is in off-grid mode, that is, MOD=1, the off-grid control loop of the DC / AC unit 103 includes a phase-locked loop, a voltage setting generation module, an output voltage loop, an output current loop, a dq conversion unit, and a control signal generation module.

[0088] The output voltage v of the generator 401 gena 、v genb 、v genc The sampling is used as the input of the phase-locked loop, and the output frequency f of the generator 401 is obtained after the phase-locked loop. gen , and then calculate the output angular velocity ω of the generator 401 gen Assigned to the input of the phase-locked loop ω ref , and then integrate the frequency ω output by the phase-locked loop to obtain the corresponding phase θ g At the same time, the three-phase current sampling value i output by the energy storage converter a 、i b 、i cConverted into i by dq conversion unit d 、i q , i0, output three-phase voltage v a 、v b 、v c Converted into V by dq conversion unit d 、v q , v0. Among them, i d and v d are the active values ​​of current and voltage respectively, i q and v q are the reactive values ​​of current and voltage respectively, i0 and v0 are 0-sequence injection.

[0089] The voltage v that the energy storage converter needs to output a0 、v b0 、v c0 The frequency input voltage is generated by the module and converted into the voltage active power given value v corresponding to the output voltage loop. d * and voltage reactive power given value v q * The output voltage loop sets the voltage active power to a given value v d * The voltage active value v obtained by dq transformation d The error calculation is performed and the calculation result is sent to the PI controller; the output result of the PI controller is used as the active given value i of the output current loop d * and the transformed current active value i d The error calculation is performed and the result is sent to the PI controller. The reactive power given value v of the output voltage loop is q * The voltage reactive value v obtained by dq transformation q The error calculation is performed and the calculation result is sent to the PI controller; the output result of the PI controller is used as the reactive power given value i of the output current loop. q * , and the current reactive value i obtained by dq transformation q The error calculation is performed and the calculation result is sent to the PI controller. The output result of the output current loop after the PI controller and the 0 sequence injection are converted into a duty cycle d through the dq conversion unit. DC / AC The control signal generating module outputs the control signal PWM corresponding to the DC / AC unit 103. DC / AC .

[0090] The above describes the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and the specification merely illustrate the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. These changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A generator access control method for an energy storage power generation system, characterized in that: The steps include: Connect the generator to the AC side of the energy storage converter through a control switch; When the energy storage converter is off-grid, the bus voltage and the SOC of the energy storage battery of the energy storage converter are collected to calculate the total power supply of the energy storage converter; If the total power supply of the energy storage converter meets the load demand, the generator is disconnected from the load through the control switch. At this time, the energy storage converter executes the off-grid control loop and acts as a voltage source to carry the load alone. If the total power supply of the energy storage converter does not meet the load demand, the output power of the generator is judged; If the generator output power is not overloaded relative to the load demand, the control switch is closed so that the generator acts as a voltage source to carry the load alone, and the energy storage converter is blocked. Otherwise, the control switch is closed so that the energy storage converter executes the grid-connected control loop to act as a current source and the generator acts as a voltage source to carry the load together. The energy storage converter includes a power generation unit and an energy storage battery. The power generation unit and the energy storage battery are connected in parallel to the DC / AC unit through a DC / DC unit and a bidirectional DC / DC unit respectively. The grid-connected control loop of the bidirectional DC / DC unit includes a battery current limiting loop, a battery current loop, and a control signal generation module; The given value of the bus voltage is used as the input of the battery current limiting loop and the error is calculated with the sampled value of the bus voltage. The calculation result is sent to the PI controller. The output of the PI controller is used as the limit value of the given value in the battery current loop. The error between the given value after limit and the current sampling value of the energy storage battery is calculated, and the calculation result is sent to the PI controller; The duty cycle output by the PI controller is sent to the control signal generation module, which outputs the control signal corresponding to the bidirectional DC / DC unit.

2. The generator access control method of the energy storage power generation system according to claim 1, characterized in that: The connection between the generator and the load includes the following processes: The generator is controlled to start and the output voltage is sampled after the generator is operating normally, which is then used as the input of the off-grid control loop of the energy storage converter. The output frequency of the generator is also sampled, and the output angular velocity of the generator is calculated and assigned to the phase-locked loop as input. After the energy storage converter completes the phase lock on the generator output, the control switch is closed to connect the generator to the system and the load, and the energy storage converter is blocked at the same time.

3. The generator access control method of the energy storage power generation system according to claim 2, characterized in that: When the generator is loaded alone, the energy storage converter is suitable for charging the energy storage battery through the power generation unit; When the energy storage battery is charged to a preset SOC, the energy storage converter is adapted to release the wave blocking and resume loading, at which point the control switch is disconnected and the generator is shut down.

4. The generator access control method of the energy storage power generation system according to claim 3, characterized in that: When the generator is loaded alone, the process of the power generation unit charging the energy storage battery is as follows: The DC / DC unit starts to release the wave again, the bidirectional DC / DC unit executes the off-grid control loop, and the power generation unit charges the energy storage battery through the DC / DC unit and the bidirectional DC / DC unit. At this time, the DC / AC unit continues to keep the wave blocked.

5. The generator access control method of the energy storage power generation system according to claim 4, characterized in that: The control process when the generator output power is overloaded relative to the load demand is as follows: The energy storage converter re-discharges and executes the grid-connected control loop; When executing the grid-connected control loop, the output voltage of the generator is sampled and used as the input of the phase-locked loop in the grid-connected control loop of the energy storage converter. The grid-connected control loop then controls the discharge power of the energy storage battery to be the difference between the load demand and the generator output power.

6. The generator access control method of the energy storage power generation system according to claim 1, characterized in that: The off-grid control loop of the bidirectional DC / DC unit includes a bus voltage loop, a battery current loop, and a control signal generation module; The given value of bus voltage is used as the input of bus voltage loop and the error is calculated with the bus voltage sampling value, and the calculation result is sent to PI controller; The output of the PI controller is limited and used as the given value of the battery current loop. The error is calculated with the current sampling value of the energy storage battery, and the calculation result is sent to the PI controller; The PI controller sends the output duty cycle to the control signal generation module, and outputs the control signal corresponding to the bidirectional DC / DC unit.

7. The generator access control method of the energy storage power generation system according to claim 1, characterized in that: The grid-connected control loop of the DC / AC unit includes a phase-locked loop, a bus voltage loop, an AC current loop, a dq conversion unit, and a control signal generation module; The grid voltage sampling value or the generator output voltage sampling value is used as the input of the phase-locked loop, and the corresponding phase and frequency are output; at the same time, the three-phase current and voltage on the AC side are converted into corresponding active value, reactive value and zero-sequence injection through the dq conversion unit; The given value of the bus voltage is used as the input of the bus voltage loop and the error calculation is performed with the bus voltage sampling value. The calculation result is sent to the PI controller to output as the active power given value of the AC current loop. The error calculation is then performed with the transformed current active value and the calculation result is sent to the PI controller. The error between the reactive power given value of the AC current loop and the current reactive power value obtained by transformation is calculated, and the calculation result is sent to the PI controller; The transformed voltage active value and voltage reactive value are fed forward with the output results of the AC current loop respectively; The two feedforward results and the 0-sequence injection are converted into a duty cycle through the dq conversion unit and sent to the control signal generation module to output the control signal corresponding to the DC / AC unit.

8. The generator access control method of the energy storage power generation system according to claim 1, characterized in that: The off-grid control loop of the DC / AC unit includes a phase-locked loop, a voltage setting generation module, an output voltage loop, an output current loop, a dq conversion unit, and a control signal generation module; The generator output voltage sampling value is used as the input of the phase-locked loop to output the corresponding phase and frequency; at the same time, the three-phase current and voltage on the AC side are converted into corresponding active value, reactive value and zero sequence through the dq conversion unit; The voltage and frequency required to be output by the energy storage converter are input into the voltage setting generation module, and converted into the voltage active value and voltage reactive value corresponding to the output voltage loop; The output voltage loop calculates the error between the voltage active value given and the transformed voltage active value, and sends the calculation result to the PI controller; The output result of the PI controller is used as the active value of the output current loop, and the error is calculated with the transformed current active value, and the calculation result is sent to the PI controller; At the same time, the output voltage loop calculates the error between the voltage reactive value and the transformed voltage reactive value, and the calculation result is sent to the PI controller; the output result of the PI controller is used as the reactive value of the output current loop, and the error is calculated between it and the transformed current reactive value, and the calculation result is sent to the PI controller; The output result of the output current loop and the 0-sequence injection are converted into a duty cycle through the dq conversion unit and sent to the control signal generation module to output the control signal corresponding to the DC / AC unit.

9. The generator access control method of the energy storage power generation system according to any one of claims 1 to 8, characterized in that: The control switch adopts a selector switch. The AC side of the energy storage converter is connected to the generator and the grid respectively through the control switch. The load is connected between the output port of the energy storage converter and the control switch. When the energy storage converter supplies power to the load alone, the control switch remains disconnected from the generator; When the generator supplies power to the load, the control switch is closed to connect the generator to the AC side of the energy storage converter.

10. The generator access control method of the energy storage power generation system according to any one of claims 1 to 8, characterized in that: The load and the generator are both connected in parallel to the AC side of the energy storage converter through branches, and the control switch is set on the branch corresponding to the generator; When the energy storage converter supplies power to the load alone, the control switch remains disconnected; When the generator supplies power to the load, the control switch is closed to connect the generator to the AC side of the energy storage converter.

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