A photovoltaic storage integrated grid-connected device and control method

Abstract

The present invention belongs to the field of photovoltaic technology, and discloses a photovoltaic-storage integrated grid-connected device, including: a grid-connected converter, a photovoltaic control module, an energy storage control module and a controller, wherein the controller controls the coordinated operation of the grid-connected converter, the photovoltaic control module and the energy storage control module; when the voltage at the grid-connected point falls into the autonomous voltage control interval, the grid-connected converter operates in the autonomous voltage control mode, and adjusts the output power downward; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module is used to control the stability of the DC voltage bus, and the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module. The embodiment of the present invention significantly improves the absorption level of distributed photovoltaic on the user side by promoting the coordinated development of photovoltaic-energy storage on the user side, avoids the abandonment of light, enhances the power controllable capacity of the interconnection line in the high-proportion distributed photovoltaic area, and ensures the safe, reliable and clean operation of the power grid with a high proportion of renewable energy.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a photovoltaic-storage integrated grid-connected device considering autonomous voltage control, and also to a photovoltaic-storage integrated grid-connected control method considering autonomous voltage control. Background Art

[0002] As the capacity of distributed photovoltaic grid-connected continues to grow, during the period of distributed photovoltaic power generation, the system voltage in some areas will increase, or even exceed the limit. Taking the qualified voltage of users as the starting point and the end point, in accordance with the principle of joint participation of sources, networks, and loads in grid management, the user voltage will be compulsorily limited to the qualified range to the maximum extent. Although this approach can solve the problem of reverse heavy overload of distribution transformers in the substation area caused by the transformation of substation area and the large amount of power transmission, there is a problem of power limitation in some time periods, which reduces the effective power generation hours of users' photovoltaic power generation and affects the user's benefits. Summary of the invention

[0003] The embodiments of the present invention provide a photovoltaic and energy storage integrated grid-connected device and control method considering autonomous voltage control to solve the problem of limited power in some periods of time in existing grid management methods. In order to have a basic understanding of some aspects of the disclosed embodiments, a simple summary is given below. This summary is not a general review, nor is it intended to identify key / important components or describe the scope of protection of these embodiments. Its sole purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

[0004] According to a first aspect of an embodiment of the present invention, a photovoltaic-storage integrated grid-connected device is provided.

[0005] In one embodiment, a photovoltaic and energy storage integrated grid-connected device includes:

[0006] Grid-connected converter, photovoltaic control module, energy storage control module and controller. The controller controls the coordinated operation of the grid-connected converter, photovoltaic control module and energy storage control module.

[0007] The AC side of the grid-connected converter is connected to the AC grid, and the DC busbar output by the grid-connected converter is connected to the photovoltaic control module and the energy storage control module respectively;

[0008] The photovoltaic control module is used for maximum power capture control of the photovoltaic module, and the energy storage control module is used for charge and discharge control of the energy storage battery. The photovoltaic control module and the energy storage control module are used as plug-and-play interfaces set on the user side to realize modular networking of photovoltaic modules and energy storage batteries;

[0009] When the grid-connected point voltage falls into the autonomous voltage control range, the grid-connected converter operates in the autonomous voltage control mode and adjusts the output power downward; the photovoltaic control module operates in the MPPT mode to achieve maximum power tracking of the photovoltaic modules; the energy storage control module is used to control the stability of the DC voltage bus, and the energy storage control module controls the energy storage battery to absorb the additional output of the photovoltaic modules.

[0010] Optionally, the energy storage control module operates in the following mode:

[0011] In the first time period, when the grid connection point voltage falls into the autonomous voltage control range, the energy storage control module controls the energy storage battery to absorb the additional output of the photovoltaic module;

[0012] In the second time period, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

[0013] Optionally, in the second time period, when it is necessary to participate in peak load regulation, the energy storage control module is used to control the energy storage battery to discharge at rated power, and the grid-connected converter is used to control the DC bus voltage to be stable, so as to achieve full transmission of the energy storage power to the grid side and participate in grid regulation; the photovoltaic control module stops running.

[0014] Optionally, the first time period and the second time period are set according to photovoltaic daily output characteristics and daily load characteristics of the entire network.

[0015] Optionally, during the period from 7:00 to 18:00 every day, when the voltage at the grid connection point falls into the autonomous voltage control interval, the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module;

[0016] Starting from 18:00 every day, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

[0017] Optionally, the rated power of the energy storage battery is configured to be greater than the maximum value of the downstream power regulation coefficient of the grid-connected converter.

[0018] Optionally, the capacity of the energy storage battery is configured to be charged or discharged at rated power for a time not less than T, where T is obtained based on the time when the voltage at the user's photovoltaic grid-connected point exceeds the lower limit of the autonomous voltage control interval every day.

[0019] Optionally, when U T1 ≤U a When the grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state;

[0020] Among them, U is the grid voltage, U T1 is the first threshold voltage, U​a It is the lower limit of the autonomous voltage control range.

[0021] Optionally, when U<U T1 When the inverter is turned off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running;

[0022] Among them, U is the grid voltage, U T1 is the first threshold voltage, U T1 <U a , U a It is the lower limit of the autonomous voltage control range.

[0023] Optionally, when U>U b When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running;

[0024] Among them, U is the grid voltage, U b It is the upper limit of the autonomous voltage control range.

[0025] According to a second aspect of an embodiment of the present invention, a photovoltaic-storage integrated grid-connected control method is provided.

[0026] In one embodiment, the above photovoltaic-storage integrated grid-connected control method controls the coordinated operation of the grid-connected converter, the photovoltaic control module, and the energy storage control module;

[0027] When the grid-connected point voltage falls into the autonomous voltage control range, the grid-connected converter operates in the autonomous voltage control mode and adjusts the output power downward; the photovoltaic control module operates in the MPPT mode to achieve maximum power tracking of the photovoltaic modules; the energy storage control module is used to control the stability of the DC voltage bus, and the energy storage control module controls the energy storage battery to absorb the additional output of the photovoltaic modules.

[0028] Optionally, when U T1 ≤U a When the grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state;

[0029] Among them, U is the grid voltage, U T1 is the first threshold voltage, U a It is the lower limit of the autonomous voltage control range.

[0030] Optionally, when U<U T1 When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running;

[0031] Among them, U is the grid voltage, U T1 is the first threshold voltage, U​T1 <U a , U a It is the lower limit of the autonomous voltage control range.

[0032] Optionally, when U>U b When the inverter is turned off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running;

[0033] Among them, U is the grid voltage, U b It is the upper limit of the autonomous voltage control range.

[0034] Optionally, the energy storage control module operates in the following mode:

[0035] In the first time period, when the grid connection point voltage falls into the autonomous voltage control range, the energy storage control module controls the energy storage battery to absorb the additional output of the photovoltaic module;

[0036] In the second time period, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

[0037] Optionally, in the second time period, when it is necessary to participate in peak load regulation, the energy storage control module is used to control the energy storage battery to discharge at rated power, and the grid-connected converter is used to control the DC bus voltage to be stable, so as to achieve full transmission of the energy storage power to the grid side and participate in grid regulation; the photovoltaic control module stops running.

[0038] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0039] In the embodiment of the present invention, when the grid connection point voltage does not fall within the autonomous voltage control interval, the energy storage system does not perform power throughput; when the grid connection point voltage falls within the autonomous voltage control interval, the autonomous voltage control strategy is used to absorb the photovoltaic peak power and control the grid connection point voltage within the target voltage to avoid the occurrence of overvoltage in the distribution station area.

[0040] During the voltage control process of the embodiment of the present invention, the photovoltaic module always operates in the MPPT mode to ensure the efficient operation of the photovoltaic module.

[0041] The embodiments of the present invention significantly improve the absorption level of distributed photovoltaics on the user side by promoting the coordinated development of photovoltaics and energy storage on the user side, avoid abandonment of light, enhance the power controllable capacity of the interconnection lines in areas with a high proportion of distributed photovoltaic stations, and ensure the safe, reliable and clean operation of power grids with a high proportion of renewable energy.

[0042] The novel photovoltaic and energy storage integrated grid-connected device of the embodiment of the present invention realizes modular networking and plug-and-play of distributed photovoltaic and energy storage systems, and reduces the difficulty of access and operation and maintenance of the photovoltaic and energy storage systems on the user side.

[0043] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0045] Figure 1 is a schematic structural diagram of a photovoltaic-storage integrated grid-connected device according to an exemplary embodiment;

[0046] Figure 2 is an operation curve diagram of an autonomous voltage control process according to an exemplary embodiment;

[0047] Figure 3 It is a flow chart of a photovoltaic-storage integrated grid-connected control method according to an exemplary embodiment. DETAILED DESCRIPTION

[0048] The following description and accompanying drawings fully illustrate the specific embodiments of this article so that those skilled in the art can practice them. Parts and features of some embodiments may be included in or replace parts and features of other embodiments. The scope of the embodiments of this article includes the entire scope of the claims, as well as all available equivalents of the claims. Herein, the terms "first", "second", etc. are only used to distinguish one element from another, without requiring or implying any actual relationship or order between these elements. In fact, the first element can also be called the second element, and vice versa. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the structure, device or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such structure, device or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the structure, device or equipment including the elements. Each embodiment is described in a progressive manner herein, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other.

[0049] The terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. in this document indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing this document and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of this document, unless otherwise specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, it can also be the internal communication of two elements, it can be a direct connection, or it can be an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0050] As used herein, the term "plurality" means two or more than two, unless otherwise specified.

[0051] In this document, the character " / " indicates that the preceding and following objects are in an "or" relationship. For example, A / B means: A or B.

[0052] In this article, the term "and / or" is a description of the association relationship between objects, indicating that three relationships may exist. For example, A and / or B means: A or B, or, A and B.

[0053] Figure 1 An embodiment of the photovoltaic-storage integrated grid-connected device of the present invention is shown.

[0054] In this embodiment, the photovoltaic and energy storage integrated grid-connected device includes: a grid-connected converter, a photovoltaic control module and an energy storage control module. The AC side of the grid-connected converter is connected to the AC power grid. The DC bus of the grid-connected converter is connected to the photovoltaic control module and the energy storage control module respectively. The photovoltaic control module is used for the maximum power capture control of the photovoltaic module. The energy storage control module is used for the charge and discharge control of the energy storage battery. The photovoltaic control module and the energy storage control module are plug-and-play interfaces set on the user side to realize the modular networking of the photovoltaic module and the energy storage battery. When the grid-connected point voltage falls into the autonomous voltage control interval, the grid-connected converter operates in the autonomous voltage control mode and adjusts the output power downward. The photovoltaic control module operates in the MPPT mode to realize the maximum power tracking of the photovoltaic module. The energy storage control module is used to control the stability of the DC voltage bus. The energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module. The photovoltaic and energy storage integrated grid-connected device also includes a controller, which controls the grid-connected converter, the photovoltaic control module and the energy storage control module to operate in coordination.

[0055] For users, they only need to connect the photovoltaic DC bus line to the photovoltaic control module of the integrated photovoltaic and storage grid-connected device, and connect the battery collection line to the energy storage control module of the integrated photovoltaic and storage grid-connected device. Through two DC interfaces, they can realize modular plug-and-play, collaborative networking and integrated operation control of photovoltaic and storage, greatly reducing the difficulty of access and operation and maintenance of the photovoltaic and storage system on the user side.

[0056] In the embodiment of the present invention, when the grid connection point voltage does not fall within the autonomous voltage control interval, the energy storage system does not perform power throughput; when the grid connection point voltage falls within the autonomous voltage control interval, the autonomous voltage control strategy is used to absorb the photovoltaic peak power and control the grid connection point voltage within the target voltage to avoid the occurrence of overvoltage in the distribution station area.

[0057] The embodiments of the present invention significantly improve the absorption level of distributed photovoltaics on the user side by promoting the coordinated development of photovoltaics and energy storage on the user side, avoid abandonment of light, enhance the power controllable capacity of the interconnection lines in areas with a high proportion of distributed photovoltaic stations, and ensure the safe, reliable and clean operation of power grids with a high proportion of renewable energy.

[0058] In one embodiment, the grid-connected converter outputs a DC bus connected in parallel to the photovoltaic control module and the energy storage control module.

[0059] In one embodiment, the photovoltaic control module controls the photovoltaic assembly to always operate in the maximum power capture (MPPT) mode. In the voltage control process of the embodiment of the present invention, the photovoltaic assembly always operates in the MPPT mode to ensure efficient operation of the photovoltaic assembly.

[0060] In one embodiment, the photovoltaic control module is a DC / DC converter.

[0061] In one embodiment, the energy storage control module sets the operation mode as follows: in the first time period, when the grid connection point voltage falls into the autonomous voltage control interval [U a , U b ], the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module; in the second time period, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

[0062] Optionally, the first time period and the second time period can be set according to the photovoltaic daily output characteristics and the daily load characteristics of the entire network. For example, during the period from 7 to 18 o'clock every day, when the grid connection point voltage falls into the autonomous voltage control interval [U a , U b ], the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic panels; starting from 18:00 every day, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

[0063] In one embodiment, in the above-mentioned second time period, when the grid needs to participate in peak load regulation, the energy storage control module is used to control the energy storage battery to discharge at rated power, and the grid-connected converter is used to control the DC bus voltage to be stable, so as to achieve full transmission of the energy storage power to the grid side and participate in grid regulation; the photovoltaic control module stops running.

[0064] In one embodiment, the energy storage control module is a DC / DC converter.

[0065] In one embodiment, when the grid voltage U falls into the autonomous voltage control interval, that is, U a ≤U≤U b When , the grid-connected converter operates in the active power-voltage droop characteristic mode, and the relationship between its output power and the grid-connected point voltage is shown in formula (1):

[0066] P t =P real -(UU a )k (1)

[0067] P t is the power control target value at the current moment, that is, the real-time output power control target;

[0068] P real is the actual output power of the current grid-connected converter;

[0069] k is the power regulation coefficient, and its magnitude is related to the rated capacity of the grid-connected converter and the deviation of the grid-connected point voltage U from the lower limit of the autonomous voltage control interval U. a is proportional to the degree.

[0070] U a is the lower limit of the autonomous voltage control interval, that is, the starting point of the autonomous voltage control of the grid-connected converter. When the grid-connected point voltage U falls into the autonomous voltage control interval, as the grid-connected point voltage increases, the grid-connected converter adjusts the output power downward to the lower limit of the autonomous voltage control interval U. a is the target voltage, and the goal is to control the grid voltage U not to exceed U b , U b It is the upper limit value of the autonomous voltage control interval to achieve the purpose of controlling the voltage at the grid connection point.

[0071] Autonomous voltage control interval lower limit U a and the upper limit of the autonomous voltage control interval U b The value is set according to relevant standards.

[0072] In one embodiment, a dead zone is provided for the power regulation coefficient k to avoid frequent reciprocating regulation of the grid-connected converter when the voltage fluctuates within a small range.

[0073] Optionally, when (UU a)<i, k=0, at this time it is the dead zone adjustment, i is the set value, which is set according to the required dead zone range, and the larger i is, the larger the dead zone range is. Optionally, i=1V.

[0074] Optionally, when (UU a )>i, the power regulation coefficient k satisfies the requirements of formula (2):

[0075]

[0076] Among them, P n is the rated power of the grid-connected converter, j is the set value. Optionally, i=1V. Optionally, j=7%.

[0077] From formula (2), we can see that as the voltage at the photovoltaic grid-connected point increases, the higher the downstream power regulation coefficient k of the grid-connected converter, the greater the degree of power reduction. For example, the autonomous voltage control interval is 105%U n ≤U≤107%U n , the maximum power regulation coefficient can reach 2jP n , taking j = 7% as an example, the maximum power regulation coefficient is 14%P n .

[0078] In one embodiment, the rated power of the energy storage battery is configured to be greater than the maximum value of the downstream power regulation coefficient of the grid-connected converter. For example, the autonomous voltage control interval is 105% U n ≤U≤107%U n , j = 7%, the maximum value of the downstream power regulation coefficient of the grid-connected converter is 14%P n , the rated power of the energy storage battery is configured as 15%P n .

[0079] In one embodiment, the capacity of the energy storage battery is configured to be charged or discharged at rated power for a time not less than T, where T is obtained based on the time that the voltage at the user's photovoltaic grid-connected point exceeds the lower limit of the autonomous voltage control interval every day. For example, the capacity of the energy storage battery is configured to be charged or discharged at rated power for a time not less than 1 hour.

[0080] In one embodiment, during the autonomous voltage control process, the control period T should be 10 to 15 seconds. In each control period, ΔU (ΔU = UU a ) and power P real Feedback control ensures that the photovoltaic output is continuously adjusted downward as the grid-connected point voltage increases. Optionally, the grid-connected converter should have a control response time of less than 60ms for each adjustment.

[0081] A specific embodiment of the autonomous voltage control mode of the grid-connected converter is given below.

[0082] This embodiment combines the requirements of the national standard GB / T29319 "Technical Regulations for the Connection of Photovoltaic Power Generation Systems to Distribution Networks" for the distributed photovoltaic operation range to formulate an autonomous voltage control range. For 380V users, that is, the photovoltaic voltage U n =380V, when the grid voltage U falls into the autonomous voltage control interval 105%U n ≤U≤107%U n When , the grid-connected converter operates in the active power-voltage droop characteristic mode, and the relationship between its output power and the grid-connected point voltage is shown in formula (3):

[0083] P t =P real -(U-105%U n )k (3)

[0084] P t is the power control target value at the current moment, that is, the real-time output power control target;

[0085] P real is the actual output power of the current grid-connected converter;

[0086] k is the power regulation coefficient, and its value is related to the rated capacity of the grid-connected converter and the deviation of U from 105% U n is proportional to the degree.

[0087] 105% U n It is the starting point for the grid-connected converter to perform autonomous voltage control. When the grid-connected point voltage U falls into the autonomous voltage control interval, that is, 105% U n ≤U≤107%U n When the grid-connected point voltage increases, the grid-connected converter automatically adjusts the output power downward and autonomously controls the output to reduce the output to 105% U n The target voltage is to control the grid voltage U not to exceed 107% U n .

[0088] When (U-105%U n )<1V, k=0, which is the dead zone of regulation. n )>1V, the power regulation coefficient k satisfies the requirement of formula (4):

[0089]

[0090] Among them, P n It can be seen from formula (4) that as the voltage of the photovoltaic grid-connected point continues to increase, the higher the downstream power adjustment coefficient k of the grid-connected converter is, the greater the degree of power reduction is. Taking j = 7% as an example, the maximum adjustment rate of the photovoltaic autonomous downstream power is 14%P nAccordingly, the rated power of the energy storage battery is configured as 15%P n , the capacity of the energy storage battery is configured to be charged or discharged at rated power for no less than 1 hour.

[0091] According to equations (3) and (4), the operating curve of the grid-connected converter during autonomous voltage control is obtained as follows: Figure 2 (AB segment curve) shown.

[0092] During the above overvoltage suppression process, the line voltage difference from the substation side to the user side is limited to 2% U n Within the range (temporarily consider the distribution transformer and the upper 10kV system as an infinite system, the low-voltage side outlet voltage of the distribution transformer is 105%U n Due to the power return, the voltage on the user side increases, but the maximum value will not exceed 107% U n ), at this time the reverse power flow is about R is the equivalent resistance of the line within the substation, that is, the maximum value of the reverse power flow allowed.

[0093] When the distribution transformer in the substation supplies power to the load at full capacity, the distribution transformer and the upper 10kV system are temporarily considered as an infinite system, and the low-voltage side outlet voltage of the distribution transformer is 105% U n , the voltage on the user side is reduced to 100% U n , the line pressure difference from the low-voltage side of the distribution transformer to the user side is 5% U n , the normal full load capacity S0 of the distribution transformer in the substation is

[0094] Therefore, relative to the full load capacity S0 of the distribution transformer, the maximum value of the photovoltaic power flow allowed to be reversed is 16% S0 through the autonomous voltage control strategy, and the suppressed photovoltaic reverse power flow is That is 84% ​​S0, thereby avoiding the reverse heavy overload problem of the distribution transformer in the substation.

[0095] In some other embodiments, for 220V users, that is, connected to the photovoltaic voltage U n =220V. When implementing the above-mentioned grid-connected converter autonomous voltage control mode, the autonomous voltage control range can be adjusted accordingly according to relevant standards.

[0096] In other embodiments, when relevant standards are changed or adjusted, when implementing the above-mentioned grid-connected converter autonomous voltage control mode, the autonomous voltage control interval can be adjusted accordingly according to the relevant standards.

[0097] In one embodiment, when U T1 ≤U a ​In the above photovoltaic energy storage integrated grid-connected device, the grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state; where U is the grid-connected point voltage, U T1 is the first threshold voltage, U a It is the lower limit of the autonomous voltage control range.

[0098] In one embodiment, when U>U b When , the grid-connected converter, energy storage control module and photovoltaic control module all stop running; where U is the grid-connected point voltage, U b It is the upper limit of the autonomous voltage control range.

[0099] In one embodiment, when U<U T1 When , the grid-connected converter, energy storage control module and photovoltaic control module all stop running; where U is the grid-connected point voltage, U T1 is the first threshold voltage, U T1 <U a , U a It is the lower limit of the autonomous voltage control range.

[0100] A specific embodiment of the operation mode of the photovoltaic and energy storage integrated grid-connected device is given below.

[0101] In this embodiment, the photovoltaic voltage U n =380V, combined with the requirements of the national standard GB / T29319 "Technical Regulations for Photovoltaic Power Generation System Access to Distribution Network" for distributed photovoltaic operation range, formulate the operation mode of photovoltaic converter in different voltage ranges, such as Figure 3 As shown, the details are as follows:

[0102] U<85%U n , the grid-connected converter, energy storage control module, and photovoltaic control module all stop running;

[0103] 85% U n ≤U<105%U n The grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state; where U is the grid-connected point voltage, U T1 is the first threshold voltage, U a is the lower limit of the autonomous voltage control range;

[0104] When U>107%U n When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running.

[0105] In other embodiments, for 220V users, when implementing the above-mentioned photovoltaic storage integrated grid-connected device, the autonomous voltage control interval, the first threshold U T1 Just make the corresponding adjustments.

[0106] In other embodiments, when the relevant standards are changed or adjusted, when implementing the above-mentioned photovoltaic storage integrated grid-connected device, the autonomous voltage control interval, the first threshold U T1 Just make the corresponding adjustments.

[0107] In another embodiment, the present invention also proposes a photovoltaic-storage integrated grid-connected control method, which controls the coordinated operation of the grid-connected converter, the photovoltaic control module, and the energy storage control module; when the grid-connected point voltage falls into the autonomous voltage control interval, the grid-connected converter operates in the autonomous voltage control mode, and downstream adjusts the output power; the photovoltaic control module operates in the MPPT mode to achieve maximum power tracking of the photovoltaic module; the energy storage control module is used to control the stability of the DC voltage bus, and the energy storage control module controls the energy storage battery to absorb the additional output of the photovoltaic module.

[0108] In one embodiment, the energy storage control module sets the operation mode as follows: in the first time period, when the grid connection point voltage falls into the autonomous voltage control interval [U a , U b ], the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module; in the second time period, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

[0109] Optionally, the above time period can be set according to the photovoltaic daily power generation characteristics and the daily load characteristics of the entire network. For example, during the period from 7 to 18 o'clock every day, when the grid connection point voltage falls into the autonomous voltage control interval [U a , U b ], the above method controls the energy storage battery to absorb the extra output of the photovoltaic module; starting from 18:00 every day, the above method controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

[0110] In one embodiment, in the above-mentioned second time period, when the grid needs to participate in peak load regulation, the energy storage control module is used to control the energy storage battery to discharge at rated power, and the grid-connected converter is used to control the DC bus voltage to be stable, so as to achieve full transmission of the energy storage power to the grid side and participate in grid regulation; the photovoltaic control module stops running.

[0111] In one embodiment, when the grid voltage U falls into the autonomous voltage control interval, that is, U a ≤U≤U bWhen , the grid-connected converter operates in the active power-voltage droop characteristic mode, and the relationship between its output power and the grid-connected point voltage is shown in formula (1):

[0112] P t =P real -(UU a )k (1)

[0113] P t is the power control target value at the current moment, that is, the real-time output power control target;

[0114] P real is the actual output power of the current grid-connected converter;

[0115] k is the power regulation coefficient, and its magnitude is related to the rated capacity of the grid-connected converter and the deviation of the grid-connected point voltage U from the lower limit of the autonomous voltage control interval U. a is proportional to the degree.

[0116] U a is the lower limit of the autonomous voltage control interval, that is, the starting point of the autonomous voltage control of the grid-connected converter. When the grid-connected point voltage U falls into the autonomous voltage control interval, as the grid-connected point voltage increases, the grid-connected converter adjusts the output power downward to the lower limit of the autonomous voltage control interval U. a is the target voltage, and the goal is to control the grid voltage U not to exceed U b , U b It is the upper limit value of the autonomous voltage control interval to achieve the purpose of controlling the voltage at the grid connection point.

[0117] Autonomous voltage control interval lower limit U a and the upper limit of the autonomous voltage control interval U b The value is set according to relevant standards.

[0118] In one embodiment, for the power regulation coefficient k, the above method is further provided with a regulation dead zone to avoid frequent reciprocating regulation of the grid-connected converter when the voltage fluctuates within a small range.

[0119] Optionally, when (UU a )<i, k=0, at this time it is the dead zone adjustment, i is the set value, which is set according to the required dead zone range, and the larger i is, the larger the dead zone range is. Optionally, i=1V.

[0120] Optionally, when (UU a )>i, the power regulation coefficient k satisfies the requirements of formula (2):

[0121]

[0122] Among them, P nis the rated power of the grid-connected converter, j is the set value. Optionally, i=1V. Optionally, j=7%.

[0123] It can be seen from formula (2) that as the voltage of the photovoltaic grid-connected point increases, the downstream power regulation coefficient k of the above method becomes higher, that is, the downstream power regulation rate becomes higher, and the degree of power reduction increases.

[0124] In one embodiment, considering that according to the above autonomous voltage control mode, the photovoltaic power autonomously performs downstream power regulation, the rated power of the energy storage battery is configured to be greater than the maximum value k of the downstream power regulation coefficient. max , the capacity is configured to charge or discharge at a rated power not less than T, the value of T depends on the daily voltage of the user's photovoltaic grid-connected point exceeding U a Optionally, the energy storage battery rated power is configured as k max +1%P n Optionally, the energy storage battery capacity is configured to be charged or discharged at rated power for no less than 1 hour.

[0125] The autonomous voltage control mode, for example, the autonomous voltage control interval is 105% U n ≤U≤107%U n , the maximum power regulation coefficient reaches 2jP n Therefore, the rated power of the energy storage battery is configured to be greater than the maximum value of the downlink power regulation coefficient, that is, 2jP n Optionally, the rated power of the energy storage battery is configured as (2j+1%)P n Taking j = 7% as an example, the maximum adjustment rate of autonomous downlink power is 14%P n Therefore, the rated power of the energy storage battery is configured to be no less than 15% P n , the capacity must be sufficient to charge or discharge at rated power for no less than 1 hour.

[0126] In one embodiment, when U T1 ≤U a In the above photovoltaic energy storage integrated grid-connected device, the grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state; where U is the grid-connected point voltage, U T1 is the first threshold voltage, U a It is the lower limit of the autonomous voltage control range.

[0127] In one embodiment, when U>U b When , the grid-connected converter, energy storage control module and photovoltaic control module all stop running; where U is the grid-connected point voltage, U b It is the upper limit of the autonomous voltage control range.​

[0128] In one embodiment, when U<U T1 When , the grid-connected converter, energy storage control module and photovoltaic control module all stop running; where U is the grid-connected point voltage, U T1 is the first threshold voltage, U T1 <U a , U a It is the lower limit of the autonomous voltage control range.

[0129] A specific embodiment of the photovoltaic-storage integrated grid-connected control method is given below.

[0130] like Figure 3 As shown, this embodiment combines the requirements of the national standard GB / T29319 "Technical Regulations for the Connection of Photovoltaic Power Generation Systems to Distribution Networks" for the distributed photovoltaic operation range to formulate an autonomous voltage control range. For 380V users, that is, the photovoltaic voltage U n =380V, when the grid voltage U falls into the autonomous voltage control interval 105%U n ≤U≤107%U n When , the grid-connected converter operates in the active power-voltage droop characteristic mode, and the relationship between its output power and the grid-connected point voltage is shown in formula (3):

[0131] P t =P real -(U-105%U n )k (3)

[0132] P t is the power control target value at the current moment, that is, the real-time output power control target;

[0133] P real is the actual output power of the current grid-connected converter;

[0134] k is the power regulation coefficient, and its value is related to the rated capacity of the grid-connected converter and the deviation of U from 105% U n is proportional to the degree.

[0135] 105% U n It is the starting point for the grid-connected converter to perform autonomous voltage control. When the grid-connected point voltage is less than 105% U n When the grid voltage U falls into the autonomous voltage control range, that is, 105% U n ≤U≤107%U n When the grid-connected point voltage increases, the grid-connected converter autonomously adjusts the output power downward and autonomously controls the output to reduce the output. The goal is to control the grid-connected point voltage U not to exceed 107% U n .

[0136] When (U-105%U n )<1V, k=0, which is the dead zone of regulation. n )>1V, the power regulation coefficient k satisfies the requirement of formula (4):

[0137]

[0138] Among them, P n It can be seen from formula (4) that as the voltage of the photovoltaic grid-connected point continues to increase, the higher the downstream power adjustment coefficient k of the grid-connected converter is, the greater the degree of power reduction is. Taking j = 7% as an example, the maximum adjustment rate of the photovoltaic autonomous downstream power is 14%P n Therefore, the rated power of the energy storage battery is configured to be no less than 15% P n , the capacity must be sufficient to charge or discharge at rated power for no less than 1 hour.

[0139] When 85%U n ≤U<105%U n When the grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state; where U is the grid-connected point voltage, U T1 is the first threshold voltage, U a is the lower limit of the autonomous voltage control range;

[0140] When U<85%U n When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running;

[0141] When U>107%U n When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running.

[0142] The present invention is not limited to the structures which have been described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A photovoltaic and energy storage integrated grid-connected device, characterized in that: include: Grid-connected converter, photovoltaic control module, energy storage control module and controller. The controller controls the coordinated operation of the grid-connected converter, photovoltaic control module and energy storage control module. The AC side of the grid-connected converter is connected to the AC grid, and the DC busbar output by the grid-connected converter is connected to the photovoltaic control module and the energy storage control module respectively; The photovoltaic control module is used for maximum power capture control of the photovoltaic module, and the energy storage control module is used for charge and discharge control of the energy storage battery. The photovoltaic control module and the energy storage control module are used as plug-and-play interfaces set on the user side to realize modular networking of photovoltaic modules and energy storage batteries; When the grid-connected point voltage falls into the autonomous voltage control range, the grid-connected converter operates in the autonomous voltage control mode and adjusts the output power downward; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module is used to control the stability of the DC voltage bus, and the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module; The rated power of the energy storage battery is configured to be greater than the maximum value of the downstream power regulation coefficient of the grid-connected converter; The capacity of the energy storage battery is configured to be charged or discharged at rated power for a time not less than T, where T is obtained based on the time when the voltage at the user's photovoltaic grid-connected point exceeds the lower limit of the autonomous voltage control interval every day; When U<U T1 When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running; Among them, U is the grid voltage, U T1 is the first threshold voltage, U T1 <U a , U a is the lower limit of the autonomous voltage control range; When U>U b When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running; Among them, U is the grid voltage, U b is the upper limit of the autonomous voltage control interval; When the grid voltage U falls into the autonomous voltage control range, that is, U a ≤U≤U b When , the grid-connected converter operates in the active power-voltage droop characteristic mode, and the relationship between its output power and the grid-connected point voltage is shown in formula (1): P t =P real -(UU a )k (1) P t is the power control target value at the current moment, that is, the real-time output power control target; P real is the actual output power of the current grid-connected converter; k is the power regulation coefficient, and its magnitude is related to the rated capacity of the grid-connected converter and the deviation of the grid-connected point voltage U from the lower limit of the autonomous voltage control interval U. a is proportional to the degree of For the power regulation coefficient k, a regulation dead zone is also set. a )<i, k=0, this is the dead zone adjustment, i is the set value, and it is set according to the required dead zone range. The larger i is, the larger the dead zone range is; when (UU a )>i, the power regulation coefficient k satisfies the requirements of formula (2): Among them, P n is the rated power of the grid-connected converter, and j is the set value.

2. The photovoltaic and energy storage integrated grid-connected device according to claim 1, characterized in that: The energy storage control module operation mode is: In the first time period, when the grid connection point voltage falls into the autonomous voltage control range, the energy storage control module controls the energy storage battery to absorb the additional output of the photovoltaic module; In the second time period, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

3. The photovoltaic and energy storage integrated grid-connected device according to claim 2, characterized in that: In the second time period, when it is necessary to participate in peak load regulation, the energy storage control module is used to control the energy storage battery to discharge at rated power, and the grid-connected converter is used to control the DC bus voltage to stabilize, so as to achieve full transmission of the energy storage power to the grid side and participate in grid regulation; the photovoltaic control module stops running.

4. The photovoltaic and energy storage integrated grid-connected device according to claim 2, characterized in that: The first time period and the second time period are set according to the photovoltaic daily output characteristics and the daily load characteristics of the entire network.

5. The photovoltaic and energy storage integrated grid-connected device according to claim 1, characterized in that: During the period from 7:00 to 18:00 every day, when the voltage at the grid connection point falls into the autonomous voltage control range, the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module; Starting from 18:00 every day, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

6. The photovoltaic and energy storage integrated grid-connected device according to claim 1, characterized in that: When U T1 ≤U a When the grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state;​ Among them, U is the grid voltage, U T1 is the first threshold voltage, U a It is the lower limit of the autonomous voltage control range.

7. A photovoltaic energy storage integrated grid-connected control method, characterized in that: Control the coordinated operation of the grid-connected converter, photovoltaic control module, and energy storage control module; When the grid-connected point voltage falls into the autonomous voltage control range, the grid-connected converter operates in the autonomous voltage control mode and adjusts the output power downward; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module is used to control the stability of the DC voltage bus, and the energy storage control module controls the energy storage battery to absorb the extra output of the photovoltaic module; The rated power of the energy storage battery is configured to be greater than the maximum value of the downstream power regulation coefficient of the grid-connected converter; The capacity of the energy storage battery is configured to be charged or discharged at rated power for a time not less than T, where T is obtained based on the time when the voltage at the user's photovoltaic grid-connected point exceeds the lower limit of the autonomous voltage control interval every day; When U<U T1 When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running; Among them, U is the grid voltage, U T1 is the first threshold voltage, U T1 <U a , U a is the lower limit of the autonomous voltage control range; When U>U b When the power is off, the grid-connected converter, energy storage control module and photovoltaic control module all stop running; Among them, U is the grid voltage, U b is the upper limit of the autonomous voltage control interval; When the grid voltage U falls into the autonomous voltage control range, that is, U a ≤U≤U b When , the grid-connected converter operates in the active power-voltage droop characteristic mode, and the relationship between its output power and the grid-connected point voltage is shown in formula (1): P t =P real -(UU a )k (1) P t is the power control target value at the current moment, that is, the real-time output power control target; P real is the actual output power of the current grid-connected converter; k is the power regulation coefficient, and its magnitude is related to the rated capacity of the grid-connected converter and the deviation of the grid-connected point voltage U from the lower limit of the autonomous voltage control interval U. a is proportional to the degree of For the power regulation coefficient k, a regulation dead zone is also set. a )<i, k=0, this is the dead zone adjustment, i is the set value, and it is set according to the required dead zone range. The larger i is, the larger the dead zone range is; when (UU a )>i, the power regulation coefficient k satisfies the requirements of formula (2): Among them, P n is the rated power of the grid-connected converter, and j is the set value.

8. A photovoltaic-storage integrated grid-connected control method as claimed in claim 7, characterized in that: Also includes: When U T1 ≤U a When the grid-connected converter is used to control the DC voltage stability and transmit the photovoltaic power to the grid-connected side to the maximum extent; the photovoltaic control module operates in the MPPT mode to achieve the maximum power tracking of the photovoltaic module; the energy storage control module operates in the hot / cold standby state;​ Among them, U is the grid voltage, U T1 is the first threshold voltage, U a It is the lower limit of the autonomous voltage control range.

9. The photovoltaic-storage integrated grid-connected control method according to claim 7, characterized in that: The energy storage control module operation mode is: In the first time period, when the grid connection point voltage falls into the autonomous voltage control range, the energy storage control module controls the energy storage battery to absorb the additional output of the photovoltaic module; In the second time period, the energy storage control module controls the energy storage battery to release the stored energy at rated power until the discharge is completed.

10. A photovoltaic energy storage integrated grid-connected control method as claimed in claim 9, characterized in that: In the second time period, when it is necessary to participate in peak load regulation, the energy storage control module is used to control the energy storage battery to discharge at rated power, and the grid-connected converter is used to control the DC bus voltage to stabilize, so as to achieve full transmission of the energy storage power to the grid side and participate in grid regulation; the photovoltaic control module stops running.

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