CN115663828B - Control method for voltage of photovoltaic energy storage bus - Google Patents
Control method for voltage of photovoltaic energy storage bus Download PDFInfo
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Abstract
The invention discloses a control method of a photovoltaic energy storage bus voltage, which comprises the following steps: s1: initially setting a first voltage compensation amount; s2: superposing the first voltage compensation quantity on a bus voltage theoretical value, and outputting a duty ratio; s3: according to the comparison condition of the duty ratio obtained in the step S2 with the first duty ratio limiting value and the second duty ratio limiting value, the current first voltage compensation amount is adjusted and returns to the step S2 or the current first voltage compensation amount is used as the target first voltage compensation amount; s4: obtaining the maximum value of the current photovoltaic voltage, comparing the theoretical value of the bus voltage with the first superposition value of the target first voltage compensation quantity and the maximum value of the current photovoltaic voltage with the second superposition value of the second voltage compensation quantity, and taking the larger value as the bus voltage target value; s5: and stabilizing the bus voltage according to the bus voltage target value. The invention not only overcomes the defect of frequent switching control loop in the prior art, but also obviously improves the overall efficiency of the system.
Description
Technical Field
The invention relates to the technical field of photovoltaic energy storage, in particular to a control method of photovoltaic energy storage bus voltage.
Background
With the improvement of the social awareness of clean energy in recent years, a photovoltaic energy storage power supply has become common equipment in our life, and photovoltaic energy storage has a plurality of key technologies, wherein the adjustment of bus voltage is one of core technologies.
The current bus voltage regulation on the market is usually performed by the following ways: (1) When the energy storage inverter runs off-grid, the bidirectional DC unit realizes the function of stabilizing the bus voltage. (2) When the energy storage inverter is in grid-connected operation, the inverter (bidirectional converter) is used for stabilizing voltage, and the energy storage inverter can be divided into charge control and discharge control. When the charging control is performed, the inverter control loop bus voltage target value is higher than the bus voltage target value of the bidirectional DC; when the discharge control is performed, the inverter control loop bus voltage target value is lower than the bus voltage target of the bidirectional DC.
However, the following two disadvantages exist with the above method: (1) The above description shows that the main bodies for executing bus voltage stabilization during off-grid control, grid-connected charging and grid-connected discharging are different, and the bus control strategies which are finally effective are also different, so that the complexity in control is increased. (2) When the photovoltaic output is connected to the bus, because the photovoltaic output power and the load at the user side are dynamically changed, especially when the photovoltaic output power is larger than the electric power for the load in grid-connected operation, a grid-connected charging strategy is executed; when the output power of the photovoltaic is smaller than the power used by the load, frequent bus control changes occur when the discharge strategy is executed, and the frequent changes inevitably affect the stability of the system, the MPPT (Maximum Power Point Tracking ) efficiency, the grid-connected current performance and the like.
The foregoing background is only for the purpose of facilitating an understanding of the principles and concepts of the invention and is not necessarily in the prior art to the present application and is not intended to be used as an admission that such background is not entitled to antedate such novelty and creativity by the present application without undue evidence prior to the present application.
Disclosure of Invention
In order to solve the technical problems, the invention provides a control method for the voltage of the photovoltaic energy storage bus, which not only overcomes the defect of frequent switching of a control loop, but also remarkably improves the efficiency of the whole photovoltaic energy storage power supply system.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
in a first aspect, the invention discloses a control method of a photovoltaic energy storage bus voltage, comprising the following steps:
s1: initially setting a first voltage compensation amount;
s2: superposing the first voltage compensation quantity to a bus voltage theoretical value to obtain a superposed bus voltage, and outputting a corresponding duty ratio according to the superposed bus voltage;
s3: comparing the duty ratio obtained in the step S2 with a first duty ratio limiting value and a second duty ratio limiting value, and if the duty ratio is smaller than the first duty ratio limiting value, reducing the current first voltage compensation amount and returning to the step S2; if the duty ratio is larger than the second duty ratio limiting value, increasing the current first voltage compensation amount and returning to the step S2; if the duty cycle is between the first duty cycle limit value and the second duty cycle limit value, taking the current first voltage compensation amount as a target first voltage compensation amount, wherein the first duty cycle limit value is smaller than the second duty cycle limit value;
s4: obtaining the maximum value of the current photovoltaic voltage, comparing the theoretical value of the bus voltage with a first superposition value of the target first voltage compensation quantity and a second superposition value of the maximum value of the current photovoltaic voltage with a second voltage compensation quantity, and taking the larger one of the first superposition value and the second superposition value as a bus voltage target value;
s5: and stabilizing the bus voltage according to the bus voltage target value.
Preferably, the step S1 specifically includes: the method comprises the steps of initially setting a first voltage compensation amount according to the running condition of an energy storage power supply system; when the energy storage power supply system is in an off-grid state or a grid-connected discharge state, setting the first voltage compensation quantity to be a positive number; and when the energy storage power supply system is in a grid-connected charging state, setting the first voltage compensation quantity as a positive number or a negative number.
Preferably, when the energy storage power supply system is in an off-grid state, the bus voltage theoretical value is a minimum bus voltage value which needs to be provided for outputting an inversion voltage signal meeting the requirement; when the energy storage power supply system is in a grid-connected discharging state or a grid-connected charging state, the bus voltage theoretical value is a minimum bus voltage value which needs to be provided for realizing the function of selling electricity to a power grid.
Preferably, in step S2, outputting the corresponding duty ratio according to the superimposed bus voltage specifically includes: and outputting a duty ratio average value of one voltage period, a duty ratio of a preset point or an average value of one continuous duty ratio in one voltage period as a corresponding duty ratio according to the superimposed bus voltage.
Preferably, wherein the second duty cycle limit is less than 100%.
Preferably, in step S3, if the duty cycle is smaller than the first duty cycle limit value, the current first voltage compensation amount is reduced and returned to step S2 by adopting a step-by-step and/or binary search method; and if the duty ratio is larger than the second duty ratio limiting value, increasing the current first voltage compensation amount in a stepping and/or dichotomy searching mode and returning to the step S2.
Preferably, the second voltage compensation amount is greater than 0.
Preferably, step S5 specifically includes:
when the energy storage power supply system is in an off-grid state, if the difference value of the current bus voltage minus the bus voltage target value is detected to be larger than a first threshold value, reducing the photovoltaic output power limit value;
when the energy storage power supply system is in a grid-connected charging state, if the difference value of the current bus voltage minus the bus voltage target value is detected to be larger than a second threshold value, reducing charging target power;
when the energy storage power supply system is in a grid-connected discharge state, if the difference value of the bus voltage target value minus the current bus voltage is detected to be larger than a third threshold value, reducing the discharge target power;
wherein the first, second and third thresholds are all greater than 0.
Preferably, the step-down photovoltaic output power limit, the step-down charging target power and the step-down discharging target power are respectively performed by adopting a proportional integral adjustment or step-size gradual change mode.
In a second aspect, the present invention also provides an energy storage power supply system, including: the system comprises a battery unit, a photovoltaic energy storage inversion unit and an energy management system; the battery cell includes: a battery pack and a battery management system; the first end of the battery pack is connected with the battery management system; the photovoltaic energy storage inversion unit comprises: the MPPT controller, DC/DC unit and bi-directional converter; the MPPT controller is characterized in that a first end of the MPPT controller is connected with the photovoltaic panel, and a second end of the MPPT controller is connected with the direct current bus; the first end of the DC/DC unit is connected with the second end of the battery pack, and the second end of the DC/DC unit is connected with the direct current bus; the first end of the bidirectional converter is connected with the direct current bus, and the second end of the bidirectional converter is connected with a power grid and a load; the energy management system is simultaneously in communication connection with the battery management system and the photovoltaic energy storage inversion unit; the energy management system calculates a bus voltage target value according to the control method of the photovoltaic energy storage bus voltage of the first aspect, and the DC/DC unit performs bus voltage stabilization according to the bus voltage target value.
Preferably, the DC/DC unit performs voltage stabilization of the bus voltage according to the bus voltage target value by using a single bus voltage ring control strategy or a bus voltage outer ring and bidirectional DC current inner ring control strategy.
Compared with the prior art, the invention has the beneficial effects that: according to the control method for the photovoltaic energy storage bus voltage, disclosed by the invention, the control of the bus voltage does not need to frequently switch the control loop according to different states such as off-grid state, grid-connected charging and grid-connected discharging, and the like, and under various running states, the function of stabilizing the bus voltage can be executed by the bidirectional DC unit, so that the control complexity of a photovoltaic energy storage power supply system is greatly reduced; in addition, the efficiency of the whole photovoltaic energy storage power supply system is improved to the greatest extent by searching the minimum first voltage compensation quantity meeting the requirement.
In a further scheme, the first voltage compensation amount is set according to different operation conditions of the energy storage power supply system, so that the efficiency of seeking the minimum first voltage compensation amount is effectively improved, and the overall efficiency of the photovoltaic energy storage power supply system is further effectively improved. In addition, under different operation conditions of the energy storage power supply system, according to whether the current bus voltage exceeds a bus voltage target value by a certain range, a supplementary strategy for reducing the photovoltaic output limit value, the charging target power of the inverter and the discharging target power of the inverter is correspondingly provided, so that the bus voltage is more stable, and the stability of the energy storage power supply system is improved.
Drawings
Fig. 1 is a schematic diagram of an architecture topology of an energy storage power supply system based on a control method of a photovoltaic energy storage busbar voltage according to a preferred embodiment of the present invention;
FIG. 2 is a flow chart illustrating the operation of the output energy storage power system;
FIG. 3 is a flow chart of a method for controlling the voltage of a photovoltaic energy storage busbar according to a preferred embodiment of the present invention;
fig. 4 is a schematic diagram of the duty cycle of the output of the bi-directional converter.
Detailed Description
The following describes embodiments of the present invention in detail. It should be emphasized that the following description is merely exemplary in nature and is in no way intended to limit the scope of the invention or its applications.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for both the fixing action and the circuit/signal communication action.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are merely for convenience in describing embodiments of the invention and to simplify the description by referring to the figures, rather than to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless explicitly defined otherwise.
The abbreviations, terms involved in the present invention are first defined and explained as follows.
Udc: DC bus voltage.
Udc_vinv: in the off-grid state, the minimum bus voltage value that needs to be provided in order to output the inverter voltage signal that satisfies the requirements is set.
Udc_vgrid: in the grid-connected state, a minimum bus voltage value is required to be provided for realizing the function of supplying power to the power grid.
Instantaneous duty cycle: after each control period is reached, the control unit calculates the duty ratio value generated to drive the switching device.
Average duty cycle: average of instantaneous duty cycle over a period of time.
Off-grid operation: and the inverter is used as voltage source equipment for actively providing voltage signals meeting requirements for users without power grid access.
Grid-connected charging: the system incorporates a grid, and a bi-directional converter (inverter) uses grid energy to recharge the battery.
Grid-connected discharge: the system incorporates a grid, a process in which a bi-directional converter (inverter) uses battery energy or photovoltaic energy to power a load or feed the grid.
EMS: energy Management System, energy management system. The EMS is a coordination control core of the whole energy storage power supply system, and a reasonable energy management strategy is an important guarantee for realizing effective utilization of renewable energy and safe and economic operation of the energy storage power supply system.
BMS: battery Management System the battery management system, commonly called battery manager, is mainly used for intelligently managing and maintaining each battery unit, preventing the battery from being overcharged and overdischarged, prolonging the service life of the battery, and monitoring the state of the battery. For an excellent BMS, it would be quite excellent to be able to estimate battery parameters of the battery pack on-line in real time to accurately estimate SOC, SOP, SOH of the battery pack, and to be able to correct errors of the initial SOC exceeding 10% and errors of the ampere-hour capacity exceeding 20% or errors of current measurement of several percent in a short time. Wherein, SOC: the state of charge reflects the remaining battery power; SOP: a state of being able to provide power (accurate estimation of SOP can maximize battery utilization efficiency), based on the discharge power or charge power that the battery pack can support at different SOCs, different temperatures; SOH: the state of health of the battery comprises two parts: ampere-hour capacity and power.
Bidirectional current transformer: the bidirectional energy storage inverter is also called as Power Conversion System, PCS for short, and is a device for realizing bidirectional conversion of electric energy. The direct current of the storage battery can be inverted into alternating current (DC-AC) to be transmitted to a power grid or used for alternating current load (load); the AC power of the grid may also be rectified to direct current (AC-DC) to charge the battery.
As shown in fig. 1, the method for controlling the voltage of the photovoltaic energy storage bus is based on a schematic diagram of an architecture topology of an energy storage power system, wherein the energy storage power system 10 comprises a battery unit 11, a photovoltaic energy storage inversion unit 12 and an EMS 13, the battery unit 11 is connected with the photovoltaic energy storage inversion unit 12 in a communication manner (specifically, through a CAN/485 communication connection), the EMS 13 is connected with the battery unit 11 and the photovoltaic energy storage inversion unit 12 in a communication manner), the battery unit 11 comprises a battery pack 111 and a BMS 112 which are connected with each other, the photovoltaic energy storage inversion unit 12 comprises an MPPT controller 121 (MPPT controller is called a "maximum power point tracking" (Maximum Power Point Tracking) solar controller), a DC/DC unit 122 (DC/DC unit is called a bidirectional DC unit) and a bidirectional converter 123, wherein the MPPT controller 121 is connected with the photovoltaic panel 20, and the bidirectional converter 123 is connected with the power grid 30 and the load 40. Solid lines between the units in the figure represent architecture topology, and double-headed arrow dashed lines represent communication topology.
Specifically, the first end of the battery pack 111 is connected to the BMS 112, the first end of the MPPT controller 121 is connected to the photovoltaic panel 20, and the second end is connected to the dc bus; the first end of the DC/DC unit 122 is connected to the second end of the battery pack 111, and the second end is connected to the direct current bus; the first end of the bidirectional converter 123 is connected with the direct current bus, and the second end is used for being connected with the power grid 30 and the load 40; the EMS 13 is simultaneously in communication connection with the BMS 112 and the photovoltaic energy storage inversion unit 12; the EMS 13 calculates a bus voltage target value according to a control method of the photovoltaic energy storage direct current bus voltage disclosed in the following preferred embodiment, and performs voltage stabilization of the bus voltage according to the bus voltage target value by the DC/DC unit.
In the architecture topology of the energy storage power supply system shown in fig. 1, the present invention only needs to stabilize the DC bus voltage by the DC/DC unit 122, and the functions of DC bus voltage algorithm logic management, inversion output target power generation and PV output limit value generation are realized by introducing the EMS 13.
Specifically, the EMS 13 collects SOP (state of power) information from the BMS 112 through a communication circuit, specifically including information of maximum charge power, maximum discharge power or maximum charge current, maximum discharge current, etc. Second, the EMS 13 collects information on the operating state of the bidirectional converter through the communication circuit, and specifically includes information on the inverter voltage, the grid power, the load power, and the like. Third, the EMS 13 collects information on the operating state of the photovoltaic panel 20, specifically including information on the input voltage, input current, power, etc. of the photovoltaic.
As shown in fig. 2, a flow chart of the working state of the output energy storage power supply system is shown, firstly, whether the grid-connected operation is performed is judged, if not, a grid-off state bus voltage algorithm is executed, if yes, whether the grid-connected charging bus voltage algorithm is executed, and if not, a grid-connected discharging bus voltage algorithm is executed. Specifically: when the energy storage power supply system detects that a power grid is connected and the voltage and the frequency of the power grid meet the requirements of grid-connected standards, the system can enter a grid-connected state, otherwise, the system operates in an off-grid state. The power control under the parallel network can be divided into grid-connected charging control and grid-connected discharging control, for example, when a user operates in a peak clipping and valley filling mode, and when the current time is in a charging time period (the system is set in advance, for example, 00:00-8:00 is set as the charging time period), the system enters a grid-connected charging operation state; similarly, when the current time is within the discharge time period, the system operates in a discharge state; in addition, according to the difference of specific functional modes, charging or discharging under the parallel network can be triggered by other reasons, if a current load is connected and the load power is greater than the photovoltaic power in the current self-service mode, the energy of the photovoltaic (corresponding to the photovoltaic panel 20 and the MPPT controller 121 in the architecture topology) and the energy of the battery (corresponding to the battery unit 11 in the architecture topology) are used for supplying power to the load, and the bidirectional converter executes a grid-connected discharging strategy for supplying power to the load.
As shown in fig. 3, the preferred embodiment of the invention discloses a control method for the voltage of a photovoltaic energy storage direct current bus, which comprises the following steps:
s1: initially setting a first voltage compensation amount U1;
s2: superposing the first voltage compensation quantity U1 on a bus voltage theoretical value Udc to obtain a superposed bus voltage, and outputting a corresponding duty ratio D by the bidirectional converter according to the superposed bus voltage;
the bus voltage theoretical value Udc is different according to the state of the energy storage power supply system.
When the energy storage power supply system is in an off-grid state, udc is udc_vinv, which represents a minimum bus voltage value required to be provided for outputting an inversion voltage signal meeting the requirement; such as: when the inversion topology of the current energy storage power supply system selects a T-type level topology, and when single-phase 230V needs to be output, the required minimum bus voltage is 230V 1.414 x 2.
When the system is in a grid-connected state, udc is udc_vgrid, which represents the minimum bus voltage value that needs to be provided in order to achieve the function of supplying power to the grid. Such as: the current detected input voltage of the grid port is 243V, and the required minimum bus voltage is 243v×1.414×2.
Because the bus voltage theoretical value Udc only considers the minimum bus voltage value required by the external environment, and does not consider the power consumption of the energy storage power supply system itself, the current carried load power or the real-time grid-connected power value and the like, when the energy storage power supply system inputs the bus voltage theoretical value Udc, the requirements of off-grid output on-load or grid-connected charging/discharging can not be met, and therefore the first voltage compensation U1 is superimposed on the basis of the bus voltage theoretical value Udc to meet the requirements. The overall efficiency (including PV output efficiency, bidirectional DC efficiency, inversion efficiency and the like) and the output capacity of the energy storage power supply system can be directly influenced by the voltage of the bus, and the overall efficiency is higher when the voltage of the bus is lower under the condition of meeting the requirement. Therefore, the minimum first voltage compensation U1 meeting the requirement is sought, so that the efficiency of the system is maximized.
For the off-grid state and the grid-connected discharge state, U1 is a positive number, namely U1>0; for grid-tied states of charge, U1 may be positive or negative. For example, taking off-grid condition as an example, a 6KW three-phase energy storage system of the present invention may be applied, the U1 value may be selected between (20V, 60V), and most preferably the U1 value is 40V.
The bidirectional converter in the invention adopts a sine wave inverter, and the bidirectional converter completes the inversion task by controlling semiconductor power switching devices (such as SCR, GTO, GTR, IGBT, power MOSFET and the like) to be turned on and off according to a specific rule, wherein the semiconductor power switching devices are parts of the sine wave inverter, and can output the wanted electric signal waveforms by controlling the semiconductor power switching devices, and the semiconductor power switching devices can adopt SCR (silicon controlled rectifier, also called Thyristor), GTO (Gate Turn-off Thyristor), GTR (Giant Transistor), IGBT (Insulated Gate Bipolar Transistor, insulated Gate bipolar field effect Transistor), power MOSFET and the like.
The semiconductor power switching device is controlled to be turned on and off according to a specific rule, and the SPWM control mode is adopted for specific control. The proportion of the energizing (conducting) time relative to the total time during a pulse cycle is referred to as the duty cycle.
By superposing the first voltage compensation quantity U1 on the bus voltage theoretical value Udc, the voltage of the input end of the bidirectional converter is udc+U1, and the output end of the bidirectional converter outputs a corresponding duty ratio with sinusoidal characteristics, as shown in fig. 4, wherein the duty ratio 0< D is less than or equal to 1.
In a specific embodiment, the bidirectional converter may adopt any one of the following modes according to the duty ratio of the udc+u1 output:
a. taking the average value of duty ratio of one voltage period (0-360 °);
b. taking the duty ratio of a specific point, such as 90 degrees and 270 degrees;
c. taking the average value of a certain section of continuous duty ratio in one voltage period, such as the average value of 60-120 degrees and the average value of 240-300 degrees.
S3: comparing the Duty ratio D obtained in the step S2 with the first Duty ratio limit value Duty1 and the second Duty ratio limit value Duty2, and if the Duty ratio D is smaller than the first Duty ratio limit value Duty1, reducing the current first voltage compensation amount U1 and returning to the step S2; if the Duty ratio D is larger than the second Duty ratio limiting value Duty2, the current first voltage compensation amount U1 is increased and the step S2 is returned; if the Duty ratio D is between the first Duty limit value Duty1 and the second Duty limit value Duty2, the current first voltage compensation amount U1 is set as the target first voltage compensation amount U1T, wherein the first Duty limit value Duty1 is smaller than the second Duty limit value Duty2.
Wherein, duty1 and Duty2 are values set according to practical situations, and Duty2 is generally less than 100%, for example, a 6KW three-phase energy storage system applying the present invention defines Duty1 to be selected between (91%, 93%), defines Duty2 to be selected between (95%, 99%), and a most preferable result is: duty 1=92%, duty 2=97%.
When D < Duty1 indicates that the bus voltage is too high, the bus voltage needs to be reduced in the next step to improve the overall efficiency, so the first voltage compensation amount U1 is reduced. When D > Duty2, it is indicated that the bus voltage is too low (e.g., d=98%, although satisfying the current requirement, it does not slightly change, because when the Duty ratio is too high, when the output power is increased too small, the problem of lowering the voltage performance quality such as voltage extinction is also brought about, which is not required for a stable energy storage power supply system), and in order to improve the overall efficiency, the bus voltage needs to be increased in the next step, so the first voltage compensation amount U1 is increased.
The current first voltage compensation amount U1 is reduced or increased, and may be stepped, binary search, or a combination of stepped and binary search.
S4: obtaining a maximum value Umax (PV) of the current photovoltaic voltage, comparing a first superposition value Udc+U1T of a bus voltage theoretical value Udc and a target first voltage compensation quantity U1T and a maximum value Umax (PV) of the current photovoltaic voltage with a second superposition value Umax (PV) +U2 of a second voltage compensation quantity U2, and taking the larger one of the first superposition value Udc+U1T and the second superposition value Umax (PV) +U2 as a bus voltage target value;
the second voltage compensation amount U2 is set according to actual requirements, and U2>0, for example: with a 6KW three-phase energy storage system of the invention, U2 is chosen between (20V, 70V), most preferably u2=40v.
In this step, the bus voltage target value is obtained from MAX ((udc+u1t), (Umax (PV) +u2)).
S5: and stabilizing the bus voltage according to the bus voltage target value.
The specific voltage stabilizing strategy can be any voltage stabilizing strategy in the prior art by a bidirectional DC unit, such as: a single bus voltage loop control strategy, a bus voltage outer loop and a bidirectional DC current inner loop control strategy.
When the energy storage power supply system is in an off-grid state, if the difference value of the current bus voltage minus the bus voltage target value is detected to be larger than a first threshold U3, the photovoltaic output power limit value is reduced; when the energy storage power supply system is in a grid-connected charging state, if the difference value of the current bus voltage minus the bus voltage target value is detected to be larger than a second threshold U5, reducing charging target power; when the energy storage power supply system is in a grid-connected discharge state, if the difference of the detected bus voltage target value minus the current bus voltage is larger than a third threshold U7, reducing the discharge target power; wherein, the first threshold U3, the second threshold U5 and the third threshold U7 are all greater than 0, for example: a 6KW three-phase energy storage system embodying the invention, defining U3 to be selected between (20V, 50V), most preferably u3=30v; u5 is selected from (20V, 50V), most preferably u5=30v; u7 is selected between (20V, 50V), most preferably u7=30v.
According to the preferred embodiment of the invention, the control loop is not required to be frequently switched according to different states such as off-grid state, grid-connected charging and grid-connected discharging, and the like, and the function of stabilizing the bus voltage is only executed by the bidirectional DC unit under various running states, so that the control complexity of the photovoltaic energy storage power supply system is greatly reduced. In addition, in the preferred embodiment of the invention, an efficiency optimization algorithm is provided under different operation conditions of the system, so that the overall efficiency of the photovoltaic energy storage power supply system can be effectively improved.
The following describes a method for controlling the voltage of the photovoltaic energy storage bus provided in the preferred embodiment of the present invention in more specific embodiments.
In a first embodiment, the bus voltage algorithm for the off-grid condition is as follows:
(1) The bus voltage target value is the maximum value determined from MAX ((udc_vinv+u1t_1), (Umax (PV) +u2_1)), where Umax (PV) is the maximum value of the currently connected photovoltaic voltage.
According to practical situations, the first voltage compensation amount u1_1 and the second voltage compensation amount u2_1 are defined as maximum and minimum, wherein u1_1 and u2_1 are greater than 0, such as u1_1=50v and u2_1=40v; because the bus voltage can directly influence the efficiency and the output capacity of the whole system, the lower the bus voltage is, the higher the whole system efficiency is, but the lower bus voltage can not ensure the requirement of off-grid output load, the specific efficiency of the whole system can be subdivided into PV output efficiency, bidirectional DC efficiency and inversion efficiency; otherwise, if the instantaneous Duty cycle is greater than the off-grid second Duty cycle limit value Duty2_1 for a plurality of times in a period of time, determining that the value of U1_1 is too small, and executing the operation of increasing U1_1; finally, a target U1_1 with the Duty ratio larger than Duty1_1 and smaller than Duty2_1 is obtained and is recorded as off-grid target first voltage compensation quantity U1T_1.
(2) The bidirectional DC stable bus voltage adopts a bus voltage outer ring and a bidirectional DC current inner ring, specifically adopts the bus voltage target value generated in the step (1) as an adjusting target of the voltage outer ring, combines the battery charging current limiting value and the discharging current limiting value collected by communication with the actual requirement of off-grid load, and performs output current limiting treatment on the voltage outer ring.
(3) Furthermore, for the topology structure of the energy storage power supply system, the PV output and the DC inversion end (where the DC bus is located in fig. 1) are designed as a common DC bus, and when the current bus voltage is detected to be greater than a "bus voltage target value+u3" (i.e. when the difference between the current bus voltage and the bus voltage target value is greater than a first threshold U3), the change of the bidirectional DC charging and discharging direction is brought about by the sudden change of the power energy.
Wherein: the maximum and minimum limits of U1_1 and U2_1, the off-grid first Duty ratio limit value Duty1_1 and the off-grid second Duty ratio limit value Duty2_1 and the first threshold U3 in the off-grid state bus voltage algorithm can be adjusted according to actual conditions. 60 °,120 °, 240 °,300 ° may be considered embodiments of the present invention, and all modifications made in this respect should be construed as being within the scope of the present invention.
In a second embodiment, the bus voltage algorithm for the grid-tie state of charge is as follows:
(1) The bus voltage target value is the maximum value obtained from MAX ((udc_vgrid+u1t_2), (Umax (PV) +u2_2)).
According to practical situations, the grid-connected charging first voltage compensation quantity U1_2 and the grid-connected charging second voltage compensation quantity U2_2 have the maximum and minimum limits, wherein U2_2 is larger than 0, and U1_2 can be positive or negative. The invention provides a logic algorithm for improving the overall efficiency of a system in a grid-connected charging direction, which specifically comprises the following steps: the invention further provides a method for dynamically changing the U1-2, which is used for monitoring the inversion output Duty ratio of the power grid voltage angles of [60 degrees, 120 degrees ] [240 degrees, 300 degrees ] and calculating the average value of the Duty ratio of the angle intervals, and if the average value Duty ratio is smaller than a preset first Duty ratio limiting value Duty 1-2 of grid-connected charging in a period of time, judging that the bus voltage is too high at the moment, and reducing the value of U1-2; otherwise, if the instantaneous Duty ratio is greater than the "grid-connected charging second Duty ratio limit value Duty2_2" for several times within a period of time, the value of U1_2 is determined to be too small, the operation of increasing U1_2 is performed, and finally, the target U1_2 with the Duty ratio greater than Duty1_2 and smaller than Duty2_2 is obtained and is recorded as the grid-connected charging target first voltage compensation amount U1T_2.
(2) The bidirectional DC stable bus voltage adopts a bus voltage outer ring and a bidirectional DC current inner ring, specifically adopts the bus voltage target value generated in the step (1) as an adjusting target of the voltage outer ring, and uses the battery charging current limit value and the battery discharging current limit value collected by communication to perform output current limiting treatment on the voltage outer ring.
(3) Furthermore, for the topology structure of the energy storage power supply system, the PV output and the dc inversion end (where the dc bus is located in fig. 1) are designed as the common dc bus, in the implementation of the present invention, the charging process prioritizes the photovoltaic power and the bidirectional converter power target is sent to the bidirectional converter through the EMS, and there is a certain hysteresis effect in the response process.
Wherein: the maximum and minimum limits of U1_2 and U2_2, the first Duty ratio limit value Duty1_2 of grid-connected charging and the second Duty ratio limit value Duty2_2 of grid-connected charging in the grid-connected charging bus voltage algorithm and the second threshold U5 value can be adjusted according to actual conditions. 60 °,120 °, 240 °,300 ° may be considered embodiments of the present invention, and all modifications made in this respect should be construed as being within the scope of the present invention.
In a third embodiment, the bus voltage algorithm for the grid-connected discharge state is as follows:
(1) The bus voltage target value is the maximum value obtained from MAX ((udc_vgrid+u1t_3), (Umax (PV) +u2_3)).
The invention provides a logic algorithm for improving the overall efficiency of a system in a grid-connected discharging direction, wherein the first voltage compensation quantity U1-3 and the second voltage compensation quantity U2-3 of the grid-connected discharging are larger than 0, and the maximum limit and the minimum limit exist according to practical situations, and the logic algorithm specifically comprises the following steps: the invention further provides a method for dynamically changing the U1-3, which is used for monitoring the inversion output Duty ratio of the power grid voltage angles of [60 degrees, 120 degrees ] [240 degrees, 300 degrees ] and calculating the average value of the Duty ratio of the angle intervals, and if the average value Duty ratio is smaller than a preset first Duty ratio limiting value Duty 1-3 of grid-connected discharge in a period of time, judging that the bus voltage is too high at the moment, and reducing the value of U1-3; otherwise, if the Duty ratio is greater than the Duty ratio limit value Duty2_3 of the grid-connected discharge for several times in a period of time, the value of U1_3 is determined to be too small, and the operation of increasing U1_3 is executed. Finally, a target U1_3 with the Duty ratio larger than Duty1_3 and smaller than Duty2_3 is obtained and is recorded as a grid-connected discharge target first voltage compensation quantity U1T_3.
(2) The bidirectional DC stable bus voltage adopts a bus voltage outer ring and a bidirectional DC current inner ring, specifically adopts the bus voltage target value generated in the step (1) as an adjusting target of the voltage outer ring, and uses the battery charging current limit value and the battery discharging current limit value collected by communication to perform output current limiting treatment on the voltage outer ring.
(3) Furthermore, for the topology structure of the energy storage power supply system, the PV output and the dc inversion end (where the dc bus is located in fig. 1) are designed as a common dc bus, when the invention is implemented, because the characteristics of jump exist in the PV output power and the inverter power target is sent to the bidirectional converter through the EMS, there is a certain hysteresis effect in the response process, and this embodiment provides a strategy for modifying the discharge target power by the bus under-voltage in the inverter control link, specifically, when the current bus voltage is detected to be less than the "bus voltage target value+u7" (i.e. the difference of the current bus voltage minus the bus voltage target value is greater than the third threshold U7), the discharge target power is reduced, and the specific method for reducing the target power may adopt manners such as PI (proportional integral adjustment) or gradual change of step length, which will not be further described herein.
Wherein: the maximum and minimum limits of U1_3 and U2_3, the first Duty limit value Duty1_3 of grid-connected discharge, the second Duty limit value Duty2_3 of grid-connected discharge and the third threshold U7 in the grid-connected charging bus voltage algorithm can be regarded as engineering experience values. 60 °,120 °, 240 °,300 ° may be considered embodiments of the present invention, and all modifications made in this respect should be construed as being within the scope of the present invention.
In the above embodiment of the present invention, under different operation conditions, complementary strategies of "reducing the photovoltaic output limit", "reducing the charging target power of the inverter", "reducing the discharging target power of the inverter" are respectively provided, so that the bus voltage is more stable, and the stability of the system is increased.
The background section of the present invention may contain background information about the problem or environment of the present invention rather than the prior art described by others. Accordingly, inclusion in the background section is not an admission of prior art by the applicant.
The foregoing is a further detailed description of the invention in connection with specific/preferred embodiments, and it is not intended that the invention be limited to such description. It will be apparent to those skilled in the art that several alternatives or modifications can be made to the described embodiments without departing from the spirit of the invention, and these alternatives or modifications should be considered to be within the scope of the invention. In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope as defined by the appended claims.
Claims (10)
1. The control method of the voltage of the photovoltaic energy storage bus is characterized by comprising the following steps of:
s1: initially setting a first voltage compensation amount;
s2: superposing the first voltage compensation quantity to a bus voltage theoretical value to obtain a superposed bus voltage, and outputting a corresponding duty ratio according to the superposed bus voltage;
s3: comparing the duty ratio obtained in the step S2 with a first duty ratio limiting value and a second duty ratio limiting value, and if the duty ratio is smaller than the first duty ratio limiting value, reducing the current first voltage compensation amount and returning to the step S2; if the duty ratio is larger than the second duty ratio limiting value, increasing the current first voltage compensation amount and returning to the step S2; if the duty cycle is between the first duty cycle limit value and the second duty cycle limit value, taking the current first voltage compensation amount as a target first voltage compensation amount, wherein the first duty cycle limit value is smaller than the second duty cycle limit value;
s4: obtaining the maximum value of the current photovoltaic voltage, comparing the theoretical value of the bus voltage with a first superposition value of the target first voltage compensation quantity and a second superposition value of the maximum value of the current photovoltaic voltage with a second voltage compensation quantity, and taking the larger one of the first superposition value and the second superposition value as a bus voltage target value;
s5: and stabilizing the bus voltage according to the bus voltage target value.
2. The method for controlling the voltage of the photovoltaic energy storage busbar according to claim 1, wherein step S1 specifically includes: the method comprises the steps of initially setting a first voltage compensation amount according to the running condition of an energy storage power supply system;
when the energy storage power supply system is in an off-grid state or a grid-connected discharge state, setting the first voltage compensation quantity to be a positive number;
and when the energy storage power supply system is in a grid-connected charging state, setting the first voltage compensation quantity as a positive number or a negative number.
3. The method for controlling the voltage of the photovoltaic energy storage bus according to claim 1, wherein outputting the corresponding duty ratio according to the superimposed bus voltage in step S2 specifically comprises: and outputting a duty ratio average value of one voltage period, a duty ratio of a preset point or an average value of one continuous duty ratio in one voltage period as a corresponding duty ratio according to the superimposed bus voltage.
4. The method of claim 1, wherein the second duty cycle limit is less than 100%.
5. The method according to claim 1, wherein in step S3, if the duty cycle is smaller than the first duty cycle limit value, the current first voltage compensation amount is reduced by a step-by-step and/or a dichotomy search method and returned to step S2; and if the duty ratio is larger than the second duty ratio limiting value, increasing the current first voltage compensation amount in a stepping and/or dichotomy searching mode and returning to the step S2.
6. The method of claim 1, wherein the second voltage compensation amount is greater than 0.
7. The method for controlling the voltage of the photovoltaic energy storage busbar according to claim 1, wherein step S5 specifically includes:
when the energy storage power supply system is in an off-grid state, if the difference value of the current bus voltage minus the bus voltage target value is detected to be larger than a first threshold value, reducing the photovoltaic output power limit value;
when the energy storage power supply system is in a grid-connected charging state, if the difference value of the current bus voltage minus the bus voltage target value is detected to be larger than a second threshold value, reducing charging target power;
when the energy storage power supply system is in a grid-connected discharge state, if the difference value of the bus voltage target value minus the current bus voltage is detected to be larger than a third threshold value, reducing the discharge target power;
wherein the first, second and third thresholds are all greater than 0.
8. The method according to claim 7, wherein the reducing the photovoltaic output power limit, the reducing the charging target power, and the reducing the discharging target power are performed by proportional integral adjustment or gradual step change, respectively.
9. An energy storage power supply system, comprising: the system comprises a battery unit, a photovoltaic energy storage inversion unit and an energy management system;
the battery cell includes: a battery pack and a battery management system; the first end of the battery pack is connected with the battery management system;
the photovoltaic energy storage inversion unit comprises: the MPPT controller, DC/DC unit and bi-directional converter; the MPPT controller is characterized in that a first end of the MPPT controller is connected with the photovoltaic panel, and a second end of the MPPT controller is connected with the direct current bus; the first end of the DC/DC unit is connected with the second end of the battery pack, and the second end of the DC/DC unit is connected with the direct current bus; the first end of the bidirectional converter is connected with the direct current bus, and the second end of the bidirectional converter is connected with a power grid and a load;
the energy management system is simultaneously in communication connection with the battery management system and the photovoltaic energy storage inversion unit;
the energy management system calculates a bus voltage target value according to the control method of the photovoltaic energy storage bus voltage according to any one of claims 1 to 8, and performs voltage stabilization of the bus voltage by the DC/DC unit according to the bus voltage target value.
10. The energy storage power supply system according to claim 9, wherein the DC/DC unit performs voltage stabilization of the bus voltage according to the bus voltage target value using a single bus voltage ring control strategy or a bus voltage outer ring and a bidirectional DC current inner ring control strategy.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108808822A (en) * | 2018-05-03 | 2018-11-13 | 上海交通大学 | A kind of photovoltaic commercial power compensation device and control method for water pump system |
| CN112865065A (en) * | 2021-03-05 | 2021-05-28 | 国网江苏省电力有限公司镇江供电分公司 | Power distribution network coordination control method and system containing high-permeability light storage |
| CN113972682A (en) * | 2020-07-21 | 2022-01-25 | 华为技术有限公司 | Voltage control method and device of direct current bus and power system |
| CN114374197A (en) * | 2021-11-29 | 2022-04-19 | 珠海格力电器股份有限公司 | Starting method and device of energy storage system |
| CN115241926A (en) * | 2022-09-16 | 2022-10-25 | 深圳市首航新能源股份有限公司 | Bus voltage control method, bus balance control method and system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8629658B1 (en) * | 2009-12-22 | 2014-01-14 | Linear Technology Corporation | Method and system for solar panel peak-power transfer using input voltage regulation |
| US8975783B2 (en) * | 2010-01-20 | 2015-03-10 | Draker, Inc. | Dual-loop dynamic fast-tracking MPPT control method, device, and system |
-
2022
- 2022-12-08 CN CN202211568210.1A patent/CN115663828B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108808822A (en) * | 2018-05-03 | 2018-11-13 | 上海交通大学 | A kind of photovoltaic commercial power compensation device and control method for water pump system |
| CN113972682A (en) * | 2020-07-21 | 2022-01-25 | 华为技术有限公司 | Voltage control method and device of direct current bus and power system |
| CN112865065A (en) * | 2021-03-05 | 2021-05-28 | 国网江苏省电力有限公司镇江供电分公司 | Power distribution network coordination control method and system containing high-permeability light storage |
| CN114374197A (en) * | 2021-11-29 | 2022-04-19 | 珠海格力电器股份有限公司 | Starting method and device of energy storage system |
| CN115241926A (en) * | 2022-09-16 | 2022-10-25 | 深圳市首航新能源股份有限公司 | Bus voltage control method, bus balance control method and system |
Non-Patent Citations (2)
| Title |
|---|
| J.Harsha Vardhana 等.Optimization of PV MPPT performance and DC link voltage ripples compensation using a duty cycle modifier.International Conference on Recent Advances and Innovations in Engineering (ICRAIE-2014).2014,第1-6页. * |
| 余刚.考虑光储的轨道交通车辆段微网控制策略研究.电子设计工程.2022,第30卷(第22期),第158-163页. * |
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