WO2017012435A1 - 一种光伏发电系统最大功率点跟踪方法 - Google Patents

一种光伏发电系统最大功率点跟踪方法 Download PDF

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WO2017012435A1
WO2017012435A1 PCT/CN2016/085406 CN2016085406W WO2017012435A1 WO 2017012435 A1 WO2017012435 A1 WO 2017012435A1 CN 2016085406 W CN2016085406 W CN 2016085406W WO 2017012435 A1 WO2017012435 A1 WO 2017012435A1
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disturbance
mppt
power
voltage
period
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黄凯伦
曾春保
陈聪鹏
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厦门科华恒盛股份有限公司
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    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05FSYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/66Regulating electric power
    • G05F1/67Regulating electric power to the maximum power available from a generator, e.g. from solar cell
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/56Power conversion systems, e.g. maximum power point trackers

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  • the invention relates to the field of photovoltaic power generation, in particular to a maximum power point tracking method for a photovoltaic power generation system.
  • the output power of the photovoltaic array is related to the illumination intensity, temperature and other factors. Under different external conditions, the photovoltaic array can operate at different and unique maximum power points.
  • the fixed step perturbation observation method is currently the more commonly used MPPT algorithm.
  • the voltage disturbance step size ⁇ U has a great influence on the system performance.
  • the voltage disturbance step size ⁇ U is too large, and the system response speed is fast, but when the maximum power point enters the steady state, the loss is also large due to the oscillation; ⁇ U is too small, the system response speed is slow, and the tracking accuracy is high, but the disturbance is stuck for a long time at the initial stage. Low power section, resulting in power loss.
  • the fixed-step disturbance observation method is likely to cause the MPPT direction to be disturbed by the power change caused by the environment, and the power is lost.
  • variable step size is used for MPPT tracking.
  • the MPPT's disturbance step change will be more severe, and the error is easily disturbed, the tracking accuracy is low, and the error tracking is easy, resulting in MPPT efficiency. Not a high problem.
  • the object of the present invention is to provide a maximum power point tracking method for a photovoltaic power generation system, which can perform adaptive variable step size, can track the maximum power point quickly, accurately, and stably, and overcome the step-by-step disturbance observation method in steps. Long selection of power loss caused by inappropriate.
  • the invention is implemented by the following scheme: a method for tracking a maximum power point of a photovoltaic power generation system, which specifically comprises the following steps:
  • Step S1 respectively collecting the output voltages u 0 (k), u x (k), u y (k), and output current i 0 of the photovoltaic module at the 0th, the xth, and the yth time of the current MPPT disturbance cycle. (k), i x (k), i y (k);
  • Step S2 acquiring the output powers P 0 (k), P x (k), and P y (k) of the photovoltaic modules at the 0th, xth, and yth times, respectively, and removing the influence of environmental factors.
  • Step S3 the disturbance power ⁇ U(k) according to the current MPPT disturbance period, the disturbance power dP P&O (k) generated by the disturbance voltage ⁇ U(k) of the current MPPT disturbance period, and the power change rate of the previous MPPT disturbance period Ratio(k) -1), obtaining the disturbance voltage step coefficient K ⁇ U (k+1) of the next MPPT disturbance period, wherein
  • Step S5 the disturbance power dP P&O (k) generated according to the current MPPT disturbance voltage ⁇ U(k), the given voltage U cmd (k) of the current MPPT disturbance period, and the disturbance voltage ⁇ U(k+1) of the next MPPT disturbance period , obtaining a given voltage U cmd (k+1) of the next MPPT disturbance period,
  • the method includes the following steps:
  • Step S21 Obtain the output powers P 0 (k), P x (k), P y (k) of the photovoltaic modules at the 0th time, the xth time, and the yth time, respectively, in the current MPPT disturbance cycle.
  • Step S24 calculating a power variation amount dP P&O (k) caused by the disturbance voltage ⁇ U(k) in the current MPPT disturbance period, wherein
  • the output power of the photovoltaic array is stable before the xth moment of the current MPPT disturbance period.
  • the method specifically includes the following steps:
  • Step S31 Acquire the power change rate Ratio (k) of the current MPPT disturbance period according to the disturbance voltage ⁇ U(k) of the current MPPT disturbance period and the disturbance power dP P&O (k) generated by the disturbance voltage ⁇ U(k) of the current MPPT disturbance period. ),among them
  • Step S32 Calculate the power change rate coefficient ⁇ (k) according to the power change rate Ratio(k-1) of the previous MPPT disturbance period and the power change rate Ratio(k) of the current MPPT disturbance period, wherein
  • Step S33 calculating a disturbance voltage step coefficient K ⁇ U (k+1) of the next MPPT disturbance period according to the power change rate Ratio(k) of the current MPPT disturbance period and the power change rate coefficient ⁇ (k),
  • Step S52 according to the given voltage U cmd (k) of the current MPPT disturbance period, the disturbance voltage ⁇ U(k+1) of the next MPPT disturbance period, and the disturbance direction of the disturbance voltage ⁇ U(k+1) of the next MMPT disturbance period Dir(k+1), which determines the MPPT given voltage U cmd (k+1) for the next MPPT disturbance period,
  • the present invention has the following beneficial effects:
  • the invention can quickly adjust the power rate according to the current MPPT disturbance period to achieve maximum power tracking, and solves the shortcomings of the tracking speed of the fixed step disturbance observation method in the prior art.
  • the maximum power tracking method of the present invention eliminates the mis-disturbance of the fixed-step MPPT algorithm, and adaptively changes the step size according to the rate of change of the modified disturbance power, and quickly, accurately and stably tracks the maximum power point of the photovoltaic component to improve MPPT conversion efficiency, with high efficiency, fast, accurate and stable tracking of maximum power point, high efficiency and so on.
  • FIG. 1 is a flow chart of a method for tracking a maximum power point of a photovoltaic power generation system according to the present invention.
  • FIG. 2 is a specific flowchart of step S2 of the present invention.
  • FIG. 3 is a specific flowchart of step S3 of the present invention.
  • the embodiment provides a maximum power point tracking method for a photovoltaic power generation system, as shown in FIG. 1 , which specifically includes the following steps:
  • Step S1 respectively collecting the output voltages u 0 (k), u x (k), u y (k), and output current i 0 of the photovoltaic module at the 0th, the xth, and the yth time of the current MPPT disturbance cycle. (k), i x (k), i y (k);
  • Step S2 acquiring the output powers P 0 (k), P x (k), and P y (k) of the photovoltaic modules at the 0th, xth, and yth times, respectively, and removing the influence of environmental factors.
  • Step S3 the disturbance power ⁇ U(k) according to the current MPPT disturbance period, the disturbance power dP P&O (k) generated by the disturbance voltage ⁇ U(k) of the current MPPT disturbance period, and the power change rate of the previous MPPT disturbance period Ratio(k) -1), obtaining the disturbance voltage step coefficient K ⁇ U (k+1) of the next MPPT disturbance period, wherein
  • Step S5 the disturbance power dP P&O (k) generated according to the current MPPT disturbance voltage ⁇ U(k), the given voltage U cmd (k) of the current MPPT disturbance period, and the disturbance voltage ⁇ U(k+1) of the next MPPT disturbance period , obtaining a given voltage U cmd (k+1) of the next MPPT disturbance period,
  • the method when the step S2 acquires the disturbance power dP P&O (k) generated by the disturbance voltage ⁇ U(k) in the current MPPT disturbance period, the method includes the following steps:
  • Step S21 Obtain the output powers P 0 (k), P x (k), P y (k) of the photovoltaic modules at the 0th time, the xth time, and the yth time, respectively, in the current MPPT disturbance cycle.
  • Step S24 calculating a power variation amount dP P&O (k) caused by the disturbance voltage ⁇ U(k) in the current MPPT disturbance period, wherein
  • the output power of the photovoltaic array is stable before the xth moment of the current MPPT disturbance period.
  • Step S31 Acquire the power change rate Ratio (k) of the current MPPT disturbance period according to the disturbance voltage ⁇ U(k) of the current MPPT disturbance period and the disturbance power dP P&O (k) generated by the disturbance voltage ⁇ U(k) of the current MPPT disturbance period. ),among them
  • Step S32 Calculate the power change rate coefficient ⁇ (k) according to the power change rate Ratio(k-1) of the previous MPPT disturbance period and the power change rate Ratio(k) of the current MPPT disturbance period, wherein
  • Step S33 calculating a disturbance voltage step coefficient K ⁇ U (k+1) of the next MPPT disturbance period according to the power change rate Ratio(k) of the current MPPT disturbance period and the power change rate coefficient ⁇ (k),
  • Step S52 according to the given voltage U cmd (k) of the current MPPT disturbance period, the disturbance voltage ⁇ U(k+1) of the next MPPT disturbance period, and the disturbance direction of the disturbance voltage ⁇ U(k+1) of the next MMPT disturbance period Dir(k+1), which determines the MPPT given voltage U cmd (k+1) for the next MPPT disturbance period,
  • the output power difference of the photovoltaic module at the xth and 0th moments of the current MPPT disturbance period is dP 1 (k), which includes the two parts of the current MPPT disturbance period, the disturbance power dP P&O (k) generated by the disturbance voltage ⁇ U(k)
  • the MPPT disturbance period changes very slowly with respect to the environmental factor.
  • the power change rate caused by environmental factors is constant, that is,
  • the power change rate Ratio(k) is smaller, and the power of the photovoltaic plate is the maximum power.
  • the rate of change Ratio(k) is approximately zero.
  • ⁇ (k) is used as the adjustment factor of the disturbance voltage step coefficient K ⁇ U (k+1) of the next MPPT disturbance period.
  • the relationship obtains the disturbance voltage of the next MPPT disturbance period, and determines the disturbance direction of the next current MPPT disturbance voltage ⁇ U(k+1) according to the magnitude of the disturbance power dP P&O (k) generated by the current MPPT disturbance voltage ⁇ U(k).
  • the power change rate Ratio(k) approaches 0 near the maximum power point as the output power of the photovoltaic module approaches. However, if it is not equal to 0, it can adaptively reduce the disturbance step size and stabilize the power loss at the maximum power point. When the output power of the photovoltaic module is abrupt, the power change rate Ratio(k) will become larger, so that the disturbance step size becomes larger, and the new maximum power point is quickly tracked.
  • the first embodiment is provided, as shown in FIG. 4, which specifically includes the following steps:
  • Step S6 respectively at the current MPPT disturbance period 0, T MPPT time to collect the output voltage u 0 (k) of the photovoltaic module, Output current i 0 (k),
  • Step S11 Obtain the power change rate Ratio (k) of the current MPPT disturbance period according to the disturbance voltage ⁇ U(k) of the current MPPT disturbance period and the disturbance power dP P&O (k) generated by the disturbance voltage ⁇ U(k) of the current MPPT disturbance period. ),among them
  • Step S12 Calculating the power change rate coefficient ⁇ (k) according to the power change rate Ratio(k-1) of the previous MPPT disturbance period and the power change rate Ratio(k) of the current MPPT disturbance period, wherein
  • Step S13 calculating a disturbance voltage step coefficient K ⁇ U (k+1) of the next MPPT disturbance period according to the power change rate Ratio(k) and the power change rate coefficient ⁇ (k) of the current MPPT disturbance period,
  • the perturbation direction dir(k) according to the given voltage U cmd (k) of the current MPPT disturbance period, the disturbance voltage ⁇ U(k+1) of the next MPPT disturbance period, and the disturbance voltage ⁇ U(k+1) of the next MMPT disturbance period +1), determining the MPPT given voltage U cmd (k+1) of the next MPPT disturbance period,

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Abstract

一种光伏发电系统最大功率点跟踪方法,包括以下步骤:步骤S1:分别在当前MPPT扰动周期的第0时刻、第x时刻以及第y时刻分别采集光伏组件的输出电压值与输出电流值;步骤S2:分别获取所述第0时刻、第x时刻以及第y时刻所述光伏组件的输出功率P 0(k)、P x(k)、P y(k),并剔除环境因素的影响,获取当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dP P&O(k);步骤S3:ΔU(k)、dP P&O(k)以及Ratio(k-1)获取下一MPPT扰动周期的扰动电压步长系数K △U(k+1);步骤S4:根K △U(k+1)获取下一MPPT扰动周期的扰动电压ΔU(k+1);步骤S5:dP P&O(k)、U cmd(k)以及ΔU(k+1),获取下一MPPT扰动周期的给定电压U cmd(k+1)。该方法可进行自适应变步长,能够快速、精确、稳定的跟踪最大功率点,克服定步长扰动观察法在步长选取不合适造成的功率损失。

Description

一种光伏发电系统最大功率点跟踪方法 技术领域
本发明涉及光伏发电领域,特别是一种光伏发电系统最大功率点跟踪方法。
背景技术
根据光伏阵列的输出功率与光照强度、温度等因数有关,在不同的外界条件下,光伏阵列可运行在不同且唯一的最大功率点上。
定步长扰动观察法是目前较为常用的MPPT算法。在定步长扰动观察法的应用中,电压扰动步长ΔU对系统性能有较大影响。电压扰动步长ΔU过大,系统响应速度快,但最大功率点附近进入稳态时,由于振荡导致损耗也大;ΔU过小,系统响应速度慢,跟踪精度高,但扰动初期长时间滞留在低功率段,造成功率损失。
另外,定步长扰动观察法在环境因素变化较快、较大的情况下,由于环境引起功率变化容易导致MPPT方向误扰动,而损失功率。
现有技术中采用变步长进行MPPT跟踪,在外接环境变化较大的情况下,MPPT的扰动步长变化会较为剧烈,容易发生误扰动,跟踪精度较低,容易导致误跟踪,造成MPPT效率不高的问题。
发明内容
有鉴于此,本发明的目的是提供一种光伏发电系统最大功率点跟踪方法,可进行自适应变步长,能够快速、精确、稳定的跟踪最大功率点,克服定步长扰动观察法在步长选取不合适造成的功率损失。
本发明采用以下方案实现:一种光伏发电系统最大功率点跟踪方法,具体包括以下步骤:
步骤S1:分别在当前MPPT扰动周期的第0时刻、第x时刻以及第y时刻分别采集光伏组件的输出电压u0(k)、ux(k)、uy(k)、输出电流i0(k)、ix(k)、iy(k);
步骤S2:分别获取所述第0时刻、第x时刻以及第y时刻所述光伏组件的输出功率P0(k)、Px(k)、Py(k),并剔除环境因素的影响,获取当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k),其中
Figure PCTCN2016085406-appb-000001
其中0<x<y≤TMPPT,TMPPT为MPPT扰动周期;
步骤S3:根据当前MPPT扰动周期的扰动电压ΔU(k)、由当前MPPT扰动周期的扰动电压ΔU(k)产生的扰动功率dPP&O(k)以及上一MPPT扰动周期的功率变化率Ratio(k-1),获取下一MPPT扰动周期的扰动电压步长系数K△U(k+1),其中
Figure PCTCN2016085406-appb-000002
步骤S4:根据下一MPPT扰动周期的扰动电压步长系数K△U(k+1)获取下一MPPT扰动周期的扰动电压ΔU(k+1),其中ΔU(k+1)=K△U(k+1)×Ustep,
Figure PCTCN2016085406-appb-000003
Ustep为光伏阵列设定的扰动电压步长常数;
步骤S5:根据当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)、当前MPPT扰动周期的给定电压Ucmd(k)以及下一MPPT扰动周期的扰动电压ΔU(k+1),获取下一MPPT扰动周期的给定电压Ucmd(k+1),
其中Ucmd(k+1)=Ucmd(k)+dir(k+1)×ΔU(k+1);
若dPP&O(k)<0,则dir(k+1)取值为dir(k+1)=-1×dir(k),否则dir(k+1)=dir(k),其中dir(k)的初始值为dir(0)=-1。
进一步地,所述步骤S2获取当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k)时,具体包括括以下步骤:
步骤S21:在当前MPPT扰动周期分别在第0时刻、第x时刻以及第y时刻获取光伏组件的输出功率P0(k)、Px(k)、Py(k),
其中P0(k)=u0(k)×i0(k),Px(k)=ux(k)×ix(k),Py(k)=uy(k)×iy(k);
步骤S22:在当前MPPT扰动周期分别计算dP1(k)与dP2(k),其中dP1(k)表示由扰动电压ΔU(k)引起的功率变化量dPP&O(k)与第0至x时刻环境因素引起的 功率变化量dPENV1(k)两者之和,dP2(k)第x至y时刻环境因素引起的功率变化量dPENV2(k),即dP1(k)=dPP&O(k)+dPENV1(k),dP2(k)=dPENV2(k);
其中dP1(k)=Px(k)-P0(k),dP2(k)=Py(k)-Px(k);
步骤S23:假设环境因素造成的功率变化率恒定,根据
Figure PCTCN2016085406-appb-000004
dP2(k)=dPENV2(k),计算第0至x时刻环境因素引起的功率变化量dPENV1(k),其中
Figure PCTCN2016085406-appb-000005
步骤S24:计算当前MPPT扰动周期由扰动电压ΔU(k)引起的功率变化量dPP&O(k),其中
Figure PCTCN2016085406-appb-000006
较佳的,所述由光伏阵列输出功率在当前MPPT扰动周期的第x时刻之前稳定。
进一步地,所述步骤S23与所述步骤S24中x=3/4TMPPT,y=TMPPT
进一步地,所述步骤S3中获取下一MPPT扰动周期的扰动电压步长系数K△U(k+1)时,具体包括以下步骤:
步骤S31:根据当前MPPT扰动周期的扰动电压ΔU(k)以及由当前MPPT扰动周期的扰动电压ΔU(k)产生的扰动功率dPP&O(k),获取当前MPPT扰动周期的功率变化率Ratio(k),其中
Figure PCTCN2016085406-appb-000007
步骤S32:根据上一MPPT扰动周期的功率变化率Ratio(k-1)以及当前MPPT扰动周期的功率变化率Ratio(k),计算功率变化率系数η(k),其中
Figure PCTCN2016085406-appb-000008
步骤S33:根据当前MPPT扰动周期的功率变化率Ratio(k)以及功率变化率系数η(k),计算下一MPPT扰动周期的扰动电压步长系数K△U(k+1),
其中,
Figure PCTCN2016085406-appb-000009
进一步地,所述步骤S5中获取下一MPPT扰动周期的给定电压Ucmd(k+1)时,具体包括以下步骤:
步骤S51:根据由当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)确定下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1),若dPP&O(k)<0,则dir(k+1)取值为dir(k+1)=-1×dir(k),否则则dir(k+1)取值为dir(k+1)=1×dir(k);其中dir(k)的初始值为dir(0)=-1;
步骤S52:根据当前MPPT扰动周期的给定电压Ucmd(k)、下一MPPT扰动周期的扰动电压ΔU(k+1)以及下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1),确定下一MPPT扰动周期的MPPT给定电压Ucmd(k+1),
其中Ucmd(k+1)=Ucmd(k)+dir(k+1)×ΔU(k+1)。
相较于现有技术,本发明具有以下有益效果:
1)环境因素会对光伏组件的输出功率有影响,本发明的最大功率跟踪方法克服传统MPPT算法中,环境因素会干扰功率的变化,导致功率误扰动,MPPT的跟踪效率低,剔除环境因素造成的功率变化,修正扰动功率,克服扰动观察法在环境变化情况下的误扰动,提高MPPT的跟踪效率。
2)本发明能够根据当前MPPT扰动周期的功率变化率快速调整实现最大功率跟踪,解决了现有技术中定步长扰动观察法跟踪速度或者较慢或者振荡较大的缺点
3)本发明的最大功率跟踪方法通过消除定步长MPPT算法的误扰动,并根据修正扰动功率的变化率自适应变步长,快速、精确、稳定的跟踪到光伏组件最大功率点,以提高MPPT转换效率,具备高效、快速、精准、稳定的跟踪最大功率点、效率高等特点。
附图说明
图1为本发明一种光伏发电系统最大功率点跟踪方法的流程图。
图2为本发明步骤S2的具体流程图。
图3为本发明步骤S3的具体流程图。
图4为发明一实施例的流程图。
具体实施方式
下面结合附图及实施例对本发明做进一步说明。
本实施例提供一种光伏发电系统最大功率点跟踪方法,如图1所示,具体包括以下步骤:
步骤S1:分别在当前MPPT扰动周期的第0时刻、第x时刻以及第y时刻分别采集光伏组件的输出电压u0(k)、ux(k)、uy(k)、输出电流i0(k)、ix(k)、iy(k);
步骤S2:分别获取所述第0时刻、第x时刻以及第y时刻所述光伏组件的输出功率P0(k)、Px(k)、Py(k),并剔除环境因素的影响,获取当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k),其中
Figure PCTCN2016085406-appb-000010
其中0<x<y≤TMPPT,TMPPT为MPPT扰动周期;
步骤S3:根据当前MPPT扰动周期的扰动电压ΔU(k)、由当前MPPT扰动周期的扰动电压ΔU(k)产生的扰动功率dPP&O(k)以及上一MPPT扰动周期的功率变化率Ratio(k-1),获取下一MPPT扰动周期的扰动电压步长系数K△U(k+1),其中
Figure PCTCN2016085406-appb-000011
步骤S4:根据下一MPPT扰动周期的扰动电压步长系数K△U(k+1)获取下一MPPT扰动周期的扰动电压ΔU(k+1),其中ΔU(k+1)=K△U(k+1)×Ustep,
Figure PCTCN2016085406-appb-000012
Ustep为光伏阵列设定的扰动电压步长常数;
步骤S5:根据当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)、当前MPPT扰动周期的给定电压Ucmd(k)以及下一MPPT扰动周期的扰动电压 ΔU(k+1),获取下一MPPT扰动周期的给定电压Ucmd(k+1),
其中Ucmd(k+1)=Ucmd(k)+dir(k+1)×ΔU(k+1);
若dPP&O(k)<0,则dir(k+1)取值为dir(k+1)=-1×dir(k),否则dir(k+1)=dir(k),其中dir(k)的初始值为dir(0)=-1。
在本实施例中,如图2所示,所述步骤S2获取当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k)时,具体包括括以下步骤:
步骤S21:在当前MPPT扰动周期分别在第0时刻、第x时刻以及第y时刻获取光伏组件的输出功率P0(k)、Px(k)、Py(k),
其中P0(k)=u0(k)×i0(k),Px(k)=ux(k)×ix(k),Py(k)=uy(k)×iy(k);
步骤S22:在当前MPPT扰动周期分别计算dP1(k)与dP2(k),其中dP1(k)表示由扰动电压ΔU(k)引起的功率变化量dPP&O(k)与第0至x时刻环境因素引起的功率变化量dPENV1(k)两者之和,dP2(k)第x至y时刻环境因素引起的功率变化量dPENV2(k),即dP1(k)=dPP&O(k)+dPENV1(k),dP2(k)=dPENV2(k);
其中dP1(k)=Px(k)-P0(k),dP2(k)=Py(k)-Px(k);
步骤S23:假设环境因素造成的功率变化率恒定,根据
Figure PCTCN2016085406-appb-000013
dP2(k)=dPENV2(k),计算第0至x时刻环境因素引起的功率变化量dPENV1(k),其中
Figure PCTCN2016085406-appb-000014
步骤S24:计算当前MPPT扰动周期由扰动电压ΔU(k)引起的功率变化量dPP&O(k),其中
Figure PCTCN2016085406-appb-000015
较佳的,所述由光伏阵列输出功率在当前MPPT扰动周期的第x时刻之前稳定。
在本实施例中,所述步骤S23与所述步骤S24中x=3/4TMPPT,y=TMPPT
在本实施例中,如图3所示,所述步骤S3中获取下一MPPT扰动周期的扰 动电压步长系数K△U(k+1)时,具体包括以下步骤:
步骤S31:根据当前MPPT扰动周期的扰动电压ΔU(k)以及由当前MPPT扰动周期的扰动电压ΔU(k)产生的扰动功率dPP&O(k),获取当前MPPT扰动周期的功率变化率Ratio(k),其中
Figure PCTCN2016085406-appb-000016
步骤S32:根据上一MPPT扰动周期的功率变化率Ratio(k-1)以及当前MPPT扰动周期的功率变化率Ratio(k),计算功率变化率系数η(k),其中
Figure PCTCN2016085406-appb-000017
步骤S33:根据当前MPPT扰动周期的功率变化率Ratio(k)以及功率变化率系数η(k),计算下一MPPT扰动周期的扰动电压步长系数K△U(k+1),
其中,
Figure PCTCN2016085406-appb-000018
在本实施例中,所述步骤S5中获取下一MPPT扰动周期的给定电压Ucmd(k+1)时,具体包括以下步骤:
步骤S51:根据由当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)确定下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1),若dPP&O(k)<0,则dir(k+1)取值为dir(k+1)=-1×dir(k),否则则dir(k+1)取值为dir(k+1)=1×dir(k);其中dir(k)的初始值为dir(0)=-1;
步骤S52:根据当前MPPT扰动周期的给定电压Ucmd(k)、下一MPPT扰动周期的扰动电压ΔU(k+1)以及下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1),确定下一MPPT扰动周期的MPPT给定电压Ucmd(k+1),
其中Ucmd(k+1)=Ucmd(k)+dir(k+1)×ΔU(k+1)。
在本实施例中,对该方法的具体原理说明如下:
在当前MPPT扰动周期第x与0时刻的光伏组件的输出功率差值为dP1(k)其包括两部分当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k)和与第0至x时刻环境因素引起的功率变化量dPENV1(k)两者之和,dP2(k)为当前MPPT扰动周期的第x至y时刻环境因素引起的功率变化量dPENV2(k),即dP2(k)=Py(k)-Px(k)=0+dPENV2(k),dP1(k)-dP2(k)=dPP&O(k)+dPENV1(k)-dPENV2(k);
在两个相邻的不长时间里,MPPT扰动周期相对环境因数变化很短暂,采用类似数学曲线线性拟合的方式,近似认为环境因素造成的功率变化率恒定,即
Figure PCTCN2016085406-appb-000019
通过计算,环境因素引起的影响,获得当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k)、当前MPPT扰动周期的功率变化率Ratio(k),
Figure PCTCN2016085406-appb-000020
计算获得当前MPPT扰动周期的功率变化率Ratio(k)与前一功率变化率系数MPPT扰动周期的功率变化率Ratio(k+1)的比值η(k),
Figure PCTCN2016085406-appb-000021
根据光伏组件的电压与功率的关系曲线,,随着光伏组件的最大功率跟踪,越靠近最大功率点,则功率变化率Ratio(k)越小,当光伏极板的输出功率为最大功率时功率变化率Ratio(k)近似为零,为了适应这样的变化趋势,本当η(k)作为下一MPPT扰动周期的扰动电压步长系数K△U(k+1)的调整系数,
通过
Figure PCTCN2016085406-appb-000022
关系获得下一MPPT扰动周期的扰动电压,并根据当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)的大小确定下一当前MPPT扰动电压ΔU(k+1)的扰动方向。
功率变化率Ratio(k)随着光伏组件输出功率越接近于最大功率点趋近于0, 但不等于0,能够自适应将扰动步长减小,稳定在最大功率点减小功率损耗。当光伏组件输出功率突变时,由功率变化率Ratio(k)将变大,使得扰动步长变大,快速跟踪上新的最大功率点。
特别地,为了更好地说明所述光伏发电系统最大功率点跟踪方法,提供实施例一,如图4所示,具体包括如下步骤:
步骤S6:分别在当前MPPT扰动周期第0、
Figure PCTCN2016085406-appb-000023
TMPPT时刻采集光伏组件的输出电压u0(k)、
Figure PCTCN2016085406-appb-000024
输出电流i0(k)、
Figure PCTCN2016085406-appb-000025
步骤S7:在当前MPPT扰动周期分别在第0、x、y时刻获取光伏组件的输出功率P0(k)、
Figure PCTCN2016085406-appb-000026
其中P0(k)=u0(k)×i0(k),
Figure PCTCN2016085406-appb-000027
步骤S8:在当前MPPT扰动周期分别计算dP1(k)、dP2(k),dP1(k)表示由扰动电压ΔU(k)引起的功率变化量dPP&O(k)与第0至
Figure PCTCN2016085406-appb-000028
时刻环境因素引起的功率变化量dPENV1(k)两者之和,dP2(k)第
Figure PCTCN2016085406-appb-000029
至TMPPT时刻环境因素引起的功率变化量dPENV2(k),即dP1(k)=dPP&O(k)+dPENV1(k),dP2(k)=dPENV2(k);
其中
Figure PCTCN2016085406-appb-000030
步骤S9:近似认为环境因素造成的功率变化率恒定,根据
Figure PCTCN2016085406-appb-000031
dP2(k)=dPENV2(k),计算第0至
Figure PCTCN2016085406-appb-000032
时刻环境因素引起的功率变化量dPENV1(k),其中dPENV1(k)=3dP2(k);
步骤S10:计算当前MPPT扰动周期由扰动电压ΔU(k)引起的功率变化量dPP&O(k),其中dPP&O(k)=dP1(k)-dPENV1(k)=dP1(k)-3dP2(k);
步骤S11:根据当前MPPT扰动周期的扰动电压ΔU(k)、由当前MPPT扰动周期的扰动电压ΔU(k)产生的扰动功率dPP&O(k),获取当前MPPT扰动周期的 功率变化率Ratio(k),其中
Figure PCTCN2016085406-appb-000033
步骤S12:根据上一MPPT扰动周期的功率变化率Ratio(k-1)、当前MPPT扰动周期的功率变化率Ratio(k),计算功率变化率系数η(k),其中
Figure PCTCN2016085406-appb-000034
步骤S13:根据当前MPPT扰动周期的功率变化率Ratio(k)、功率变化率系数η(k),计算下一MPPT扰动周期的扰动电压步长系数K△U(k+1),
其中,
Figure PCTCN2016085406-appb-000035
步骤S14:根据下一MPPT扰动周期的扰动电压步长系数K△U(k+1)获取下一MPPT扰动周期的扰动电压ΔU(k+1),其中ΔU(k+1)=K△U(k+1)×Ustep,
Figure PCTCN2016085406-appb-000036
Ustep为光伏系统设定的扰动电压步长常数;
步骤S15:根据由当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)确定下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1)。设置dir(k)的初始值为dir(0)=-1。若dPP&O(k)<0,则dir(k+1)取值为dir(k+1)=-1×dir(k),否则dir(k+1)取值为dir(k+1)=1×dir(k);
根据当前MPPT扰动周期的给定电压Ucmd(k)、下一MPPT扰动周期的扰动电压ΔU(k+1)、下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1),确定下一MPPT扰动周期的MPPT给定电压Ucmd(k+1),
其中Ucmd(k+1)=Ucmd(k)+dir(k+1)×ΔU(k+1)。
本发明中x,y的取值不限于具体实施例,以上仅为本发明实施例中一个较 佳的实施方案。但是,本发明并不限于上述实施方案,凡按本发明方案所做的任何均等变化和修饰,所产生的功能作用未超出本方案的范围时,均属于本发明的保护范围。

Claims (6)

  1. 一种光伏发电系统最大功率点跟踪方法,其特征在于:包括以下步骤:
    步骤S1:分别在当前MPPT扰动周期的第0时刻、第x时刻以及第y时刻分别采集光伏组件的输出电压u0(k)、ux(k)、uy(k)、输出电流i0(k)、ix(k)、iy(k);
    步骤S2:分别获取所述第0时刻、第x时刻以及第y时刻所述光伏组件的输出功率P0(k)、Px(k)、Py(k),并剔除环境因素的影响,获取当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k),其中
    Figure PCTCN2016085406-appb-100001
    其中0<x<y≤TMPPT,TMPPT为MPPT扰动周期;
    步骤S3:根据当前MPPT扰动周期的扰动电压ΔU(k)、由当前MPPT扰动周期的扰动电压ΔU(k)产生的扰动功率dPP&O(k)以及上一MPPT扰动周期的功率变化率Ratio(k-1),获取下一MPPT扰动周期的扰动电压步长系数K△U(k+1),其中
    Figure PCTCN2016085406-appb-100002
    步骤S4:根据下一MPPT扰动周期的扰动电压步长系数K△U(k+1)获取下一MPPT扰动周期的扰动电压ΔU(k+1),其中ΔU(k+1)=K△U(k+1)×Ustep,
    Figure PCTCN2016085406-appb-100003
    Ustep为光伏阵列设定的扰动电压步长常数;
    步骤S5:根据当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)、当前MPPT扰动周期的给定电压Ucmd(k)以及下一MPPT扰动周期的扰动电压ΔU(k+1),获取下一MPPT扰动周期的给定电压Ucmd(k+1),
    其中Ucmd(k+1)=Ucmd(k)+dir(k+1)×ΔU(k+1);
    若dPP&O(k)<0,则dir(k+1)取值为dir(k+1)=-1×dir(k),否则dir(k+1)=dir(k),其中dir(k)的初始值为dir(0)=-1。
  2. 根据权利要求1所述的一种光伏发电系统最大功率点跟踪方法,其特征在于:所述步骤S2获取当前MPPT扰动周期由扰动电压ΔU(k)产生的扰动功率dPP&O(k)时,具体包括以下步骤:
    步骤S21:在当前MPPT扰动周期分别在第0时刻、第x时刻以及第y时刻获取光伏组件的输出功率P0(k)、Px(k)、Py(k),
    其中P0(k)=u0(k)×i0(k),Px(k)=ux(k)×ix(k),Py(k)=uy(k)×iy(k);
    步骤S22:在当前MPPT扰动周期分别计算dP1(k)与dP2(k),其中dP1(k)表示由扰动电压ΔU(k)引起的功率变化量dPP&O(k)与第0至x时刻环境因素引起的功率变化量dPENV1(k)两者之和,dP2(k)第x至y时刻环境因素引起的功率变化量dPENV2(k),即dP1(k)=dPP&O(k)+dPENV1(k),dP2(k)=dPENV2(k);
    其中dP1(k)=Px(k)-P0(k),dP2(k)=Py(k)-Px(k);
    步骤S23:假设环境因素造成的功率变化率恒定,根据dP2(k)=dPENV2(k),计算第0至x时刻环境因素引起的功率变化量dPENV1(k),其中
    Figure PCTCN2016085406-appb-100005
    步骤S24:计算当前MPPT扰动周期由扰动电压ΔU(k)引起的功率变化量dPP&O(k),其中
    Figure PCTCN2016085406-appb-100006
  3. 根据权利要求2述的一种光伏发电系统最大功率点跟踪方法,其特征在于:
    所述由光伏阵列输出功率在当前MPPT扰动周期的第x时刻之前稳定。
  4. 根据权利要求2述的一种光伏发电系统最大功率点跟踪方法,其特征在于:
    所述步骤S23与所述步骤S24中x=3/4TMPPT,y=TMPPT
  5. 根据权利要求1所述的一种光伏发电系统最大功率点跟踪方法,其特征在于:所述步骤S3中获取下一MPPT扰动周期的扰动电压步长系数K△U(k+1)时,具体包括以下步骤:
    步骤S31:根据当前MPPT扰动周期的扰动电压ΔU(k)以及由当前MPPT扰 动周期的扰动电压ΔU(k)产生的扰动功率dPP&O(k),获取当前MPPT扰动周期的功率变化率Ratio(k),其中
    Figure PCTCN2016085406-appb-100007
    步骤S32:根据上一MPPT扰动周期的功率变化率Ratio(k-1)以及当前MPPT扰动周期的功率变化率Ratio(k),计算功率变化率系数η(k),其中
    Figure PCTCN2016085406-appb-100008
    步骤S33:根据当前MPPT扰动周期的功率变化率Ratio(k)以及功率变化率系数η(k),计算下一MPPT扰动周期的扰动电压步长系数K△U(k+1),
    其中,
    Figure PCTCN2016085406-appb-100009
  6. 据权利要求1所述的一种光伏发电系统最大功率点跟踪方法,其特征在于:所述步骤S5中获取下一MPPT扰动周期的给定电压Ucmd(k+1)时,具体包括以下步骤:
    步骤S51:根据由当前MPPT扰动电压ΔU(k)产生的扰动功率dPP&O(k)确定下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1),若dPP&O(k)<0,则dir(k+1)取值为dir(k+1)=-1×dir(k),否则dir(k+1)取值为dir(k+1)=1×dir(k);其中dir(k)的初始值为dir(0)=-1;
    步骤S52:根据当前MPPT扰动周期的给定电压Ucmd(k)、下一MPPT扰动周期的扰动电压ΔU(k+1)以及下一MMPT扰动周期的扰动电压ΔU(k+1)的扰动方向dir(k+1),确定下一MPPT扰动周期的MPPT给定电压Ucmd(k+1),
    其中Ucmd(k+1)=Ucmd(k)+dir(k+1)×ΔU(k+1)。
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CN113162019A (zh) * 2021-04-15 2021-07-23 中国石油大学(北京) 光伏发电系统及其控制方法
CN114546023A (zh) * 2022-02-25 2022-05-27 南京工程学院 一种光伏发电系统的最大功率点跟踪方法
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