技术领域technical field
本发明光伏发电控制技术领域，尤其涉及一种微网系统中光伏变换器自治模式切换控制方法。The present invention is in the technical field of photovoltaic power generation control, in particular to a method for controlling autonomous mode switching of photovoltaic converters in a microgrid system.
背景技术Background technique
近年来，基于多变换器的智能微电网、多变换级的多能集成系统引起越来越多的研究兴趣，光伏作为清洁和易获取能源，在类似系统中所占的比例越来越高。这也引起了用户侧电网形态的变化，正在由传统被动消纳型到同时具备消纳和发生能力、工作模式多样化等特征过渡。In recent years, multi-converter-based smart microgrids and multi-conversion-level multi-energy integrated systems have attracted increasing research interest. As a clean and accessible energy source, photovoltaics account for an increasing proportion of similar systems. This has also caused a change in the form of the power grid on the user side, which is transitioning from a traditional passive consumption type to one that has both consumption and generation capabilities and diversified working modes.
在孤岛微网或功率限制的多能系统中，在特定工作条件下，直流母线或交流母线(分别由储能和电网实现支撑)不具备足够的电能吸收能力，过剩的光伏电能将会引起电压的升高导致系统过压保护。解决上述难题的一种方法是根据系统的要求改变光伏变换器工作模式，即在MPPT运行时使用开路电压、扰动观测、电导增量等传统算法实现最大功率跟踪，当由于市电异常或功率达到变换器限值时，直流母线或交流母线不具足够支撑能力时转为控制光伏变换器的输出电压以实现电压稳定。两种模式下，对于光伏DC-DC变换器，受控量分别是变换器的输入电压和输出电压，其控制对象传递函数并不相同，因此在模式切换时需要控制环路和PI参数的重新设定，即控制结构重新配置。这也是当前大部分应用中采用的方法，但这种方法一方面在切换时需要改变控制器的PI参数以适应不同的控制目标；另一方面为了使切换平滑，还需要在两个PI环路切换瞬间以上一控制结构的输出来初始化另一个PI的积分输出环节；此外，为了防止母线检测扰动或在检测点附近工作时出现的系统模式振荡，通常需要使用窗口比较器来辅助阈值检测，窗口电压过小无法保证模式判断准确性，可能在两种模式之间来回切换，如果窗口电压设置过大又将一定程度上影响系统的动态响应，这些都增加了的控制难度。In islanded microgrids or power-limited multi-energy systems, under certain operating conditions, the DC bus or AC bus (supported by energy storage and grid, respectively) does not have sufficient power absorption capacity, and excess photovoltaic power will cause voltage The rise of the system causes the overvoltage protection of the system. One way to solve the above problems is to change the working mode of the photovoltaic converter according to the requirements of the system, that is, to use traditional algorithms such as open circuit voltage, disturbance observation, and conductance increment to achieve maximum power tracking during MPPT operation. When the converter is limited, when the DC bus or the AC bus does not have enough supporting capacity, it is turned to control the output voltage of the photovoltaic converter to achieve voltage stability. In the two modes, for the photovoltaic DC-DC converter, the controlled variables are the input voltage and output voltage of the converter, respectively, and the transfer functions of the control objects are different. Therefore, the control loop and PI parameters need to be reworked when the mode is switched. settings, i.e. control structure reconfiguration. This is also the method used in most of the current applications, but on the one hand, this method needs to change the PI parameters of the controller during switching to adapt to different control objectives; on the other hand, in order to make the switching smooth, two PI loops are required The output of the previous control structure initializes the integral output link of the other PI at the switching moment; in addition, in order to prevent the bus detection disturbance or the system mode oscillation that occurs when working near the detection point, a window comparator is usually used to assist the threshold detection, the window If the voltage is too small, the accuracy of mode judgment cannot be guaranteed, and it may switch back and forth between the two modes. If the window voltage is set too large, it will affect the dynamic response of the system to a certain extent, which increases the difficulty of control.
当前有少量应用中采用修改MPPT算法的方式来直接调节变换器的输入功率，从而保持控制环路结构不变，并能够调整和限制光伏变换器的输出功率。然而这需要能量管理系统或上层控制器发送参考功率值，在协调控制过程中依赖通信的及时性和鲁棒性，带来了成本的上升和可靠性下降。另外，已有的修改MPPT算法实现功率限制的方法中，反向扰动和正向扰动的频率、步长通常保持一致，这在功率调整较缓慢进入受限状态的应用中能够较好工作，但如果是并网变换器突发故障或离网系统中负载瞬态投切，而储能电池满充或容量配比较小等情况下，传统方法应用受到一定的限制。At present, there are a small number of applications that modify the MPPT algorithm to directly adjust the input power of the converter, so as to keep the control loop structure unchanged, and can adjust and limit the output power of the photovoltaic converter. However, this requires the energy management system or the upper-layer controller to send the reference power value, and relies on the timeliness and robustness of the communication during the coordinated control process, which leads to an increase in cost and a decrease in reliability. In addition, in the existing method of modifying the MPPT algorithm to realize the power limit, the frequency and step size of the reverse disturbance and the forward disturbance are usually the same, which can work well in the application where the power adjustment is slow to enter the limited state, but if When the grid-connected converter suddenly fails or the load is switched transiently in the off-grid system, and the energy storage battery is fully charged or the capacity allocation is relatively small, the application of the traditional method is limited to a certain extent.
发明内容SUMMARY OF THE INVENTION
针对上述技术问题，本发明提出了一种微网系统中光伏变换器自治模式切换控制方法，包括：In view of the above technical problems, the present invention proposes a method for controlling the autonomous mode switching of photovoltaic converters in a microgrid system, including:
步骤1：对光伏变换器的直流母线电压进行监视；Step 1: Monitor the DC bus voltage of the photovoltaic converter;
步骤2：当母线电压值在额定值以内时光伏变换器执行MPPT算法；Step 2: When the bus voltage value is within the rated value, the photovoltaic converter executes the MPPT algorithm;
步骤3：当母线电压值超过第一电压阈值时光伏变换器转为执行反向扰动观测法来限制功率；Step 3: When the bus voltage value exceeds the first voltage threshold, the photovoltaic converter switches to the reverse disturbance observation method to limit the power;
步骤4：当母线电压值超过第二电压阈值时光伏变换器采用改变扰动步长来控制功率。Step 4: When the bus voltage value exceeds the second voltage threshold, the photovoltaic converter controls the power by changing the disturbance step size.
所述步骤2包括：如果光伏功率增量为正，而电压增量为正，则继续正方向扰动电压，若电压增量为负，则反方向扰动电压；如果功率增量为负，而电压增量为正，则反向扰动电压，若电压增量为负，则正向扰动电压。The step 2 includes: if the photovoltaic power increment is positive and the voltage increment is positive, continue to perturb the voltage in the positive direction; if the voltage increment is negative, perturb the voltage in the reverse direction; if the power increment is negative, and the voltage If the increment is positive, the voltage will be disturbed in the reverse direction, and if the voltage increment is negative, the voltage will be disturbed in the forward direction.
所述反向扰动观测法与MPPT算法的扰动方向相反，扰动频率为数千赫兹，接近开关和控制频率的1/3～1/2。The reverse disturbance observation method is opposite to the disturbance direction of the MPPT algorithm, and the disturbance frequency is several kilohertz, which is 1/3 to 1/2 of the proximity switch and control frequency.
所述改变扰动步长来控制功率包括：当光伏剩余功率过大时增加扰动步长以降低其输出功率，当光伏剩余功率与负载消耗接近一致时减少扰动步长以防止电压振荡。The changing the disturbance step size to control the power includes: increasing the disturbance step size to reduce the output power when the photovoltaic residual power is too large, and reducing the disturbance step size to prevent voltage oscillation when the photovoltaic residual power is close to the load consumption.
所述步骤4包括：The step 4 includes:
根据光伏变换器输入输出功率差值动态改变反向扰动步长，以实现光伏输入能量相比输出需求过剩较多时，以大的扰动步长削弱光伏输出能力，当输入输出近似一致时，扰动步长接近为0；当光伏变换器输入输出功率差值下降至较小时，且母线电压继续上升超过第一电压阈值时，直接在控制环路上叠加反馈量，实现母线电压的可靠箝位。The reverse disturbance step size is dynamically changed according to the difference between the input and output power of the photovoltaic converter, so that when the photovoltaic input energy exceeds the output demand, the photovoltaic output capacity is weakened with a large disturbance step size. When the input and output are approximately the same, the disturbance step The length is close to 0; when the difference between the input and output power of the photovoltaic converter drops to a small value, and the bus voltage continues to rise beyond the first voltage threshold, the feedback amount is directly superimposed on the control loop to achieve reliable clamping of the bus voltage.
本发明的有益效果：Beneficial effects of the present invention:
1、拓展了光伏变换器的工作模式，能够在MPPT和限功率两种模式之间切换，满足多能变换系统中的特定工作条件。1. Expanded the working mode of the photovoltaic converter, which can switch between MPPT and limited power modes to meet the specific working conditions in the multi-energy conversion system.
2、不改变控制环路结构，只需要一套控制环路中PI控制器的参数整定，避免切换时的瞬态问题。2. The structure of the control loop is not changed, only one set of parameters of the PI controller in the control loop is needed to avoid transient problems during switching.
3、不依赖及时和可靠的通信交互，能够避免通信干扰造成的相关问题。基于功率平衡原理调整限功率模式下的扰动步长，即使限功率数量变化较大时也能够快速箝位母线电压，同时设计了第二阈值检测调整，防止进入过压保护引起停机，增强系统的可靠性。3. It does not rely on timely and reliable communication interaction, and can avoid related problems caused by communication interference. Based on the power balance principle, the disturbance step size in the power-limiting mode is adjusted, and the bus voltage can be quickly clamped even when the power-limiting quantity changes greatly. At the same time, a second threshold detection adjustment is designed to prevent the shutdown caused by entering the overvoltage protection, and enhance the system reliability. reliability.
4、实现了功率流和信息流的解耦，模式切换由变换器自身传感器根据模拟量检测判断，能够同时满足无通信和快速、平滑切换两方面需求，以更好满足应对微网或多能系统中的极端工况条件。4. The decoupling of power flow and information flow is realized, and the mode switching is judged by the converter's own sensor according to the analog detection, which can meet the requirements of no communication and fast and smooth switching at the same time, so as to better meet the needs of micro-grid or multi-energy extreme operating conditions in the system.
附图说明Description of drawings
图1.光伏DC-DC变换器的原理电路图Figure 1. Schematic circuit diagram of a photovoltaic DC-DC converter
图2.最大功率跟踪模式下控制系统结构图Figure 2. Control system block diagram in MPPT mode
图3.母线电压稳定模式下控制系统结构图Figure 3. Structure diagram of control system in bus voltage stabilization mode
图4.具备反向扰动观测功能的控制流程图Figure 4. Control flow chart with reverse disturbance observation function
图5实验测试平台示意图Figure 5 Schematic diagram of the experimental test platform
图6光伏模拟器设定的P-V和I-V曲线图Fig. 6 P-V and I-V curves of PV simulator settings
图7 MPPT向限功率模式切换实验波形图Figure 7. Experimental waveform of switching from MPPT to limited power mode
图8解除功率限制后恢复MPPT的过渡过程图Figure 8. Transition process diagram of MPPT recovery after power limitation is lifted
具体实施方式Detailed ways
本发明提出了一种微网系统中光伏变换器自治模式切换控制方法，包括：The present invention provides a method for controlling autonomous mode switching of photovoltaic converters in a microgrid system, including:
步骤1：对光伏变换器的直流母线电压进行监视；Step 1: Monitor the DC bus voltage of the photovoltaic converter;
步骤2：当母线电压值在额定值以内时光伏变换器执行MPPT算法；Step 2: When the bus voltage value is within the rated value, the photovoltaic converter executes the MPPT algorithm;
步骤3：当母线电压值超过第一电压阈值时光伏变换器转为执行反向扰动观测法来限制功率；Step 3: When the bus voltage value exceeds the first voltage threshold, the photovoltaic converter switches to the reverse disturbance observation method to limit the power;
步骤4：当母线电压值超过第二电压阈值时光伏变换器采用改变扰动步长来控制功率。Step 4: When the bus voltage value exceeds the second voltage threshold, the photovoltaic converter controls the power by changing the disturbance step size.
所述步骤2包括：如果光伏功率增量为正，而电压增量为正，则继续正方向扰动电压，若电压增量为负，则反方向扰动电压；如果功率增量为负，而电压增量为正，则反向扰动电压，若电压增量为负，则正向扰动电压。The step 2 includes: if the photovoltaic power increment is positive and the voltage increment is positive, continue to perturb the voltage in the positive direction; if the voltage increment is negative, perturb the voltage in the reverse direction; if the power increment is negative, and the voltage If the increment is positive, the voltage will be disturbed in the reverse direction, and if the voltage increment is negative, the voltage will be disturbed in the forward direction.
所述反向扰动观测法与MPPT算法的扰动方向相反，扰动频率为数千赫兹，接近开关和控制频率的1/3～1/2。The reverse disturbance observation method is opposite to the disturbance direction of the MPPT algorithm, and the disturbance frequency is several kilohertz, which is 1/3 to 1/2 of the proximity switch and control frequency.
所述改变扰动步长来控制功率包括：当光伏剩余功率过大时增加扰动步长以降低其输出功率，当光伏剩余功率与负载消耗接近一致时减少扰动步长以防止电压振荡。The changing the disturbance step size to control the power includes: increasing the disturbance step size to reduce the output power when the photovoltaic residual power is too large, and reducing the disturbance step size to prevent voltage oscillation when the photovoltaic residual power is close to the load consumption.
所述步骤4包括：The step 4 includes:
根据光伏变换器输入输出功率差值动态改变反向扰动步长，以实现光伏输入能量相比输出需求过剩较多时，以大的扰动步长削弱光伏输出能力，当输入输出近似一致时，扰动步长接近为0；当光伏变换器输入输出功率差值下降至较小时，且母线电压继续上升超过第一电压阈值时，直接在控制环路上叠加反馈量，实现母线电压的可靠箝位。The reverse disturbance step size is dynamically changed according to the difference between the input and output power of the photovoltaic converter, so that when the photovoltaic input energy exceeds the output demand, the photovoltaic output capacity is weakened with a large disturbance step size. When the input and output are approximately the same, the disturbance step The length is close to 0; when the difference between the input and output power of the photovoltaic converter drops to a small value, and the bus voltage continues to rise beyond the first voltage threshold, the feedback amount is directly superimposed on the control loop to achieve reliable clamping of the bus voltage.
下面结合附图，对实施例作详细说明。The embodiments are described in detail below with reference to the accompanying drawings.
1、对光伏Boost变换器的环路控制1. Loop control of photovoltaic boost converter
光照、温度等环境因素变化引起光伏阵列P-V曲线变动，不同条件下最大功率与光伏电池的输出电压有非线性对应关系，光伏变换器的最大功率跟踪是通过对光伏电池电压的控制实现的。因此对图1所示的Boost光伏DC-DC变换器，在MPPT模式下控制环路结构如图2所示，控制对象为变换器的输入电压vpv。The change of environmental factors such as light and temperature causes the PV curve of the photovoltaic array to change. Under different conditions, the maximum power has a nonlinear correspondence with the output voltage of the photovoltaic cell. The maximum power tracking of the photovoltaic converter is realized by controlling the voltage of the photovoltaic cell. Therefore, for the Boost photovoltaic DC-DC converter shown in Figure 1, the control loop structure is shown in Figure 2 in the MPPT mode, and the control object is the input voltage vpv of the converter.
MPPT模式下，光伏变换器跟踪光伏电池能够输出的最大功率，该功率能够被储能变换器或并网变换器全部吸收。当电网异常或变换器受限情况下，最大功率跟踪的输出功率超过系统所需，会引起直流母线电压上升导致不可控。因此，需要在这些情况下相应地改变光伏变换器的控制结构，由控制变换器的输入转而稳定变换器输出，以得到稳定的直流母线电压，对应的控制环路结构如图3所示，控制对象为直流母线电压。即光伏变换器在MPPT运行时为恒功率源控制模式，母线电压由并网变换器或储能系统支撑，当失去电压支撑能力后，光伏变换器应当及时转为电压控制模式，完成对母线电压支撑。In MPPT mode, the photovoltaic converter tracks the maximum power that the photovoltaic cell can output, and this power can be fully absorbed by the energy storage converter or grid-connected converter. When the grid is abnormal or the converter is limited, the output power of the maximum power tracking exceeds the system requirement, which will cause the DC bus voltage to rise and become uncontrollable. Therefore, it is necessary to change the control structure of the photovoltaic converter correspondingly in these cases, and turn the input of the control converter to stabilize the output of the converter to obtain a stable DC bus voltage. The corresponding control loop structure is shown in Figure 3. The control object is the DC bus voltage. That is, the photovoltaic converter is in constant power source control mode during MPPT operation, and the bus voltage is supported by the grid-connected converter or energy storage system. support.
两种控制模式下，虽然主电路结构没有变化，但控制对象发生了改变，对应的控制—输出传递函数也有较大的变化，因此通过小信号模型设计控制参数必然会有不同的结果。同时，在使用数字控制PI实现时，为了减小控制环路切换时带来的瞬态和震颤，需要使用当前环路控制器PI的当前输出值来初始化要切换到的环路PI输出初值。In the two control modes, although the main circuit structure has not changed, the control object has changed, and the corresponding control-output transfer function has also changed greatly. Therefore, the design of control parameters through the small signal model will inevitably lead to different results. At the same time, when using digital control PI to achieve, in order to reduce the transient and chatter caused by the control loop switching, it is necessary to use the current output value of the current loop controller PI to initialize the initial output value of the loop PI to be switched to .
基于此，本发明中使用单套控制环路，即仅控制光伏变换器的输入电压间接实现功率限制模式下母线电压的箝位。Based on this, a single control loop is used in the present invention, that is, only the input voltage of the photovoltaic converter is controlled to indirectly realize the clamping of the bus voltage in the power limiting mode.
2、正向和反向扰动观测算法2. Forward and reverse disturbance observation algorithm
兼容功率限制模式是通过修改MPPT算法实现的，传统的MPPT跟踪算法有较多成熟方法，这里选用了最简单易实现的扰动观测方法。扰动观测法的两个主要指标分别为扰动周期和扰动步长。The compatible power limit mode is realized by modifying the MPPT algorithm. There are many mature methods in the traditional MPPT tracking algorithm. Here, the most simple and easy-to-implement disturbance observation method is selected. The two main indicators of the perturbation observation method are the perturbation period and the perturbation step size.
实现MPPT的扰动观测采用固定周期和固定步长法，在数字控制器的中断例程里采样输入电压电流、母线电压和输出电流，计算对应的瞬时输入输出功率。通过计数方法，以10Hz的频率执行MPPT算法跟踪，以5kHz频率执行功率限制算法。The disturbance observation of MPPT adopts fixed period and fixed step method. Input voltage and current, bus voltage and output current are sampled in the interrupt routine of the digital controller, and the corresponding instantaneous input and output power is calculated. By counting method, the MPPT algorithm tracking is performed at a frequency of 10 Hz and the power limiting algorithm is performed at a frequency of 5 kHz.
在MPPT算法中，得到本次光伏电压与上次保存电压做差得到电压增量，计算本次瞬时功率并与上一次做差判断功率增量。如果功率增量为正，而本次电压增量为正，则继续正方向扰动电压，若本次电压增量为负，则反方向扰动电压；如果功率增量为负，而本次电压增量为正，则反向扰动电压，若本次电压增量为负，则正向扰动电压。In the MPPT algorithm, the difference between the current photovoltaic voltage and the last saved voltage is obtained to obtain the voltage increment, the current instantaneous power is calculated, and the difference between the current photovoltaic voltage and the last one is used to judge the power increment. If the power increment is positive and the current voltage increment is positive, the voltage will continue to be disturbed in the positive direction; if the current voltage increment is negative, the voltage will be disturbed in the reverse direction; if the power increment is negative, the current voltage increase If the amount is positive, the voltage will be disturbed in the reverse direction. If the current voltage increment is negative, the voltage will be disturbed in the forward direction.
功率限制算法与MPPT的扰动方向相反，实现功率的反向调整。控制框图的流程图如图4所示。The power limit algorithm is opposite to the disturbance direction of MPPT, and realizes the reverse adjustment of power. The flow chart of the control block diagram is shown in Figure 4.
3、变步长扰动观测3. Variable step size disturbance observation
在传统正向扰动观测法中，步长过大容易在最大功率点来回震荡，步长过小则MPPT的追踪时间过长，变步长调整能较好解决这一难题，通常是以当前光伏电池电压与最大工作点电压差作为扰动步长的调整依据。In the traditional forward disturbance observation method, if the step size is too large, it is easy to oscillate back and forth at the maximum power point. If the step size is too small, the MPPT tracking time will be too long. Variable step size adjustment can better solve this problem. The difference between the battery voltage and the maximum operating point voltage is used as the adjustment basis for the disturbance step size.
本发明中对扰动瞬态调整要求最高的是正向扰动观测向反向扰动观测切换的过程，切换前变换器输出光伏电池的最大功率，当电网异常或并网变换器限流后，光伏输出过剩的功率额度、网侧惯性和变换器限流设置的时间常数、直流母线电容大小共同决定了母线电压上升的速率，要求能够在直流母线电压达到第一阈值时转为反向扰动观测，并在初始时刻以较大的反向步长扰动，以限制直流母线电压的继续上升，随后该步长逐渐减小以防止母线电压下降过多造成较大的电压纹波。In the present invention, the highest requirement for disturbance transient adjustment is the process of switching from forward disturbance observation to reverse disturbance observation. Before switching, the converter outputs the maximum power of the photovoltaic cell. When the grid is abnormal or the grid-connected converter is current limited, the photovoltaic output is excessive. The power rating, grid-side inertia, time constant of the converter current limit setting, and the size of the DC bus capacitor jointly determine the rate of bus voltage rise, and it is required to be able to switch to reverse disturbance observation when the DC bus voltage reaches the first threshold At the initial moment, a larger reverse step size is used to limit the continuous rise of the DC bus voltage, and then the step size is gradually reduced to prevent the bus voltage from dropping too much and causing larger voltage ripple.
根据光伏的输入输出功率差值动态改变反向扰动步长，以实现光伏输入能量相比输出需求过剩较多时，以较大的步长削弱光伏输出能力，当输入输出近似一致时，该步长接近为0。在反向扰动观测过程中，对应的步长为：Dynamically change the reverse disturbance step size according to the difference between the input and output power of the photovoltaics, so that when the input energy of the photovoltaics exceeds the output demand, the output capacity of the photovoltaics is weakened with a larger step size. When the input and output are approximately the same, the step size close to 0. In the process of reverse disturbance observation, the corresponding step size is:
dV2＝k(ppv-po)dV2 =k(ppv -po )
限功率算法下使用的采样滤波频率较高，当光伏变换器输入输出功率差值下降至较小时，由于传感器误差可能判断出输入功率小于输出功率，此情况下停止扰动，但实际输入功率可能略高于输出功率引起母线继续上升，为了避免母线过压引入第二阈值检测，当母线电压继续上升超过该阈值时，直接在控制环路上叠加反馈量，实现母线电压的可靠箝位。The sampling filtering frequency used in the power limiting algorithm is relatively high. When the difference between the input and output power of the photovoltaic converter decreases to a small value, it may be judged that the input power is less than the output power due to sensor errors. In this case, the disturbance is stopped, but the actual input power may be slightly smaller. Higher than the output power will cause the bus to continue to rise. In order to avoid the introduction of the second threshold detection by the bus overvoltage, when the bus voltage continues to rise beyond the threshold, the feedback amount is directly superimposed on the control loop to achieve reliable clamping of the bus voltage.
4、主要实验结果4. Main experimental results
为了验证提出的自治切换控制方法的有效性，使用光伏模拟器和Boost变换器充当光伏阵列和DC-DC变换器，使用具备电网回馈功能且可限制电流或功率的双向可编程电源作为并网变换器，搭建如图5所示的实验测试平台。In order to verify the effectiveness of the proposed autonomous switching control method, a photovoltaic simulator and a boost converter are used as photovoltaic arrays and DC-DC converters, and a bidirectional programmable power supply with grid feedback function that can limit current or power is used as grid-connected converters , and build the experimental test platform as shown in Figure 5.
光伏模拟器使用软件预设光伏曲线，模拟环境参数为恒定光照1000和室温25℃条件，最大功率点为光伏电池电压109V，对应610W输出功率，图6为光伏模拟器的P-V和I-V曲线，可以看出在109V左侧和右侧，光伏输出功率分别为近似单调递增和单调递减，在非最大功率点时光伏面板电压越低其输出功率也越小。并网逆变器直流母线电压额定值为190V，设定DC-DC变换器状态切换的母线电压阈值为200V。The photovoltaic simulator uses the software to preset the photovoltaic curve. The simulated environment parameters are constant illumination of 1000 and room temperature of 25 °C. The maximum power point is the photovoltaic cell voltage of 109V, corresponding to 610W output power. Figure 6 shows the P-V and I-V curves of the photovoltaic simulator, which can be It can be seen that on the left and right sides of 109V, the photovoltaic output power is approximately monotonically increasing and monotonically decreasing, respectively. When the photovoltaic panel voltage is not at the maximum power point, the lower the photovoltaic panel voltage, the smaller the output power. The rated DC bus voltage of the grid-connected inverter is 190V, and the bus voltage threshold for state switching of the DC-DC converter is set to 200V.
波形图7和图8对应相关实验结果，图中CH1、CH2通道分别对应Boost变换器的输出和输入电压。在MPPT的稳定跟踪状态下，并网变换器向电网回馈610W功率，此时调整并网变换器功率限制值到400W，从波形图7看出DC-DC变换器能够迅速调整并减小光伏变换器输入侧电压，光伏电压降低到75V左右对应约400V的输出功率，此时光伏变换器的输入输出功率接近一致，直流母线电压被箝位。图8为解除并网变换器功率限制后变换器从限制功率模式到MPPT的过渡过程，电压逐渐上升对应其输出功率逐渐增大，最终实现在最大功率点附近稳态工作。实验结果验证了MPPT和限功率模式相互转换方法的有效性。The waveforms in Figure 7 and Figure 8 correspond to the relevant experimental results. The CH1 and CH2 channels in the figure correspond to the output and input voltages of the Boost converter, respectively. In the stable tracking state of MPPT, the grid-connected converter feeds back 610W power to the grid. At this time, the power limit value of the grid-connected converter is adjusted to 400W. It can be seen from the waveform diagram 7 that the DC-DC converter can quickly adjust and reduce the photovoltaic conversion. The input side voltage of the photovoltaic converter is reduced to about 75V, which corresponds to an output power of about 400V. At this time, the input and output power of the photovoltaic converter is close to the same, and the DC bus voltage is clamped. Figure 8 shows the transition process of the converter from the limited power mode to the MPPT after the power limit of the grid-connected converter is lifted. The voltage gradually increases corresponding to the gradual increase of its output power, and finally the steady state operation near the maximum power point is realized. The experimental results verify the effectiveness of the mutual conversion method between MPPT and limited power mode.
此实施例仅为本发明较佳的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应该以权利要求的保护范围为准。This embodiment is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. , all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
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