技术领域technical field
本发明涉及一种并网逆变器电网电压特定次分量前馈的控制方法，尤其涉及一种用于弱 电网下提升并网逆变器并网电流谐波抑制效果的电网电压特定次分量前馈的控制策略，属于 新能源并网发电领域。The present invention relates to a grid-connected inverter grid voltage specific sub-component feedforward control method, in particular to a grid-connected inverter grid-connected current harmonic suppression effect of a grid-connected inverter specific sub-component feedforward control method Feedback control strategy belongs to the field of new energy grid-connected power generation.
背景技术Background technique
近年来，为了应对能源危机和环境污染等问题，以风能和太阳能为代表的可再生能源正 得到越来越广泛的利用。并网逆变器作为分布式可再生发电单元与电网之间的接口，正成为 国内外学者研究的热点。但随着分布式发电系统并网功率的增加和接入电网位置的广泛分布， 电网越来越呈现出弱电网的特性，电网电压中的背景谐波含量也越来越丰富。电网电压背景 谐波将会引起并网逆变器并网电流畸变，引起设备损耗增加、利用率和使用寿命下降等问题。 也会影响继电保护和计量装置的可靠性及准确性。In recent years, in order to cope with energy crisis and environmental pollution, renewable energy represented by wind energy and solar energy is being used more and more widely. Grid-connected inverters, as the interface between distributed renewable generation units and the grid, are becoming a research hotspot among scholars at home and abroad. However, with the increase of grid-connected power of distributed generation systems and the wide distribution of access grid locations, the grid is increasingly showing the characteristics of a weak grid, and the background harmonic content in the grid voltage is becoming more and more abundant. Grid voltage background Harmonics will cause grid-connected inverters to distort the grid-connected current, causing problems such as increased equipment loss, decreased utilization and service life. It will also affect the reliability and accuracy of relay protection and metering devices.
为保证接入并网逆变器后电网仍安全、稳定且高质量运行，国内外制定了一系列并网逆 变器接入标准和技术规范，如我国制定的国家标准GB/T 19939-2005《光伏系统并网技术要 求》、国家电网公司企业标准Q/GDW 617-2011《光伏电站接入电网技术规定》和国际标准 IEEE Std.1547.1a-2015、IEEE Std.1547-2018等。这些标准和技术规范均对并网电流的谐波含 量做出了明确限制。因此，为满足相关并网电流谐波标准，并网逆变器必须能够有效抑制电 网电压背景谐波引起的并网电流谐波。In order to ensure the safe, stable and high-quality operation of the grid after the grid-connected inverter is connected, a series of grid-connected inverter access standards and technical specifications have been formulated at home and abroad, such as the national standard GB/T 19939-2005 formulated by my country "Technical Requirements for Grid-Connection of Photovoltaic Systems", State Grid Corporation of China Enterprise Standard Q/GDW 617-2011 "Technical Regulations for Connecting Photovoltaic Power Plants to the Grid", and international standards IEEE Std.1547.1a-2015, IEEE Std.1547-2018, etc. These standards and technical specifications have made clear restrictions on the harmonic content of grid-connected current. Therefore, in order to meet the relevant grid-connected current harmonic standards, the grid-connected inverter must be able to effectively suppress the grid-connected current harmonics caused by the background harmonics of the grid voltage.
要提高并网逆变器对电网电压背景谐波引起的并网电流谐波的抑制能力，有两种基本的 方法：1)提高并网电流环的环路增益；2)采用电网电压前馈控制。To improve the ability of the grid-connected inverter to suppress the grid-connected current harmonics caused by the background harmonics of the grid voltage, there are two basic methods: 1) increase the loop gain of the grid-connected current loop; 2) adopt grid voltage feed-forward control.
提高并网电流环的环路增益有采用多谐振调节器或重复控制器的方法，但是采用多谐振 调节器方法会影响系统的环路增益，可能导致系统不稳定；重复控制的不足是并网逆变器的 动态性能较差。如果将电网电压采样，并通过合适的传递函数叠加到并网逆变器的调制波vM中，与电网电压对并网电流产生的影响进行对消，同样可以实现并网电流谐波分量的抑制， 该方法即为电网电压前馈控制策略。There are ways to improve the loop gain of the grid-connected current loop by using a multi-resonance regulator or a repetitive controller, but the method of using a multi-resonance regulator will affect the loop gain of the system and may cause system instability; the disadvantage of repeated control is that the grid-connected The dynamic performance of the inverter is poor. If the grid voltage is sampled and superimposed on the modulation wave vM of the grid-connected inverter through a suitable transfer function, and the influence of the grid voltage on the grid-connected current is cancelled, the harmonic component of the grid-connected current can also be achieved. Inhibition, this method is the grid voltage feed-forward control strategy.
现有研究针对单相LCL型并网逆变器提出电网电压全前馈控制方法，推导了完全消除电 网电压对并网电流影响的电网电压全前馈函数，从而大大提高了并网逆变器对高次谐波的抑 制能力。但由于数字控制延时的影响，电网电压全前馈的并网电流谐波抑制效果会变差，并 且会在并网逆变器输出阻抗中引入负相移，恶化逆变器在弱电网下的稳定性。The existing research proposes a grid voltage full feed-forward control method for the single-phase LCL grid-connected inverter, and derives a grid voltage full feed-forward function that completely eliminates the influence of the grid voltage on the grid-connected current, thereby greatly improving the efficiency of the grid-connected inverter. The ability to suppress high-order harmonics. However, due to the influence of digital control delay, the harmonic suppression effect of grid-connected current with full feed-forward of grid voltage will become worse, and will introduce negative phase shift in the output impedance of grid-connected inverter, which will deteriorate the performance of inverter in weak grid. stability.
因此，如何在保证逆变器在弱电网下稳定的同时，提升对并网电流谐波的抑制效果是本 领域研究人员亟需解决的问题。Therefore, how to improve the suppression effect of grid-connected current harmonics while ensuring the stability of the inverter in a weak grid is a problem that researchers in this field need to solve urgently.
发明内容Contents of the invention
本发明为了解决现有技术中存在的问题，提供一种弱电网下并网逆变器电网电压特定次 分量前馈的控制方法，该方法能够保证并网逆变器系统在弱电网下稳定的同时，提升对并网 电流谐波的抑制效果。In order to solve the problems existing in the prior art, the present invention provides a feedforward control method for a specific secondary component of grid voltage of a grid-connected inverter under a weak grid, which can ensure the stability of the grid-connected inverter system under a weak grid At the same time, the suppression effect on grid-connected current harmonics is improved.
为了达到上述目的，本发明提出的技术方案为：一种电网电压特定次分量前馈的并网逆 变器控制方法，包括如下步骤：In order to achieve the above purpose, the technical solution proposed by the present invention is: a grid-connected inverter control method for grid voltage specific secondary component feedforward, including the following steps:
步骤一、采集并网逆变器电网电压vpcc，电容电流iC和并网电流i2；Step 1. Collect the grid voltage vpcc of the grid-connected inverter, the capacitor current iC and the grid-connected current i2 ;
步骤二、通过锁相环单元获得与vpcc同步的相位θ和角频率ω，将相位θ和外部电压环 产生的电流幅值I*一起作为并网电流指令表达式为将i2的采样信号与指令进 行比较得到误差信号，将误差信号送入电流调节器Gi(s)；Step 2. Obtain the phase θ and angular frequency ω synchronized with vpcc through the phase-locked loop unit, and use the phase θ and the current amplitude I* generated by the external voltage loop as the grid-connected current command The expression is Combine the sampling signal of i2 with the instruction The error signal is obtained by comparison, and the error signal is sent to the current regulator Gi (s);
步骤三、将电流调节器的输出减去电容电流iC的采样信号，再加上电网电压vpcc的前馈 量，作为调制信号vM，将调制信号vM与三角载波比较，通过单极性倍频的正弦脉宽调制得 到逆变桥各开关管的控制信号。Step 3: Subtract the sampling signal of the capacitive current iC from the output of the current regulator, and add the feedforward value of the grid voltage vpcc as the modulation signal vM , compare the modulation signal vM with the triangular carrier, and pass the unipolar The control signal of each switch tube of the inverter bridge is obtained by the sinusoidal pulse width modulation of the characteristic frequency multiplication.
对上述技术方案的进一步设计为：所述电网电压vpcc的前馈量，是将电网电压vpcc送入特 定次前馈函数Gshff(s)产生的输出量，所述前馈函数的表达式为：The further design of the above technical solution is: the feed-forward amount of the grid voltage vpcc is the output generated by sending the grid voltage vpcc into a specific secondary feed-forward function Gshff (s), and the expression of the feed-forward function The formula is:
Gshff(s)＝Gff(s)Hf(s)Gshff (s) = Gff (s)Hf (s)
其中，Gff(s)是电网电压全前馈函数，其表达式为：Among them, Gff (s) is the full feed-forward function of the grid voltage, and its expression is:
Hi1是电容电流反馈系数，KPWM是逆变桥的传递函数，L1为逆变器侧电感，C为滤波电容；Hi1 is the capacitor current feedback coefficient, KPWM is the transfer function of the inverter bridge, L1 is the inductance of the inverter side, and C is the filter capacitor;
Hf(s)是由若干谐振环节组成的滤波器函数，其表达式为：Hf (s) is a filter function composed of several resonance links, and its expression is:
Hf(s)＝∑Rk(s)Hf (s) = ΣRk (s)
k是谐波次数，ωi是谐振项带宽，ωk为特征频率，ωo为基波角频率。k is the harmonic order, ωi is the bandwidth of the resonant item, ωk is the characteristic frequency, and ωo is the fundamental angular frequency.
所述谐振环节，通过调整其参数，可以起到补偿效果，提升并网电流的谐波抑制效果； 谐振环节的特征频率ωk随通过锁相环得到的基波频率ωo的改变而改变，从而实现对电网电 压频率的自适应，即ωk＝kωo。The resonance link, by adjusting its parameters, can play a compensation effect and improve the harmonic suppression effect of the grid-connected current; the characteristic frequency ωk of the resonance link changes with the change of the fundamental frequency ωo obtained by the phase-locked loop, In this way, the self-adaptation to the grid voltage frequency is realized, that is, ωk =kωo .
所述锁相环单元为同步旋转坐标系锁相环，同步旋转坐标系锁相环基于电网电压瞬时值 采样，对电网电压谐波有一定的抑制能力。The phase-locked loop unit is a synchronous rotating coordinate system phase-locked loop, and the synchronous rotating coordinate system phase-locked loop is based on the sampling of the instantaneous value of the grid voltage, and has a certain ability to suppress the harmonics of the grid voltage.
所述电流调节器Gi(s)，为比例谐振调节器，其表达式为：The current regulator Gi (s) is a proportional resonance regulator, and its expression is:
其中，Kp为比例系数，Kr为谐振系数，ωo＝2πfo为基波角频率，ωi为考虑-3dB要求的谐振项 带宽，即在ωo±ωi处谐振项的增益为0.707Kr。Among them, Kp is the proportional coefficient, Kr is the resonance coefficient, ωo = 2πfo is the fundamental angular frequency, ωi is the bandwidth of the resonance item considering the requirement of -3dB, that is, the gain of the resonance item at ωo ±ωi is 0.707Kr .
本发明的有益效果为：The beneficial effects of the present invention are:
本发明通过在电网电压前馈通路中加入由一系列谐振环节组成的滤波器的方式，仅提取 电网电压中的特定次分量进行前馈，既能保证并网逆变器的稳定性，且可以通过调整加入的 谐振环节的特征频率和谐振项系数，可以实现比电网电压全前馈更好的谐波抑制效果。By adding a filter composed of a series of resonant links in the feedforward path of the grid voltage, the present invention only extracts specific subcomponents in the grid voltage for feedforward, which can not only ensure the stability of the grid-connected inverter, but also can By adjusting the characteristic frequency of the added resonance link and the coefficient of the resonance item, a better harmonic suppression effect than that of the grid voltage full feed-forward can be achieved.
附图说明Description of drawings
图1是本发明中LCL型并网逆变器拓扑及其控制结构示意图(z域)。Fig. 1 is a schematic diagram (z-domain) of the topology and control structure of the LCL type grid-connected inverter in the present invention.
图2是本发明中LCL型并网逆变器的s域数学模型。Fig. 2 is the s-domain mathematical model of the LCL grid-connected inverter in the present invention.
图3是本发明中LCL型并网逆变器等效数学模型。Fig. 3 is an equivalent mathematical model of the LCL type grid-connected inverter in the present invention.
图4是本发明中电网电压前馈的原理数学模型。Fig. 4 is the principle mathematical model of grid voltage feed-forward in the present invention.
图5是本发明中LCL型并网逆变器系统等效电路。Fig. 5 is an equivalent circuit of the LCL type grid-connected inverter system in the present invention.
图6是本发明中电网电压前馈的等效数学模型一。Fig. 6 is the first equivalent mathematical model of grid voltage feed-forward in the present invention.
图7是本发明中电网电压前馈的等效数学模型二。Fig. 7 is the second equivalent mathematical model of grid voltage feed-forward in the present invention.
图8是本发明中电网电压前馈的等效数学模型三。Fig. 8 is the third equivalent mathematical model of grid voltage feed-forward in the present invention.
图9是本发明中电网电压全前馈对消项FV(s)的伯德图。Fig. 9 is a Bode diagram of the grid voltage full feed-forward cancellation item FV(s) in the present invention.
图10是本发明中电网电压全前馈作用矢量示意图。Fig. 10 is a schematic diagram of the grid voltage full feed-forward action vector in the present invention.
图11是本发明中并网逆变器输出阻抗和电网阻抗伯德图。Fig. 11 is a Bode diagram of the grid-connected inverter output impedance and grid impedance in the present invention.
图12是本发明中电网电压特定次分量前馈数学模型。Fig. 12 is a feed-forward mathematical model of a specific secondary component of grid voltage in the present invention.
图13是本发明中并网逆变器输出阻抗和电网阻抗伯德图。Fig. 13 is a Bode diagram of the grid-connected inverter output impedance and grid impedance in the present invention.
图14是本发明中谐振环节补偿机理图。Fig. 14 is a diagram of the compensation mechanism of the resonance link in the present invention.
图15是本发明中在弱电网下不采用前馈时的仿真波形图。Fig. 15 is a simulation waveform diagram when feedforward is not used under a weak grid in the present invention.
图16是本发明中在强电网下采用电网电压全前馈时的仿真波形图。Fig. 16 is a simulation waveform diagram of the present invention when full feed-forward of the grid voltage is adopted under a strong grid.
图17是本发明中在弱电网下采用电网电压全前馈时的仿真波形图。Fig. 17 is a simulation waveform diagram of the present invention when full feed-forward of the grid voltage is adopted under a weak grid.
图18是本发明中在弱电网下采用电网电压特定次分量前馈时的仿真波形图。Fig. 18 is a simulation waveform diagram of the present invention when a specific secondary component of the grid voltage is used for feed-forward under a weak grid.
图19是电网电压基波频率为49.5Hz时采用电网电压特定次分量前馈时的仿真波形图。Fig. 19 is a simulation waveform diagram when the fundamental frequency of the grid voltage is 49.5 Hz and the specific secondary component of the grid voltage is used to feed forward.
图20是电网电压基波频率为50.5Hz时采用电网电压特定次分量前馈时的仿真波形图。Fig. 20 is a simulation waveform diagram when the fundamental frequency of the grid voltage is 50.5 Hz and the specific secondary component of the grid voltage is used to feed forward.
具体实施方式Detailed ways
下面结合附图以及具体实施例对本发明进行详细说明。The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.
对比例comparative example
本发明涉及的LCL型并网逆变器拓扑及其控制结构如图1所示，其中，L1为逆变器侧电 感，C为滤波电容，L2为网侧电感，它们构成LCL滤波器。对并网逆变器而言，其首要目标 是控制并网电流i2，使其与电网电压vg(vpcc)同步，并使其幅值跟踪给定值I*。The LCL type grid-connected inverter topology and its control structure involved in the present invention are shown in Figure1 , where L1 is the inverter side inductance, C is the filter capacitor, andL2 is the grid side inductance, which constitute the LCL filter . For the grid-connected inverter, its primary goal is to control the grid-connected current i2 , make it synchronize with the grid voltage vg (vpcc ), and make its amplitude track the given value I* .
本对比例的并网逆变器控制方法中vg的相位θ和角频率ω由锁相环单元获得，I*由外部 电压环产生。由于电压环的响应速度远低于并网电流环，因此可以对并网电流环进行单独分 析。在图1中，Hv和Hi2分别为vg和i2的采样系数。将相位θ和外部电压环产生的电流幅值 I*一起作为并网电流指令将i2的采样信号与指令进行比较得到误差信号，得到的误差信 号送入电流调节器Gi(z)。通过反馈电容电流iC实现LCL滤波器谐振尖峰的有源阻尼，Hi1为 其反馈系数。将电流调节器的输出信号电容电流反馈信号作差，产生调制波信号vM。将vM与三角载波比较，通过单极性倍频的正弦脉宽调制，即可得到逆变桥各开关管的控制信号， 经驱动保护电路控制单相全桥逆变器功率器件的开通和关断。本对比例中，并网逆变器的控 制环路里未加入电网电压前馈。In the grid-connected inverter control method of this comparative example, the phase θ and angular frequency ω of vg are obtained by the phase-locked loop unit, and I* is generated by the external voltage loop. Since the response speed of the voltage loop is much lower than that of the grid-connected current loop, the grid-connected current loop can be analyzed separately. In Fig. 1, Hv and Hi2 are the sampling coefficients of vg and i2 respectively. Take the phase θ and the current amplitude I* generated by the external voltage loop together as the grid-connected current command Combine the sampling signal of i2 with the instruction The error signal is obtained by comparison, and the obtained error signal is sent to the current regulator Gi (z). The active damping of the resonance peak of the LCL filter is realized through the feedback capacitor current iC , and Hi1 is its feedback coefficient. The capacitor current feedback signal of the output signal of the current regulator is subtracted to generate the modulated wave signal vM . Comparing vM with the triangular carrier wave, the control signal of each switch tube of the inverter bridge can be obtained through the sinusoidal pulse width modulation of unipolar frequency multiplication, and the opening and closing of the single-phase full-bridge inverter power device is controlled by the driving protection circuit. off. In this comparative example, the grid voltage feed-forward is not added to the control loop of the grid-connected inverter.
下面通过一系列等效模型对上述对比例所述控制方法下并网逆变器的稳定性进行判断。Next, a series of equivalent models are used to judge the stability of the grid-connected inverter under the control method described in the above comparative example.
图2给出了对应于图1的LCL型并网逆变器的s域模型，KPWM等于Vin/Vtri，(Vin为输入电压，Vtri指三角载波的幅值)。Gd(s)为数字控制延时环节，包括一拍计算延时和半拍PWM延时，其表达式为：Gd(s)＝e-1.5sTs。对图2的数学模型作等效变换，可以化简为图3的形式。其中，Figure 2 shows the s-domain model corresponding to the LCL type grid-connected inverter in Figure 1, KPWM is equal to Vin /Vtri , (Vin is the input voltage, Vtri refers to the amplitude of the triangular carrier wave). Gd (s) is a digital control delay link, including a one-beat calculation delay and a half-beat PWM delay, and its expression is: Gd (s) = e-1.5sTs . The equivalent transformation of the mathematical model in Figure 2 can be simplified to the form in Figure 3. in,
闭环系统的环路增益为：The loop gain of the closed loop system is:
对图3中的i2的反馈点后移，可以得到如图4所示的等效模型(除–Zo(s)支路)，从图4可 以直观地求出并网逆变器的输出阻抗：If the feedback point of i2 in Fig. 3 is shifted backward, the equivalent model shown in Fig. 4 can be obtained (excluding the -Zo (s) branch), and the grid-connected inverter can be intuitively calculated from Fig. 4 Output Impedance:
逆变器的并网电流表达式为：The grid-connected current expression of the inverter is:
如图4所示，可以通过从vpcc引入一条传函为–Zo(s)的支路，等效于在电网输出端并联一 个大小为–Zo(s)的阻抗，如图5等效电路所示，这样系统输出阻抗被理想地校正为无穷大，并 网电流谐波被完全消除。As shown in Figure 4, by introducing a branch with a transfer function of –Zo (s) from vpcc , it is equivalent to connecting an impedance of –Zo (s) in parallel at the output end of the grid, as shown in Figure 5, etc. As shown in the effective circuit, the output impedance of the system is ideally corrected to infinity, and the grid-connected current harmonics are completely eliminated.
将图4中的前馈点移到调制波前，即得到理想的电网电压全前馈传递函数：Moving the feedforward point in Figure 4 to the modulation wavefront, the ideal grid voltage full feedforward transfer function is obtained:
但是由于超前环节1/Gd(s)无法物理实现，实际上能够采用的全前馈函数为：However, since the advance link 1/Gd (s) cannot be realized physically, the full feed-forward function that can actually be used is:
采用了电网电压前馈的等效数学模型如图6所示。为了更直观地分析电网电压全前馈对 并网逆变器输出阻抗的影响，图7和图8对电网电压全前馈支路做了进一步等效，其中，The equivalent mathematical model using grid voltage feed-forward is shown in Figure 6. In order to more intuitively analyze the influence of grid voltage full feedforward on the output impedance of the grid-connected inverter, Fig. 7 and Fig. 8 make a further equivalent for the grid voltage full feedforward branch, where,
FF(s)＝1-FV(s)＝1-Gd(s)(9)FF(s)=1-FV(s)=1-Gd (s)(9)
此时系统输出阻抗表达式为：At this time, the system output impedance expression is:
其中FV(s)为电网电压全前馈引入的对消项，FF(s)为电网电压作用剩余项，Zo_nff(s)表示 无前馈时系统的输出阻抗，Zo_ff(s)表示加入全前馈时系统的输出阻抗。若在模拟控制下，电 网电压全前馈可以理想实现，对消项FV(s)＝1，剩余项FF(s)＝0,表示电网电压对并网电流的影 响被完全消除。Among them, FV(s) is the cancellation item introduced by full feed-forward of grid voltage, FF(s) is the residual item of grid voltage action, Zo_nff (s) represents the output impedance of the system without feed-forward, and Zo_ff (s) represents the addition of The output impedance of the system at full feedforward. Under analog control, full grid voltage feed-forward can be ideally realized, the cancellation item FV(s)=1, and the remaining item FF(s)=0, which means that the influence of the grid voltage on the grid-connected current is completely eliminated.
图9给出了FV(s)的频率响应曲线，可以看出，在低频时，FV(s)的增益近似为1，相位有 微小的滞后。图10给出了较低频时(f<2KHz)电网电压全前馈矢量作用示意图，可以看出， 电网电压全前馈引入的对消项滞后代表原电网电压作用的“1”矢量Δθd，矢量电网电压剩余 矢量FF(s)超前“1”矢量Δθ，低频时，Δθ≈90°，根据式(9)可知，这说明着采用电网电压全 前馈的系统的输出阻抗Zo_ff(s)将滞后Zo_nff(s)约90°。这与图11所示的并网逆变器输出阻抗伯 德图相符。Figure 9 shows the frequency response curve of FV(s), it can be seen that at low frequencies, the gain of FV(s) is approximately 1, and the phase has a slight lag. Fig. 10 shows a schematic diagram of the grid voltage full feed-forward vector action at a lower frequency (f<2KHz). It can be seen that the cancellation term introduced by the grid voltage full feed-forward lags behind the "1" vector Δθd representing the original grid voltage action , the vector grid voltage residual vector FF(s) leads the "1" vector Δθ, and at low frequency, Δθ≈90°, according to formula (9), it can be known that the output impedance Zo_ff (s ) will lag Zo_nff (s) by about 90°. This is consistent with the grid-connected inverter output impedance Bode plot shown in Figure 11.
基于阻抗的并网逆变器稳定性判据为：The stability criterion of grid-connected inverter based on impedance is:
根据图5所示的并网逆变器等效电路(忽略–Zo(s)支路)，可以得到并网电流的表达式为：According to the equivalent circuit of the grid-connected inverter shown in Figure 5 (ignoring the –Zo (s) branch), the expression of the grid-connected current can be obtained as:
上式可改写为：The above formula can be rewritten as:
其中，N(s)为：Among them, N(s) is:
由于不考虑电网阻抗的情况下，即Zg(s)＝0时，并网逆变器设计为稳定系统，因此式(12) 中的(is(s)-vg(s)/Zo(s))不含右半平面极点。那么，在考虑电网阻抗的情况下，并网逆变器的稳 定性取决于N(s)是否稳定。从式(13)可以看出，N(s)可等效为前向通路传递函数为1，反馈通 路传递函数为Zg(s)/Zo(s)的负反馈闭环控制系统传递函数，Zg(s)/Zo(s)为该系统的等效环路增 益。根据线性控制理论可知，若Zg(s)/Zo(s)满足Nyquist稳定性判据，则N(s)稳定，因而，并 网系统也稳定。Since the grid-connected inverter is designed as a stable system when the grid impedance is not considered, that is, when Zg (s) = 0, the (is (s)-vg (s)/Zo (s)) does not contain right-half-plane poles. Then, considering the grid impedance, the stability of the grid-connected inverter depends on whether N(s) is stable. It can be seen from formula (13) that N(s) can be equivalent to the transfer function of the negative feedback closed-loop control system with the transfer function of the forward path being 1 and the transfer function of the feedback path being Zg (s)/Zo (s), Zg (s)/Zo (s) is the equivalent loop gain of the system. According to the linear control theory, if Zg (s)/Zo (s) satisfies the Nyquist stability criterion, then N (s) is stable, therefore, the grid-connected system is also stable.
根据上述推导，基于阻抗的并网逆变器稳定性判据总结如下：According to the above derivation, the impedance-based grid-connected inverter stability criterion is summarized as follows:
1.并网逆变器在强电网下能够稳定工作；1. The grid-connected inverter can work stably under the strong grid;
2.阻抗比Zg(s)/Zo(s)满足Nyquist稳定性判据。即，Zg(s)和Zo(s)的幅频曲线不存在交截或 者虽然存在交截，但交截频率fi处的相位裕度为正。这里的相位裕度的表达式为：2. The impedance ratio Zg (s)/Zo (s) satisfies the Nyquist stability criterion. That is, the magnitude-frequency curves of Zg (s) and Zo (s) do not have an intersection or although there is an intersection, the phase margin at the intersection frequency fi is positive. The expression for the phase margin here is:
PM＝180°-(∠Zg(j2πfi)-∠Zo(j2πfi)) (14)PM＝180°-(∠Zg (j2πfi )-∠Zo (j2πfi )) (14)
根据基于阻抗的并网逆变器稳定性判据，为保证弱电网下并网逆变器的稳定工作，阻抗 比Zg(s)/Zo(s)需满足Nyquist稳定判据。采用伯德图进行分析时，根据式(14)，这就要求Zg(s) 与Zo(s)幅频曲线交截点的相位差应小于180°，因为Zg(s)相位恒为90°。也就意味着交截频率 处，Zo(s)的相位要高于-90°。According to the grid-connected inverter stability criterion based on impedance, in order to ensure the stable operation of the grid-connected inverter in a weak grid, the impedance ratio Zg (s)/Zo (s) needs to satisfy the Nyquist stability criterion. When Bode diagram is used for analysis, according to formula (14), it is required that the phase difference between the intersection points of the amplitude-frequency curves of Zg (s) and Zo (s) should be less than 180°, because the phase of Zg (s) is constant is 90°. That means that at the crossover frequency, the phase of Zo (s) is higher than -90°.
从图11可以看出，Lg为43μH时，加入电网电压全前馈的并网逆变器的Zo(s)与Zg(s)的幅 频曲线在约4kHz处交截，Zo(s)的相位约为-90°，并网逆变器处于临界稳定。当Lg增大时， Zg(s)幅频曲线上移，加入电网电压全前馈的并网逆变器的Zo(s)在幅频曲线交截点处的相位将 低于-90°，并网逆变器出现不稳定。而无电网电压前馈控制的并网逆变器的Zo(s)相位在全频 段高于-90°，并网逆变器具有良好的稳定性。It can be seen from Figure 11 that when Lg is 43 μH, the amplitude-frequency curves of Zo (s) and Zg (s) of the grid-connected inverter with grid voltage full feed-forward intersect at about 4 kHz, and Zo The phase of (s) is about -90°, and the grid-connected inverter is critically stable. When Lg increases, the amplitude-frequency curve of Zg (s) moves up, and the phase of Zo (s) at the intersection point of the amplitude-frequency curve will be lower than - 90°, the grid-connected inverter becomes unstable. However, the Zo (s) phase of the grid-connected inverter without grid voltage feed-forward control is higher than -90° in the whole frequency band, and the grid-connected inverter has good stability.
实施例Example
本实施例在上述对比例基础上在前馈通路中加入若干谐振环节，仅提取电网电压的特定 次分量进行前馈，即将电流调节器的输出减去电容电流iC的采样信号，再加上电网电压vpcc的前馈量，作为调制信号vM。如图12所示，本实施例可以解决系统在弱电网下不稳定的问 题，加入的特定次分量前馈函数为：In this embodiment, several resonant links are added to the feedforward path on the basis of the above comparative example, and only specific subcomponents of the grid voltage are extracted for feedforward, that is, the output of the current regulator minus the sampling signal of the capacitor current iC , plus The feed-forward amount of grid voltage vpcc is used as modulation signal vM . As shown in Figure 12, this embodiment can solve the problem of instability of the system under a weak power grid, and the specific secondary component feedforward function added is:
Gshff(s)＝Gff(s)Hf(s) (15)Gshff (s) = Gff (s) Hf (s) (15)
这里选取3，5，7，21，23次谐波为例进行说明，采用了特定次分量前馈函数后的系统 输出阻抗伯德图如图13所示，从图中可以看出幅频曲线交截频段外的3，5，7次谐波频率处， 系统输出阻抗被校正到很高，表示这些频率处的并网电流谐波得到了很好的抑制效果。幅频 曲线交交截频段内的21，23次谐波频率处系统的输出阻抗相位均在-90°以上，并网逆变器系 统稳定。Here we take the 3rd, 5th, 7th, 21st, and 23rd harmonics as examples for illustration. The Bode diagram of the system output impedance after using a specific subcomponent feedforward function is shown in Figure 13. It can be seen from the figure that the amplitude-frequency curve At the 3rd, 5th, and 7th harmonic frequencies outside the cut-off frequency band, the system output impedance is corrected to be very high, which means that the grid-connected current harmonics at these frequencies have been well suppressed. The output impedance phases of the system at the 21st and 23rd harmonic frequencies in the amplitude-frequency curve intersection and interception frequency band are all above -90°, and the grid-connected inverter system is stable.
本实施例加入的谐振环节不仅起到提取电网电压特定次分量的作用，还起到补偿电网电 压全前馈对消项FV(s)的作用，以取得更好的并网电流谐波抑制效果。其补偿机理如图14所 示，微调谐振环节Rk(s)的谐振项系数Krk和特征频率ωk，可以使得谐振环节在谐波频率fk处 有正相角Δθd，增益应为1/FV(jωk)。理想情况下FV(s)可以被补偿为“1”矢量，电网电压作 用剩余矢量FF(s)变为0，系统输出阻抗无穷大，该频率处的并网电流谐波被抑制到0。The resonance link added in this embodiment not only plays the role of extracting the specific subcomponent of the grid voltage, but also plays the role of compensating the full feed-forward cancellation item FV(s) of the grid voltage, so as to achieve better harmonic suppression effect of grid-connected current . Its compensation mechanism is shown in Figure 14. Fine-tuning the resonance term coefficient Krk and characteristic frequency ωk of the resonant link Rk (s) can make the resonant link have a positive phase angle Δθd at the harmonic frequency fk , and the gain should be 1/FV(jωk ). Ideally, FV(s) can be compensated as a "1" vector, the grid voltage action residual vector FF(s) becomes 0, the system output impedance is infinite, and the grid-connected current harmonics at this frequency are suppressed to 0.
但若谐波频率ωk在交截频段内，FV(s)若仍被补偿为“1”矢量，会导致系统输出阻抗相 角低于-90°，并网逆变器系统不稳定；所以要牺牲一定的补偿效果，优先保证系统的稳定性， 因此图14中21,23次谐波频率处系统输出阻抗没有被校正到很高。However, if the harmonic frequency ωk is within the intercept frequency band, if FV(s) is still compensated as a "1" vector, the phase angle of the system output impedance will be lower than -90°, and the grid-connected inverter system will be unstable; therefore To sacrifice a certain compensation effect, the priority is to ensure the stability of the system, so the system output impedance at the 21st and 23rd harmonic frequencies in Figure 14 has not been corrected to be very high.
除此之外，由于电网电压基波频率往往存在±0.5Hz的波动，因此在谐振环节中加入了 自适应调节方法，使谐振环节的特征频率ωk随锁相环得到的vpcc的角频率ω的改变而改变， 具体为ωk＝kωo。In addition, since the fundamental frequency of the grid voltage often fluctuates by ±0.5Hz, an adaptive adjustment method is added to the resonance link, so that the characteristic frequency ωk of the resonance link follows the angular frequency of vpcc obtained by the phase-locked loop ω changes, specifically ωk = kωo .
下面给出本发明的一个仿真实例：A simulation example of the present invention is given below:
根据表1给出的6kW单相LCL型并网逆变器参数，在Matlab中搭建仿真模型进行仿真， 表2给出了电网电压注入谐波的含量。图15给出了弱电网下无电网电压前馈时并网系统的电 网电压和并网电流仿真波形，可以看出，并网电流有明显的畸变，总谐波畸变率(Total Harmonics Distortion,THD)很高。图16给出了强电网下使用电网电压全前馈策略的仿真波形， 此时并网电流谐波的抑制效果较好，THD＝0.79％；然而在弱电网下，当Lg＝43μH时，如图17 所示，并网电流开始出现明显的振荡，说明并网逆变器系统开始不稳，当电网阻抗进一步增 大，并网电流的振荡更加剧烈。图18给出在Lg＝2.6mH的条件下，采用电网电压特定次分量 前馈的仿真波形图，可以看出，在弱电网情况下采用本发明中的电网电压特定次分量前馈后， 并网逆变器系统稳定，并网电流谐波的抑制效果非常好，THD仅有0.49％。在电网电压基波 频率波动时采用本发明中的前馈控制方法，如图19和图20所示，由于自适应调节方法的作 用，并网电流的正弦度依然很高，THD分别仅有0.64％和0.48％。According to the parameters of the 6kW single-phase LCL grid-connected inverter given in Table 1, a simulation model is built in Matlab for simulation. Table 2 shows the content of harmonics injected into the grid voltage. Figure 15 shows the grid voltage and grid current simulation waveforms of the grid-connected system without grid voltage feedforward under a weak grid. It can be seen that the grid-connected current has obvious distortion, and the total harmonic distortion (Total Harmonics Distortion, THD ) is very high. Figure 16 shows the simulation waveform of using the grid voltage full feed-forward strategy in a strong grid. At this time, the suppression effect of grid-connected current harmonics is better, THD = 0.79%. However, in a weak grid, when Lg = 43μH, As shown in Figure 17, the grid-connected current begins to oscillate obviously, indicating that the grid-connected inverter system begins to be unstable. When the grid impedance further increases, the grid-connected current oscillates more violently. Fig. 18 shows the simulated waveform diagram of the grid voltage specific sub-component feedforward under the condition of Lg = 2.6mH. It can be seen that after the grid voltage specific sub-component feedforward is adopted in the case of a weak grid, The grid-connected inverter system is stable, and the suppression effect of grid-connected current harmonics is very good, and the THD is only 0.49%. The feed-forward control method in the present invention is adopted when the fundamental frequency of the grid voltage fluctuates, as shown in Figure 19 and Figure 20, due to the effect of the adaptive adjustment method, the sine degree of the grid-connected current is still very high, and the THD is only 0.64 % and 0.48%.
表1 6kW单相LCL型并网逆变器仿真参数Table 1 Simulation parameters of 6kW single-phase LCL grid-connected inverter
表2电网电压注入谐波含量Table 2 Grid voltage injection harmonic content
本发明的技术方案不局限于上述各实施例，凡采用等同替换方式得到的技术方案均落在 本发明要求保护的范围内。The technical solutions of the present invention are not limited to the above-mentioned embodiments, and all technical solutions obtained by adopting equivalent replacement methods all fall within the protection scope of the present invention.
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910318498.9ACN110233494A (en) | 2019-04-19 | 2019-04-19 | A kind of control method of grid-connected inverter of the specific component of degree n n feedforward of network voltage |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910318498.9ACN110233494A (en) | 2019-04-19 | 2019-04-19 | A kind of control method of grid-connected inverter of the specific component of degree n n feedforward of network voltage |
| Publication Number | Publication Date |
|---|---|
| CN110233494Atrue CN110233494A (en) | 2019-09-13 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910318498.9APendingCN110233494A (en) | 2019-04-19 | 2019-04-19 | A kind of control method of grid-connected inverter of the specific component of degree n n feedforward of network voltage |
| Country | Link |
|---|---|
| CN (1) | CN110233494A (en) |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110718934A (en)* | 2019-10-12 | 2020-01-21 | 兰州理工大学 | LLCL grid-connected inverter resonance suppression method adapting to power grid impedance change |
| CN112671010A (en)* | 2021-01-14 | 2021-04-16 | 国网陕西省电力公司电力科学研究院 | Virtual impedance-based fan grid-connected subsynchronous oscillation suppression and high-frequency harmonic suppression method |
| CN113644836A (en)* | 2021-07-28 | 2021-11-12 | 江苏南自通华智慧能源股份有限公司 | A robust control method for LCL grid-connected inverter |
| CN114640123A (en)* | 2020-12-15 | 2022-06-17 | 新疆金风科技股份有限公司 | Feedforward control method and device of grid-connected inverter, medium and wind generating set |
| WO2022127268A1 (en)* | 2020-12-15 | 2022-06-23 | 新疆金风科技股份有限公司 | Wind turbine generator system, and grid-tie inverter and feedforward control method therefor and apparatus thereof |
| CN116247735A (en)* | 2022-10-18 | 2023-06-09 | 国网新源控股有限公司 | Full-power frequency converter network side converter control method and device |
| CN117748572A (en)* | 2023-11-09 | 2024-03-22 | 中国矿业大学 | Method and system for adjusting grid voltage feedforward regulator of grid-connected inverter |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108879782A (en)* | 2018-08-01 | 2018-11-23 | 国网重庆市电力公司电力科学研究院 | Gird-connected inverter optimal control method based on double-smoothing voltage feed-forward control |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108879782A (en)* | 2018-08-01 | 2018-11-23 | 国网重庆市电力公司电力科学研究院 | Gird-connected inverter optimal control method based on double-smoothing voltage feed-forward control |
| Title |
|---|
| 张笠君等: ""并网逆变器谐波电流抑制研究中的准无穷大输出阻抗概念与应用"", 《电源学报》* |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110718934A (en)* | 2019-10-12 | 2020-01-21 | 兰州理工大学 | LLCL grid-connected inverter resonance suppression method adapting to power grid impedance change |
| CN114640123A (en)* | 2020-12-15 | 2022-06-17 | 新疆金风科技股份有限公司 | Feedforward control method and device of grid-connected inverter, medium and wind generating set |
| WO2022127268A1 (en)* | 2020-12-15 | 2022-06-23 | 新疆金风科技股份有限公司 | Wind turbine generator system, and grid-tie inverter and feedforward control method therefor and apparatus thereof |
| CN114640123B (en)* | 2020-12-15 | 2024-12-20 | 金风科技股份有限公司 | Feedforward control method and device for grid-connected inverter, medium and wind turbine generator set |
| CN112671010A (en)* | 2021-01-14 | 2021-04-16 | 国网陕西省电力公司电力科学研究院 | Virtual impedance-based fan grid-connected subsynchronous oscillation suppression and high-frequency harmonic suppression method |
| CN113644836A (en)* | 2021-07-28 | 2021-11-12 | 江苏南自通华智慧能源股份有限公司 | A robust control method for LCL grid-connected inverter |
| CN113644836B (en)* | 2021-07-28 | 2023-02-28 | 江苏南自通华智慧能源股份有限公司 | A Robust Control Method Applicable to LCL Type Grid-connected Inverter |
| CN116247735A (en)* | 2022-10-18 | 2023-06-09 | 国网新源控股有限公司 | Full-power frequency converter network side converter control method and device |
| CN117748572A (en)* | 2023-11-09 | 2024-03-22 | 中国矿业大学 | Method and system for adjusting grid voltage feedforward regulator of grid-connected inverter |
| Publication | Publication Date | Title |
|---|---|---|
| CN110233494A (en) | A kind of control method of grid-connected inverter of the specific component of degree n n feedforward of network voltage | |
| CN110429600B (en) | Grid-connected inverter control method for capacitor voltage proportional differential feedback | |
| CN109149646B (en) | Active damper capable of improving stability of inverter grid-connected system and adjusting power | |
| CN105244919B (en) | A robust delay compensation grid-connected control method for LCL inverters | |
| CN104104110B (en) | A kind of single-phase photovoltaic grid-connected inverter control method with quality of power supply regulatory function | |
| CN105763094B (en) | A kind of inverter control method controlled based on electric voltage feed forward and recombination current | |
| CN106229991A (en) | A kind of Vienna Rectifier being applicable in the case of disturbance occurs in line voltage | |
| CN109524992B (en) | Grid-connected converter self-adaptive control method and control system under weak grid | |
| CN108879781A (en) | A kind of grid-connected current control method based on virtual impedance correction method | |
| CN105743091B (en) | A kind of double close-loop decoupling control method of Active Power Filter-APF | |
| CN204886199U (en) | A Power Electronic Transformer for Unbalanced and Nonlinear Loads | |
| CN103078322B (en) | Harmonic controller for energy-storing system of wind-power plant and parameter-setting method thereof | |
| CN103606954A (en) | Novel grid-connected photovoltaic power generation control method | |
| CN105006825A (en) | Power electronic transformer enabling high quality of electric energy output, and control method thereof | |
| CN107134936A (en) | A kind of inverter active damping control method based on overall-finished housing | |
| CN110011364A (en) | A control method to reduce the influence of active power load fluctuation on system stability | |
| CN103490653A (en) | Secondary ripple reduction control system and control method for photovoltaic grid-connected currents and direct current voltage | |
| CN113489049A (en) | Grid-connected inverter grid-side current control method | |
| CN106253337A (en) | A kind of impedance adapter for multiple stage grid-connected inverters system of calming | |
| CN103972922A (en) | Photovoltaic grid connection control method on basis of improved quasi-resonance control and repeated control | |
| CN202817792U (en) | Micro-source gird connection and power quality control system | |
| CN117878878A (en) | Self-adaptive impedance remodelling method and device based on power grid parameter identification technology | |
| CN102611339B (en) | Current control method for three-phase rectifying device | |
| CN109327048B (en) | Robust phase locking system and method for grid-connected converter | |
| CN108448583A (en) | An Improved Regulator Applied to Grid-connected Inverter in Weak Grid |
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication | Application publication date:20190913 |