CN105162162A

CN105162162A - Phase perturbation based island detection system for distributed gird-connected inverter

Info

Publication number: CN105162162A
Application number: CN201510565709.0A
Authority: CN
Inventors: 王萍; 贝太周
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2015-09-07
Filing date: 2015-09-07
Publication date: 2015-12-16

Abstract

A distributed grid-connected inverter island detection system based on phase disturbance, including: a voltage controller, a multiplier, and an adder whose input terminals are respectively connected to the DC bus voltage and the set DC bus standard voltage value, which are connected in series , a current controller and a pulse width modulation generator that outputs four trigger pulse signals for driving a single-phase H-bridge inverter in a single-phase distributed grid-connected power generation system, and is connected in series in sequence: the input terminal is connected to the single-phase distributed An orthogonal signal generator, a synchronous phase locker, a phase perturbation unit and a threshold judging unit at the voltage end of the common coupling point of the grid-connected power generation system, the output of the phase perturbation unit is connected to the input terminal of the multiplier. The invention has the rapidity of island detection, its own stability, and the possibility of being used as an island detection standard, and at the same time meets the requirements for the qualified rate of power quality, and provides important practical applications for the safe operation of distributed new energy grid-connected power generation systems value.

Description

A Distributed Grid-connected Inverter Islanding Detection System Based on Phase Perturbation

技术领域 technical field

本发明涉及一种孤岛检测系统。特别是涉及一种基于相位扰动的分布式并网逆变器孤岛检测系统。 The invention relates to an island detection system. In particular, it relates to a distributed grid-connected inverter islanding detection system based on phase disturbance.

背景技术 Background technique

考虑到新型可再生能源清洁无污染及储量丰富等诸多强力优势，能源产业的结构调整正在世界范围内广泛兴起。发展新型可再生替代能源，提高清洁电力供应，从长远考虑，无论在技术提高、环境保护，还是在经济发展等方面都将会有实质性的促进意义。 Considering the advantages of clean, non-polluting and abundant reserves of new renewable energy, the structural adjustment of the energy industry is widely emerging around the world. In the long run, the development of new renewable alternative energy sources and the improvement of clean power supply will have substantial promotion significance in terms of technological improvement, environmental protection, and economic development.

以太阳能、风能、生物质能等主导型可再生能源建立发展起来的分布式发电系统旨在为用户提供优质、清洁、高效能的电力资源。分布式发电系统以其经济、高效等诸多优势，业已在可再生电力能源产业中获得了新发展。分布式发电系统中的孤岛现象通常理解为：当主电网因电气故障、检修或误操作等原因与分布式发电系统失联后，发电系统作为独立电源将继续对本地负载供电，形成独立不可控的自给电力系统。按照孤岛检测标准UL17417和IEEEStd1547的相关规定，任何分布式并网发电系统必须具有孤岛检测功能，并在规定时间内迅速完成检测，及时封锁逆变器。 The distributed power generation system developed by leading renewable energy such as solar energy, wind energy, and biomass energy aims to provide users with high-quality, clean, and efficient power resources. Distributed power generation system has achieved new development in the renewable electric energy industry due to its economical, high-efficiency and many other advantages. The island phenomenon in the distributed generation system is generally understood as: when the main grid loses connection with the distributed generation system due to electrical failure, maintenance or misoperation, the power generation system will continue to supply power to the local load as an independent power source, forming an independent and uncontrollable power grid. self-sufficient power system. According to the relevant provisions of the island detection standard UL17417 and IEEEStd1547, any distributed grid-connected power generation system must have the island detection function, and the detection should be completed quickly within the specified time, and the inverter should be blocked in time.

按照最新的划分标准，可将现有的孤岛检测方法大致分为主动式检测、被动式检测和通信式检测三大类。被动式检测方法易于实现，同时不会侵害配电网的电能质量，但是该方法中存在较大的孤岛检测盲区，从而严重影响了自身的检测精度；通信式检测方法虽然拥有实时性强、稳定性高、对电能无侵害等突出优势，但是高成本所引起的低利润问题成为自身无法被广泛使用的主要原因。与以上两种方法相比，主动式检测方法所具有的检测精度高、可减小甚至消除检测盲区的优势更加适用于实际的工业应用。 According to the latest classification standard, the existing islanding detection methods can be roughly divided into three categories: active detection, passive detection and communication detection. The passive detection method is easy to implement and will not infringe on the power quality of the distribution network, but there is a large island detection blind spot in this method, which seriously affects its own detection accuracy; although the communication detection method has strong real-time performance and stability High, no infringement on electric energy and other outstanding advantages, but the problem of low profit caused by high cost has become the main reason why it cannot be widely used. Compared with the above two methods, the active detection method has the advantages of high detection accuracy and can reduce or even eliminate detection blind spots, which is more suitable for practical industrial applications.

主动式检测方法通常采用对逆变器控制中的某个参量(如电流频率、电流相位、电流幅值、电流谐波和电压等)施加扰动的措施，来观测公共耦合点(PCC)处的某些参量变化，来判断是否发生孤岛。主动式检测方法的首要问题是扰动信号的选定。如果扰动信号频率过高，则会放大本地负载品质因数的作用，导致孤岛难检；如果采用偶次谐波作为扰动，又不得不面对偶次谐波难以消除的困扰。纵观与孤岛检测相关的大部分文献资料，很少有学者结合电压同步技术提出相应的孤岛检测新方法。此类方法的关键在于如何保证施加的扰动不会改变或影响同步提取信号中的电压过零点的位置。 The active detection method usually adopts a measure of disturbance to a certain parameter in the inverter control (such as current frequency, current phase, current amplitude, current harmonics and voltage, etc.) to observe the point of common coupling (PCC). Certain parameters change to determine whether islanding occurs. The primary problem of the active detection method is the selection of the disturbance signal. If the frequency of the disturbance signal is too high, the effect of the local load quality factor will be amplified, making it difficult to detect isolated islands; if even harmonics are used as disturbances, you have to face the problem that even harmonics are difficult to eliminate. Looking at most of the literature related to islanding detection, few scholars have put forward corresponding new methods of islanding detection combined with voltage synchronization technology. The key of this kind of method is how to ensure that the applied disturbance will not change or affect the position of the voltage zero-crossing point in the synchronous extraction signal.

发明内容 Contents of the invention

本发明所要解决的技术问题是，提供一种当分布式发电系统由并网运行转为孤岛运行时，孤岛检测系统能够在尽可能短的时间内完成检测并及时封锁逆变器的基于相位扰动的分布式并网逆变器孤岛检测系统。 The technical problem to be solved by the present invention is to provide an island detection system that can complete the detection in the shortest possible time and block the inverter in time based on phase disturbance when the distributed power generation system changes from grid-connected operation to island operation. Distributed grid-connected inverter island detection system.

本发明所采用的技术方案是：一种基于相位扰动的分布式并网逆变器孤岛检测系统，用于控制单相分布式并网发电系统，包括有依次串联连接的：输入端分别连接直流母线电压和设定的直流母线标准电压值的电压控制器、用于将电压控制器输出的并网电流的基准幅值与单位化的并网基准电流相乘得到并网基准电流的乘法器、用于将乘法器输出的并网基准电流与极性取负的实际的并网采样电流求和的加法器、电流控制器和对电流控制器输出的信号进行脉冲宽度调制输出驱动单相分布式并网发电系统中的单相H桥逆变器的四路触发脉冲信号的脉冲宽度调制发生器，还包括有，依次串联连接的：输入端连接单相分布式并网发电系统公共耦合点的电压端，用于产生两相正交电压的正交信号发生器、用于在正交信号发生器输出信号基础上获取电网相位角的同步锁相器、用于产生与并网电流的基准幅值相乘的单位化的并网基准电流的相位扰动单元以及用于进行电压阈值判断的基于跳跃Goertzel滤波器的阈值判断单元，其中，所述的相位扰动单元的输出连接乘法器的输入端。 The technical solution adopted in the present invention is: a distributed grid-connected inverter island detection system based on phase disturbance, which is used to control a single-phase distributed grid-connected power generation system, including sequentially connected in series: the input terminals are respectively connected to DC A voltage controller for the bus voltage and the set DC bus standard voltage value, a multiplier for multiplying the grid-connected current reference amplitude output by the voltage controller with the unitized grid-connected reference current to obtain the grid-connected reference current, An adder for summing the grid-connected reference current output by the multiplier and the actual grid-connected sampling current whose polarity is negative, the current controller and pulse width modulation of the signal output by the current controller output drive single-phase distributed The pulse width modulation generator of the four-way trigger pulse signal of the single-phase H-bridge inverter in the grid-connected power generation system also includes, sequentially connected in series: the input terminal is connected to the public coupling point of the single-phase distributed grid-connected power generation system The voltage terminal is used to generate a quadrature signal generator for two-phase quadrature voltage, a genlock for obtaining the grid phase angle based on the output signal of the quadrature signal generator, and a reference amplitude for generating grid-connected current The phase perturbation unit of the unitized grid-connected reference current for value multiplication and the threshold judgment unit based on the jumping Goertzel filter for voltage threshold judgment, wherein the output of the phase perturbation unit is connected to the input end of the multiplier.

所述的正交信号发生器包括有依次串接的第一加法器、第一放大器、第二加法器以及第一积分器，其中，所述第一加法器的一个输入端作为正交信号发生器的输入端连接单相分布式并网发电系统公共耦合点的电压端，第一积分器的输出分三路：第一路直接作为正交信号发生器的第一输出端，第二路极性取负后与第一加法器的另一个输入端相连接，第三路连接以及全通滤波器的输入端，所述全通滤波器的输出分两路：第一路直接作为正交信号发生器的第二输出端，第二路极性取负后与第二加法器的另一个输入端相连接。 The quadrature signal generator includes a first adder, a first amplifier, a second adder and a first integrator connected in series in sequence, wherein one input terminal of the first adder is generated as a quadrature signal The input terminal of the integrator is connected to the voltage terminal of the common coupling point of the single-phase distributed grid-connected power generation system, and the output of the first integrator is divided into three routes: the first channel is directly used as the first output terminal of the quadrature signal generator, and the second channel is Connect with the other input end of the first adder after taking the negation, the third road connection and the input end of the all-pass filter, the output of the all-pass filter is divided into two roads: the first road is directly used as the quadrature signal The second output terminal of the generator is connected to the other input terminal of the second adder after the polarity of the second path is negative.

所述的同步锁相器包括有：依次串接的第三加法器、第二放大器、第三乘法器、第二积分器以及mod运算器，其中，所述mod运算器的输出端构成同步锁相器的输出端，用于输出电网相位角，所述第三加法器的输入端分别连接第一乘法器和第二乘法器的输出端，所述第一乘法器的一个输入端直接连接正交信号发生器的第一路输出端，第一乘法器的另一个输入端通过第一二阶低通滤波器接连接正交信号发生器的第一路输出端，第二乘法器的一个输入端直接连接正交信号发生器的第二路输出端，第二乘法器的另一个输入端通过第二二阶低通滤波器接连接正交信号发生器的第二路输出端，所述第三乘法器的输入端还连接电压补偿器的输出端，所述电压补偿器的输入端分别连接第一二阶低通滤波器的输出端以及第二二阶低通滤波器的输出端。 The genlock includes: a third adder, a second amplifier, a third multiplier, a second integrator and a mod operator connected in series in sequence, wherein the output of the mod operator constitutes a genlock The output terminal of the phase device is used to output the grid phase angle, the input terminal of the third adder is respectively connected to the output terminals of the first multiplier and the second multiplier, and one input terminal of the first multiplier is directly connected to the positive The first output terminal of the quadrature signal generator, the other input terminal of the first multiplier is connected to the first output terminal of the quadrature signal generator through the first second-order low-pass filter, and one input terminal of the second multiplier The end is directly connected to the second output end of the quadrature signal generator, and the other input end of the second multiplier is connected to the second output end of the quadrature signal generator through a second second-order low-pass filter. The input terminal of the triple multiplier is also connected to the output terminal of the voltage compensator, and the input terminal of the voltage compensator is respectively connected to the output terminal of the first second-order low-pass filter and the output terminal of the second second-order low-pass filter.

所述的相位扰动单元包括有依次串接的第三放大器、正弦运算器、第四放大器、第四加法器和余弦运算器，其中，所述第三放大器的输入端和第四加法器的另一个输入端共同连接同步锁相器的输出端，所述余弦运算器的输出端构成相位扰动单元的输出端连接所述乘法器的一个输入端。 The phase perturbation unit includes a third amplifier, a sine operator, a fourth amplifier, a fourth adder and a cosine operator connected in series, wherein, the input terminal of the third amplifier and the other of the fourth adder One input end is commonly connected to the output end of the genlock, and the output end of the cosine calculator constitutes a phase disturbance unit, and the output end is connected to an input end of the multiplier.

所述的孤岛检测实现单元包括有依次连接的采样电路和跳跃Goertzel滤波器，其中，所述的采样电路的输入端连接单相分布式并网发电系统公共耦合点的电压端，所述跳跃Goertzel滤波器的输出电压作为单相分布式并网发电系统的检测电压，与已设定的电压阈值进行对比，当输出电压大于等于设定的电压阈值时，脉冲宽度调制发生器不输出四路触发脉冲信号，单相分布式并网发电系统中的单相H桥逆变器不工作，当输出电压小于设定的电压阈值时，脉冲宽度调制发生器输出四路触发脉冲信号，单相分布式并网发电系统中的单相H桥逆变器工作。 The islanding detection implementation unit includes a sequentially connected sampling circuit and a jumping Goertzel filter, wherein the input end of the sampling circuit is connected to the voltage end of the common coupling point of the single-phase distributed grid-connected power generation system, and the jumping Goertzel filter The output voltage of the filter is used as the detection voltage of the single-phase distributed grid-connected power generation system, and is compared with the set voltage threshold. When the output voltage is greater than or equal to the set voltage threshold, the pulse width modulation generator does not output the four-way trigger Pulse signal, the single-phase H-bridge inverter in the single-phase distributed grid-connected power generation system does not work, when the output voltage is lower than the set voltage threshold, the pulse width modulation generator outputs four trigger pulse signals, single-phase distributed A single-phase H-bridge inverter works in a grid-connected power generation system.

所述的跳跃Goertzel滤波器包括有：依次串接的梳状滤波器、第五加法器、第五放大器和第六加法器，其中，第五加法器的输出端又经过第一延迟单元后分成三路：第一路通过第六放大器连接第五加法器的一个输入端，第二路通过第二延迟单元后再极性取负连接第五加法器的另一个输入端，第三路直接极性取负后连接第六加法器的又一个输入端，所述梳状滤波器的输入端连接采样电路的输出端，所述第六加法器的输出端构成跳跃Goertzel滤波器的输出电压。 The jumping Goertzel filter includes: sequentially connected comb filter, the fifth adder, the fifth amplifier and the sixth adder, wherein the output of the fifth adder is divided into after the first delay unit Three ways: the first way is connected to an input end of the fifth adder through the sixth amplifier, the second way is connected to the other input end of the fifth adder after passing through the second delay unit, and the third way is directly connected to the other input end of the fifth adder. Connect another input end of the sixth adder after taking the negative, the input end of the comb filter is connected to the output end of the sampling circuit, and the output end of the sixth adder constitutes the output voltage of the jumping Goertzel filter.

所述的梳状滤波器包括有第七加法器，所述第七加法器的一个输入端直接连接采样电路的输出端，第七加法器的另一个输入端通过第三延迟单元连接采样电路的输出端，所述第七加法器的输出连接第五加法器的输入端。 The comb filter includes a seventh adder, one input of the seventh adder is directly connected to the output of the sampling circuit, and the other input of the seventh adder is connected to the sampling circuit through the third delay unit. The output terminal, the output of the seventh adder is connected to the input terminal of the fifth adder.

本发明的一种基于相位扰动的分布式并网逆变器孤岛检测系统，具备以下优势：一个是孤岛检测的快速性，快速性的实现通常需要依托具有较少运算量的数据处理算法来完成；另一个是应当保证方法自身的稳定性以及作为孤岛检测标准的可能性，同时该方法也应该同时满足对电能质量合格率的要求，从而为分布式新能源并网发电系统的安全运行提供重要的实际应用价值和理论指导意义。本发明具有如下技术效果： A distributed grid-connected inverter islanding detection system based on phase disturbance of the present invention has the following advantages: one is the rapidity of islanding detection, and the realization of rapidity usually needs to rely on a data processing algorithm with a small amount of calculation to complete The other is to ensure the stability of the method itself and the possibility of being used as an island detection standard. At the same time, the method should also meet the requirements for the pass rate of power quality, so as to provide important information for the safe operation of distributed new energy grid-connected power generation systems. practical application value and theoretical guiding significance. The present invention has following technical effect:

(1)所采用的单相并网系统下的同步锁相器，能够快速实现从单相电网电压到两相正交电压的构建，同时构建的两相正交电压之间由对各次谐波具有相同增益的全通滤波器连接，因此含有相同的总谐波畸变率，这就消除两相正交电压中因谐波不平衡带来的锁相精度问题。 (1) The synchrolocker used in the single-phase grid-connected system can quickly realize the construction from the single-phase grid voltage to the two-phase quadrature voltage, and the two-phase quadrature voltage constructed at the same time is controlled by the The wave has the same gain all-pass filter connection, therefore contains the same total harmonic distortion rate, which eliminates the phase-locking accuracy problem caused by harmonic imbalance in the two-phase quadrature voltage.

(2)所采用的单相并网系统下的同步锁相器，能够快速准确地获取电网的相位信息，同时该锁相器也具有对电网参数突变较强的鲁棒性和频率调整的快速性。 (2) The synchrolocker used in the single-phase grid-connected system can quickly and accurately obtain the phase information of the power grid. At the same time, the phase locker also has strong robustness to sudden changes in grid parameters and fast frequency adjustment. sex.

(3)所采用的相位扰动注入法，能够保证注入的相位扰动不会改变电网相位信息中电压过零点的位置，这样就保证了分布式新能源并网发电系统在并网模式下能够以单位功率因数运行。 (3) The phase disturbance injection method adopted can ensure that the injected phase disturbance will not change the position of the voltage zero-crossing point in the phase information of the power grid, thus ensuring that the distributed new energy grid-connected power generation system can operate at a unit rate in the grid-connected mode. Power factor operation.

(4)通过对相位扰动系数的合理选值，能够实现对并网电流总谐波畸变率变化的可控性，从而可以有效控制该方案对电能质量的损害程度。 (4) Through the reasonable selection of the phase disturbance coefficient, the controllability of the change of the total harmonic distortion rate of the grid-connected current can be realized, so that the degree of damage to the power quality of the scheme can be effectively controlled.

(5)用于孤岛检测的谐波分量提取算法具有较低的数据运算量，保证了整个孤岛检测系统能够在很短的时间内迅速完成孤岛检测。 (5) The harmonic component extraction algorithm used for islanding detection has a low amount of data calculation, which ensures that the entire islanding detection system can quickly complete islanding detection in a very short time.

(6)由于该方案中总谐波畸变率是可控的，采用的谐波分量提取算法是稳定的，因此，整个孤岛检测系统也是可靠的，作为一种孤岛检测标准的可能性很高。 (6) Since the total harmonic distortion rate in this scheme is controllable and the harmonic component extraction algorithm adopted is stable, the entire islanding detection system is also reliable, and it is highly possible to use it as an islanding detection standard.

附图说明 Description of drawings

图1是单相分布式并网发电系统框图，其中， Figure 1 is a block diagram of a single-phase distributed grid-connected power generation system, in which,

V_dc：逆变器直流母线侧电压，因电压值较高，又称为直流母线高压； V _dc : DC bus side voltage of the inverter, also known as DC bus high voltage because of its high voltage value;

单相H桥逆变器A：输入端接直流母线高压，输出端接LC滤波器(滤除逆变器输出电流中的高频分量)；单相H桥逆变器A中的四个开关管选用IGBT，开关管的门极受PWM触发脉冲驱动； Single-phase H-bridge inverter A: the input terminal is connected to the high voltage of the DC bus, and the output terminal is connected to the LC filter (to filter out high-frequency components in the inverter output current); four switches in the single-phase H-bridge inverter A The tube is IGBT, and the gate of the switching tube is driven by the PWM trigger pulse;

v_PCC和i_inv分别为公共耦合点处的电压，并网电流(变量解释适用于图2)； v _PCC and i _inv are the voltage at the common coupling point and grid-connected current respectively (variable explanation applies to Figure 2);

本地负载：由电阻、电感及电容并联构成RLC并联负载，主要用于孤岛检测； Local load: RLC parallel load composed of resistors, inductors and capacitors connected in parallel, mainly used for island detection;

图2是本发明基于相位扰动的分布式并网逆变器孤岛检测系统整体框图，其中， Fig. 2 is an overall block diagram of the islanding detection system of distributed grid-connected inverters based on phase disturbance in the present invention, wherein,

V_dc：直流母线高压V_{dc_ref}：设定的直流母线高压标准值 V _dc : DC bus high voltage V _{dc_ref} : set DC bus high voltage standard value

I^* _inv：并网电流幅值基准cosθ_inv ^*：单位化的并网基准电流 I ^* _inv : Grid-connected current amplitude reference cosθ _inv ^* : Unitized grid-connected reference current

i^* _inv：并网基准电流θ_g：由PLL得到的准确的电网相位角 i ^* _inv : Grid-connected reference current θ _g : Accurate grid phase angle obtained by PLL

θ_inv ^*：逆变器并网控制的相位基准角，由θ_g和注入的相位扰动量叠加而成； θ _inv ^* : The phase reference angle of the grid-connected control of the inverter, which is formed by superimposing θ _g and the injected phase disturbance;

图3是本发明的新型正交信号发生器框图； Fig. 3 is a novel quadrature signal generator block diagram of the present invention;

图4是本发明的同步锁相器的结构框图； Fig. 4 is the structural block diagram of genlock of the present invention;

图5是本发明中的相位扰动单元结构框图； Fig. 5 is a structural block diagram of a phase perturbation unit in the present invention;

图6是本发明中的扰动相位对同步锁相结果影响的仿真图； Fig. 6 is the emulation figure that the disturbance phase in the present invention influences on the genlock result;

图7是本发明中的扰动相位对并网电流影响的仿真图； Fig. 7 is a simulation diagram of the influence of the disturbance phase on the grid-connected current in the present invention;

图8是本发明中所用分布式并网发电系统的简化电路图； Fig. 8 is a simplified circuit diagram of the distributed grid-connected power generation system used in the present invention;

图9是本发明跳跃Goertzel滤波器的结构框图； Fig. 9 is the structural block diagram of jumping Goertzel filter of the present invention;

图10是电网电压仿真图； Fig. 10 is a grid voltage simulation diagram;

图11是借助本发明的正交信号发生器构建的两相正交电压v_α和v_β的仿真图； Fig. 11 is the simulation diagram of the two-phase quadrature voltage v _α and v _β constructed by means of the quadrature signal generator of the present invention;

图12是同步锁相器的频率自适应调整动态响应曲线图； Fig. 12 is a frequency adaptive adjustment dynamic response curve diagram of the genlock;

图13是本发明中当本地负载为纯电阻负载时检测到的v_PCC波形图； Fig. 13 is the v _PCC waveform diagram detected when the local load is a pure resistance load in the present invention;

图14是本发明当本地负载为纯电阻负载时检测到的逆变器并网电流i_inv的波形图； Fig. 14 is a waveform diagram of the inverter grid-connected current i _inv detected when the local load is a pure resistance load in the present invention;

图15是本发明中当本地负载为纯电阻负载时采用跳跃Goertzel滤波器检测到的公共耦合点处三次谐波电压的波形图； Fig. 15 is a waveform diagram of the third harmonic voltage at the public coupling point detected by a jumping Goertzel filter when the local load is a pure resistance load in the present invention;

图16是本发明中当本地负载为RLC并联负载时检测到的v_PCC波形图； Fig. 16 is the v _PCC waveform diagram detected when the local load is an RLC parallel load in the present invention;

图17是本发明中当本地负载为RLC并联负载时检测到的逆变器并网电流i_inv的波形图； Fig. 17 is a waveform diagram of the inverter grid-connected current i _inv detected when the local load is an RLC parallel load in the present invention;

图18是本发明中当本地负载为RLC并联负载时采用跳跃Goertzel滤波器检测到的公共耦合点处三次谐波电压的波形图。 FIG. 18 is a waveform diagram of the third harmonic voltage at the common coupling point detected by using a jump Goertzel filter when the local load is an RLC parallel load in the present invention.

图中 in the picture

A：单相H桥逆变器B：LC滤波器 A: Single-phase H-bridge inverter B: LC filter

C：本地负载D：断路器 C: local load D: circuit breaker

E：电网1：电压控制器 E: Grid 1: Voltage Controller

2：乘法器3：加法器 2: Multiplier 3: Adder

4：电流控制器5：脉冲宽度调制发生器 4: Current Controller 5: Pulse Width Modulation Generator

6：正交信号发生器7：同步锁相器 6: Quadrature signal generator 7: Genlocker

8：相位扰动单元9：孤岛检测实现单元 8: Phase disturbance unit 9: Island detection implementation unit

61：第一加法器62：第一放大器 61: first adder 62: first amplifier

63：第二加法器64：第一积分器 63: second adder 64: first integrator

65：全通滤波器71：第一二阶低通滤波器 65: All-pass filter 71: First and second-order low-pass filter

72：第一乘法器73：第二二阶低通滤波器 72: first multiplier 73: second second-order low-pass filter

74：第二乘法器75：第三加法器 74: second multiplier 75: third adder

76：第二放大器77：电压补偿器 76: second amplifier 77: voltage compensator

78：第三乘法器79：第二积分器 78: third multiplier 79: second integrator

710：mod运算器81：第三放大器 710: mod operator 81: third amplifier

82：正弦运算器83：第四放大器 82: Sine operator 83: Fourth amplifier

84：第四加法器85：余弦运算器 84: fourth adder 85: cosine calculator

91：采样电路92：跳跃Goertzel滤波器 91: Sampling Circuits 92: Jumping Goertzel Filters

921：梳状滤波器922：第五加法器 921: comb filter 922: fifth adder

923：第五放大器924：第六加法器 923: fifth amplifier 924: sixth adder

925：第一延迟单元926：第六放大器 925: first delay unit 926: sixth amplifier

927：第二延迟单元9211：第七加法器 927: second delay unit 9211: seventh adder

9212：第三延迟单元 9212: Third Delay Unit

具体实施方式 Detailed ways

下面结合实施例和附图对本发明的一种基于相位扰动的分布式并网逆变器孤岛检测系统做出详细说明。 A phase disturbance-based distributed grid-connected inverter islanding detection system of the present invention will be described in detail below with reference to embodiments and drawings.

由于本发明的一种基于相位扰动的分布式并网逆变器孤岛检测系统是在相位扰动基础上提出并建立起来的，因此，整个孤岛检测系统能够有效实现的必要前提是该系统对电网相位信息的准确快速捕获；虽然主动式孤岛检测方法会不可避免地向配电网中注入少量的谐波进而影响总谐波畸变率(THD)，但是在方法的具体实现中应力求做到对总谐波畸变率变化的可控性；当分布式发电系统由并网运行转为孤岛运行时，孤岛检测系统应在尽可能短的时间内完成检测并及时封锁逆变器，这就要求所提出的孤岛检测算法中应包含尽量少的数据运算量。因此，本发明中着重解决和实现以下几个问题： Since the phase disturbance-based distributed grid-connected inverter islanding detection system of the present invention is proposed and established on the basis of phase disturbances, the necessary prerequisite for the effective implementation of the entire islanding detection system is that the system has a good understanding of the grid phase Accurate and fast capture of information; although the active islanding detection method will inevitably inject a small amount of harmonics into the distribution network and affect the total harmonic distortion (THD), but in the specific implementation of the method, we should strive to achieve the overall The controllability of the change of harmonic distortion rate; when the distributed power generation system changes from grid-connected operation to island operation, the island detection system should complete the detection in the shortest possible time and block the inverter in time, which requires the proposed The island detection algorithm should contain as little data computation as possible. Therefore, in the present invention, focus on solving and realizing the following problems:

(1)所采用的单相并网系统下的同步锁相器，应该快速实现从单相电网电压到两相正交电压的构建，构建的两相正交电压应该具有相同的总谐波畸变率，消除两相正交电压中因谐波不平衡带来的锁相精度问题。 (1) The genlock used in the single-phase grid-connected system should quickly realize the construction from the single-phase grid voltage to the two-phase quadrature voltage, and the constructed two-phase quadrature voltage should have the same total harmonic distortion rate, eliminating the phase-locking accuracy problem caused by harmonic imbalance in the two-phase quadrature voltage.

(2)所采用的单相并网系统下的同步锁相器，应该具有快速准确地获取电网相位信息的能力，同时具备对电网参数突变较强的鲁棒性和频率调整的快速性。 (2) The synchrolock used in the single-phase grid-connected system should have the ability to quickly and accurately obtain the phase information of the grid, and at the same time have strong robustness to sudden changes in grid parameters and rapid frequency adjustment.

(3)所采用的相位扰动的注入实现，应该平衡好相位扰动量与电网相位信息的关系，保证注入的相位扰动量不会改变或影响电网相位信息中电压过零点的位置。 (3) The implementation of the injection of phase disturbance should balance the relationship between the phase disturbance and the phase information of the power grid, so as to ensure that the injected phase disturbance will not change or affect the position of the voltage zero-crossing point in the phase information of the power grid.

(4)为了降低对电能质量的损害程度，由扰动相位带来的并网电流总谐波畸变率应当是可控的。 (4) In order to reduce the degree of damage to the power quality, the total harmonic distortion rate of the grid-connected current brought by the disturbance phase should be controllable.

(5)用于孤岛检测的算法应当具有较低的数据运算量，从而保证整个孤岛检测系统能够在更短的时间内迅速完成孤岛检测，以维系分布式新能源并网发电系统的可靠运行。 (5) The algorithm used for island detection should have a low amount of data calculation, so as to ensure that the entire island detection system can quickly complete the island detection in a shorter time, so as to maintain the reliable operation of the distributed new energy grid-connected power generation system.

本发明的一种基于相位扰动的分布式并网逆变器孤岛检测系统所对应的单相分布式并网发电系统如图1所示，对于220V的交流电网而言，分布式并网发电系统中逆变器直流侧的直流母线电压V_dc选定为400V。逆变器采用的是受单极性PWM调制能实现并网电流可控的单相H桥拓扑，逆变器输出电流经过LC滤波器的滤波作用，内部的高频谐波分量被有效消除。当图1中的断路器闭合时，逆变器输出电流注入电网；当断路器断开时，逆变器输出电流可用于对本地RLC负载供电。 The single-phase distributed grid-connected power generation system corresponding to the phase disturbance-based distributed grid-connected inverter island detection system of the present invention is shown in Figure 1. For a 220V AC power grid, the distributed grid-connected power generation system The DC bus voltage V _dc of the DC side of the inverter is selected as 400V. The inverter adopts a single-phase H-bridge topology that can realize controllable grid-connected current by unipolar PWM modulation. The output current of the inverter is filtered by the LC filter, and the internal high-frequency harmonic components are effectively eliminated. When the circuit breaker in Figure 1 is closed, the inverter output current is injected into the grid; when the circuit breaker is open, the inverter output current can be used to supply power to the local RLC load.

如图2所示，本发明的一种基于相位扰动的分布式并网逆变器孤岛检测系统，是用于控制单相分布式并网发电系统，主要是在并网控制策略的基础上建立起来的，包括有依次串联连接的：输入端分别连接直流母线电压V_dc和设定的直流母线标准电压值V_{dc_ref}的电压控制器1、用于将电压控制器1输出的并网电流的基准幅值I^* _inv与单位化的并网基准电流cosθ_inv ^*相乘得到并网基准电流i^* _inv的乘法器2、用于将乘法器2输出的并网基准电流i^* _inv与极性取负的实际的并网采样电流i^* _inv求和的加法器3、电流控制器4和对电流控制器4输出的信号进行脉冲宽度调制输出驱动单相分布式并网发电系统中的单相H桥逆变器A的四路触发脉冲信号PWM1～PWM4的脉冲宽度调制发生器5，还包括有，依次串联连接的：输入端连接单相分布式并网发电系统公共耦合点PCC的电压端，用于产生两相正交电压的正交信号发生器6、用于在正交信号发生器6输出信号基础上获取电网相位角的同步锁相器7、用于产生与并网电流的基准幅值I^* _inv相乘的单位化的并网基准电流cosθ_inv ^*的相位扰动单元8以及用于进行电压阈值判断的基于跳跃Goertzel滤波器的阈值判断单元9，其中，所述的相位扰动单元8的输出连接乘法器2的输入端。 As shown in Figure 2, a distributed grid-connected inverter island detection system based on phase disturbance of the present invention is used to control single-phase distributed grid-connected power generation systems, and is mainly established on the basis of grid-connected control strategies connected in series, including: a voltage controller 1 whose input terminals are respectively connected to the DC bus voltage V _dc and the set DC bus standard voltage value V _{dc_ref} , and a reference for the grid-connected current output by the voltage controller 1 Amplitude I ^* _inv is multiplied by the unitized grid-connected reference current cosθ _inv ^* to obtain the multiplier 2 of the grid-connected reference current i ^* _inv , which is used to obtain the grid-connected reference current i ^* _inv output by the multiplier 2 and the polarity Negative actual grid-connected sampling current i ^* _inv summing adder 3, current controller 4 and pulse width modulation output on the signal output by current controller 4 to drive single-phase H in a single-phase distributed grid-connected power generation system The pulse width modulation generator 5 of the four-way trigger pulse signals PWM1-PWM4 of the bridge inverter A also includes, sequentially connected in series: the input end is connected to the voltage end of the common coupling point PCC of the single-phase distributed grid-connected power generation system, A quadrature signal generator 6 for generating two-phase quadrature voltages, a genlock 7 for obtaining the grid phase angle based on the output signal of the quadrature signal generator 6, and a reference amplitude for generating grid-connected currents The phase perturbation unit 8 of the unitized grid-connected reference current cosθ _inv ^* multiplied by the value I ^* _inv and the threshold judgment unit 9 based on the jumping Goertzel filter for voltage threshold judgment, wherein the phase disturbance unit 8 The output of is connected to the input of multiplier 2.

本发明的一种基于相位扰动的分布式并网逆变器孤岛检测系统的主要工作原理为：将输入的直流母线电压V_dc、设定的直流母线电压标准值V_{dc_ref}输入到电压控制器，电压控制器的输出作为并网电流的幅值基准I^* _inv，该幅值基准与单位化的并网基准电流cosθ_inv ^*相乘，得到并网基准电流i^* _inv，该并网基准电流与实际的并网采样电流i^* _inv作差，其差值输送到电流控制器，将电流控制器的输出输送到PWM发生器，通过PWM发生器产生的四路触发脉冲PWM1～PWM4来驱动图1中所示的单相H桥逆变器中的四个开关管，实现从直流到交流的逆变过程，逆变器的输出电流经过图1中的LC滤波器，得到与电网电压同频同相的并网电流后注入电网。 The main working principle of a distributed grid-connected inverter island detection system based on phase disturbance of the present invention is: input the input DC bus voltage V _dc and the set DC bus voltage standard value V _{dc_ref} to the voltage controller, The output of the voltage controller is used as the amplitude reference I ^* _inv of the grid-connected current, which is multiplied by the unitized grid-connected reference current cosθ _inv ^* to obtain the grid-connected reference current i ^* _inv , which is equal to The actual grid-connected sampling current i ^* _inv makes a difference, and the difference is sent to the current controller, and the output of the current controller is sent to the PWM generator, and the four trigger pulses PWM1~PWM4 generated by the PWM generator are used to drive Figure 1 The four switching tubes in the single-phase H-bridge inverter shown in , realize the inversion process from DC to AC, and the output current of the inverter passes through the LC filter in Figure 1, and obtains the same frequency and phase as the grid voltage The grid-connected current is injected into the grid.

本发明的基于相位扰动的分布式并网逆变器孤岛检测系统在具体算法上与并网控制策略相互依存，不可分割。具体来讲，公共耦合点PCC处的电压v_PCC经过本发明中提出的QSG(正交信号发生器)和PLL(锁相环)后，得到了准确的电网相位角θ_g，该相位角与注入的相位扰动量叠加，其结果作为逆变器并网控制的相位基准角θ_inv ^*，该相位基准角经过余弦运算后，得到单位化的并网基准电流cosθ_inv ^*，该结果再与并网电流的幅值基准I^* _inv相乘，乘积作为并网基准电流i^* _inv，参与逆变器的并网控制。由于注入的相位扰动会在并网电流中产生一定量的三次谐波电流分量，该三次谐波电流分量将在公共耦合点PCC处产生相应的三次谐波电压分量。在孤岛检测算法中，采用本发明中设计的跳跃Goertzel滤波器对三次谐波电压分量进行提取。当分布式发电系统的工作模式由并网运行转为孤岛运行时，如果检测到的公共耦合点PCC处的三次谐波电压分量超过了在孤岛检测算法中预设的孤岛检测阈值，控制系统迅速完成孤岛检测，及时封锁逆变器。 The phase disturbance-based distributed grid-connected inverter island detection system of the present invention is interdependent and inseparable from the grid-connected control strategy in specific algorithms. Specifically, after the voltage v _{PCC at the point of public coupling PCC} passes through the QSG (Quadrature Signal Generator) and PLL (Phase Locked Loop) proposed in the present invention, an accurate grid phase angle θ _g is obtained, which is the same as The injected phase disturbances are superimposed, and the result is used as the phase reference angle θ _inv ^* of the grid-connected control of the inverter. After the cosine operation of the phase reference angle, the unitized grid-connected reference current cosθ _inv ^* is obtained, and the result is combined with the parallel The amplitude reference I ^* _inv of the grid current is multiplied, and the product is used as the grid-connected reference current i ^* _inv to participate in the grid-connected control of the inverter. Since the injected phase disturbance will generate a certain amount of third harmonic current component in the grid-connected current, the third harmonic current component will generate a corresponding third harmonic voltage component at the common coupling point PCC. In the island detection algorithm, the jumping Goertzel filter designed in the present invention is used to extract the third harmonic voltage component. When the working mode of the distributed generation system changes from grid-connected operation to island operation, if the detected third harmonic voltage component at the common coupling point PCC exceeds the island detection threshold preset in the island detection algorithm, the control system will quickly Complete the island detection and block the inverter in time.

如图3所示，所述的正交信号发生器6包括有依次串接的第一加法器61、第一放大器62、第二加法器63以及第一积分器64，其中，所述第一加法器61的一个输入端作为正交信号发生器6的输入端连接单相分布式并网发电系统公共耦合点PCC的电压端，第一积分器64的输出分三路：第一路直接作为正交信号发生器6的第一输出端v_α，第二路极性取负后与第一加法器61的另一个输入端相连接，第三路连接全通滤波器65的输入端，所述全通滤波器65的输出分两路：第一路直接作为正交信号发生器6的第二输出端v_β，第二路极性取负后与第二加法器63的另一个输入端相连接。 As shown in Figure 3, the quadrature signal generator 6 includes a first adder 61, a first amplifier 62, a second adder 63 and a first integrator 64 connected in series in sequence, wherein the first One input end of the adder 61 is used as the input end of the quadrature signal generator 6 to connect the voltage end of the common coupling point PCC of the single-phase distributed grid-connected power generation system, and the output of the first integrator 64 is divided into three paths: the first path directly serves as The first output terminal v _α of the quadrature signal generator 6 is connected to the other input terminal of the first adder 61 after the polarity of the second channel is negative, and the third channel is connected to the input terminal of the all-pass filter 65, so The output of the all-pass filter 65 is divided into two paths: the first path is directly used as the second output terminal v _β of the quadrature signal generator 6, and the second path is connected to the other input end of the second adder 63 after the polarity of the second path is negative. connected.

本发明中，通过图3所示的新型正交信号发生器，可根据输入的单相电网电压信号，产生同步锁相器所需的两相正交电压v_α和v_β。这种类型的正交信号发生器可以提供具有相同谐波畸变率(THD)的输出信号，即v_α和v_β，防止由于所含谐波不同带来的锁相精度问题。图3中正交信号发生器的传递函数为 In the present invention, through the novel quadrature signal generator shown in FIG. 3 , the two-phase quadrature voltages v _α and v _β required by the synchronous locker can be generated according to the input single-phase grid voltage signal. This type of quadrature signal generator can provide output signals with the same harmonic distortion rate (THD), namely v _α and v _β , preventing phase-locking accuracy problems caused by different harmonics contained. The transfer function of the quadrature signal generator in Fig. 3 is

$\{\begin{matrix} \frac{{V V}_{α α} ((s the s))}{{V V}_{g g} ((s the s))} = = \frac{{kω kω}_{o o} (({ω ω}_{o o} + + s the s))}{{s the s}^{22} + + {kω kω}_{o o} s the s + + ((11 + + k k)) {ω ω}_{o o}^{22}} \\ \frac{{V V}_{β β} ((s the s))}{{V V}_{g g} ((s the s))} = = \frac{{kω kω}_{o o} (({ω ω}_{o o} - - s the s))}{{s the s}^{22} + + {kω kω}_{o o} s the s + + ((11 + + k k)) {ω ω}_{o o}^{22}} \end{matrix} - - - - - - ((11))$

式中，ω_o表示估计的电网基波频率，k表示正交信号发生器的增益。 In the formula, ω _o represents the estimated fundamental frequency of the power grid, and k represents the gain of the quadrature signal generator.

在不考虑电网谐波影响的前提下，假设单相电网电压信号可表示为v_g＝Vcosωt，其中V和ω分别为电网电压的幅值和实际的电网基波频率，则当估计的电网基波频率等于实际的电网基波频率时，即ω_o＝ω，经过图3所示的正交信号发生器后，得到任意时刻的两相输出电压分别为 Without considering the influence of grid harmonics, assuming that the single-phase grid voltage signal can be expressed as v _g = Vcosωt, where V and ω are the amplitude of the grid voltage and the actual grid fundamental frequency respectively, then when the estimated grid fundamental When the wave frequency is equal to the actual power grid fundamental wave frequency, that is, ω _o = ω, after passing through the quadrature signal generator shown in Figure 3, the two-phase output voltages at any time are obtained as

${{\begin{matrix} {v v}_{α α} ((t t)) = = V V cos cos ω ω t t - - {Ve Ve}^{- - \frac{k k ω ω}{22} t t} [[{coshξ coshξ}_{d d} ω ω t t - - \frac{{ksinhξ ksinhξ}_{d d} ω ω t t}{\sqrt{22} {ξ ξ}_{d d}}]] \\ {v v}_{β β} ((t t)) = = V V sin sin ω ω t t - - \frac{11 + + k k}{{ξ ξ}_{d d}} {Ve Ve}^{- - \frac{k k ω ω}{22} t t} {sinhξ sinhξ}_{d d} ω ω t t \end{matrix} - - - - - - ((22))$

式中， $ξ_{d} = \sqrt{1 + k - \frac{1}{4} k^{2}} .$ In the formula, $ξ_{d} = \sqrt{1 + k - \frac{1}{4} k^{2}} .$

稳态条件下，两相输出电压可分别表示为 Under steady-state conditions, the two-phase output voltages can be expressed as

$\{\begin{matrix} {v v}_{α α} = = V V cos cos ω ω t t \\ {v v}_{β β} = = V V sin sin ω ω t t \end{matrix} - - - - - - ((33))$

从式(3)中可以发现，当处于稳态条件下，由图3所示的正交信号发生器得到的两相输出电压v_α和v_β是严格正交的。 It can be found from the formula (3) that when it is in a steady state condition, the two-phase output voltage v _α and v _β obtained by the quadrature signal generator shown in Fig. 3 are strictly orthogonal.

对于二阶系统而言，可用整定时间t_s＝4.6τ来大致估计整定时间。在式(2)中，时间常数τ＝2/kω，因此，对于已给定的整定时间t_s，图3中所示的正交信号发生器的增益k可计算如下： For a second-order system, the settling time can be roughly estimated by using the settling time t _s =4.6τ. In formula (2), the time constant τ=2/kω, therefore, for a given settling time t _s , the gain k of the quadrature signal generator shown in Fig. 3 can be calculated as follows:

$k k = = \frac{9.2 9.2}{{t t}_{s the s} ω ω} - - - - - - ((44))$

如图4所示，所述的同步锁相器7包括有：依次串接的第三加法器75、第二放大器76、第三乘法器78、第二积分器79以及mod运算器710，其中，所述mod运算器710的输出端构成同步锁相器7的输出端，用于输出电网相位角θ_g，所述第三加法器75的输入端分别连接第一乘法器72和第二乘法器74的输出端，所述第一乘法器72的一个输入端直接连接正交信号发生器6的第一路输出端v_α，第一乘法器72的另一个输入端通过第一二阶低通滤波器71接连接正交信号发生器6的第一路输出端v_α，第二乘法器74的一个输入端直接连接正交信号发生器6的第二路输出端v_β，第二乘法器74的另一个输入端通过第二二阶低通滤波器73接连接正交信号发生器6的第二路输出端v_β，所述第三乘法器78的输入端还连接电压补偿器77的输出端，所述电压补偿器77的输入端分别连接第一二阶低通滤波器71的输出端v_αL以及第二二阶低通滤波器73的输出端v_βL。 As shown in Figure 4, the described genlock 7 includes: a third adder 75, a second amplifier 76, a third multiplier 78, a second integrator 79 and a mod operator 710 connected in series in sequence, wherein , the output end of the mod operator 710 constitutes the output end of the genlock 7 for outputting the grid phase angle θ _g , and the input end of the third adder 75 is respectively connected to the first multiplier 72 and the second multiplier The output terminal of the device 74, one input terminal of the first multiplier 72 is directly connected to the first output terminal v _α of the quadrature signal generator 6, and the other input terminal of the first multiplier 72 is passed through the first second-order low The pass filter 71 is connected to the first output terminal v _α of the quadrature signal generator 6, and one input terminal of the second multiplier 74 is directly connected to the second output terminal v _β of the quadrature signal generator 6, and the second multiplier The other input terminal of the multiplier 74 is connected to the second output terminal v _β of the quadrature signal generator 6 through the second second-order low-pass filter 73, and the input terminal of the third multiplier 78 is also connected to the voltage compensator 77 The output terminal of the voltage compensator 77 is respectively connected to the output terminal v _αL of the first second-order low-pass filter 71 and the output terminal v _βL of the second second-order low-pass filter 73 .

如果考虑到实际电网背景下的谐波扰动，那么在稳态条件下通过正交信号发生器所产生的v_α和v_β中同样会混入一定量的谐波分量，为了能够有效削弱这些谐波分量，在图4所示的同步锁相器实现框图中，特别引入如式(5)所描述了二阶低通滤波器。 If the harmonic disturbance in the actual power grid background is considered, a certain amount of harmonic components will also be mixed into v _α and v _β generated by the quadrature signal generator under steady-state conditions. In order to effectively weaken these harmonics Component, in the genlock implementation block diagram shown in Figure 4, a second-order low-pass filter is specially introduced as described in formula (5).

$S S O o L L F f ((s the s)) = = \frac{{ω ω}_{o o}^{22}}{{s the s}^{22} + + \sqrt{22} {ω ω}_{o o} s the s + + {ω ω}_{o o}^{22}} - - - - - - ((55))$

式(5)所述二阶低通滤波器的幅相特性方程为 The amplitude-phase characteristic equation of the second-order low-pass filter described in formula (5) is

$\{\begin{matrix} H h = = | | S S O o L L F f ((j j ω ω)) | | = = \frac{{ω ω}_{o o}^{22}}{\sqrt{{((\sqrt{22} {ωω ωω}_{o o}))}^{22} + + {(({ω ω}^{22} + + {ω ω}_{o o}^{22}))}^{22}}} \\ P P = = &angle; &angle; S S O o L L F f ((j j ω ω)) = = - - arccos arccos \frac{{ω ω}_{o o}^{22} - - {ω ω}^{22}}{\sqrt{{((\sqrt{22} {ωω ωω}_{o o}))}^{22} + + {(({ω ω}^{22} + + {ω ω}_{o o}^{22}))}^{22}}} \end{matrix} - - - - - - ((66))$

当正交信号发生器的输出电压v_α和v_β各自通过二阶低通滤波器滤波后(如图4所示)，得到的响应输出可分别表示为 When the output voltages v _α and v _β of the quadrature signal generator are respectively filtered by the second-order low-pass filter (as shown in Figure 4), the obtained response outputs can be expressed as

${{\begin{matrix} {v v}_{α α L L} = = H h V V cos cos ((ω ω t t + + P P)) \\ {v v}_{β β L L} = = H h V V sin sin ((ω ω t t + + P P)) \end{matrix} - - - - - - ((77))$

按照式(8)所示的调整律来设计同步锁相器中的频率自适应控制器。 Design the frequency adaptive controller in the genlock according to the adjustment law shown in formula (8).

${\overset{\cdot \cdot}{ω ω}}_{o o} = = - - δ δ \cdot &Center Dot; \frac{{v v}_{α α L L} {v v}_{α α} + + {v v}_{β β L L} {v v}_{β β}}{{v v}_{α α L L}^{22} + + {v v}_{β β L L}^{22}} - - - - - - ((88))$

式中，δ为频率自适应调整系数。 In the formula, δ is the frequency adaptive adjustment coefficient.

将式(3)和式(7)代入式(8)，在估计的电网基波频率近似等于实际的电网基波频率时，化简得到 Substituting formula (3) and formula (7) into formula (8), when the estimated power grid fundamental frequency is approximately equal to the actual power grid fundamental frequency, simplifying to get

${\overset{\cdot &Center Dot;}{ω ω}}_{o o} = = 22 δ δ \frac{ω ω - - {ω ω}_{o o}}{ω ω} - - - - - - ((99))$

式(9)所示的频率自适应调整律的动态调整过程为：当ω>ω_o时，可自动调整ω_o使其线性增大；当ω<ω_o时，又可及时调整ω_o使其线性减小；当ω_o经过自适应调整等于ω时，ω_o保持不变。频率自适应调整的过程，同时又是锁相器对电网相位自调整输出的过程。经过频率自适应调整获得电网基波频率后再经过mod运算，即可得到电网的相位角θ_g。 The dynamic adjustment process of the frequency adaptive adjustment law shown in formula (9) is: when ω>ω _o , ω _o can be automatically adjusted to make it increase linearly; when ω<ω _o , ω _o can be adjusted in time so that It decreases linearly; when ω _o is adaptively adjusted to be equal to ω, ω _o remains unchanged. The process of frequency self-adaptive adjustment is also the process of the phase locker to self-adjust the output of the grid phase. The fundamental frequency of the power grid is obtained through frequency adaptive adjustment, and then mod operation is performed to obtain the phase angle θ _g of the power grid.

频率自适应调整系数δ的取值，可按照式(10)，根据给定的时间常数η来求得。时间常数η通常可取一个工频周期，即20ms。 The value of the frequency adaptive adjustment coefficient δ can be obtained according to the given time constant η according to formula (10). The time constant η usually takes one power frequency cycle, namely 20ms.

$δ δ = = \frac{ω ω}{22 η η} - - - - - - ((1010))$

值得注意的是，式(10)所示的频率自适应调整系数δ在取值上不受电网电压幅值的影响，因此在式(9)所示的频率自适应调整过程中，即便有电压波动，也不会影响同步锁相器对电网频率及电网相位的快速捕获，因此，式(8)所述的频率跟踪方案对电网幅值波动具有良好的鲁棒性。 It is worth noting that the frequency adaptive adjustment coefficient δ shown in equation (10) is not affected by the grid voltage amplitude, so in the frequency adaptive adjustment process shown in equation (9), even if there is voltage Fluctuations will not affect the fast capture of grid frequency and grid phase by the genlock. Therefore, the frequency tracking scheme described in formula (8) has good robustness to grid amplitude fluctuations.

如图5所示，所述的相位扰动单元8包括有依次串接的第三放大器81、正弦运算器82、第四放大器83、第四加法器84和余弦运算器85，其中，所述第三放大器81的输入端和第四加法器84的另一个输入端共同连接同步锁相器7的输出端θ_g，所述余弦运算器85的输出端构成相位扰动单元8的输出端cosθ_inv ^*连接所述乘法器2的一个输入端。 As shown in Figure 5, the phase perturbation unit 8 includes a third amplifier 81, a sine operator 82, a fourth amplifier 83, a fourth adder 84 and a cosine operator 85 connected in series, wherein the first The input end of the three amplifiers 81 and the other input end of the fourth adder 84 are commonly connected to the output end θ _g of the genlock 7 , and the output end of the cosine operator 85 constitutes the output end cosθ _inv ^* of the phase perturbation unit 8 connected to one input of the multiplier 2.

按照前面所述的注入的相位扰动不能改变电网相位信号中电压过零点位置的原则，方案中将一个由正弦函数确定的扰动量σ_inj注入到当前电网锁相角θ_g中，作为分布式发电系统并网控制中的相位基准角。具体实现框图如图5所示。 According to the principle that the injected phase disturbance cannot change the voltage zero-crossing position in the grid phase signal, in the scheme, a disturbance amount σ _inj determined by a sine function is injected into the current grid phase-locked angle θ _g as a distributed generation Phase reference angle in grid-connected control of the system. The specific implementation block diagram is shown in Figure 5.

图5中，注入的相位扰动量为 In Figure 5, the injected phase disturbance is

σ_inj＝μsin2θ_g(11) σ _inj = μ sin2θ _g (11)

式中，μ为用于孤岛检测时的相位扰动系数。 In the formula, μ is the phase disturbance coefficient used for islanding detection.

此时，含有扰动的相位基准如式(12)所示： At this time, the phase reference with disturbance is shown in formula (12):

${θ θ}_{i i n no v v}^{* *} = = {θ θ}_{g g} + + {σ σ}_{i i n no j j} = = {θ θ}_{g g} + + μ μ s the s i i n no 22 {θ θ}_{g g} - - - - - - ((1212))$

图6显示了加入的扰动相位对同步锁相结果的影响。图6中实线表示加入扰动后的相位角θ_inv ^*，即并网控制中的相位基准值；虚线表示未加扰动量时锁相环输出的无扰动相位角θ_g。与无扰动时输出的相位角θ_g相比，加入的扰动量不影响过零点和峰值处的相位，但在其他位置则会产生一定程度上的相位偏移。 Figure 6 shows the effect of the added perturbation phase on the genlock result. The solid line in Fig. 6 represents the phase angle θ _inv ^* after adding disturbance, that is, the phase reference value in grid-connected control; the dotted line represents the non-disturbance phase angle θ _g output by the PLL when no disturbance is added. Compared with the output phase angle θ _g without disturbance, the amount of disturbance added does not affect the phase at the zero-crossing point and the peak, but it will produce a certain degree of phase shift at other positions.

结合式(12)，可以得到并网基准电流为 Combined with (12), the grid-connected reference current can be obtained as

${I I}_{i i n no v v}^{* *} {cosθ cosθ}_{i i n no v v}^{* *} = = {I I}_{i i n no v v}^{* *} c c o o s the s (({θ θ}_{g g} + + μ μ s the s i i n no 22 {θ θ}_{g g})) - - - - - - ((1313))$

在5kW并网逆变器上进行仿真，得到的并网基准电流i^* _inv的波形如图7所示。从图7上可以看出，在基准电流波形的过零点及峰值处，相位上不受外加扰动相位的影响。 The simulation is carried out on a 5kW grid-connected inverter, and the waveform of the grid-connected reference current i ^* _inv obtained is shown in Figure 7. It can be seen from Figure 7 that at the zero-crossing point and peak value of the reference current waveform, the phase is not affected by the phase of the external disturbance.

当相位扰动系数μ取值足够小时，式(13)可进一步化简，得到 When the value of the phase disturbance coefficient μ is small enough, formula (13) can be further simplified to get

$\begin{matrix} {I I}_{i i n no v v}^{* *} {cosθ cosθ}_{i i n no v v}^{* *} = = {I I}_{i i n no v v}^{* *} ((11 - - \frac{μ μ}{22})) {cosθ cosθ}_{g g} + + {I I}_{i i n no v v}^{* *} \frac{μ μ}{22} cos cos 33 {θ θ}_{g g} \\ \approx \approx {I I}_{i i n no v v}^{* *} {cosθ cosθ}_{g g} + + {I I}_{i i n no v v}^{* *} \frac{μ μ}{22} cos cos 33 {θ θ}_{g g} \end{matrix} - - - - - - ((1414))$

式(14)中的三次谐波电流分量可独立地表示为 The third harmonic current component in formula (14) can be independently expressed as

${i i}_{i i n no v v__150150 H h z z} = = {I I}_{i i n no v v}^{* *} \frac{μ μ}{22} c c o o s the s 33 {θ θ}_{g g} - - - - - - ((1515))$

式(11)所描述的相位扰动量σ_inj在逆变器并网控制的基准电流中产生了如式(15)中所描述的三次谐波电流分量。并网电流的总谐波畸变率及三次谐波电流分量的百分比可根据相位扰动系数μ来确定。因此，并网电流中的总谐波畸变率及三次谐波电流分量是可控的。不同μ值情况下对应的总谐波畸变率及三次谐波含量的百分比如表1所示。 The phase disturbance σ _inj described in Equation (11) produces the third harmonic current component as described in Equation (15) in the reference current of inverter grid-connected control. The total harmonic distortion rate of the grid-connected current and the percentage of the third harmonic current component can be determined according to the phase disturbance coefficient μ. Therefore, the total harmonic distortion rate and the third harmonic current component in grid-connected current are controllable. Table 1 shows the corresponding total harmonic distortion rate and the percentage of the third harmonic content under different μ values.

表1不同μ值时并网电流的THD及三次谐波含量 Table 1 THD and third harmonic content of grid-connected current at different μ values

根据对并网逆变器电能质量相关标准中规定的并网电流总谐波畸变率不能超过5％，以及注入电网的三次谐波电流必须低于4％的技术要求，按照表1给出的数据，如果采用本文所提的相位扰动注入法进行孤岛检测，需要考虑到并网逆变器引起的电能质量问题和接入电网背景谐波，那么扰动系数μ的取值上限应低于0.08，且应根据实际工程条件具体给出。 According to the technical requirements that the total harmonic distortion rate of grid-connected current cannot exceed 5% and the third harmonic current injected into the grid must be lower than 4% in the relevant standards for power quality of grid-connected inverters, according to Table 1 Data, if the phase disturbance injection method proposed in this paper is used for islanding detection, it is necessary to consider the power quality problems caused by the grid-connected inverter and the background harmonics connected to the grid, then the upper limit of the disturbance coefficient μ should be lower than 0.08, And should be given according to the actual engineering conditions.

如图2所示，所述的孤岛检测实现单元9包括有依次连接的采样电路91和跳跃Goertzel滤波器92，其中，所述的采样电路91的输入端连接单相分布式并网发电系统公共耦合点PCC的电压端，所述跳跃Goertzel滤波器92的输出电压v_m(n)作为单相分布式并网发电系统的检测电压，与已设定的电压阈值进行对比，当输出电压v_m(n)大于等于设定的电压阈值时，脉冲宽度调制发生器5不输出四路触发脉冲信号PWM1～PWM4，单相分布式并网发电系统中的单相H桥逆变器A不工作，当输出电压v_m(n)小于设定的电压阈值时，脉冲宽度调制发生器5输出四路触发脉冲信号PWM1～PWM4，单相分布式并网发电系统中的单相H桥逆变器A工作。 As shown in Figure 2, the islanding detection implementation unit 9 includes a sequentially connected sampling circuit 91 and a jumping Goertzel filter 92, wherein the input end of the sampling circuit 91 is connected to the single-phase distributed grid-connected power generation system common At the voltage terminal of the coupling point PCC, the output voltage v _m (n) of the jumping Goertzel filter 92 is used as the detection voltage of the single-phase distributed grid-connected power generation system, and compared with the preset voltage threshold, when the output voltage v _m (n) When greater than or equal to the set voltage threshold, the pulse width modulation generator 5 does not output four trigger pulse signals PWM1-PWM4, and the single-phase H-bridge inverter A in the single-phase distributed grid-connected power generation system does not work, When the output voltage v _m (n) is less than the set voltage threshold, the pulse width modulation generator 5 outputs four trigger pulse signals PWM1~PWM4, and the single-phase H-bridge inverter A in the single-phase distributed grid-connected power generation system Work.

关于孤岛检测阈值的设定。分布式发电系统分别工作于并网模式和孤岛模式时，公共耦合点处的复阻抗不同，导致此处的三次谐波电压也相应不同。这一点可用于设定孤岛检测阈值的依据。为便于分析和陈述，图8给出了单相分布式并网发电系统的简化电路。 About the setting of island detection threshold. When the distributed generation system works in grid-connected mode and island mode respectively, the complex impedance at the common coupling point is different, resulting in the corresponding difference in the third harmonic voltage here. This can be used as a basis for setting the islanding detection threshold. For the convenience of analysis and presentation, Figure 8 shows the simplified circuit of the single-phase distributed grid-connected power generation system.

当分布式发电系统工作于并网模式时，公共耦合点处的复阻抗为本地负载复阻抗与电网复阻抗的并联，研究发现，在通常情况下，电网中三次谐波的阻抗值远远小于本地负载对应三次谐波时的阻抗值，即|Z_{g_150Hz}||Z_{L_150Hz}|，此时，公共耦合点处的三次谐波电压矢量可表示为 When the distributed generation system works in the grid-connected mode, the complex impedance at the public coupling point is the parallel connection of the local load complex impedance and the grid complex impedance. It is found that under normal circumstances, the impedance value of the third harmonic in the grid is much smaller than The impedance value when the local load corresponds to the third harmonic, that is, |Z _{g_150Hz} ||Z _{L_150Hz} |, at this time, the third harmonic voltage vector at the common coupling point can be expressed as

$\begin{matrix} {\overset{\cdot \cdot}{V V}}_{P P C C C C__150150 H h z z} = = (({\overset{\cdot &Center Dot;}{Z Z}}_{L L__150150 H h z z} | | | | {\overset{\cdot \cdot}{Z Z}}_{g g__150150 H h z z})) \cdot &Center Dot; {\overset{\cdot &Center Dot;}{I I}}_{i i n no v v__150150 H h z z} \\ \approx \approx {\overset{\cdot \cdot}{Z Z}}_{g g__150150 H h z z} \cdot \cdot {I I}_{i i n no v v__150150 H h z z} \end{matrix} - - - - - - ((1616))$

当分布式发电系统工作于孤岛模式时，公共耦合点处的复阻抗即为本地负载的复阻抗，因此，公共耦合点处的三次谐波电压矢量表达式为 When the distributed generation system works in island mode, the complex impedance at the common coupling point is the complex impedance of the local load, therefore, the vector expression of the third harmonic voltage at the common coupling point is

${\overset{\cdot &Center Dot;}{V V}}_{P P C C C C__150150 H h z z} = = {\overset{\cdot \cdot}{Z Z}}_{L L__150150 H h z z} \cdot &Center Dot; {\overset{\cdot \cdot}{I I}}_{i i n no v v__150150 H h z z} - - - - - - ((1717))$

本地RLC负载的阻抗可根据式(18)求得。 The impedance of the local RLC load can be obtained according to formula (18).

$| | {\overset{\cdot &Center Dot;}{Z Z}}_{L L__150150 H h z z} | | = = \frac{11}{\sqrt{{((\frac{11}{R R}))}^{22} + + {((22 π π \cdot &Center Dot; 150150 C C - - \frac{11}{22 π π \cdot \cdot 150150 L L}))}^{22}}} - - - - - - ((1818))$

式(18)中，本地RLC负载中的电阻R、电感L和电容C通常按照式(19)取值。 In formula (18), the resistance R, inductance L and capacitance C in the local RLC load are usually taken according to formula (19).

$\{\begin{matrix} R R = = \frac{{V V}^{22}}{P P} \\ L L = = \frac{{V V}^{22}}{22 {πf πf}_{r r} {PQ PQ}_{f f}} \\ C C = = \frac{{PQ PQ}_{f f}}{22 {πf πf}_{r r} {V V}^{22}} \end{matrix} - - - - - - ((1919))$

式(19)中，V为电网电压的有效值，P为并网逆变器提供的有功功率，f_r为RLC负载的谐振频率，Q_f为RLC负载的品质因数。在做孤岛检测时，f_r、Q_f通常分别取值为50Hz和2.5。 In formula (19), V is the effective value of the grid voltage, P is the active power provided by the grid-connected inverter, f _r is the resonant frequency of the RLC load, and Q _f is the quality factor of the RLC load. When doing island detection, f _r and Q _f are usually taken as 50Hz and 2.5 respectively.

因为|Z_{g_150Hz}||Z_{L_150Hz}|，所以当分布式发电系统产生孤岛效应时，v_PCC中的三次谐波分量会变大，因此，可由式(16)计算的电压有效值作为孤岛检测的阈值，以此判定分布式发电系统是否处于孤岛运行。 Because of |Z _{g_150Hz} ||Z _{L_150Hz} |, when the islanding effect occurs in the distributed generation system, the third harmonic component in v _PCC will become larger, therefore, the voltage effective value calculated by formula (16) can be used as the threshold of islanding detection , so as to determine whether the distributed generation system is operating in an island.

(2)、公共耦合点处三次谐波分量的提取 (2), the extraction of the third harmonic component at the common coupling point

在对实数信号进行连续采样并计算DFT频谱时，式(20)所述的滑动型DFT滤波器因具有较少运算量得到广泛关注，但是在对滤波器系数进行近似数值运算时，所取的截断误差极易导致自身边界的非稳定性。为了保证频谱分析时同样具有较少的运算量，同时维护自身的稳定性，一个有效的措施便是对式(20)所描述的滑动型DFT滤波器的z域传递函数作形如式(21)的变换，由此构成新型的跳跃Goertzel滤波器。 When continuously sampling real signals and calculating the DFT spectrum, the sliding DFT filter described in Equation (20) has received widespread attention because of its low computational complexity. However, when performing approximate numerical operations on the filter coefficients, the obtained The truncation error can easily lead to the instability of its own boundary. In order to ensure that the spectrum analysis also has less computation and maintain its own stability, an effective measure is to formulate the z-domain transfer function of the sliding DFT filter described in equation (20) as in equation (21 ) transformation, thus forming a new type of jumping Goertzel filter.

${H h}_{S S D D. F f T T} ((z z)) = = \frac{11 - - {z z}^{- - N N}}{11 - - {e e}^{j j 22 π π m m / / N N} {z z}^{- - 11}} - - - - - - ((2020))$

$\begin{matrix} {H h}_{H h G G} ((z z)) = = \frac{{e e}^{j j 22 π π m m / / N N} ((11 - - {e e}^{- - j j 22 π π m m / / N N} {z z}^{- - 11})) ((11 - - {z z}^{- - N N}))}{((11 - - {e e}^{- - j j 22 π π m m / / N N} {z z}^{- - 11})) ((11 - - {e e}^{j j 22 π π m m / / N N} {z z}^{- - 11}))} \\ = = \frac{(({e e}^{j j 22 π π m m / / N N} - - {z z}^{- - 11})) ((11 - - {z z}^{- - N N}))}{11 - - 22 cos cos ((22 π π m m / / N N)) {z z}^{- - 11} + + {z z}^{- - 11}} \end{matrix} - - - - - - ((21 twenty one))$

在式(20)和式(21)中，N为工频周期内总的采样点数，m为与扰动频率相对应的特定频点。若扰动频率、采样频率和电网基波频率分别表示为f_dist、f_sam和f_g，则N和m可按照式(22)进行取值。 In formulas (20) and (21), N is the total number of sampling points in the power frequency cycle, and m is the specific frequency point corresponding to the disturbance frequency. If the disturbance frequency, sampling frequency and grid fundamental frequency are denoted as f _dist , f _sam and f _g respectively, then N and m can be determined according to formula (22).

${{\begin{matrix} N N = = {f f}_{s the s a a m m} / / {f f}_{g g} \\ m m = = {f f}_{d d i i s the s t t} / / {f f}_{s the s a a m m} \end{matrix} - - - - - - ((22 twenty two))$

按照式(21)进行跳跃Goertzel滤波器的设计实现。如图9所示，所述的跳跃Goertzel滤波器92包括有：依次串接的梳状滤波器921、第五加法器922、第五放大器923和第六加法器924，其中，第五加法器922的输出端又经过第一延迟单元925后分成三路：第一路通过第六放大器926连接第五加法器922的一个输入端，第二路通过第二延迟单元927后再极性取负连接第五加法器922的另一个输入端，第三路直接极性取负后连接第六加法器924的又一个输入端，所述梳状滤波器921的输入端连接采样电路91的输出端，所述第六加法器924的输出端构成跳跃Goertzel滤波器92的输出电压v_m(n)。 According to the formula (21), the design and implementation of the jumping Goertzel filter is carried out. As shown in FIG. 9 , the skipped Goertzel filter 92 includes: a comb filter 921, a fifth adder 922, a fifth amplifier 923 and a sixth adder 924 connected in series in sequence, wherein the fifth adder The output end of 922 is divided into three paths after passing through the first delay unit 925: the first path is connected to an input end of the fifth adder 922 through the sixth amplifier 926, and the polarity is taken negative after the second path passes through the second delay unit 927 Connect the other input end of the fifth adder 922, connect another input end of the sixth adder 924 after the direct polarity of the third path is negative, the input end of the comb filter 921 is connected to the output end of the sampling circuit 91 , the output terminal of the sixth adder 924 constitutes the output voltage v _m (n) of the jumping Goertzel filter 92 .

所述的梳状滤波器921包括有第七加法器9211，所述第七加法器9211的一个输入端直接连接采样电路91的输出端，第七加法器9211的另一个输入端通过第三延迟单元9212连接采样电路91的输出端，所述第七加法器9211的输出连接第五加法器922的输入端。 The comb filter 921 includes a seventh adder 9211, one input end of the seventh adder 9211 is directly connected to the output end of the sampling circuit 91, and the other input end of the seventh adder 9211 passes through the third delay The unit 9212 is connected to the output terminal of the sampling circuit 91 , and the output of the seventh adder 9211 is connected to the input terminal of the fifth adder 922 .

图9中，中间变量w_m(n)及输出变量v_m(n)的数值运算关系如式(23)和式(24)所示。 In Fig. 9, the numerical operation relationship between the intermediate variable w _m (n) and the output variable v _m (n) is shown in formula (23) and formula (24).

$\begin{matrix} {w w}_{m m} ((n no)) = = 22 {w w}_{m m} ((n no - - 11)) \cdot &Center Dot; cos cos \frac{22 π π m m}{N N} - - {w w}_{m m} ((n no - - 22)) \\ + + {v v}_{P P C C C C} ((n no)) - - {v v}_{P P C C C C} ((n no - - N N)) \end{matrix} - - - - - - ((23 twenty three))$

${v v}_{m m} ((n no)) = = {w w}_{m m} ((n no)) {e e}^{j j 22 π π m m / / N N} - - {w w}_{m m} ((n no - - 11)) - - - - - - ((24 twenty four))$

将式(24)展开，有 Expanding formula (24), we have

${v v}_{m m} ((n no)) = = {w w}_{m m} ((n no)) c c o o s the s \frac{22 π π m m}{N N} - - {w w}_{m m} ((n no - - 11)) + + {jw jw}_{m m} ((n no)) s the s i i n no \frac{22 π π m m}{N N} - - - - - - ((2525))$

从式(25)可以看出：根据n时刻和n-1时刻中间变量的频谱值，经过2个实数加法和1个复数加法运算后，便可得到n时刻谐波电压的频谱值，而滑动DFT滤波器则需要6个实数乘法和3个复数加法运算才能得到同样的结果。因此，采用跳跃Goertzel滤波器计算n时刻谐波电压的频谱值，将会大大降低运算量。n时刻采样值的m次频谱值可由式(26)计算求得。 It can be seen from formula (25): according to the spectrum value of the intermediate variable at time n and n-1, after two real additions and one complex addition, the spectrum value of the harmonic voltage at n time can be obtained, and the sliding The DFT filter requires 6 real multiplications and 3 complex additions to get the same result. Therefore, using the jumping Goertzel filter to calculate the spectrum value of the harmonic voltage at time n will greatly reduce the amount of calculation. The m-time spectrum value of the sampling value at n time can be obtained by formula (26).

$| | {v v}_{m m} ((n no)) | | = = \sqrt{{(({w w}_{m m} ((n no)) \cdot &Center Dot; c c o o s the s \frac{22 π π m m}{N N} - - {w w}_{m m} ((n no - - 11))))}^{22} + + {(({w w}_{m m} ((n no)) \cdot \cdot s the s i i n no \frac{22 π π m m}{N N}))}^{22}} - - - - - - ((2626))$

通过式(26)求得三次谐波电压值，将其与由式(16)确定的孤岛检测阈值作比较，即可判断分布式发电系统是否发生孤岛。 The third harmonic voltage value is obtained by formula (26), and compared with the islanding detection threshold determined by formula (16), it can be judged whether islanding occurs in the distributed generation system.

本发明的一种基于相位扰动的分布式并网逆变器孤岛检测系统： A distributed grid-connected inverter island detection system based on phase disturbance of the present invention:

(1)在构造正交信号发生器产生两相正交电压v_α和v_β过程中，能够保证动态响应的快速性，同时构建的两相正交电压含有相同的总谐波畸变率，这就消除了两相正交电压中因谐波不平衡带来的锁相精度问题。按照本发明中的设计方案，对220V/50Hz的电网电压信号进行了必要的仿真验证。正交信号发生器的增益k按照式(4)以整定时间t_s＝10ms取值，图10和图11所示的仿真结果表明，经过10ms的整定时间，即可实现两相正交电压的构建。 (1) In the process of constructing the quadrature signal generator to generate the two-phase quadrature voltages v _α and v _β , the rapidity of the dynamic response can be guaranteed, and the constructed two-phase quadrature voltages at the same time contain the same total harmonic distortion rate, which means The phase-locking accuracy problem caused by harmonic imbalance in the two-phase quadrature voltage is eliminated. According to the design scheme in the present invention, the necessary simulation verification is carried out for the 220V/50Hz grid voltage signal. The gain k of the quadrature signal generator is taken according to formula (4) with a settling time t _s =10ms. The simulation results shown in Fig. 10 and Fig. 11 show that after a settling time of 10ms, the two-phase quadrature voltage can be realized Construct.

(2)图5中同步锁相器的频率自适应控制器消除了电网幅值变化对频率调整动态响应速度的影响。原因在于控制器的设计实现中添加了电压补偿器。按照图4所示的设计方案，对220V/50Hz的电网电压信号进行了必要的仿真。仿真过程中，设定电压幅值在t＝0.02s时刻由311V下降至249V，在t＝0.04s时刻，电网基波频率由50Hz降为45Hz，时间常数η设定为20ms，仿真结果如图12所示。从仿真结果上可以看出，设计方案中的频率自适应控制器可以保证频率自适应调整的动态响应时间能够摆脱电网幅值变化产生的影响，因此具有较快的响应速度。 (2) The frequency adaptive controller of the genlock in Fig. 5 eliminates the influence of the power grid amplitude change on the dynamic response speed of frequency adjustment. The reason is that a voltage compensator is added in the design and implementation of the controller. According to the design scheme shown in Figure 4, the necessary simulations have been carried out on the 220V/50Hz grid voltage signal. During the simulation process, the set voltage amplitude drops from 311V to 249V at t=0.02s, and at t=0.04s, the fundamental frequency of the power grid drops from 50Hz to 45Hz, and the time constant η is set to 20ms. The simulation results are shown in the figure 12 shown. It can be seen from the simulation results that the frequency adaptive controller in the design scheme can ensure that the dynamic response time of the frequency adaptive adjustment can get rid of the influence of the amplitude change of the power grid, so it has a faster response speed.

(3)注入的扰动相位对锁相输出及并网电流的影响。按照本发明提出的方案，进行了相关的仿真验证，仿真结果分别如图6和图7所示。图6和图7所示的仿真结果均显示出加入的相位扰动量不会改变过零点和峰值处的相位，但在其他位置则会产生一定程度的相位偏移，从而保证了分布式发电系统在并网运行模式下，即使受扰动相位的影响，仍然能够以单位功率因数稳定运行。这一点，可以从图7所示的仿真结果中直观地观察出来。 (3) The influence of the injected disturbance phase on the phase-locked output and grid-connected current. According to the solution proposed by the present invention, related simulation verification is carried out, and the simulation results are shown in Fig. 6 and Fig. 7 respectively. The simulation results shown in Figure 6 and Figure 7 both show that the added phase disturbance will not change the phase at the zero-crossing point and the peak point, but will produce a certain degree of phase shift at other positions, thus ensuring the distributed generation system In the grid-connected operation mode, it can still run stably with unity power factor even if it is affected by the disturbance phase. This point can be observed intuitively from the simulation results shown in Figure 7.

(4)孤岛检测的快速实现。为了更好地评估孤岛检测的性能，在弱电网(纯电感电网阻抗，L_g＝1.8mH)条件下进行了仿真测试。测试时间为0.3s，0.11s时刻逆变器工作状态由并网运行瞬时切换为孤岛运行。仿真参数设置如下：直流侧电压为400V，电网参数为220V/50Hz，电网内抗1.8mH，LC滤波器参数为5mH/47nF，开关管的开关频率为20kHz，采样频率为1kHz，相位扰动系数μ为0.06，频率自适应调整系数δ按照式(10)进行取值计算为δ＝7850。以下测试结果按照本地负载为纯电阻负载(R＝17.48Ω)和RLC并联负载两种情况依次给出，本地RLC并联负载的谐振频率设置为50Hz，负载的品质因数Q为2.5(相应参数设置为R＝174.8Ω，L＝220mH，C＝45μF)。两种测试负载情况下的仿真结果分别如图13、图14、图15和图16、图17、图18所示。从仿真图上可以看出，在纯电阻负载和RLC并联负载情况下，本发明中的孤岛检测算法可分别在70ms和50ms内迅速完成孤岛检测，并封锁逆变器，以上两种负载情形下的检测封锁时间均符合IEEE929-2000标准。 (4) Rapid implementation of island detection. In order to better evaluate the performance of the islanding detection, a simulation test is carried out under the condition of a weak grid (purely inductive grid impedance, L _g =1.8mH). The test time is 0.3s. At 0.11s, the working state of the inverter is switched from grid-connected operation to island operation instantaneously. The simulation parameters are set as follows: the DC side voltage is 400V, the power grid parameters are 220V/50Hz, the grid internal resistance is 1.8mH, the LC filter parameters are 5mH/47nF, the switching frequency of the switching tube is 20kHz, the sampling frequency is 1kHz, and the phase disturbance coefficient μ is 0.06, and the frequency adaptive adjustment coefficient δ is calculated as δ=7850 according to formula (10). The following test results are given in turn according to the two cases where the local load is a pure resistance load (R=17.48Ω) and an RLC parallel load. The resonant frequency of the local RLC parallel load is set to 50Hz, and the quality factor Q of the load is 2.5 (the corresponding parameters are set to R=174.8Ω, L=220mH, C=45μF). The simulation results under the two test load conditions are shown in Fig. 13, Fig. 14, Fig. 15 and Fig. 16, Fig. 17, and Fig. 18 respectively. As can be seen from the simulation diagram, under the conditions of pure resistance load and RLC parallel load, the islanding detection algorithm in the present invention can quickly complete the islanding detection within 70ms and 50ms respectively, and block the inverter. The detection blockage time is in line with the IEEE929-2000 standard.

Claims

1. based on a distributed grid-connected inverter alone island detection system for phase perturbation, for controlling single-phase distributed grid-connected electricity generation system, including and being sequentially connected in series: input connects DC bus-bar voltage (V respectively _dc) and setting DC bus standard voltage value (V _{dc_ref}) voltage controller (1), the reference amplitude (I of grid-connected current for voltage controller (1) is exported ^* _inv) with unitization grid-connected reference current (cos θ _inv ^*) being multiplied obtains grid-connected reference current (i ^* _inv) multiplier (2), grid-connected reference current (i for multiplier (2) is exported ^* _inv) get the grid-connected sample rate current (i of negative reality with polarity ^* _inv) adder (3) of suing for peace, current controller (4) and the pulse width modulation generator (5) that pulse width modulation exports four road start pulse signals (PWM1 ~ PWM4) of the single-phase H bridge inverter (A) driven in single-phase distributed grid-connected electricity generation system is carried out to the signal that current controller (4) exports, it is characterized in that, also include, be sequentially connected in series: input connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling (PCC), for generation of the orthogonal signal generator (6) of two-phase quadrature voltage, for the genlock device (7) at upper acquisition grid phase angle, orthogonal signal generator (6) output signal basis, for generation of the reference amplitude (I with grid-connected current ^* _inv) unitization grid-connected reference current (the cos θ that is multiplied _inv ^*) phase perturbation unit (8) and the threshold decision unit (9) based on jump Goertzel filter for carrying out voltage threshold judgement, wherein, the output of described phase perturbation unit (8) connects the input of multiplier (2).

2. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described orthogonal signal generator (6) includes the first adder (61) be connected in series successively, first amplifier (62), second adder (63) and first integrator (64), wherein, an input of described first adder (61) connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling (PCC) as the input of orthogonal signal generator (6), the output of first integrator (64) divides three tunnels: the first via is directly as the first output (v of orthogonal signal generator (6) _α), second tunnel polarity is connected with another input of first adder (61) after getting and bearing, the input of the 3rd tunnel connection and all-pass filter (65), the output of described all-pass filter (65) divides two-way: the first via is directly as the second output (v of orthogonal signal generator (6) _β), the second tunnel polarity is connected with another input of second adder (63) after getting and bearing.

3. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described genlock device (7) includes: the 3rd adder (75) be connected in series successively, the second amplifier (76), the 3rd multiplier (78), second integral device (79) and mod arithmetic unit (710), wherein, the output of described mod arithmetic unit (710) forms the output of genlock device (7), for exporting grid phase angle (θ _g), the input of described 3rd adder (75) connects the output of the first multiplier (72) and the second multiplier (74) respectively, and an input of described first multiplier (72) directly connects the first via output (v of orthogonal signal generator (6) _α), another input of the first multiplier (72) meets the first via output (v of orthogonal signal generator (6) in succession by the first second-order low-pass filter (71) _α), an input of the second multiplier (74) directly connects the second road output (v of orthogonal signal generator (6) _β), another input of the second multiplier (74) meets the second road output (v of orthogonal signal generator (6) in succession by the second second-order low-pass filter (73) _β), the input of described 3rd multiplier (78) also connects the output of voltage compensator (77), and the input of described voltage compensator (77) connects the output (v of the first second-order low-pass filter (71) respectively _{α L}) and the output (v of the second second-order low-pass filter (73) _{β L}).

4. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described phase perturbation unit (8) includes the 3rd amplifier (81), sine operation device (82), the 4th amplifier (83), the 4th adder (84) and the cos operation device (85) that are connected in series successively, wherein, input and another input of the 4th adder (84) of described 3rd amplifier (81) are connected the output (θ of genlock device (7) jointly _g), the output of described cos operation device (85) forms output (the cos θ of phase perturbation unit (8) _inv ^*) connect an input of described multiplier (2).

5. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 1, it is characterized in that, described islanding detect realizes unit (9) and includes the sample circuit (91) and jump Goertzel filter (92) that connect successively, wherein, the input of described sample circuit (91) connects the voltage end of single-phase distributed grid-connected electricity generation system point of common coupling (PCC), the output voltage (v of described jump Goertzel filter (92) _m(n)) as the detection voltage of single-phase distributed grid-connected electricity generation system, contrast with the voltage threshold set, as output voltage (v _m(n)) when being more than or equal to the voltage threshold of setting, pulse width modulation generator (5) does not export four road start pulse signals (PWM1 ~ PWM4), single-phase H bridge inverter (A) in single-phase distributed grid-connected electricity generation system does not work, as output voltage (v _m(n)) when being less than the voltage threshold of setting, pulse width modulation generator (5) exports four road start pulse signals (PWM1 ~ PWM4), single-phase H bridge inverter (A) work in single-phase distributed grid-connected electricity generation system.

6. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 5, it is characterized in that, described jump Goertzel filter (92) includes: the comb filter (921) be connected in series successively, slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922), 5th amplifier (923) and the 6th adder (924), wherein, the output of slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922) is divided into three tunnels again after the first delay cell (925): the first via connects an input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922) by the 6th amplifier (926), second tunnel by after the second delay cell (927) again polarity get another input of negative connection slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922), the 3rd direct polarity in tunnel gets negative rear another input connecting the 6th adder (924), the input of described comb filter (921) connects the output of sample circuit (91), the output of described 6th adder (924) forms the output voltage (v of jump Goertzel filter (92) _m(n)).

7. a kind of distributed grid-connected inverter alone island detection system based on phase perturbation according to claim 6, it is characterized in that, described comb filter (921) includes the 7th adder (9211), an input of described 7th adder (9211) directly connects the output of sample circuit (91), another input of 7th adder (9211) connects the output of sample circuit (91) by the 3rd delay cell (9212), the output of described 7th adder (9211) connects the input of slender acanthopanax musical instruments used in a Buddhist or Taoist mass (922).