WO2023077740A1 - 一种并网变流器直流电容同步控制系统及方法 - Google Patents

一种并网变流器直流电容同步控制系统及方法 Download PDF

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WO2023077740A1
WO2023077740A1 PCT/CN2022/088665 CN2022088665W WO2023077740A1 WO 2023077740 A1 WO2023077740 A1 WO 2023077740A1 CN 2022088665 W CN2022088665 W CN 2022088665W WO 2023077740 A1 WO2023077740 A1 WO 2023077740A1
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voltage
grid
control
power
amplitude
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尚磊
韩春伊
董旭柱
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武汉大学
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00—Adapting or protecting infrastructure or their operation
    • Y02A30/60—Planning or developing urban green infrastructure

Definitions

  • the invention belongs to the technical field of synchronous control of DC capacitors, in particular to a system and method for synchronous control of DC capacitors of grid-connected converters.
  • the frequency is determined by the rotor of the synchronous generator.
  • the rotor can provide frequency support, suppress frequency fluctuations, and stabilize the system.
  • frequency control technologies such as using phase-locked loops for vector control to achieve frequency adjustment.
  • This method provides accurate synchronization signals to the system, and generates internal feedback relative to the grid according to the feedback of the system (current, voltage).
  • Various physical quantities of electric potential enable the control system to stably adjust the frequency and voltage of the system.
  • the frequency control signal is obtained, and multiplied by the frequency quick response difference rate to get The power signals are exchanged, thereby performing frequency modulation.
  • the above method can realize the rapid response of the power station, actively reduce or increase the active power output, actively participate in frequency regulation, and can realize rapid frequency regulation according to commands.
  • the frequency modulation method using a phase-locked loop for vector control often has complex current-voltage coupling differential calculations, which greatly increases the complexity of control and the redundancy of calculations.
  • the use of virtual synchronous machines also requires power coupling, which adds complex control links.
  • the present invention provides a method of controlling the DC side capacitor voltage to enable the system to realize frequency adjustment without using phase-locked loop synchronization.
  • a method for synchronously controlling a DC capacitor of a grid-connected converter comprising the following steps:
  • Step 1 Use the AC voltage sensor to collect the terminal voltage U t of the grid inverter, use the AC current sensor to collect the terminal current I s , and use the park transformation to obtain u t ⁇ , u t ⁇ , is ⁇ , and is ⁇ ; the transformation formula is:
  • Step 2 Calculate and obtain the DC control signal ⁇ U dc : use the DC voltage sensor to collect the capacitor voltage as the DC voltage U dc , and obtain U dc ' through mathematical transformation.
  • the mathematical transformation refers to the transformation with U dc as the base and rational numbers as the exponent, namely Mathematical forms such as U dc 2 , U dc 3, etc. After that, the difference between U dc ' and the reference value U ref is made by the first adder to obtain the DC control signal ⁇ U dc ;
  • Step 3 pass the DC control signal ⁇ U dc obtained in step 2 through the DC voltage regulator to obtain the phase angle ⁇ of the internal potential;
  • Step 5 using the reactive power deviation ⁇ Q obtained in step 4 to obtain the internal potential amplitude E through the reactive voltage controller;
  • Step 6 Coupling the phase angle and amplitude of the reference voltage obtained in step 3 and step 5 to obtain a reference voltage V ref , which controls the inverter through the VSC link.
  • the method for obtaining the internal potential phase angle ⁇ described in step 3 is: the DC control signal ⁇ U dc passes through the transfer function G ⁇ (s) to obtain the equivalent internal potential phase angle ⁇ * , ⁇ * is added to the initial frequency value f init by the second adder to obtain the phase angle ⁇ of the internal potential.
  • the form of the transfer function G ⁇ (s) includes proportional control or proportional integral control.
  • the method for obtaining the amplitude of the internal potential described in step 5 is: the reactive power deviation is added to the rated deviation by the third adder, and the transfer function GE (s) is used to obtain The relative amplitude is added to the initialization amplitude V init by the fourth adder to obtain the reference voltage amplitude E, and the form of the transfer function GE (s) includes proportional control or proportional integral control.
  • the system adopting the above-mentioned synchronous control method for the DC capacitor of the grid-connected converter includes a DC capacitor, an inverter, a filter, and a grid connected in sequence, a computing unit connected between the filter and the grid, and a wireless grid connected to the computing unit.
  • the DC voltage regulator includes a first adder, a multiplier, and a second adder;
  • the reactive voltage controller includes a third adder, a multiplier, and a fourth adder device.
  • the above-mentioned grid-connected converter DC capacitor synchronous control system includes the DC capacitor for isolation and energy storage from DC to AC transmission; the inverter for converting from DC to AC; The filtered filter; the computing unit that realizes the instantaneous power calculation through the electric quantity information collected by the voltage and current sensor; realizes the DC voltage regulator whose input parameter is DC voltage and the output parameter is internal potential phase angle control; realizes that the input parameter is instantaneous without The reactive voltage controller whose power output parameter is controlled by the internal potential amplitude; the transfer function G ⁇ (s) characterizes the physical and mathematical relationship between the input and output parameters of the DC voltage regulator; The physical-mathematical relationship between the input and output parameters of the power-voltage controller.
  • the present invention solves the problems of complex energy support frequency adjustment and control and many algebraic loops in the traditional power system, and at the same time provides a solution to the system instability problem caused by the use of phase-locked loops under weak grid conditions.
  • this invention uses the DC capacitor voltage as the input, and generates the internal phase angle of the reference voltage through the DC voltage controller to realize the frequency synchronization of the system, realize the active participation of new energy in frequency modulation, and add voltage Control and solve frequency and voltage support problems.
  • Fig. 1 is a schematic diagram of an inverter grid-connected structure provided by an example of the present invention
  • Fig. 2 is a schematic diagram of a DC capacitance synchronous control strategy of an example of the present invention
  • Fig. 3 is a structural schematic diagram of a reactive voltage controller of an example of the present invention.
  • Fig. 4 is a structural schematic diagram of an example DC voltage regulator of the present invention.
  • Figure 5 is a basic schematic diagram of a potential amplitude regulator in one embodiment of the present invention.
  • Fig. 6 is a basic schematic diagram of an internal potential phase angle for DC voltage generation according to an embodiment of the present invention.
  • this embodiment uses the method of controlling the capacitor voltage on the DC side to make the system realize the frequency without using the phase-locked loop for synchronization. Adjustment function.
  • a grid-connected converter DC capacitor synchronous control system includes DC capacitors, inverters, filters, and power grids connected in sequence, connected to the filter
  • the computing unit between the inverter and the power grid, the reactive voltage controller connected to the computing unit, the DC voltage regulator connected to the DC capacitor, the reference voltage generator connected to the inverter, and the reference voltage generator connected to the DC voltage regulator respectively
  • the inverter is connected with the reactive voltage controller; it also includes an AC voltage sensor and an AC current sensor connected with the inverter, and a DC voltage sensor connected with the DC capacitor.
  • the DC voltage regulator includes: a first adder, a multiplier, and a second adder; the reactive voltage controller includes: a third adder, a multiplier, and a fourth adder.
  • This implementation is based on the control method of the DC capacitor synchronous control system of the grid-connected converter.
  • the real-time reactive power is obtained through the power calculation unit, and the DC capacitors are respectively obtained after transformation.
  • Control signal and reactive power control signal The DC control signal passes through the DC voltage regulator to obtain the phase angle ⁇ of the internal potential, and the reactive control signal passes through the reactive voltage controller to obtain the amplitude E of the internal potential.
  • the two are coupled to obtain a reference voltage, and the inverter is controlled by the VSC link. Control, to achieve control closed loop, so as to achieve frequency control.
  • the method for obtaining the internal potential phase angle in S3 is shown in Figure 4: the DC control signal ⁇ U dc passes through the transfer function G ⁇ (s) to obtain the equivalent internal potential phase angle ⁇ * , and ⁇ * passes through the second adder and the initial frequency value Finit is added to get the phase angle ⁇ of the internal potential.
  • the method for obtaining the amplitude of the internal potential in S5 is shown in Figure 3: the reactive power deviation is added to the rated deviation by the third adder, the relative amplitude is obtained through the transfer function G E (s), and the fourth adder and The initialization amplitude V init is added to obtain the reference voltage amplitude E.
  • a grid-connected converter DC capacitor synchronous control system a grid-connected system model of a capacitor voltage control strategy is established.
  • the grid-connected structure includes: DC voltage, DC capacitor, inverter, filter, AC voltage sensor, AC current sensor, DC voltage sensor, node load, integrator, DC voltage regulator, reactive voltage controller, reference voltage generator.
  • the control method based on the DC capacitor synchronous control system of the grid-connected converter, as shown in Figure 2, includes the following steps:
  • the collected terminal voltage U t and terminal current I s are calculated by the calculation unit to obtain the real-time reactive power Q e .
  • the real-time reactive power Qe is passed through the internal potential amplitude regulator to obtain the internal potential reference amplitude E, as shown in Figure 5, the process of obtaining the internal potential reference amplitude is as follows:
  • the control signal ⁇ Q of the potential amplitude regulator is obtained by adding the instantaneous reactive power and the reference reactive power.
  • the reference reactive power is taken as 0;
  • the obtained DC control signal ⁇ U dc is added to the reference frequency finit through an adder , and then the reference phase angle ⁇ ' is obtained through an integral link.
  • the reference frequency finit is set to 50Hz in this example, and the integral link coefficient is 100 ⁇ ;

Abstract

本发明涉及直流电容同步控制技术，具体涉及一种并网变流器直流电容同步控制系统及方法，该方法通过采集逆变器端电压、端电流、直流电容电压作为输入信号，通过功率计算单元获得实时无功功率，经过变换分别获得直流控制信号和无功控制信号。直流控制信号经过直流电压调节器得到内电势的相角δ，无功控制信号经过无功电压控制器得到内电势幅值E，两者经过耦合，得到参考电压，经过VSC环节对逆变器进行控制，实现控制闭环，从而实现频率控制。该控制方法使用直流电容电压为输入量，通过直流电压控制器产生参考电压内相角，实现系统的频率同步，实现新能源主动参与调频，加入电压控制、解决频率和电压支撑等问题。

Description

一种并网变流器直流电容同步控制系统及方法 技术领域
本发明属于直流电容同步控制技术领域，特别涉及一种并网变流器直流电容同步控制系统及方法。
背景技术
传统电力系统中，频率由同步发电机的转子决定，当电网频率出现扰动时，转子可提供频率支撑，抑制频率波动，使系统达到稳定。
近年来，随着新能源发电占比逐渐增高，导致电网中传统电力系统的转动惯量减小，电网的调频能力减弱，频率响应特性变差，电网频率控制问题日益突出，电网的频率问题时常发生。新能源发电频率响应速度慢，常常使得常规机组运行调频压力过大，且大量新能源接入电网往往会带来电网频率调节能力下降、电网对新能源适应性不足、多电力电子设备交互引起系统频率振荡等问题。因此制定适合新能源电站的调频方法尤为重要。
现在已有多种频率控制的技术，例如使用锁相环进行矢量控制实现频率调整，这种方法提供给系统准确的同步信号，根据系统的反馈量(电流、电压)，产生相对于电网的内电势的各种物理量，使控制系统能够稳定调节系统的频率和电压。使用虚拟同步技术，实现虚拟同步惯量的同时模拟同步机的调速机，实现调频。使用功率同步技术，结合有功频率下垂曲线进行频率快速响应，通过检测网侧频率，与额定频率动作门槛值相减，与额定频率做差，得到频率控制信号，乘频率快速响应调差率，得到交换功率信号，从而进行调频。以上方法可以实现电站的快速反应、主动减少或者增加有功输出，主动参与调频、能够根据命令实现快速调频。但是，使用锁相环进行矢量控制的调频方法往往存在复杂的电流电压耦合微分计算，大大增加了控制的复杂程度和计算的冗余程度。使用虚拟同步机同样需要进行功率耦合，增加复杂的控制环节。使用功率同步技术，在含大量新能源的电网当中对频率的支撑性不够，系统惯性不足，会对电网带来安全稳定运行的威胁。且在弱电网中，系统的惯性不足，锁相环的动态性能变差，会使系统失去稳定，影响供电质量和系统安全稳定运行。
发明内容
针对背景技术存在的问题，本发明提供一种利用控制直流侧电容电压使该系 统在不使用锁相环同步的情况下实现频率调节。
为解决上述技术问题，本发明采用如下技术方案：
一种并网变流器直流电容同步控制方法，包括以下步骤：
步骤1、使用交流电压传感器采集电网逆变器端电压U t，使用交流电流传感器采集端电流I s，使用park变换得到u tα、u tβ、i sα、i sβ；变换公式为：
Figure PCTCN2022088665-appb-000001
步骤2、计算获得直流控制信号ΔU dc：使用直流电压传感器采集电容电压为直流电压U dc，经数学变换得U dc'，该数学变换指以U dc为底，有理数为指数的变换，即
Figure PCTCN2022088665-appb-000002
U dc 2、U dc 3等数学形式，之后U dc'与参考值U ref经第一加法器做差，得到直流控制信号ΔU dc；
步骤3、将步骤2到的直流控制信号ΔU dc经过直流电压调节器得到内电势的相角δ；
步骤4、计算实时无功功率：根据式Q e＝-u tαi sβ+u tβi sα计算系统瞬时无功功率；将计算得到的无功功率与额定功率Q ref经第三加法器做差，得到功率偏差ΔQ；
步骤5、将步骤4得到的无功偏差ΔQ经无功电压控制器得到内电势幅值E；
步骤6、将步骤3与步骤5得到的参考电压相角和幅值进行耦合，得到参考电压V ref，参考电压V ref经VSC环节对逆变器进行控制。
在上述并网变流器直流电容同步控制方法中，步骤3所述得到内电势相角δ的方法为：直流控制信号ΔU dc经过传递函数G δ(s)得到等效内电势相角θ *，θ *通过第二加法器与频率初始值f init相加，得到内电势的相角δ，传递函数G δ(s)的形式包括比例控制或比例积分控制。
在上述并网变流器直流电容同步控制方法中，步骤5所述得到内电势幅值的方法为：无功偏差经第三加法器与额定偏差相加，经过传递函数G E(s)得到相对幅值，经第四加法器与初始化幅值V init相加得到参考电压幅值E，传递函数G E(s)的形式包括比例控制或比例积分控制。
在上述并网变流器直流电容同步控制系统的控制方法中，步骤6所述参考电压相角和幅值进行耦合的过程如下：利用参考电压幅值E和内电势相角δ经过计算式V d＝E*cos(δ)和V q＝E*sin(δ)得到在dq坐标轴下的值，再经过park反变换得到参考电压V ref。
采用上述的并网变流器直流电容同步控制方法的系统，包括依次连接的直流电容、逆变器、滤波器、电网，连接于滤波器与电网之间的计算单元，与计算单元连接的无功电压控制器，与直流电容器相连的直流电压调节器，与逆变器相连的参考电压生成器，参考电压生成器分别与直流电压调节器和无功电压控制器相连；还包括与逆变器相连的交流电压传感器和交流电流传感器，与直流电容相连的直流电压传感器。
在上述的并网变流器直流电容同步控制系统中，直流电压调节器包括第一加法器、乘法器、第二加法器；无功电压控制器包括第三加法器、乘法器和第四加法器。
在上述的并网变流器直流电容同步控制系统中，包括由直流输电到交流输电的隔离与能量存储的直流电容；由直流电到交流电的转换的逆变器；将变换器交流测的谐波滤除的滤波器；通过电压电流传感器采集的电量信息实现瞬时功率计算的计算单元；实现对输入参数为直流电压输出参数为内电势相角控制的直流电压调节器；实现对输入参数为瞬时无功功率输出参数为内电势幅值控制的无功电压控制器；传递函数G δ(s)表征了直流电压调节器输入输出参数之间的物理数学关系；传递函数G E(s)表征了无功电压控制器输入输出参数之间的物理数学关系。
与现有技术相比，本发明解决了传统电力系统能源支撑频率调节控制复杂，代数环多的问题，同时为弱电网工况下使用锁相环带来的系统不稳定问题提供了解决思路，改变传统使用锁相环进行系统频率同步的问题，本发明使用直流电容 电压为输入量，通过直流电压控制器产生参考电压内相角，实现系统的频率同步，实现新能源主动参与调频，加入电压控制、解决频率和电压支撑等问题。
附图说明
图1是本发明一个实例提供的逆变器并网结构示意图；
图2是本发明一个实例直流电容同步控制策略示意图；
图3是本发明一个实例无功电压控制器结构示意图；
图4是本发明一个实例直流电压调节器的结构示意图。
图5是本发明一个实施例内电势幅值调节器的基本示意图；
图6是本发明一个实施例直流电压生成内电势相角的基本示意图。
具体实施方式
下面将结合本发明实施例对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动的前提下所获得的所有其他实施例，都属于本发明保护的范围。
需要说明的是，在不冲突的情况下，本发明中的实施例及实施例中的特征可以相互组合。
下面结合具体实施例对本发明作进一步说明，但不作为本发明的限定。
为了解决现有的光伏主动参与系统调频控制策略的复杂性，冗余性等问题，本实施例利用控制直流侧电容电压的方法，使该系统在不使用锁相环进行同步的前提下实现频率调节功能。
本实施例是通过以下技术方案来实现的，如图1所示，一种并网变流器直流电容同步控制系统，包括依次连接的直流电容、逆变器、滤波器、电网，连接于滤波器与电网之间的计算单元，与计算单元连接的无功电压控制器，与直流电容器相连的直流电压调节器，与逆变器相连的参考电压生成器，参考电压生成器分别与直流电压调节器和无功电压控制器相连；还包括与逆变器相连的交流电压传感器和交流电流传感器，与直流电容相连的直流电压传感器。
而且，直流电压调节器包括：第一加法器、乘法器、第二加法器；无功电压控制器包括：第三加法器、乘法器和第四加法器。
本实施基于并网变流器直流电容同步控制系统的控制方法，通过采集逆变器 端电压、端电流、直流电容电压作为输入信号，通过功率计算单元获得实时无功功率，经过变换分别获得直流控制信号和无功控制信号。直流控制信号经过直流电压调节器得到内电势的相角δ，无功控制信号经过无功电压控制器得到内电势幅值E，两者经过耦合，得到参考电压，经过VSC环节对逆变器进行控制，实现控制闭环，从而实现频率控制。包括以下步骤：
S1，使用交流电压传感器采集电网逆变器端电压U t，使用交流电流传感器采集端电流I s，使用park变换得到u tα、u tβ、i sα、i sβ。需要说明的是，park变换是一种坐标变换，由abc坐标变换到dq0坐标当中。变换公式为：
Figure PCTCN2022088665-appb-000003
S2，计算获得直流控制信号ΔU dc：使用直流电压传感器采集电容电压为直流电压U dc，经数学变换得
Figure PCTCN2022088665-appb-000004
之后U dc'与参考值U ref经第一加法器做差，得到直流控制信号ΔU dc；
S3，将S2到的直流控制信号ΔU dc经过直流电压调节器得到内电势的相角δ；
S4：计算实时无功功率：根据式Q e＝-u tαi sβ+u tβi sα计算系统瞬时无功功率。将计算得到的无功功率与额定功率Q ref经第三加法器做差，得到功率偏差ΔQ；
S5，将S4得到的无功偏差ΔQ经无功电压控制器得到内电势幅值E；
S6，将S3与S5得到的参考电压幅值和相角进行耦合，得到参考电压V ref，参考电压经VSC环节对逆变器进行控制。
并且，S3得到内电势相角的方法如图4所示：直流控制信号ΔU dc经过传递函数G δ(s)得到等效内电势相角θ *，θ *通过第二加法器与频率初始值f init相加，得到内电势的相角δ。
并且，S5中得到内电势幅值的方法如图3所示：无功偏差经第三加法器与 额定偏差相加，经过传递函数G E(s)得到相对幅值，经第四加法器与初始化幅值V init相加得到参考电压幅值E。
并且，S6中耦合过程如下：利用E和δ经过计算式V d＝E*cos(δ)和V q＝E*sin(δ)得到在dq坐标轴下的值，再经过park反变换得到三相的考电压V ref。
具体实施时，一种并网变流器直流电容同步控制系统，建立电容电压控制策略的并网系统模型。如图1所示，并网结构包括：直流电压、直流电容、逆变器、滤波器、交流电压传感器、交流电流传感器、直流电压传感器、节点负荷、积分器、直流电压调节器、无功电压控制器、参考电压生成器。
基于并网变流器直流电容同步控制系统的控制方法，如图2所示，包括以下步骤：
1)使用直流电压传感器采集电容电压为直流电压U dc，使用交流电压传感器采集逆变器端电压U t，使用交流电流传感器采集逆变器端电流I s；
2)将采集得到的端电压U t和端电流I s经过计算单元计算得到实时无功功率Q e。将实时无功功率Q e经内电势幅值调节器得到内电势参考幅值E，如图5所示，得到内电势参考幅值的过程如下：
2.1)电势幅值调节器由瞬时无功功率与参考无功功率相加得控制信号ΔQ，在本例中取参考无功功率为0；
2.2)将无功控制信号ΔQ经过积分环节得到电势幅值E，取无功电压下垂系数K c为0.1，内电势幅值E的表达式为：
Figure PCTCN2022088665-appb-000005
3)将采集得到的直流电压U dc输送进直流电压调节器中，经过控制计算得到内电势的相角δ，如图6所示，得到内电势相角的过程如下：
3.1)将参考电压的平方减去直流电压U dc的平方得到直流控制信号ΔU dc，计算公式为ΔU dc＝1-U dc 2。其中，U dc使用标幺值，基准值U B在本例中为1200V， 则
Figure PCTCN2022088665-appb-000006
U dc'为实际直流电压值；
3.2)将得到的直流控制信号ΔU dc经过加法器与参考频率f init相加，之后通过积分环节得到参考相角δ'。其中参考频率f init在本例中设置为50Hz,积分环节系数为100π；
3.3)将得到的直流控制信号ΔU dc经比例环节后与参考相角δ'经加法器相加得到内电势相角δ。其中比例系数在本例中设置为10。即内电势相角计算方法为
Figure PCTCN2022088665-appb-000007
4)将得到的内电势相角δ和内电势幅值E经过参考电压生成器耦合成为三相参考电压V ref，随后作为控制信号控制逆变器的开断；
4.1)耦合过程如下：利用E和δ经过计算式V d＝E*cos(δ)和V q＝E*sin(δ)得到在dq坐标轴下的值，再经过park反变换得到三相的考电压V ref。
以上仅为本发明较佳的实施例，并非因此限制本发明的实施方式及保护范围，对于本领域技术人员而言，应当能够意识到凡运用本发明说明书内容所作出的等同替换和显而易见的变化所得到的方案，均应当包含在本发明的保护范围内。

Claims (7)

  1. 一种并网变流器直流电容同步控制方法，其特征在于：包括以下步骤：
    步骤1、使用交流电压传感器采集电网逆变器端电压U t，使用交流电流传感器采集端电流I s，使用park变换得到u tα、u tβ、i sα、i sβ；变换公式为：
    Figure PCTCN2022088665-appb-100001
    步骤2、计算获得直流控制信号ΔU dc：使用直流电压传感器采集电容电压为直流电压U dc，经数学变换得U dc'，该数学变换指以U dc为底，有理数为指数的变换，即
    Figure PCTCN2022088665-appb-100002
    U dc 2、U dc 3等数学形式，之后U dc'与参考值U ref经第一加法器做差，得到直流控制信号ΔU dc；
    步骤3、将步骤2到的直流控制信号ΔU dc经过直流电压调节器得到内电势的相角δ；
    步骤4、计算实时无功功率：根据式Q e＝-u tαi sβ+u tβi sα计算系统瞬时无功功率；将计算得到的无功功率与额定功率Q ref经第三加法器做差，得到功率偏差ΔQ；
    步骤5、将步骤4得到的无功偏差ΔQ经无功电压控制器得到内电势幅值E；
    步骤6、将步骤3与步骤5得到的参考电压相角和幅值进行耦合，得到参考电压V ref，参考电压V ref经VSC环节对逆变器进行控制。
  2. 根据权利要求1所述的并网变流器直流电容同步控制方法，其特征在于：步骤3所述得到内电势相角δ的方法为：直流控制信号ΔU dc经过传递函数G δ(s)得到等效内电势相角θ *，θ *通过第二加法器与频率初始值f init相加，得到内电势的相角δ，传递函数G δ(s)的形式包括比例控制或比例积分控制。
  3. 根据权利要求1所述的并网变流器直流电容同步控制方法，其特征在于：步骤5所述得到内电势幅值的方法为：无功偏差经第三加法器与额定偏差相加， 经过传递函数G E(s)得到相对幅值，经第四加法器与初始化幅值V init相加得到参考电压幅值E，传递函数G E(s)的形式包括比例控制或比例积分控制。
  4. 根据权利要求1所述的并网变流器直流电容同步控制方法，其特征在于：步骤6所述参考电压相角和幅值进行耦合的过程如下：利用参考电压幅值E和内电势相角δ经过计算式V d＝E*cos(δ)和V q＝E*sin(δ)得到在dq坐标轴下的值，再经过park反变换得到参考电压V ref。
  5. 一种采用权利要求1至4中任一项所述的并网变流器直流电容同步控制方法的系统，其特征在于：包括依次连接的直流电容、逆变器、滤波器、电网，连接于滤波器与电网之间的计算单元，与计算单元连接的无功电压控制器，与直流电容器相连的直流电压调节器，与逆变器相连的参考电压生成器，参考电压生成器分别与直流电压调节器和无功电压控制器相连；还包括与逆变器相连的交流电压传感器和交流电流传感器，与直流电容相连的直流电压传感器。
  6. 根据权利要求5所述的并网变流器直流电容同步控制系统，其特征在于：直流电压调节器包括第一加法器、乘法器、第二加法器；无功电压控制器包括第三加法器、乘法器和第四加法器。
  7. 根据权利要求5所述的并网变流器直流电容同步控制系统，其特征在于：包括由直流输电到交流输电的隔离与能量存储的直流电容；由直流电到交流电的转换的逆变器；将变换器交流测的谐波滤除的滤波器；通过电压电流传感器采集的电量信息实现瞬时功率计算的计算单元；实现对输入参数为直流电压输出参数为内电势相角控制的直流电压调节器；实现对输入参数为瞬时无功功率输出参数为内电势幅值控制的无功电压控制器；传递函数G δ(s)表征了直流电压调节器输入输出参数之间的物理数学关系；传递函数G E(s)表征了无功电压控制器输入输出参数之间的物理数学关系。
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