WO2023088124A1 - 基于模型预测虚拟同步机的逆变器频率自适应控制方法 - Google Patents
基于模型预测虚拟同步机的逆变器频率自适应控制方法 Download PDFInfo
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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
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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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
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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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
Definitions
- the invention belongs to the technical field of power electronics, and in particular relates to a model prediction virtual synchronous machine inverter control method considering the direction of frequency offset.
- microgrid As an effective form of distributed energy utilization, microgrid has the ability to transmit electric energy and provide grid support, and is an important way to effectively utilize renewable energy and an important supplement to large power grids.
- Microgrid has two modes of grid-connected operation and island operation. In the island mode, the microgrid loses the support of the large grid and can only rely on its internal distributed energy, micro gas turbines and energy storage to support the common bus voltage and frequency. Since the microgrid with distributed energy lacks the rotational kinetic energy of the synchronous generator in the large power grid, especially when the proportion of distributed energy gradually increases, the inertia of the microgrid decreases and the stability weakens.
- the virtual synchronous generator technology can simulate the electromechanical transient characteristics of the synchronous generator, so that the inverter in the island mode can have the external characteristics of the synchronous generator such as inertia, damping, primary frequency regulation, and reactive voltage regulation. Therefore, the virtual synchronous generator technology can effectively increase the system inertia and help to improve the stability of the microgrid in the island mode.
- the inertia set by the virtual synchronous machine is large, once the system frequency deviates from the fundamental frequency, it is difficult to return, which is not conducive to the adjustment of system power distribution.
- the inertia set by the virtual synchronous machine is small, the anti-disturbance ability of the microgrid is weak, and the system stability is poor. When switching loads, it is easy to cause system oscillation or even system instability, and the control effect is not good.
- the present invention provides a model-predicted virtual synchronous machine inverter control method considering the direction of frequency offset, which is used to improve system flexibility.
- the present invention discloses a model prediction virtual synchronous machine inverter control method considering the frequency offset direction, including:
- the way to obtain the absolute value of the current frequency based on the fundamental frequency of the inverter and the absolute value of the steady state based on the fundamental frequency is:
- Detect the system frequency output by the inverter in the island mode of the microgrid calculate the steady-state frequency of the system from the current power of the inverter, and determine the absolute value of the current frequency based on the fundamental frequency and the absolute value of the steady-state based on the fundamental frequency.
- the cost function considering the frequency offset state includes the minimization objective of the prediction domain of the frequency offset fluctuation value, and also includes the minimization objective of the prediction domain of the frequency regression fluctuation value.
- the assignment of the deviation state weight factor matrix, regression state weight factor matrix and power fluctuation penalty factor matrix is different;
- the optimization of the prediction domain output about the frequency regression fluctuation value is mainly achieved through assignment.
- the optimal virtual power is calculated according to the optimal virtual power increment value and the virtual power.
- the optimal virtual power after calculating the optimal virtual power, it also includes the step of correcting the optimal virtual power, judging whether the calculated optimal virtual power exceeds the optional range of virtual power, if it exceeds, then re-acquire the basic frequency based on the inverter The absolute value of the current frequency and the steady-state absolute value based on the fundamental frequency calculate the optimal virtual power again;
- the calculated optimal virtual power is directly input into the swing equation of the virtual synchronous machine, and the calculated virtual angular velocity is output to the integration link to adjust the frequency with the optimal virtual power.
- the present invention discloses a model prediction virtual synchronous machine inverter control system considering the direction of frequency offset, including:
- a frequency offset state judging module configured to obtain the absolute value of the current frequency based on the fundamental frequency of the inverter and the absolute value of the steady state based on the fundamental frequency;
- a frequency adjustment module configured to set a corresponding prediction output domain according to the frequency offset state, and construct a cost function considering the frequency offset state;
- the present invention considers the frequency offset state to achieve different frequency adjustment objectives, that is, when the frequency deviates from the base frequency, the frequency change rate is effectively reduced, so that the frequency Slowly offset; and when the frequency returns to the fundamental frequency from a non-fundamental value, it is effective to increase the frequency change rate quickly, so that the frequency returns quickly. Effectively improve the dynamic characteristics of the system frequency.
- the present invention realizes that the system frequency deviates from the fundamental frequency state or the system frequency by comparing the absolute value
- the method of judging the state of frequency regression to the fundamental frequency is simple and reliable.
- the present invention can effectively reduce the change rate of the system frequency and slow down the process of the system frequency deviating from the fundamental frequency when the system frequency moves to the deviated fundamental frequency direction.
- the present invention can effectively increase the change rate of the system frequency and accelerate the process of returning the system frequency to the fundamental frequency when the system frequency moves toward the returning fundamental frequency.
- the present invention realizes the frequency control considering the frequency offset state based on the predictive control of the virtual synchronous machine model, and is suitable for digital controllers, which has great significance for the application of inverters.
- Fig. 1 is a schematic control block diagram of an embodiment of the present invention
- Fig. 2 is a schematic diagram of judging an offset state according to an embodiment of the present invention.
- Figure 3 is the frequency waveform of the virtual synchronous generator method and the frequency waveform of this patent under different load switching states;
- Fig. 4 is a flow chart of model predictive control of a virtual synchronous generator according to an embodiment of the invention.
- the existing virtual synchronous generator technology used for inverters is difficult to return once the system frequency deviates from the fundamental frequency under the condition of large inertia.
- the anti-disturbance ability of the microgrid system is weak, and the system stability is poor, resulting in poor control effect.
- the present embodiment provides a model prediction virtual synchronous machine inverter control method considering the frequency offset direction.
- the model-predicted virtual synchronous machine inverter control method considering the direction of frequency offset in this embodiment, within one control cycle includes:
- Step 1 Detect the system frequency ⁇ m output by the inverter in the island mode of the microgrid, calculate the system steady-state frequency ⁇ ref from the current output power of the inverter, and the absolute value of the frequency based on the fundamental frequency
- the system frequency ⁇ m is the output frequency of the inverter
- the steady-state frequency ⁇ ref is obtained from the P- ⁇ curve of the droop control of the inverter.
- Step 2 In order to judge the system frequency offset state, compare the absolute value of the current frequency value ⁇ m based on the fundamental frequency
- Figure 2 shows the waveform of the system frequency and the absolute value of the frequency based on the fundamental frequency. It can be seen from the simulation results that under different load switching states, the system frequency is in a deviation state, and the absolute value of the frequency is less than the absolute value of the expected frequency; the system frequency is in the return state , the absolute value of the frequency is greater than the absolute value of the expected frequency.
- Step 3 According to the frequency offset state, set the corresponding prediction output domain, and construct a cost function considering the frequency offset state, which includes the minimization target of the prediction domain of the frequency offset fluctuation value, and also includes the minimization of the prediction domain of the frequency regression fluctuation value Target.
- j) of the frequency regression fluctuation value, set the expected value R b (k+1) [0 0 ... 0] T in the regression state.
- ⁇ m (k+1) ⁇ m (k+1)- ⁇ m (k)
- T s is the control period
- J is the moment of inertia
- P m is the virtual power
- P out is the output power
- D is the damping coefficient
- the prediction domain as p steps, assuming that the system reaches a stable state at the mth step. Furthermore, the prediction domain output W pd (j+1
- ⁇ ref is the expected value of the steady-state frequency.
- ⁇ d is the weight factor matrix of deviation state
- ⁇ b is the weight factor matrix of regression state
- Step 4 In order to achieve the frequency optimization control target under different offset states, the assignments of matrices ⁇ d , ⁇ b and ⁇ are different according to different frequency offset states.
- the weight factor and the penalty factor are assigned to calculate the optimal virtual power increment value in the frequency regression state, so as to accelerate the return of the system frequency ⁇ m to the fundamental frequency, effectively and quickly increase the frequency change rate, so as to realize about
- j) of the frequency regression fluctuation value ⁇ b is mainly optimized, and its assignment is as follows
- the optimal virtual power increment ⁇ P * (k) under different frequency offset states is calculated.
- Step 5 Calculate the optimal virtual power according to the optimal virtual power incremental value and virtual power, and its expression is
- the calculated virtual angular velocity ⁇ m is output to the integration link to realize the optimal virtual power adjustment frequency.
- the system frequency finally realizes the frequency adjustment considering the frequency offset state through the optimal virtual power injection virtual synchronous generation swing equation.
- the technical solution of the present invention includes establishment of a virtual synchronous machine incremental model, determination of system frequency offset status, cost function considering frequency offset status, optimization of virtual power increment, and virtual power adjustment frequency.
- the present invention uses the absolute value of the frequency offset based on the fundamental frequency to judge the system frequency offset state, and then sets the frequency optimization target under different frequency offset states.
- the invention considers the frequency offset direction, and realizes adjusting the system frequency by optimizing the virtual power in different offset states based on the model prediction method of the virtual synchronous machine.
- the frequency deviates from the fundamental frequency
- the frequency changes slowly to suppress the frequency deviation; and when the frequency returns to the fundamental frequency, the frequency change is accelerated to promote the frequency to quickly return to the fundamental frequency.
- the feature of model prediction and real-time optimization improves the control effect.
- the invention can solve the impact on the frequency when the load of the micro-grid is switched, the implementation method is simple and reliable, and has great significance for the application of the inverter.
- the invention is a real-time optimization process, realizes the optimal adjustment of the system frequency in the frequency deviation state and the frequency return state, and improves the performance of the inverter.
- the present invention is not limited to the specific actual requirements of the microgrid, and is not limited to the topology of the inverter, and is applicable to single-phase busbar and three-phase busbar forms of the microgrid.
- the present invention is not limited to the form of the DC side power supply of the inverter, and is applicable to different occasions such as low voltage, medium voltage, and high voltage, and has strong expansibility and practicability.
- Figure 3 shows the frequency waveform controlled by the fixed inertial virtual synchronous generator and the frequency waveform of the patented method. It can be seen from the simulation results that in different load switching states, when the frequency deviates from the fundamental frequency, the frequency deviation speed of the patented method Less than the frequency offset speed of the virtual synchronous generator; when the frequency returns to the fundamental frequency, the frequency offset speed of the patent method is greater than the frequency offset speed of the virtual synchronous generator.
- it also includes a virtual synchronous machine inverter, which is controlled by the above method to achieve different frequency adjustment goals, that is: when the frequency deviates from the base frequency, the frequency change rate is effectively reduced to slowly shift the frequency; And when the frequency returns to the fundamental frequency from the non-fundamental frequency value, it is effective to increase the frequency change rate quickly, so that the frequency returns quickly.
- a virtual synchronous machine inverter which is controlled by the above method to achieve different frequency adjustment goals, that is: when the frequency deviates from the base frequency, the frequency change rate is effectively reduced to slowly shift the frequency; And when the frequency returns to the fundamental frequency from the non-fundamental frequency value, it is effective to increase the frequency change rate quickly, so that the frequency returns quickly.
- the purpose of this embodiment is to provide a computing device, including a memory, a processor, and a computer program stored in the memory and operable on the processor, and the processor implements the steps of the above method when executing the program.
- the purpose of this embodiment is to provide a computer-readable storage medium.
- a computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, the steps of the above-mentioned method are executed.
- the purpose of this embodiment is to provide a model-predicted virtual synchronous machine inverter control system considering the frequency offset direction, including:
- a frequency offset state judgment module is used to obtain the absolute value of the current frequency based on the fundamental frequency of the inverter and the absolute value of the steady state based on the fundamental frequency;
- a frequency adjustment module configured to set a corresponding prediction output domain according to the frequency offset state, and construct a cost function considering the frequency offset state;
- the steps involved in the devices of the above embodiments 2, 3 and 4 correspond to the method embodiment 1, and for specific implementation, please refer to the relevant description of the embodiment 1.
- the term "computer-readable storage medium” shall be construed to include a single medium or multiple media including one or more sets of instructions; and shall also be construed to include any medium capable of storing, encoding, or carrying A set of instructions to execute and cause the processor to execute any method in the present invention.
- each module or each step of the present invention described above can be realized by a general-purpose computer device, optionally, they can be realized by a program code executable by the computing device, thereby, they can be stored in a memory
- the device is executed by a computing device, or they are made into individual integrated circuit modules, or multiple modules or steps among them are made into a single integrated circuit module for realization.
- the invention is not limited to any specific combination of hardware and software.
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Abstract
本发明提出了考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,包括:获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值;通过比较上述两个绝对值判断频率偏移状态:处于偏离基频的状态或回归基频的状态;根据频率偏移状态,设定相应预测输出域,构建考虑频率偏移状态的成本函数;基于所述成本函数计算最优虚拟功率增量值,继而计算最优虚拟功率,将最优虚拟功率输入至虚拟同步机的摆动方程,根据输出值进行频率调整。本发明在不更改虚拟同步发电机的转动惯量和阻尼系数的前提下,考虑频率偏移状态实现不同的频率调节目标。
Description
本发明要求于2021年11月17日提交中国专利局、申请号为202111361656.2、发明名称为“考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法”的中国专利申请的优先权,其全部内容通过引用结合在本发明中。
本发明属于电力电子技术领域,尤其涉及考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法。
本部分的陈述仅仅是提供了与本发明相关的背景技术信息,不必然构成在先技术。
作为分布式能源的有效利用形式,微电网具有传输电能和提供电网支撑的能力,是可再生能源有效利用的重要途径和大电网的重要补充。微电网具有并网运行和孤岛运行两种模式。孤岛模式下,微电网失去大电网支撑,仅能依靠其内部的分布式能源、微型燃气轮机和储能来支撑公共母线电压和频率。由于含分布式能源的微电网缺乏像大电网中同步发电机的旋转动能,特别是当分布式能源比例逐渐增加时,微电网惯量随之降低,稳定性减弱。而虚拟同步发电机技术能够模拟同步发电机的机电暂态特性,使孤岛模式下逆变器具有同步发电机组的惯性、阻尼、一次调频、无功调压等外特性。因此,虚拟同步发电机技术能有效增加***惯性,有助于提升孤岛模式下微电网的稳定性。
发明人在研究中发现,传统的虚拟同步发电机技术中惯性参数固定,难以适应复杂的微电网环境。当虚拟同步机设定的惯性较大时,***频率一旦偏离基频就很难返回,不利于***功率分配调节。相反,当虚拟同步 机设定的惯性较小时,微电网的抗扰能力弱,***稳定性差,负荷投切时易导致***振荡甚至***失稳,控制效果不佳。
发明内容
为克服上述现有技术的不足,本发明提供了考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,用于提升***弹性。
为实现上述目的,本发明的一个或多个实施例提供了如下技术方案:
第一方面,本发明公开了考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,包括:
获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值;
通过比较上述两个绝对值判断频率偏移状态:处于偏离基频的状态或回归基频的状态;
根据频率偏移状态,设定相应预测输出域,构建考虑频率偏移状态的成本函数;
基于所述成本函数计算最优虚拟功率增量值,继而计算最优虚拟功率,将最优虚拟功率输入至虚拟同步机的摆动方程,根据输出值进行频率调整。
作为进一步的实施方式,获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值的方式为:
检测微电网孤岛模式下逆变器输出的***频率,由逆变器当前功率计算***稳态频率,确定基于基频的当前频率绝对值和基于基频的稳态绝对值。
作为进一步的实施方式,判断频率偏移状态时,基于基频的当前频率绝对值小于基于基频的稳态绝对值时,处于偏离基频的状态;
基于基频的当前频率绝对值大于基于基频的稳态绝对值时,处于回归基频的状态。
作为进一步的实施方式,所述考虑频率偏移状态的成本函数包含频率偏移波动值的预测域最小化目标,也包含频率回归波动值预测域最小化目 标。
作为进一步的实施方式,根据频率偏移状态不同,偏离状态权重因子矩阵、回归状态权重因子矩阵及功率波动惩罚因子矩阵的赋值不同;
其中,频率偏离状态下,通过赋值以实现关于频率偏离波动值的预测域输出最优化为主;
频率回归状态下,通过赋值以实现关于频率回归波动值的预测域输出最优化为主。
作为进一步的实施方式,根据最优虚拟功率增量值和虚拟功率计算最优虚拟功率。
作为进一步的实施方式,计算最优虚拟功率之后还包括校正最优虚拟功率的步骤,判断计算的最优虚拟功率是否超出虚拟功率可选范围,如超出,则重新获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值,再次计算最优虚拟功率;
否则,直接将计算得到的最优虚拟功率输入到虚拟同步机的摆动方程中,将计算得到虚拟角速度输出到积分环节,进行最优虚拟功率调整频率。
第二方面,本发明公开了考虑频率偏移方向的模型预测虚拟同步机逆变器控制***,包括:
频率偏移状态判断模块,用于获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值;
通过比较上述两个绝对值判断频率偏移状态:处于偏离基频的状态或回归基频的状态;
频率调整模块,用于根据频率偏移状态,设定相应预测输出域,构建考虑频率偏移状态的成本函数;
基于所述成本函数计算最优虚拟功率增量值,继而计算最优虚拟功率,将最优虚拟功率输入至虚拟同步机的摆动方程,根据输出值进行频率调整。
以上一个或多个技术方案存在以下有益效果:
1、本发明在不更改虚拟同步发电机的转动惯量和阻尼系数的前提下,考虑频率偏移状态实现不同的频率调节目标,即:当频率偏离基频时,有效降低频率变化速率,使频率缓慢偏移;而当频率从非基频值回归基频时,有效快提高频率变化速率,使频率快速回归。有效提升***频率的动态特性。
2、本发明通过比较当前频率值基于基频的绝对值|ω
m0(k)|和稳态频率值基于基频的绝对值|ω
ref0(k)|,实现***频率偏离基频状态或者***频率回归基频状态的判断,方法简单可靠。
3、本发明基于模型预测方法,在***频率向偏离的基频方向移动时,能够有效的降低***频率的变化率,减缓***频率偏离基频的过程。
4、本发明基于模型预测方法,在***频率向回归的基频方向移动时,能够有效的提高***频率的变化率,加速***频率回归基频的过程。
5、本发明在离散域下,基于虚拟同步机模型预测控制实现考虑频率偏移状态的频率控制,适用于数字控制器,这对逆变器的应用具有很大的意义。
本发明附加方面的优点将在下面的描述中部分给出,部分将从下面的描述中变得明显,或通过本发明的实践了解到。
构成本发明的一部分的说明书附图用来提供对本发明的进一步理解,本发明的示意性实施例及其说明用于解释本发明,并不构成对本发明的不当限定。
图1为本发明实施例示意控制框图;
图2为本发明实施例的偏移状态判断示意图;
图3为不同负载切换状态下,采用虚拟同步发电机方法频率波形和采用本专利的频率波形;
图4为发明实施例的虚拟同步发电机模型预测控制流程图。
应该指出,以下详细说明都是示例性的,旨在对本发明提供进一步的说明。除非另有指明,本文使用的所有技术和科学术语具有与本发明所属技术领域的普通技术人员通常理解的相同含义。
需要注意的是,这里所使用的术语仅是为了描述具体实施方式,而非意图限制根据本发明的示例性实施方式。
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。
实施例一
正如背景技术所介绍的,现有用于逆变器的虚拟同步发电机技术在大惯性条件下,***频率一旦偏离基频就很难返回。而在小惯性条件下,微电网***抗扰能力弱,***稳定性差,导致其控制效果不佳。为解决此问题,本实施例提供了一种考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法。
具体地,如图1和图4所示,本实施例的考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,在一个控制周期内,其包括:
步骤1:检测微电网孤岛模式下逆变器输出的***频率ω
m,由逆变器当前输出功率计算***稳态频率ω
ref,基于基频的频率绝对值|ω
m0(k)|是***频率ω
m与基频ω
0差值的绝对值;基于基频的稳态频率绝对值|ω
ref0(k)|是稳态频率ω
ref与基频ω
0差值的绝对值。
具体的,确定基于基频ω
0的第k时刻频率绝对值|ω
m0(k)|和基于基频ω
0的稳态绝对值|ω
ref0(k)|,其计算公式如下
在该步骤中,***频率ω
m为逆变器的输出频率,稳态频率ω
ref由逆变器的下垂控制的P-ω曲线得到。
步骤2:为判断***频率偏移状态,比较当前频率值ω
m基于基频的绝对值|ω
m0(k)|和稳态频率值ω
ref基于基频的绝对值|ω
ref0(k)|,其判定公式如下
为实现考虑频率偏移转状态的频率控制,需要判断***频率当前状态。
当|ω
m0(k)|-|ω
ref0(k)|<0时,判定***频率ω
m处于偏离基频状态;
当|ω
m0(k)|-|ω
ref0(k)|>0时,判定***频率ω
m处于返回基频状态。
图2为***频率和基于基频的频率绝对值波形,由仿真结果可以看到,在不同负载切换状态下,***频率处于偏离状态下,频率绝对值小于期望频率绝对值;***频率处于返回状态下,频率绝对值大于期望频率绝对值。
步骤3:根据频率偏移状态,设定相应预测输出域,构建考虑频率偏移状态的成本函数,即包含频率偏移波动值的预测域最小化目标,也包含频率回归波动值预测域最小化目标。
其中,当***频率ω
m处于偏离基频状态时,构建频率偏移波动值的预测域输出W
pd(j+1|j),即由j时刻预测j+1时刻值(j=k;k+1…),设定偏离状态下的期望值R
d(k+1)=[0 0 ... 0]
T(k+1时刻期望值);当***频率ω
m处于回归基频状态时,构建频率回归波动值的预测域输出W
pb(j+1|j),设定回归状态下的期望值R
b(k+1)=[0 0 ... 0]
T。
进而,通过优化增量型模型中虚拟功率增量值,实现不同状态下***频率ω
m的有效调节。
为适应频率偏离状态下和频率回归状态下不同的优化目标,构建考虑频率偏移状态的成本函数F
p。
下面详细说明推导过程:
由虚拟同步发电机技术摆动方程的离散模型推导出增量型模型,其计算公式如下:
Δω
m(k+1)=ω
m(k+1)-ω
m(k)
=A
eΔω
m(k)+B
uΔP
m(k)+B
dΔP
out(k)
1).当***频率偏离基频状态时,定义频率偏移波动值ω
d为
ω
d(j)=ω
m(j)-ω
m(k)(j=k,k+1,...,p)
定义预测域为p步,假设第m步***到达稳定状态。进而,则关于频率偏移波动值ω
d的预测域输出W
pd(j+1|j)为
W
pd(j+1|j)=S
xΔω
d(j)+Iω
d(j)+S
dΔP
out(j)+S
uΔP(j)
2).当频率从偏离值回归基频时,定义频率回归波动值ω
b为
ω
b(j)=ω
m(j)-ω
ref j=k,k+1,...,p
其中,ω
ref为稳态频率期望值。
进而,关于频率回归波动值ω
b的预测域输出W
pb(j+1|j)为
W
pb(j+1|j)=S
xΔω
b(j)+Iω
b(j)+S
dΔP
out(j)+S
uΔP(j)
因此,当频率偏离基频时,为实现频率缓慢偏移,频率偏离波动值ω
d的预测域输出W
pd(j+1|j)应是0,即R
d(k+1)=[0 0 ... 0]
T;当频率从偏离值回归基频时,为实现频率加速回归,频率回归波动值ω
b的预测域输出W
pb(j+1|j)是0,即R
b(k+1)=[0 0 ... 0]
T。
进而,将关于频率偏离波动值ω
d的预测域输出W
pd(j+1|j)和关于频率回归波动值ω
b的预测域输出W
pb(j+1|j)整合,构建考虑频率偏移状态的成本函数如下
F
p=min{||Γ
dW
pd(k+1∣k)-R
d(k+1)||
2+||Γ
bW
pb(k+1∣k)-R
b(k+1)||
2+||Γ
pΔP(k)||
2}
其中,Γ
d为偏离状态权重因子矩阵,Γ
b为回归状态权重因子矩阵,Γ功率波动惩罚因子矩阵。
步骤4:为实现不同偏移状态下的频率优化控制目标,根据频率偏移状态不同,矩阵Γ
d、Γ
b和Γ的赋值有所不同。
当***频率偏离基频状态时,赋值以优化频率变化率最小的权重因子和惩罚因子,计算频率偏移状态下最优虚拟功率增量值,减缓***频率ω
m的偏离,有效降低频率变化速率。
具体的,频率偏离状态下,以实现关于频率偏离波动值ω
d的预测域输出W
pd(j+1|j)最优化为主,其赋值如下
当频率回归基频状态时,赋值以优化稳态值与频率的差值最小的权重因子和惩罚因子,计算最优虚拟功率增量值。
具体的,***频率回归基频状态下,赋值权重因子和惩罚因子来计算频率回归状态下最优虚拟功率增量值,加速***频率ω
m回归基频,有效快提高频率变化速率,以实现关于频率回归波动值ω
b的预测域输出W
pb(j+1|j)最优化为主,其赋值如下
根据极值理论,计算不同频率偏移状态下的最优化虚拟功率增量 ΔP
*(k)。
步骤5:根据最优虚拟功率增量值和虚拟功率计算最优虚拟功率,其表达式为
P
*(k)=ΔP
*(k)+P(k)
为保证***的可靠性,需判定最优虚拟功率P
*(k)是否超过其可调范围,在校正虚拟功率的正确性,是否超出虚拟功率可选范围,如错误,则返回步骤1;否则,将计算得到的虚拟功率输入到虚拟同步机的摆动方程中,即
将计算得到虚拟角速度ω
m输出到积分环节,实现最优虚拟功率调整频率。
本发明中,***频率最终是通过最优虚拟功率注入虚拟同步发电摆动方程实现考虑频率偏移状态的频率调节。
需要说明的是,本发明技术方案包括虚拟同步机增量模型建立、***频率偏移状态判定、考虑频率偏移状态的成本函数、虚拟功率增量的优化、虚拟功率调整频率。本发明采用基于基频的频率偏移绝对值来判定***频率偏移状态,进而设定不同频率偏移状态下的频率优化目标。
本发明考虑频率偏移方向,基于虚拟同步机的模型预测方法,实现通过优化不同偏移状态下虚拟功率来调节***频率。当频率偏离基频时,频率变化缓慢以抑制频率偏移;而当频率回归基频时,加快频率变化以促使频率快速返回基频。同时,模型预测实时优化的特点提升了控制效果。本发明能够解决微电网负载投切时对频率的影响,实施方法简单可靠,对逆变器的应用具有很大的意义。
本发明是实时优化过程,在频率偏离状态和频率回归状态下实现***频率的最优调节,提升逆变器性能。
另外,本发明不局限于特定的微电网实际需求,不局限于逆变器拓扑, 适用于微电网单相母线和三相母线形式。同时,本发明不局限于逆变器直流侧电源形式,适用于用低压、中压、高压等不同场合,具有较强的扩展性和实用性。
仿真案例
图3为采用固定惯性虚拟同步发电机控制的频率波形和本专利方法的频率波形,由仿真结果可以看到,在不同负荷切换状态下,当频率偏离基频时,本专利方法频率偏移速度小于虚拟同步发电机频率偏移速度;当频率返回基频时,本专利方法频率偏移速大于虚拟同步发电机频率偏移速度。
通过以上仿真结果可知,本发明提出的考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法可以有效提升逆变器调节频率动态特性能力。
在另一实施例子中,还包括虚拟同步机逆变器,采用上述方法进行控制,实现不同的频率调节目标,即:当频率偏离基频时,有效降低频率变化速率,使频率缓慢偏移;而当频率从非基频值回归基频时,有效快提高频率变化速率,使频率快速回归。
实施例二
本实施例的目的是提供一种计算装置,包括存储器、处理器及存储在存储器上并可在处理器上运行的计算机程序,所述处理器执行所述程序时实现上述方法的步骤。
实施例三
本实施例的目的是提供一种计算机可读存储介质。
一种计算机可读存储介质,其上存储有计算机程序,该程序被处理器执行时执行上述方法的步骤。
实施例四
本实施例的目的是提供考虑频率偏移方向的模型预测虚拟同步机逆变器控制***,包括:
频率偏移状态判断模块,用于获得基于逆变器基频的当前频率绝对值 和基于基频的稳态绝对值;
通过比较上述两个绝对值判断频率偏移状态:处于偏离基频的状态或回归基频的状态;
频率调整模块,用于根据频率偏移状态,设定相应预测输出域,构建考虑频率偏移状态的成本函数;
基于所述成本函数计算最优虚拟功率增量值,继而计算最优虚拟功率,将最优虚拟功率输入至虚拟同步机的摆动方程,根据输出值进行频率调整。
以上实施例二、三和四的装置中涉及的各步骤与方法实施例一相对应,具体实施方式可参见实施例一的相关说明部分。术语“计算机可读存储介质”应该理解为包括一个或多个指令集的单个介质或多个介质;还应当被理解为包括任何介质,所述任何介质能够存储、编码或承载用于由处理器执行的指令集并使处理器执行本发明中的任一方法。
本领域技术人员应该明白,上述本发明的各模块或各步骤可以用通用的计算机装置来实现,可选地,它们可以用计算装置可执行的程序代码来实现,从而,可以将它们存储在存储装置中由计算装置来执行,或者将它们分别制作成各个集成电路模块,或者将它们中的多个模块或步骤制作成单个集成电路模块来实现。本发明不限制于任何特定的硬件和软件的结合。
上述虽然结合附图对本发明的具体实施方式进行了描述,但并非对本发明保护范围的限制,所属领域技术人员应该明白,在本发明的技术方案的基础上,本领域技术人员不需要付出创造性劳动即可做出的各种修改或变形仍在本发明的保护范围以内。
Claims (10)
- 考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,其特征是,包括:获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值;通过比较上述两个绝对值判断频率偏移状态:处于偏离基频的状态或回归基频的状态;根据频率偏移状态,设定相应预测输出域,构建考虑频率偏移状态的成本函数;基于所述成本函数计算最优虚拟功率增量值,继而计算最优虚拟功率,将最优虚拟功率输入至虚拟同步机的摆动方程,根据输出值进行频率调整。
- 如权利要求1所述的考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,其特征是,获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值的方式为:检测微电网孤岛模式下逆变器输出的***频率,由逆变器当前功率计算***稳态频率,确定基于基频的当前频率绝对值和基于基频的稳态绝对值。
- 如权利要求1所述的考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,其特征是,判断频率偏移状态时,基于基频的当前频率绝对值小于基于基频的稳态绝对值时,处于偏离基频的状态;基于基频的当前频率绝对值大于基于基频的稳态绝对值时,处于回归基频的状态。
- 如权利要求1所述的考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,其特征是,所述考虑频率偏移状态的成本函数包含频率偏移 波动值的预测域最小化目标,也包含频率回归波动值预测域最小化目标;优选的,根据频率偏移状态不同,偏离状态权重因子矩阵、回归状态权重因子矩阵及功率波动惩罚因子矩阵的赋值不同;其中,频率偏离状态下,通过赋值以实现关于频率偏离波动值的预测域输出最优化为主;频率回归状态下,通过赋值以实现关于频率回归波动值的预测域输出最优化为主。
- 如权利要求1所述的考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,其特征是,根据最优虚拟功率增量值和虚拟功率计算最优虚拟功率。
- 如权利要求1-5任一所述的考虑频率偏移方向的模型预测虚拟同步机逆变器控制方法,其特征是,计算最优虚拟功率之后还包括校正最优虚拟功率的步骤,判断计算的最优虚拟功率是否超出虚拟功率可选范围,如超出,则重新获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值,再次计算最优虚拟功率;否则,直接将计算得到的最优虚拟功率输入到虚拟同步机的摆动方程中,将计算得到虚拟角速度输出到积分环节,进行最优虚拟功率调整频率。
- 考虑频率偏移方向的模型预测虚拟同步机逆变器控制***,其特征是,包括:频率偏移状态判断模块,用于获得基于逆变器基频的当前频率绝对值和基于基频的稳态绝对值;通过比较上述两个绝对值判断频率偏移状态:处于偏离基频的状态或 回归基频的状态;频率调整模块,用于根据频率偏移状态,设定相应预测输出域,构建考虑频率偏移状态的成本函数;基于所述成本函数计算最优虚拟功率增量值,继而计算最优虚拟功率,将最优虚拟功率输入至虚拟同步机的摆动方程,根据输出值进行频率调整。
- 一种计算装置,包括存储器、处理器及存储在存储器上并可在处理器上运行的计算机程序,其特征是,所述处理器执行所述程序时实现上述权利要求1-6任一所述方法的步骤。
- 一种计算机可读存储介质,其上存储有计算机程序,其特征是,该程序被处理器执行时执行上述权利要求1-6任一所述方法的步骤。
- 虚拟同步机逆变器,采用上述权利要求1-6任一所述方法进行控制,进行不同的频率调节目标。
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