A method for suppressing subsynchronous oscillation of power grid

Abstract

The present invention provides a method for suppressing subsynchronous oscillations of a power grid, and the method includes a subsynchronous oscillation detection algorithm for a power grid and a subsynchronous oscillation suppression algorithm for a power grid. The method obtains the subsynchronous component contained in the voltage of the power grid system and each modal frequency in the subsynchronous component by calculating the subsynchronous oscillation detection algorithm for the power grid; then calculates the current control command required by the suppression device by the subsynchronous oscillation suppression algorithm for the power grid; and injects the command current into the power grid by the suppression device to improve the damping of the characteristic frequency of the system. The method of the present invention can detect the subsynchronous component in the power grid, extract the characteristic frequency, calculate the required current command by the suppression algorithm, and inject the command current into the power grid by the suppression device, thereby improving the damping characteristics of the power grid at the characteristic frequency, thereby eliminating the accelerated attenuation of the subsynchronous oscillation of the power grid, and slowing down and eliminating the risk of subsynchronous resonance of the power grid.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering and automation technology, and in particular to a method for suppressing subsynchronous oscillation of a power grid. Background Art

[0002] Subsynchronous oscillation is one of the common hazards in power grids. In recent years, with the development of power systems, subsynchronous oscillation has become common. In many areas, thermal power plant generators have caused subsynchronous resonance and oscillation due to the transformation of the series compensation and DC transmission systems of nearby lines, which has seriously affected the safe and stable operation of power plants. The subsynchronous oscillation has caused frequent unit tripping incidents in power plants. At the same time, the rapid development of wind power and new energy has also derived similar subsynchronous oscillation problems, which has greatly restricted the development of new energy, and even caused serious consequences.

[0003] In order to avoid serious consequences of subsynchronous oscillation in power grids, various measures have been used in engineering practice to suppress the occurrence of subsynchronous oscillation, such as SSR-DS, GTSDC, SEDC and other equipment.

[0004] Existing subsynchronous oscillation suppression devices are all used to protect specific areas and suppress characteristic frequency oscillations. Most of them use speed signals to calculate suppression instructions through modal filters. Subsynchronous suppression signals are injected into the machine end or excitation through a controllable current source or voltage source to generate positive damping to suppress the subsynchronous oscillation of the generator.

[0005] However, the traditional method of suppressing subsynchronous oscillations is only effective for the characteristic frequencies of specific devices in the system and does not fundamentally solve the subsynchronous oscillation problem of the system. At the same time, with the increase in the number of suppression devices, there is a great risk of resonance between the suppression devices without unified coordination, which affects the ultimate suppression effect.

[0006] Therefore, the inventors have proposed a method for detecting and suppressing subsynchronous oscillations in a power grid system, and from the perspective of the power grid system, comprehensively manage the subsynchronous oscillation problem in the system. Summary of the invention

[0007] In order to solve the technical problems raised by the background technology, the present invention provides a method for suppressing subsynchronous oscillations of a power grid, which can detect subsynchronous components in the power grid, extract characteristic frequencies, calculate the required current instructions through a suppression algorithm, and inject command currents into the power grid through a suppression device, thereby improving the damping characteristics of the power grid at the characteristic frequency, thereby eliminating the accelerated attenuation of subsynchronous oscillations of the power grid, and mitigating and eliminating the risk of subsynchronous resonance of the power grid.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for suppressing subsynchronous oscillation of a power grid, the method comprising a subsynchronous oscillation detection algorithm for a power grid and a subsynchronous oscillation suppression algorithm for a power grid. The method obtains the subsynchronous component contained in the voltage of the power grid system and each modal frequency in the subsynchronous component by calculating the subsynchronous oscillation detection algorithm for the power grid; then calculates the current control command required by the suppression device by the subsynchronous oscillation suppression algorithm for the power grid; and injects the command current into the power grid by the suppression device to improve the damping of the system characteristic frequency.

[0010] The subsynchronous oscillation detection algorithm of the power grid includes: the grid voltage Uabc is transformed into the system voltage Ud in the dq coordinate system, Ud is passed through a low-pass filter LPF to obtain the voltage amplitude Ud1, and a subtractor is passed to obtain the subsynchronous component Um=Ud-Ud1. At this time, the subsynchronous component Um is calculated through discrete Fourier DFT to obtain multiple subsynchronous component modulus values, and then the various modal frequencies in the system are calculated through frequency sweep analysis.

[0011] The low pass filter LPF uses a low pass filter below 5 Hz.

[0012] The subsynchronous oscillation suppression algorithm of the power grid includes: passing the subsynchronous component Um of the power grid system voltage through the first bandpass filter BPF1 to extract the first system modal component, and then passing it through the proportional phase shifter to calculate the suppression current instruction Iqref1 required for the first mode; correspondingly, according to the number of modal frequencies n calculated by the subsynchronous oscillation detection algorithm of the power grid, the subsynchronous component Um of the power grid system voltage is passed through the second to nth bandpass filters BPF2~BPFn, and finally n system modal components are extracted, and finally the total current control instruction Iqref is obtained through instruction distribution calculation.

[0013] The command allocation calculation is as follows: summing up each modal suppression current command Iqref1...Iqrefn, that is, The coefficient allocation and addition calculation can also be performed according to the capacity requirements of each mode, that is,

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1) The present invention is different from the traditional subsynchronous oscillation suppression method. It does not suppress subsynchronous oscillations for a certain power plant or generator set, so there is no need for a speed signal. Instead, it monitors the voltage of the power grid system to comprehensively manage the subsynchronous oscillation problem in the power grid. The present invention innovatively comprehensively manages the subsynchronous oscillation problem of the generator sets in the power grid. The traditional method of suppressing subsynchronous oscillations of generator sets only suppresses the modal subsynchronous oscillation of a single generator set in a certain power plant, while multiple generator sets in multiple power plants in the power grid system often have subsynchronous oscillation problems. The present method calculates the subsynchronous component contained in the power grid system voltage and each modal frequency in the subsynchronous component through the power grid subsynchronous oscillation detection algorithm; then calculates the current control command required by the suppression device through the power grid subsynchronous oscillation suppression algorithm; injects the command current into the power grid through the suppression device to improve the damping of the system characteristic frequency;

[0016] 2) Compared with traditional subsynchronous oscillation suppression, the present invention does not require a speed signal, so there is no need to connect a speed probe to each generator set, which reduces production costs, while reducing external access equipment for the generator sets, reducing equipment downtime and maintenance time, and improving production efficiency. At the same time, the present invention conducts comprehensive management of subsynchronous oscillations of all generator sets in the system, greatly reducing the number of suppression devices that need to be connected to the system to suppress subsynchronous oscillations, and greatly reducing the cost of managing subsynchronous oscillation problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of the system structure of an embodiment of the present invention;

[0018] Figure 2 is a schematic diagram of a subsynchronous oscillation detection algorithm of the present invention;

[0019] Figure 3 Schematic diagram of the subsynchronous oscillation suppression algorithm of the present invention. DETAILED DESCRIPTION

[0020] The specific implementation modes provided by the present invention are described in detail below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, the structural diagram of an embodiment of the present invention injects current of a characteristic frequency into a power grid through a controllable current source or voltage source, thereby improving the damping characteristics of the power grid at the characteristic frequency, thereby eliminating the accelerated attenuation of subsynchronous oscillations of the power grid, and mitigating and eliminating the risk of subsynchronous resonance of the power grid.

[0022] The present invention is different from the traditional subsynchronous oscillation suppression method. It does not suppress subsynchronous oscillations for a certain power plant or generator set, so it does not require a speed signal. Instead, it monitors the voltage of the power grid system to comprehensively manage the subsynchronous oscillation problem in the power grid.

[0023] The present invention innovatively comprehensively manages the subsynchronous oscillation problem of generator sets in the power grid. The traditional method for suppressing subsynchronous oscillation of generator sets only suppresses the modal subsynchronous oscillation of a single generator set in a power plant, while multiple generator sets in multiple power plants in the power grid system often have subsynchronous oscillation problems. The method calculates the subsynchronous component contained in the power grid system voltage and each modal frequency in the subsynchronous component through the power grid subsynchronous oscillation detection algorithm; then calculates the current control command required by the suppression device through the power grid subsynchronous oscillation suppression algorithm; injects the command current into the power grid through the suppression device to improve the damping of the system characteristic frequency.

[0024] like Figure 2 As shown, the subsynchronous oscillation detection algorithm of the power grid includes: the grid voltage Uabc is transformed into the system voltage Ud in the dq coordinate system, Ud is passed through a low-pass filter LPF to obtain the voltage amplitude Ud1, and a subsynchronous component Um=Ud-Ud1 is obtained through a subtractor. At this time, the subsynchronous component Um is calculated through discrete Fourier DFT to obtain multiple subsynchronous component modulus values, and then the various modal frequencies in the system are calculated through frequency sweep analysis.

[0025] The low pass filter LPF uses a low pass filter below 5 Hz.

[0026] The coordinate transformation calculation formula is:

[0027]

[0028]

[0029] The three-phase grid voltages Ua, Ub, and Uc, the sinθ, and cosθ, the phase θ is the phase of the grid voltage Ua.

[0030] like Figure 3 As shown, the subsynchronous oscillation suppression algorithm of the power grid includes: passing the subsynchronous component Um of the power grid system voltage through the first bandpass filter BPF1 to extract the first system modal component, and then passing it through the proportional phase shifter to calculate the suppression current instruction Iqref1 required for the first mode; correspondingly, according to the number of modal frequencies n calculated by the subsynchronous oscillation detection algorithm of the power grid, the subsynchronous component Um of the power grid system voltage is passed through the second to nth bandpass filters BPF2~BPFn, and finally n system modal components are extracted, and finally the total current control instruction Iqref is obtained through instruction distribution calculation.

[0031] The command allocation calculation is as follows: summing up each modal suppression current command Iqref1...Iqrefn, that is, The coefficient allocation and addition calculation can also be performed according to the capacity requirements of each mode, that is,

[0032] Compared with traditional subsynchronous oscillation suppression, the present invention does not require a speed signal, so there is no need to connect a speed probe to each generator set, which reduces production costs, while reducing external access equipment for the generator sets, reducing equipment downtime and maintenance time, and improving production efficiency. At the same time, the invention comprehensively controls the subsynchronous oscillations of all generator sets in the system, greatly reducing the number of suppression devices that need to be connected to the system to suppress subsynchronous oscillations, and greatly reducing the cost of controlling subsynchronous oscillation problems.

[0033] The above embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the above embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.

Claims

1. A method for suppressing subsynchronous oscillation of a power grid, the method comprising a subsynchronous oscillation detection algorithm for a power grid and a subsynchronous oscillation suppression algorithm for a power grid; It is characterized in that The method described herein obtains the subsynchronous component contained in the grid system voltage and each modal frequency in the subsynchronous component by calculating the subsynchronous oscillation detection algorithm of the grid; and then calculates the current control instruction required by the suppression device by the subsynchronous oscillation suppression algorithm of the grid; By injecting command current into the power grid through the suppression device, the damping of the system characteristic frequency is improved; The subsynchronous oscillation detection algorithm of the power grid includes: the grid voltage Uabc is transformed into the system voltage Ud in the dq coordinate system, Ud is passed through a low-pass filter LPF to obtain the voltage amplitude Ud1, and a subtractor is passed to obtain the subsynchronous component Um=Ud-Ud1. At this time, the subsynchronous component Um is calculated through discrete Fourier DFT to obtain multiple subsynchronous component modulus values, and then the various modal frequencies in the system are calculated through frequency sweep analysis.

2. A method for suppressing subsynchronous oscillation of a power grid according to claim 1, characterized in that: The low pass filter LPF uses a low pass filter below 5 Hz.

3. A method for suppressing subsynchronous oscillation of a power grid according to claim 1, characterized in that: The subsynchronous oscillation suppression algorithm of the power grid includes: passing the subsynchronous component Um of the power grid system voltage through the first bandpass filter BPF1 to extract the first system modal component, and then passing it through the proportional phase shifter to calculate the suppression current instruction Iqref1 required for the first mode; correspondingly, according to the number of modal frequencies n calculated by the subsynchronous oscillation detection algorithm of the power grid, the subsynchronous component Um of the power grid system voltage is passed through the second to nth bandpass filters BPF2~BPFn, and finally n system modal components are extracted, and finally the total current control instruction Iqref is obtained through instruction distribution calculation.

4. A method for suppressing subsynchronous oscillation of a power grid according to claim 3, characterized in that: The command allocation calculation is as follows: summing up each modal suppression current command Iqref1...Iqrefn, that is, Iqref= Or according to the capacity requirements of each mode, the coefficient allocation and addition calculation are performed, that is,

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