Method for suppressing broadband oscillation of energy storage power station

Abstract

The invention discloses a method for suppressing broadband oscillation of an energy storage power station. The suppression method adopted by the invention comprises the following steps: if broadband oscillation information is detected and the oscillation amplitude is greater than a preset value, judging whether oscillation is in a divergent, convergent or equal-amplitude form through an amplitude comparison method, and if the oscillation is in the convergent form, not adjusting and belonging to a normal phenomenon; if the mode is a divergent or constant amplitude mode, the next step is adopted for intervention; a proportionality coefficient and an integral coefficient of a PI controller in the energy storage converter control system are switched to another set of parameters which are input in advance; after the parameters are switched, if the oscillation is still in a divergent or constant-amplitude form, the next step is adopted for further intervention; if the oscillation is changed into a convergent form, adjustment is not carried out any more; and according to an oscillation divergence slope formula, carrying out dynamic locking on the energy storage converter of which the oscillation is still in a divergence or constant-amplitude form after parameter switching so as to suppress the oscillation. According to the invention, generation of broadband oscillation can be effectively suppressed.

Description

Technical Field

[0001] The invention belongs to the technical field of energy storage grid connection, and specifically is a method for suppressing broadband oscillation of an energy storage power station. Background Art

[0002] Energy storage plays a vital role in integrating and optimizing new energy applications. By arranging and installing energy storage power stations, it is possible to effectively balance supply and demand, improve energy reliability and stability, and support the grid's regulation capabilities, reducing the impact of renewable energy volatility on the grid. However, the key device for the interaction between energy storage power stations and the grid is a power electronic device. In the case of incompatible parameters and complex grid operation, unstable phenomena such as power oscillation will occur, which is not conducive to the stable operation of the grid.

[0003] At present, the method combining eigenvalue method and time domain simulation is usually used to analyze the influencing factors of the stability of energy storage grid-connected systems, which is used to guide the setting of key parameters such as proportional integral controllers. However, in actual projects, the operation mode of the power grid and the user load are constantly changing, and the range of system impedance characteristics is difficult to traverse in the design stage. Therefore, after the energy storage grid is connected to the grid, broadband oscillations often occur in energy storage power stations. It is necessary to propose a set of practical and effective methods to suppress broadband oscillations for actual field projects. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for suppressing broadband oscillations of an energy storage power station. The method can intervene in advance in a variety of ways at the beginning of oscillations in the energy storage power station, quickly and actively change the impedance characteristics of the energy storage power station online, destroy the resonant relationship between the energy storage power station and the power grid system, and thus effectively suppress the occurrence of broadband oscillations.

[0005] To this end, the present invention adopts the following technical solution: a method for suppressing broadband oscillation of an energy storage power station, comprising:

[0006] Step 1: Under normal operation, a broadband oscillation detection system is put into operation to detect broadband oscillation information of electrical quantity signals of the energy storage power station in real time;

[0007] Step 2: If broadband oscillation information is detected and the oscillation amplitude is greater than a preset value, the amplitude comparison method is used to determine whether the oscillation is divergent, convergent or equal-amplitude. If it is convergent, no adjustment is made, which is a normal phenomenon. If it is divergent or equal-amplitude, step 3 is used for intervention.

[0008] Step 3, switching the proportional coefficient and integral coefficient of the PI controller in the energy storage converter control system to another set of parameters that have been input in advance; after the parameter switching, if the oscillation is still in a divergent or equal-amplitude form, further intervention is performed using step 4; if the oscillation becomes a convergent form, no further adjustment is performed;

[0009] Step 4: According to the oscillation divergence slope formula, the energy storage converter whose oscillation is still divergent or equal amplitude after the parameter switching in step 3 is dynamically locked to suppress the oscillation; at the same time, the remaining unlocked energy storage converters are operated according to the maximum power that can be overloaded for a long time to partially or fully compensate for the active power;

[0010] Step 5: After the oscillation completely disappears, analyze the cause of the oscillation and implement a recovery strategy for the energy storage power station based on the analysis results.

[0011] Preferably, in step 1, the broadband oscillation detection system uses fast Fourier transform to calculate the collected voltage and current signals to obtain the oscillation frequency f z and the corresponding amplitude A m .

[0012] Preferably, in step 2, the amplitude comparison method adopts a moving window comparison mode, that is, at the oscillation frequency f z Compare the corresponding amplitudes A of the five oscillation cycles in the corresponding five oscillation cycle time windows. m At the same time, when the latest oscillation cycle occurs, the earliest oscillation cycle in the time window is excluded, and the time window always moves forward following the latest time.

[0013] More preferably, in step 2, when the amplitude comparison method is used to determine the oscillation, if the amplitude A m gradually increases, it is a divergent form; if the amplitude A m If the amplitude A is basically unchanged, it is in the form of equal amplitude. m gradually decreases, it is a convergent form; if the amplitude A m If it increases first and then decreases, it is considered to be a convergent form; if the amplitude A m If it decreases first and then increases, it is considered a divergent pattern.

[0014] Preferably, in step 3, the proportional coefficient and integral coefficient of the PI controller in the other set of parameters are completed by the test work in the grid-connected stage, and the impedance characteristics of the energy storage converter corresponding to the two sets of PI controller parameters (i.e., the proportional coefficient and the integral coefficient) are significantly different, so as to better play the role of oscillation suppression.

[0015] Preferably, in step 4, the number of energy storage converters whose oscillation is still divergent or equal amplitude after the parameter switching in step 3 is m0, which is 5% to 10% of the total number N of energy storage converters in the energy storage power station, and is determined according to the influence of the number of energy storage converter blocking on the impedance characteristics of the energy storage power station. If the impedance characteristics of the energy storage power station can be changed more quickly with a small number of energy storage converter blocking, then m0 can be smaller, otherwise, it can be larger.

[0016] More preferably, in step 4, according to the oscillation divergence slope formula, the calculation formula for the number of dynamic lockouts of the energy storage converter is as follows:

[0017]

[0018] Where m is the number of dynamic lockouts of the energy storage converter, k1 is less than 0, k2 is greater than 0, and p1>p2, dA m / dt is the slope of the oscillation amplitude change; k1 is the oscillation convergence coefficient, k2 is the oscillation divergence coefficient, p1 is the oscillation divergence converter blocking coefficient, and p2 is the oscillation convergence converter blocking coefficient. In general, if the oscillation divergence is more severe, the more energy storage converters will be blocked and the faster the blocking speed will be; if the oscillation gradually converges, the blocked energy storage converters can gradually turn to unlocked, but the number and speed of unlocked converters are lower than those of locked converters.

[0019] Preferably, in step 2, for voltage, the preset value is 5% of the fundamental wave rated voltage; for current, the preset value is 5% of the fundamental wave real-time current.

[0020] Preferably, the energy storage power station comprises a plurality of energy storage units, a static VAR generator and a step-up transformer; the plurality of energy storage units and the static VAR generator are connected to the AC bus and are connected to the high voltage grid after the step-up transformer.

[0021] More preferably, the energy storage unit comprises an energy storage battery, an energy storage inverter and a unit transformer. The energy storage battery is installed on the DC side of the energy storage inverter. The energy storage inverter converts the DC power output by the energy storage battery into AC power, which is then connected to the AC bus after being stepped up by the unit transformer.

[0022] Compared with the prior art, the present invention has the following beneficial effects: the present invention can intervene in advance in a variety of ways at the beginning of oscillation in the energy storage power station, quickly and actively change the impedance characteristics of the energy storage power station online, destroy the resonant relationship between the energy storage power station and the power grid system, and thus effectively suppress the occurrence of broadband oscillations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a method for suppressing broadband oscillation of an energy storage power station. DETAILED DESCRIPTION

[0024] In order to describe the present invention more specifically, the technical solution and related principles of the present invention are described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0025] The energy storage power station contains multiple energy storage units, static VAR generators and step-up transformers; multiple energy storage units and static VAR generators are connected to the AC bus with a lower voltage such as 35kV, and then connected to the high-voltage power grid after the step-up transformer. The energy storage unit contains energy storage batteries, energy storage converters and unit transformers. The energy storage batteries are installed on the DC side of the energy storage converters. The energy storage converters convert the DC power output by the energy storage batteries into AC power, which is stepped up to 35kV and other voltages through the unit transformers and connected to the AC bus.

[0026] This embodiment provides a method for suppressing broadband oscillation of an energy storage power station. Figure 1 As shown, the specific steps are as follows:

[0027] 1. Step (1)

[0028] Under normal operation, the broadband oscillation detection system is put into use to detect broadband oscillation information of electrical quantity signals such as voltage and current of the energy storage power station in real time. The broadband oscillation detection system generally uses fast Fourier transform to calculate the collected voltage and current signals to obtain the oscillation frequency f z and the corresponding amplitude A m .

[0029] 2. Step (2)

[0030] If broadband oscillation information is detected and the oscillation amplitude is greater than the preset value, the amplitude comparison method is used to determine whether the oscillation is divergent, convergent or equal-amplitude. If it is convergent, no adjustment is made, which is a normal phenomenon; if it is divergent or equal-amplitude, step 3 is used for intervention.

[0031] For voltage, the preset value is 5% of the fundamental wave rated voltage; for current, the preset value is 5% of the fundamental wave real-time current.

[0032] The amplitude comparison method uses a moving window comparison mode, that is, at the oscillation frequency f z In the corresponding 5 oscillation cycle time window, compare the corresponding amplitudes A of the 5 oscillation cycles m At the same time, when the latest oscillation cycle is generated, the earliest oscillation cycle in the time window is excluded, and the time window always moves forward with the latest time. m gradually increases, it is a divergent form; if the amplitude A m If the amplitude A is basically unchanged, it is in the form of equal amplitude. m gradually decreases, it is a convergent form; if the amplitude A m It increases first and then decreases, which can be regarded as a convergent form; if the amplitude A m If it decreases first and then increases, it can be considered a divergent pattern.

[0033] 3. Step (3)

[0034] Immediately switch the proportional coefficient and integral coefficient of the PI controller in the energy storage converter control system to another set of parameters that have been input in advance. After the parameter switch, if the oscillation is still divergent or equal amplitude, further intervention is performed using step 4; if the oscillation becomes convergent, no further adjustment is made.

[0035] The proportional coefficient and integral coefficient of the PI controller in the other set of parameters are completed by the test work in the grid-connected stage. In principle, the difference in the impedance characteristics of the energy storage converter corresponding to the two sets of PI controller parameters should be as large as possible, so that the oscillation suppression effect can be better achieved.

[0036] 4. Step (4)

[0037] Immediately lock the m0 energy storage converters in the energy storage power station, and dynamically lock the energy storage converters according to the oscillation divergence slope formula to suppress oscillation. At the same time, the remaining unlocked energy storage converters operate at the maximum power that can be overloaded for a long time to partially or fully compensate for the active power.

[0038] In step 3, after the parameter switching, the number of energy storage converters whose oscillation is still divergent or equal amplitude is m0, which can be 5% to 10% of the total number N of energy storage converters in the energy storage power station, depending on the influence of the number of energy storage converter blocking on the impedance characteristics of the energy storage power station. If the impedance characteristics of the energy storage power station can be changed more quickly with a small number of energy storage converter blocking, then m0 can be smaller, otherwise, it can be larger.

[0039] According to the oscillation divergence slope formula, the calculation formula for the number of dynamic lockouts of the energy storage converter is as follows:

[0040]

[0041] Where, m is the number of dynamic lockouts of the energy storage converter, k1 is the oscillation convergence coefficient, k2 is the oscillation divergence coefficient, p1 is the oscillation divergence converter lockout coefficient, and p2 is the oscillation convergence converter lockout coefficient. k1 is less than 0, k2 is greater than 0, and p1>p2, dA m / dt is the slope of the oscillation amplitude change, k1 can be -0.1, k2 can be 0.05, p1 can be 1 to 2, and p2 can be 0.5 to 1. In general, if the oscillation diverges more severely, the more locked energy storage converters there are, and the faster the locking speed is; if the oscillation gradually converges, the locked energy storage converters can gradually turn to unlocked, but the number and speed of unlocked converters are lower than those in the locked case.

[0042] 5. Step (5)

[0043] After the oscillation completely disappears, the cause of the oscillation is analyzed, and based on the analysis results, a recovery strategy is implemented for the energy storage power station.

[0044] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for suppressing broadband oscillation of an energy storage power station, characterized in that: include: Step 1: Under normal operation, a broadband oscillation detection system is put into operation to detect broadband oscillation information of electrical quantity signals of the energy storage power station in real time; Step 2: If broadband oscillation information is detected and the oscillation amplitude is greater than a preset value, the amplitude comparison method is used to determine whether the oscillation is divergent, convergent or equal amplitude. If it is a convergent form, no adjustment is made, which is a normal phenomenon. If it is a divergent or equal-amplitude form, use step 3 to intervene; Step 3, switching the proportional coefficient and integral coefficient of the PI controller in the energy storage converter control system to another set of parameters that have been input in advance; after the parameter switching, if the oscillation is still in a divergent or equal-amplitude form, further intervention is performed using step 4; if the oscillation becomes a convergent form, no further adjustment is performed; Step 4: According to the oscillation divergence slope formula, the energy storage converter whose oscillation is still divergent or equal amplitude after the parameter switching in step 3 is dynamically locked to suppress the oscillation; at the same time, the remaining unlocked energy storage converters are operated according to the maximum power that can be overloaded for a long time to partially or fully compensate for the active power; Step 5: After the oscillation completely disappears, analyze the cause of the oscillation and implement a recovery strategy for the energy storage power station based on the analysis results.

2. The method for suppressing broadband oscillation of an energy storage power station according to claim 1, characterized in that: In step 1, the broadband oscillation detection system uses fast Fourier transform to calculate the collected voltage and current signals to obtain the oscillation frequency f z and the corresponding amplitude A m .

3. The method for suppressing broadband oscillation of an energy storage power station according to claim 1, characterized in that: In step 2, the amplitude comparison method adopts a moving window comparison mode, that is, at the oscillation frequency f z Compare the corresponding amplitudes A of the five oscillation cycles in the corresponding five oscillation cycle time windows. m At the same time, when the latest oscillation cycle occurs, the earliest oscillation cycle in the time window is excluded, and the time window always moves forward following the latest time.

4. The method for suppressing broadband oscillation of an energy storage power station according to claim 3, characterized in that: In step 2, when the amplitude comparison method is used to determine the oscillation, if the amplitude A m gradually increases, it is a divergent form; if the amplitude A m Basically unchanged, it is in the form of equal amplitude; if the amplitude A m gradually decreases, it is a convergent form; if the amplitude A m If it increases first and then decreases, it is considered to be a convergent form; if the amplitude A m If it decreases first and then increases, it is considered a divergent pattern.

5. The method for suppressing broadband oscillation of an energy storage power station according to claim 1, characterized in that: In the step 3, the proportional coefficient and integral coefficient of the PI controller in the other set of parameters are completed by the test work in the grid-connected stage, and the impedance characteristics of the energy storage converter corresponding to the two sets of PI controller parameters are obviously different.

6. The method for suppressing broadband oscillation of an energy storage power station according to claim 1, characterized in that: In step 4, the number of energy storage converters whose oscillations are still divergent or equal-amplitude after the parameter switching in step 3 is m0, which is 5% to 10% of the total number N of energy storage converters in the energy storage power station, depending on the influence of the number of locked energy storage converters on the impedance characteristics of the energy storage power station.

7. The method for suppressing broadband oscillation of an energy storage power station according to claim 6, characterized in that: In step 4, according to the oscillation divergence slope formula, the calculation formula for the number of dynamic lockouts of the energy storage converter is as follows: Where m is the number of dynamic lockouts of the energy storage converter, k1 is less than 0, k2 is greater than 0, and p1>p2, dA m / dt is the slope of the oscillation amplitude change; k1 is the oscillation convergence coefficient, k2 is the oscillation divergence coefficient, p1 is the oscillation divergence converter blocking coefficient, and p2 is the oscillation convergence converter blocking coefficient.

8. The method for suppressing broadband oscillation of an energy storage power station according to claim 1, characterized in that: In step 2, for voltage, the preset value is 5% of the fundamental wave rated voltage; for current, the preset value is 5% of the fundamental wave real-time current.

9. The method for suppressing broadband oscillation of an energy storage power station according to claim 1, characterized in that: The energy storage power station comprises a plurality of energy storage units, a static VAR generator and a step-up transformer; the plurality of energy storage units and the static VAR generator are connected to an AC bus and are connected to a high-voltage power grid after passing through a step-up transformer.

10. The method for suppressing broadband oscillation of an energy storage power station according to claim 9, characterized in that: The energy storage unit comprises an energy storage battery, an energy storage converter and a unit transformer. The energy storage battery is installed on the DC side of the energy storage converter. The energy storage converter converts the DC power output by the energy storage battery into AC power, which is then connected to the AC bus after being stepped up by the unit transformer.

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