A method for suppressing wide frequency oscillation of an energy storage power station

Abstract

The application discloses a kind of energy storage power station wide frequency oscillation suppression method.The suppression method used in the application comprises: if wide frequency oscillation information is detected and oscillation amplitude is greater than preset value, then judge oscillation as divergent, convergent or equal amplitude form by amplitude comparison method, if it is convergent form, then do not adjust, it is normal phenomenon;If it is divergent or equal amplitude form, then adopt next step to intervene;The proportional coefficient and integral coefficient of PI controller in energy storage converter control system are switched to another set of parameters input in advance;After parameter switching, if oscillation is still divergent or equal amplitude form, then adopt next step to further intervene;If oscillation becomes convergent form, then do not adjust any more;According to oscillation divergence slope formula, dynamic lockout is carried out to energy storage converter whose oscillation is still divergent or equal amplitude form after parameter switching, to suppress oscillation.The application can effectively suppress the occurrence of wide frequency oscillation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage grid connection, and particularly relates to a method for suppressing wide-frequency oscillation of an energy storage power station. BACKGROUND

[0002] In the integration and optimization of new energy applications, energy storage plays a crucial role. By arranging and installing energy storage power stations, the supply and demand can be effectively balanced, the reliability and stability of energy can be improved, and the regulation capacity of the power grid can be supported, thereby reducing the impact of the volatility of renewable energy on the power grid. However, the key device for the interaction between the energy storage power station and the power grid adopts a power electronic device. In the case of parameter mismatch, complex power grid operation mode, and the like, unstable phenomena such as power oscillation may occur, which is not conducive to the stable operation of the power grid.

[0003] At present, a method combining the eigenvalue method and time domain simulation is usually used to analyze the influencing factors of the stability of the energy storage grid connection system, which is used to guide the setting of key parameters such as proportional integral controllers. However, in actual engineering, the power grid operation mode and 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 connection is operated, wide-frequency oscillation phenomena often occur in the energy storage power station, and it is necessary to propose a set of practical and effective method for suppressing wide-frequency oscillation. SUMMARY

[0004] In view of the problems in the prior art, the application provides a method for suppressing wide-frequency oscillation of an energy storage power station, which can intervene in advance through multiple ways at the beginning of oscillation of the energy storage power station, quickly and actively change the impedance characteristics of the energy storage power station online, destroy the resonance relationship between the energy storage power station and the power grid system, and effectively suppress the occurrence of wide-frequency oscillation.

[0005] To this end, the application adopts the following technical solution: a method for suppressing wide-frequency oscillation of an energy storage power station, comprising:

[0006] Step 1, in a normal operation condition, a wide-frequency oscillation detection system is put into operation, and wide-frequency oscillation information of an electrical quantity signal of the energy storage power station is detected in real time;

[0007] Step 2, if the wide-frequency oscillation information is detected and the oscillation amplitude is greater than a preset value, it is judged by an amplitude comparison method 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 adopted for intervention;

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

[0009] Step 4, according to the oscillation divergence slope formula, the dynamic locking of the energy storage converter whose oscillation is still divergent or equal amplitude after the parameter switching in step 3 is carried out to suppress the oscillation; at the same time, the remaining energy storage converters not locked are operated according to the maximum power that can be overloaded for a long time to partially or completely compensate for the active power;

[0010] Step 5, after the oscillation completely disappears, the oscillation cause is analyzed, and the recovery strategy is carried out on the energy storage power station according to the analysis result.

[0011] Preferably, in step 1, the wideband oscillation detection system adopts 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, the change trend of the amplitudes A m of five oscillation cycles corresponding to the oscillation frequency f z is compared; 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 following the latest time.

[0013] More preferably, in step 2, when the amplitude comparison method judges the oscillation, if the amplitude A m gradually increases, it is divergent; if the amplitude A m is basically unchanged, it is equal amplitude; if the amplitude A m gradually decreases, it is convergent; if the amplitude A m first increases and then decreases, it is considered as convergent; if the amplitude A m first decreases and then increases, it is considered as divergent.

[0014] Preferably, in step 3, the proportional coefficient and the 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 converters corresponding to the two sets of PI controller parameters (i.e. proportional coefficient and integral coefficient) are obviously different, so that the oscillation suppression effect is better.

[0015] Preferably, in step 4, the energy storage converters whose oscillation is still divergent or equal amplitude after the parameter switching in step 3 are m0, which is 5% to 10% of the total number N of energy storage converters in the energy storage power station, according to the influence of the number of energy storage converters locked on the impedance characteristics of the energy storage power station. If the number of energy storage converters locked can quickly change the impedance characteristics of the energy storage power station, m0 can be smaller, otherwise, it can be larger.

[0016] More preferably, in the step 4, the number of dynamic closed energy storage converters is calculated according to the oscillation divergence slope formula as follows:

[0017]

[0018] Wherein, m is the number of dynamic closed energy storage converters, 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 locking coefficient, and p2 is the oscillation convergence converter locking coefficient. Overall, the more severe the oscillation divergence, the more energy storage converters are locked, and the faster the locking speed. If the oscillation gradually converges, the locked energy storage converters can gradually be unlocked, but the number and speed of unlocking are lower than those of locking.

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

[0020] Preferably, the energy storage power station comprises a plurality of energy storage units, static var generators and step-up transformers; the plurality of energy storage units and static var generators are connected to an AC bus and are connected to a high-voltage power grid through the step-up transformers.

[0021] More preferably, 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, and the AC power is connected to the AC bus through the unit transformer after being stepped up.

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

[0023] Figure 1 The flowchart of the method for suppressing wideband oscillation of the energy storage power station. DETAILED DESCRIPTION

[0024] In order to more specifically describe the present application, the technical solutions of the present application and related principles are described in detail below in combination with the drawings and specific embodiments.

[0025] The energy storage power station comprises a plurality of energy storage units, static var generators and voltage boost transformers; the plurality of energy storage units and static var generators are connected to a 35kV or lower voltage AC bus, and are connected to a high-voltage power grid through the voltage boost transformers. 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, the AC power is boosted to 35kV or lower voltage through the unit transformer, and is connected to the AC bus.

[0026] The embodiment provides a method for suppressing wide-frequency oscillation of an energy storage power station, as shown in the figure, the specific steps are as follows: Figure 1

[0027] 1. Step (1)

[0028] In a normal operation condition, a wide-frequency oscillation detection system is put into operation to detect wide-frequency oscillation information of voltage, current and other electrical quantity signals of the energy storage power station in real time. The wide-frequency oscillation detection system generally adopts fast Fourier transform to calculate the voltage and current signals collected, to obtain an oscillation frequency f z and a corresponding amplitude A m .

[0029] 2. Step (2)

[0030] If the wide-frequency oscillation information is detected and the oscillation amplitude is greater than a preset value, it is determined by an amplitude comparison method whether the oscillation is in a divergent, convergent or constant-amplitude form. If the oscillation is in a convergent form, no adjustment is made, which is a normal phenomenon. If the oscillation is in a divergent or constant-amplitude form, step 3 is adopted for intervention.

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

[0032] The amplitude comparison method adopts a moving window comparison mode, that is, the change trend of the amplitudes A m of five oscillation cycles corresponding to the oscillation frequency f z is compared in a time window of five oscillation cycles. Meanwhile, when a latest oscillation cycle is generated, the earliest oscillation cycle in the time window is excluded, and the time window always moves forward following the latest time. If the amplitude A m gradually increases, the oscillation is in a divergent form. If the amplitude A m remains basically unchanged, the oscillation is in a constant-amplitude form. If the amplitude A m gradually decreases, the oscillation is in a convergent form. If the amplitude A m first increases and then decreases, the oscillation can be regarded as a convergent form. If the amplitude A m first decreases and then increases, the oscillation can be regarded as a divergent form.

[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 switching, if the oscillation is still divergent or equal amplitude, further intervention is adopted in step 4; if the oscillation becomes convergent, it is no longer adjusted.

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

[0036] 4. Step (4)

[0037] Immediately lock m0 energy storage converters in the energy storage power station, and carry out dynamic locking of the energy storage converter according to the oscillation divergence slope formula to suppress the oscillation. At the same time, the remaining energy storage converters not locked run according to the maximum power that can be overloaded for a long time to partially or completely compensate for the active power.

[0038] The energy storage converters whose oscillation is still divergent or equal amplitude after the parameter switching in step 3 are 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 locking on the impedance characteristics of the energy storage power station. If the number of energy storage converter locking can quickly change the impedance characteristics of the energy storage power station, m0 can be smaller, otherwise, it can be larger.

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

[0040]

[0041] Wherein, m is the number of dynamic locking of energy storage converters, k1 is the oscillation convergence coefficient, k2 is the oscillation divergence coefficient, p1 is the oscillation divergence converter locking coefficient, and p2 is the oscillation convergence converter locking 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. Overall, the more the energy storage converters are locked, the faster the locking speed is if the oscillation divergence is more severe; if the oscillation gradually converges, the energy storage converters that have been locked can be gradually unlocked, but the number and speed of unlocking are lower than those of locking.

[0042] 5. Step (5)

[0043] After the oscillation completely disappears, the oscillation reason is analyzed, and according to the analysis result, the recovery strategy is carried out again on the energy storage power station.

[0044] The above merely illustrates the embodiments of the present application but should not be taken as limitations. Various changes and modifications can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the scope of claims of the present application.

Claims

1. A method for suppressing broadband oscillations in an energy storage power station, characterized in that, include: Step 1: Under normal operating conditions, activate the broadband oscillation detection system 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 the preset value, the amplitude comparison method is used to determine whether the oscillation is divergent, convergent or constant amplitude. If it is convergent, no adjustment is made, which is a normal phenomenon. If the amplitude is divergent or constant, then step 3 should be used to intervene; Step 3: Switch the proportional and integral coefficients of the PI controller in the energy storage converter control system to another set of parameters that have been pre-input; after the parameter switching, if the oscillation is still divergent or constant amplitude, then step 4 is used for further intervention; if the oscillation becomes convergent, no further adjustment is needed. Step 4: Dynamic blocking is implemented for energy storage converters whose oscillations are still divergent or constant amplitude after parameter switching in Step 3. This includes calculating the number of energy storage converters to be dynamically blocked based on the oscillation divergence slope formula, where the slope is the slope of the change in oscillation amplitude. At the same time, the remaining unblocked energy storage converters operate at the maximum power that can be overloaded for a long time to partially or completely compensate for active power. Step 5: After the oscillation has completely disappeared, conduct an analysis of the cause of the oscillation, and then implement a recovery strategy for the energy storage power station based on the analysis results.

2. The method for suppressing broadband oscillations in 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 oscillation frequency f from the acquired voltage and current signals. z and corresponding amplitude A m .

3. The method for suppressing broadband oscillations in an energy storage power station according to claim 1, characterized in that, In step 2, the amplitude comparison method uses a moving window comparison mode, that is, at the oscillation frequency f z Within the corresponding 5 oscillation cycle time windows, compare the amplitude A corresponding to the 5 oscillation cycles. m The trend of change; 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.

4. The method for suppressing broadband oscillations in an energy storage power station according to claim 3, characterized in that, In step 2, when judging oscillation using the amplitude comparison method, if the amplitude A m If it gradually increases, it becomes a divergent form; if the amplitude A m If the amplitude remains basically unchanged, it is a constant amplitude form; if the amplitude A m If it gradually decreases, it is a convergent form; if the amplitude A m If the amplitude A first increases and then decreases, it is considered a convergent form; if the amplitude A m If the value decreases first and then increases, it is considered a divergent pattern.

5. The method for suppressing broadband oscillations in an energy storage power station according to claim 1, characterized in that, In step 3, the proportional coefficient and integral coefficient of the PI controller in the other set of parameters are completed by the grid connection test. The impedance characteristics of the energy storage converters corresponding to the two sets of PI controller parameters are significantly different.

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

7. The method for suppressing broadband oscillations in an energy storage power station according to claim 6, characterized in that, In step 4, based on 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 for 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 lockout coefficient, and p2 is the oscillation convergence converter lockout coefficient.

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

9. The method for suppressing broadband oscillations in an energy storage power station according to claim 1, characterized in that, The energy storage power station contains multiple energy storage units, a static var generator (SVA) and a step-up transformer; the multiple energy storage units and the SVA are connected to the AC bus and then connected to the high-voltage power grid via the step-up transformer.

10. The method for suppressing broadband oscillations in an energy storage power station according to claim 9, characterized in that, The energy storage unit includes 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 from the energy storage battery into AC power, which is then stepped up by the unit transformer and connected to the AC bus.

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