Power oscillation suppression method and system for grid-type diesel-storage parallel system facing oilfield shock load

Abstract

The application discloses a network-constructing type diesel storage parallel system power oscillation suppression method and system for oil field impact load, and the method comprises the following steps: detecting the voltage and current of the output end of a storage converter and a load, calculating the output power of the storage converter and the total power of the load after the impact load is input, obtaining an output angular frequency compensation value through calculation, and adjusting the output angular frequency of the storage converter in real time by using the output angular frequency compensation value, so that the angular frequency of the storage converter can quickly track the angular frequency of a diesel generator, thereby reducing the angular frequency difference between the storage converter and the diesel generator, and effectively suppressing the low-frequency power oscillation of the network-constructing type diesel storage parallel system under the oil field impact load.

Description

Technical Field

[0001] The present invention relates to the field of independent power supply systems for oil fields and control technologies thereof, in particular to a method and system for suppressing power oscillation of a grid-type diesel-storage parallel system facing oil field impact loads. Background Art

[0002] Due to geographical constraints, the power grid in oilfield areas is underdeveloped, difficult to maintain, and costly. This results in a weak and unstable grid, making power failures such as voltage sags, frequency overshoots, and temporary blackouts extremely difficult to avoid. Therefore, distributed diesel generator sets and uninterruptible energy storage (UPS) are often used to form a parallel diesel-storage system to provide stable power to critical loads, replacing the main grid. However, unlike large-scale power grids, UPS systems have limited capacity. During oilfield drilling, surge loads are often encountered, posing challenges to system stability. These surge loads exhibit periodic, discrete behavior and high peak power, often several times the average power.

[0003] Unlike multi-storage parallel systems, in diesel-storage parallel systems, the parameters of the diesel generators are fixed and black-boxed. Therefore, when pulse loads are applied, power oscillations in these systems can only be addressed by improving the controllers of the energy storage converters. This makes oscillation suppression in these systems difficult. Therefore, a grid-based diesel-storage parallel system and a power oscillation suppression method are needed for oilfield shock loads.

[0004] CN112271723A discloses a dynamic synchronous torque control method and system for a high-overload energy conversion power supply. By dynamically adjusting the virtual torque of the converter within the power supply, this method reduces the difference in angular frequency acceleration between the diesel engine and the converter, effectively suppressing low-frequency power oscillations when the diesel engine and converter are connected in parallel, and achieving multi-channel synchronous power supply under overload conditions. However, this method requires establishing communication between the SG and VSG using a bidirectional communication line. The oscillation suppression effect is easily affected by communication line delays. In practice, the angular frequency of the diesel engine prime mover is extremely difficult to measure, which can easily introduce interference to the controller. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for suppressing power oscillation of a grid-type diesel-storage parallel system under oil field impact load, in view of the shortcomings of the existing technology, so as to effectively suppress the low-frequency power oscillation of the grid-type diesel-storage parallel system under oil field impact load.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is: a network-oriented diesel storage parallel system power oscillation suppression method for oil field impact load, the diesel storage parallel system contains multiple diesel generator sets and at least one energy storage converter, the multiple diesel generator sets and the energy storage converter are connected to the load through a bus, and the load contains conventional load and impact load; the method comprises the following steps:

[0007] S1, sampling the three-phase voltage and three-phase current of the energy storage converter output, and the three-phase voltage and three-phase current at the load end;

[0008] S2, calculating the instantaneous active output power and the reactive output power of the energy storage converter, calculating the output power angle of the energy storage converter using the instantaneous active output power, the output angular frequency, the active power rated value, the angular frequency rated value and the angular frequency compensation value, and calculating the output electromotive force of the energy storage converter using the reactive power value, the output voltage value of the energy storage converter and its rated value:

[0009]

[0010] Wherein, P n , Q n , U n and ω n are the active power rated value, the reactive power rated value, the output voltage rated value and the output angular frequency rated value respectively; J and D are the rotational inertia and the damping coefficient of the energy storage converter respectively, K q is the inertia coefficient, D q is the reactive droop coefficient; E and ω are the actual output values of the output electromotive force and the output angular frequency respectively, P cal is the angular frequency compensation value, θ is the output phase, λ is the ratio of the rated capacity of the energy storage converter to the total rated capacity of the system, P e and Q e are the instantaneous active output power and the reactive output power of the energy storage converter respectively;

[0011] S3, using the calculated output electromotive force E and output phase θ to PWM modulate the energy storage converter output voltage control signal to obtain the energy storage converter switch tube control drive signal.

[0012] The application detects the voltage and current of the output end of the energy storage converter and the load, calculates the output power of the energy storage converter and the total power of the load after the impact load is input, obtains the output angular frequency compensation value through calculation, adjusts the output angular frequency of the energy storage converter in real time by using the output angular frequency compensation value, makes the angular frequency of the energy storage converter quickly track the angular frequency of the diesel generator, thereby reduces the angular frequency difference between the energy storage converter and the diesel generator, and effectively suppresses the low-frequency power oscillation of the network-structured diesel storage parallel system under the impact load of the oil field. The voltage and current data used in the control link of the control method can be directly detected by the data acquisition module on the mainboard and directly processed by the control chip, so it is not necessary to consider the data loss and transmission delay during communication. Moreover, the control method directly uses the power calculation value to compensate the angular frequency of the system, omits the angular frequency measurement link of the diesel generator prime mover, reduces the program complexity, and avoids the inaccurate control caused by the inaccurate measurement of the angular frequency of the diesel generator prime mover.

[0013] The calculation formula of the angular frequency compensation value Pcal is: P cal = K ω (λP L -P e ); wherein, P L is the load power, K ω is the compensation coefficient, and λ is the ratio of the rated capacity of the energy storage converter to the total rated capacity of the system. The angular frequency of the energy storage system is compensated by using the calculated compensation value P cal , which can effectively reduce the angular frequency difference between the diesel generator and the energy storage converter when the load suddenly changes, thereby suppressing the low-frequency power oscillation of the system under the impact load.

[0014] Wherein, P n is the rated value of the active power output by the energy storage converter, P Gni is the rated value of the active power output by the i-th diesel generator, and m is the number of diesel generators. As can be seen from the formula, in the control method, the control parameters can be adjusted according to the number of diesel generators in the system, so that the control method is still applicable when multiple diesel generators and energy storage systems are connected in parallel.

[0015] When the system is in a steady state, the calculation formula of the instantaneous active output power P e of the energy storage converter is: P e = λP L . According to the calculation formula of P cal , when the system is in a steady state, P cal is 0, so the newly introduced link does not introduce additional steady-state deviation to the excitation link, which means that the method does not affect the static power distribution between the diesel generator and the energy storage converter.

[0016] In the present invention, the output voltage control signal of the energy storage converter is PWM modulated to obtain the modulation wave e a 、e b 、e c The calculation formula is:

[0017]

[0018] As an inventive concept, the present invention also provides a grid-type diesel-storage parallel control system for oil field impact loads, which includes one or more processors and a memory; one or more programs are stored on the memory, and when the one or more programs are executed by the one or more processors, the one or more processors implement the steps of the above method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) Under the action of oilfield impact loads, the present invention collects the output power of the diesel generator and the energy storage converter. By adding the output power calculation value to the energy storage converter control link, the energy storage converter is rationally controlled, effectively suppressing the low-frequency oscillation of the output power of the diesel generator and the energy storage converter under short-term high overload impact loads generated during oilfield work, and smoothing the output power of both.

[0021] 2) Due to the black box nature of the diesel generator, its parameters cannot be measured. The present invention only needs to effectively control the energy storage converter so that the output angular frequency of the energy storage converter can track the angular frequency of the diesel generator to quickly suppress power oscillations caused by sudden load changes.

[0022] 3) The present invention calculates the measured output power as a frequency compensation signal to perform frequency compensation on the energy storage converter. After calculation, under steady-state conditions, the calculated frequency compensation value is 0. Therefore, the newly introduced link does not introduce additional steady-state deviation to the excitation link, which means that the proposed method does not affect the static power distribution between the diesel generator and the energy storage converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a grid-type diesel-storage parallel system structure;

[0024] Figure 2 This is a control block diagram of a grid-type diesel-storage parallel system and a power oscillation suppression method for oilfield impact loads according to an embodiment of the present invention;

[0025] Figure 3 The conventional control method and the power oscillation suppression method of the embodiment of the present invention are respectively the output frequency Δω of the diesel generator and the converter under the impact load. 12 The difference between the power and the e12Comparison of time domain curves;

[0026] Figure 4 This is the output power waveform of the diesel-storage parallel system before and after the power oscillation suppression method proposed in the embodiment of the present invention is introduced. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0028] Example 1

[0029] like Figure 1 As shown in FIG, the grid-type diesel storage parallel system structure of the embodiment of the present invention includes multiple diesel generators and energy storage converters, and the load (load) includes normal load and impact load. Figure 1 Medium X t1 ~X t3 They are the output impedances of the three diesel generators, X t4 is the output impedance of the energy storage converter, SW1~SW4 are switches; u abc and i abc are the three-phase voltage and current output by the energy storage converter, u g1abc ~u g3abc and i g1abc ~i g3abc Output three-phase voltage and current for three diesel generators respectively; u Labc and i Labc It is the three-phase voltage and current at the load end, where the load current is the total current, including conventional load and impact load.

[0030] In the embodiment of the present invention, a grid-type diesel-storage parallel system for oil field impact load is provided with a diesel generator and an energy storage converter as an example for description.

[0031] Hereinafter, a diesel generator and an energy storage converter are used as examples to illustrate a grid-connected diesel-storage parallel system for oilfield impact loads and a method for suppressing power oscillations according to an embodiment of the present invention.

[0032] like Figure 2 As shown, the specific implementation process of the grid-type diesel-storage parallel system and power oscillation suppression method for oil field impact loads according to the embodiment of the present invention includes:

[0033] The instantaneous active output power and the reactive output power of the energy storage converter are calculated using the collected voltage and current signals, the converter output power angle is calculated using the active power, the output angular velocity, the active power rated value, the angular frequency rated value and the angular frequency compensation value, and the converter output electromotive force is calculated using the reactive power value, the converter output voltage value and the rated value thereof, and the calculation formulae are as follows:

[0034]

[0035] In the formula, P n , Q n , U n and ω n are the active power rated value, the reactive power rated value, the output voltage rated value and the output angular frequency rated value respectively; J and D are the VSG rotational inertia and the damping coefficient respectively, K q is the inertia coefficient, D q is the reactive droop coefficient; E and ω are the output electromotive force and the output angular frequency actual output value respectively, P cal is the angular frequency compensation value, θ is the output phase, and λ is the ratio of the rated capacity of the energy storage converter to the total rated capacity of the system; P e and Q e are the output active power and the output reactive power of the energy storage converter respectively.

[0036] The angular frequency compensation value of the energy storage converter is calculated using the load output power and the energy storage converter output power, and the calculation formula is as follows

[0037] P cal = K ω (λP L -P e );

[0038] In the formula, P L is the load power, K ω is the compensation coefficient, and λ is the ratio of the rated capacity of the energy storage converter to the total rated capacity of the system, and the calculation formula is as follows

[0039] λ = P n / (P n + P Gn );

[0040] In the formula, P n is the energy storage converter output active power rated value, and P Gn is the diesel generator output active power rated value. In the embodiment of the present application, the diesel generator and the energy storage converter have the same rated capacity, and the power oscillation suppression method of the grid-connected diesel- energy storage parallel system is analyzed and described.

[0041] When the system does not have power oscillation, the instantaneous output power P eIt can be calculated as:

[0042] P e =λP L ;

[0043] According to P cal The calculation formula shows that P cal The steady-state value of is 0, so the newly introduced link does not introduce additional steady-state deviation to the excitation link, which means that the proposed method does not affect the static power distribution between the diesel generator and the energy storage converter.

[0044] The inverter modulation wave can be generated by calculating the inverter output electromotive force E and output phase θ. The modulation wave calculation formula is:

[0045]

[0046] The three-phase modulation wave intersects with the carrier of the PWM modulator to obtain the driving signals of the six switching tubes of the three-phase inverter bridge.

[0047] like Figure 3 As shown, the output frequency difference Δω between the diesel generator and the energy storage converter under pulse load is respectively obtained by the conventional control method and the power oscillation suppression method of the embodiment of the present invention. 12 and output power ΔP e12 When the energy storage converter is controlled by conventional control method, the difference Δω between the output frequency of the diesel generator and the converter is 12 The maximum value is greater than 0.7rad / s, and the output power ΔP e12 The maximum value is greater than 4kW; and when the energy storage converter is controlled by the power oscillation suppression method proposed in the present invention, the difference Δω between the output frequency of the diesel generator and the converter 12 The maximum value is less than 0.2rad / s and the output power ΔP e12 The maximum value is less than 1kW, which shows that the proposed control method can effectively reduce the difference in output frequency and output power between the diesel generator and the energy storage converter under pulse load.

[0048] like Figure 4 As shown in FIG. 1 , the output power waveform of the diesel-storage parallel system before and after the power oscillation suppression method is introduced in the embodiment of the present invention; P e1 is the output power of the diesel generator, P e2is the output power of the energy storage converter; in the initial state, the diesel generator and the energy storage converter work together and the output power is evenly shared. When the pulse load is connected at 0.1s, the inconsistent rotational inertia of the two leads to large power oscillations. After 0.4s, after the power oscillation suppression method proposed in the present invention is introduced, the power oscillation is significantly reduced, indicating that the power oscillation suppression method proposed in the present invention can effectively suppress the low-frequency power oscillation of the grid-type diesel-storage parallel system under impact load and realize the equal distribution of the output power of the diesel-storage parallel system.

[0049] Example 2

[0050] Embodiment 2 of the present invention provides a grid-type diesel-storage parallel control system for oilfield shock loads corresponding to the above-mentioned embodiment 1, comprising: one or more processors, a memory and one or more programs stored thereon, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the steps of the power oscillation suppression method of the grid-type diesel-storage parallel system of the above-mentioned embodiment 1 of the present invention. In some implementations, the memory may be a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk storage. In other implementations, the processor may be various types of general-purpose processors such as a central processing unit, a digital signal processor, etc., which are not limited here.

[0051] The energy storage converter in the embodiment of the present invention adopts grid-type control and can operate in both off-grid mode and grid-connected mode.

[0052] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0053] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for suppressing power oscillations in a grid-type diesel-storage parallel system for oilfield impact loads, wherein the diesel-storage parallel system comprises multiple diesel generator sets and at least one energy storage converter, wherein the multiple diesel generator sets and the energy storage converter are connected to loads via a bus, and the loads include normal loads and impact loads; characterized in that: The method comprises the following steps: S1, sampling the three-phase voltage and three-phase current output by the energy storage converter, as well as the three-phase voltage and three-phase current at the load end; S2. Calculate the instantaneous active output power and reactive output power of the energy storage converter. Calculate the output power angle of the energy storage converter using the instantaneous active output power, output angular frequency, active power rating, angular frequency rating, and angular frequency compensation value. Calculate the output electromotive force of the energy storage converter using the reactive power value, the output voltage value of the energy storage converter, and its rated value: Among them, P n , Q n 、U n and ω n They are respectively the active power rating, reactive power rating, output voltage rating and output angular frequency rating; J and D are respectively the moment of inertia and damping coefficient of the energy storage converter, K q is the inertia coefficient, D q is the reactive droop coefficient; E and ω are the actual output values ​​of output electromotive force and output angular frequency respectively, P cal is the angular frequency compensation value, θ is the output phase, λ is the ratio of the rated capacity of the energy storage converter to the total rated capacity of the system, P e and Q e are the instantaneous active output power and reactive output power of the energy storage converter respectively; S3. Using the calculated output electromotive force E and output phase θ, perform PWM modulation on the output voltage control signal of the energy storage converter to obtain a switch control drive signal of the energy storage converter; Angular frequency compensation value P cal The calculation formula is: cal =K ω (λP L -P e ); where P L is the load power, K ω is the compensation coefficient, λ is the ratio of the rated capacity of the energy storage converter to the total rated capacity of the system; Among them, P n is the rated output active power of the energy storage converter, P Gni is the rated output active power of the i-th diesel generator, and m is the number of diesel generators.

2. The method for suppressing power oscillation of a grid-type diesel-storage parallel system for oilfield shock load according to claim 1 is characterized in that: When the diesel-storage parallel system is in steady state, the instantaneous active output power P e The calculation formula is: e =λP L .

3. The method for suppressing power oscillation of a grid-type diesel-storage parallel system for oilfield shock load according to claim 1 is characterized in that: The output voltage control signal of the energy storage converter is PWM modulated to obtain the modulation wave e a 、e b 、e c The calculation formula is:

4. A grid-type diesel storage parallel control system for oilfield impact loads, characterized by: The method comprises one or more processors and a memory; the memory stores one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors implement the steps of the method according to any one of claims 1 to 3.

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