Method and system for suppressing power oscillation of network construction type diesel-storage parallel system facing oil field impact load

Abstract

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

Description

Technical Field

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

[0002] Due to geographical restrictions, the power grid construction in the oil field area is imperfect, difficult to maintain and costly, resulting in a weak grid structure and poor stability. It is extremely difficult to avoid power failures such as voltage sag, frequency over-limit, and temporary power outages. Therefore, distributed diesel generator sets and uninterruptible energy storage are often used to form a diesel-storage parallel system to replace the stable large power grid to provide stable power supply for important loads. However, unlike large power grids, the system capacity of the diesel-storage power supply system is limited. During the oil field drilling process, impact loads are often put into use, which poses a challenge to the stable operation of the system. This type of impact load is periodically discrete and has a high peak power, which is several times its average power.

[0003] Different from the multi-energy storage parallel system, in the diesel-storage parallel system, since the parameters of the diesel generator set are fixed and black-boxed, when the pulse load is connected, the power oscillation of the diesel-storage parallel system can only be achieved by improving the controller of the energy storage converter, which makes it difficult to suppress the oscillation of the diesel-storage parallel system. Therefore, a grid-type diesel-storage parallel system and a power oscillation suppression method for oil field impact loads are needed.

[0004] CN112271723A discloses a high overload energy conversion power supply dynamic synchronous torque control method and system, which reduces the difference in angular frequency acceleration between the diesel engine and the converter by dynamically adjusting the virtual torque of the converter inside the power supply, effectively suppresses the low-frequency power oscillation under the parallel connection of the diesel engine and the converter, and realizes the synchronous power supply of multiple channels under overload conditions. However, the above method requires the establishment of communication between SG and VSG and the use of a two-way communication line for transmission. The oscillation suppression effect is easily affected by the delay of the communication line, and in practice, the angular frequency of the diesel engine prime mover is extremely difficult to measure, which easily introduces 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] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for suppressing power oscillation of a grid-type diesel-storage parallel system for oil field impact load, wherein the diesel-storage parallel system comprises a plurality of diesel generator sets and at least one energy storage converter, wherein the plurality of diesel generator sets and the energy storage converter are connected to loads through a bus, and the loads comprise conventional loads and impact loads; the method comprises the following steps:

[0007] 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;

[0008] 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, and 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:

[0009]

[0010] 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 the 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;

[0011] S3. Using the calculated output electromotive force E and output phase θ, PWM modulation is performed on the output voltage control signal of the energy storage converter to obtain the switch tube control drive signal of the energy storage converter.

[0012] The present invention detects the output end of the energy storage converter and the load voltage and current, calculates the output power of the energy storage converter and the total load power after the impact load is put into use, obtains the output angular frequency compensation value through calculation, and uses the output angular frequency compensation value to adjust the output angular frequency of the energy storage converter in real time, so that the angular frequency of the energy storage converter quickly tracks the angular frequency of the diesel generator, thereby reducing the angular frequency difference between the energy storage converter and the diesel generator, and effectively suppressing the low-frequency power oscillation of the grid-type diesel storage parallel system under the impact load of the oil field. The voltage and current data of the control link used in the control method of the present invention can be directly detected by the data acquisition module on the mainboard and directly processed by the control chip, so there is no need to consider data loss and transmission delay during communication. Moreover, the control method proposed by the present invention directly uses the power calculation value to compensate the system angular frequency, omits the angular frequency measurement link of the diesel engine, reduces the complexity of the program, and avoids the inaccurate control caused by inaccurate angular frequency measurement of the diesel engine.

[0013] The calculation formula of angular frequency compensation value Pcal is: cal =K ω (λP L -P e ), where 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. cal Angular frequency compensation of the energy storage system can effectively reduce the angular frequency difference between the diesel generator and the energy storage converter when the load changes suddenly, thereby suppressing the low-frequency power oscillation of the system under impact load.

[0014] Among them, P n is the rated value of the output active power of the energy storage converter, P Gni is the rated value of the active power output of the i-th diesel generator, and m is the number of diesel generators. It can be seen from the formula that in the control method of the present invention, the control parameters can be adjusted as the number of diesel generators in the system changes, so that when multiple diesel generators are connected in parallel with the energy storage system, the control method of the present invention is still applicable.

[0015] When the system is in steady state, the instantaneous active output power P of the energy storage converter is e The calculation formula is: e =λP L According to P cal From the calculation formula, we can know that when the system is in steady state, P cal 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.

[0016] In the present invention, the output voltage control signal of the energy storage converter is PWM modulated to obtain a 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 impact load of the oil field, the present invention collects the output power of the diesel generator and the energy storage converter, and reasonably controls the energy storage converter by adding the output power calculation value to the energy storage converter control link, effectively suppressing the low-frequency oscillation of the output power of the diesel generator and the energy storage converter under the short-term high overload impact load generated in the oil field work, and smoothing the output power of the two.

[0021] 2) Since the diesel generator is a black box, 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 deviations 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 To construct 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 oil field impact loads according to an embodiment of the present invention;

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

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

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] like Figure 1 As shown, 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 conventional load and impact load. Figure 1 Medium X t1 ~X t3 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 The three-phase voltage and current are output by three diesel generators respectively; 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 explanation.

[0031] Hereinafter, a diesel generator and an energy storage converter are taken as examples to illustrate the grid-connected diesel-storage parallel system for oil field impact load and the power oscillation suppression method 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 of the embodiment of the present invention includes:

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

[0034]

[0035] Where 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 VSG moment of inertia and damping coefficient, 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 The active power and reactive power are output for 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. The calculation formula is:

[0037] P cal =K ω (λP L -P e );

[0038] Among them, 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, and its calculation formula is:

[0039] λ=P n / (P n +P Gn );

[0040] Among them, P n Output active power rating of the energy storage converter, P Gn In the embodiment of the present invention, the power oscillation suppression method of the grid-connected diesel-storage parallel system proposed by the present invention is analyzed and explained by assuming that the rated capacity of the diesel generator and the energy storage converter are the same.

[0041] When the system does not experience power oscillation, the instantaneous output power of the energy storage converter is P eIt can be calculated as:

[0042] P e =λP L ;

[0043] According to P cal From the calculation formula, we know 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 signal of the six switching tubes of the three-phase inverter bridge.

[0047] like Figure 3 As shown, the conventional control method and the power oscillation suppression method of the embodiment of the present invention respectively use the output frequency difference Δω between the diesel generator and the energy storage converter under pulse load. 12 and output power ΔP e12 The time domain curve comparison diagram; When the energy storage converter is controlled using the conventional control method, the difference Δω between the output frequency of the diesel generator and the converter 12 The maximum value is greater than 0.7rad / s, 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. A pulse load is connected at 0.1s. Due to the inconsistent rotational inertia of the two, a large power oscillation occurs. After 0.4s, the power oscillation is significantly reduced after the power oscillation suppression method proposed in the present invention is introduced. This shows 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 impact loads corresponding to the above-mentioned embodiment 1, including: one or more processors, a memory and one or more programs stored thereon, 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-connected 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 other 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 falling within the scope of the present application.

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

Claims

1. A method for suppressing power oscillation of a grid-type diesel-storage parallel system for oilfield impact loads, wherein the diesel-storage parallel system comprises a plurality of diesel generator sets and at least one energy storage converter, wherein the plurality of diesel generator sets and the energy storage converter are connected to loads via a bus, and the loads comprise conventional loads and impact loads; It is 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, and 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, PWM modulation is performed on the output voltage control signal of the energy storage converter to obtain the switch tube control drive signal of the energy storage converter.

2. The method for suppressing power oscillation of a grid-type diesel-storage parallel system for oil field impact load according to claim 1 is characterized in that: Angular frequency compensation value P cal The calculation formula is: cal =K ω (λP L -P e ); Among them, 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.

3. The method for suppressing power oscillation of a grid-type diesel-storage parallel system for oil field impact load according to claim 2 is characterized in that: Among them, P n is the rated value of the output active power of the energy storage converter, P Gni is the rated active power output of the i-th diesel generator, m is the number of diesel generators.

4. The method for suppressing power oscillation of a grid-type diesel-storage parallel system for oil field impact load according to claim 2 or 3, 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 .

5. The method for suppressing power oscillation of a grid-type diesel-storage parallel system for oil field impact load according to claim 1 is characterized in that: The output voltage control signal of the energy storage converter is modulated by PWM, and the modulated wave e is obtained. a 、e b 、e c The calculation formula is:

6. A grid-type diesel storage parallel control system for oil field impact load, characterized in that: The method comprises one or more processors and a memory; one or more programs are stored in 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 method according to any one of claims 1 to 5.

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