A frequency control method and system for a gas internal combustion engine in cooperation with a light storage

Abstract

The present application relates to the technical field of micro-grid power coordination control, and provides a frequency control method and system for gas internal combustion engine and photovoltaic storage coordination, comprising: when power fluctuation occurs at a load end, calculating the active power variation of the load end through a power delay link; taking the active power of the photovoltaic storage system calculated based on the active power variation of the load end as the active power reference value in the inverter power control, controlling the inverter, so that the active power variation caused by the power fluctuation of the load end is instantaneously borne by the photovoltaic storage system, and the active power variation instantaneously borne by the photovoltaic storage system is transferred to the gas internal combustion engine group within a time constant. The problem of large frequency rise or drop caused by the gas internal combustion engine responding to the power fluctuation of the load end alone is solved, so as to ensure the stability of the micro-grid frequency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of micro-grid power coordination control, and particularly relates to a frequency control method and system for a gas internal combustion engine and a photovoltaic storage system. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] Biomass energy includes environmentally friendly gas, straw gas, biogas and other renewable energy fuels. When biomass energy is used as a power supply fuel, a gas internal combustion engine can improve the energy conversion efficiency of biomass power generation. In order to fully utilize new energy, a biomass micro-grid power supply system is usually formed by a biomass gas internal combustion generator and a photovoltaic storage power source, and provides power for a load.

[0004] When the biomass micro-grid operates in an island mode, the gas internal combustion synchronous generator will serve as a main power source in the biomass micro-grid to ensure the stability of the micro-grid voltage and frequency. Since the heat value of biomass energy is lower than that of natural gas and other fuels in a unit volume, and due to the structural characteristics of the gas internal combustion engine, the load tracking capability of the biomass gas internal combustion engine is poor, and the instantaneous power response speed is slow. When a large power fluctuation occurs at the load end of the biomass micro-grid, the frequency of the micro-grid system will drop or rise greatly, exceeding the frequency standard specified by the power system. At this time, the gas internal combustion engine group alone cannot guarantee the stability of the frequency of the micro-grid system. SUMMARY

[0005] In order to solve the technical problems in the background art, the present application provides a frequency control method and system for a gas internal combustion engine and a photovoltaic storage system, which cooperatively adjusts the output power of the gas internal combustion engine and the photovoltaic storage system when a load fluctuation occurs in a micro-grid, solves the problem of a large frequency rise or drop caused by the gas internal combustion engine responding to the load end power fluctuation alone, and ensures the stability of the frequency of the micro-grid.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A first aspect of the present application provides a frequency control method for a gas internal combustion engine and a photovoltaic storage system, which comprises:

[0008] When a power fluctuation occurs at the load end, the active power variation of the load end is calculated through a power time delay link;

[0009] The active power variation of the load end is calculated based on the active power variation of the photovoltaic storage system, and the active power variation of the photovoltaic storage system is taken as the active power reference value in the inverter power control, so that the active power variation caused by the power fluctuation of the load end is instantaneously borne by the photovoltaic storage system, and the active power variation instantaneously borne by the photovoltaic storage system is transferred to the gas internal combustion engine set within a time constant.

[0010] Further, the method for calculating the active power variation of the load end comprises:

[0011] The three-phase voltage and current of the load end are obtained and are subjected to Park transformation, respectively, to obtain the voltage component and current component of the load end after Park transformation;

[0012] The instantaneous active power of the load end is calculated based on the voltage and current components after Park transformation.

[0013] The active power variation of the load end is obtained after the active power of the load end is controlled by a time delay link.

[0014] Further, the active power borne by the photovoltaic storage system is the sum of the active power variation of the load end and the inherent charging and discharging power of the photovoltaic storage system.

[0015] Further, the specific steps for controlling the inverter comprise:

[0016] The three-phase voltage and current of the output end of the inverter are obtained and are subjected to Park transformation, respectively, to obtain the voltage component and current component of the output end of the inverter after Park transformation;

[0017] The inner loop current reference quantity is calculated based on the active power reference value in the inverter power regulation and the voltage component of the output end of the inverter after Park transformation.

[0018] The inner loop current reference quantity is subtracted from the current component of the output end of the inverter after Park transformation, and the difference is sequentially subjected to proportional integral control and Park inverse transformation to obtain a pulse width modulation signal for controlling the power output of the inverter, and the obtained pulse width modulation signal is used to control the opening and closing of the thyristor of the inverter to control the output current of the inverter end.

[0019] Further, the time constant is calculated based on the maximum variation of the transient frequency allowed by the power system, the regulation time for recovering the frequency from the transient state to the steady state, the initial power steady state operating point of the gas internal combustion engine, and the instantaneous maximum load active power fluctuation allowed by the micro-grid.

[0020] The second aspect of the present application provides a frequency control system of a gas internal combustion engine and photovoltaic storage system, which comprises:

[0021] a load end power change determination module configured to calculate an active power change amount of the load end through a power delay link when a power fluctuation occurs at the load end;

[0022] a cooperative control module configured to take active power of the optical storage system calculated based on the active power change amount of the load end as an active power reference value in inverter power control, and control the inverter so that the active power change amount caused by the power fluctuation at the load end is instantaneously borne by the optical storage system, and the active power change amount instantaneously borne by the optical storage system is transferred to the gas internal combustion engine set within a time constant.

[0023] Further, the active power borne by the optical storage system is a sum of the active power change amount of the load end and inherent charge-discharge power of the optical storage system.

[0024] Further, the time constant is calculated based on a maximum transient frequency change amount allowed by the power system, a regulation time for recovering the frequency from the transient state to the steady state, an initial power steady state operating point of the gas internal combustion engine, and a maximum instantaneous load active power fluctuation allowed by the micro-grid.

[0025] A third aspect of the present application provides a computer readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the steps of the frequency control method of the gas internal combustion engine cooperating with the optical storage as described above.

[0026] A fourth aspect of the present application provides a computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the frequency control method of the gas internal combustion engine cooperating with the optical storage as described above when executing the program.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] The present application provides a frequency control method of a gas internal combustion engine cooperating with an optical storage, which aims at the frequency problem caused by a large power fluctuation at a load end of a micro-grid under off-grid conditions of the micro-grid, analyzes the frequency modulation mechanism of the gas internal combustion engine under off-grid operation conditions of the micro-grid, obtains the relationship between the output power of the gas internal combustion engine and the frequency change of the micro-grid, and realizes the control of the frequency of the micro-grid through the power cooperative regulation of the gas internal combustion engine and the optical storage, thereby solving the problem of a large frequency rise or drop caused by the gas internal combustion engine responding to the power fluctuation at the load end alone, and ensuring the stability of the frequency of the micro-grid.

[0029] The application provides a frequency control method of a gas internal combustion engine and a light storage system, which controls the frequency of a micro-grid by cooperatively adjusting the active power output by the biomass gas internal combustion engine and the light storage system, and the essence of the cooperative control process is to utilize the fast power response characteristic of the light storage system to reduce the active power variation of the load required to be responded by the gas internal combustion engine group, so as to reduce the maximum variation of the frequency of the micro-grid. BRIEF DESCRIPTION OF DRAWINGS

[0030] The drawings accompanying the specification of the application form a part of the specification and serve to further illustrate the application, the illustrative embodiments of the application and the description thereof serve to explain the application without imposing undue limitation on the application.

[0031] Figure 1 is a flow chart of the frequency control method of the gas internal combustion engine and the light storage system according to the first embodiment of the application;

[0032] Figure 2 is a schematic diagram of the active power output by the light storage system after the frequency control according to the first embodiment of the application;

[0033] Figure 3 is a schematic diagram of the power distribution of the gas internal combustion engine, the light storage system and the load according to the first embodiment of the application;

[0034] Figure 4 is a schematic diagram of the power cooperative control of the gas internal combustion engine and the light storage system according to the first embodiment of the application;

[0035] Figure 5 is a schematic diagram of the frequency waveform of the micro-grid before and after the frequency control according to the first embodiment of the application;

[0036] Figure 6 is a schematic diagram of the active power waveform of the gas internal combustion engine before and after the control according to the first embodiment of the application;

[0037] Figure 7 is a schematic diagram of the active power waveform of the light storage system before and after the control according to the first embodiment of the application;

[0038] Figure 8 is a schematic diagram of the frequency waveform of the micro-grid when the load fluctuation size and the time constant of the delay time are different according to the first embodiment of the application;

[0039] Figure 9 is a schematic diagram of the active power of the gas internal combustion engine when the load fluctuation size and the time constant of the delay time are different according to the first embodiment of the application;

[0040] Figure 10 is a schematic diagram of the active power of the light storage system when the load fluctuation size and the time constant of the delay time are different according to the first embodiment of the application. DETAILED DESCRIPTION

[0041] The application will be further described below in connection with the accompanying drawings and examples.

[0042] It should be noted that the following detailed description is illustrative only, and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0043] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0044] Example 1

[0045] The present embodiment provides a frequency control method of a gas internal combustion engine and a light storage system. When the micro-grid is in off-grid operation, the frequency stability of the micro-grid is taken as the control target. When the load end has a power fluctuation, a power delay link is introduced to calculate the active power variation ΔP of the load at time t, and the light storage system instantaneously bears all the active power fluctuations caused by the load fluctuation. The maximum transient frequency variation Δf max , the adjustment time Δt max for the frequency to recover from the transient state to the steady state, the initial power steady state operating point P0 of the gas internal combustion engine, and the maximum instantaneous load active power fluctuation ΔP Ltmax allowed by the micro-grid are taken as the critical indicators to determine the value of the time constant Ts of the delay link. The time constant Ts of the delay link is taken as the charge and discharge time constant of the energy storage system, and the part of the load power fluctuation instantaneously borne by the light storage system is transferred to the gas internal combustion engine within the time constant Ts, so that the micro-grid system reaches a new power balance point, i.e. the power collaborative control of the gas internal combustion engine and the light storage system is completed, to ensure the stability of the micro-grid frequency. The key to realizing this process is to introduce a delay link in the power response characteristics of the gas internal combustion engine and the light storage system. The micro-grid system includes an internal combustion engine group, a load, an inverter, and a light storage system. The internal combustion engine group adopts a biomass gas internal combustion engine. In order to simplify the structure, the photovoltaic cell and the hybrid energy storage are replaced by an equivalent DC power supply, the gas internal combustion engine is replaced by an AC voltage source, and the DC system (light storage system) is supplied to the load together with the gas internal combustion engine (internal combustion engine group) through the inverter, as shown in Figure 1 , where U dc is the DC source voltage, L and C are the filter inductance and filter capacitance respectively, i B , and uB are the output current and output voltage of the inverter respectively, u L L are the voltage and total current at the load end respectively. When the load fluctuates in the micro-grid, the total power P L at the load end is monitored in real time. By introducing a power delay link 1 / (Ts+1), the difference between P L and its instantaneous value after passing through the delay link can obtain the instantaneous power change ΔP at the load end. When the appropriate power delay time constant Ts is set, the change will gradually decay to zero.

[0046] The frequency control method of the gas internal combustion engine in cooperation with the light storage is applicable to the micro-grid under off-grid conditions. The frequency control method of the gas internal combustion engine in cooperation with the light storage provided by the embodiment comprises the following steps as shown in the figure: Figure 1

[0047] Step 1, obtain the three-phase voltage and current at the load end, and obtain the active power at the load end by the power calculation link after Park transformation (dq transformation). That is, when the load fluctuates in the micro-grid, the total power P L at the load end is monitored in real time.

[0048] Among them, the expressions of the three-phase voltage u L and current i L at the load end are respectively:

[0049] u L =[u La u Lb u Lc ] T

[0050] i L =[i La i Lb i Lc ] T

[0051] In the formula, u La , u Lb and u Lc are the a-phase, b-phase and c-phase voltages at the load end, and i La , i Lb and i Lc are the a-phase, b-phase and c-phase currents at the load end.

[0052] Because there is a phase coupling relationship between the three-phase alternating current voltage and current, in order to simplify the inverter control method, the three-phase voltage and current at the load end are respectively transformed by Park to obtain the direct current in the dq axis synchronous rotating coordinate system, that is, the voltage component and current component of the load end after Park transformation are: ​​

[0053] [u Ld u Lq ] T =T abc-dq ·[u La u Lb u Lc ] T

[0054] [i Ld i Lq ] T =T abc-dq ·[i La i Lb i Lc ] T

[0055] wherein T abc-dq represents the Park transformation.

[0056] Based on the voltage and current components after the Park transformation, the instantaneous active power P L and the reactive power Q L at the load end are calculated as follows:

[0057]

[0058] Step 2, the active power variation at the load end that can be obtained by controlling the active power output at the load end through the time delay element 1 / (Ts+1) is:

[0059]

[0060] wherein Ts is the power time delay constant.

[0061] When the micro-grid experiences different degrees of load fluctuation, the value of the time delay constant Ts in the time delay element can be determined according to the frequency safety standard of the power system, the operating condition of the gas internal combustion engine unit, and the maximum active power fluctuation allowed to occur in the micro-grid. Taking a sudden load surge as an example, Figure 2 is the active power output by the light storage system after the power collaborative control. From Figure 2 , it can be seen that the value of the time delay constant Ts will determine how fast the light storage system transfers the power variation it instantaneously assumes to the gas internal combustion engine unit. If the value of Ts is too large, the light storage system will release too much power, which will require a large capacity of the energy storage; if the value of Ts is too small, the light storage system will release energy too fast, which will cause the system frequency to fluctuate again. The factors that affect the frequency regulation capability of the micro-grid are: the size of the power frequency response capability of the gas internal combustion engine unit itself, the initial power operating point of the gas internal combustion engine unit, the maximum variation of the transient frequency specified by the power system, and the maximum recovery time of the frequency from the start of fluctuation to the recovery to the steady state.

[0062] Let the total capacity of the gas internal combustion engine be P. N The maximum allowable load fluctuation in a microgrid system is ΔP. Ltmax =σP N Where σ is the load fluctuation proportionality coefficient, 0≤σ≤1; the initial power steady-state operating point of the gas internal combustion engine is P. m =P0, P m Let P0 be the mechanical power output of the internal combustion engine, and P0 be the first steady-state operating point of the mechanical power. The maximum permissible frequency change during transient changes in the microgrid system frequency is defined as Δf. max =|f * -f H-L |,f * =f N It is the frequency of 50Hz specified by the power system, where f H-L This refers to the magnitude of the lowest or highest frequency value during the transient frequency change of the microgrid system; when load fluctuations occur in the microgrid, Δt is defined as t m -t0 is the time required for the frequency to drop to its lowest point (or rise to its highest point) from steady state for the first time, and is defined as approximately the adjustment time Δt for the frequency to recover from transient to steady state as specified by the power system. max Half of that is, Δt = Δt max / 2; Therefore, in this embodiment, the power delay time constant is:

[0063]

[0064] In the formula, f N The rated frequency is 50Hz; k n This is the power-frequency droop coefficient of a gas internal combustion engine.

[0065] Step 3: Based on the change in active power at the load end and the inherent charging and discharging power P of the photovoltaic-storage system (energy storage itself) B * The active power required by the photovoltaic-storage system to handle load fluctuations is calculated and used as a reference value for active power in inverter power control. The active power required by the photovoltaic-storage system is the sum of the change in active power at the load end and the inherent charging and discharging power of the photovoltaic-storage system.

[0066]

[0067] That is, the active power required by the photovoltaic-storage system and the active power required by the gas turbine internal combustion engine can be expressed as follows:

[0068]

[0069] This invention only studies the frequency characteristics of microgrids, therefore only the active power reference value in power control is set, and the reactive power reference value is not specified. The value of the zero phase sequence current is set to zero.

[0070] Therefore, the active power reference value and the reactive power reference value in the inverter power regulation are:

[0071]

[0072] Wherein, k SOC is the power gain signal, P SOC is a set constant value.

[0073] The active power of the light storage system calculated based on the active power change of the load end is taken as the active power reference value in the inverter power control, and the inverter is controlled to make the active power change caused by the power fluctuation of the load end be instantaneously borne by the light storage system, and the active power change instantaneously borne by the light storage system is transferred to the gas internal combustion engine set within a time constant, specifically steps 4-7:

[0074] Step 4, obtain the three-phase voltage u B and the three-phase current i B at the output end of the inverter:

[0075] u B =[u Ba u Bb u Bc ] T

[0076] i B =[i Ba i Bb i Bc ] T

[0077] In the formula, u Ba , u Bb and u Bc are the a-phase, b-phase and c-phase voltages at the output end of the inverter, i Ba , i Bb and i Bc are the a-phase, b-phase and c-phase currents at the output end of the inverter.

[0078] Step 5, the voltage and current obtained by respectively performing park transformation (dq decomposition) on the three-phase voltage and three-phase current at the output end of the inverter, i.e. the voltage component and current component after park transformation of the inverter output end are respectively:

[0079] [u Bd u Bq ] T =T abc-dq ·[u Ba u Bb uBc ] T

[0080] [i Bd i Bq ] T =T abc-dq ·[i Ba i Bb i Bc ] T

[0081] The micro-grid voltage u B is transformed from the abc three-phase coordinate system to the dq coordinate system, and the d-axis voltage u Bd becomes a constant, and the q-axis voltage u Bq is zero.

[0082] Step 6, based on the active power reference value and the reactive power reference value in the inverter power regulation, and the voltage components of the inverter output end after Park transformation, the inner loop current reference quantity is calculated:

[0083]

[0084] Step 7, the inner loop current reference quantity i dref and i qref are subtracted from the current components i Bd and i Bq of the inverter output end after Park transformation, and the difference values are sequentially passed through a proportional-integral controller and a Park inverse transformation to obtain a pulse width modulation signal (PWM signal) for controlling the power output of the inverter (that is, the difference values are taken as the adjustment signal to input to the proportional-integral controller, and after PI adjustment, the voltage reference signal u * dref and u * qref (inverse of the inverter voltage outer loop control) in the dq coordinate system are obtained, and then the Park inverse transformation is performed to obtain the final PWM signal for controlling the power output of the inverter), and the obtained PWM modulation signal is used to control the opening and closing of the inverter thyristor to control the output current of the inverter, thereby changing the size of the actual output power of the optical storage system. At this time, the power of the gas internal combustion engine and the optical storage system is realized, and the stability of the micro-grid frequency when the micro-grid energy fluctuates is ensured.

[0085] The principle of the frequency control method for the gas internal combustion engine and the optical storage system provided in the embodiment is:

[0086] The relationship between the speed and the torque of the gas internal combustion engine can be expressed as:

[0087]

[0088] wherein J is the moment of inertia of the internal combustion engine, a constant; ω is the angular velocity of the gas internal combustion synchronous generator; T m is the mechanical torque output by the internal combustion engine; T Ln is the load torque.

[0089] The corresponding relationship between the synchronous generator speed n, the angular velocity ω, the pole pair number p, the power P and the torque T is as follows:

[0090]

[0091] Therefore, the corresponding relationship between the power output by the gas internal combustion engine and the micro-grid frequency is as follows:

[0092]

[0093] wherein f is the actual frequency of the micro-grid system; f N is the rated frequency 50Hz; P m is the mechanical power output by the internal combustion engine, P Ln is the load end power required to be borne by the internal combustion engine.

[0094] The present application ignores the mechanical loss of the gas internal combustion engine, that is, it is assumed that the mechanical power P m output by the gas internal combustion engine is equal to the active power P Ln required by the load end borne by the internal combustion engine when the micro-grid system is in stable operation, and the droop coefficient k n of the gas internal combustion engine is defined as k 2 =144πJ / 191p Ln Therefore, the relationship between the power output by the gas internal combustion engine and the micro-grid frequency can be expressed as:

[0095]

[0096] As can be seen from the above formula, when the micro-grid system is stable, the mechanical power output by the gas internal combustion engine is equal to the total load power, that is, the value of (P Ln -P m ) is equal to zero, so the frequency of the micro-grid system can be maintained near the rated frequency 50Hz; when the active power of the load end changes suddenly, the mechanical power output by the internal combustion engine cannot respond instantaneously, so in the initial stage of load change, the value of (P Ln -P m ) will be larger, so the frequency of the micro-grid system will drop greatly, and the length of time from the start of fluctuation to the recovery of the micro-grid system to stability is related to the size of the load instantaneous change ΔP and the power response speed of the gas internal combustion engine.

[0097] Based on the analysis of the aforementioned power characteristics, the proposed approach for power coordination control is as follows: The active power fluctuations caused by load fluctuations are initially handled by the photovoltaic-storage system (PV-SES). Then, at a set rate, the instantaneously increased power from the PV-SES is transferred to the gas-fired internal combustion engine (GC-ECU). This reduces the initial rate of change of the system frequency during load fluctuations, thereby decreasing the maximum frequency fluctuation of the microgrid system and ensuring that the microgrid frequency conforms to the power system's frequency regulations. During this control process, the GC-ECU remains the primary power source in the biomass microgrid, while the PV-SES only participates in power regulation during load fluctuations, thus meeting the microgrid's frequency regulation requirements.

[0098] Let P L P represents the total active power at the load end. B * The charging and discharging power of the photovoltaic-energy storage system itself is a constant; the total output power of the energy storage is P. B The total output power required by the gas internal combustion engine is P. Ln The power balance relationship of a microgrid system can then be expressed as:

[0099]

[0100] To implement the control method proposed in this invention, the energy signal when a power surge occurs at the load end is divided into two parts, which can be represented as:

[0101]

[0102] Wherein, 1 / (Ts+1) is the introduced power delay element; Ts is the delay time constant in the delay element; ΔP is the instantaneous change in active power when energy fluctuation occurs at the load end.

[0103] Depend on Figure 3 The power distribution diagram of the gas internal combustion engine, photovoltaic energy storage system, and load shows that by real-time monitoring of the total power P at the load end... L , will P L The instantaneous power change ΔP at the load end can be obtained by subtracting the instantaneous value after the delay period. When a suitable power delay time constant Ts is set, this change will gradually decay to zero. Therefore, when load fluctuations occur, the active power required by the photovoltaic-storage system and the active power required by the gas turbine engine can be expressed as follows:

[0104]

[0105] From the above formula, when the load end occurs power fluctuation, the initial value of instantaneous power change ΔP is maximum, at this time the optical storage system is instantaneously undertaken, the total power output of the gas internal combustion engine group is unchanged; subsequently the value of ΔP gradually decays to zero, at this time the total power undertaken by the optical storage system gradually recovers to the initial state P in a certain time B * At the same time, the gas internal combustion engine group increases the output of active power in the same time, and the part of power change ΔP is undertaken by itself. Figure 4 , Figure 4 P L0 is the initial state total active power of the load, P Ln0 is the initial state output total active power of the internal combustion engine, P Lt is the total active power after the sudden load increase, P Lnt is the total active power output of the internal combustion engine after reaching a new power balance.

[0106] Suppose that the mechanical power output of the gas internal combustion engine in the steady state of the micro-grid system is P The load fluctuation size at t moment is ΔP Lt , that is, at t moment At this time, the relationship between the output power of the gas internal combustion engine and the micro-grid frequency when the gas internal combustion engine and the optical storage power are cooperatively regulated can be obtained as follows:

[0107]

[0108] The core idea of the control method proposed in the application is to utilize the fast power response characteristic of the optical storage system, so that the large load active power change ΔP originally required to be responded by the gas internal combustion engine group is reduced, thereby reducing the maximum change of the micro-grid system frequency when the load fluctuation of the micro-grid occurs, so as to ensure the stability of the micro-grid frequency.

[0109] The system model of the micro-grid is built on the MATLAB / Simulink simulation platform, and the specific parameter information of the system simulation model of the micro-grid is shown in Table 1.

[0110] Table 1, specific parameter information of each module of the micro-grid

[0111]

[0112] Verify the effectiveness of the gas internal combustion engine and optical storage power cooperative control strategy:

[0113] The first case: the gas engine as the main power source adopts V / f control, the photovoltaic storage inverter adopts constant power control, the active power of the photovoltaic storage constant output is 2 kW, the whole micro-grid system starts with 23 kW load, and the load suddenly increases by 3 kW and suddenly decreases by 3 kW at 10 s and 20 s respectively. The simulation result is taken as the basic control group, and the total simulation time is set to 27 s;

[0114] The second case: the gas engine and the photovoltaic storage system adopt the power coordination control method proposed in the embodiment, the photovoltaic storage constant output active power is 2 kW when the micro-grid system is stable, the whole micro-grid system starts with 23 kW load, and the load suddenly increases by 3 kW and suddenly decreases by 3 kW at 10 s and 20 s respectively. The simulation result is compared with the basic control group in the first case, the total simulation time is set to 27 s, and the time constant is 1. Based on the simulation experiment of the above two cases, the simulation results are shown in Figure 5 、 Figure 6 and Figure 7 .

[0115] In the simulation process of Figure 5 、 Figure 6 and Figure 7 , the curve before power coordination control represents the simulation curve of the gas engine alone for power regulation when the load fluctuates, and the curve after power coordination control is the simulation curve after adopting the power coordination control; taking the sudden increase of 3 kW load at 10 s in the micro-grid system as an example.

[0116] When the power coordination control is not adopted, the photovoltaic storage system adopts constant power control mode, Figure 7 the output power of the photovoltaic storage is 2 kW and does not change; Figure 6 the gas engine needs to bear the whole load increment, and the output power of the gas engine increases from 21 kW to 24 kW and remains stable after 2 s. Since the gas engine as the main power source has a slow instantaneous power response speed, the frequency of the micro-grid with the gas engine as the main power source in Figure 5 drops from 50 Hz to 49.15 Hz, which is lower than the minimum value 49.5 Hz of the frequency operation specified by the power system, and the frequency of the biomass micro-grid is unstable.

[0117] When the power coordination control is adopted, the output power of the photovoltaic storage is controlled by the inverter, and when the load suddenly increases by 3 kW at 10 s, Figure 7 the active power of the photovoltaic storage system increases from 2 kW to 5 kW instantaneously, and then decreases to 2 kW in an exponential curve way within 4 s, and at the same time, Figure 6 the active power of the gas engine represented by the curve after power coordination control also increases from 21 kW to 24 kW within 4 s, and after adopting the power coordination control methodFigure 5 The frequency of the microgrid is raised from the minimum drop of 49.15 Hz to 49.52 Hz, and the minimum value of the system frequency after the cooperative control is higher than 49.5 Hz, which meets the frequency standard of the power system.

[0118] Therefore, through the analysis of the above two simulation results, the frequency control method of the gas internal combustion engine and the light storage cooperation proposed in the application can ensure the stability of the microgrid frequency. When the microgrid suddenly reduces the load, the situation is similar.

[0119] The influence of different values of the time delay constant Ts on the frequency modulation capacity of the system:

[0120] The first case: Ts=1, the gas internal combustion engine and the light storage power cooperative control, the entire microgrid system starts with a 23kW load, the light storage constantly outputs an active power of 2kW when the system is stable, the gas internal combustion engine set capacity is 30kW, and the load is suddenly increased by 3kW and suddenly reduced by 3kW at 10s and 20s respectively, the total simulation time is set to 27s, and the simulation results are shown in the "Ts=1" curve in Figure 8 , Figure 9 and Figure 10 .

[0121] The second case: Ts=3, the gas internal combustion engine and the light storage power cooperative control, the entire microgrid system starts with a 23kW load, the light storage constantly outputs an active power of 2kW when the system is stable, the gas internal combustion engine set capacity is 30kW, and the load is suddenly increased by 6kW and suddenly reduced by 6kW at 10s and 20s respectively, the total simulation time is set to 27s, and the simulation results are shown in the "Ts=3" curve in Figure 8 , Figure 9 and Figure 10 .

[0122] Taking the sudden load increase as an example, it can be seen from Figure 9 and Figure 10 that since the value of the time delay constant Ts is increased, the time for the light storage to recover to 2kW after instantaneously bearing 3kW and 6kW of load fluctuation at 10s is increased from 2.5s to 10s; it can be seen from Figure 8 that when the microgrid system respectively has a load fluctuation of 10% (3kW) and 20% (6kW) of the gas internal combustion engine set capacity, by increasing the value of the time delay constant Ts, the maximum drop value of the microgrid system frequency can be maintained above 49.5Hz, so that the frequency of the microgrid is within the standard of the power system.

[0123] Therefore, through the simulation result analysis of the above two cases, it can be concluded that by increasing the value of the time delay constant Ts, the maximum load fluctuation allowed by the micro-grid can be increased, and the power regulation capability of the micro-grid system can be improved. When the micro-grid suddenly reduces the load, the situation is similar.

[0124] In summary, through the analysis of the simulation results of the four cases, the effectiveness of the method can be verified, the stability of the system frequency of the micro-grid during load fluctuation can be ensured, and the power quality of the micro-grid can be improved. Moreover, by increasing the value of the time delay constant in the control method, the maximum instantaneous active power fluctuation value that the micro-grid system can withstand can also be increased, further improving the frequency regulation capability of the micro-grid system.

[0125] Embodiment Two

[0126] The embodiment provides a frequency control system of a gas internal combustion engine and a light storage cooperation, which specifically comprises the following modules:

[0127] A load end power change determination module configured to calculate the active power change of the load end through a power delay link when the load end fluctuates;

[0128] A cooperative control module configured to take the active power of the light storage system calculated based on the active power change of the load end as the active power reference value in the inverter power control, control the inverter, so that the active power change caused by the power fluctuation of the load end is temporarily borne by the light storage system, and the active power change temporarily borne by the light storage system is transferred to the gas internal combustion engine set within a time constant.

[0129] The active power of the light storage system is the sum of the active power change of the load end and the inherent charging and discharging power of the light storage system.

[0130] The time constant is calculated based on the maximum transient frequency change allowed by the power system, the regulation time for the frequency to recover from transient state to steady state, the initial power steady state operating point of the gas internal combustion engine, and the maximum instantaneous load active power fluctuation allowed by the micro-grid.

[0131] It should be noted that each module in the embodiment corresponds to each step in Embodiment One, and the specific implementation process is the same, which will not be repeated here.

[0132] Embodiment Three

[0133] The embodiment provides a computer readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the frequency control method of the gas internal combustion engine and the light storage cooperation in Embodiment One.

[0134] Embodiment Four

[0135] The embodiment provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the frequency control method of the gas internal combustion engine and the light storage cooperation as described in the above embodiment one when executing the program.

[0136] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage, etc.) containing computer-usable program code.

[0137] The present application is described with reference to flowcharts and / or block diagrams of the method, device (system), and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for carrying out the functions specified in the flowcharts and / or block diagrams.

[0138] These computer program instructions can also be stored in a computer-readable memory capable of guiding the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a product including instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for carrying out the functions specified in the flowcharts and / or block diagrams.

[0139] These computer program instructions can also be loaded into a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable data processing apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for carrying out the functions specified in the flowcharts and / or block diagrams.

[0140] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing relevant hardware, and the program can be stored in a computer readable storage medium. When the program is executed, the program can include the processes of the above-mentioned embodiment methods. The storage medium can be a magnetic disc, an optical disc, a read-only memory (ROM), a random access memory (RAM) or the like.

[0141] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement and the like within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of frequency control of a gas internal combustion engine in cooperation with a light storage, characterized by, The method comprises the steps of: When the load end has a power fluctuation, the active power variation of the load end is calculated through a power delay link; The active power borne by the optical storage system, which is calculated based on the active power variation of the load end, is taken as an active power reference value in the inverter power control, and the inverter is controlled so that the active power variation caused by the power fluctuation of the load end is borne by the optical storage system instantaneously, and the active power variation borne by the optical storage system is transferred to the gas internal combustion engine set within a time constant; The specific steps of controlling the inverter are: The three-phase voltage and three-phase current at the output end of the inverter are obtained, and are subjected to Park transformation respectively to obtain the voltage component and current component of the inverter after Park transformation; Based on the active power reference value in the inverter power regulation and the voltage component of the inverter after Park transformation, an inner loop current reference is calculated; The inner loop current reference and the current component of the inverter after Park transformation are subtracted, and the difference is subjected to proportional integral controller and Park inverse transformation in sequence to obtain a pulse width modulation signal for controlling the power output of the inverter, and the obtained pulse width modulation signal is used to control the breaking of the inverter thyristor to control the output current at the inverter end; The power delay time constant is: where Ts is the power time delay constant, P0 is the first steady state operating point of mechanical power, ΔP Ltmax is the maximum load fluctuation allowed to occur in the microgrid system, Δf max is the maximum frequency variation, Δt max is the regulation time for transient recovery to steady state, f N is the rated frequency 50 Hz; k n is the power frequency droop coefficient of the gas internal combustion engine; By real-time monitoring the total power P L , P L and the instantaneous value after the time delay link, the instantaneous power change ΔP of the load end is obtained, and after setting a suitable power delay time constant Ts, the change will gradually decay to zero. When the load fluctuates, the active power required to be borne by the optical storage system and the active power required to be borne by the gas internal combustion engine are respectively represented as: In the formula, P B is the active power assumed by the optical storage system, is the charge and discharge power of the optical storage system itself, P Ln is the active power required to be assumed by the internal combustion engine.

2. A method of frequency control of a gas internal combustion engine in cooperation with a light storage according to claim 1, characterized by, The calculation method of the active power variation of the load end is: The three-phase voltage and three-phase current at the load end are obtained, and are subjected to Park transformation respectively to obtain the voltage component and current component of the load end after Park transformation; Based on the voltage and current components after Park transformation, the instantaneous active power of the load end is calculated; After the active power of the load end is controlled through a delay link, the active power variation of the load end is obtained.

3. A method of frequency control of a gas internal combustion engine in cooperation with a light storage according to claim 1, characterized by, The active power borne by the optical storage system is the sum of the active power variation of the load end and the inherent charge-discharge power of the optical storage system.

4. A method of frequency control of a gas internal combustion engine in cooperation with a light storage according to claim 1, characterized by, The time constant is calculated based on the maximum transient frequency variation allowed by the power system, the regulation time for the frequency to recover from the transient state to the steady state, the initial power steady state operating point of the gas internal combustion engine, and the maximum instantaneous load active power fluctuation allowed by the microgrid.

5. A frequency control system for a gas internal combustion engine in cooperation with a light storage system, using the method as claimed in claim 1, characterized in that, The method comprises the steps of: a load end power variation determination module configured to calculate the active power variation of the load end through a power delay link when the load end has a power fluctuation; a cooperative control module configured to take the active power borne by the optical storage system, which is calculated based on the active power variation of the load end, as an active power reference value in the inverter power control, and control the inverter so that the active power variation caused by the power fluctuation of the load end is borne by the optical storage system instantaneously, and the active power variation borne by the optical storage system is transferred to the gas internal combustion engine set within a time constant.

6. A frequency control system for a gas internal combustion engine in cooperation with a light storage as claimed in claim 5, characterized in that, The active power borne by the optical storage system is the sum of the active power variation of the load end and the inherent charge-discharge power of the optical storage system.

7. A frequency control system for a gas internal combustion engine in cooperation with a light storage system as claimed in claim 5, characterized in that, The time constant is calculated based on the maximum transient frequency variation allowed by the power system, the regulation time for the frequency to recover from the transient state to the steady state, the initial power steady state operating point of the gas internal combustion engine, and the maximum instantaneous load active power fluctuation allowed by the microgrid.

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program, when executed by the processor, implements the steps of a method of frequency control of a gas internal combustion engine in cooperation with a photovoltaic storage according to any one of claims 1-4.

9. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor, when executing the program, implements the steps of a method of frequency control of a gas internal combustion engine in cooperation with a photovoltaic storage according to any one of claims 1-4.

Images