Self-optimizing tuning method for inertia damping in diesel-storage hybrid power plants for pulse loads

Abstract

A method for self-optimizing the inertia damping of a diesel-storage hybrid power station for pulse loads is disclosed. The method comprises constructing a diesel-storage hybrid power station model including a diesel generator, an energy storage system, and a pulse load. The energy storage system uses a rotor swing equation to simulate the inertia and damping characteristics of the diesel generator and reflects the output power difference between the diesel generator and the energy storage converter through normalized oscillation power. During the self-optimizing tuning stage, the initial value theorem is used to obtain the initial value of the angular velocity difference under a unit step to decouple the inertia parameter and damping parameter in the oscillation power, and the inertia parameter is adjusted. The final value theorem is then used to obtain the final value of the oscillation power under a unit step to decouple the inertia parameter and damping parameter in the oscillation power, and the damping parameter is adjusted. The method can achieve automatic matching of VSG parameters when the SG inertia and damping are unknown, thereby improving the SG-VSG power synchronization of the ship power system diesel-storage hybrid power station and suppressing continuous power deviation or even instability caused by mismatch between the SG-VSG inertia and damping parameters.

Description

Technical Field

[0001] The present invention relates to a technology in the field of hybrid power station control, in particular to a method for self-optimizing inertia damping of a diesel-storage hybrid power station for pulse loads. Background Art

[0002] Under pulsed loads, the use of virtual synchronous generator (VSG) control in energy storage can cause the dynamic output power of diesel-storage power plants to oscillate continuously, exacerbating power asynchrony between the VSG and synchronous generator (SG), and even leading to system instability. The main cause of this problem is the mismatch between the inertia and damping parameters of the VSG and those of the SG. However, since the inertia and damping parameters of the ship's power plant SG may be unavailable for confidentiality reasons or may drift due to equipment aging, it is difficult to adapt the VSG parameters to the SG parameters. Summary of the Invention

[0003] In view of the fact that the existing technology does not consider the continuous disturbance of the pulse load to the system and the power oscillation phenomenon of the synchronous generator when the inertia and damping are unknown, and the power asynchrony between the VSG and SG and the system instability caused by it in the scenario of single load mutation, the present invention proposes a self-optimizing tuning method for inertia and damping of a diesel-storage hybrid power station for pulse loads. The method can realize automatic matching of VSG parameters when the SG inertia and damping are unknown, thereby improving the SG-VSG power synchronization of the diesel-storage hybrid power station of the ship power system and reducing the continuous power deviation or even instability caused by the mismatch between the SG-VSG inertia parameters and damping parameters.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a self-optimizing tuning method for inertia damping of a diesel-storage hybrid power station for pulse loads. After constructing a diesel-storage hybrid power station model including a diesel generator, an energy storage system and a pulse load, the energy storage system uses a rotor swing equation to simulate the inertia and damping characteristics of the diesel generator and reflects the difference in output power between the diesel generator and the energy storage converter through normalized oscillation power. In the self-optimizing tuning stage, an initial value theorem is used to obtain an initial value of the angular velocity difference under a unit step to decouple the inertia parameter and the damping parameter in the oscillation power, and the inertia parameter is tuned. Then, a final value theorem is used to obtain a final value of the oscillation power under a unit step to decouple the inertia parameter and the damping parameter in the oscillation power, and the damping parameter is tuned.

[0006] The present invention relates to a system for implementing the above-mentioned method, comprising: an SG measurement unit, a VSG measurement unit, a load measurement unit, a determination unit and a parameter setting unit, wherein: the SG measurement unit, the VSG measurement unit and the load measurement unit perform data acquisition processing based on system operation information, the determination unit performs load status determination processing based on load measurement unit information, and obtains a result of whether parameter setting is started; the parameter setting unit performs parameter setting processing based on the SG measurement unit, the VSG measurement unit and the start-up determination information to obtain a parameter setting result.

[0007] Technical Effects

[0008] The present invention realizes the decoupling of the inertia parameter and damping parameter setting and the automatic adjustment of the VSG control parameters to adapt the SG characteristics through the initial value theorem and the final value theorem of the frequency domain model, thereby smoothing the diesel storage power oscillation problem under pulse load. The problem of power oscillation and even instability is solved from the root by matching the VSG parameters with the SG, and a targeted VSG parameter setting strategy is proposed in combination with the pulse load characteristics. Compared with the traditional method of manual trial and error adjustment when the SG inertia and damping parameters are unknown, the present invention realizes the automatic matching of the VSG inertia parameters and damping parameters to the SG, and achieves the active optimization of the VSG parameters: after the parameter setting is completed, there is no need to add other control systems, which greatly saves the setting resources. Compared with the solution with the help of additional control, it has a permanent effect, and the present invention can eliminate the power oscillation from the root, which has a better effect. It solves the problem that most of the existing technologies are aimed at single load mutation conditions and do not fully consider the continuous disturbance brought to the system by the pulse load. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematic diagram of diesel storage system under pulse load;

[0010] Figure 2 It is a schematic diagram of the pulse load power waveform;

[0011] Figure 3 This is the control flow chart for adaptive tuning of inertia parameters;

[0012] Figure 4 Schematic diagram of VSG and SG output power;

[0013] Figure 5 Schematic diagram of VSG-SG oscillation power;

[0014] Figure 6 This is a schematic diagram of the VSG inertia parameter setting value;

[0015] Figure 7 Schematic diagram of VSG and SG output power;

[0016] Figure 8Schematic diagram of VSG-SG oscillation power;

[0017] Figure 9 Schematic diagram of VSG damping parameter setting values. DETAILED DESCRIPTION

[0018] This embodiment relates to a method for self-optimizing inertia damping in a diesel-storage hybrid power plant for pulse loads, including:

[0019] Step 1: Construct Figure 1 The diesel-storage hybrid power plant model shown includes a diesel generator, an energy storage system and pulse loads.

[0020] The diesel generator includes: a diesel engine, a synchronous generator (SG) and its control system. Due to different unit combinations during the operation of the system, the inertia parameters and damping parameters obtained by the aggregation of the diesel generator sets are unknown.

[0021] The energy storage system includes: an energy storage battery, a DC-AC converter and its control system, wherein: the energy storage converter adopts VSG grid control and supplies power synchronously with the diesel generator set.

[0022] like Figure 1 As shown in Figure 1, u1 and u2 represent the output voltages of VSG and SG respectively. i1 and i2 represent the output currents of VSG and SG respectively. SW1 and SW2 are the parallel switches of the energy storage converter and diesel generator respectively. line1 and Z line2 are the line impedances of VSG and SG respectively. m1 is the input torque of the synchronous generator, U dc is the DC side voltage of the DC-AC converter.

[0023] like Figure 2 As shown in the figure, the power waveform of the pulse load represented by the electronic radar is shown. In the figure, T1 is the pulse on time, T2 is the pulse off time, and T is the pulse period. The period of the pulse load is generally greater than 100ms. The average power P av =P p d+P s (1-d), dynamic power Where: P p is the peak power of the pulse load, P s is the steady-state power, d is the duty cycle of the pulse power, P d is the dynamic power P L2 The peak value of the pulse load. The frequency domain equation is: ΔP load (s)=P d (1-e -sdT ) / [s(1-e -sT )].

[0024] Step 2: Based on the diesel-storage hybrid power plant model constructed in step 1, VSG parameters are optimized, including:

[0025] Step 2.1 Energy storage simulates the inertia and damping characteristics of the diesel generator through the rotor swing equation, specifically: Among them: variables related to the energy storage converter are represented by subscript "1", and variables related to the diesel generator are represented by subscript "2". n1 and P n2 are the rated power of energy storage converter and diesel generator respectively, P e1 and P e2 are the electromagnetic power output by the energy storage converter and the diesel generator, ω n is the rated angular frequency of the system, ω1 and ω2 are the virtual angular frequency of the energy storage converter and the rotor speed of the diesel generator respectively, J1 and J2 are the inertia parameters of the energy storage converter and the diesel generator, D p1 and D p2 are the damping parameters of energy storage converter and diesel generator respectively. The rated power of diesel generator P n2 , output reactance X f2 The parameters can be adjusted according to the equipment nameplate. Therefore, the rated power P of the energy storage converter is n1 , output reactance X f1 Can be configured according to the diesel generator parameter ratio: P n1 / P n2 =X f1 / X f2 =m.

[0026] Step 2.2: Obtain the system oscillation power and angular acceleration difference transfer function through the VSG-SG small signal model:

[0027] By oscillation power ΔP 12 Reflects the difference in output power between the diesel generator and the energy storage converter: ΔP 12 =P e1 / m1-P e2 / m2, where: m1 and m2 are the VSG and SG reference powers respectively, which are set proportionally according to the rated power of the energy storage converter and the diesel generator; the electromagnetic power P of the energy storage converter and the diesel generator e1 and P e2 Equal to the line transmission power, k1 / m1=k2 / m2=k. The angular acceleration difference Δa is obtained 12 The transfer function with respect to load variation is: Among them: α0~α3 expression is: Oscillation power ΔP 12 for:

[0028] Step 2.3: Optimize the VSG inertia parameters. To decouple the inertia and damping parameters from the oscillation power, use the initial value theorem to find the initial value of the angular velocity difference under a unit step. Specifically,

[0029] Since there is no ideal instantaneous sudden increase or decrease in load during actual system operation, the load generally reaches steady state after a relatively fast ramp-up process. Therefore, the first peak of the angular acceleration difference occurs after the load power has completed its ramp-up, which can be roughly regarded as the initial value of the angular acceleration difference. Since the ideal instantaneous sudden increase or decrease in load is the worst case, the theoretical angular acceleration difference is always greater than the actual measured initial value of the angular acceleration difference. Assume that the initial value of the angular acceleration difference during actual system operation is Δa 12s , and the VSG inertia parameter is known to be J1, then based on Δa 12s And the above formula is used to adjust the SG inertia parameters Set the VSG inertia parameter setting value J1=m1J2 * / m2, the VSG inertia parameter can be continuously approached to the SG inertia parameter, which can reduce the angular acceleration difference and thus reduce the power oscillation. When the controller detects the rising edge of the pulse power, the VSG inertia parameter J1 is adjusted once and repeatedly adjusted until the oscillation power is eliminated. The inertia parameter adaptive adjustment control process is as follows Figure 3 shown.

[0030] Step 2.4: Optimizing the VSG damping parameters: To decouple the inertia and damping parameters from the oscillation power, the final value theorem is used to calculate the final value of the oscillation power under a unit step. Specifically,

[0031] The average oscillation power within a pulse load cycle is specifically: The VSG damping parameter is known to be D p1 , get the SG damping parameter D p2 * : Set the VSG damping parameter setting value D p1 =D p2 * , the VSG damping parameter can be adjusted to the SG inertia parameter to reduce the oscillation power. When the controller detects the rising edge of the pulse power, the VSG inertia parameter D p1 Perform a tuning operation and repeat the tuning operation until the oscillating power is eliminated.

[0032] After specific actual experiments, an experimental platform for a diesel-storage hybrid power station was built, consisting of a diesel generator, an energy storage converter, a pulse load, and a conventional load. The specific parameters are as follows: the system rated frequency is 50Hz, the conventional load is 40kW. The pulse load parameters are shown in Table 1: the pulse load period T = 500ms, the duty cycle d = 0.5, the peak power Pd =20kW. The parameters of the energy storage converter (VSG) are shown in Tables 2 and 3. The rated capacity P n1 =20kW, base capacity m1 = 20kW, line impedance X f1 =0.471Ω, scenario 1 inertia parameter J1 = 2kg·m2, damping parameter D p1 =20.28W / s, scenario 2 inertia parameter J1 = 1kg·m2, damping parameter D p1 =40.56W / s. The parameters of the diesel generator (SG) are shown in Tables 2 and 3. The rated capacity P n2 =20kW, base capacity m2 = 20kW, line impedance X f2 =0.471Ω, inertia parameter J2 = 1kg·m2, damping parameter D p2 =20.28W / s.

[0033] Table 1 Parameters of pulse load

[0034]

[0035] Scenario 1: Inertia parameter tuning

[0036] To verify the effectiveness of the inertia parameter tuning method, the parameters of the energy storage converter and diesel generator are set on the experimental platform of the diesel-storage hybrid power station as shown in Table 2.

[0037] Table 2 Parameters of diesel-storage hybrid power station

[0038]

[0039] The specific simulation results and analysis are as follows: Based on the parameter tuning method, the output power and oscillation power of VSG and SG are respectively as follows: Figure 4 and Figure 5 As shown in the figure. At 1s, the pulse load is put into operation. At this time, due to the serious mismatch between the inertia parameters of VSG and SG, the transient power imbalance between VSG and SG is also more obvious, and the maximum oscillation power reaches 27.5%. Subsequently, the method proposed in this paper begins to optimize the inertia parameters of VSG. The specific process is as follows: Figure 8 As shown in the figure, the VSG inertia parameters gradually approach the SG inertia parameters 1kg·m 2 Parameter tuning is basically completed in 4 seconds (about 5 to 6 pulse cycles). At this time, the output power between VSG and SG remains synchronized, and the oscillation power is less than 1%.

[0040] Scenario 2: Damping parameter tuning

[0041] To verify the effectiveness of the damping parameter tuning method, the parameters of the energy storage converter and diesel generator are set on the experimental platform of the diesel-storage hybrid power station as shown in Table 3.

[0042] Table 3 Parameters of diesel-storage hybrid power station

[0043]

[0044] The specific simulation results and analysis are as follows: Based on the parameter tuning method in this chapter, the output power and oscillation power of VSG and SG are respectively as follows: Figure 7 and Figure 8 As shown in Figure 1. At 1s, the pulse load is applied. At this time, due to the serious mismatch between the damping parameters of VSG and SG, the problem of uneven distribution occurs between VSG and SG, and the maximum oscillation power reaches 43.2%. Subsequently, the method proposed in this paper begins to adjust the VSG damping parameters. The specific process is as follows: Figure 9 As shown in the figure, it can be seen that the VSG inertia parameter gradually approaches the SG inertia parameter 20.28W·s, and the parameter tuning is basically completed in 2s (about 1 to 2 pulse cycles).

[0045] Compared with the existing technology, this method greatly improves the power synchronization rate through the automatic parameter adjustment link based on the initial value of the SG-VSG angular acceleration and the average oscillation power. After adopting the existing technology, the oscillation power will be reduced to 7-11%. After adopting this method, the oscillation power will be reduced to less than 1%.

[0046] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for self-optimizing inertia damping in a diesel-storage hybrid power station for pulse loads, characterized by: After constructing a diesel-storage hybrid power station model that includes a diesel generator, an energy storage system, and a pulse load, the energy storage system uses the rotor swing equation to simulate the inertia and damping characteristics of the diesel generator and reflects the difference in output power between the diesel generator and the energy storage converter through normalized oscillation power. In the self-optimization tuning stage, the initial value theorem is used to obtain the initial value of the angular velocity difference under unit step to decouple the inertia parameter and damping parameter in the oscillation power, and the inertia parameter is tuned. Then, the final value theorem is used to obtain the final value of the oscillation power under unit step to decouple the inertia parameter and damping parameter in the oscillation power, and the damping parameter is tuned. The diesel-storage hybrid power station model includes a diesel generator, an energy storage system, and a pulse load, wherein: The diesel generator includes: a diesel engine, a synchronous generator (SG) and its control system. Due to the different unit combinations in the system during operation, the inertia parameters and damping parameters obtained by the aggregation of the diesel generator sets are unknown; The energy storage system includes: energy storage batteries, DC-AC converters and their control systems, wherein: the energy storage converters adopt VSG grid control and are synchronously powered by the diesel generator set; The average power of the pulse load , dynamic power , where: P p is the peak power of the pulse load, P s is the steady-state power, d is the duty cycle of the pulse power, P d is the dynamic power P L2 The peak value of the pulse load frequency domain equation is: , T is the pulse period; The rotor swing equation is used to simulate the inertia and damping characteristics of the diesel generator and the normalized oscillation power is used to reflect the difference in output power between the diesel generator and the energy storage converter. Specifically, the following method is used to obtain: 1) Simulate the inertia and damping characteristics of the diesel generator through the rotor swing equation: , , where: variables related to the energy storage converter are represented by subscript "1", variables related to the diesel generator are represented by subscript "2", P n1 and P n2 are the rated power of energy storage converter and diesel generator respectively, P e1 and P e2 are the electromagnetic power output by the energy storage converter and the diesel generator, ω n is the rated angular frequency of the system, ω1 and ω2 are the virtual angular frequency of the energy storage converter and the rotor speed of the diesel generator respectively, J1 and J2 are the inertia parameters of the energy storage converter and the diesel generator, D p1 and D p2 are the damping parameters of the energy storage converter and diesel generator respectively, and the rated power of the diesel generator P n2 , output reactance X f2 The parameters can be adjusted according to the equipment nameplate, so the rated power of the energy storage converter P n1 , output reactance X f1 It can be configured according to the diesel generator parameter ratio: ; 2) The system oscillation power and angular acceleration difference transfer function are obtained through the VSG-SG small signal model: the oscillation power ΔP 12 Reflects the difference in output power between the diesel generator and the energy storage converter: , where: m1 and m2 are the reference powers of VSG and SG respectively, which are set proportionally according to the rated power of energy storage converter and diesel generator; the electromagnetic power P of energy storage converter and diesel generator e1 and P e2 is equal to the line transmission power, , we get the angular acceleration difference Δa 12 The transfer function with respect to load variation is: , where: α0~α3 expression is: ; Oscillation power ΔP 12 The transfer function with respect to load variation is: ; The self-optimizing tuning stage specifically includes: a) Using the initial value theorem, find the initial value of the angular velocity difference under the unit step, specifically: Since there is no ideal instantaneous sudden increase / decrease in load during the actual operation of the system, the load generally reaches a steady state after a relatively fast ramp-up process. Therefore, the first peak of the angular acceleration difference appears after the load power has completed the ramp-up, which is approximately regarded as the initial value of the angular acceleration difference. The ideal instantaneous sudden increase / decrease in load is the worst case, so the theoretical angular acceleration difference is always greater than the actual measured initial value of the angular acceleration difference. Assuming that the initial value of the angular acceleration difference during the actual operation of the system is Δa 12s , and the VSG inertia parameter is known to be J1, then based on Δa 12s And using the initial value theorem, find the initial value of the angular velocity difference under the unit step, and adjust to obtain the SG inertia parameter ; Set the VSG inertia parameter setting value J1=m1J2 * / m2, so that the VSG inertia parameter is constantly approaching the SG inertia parameter, reducing the angular acceleration difference and thus reducing the power oscillation. When the controller detects the rising edge of the pulse power, the VSG inertia parameter J1 is adjusted once and repeatedly adjusted until the oscillation power is eliminated; b) Using the final value theorem, find the final value of the oscillating power under a unit step, specifically: , the average oscillation power within a pulse load cycle is specifically: , the VSG damping parameter is known to be D p1 , get the SG damping parameter D p2 * : , set the VSG damping parameter setting value D p1 =D p2 * , adjust the VSG damping parameter to the SG inertia parameter to reduce the oscillation power, and adjust the VSG inertia parameter D when the controller detects the rising edge of the pulse power. p1 Perform a tuning operation and repeat the tuning operation until the oscillating power is eliminated.

2. A self-optimizing system for inertia damping of a diesel-storage hybrid power station for pulse loads that implements the method of claim 1, characterized in that: include: SG measurement unit, VSG measurement unit, load measurement unit, judgment unit and parameter setting unit, wherein: the SG measurement unit, VSG measurement unit and load measurement unit perform data acquisition and processing according to the system operation information, the judgment unit load measurement unit information, perform load status judgment processing, and obtain the result of whether the parameter setting is started; the parameter setting unit performs parameter setting processing according to the SG measurement unit, VSG measurement unit and the start judgment information to obtain the parameter setting result.

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