A method for coordinated control of generator-hybrid energy storage in aircraft high voltage DC power grid

Abstract

The present invention discloses a generator-hybrid energy storage coordinated control method in an aircraft high-voltage direct current power grid, and belongs to the field of aviation electrical engineering technology. The coordinated control method described in the present invention first introduces a virtual impedance droop loop in the control loop of the generator, lithium battery and supercapacitor to divide the output current of the three; then the bus voltage set value of each loop is compensated and corrected to correct the voltage drop caused by the droop control; finally, the charge state of the lithium battery and the supercapacitor is adjusted by adjusting the voltage compensation parameters to avoid the lithium battery and the supercapacitor from working beyond the limit. The present invention solves the problem of main power supply power pulsation in the traditional hybrid energy storage control strategy, coordinates the main power supply with the hybrid energy storage, and reduces the output power pulsation of the generator; integrates the bus voltage compensation and the charge state adjustment of the energy storage in one loop, simplifies the complexity of the control strategy, and improves the reliability of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of aviation electrical engineering, and in particular relates to a generator-hybrid energy storage coordinated control method in an aircraft high-voltage direct current power grid. Background Art

[0002] With the introduction of the concept of multi-electric and all-electric aircraft and the development of high-voltage DC power supply systems, various types of airborne electrical equipment have increased dramatically, and the load has shown the characteristics of multi-electric, high-power and non-linear. Non-linear loads cause frequent power pulsations in the aircraft power grid during switching or normal operation. This power pulsation will cause large output power pulsations of the generator, severe heating, large bus voltage fluctuations, reduced power quality, etc., ultimately affecting the safe and reliable operation of the power grid.

[0003] In order to solve the problem of power pulsation in DC power grid, a hybrid energy storage system composed of lithium batteries and supercapacitors is currently widely used to smooth out the fluctuations of the power grid and maintain the power balance of the system. In terms of the control strategy of the hybrid energy storage system, the control idea of ​​frequency division is generally adopted, with supercapacitors responding to high-frequency components and lithium batteries responding to low-frequency components, thereby giving full play to the advantages of both. Common frequency division control strategies can be divided into two categories: centralized control strategies based on filters and distributed control strategies based on droop control. In terms of the optimization of control strategies, there are dynamic adjustment of cutoff frequency, adjustment of energy storage charge state, voltage recovery adjustment, etc.

[0004] At present, the research on hybrid energy storage control strategy only considers the control and current distribution between supercapacitors and lithium batteries, and does not realize the coordinated control of the main power supply and hybrid energy storage. Although the voltage is stable, the output power on the main power supply side still fluctuates greatly, so the power pulsation is not truly smoothed. In addition, the optimization of the control strategy requires the introduction of multiple links, which increases the complexity of the control strategy and reduces its reliability. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and propose a generator-hybrid energy storage coordinated control method in an aircraft high-voltage DC power grid. The purpose of the present invention is to coordinate the control of the generator, lithium battery and supercapacitor, and integrate the optimization of multiple control strategies, effectively reduce the current pulsation of the generator, reduce the complexity of the control strategy, and improve the system reliability.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] A generator-hybrid energy storage coordinated control method in an aircraft high-voltage direct current grid, the aircraft high-voltage direct current grid comprising a high-voltage direct current generator, a hybrid energy storage unit, a 270V direct current bus and a load, wherein the high-voltage direct current generator is connected to the 270V direct current bus via a filter capacitor, the hybrid energy storage unit is composed of a lithium battery and a super capacitor, the lithium battery and the super capacitor are respectively connected to the 270V direct current bus via corresponding charge and discharge regulators, and the load is directly connected to the 270V direct current bus;

[0008] The generator-hybrid energy storage coordinated control method belongs to a distributed control method, which completes the coordinated control of the three by controlling the voltage regulator of the generator, the charging and discharging regulators corresponding to the lithium battery and the supercapacitor, and is characterized in that it includes the following steps:

[0009] Step 1: Introduce a virtual impedance droop loop in front of the voltage and current loops in the control loops of the generator, lithium battery and supercapacitor to achieve the response of the three to different frequency bands of the load current;

[0010] Step 2: Correct the given values ​​of the bus voltage in the control loops of the generator, lithium battery and supercapacitor, and add voltage compensation control to avoid bus voltage drop caused by droop control;

[0011] Step 3: Monitor the state of charge of the lithium battery and supercapacitor in real time. When the state of charge exceeds the normal operating range, adjust the parameters of the voltage compensation control described in step 2 to adjust the state of charge of the energy storage device to restore it to the normal range to avoid the lithium battery and supercapacitor from operating beyond the limit.

[0012] Preferably, step one includes introducing a virtual inductor on the generator side, introducing a virtual resistor on the lithium battery side, and introducing a virtual capacitor and resistor in parallel on the supercapacitor side, so that the output current of the generator, lithium battery and supercapacitor has the following relationship with the load current: the generator responds to the low-frequency component of the load current, and its frequency response range is [0, ω1]; the lithium battery responds to the medium-frequency component of the load current, and its frequency response range is [ω1, ω2]; the supercapacitor responds to the high-frequency component of the load current, and its frequency response range is [ω2, +∞], wherein ω1 and ω2 are the dividing points between the generator current and the lithium battery current, and between the lithium battery current and the supercapacitor current, respectively; ω1 and ω2 are reasonably set in combination with the requirements of the working frequency bands of the generator, lithium battery and supercapacitor, and the virtual impedance value in the droop control loop corresponding to each source is calculated.

[0013] Preferably, the step 2 includes collecting the real-time voltage value v of the 270V DC busbar Bus , and the voltage given value v ref Make a difference, and get Δv by proportional-integral adjustment. refAdd together to get the new voltage set value v of the control loop * ref , to compensate for the voltage drop caused by the droop control in the control loops of the generator, lithium battery and supercapacitor.

[0014] Preferably, in step 2, under normal working conditions, the proportional-integral adjustment parameters of the voltage compensation in each control loop take the same value.

[0015] Preferably, the step three includes setting the integral parameter k in the proportional-integral regulation of the voltage compensation in the control loop when the state of charge of the lithium battery and the supercapacitor exceeds the normal working range. * i Under normal working conditions, the integral parameter k i And the relationship between the charge state change rate is

[0016]

[0017] Among them, α1 and α2 are constants, SOC is the state of charge, SOC min and SOC max are the minimum and maximum values ​​of SOC respectively.

[0018] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0019] The method of the present invention first introduces a virtual impedance droop loop into the control loop of the generator, lithium battery and supercapacitor to divide the output current of the three; then the bus voltage set value of each loop is compensated and corrected to correct the voltage drop caused by the droop control; finally, the state of charge of the lithium battery and supercapacitor is adjusted by adjusting the voltage compensation parameters to avoid the lithium battery and supercapacitor from working beyond the limit. The present invention solves the problem of main power supply power pulsation in the traditional hybrid energy storage control strategy by introducing virtual impedance into the control loop of the generator, lithium battery and supercapacitor, coordinates the main power supply with the hybrid energy storage, and reduces the output power pulsation of the generator; and integrates the compensation control of the bus voltage and the over-limit control of the energy storage charge state into one loop, which simplifies the control strategy and improves the reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a system structure diagram of Embodiment 1

[0021] Figure 2 This is a system control block diagram of Embodiment 1

[0022] Figure 3 The energy storage state of charge adjustment principle diagram of embodiment 1

[0023] Figure 4The generator, lithium battery and supercapacitor frequency division current waveform diagram of the simulation result of Example 1;

[0024] Figure 5 The bus voltage regulation waveform diagram of the simulation result of the first embodiment;

[0025] Figure 6 The supercapacitor state of charge adjustment waveform diagram of the simulation result of Example 1. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto.

[0027] Embodiment 1

[0028] This embodiment provides a method for coordinated control of generators and hybrid energy storage in an aircraft high voltage DC power grid. Figure 1 As shown, the aircraft high-voltage DC power grid includes a high-voltage DC generator, a hybrid energy storage unit, a 270V DC bus and a load, wherein the high-voltage DC generator is connected to the 270V DC bus via a filter capacitor, the hybrid energy storage unit is composed of a lithium battery and a super capacitor, the lithium battery and the super capacitor are respectively connected to the 270V DC bus via corresponding charge and discharge regulators, and the load is directly connected to the 270V DC bus. In this embodiment, the charge and discharge regulator of the energy storage adopts a bidirectional DC / DC converter based on Buck-Boost.

[0029] The generator-hybrid energy storage coordinated control method is a distributed control method, which completes the coordinated control of the three by controlling the voltage regulator of the generator, the charging and discharging regulators corresponding to the lithium battery and the supercapacitor. It includes the following steps:

[0030] Step 1: Introduce a virtual impedance droop loop in front of the voltage and current loops in the control loops of the generator, lithium battery and supercapacitor to achieve the response of the three to different frequency bands of the load current;

[0031] Step 2: Correct the given values ​​of the bus voltage in the control loops of the generator, lithium battery and supercapacitor, and add voltage compensation control to avoid bus voltage drop caused by droop control;

[0032] Step 3: Monitor the state of charge of the lithium battery and supercapacitor in real time. When the state of charge exceeds the normal operating range, adjust the voltage compensation parameters described in step 2 to adjust the state of charge of the energy storage device to restore it to the normal range to prevent the lithium battery and supercapacitor from operating beyond the limit.

[0033] like Figure 2 The system control block diagram provided by the present invention is shown in FIG. 1 , in which a virtual inductor L is introduced in front of the voltage and current loop of the generator control loop.G , introduce a virtual resistor R on the lithium battery side B , introduce virtual capacitor C on the supercapacitor side SC and virtual resistor R SC Parallel R SC / / C SC After the designed virtual impedance is introduced, the relationship between the output current of the generator, lithium battery and supercapacitor and the load current is:

[0034]

[0035] Among them, i oG is the output current of the generator, i oB and i oSC are the output currents of lithium battery and supercapacitor after connecting to charge and discharge regulator, i Load is the load current, and s is the differential operator.

[0036] The above three equations can be further simplified to:

[0037]

[0038] Among them, ω1 and ω2 are the frequency division points between the generator current and the lithium battery current, and between the lithium battery current and the supercapacitor current, respectively. According to the above three equations, it can be seen that the generator responds to the low-frequency component of the load current, the lithium battery responds to the medium-frequency component of the load current, and the supercapacitor responds to the high-frequency component of the load current. Combined with the requirements of the operating frequency bands of the generator, lithium battery and supercapacitor, the virtual impedance value in the droop control loop corresponding to each source can be calculated by setting reasonable ω1 and ω2.

[0039] Furthermore, in step 2, the bus voltage compensation is specifically as follows: collecting the real-time voltage value v of the 270V DC bus Bus , and the voltage given value v ref Make a difference, and get Δv by proportional-integral adjustment. ref Add together to get the new voltage set value v of the control loop * ref , to compensate for the voltage drop caused by the droop control in the control loops of the generator, lithium battery and supercapacitor.

[0040] Furthermore, under normal working conditions, the proportional-integral adjustment parameters of the voltage compensation in each control loop take the same value.

[0041] Furthermore, in this embodiment, the normal operating range of the lithium battery state of charge is set to 25%-75%, and the normal operating range of the supercapacitor state of charge is set to 15%-85%. The adjustment principle for the lithium battery and supercapacitor state of charge is shown as follows:

[0042]

[0043] Among them, I oG is the steady-state value of the generator output current, I oB and I oSC are the steady-state values ​​of the output current after the lithium battery and supercapacitor are connected to the charge and discharge regulator, I Load is the steady-state value of the load current, ΔV GB The difference between the voltage at the generator and the voltage at the lithium battery charging and discharging regulator, ΔV GS It is the difference between the voltage at the generator and the voltage at the output of the supercapacitor converter.

[0044] According to the above formula, when the difference between the generator and the hybrid energy storage terminal voltage is changed, the generator can charge the energy storage device or the energy storage device can discharge to bear the output current of the generator. Therefore, in step 2 of this embodiment, the voltage compensation parameters are set to be consistent under normal working conditions, so that ΔV GB With ΔV GS Both are 0.

[0045] like Figure 3 This is the energy storage charge state adjustment principle diagram provided by the present invention. When the charge state of the lithium battery and supercapacitor exceeds the normal working range, the integral parameter ki in the proportional-integral adjustment of the voltage compensation is changed to make the terminal voltage produce a terminal voltage difference during the adjustment process, so that it can be charged and discharged and finally return to the normal working range. The adjusted integral parameter k * i The relationship between the integral parameter ki and the charge state change rate under normal working conditions is:

[0046]

[0047] Among them, α1 and α2 are constants, SOC is the state of charge, SOC min and SOC max are the minimum and maximum values ​​of SOC respectively.

[0048] like Figure 4-6 This is a schematic diagram of the simulation results provided by the present invention. It can be seen from the figure that in this embodiment, the generator, lithium battery and supercapacitor realize the frequency response of the load current, and the 270V DC bus voltage pulsation is basically within 2V, realizing voltage compensation, and timely recovery when the energy storage charge state exceeds the normal range (taking the supercapacitor as an example), verifying the effectiveness of the invented coordinated control method.

[0049] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A generator-hybrid energy storage coordinated control method in an aircraft high-voltage DC power grid, the aircraft high-voltage DC power grid comprising a high-voltage DC generator, a hybrid energy storage unit, a 270V DC bus and a load, wherein: The high-voltage DC generator is connected to the 270V DC busbar via a filter capacitor, the hybrid energy storage unit is composed of a lithium battery and a supercapacitor, the lithium battery and the supercapacitor are respectively connected to the 270V DC busbar via corresponding charge and discharge regulators, and the load is directly connected to the 270V DC busbar; The generator-hybrid energy storage coordinated control method belongs to a distributed control method, which completes the coordinated control of the three by controlling the voltage regulator of the generator, the charging and discharging regulators corresponding to the lithium battery and the supercapacitor, and is characterized in that it includes the following steps: Step 1: Introduce a virtual impedance droop loop in front of the voltage and current loops in the control loops of the generator, lithium battery and supercapacitor to achieve the response of the three to different frequency bands of the load current; Step 2: Correct the given values ​​of the bus voltage in the control loops of the generator, lithium battery and supercapacitor, and add voltage compensation control to avoid bus voltage drop caused by droop control; Step 3: Monitor the state of charge of the lithium battery and the supercapacitor in real time. When the state of charge exceeds the normal working range, adjust the parameters of the voltage compensation control described in step 2 to adjust the state of charge of the energy storage device to restore it to the normal range, so as to avoid the lithium battery and the supercapacitor from working beyond the limit. The step 1 includes introducing a virtual inductor on the generator side, introducing a virtual resistor on the lithium battery side, and introducing a virtual capacitor and resistor in parallel on the supercapacitor side, so that the output current of the generator, the lithium battery and the supercapacitor have the following relationship with the load current: the generator responds to the low-frequency component of the load current, and its frequency response range is [0, ω1]; the lithium battery responds to the medium-frequency component of the load current, and its frequency response range is [ω1, ω2]; the supercapacitor responds to the high-frequency component of the load current, and its frequency response range is [ω2, +∞], wherein ω1 and ω2 are the dividing points between the generator current and the lithium battery current, and between the lithium battery current and the supercapacitor current, respectively; ω1 and ω2 are reasonably set in combination with the requirements of the working frequency bands of the generator, the lithium battery and the supercapacitor, and the virtual impedance value in the droop control loop corresponding to each source is calculated.

2. The method for coordinated control of generator-hybrid energy storage in an aircraft high voltage DC power grid according to claim 1, characterized in that: The second step includes collecting the real-time voltage value V of the 270V DC busbar. Bus , and the voltage given value v ref Make a difference, and get Δv by proportional-integral adjustment. ref Add together to get the new voltage set value v of the control loop * ref , to compensate for the voltage drop caused by the droop control in the control loops of the generator, lithium battery and supercapacitor.

3. A method for coordinated control of generators and hybrid energy storage in an aircraft high voltage DC power grid according to claim 1 or 2, characterized in that: In the step 2, under normal working conditions, the proportional-integral adjustment parameters of the voltage compensation in each control loop take the same value.

4. The method for coordinated control of generator-hybrid energy storage in an aircraft high voltage DC power grid according to claim 1, characterized in that: The step three includes setting the integral parameter k in the proportional-integral regulation of the voltage compensation in the control loop when the state of charge of the lithium battery and the supercapacitor exceeds the normal working range. * i Under normal working conditions, the integral parameter k i And the relationship between the charge state change rate is Among them, α1 and α2 are constants, SOC is the state of charge, SOC min and SOC max are the minimum and maximum values ​​of SOC respectively.

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