A relay protection method for aviation multi-bus DC hybrid power system

Abstract

The present invention relates to the field of aviation microgrid relay protection technology, and more specifically, to a relay protection method for aviation multi-bus DC hybrid power system. The method includes the following steps: determining the current direction of the microgrid line in the aviation multi-bus DC hybrid power system; establishing the voltage, current and power relationship of each node in the aviation multi-bus DC hybrid power system; calculating the current\voltage threshold of each node, collecting the current\voltage value of the corresponding node, and judging whether it exceeds the current\voltage threshold. If it exceeds, executing the first relay protection action; predicting the current\voltage value of each node, collecting the current value and voltage value of the corresponding node, and judging whether the preset comparison condition is met. If not, executing the second relay protection action. The relay protection method for aviation multi-bus DC hybrid power system proposed by the present invention can accurately locate the fault location and size in advance, and provide an accurate basis for subsequent protection actions.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation microgrid relay protection, and more specifically, to a relay protection method for an aviation multi-bus DC hybrid power system. Background Art

[0003] With the continuous development of the carbon reduction trend, more electric aircraft has gradually become one of the main development trends of aviation aircraft. The microgrid structure of more electric aircraft is completely different from the traditional grid structure. It uses a large number of power electronic equipment, making its operating state more complex and changeable. At the same time, since aircraft mostly work at high altitudes, higher requirements are also placed on the fault protection of microgrids.

[0004] The hybrid electric propulsion system combines the advantages of traditional thermal engines and electric propulsion, and can effectively solve the problems of insufficient endurance and mileage of pure electric aircraft and serious pollution of traditional powered aircraft. Similar to new energy vehicles, the configurations of aircraft microgrids are mainly series, parallel and hybrid. Although parallel and hybrid systems may be better than series systems in terms of fuel consumption, the series system has a unique advantage in completely decoupling the propeller and transmission system, which enables the aircraft to have better internal and external flow field coupling and the potential for integrated fuselage and wing design, thereby reducing propulsion power consumption requirements and reducing the power requirements of power system components from the initial demand side, thereby obtaining the advantages of reducing the aircraft's own weight and reducing overall energy consumption.

[0005] DC microgrids are flexible and easy to expand, but they contain a large number of power electronic equipment, have complex operating conditions, have large short-circuit current impacts, and do not have zero crossings. Compared with traditional microgrids, the series hybrid system used in aircraft has both fuel-power-thrust and battery-thrust working modes. At the same time, considering the internal structure of the aircraft and the various complex and changeable conditions during flight, fault detection and removal are particularly difficult.

[0006] Therefore, there is an urgent need for a key technology for aircraft DC microgrid relay protection that can quickly and reliably detect and eliminate faults. Summary of the invention

[0007] The purpose of the present invention is to provide a relay protection method for an aviation multi-bus DC hybrid power system, so as to solve the problem in the prior art that it is difficult to quickly and reliably detect and eliminate faults in an aviation multi-bus DC hybrid power system.

[0008] In order to achieve the above object, the present invention provides a relay protection method for an aviation multi-bus DC hybrid power system, comprising the following steps:

[0009] Determine the direction of microgrid line current within an aviation multi-bus DC hybrid system;

[0010] Establish the voltage, current and power relationship of each node in the aviation multi-bus DC hybrid power system;

[0011] Calculate the current / voltage threshold of each node, collect the current / voltage value of the corresponding node, and determine whether it exceeds the current / voltage threshold. If it exceeds, execute the first relay protection action;

[0012] Predict the current and voltage values ​​of each node, collect the current and voltage values ​​of the corresponding nodes, and determine whether the preset comparison conditions are met. If not, execute the second relay protection action.

[0013] In one embodiment, the multi-bus DC hybrid power system includes multiple DC buses, each bus is provided with a power generation device, a plurality of energy storage devices and a plurality of load devices, and a node includes an energy storage device, a load device and a corresponding bus.

[0014] In one embodiment, the calculating of the current / voltage threshold of each node, collecting the current / voltage value of the corresponding node, and determining whether the current / voltage threshold is exceeded further includes:

[0015] Calculate the voltage threshold and current threshold of a single DC bus and the corresponding energy storage device and load device;

[0016] The current and voltage values ​​of a single DC bus and the corresponding energy storage device and load device are collected at a certain sampling period, and the collected current value is compared with the current threshold to determine whether it exceeds the current threshold; the collected voltage value is compared with the voltage threshold to determine whether it exceeds the voltage threshold.

[0017] In one embodiment, predicting the current / voltage value of each node, collecting the current value and voltage value of the corresponding node, and judging whether the preset comparison condition is met further includes:

[0018] Predicting the voltage value or current value of a single DC bus and the corresponding energy storage device and load device to generate corresponding voltage prediction value or current prediction value;

[0019] The current and voltage values ​​of a single DC bus and the corresponding energy storage device and load device are collected at a certain sampling period, and the collected current value is compared with the current prediction value to determine whether the preset conditions are met. The collected voltage value is compared with the voltage preset value to determine whether the preset conditions are met.

[0020] In one embodiment, the collected current value and current threshold, voltage value and voltage threshold satisfy the following expressions:

[0021]

[0022] Among them, U is the rated working voltage value, a is the threshold coefficient;

[0023] U bus is the voltage value of a single DC bus, U bus(min) is the minimum operating voltage value of a single DC bus;

[0024] U bat is the voltage value of the energy storage device collected, U bat(min) is the minimum operating voltage value of the energy storage device;

[0025] U motor is the voltage value of the load device collected, U motor(min) is the minimum operating voltage value of the load device;

[0026] I bus is the current value of a single DC bus collected, I bus(max) is the maximum operating current value of a single DC bus;

[0027] I bat is the current value of the energy storage device collected, I bus(max) is the maximum operating current value of the energy storage device;

[0028] I motor is the current value of the load device collected, I motor(max) It is the maximum operating current value of the load device.

[0029] In one embodiment, the establishing of the voltage, current and power relationship of each node in the aviation multi-bus DC hybrid power system further includes:

[0030] According to the aircraft design operation status planning, the maximum output power of the multi-bus DC hybrid power system is determined.

[0031] In one embodiment, the predicting of the current / voltage value of each node further comprises the following steps:

[0032] According to the control instructions and the short-term history records of voltage and current, the voltage and current values ​​of a single DC bus and the corresponding energy storage device and load device at the next sampling moment are predicted to generate voltage and current prediction values.

[0033] In one embodiment, multiple prediction methods are used to obtain voltage / current prediction values, and the obtained voltage / current prediction values ​​are weighted and then compared with the corresponding collected voltage / current values.

[0034] In one embodiment, the predicting of the current / voltage value of each node further includes the following steps:

[0035] The voltage and current values ​​of each single DC bus and the corresponding energy storage device and load device are calculated based on the control instructions;

[0036] Based on the linear prediction formula and the voltage / current short-term historical records, the first predicted value of the voltage / current at the next sampling moment is calculated.

[0037] In one embodiment, the predicting of the current / voltage value of each node further includes the following steps:

[0038] The voltage and current values ​​of each single DC bus and the corresponding energy storage device and load device are calculated based on the control instructions;

[0039] Based on system modeling and simulation combined with voltage and current short-term historical records, the second predicted value of voltage and current at the next sampling moment is calculated.

[0040] In one embodiment, the collecting of the current value and the voltage value of the corresponding node to determine whether a preset comparison condition is met, and if not, executing the second relay protection action, further includes the following steps:

[0041] In a comparison cycle, the collected value of voltage / current is compared with the predicted value to obtain a first deviation value. If the first deviation value is greater than a first comparison threshold, an alarm is issued;

[0042] In the next comparison cycle, the collected voltage and current values ​​are compared with the predicted values ​​to obtain a second deviation value. If the second deviation value is greater than the second comparison threshold, the passive protection device is triggered to locate the fault position, remove the fault and report it to the controller.

[0043] In one embodiment, the method further comprises the following steps:

[0044] Cyclic sampling is performed at a preset sampling period to detect whether an emergency stop input signal, a generator fault signal or a motor fault signal is received;

[0045] If an emergency stop input signal, generator fault signal or motor fault signal is detected, it is considered that a fault has occurred and an active relay protection control signal is triggered, causing each power output component in the system to stop working and be locked.

[0046] In one embodiment, the first relay protection action and / or the second relay protection action further includes the following steps:

[0047] Use a DC circuit breaker to cut off the faulty node.

[0048] In one embodiment, after the DC circuit breaker is used to cut off the fault node, the following steps are also included:

[0049] The circuit breaker keeps disconnecting the faulty node until a manual reset signal is received.

[0050] The aviation multi-bus DC hybrid power system relay protection method proposed in the present invention has the ability to accurately locate the fault position and size in advance, thereby providing an accurate basis for subsequent protection actions, and has a certain power protection capability to ensure that the aircraft can land safely. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always represent the same features, wherein:

[0052] Figure 1 A schematic diagram of a microgrid circuit structure of an aviation multi-bus DC hybrid power system according to an embodiment of the present invention is disclosed;

[0053] Figure 2 A connection diagram of a coordination controller of an aviation multi-bus DC hybrid power system according to an embodiment of the present invention is disclosed;

[0054] Figure 3 A flow chart of a relay protection method for an aviation multi-bus DC hybrid power system according to an embodiment of the present invention is disclosed;

[0055] Figure 4 A flow chart of a coordinated controller collecting fault signals at regular intervals according to an embodiment of the present invention is disclosed;

[0056] Figure 5 A schematic diagram of a cut-off principle of a DC circuit breaker according to an embodiment of the present invention is disclosed;

[0057] Figure 6 A logic relationship diagram of a manual reset signal and other signals according to an embodiment of the present invention is disclosed.

[0058] The meanings of the reference numerals in the figures are as follows:

[0059] 100 turboshaft engines;

[0060] 200 generators;

[0061] 310 a first AC / DC converter;

[0062] 320 second AC / DC converter;

[0063] 410 first battery;

[0064] 420 second battery;

[0065] 511 a first motor; 512 a second motor; 521 a third motor; 522 a fourth motor;

[0066] 611 a first DC circuit breaker; 612 a second DC circuit breaker; 613 a third DC circuit breaker; 614 a fourth DC circuit breaker;

[0067] 621 fifth DC circuit breaker; 622 sixth DC circuit breaker; 623 seventh DC circuit breaker; 624 eighth DC circuit breaker;

[0068] 711 a first sensor; 712 a second sensor; 713 a third sensor; 714 a fourth sensor;

[0069] 721 a fifth sensor; 722 a sixth sensor; 723 a seventh sensor; 724 an eighth sensor;

[0070] 811 a first bidirectional DC / DC converter; 812 a first electric regulator; 813 a second electric regulator;

[0071] 821 a second bidirectional DC / DC converter; 822 a third electric regulator; 823 a fourth electric regulator;

[0072] 900 coordination controller; 901 hardware protection circuit. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention and are not used to limit the invention.

[0074] The operating environment of aviation microgrids is complex, with variable load demands and extremely high requirements for power stability to ensure the safety of aircraft when operating at high altitudes. The hybrid power system of aircraft is different from the traditional microgrid structure. It has multiple working modes such as fuel-power generation-thrust, battery-thrust, fuel-thrust, etc. In addition, it is necessary to consider the internal structure of the aircraft and various complex situations that may arise during the flight. To ensure flight safety, when a fault occurs, the fault must be quickly removed and the aircraft must have a certain amount of power to achieve a safe landing, thereby minimizing losses.

[0075] Therefore, higher requirements are placed on fault detection, location and removal, especially when dealing with the fluctuation impact of sudden power removal on the entire system, which is particularly difficult to handle. Therefore, fast and reliable detection and removal of faults is the key technology of aviation microgrid relay protection, and it is also an important link to ensure the safe and stable operation of aircraft DC microgrids.

[0076] In view of the different complex electromagnetic environment of aircraft microgrids compared to ground microgrids, the present invention proposes a new relay protection method for aviation multi-bus DC hybrid power system that can be used for ground testing. The multi-bus DC hybrid power system in the present invention usually includes 2 or more DC buses, and each bus is provided with a number of power generation devices, a number of energy storage devices and a number of load devices.

[0077] Figure 1 The schematic diagram of the microgrid circuit structure of an aviation multi-bus DC hybrid power system according to an embodiment of the present invention is disclosed. Figure 1 The embodiment shown is a dual-bus DC hybrid power system, in which each DC bus has two electric motors as the propulsion power device of the aircraft, and a battery with charging and discharging functions as an energy storage device to perform power compensation and power recovery under different operating conditions of the aircraft.

[0078] The generator 200 is used as a power generation device. The first battery 410 and the second battery 420 are used as energy storage devices. In other embodiments, the energy storage device may also be a super capacitor.

[0079] The output end of the turboshaft engine 100 is connected to the generator 200 through a coupling, and the corresponding engine output power P engine .

[0080] The output end of the generator 200 is connected to the first AC / DC converter 310 and the second AC / DC converter 320 respectively.

[0081] The first AC / DC converter 310 and the second AC / DC converter 320 are connected to the first DC bus and the second DC bus respectively after passing through the hardware protection circuit 901 .

[0082] The first DC bus is provided with a first DC circuit breaker 611, a first sensor 711 and a second sensor 712 in sequence;

[0083] The first DC bus is provided with a first motor 511, a second motor 512 and a first battery 410;

[0084] A first electric regulator 812, a third DC circuit breaker 613 and a third sensor 713 are sequentially arranged between the first motor 511 and the first DC bus;

[0085] A second electric regulator 813, a fourth DC circuit breaker 614 and a fourth sensor 714 are sequentially arranged between the second motor 512 and the first DC bus;

[0086] A first bidirectional DC / DC converter 811 and a second DC circuit breaker 612 are sequentially arranged between the first battery 410 and the first DC bus.

[0087] Similarly, a fifth DC circuit breaker 621, a fifth sensor 721 and a sixth sensor 722 are sequentially arranged on the second DC bus;

[0088] The second DC bus is provided with a third motor 521, a fourth motor 522 and a second battery 420;

[0089] A third electric regulator 822, a seventh DC circuit breaker 623 and a seventh sensor 723 are sequentially arranged between the third motor 521 and the second DC bus;

[0090] A fourth electric regulator 823, an eighth DC circuit breaker 624 and an eighth sensor 724 are sequentially arranged between the fourth motor 522 and the second DC bus;

[0091] A second bidirectional DC / DC converter 821 and a sixth DC circuit breaker 622 are sequentially arranged between the second battery 420 and the second DC bus.

[0092] Figure 2 A schematic diagram of the connection of a coordination controller of an aviation multi-bus DC hybrid power system according to an embodiment of the present invention is disclosed. Figure 1 and Figure 2 As shown, the dual-bus DC hybrid power system further includes a coordination controller 900:

[0093] The coordination controller 900 is connected to the hardware protection circuit 901 and is used to control the hardware protection circuit to perform a protection action of cutting off the circuit;

[0094] The coordination controller 900 is connected to the first DC circuit breaker 611 to the fourth DC circuit breaker 614 and the fifth DC circuit breaker 621 to the eighth DC circuit breaker 624 respectively, and is used to control the DC circuit breaker corresponding to the fault node to perform a protection action of cutting off the circuit;

[0095] The coordination controller 900 is connected to the first sensor 711 to the fourth sensor 714 and the fifth sensor 721 to the eighth sensor 724 respectively, and is used to receive the voltage or current signal sent by the sensor;

[0096] The coordination controller 900 is connected to the first electric regulator 812, the second electric regulator 813, the third electric regulator 822, and the fourth electric regulator 823 respectively, and is used to control the speed of the motor;

[0097] The coordination controller 900 is connected to the first bidirectional DC / DC converter 811 and the second bidirectional DC / DC converter 821 respectively, and is used to control and realize the bidirectional flow of DC power.

[0098] The present invention proposes a relay protection method for an aviation multi-bus DC hybrid power system, comprising the following steps:

[0099] Step S1, determining the current direction of the microgrid line in the aviation multi-bus DC hybrid power system;

[0100] Step S2, establishing the voltage, current and power relationship of each node in the aviation multi-bus DC hybrid power system;

[0101] Step S3, calculating the current / voltage threshold of each node, collecting the current / voltage value of the corresponding node, and judging whether it exceeds the current / voltage threshold. If it exceeds, executing the first relay protection action;

[0102] Step S4, predict the current / voltage value of each node, collect the current value and voltage value of the corresponding node, and determine whether the preset comparison condition is met. If not, execute the second relay protection action.

[0103] Although the above methods are illustrated and described as a series of actions for the sake of simplicity of explanation, it should be understood and appreciated that these methods are not limited by the order of the actions, because according to one or more embodiments, some actions may occur in different orders and / or concurrently with other actions from the illustrations and descriptions herein or not illustrated and described herein but understandable to those skilled in the art. In particular, steps 3 and 4 may be in a parallel relationship and do not necessarily have to be performed sequentially.

[0104] Compared with traditional technologies, the aviation multi-bus DC hybrid power system relay protection method proposed in this invention has the ability to accurately locate the fault location and size in advance, thereby providing an accurate basis for subsequent protection actions. In addition, this method also uses simulation technology to scientifically evaluate the fault removal strategy, maximize the protection of the hybrid power system's output power, ensure the safety of the aircraft when operating at high altitudes, and minimize losses.

[0105] The following is Figure 1 and Figure 2 Taking the DC hybrid power system shown in the figure as an example, the relay protection method of the aviation multi-bus DC hybrid power system proposed by the present invention is described. The method mainly includes the following steps, some of which can be omitted or transformed into other contents, but the key steps remain unchanged.

[0106] Figure 3 A flow chart of a relay protection method for an aviation multi-bus DC hybrid power system according to an embodiment of the present invention is disclosed. Figures 1 to 3 As shown, the aviation multi-bus DC hybrid power system relay protection method proposed by the present invention comprises the following steps:

[0107] Step S1, determining the current direction of the microgrid line in the aviation multi-bus DC hybrid power system.

[0108] The multi-bus DC hybrid power system includes multiple DC buses, each bus is provided with a power generation device, a plurality of energy storage devices and a plurality of load devices, and a node includes an energy storage device, a load device and a corresponding bus.

[0109] In this embodiment, without considering the low-voltage bus, the main circuit of the aircraft DC microgrid line is actually two independent DC buses, each bus includes three nodes, namely, a power generation device node, a load device node and an energy storage device node. The power generation device node is the generator 200, and the load device node is the first motor to the fourth motor.

[0110] In this embodiment, the energy storage device node refers to the first battery 410 and the second battery 420, which have charging and discharging functions, so the current direction thereof is variable and uncertain.

[0111] In this embodiment, the positive direction of the current in the system is defined as follows:

[0112] It is stipulated that the current is in the positive direction from the generator to the DC bus and then to the motor, and the current is in the positive direction from the battery to the DC bus and then to the motor.

[0113] For example, the direction from the generator 200 to the first DC bus and then to the first motor 511 is the positive direction of the current, and the direction from the first battery 410 to the first DC bus and then to the first motor 511 is the positive direction of the current.

[0114] Step S2: establishing the voltage, current and power relationship of each node in the aviation multi-bus DC hybrid power system.

[0115] Furthermore, according to the aircraft design operation status planning, the relationship between the voltage, current and power of the aviation multi-bus DC hybrid power system in actual use of the aircraft is determined.

[0116] In this embodiment, without considering losses such as line loss and copper loss, the main power of the system comes from the engine and the energy storage node.

[0117] Since the energy storage node is a battery, the maximum power amplitude P that the entire system can output out(max) The values ​​are:

[0118] P out(max) =P engine(max) +P bat1(max) +P bat2(max) ;

[0119] Among them, P engine(max) represents the maximum output power of the turboshaft engine 100;

[0120] P bat1(max) represents the maximum output power of the first battery 410;

[0121] P bat2(max) represents the maximum output power of the second battery 420;

[0122] Furthermore, the relationship between voltage, current and power on a single DC bus in a microgrid is shown below;

[0123]

[0124] Among them, I bus(max) is the maximum current on a single DC bus;

[0125] I bus is the current value on a single DC bus;

[0126] I bat_out(max) The maximum output current of a single battery system on a single DC bus;

[0127] I bat_in(max) The maximum input current of a single battery system on a single DC bus;

[0128] I motor(max) It is the maximum input current of a single motor on a single DC bus;

[0129] I motor Enter the current value for a single motor on a single DC bus.

[0130] Step S3, calculate the current\voltage threshold of each node, collect the current\voltage value of the corresponding node, and determine whether it exceeds the current\voltage threshold. If it exceeds, execute the first relay protection action.

[0131] Furthermore, for a single DC bus in a microgrid, the collected current value and current threshold, voltage value and voltage threshold satisfy the following expressions:

[0132]

[0133] Wherein, U is the rated operating voltage, in this example, U is 540V;

[0134] a is a threshold coefficient. In this embodiment, a=1.2;

[0135] U bus is the voltage value of a single DC bus collected;

[0136] U bus(min) It is the minimum operating voltage value of a single DC bus;

[0137] U bat is the voltage value of the collected battery system;

[0138] Ubat(min) is the minimum operating voltage value of the battery system;

[0139] U motor is the collected voltage value of the motor;

[0140] U motor(min) is the minimum operating voltage value of the motor;

[0141] I bus(max) is the maximum operating current value on a single DC bus;

[0142] I bus is the current value of a single DC bus collected;

[0143] I bat(max) is the maximum operating current value of the battery system;

[0144] I bat is the current value of the collected battery system;

[0145] I motor is the current value of the motor collected;

[0146] I motor(max) It is the maximum operating current value of the motor.

[0147] In this embodiment, the motor serves as a load device and the battery system serves as an energy storage device.

[0148] When the bus voltage U bus Lower than U motor(min) The motor will automatically stop when

[0149] In order to improve the reliability of the system, when the power flow direction is clear, the corresponding voltage and current thresholds can be set for each node on the aircraft microgrid line. If the sampling results exceed the set thresholds within the continuous sampling time, it can be judged that a fault has occurred.

[0150] Specifically, sensors are used to obtain information such as bus voltage, battery system voltage, motor voltage, bus current, battery system current, and motor current in the system.

[0151] like Figure 1 and Figure 2 As shown, the sensors include first sensor 711 to fourth sensor 714, fifth sensor 721 to eighth sensor 724. The sensors can be either current sensors or voltage sensors. Obtaining system information through sensor sampling is a very mature technology in the circuit field and can be easily implemented by those skilled in the art, which will not be described in detail here.

[0152] More specifically, the ADC of the coordination controller 900 performs cyclic sampling at a preset sampling period of 0.5 ms, and sets a comparison circuit to compare the sampled current\voltage value with the set current\voltage threshold. If the sampled value exceeds the threshold, the first relay protection action is executed;

[0153] In this embodiment, the first relay protection action includes: triggering an active relay protection control signal to stop each power output component in the system from working and performing locking.

[0154] Figure 4 A flow chart of a coordinated controller collecting fault signals at regular intervals according to an embodiment of the present invention is disclosed. Figure 4 As shown, the ADC of the coordination controller 900 performs cyclic sampling at a preset sampling period of 0.5ms to detect whether an emergency stop input signal, a generator fault signal, or a motor fault signal is received. When an emergency stop input signal, a generator fault signal, or a motor fault signal is detected, it is considered that a fault has occurred and a relay protection control signal is triggered;

[0155] The ADC timing of the coordination controller 900 performs cyclic sampling with a preset sampling period of 0.5ms to collect the first bus voltage, the first bus current, the second bus voltage, the second bus current, the first bidirectional DC / DC converter current (first battery current), the second bidirectional DC / DC converter current (second battery current), and the currents of the first to fourth motors. When the conditions of step S3 or step S4 are met, it is considered that a fault has occurred, triggering the relay protection control signal and executing the corresponding relay protection action.

[0156] Step S4, predict the current / voltage value of each node, collect the current value and voltage value of the corresponding node, and determine whether the preset comparison condition is met. If not, execute the second relay protection action.

[0157] When the aircraft is operating normally, the power demand mostly changes with instructions, and there is basically no large sudden change in power.

[0158] Furthermore, based on the control instructions and the voltage / current short-term historical records, the voltage / current values ​​of a single DC bus and the corresponding energy storage device and load device at the next sampling moment are predicted to generate voltage / current prediction values.

[0159] In this embodiment, in this example, the bus voltage stability control target is 540V, and the current value of each node at the next sampling moment is predicted based on the control instruction and the current recorded in the short-term history.

[0160] Specifically, the voltage and current values ​​of each single DC bus and the corresponding energy storage device and load device are calculated based on the control instruction.

[0161] The current value of each node is calculated based on the control instruction, and the corresponding expression is as follows:

[0162]

[0163] Among them, P control It is the total power value required to be output by the control instruction;

[0164] P bat_control It is the power value that the control instruction requires the battery to output (it may be absorbed power);

[0165] P motor_control It is the output power value of a single motor required by the control instruction;

[0166] I bus_control It is the calculated value of the current on a single DC bus under the control command;

[0167] I bat(out / in)_control It is the calculated value of the input current or output current of the battery system under the control command;

[0168] U bus is the voltage value on a single DC bus;

[0169] I motor_control It is the calculated value of the motor input current under the control command;

[0170] The voltage value of each node is calculated based on the control instruction in a similar manner to the current value, which will not be described in detail here.

[0171] Furthermore, based on the linear prediction formula combined with the voltage\current short-term historical records, a first predicted value of the voltage\current at the next sampling moment is calculated.

[0172] Taking the prediction of current value as an example, when the power changes, the voltage remains constant, and the current at each node will increase or decrease at a certain slope. The specific expression of the linear prediction formula is as follows:

[0173] f b (x) = (1 + η)f a (x)

[0174] Among them, f b (x) is the current value predicted at time t, set as the first predicted current / pre1 ;

[0175] η is the slope of the formula curve;

[0176] The value of the slope can be obtained by analyzing historical experimental data.

[0177] Furthermore, based on system modeling and simulation combined with voltage and current short-term historical records, a second predicted value of voltage and current at the next sampling moment is calculated.

[0178] In this embodiment, an industrial computer is used to model the system and run the simulation program in real time. When the control instruction changes, the simulation program will also show it accordingly, and the result obtained in the simulation is used as the second predicted current I pre2 ;

[0179] In order to ensure that the simulation results are closest to the actual situation, the simulation model is established with the actual parameters of the hybrid power system as model parameters.

[0180] The model parameters are obtained through component tests and hybrid powertrain network topology.

[0181] The simulation system can use simulation software or hardware devices such as Simulink, PSASP, PSS / E, PSD-BPA, EMPT / APT, RT-LAB, Speedgoad, etc.

[0182] In this embodiment, a MATLAB-based Simulink environment is selected because the Simulink software is highly portable and can be easily converted into languages ​​such as C. It can be applied to devices and has low hardware requirements.

[0183] The voltage value is predicted in a similar manner to the current value and will not be described in detail here.

[0184] like Figure 1 and Figure 2 As shown, the ADC in the coordination controller 900 performs cyclic sampling at a preset sampling period Δt=0.5ms. The sensor uploads the acquired voltage\current information to the coordination controller 900, and compares the sampled value with the controller prediction value in each sampling period.

[0185] The first predicted value and the second predicted value are weighted and compared with the sampled value. More specifically, the sampled value of the current value is compared with the controller predicted value, and the following expression needs to be satisfied:

[0186] ρ+ν=1

[0187] Wherein, ρ and ν represent weight values ​​of the first predicted current and the second predicted current respectively;

[0188] m is the first prediction coefficient. In this embodiment, m=0.8;

[0189] n is the second prediction coefficient. In this embodiment, n=1.2;

[0190] I bus_pre1is the first predicted value of the current value of a single DC bus;

[0191] I bus_pre2 is a second predicted value of the current value of a single DC bus;

[0192] I bus_ADC is the current value of a single DC bus collected;

[0193] I bat_pre1 is a first predicted value of the current value of the battery system;

[0194] I bat_pre2 is a second predicted value of the current value of the battery system;

[0195] I bat_ADC is the current value of the collected battery system;

[0196] I motor_pre1 is a first predicted value of the current value of the motor;

[0197] I motor_pre2 is a second predicted value of the current value of the motor;

[0198] I motor_ADC is the collected motor current value.

[0199] The expression for comparing the sampled value of the voltage value with the predicted value of the controller is similar to that of the current value and will not be repeated here.

[0200] The second relay protection action can be designed differently according to its own characteristics. It can be the same as the first relay protection action, or it can be further optimized as follows.

[0201] Furthermore, the second relay protection action may include:

[0202] In a comparison cycle, the collected value of voltage / current is compared with the predicted value to obtain a first deviation value. If the first deviation value is greater than a first comparison threshold, an alarm is issued;

[0203] In the next comparison cycle, the collected voltage and current values ​​are compared with the predicted values ​​to obtain a second deviation value. If the second deviation value is greater than the second comparison threshold, the passive protection device is triggered to locate the fault position, remove the fault and report it to the controller.

[0204] In this embodiment, the first comparison period is 10 consecutive sampling periods.

[0205] Furthermore, the first relay protection action and / or the second relay protection action of step S3 or step S4 further includes:

[0206] When the coordination controller 900 detects that a line fault occurs, it immediately drives the DC circuit breaker to cut off the faulty node.

[0207] like Figure 4 As shown, when the coordination controller 900 monitors that a line fault occurs, it will immediately drive the corresponding DC circuit breaker to disconnect and send a fault locking signal.

[0208] Considering that the motor works at a speed of about 3000rpm (50Hz), the corresponding cycle time is 20ms, and the current DC circuit breaker can cut off the circuit current within microseconds. Therefore, the existing DC circuit breaker circuit cutting scheme can be transplanted and used in the aircraft DC microgrid under study;

[0209] Figure 5 The schematic diagram of the removal of a DC circuit breaker according to an embodiment of the present invention is disclosed. Figure 5 As shown, the power resistor R1 is 120kW. When overvoltage is detected, the transistor is turned on and the DC circuit breaker starts to work.

[0210] Figure 6 The logical relationship diagram of the manual reset signal and other signals according to an embodiment of the present invention is disclosed, such as Figure 6 As shown, after the DC circuit breaker is used to cut off the fault node, the following steps are also included:

[0211] The DC circuit breaker keeps disconnecting the faulty node until a manual reset signal is received.

[0212] In this embodiment, the sensor detects that the threshold value has been exceeded, and the sensor sampling value deviates from the predicted value. The external manual emergency stop button, the generator fault signal input, and the coordinated controller protection action input will all perform a locking action, and the turbojet engine fuel solenoid valve will close the output.

[0213] If the reset button is not pressed before the error is completely corrected, the DC circuit breaker will remain in the state of disconnecting the faulty node and will require manual reset to ensure safety.

[0214] The present invention proposes a relay protection method for an aviation multi-bus DC hybrid power system. The method is aimed at the microgrid circuit of the aviation multi-bus DC hybrid power system with a multi-bus structure, and provides a new idea for the microgrid fault protection strategy of the aircraft. Through this method, the fault diagnosis of the aircraft during high-altitude operation can be effectively protected, and the faulty part can be removed in time. At the same time, it has a certain power protection capability to ensure that the aircraft can land safely.

[0215] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0216] Those skilled in the art will appreciate that information, signals, and data may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips cited throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0217] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or a combination of the two. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. The technician may implement the described functionality in different ways for each specific application, but such implementation decisions should not be interpreted as resulting in a departure from the scope of the present invention.

[0218] The various illustrative logic modules and circuits described in conjunction with the embodiments disclosed herein may be implemented or executed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in cooperation with a DSP core, or any other such configuration.

[0219] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor so that the processor can read and write information from / to the storage medium. In an alternative, a storage medium may be integrated into a processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and the storage medium may reside in a user terminal as discrete components.

[0220] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented as a computer program product in software, each function may be stored on or transmitted by a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, including any medium that facilitates the transfer of a computer program from one place to another. Storage media may be any available medium that can be accessed by a computer. As an example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of an instruction or data structure and can be accessed by a computer. Any connection is also properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, a server, or other remote source using a coaxial cable, a fiber optic cable, a twisted pair, a digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves are included in the definition of the medium. As used herein, disk and disc include compressed discs.

[0221] Computer-readable media may include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0222] The above embodiments are provided for persons familiar with the art to implement or use the present invention. Personnel familiar with the art can make various modifications or changes to the above embodiments without departing from the inventive concept of the present invention. Therefore, the protection scope of the present invention is not limited to the above embodiments, but should be the maximum scope of the innovative features mentioned in the claims.

Claims

1. A relay protection method for an aviation multi-bus DC hybrid power system, characterized in that: The following steps are involved: Determine the direction of microgrid line current within an aviation multi-bus DC hybrid system; Establish the voltage, current and power relationship of each node in the aviation multi-bus DC hybrid power system; Calculate the current / voltage threshold of each node, collect the current / voltage value of the corresponding node, and determine whether it exceeds the current / voltage threshold. If it exceeds, execute the first relay protection action; Predict the current and voltage values ​​of each node, collect the current and voltage values ​​of the corresponding nodes, and determine whether the preset comparison conditions are met. If not, execute the second relay protection action.

2. The aviation multi-bus DC hybrid power system relay protection method according to claim 1, characterized in that: The multi-bus DC hybrid power system includes multiple DC buses, each bus is provided with a power generation device, a plurality of energy storage devices and a plurality of load devices, and a node includes an energy storage device, a load device and a corresponding bus.

3. The relay protection method for aviation multi-bus DC hybrid power system according to claim 1, characterized in that: The calculating of the current / voltage threshold of each node, collecting the current / voltage value of the corresponding node, and determining whether the current / voltage threshold is exceeded further includes: Calculate the voltage threshold and current threshold of a single DC bus and the corresponding energy storage device and load device; The current and voltage values ​​of a single DC bus and the corresponding energy storage device and load device are collected at a certain sampling period, and the collected current value is compared with the current threshold to determine whether it exceeds the current threshold; the collected voltage value is compared with the voltage threshold to determine whether it exceeds the voltage threshold.

4. The relay protection method for aviation multi-bus DC hybrid power system according to claim 1, characterized in that: The predicting of the current / voltage value of each node, collecting the current value and voltage value of the corresponding node, and judging whether the preset comparison condition is met further includes: Predicting the voltage value or current value of a single DC bus and the corresponding energy storage device and load device to generate corresponding voltage prediction value or current prediction value; The current and voltage values ​​of a single DC bus and the corresponding energy storage device and load device are collected at a certain sampling period, and the collected current value is compared with the current prediction value to determine whether the preset conditions are met. The collected voltage value is compared with the voltage preset value to determine whether the preset conditions are met.

5. The aviation multi-bus DC hybrid power system relay protection method according to claim 1, characterized in that: The collected current value and current threshold, voltage value and voltage threshold satisfy the following expressions: Among them, U is the rated working voltage value, a is the threshold coefficient; U bus is the voltage value of a single DC bus, U bus(min) is the minimum operating voltage value of a single DC bus; U bat is the voltage value of the energy storage device collected, U bat(min) is the minimum operating voltage value of the energy storage device; U motor is the voltage value of the load device collected, U motor(min) is the minimum operating voltage value of the load device; I bus is the current value of a single DC bus collected, I bus(max) is the maximum operating current value of a single DC bus; I bat is the current value of the energy storage device collected, I bus(max) is the maximum operating current value of the energy storage device; I motor is the current value of the load device collected, I motor(max) It is the maximum operating current value of the load device.

6. The aviation multi-bus DC hybrid power system relay protection method according to claim 1, characterized in that: The establishing of the voltage, current and power relationship of each node in the aviation multi-bus DC hybrid power system further includes: According to the aircraft design operation status planning, the maximum output power of the multi-bus DC hybrid power system is determined.

7. The aviation multi-bus DC hybrid power system relay protection method according to claim 1, characterized in that: The predicting of the current / voltage value of each node further comprises the following steps: According to the control instructions and the short-term history records of voltage and current, the voltage and current values ​​of a single DC bus and the corresponding energy storage device and load device at the next sampling moment are predicted to generate voltage and current prediction values.

8. The aviation multi-bus DC hybrid power system relay protection method according to claim 7, characterized in that: The following steps are also included: A variety of prediction methods are used to obtain voltage and current prediction values, which are weighted and then compared with the corresponding collected voltage and current values.

9. The aviation multi-bus DC hybrid power system relay protection method according to claim 8, characterized in that: The predicting of the current / voltage value of each node further includes the following steps: The voltage and current values ​​of each single DC bus and the corresponding energy storage device and load device are calculated based on the control instructions; Based on the linear prediction formula and the voltage / current short-term historical records, the first predicted value of the voltage / current at the next sampling moment is calculated.

10. The aviation multi-bus DC hybrid power system relay protection method according to claim 8, characterized in that: The predicting of the current / voltage value of each node further includes the following steps: The voltage and current values ​​of each single DC bus and the corresponding energy storage device and load device are calculated based on the control instructions; Based on system modeling and simulation combined with voltage and current short-term historical records, the second predicted value of voltage and current at the next sampling moment is calculated.

11. The aviation multi-bus DC hybrid power system relay protection method according to claim 1, characterized in that: The collecting of the current value and the voltage value of the corresponding node to determine whether a preset comparison condition is met, and if not, executing the second relay protection action, further includes the following steps: In a comparison cycle, the collected value of voltage / current is compared with the predicted value to obtain a first deviation value. If the first deviation value is greater than a first comparison threshold, an alarm is issued; In the next comparison cycle, the collected voltage and current values ​​are compared with the predicted values ​​to obtain a second deviation value. If the second deviation value is greater than the second comparison threshold, the passive protection device is triggered to locate the fault position, remove the fault and report it to the controller.

12. The aviation multi-bus DC hybrid power system relay protection method according to claim 1, characterized in that: The following steps are also included: Perform cyclic sampling at a preset sampling period to detect whether an emergency stop input signal, a generator fault signal or a motor fault signal is received; If an emergency stop input signal, generator fault signal or motor fault signal is detected, it is considered that a fault has occurred and an active relay protection control signal is triggered, causing each power output component in the system to stop working and be locked.

13. The aviation multi-bus DC hybrid power system relay protection method according to claim 1, characterized in that: The first relay protection action and / or the second relay protection action further comprises the following steps: Use DC circuit breaker to cut off the fault node.

14. The aviation multi-bus DC hybrid power system relay protection method according to claim 13, characterized in that: After the DC circuit breaker is used to cut off the fault node, the following steps are also included: The DC circuit breaker keeps disconnecting the faulty node until a manual reset signal is received.

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