CN108736481A - A kind of aviation more electric engin AC/DC mixed power system and its design method - Google Patents

Abstract

The present invention provides an AC-DC hybrid power system of an aviation multi-electric engine and a design method thereof. The AC-DC hybrid power system of an aviation multi-electric engine includes two parallel built-in variable frequency AC The output end of the starter/generator is connected to an AC/DC converter, the output end of the AC/DC converter is connected to a DC bus, and the DC bus is connected to a DC/AC converter, a bidirectional DC/DC converter, and a DC/AC converter The AC bus is connected as an output, the bidirectional DC/DC converter is connected with a battery; both the DC bus and the AC bus are connected with a load; the AC/DC converter is an autotransformer active filter rectifier, and the DC/DC The AC converter is an inverter using virtual synchronous generator technology. The invention solves the problem that the power generation capacity of the traditional power system of the existing aero-engine cannot meet the use requirements of the aero-engine with more electric power.

Description

An AC-DC Hybrid Power System and Design Method for Aviation Multi-Electric Engine

technical field

The invention belongs to the technical field of aviation multi-electric engines, and in particular relates to a power system design method for aviation multi-electric engines.

Background technique

The generator on a traditional aero engine realizes power supply by extracting shaft power, which is generally installed on the casing, and has a small power generation capacity. The concept of multi-electric engine proposes to use electric energy to replace traditional secondary energy such as hydraulic energy, pneumatic energy, and mechanical energy. On the one hand, it can reduce the volume and weight of the aero-engine, reduce the complexity of accessories, and also facilitate the maintenance and repair of equipment , Improve the reliability of aero-engine operation. The multi-electric engine adopts a built-in starter/generator, which makes the structure of the engine compact, reduces the windward area, and is conducive to further improving fuel efficiency. Therefore, it is the development direction of future aero engines.

Due to the small power generation capacity of traditional aero-engines, its power supply system has experienced 28V DC, 115V400Hz AC or a hybrid power system combining the two. Therefore, it is necessary to study a new type of power system. At present, the power supply systems of multi-electric engine power systems that have been applied include 270V high-voltage DC (mainly used on F-35) and variable frequency AC (mainly used on A380 and B787). Compared with the traditional power supply system, 270V high-voltage DC power supply The system has the advantages of high power generation efficiency, light power generation and distribution system, easy to achieve uninterrupted power supply, and high reliability; and in order to reduce the quality of the distribution network, the frequency of the frequency conversion AC power supply system can output AC power up to 360 ~ 800Hz, which is effective Reduced the weight of electromagnetic equipment. Since the current mainstream power supply system is still dominated by variable speed and constant frequency and constant speed and constant frequency, if a new power supply system is adopted, it will inevitably face the situation of large-scale replacement of electrical equipment or the addition of many power electronic converters to existing equipment. Therefore, the advisable solution is to use high-voltage DC power supply locally in some necessary occasions, and most of the electrical equipment is still powered by constant-frequency AC.

Contents of the invention

In order to solve the above-mentioned problem that the power generation capacity of the traditional power system of the aero-engine cannot meet the requirements of the use of the aero-multi-electric engine, the purpose of the present invention is to provide a design method for the AC-DC hybrid power system of the aero-multi-electric engine.

To achieve the above object, the present invention adopts the following technical solutions:

An AC-DC hybrid power system for an aviation multi-electric engine, including two parallel built-in variable frequency AC starters/generators, each built-in variable frequency AC starter/generator is connected to an AC/DC converter at the output end, AC/DC The output end of the converter is connected to a DC bus, the DC bus is connected to a DC/AC converter, a bidirectional DC/DC converter, the DC/AC converter is connected to an AC bus as an output, and the bidirectional DC/DC converter is connected to a battery; Both the DC bus and the AC bus are connected with loads;

The AC/DC converter is an autotransformer active filter rectifier consisting of a three-phase AC power supply, a polygonal autotransformer, a three-phase uncontrolled rectifier bridge, a parallel active power filter on the DC side, a balance reactor and an output load Composition; the three-phase AC power supply is connected to the polygonal autotransformer, the polygonal autotransformer is connected to the three-phase uncontrolled rectifier bridge, the output terminal of the three-phase uncontrolled rectifier bridge is connected to the DC side parallel active power filter, and the parallel active power filter The output end of the circuit is connected to the balance reactor, and the balance reactor is connected to the output load;

The DC/AC converter is an inverter using virtual synchronous generator technology.

The rated voltage of the DC bus is 270V, the rated voltage of the AC bus is 115V, and the frequency is 400Hz.

The polygonal autotransformer is a twelve-pulse autotransformer.

A method for designing an AC-DC hybrid power system of an aviation multi-electric engine, comprising the following steps:

Step 1: Combine the active power filter with the polygonal connection autotransformer rectifier, design the autotransformer active filter rectifier, and connect the autotransformer active filter rectifier to the built-in variable frequency AC starter/generator Between the DC busbar; the autotransformer active filter rectifier is composed of a three-phase AC power supply, a polygonal autotransformer, a three-phase uncontrolled rectifier bridge, a parallel active power filter on the DC side, a balance reactor and an output load. The polygonal autotransformer adopts a twelve-pulse autotransformer, and connects the DC-side parallel active power filter at the output end of the three-phase uncontrolled rectifier bridge to realize the active filtering of a single three-phase uncontrolled rectifier bridge. The source power filter is followed by a balance reactor to stabilize the output voltage of the DC side;

Step 2, using an inverter using virtual synchronous generator technology as a DC/AC converter, and connecting the DC/AC converter between the DC bus and the AC bus to keep the voltage amplitude and frequency of the AC bus stable;

Step 3, using a storage battery and a bidirectional DC/DC converter to compensate the power of the DC bus, so that the voltage of the DC bus can be maintained near the rated voltage;

Step 4: Use the autotransformer active filter rectifier in step 1 as an AC/DC converter, the DC/AC converter in step 2, the storage battery in step 3, and the bidirectional DC/DC converter as part of the designed power system , connected with the power generation part, DC bus, AC bus and load to complete the overall design.

In the second step, the characteristics of active frequency regulation and reactive voltage regulation of the virtual synchronous generator are described as follows:

θ=∫ωdt

Its reactive power regulation characteristics can be described as follows:

In the formula, J is the moment of inertia of the rotor, is the first derivative of J, T _m is the mechanical torque, T _e is the electromagnetic torque, D _p is the damping coefficient, θ is the rotor angle, is the first derivative of θ, ω is the angular velocity of the rotor, Q _set is the given reactive power, D _q is the droop coefficient, U ₀ is the effective value of the output voltage, U _n is the effective value of the rated voltage, and E _m is the effective value of the modulation wave value, Q _e is the electromagnetic power;

The above formula outputs the amplitude and angular velocity of the modulated wave, and the trigger signal of the inverter switch tube is obtained through the modulation of the carrier.

In the third step, the bidirectional DC/DC converter integrates the Buck circuit and the Boost circuit into one circuit. The circuit has two switching tubes, and the bidirectional flow of energy can be realized by controlling the switching of the switching tubes. When the high-voltage DC When the bus voltage is lower than 265V, the bidirectional DC/DC converter works in Boost mode. At this time, the energy of the battery flows to the high-voltage DC bus. On the contrary, when the high-voltage DC bus voltage is higher than 275V, the bidirectional DC/DC converter Working in Buck mode, the battery absorbs the excess energy of the high-voltage DC bus, so that its voltage is stabilized near the rated value.

In the fourth step, the rated voltage of the DC bus is 270V, the rated voltage of the AC bus is 115V, and the frequency is 400Hz; the power generation part is two built-in variable frequency AC starters/generators connected in parallel.

Beneficial effect: the present invention has the following advantages:

1. According to the working requirements of the aviation multi-electric engine power system, the present invention proposes an AC-DC hybrid power system based on maintaining the stability of the AC-DC bus, and conducts steady-state research on the new power system.

2. The present invention firstly designs the overall structure of the AC/DC hybrid power system aiming at the power consumption characteristics of the multi-electric motor. This structure avoids the constant speed transmission device, and at the same time, in order to take advantage of the advantages of light weight, high reliability and easy uninterrupted power supply of the 270V high-voltage DC power distribution system, some DC loads such as the flight control system are powered by the 270V DC bus. In order to avoid the problem of large-scale replacement of electrical equipment caused by changes in the power supply system, a parallel connection of multiple virtual synchronous generators (VSGs) is used to invert 270V DC into 115V400Hz AC for most electrical equipment.

3. Considering that the AC/DC converters adopted on the current aero-engine are still based on transformer rectifier TRU and autotransformer rectifier ATRU, the present invention proposes to redesign traditional TRU and ATRU by using active filter circuit, On the one hand, it can meet the high-power transmission requirements of the engine, realize the low harmonic content of the input current, and reduce the volume and weight.

4. The DC/AC converter on the traditional aero-engine is an aviation static converter, and its main function is to convert the electric energy of the DC power supply or the aviation storage battery into AC power for use by electrical equipment. With the introduction of the concept of aviation multi-electric engines, traditional aviation static converters can no longer meet the requirements of large power capacity, and at the same time, airborne equipment has higher and higher requirements for power quality. Therefore, it is necessary to try to integrate multi-DC/AC The technology of parallel operation of converters is applied in the aviation field. On the one hand, it can reduce the capacity of a single DC/AC converter, and can also realize redundant functions to ensure reliable power supply.

The invention starts from ensuring the stability of the power system of the aviation multi-electric engine and ensuring the reasonable distribution of load power, and proposes to use the VSG to design the aviation DC/AC converter. Compared with the control scheme of the traditional DC/AC converter, it can simulate the characteristics of synchronous generator active frequency modulation and reactive power voltage regulation through the control algorithm to ensure the stability of the system, and at the same time realize the reasonable load distribution between the converters. distribute.

5. There is a sudden change in the load of the aero-engine in different flight states, which will lead to fluctuations in the bus voltage. The present invention aims at the stability of the high-voltage DC bus voltage, and proposes to use a battery and a bidirectional DC/DC converter to control the voltage of the high-voltage DC bus. The voltage is compensated to maintain it near the rated voltage.

6. Simulation results show that the proposed AC-DC hybrid power system meets the requirements of the US military for airborne power.

Description of drawings

Fig. 1 is the general structural diagram of the AC and DC power system of the aviation multi-electric engine of an embodiment of the present invention;

Fig. 2 is the autotransformer active filter rectifier of an embodiment of the present invention;

Fig. 3 is the equivalent circuit diagram of the DC side parallel type APF of an embodiment of the present invention;

Fig. 4 is the digital voltage regulator of an embodiment of the present invention;

Fig. 5a-Fig. 5b is the response curve diagram of the high-voltage DC bus bar of an embodiment of the present invention;

Fig. 6a-Fig. 6d is the AC bus response curve diagram of an embodiment of the present invention;

In the figure, 1-built-in variable frequency AC starter/generator, 2-AC/DC converter, 3-DC bus, 4-DC/AC converter, 5-bidirectional DC/DC converter, 6-battery, 7- AC bus, 8-load.

Detailed ways

Below in conjunction with embodiment the present invention is further explained.

In the accompanying drawings and embodiments of the present invention, the meanings of each abbreviation are:

APF: active power filter;

ATRU: polygonal connection autotransformer rectifier;

ATPFRU: autotransformer active filter rectifier;

VSG: Virtual Synchronous Generator

DC: direct current;

AC: AC;

GEN: alternator;

Loads: load.

Example

As shown in Figure 1, an AC-DC hybrid power system for an aviation multi-electric engine includes two parallel built-in variable frequency AC starters/generators 1, and the output end of each built-in variable frequency AC starter/generator 1 is connected to an AC /DC converter 2, the output end of AC/DC converter 2 is connected to DC bus 3, DC bus 3 is connected to DC/AC converter 4, bidirectional DC/DC converter 5, and DC/AC converter 4 is connected to AC The bus 7 is used as an output, and the bidirectional DC/DC converter 5 is connected to the battery 6; the DC bus 3 and the AC bus 7 are both connected to the load 8;

As shown in Figure 2, the AC/DC converter is an autotransformer active filter rectifier consisting of a three-phase AC power supply, a polygonal autotransformer, a three-phase uncontrolled rectifier bridge, a parallel active power filter on the DC side, a balance reactor and Output load composition; three-phase AC power supply connected to polygonal autotransformer, polygonal autotransformer connected to three-phase uncontrolled rectifier bridge, output terminal of three-phase uncontrolled rectifier bridge connected to DC side parallel active power filter, parallel active power filter The output end of the filter is connected to the balance reactor, and the balance reactor is connected to the output load;

The DC/AC converter is an inverter using virtual synchronous generator technology.

The rated voltage of the DC bus is 270V, the rated voltage of the AC bus is 115V, and the frequency is 400Hz.

The polygonal autotransformer is a twelve-pulse autotransformer.

The design method of the AC-DC hybrid power system of the aviation multi-electric engine is as follows:

1. Design of AC-DC hybrid power system

The traditional constant-speed constant-frequency power supply system requires a constant-speed transmission device to convert the constantly changing engine speed into a constant speed input generator, but the device has a large volume and weight, a complex structure, and difficult maintenance, which is critical for improving engine efficiency. Unfavorable; if a variable-speed constant-frequency power supply system is adopted, it is necessary to increase a converter to convert a part of the variable-frequency alternating current into a constant-frequency output, and the added converter is mainly composed of high-power power electronic devices, which have poor overload capacity, Low reliability and other disadvantages, so there are not many models using this power supply system. Based on the above analysis, the present invention proposes an AC and DC hybrid power system.

1.1 Overall design of AC/DC hybrid power system

Figure 1 shows the power system structure proposed by the present invention, the rated voltage of the high-voltage DC bus is 270V, the rated voltage of the AC bus is 115V, and the frequency is 400Hz. Wherein the power generation part is two parallel built-in variable frequency AC starters/generators, and the AC/DC converter is the autotransformer active filter rectifier ATPFRU designed by the present invention, and its function is to rectify the variable frequency alternating current output by the generator into 270V DC output, the DC/AC converter is an inverter using virtual synchronous generator technology, and its function is to invert 270V DC into 115V400Hz AC output. In addition, in order to ensure the stability of the DC bus voltage, a bidirectional DC/DC converter is used to transmit power between the battery and the DC bus to compensate the DC bus voltage in real time. In addition, there are loads on both buses.

It can be seen from Figure 1 that this topology avoids the constant-speed transmission device, and at the same time, in order to take advantage of the 270V high-voltage DC power distribution system's advantages of light weight, high reliability, and easy realization of uninterrupted power supply, some DC loads such as the flight control system are controlled by the 270V DC bus powered by. In order to avoid the problem of large-scale replacement of electrical equipment caused by the change of the power supply system, the scheme of parallel connection of multiple VSGs is used to invert the 270V DC power into 115V400Hz AC power for most electrical equipment.

1.2, AC/DC converter design

At present, the AC/DC converters used in aero-engines are still dominated by transformer rectifiers TRU and autotransformer rectifiers ATRU. For example, B787 uses ATRU and TRU to rectify 230V variable frequency alternating current to 270V direct current and 28V direct current respectively. In the development process of TRU and ATRU, the basic idea is to achieve the purpose of harmonic control by increasing the number of rectifier bridges. The more pulses of TRU and ATRU, the smaller the ripple of output voltage and the harmonic content of input current. However, the disadvantage of this idea is that the high number of pulses also leads to an increase in the volume and weight of the equipment, and it is also a challenge to the reliable operation of the engine. Considering that an aero engine is a device requiring high reliability, it is more feasible to improve the existing scheme on the premise of ensuring safety, so the present invention proposes to redesign traditional TRU and ATRU by using active filter circuit , On the one hand, it can meet the high-power transmission requirements of the engine, realize low harmonic content of the input current, and reduce the volume and weight.

Figure 2 shows the autotransformer active filter rectifier designed by the present invention, which consists of a three-phase AC power supply, a polygonal autotransformer, a three-phase uncontrolled rectifier bridge, a parallel active power filter, a balance reactor and output load composition. The device uses a twelve-pulse autotransformer as the main structure, and the autotransformer chooses a polygonal structure. A three-phase active power filter is connected in parallel on the output DC side of the rectifier bridge to realize active filtering of a single rectifier bridge. A reactor is connected after the power filter to stabilize the output voltage of the DC side.

Because the 12k±1 harmonic of the input current is the main source of the total harmonic content, and the output voltage of the DC side is 12 pulses, so if proper control is applied to make the waveform of the DC side current consistent with the DC side voltage, then in AC The same phase relationship will also exist on the AC side, that is, the current and voltage waveforms on the AC side will also remain consistent. At this time, viewed from the AC side, the rectifier bridge, the parallel APF on the DC side, and the load are equivalent to an equivalent resistance, thereby realizing the control of harmonics. Figure 3 shows the equivalent circuit diagram of the proposed topology.

It can be seen from Figure 3 that when Sp1 and Sn1 are closed, the filter inductor is directly connected to the power supply, and at this time the power supply charges the filter inductor, that is, the inductor current increases, as follows:

Among them, U _pm and U _mn are the upper and lower half bridge voltages respectively, U _Lp and i _Lp correspond to the voltage and current of L _p , U _Ln and i _Ln correspond to the voltage and current of Ln, when Sp2 and Sn2 are closed, the filter inductance The voltage across both ends can be expressed as:

U _Cp corresponds to the voltage of _Cp , and U _Cn corresponds to the voltage of _Cn . It can be seen from the above formula that the voltage across the inductor decreases, that is, the inductor current decreases. It can be seen from the above analysis that the voltage across the filter inductor can be positive or negative, that is, the inductor current can be increased or decreased, and the current is controllable. By applying appropriate control, the phase of the DC side current is consistent with the phase of the DC side voltage, that is, the purpose of harmonic control is achieved.

1.3, DC/AC converter design

The DC/AC converter on a traditional aero-engine is an aeronautical static converter, and its main function is to convert the electrical energy of a DC power supply or an aviation battery into an alternating current for electrical equipment. With the introduction of the concept of aviation multi-electric engines, traditional aviation static converters can no longer meet the requirements of large power capacity, and at the same time, airborne equipment has higher and higher requirements for power quality. Therefore, it is necessary to try to integrate multi-DC/AC The technology of parallel operation of converters is applied in the aviation field. On the one hand, it can reduce the capacity of a single DC/AC converter, and can also realize redundant functions to ensure reliable power supply.

The invention starts from ensuring the stability of the power system of the aviation multi-electric engine and ensuring the reasonable distribution of load power, and proposes to use the VSG to design the aviation DC/AC converter. Compared with the control scheme of the traditional DC/AC converter, it can simulate the characteristics of synchronous generator active frequency modulation and reactive power voltage regulation through the control algorithm to ensure the stability of the system, and at the same time realize the reasonable load distribution between the converters. distribute.

VSG can simulate the inertia of a synchronous generator, and its active frequency modulation characteristics can be expressed by the torque formula of the mechanical part of the generator:

θ=∫ωdt (6)

Its reactive power regulation characteristics can be described as follows:

In the formula, J is the moment of inertia of the rotor, T _m is the mechanical torque, T _e is the electromagnetic torque, D _p is the damping coefficient, θ is the rotor angle, ω is the angular velocity of the rotor, Q _set is the given reactive power, D _q is the droop coefficient, U ₀ is the effective value of the output voltage, U _n is the effective value of the rated voltage, and E _m is the effective value of the modulation wave. Formulas (5) and (7) output the amplitude and angular velocity of the modulated wave respectively, and the trigger signal of the inverter switch tube is obtained through the modulation of the carrier.

2. Steady-state characteristics research

Aeroengines will face sudden load changes in different flight states, which will lead to fluctuations in the bus voltage, so it is necessary to take necessary measures to ensure the stability of the bus voltage. The invention takes the stable operation of the AC and DC power system of the aviation multi-electric engine as the starting point to conduct research.

2.1. Generator voltage regulation system

The voltage regulator is one of the measures to maintain the voltage stability of the power system. The early voltage regulator was a vibration type or a carbon chip type. Since the 1950s and 1960s, it was replaced by a magnetic amplifier type and a transistor type voltage regulator. It is widely used application. In the past two decades, with the emergence of microprocessors, digital voltage regulators have been paid attention to. They are not sensitive to frequency changes, and at the same time avoid the problem of parameter changes in analog circuit components, so they are used in variable frequency AC power generation. machine has great advantages. Figure 4 shows a typical digital voltage regulator control block diagram:

The role of the voltage regulator is not only to stabilize the output voltage of a single generator, but also to achieve even distribution of power by adjusting the excitation current in the case of multiple generators connected in parallel.

2.2. Research on steady-state characteristics of HVDC bus voltage

There is a sudden change in the load of the aero-engine in different flight states, which will lead to fluctuations in the bus voltage. The present invention aims at the stability of the high-voltage DC bus voltage, and proposes to use a battery and a bidirectional DC/DC converter to control the voltage of the high-voltage DC bus. Compensation to maintain it near the rated voltage.

The bidirectional DC/DC converter integrates the Buck circuit and the Boost circuit in one circuit, and the circuit has two switching tubes, and the bidirectional flow of energy can be realized by controlling the switching of the switching tubes. In the present invention, when the high-voltage DC bus When the voltage is lower than 265V, the bidirectional DC/DC converter works in Boost mode. At this time, the energy of the battery flows to the high-voltage DC bus. Conversely, when the voltage of the high-voltage DC bus is higher than 275V, the bidirectional DC/DC converter works. In Buck mode, the battery absorbs the excess energy of the high-voltage DC bus, so that its voltage is stabilized near the rated value. The traditional integer-order PI controller is still the most widely used controller. Compared with the integer-order PI controller, the fractional-order PI controller has better dynamic performance, but the parameter determination is also more complicated, so this embodiment uses Fractional order PI controllers are designed.

2.3 Research on the Steady-state Characteristics of AC Bus

Airborne electronic equipment such as flight control systems require constant frequency AC power supply. Therefore, for the stability of the AC bus, in addition to ensuring that the voltage amplitude is stable near the rated value, the frequency should also be stable.

The VSG used in the present invention is a research hotspot in the field of photovoltaic grid connection at present. Compared with traditional inverters, it has the following advantages: 1) It can simulate the characteristics of synchronous generator active power frequency modulation. , the system inertia will keep the frequency at the rated frequency, and the system inertia requires an energy storage device on the DC side to release or absorb energy in a short time. Therefore, the storage battery and the bidirectional DC/DC converter proposed by the present invention have two functions, one is to maintain the voltage stability of the high-voltage DC bus, and the other is to provide system inertia for the VSG. 2) VSG can also simulate the characteristics of reactive voltage regulation of synchronous generators to maintain voltage stability.

3. Simulation result analysis

In order to meet the development requirements of aviation airborne power systems, the US military issued MIL-STD-704F to ensure the safe and reliable operation of aircraft power systems, which have specific requirements for the characteristics of each AC and DC bus. Its requirements for the steady-state characteristics of the airborne power supply are shown in Table 1 and Table 2:

Table 1 Constant frequency AC power supply standard

Its requirements for the DC bus are shown in Table 2:

Table 2 270V DC power supply standard

The simulation verification is divided into two parts: 1) the verification of the harmonic suppression of the AC/DC converter ATPFRU proposed in the present invention; 2) the research verification of the stability of the AC/DC power system.

3.1. ATPFRU Harmonic Suppression Verification Analysis

It can be seen from the foregoing that the 12k±1 order harmonic of the input current is the main source of the total harmonic content, so the present invention only analyzes the above-mentioned harmonics. In the simulation model, the filter inductance is 4mH, and the filter capacitor is 6mF. Table 3 shows 12 pulses ATRU and each order harmonic content of ATPFRU proposed by the present invention:

Table 3 Harmonic content before and after filtering

It can be seen from Table 3 that each harmonic content drops below 2%, and the total harmonic content drops below 4%, meeting the US military aviation power supply standard.

3.2 Research on Steady-state Characteristics of AC-DC Power System

The present invention simulates different working states of the aero-engine by suddenly increasing and decreasing the load. Figure 5a and Figure 5b show the voltage waveform diagram of the high-voltage DC bus when the load changes suddenly and the amplitude conversion curve diagram of the input current:

The first 1s of system operation is the start-up phase, which is not considered here. At t=1.5s, a 33% load is added suddenly, and the DC voltage has a drop at this time. Under the adjustment of the voltage regulator, it takes about 1s to stabilize again; at t=2.5s, the load is cut off, Now the voltage rises to 275V, which is due to the voltage regulation boundary of the bidirectional DC/DC converter set by the present invention being 275V. In this state, the DC bus delivers energy to the storage battery, and the voltage regulator reduces the excitation current at the same time , to reach stability again through a time of about 0.5s. It can be seen that the entire regulation process of the voltage meets the standards of the U.S. military high-voltage DC bus. Figures 6a-6d show the voltage and power waveforms of parallel VSGs:

It can be seen from Figures 6a-6d that the load is suddenly added and decreased at t=1.5s and t=2.5s respectively. At this time, the two VSGs work in parallel, and they share the load. At t=4s, the fault of VSG1 is simulated. At this time, VSG1 is disconnected, and all load power is borne by VSG2.

When the load is suddenly added at t=1.5s, the voltage amplitude and frequency of the AC bus temporarily drop back at this time. Because VSG can simulate the characteristics of synchronous generator active voltage regulation and reactive voltage regulation, the voltage amplitude and frequency are very fast Stabilize to the command value, similarly at t=2.5s, the voltage amplitude and frequency have a brief increase. At t=4s, VSG1 is disconnected. At this time, the entire load power is borne by VSG2, which is equivalent to a sudden load, so the voltage amplitude and frequency drop temporarily. During the entire adjustment process, the voltage amplitude of the AC bus is stable at 115V Nearby, the voltage frequency is stable around 400Hz, meeting the US military standard for constant frequency AC voltage.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (7)

1. A kind of AC-DC hybrid power system of aviation multi-electric engine, it is characterized in that: comprise two parallel built-in variable frequency AC starter/generators, the output end of each built-in variable frequency AC starter/generator is connected with AC/DC Converter, the output end of the AC/DC converter is connected to the DC bus, the DC bus is connected to the DC/AC converter, the bidirectional DC/DC converter, the DC/AC converter is connected to the AC bus as an output, and the bidirectional DC/DC The converter is connected with a battery; both the DC bus and the AC bus are connected with loads; The AC/DC converter is an autotransformer active filter rectifier. The autotransformer active filter rectifier consists of a three-phase AC power supply, a polygonal autotransformer, a three-phase uncontrolled rectifier bridge, and a parallel active power supply on the DC side. Composed of filters, balanced reactors and output loads; the three-phase AC power supply is connected to a polygonal autotransformer, the polygonal autotransformer is connected to a three-phase uncontrolled rectifier bridge, and the output terminal of the three-phase uncontrolled rectifier bridge is connected to the DC side parallel active power filter The output terminal of the shunt active power filter is connected to the balance reactor, and the balance reactor is connected to the output load; The DC/AC converter is an inverter using virtual synchronous generator technology. 2. The AC-DC hybrid power system for aviation multi-electric engines according to claim 1, characterized in that: the rated voltage of the DC bus is 270V, the rated voltage of the AC bus is 115V, and the frequency is 400Hz. 3. The AC-DC hybrid power system of an aviation multi-electric engine according to claim 1, wherein the polygonal autotransformer is a twelve-pulse autotransformer. 4. A method for designing an AC-DC hybrid power system of an aviation multi-electric engine, characterized in that: comprising the following steps: Step 1: Combine the active power filter with the polygonal connection autotransformer rectifier, design the autotransformer active filter rectifier, and connect the autotransformer active filter rectifier to the built-in variable frequency AC starter/generator Between the DC busbar; the autotransformer active filter rectifier is composed of a three-phase AC power supply, a polygonal autotransformer, a three-phase uncontrolled rectifier bridge, a parallel active power filter on the DC side, a balance reactor and an output load. The polygonal autotransformer adopts a twelve-pulse autotransformer, and connects the DC-side parallel active power filter at the output end of the three-phase uncontrolled rectifier bridge to realize the active filtering of a single three-phase uncontrolled rectifier bridge. The source power filter is followed by a balance reactor to stabilize the output voltage of the DC side; Step 2, using an inverter using virtual synchronous generator technology as a DC/AC converter, and connecting the DC/AC converter between the DC bus and the AC bus to keep the voltage amplitude and frequency of the AC bus stable; Step 3, using a storage battery and a bidirectional DC/DC converter to compensate the power of the DC bus, so that the voltage of the DC bus can be maintained near the rated voltage; Step 4: Use the autotransformer active filter rectifier in step 1 as an AC/DC converter, the DC/AC converter in step 2, the storage battery in step 3, and the bidirectional DC/DC converter as part of the designed power system , connected with the power generation part, DC bus, AC bus and load to complete the overall design. 5. The method for designing an AC-DC hybrid power system of an aviation multi-electric engine according to claim 4, characterized in that: in said step 2, the active frequency modulation and reactive voltage regulation characteristics of the virtual synchronous generator are described as follows: θ=∫ωdt Its reactive power regulation characteristics can be described as follows: In the formula, J is the moment of inertia of the rotor, is the first derivative of J, T _m is the mechanical torque, T _e is the electromagnetic torque, D _p is the damping coefficient, θ is the rotor angle, is the first derivative of θ, ω is the angular velocity of the rotor, Q _set is the given reactive power, D _q is the droop coefficient, U ₀ is the effective value of the output voltage, U _n is the effective value of the rated voltage, and E _m is the effective value of the modulation wave value, Q _e is the electromagnetic power; The above formula outputs the amplitude and angular velocity of the modulated wave, and the trigger signal of the inverter switch tube is obtained through the modulation of the carrier. 6. The method for designing an AC-DC hybrid power system for an aero-engine with multiple electric motors according to claim 4, characterized in that: in said step 3, the bidirectional DC/DC converter integrates the Buck circuit and the Boost circuit in one circuit, the The circuit has two switch tubes, and the two-way flow of energy can be realized by controlling the on-off of the switch tubes. When the high-voltage DC bus voltage is lower than 265V, the bidirectional DC/DC converter works in Boost mode. At this time, the energy of the battery On the contrary, when the voltage of the high-voltage DC bus is higher than 275V, the bidirectional DC/DC converter works in Buck mode, and the battery absorbs the excess energy of the high-voltage DC bus, so that its voltage is stabilized near the rated value. 7. The method for designing an AC/DC hybrid power system for an aviation multi-electric engine according to claim 4, wherein in said step 4, the rated voltage of the DC bus is 270V, the rated voltage of the AC bus is 115V, and the frequency is 400Hz ; The power generation part is two parallel built-in variable frequency AC starters/generators.