Hybrid power system based on open winding generator and control method thereof

Abstract

The invention discloses a hybrid power system based on an open winding generator and a control method thereof, and relates to the technical field of generator control, a first output end of a double-shaft turboshaft engine is connected with a first generator, the first generator is an open winding generator, and the tail end of a three-phase winding of the first generator is connected with a first converter; the first converter is connected with a first capacitor, the first capacitor is connected with a load in parallel, the head end of a three-phase winding of the first generator is connected with a second converter, the second converter is connected with a second capacitor, the second capacitor is connected with a battery energy storage system and a third capacitor in parallel, and a second output end of the double-shaft turboshaft engine is connected with a second generator. The head ends of the three-phase windings of the second generator are connected, the tail ends of the three-phase windings of the second generator are connected with the third converter, and the third converter is connected with the third capacitor. The weight and the size of the hybrid power system can be reduced, and the power-to-weight ratio of the hybrid power system is increased.

Description

Technical Field

[0001] The present application relates to the technical field of generator control, and in particular to a hybrid power system based on an open-winding generator and a control method thereof. Background Art

[0002] A hybrid power system refers to a system with two or more power sources, which can output energy to the outside separately or together through related control devices. At present, the more common hybrid power systems are basically composed of two power sources: engine-generator and energy storage device. The engine generally uses gasoline engine / diesel engine and gas turbine. Compared with gasoline engine / diesel engine, gas turbine has a higher power-to-weight ratio, that is, under the condition of outputting the same power, the weight of gas turbine is smaller than that of gasoline engine / diesel engine, and the structure is simpler and easier to maintain. At present, there are some hybrid power system designs based on gas turbines, and there are also many applications for the design of hybrid power system based on dual-shaft turboshaft engine. In the hybrid power system, the engine and generator transmit power through mechanical connection and drive the generator to rotate and generate electricity. The three-phase electricity output by the generator is controlled by the converter to obtain direct current. The direct current is connected in parallel with the DC bus of the battery energy storage system to supply power to the load together. In order to match the voltage level of the load, the battery energy storage system usually needs to add a DC / DC voltage conversion circuit without increasing the number of batteries in series to play the role of boosting and stabilizing the voltage. At this time, the battery energy storage system supplies power to the load through the DC / DC voltage conversion circuit.

[0003] In order to match the voltage level of the battery energy storage system and the load, the above-mentioned hybrid system needs to add a DC / DC voltage conversion circuit, which will increase the weight and volume of the hybrid system. This has obvious disadvantages in the hybrid system of land and air vehicles that have extremely stringent requirements on the power-to-weight ratio, especially in air flight conditions. The increase in weight may even make it impossible to take off. Summary of the invention

[0004] The purpose of the present application is to provide a hybrid power system based on an open-winding generator and a control method thereof, which does not require an additional DC / DC voltage conversion circuit, reduces the weight and volume of the hybrid power system, and improves the power-to-weight ratio of the hybrid power system.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a hybrid power system based on an open-winding generator, the hybrid power system based on the open-winding generator comprising: a dual-shaft turboshaft engine, a first generator, a second generator, a battery energy storage system, a first converter, a second converter, a third converter, a first capacitor, a second capacitor and a third capacitor;

[0007] The first output end of the dual-shaft turboshaft engine is connected to the first generator; the first generator is an open-winding generator; the end of the three-phase winding of the first generator is connected to the first converter, the first converter is connected to the first capacitor, and the first capacitor is connected in parallel with the load; the head end of the three-phase winding of the first generator is connected to the second converter, the second converter is connected to the second capacitor, and the second capacitor is connected in parallel with the battery energy storage system and the third capacitor respectively; wherein the head end of the three-phase winding includes an A end, a B end and a C end, and the end of the three-phase winding includes an X end, a Y end and a Z end;

[0008] The second output end of the dual-shaft turboshaft engine is connected to the second generator; the head ends of the three-phase windings of the second generator are connected, the ends of the three-phase windings of the second generator are connected to the third converter, and the third converter is connected to the third capacitor.

[0009] In a second aspect, the present application provides a control method for a hybrid power system based on an open-winding generator, and controls the above-mentioned hybrid power system based on an open-winding generator. The control method for the hybrid power system based on an open-winding generator includes:

[0010] Based on the battery SOC of the battery energy storage system, power coordination is performed on the output power of the first generator, the injection power of the second generator, the output power of the battery energy storage system and the required power of the load to determine the output power of the battery energy storage system, the output power of the first converter and the output power of the second converter.

[0011] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0012] The present application provides a hybrid power system based on an open-winding generator and a control method thereof, wherein a first output end of a dual-shaft turboshaft engine is connected to a first generator, the first generator is an open-winding generator, the end of a three-phase winding of the first generator is connected to a first converter, the first converter is connected to a first capacitor, the first capacitor is connected in parallel with a load, the head end of the three-phase winding of the first generator is connected to a second converter, the second converter is connected to a second capacitor, the second capacitor is connected in parallel with a battery energy storage system and a third capacitor, respectively, the second output end of the dual-shaft turboshaft engine is connected to a second generator, the head end of the three-phase winding of the second generator is connected, the end of the three-phase winding of the second generator is connected to a third converter, the third converter is connected to a third capacitor, so that the battery energy storage system supplies power to the load through the second converter, the first generator and the first converter, and there is no need to add an additional DC / DC voltage conversion circuit, thereby reducing the weight and volume of the hybrid power system and improving the power-to-weight ratio of the hybrid power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 A schematic diagram of an improved configuration of a hybrid power system based on an open-winding generator provided in Example 1 of the present application.

[0015] Figure 2 A flow chart of the power coordination algorithm provided in Example 2 of the present application.

[0016] Figure 3 This is a schematic diagram showing that the voltage vector allocation provided in Example 2 of the present application cannot be implemented.

[0017] Figure 4 A schematic diagram showing how voltage vector allocation according to Embodiment 2 of the present application can be implemented.

[0018] Figure 5 A schematic diagram of voltage vector distribution provided in Example 2 of the present application. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] Example 1

[0021] This embodiment improves the generator topology structure of a hybrid power system based on a dual-shaft turboshaft engine, thereby providing an improved configuration of a hybrid power system, which can eliminate the DC / DC voltage conversion circuit and further improve the power-to-weight ratio of the hybrid power system, and is suitable for hybrid power systems of land and air vehicles.

[0022] like Figure 1 As shown, this embodiment provides a hybrid power system based on an open-winding generator, and the hybrid power system based on an open-winding generator includes: a dual-shaft turboshaft engine, a first generator (i.e. Figure 1 The low-pressure shaft generator in the second generator (i.e. Figure 1 The high-voltage shaft generator in the Figure 1 The converter 1 in the figure), the second converter (i.e. Figure 1The converter 2 in the embodiment), the third converter (i.e. Figure 1 Converter 3 in the embodiment of the present invention), a first capacitor C1, a second capacitor C2 and a third capacitor C3.

[0023] A twin-shaft turboshaft engine is a turboshaft engine with dual output shafts. The twin-shaft turboshaft engine includes a high-pressure turbine and a low-pressure turbine. The output end of the low-pressure turbine is the first output end of the twin-shaft turboshaft engine. The high-pressure turbine is connected to a compressor, and the output end of the compressor is the second output end of the twin-shaft turboshaft engine.

[0024] The first output end of the dual-shaft turboshaft engine is connected to the first generator, which is an open-winding generator. The end of the three-phase winding of the first generator is connected to the first converter, the first converter is connected to the first capacitor C1, and the first capacitor C1 is connected in parallel with the load RL. The head end of the three-phase winding of the first generator is connected to the second converter, the second converter is connected to the second capacitor C2, and the second capacitor C2 is connected in parallel with the battery energy storage system and the third capacitor C3, respectively. Among them, the head end of the three-phase winding includes the A end, the B end and the C end, and the end of the three-phase winding includes the X end, the Y end and the Z end.

[0025] The second output end of the dual-shaft turboshaft engine is connected to the second generator, the head ends of the three-phase windings of the second generator are connected, the ends of the three-phase windings of the second generator are connected to the third converter, and the third converter is connected to the third capacitor C3.

[0026] In this embodiment, the hybrid power system based on the open-winding generator further includes: a first reducer and a second reducer. The first reducer is located between the dual-shaft turboshaft engine and the first generator, and the first reducer is respectively connected to the first output end of the dual-shaft turboshaft engine and the first generator. The second reducer is located between the dual-shaft turboshaft engine and the second generator, and the second reducer is respectively connected to the second output end of the dual-shaft turboshaft engine and the second generator.

[0027] In this embodiment, the converter includes a first branch, a second branch and a third branch. The first end of the first branch, the first end of the second branch and the first end of the third branch are connected to form the first end of the converter. The second end of the first branch, the second end of the second branch and the second end of the third branch are connected to form the second end of the converter. The first branch, the second branch and the third branch each include two power devices connected in series, and the connection point of the two power devices is the midpoint. The power device may be an IGBT (Insulated Gate Bipolar Transistor).

[0028] In this embodiment, the converters are a first converter, a second converter and a third converter.

[0029] When the converter is the first converter, the X end of the first generator is connected to the midpoint a2 of the first branch of the first converter, the Y end of the first generator is connected to the midpoint b2 of the second branch of the first converter, the Z end of the first generator is connected to the midpoint c2 of the third branch of the first converter, the first end of the first capacitor C1 is connected to the first end of the first converter, and the second end of the first capacitor C1 is connected to the second end of the first converter.

[0030] When the converter is the second converter, the A end of the first generator is connected to the midpoint a1 of the first branch of the second converter, the B end of the first generator is connected to the midpoint b1 of the second branch of the second converter, the C end of the first generator is connected to the midpoint c1 of the third branch of the second converter, the first end of the second capacitor C2 is connected to the first end of the second converter, and the second end of the second capacitor C2 is connected to the second end of the second converter.

[0031] When the converter is the third converter, the X end of the second generator is connected to the midpoint a3 of the first branch of the third converter, the Y end of the second generator is connected to the midpoint b3 of the second branch of the third converter, the Z end of the second generator is connected to the midpoint c3 of the third branch of the third converter, the first end of the third capacitor C3 is connected to the first end of the third converter, and the second end of the third capacitor C3 is connected to the second end of the third converter.

[0032] This embodiment proposes a hybrid power system based on an open-winding generator, in which a high-pressure shaft and a low-pressure shaft are led out from a dual-shaft turboshaft engine through a reducer, the high-pressure shaft is connected to the high-pressure shaft generator, and the low-pressure shaft is connected to the low-pressure shaft generator. The low-pressure shaft generator adopts an open-winding topology structure, and both sides of the three-phase winding are open, respectively connected to a first converter and a second converter. The three-phase electricity on the first converter side is rectified by the first converter to supply power to the load, and the three-phase electricity on the second converter side is rectified by the second converter and connected in parallel to the DC input end of the third converter connected to the battery energy storage system and the high-pressure shaft generator. The DC voltage output by the battery energy storage system is fixed. For the traditional configuration of the hybrid power system, the battery energy storage system is directly connected in parallel at both ends of the load to provide DC power to the load. Therefore, in order to match the DC voltage of the load, it is necessary to additionally introduce a DC / DC voltage conversion circuit between the battery energy storage system and the load. For the improved configuration of the hybrid power system proposed in this embodiment, the battery energy storage system inputs power to the low-voltage shaft generator through the second inverter, and the low-voltage shaft generator inputs power to the load through the first inverter, thereby reducing the total power that the low-voltage shaft generator needs to generate, and indirectly powers the load. It can also be understood that the battery energy storage system powers the load through the DC / AC conversion of the second inverter and then through the AC / DC conversion of the first inverter. The first inverter and the second inverter The converter replaces the DC / DC voltage conversion circuit in the traditional configuration. Since there are power devices, capacitors, and inductors in the DC / DC voltage conversion circuit, this embodiment only requires the first converter, the second converter, the first capacitor C1 and the second capacitor C2. The first converter and the second converter only include power devices. Compared with the first capacitor C1 and the second capacitor C2, the capacitor used in the DC / DC voltage conversion circuit is larger, and the DC / DC voltage conversion circuit requires additional inductance, which will result in a larger volume and weight. Therefore, the volume and weight of the DC / DC voltage conversion circuit are larger. This embodiment matches the voltage level of the load end and the battery energy storage system end by changing the generator topology structure, thereby eliminating the DC / DC voltage conversion circuit under the traditional configuration, thereby improving the power-to-weight ratio of the hybrid power system.

[0033] The twin-shaft turboshaft engine of this embodiment can also be replaced by other engines with dual output shafts.

[0034] Example 2

[0035] This embodiment provides a control method for a hybrid power system based on an open-winding generator, which controls the hybrid power system based on an open-winding generator described in Embodiment 1. The control method for the hybrid power system based on an open-winding generator includes:

[0036] Based on the battery SOC (State of Charge) of the battery energy storage system, power coordination is performed on the output power of the first generator, the injection power of the second generator, the output power of the battery energy storage system and the required power of the load to determine the output power of the battery energy storage system, the output power of the first converter and the output power of the second converter.

[0037] For the improved configuration of the hybrid power system described in Example 1, the dual-shaft turboshaft engine can output a steady-state operating point based on the required power of the load and its own fuel economy. The steady-state operating point includes the speed N_L of the first generator, the speed N_H of the second generator and the injected power P_HM of the second generator, thereby further realizing power coordination among the first generator, the second generator, the battery energy storage system and the load, and realizing power distribution of the converters on both sides of the first generator.

[0038] like Figure 2 As shown, based on the battery SOC of the battery energy storage system, the output power of the first generator, the injection power of the second generator, the output power of the battery energy storage system and the required power of the load are coordinated to determine the output power of the battery energy storage system, the output power of the first converter and the output power of the second converter, specifically including:

[0039] (1) Obtain the required power of the load.

[0040] (2) Based on the required power of the load, the output power of the first converter is determined.

[0041] Determining the output power of the first converter based on the required power of the load specifically includes: taking the required power of the load as input, and determining the output power of the first converter using a first calculation formula.

[0042] The first calculation formula is:

[0043] P_L1=P_need(1)

[0044] In formula (1), P_L1 is the output power of the first converter; P_need is the required power of the load.

[0045] (3) Taking the required power of the load as input, the injection power of the second generator is determined based on the fuel economy optimal control strategy.

[0046] According to the load demand power P_need, the steady-state operating point can be obtained according to the dual-shaft turboshaft engine fuel economy optimal control strategy. The steady-state operating point includes the speed N_L of the first generator, the speed N_H of the second generator and the injected power P_HM of the second generator.

[0047] The injection power \(P_{HM}\) of the second generator, the required power \(P_{need}\) of the load, the output power \(P_{L}\) of the first generator, and the output power \(P_{battery}\) of the battery energy storage system satisfy the following relationship:

[0048] \(P_{HM}+P_{need}=P_{L}+P_{battery}\ (2)\)

[0049] For the system composed of the second generator + two - shaft turboprop engine, the second generator outputs power. For the system composed of the second generator + battery energy storage system + first generator + load, the second generator absorbs power, so power needs to be injected into it. Equation (2) is the power relationship among the components in the system composed of the second generator + battery energy storage system + first generator + load, and it always holds.

[0050] It should be noted that for the second generator and the load, when power is injected into them, the injection power of the second generator and the required power of the load are positive. In this embodiment, the injection power of the second generator and the required power of the load are always positive. For the first generator and the battery energy storage system, when they output power, the output power of the first generator and the output power of the battery energy storage system are positive. In this embodiment, the positive and negative of the output power of the first generator and the output power of the battery energy storage system are unknown and need to be determined later.

[0051] (4) Obtain the battery SOC of the battery energy storage system.

[0052] (5) Determine whether the battery SOC is within the first preset range to obtain the first judgment result.

[0053] The first preset range can be \(0.4 < SOC_{bat}<0.6\), where \(SOC_{bat}\) is the battery SOC.

[0054] (6) If the first judgment result is yes, the battery energy storage system is in the charging state. The first generator provides power for the battery energy storage system and the second generator. Determine that the output power of the battery energy storage system is negative. Based on the output power of the battery energy storage system and the injection power of the second generator, determine the output power of the second converter.

[0055] When \(0.4 < SOC_{bat}<0.6\), the battery energy storage system is charging. The first generator provides the output power of the battery energy storage system and the injection power of the second generator. At this time, the output power of the battery energy storage system is negative. Since the magnitude of the output power of the battery energy storage system is known and the positive and negative of the output power of the battery energy storage system are determined, the output power of the battery energy storage system can be determined. Then, combined with the injection power of the second generator and the required power of the load, the output power of the first generator can be determined using Equation (2).

[0056] The output power of the second converter is determined based on the output power of the battery energy storage system and the injection power of the second generator, specifically comprising: taking the output power of the battery energy storage system and the injection power of the second generator as input, and using a second calculation formula to determine the output power of the second converter.

[0057] The second calculation formula is:

[0058] P_L2=P_HM-P_battery(3)

[0059] In formula (3), P_L2 is the output power of the second converter; P_HM is the injection power of the second generator; and P_battery is the output power of the battery energy storage system.

[0060] The output power P_L of the first generator is:

[0061] P_L=P_L2+P_L1(4)

[0062] (7) If the first determination result is no, determine whether the battery SOC is within a second preset range, wherein the lower limit of the second preset range is greater than or equal to the upper limit of the first preset range.

[0063] The second preset range can be 0.6 <SOC_bat<0.8。

[0064] (8) If so, determine whether the absolute value of the output power of the battery energy storage system is less than the absolute value of the injected power of the second generator to obtain a second determination result.

[0065] (9) If the second judgment result is yes, the battery energy storage system is in a discharging state, and the first generator and the battery energy storage system jointly provide power to the second generator, and the output power of the battery energy storage system is determined to be positive. Based on the output power of the battery energy storage system and the injection power of the second generator, the output power of the second converter is determined.

[0066] If |P_battery|<|P_HM|, the battery energy storage system is discharged, and the injection power of the second generator is provided by the battery energy storage system and the first generator. At this time, it is determined that the output power of the battery energy storage system is positive.

[0067] (10) If the second judgment result is no, the battery energy storage system is in a discharging state, and the battery energy storage system provides power to the first generator and the second generator, and the output power of the battery energy storage system is determined to be positive. Based on the output power of the battery energy storage system and the injection power of the second generator, the output power of the second converter is determined.

[0068] If |P_battery|>|P_HM|, the battery energy storage system discharges, and the battery energy storage system fully provides the injection power of the second generator. The remaining output power flows to the first generator. At this time, the output power of the battery energy storage system is determined to be positive, and the battery energy storage system indirectly supplies power to the load through the first generator, that is, the first generator absorbs power from the battery energy storage system through the second converter, and then provides power to the load through the first converter.

[0069] Through the above power coordination algorithm, the power distribution coordination between the first generator and the battery energy storage system is carried out to determine the power flow direction and magnitude of the windings on both sides of the battery energy storage system and the first generator, that is, to determine the output power of the battery energy storage system, the output power of the first converter and the output power of the second converter. It should be noted that each power in formula (1) to formula (4) has a positive and negative direction.

[0070] There is a vector distribution relationship between the three-phase voltage on the first converter side, the three-phase voltage on the second converter side and the voltage generated by the first generator. The DC voltage levels on the first converter side and the second converter side can be adjusted by adjusting the voltage vector distribution relationship, thereby realizing effective distribution of the output voltage vector by utilizing the voltage vector distribution relationship under the open winding topology structure on the basis of power coordination.

[0071] In this embodiment, after determining the output power of the battery energy storage system, the output power of the first converter, and the output power of the second converter, the control method of the hybrid power system based on the open-winding generator further includes: allocating the output voltage vector of the first generator based on the output power of the battery energy storage system to obtain a first output voltage vector of the first converter and a second output voltage vector of the second converter, specifically including:

[0072] (1) Based on the output voltage vector of the first generator, the DC voltage of the first converter and the DC voltage of the second converter, a first regular hexagon and a second regular hexagon are determined, and the side length of the first regular hexagon is equal to U dc1 is the DC voltage of the first converter, and the side length of the second regular hexagon is equal to U dc2 is the DC voltage of the second converter, and the line segment from the center point of the second regular hexagon to the center point of the first regular hexagon is the output voltage vector of the first generator.

[0073] There is a voltage vector distribution relationship between the windings on both sides of the first generator, that is, the output voltage vector generated by the first generator is distributed to the windings on both sides, and the first converter and the second converter are used to modulate and stabilize the voltage respectively. During the modulation process, the first converter and the second converter both have a modulation range. The larger the DC voltage, the larger the corresponding modulation range. The DC voltage on the first converter side is equal to the load voltage. If the load voltage is 900V, the DC voltage on the first converter side is 900V, and the DC voltage on the second converter side is equal to the output voltage of the battery energy storage system. If the output voltage of the battery energy storage system is 450V, the DC voltage on the second converter side is 450V. The premise for the above voltage vector distribution process to proceed normally is that the voltage modulated by the first converter and the second converter (that is, the first output voltage vector of the first converter and the second output voltage vector of the second converter) does not exceed their respective corresponding modulation ranges. The modulation range corresponding to the first converter is a first regular hexagon, and the modulation range corresponding to the second converter is a second regular hexagon, such as Figure 3 and Figure 4 As shown, Figure 3 Because the voltage modulated by the first converter and the second converter exceeds their respective corresponding modulation ranges, voltage vector distribution cannot be achieved. Figure 4 Because the voltages modulated by the first converter and the second converter do not exceed their respective corresponding modulation ranges, it can be considered that the first regular hexagon and the second regular hexagon have an intersection, so the voltage vector allocation can be achieved. And the voltage vector allocation satisfies the following relationship:

[0074]

[0075] In formula (5), is the output voltage vector of the first generator; is a first output voltage vector of the first converter; is the second output voltage vector of the second converter.

[0076] (2) Determine the linear equations of the sides and diagonals of the first regular hexagon and the sides and diagonals of the second regular hexagon respectively, and obtain 18 first linear equations.

[0077] On the basis that the voltage vector distribution can be realized normally, for the open-winding generator, the current flow direction of the windings on both sides is the same, then the output power of the first converter and the output power of the second converter are:

[0078]

[0079] In the above formula, is the output current vector of the first generator.

[0080] like Figure 5 As shown, Figure 5In the figure, A1-B1-C1-D1-E1-F1 forms the first regular hexagon, O1 is the center point of the first regular hexagon, A2-B2-C2-D2-E2-F2 forms the second regular hexagon, O2 is the center point of the second regular hexagon, That is That is That is The second output voltage vector of the second converter The starting point O2 is perpendicular to The vertical line l of the second converter is When the end point P of is located on the vertical line l, the power distribution results of the output power of the first converter and the output power of the second converter calculated by the above formula (6) and formula (7) are the same, that is, the power distribution results obtained at any point on the vertical line l are the same, so the vertical line l is called the equal power distribution line, and the point P is called the power distribution point. Similarly, all lines parallel to the vertical line l are equal power distribution lines, called l current is the equal power distribution line corresponding to the current voltage vector distribution point, l min , l max The equal power distribution lines corresponding to the minimum power distribution and the maximum power distribution of the first converter are obtained respectively. At any time, the equal power distribution lines on both sides of the first generator are between l min and l max For a group (P_L1, P_L2), there is an equal power distribution line. Different points on the equal power distribution line correspond to two groups of converter output voltage vectors. When determining the power distribution point by the equal power distribution line, the intersection with the side or diagonal of the regular hexagon (the first regular hexagon or the second regular hexagon) should be found as much as possible to achieve the purpose of reducing the switching frequency of the converter. This is because when the vertex of the voltage vector is located on the side of the regular hexagon, or the voltage vector is collinear with the diagonal of the regular hexagon, the switching frequency of the voltage vector modulation is lower. Therefore, select one side or diagonal of the regular hexagon as the first line segment and select the equal power distribution line l current As the second line segment, the intersection of the first line segment and the second line segment is taken as point P to distribute the voltage, which can effectively reduce the switching frequency.

[0081] Select O2 as the coordinate origin, Figure 5 The horizontal axis is the x-axis and the vertical axis is the y-axis, defining the coordinate system.

[0082] The slopes k1, k2 and intercepts b1, b2 of the sides and diagonals of the first regular hexagon corresponding to the first converter and the second regular hexagon corresponding to the second converter are shown in Table 1 below:

[0083] Table 1 Slopes and intercepts corresponding to the sides and diagonals of a regular hexagon

[0084]

[0085] In Table 1, k1 is the slope of the side or diagonal in the first regular hexagon, k2 is the slope of the side or diagonal in the second regular hexagon, b1 is the intercept of the side or diagonal in the first regular hexagon, b2 is the intercept of the side or diagonal in the second regular hexagon, is the component of the output voltage vector of the first generator on the α-axis; is the component of the output voltage vector of the first generator on the β axis.

[0086] (3) Based on the output power of the battery energy storage system and the output current vector of the first generator, the linear equation of the equal power distribution line is determined to obtain the second linear equation. The power distribution results determined at any point on the equal power distribution line are the same. The power distribution results refer to the output power of the first converter and the output power of the second converter.

[0087] Equal power distribution line current The equation of the straight line is:

[0088]

[0089] In formula (8), y is the y coordinate; for The projection in the α-β coordinate system, the α-β coordinate system is a two-phase stationary coordinate system; is the component of the output current vector of the first generator on the α-axis; is the component of the output current vector of the first generator on the β axis; x is the x coordinate; P_battery is the output power of the battery energy storage system.

[0090] (4) For each first straight line equation, the coordinates of the intersection point are determined based on the first straight line equation and the second straight line equation.

[0091] From Table 1, we can see that there are 18 line segments to be selected. Assume that the equal power distribution line l current The intersection point with the i-th line segment among the 18 line segments to be selected is P(x i ,y i ), i=1~18, then:

[0092]

[0093] In formula (9), x i ,y i are the x-coordinate and y-coordinate of the ith intersection point, respectively. The ith intersection point is the intersection point of the equal power distribution line and the ith line segment; k m 、b m They are equal power distribution lines lcurrent The slope and intercept of k i , b i are the slope and intercept of the ith line segment respectively.

[0094] (5) Based on the coordinates of all intersection points, determine the optimal intersection point.

[0095] Based on the coordinates of all intersections, the optimal intersection is determined, specifically including: for each intersection, taking the coordinates of the intersection as input, and using a voltage calculation formula to determine the components of the first output voltage vector of the first converter and the components of the second output voltage vector of the second converter; taking the components of the first output voltage vector of the first converter and the components of the second output voltage vector of the second converter as input, and using an evaluation function to calculate the evaluation value corresponding to the intersection; and selecting the intersection with the smallest evaluation value as the optimal intersection.

[0096] The voltage calculation formula is:

[0097]

[0098] In the above formula, u α1 (i) is the component of the first output voltage vector of the first converter corresponding to the i-th intersection on the α-axis; is the component of the output voltage vector of the first generator on the α axis; i is the x coordinate of the i-th intersection point; u β1 (i) is the component of the first output voltage vector of the first converter corresponding to the i-th intersection on the β-axis; is the component of the output voltage vector of the first generator on the β axis; i is the y coordinate of the i-th intersection point; u α2 (i) is the component of the second output voltage vector of the second converter corresponding to the i-th intersection on the α-axis; u β2 (i) is the component of the second output voltage vector of the second converter corresponding to the i-th intersection on the β-axis.

[0099] In order to select the optimal intersection point P, the evaluation function is defined as:

[0100]

[0101] In formula (12), S c (i) is the evaluation value corresponding to the i-th intersection point; is the first output voltage vector of the first converter corresponding to the i-th intersection; is the second output voltage vector of the second converter corresponding to the i-th intersection.

[0102] Evaluation function S c (i) The smaller, and The smaller the angle is, the closer the power factors of the first converter and the second converter are, and the smaller the modulation error of the converter is. Therefore, the selection of S c (i) The smallest (x i ,y i ) as the coordinates of the optimal intersection point.

[0103] (6) Based on the coordinates of the optimal intersection point, a first output voltage vector of the first converter and a second output voltage vector of the second converter are determined.

[0104] What is finally obtained is the output voltage vector of the first converter and the second converter, which can be used for PWM control of the converter later.

[0105] This embodiment proposes an improved configuration of a hybrid power system based on an open-winding generator and a control method thereof, which matches the voltage levels of the load end and the battery energy storage system end by changing the generator topology structure, that is, adopting an open-winding topology to match the voltage level between the battery energy storage system end and the load end, eliminating the DC / DC voltage conversion circuit under the traditional configuration, thereby improving the power-to-weight ratio of the hybrid power system, and further performing power coordination to achieve stable operation of the hybrid power system, and then performing voltage vector distribution to further optimize the control of the converter and reduce the switching frequency of the converter.

[0106] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A hybrid power system based on an open winding generator, characterized in that: The hybrid power system based on the open-winding generator includes: a dual-shaft turboshaft engine, a first generator, a second generator, a battery energy storage system, a first converter, a second converter, a third converter, a first capacitor, a second capacitor and a third capacitor; The first output end of the dual-shaft turboshaft engine is connected to the first generator; the first generator is an open-winding generator; the end of the three-phase winding of the first generator is connected to the first converter, the first converter is connected to the first capacitor, and the first capacitor is connected in parallel with the load; the head end of the three-phase winding of the first generator is connected to the second converter, the second converter is connected to the second capacitor, and the second capacitor is connected in parallel with the battery energy storage system and the third capacitor respectively; wherein the head end of the three-phase winding includes an A end, a B end and a C end, and the end of the three-phase winding includes an X end, a Y end and a Z end; The second output end of the dual-shaft turboshaft engine is connected to the second generator; the head ends of the three-phase windings of the second generator are connected, the ends of the three-phase windings of the second generator are connected to the third converter, and the third converter is connected to the third capacitor.

2. The hybrid power system based on an open-winding generator according to claim 1, characterized in that: The hybrid power system based on the open-winding generator further includes: a first speed reducer and a second speed reducer; The first reducer is located between the dual-shaft turboshaft engine and the first generator; the first reducer is respectively connected to the first output end of the dual-shaft turboshaft engine and the first generator; The second reducer is located between the dual-shaft turboshaft engine and the second generator; the second reducer is respectively connected to the second output end of the dual-shaft turboshaft engine and the second generator.

3. The hybrid power system based on an open-winding generator according to claim 1, characterized in that: The converter includes a first branch, a second branch and a third branch, wherein a first end of the first branch, a first end of the second branch and a first end of the third branch are connected to form a first end of the converter; a second end of the first branch, a second end of the second branch and a second end of the third branch are connected to form a second end of the converter; the first branch, the second branch and the third branch each include two power devices connected in series, and a connection point of the two power devices is a midpoint; Wherein, the converters are a first converter, a second converter and a third converter; When the converter is a first converter, the X end of the first generator is connected to the midpoint of the first branch of the first converter, the Y end of the first generator is connected to the midpoint of the second branch of the first converter, and the Z end of the first generator is connected to the midpoint of the third branch of the first converter; the first end of the first capacitor is connected to the first end of the first converter, and the second end of the first capacitor is connected to the second end of the first converter; When the converter is the second converter, the A end of the first generator is connected to the midpoint of the first branch of the second converter, the B end of the first generator is connected to the midpoint of the second branch of the second converter, and the C end of the first generator is connected to the midpoint of the third branch of the second converter; the first end of the second capacitor is connected to the first end of the second converter, and the second end of the second capacitor is connected to the second end of the second converter; When the converter is a third converter, the X end of the second generator is connected to the midpoint of the first branch of the third converter, the Y end of the second generator is connected to the midpoint of the second branch of the third converter, and the Z end of the second generator is connected to the midpoint of the third branch of the third converter; the first end of the third capacitor is connected to the first end of the third converter, and the second end of the third capacitor is connected to the second end of the third converter.

4. A control method for a hybrid power system based on an open-winding generator, which controls the hybrid power system based on an open-winding generator according to any one of claims 1 to 3, characterized in that: The control method of the hybrid power system based on the open-winding generator includes: Based on the battery SOC of the battery energy storage system, power coordination is performed on the output power of the first generator, the injection power of the second generator, the output power of the battery energy storage system and the required power of the load to determine the output power of the battery energy storage system, the output power of the first converter and the output power of the second converter.

5. The control method of the hybrid power system based on the open-winding generator according to claim 4, characterized in that: Based on the battery SOC of the battery energy storage system, the output power of the first generator, the injection power of the second generator, the output power of the battery energy storage system and the required power of the load are coordinated to determine the output power of the battery energy storage system, the output power of the first converter and the output power of the second converter, specifically including: Get the required power of the load; Determining the output power of the first converter based on the required power of the load; Taking the required power of the load as input, determining the injection power of the second generator based on the fuel economy optimal control strategy; Obtain the battery SOC of the battery energy storage system; Determine whether the battery SOC is within a first preset range, and obtain a first determination result; If the first judgment result is yes, the battery energy storage system is in a charging state, the first generator provides power to the battery energy storage system and the second generator, and the output power of the battery energy storage system is determined to be negative; based on the output power of the battery energy storage system and the injected power of the second generator, the output power of the second converter is determined; If the first judgment result is no, then judging whether the battery SOC is within a second preset range; the lower limit of the second preset range is greater than or equal to the upper limit of the first preset range; If yes, determine whether the absolute value of the output power of the battery energy storage system is less than the absolute value of the injected power of the second generator to obtain a second determination result; If the second judgment result is yes, the battery energy storage system is in a discharging state, the first generator and the battery energy storage system jointly provide power to the second generator, and the output power of the battery energy storage system is determined to be positive; based on the output power of the battery energy storage system and the injected power of the second generator, the output power of the second converter is determined; If the second judgment result is no, the battery energy storage system is in a discharging state, and the battery energy storage system provides power to the first generator and the second generator, and the output power of the battery energy storage system is determined to be positive; based on the output power of the battery energy storage system and the injected power of the second generator, the output power of the second converter is determined.

6. The control method of the hybrid power system based on the open-winding generator according to claim 5, characterized in that: Determining the output power of the first converter based on the required power of the load specifically includes: taking the required power of the load as input, and determining the output power of the first converter using a first calculation formula; The first calculation formula is: P_L1 = P_need; Wherein, P_L1 is the output power of the first converter; P_need is the required power of the load.

7. The control method of the hybrid power system based on the open-winding generator according to claim 5, characterized in that: Determining the output power of the second converter based on the output power of the battery energy storage system and the injection power of the second generator, specifically comprising: using the output power of the battery energy storage system and the injection power of the second generator as input, and using a second calculation formula to determine the output power of the second converter; The second calculation formula is: P_L2 = P_HM - P_battery; Among them, P_L2 is the output power of the second converter; P_HM is the injection power of the second generator; P_battery is the output power of the battery energy storage system.

8. The control method of a hybrid power system based on an open-winding generator according to claim 4, characterized in that: After determining the output power of the battery energy storage system, the output power of the first converter, and the output power of the second converter, the control method of the hybrid power system based on the open-winding generator further includes: allocating the output voltage vector of the first generator based on the output power of the battery energy storage system to obtain a first output voltage vector of the first converter and a second output voltage vector of the second converter, specifically including: Based on the output voltage vector of the first generator, the DC voltage of the first converter and the DC voltage of the second converter, a first regular hexagon and a second regular hexagon are determined; the side length of the first regular hexagon is equal to U dc1 is the DC voltage of the first converter, and the side length of the second regular hexagon is equal to U dc2 is the DC voltage of the second converter; the line segment from the center point of the second regular hexagon to the center point of the first regular hexagon is the output voltage vector of the first generator; Determine the straight line equations of the sides and diagonals of the first regular hexagon and the sides and diagonals of the second regular hexagon respectively, and obtain 18 first straight line equations; Based on the output power of the battery energy storage system and the output current vector of the first generator, determine the straight line equation of the equal power distribution line to obtain the second straight line equation; the power distribution results determined at any point on the equal power distribution line are the same, and the power distribution results refer to the output power of the first converter and the output power of the second converter; For each of the first straight line equations, determining the coordinates of an intersection point based on the first straight line equation and the second straight line equation; Based on the coordinates of all the intersection points, determining the optimal intersection point; Based on the coordinates of the optimal intersection point, a first output voltage vector of the first converter and a second output voltage vector of the second converter are determined.

9. The control method of the hybrid power system based on the open-winding generator according to claim 8, characterized in that: The linear equation of the equal power distribution line is: Where y is the y coordinate; is the component of the output current vector of the first generator on the α-axis; is the component of the output current vector of the first generator on the β axis; x is the x coordinate; P_battery is the output power of the battery energy storage system.

10. The control method of a hybrid power system based on an open-winding generator according to claim 8, characterized in that: Based on the coordinates of all the intersection points, determining the optimal intersection point specifically includes: For each of the intersection points, using the coordinates of the intersection point as input, using a voltage calculation formula to determine the components of the first output voltage vector of the first converter and the components of the second output voltage vector of the second converter; using the components of the first output voltage vector of the first converter and the components of the second output voltage vector of the second converter as input, using an evaluation function to calculate an evaluation value corresponding to the intersection point; Selecting the intersection point with the smallest evaluation value as the optimal intersection point; The voltage calculation formula is: Among them, u α1 (i) is the component of the first output voltage vector of the first converter corresponding to the i-th intersection on the α-axis; is the component of the output voltage vector of the first generator on the α axis; i is the x coordinate of the i-th intersection point; u β1 (i) is the component of the first output voltage vector of the first converter corresponding to the i-th intersection on the β-axis; is the component of the output voltage vector of the first generator on the β axis; i is the y coordinate of the i-th intersection point; u α2 (i) is the component of the second output voltage vector of the second converter corresponding to the i-th intersection on the α-axis; u β2 (i) is the component of the second output voltage vector of the second converter corresponding to the i-th intersection on the β-axis; The evaluation function is: WITH c (i)=(in α1 (and)) 2 +(in β1 (and)) 2 +(in α2 (and)) 2 +(in β2 (and)) 2 ; Among them, S c (i) is the evaluation value corresponding to the i-th intersection point.

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