A hybrid power system based on open-winding generator and control method thereof

Abstract

The present application discloses a hybrid power system based on an open-winding generator and a control method thereof, which relates to the field of generator control technology. The first output end of a dual-shaft turboshaft engine is connected to a first generator, which is an open-winding generator. The end of the three-phase winding of the first generator is connected to a first converter, which is connected to a first capacitor, which 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, which is connected to a second capacitor, which 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, which is connected to a third capacitor. The present application can reduce the weight and volume of the hybrid power system and improve the power-to-weight ratio of the hybrid power system.

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 system is a system with two or more power sources that, through related control devices, enables each power source to output energy individually or collectively. Currently, the more common hybrid systems are basically composed of two power sources: an engine-generator and an energy storage device. The engines are generally gasoline / diesel engines and gas turbines. Compared with gasoline / diesel engines, gas turbines have a higher power-to-weight ratio. That is, under the condition of outputting the same power, the gas turbine is lighter than the gasoline / diesel engine, and the structure is simpler and easier to maintain. Currently, there are some hybrid system designs based on gas turbines, and there are also many applications for hybrid system designs based on dual-shaft turboshaft engines. In a hybrid system, the engine and generator transmit power through a mechanical connection and drive the generator to rotate and generate electricity. The three-phase electricity output by the generator is rectified by a converter to obtain DC power. This DC power is connected in parallel with the DC bus of the battery energy storage system to jointly power the load. To match the voltage level of the load, a battery energy storage system typically requires the addition of a DC / DC voltage conversion circuit to boost and stabilize the voltage without increasing the number of series-connected batteries. The battery energy storage system then powers the load through the DC / DC voltage conversion circuit.

[0003] In order to match the voltage levels 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 is obviously disadvantageous in the hybrid system of land and air vehicles with extremely stringent requirements on power-to-weight ratio. Especially in the flying condition, the increased weight may even make it impossible to take off. Summary of the Invention

[0004] The purpose of this 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 twin-shaft turboshaft engine is connected to a first generator; the first generator is an open-winding generator; the end of the three-phase winding of the first generator is connected to a first converter, the first converter is connected to a 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 a second converter, the second converter is connected to a 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 method for controlling a hybrid power system based on an open-winding generator, for controlling the hybrid power system based on the open-winding generator. The method for controlling the hybrid power system based on the 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 the first output end of a dual-shaft turboshaft engine is connected to a first generator, which is an open-winding generator, the end of the 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 the 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, and 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, without the 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 following briefly introduces the drawings required for use in the embodiments. 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 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 This is a schematic diagram of the voltage vector distribution provided in Example 2 of the present application.

[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 this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts 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, 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-voltage shaft generator in the second generator (i.e. Figure 1 High-voltage shaft generator in the battery energy storage system, the first converter (i.e. Figure 1 Converter 1 in), the second converter (i.e. Figure 1Converter 2 in), the third converter (i.e. Figure 1 Converter 3 in), first capacitor C1, second capacitor C2 and 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 the 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 twin-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, which is connected to the first capacitor C1, which 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, which is connected to the second capacitor C2, which is connected in parallel with the battery energy storage system and the third capacitor C3. 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 speed reducer and a second speed reducer. The first speed reducer is located between the twin-shaft turboshaft engine and the first generator, and is respectively connected to the first output terminal of the twin-shaft turboshaft engine and the first generator. The second speed reducer is located between the twin-shaft turboshaft engine and the second generator, and is respectively connected to the second output terminal of the twin-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 between 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 a 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 derived 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, with both sides of the three-phase winding open and connected to a first converter and a second converter respectively. The three-phase electricity on the first converter side is rectified by the first converter and then supplied to the load. The three-phase electricity on the second converter side is rectified by the second converter and then 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 in the traditional configuration 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 converter, and the low-voltage shaft generator inputs power to the load through the first converter, thereby reducing the total power that the low-voltage shaft generator needs to generate, and indirectly supplies power to the load. It can also be understood that the battery energy storage system supplies power to the load through the DC / AC conversion of the second converter and then through the AC / DC conversion of the first converter. The first converter and the second converter The converter replaces the DC / DC voltage conversion circuit in the traditional configuration. Since the DC / DC voltage conversion circuit contains power devices, capacitors, and inductors, this embodiment only requires a first converter, a second converter, a first capacitor C1, and a 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 inductors, 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 levels of the load end and the battery energy storage system end by changing the generator topology structure, eliminating the DC / DC voltage conversion circuit in the traditional configuration, thereby improving the power-to-weight ratio of the hybrid system.

[0033] The dual-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 Example 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, 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, 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. Specifically, the following steps are performed:

[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 and the dual-shaft turboshaft engine fuel economy optimal control strategy, a steady-state operating point can be obtained. 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] 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 includes: using the output power of the battery energy storage system and the injection power of the second generator as inputs, 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 judgment result is no, determine whether the battery SOC is within a second preset range, and 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, and 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, the output power of the battery energy storage system is determined to be 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 BESS discharges, fully providing the second generator's injected power. The remaining output power flows to the first generator. At this point, the BESS output power is determined to be positive, and the BESS indirectly supplies power to the load via the first generator. That is, the first generator absorbs power from the BESS via the second converter, and then supplies power to the load via the first converter.

[0069] The power coordination algorithm described above coordinates the power distribution between the first generator and the battery energy storage system, determining the power flow direction and magnitude of the windings on both sides of the battery energy storage system and the first generator. This determines 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 equations (1)-(4) has a positive or 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. By adjusting the voltage vector distribution relationship, the DC voltage levels on the first converter side and the second converter side can be adjusted, 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 for the hybrid power system based on an 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 respectively perform modulation and voltage stabilization. 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 voltages 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) do not exceed their respective corresponding modulation ranges. The modulation range corresponding to the first converter is the first regular hexagon, and the modulation range corresponding to the second converter is the second regular hexagon, such as Figure 3 and Figure 4 As shown, Figure 3 Because the voltages modulated by the first converter and the second converter exceed their respective 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 modulation ranges, it can be considered that the first regular hexagon and the second regular hexagon have an intersection, so the voltage vector distribution can be achieved. The voltage vector distribution 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 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.

[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, then when the second output voltage vector of the second converter 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 corresponding equal power distribution lines when the first converter obtains the minimum power distribution and the maximum power distribution are respectively, then 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, one side or diagonal of the regular hexagon is selected as the first line segment, and the equal power distribution line is selected. current As the second line segment, the intersection of the first line segment and the second line segment is used 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 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 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 i-th 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, using 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; 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, and using an evaluation function to calculate the evaluation value corresponding to the intersection; 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; x 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 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 hybrid power system configuration based on an open-winding generator and its control method. By changing the generator topology to match the voltage levels between the load and battery energy storage systems, an open-winding topology is adopted to match the voltage levels between the battery energy storage system and the load. This eliminates the need for a conventional DC / DC voltage conversion circuit, thereby improving the power-to-weight ratio of the hybrid power system. Furthermore, power coordination is performed to achieve stable operation of the hybrid power system. Voltage vector distribution is then performed to further optimize the control of the converter and reduce its switching frequency.

[0106] The technical features of the above embodiments can 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 document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may 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 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 the third converter, and the third converter is connected to the third capacitor; When controlling the hybrid power system based on the open-winding generator, power coordination is performed on the output power of the first generator, the injected power of the second generator, the output power of the battery energy storage system, and the required power of the load based on the battery SOC of the battery energy storage system 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; Based on the output power of the battery energy storage system, the output voltage vector of the first generator is distributed to obtain the first output voltage vector of the first converter and the second output voltage vector of the second converter, specifically including: determining a first regular hexagon and a second regular hexagon 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; 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 by any point on the equal power distribution line are the same, and the power distribution result refers to the output power of the first converter and the output power of the second converter; for each of the first straight line equations, determine the coordinates of the intersection based on the first straight line equation and the second straight line equation; based on the coordinates of all the intersections, determine the optimal intersection; based on the coordinates of the optimal intersection, determine the first output voltage vector of the first converter and the second output voltage vector of the second converter; The straight line 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.

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 connected to the first output end of the dual-shaft turboshaft engine and the first generator respectively; The second reducer is located between the dual-shaft turboshaft engine and the second generator; the second reducer is connected to the second output end of the dual-shaft turboshaft engine and the second generator respectively.

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. 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 a 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 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 the connection point of the two power devices is the 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 terminal of the first generator is connected to the midpoint of the first branch of the second converter, the B terminal of the first generator is connected to the midpoint of the second branch of the second converter, and the C terminal of the first generator is connected to the midpoint of the third branch of the second converter; the first terminal of the second capacitor is connected to the first terminal of the second converter, and the second terminal of the second capacitor is connected to the second terminal 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 method for controlling 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; 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 for 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 comprising: 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, to obtain 18 first straight line equations; Determining a straight line equation of an equal power distribution line based on the output power of the battery energy storage system and the output current vector of the first generator to obtain a second straight line equation; wherein the power distribution result determined at any point on the equal power distribution line is the same, and the power distribution result refers 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; determining an optimal intersection point based on the coordinates of all the intersection points; determining a first output voltage vector of the first converter and a second output voltage vector of the second converter based on the coordinates of the optimal intersection point; The straight line 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.

5. The control method of a hybrid power system based on an open-winding generator according to claim 4, characterized in that: 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. Specifically, the following steps are performed: Get the required power of the load; determining an output power of the first converter based on a required power of the load; Taking the load power requirement as input, the injection power of the second generator is determined based on the fuel economy optimal control strategy; Obtain the battery SOC of the battery energy storage system; Determining whether the battery SOC is within a first preset range to 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 injection power of the second generator, the output power of the second converter is determined; If the first judgment result is no, determining 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 so, determining 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, and obtaining 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 injection 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 injection 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 using a first calculation formula to determine the output power of the first converter; 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 a hybrid power system based on an 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 injected power of the second generator, specifically comprising: using the output power of the battery energy storage system and the injected power of the second generator as inputs, and determining the output power of the second converter using a second calculation formula; 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: 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, 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 a voltage calculation formula; 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, calculate an evaluation value corresponding to the intersection point using an evaluation function; 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; x 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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