Series-parallel hybrid power ship power system and control method thereof

Abstract

The invention discloses a series-parallel hybrid power ship power system, which comprises two groups of main propulsion diesel engines and two groups of shaft-driven motors which are respectively connected with propellers through gear boxes, and further comprises a shaft-driven frequency converter connected with the shaft-driven motors, a DC-BUS connected with the shaft-driven frequency converter, and a DC / DC converter, a controllable rectifier and a daily inverter power supply which are connected with the DC-BUS, the controllable rectifier and the DC / DC converter are respectively connected with a diesel generating set and a power battery pack; the invention further discloses a mode switching control method. According to different operation working conditions of the ship, the corresponding working modes of the hybrid power system are started, and related propulsion equipment and a power supply device are applied, so that the requirements of ship functions and navigational speed are met, the operation economy of ship power equipment is improved, and the life cycle of the ship power equipment is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of ship electrical control, and specifically designs a series-parallel hybrid power ship power system, and a working mode switching control method thereof. Background Art

[0002] At present, there are more and more hybrid ship types, among which the most common are parallel ships that are jointly driven by main propulsion diesel engines and shaft belt motors, and series ships that are powered by a combination of diesel generator sets and power battery packs.

[0003] These two types of ships have their own advantages and disadvantages. When a parallel-type ship is anchored in the sea, the battery pack alone is responsible for the entire ship's electricity consumption, which is difficult to meet the needs of long-term anchoring. The power propulsion of a series-type ship is completely provided by the motor, and the power response of the ship is insufficient.

[0004] Combining the power types of parallel and series ships to meet various ship usage scenarios is a development direction for future hybrid ships. Summary of the invention

[0005] One of the objectives of the present invention is to provide a series-parallel hybrid power ship power system.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a series-parallel hybrid power ship power system, including two sets of main propulsion diesel engines and two sets of shaft belt motors connected to propellers through gear boxes respectively, and also including a shaft generator inverter connected to the shaft belt motor and a DC-BUS connected to the shaft generator inverter, as well as a DC / DC converter connected to the DC-BUS, a controllable rectifier and a daily inverter power supply for supplying power to the entire ship, wherein the controllable rectifier and the DC / DC converter are respectively connected to a diesel generator set and a power battery pack, and the DC-BUS is composed of a DC-BUS bus A and a DC-BUS bus B connected by a solid-state switch.

[0007] The series-parallel hybrid power system for ships has two sets of shaft belt motors connected to the AC bus of the shaft generator inverter, two sets of main propulsion diesel engines and a diesel generator set connected to the AC bus of the controllable rectifier, a power battery pack connected to the AC bus of the DC / DC converter, and the DC bus of the shaft generator inverter and the daily inverter power supply as well as the DC bus of the DC / DC converter and the controllable rectifier are respectively connected to the DC-BUS.

[0008] The second object of the present invention is to provide a control method for a series-parallel hybrid power system of a ship. According to the characteristic curves of a propulsion diesel engine, a diesel generator set, a shaft motor and a power battery set, a control strategy is formulated to meet various operating conditions of the ship, and at the same time, the propulsion diesel engine and the diesel generator are operated near the optimal fuel consumption point to reduce the fuel consumption of the whole ship. The steps are:

[0009] a) Determine the driving mode of the hybrid ship: determine the current required speed of the propeller according to the position information of the propulsion handle in the cab, determine the ship driving mode according to the required speed, the input mode and working mode of the main propulsion diesel engine and the shaft motor, and select single motor drive, propulsion diesel engine drive or propulsion diesel engine and motor combined drive; when the propulsion required speed is low, the ship is only propelled by the shaft motor in speed mode; when the propulsion required speed increases, the main propulsion diesel engine and the shaft motor are put into use, the main propulsion diesel engine adjusts the speed according to the position of the propulsion handle, and the shaft motor operates in torque mode. The torque of the motor absorbs the surplus power of the main propulsion diesel engine and makes it work at the highest efficiency point; when the propulsion demand speed is too high, the main propulsion diesel engine and the shaft belt motor are put into use in parallel, and the shaft belt motor operates in torque mode and drives the propeller together with the main propulsion diesel engine by providing positive torque; when the ship driving mode is determined by the required speed, in order to prevent the handle from shaking back and forth in the speed range of motor drive and diesel engine drive, causing the main propulsion diesel engine of the gearbox to frequently engage and disengage, it is necessary to add a dead zone interval between the speed range of motor drive and diesel engine drive. When the handle position is in the dead zone interval, the engagement state of the gearbox remains unchanged;

[0010] b) Determine the number and power value of diesel generator sets: Determine the number and power of diesel generator sets to be put into operation according to the power of the shaft generator inverter, the power of the current daily inverter power supply and the current power of the power battery pack, so as to make them work at a higher efficiency point as much as possible; when the ship is driven by the propulsion diesel engine, the shaft motor is in the power generation mode, absorbing the surplus power of the main propulsion diesel engine to ensure that the main propulsion diesel engine is at a higher working efficiency as much as possible. When the shaft motor generates electricity and feeds energy back to the DC-BUS, it is also necessary to consider the power of the power battery pack to prevent the battery from overcharging. On the basis of not overcharging or over-discharging the power battery pack, the diesel generator set is operated at the highest efficiency point as much as possible; the surplus power Psur of the propulsion diesel engine working at the highest efficiency point at the current speed is calculated through the efficiency curve of the main propulsion diesel engine: if the surplus power is less than the current daily load power, the shaft motor generates electricity and runs at the surplus power; if the surplus power is greater than the current daily load power, it is necessary to refer to the power of the lithium battery pack. When the power of the lithium battery pack is too high, the power generation power needs to be reduced to below the daily load power;

[0011] c) Determine the DC voltage set value of the controlled rectifier: Based on the actual value of the current DC-BUS voltage, adjust the DC voltage set value of the controlled rectifier through the PI regulator to control the power of the diesel generator set to the value determined in step b); Adjust the DC / DC converter to control the charging and discharging current of the lithium battery pack: According to the power of the controlled rectifier, the daily inverter and the shaft generator frequency converter, adjust the DC / DC converter to control the charging and discharging of the power battery pack in real time.

[0012] Furthermore, in addition to considering the maximum efficiency point of the main propulsion diesel engine, the power generation power of the shaft motor also needs to consider the current daily load size and the power of the power battery pack: when the daily load is too small and the battery power is high, the shaft motor should stop generating electricity; when the shaft motor is generating electricity normally, the power generation power of the shaft motor is indirectly controlled by controlling the charging and discharging current of the DC / DC converter to the power battery pack.

[0013] Furthermore, the number and power of the diesel generator sets should be based on the power of the shaft motor, the daily load size and the power of the power battery pack, and the priority of shaft motor power generation is higher than that of the diesel generator sets; the diesel generator sets mainly work in ship electric propulsion mode and marine docking mode.

[0014] Furthermore, the power control of the shaft belt motor is based on the current daily load power P load And the power battery pack SOC bat is the input quantity, and the output shaft generates the power P of the inverter. motor ; Reference surplus power P sur Formulate daily load power P load Fuzzy interval: daily load power P load When it is too small and the battery power is high, the shaft belt motor needs to be stopped for power generation.

[0015] Furthermore, when the ship is in motor drive mode or docking mode at sea, the diesel generator set is started according to actual demand: the number of start-up units can be managed in a logical threshold manner, with the busbar load P DC And the power battery pack SOC bat The logic rule is the state condition. The logic rule makes the diesel generator set work at the highest efficiency point as much as possible, while ensuring that the power battery pack is not overcharged or over-discharged. In order to prevent the frequent start-up of the diesel generator set caused by the edge jitter of the logic rule point, the busbar load P DC And the power battery pack SOC bat The dead zone is also set for judging the status condition; the diesel generator set is based on the busbar load P DC And the power battery pack SOC bat Determine the power supply to DC-BUS, where the busbar load P DC = Daily load power P load +Power P of the shaft inverter (6) motor .

[0016] The beneficial effects of the present invention are as follows: the control method of the present invention enables the corresponding working mode of the hybrid power system for different operating conditions of the ship, and applies relevant propulsion equipment and power supply devices to adapt to the ship's functions and speed requirements, and to improve the operating economy and life cycle of the ship's power equipment. The control method adopted by the present invention can realize the distribution of ship propulsion power between the main engine power and the shaft motor power, and at the same time adjust the power distribution of the power battery and the diesel generator set according to the shaft motor power and the daily load size. It is suitable for ships that are jointly driven by the main propulsion diesel engine and the shaft motor, and are powered by a diesel generator set and a power battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the power system of the present invention;

[0018] Figure 2 It is the principle diagram of the control method of the present invention;

[0019] Figure 3 The membership functions of fuzzy rule input and output on their respective intervals.

[0020] The reference numerals of the figures are: 1 - diesel generator set, 2 - power battery pack, 3 - DC / DC converter, 4 - controllable rectifier, 5 - daily inverter, 6 - shaft generator frequency converter, 7 - shaft belt motor, 8 - main propulsion diesel engine. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and examples, but the examples should not be construed as limiting the present invention.

[0022] Reference Figure 1 As shown, the hybrid power system device of the present invention is composed of a diesel generator set 1, a power battery set 2, a DC / DC converter 3, a controllable rectifier 4, a daily inverter power supply 5, a shaft generator frequency converter 6, a shaft belt motor 7, a main propulsion diesel engine 8 and a gearbox 9. The DC / DC converter 3 is used to control the charging and discharging of the power battery set 2 and the DC bus voltage, the controllable rectifier 4 is used to control the output power of the diesel generator set 1, the daily inverter power supply 5 is used to supply power to the daily load of the whole ship, the shaft generator frequency converter 6 is used to control the shaft belt motor 7, and the main propulsion diesel engine 8 and the shaft belt motor 7 are connected to the propeller through the gearbox.

[0023] The DC-BUS is composed of a DC-BUS bus A and a DC-BUS bus B connected by a solid-state switch; a group of diesel generator sets 1 and a controllable rectifier 4 are connected in series and connected to the DC-BUS bus A, a group of shaft motors 7 and shaft generator frequency converters 6 are connected in series and connected to the DC-BUS bus A, a group of power battery packs 2 and DC / DC converters 3 are connected in series and connected to the DC-BUS bus A, a daily inverter power supply 5 is connected to the DC-BUS bus A, and another group of diesel generator sets 1 and a controllable rectifier 4 are connected in series and connected to the DC-BUS bus B, another group of shaft motors 7 and shaft generator frequency converters 6 are connected in series and connected to the DC-BUS bus B, another group of power battery packs 2 and DC / DC converters 3 are connected in series and connected to the DC-BUS bus B, and another daily inverter power supply 5 is connected to the DC-BUS bus B, thereby forming a series-parallel hybrid power ship power system. The two sets of shaft belt motors 7 are connected to the AC bus of the shaft generator inverter 6, the two sets of main propulsion diesel engines 8 and the diesel generator set 1 are connected to the AC bus of the controllable rectifier 4, the power battery pack 2 is connected to the AC bus of the DC / DC converter 3, the DC bus of the shaft generator inverter 6 and the daily inverter power supply 5, and the DC bus of the DC / DC converter 3 and the controllable rectifier 4 are respectively connected to the DC-BUS.

[0024] Reference Figure 2 As shown, the present invention discloses a mode switching control method for a series-parallel hybrid power ship power system, and the steps are as follows.

[0025] a) Determine the driving mode of the hybrid ship: determine the current required speed of the propeller according to the position information of the propulsion handle in the cab, and determine the propulsion mode: single motor drive, propulsion diesel engine drive, or propulsion diesel engine and motor combined drive. The relationship between the required speed and the propulsion mode is shown in the following table.

[0026] Required speed ＜L L~M M~H ＞H Advancement mode Single motor Status unchanged Main propulsion diesel engine Main propulsion diesel engine + electric motor

[0027] In the single motor propulsion mode, the motor end of the gearbox 9 is connected, and the main propulsion diesel engine end is not connected. In the diesel engine propulsion mode, the motor and the diesel engine end are connected, and the motor rotates with the diesel engine. The motor power is controlled by adjusting the forward and reverse torque of the battery.

[0028] b) In the propulsion diesel engine driving mode, the power generation of the shaft belt motor 7 is determined.

[0029] The shaft motor power needs to consider the following factors: the surplus power P of the propulsion diesel engine at the highest efficiency point at the current speed sur , current daily load power P load ;, power battery pack SOC bat Therefore, a fuzzy logic method can be used to control the shaft belt motor power, with the current daily load power P loadAnd the power battery pack SOC bat is the input quantity, and the output quantity is the power P of the shaft-to-frequency converter motor .

[0030] The load power P load The formulation of fuzzy intervals should refer to P sur , a new variable can be introduced Because P load > 0 Here we only consider P0 in the range of -2 to 2. load >2×P sur When the daily load is too large, the shaft generator can directly operate at the surplus power P sur Point, no need to judge.

[0031] In order to ensure that the power of the entire ship is not affected, it is necessary to limit the power of the shaft generator to no more than P sur The units and size ranges of the input and output quantities of fuzzy rules are different. First, we need to bat , P motor Convert the quantization level to an interval symmetric to 0:

[0032] P0: -2~2, corresponding to X: -2~2X=P0

[0033] SOC bat :50~90%, corresponding to Y:-2~2Y=(SOC SC -70) / 10,

[0034] P motor :0~P sur , corresponding to Z: -2~2

[0035] Where P0, SOC bat , P motor The fuzzy sets include VL, L, M, H and VH, which represent very low, low, medium, high and very high respectively. The size of the membership function is in the interval [0, 1]. The closer to 1, the higher the degree of membership to the fuzzy set. When the membership function is 0, it means that it does not belong to the fuzzy set. The membership function of the fuzzy rule input and output in their respective intervals is as follows: Figure 3 .

[0036] By observing the membership function, we can find that, except for the point where the membership is 1, the input and output of the system have a membership relationship with the two fuzzy sets in their respective intervals. Figure 3 The membership function in can be expressed in the form of function equation as follows:

[0037] VL(X)=max(0,1-|2+X|)VL(Y)=max(0,1-|2+Y|)VL(Z)=max(0,1-|2+Z|)

[0038] L(X)=max(0,1-|1+X|)L(Y)=max(0,1-|1+Y|)L(Z)=max(0,1-|1+Z|)

[0039] M(X)=max(0,1-|X|)M(Y)=max(0,1-|Y|)M(Z)=max(0,1-|Z|)

[0040] H(X)=max(0,1-|X-1|)H(Y)=max(0,1-|Y-1|)H(Z)=max(0,1-|Z-1|)

[0041] VH(X)=max(0,1-|X-2|) VH(Y)=max(0,1-|Y-2|) VH(Z)=max(0,1-|Z-2|).

[0042] According to the actual situation of the hybrid power system, fuzzy rules are designed. Under the premise of overcharging the battery, the shaft generator is made to absorb as much surplus power P of the propulsion diesel engine as possible. sur ;The rules for designing fuzzy logic control are shown in the following table.

[0043]

[0044] According to the membership function curve, P0, SOC bat There are at most two fuzzy sets with values, corresponding to the four cases in the above rule table. These 25 rules are expressed in function form:

[0045] UC1(X,Y,Z)=VL(X)·VL(Y)·H(Z)

[0046] UC2(X,Y,Z)=VL(X)·L(Y)·M(Z)

[0047] UC3(X,Y,Z)=VL(X)·M(Y)·L(Z)

[0048] M

[0049] UC25(X,Y,Z)=VH(X)·VH(Y)·VH(Z).

[0050] The output P obtained by fuzzy rules motor It is a blur amount, and such blur amount cannot be used directly.

[0051] Therefore, a certain method is needed to defuzzify. The present invention adopts the algebraic level-addition-center of gravity method: Substitute the system input X and Y into the above formula to obtain the function about z Observe the membership function of Z and bring the inflection point between the fuzzy sets into the above formula for defuzzification:

[0052] z1=-3z2=-2.25z3=-1.5z4=-0.75

[0053] z5=0z6=0.75z7=1.5z8=2.25z9=3,

[0054]

[0055] The obtained Z is P motor The value after quantization level conversion can be obtained by reverse calculation. motor value.

[0056] The fuzzy control and logic threshold control strategies mentioned in the present invention require little computation, are easy to implement in a ship PMS system, and fully consider the fuel economy of the ship and the rationality of charging and discharging of the power battery pack.

[0057] c) Determine the number and power of diesel generator sets to be put into use.

[0058] When the power battery pack cannot meet the current DC bus load power (including shaft motor power and daily load power), it is necessary to start the diesel generator set to assist in power supply. Diesel generator sets are mainly used in ship electric working conditions and offshore docking mode; the number of diesel generator sets to be started can be managed by a logical threshold, based on the bus load P DC And the power battery pack SOC bat The state condition is the number of diesel generator sets started as the control output. The logic rule makes the diesel generator set work at the highest efficiency point as much as possible, while ensuring that the power battery pack is not overcharged or over-discharged; when P DC <0 means the shaft motor is in power generation mode and the power generation is greater than the daily load power. At this time, the diesel generator set does not need to be started, and the power battery pack is charged to absorb the busbar power. Therefore, the logic rule only needs to consider P DC >0, the specific control rules are shown in Table 3, where P η It is the power of the diesel generator set at the highest efficiency point.

[0059]

[0060] Under the status condition judgment in the above table, there are 25 status combinations.

[0061] In order to prevent the busbar power busbar load P DC And the power battery pack SOCbat The jitter at the edge of the regular interval causes the diesel generator set to start and stop frequently, and a dead zone state is set for the regular point where the number of diesel generator sets starts changes. The state point where the number of diesel generator sets starts switches represents the dead zone state and the default value in the form of (a, b). The meaning of (a, b) is as follows: when the number of diesel generator sets running before the hybrid system enters this state is a or b, the transportation number of diesel generator sets is maintained unchanged; otherwise, after entering this state, the number of diesel generator sets started is controlled to a. If the dead zone mode only maintains the state of the previous moment unchanged, then the bus load P DC Sudden increases and decreases across intervals may cause the number of diesel generator sets in operation to be seriously inconsistent with actual demand. Therefore, when the number of diesel generator sets in operation does not meet the two conditions specified in the dead zone, the number of diesel generator sets in operation needs to be controlled to the default value.

[0062] The control method of the present invention can adapt to various operating conditions of ships, and can realize the distribution of ship propulsion power between the main engine power and the shaft motor power, while adjusting the power distribution of the power battery and the diesel generator set according to the shaft motor power and the daily load size.

[0063] The above embodiments are only illustrative of the principles and effects of the present invention, as well as some embodiments of its application. For those skilled in the art, several modifications and improvements may be made without departing from the creative concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A series-parallel hybrid power ship power system, characterized in that: The invention comprises two sets of main propulsion diesel engines (8) and shaft belt motors (7) connected to propellers through gear boxes, respectively, and also comprises a shaft generator frequency converter (6) connected to the shaft belt motor (7) and a DC-BUS connected to the shaft generator frequency converter (6), as well as a DC / DC converter (3), a controllable rectifier (4) and a daily inverter power supply (5) connected to the DC-BUS, wherein the controllable rectifier (4) and the DC / DC converter (3) are respectively connected to a diesel generator set (1) and a power battery set (2), and the DC-BUS is composed of a DC-BUS bus A and a DC-BUS bus B connected through a solid-state switch.

2. A series-parallel hybrid power ship power system according to claim 1, characterized in that: The two groups of shaft belt motors (7) are connected to the AC bus of the shaft generator frequency converter (6), the two groups of main propulsion diesel engines (8) and the diesel generator set (1) are connected to the AC bus of the controllable rectifier (4), the power battery pack (2) is connected to the AC bus of the DC / DC converter (3), the DC bus of the shaft generator frequency converter (6) and the daily inverter (5) and the DC bus of the DC / DC converter (3) and the controllable rectifier (4) are respectively connected to the DC-BUS.

3. A control method for a ship power system according to claim 1, characterized in that: The steps are: a), determining the current required speed of the propeller according to the position information of the propulsion handle, and selecting single motor drive, propulsion diesel engine drive or propulsion diesel engine and motor combined drive according to the required speed: when the required speed is low, the ship is propelled by the shaft belt motor (7) in the speed mode only; when the propulsion required speed increases, the main propulsion diesel engine (8) and the shaft belt motor (7) are put into use, and the shaft belt motor (7) operates in the torque mode to absorb the surplus power of the main propulsion diesel engine (8); when the propulsion required speed is too high, the main propulsion diesel engine (8) and the shaft belt motor (7) are put into use in parallel, and the shaft belt motor (7) operates in the torque mode and drives the propeller together with the main propulsion diesel engine (8) by providing positive torque; b) according to the power of the shaft generator inverter (6), the power of the current daily inverter power supply (5) and the current power of the power battery pack (2), the number and power of the diesel generator sets (1) put into operation are determined; when the propulsion diesel engine is driven, the shaft belt motor (7) is in the power generation mode, absorbing the surplus power of the main propulsion diesel engine (8), and the shaft belt motor (7) generates electricity to feed back energy to the DC-BUS so that the diesel generator sets (1) operate at the highest efficiency point; c) Based on the actual value of the current DC-BUS voltage, the DC voltage set value of the controllable rectifier (4) is adjusted by the PI regulator to control the determined value of the power of the diesel generator set (1); and the charging and discharging control of the power battery set (2) by the DC / DC converter (3) is adjusted in real time according to the power of the controllable rectifier (4), the daily inverter (5) and the shaft generator frequency converter (6).

4. The control method of a series-parallel hybrid power ship power system according to claim 3, characterized in that: As described above, the shaft belt motor (7) stops generating electricity when the daily load is too small and the battery power is high; when the shaft belt motor (7) generates electricity normally, the power generation power is indirectly controlled by controlling the charging and discharging current of the power battery pack (2) by the DC / DC converter (3).

5. The control method of a series-parallel hybrid power ship power system according to claim 3, characterized in that: The diesel generator set (1) controls the input quantity and power size based on the power of the shaft belt motor (7), the daily load size and the power of the power battery group, and ensures that the shaft belt motor (7) has a higher priority than the diesel generator set (1).

6. A control method for a series-parallel hybrid power ship power system according to claim 3, 4 or 5, characterized in that: The power control of the shaft belt motor (7) is based on the current daily load power P load And the power battery pack SOC bat is the input quantity, and the output shaft generates the power P of the frequency converter (6) motor ; Reference surplus power P sur Formulate daily load power P load Fuzzy interval: daily load power P load When the power level is too low and the battery power level is high, the shaft belt motor (7) is stopped from generating power.

7. The control method of a series-parallel hybrid power ship power system according to claim 6, characterized in that: When the ship is in motor drive mode or docking mode, the diesel generator set (1) is started according to actual demand: the number of generators to be started is based on the busbar load P DC And the power battery pack SOC bat The diesel generator set (1) is operated at a high efficiency point, and the power battery set (2) is ensured not to be overcharged or over-discharged. DC And the power battery pack SOC bat The dead zone is set for judging the state condition; the diesel generator set (1) is set according to the busbar load P DC And the power battery pack SOC bat Determine the power supply to DC-BUS, where the busbar load P DC = Daily load power P load +Power P of the shaft inverter (6) motor .

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