An ac-dc conversion device for a marine electric propulsion system

Abstract

The application provides a kind of AC-DC conversion device of ship electric propulsion system, including the AC rectifier unit connected in turn, DC bus unit, propulsion inverter unit and propulsion motor, and dynamic coordination control unit, dynamic coordination control unit gathers propulsion motor speed, electromagnetic torque, power fluctuation rate and DC bus voltage deviation and other operating parameters, constructs propulsion state disturbance characterization factor, and establishes dynamic disturbance threshold based on statistical quantile, realizes propulsion disturbance state identification;After detecting propulsion disturbance, the trend of propulsion side power change is predicted by power prediction model, and the equivalent inertia parameter, energy storage compensation power and AC-DC channel equivalent impedance parameter are dynamically adjusted, so as to realize AC-DC power coordination regulation, reduce the influence of propulsion load fluctuation on DC bus stability.The application can improve the dynamic stability and anti-disturbance ability of ship electric propulsion system in complex sea conditions.

Description

Technical Field

[0001] This invention belongs to the field of integrated electric propulsion technology for ships, and specifically relates to an AC / DC converter used in a ship electric propulsion system. Background Technology

[0002] With the development of integrated electric propulsion technology, ship propulsion systems are gradually shifting from traditional mechanical transmission structures to AC / DC hybrid power supply structures. Existing ship electric propulsion systems typically consist of generator sets, AC buses, AC / DC converters, DC buses, propulsion inverter units, and propulsion motors. Among these, the AC / DC converters are responsible for the energy transfer between AC and DC power and for maintaining the power balance of the propulsion system.

[0003] Due to the inherent uncertainty of the ship's navigation environment, the propulsion system is susceptible to factors such as wave disturbances, propeller cavitation effects, and non-uniform wake distribution during operation, resulting in significant dynamic fluctuations in propulsion load. When the hull undergoes heave or pitching motions, the propeller immersion depth continuously changes, causing periodic fluctuations in propulsion load.

[0004] The propulsion load torque typically satisfies T p =K q ρn m 2 D 5 K q Where ρ is the propeller torque coefficient, ρ is the seawater density, and n is the propeller torque coefficient. m Let D be the propeller speed and D be the propeller diameter. The output power of the propulsion motor satisfies P. m =T e ω m T e For the electromagnetic torque of the motor, ω m To increase the propulsion motor's angular velocity, under complex sea conditions, when the propeller partially emerges from or re-enters the water, the propulsion load changes rapidly within a short period, causing significant fluctuations in the propulsion motor's output power. Since these propulsion power fluctuations propagate to the DC side through the AC-DC converter, and given the dynamic relationship of the DC bus... V dc P is the DC bus voltage. in P_m is the input power of the AC / DC converter and P_m is the output power of the propulsion side, which can easily cause power imbalance on the DC bus.

[0005] When the propulsion load suddenly decreases, transient overvoltages can easily occur on the DC side; conversely, when the propulsion load increases rapidly, the system is prone to bus voltage drops. In severe cases, this can further lead to problems such as overcurrent in the propulsion inverter unit, torque fluctuations in the propulsion motor, and oscillations in the AC / DC system.

[0006] Most existing shipboard AC / DC converters employ fixed-parameter control, with their control logic primarily relying on feedback regulation of electrical parameters such as voltage and current. When the propulsion system is subjected to sea state disturbances, this control method often only compensates after fluctuations have already occurred at the busbar, making it difficult to intervene in advance to address changes in propulsion load, thus limiting its dynamic response capability.

[0007] In addition, although some existing technologies have introduced energy storage compensation or virtual inertia control, most of them are only based on bus voltage deviation for adjustment. They lack correlation analysis of the propulsion side operation status and cannot accurately reflect the real load change trend of the propulsion system. Therefore, AC / DC power coupling oscillation problems are still likely to occur under complex sea conditions.

[0008] Therefore, there is a need for an AC / DC converter that can identify propulsion disturbances in advance by combining changes in the propulsion side operating status and dynamically adjust the AC / DC power flow process to improve the operational stability of the ship's electric propulsion system under complex operating conditions. Summary of the Invention

[0009] To address the aforementioned technical problems in existing technologies, this invention proposes an AC / DC converter for power disturbance suppression in a ship electric propulsion system. By constructing a propulsion state disturbance characterization factor, the operating state of the propulsion system is identified, and the AC / DC power is coordinated and adjusted according to the dynamic change characteristics of the propulsion side, thereby reducing the impact of propulsion disturbances on the stability of the DC bus.

[0010] The technical solution adopted by this invention to solve its technical problem is: an AC / DC conversion device for a ship electric propulsion system, comprising an AC rectifier unit connected to the ship's AC power grid, a DC bus unit connected to the AC rectifier unit, and a propulsion inverter unit connected to the DC bus unit via the DC bus. The propulsion inverter unit is connected to a propulsion motor, and the DC bus is connected to an energy storage and regulation unit. It also includes a dynamic coordination and control unit connected to the AC rectifier unit, the DC bus unit, the propulsion inverter unit, the energy storage and regulation unit, and the propulsion motor, respectively. The dynamic coordination and control unit includes a sequentially connected operating parameter acquisition module and a disturbance... The system comprises a state recognition module, a power trend prediction module, a coordination strategy generation module, and a control execution module. An AC rectifier unit converts the AC power output from the ship's AC bus into DC power and establishes a stable DC bus. An energy storage and regulation unit connected to the DC bus unit provides dynamic energy compensation when propulsion load fluctuates. A propulsion inverter unit connected to the propulsion motor drives its operation. A dynamic coordination and control unit connected to the AC rectifier unit, propulsion inverter unit, and energy storage and regulation unit collects propulsion motor operating state parameters and establishes a propulsion state disturbance characterization factor based on these parameters. Used to identify the disturbance state of the propulsion system, based on the propulsion state disturbance characterization factor F.d The propulsion system disturbance state is assessed; the disturbance threshold is dynamically determined using a statistical distribution method, i.e., the dynamic coordination and control unit establishes a dynamic disturbance threshold F based on the statistical distribution of the propulsion state disturbance characterization factors. th =Q 0.95 (F d ), where F th Q is the dynamic perturbation threshold. 0.95 The 95th quantile function of the propulsion state perturbation characterization factor; when the propulsion state perturbation characterization factor F d Exceeding the dynamic disturbance threshold F th When the system determines that the propulsion side has entered a disturbance operation state, it activates the AC / DC power coordination and regulation mechanism to dynamically adjust the output power according to the degree of disturbance: when the propulsion load suddenly decreases, the dynamic coordination and control unit controls the energy storage regulation unit to quickly absorb excess power to suppress DC bus overvoltage; when the propulsion load suddenly increases, the energy storage regulation unit releases compensation power to the DC bus to reduce the DC bus voltage drop amplitude; where λ i X represents the weighting coefficients for the corresponding state parameters. i Here, n represents the normalized state variables, and n is the number of state parameters.

[0011] Furthermore, the operating state parameters include motor speed, electromagnetic torque, stator current, and DC bus voltage variation; the state variables include propulsion motor speed deviation, electromagnetic torque variation rate, propulsion power fluctuation rate, and DC bus voltage deviation; and the dynamic coordination control unit is defined by the formula... The collected parameters are normalized, and then the state parameters are input into the propulsion state disturbance analysis module to construct the propulsion state disturbance characterization factor. , where ΔV dc This represents the DC bus voltage deviation.

[0012] Furthermore, the dynamic coordination control unit establishes a power prediction model based on the power change trend on the propulsion side, and dynamically adjusts the output power of the AC / DC converter. The prediction relationship satisfies... ,in To predict propulsion power for the next moment, P m (k) represents the propulsion power at the current moment, ΔP m (k) represents the change in propulsion power, β is the prediction adjustment coefficient, and k is the discrete time index.

[0013] Furthermore, the dynamic coordination and control unit calibrates the weights of each parameter based on historical operational test data and updates the disturbance statistical distribution using a sliding time window method. ,in The sliding window length is specified. When the system detects a decreasing trend in propulsion load, the energy storage regulation unit enters charging mode to absorb excess energy on the propulsion side. When the propulsion load increases rapidly, the energy storage regulation unit enters discharging mode to provide power support to the DC bus.

[0014] Furthermore, the aforementioned dynamic coordination and control unit improves the system's short-term stability by constructing a dynamic equivalent inertia model, and its dynamic relationship satisfies J e P is the dynamic equivalent inertia coefficient. in For the input power of the AC / DC converter, D e J is the damping adjustment coefficient and the dynamic equivalent inertia coefficient. e =J0+K j (F d -F th ), where J0 is the fundamental inertia parameter, K j The gain is adjusted for inertia.

[0015] Furthermore, the dynamic coordination control unit also dynamically adjusts the equivalent impedance parameter according to the degree of propulsion disturbance to reduce the propagation speed of the propulsion disturbance to the DC bus: R e =R0+K r F d Where R0 is the basic equivalent resistance, K r This is the impedance adjustment coefficient.

[0016] Furthermore, the dynamic coordination control unit further constructs a dynamic equivalent impedance model. By adjusting the equivalent parameters of the AC / DC power transfer channel, it reduces the propagation speed of propulsion disturbances to the DC side, and its equivalent relationship satisfies... Z e For dynamic equivalent impedance; R e L e And C e These represent the dynamic equivalent resistance, dynamic equivalent inductance, and dynamic equivalent capacitance, respectively, and s is the Laplace operator.

[0017] Furthermore, the rotational speed deviation of the propulsion motor satisfies Δω m =ω m -ω0, where ω m The propulsion motor's actual angular velocity is given by ω0, which is the rated angular velocity of the propulsion motor; the propulsion power fluctuation rate satisfies... The output power of the energy storage regulation unit meets P. c =K f ΔP m , where P c To compensate for energy storage power, K f ΔP is the dynamic adjustment coefficient. m To advance the change in power.

[0018] The beneficial effects of the present invention are as follows: Compared with the prior art, the AC / DC converter of the present invention no longer relies solely on the bus voltage or current parameters for passive feedback adjustment, but instead establishes a propulsion disturbance characterization mechanism in conjunction with the propulsion side operating status. This enables the early identification of propulsion load change trends and dynamic adjustment of AC / DC power distribution relationships, thereby improving the dynamic stability of the system under complex sea conditions. Attached Figure Description

[0019] Figure 1 This is a system composition diagram of the AC / DC converter of the present invention.

[0020] The labels for each figure are as follows: 1—AC rectifier unit, 2—DC bus unit, 3—propulsion inverter unit, 4—energy storage regulation unit, 5—dynamic coordination control unit, 51—operation parameter acquisition module, 52—disturbance status identification module, 53—power trend prediction module, 54—coordination strategy generation module, 55—control execution module. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings. The embodiments are illustrated in the drawings, and the same reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] like Figure 1 As shown, this invention proposes an AC / DC converter for power disturbance suppression in a ship electric propulsion system. This device is applied to a ship integrated electric propulsion system, constructs a disturbance characterization factor based on the propulsion side operating state, and realizes dynamic coordinated control of AC and DC power.

[0023] The AC / DC converter includes an AC rectifier unit 1, a DC bus unit 2, a propulsion inverter unit 3, and a propulsion motor connected in sequence, and a dynamic coordination control unit 5 connected to the AC rectifier unit 1, DC bus unit 2, propulsion inverter unit 3, and propulsion motor respectively. The DC bus unit 2 and propulsion inverter unit 3 are connected by a DC bus, which is connected to the dynamic coordination control unit 5 via an energy storage and regulation unit 4. The dynamic coordination control unit 5 includes an operating parameter acquisition module 51, a disturbance state identification module 52, a power trend prediction module 53, a coordination strategy generation module 54, and a control execution module 55 connected in sequence. The input terminal of AC rectifier unit 1 is connected to the ship's AC bus to convert the AC power output from the ship's AC bus into DC power and establish a stable DC bus. The output terminal of AC rectifier unit 1 is connected to DC bus unit 2. Energy storage and regulation unit 4 is connected to DC bus unit 2 and is connected to DC bus through a bidirectional conversion interface. It is used to perform dynamic energy compensation for the system when the propulsion load fluctuates. Propulsion inverter unit 3 is connected to the output side of DC bus and is connected to the propulsion motor to drive the propulsion motor. Dynamic coordination and control unit 5 is connected to AC rectifier unit 1, propulsion inverter unit 3 and energy storage and regulation unit 4 respectively.

[0024] The dynamic coordination and control unit 5 collects propulsion motor operating status parameters in real time, including propulsion motor speed, electromagnetic torque, stator current, and DC bus voltage changes, and constructs propulsion state disturbance characterization factors. Used to identify the disturbance state of the propulsion system, where F d To advance the state perturbation characterization factor, λ i X represents the weighting coefficients for the state parameters. i Here, n represents the normalized state variables, and n is the number of state parameters.

[0025] To improve the accuracy of disturbance identification, this invention uses a statistical distribution method to dynamically determine the disturbance threshold. Specifically, the dynamic coordination control unit 5 establishes a dynamic disturbance threshold F based on the statistical distribution of the propulsion state disturbance characterization factors. th =Q 0.95 (F d ), where F th Q is the dynamic perturbation threshold. 0.95 The 95th percentile function of the propulsion state disturbance characterization factor is used. When the propulsion state disturbance characterization factor exceeds the dynamic disturbance threshold, the system determines that the propulsion side has entered a disturbance operation state and initiates the AC / DC power coordination and adjustment mechanism.

[0026] The dynamic coordination and control unit 5 establishes a propulsion state disturbance characterization factor based on the collected parameters, and then uses the propulsion state disturbance characterization factor F... dThe dynamic coordination control unit 5 determines the disturbance state of the propulsion system and dynamically adjusts the AC / DC power distribution relationship. When the propulsion load suddenly decreases, the dynamic coordination control unit 5 controls the energy storage regulation unit 4 to quickly absorb excess power to suppress DC bus overvoltage. When the propulsion load suddenly increases, the energy storage regulation unit 4 releases compensation power to the DC bus to reduce the DC bus voltage drop.

[0027] The state variables include propulsion motor speed deviation, electromagnetic torque change rate, propulsion power fluctuation rate, and DC bus voltage deviation. The dynamic coordination control unit 5 normalizes the collected parameters. The normalized state parameters are input into the propulsion state disturbance analysis module to construct the propulsion state disturbance characterization factor. , where ΔV dc This represents the DC bus voltage deviation.

[0028] The dynamic coordination control unit 5 establishes a power prediction model based on the power change trend on the propulsion side, and dynamically adjusts the output power of the AC / DC converter. Its prediction relationship satisfies... ,in To predict propulsion power for the next moment, P m (k) represents the propulsion power at the current moment, ΔP m (k) represents the change in propulsion power, β is the prediction adjustment coefficient, and k is the discrete time index.

[0029] The system calibrates the weights of each parameter based on historical operational test data and updates the disturbance statistical distribution using a sliding time window method. ,in This represents the length of the sliding window.

[0030] The dynamic coordination control unit 5 updates the dynamic disturbance threshold F based on the disturbance data within the sliding window. th (k)=Q 0.95 (W(k)), when F d >F th When the system determines that the propulsion system has entered a state of strong disturbance, the dynamic coordination control unit 5 adjusts the output power of the AC-DC converter in advance according to the trend of propulsion load change, and controls the energy storage regulation unit to participate in power buffering.

[0031] When the system detects a decreasing trend in propulsion load, the energy storage regulation unit 4 enters charging mode to absorb excess energy on the propulsion side; when the propulsion load increases rapidly, the energy storage regulation unit 4 enters discharging mode to provide power support to the DC bus.

[0032] To mitigate the impact of sudden changes in propulsion load on the system, this invention further introduces a dynamic inertia compensation mechanism. The dynamic coordination control unit 5 improves the system's short-term stability by constructing an equivalent inertia model, and its dynamic relationship satisfies: J e P is the dynamic equivalent inertia coefficient. in For the input power of the AC / DC converter, D e This is the damping adjustment coefficient.

[0033] When the propulsion load suddenly decreases, the dynamic coordination control unit 5 controls the energy storage regulation unit 4 to quickly absorb excess power to suppress DC bus overvoltage; when the propulsion load suddenly increases, the energy storage regulation unit 4 releases compensation power to the DC bus to reduce the bus voltage drop.

[0034] At the same time, the dynamic coordination control unit 5 adjusts the equivalent inertia coefficient in real time: J e =J0+K j (F d -F th ), where J0 is the fundamental inertia parameter, K j The gain is adjusted for inertia.

[0035] When the disturbance level increases, the system automatically increases the equivalent inertia to reduce the rate of change of system frequency and improve the dynamic stability of AC / DC system.

[0036] Furthermore, the dynamic coordination control unit 5 dynamically adjusts the equivalent impedance parameter according to the degree of propulsion disturbance to reduce the propulsion disturbance propagation speed to the DC bus: R e =R0+K r F d Where R0 is the basic equivalent resistance, K r This is the impedance adjustment coefficient.

[0037] Furthermore, this invention establishes a dynamic equivalent impedance model, which reduces the propagation velocity of propulsion disturbances to the DC side by adjusting the equivalent parameters of the AC / DC power transfer channel. The equivalent relationship satisfies... Z e For dynamic equivalent impedance; R e L e And C e These represent the dynamic equivalent resistance, dynamic equivalent inductance, and dynamic equivalent capacitance, respectively, and s is the Laplace operator.

[0038] The speed deviation of the propulsion motor in this invention satisfies Δω m =ω m -ω0, where ω m The propulsion motor's actual angular velocity is given by ω0, which is the rated angular velocity of the propulsion motor; the propulsion power fluctuation rate satisfies... The output power of the energy storage regulation unit 4 meets the requirements of P. c =K f ΔP m , where P c To compensate for energy storage power, K f ΔP is the dynamic adjustment coefficient. m To advance the change in power.

[0039] Through the above methods, the present invention can identify the trend of power change on the propulsion side in advance when the propulsion system is disturbed by complex sea conditions, and dynamically adjust the AC and DC power flow process, thereby reducing DC bus power oscillation and improving the operational stability of the ship's electric propulsion system.

[0040] The embodiments are merely illustrative of the principles and effects of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. An AC / DC converter for a ship electric propulsion system, characterized in that: The system includes an AC rectifier unit (1) connected to the ship's power grid, a DC bus unit (2) connected to the AC rectifier unit (1), and a propulsion inverter unit (3) connected to the DC bus unit (2) via the DC bus. The propulsion inverter unit (3) is connected to the propulsion motor, and the DC bus is connected to the energy storage regulation unit (4). The system also includes a dynamic coordination control unit (5) connected to the AC rectifier unit (1), the DC bus unit (2), the propulsion inverter unit (3), the energy storage regulation unit (4), and the propulsion motor, respectively. The dynamic coordination control unit (5) includes a sequentially connected operating parameter acquisition module (51), a disturbance state identification module (52), a power trend prediction module (53), a coordination strategy generation module (54), and a control execution module (55). The AC rectifier unit (1) converts AC power into DC power. The energy storage regulation unit (4) performs dynamic energy compensation for the system when the propulsion load fluctuates. The propulsion inverter unit (3) drives the propulsion motor. The dynamic coordination control unit (5) collects the operating state parameters of the propulsion motor and constructs a propulsion state disturbance characterization factor. To determine the disturbance state of the propulsion system, a dynamic disturbance threshold F is established based on the statistical distribution of the disturbance characterization factors. th =Q 0.95 (F d ), where Q 0.95 The 95th percentile function of the propulsion state perturbation characterization factor; propulsion state perturbation characterization factor F d Exceeding the dynamic disturbance threshold F th When the propulsion side is determined to be in a disturbance operation state, the output power is dynamically adjusted according to the degree of disturbance: when the propulsion load suddenly decreases, the energy storage regulation unit (4) is controlled to quickly absorb excess power to suppress DC bus overvoltage; when the propulsion load suddenly increases, the energy storage regulation unit (4) releases compensation power to the DC bus to reduce the DC bus voltage drop amplitude; where λ i X represents the weighting coefficients for the state parameters. i Here, n represents the normalized state variables, and n is the number of state parameters.

2. The AC / DC converter for a ship electric propulsion system according to claim 1, characterized in that, The operating state parameters include motor speed, electromagnetic torque, stator current, and DC bus voltage variation. The state variables include propulsion motor speed deviation, electromagnetic torque variation rate, propulsion power fluctuation rate, and DC bus voltage deviation. The dynamic coordination control unit (5) uses the formula... The collected parameters are normalized and then input into the propulsion state disturbance analysis module to construct propulsion state disturbance characterization factors. , where ΔV dc This represents the DC bus voltage deviation.

3. An AC / DC converter for a ship electric propulsion system according to claim 1 or 2, characterized in that, The dynamic coordination control unit (5) establishes a power prediction model based on the power change trend on the propulsion side. ,in To predict propulsion power for the next moment, P m (k) represents the propulsion power at the current moment, ΔP m (k) represents the change in propulsion power, β is the prediction adjustment coefficient, and k is the discrete time index.

4. The AC / DC converter for a ship electric propulsion system according to claim 3, characterized in that, The dynamic coordination control unit (5) calibrates the weights of each parameter and updates the disturbance statistical distribution using a sliding time window method. ,in The sliding window length is used; when the system detects a downward trend in propulsion load, the energy storage regulation unit (4) enters the charging mode to absorb excess energy on the propulsion side; when the propulsion load increases rapidly, the energy storage regulation unit (4) enters the discharging mode to provide power support to the DC bus.

5. The AC / DC converter for a ship electric propulsion system according to claim 4, characterized in that, The aforementioned dynamic coordination control unit (5) constructs a dynamic equivalent inertia model to improve the system's short-term stability capability. , where P in For the input power of the AC / DC converter, D e J is the damping adjustment coefficient and the dynamic equivalent inertia coefficient. e =J0+K j (F d -F th ), where J0 is the fundamental inertia parameter, K j The gain is adjusted for inertia.

6. The AC / DC converter for a ship electric propulsion system according to claim 5, characterized in that, The dynamic coordination control unit (5) dynamically adjusts the equivalent impedance parameter R according to the degree of propulsion disturbance. e =R0+K r F d To reduce the propagation speed of propagation disturbances to the DC bus, where R0 is the basic equivalent resistance and K r This is the impedance adjustment coefficient.

7. The AC / DC converter for a ship electric propulsion system according to claim 5, characterized in that, Dynamic Coordination and Control Unit (5) Constructs Dynamic Equivalent Impedance Model By adjusting the equivalent parameters of the AC / DC power transfer channel, the propagation speed of the propagation disturbance to the DC side is reduced, where R e L e And C e These represent the dynamic equivalent resistance, dynamic equivalent inductance, and dynamic equivalent capacitance, respectively, and s is the Laplace operator.

8. The AC / DC converter for a ship electric propulsion system according to claim 5, characterized in that, The aforementioned rotational speed offset satisfies Δω m =ω m -ω0, where ω m ω is the actual angular velocity, and ω0 is the rated angular velocity; the propulsion power fluctuation rate satisfies The energy storage regulation unit (4) outputs power that satisfies P. c =K f ΔP m , where P c For energy storage to compensate for power, K f ΔP is the dynamic adjustment coefficient. m To advance the change in power.

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