Ultra-wide range high-precision DC shore power control device

Abstract

The present invention relates to an ultra-wide range high-precision DC shore power control device, comprising an on-load tap-changing transformer and a multi-module parallel rectifier conversion unit; the on-load tap-changing transformer inputs an AC input voltage, and an output end is connected to the multi-module parallel rectifier conversion unit; the multi-module parallel rectifier conversion unit is divided into two groups, each having the same number of rectifier modules, each rectifier module input is the secondary winding voltage of the on-load tap-changing transformer, and output is DC, and the DC outputs of the rectifier modules in each group are connected in parallel; a parallel switch is provided between the two groups of DC outputs; when the switch is disconnected, the two DC outputs operate independently; when the switch is closed, the two groups of DC outputs operate in parallel, and the positive pole or negative pole of the first group of DC outputs is connected to the positive pole or negative pole of the second group of DC outputs, respectively.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current shore power, and in particular to an ultra-wide range and high-precision direct current shore power control device. Background Art

[0002] DC shore power equipment is a set of electrical equipment located at the dock or shore. This equipment converts the dock's AC power into DC power, which is used to provide DC power to various types of ships to ensure ship operation and maintenance needs. Different types of ships require different DC shore power voltages, ranging from as low as DC200V to as high as DC1000V. In addition, to ensure the stable and reliable operation of precision equipment on ships, the DC voltage accuracy is generally expected to be as high as possible.

[0003] The current common solution is to provide different specifications of DC shore power equipment for different types of ships. This results in high total procurement costs, low utilization of a single shore power system, large occupation of valuable dock space, and difficulty in use and maintenance. In addition, the output voltage accuracy of these shore power devices is often low (generally around 2%), which cannot ensure the stable operation of the ship's precision equipment. Summary of the Invention

[0004] The wide-range, high-precision DC shore power proposed in this invention decouples the inherent contradiction between wide range and high precision by optimizing hardware and software design, achieving wide-range, high-precision voltage output, and ensuring the DC shore power needs of various types of ships with one set of equipment.

[0005] The present invention provides an ultra-wide range high-precision DC shore power control device, which includes an on-load tap-changing transformer and a multi-module parallel rectifier conversion unit;

[0006] The on-load tap-changing transformer inputs an AC input voltage, and the output end is connected to a multi-module parallel rectifier conversion unit; the multi-module parallel rectifier conversion unit is divided into two groups, each having the same number of rectifier modules, the input of each rectifier module is the secondary winding voltage of the on-load tap-changing transformer, and the output is DC, and the DC outputs of the rectifier modules in each group are connected in parallel;

[0007] There is a parallel switch between the two sets of DC outputs; when the switch is open, the two DC outputs operate independently; when the switch is closed, the two sets of DC outputs operate in parallel, connecting the positive or negative pole of the first set of DC outputs to the positive or negative pole of the second set of DC outputs respectively.

[0008] Furthermore, the on-load tap-changing transformer can adjust the gear according to the output voltage, thereby changing the secondary voltage of the transformer. When the DC shore power device requires a lower output voltage, the on-load tap-changing switch is adjusted to a high gear, the AC input voltage amplitude of the rectifier module is low, and the rectifier module accordingly outputs a lower DC voltage; when the DC shore power device requires a higher output voltage, the on-load tap-changing switch is adjusted to a low gear, the AC input voltage amplitude of the rectifier module is high, and the rectifier module accordingly outputs a higher DC voltage.

[0009] Furthermore, the ultra-wide range high-precision DC shore power control device uses nonlinear multi-stage sampling to control the output voltage; the result obtained by the sampling circuit is proportional to the actual output voltage:

[0010] v s =kv o =k(V ref +v e )=kV ref (1+a)

[0011] v s is the output voltage sampling signal, k is the sampling coefficient, which is generally a fixed value much smaller than 1, v o is the actual output voltage, which is equal to the given voltage V ref and error value v e The sum of the variables a and v is the error value e Relative voltage given V ref The ratio value of

[0012] In order to solve the problem of high-precision sampling at low voltage output, a nonlinear high-order sampling method is adopted:

[0013] v s2 =(kv o ) n =(kV ref ) n (1+a) n

[0014] v s2 is the output voltage feedback using the nonlinear high-order sampling method, n is the nonlinear sampling magnification; a is relatively small, based on the approximate relationship (1+a) n ≈1+a is equivalent to:

[0015] v s =(kV ref ) n (1+na)

[0016] By increasing the weight of the error in the entire output voltage signal by n times, the sampling accuracy can be greatly improved.

[0017] Furthermore, the ultra-wide range high-precision DC shore power control device adopts series compound control;

[0018] The ultra-wide range high-precision DC shore power control device includes a proportional-integral controller and a step tracking controller using a time-sharing series structure;

[0019] When using a proportional-integral controller:

[0020] v c =k p ·v e +k i ·∫v e dt

[0021] v e is the output voltage error, v c is the controller output, which corresponds to the duty cycle of the power device, k p 、k i are the proportional and integral coefficients of the proportional-integral controller respectively;

[0022] When the step tracking controller determines that the error is positive, the controller output is increased at a fixed minimum resolution, thereby slightly increasing the output voltage; when the step tracking controller determines that the error is negative, the controller output is reduced at a fixed minimum resolution, thereby slightly decreasing the output voltage;

[0023] Proportional-integral control plays a role of coarse adjustment. After the actual voltage approaches the given value, step tracking control is used to play a role of fine adjustment, ultimately making the output voltage accurately track the given value.

[0024] Furthermore, the ultra-wide range, high-precision DC shore power control device is also equipped with a local distribution box, shore power connection box and remote monitoring system;

[0025] The DC voltage output by the ultra-wide range high-precision DC shore power control device is connected to the local distribution box;

[0026] The local distribution box includes a circuit breaker and voltage and current detectors for on-off control and monitoring of DC shore power output;

[0027] The output of the local distribution box is connected to the DC shore power box at the dock via a cable. The DC shore power box includes a circuit breaker and voltage and current detection instruments for on-off control and monitoring of the DC shore power and the ship.

[0028] The remote monitoring system connects the ultra-wide range, high-precision DC shore power control device, the local distribution box and the DC shore power box via optical fiber to obtain the main operating parameters of each device.

[0029] Furthermore, the rectification and conversion unit is a step-down conversion unit, and the relationship between its DC output voltage and AC input voltage is:

[0030] V o =MV in

[0031] V o is the DC output voltage of the rectifier module, M is the modulation ratio of the rectifier module, V in It is the AC input voltage amplitude of the rectifier module, that is, the voltage amplitude output by the on-load tap-changer.

[0032] The beneficial effects of the present invention are:

[0033] This invention proposes a DC shore power main circuit topology with an on-load tap-changing switch as the front stage and multiple parallel rectifier modules as the back stage. This main circuit topology achieves both an ultra-wide output range and high precision, overcoming the limitations of existing DC shore power systems that cannot achieve both. The DC shore power system of this invention can be used to provide shore power to various types of ships, thereby saving terminal investment, reducing terminal space usage, and alleviating equipment maintenance workload.

[0034] The most unique improvement of the present invention is that, starting from the closed-loop control loop of DC shore power, in the sampling link that has a significant impact on the output voltage accuracy, unlike the conventional use of ultra-high-precision sampling hardware, a software-based nonlinear multi-order sampling algorithm is adopted, which improves the output voltage sampling accuracy and resolution, thereby improving the output voltage accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The advantages of the above and additional aspects of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0036] Figure 1 This is a main circuit block diagram of the ultra-wide range high-precision DC shore power control device of the present invention.

[0037] Figure 2 This is a flow chart of the on-load tap changer shift control program of the ultra-wide range high-precision DC shore power control device of the present invention;

[0038] Figure 3 This is a closed-loop control block diagram of a DC shore power device of the ultra-wide range high-precision DC shore power control device of the present invention;

[0039] Figure 4 This is a block diagram of the series composite control principle of the ultra-wide range high-precision DC shore power control device of the present invention;

[0040] Figure 5 This is a flow chart of the series composite control program of the ultra-wide range high-precision DC shore power control device of the present invention;

[0041] Figure 6This is a simplified diagram of the DC shore power system network topology of the ultra-wide range high-precision DC shore power control device of the present invention. DETAILED DESCRIPTION

[0042] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features therein can be combined with each other without conflict.

[0043] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0044] Example 1

[0045] As attached Figure 1 As shown, the present invention provides an ultra-wide range high-precision DC shore power control device. The input of the DC shore power control device is AC voltage. Since DC shore power usually has a large power, the AC input voltage is generally three-phase AC6.6kV or AC10kV.

[0046] The ultra-wide range and high-precision DC shore power control device consists of two stages: the front stage is an on-load tap-changing transformer, and the back stage is a multi-module parallel rectifier conversion unit.

[0047] The AC input voltage is connected to the on-load tap-changing transformer of the DC shore power supply. The secondary side of the on-load tap-changing transformer has multiple windings, each of which is connected to a rectifier module.

[0048] An on-load tap-changing transformer consists of a mechanical multi-position on-load tap-changing switch and a multi-winding step-down phase-shifting transformer. Adjusting the on-load tap-changing switch position changes the number of turns on the primary winding of the multi-winding step-down phase-shifting transformer, thereby adjusting the transformer's transformation ratio and ultimately the secondary voltage. The transformer employs a single primary winding and multiple secondary windings. The output voltage of the secondary windings serves as the input for multiple rectifier modules in the subsequent stage, with each winding voltage phase-shifted by a certain angle. These multiple phase-shifted voltages, combined with the multiple rectifier modules in the subsequent stage, form a multi-pulse rectifier circuit, significantly reducing input AC current harmonics and improving the input power factor.

[0049] Corresponding to the ship's port and starboard DC busbars, the rectifier modules of the DC shore power device are divided into two groups, each group containing the same number of rectifier modules. The input of each rectifier module is the secondary winding voltage of the on-load tap-changing transformer, and the output is DC. The DC outputs of the rectifier modules in each group are connected in parallel.

[0050] The rectifier module converts the AC voltage output by the transformer's secondary winding into the DC voltage required by various types of ships. It primarily consists of a power unit, a filter unit, and a corresponding control unit. The power unit can employ various topologies, including a thyristor phase-controlled rectifier module, a diode-uncontrolled rectifier + DC / DC two-stage conversion module, or a PWM rectifier + DC / DC two-stage conversion module. The filter unit typically uses a second-order LC filter, which significantly removes harmonics from the power unit's output voltage and produces a flat DC voltage. The control unit primarily includes the sampling circuit, controller, and drive circuit necessary for closed-loop control.

[0051] There is a parallel switch between the two DC outputs of the DC shore power control device (attached Figure 1 Q1 in Figure 1 is used to achieve independent or parallel operation of the two DC outputs. This parallel switch is typically a 3P circuit breaker or disconnector. When the two DC outputs operate independently, Q1 is disconnected. When the two DC outputs operate in parallel, Q1 is closed, connecting the positive / negative terminals of DC output 1 to the positive / negative terminals of DC output 2, respectively.

[0052] Example 2

[0053] More specifically, this embodiment also addresses the fact that different types of ships require different DC shore power voltages, ranging from below DC200V to as high as DC1000V. The existing solution is to configure a set of DC shore power equipment for each type of ship, which results in high total procurement costs, low utilization of a single shore power equipment, large occupation of valuable dock space, and difficulty in use and maintenance. Therefore, the present invention proposes an ultra-wide output range solution:

[0054] In the attached Figure 1 The DC shore power control device shown uses an on-load tap-changing transformer in the front stage and a rectifier conversion unit in the back stage.

[0055] The rectifier conversion unit is a step-down converter, and the relationship between its DC output voltage and AC input voltage is:

[0056] V o =MV in (1)

[0057] In the above formula, V o is the DC output voltage of the rectifier module, V in is the AC input voltage amplitude of the rectifier module, that is, the voltage amplitude of the on-load tap changer output; M is the modulation ratio of the rectifier module, which corresponds to the duty cycle of the drive signal of the power module in the rectifier module and is an adjustable value less than 1. To ensure the dynamic performance of the rectifier module and improve control accuracy, this variable is generally set between 0.8 and 0.9.

[0058] It can be seen that since the modulation ratio M of the rectifier module is limited to between 0.8 and 0.9, when the AC input voltage of the rectifier module remains unchanged, the output voltage adjustment range of the rectifier module is limited. In the application example of this embodiment, an on-load tap-changing transformer is configured in the front stage of the rectifier module. The transformer can intelligently adjust the gear according to the output voltage, thereby changing the secondary voltage of the transformer, that is, changing the AC input voltage of the rectifier module. When the DC shore power device requires a lower output voltage, the on-load tap-changing switch is adjusted to a high gear, the AC input voltage amplitude of the rectifier module is low, and the rectifier module outputs a lower DC voltage accordingly; when the DC shore power device requires a higher output voltage, the on-load tap-changing switch is adjusted to a low gear, the AC input voltage amplitude of the rectifier module is high, and the rectifier module outputs a higher DC voltage accordingly. The flow chart of the intelligent adjustment strategy of the on-load tap-changing switch gear is shown in FIG. Figure 2 shown.

[0059] Example 3

[0060] This embodiment also proposes a high-precision output voltage solution based on a DC shore power control device.

[0061] 1. Nonlinear multi-stage sampling

[0062] Attachment Figure 3 This is a closed-loop control block diagram of a DC shore power device using the present invention. The rightmost side of the figure shows the DC output voltage reference. After comparing this voltage reference with the actual voltage sample, the error is sent to the closed-loop controller for calculation. The closed-loop controller calculates the error between the reference and actual values ​​using a specific control algorithm and outputs a control signal. This control signal controls the drive duty cycle of the power device, thereby adjusting the output voltage to achieve output voltage tracking of the reference voltage.

[0063] From the attached Figure 3 As can be seen from the closed-loop control block diagram, the sampling link is an important link in the entire closed-loop control logic. It plays the role of sampling the actual voltage, and then the voltage error can be calculated. Only after the controller obtains the accurate error can it make quick and precise adjustments to achieve voltage tracking.

[0064] In previous applications, linear sampling circuits such as voltage Hall sensors are generally used for sampling, and the result obtained by the sampling circuit is proportional to the actual output voltage.

[0065] v s =kv o =k(V ref +v e )=kV ref (1+a) (2)

[0066] In the above formula, v s is the output voltage sampling signal, k is the sampling coefficient, which is generally a fixed value much smaller than 1, v ois the actual output voltage, which is equal to the given voltage V ref and error value v e The variable a is the error value v e Relative voltage given V ref The ratio value.

[0067] For a high-precision DC power supply, the output voltage accuracy (the ratio of the output voltage error to the given voltage) is required to be no greater than ±0.5%, and the value a in formula (2) is required to be no greater than ±0.5%.

[0068] Because the DC shore power device has an ultra-wide output range, up to DC1000V, a 0.5% error corresponds to 5V, and the sampling circuit can still accurately sample this voltage and accurately extract the error value; however, at the output voltage lower limit of DC100V, a 0.5% error corresponds to 0.5V. Since both the sensor and the sampling circuit are designed for the maximum DC1000V, DC100±0.5V is around 10% of the full scale, making it difficult for the sensor and sampling circuit to achieve high-precision sampling.

[0069] In order to solve the problem of high-precision sampling at low voltage output, the nonlinear high-order sampling method shown in the following formula (3) can be used.

[0070] v s2 =(kv o ) n =(kV ref ) n (1+a) n (3)

[0071] In the above formula, v s2 is the output voltage feedback using the nonlinear high-order sampling method, n is the nonlinear sampling magnification, which is a constant greater than 1, so (kV ref ) n is a constant, and because a is generally small (±0.5%), the equivalent infinitesimal approximation (1+a) is applied n ≈1+a, formula (3) is equivalent to:

[0072] v s =(kV ref ) n (1+na) (4)

[0073] Compared with formula (2), it can be seen from formula (4) that by performing n-th power operation on the sampled output voltage signal in the controller, the weight of the error in the entire output voltage signal can be increased by n times, and the sampling accuracy can be greatly improved.

[0074] It can be seen that the larger the value of the nonlinear sampling ratio n, the more conducive it is to improving the sampling accuracy. However, considering the size limit of the data type and the calculation time in the controller, the value of n generally does not exceed 4.

[0075] 2. Series compound control

[0076] from Figure 3 As can be seen from the closed-loop control block diagram of the DC shore power device, the controller is also an important part of the entire control loop. Its function is to adjust the duty cycle of the power device drive signal according to the DC output voltage error, and then adjust the output voltage to make it track the voltage setting.

[0077] The controller of current DC shore power devices mostly adopts proportional-integral controller, and its mathematical expression is as follows:

[0078] v c =k p ·v e +k i ·∫v e dt (5)

[0079] In the above formula, v e is the output voltage error, v c is the controller output, which corresponds to the duty cycle of the power device, k p 、k i are the proportional and integral coefficients of the proportional-integral controller, respectively. Theoretically, for DC output, proportional-integral control can achieve zero-static tracking. However, in actual engineering practice, due to noise interference, load disturbances, and other factors, the system is actually constantly in a dynamic adjustment process, causing the output voltage to fluctuate around the given value.

[0080] From formula (5), it can be seen that when the error is positive, it means that the output voltage is less than the given value. Then, through proportional and integral operations, the adjustment amount v c When the error is negative, it means that the output voltage is greater than the given value. Then, the adjustment value v is adjusted by proportional and integral operation. c As the voltage decreases, the output voltage decreases accordingly. The aforementioned regulation principle demonstrates that the controller acts like a spring. The spring's inertia (corresponding to the integral element in the controller) causes the output voltage to swing around the set voltage. Due to the DC shore power supply, this swing often results in output voltage accuracy exceeding the specified value.

[0081] From the analysis, it can be seen that the inherent integral relationship of the proportional-integral controller causes the output voltage to fluctuate around the given value. To overcome this shortcoming, when it is determined that the deviation between the output voltage and the given value is within a small range (such as ±2%), the controller is switched from a proportional-integral controller to a step tracking controller, and the two controllers are a time-sharing series structure.

[0082] The principle of the step tracking controller is that when the judgment error is positive, it means that the output voltage is less than the given value, and the controller increases the controller output with a fixed minimum resolution (such as the numerical control amount 1), thereby slightly increasing the output voltage; when the judgment error is negative, it means that the output voltage is greater than the given value, and the controller reduces the controller output with a fixed minimum resolution (such as the numerical control amount 1), thereby slightly reducing the output voltage.

[0083] It can be seen that in the above-mentioned series compound control, conventional proportional-integral control plays a role of coarse adjustment, and step tracking control is used after the actual voltage approaches the given value to play a role of fine adjustment, so that the output voltage can accurately track the given value.

[0084] Figure 4 and Figure 5 The principle block diagram and program flow chart of the above-mentioned series compound control are given respectively.

[0085] 3. Distributed Adaptive Correction

[0086] In actual engineering applications, due to the influence of environmental factors such as device aging and temperature, the characteristics of the sampling circuit change after running for a period of time, which in turn leads to an increase in the output voltage accuracy deviation.

[0087] In the past, the common practice was to have a built-in standard voltage source in the device. The control system would periodically sample this standard voltage source and then use it as a standard to correct the actual sampled signal. This approach helped to improve the time stability of the output voltage accuracy, but it also had the following problems:

[0088] 1) The standard voltage source is generally built-in at the circuit board level and cannot be disassembled or maintained, making regular calibration impossible. As a result, its accuracy cannot be guaranteed over time.

[0089] 2) The system has only this single reference. Failure of this standard voltage source will result in the inability to stably control the voltage accuracy over a long period of time, affecting reliability.

[0090] To improve the temporal stability of the DC shore power system's output voltage, a distributed adaptive correction method is proposed based on system realities. This method leverages the existing built-in standard voltage source and utilizes external DC shore power distribution boxes, shore power connection boxes, and third-party voltage detection equipment in the remote monitoring system to achieve multi-point mutual verification, avoiding the potential for accuracy loss caused by reliance on a single point.

[0091] Some DC shore power devices are also equipped with local distribution boxes, shore power connection boxes and remote monitoring systems. The AC voltage is connected to the DC shore power device, converted into DC voltage by a dedicated power electronic conversion device, and then connected to the local distribution box. The local distribution box is equipped with circuit breakers, voltage and current detection instruments, etc. for on-off control and monitoring of DC shore power output. The output of the local distribution box is connected to the DC shore power box at the dock via a cable. The DC shore power box is also equipped with circuit breakers and voltage and current detection instruments for on-off control and monitoring of DC shore power and ships. The remote monitoring system connects the DC shore power device, the local distribution box and the DC shore power box through optical fiber to obtain the main operating parameters of each device. Figure 6 A simplified diagram of the monitoring network system of the DC shore power system is given.

[0092] exist Figure 6 In the monitoring system ring network shown, all devices can access each other via network protocols. To this end, the DC shore power supply device can read voltage data from third-party calibration instruments in the local distribution box and the DC shore power box, compare it with its own sampled data, and automatically correct the sampled signal. Furthermore, manual corrections can be made by entering measured values ​​into the monitoring system's data correction interface.

[0093] From the above analysis, it can be seen that the distributed adaptive correction method based on multiple sources proposed in the present invention does not rely on a single reference source, and the data sources are all reliable data from third-party calibration instruments, which greatly improves the time stability of the output voltage accuracy.

[0094] The present invention is not limited to the above-mentioned specific embodiments. A person skilled in the art can implement the present invention in a variety of other specific embodiments based on the embodiments and the contents disclosed in the drawings. Therefore, any design that adopts the design structure and ideas of the present invention and makes some simple transformations or changes falls within the scope of protection of the present invention.

Claims

1. An ultra-wide range high-precision DC shore power control device, characterized in that: The ultra-wide range high-precision DC shore power control device includes an on-load tap-changing transformer and a multi-module parallel rectifier conversion unit; The on-load tap-changing transformer inputs an AC input voltage, and the output end is connected to a multi-module parallel rectifier conversion unit; the multi-module parallel rectifier conversion unit is divided into two groups, each having the same number of rectifier modules, the input of each rectifier module is the secondary winding voltage of the on-load tap-changing transformer, and the output is DC, and the DC outputs of the rectifier modules in each group are connected in parallel; There is a parallel switch between the two sets of DC outputs; when the switch is open, the two DC outputs operate independently; when the switch is closed, the two sets of DC outputs operate in parallel, connecting the positive or negative pole of the first set of DC outputs to the positive or negative pole of the second set of DC outputs respectively; The ultra-wide range high-precision DC shore power control device uses nonlinear multi-stage sampling to control the output voltage; the result obtained by the sampling circuit is proportional to the actual output voltage: v s =kv o =k(V ref +v e )=kV ref (1+a) v s is the output voltage sampling signal, k is the sampling coefficient, which is generally a fixed value much smaller than 1, v o is the actual output voltage, which is equal to the given voltage V ref and error value v e The sum of the variables a and v is the error value e Relative voltage given V ref The ratio value of In order to solve the problem of high-precision sampling at low voltage output, a nonlinear high-order sampling method is adopted: in s2 =(kv o ) n =(kV ref ) n (1+a) n v s2 is the output voltage feedback using the nonlinear high-order sampling method, n is the nonlinear sampling magnification; based on the approximate relationship (1+a) n ≈1+a is equivalent to: v s =(kV ref ) n (1+na) Increase the weight of the error in the entire output voltage signal by n times; The ultra-wide range high-precision DC shore power control device adopts series compound control; The ultra-wide range high-precision DC shore power control device includes a proportional-integral controller and a step tracking controller using a time-sharing series structure; When using a proportional-integral controller: v c =k p ·v e +k i ·∫v e dt v e is the output voltage error, v c is the controller output, which corresponds to the duty cycle of the power device, k p 、k i are the proportional and integral coefficients of the proportional-integral controller respectively; When the step tracking controller determines that the error is positive, the controller output is increased at a fixed minimum resolution, thereby slightly increasing the output voltage; when the step tracking controller determines that the error is negative, the controller output is reduced at a fixed minimum resolution, thereby slightly decreasing the output voltage; Proportional-integral control plays a role of coarse adjustment. After the actual voltage approaches the given value, step tracking control is used to play a role of fine adjustment, ultimately making the output voltage accurately track the given value.

2. The ultra-wide range high-precision DC shore power control device according to claim 1 is characterized in that: The on-load tap-changing transformer can adjust the gear according to the output voltage, thereby changing the secondary voltage of the transformer. When the DC shore power device requires a lower output voltage, the on-load tap-changing switch is adjusted to a high gear, the AC input voltage amplitude of the rectifier module is low, and the rectifier module outputs a lower DC voltage accordingly; when the DC shore power device requires a higher output voltage, the on-load tap-changing switch is adjusted to a low gear, the AC input voltage amplitude of the rectifier module is high, and the rectifier module outputs a higher DC voltage accordingly.

3. The ultra-wide range high-precision DC shore power control device according to claim 1 is characterized in that: The ultra-wide range, high-precision DC shore power control device is also equipped with a local distribution box, a shore power connection box and a remote monitoring system; The DC voltage output by the ultra-wide range high-precision DC shore power control device is connected to the local distribution box; The local distribution box includes a circuit breaker and voltage and current detectors for on-off control and monitoring of DC shore power output; The output of the local distribution box is connected to the DC shore power box at the dock via a cable. The DC shore power box includes a circuit breaker and voltage and current detection instruments for on-off control and monitoring of the DC shore power and the ship. The remote monitoring system connects the ultra-wide range, high-precision DC shore power control device, the local distribution box and the DC shore power box via optical fiber to obtain the main operating parameters of each device.

4. The ultra-wide range high-precision DC shore power control device according to claim 2, characterized in that: The rectifier conversion unit is a step-down converter, and the relationship between its DC output voltage and AC input voltage is: V o =MV in V o is the DC output voltage of the rectifier module, M is the modulation ratio of the rectifier module, V in It is the AC input voltage amplitude of the rectifier module, that is, the voltage amplitude output by the on-load tap-changer.

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