A method and system for testing micro-power consumption and full power of shore-based variable frequency power supply under weak power grid conditions

Abstract

The present invention relates to a shore-based variable frequency power supply micro-power consumption full-power test method and system under weak power grid conditions, wherein the power supply variable frequency power supply V1 includes a frequency converter VFP1, the shore-based variable frequency power supply V2 includes a frequency converter VFP2, the energy-feeding load power supply V3 includes a frequency converter VFP3, the input end of the frequency converter VFP1 is connected to the shore-based high-voltage power supply, the output end of the frequency converter VFP1 is connected to the input end of the frequency converter VFP2, the output end of the frequency converter VFP2 is connected to the input end of the frequency converter VFP3, and the output end of the frequency converter VFP3 is respectively connected to the output end of the frequency converter VFP1 and the input end of the frequency converter VFP2; the energy-feeding load power supply V3 is used as a simulated load to test the shore-based variable frequency power supply V2, and after the shore-based variable frequency power supply V2 is tested, the shore-based variable frequency power supply V2 is put into use. The advantages of the present invention are: after the test loop forms a loop, no actual work is required, only the current needs to be increased to a predetermined test value, the energy consumption is small, and the power grid does not need to provide a large capacity.

Description

Technical Field

[0001] The invention relates to a control technology for a power electronic equipment detection system, and in particular to a method and system for testing micro-power consumption and full-power of a shore-based variable frequency power supply under weak power grid conditions. Background Art

[0002] Shore-based variable frequency power supply is a system that obtains power supply by connecting to the shore power grid while the ship is docked in the port. This system is also called shore power system or shore power interface, and plays an important role in the shipping industry. Its main function is to provide stable power to replace the generator set inside the ship, thereby reducing fuel consumption and environmental impact. Compared with the traditional low-voltage shore power system, the high-voltage shore power system is able to provide higher voltage and power. This makes it particularly suitable for large ships and equipment that requires a lot of electricity, such as the ship's refrigerated cargo hold, the operation and maintenance of ship equipment, etc. The high-voltage shore power system not only improves the efficiency of ship operations, but also helps ships reduce noise and emissions while in port, which meets the environmentally friendly requirements of modern society.

[0003] There are currently two main methods for full-load testing of shore-based high-voltage variable-frequency power supplies:

[0004] 1. Motor or reactor as load test

[0005] Use a motor or reactor as a load for testing; connect the load to the shore power output to test the load's active power or reactive power output. This method is relatively simple and direct, but the test content is limited, mainly focusing on a single active power output or reactive power output, and can only test active or reactive power, and cannot simulate the actual situation.

[0006] 2. The shore-based high-voltage variable frequency power supply test equipment is connected to the power grid to form a closed-loop test

[0007] Connect the output of the shore power supply to a dedicated shore power supply test device, and then feed back the energy of the dedicated shore power supply test device to the input of the shore-based power supply under test, forming a closed test loop. This method is relatively complex and requires the support of dedicated shore power supply test equipment, and requires the grid side to have sufficient capacity to support the operation of the dedicated shore power supply test equipment. Summary of the invention

[0008] The purpose of the present invention is to provide a method and system for testing micro-power consumption full-power of a shore-based variable frequency power supply under weak power grid conditions. A test loop is adopted to enable the energy-feeding power supply to have good grid adaptability. The test system can adapt to an environment with small grid capacity, reduce energy consumption, have a simple structure, and be easy to implement.

[0009] To achieve the above object, the present invention is implemented through the following technical solutions:

[0010] A method for testing the micro-power consumption of a shore-based variable frequency power supply under weak power grid conditions includes the following contents:

[0011] The energy-feeding load power supply V3 is used as a simulated load to test the shore-based variable frequency power supply V2. After the shore-based variable frequency power supply V2 is tested, the shore-based variable frequency power supply V2 is put into use.

[0012] After the shore-based variable frequency power supply V2 and the energy-feeding load power supply V3 reach a predetermined value, the shore-based variable frequency power supply V2 and the energy-feeding load power supply V3 do not actually work, and only consume no-load power to complete the shore-based variable frequency power supply full-load test, and the method includes:

[0013] Use power supply variable frequency power supply V1 to power the test loop;

[0014] The shore-based high-voltage power supply is only used to provide the no-load power loss of the test loop;

[0015] The output voltage and frequency of the energy-feeding load power supply V3 are adjusted so that in the test loop, energy is fed back to the input end of the shore-based variable frequency power supply V2 through the energy-feeding load power supply V3, and the output power of the shore-based variable frequency power supply V2 is measured in real time;

[0016] Continue to adjust the output current of the energy-feeding load power supply V3 to increase the current to the rated current. When the energy-feeding load power supply V3 is increased to the rated power, the shore-based variable frequency power supply V2 also increases to the rated power.

[0017] After the shore-based variable frequency power supply V2 is loaded to the full load current, it runs uninterruptedly and runs continuously to the set time when the current remains unchanged;

[0018] After the set time is reached, the shore-based variable frequency power supply V2 is operated to reduce the current. After the current drops to 0, it is shut down and the test ends.

[0019] The energy-feeding load power supply V3 samples the shore-based high-voltage power supply voltage and obtains the αβ-axis voltage through Clark transformation. The high-frequency harmonics are filtered out through a double generalized second-order integrator. The q-axis voltage signal is obtained through pack transformation for phase-locked control, and finally a stable grid voltage reference phase is obtained;

[0020] Through the grid voltage reference phase, the sampled shore-based high-voltage power supply current is converted into the dq axis current in the rotating coordinate system, and is respectively calculated with the d axis voltage to obtain the active power and reactive power, which are used as the power feedback signal for power closed-loop control. The formula for calculating the modulation wave is as follows:

[0021] P=1.5*I d *U d ①

[0022] In formula ①, I drepresents the d-axis current, U d represents the d-axis voltage, and P represents the active power of the energy-feeding load power supply V3;

[0023] Q=-1.5*I q *U d ②

[0024] In formula ②, Q represents the reactive power of the energy-feeding load power supply V3;

[0025] The PI controller outputs a current closed-loop current reference value through a power closed-loop to calculate the proportional integral value required for the modulation wave;

[0026] The dq axis voltage signal is obtained through current closed loop and decoupling regulation to calculate the voltage value required for the modulation wave;

[0027] The modulation wave is obtained by pack inverse transformation, and the modulation wave is superimposed on the carrier to obtain the PWM wave, which is used to drive the IGBT to work;

[0028] The driving signal is obtained through PWM modulation to drive the power unit to complete the active / reactive power regulation of the energy-feeding load power supply V3;

[0029] By setting the active / reactive given signal of the power closed loop, the active / reactive power output by the energy-feeding load power supply V3 is adjusted.

[0030] A shore-based variable frequency power supply micro-power consumption full-power test system, the test system includes a test loop, the test loop includes a power supply variable frequency power supply V1, a shore-based variable frequency power supply V2, and a feeding load power supply V3, the power supply variable frequency power supply V1 includes a frequency converter VFP1, the shore-based variable frequency power supply V2 includes a frequency converter VFP2, the feeding load power supply V3 includes a frequency converter VFP3, the input end of the frequency converter VFP1 is connected to the shore-based high voltage power supply, the output end of the frequency converter VFP1 is connected to the input end of the frequency converter VFP2, the output end of the frequency converter VFP2 is connected to the input end of the frequency converter VFP3, and the output end of the frequency converter VFP3 is respectively connected to the output end of the frequency converter VFP1 and the input end of the frequency converter VFP2; the frequency converter VFP1 and the frequency converter VFP3 are both voltage source type phase-shifted frequency converters composed of multi-level power units connected in series.

[0031] The inverter VFP2 includes a voltage source phase-shift inverter composed of a resistor cabinet and a multi-level power unit connected in series. The output end of the resistor cabinet is connected to the input end of the voltage source phase-shift inverter, the input end of the resistor cabinet is connected to the input end of the shore-based variable frequency power supply V2, and the output end of the voltage source phase-shift inverter is the output end of the shore-based variable frequency power supply V2.

[0032] The frequency converter VFP3 includes a rectifier, an inverter, and a step-up transformer. One side port of the rectifier is connected to the secondary side of the phase-shifting transformer, the primary side of the phase-shifting transformer is connected to the input end of the shore-based variable frequency power supply V2 through circuit breaker 2, the other side port of the rectifier is connected to one side port of the inverter, the other side port of the inverter is connected to one side port of the step-up transformer, the other side port of the step-up transformer is connected in series with filter 2 and an isolation transformer, and the output end of the isolation transformer is connected to the output end of the shore-based variable frequency power supply V2.

[0033] The voltage source phase-shifted inverter is a three-phase AC-DC-AC voltage source inverter, including a rectifier side and an inverter side.

[0034] The output end of the voltage source phase-shifting inverter is connected to the input end of filter one, the output end of filter one is connected to the output end of the power supply variable frequency power supply V1 or the output end of the energy feeding load power supply V3, and the input end of the voltage source phase-shifting inverter is connected to the input end of the power supply variable frequency power supply V1 or the input end of the energy feeding load power supply V3 through circuit breaker one.

[0035] A transformer is connected between the circuit breaker 1 of the frequency converter VFP3 and the input end of the energy feeding load power supply V3, and the filter 1 of the frequency converter VFP3 is connected to the output end of the energy feeding load power supply V3 through the circuit breaker 3.

[0036] The voltage source phase-shifted inverter is an AC-DC-AC three-phase diode uncontrolled rectification / single-phase inverter output voltage source inverter, wherein the inverter device may be an IGBT.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. After the test loop is formed, no actual work is required. It only needs to increase the current to the predetermined value for the test. The energy consumption is small, and the power grid does not need to provide large capacity.

[0039] 2. Both inverters VFP1 and VFP3 are voltage source phase-shifted inverters composed of multi-level power units connected in series. They can approximate sine waves through more levels, thereby reducing the harmonic content in the output voltage, reducing harmonic distortion, and achieving higher output voltage quality. Multi-level technology allows high-quality output voltage to be achieved at a lower switching frequency, thereby reducing switching losses and electromagnetic interference.

[0040] 3. The multi-level structure of the inverter VFP2 reduces the voltage borne by a single power switch, reduces dv / dt (voltage change rate), reduces the stress on the motor and cable insulation, and improves the reliability of the system. The multi-level structure can more effectively control the power factor, reduce energy loss, and improve the overall efficiency of the system; the multi-level inverter can adopt a modular design, increase or decrease power units to adapt to different voltage levels and power requirements, and improve the flexibility and scalability of the system;

[0041] 4. In actual use, the load of the shore-based variable frequency power supply V2 is the energy-feeding load power supply V3. By using the variable frequency power supply (energy-feeding load power supply V3) as the load, various load conditions under actual working conditions can be simulated, including different parameters such as voltage, current and power factor, which is helpful to comprehensively evaluate the performance and responsiveness of the shore-based variable frequency power supply; the variable frequency power supply as a load can flexibly adjust parameters such as output voltage, frequency and phase to achieve more precise control of the test conditions, and can test the stability and compatibility of the shore-based variable frequency power supply under various power grid conditions; by feeding the output of the variable frequency power supply back to the system, an energy closed loop can be formed. This design reduces the power consumption of the actual power grid, because the active power circulates inside the test loop, and the power grid only compensates for the test loop loss, which not only improves the test efficiency, but also reduces the load and cost of the power grid;

[0042] 5. Through AC / DC large-capacity power supply frequency conversion power supply, it can solve the problems of unstable grid voltage and excessive instantaneous power when testing large-capacity frequency conversion power supply;

[0043] 6. The variable frequency power supply adopts dual second-order generalized integrator phase-locked loop DSOGI-PLL and power and current dual closed-loop control technology. The dual second-order generalized integrator phase-locked loop DSOGI-PLL is an advanced phase-locked technology that can accurately extract the phase and frequency information of the grid voltage. It can effectively deal with voltage imbalance, harmonics and noise interference in the grid, and ensure that the variable frequency power supply can synchronize with the phase and frequency changes of the grid in real time. This is especially important for grid-connected operation because it ensures a stable connection between the variable frequency power supply and the grid; through dual closed-loop control of power and current, the variable frequency power supply can achieve fast and accurate power and current regulation. This control strategy can maintain the stability of output current and power in the case of grid voltage fluctuations and load changes, ensuring the quality of power;

[0044] 7. The inverter VFP2 of the shore-based variable frequency power supply V2 adopts two structures: a multi-level power unit inverter structure, which has low output voltage harmonics, low switching frequency, high efficiency, and can realize modular design; a high-voltage cascade inverter structure, which can achieve extremely high output voltage, large output power, can use standard power devices, and has high system reliability;

[0045] 8. The inverter VFP1 and inverter VFP3 have the same structure and both use a voltage source type composed of multi-level power units in series, with high output voltage quality: the multi-level structure can generate an output voltage waveform close to a sine wave, reducing the total harmonic distortion THD, which helps to reduce harmonic losses and electromagnetic interference EMI, and improve power quality; it has lower switching frequency and loss: because the multi-level technology provides a smoother voltage step, the required switching frequency is lower, thereby reducing switching losses and thermal stress of the equipment, which has a significant effect on improving system efficiency and reducing cooling requirements; it has lower dv / dt stress: the voltage of each power unit is lower, thereby reducing the dv / dt (voltage change rate) of the output voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a main circuit diagram of the shore-based variable frequency power supply micro-power consumption full-power test system under weak power grid conditions.

[0047] Figure 2 It is a schematic diagram of the main circuit of the power supply variable frequency power supply V1 and the energy feeding load power supply V3.

[0048] Figure 3 It is a unit structure diagram of the power supply variable frequency power supply V1.

[0049] Figure 4 This is the main circuit diagram of shore-based variable frequency power supply V2 Figure 1 .

[0050] Figure 5 This is the main circuit diagram of shore-based variable frequency power supply V2 Figure 2 .

[0051] Figure 6 It is the control block diagram of the test loop.

[0052] Figure 7 It is the control block diagram of the shore-based variable frequency power supply micro-power full-power test system under weak power grid conditions. DETAILED DESCRIPTION

[0053] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0054] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0055] [Example 1]

[0056] See Figure 1A shore-based variable frequency power supply micro-power consumption full-power test system under weak power grid conditions includes a test loop, the test loop includes a power supply variable frequency power supply V1, a shore-based variable frequency power supply V2, and a feeding load power supply V3. The input end of the power supply variable frequency power supply V1 is connected to the shore-based high-voltage power supply AC10KV / 50HZ, the output end of the power supply variable frequency power supply V1 is connected to the input end of the shore-based variable frequency power supply V2, the output end of the shore-based variable frequency power supply V2 is connected to the input end of the feeding load power supply V3, and the output end of the feeding load power supply V3 is respectively connected to the output end of the power supply variable frequency power supply V1 and the input end of the shore-based variable frequency power supply V2.

[0057] See Figure 1 ,See Figure 4 ,See Figure 5 The shore-based variable frequency power supply V2 includes a frequency converter VFP2. One structure of the frequency converter VFP2 is: the frequency converter VFP2 includes a voltage source type phase-shifting frequency converter composed of a resistor cabinet and a multi-level power unit connected in series. The resistor cabinet is used to prevent the power grid (shore-based high voltage power supply AC10KV / 50HZ) from being impacted by excessive current when charging starts. The output end of the resistor cabinet is connected to the input end of the voltage source type phase-shifting frequency converter, and the input end of the resistor cabinet is connected to the input end of the shore-based variable frequency power supply V2. The output end of the voltage source type phase-shifting frequency converter is the output end of the shore-based variable frequency power supply V2; another structure of the frequency converter VFP2 is: the frequency converter VFP3 includes a rectifier, an inverter, and a step-up transformer. One side port of the rectifier is connected to the secondary side of the phase-shifting transformer. The primary side of the phase-shifting transformer is connected to the input end of the shore-based variable frequency power supply V2 through the circuit breaker QF2, the other side port of the rectifier is connected to one side port of the inverter, the other side port of the inverter is connected to one side port of the step-up transformer, the other side port of the step-up transformer is connected in series with filter 2 and an isolation transformer, the output end of the isolation transformer is connected to the output end of the shore-based variable frequency power supply V2; the inverter VFP2 of the shore-based variable frequency power supply V2 adopts two structures respectively, a multi-level power unit inverter structure, with low output voltage harmonics, low switching frequency, high efficiency, and modular design, and a high-voltage cascade inverter structure that can achieve extremely high output voltage, large output power, can use standard power devices, and has high system reliability.

[0058] See Figure 1-Figure 3The power supply variable frequency power supply V1 includes a frequency converter VFP1, and the energy feeding load power supply V3 includes a frequency converter VFP3. Both the frequency converter VFP1 and the frequency converter VFP3 are voltage source type phase shift frequency converters composed of multi-level power units connected in series, wherein the voltage source type phase shift frequency converter is a three-phase AC-DC-AC type voltage source type frequency converter, including a rectifier side and an inverter side. The output end of the voltage source type phase shift frequency converter is connected to the input end of the filter one, and the output end of the filter one is connected to the output end of the power supply variable frequency power supply V1 or the input end of the energy feeding load power supply V3 through a circuit breaker QF3. The input end of the voltage source phase-shifting inverter is connected to the input end of the power supply frequency conversion power supply V1 or the input end of the energy feeding load power supply V3 through the circuit breaker QF1 and the transformer connected in series. The transformer is a step-up transformer or a step-down transformer. Because different output voltages need to be converted into 10KV, a step-up transformer or a step-down transformer is required. The filter of the inverter VFP3 is connected to the output end of the energy feeding load power supply V3 through the circuit breaker QF3; the voltage source phase-shifting inverter is an AC-DC-AC three-phase diode The voltage source inverter with uncontrolled rectification / single-phase inverter output, where the inverter device can be IGBT, IGCT, or IEGT; the input end of the inverter VFP1-VFP3 is equipped with a circuit breaker to facilitate the installation, disassembly and maintenance of the inverter. The output end of the inverter VFP3 is equipped with a circuit breaker QF4. When the circuit breaker is closed, the grid is connected. When the output voltage of the energy-feeding load power supply V3 rises to the rated voltage, QF3 is closed for grid connection. When the output voltage is 11kV, a step-down transformer is required to convert the voltage to 10kV When the output voltage is 6.6kV, a step-up transformer is required to convert the voltage to 10kV. The inverter VFP1 and inverter VFP3 have the same structure and both use a voltage source phase-shifted inverter composed of multi-level power units in series. The output voltage has higher quality: the multi-level inverter can approximate a sine wave through more levels, thereby reducing the harmonic content in the output voltage and reducing harmonic distortion; the switching frequency is reduced: multi-level technology allows high-quality output voltage at a lower switching frequency, thereby reducing switching losses and electromagnetic interference.

[0059] See Figure 6 ,See Figure 7A shore-based variable frequency power supply micro-power consumption full-power test method under weak power grid conditions is applicable to the case of small power grid capacity. The shore-based variable frequency power supply V2 is tested by using a feeding load power supply V3 as a simulated load. After the shore-based variable frequency power supply V2 is tested, the shore-based variable frequency power supply V2 is put into use. After the shore-based variable frequency power supply V2 and the feeding load power supply V3 reach a predetermined value, although the operating current of the shore-based variable frequency power supply V2 and the feeding load power supply V3 reaches the rated current value of the shore-based variable frequency power supply V2, the shore-based variable frequency power supply V2 and the feeding load power supply V3 do not work, and the shore-based variable frequency power supply V2 and the feeding load power supply V3 do not generate power consumption, which is used to complete the shore-based variable frequency power supply full-load test. The method includes:

[0060] 1. Use power supply variable frequency power supply V1 to power the test loop.

[0061] 2. The power grid only provides no-load losses for variable frequency power supply V1, shore-based variable frequency power supply V2 and energy-feeding load power supply V3.

[0062] During the test, the grid provides no-load losses for the variable frequency power supply V1, the shore-based variable frequency power supply V2 and the energy feeding load power supply V3. In this case, the shore-based high voltage power supply capacity can be very large, and there is no requirement for the capacity of the grid itself. In this case, full power testing can be performed even when the grid is small.

[0063] 3. Adjust the output of the energy-feeding power supply

[0064] The amplitude and phase of the output voltage of the energy-feeding load power supply V3 are adjusted to form a stable power cycle in the test loop. This means that the test equipment (i.e., the energy-feeding load power supply V3) feeds back part of the energy to the input end of the shore-based power supply under test (i.e., the shore-based variable frequency power supply V2) to maintain a continuous power cycle. The energy is fed back to the input end of the shore-based variable frequency power supply V2 through the energy-feeding load power supply V3, and the power at the input end of the shore-based variable frequency power supply V2 is measured in real time. By effectively managing the energy cycle, the shore-based high-voltage power supply AC10KV / 50HZ can perform comprehensive power testing under the condition of limited grid capacity. This is crucial to ensuring equipment performance and compliance with regulatory requirements, and is especially suitable for ships and other scenarios requiring high-power power supplies.

[0065] 4. Control and regulation

[0066] Adjust the output voltage and current of the energy-feeding load power supply V3 to simulate different loads and complete the power test.

[0067] The energy-feeding load power supply V3 samples the shore-based high-voltage power supply voltage and obtains the αβ-axis voltage through Clark transformation. The high-frequency harmonics are filtered out through a double generalized second-order integrator. The q-axis voltage signal is obtained through pack transformation for phase-locked control, and finally a stable grid voltage reference phase is obtained;

[0068] Through the grid voltage reference phase, the sampled shore-based high-voltage power supply current is converted into the dq axis current in the rotating coordinate system, and is respectively calculated with the d axis voltage to obtain the active power and reactive power, which are used as the power feedback signal for power closed-loop control. The formula for calculating the modulation wave is as follows:

[0069] P=1.5*I d *U d ①

[0070] In formula ①, I d represents the d-axis current, U d represents the d-axis voltage, and P represents the active power of the energy-feeding load power supply V3;

[0071] Q=-1.5*I q *U d ②

[0072] In formula ②, Q represents the reactive power of the energy-feeding load power supply V3;

[0073] The PI controller outputs the closed-loop current reference value through the power closed-loop to calculate the proportional integral value required for the modulation wave;

[0074] The dq axis voltage signal is obtained through current closed loop and decoupling regulation to calculate the voltage value required for the modulation wave;

[0075] The modulation wave is obtained by pack inverse transformation, and the modulation wave is superimposed on the carrier to obtain the PWM wave, which is used to drive the IGBT to work;

[0076] The driving signal is obtained through PWM modulation to drive the power unit to complete the active / reactive power regulation of the energy-feeding load power supply V3;

[0077] By setting the active / reactive given signal of the power closed loop, the active / reactive power output by the energy-feeding load power supply V3 is adjusted.

[0078] [Example 2]

[0079] In this embodiment, a shore-based variable frequency power supply micro-power consumption full-power test method and system under weak power grid conditions are the same as those in Embodiment 1, and a description of the test process is added thereto, and the contents are as follows:

[0080] Start the power supply variable frequency power supply V1, and increase the output voltage and frequency to the preset value 10kv / 50hz through the frequency converter VFP1;

[0081] The power supply variable frequency power supply V1 supplies power to the shore-based variable frequency power supply V2;

[0082] Start the shore-based variable frequency power supply V2, and increase the output voltage and frequency to the preset value of 1.1 kV / 0.66 kV 60 Hz through the frequency converter VFP2;

[0083] The shore-based variable frequency power supply V2 supplies power to the energy-feeding load power supply V3;

[0084] Start the energy-feeding load power supply V3, and increase the output voltage and frequency to the preset value 10kv / 50hz through the frequency converter VFP3;

[0085] The energy-feeding load power supply V3 feeds electric energy back to the input end of the shore-based variable frequency power supply V2, adjusts the output voltage and current of the energy-feeding load power supply V3, makes the active power circulate in the loop, and makes the test equipment feed back part of the energy to the input end of the shore-based power supply under test, so as to maintain a continuous power cycle.

[0086] Testing process:

[0087] The power supply variable frequency power supply V1 and the energy feeding load power supply V3 are used as test equipment to test the shore-based variable frequency power supply V2. The power grid is responsible for testing the power supply variable frequency power supply V1, the shore-based variable frequency power supply V2 and the energy feeding load power supply V3. A large-capacity power grid is not required. After the test, the shore-based variable frequency power supply V2 equipment can be put into use. The content is as follows:

[0088] 1. After the grid power supply reaches QF1, QF1 is closed.

[0089] 2. Start the inverter VFP1, and then VFP1 starts to increase the frequency and voltage, raising the voltage and frequency to 10kV, 50Hz, and starts to output through the filter. V1 startup is completed.

[0090] 3. Close the QF2 circuit breaker.

[0091] 4. Start the inverter VFP2, which starts to increase the frequency and voltage, raising the voltage and frequency to 11 kV / 6.6 kV60 Hz, and prepares to increase or decrease the voltage through the filter.

[0092] 5. If it is 11kV, it will be converted to 10kV 60Hz through a step-down transformer; if it is 6.6kV, it will be converted to 10kV 60Hz through a step-up transformer. V2 startup is completed.

[0093] 6. Close QF3 and start the inverter VFP3. VFP3 begins to increase the frequency and voltage, raising the voltage and frequency to 10kV, 50Hz, and prepares for grid-connected output through the filter.

[0094] 7. When the output phase angle, frequency and amplitude of inverter VFP3 are consistent with those of VFP1, grid-connected startup begins.

[0095] 8. Start to load current to VFP2 until the current reaches full load and then start testing.

[0096] 9. After being loaded to the full load current, the equipment starts to run uninterruptedly and cannot be shut down or the current reduced to ensure that the equipment runs for the rated time with the current unchanged (the rated time is calculated by the equipment manufacturer based on the technical agreement).

[0097] 10. After reaching the rated time, VFP2 is operated to reduce the current. After the current drops to 0, it is shut down.

[0098] After the test loop of the present invention forms a loop, it does not need to actually do work, but only needs to increase the current to the predetermined test value, so the energy consumption is small, and the power grid does not need to provide a large capacity; the inverter VFP1 and the inverter VFP3 are both voltage source phase-shifted inverters composed of multi-level power units in series, which can approximate a sine wave through more levels, thereby reducing the harmonic content in the output voltage, reducing harmonic distortion, and having a higher output voltage quality; the multi-level technology allows high-quality output voltage to be achieved at a lower switching frequency, thereby reducing switching losses and electromagnetic interference; the multi-level structure of the inverter VFP2 reduces the voltage borne by a single power switch, reduces dv / dt (voltage change rate), reduces stress on motor and cable insulation, and improves system reliability. The multi-level structure can more effectively control the power factor, reduce power loss, and improve the overall efficiency of the system; the multi-level structure can effectively control the power factor, reduce power loss, and improve the overall efficiency of the system; The inverter can adopt a modular design, adding or reducing power units to adapt to different voltage levels and power requirements, and improving the flexibility and scalability of the system; in actual use, the load of the shore-based variable frequency power supply V2 is the energy-feeding load power supply V3. By using the variable frequency power supply (energy-feeding load power supply V3) as the load, various load conditions under actual working conditions can be simulated, including different voltages, currents, power factors and other parameters, which is helpful to comprehensively evaluate the performance and responsiveness of the shore-based variable frequency power supply; the variable frequency power supply as a load can flexibly adjust the output voltage, frequency, phase and other parameters to achieve more precise control of the test conditions, and can test the stability and compatibility of the shore-based variable frequency power supply under various power grid conditions; By feeding the output of the variable frequency power supply back to the system, an energy closed loop can be formed. This design reduces the actual power grid's energy consumption, because the active power circulates inside the test loop, and the power grid only compensates for the test loop loss, which not only improves the test efficiency, but also reduces the load and cost of the power grid; through the AC-DC-AC large-capacity power supply variable frequency power supply, it can solve the problems of unstable grid voltage and excessive instantaneous power when testing large-capacity variable frequency power supplies; the variable frequency power supply adopts dual second-order generalized integrator phase-locked loop DSOGI-PLL and power and current dual closed-loop control technology. The dual second-order generalized integrator phase-locked loop DSOGI-PLL is an advanced phase-locked technology that can accurately extract the phase and frequency information of the grid voltage. It can effectively deal with voltage imbalance, harmonics and noise interference in the power grid, and ensure that the variable frequency power supply can synchronize with the phase and frequency changes of the power grid in real time. This is especially important for grid-connected operation because it ensures a stable connection between the variable frequency power supply and the power grid; through dual closed-loop control of power and current, the variable frequency power supply can achieve fast and accurate power and current regulation. This control strategy can maintain the stability of output current and power in the case of grid voltage fluctuations and load changes, and ensure the quality of power; the inverter VFP2 of the shore-based variable frequency power supply V2 adopts two structures, a multi-level power unit inverter structure, with low output voltage harmonics, low switching frequency, high efficiency, and modular design;The high-voltage cascade inverter structure can achieve extremely high output voltage, large output power, can use standard power devices, and has high system reliability; the inverter VFP1 and the inverter VFP3 have the same structure and both use a voltage source type composed of multi-level power units in series, with high output voltage quality: the multi-level structure can generate an output voltage waveform close to a sine wave, reducing the total harmonic distortion THD, which helps to reduce harmonic losses and electromagnetic interference EMI, and improve power quality; it has lower switching frequency and loss: because the multi-level technology provides a smoother voltage step, the required switching frequency is lower, thereby reducing switching losses and thermal stress of the equipment, which has a significant effect on improving system efficiency and reducing cooling requirements; it has lower dv / dt stress: the voltage of each power unit is lower, thereby reducing the dv / dt (voltage change rate) of the output voltage. ;

Claims

1. A method for testing the micro-power consumption of a shore-based variable frequency power supply under weak power grid conditions, characterized in that: Includes the following: The energy-feeding load power supply (V3) is used as a simulated load to test the shore-based variable frequency power supply (V2). After the shore-based variable frequency power supply (V2) is tested, the shore-based variable frequency power supply (V2) is put into use; After the shore-based variable frequency power supply (V2) and the energy-feeding load power supply (V3) reach a predetermined value, the shore-based variable frequency power supply (V2) and the energy-feeding load power supply (V3) do not actually perform work, and only consume no-load power to complete the shore-based variable frequency power supply full-load test. The method includes: Use the power supply variable frequency power supply (V1) to power the test loop; The shore-based high-voltage power supply is only used to provide the no-load power loss of the test loop; The output voltage and frequency of the energy-feeding load power supply (V3) are adjusted so that in the test loop, energy is fed back to the input end of the shore-based variable frequency power supply (V2) through the energy-feeding load power supply (V3), and the output power of the shore-based variable frequency power supply (V2) is measured in real time; Continue to adjust the output current of the energy-feeding load power supply (V3) and increase the current to the rated current. When the energy-feeding load power supply (V3) increases to the rated power, the shore-based variable frequency power supply (V2) also increases to the rated power. After the shore-based variable frequency power supply (V2) is loaded to the full load current, it will run uninterruptedly and continue to run until the set time when the current remains unchanged; After the set time is reached, the shore-based variable frequency power supply (V2) is operated to reduce the current. After the current drops to 0, it is shut down and the test ends. The energy-feeding load power supply (V3) samples the shore-based high-voltage power supply voltage and obtains the αβ-axis voltage through Clark transformation, filters out high-frequency harmonics through a double generalized second-order integrator, obtains the q-axis voltage signal through pack transformation, performs phase-locked control, and finally obtains a stable grid voltage reference phase; Through the grid voltage reference phase, the sampled shore-based high-voltage power supply current is converted into the dq axis current in the rotating coordinate system, and is respectively calculated with the d axis voltage to obtain the active power and reactive power, which are used as the power feedback signal for power closed-loop control. The formula for calculating the modulation wave is as follows: P=1.5*I d *IN d ① In formula ①, I d represents the d-axis current, U d represents the d-axis voltage, and P represents the active power of the energy-feeding load power supply (V3); Q=-1.5*I q *U d ② In formula ②, Q represents the reactive power of the energy-feeding load power supply (V3); The PI controller outputs a current closed-loop current reference value through a power closed-loop to calculate the proportional integral value required for the modulation wave; The dq axis voltage signal is obtained through current closed loop and decoupling regulation to calculate the voltage value required for the modulation wave; The modulation wave is obtained by pack inverse transformation, and the modulation wave is superimposed on the carrier to obtain the PWM wave, which is used to drive the IGBT to work; The driving signal is obtained through PWM modulation to drive the power unit and complete the active / reactive power regulation of the energy-feeding load power supply (V3); By setting the active / reactive given signal of the power closed loop, the active / reactive power output by the energy-feeding load power supply (V3) is adjusted.

2. A shore-based variable frequency power supply micro-power consumption full-power test system for implementing the method described in claim 1, characterized in that: The test system comprises a test loop, the test loop comprises a power supply variable frequency power supply (V1), a shore-based variable frequency power supply (V2), and a power feeding load power supply (V3); the power supply variable frequency power supply (V1) comprises a frequency converter VFP1, the shore-based variable frequency power supply (V2) comprises a frequency converter VFP2, the power feeding load power supply (V3) comprises a frequency converter VFP3, the input end of the frequency converter VFP1 is connected to the shore-based high voltage power supply, the output end of the frequency converter VFP1 is connected to the input end of the frequency converter VFP2, the output end of the frequency converter VFP2 is connected to the input end of the frequency converter VFP3, and the output end of the frequency converter VFP3 is respectively connected to the output end of the frequency converter VFP1 and the input end of the frequency converter VFP2; the frequency converter VFP1 and the frequency converter VFP3 are both voltage source type phase shift frequency converters composed of multi-level power units connected in series.

3. A shore-based variable frequency power supply micro-power consumption full-power test system according to claim 2, characterized in that: The inverter VFP2 comprises a voltage source phase-shift inverter composed of a resistor cabinet and a multi-level power unit connected in series, the output end of the resistor cabinet is connected to the input end of the voltage source phase-shift inverter, the input end of the resistor cabinet is connected to the input end of the shore-based variable frequency power supply (V2), and the output end of the voltage source phase-shift inverter is the output end of the shore-based variable frequency power supply (V2).

4. A shore-based variable frequency power supply micro-power consumption full-power test system according to claim 2, characterized in that: The frequency converter VFP3 comprises a rectifier, an inverter and a step-up transformer. One side port of the rectifier is connected to the secondary side of the phase-shifting transformer. The primary side of the phase-shifting transformer is connected to the input end of the shore-based variable frequency power supply (V2) through a second circuit breaker. The other side port of the rectifier is connected to one side port of the inverter. The other side port of the inverter is connected to one side port of the step-up transformer. The other side port of the step-up transformer is connected in series with a second filter and an isolation transformer. The output end of the isolation transformer is connected to the output end of the shore-based variable frequency power supply (V2).

5. A shore-based variable frequency power supply micro-power consumption full-power test system according to claim 2 or 3, characterized in that: The voltage source phase-shifting inverter is a three-phase AC-DC-AC voltage source inverter, including a rectifier side and an inverter side.

6. A shore-based variable frequency power supply micro-power consumption full-power test system according to claim 2, characterized in that: The output end of the voltage source type phase shift inverter is connected to the input end of filter one, the output end of filter one is connected to the output end of the power supply variable frequency power supply (V1) or the output end of the energy feeding load power supply (V3), and the input end of the voltage source type phase shift inverter is connected to the input end of the power supply variable frequency power supply (V1) or the input end of the energy feeding load power supply (V3) through circuit breaker one.

7. A shore-based variable frequency power supply micro-power consumption full-power test system according to claim 2, characterized in that: A transformer is connected between the circuit breaker 1 of the frequency converter VFP3 and the input end of the energy feeding load power supply (V3), and the filter 1 of the frequency converter VFP3 is connected to the output end of the energy feeding load power supply (V3) through the circuit breaker 3.

8. A shore-based variable frequency power supply micro-power consumption full-power test system according to claim 6, characterized in that: The voltage source phase-shifting inverter is an AC-DC-AC three-phase diode uncontrolled rectification / single-phase inverter output voltage source inverter, wherein the inverter device is an IGBT.

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