A control method and device for a virtual synchronous PEM electrolytic water hydrogen production module

Abstract

The present invention discloses a control method for a virtual synchronous PEM electrolytic water hydrogen production module, and also discloses a device with the control method for the virtual synchronous PEM electrolytic water hydrogen production module. In the existing PEM hydrogen production device, the control method integrates a PWM three-phase converter with a load virtual synchronous control function for control, enabling the existing PEM electrolytic water hydrogen production module to have the autonomous operation and active management functions of active power - frequency and reactive power - voltage output at various time scales, and endowing the device with the operating external characteristics such as the inertia, damping characteristics, active power frequency modulation, and reactive power voltage regulation of a synchronous generator set, which can respond to the adjustment of the grid voltage / frequency and provide active and reactive power support for the grid. It promotes the friendly interaction between the PEM hydrogen production module and the power grid, and helps to improve the active power balance and voltage stability.

Description

Technical Field

[0001] The present invention relates to the field of gas-electricity integration and adjustable load active support, and particularly relates to a control method and device for a virtual synchronous PEM electrolytic water hydrogen production module. Background Art

[0002] In recent years, with the continuous progress of technology, the construction of a new power system in China has also been advancing rapidly. Since the 21st century, power electronic devices represented by new energy grid-connected inverters and controllable load rectifiers have been connected to the grid at a rapid pace. Conventional converters have a fast response speed, but almost no moment of inertia and are difficult to participate in grid regulation, and cannot provide necessary voltage and frequency support for a new power system with an increasing proportion of distributed power sources and renewable energy generation. The access of small-inertia, fast, and high-frequency power electronic systems to large-inertia, low-speed, and power-frequency power systems has brought about many adaptability problems such as not participating in grid regulation, not supporting grid fault recovery, difficult management and control, frequent plugging and unplugging, and weak robustness in dynamic and steady-state processes. Therefore, in the context of the large-scale access of new energy and controllable loads, it is imperative to tap the active support potential of adjustable loads.

[0003] At the same time, the energy crisis and environmental pollution are becoming increasingly severe. Developing renewable energy and taking the path of sustainable development have become the research focus of scholars in various countries. Promoting energy structure reform and realizing the low-carbon and clean nature of energy are also the inevitable ways for China's sustainable development. However, due to problems such as the intermittency, intermittence, and difficulty in storage and transportation of solar energy, wind energy and other renewable energies, an efficient and clean energy carrier is needed as a bridge between renewable energy and users. Hydrogen energy is recognized as the most promising energy carrier in the future due to its clean and efficient characteristics. Among current various hydrogen production technologies, using the electric energy generated by renewable energy as power to electrolyze water is the most mature and promising technology, and is regarded as the best way to the hydrogen economy. Electrolyzing water is a process in which electric energy is used as power to decompose water into hydrogen and oxygen. The overall reaction formula is: 2H2O + electric energy

[0004] →2H2 + O2.

[0005] As the most concerned technology among various water electrolysis technologies, the proton exchange membrane electrolytic cell (PEM) has the advantages of high current density, renewable, pollution-free, fast startup speed, etc. compared with alkaline electrolytic cells and solid oxide electrolytic cells. The advantages of PEM electrolytic cells in terms of power regulation range, power change adaptability, etc. determine that it has broad application prospects in future new power systems. Especially as an emerging energy storage technology, it can achieve large-scale long-cycle energy storage in the field of wind / solar power generation, and can also act as a green hydrogen production device for actively supporting the power grid when coupled with wind / solar power generation systems.

[0006] Therefore, the PEM electrolytic water hydrogen production device will be a load resource that cannot be ignored in the future power system and has good adjustability. Developing a grid-friendly virtual synchronous PEM electrolytic water hydrogen production product to promote the full consumption of renewable energy generation and actively support the power grid in all aspects is an urgent need under the background of building a new power system. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention proposes a PEM electrolytic water hydrogen production method based on virtual synchronous control technology, enabling the existing PEM electrolytic water hydrogen production module to have the autonomous operation and active management functions of active-power / frequency and reactive-power / voltage output on various time scales; and enabling the existing PEM hydrogen production device to have the operating external characteristics such as the inertia, damping characteristics, active power frequency modulation, and reactive power voltage regulation of a synchronous generator set, which can respond to the adjustment of the grid voltage / frequency and provide active and reactive power support for the power grid. It promotes the friendly interaction between the PEM hydrogen production module and the power grid, helps to improve the active power balance and voltage stability; at the same time, enables the power grid to have more adjustable load resources that actively support the power grid, promoting the consumption of renewable energy and the production of green hydrogen.

[0008] The present invention also proposes a device with the above-mentioned control method for the virtual synchronous PEM electrolytic water hydrogen production module.

[0009] The control method for the virtual synchronous PEM electrolytic water hydrogen production module according to the first aspect embodiment of the present invention is characterized in that:

[0010] Combining a PWM three-phase converter with load virtual synchronous control function with the PEM hydrogen production device;

[0011] Enabling the PEM hydrogen production module to sense the state of the power grid and automatically adjust the absorbed power;

[0012] Connecting to the power supply system based on a high-frequency PWM rectifier circuit;

[0013] Adjusting the target grid connection frequency based on autonomous active power frequency modulation control;

[0014] Adjusting the target output voltage amplitude based on autonomous reactive power voltage regulation control.

[0015] The virtual synchronous PEM electrolytic water hydrogen production module control method according to the embodiments of the present invention has at least the following beneficial effects: When the PEM electrolytic water hydrogen production module transformed by this method is connected to the target energy system, it can operate autonomously on both the active power-frequency and reactive power-voltage output aspects at each time scale, and actively manage the power quality of the power grid. It boosts the application of the PEM electrolytic water hydrogen production device, further alleviates the volatility and randomness of the renewable energy system in the future integrated energy application scenario, and provides more green hydrogen resources. It reduces the standby capacity and cost of the equipment in the energy storage and grid connection parts of the integrated energy system.

[0016] According to some embodiments of the present invention, in the step of combining the PWM three-phase converter with load virtual synchronous control function and the PEM hydrogen production device, the electrolytic water hydrogen production module can simulate the internal electromagnetic conversion mechanism and external operating characteristics of a synchronous generator, so that the PEM hydrogen production device block has an inertia mechanism.

[0017] According to some embodiments of the present invention, the high-frequency PWM rectifier circuit includes an AC interface and a DC interface, where:

[0018] The AC interface adopts an H-bridge AC / DC rectifier circuit to rectify the grid voltage into a DC voltage of 600V;

[0019] The DC interface adopts an isolated DC / DC converter to convert the 600V DC voltage into the DC voltage required by the PEM electrolytic cell.

[0020] According to some embodiments of the present invention, the torque control is a cascaded frequency-torque double closed-loop structure, which consists of an inner frequency loop and an outer torque loop.

[0021] According to some embodiments of the present invention, the reactive power control adopts a double closed-loop control structure, which consists of an outer power loop and an inner current loop.

[0022] According to the embodiments of the second aspect of the present invention, a virtual synchronous PEM electrolytic water hydrogen production module control device is characterized by including:

[0023] A virtual synchronous module that combines a PWM three-phase converter with load virtual synchronous control function and a PEM hydrogen production device;

[0024] A power adjustment module, and the PEM hydrogen production module that can apply virtual synchronous motor technology can sense the state of the power grid and automatically adjust the speed of absorbing power;

[0025] A wiring module that can be connected to the power supply system based on the high-frequency PWM rectifier circuit;

[0026] A frequency adjustment module that can adjust the target grid connection frequency based on autonomous active power frequency modulation control;

[0027] A torque control module capable of performing torque control based on the simulated rotor motion equation of a synchronous generator;

[0028] A voltage regulation module capable of regulating the amplitude of the target output voltage based on autonomous reactive voltage regulation control.

[0029] The virtual synchronous PEM electrolytic water hydrogen production module control device according to an embodiment of the present invention has at least the following beneficial effects: When the virtual synchronous PEM electrolytic water hydrogen production module is connected to the target energy system, it can operate autonomously in terms of both active - frequency and reactive - voltage output at various time scales, and actively manage the power quality of the power grid. And it restricts the volatility and randomness of the renewable energy system in future integrated energy application scenarios, while providing green hydrogen locally. It reduces the standby capacity and cost of the equipment in the energy storage and grid - connection parts of the integrated energy system, and at the same time reduces the hydrogen storage and transportation costs.

[0030] According to some embodiments of the present invention, the virtual synchronous module can enable the electrolytic water hydrogen production module to simulate the internal electromagnetic conversion mechanism and external operating characteristics of a synchronous generator, so that the PEM hydrogen production device block has an inertia mechanism.

[0031] According to some embodiments of the present invention, the high - frequency PWM rectifier circuit includes an AC interface and a DC interface, where:

[0032] The AC interface adopts an H - bridge AC / DC rectifier circuit for rectifying the grid voltage into a DC voltage of 600V;

[0033] The DC interface adopts an isolated DC / DC converter for converting the 600V DC voltage into the DC voltage required by the PEM electrolytic cell.

[0034] According to some embodiments of the present invention, the torque control is a cascaded frequency - torque double - closed - loop structure, composed of a frequency inner loop and a torque outer loop.

[0035] According to some embodiments of the present invention, the reactive power control adopts a double - closed - loop control structure, composed of a power outer loop and a current inner loop.

[0036] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0037] The above - mentioned and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0038] Figure 1 It is a schematic diagram of the steps of the virtual synchronous PEM electrolytic water hydrogen production module control method according to an embodiment of the present invention;

[0039] Figure 2 This is the grid - connection control structure diagram of the virtual - synchronous PEM electrolytic water hydrogen production module according to the embodiment of the present invention;

[0040] Figure 3 This is the main circuit diagram for supplying power to the electrolyzer of the virtual - synchronous PEM electrolytic water hydrogen production module according to the embodiment of the present invention;

[0041] Figure 4 This is the control schematic diagram of the virtual - synchronous PEM hydrogen production module according to the embodiment of the present invention;

[0042] Figure 5 This is the schematic diagram of the voltage - current double - closed - loop control structure according to the embodiment of the present invention;

[0043] Figure 6 This is the voltage rotating vector diagram according to the embodiment of the present invention;

[0044] Figure 7 This is the schematic diagram of the structure of the frequency - phase synchronization controller according to the embodiment of the present invention;

[0045] Figure 8 This is the schematic diagram of the structure of the amplitude - synchronization controller according to the embodiment of the present invention;

[0046] Figure 9 This is the schematic diagram of the primary voltage regulation curve of the synchronous generator according to the embodiment of the present invention;

[0047] Figure 10 This is the schematic diagram of the reactive power loop control structure provided by the embodiment of the present invention;

[0048] Figure 11 This is the schematic diagram of the structure block diagram of the control device of the virtual - synchronous PEM electrolytic water hydrogen production module according to the embodiment of the present invention. Detailed implementation manners

[0049] The following details the embodiments of the present invention. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0050] In the description of the present invention, the meaning of several is one or more, the meaning of multiple is more than two, greater than, less than, exceeding, etc. are understood not to include the present number, and above, below, within, etc. are understood to include the present number. If there is a description of first and second, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0051] The present invention proposes a control method for a virtual synchronous PEM electrolytic water hydrogen production module. Referring to Figure 1 , this method at least includes the following steps:

[0052] Step S100: Connect a PWM three-phase converter with load virtual synchronous control function to the PEM hydrogen production device.

[0053] In the existing PEM hydrogen production device, a PWM three-phase converter with load virtual synchronous control function is incorporated for control, enabling it to simulate the internal electromagnetic conversion mechanism and external operating characteristics of a synchronous generator, so that the PEM hydrogen production device block has an inertia mechanism.

[0054] Step S200: Enable the PEM hydrogen production module to sense the state of the power grid and automatically adjust the speed of absorbing power.

[0055] Referring to Figure 2 , the PEM hydrogen production module applying virtual synchronous motor technology can sense the state of the power grid and collect the frequency and voltage information of the connected power grid in real time. The main circuit is the same as that of a traditional PWM rectifier, consisting of a three-phase bridge circuit and an L filter, which mainly includes a voltage source converter, a filter inductor, a DC filter, an AC filter, etc.

[0056] Step S300: Connect to the power supply system based on a high-frequency PWM rectifier circuit.

[0057] The circuit is a high-frequency isolated PWM rectifier circuit. The PWM rectifier circuit includes an AC interface and a DC interface. The AC interface uses an H-bridge AC / DC rectifier circuit to rectify the grid voltage into a DC voltage of 600V; the DC interface uses an isolated DC / DC converter to convert the 600V DC voltage into the DC voltage required by the PEM electrolytic cell.

[0058] Referring to Figure 3 , the front stage of the main circuit for supplying power to the electrolytic cell of the virtual synchronous PEM electrolytic water hydrogen production module is PWM rectification, and the rear stage is an isolated DC / DC circuit, finally supplying power to the electrolytic cell.

[0059] Step S400: Perform torque control by simulating the rotor motion equation of a synchronous generator.

[0060] Adopt autonomous active frequency modulation control, perform torque control by simulating the "rotor motion equation of a synchronous generator". The active power control is a cascaded frequency–torque double closed-loop structure, consisting of a frequency inner loop and a torque outer loop.

[0061] Step S500: Adjust the amplitude of the target output voltage based on autonomous reactive power voltage regulation control.

[0062] Adopt independent reactive power voltage regulation control to adjust the amplitude of the target output voltage. The reactive power control adopts a double-closed-loop control structure, which consists of a power outer loop and a current inner loop.

[0063] Take the example of using electrolytic water to produce hydrogen under the condition of a highway energy network including a photovoltaic power generation system. Referring to the refueling situation required by fuel cell vehicles, a 250kW virtual synchronous PEM electrolytic water hydrogen production system of this patent can be configured.

[0064] Furthermore, in order to describe the purpose of this application in more detail, this application provides a Figure 4 The control structure diagram of the load virtual synchronous machine, its control is mainly divided into five parts: DC side voltage loop, rotor motion equation (active power loop), reactive power loop, electromagnetic equation and current inner loop control.

[0065] (1) DC side voltage loop control

[0066] The DC side voltage passes through PI control to obtain the given value of the DC current, and then multiplies it by the opposite number of the voltage given value to obtain the given value of the active power P set :

[0067] P set =-U dc * (U dc * -U dc (K p +K i / s) (1)

[0068] In the formula, U dc * is the reference value of the DC side voltage; U dc is the DC side voltage; K p and K i are the proportional and integral coefficients of the PI controller respectively.

[0069] The load virtual synchronous machine control method directly controls the output voltage and frequency through the active power control loop and the reactive power control loop, realizing the unification of off-grid and grid-connected control methods. This quasi-power control method is simple and easy to implement, but to a certain extent, it loses the control of the machine-side voltage and current of the load virtual synchronous machine, and cannot reflect the fast and accurate characteristics of power electronic control. Therefore, in order to quickly and accurately control the voltage and current of the system and improve the dynamic characteristics of the system, this section integrates the control characteristics of the load virtual synchronous generator and further cascades the voltage and current double-closed-loop control on the basis of the power loop of the load virtual synchronous machine.

[0070] The control block diagram of the voltage and current double-closed-loop in the synchronous dq rotating coordinate system is as Figure 5As shown, the amplitude of the reactive loop output voltage is used as the reference command value of the voltage outer loop, which is compared with the feedback capacitor voltage value. After PI regulation, the deviation is output as the reference command value of the current inner loop. This command value is compared with the feedback inductor current value and then passes through a proportional link to generate a voltage modulation wave signal. Finally, through modulation, a PWM signal is generated to drive the on and off of the switching tube. Through the abc-dq coordinate transformation combined with the PI regulator, the zero-error regulation of the AC system is realized, and the cross decoupling of the d-axis and q-axis electrical quantities is realized through the coupling term feedback.

[0071] (2) Rotor motion equation (active loop control)

[0072] The active loop output of the load virtual synchronous machine is the frequency of the rectifier modulation wave. The number of pole pairs of the virtual synchronous machine is set to 1, and generally the second-order model of the synchronous motor is used to simulate the rotor inertia and damping factor. The torque equation of the synchronous motor, that is, the rotor motion equation, can be expressed as:

[0073]

[0074] where: θ is the power angle of the generator, rad; ω is the mechanical angular velocity, which is also the electrical angular velocity of the synchronous motor, rad / s; ω n is the grid synchronous angular velocity, rad / s; J is the moment of inertia of the synchronous motor, kg·m2; T e , T m and T d are the electromagnetic torque, mechanical torque and damping torque of the synchronous motor respectively, N·m; the electromagnetic torque of the motor can be obtained from the electromagnetic power, that is, T e ≈P e / ω n ; D p is the damping coefficient of the virtual synchronous motor, N·m / s / rad. Due to the existence of the constants J and D p , the load virtual synchronous machine shows the ability of mechanical inertia and damping power oscillation during the grid voltage / frequency disturbance and load switching process.

[0075] From equation (2), we can get

[0076] θ = (P ref - P e + D p ω n ) / s / (Js + D p ) (3)

[0077] In the formula, θ is the power angle of the generator, rad / s; J is the moment of inertia of the synchronous motor, kg·m2; p ref is the control output of the PI regulator of the DC bus voltage; D p is the damping coefficient of the virtual synchronous motor, Nm / s / rad; ωn is the synchronous angular velocity of the power grid, in rad / s.

[0078] By adjusting the mechanical torque T of the virtual synchronous machine m , the adjustment of the active power command in the AC interface is realized; T m consists of two parts: the rated torque command T0 and the frequency deviation feedback command ΔT, where T0 is expressed as:

[0079] T0 = P ref / ω (4)

[0080] where, P ref is the active power command of the grid-connected inverter. In the charge and discharge circuit, P ref is the control output of the PI regulator of the DC bus voltage; the adjustment of the frequency response is realized through a virtual frequency modulation unit, and the virtual frequency modulation unit is taken as a proportional link, that is, the mechanical torque deviation command ΔT is expressed as:

[0081] ΔT = k f (f - f0) (5)

[0082] where, f is the frequency of the terminal voltage of the virtual synchronous machine, f0 is the rated frequency of the power grid, and k f is the frequency response coefficient, which is a constant negative number.

[0083] The current given value obtained by PI controlling the DC side voltage is multiplied by the voltage given value to obtain the T of the active power e given value:

[0084]

[0085] In the formula, U abcref is the given value of the DC side voltage; U dc * is the reference value of the DC side voltage; U dc is the DC side voltage; K p and K i are the proportional and integral coefficients of the PI controller respectively.

[0086] According to the instantaneous power calculation formula, it can be known that

[0087]

[0088] First, consider the synchronous control of frequency and phase. Since phase and frequency can be converted into each other through integration and differentiation, it can be considered to realize the synchronization of the inverter frequency and phase in one controller. Figure 6 The figure shows the frequency and phase relationship diagram between the grid voltage vector and the output voltage vector of the load virtual synchronous machine. Among them, the grid voltage rotates at the angular frequency ω g , and the phase is The output voltage of the load virtual synchronous machine rotates at angular frequency ω with a phase of θ. Taking the grid voltage vector as the d-axis and ω g as the rotational angular velocity to establish a synchronous rotating coordinate system, the phase difference between the output voltage of the load virtual synchronous machine and the grid voltage is Δθ. It can be seen from Figure 6 that the component of the output voltage vector of the load virtual synchronous machine on the d-axis is V d , which is consistent with the grid voltage in terms of frequency and phase and rotates synchronously. Then the asynchronous quantity between the load virtual synchronous machine and the grid voltage is manifested as the q-axis component V q . If V q can be controlled to decrease to zero, the voltage of the load virtual synchronous machine can track the grid voltage vector and maintain synchronous operation. Therefore, a frequency and phase synchronization controller can be designed starting from controlling the q-axis component.

[0089] Figure 6 As shown, this is the frequency and phase synchronization controller used in this paper. The voltage vectors of the grid and the load virtual synchronous machine rotate at their respective speeds. To control the output voltage vector of the boost inverter, it is first necessary to lock the phase of the grid voltage. Using a typical software phase-locked loop SPLL in a two-phase synchronous rotating coordinate system, the grid voltages V ga , V gb , V gc obtain the dq component values in the rotating coordinate system through CLARK transformation and PARK transformation. After subtracting the q-axis component V gq from the reference value 0 and passing through PI regulation, the corrected value of the angular frequency ω is obtained. After adding it to the reference value ω n (usually taking the rated value), the grid angular frequency is obtained. After integration, the grid phase angle value is obtained, and then after sine and cosine calculations, it participates in the PARK transformation calculation. This is the calculation process of a typical phase-locked loop. For the output voltage U ca , U cb , U cc of the load virtual synchronous machine, after PARK transformation with the grid phase angle value calculated by the phase-locked loop as the angle reference, the dq component values U cgd , U cgq in the grid rotating coordinate system are obtained. Due to the phase difference with the grid voltage, the calculated q-axis component is not 0, and this value reflects the frequency and phase difference between the microgrid voltage and the grid voltage. When the q-axis component is 0, on the voltage vector diagram, both the microgrid voltage and the grid voltage are on the d-axis and coincide, with a phase difference of 0. Therefore, after subtracting the q-axis component U cgq from the reference value 0 and passing through PI regulation, the compensation amount ω comp of the angular frequency can be obtained. Adding it to the output angular frequency ω of the active control loop can adjust the frequency and phase of the inverter output voltage, and finally track the grid voltage to achieve synchronization of the frequency and phase with the grid.

[0090] As Figure 7 shown, the main idea of the frequency-phase synchronization controller is to calculate the frequency compensation amount required for the terminal voltage of the load virtual synchronous machine to track the grid voltage. It obtains the frequency correction amount through phase-locking and PI regulation, involving two variables of frequency and phase, and there are many conversion links. The adjustment amount required for the amplitude synchronization controller is only one for the voltage amplitude, and the control can be relatively simplified.

[0091] Figure 8 is the synchronization controller for the voltage amplitude. Compared with the frequency-phase synchronization, the synchronization structure of the amplitude is relatively simple. Compared with Figure 2-11 , when synchronizing, the reference voltage amplitude is changed from to the grid voltage amplitude At the same time, since the primary voltage regulation is equivalent to a proportional link and is a kind of regulated with error, it cannot accumulate the error. In order to achieve the error-free tracking of the rectifier output voltage to the grid voltage, an integral link K i / s (K i is the integral coefficient) is added, and together with the droop link D q constitutes a PI regulator to calculate the reactive power correction amount ΔQ, participate in the control of the reactive power loop, and change the output voltage command value to make the rectifier output voltage amplitude synchronized with the grid.

[0092] When the synchronization effects of the frequency-phase and voltage amplitude reach the accuracy requirements, the switch can be closed to make the inverter smoothly connected to the grid. It is worth mentioning that when the synchronization is successfully connected to the grid, the synchronization controller should be removed, and the frequency reference value and voltage amplitude reference value should be restored to the locally manually set values, and the control structure of the load virtual synchronous machine should be restored to make the load virtual synchronous machine simulate a synchronous generator and automatically adjust the output power according to the deviation between the local voltage and the grid voltage situation to participate in the regulation of the grid.

[0093] (3) Reactive power loop control

[0094] The control strategy of the load virtual synchronous motor is as follows: after obtaining the virtual synchronous motor transient electromotive force E p and the power angle δ (or the mechanical angle θ of the rotor) of the virtual synchronous motor in active power regulation, reactive power regulation, mechanical equation and electromagnetic equation, on the basis of obtaining the electromotive force voltage e abc , the command value of the three-phase output current of the grid is obtained, and then under the action of the proportional resonance control strategy, it is ensured that the actual grid-connected three-phase output current i abc tracks its command value i refabc .

[0095] The reactive power loop mainly simulates the reactive power-voltage droop characteristic of the virtual synchronous machine to obtain the voltage amplitude:

[0096] Es =(Q set +D u (U ref -U n )-Q e ) / K q s+E0(8)

[0097] Then, according to the output E of the reactive power loop s and the θ obtained from the active power loop, the three-phase modulation waves e am , e bm and e cm have the following expressions:

[0098]

[0099] In the formula: e abc is the virtual synchronous machine electromotive force, that is, the three phases on the AC side of the converter; u abc is the terminal voltage of the synchronous machine, that is, the three-phase voltage at the PCC point, analogous to the synchronous machine terminal voltage; E m is the effective value of the load virtual synchronous machine electromotive force.

[0100] Due to the voltage division effect of the synchronous reactance and resistance, when the output current increases, the output voltage of the synchronous generator will decrease. The synchronous generator controls the transient electromotive force by changing the magnitude of the excitation current to maintain the stability of the output voltage. In the topology of the rectifier, the stability of the capacitor voltage can be maintained by controlling the magnitude of the output voltage at the midpoint of the bridge arm, simulating the excitation control function of the synchronous generator.

[0101] The synchronous generator excitation controller controls the current quantity, while in the inverter, the equivalent control is the voltage quantity. Therefore, by simulating the synchronous generator excitation current control method, the control equation of the inverter bridge arm midpoint voltage can be obtained as follows:

[0102]

[0103] Among them: E is the effective value of the output phase voltage of the inverter bridge arm, U ref is the effective value of the converter capacitor reference voltage, U o is the effective value of the actual capacitor voltage, and G(s) is the transfer function of the power control regulator. Comparing with the active control loop, the excitation control link can be analogized to the inertia integral link in the active loop. At the same time, in order to achieve zero-error regulation, G(s) is selected as a PI controller.

[0104] Similarly, the primary voltage regulation equation of the synchronous generator is as follows:

[0105]

[0106] Among them: Q eis the reactive power actually output by the synchronous generator, Q set is the set reactive power given value, D u is the reactive power-voltage droop coefficient, U n is the rated effective value of the output voltage. Combining equations (10) and (11), we can eliminate the common quantity U ref After sorting out, the reactive power-voltage control equation combining primary voltage regulation and excitation control can be obtained:

[0107]

[0108] Considering the similarity with the active power control loop structure, the reactive power droop coefficient is combined with the excitation regulator transfer function, and D u / G(s)=Ks, then equation (12) can be written as:

[0109]

[0110] Among them, U0 is the effective value of the output voltage, U n is the rated voltage effective value. set is the reactive power given, Q e is the actual reactive power output by the rectifier, D u is the droop coefficient, and the grid voltage variation is introduced to give the grid voltage amplitude reference through the droop mechanism. G(s) is the regulator of the excitation controller, which is selected as an integral regulator.

[0111] Compared with equation (2-23), K can be equivalent to the inertia coefficient of the reactive power-voltage control loop. According to equation (13), the load virtual synchronous machine reactive power loop control structure can be designed as follows: Figure 10 shown.

[0112] For the droop coefficient D q The selection of , considers the two stable states before and after the voltage amplitude and reactive power change. During stable operation, Q set with U n is a fixed value, then according to formula (13), D can be calculated by taking the difference between the previous and next stable states. u :

[0113]

[0114] According to formula (14), the droop coefficient D can be designed according to the reactive power demand corresponding to the voltage amplitude change. u For the reactive inertia coefficient K, its role in the control loop is reflected as the adjustment rate of the output voltage command under the action of the primary voltage regulation link, which can be selected according to the actual voltage change speed requirements. Similar to the active control loop, the calculation of reactive power can be obtained through instantaneous power theory calculation:

[0115] Q e = 1.5(v d i q - v q i d )(15)

[0116] Compared with the primary voltage regulation of traditional droop control, the reactive power loop control of the load virtual synchronous machine takes into account the electromagnetic transient characteristics of the synchronous generator and simulates the excitation regulation function. The introduction of the inertia link helps the voltage to smoothly fluctuate and transition to a new steady state. The inertia parameter K q is flexibly variable and can adapt to the control requirements of different power levels and regulation speeds. The output value of the reactive power loop is used as the command value of the amplitude of the voltage modulation wave to participate in the subsequent control calculation.

[0117] Combining the phase angle value θ obtained from the active power control loop calculation and the voltage value obtained from the reactive power loop calculation, three-phase voltage modulation waves E a 、E b 、E c can be generated, as shown in Equation (16):

[0118]

[0119] (4) Electromagnetic equations:

[0120] According to the generator convention, the electromagnetic equations of the synchronous machine can be expressed as:

[0121] i abc = (e abc - u abc ) / (Ls + R) (17)

[0122] In the formula, i abc is the output current of the virtual synchronous machine, that is, the three-phase AC side current; in the formula, L is the stator inductance of the synchronous machine, that is, the filtering inductance of the AC interface; R is the resistance of the synchronous machine, that is, the parasitic resistance of the AC interface filter.

[0123] According to Kirchhoff's principle, the electromagnetic equations of the load virtual synchronous machine are expressed as:

[0124]

[0125] The synchronous machine adjusts its reactive power output and terminal voltage through the excitation controller. Similarly, the terminal voltage and reactive power of the virtual synchronous machine can be adjusted by adjusting the virtual electromotive force E p of the virtual synchronous machine model. The virtual electromotive force command E p of the virtual synchronous machine includes: the no-load electromotive force E0 of the machine, the electromotive force ΔE Q reflecting the reactive power regulation, and the electromotive force ΔE U。

[0126] Partial electromotive force ΔE for reactive power regulation Q Expressed as:

[0127] ΔE Q = k q (Q ref - Q) (19)

[0128] where k q is the reactive power regulation coefficient, ΔE Q is the reactive power command of the AC interface, Q is the instantaneous reactive power output at the machine terminal of the AC interface, and Q is expressed as:

[0129]

[0130] where: u a 、u b and u c are the three-phase machine terminal voltages of the load virtual synchronous machine respectively;

[0131] Partial electromotive force ΔE for machine terminal voltage regulation U , ΔE U is equivalent to the automatic voltage regulator (AVR) of the load virtual synchronous machine. The automatic voltage regulator is simplified to a proportional link, then ΔE U is expressed as:

[0132] ΔE U = k v (U ref - U) (21)

[0133] where U ref and U are the command value and the true value of the effective value of the machine terminal line voltage respectively, and k v is the voltage regulation coefficient;

[0134] The electromotive force of the virtual synchronous machine is:

[0135] E p = E0 + ΔE Q + ΔE U (22)

[0136] (5) Current inner loop control

[0137] The reference value i abcref of the output current of the virtual synchronous machine can be obtained from the electromagnetic equation. Under the action of the PR controller, three-phase modulation signals are obtained, thereby controlling the on-off of the switching tubes of the inverter. The actual value of the grid-connected current quickly and accurately tracks the given value, which can effectively reduce the harmonic current of the grid interaction current.

[0138] According to Kirchhoff's law, the mathematical model of a single-side converter station in a three-phase static coordinate system can be obtained:

[0139]

[0140]

[0141] In the formula: L is the stator inductance of the synchronous motor, that is, the filtering inductance of the AC interface; R is the resistance of the synchronous motor, that is, the parasitic resistance of the AC interface filter; i abc is the output current of the virtual synchronous machine, that is, the three-phase AC side current; u abc is the terminal voltage of the synchronous motor, that is, the three-phase voltage at the PCC point; e abc is the electromotive force of the virtual synchronous motor, that is, the three-phase voltage on the AC side of the converter; C dc is the DC side filtering capacitor; U dc is the DC side voltage; I dc is the current flowing into the converter; I L is the load current.

[0142] When the loss of the commutation reactor is ignored and the power grid connected to the rectifier is regarded as an infinite system, the active power P and reactive power Q transmitted between the AC power grid and the rectifier are respectively

[0143]

[0144] In the formula: U G is the effective value of the phase voltage of the AC power grid; E is the effective value of the phase voltage on the AC side of the converter; δ is the phase difference between U G and E; X is the sum of the impedances between the converter station and the AC system.

[0145] It can be seen from formula (25) that the active power mainly depends on the phase angle difference δ between U G and E, while the reactive power mainly depends on the converter voltage amplitude E. Therefore, it can be regarded as a synchronous motor. Changing the phase angle difference between the internal electromotive force of the synchronous motor and the grid voltage can change the active power injected into the network. Adjusting the excitation of the synchronous motor and changing the magnitude of the motor terminal voltage will affect the transmission of reactive power.

[0146] Another embodiment of the present application provides a virtual synchronous PEM electrolytic water hydrogen production module control device, as Figure 11 shown. The device 20 includes: a virtual synchronous module 201, a power adjustment module 202, a wiring module 203, a torque control module 204, and a voltage regulation module 205.

[0147] The virtual synchronous module 201 connects the PWM three-phase converter with load virtual synchronous control function to the PEM hydrogen production device;

[0148] The power adjustment module 202, and the PEM hydrogen production module capable of applying the virtual synchronous motor technology can sense the state of the power grid and automatically adjust the speed of absorbing power.

[0149] The wiring module 203 can be connected to the power supply system based on the high-frequency PWM rectifier circuit.

[0150] The torque control module 204 can perform torque control based on the analog synchronous generator rotor motion equation.

[0151] The voltage regulation module 205 can adjust the amplitude of the target output voltage based on autonomous reactive voltage regulation control.

[0152] When the virtual synchronous PEM electrolytic water hydrogen production module of the embodiment of the present application is connected to the target energy system, it can operate autonomously on both the active - frequency and reactive - voltage output aspects at each time scale, and actively manage the power quality of the power grid. And it restricts the volatility and randomness of the renewable energy system in the future integrated energy application scenario, while providing green hydrogen locally. It reduces the standby capacity and cost of the equipment in the energy storage and grid - connection parts of the integrated energy system, and at the same time reduces the hydrogen storage and transportation costs.

[0153] Furthermore, the virtual synchronous module can enable the electrolytic water hydrogen production module to simulate the internal electromagnetic conversion mechanism and external operating characteristics of a synchronous generator, so that the PEM hydrogen production device block has an inertia mechanism.

[0154] Furthermore, the high - frequency PWM rectifier circuit includes an AC interface and a DC interface, where:

[0155] The AC interface uses an H - bridge AC / DC rectifier circuit to rectify the grid voltage into a DC voltage of 600V.

[0156] The DC interface uses an isolated DC / DC converter to convert the 600V DC voltage into the DC voltage required by the PEM electrolytic cell.

[0157] Furthermore, the torque control is a cascaded frequency - torque double - closed - loop structure, composed of a frequency inner loop and a torque outer loop.

[0158] Furthermore, the reactive power control adopts a double - closed - loop control structure, composed of a power outer loop and a current inner loop.

[0159] The above has described the embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above - mentioned embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge scope of those of ordinary skill in the art.

Claims

1. A control method for a virtual synchronous PEM electrolytic water hydrogen production module, characterized in that: A PWM three-phase converter with load virtual synchronous control function is combined with a PEM hydrogen production device; The PEM hydrogen production device can sense the state of the power grid and automatically adjust the absorbed power; Based on a high-frequency PWM rectifier circuit connected to the power supply system; Based on autonomous active frequency modulation control, the grid connection frequency is adjusted; Based on autonomous reactive voltage regulation control, the amplitude of the output voltage is adjusted.

2. The method according to claim 1, characterized in that In the step of connecting the PWM three-phase converter with load virtual synchronous control function to the PEM hydrogen production device, the electrolytic water hydrogen production module can simulate the internal electromagnetic conversion mechanism and external operating characteristics of a synchronous generator, so that the PEM hydrogen production device has an inertia mechanism and damping resources.

3. The method according to claim 1, wherein The high-frequency PWM rectifier circuit includes an AC interface and a DC interface, where: The AC interface uses an H-bridge AC / DC rectifier circuit to rectify the grid voltage into a DC voltage of 600V; The DC interface uses an isolated DC / DC converter to convert the 600V DC voltage into the DC voltage required by the PEM electrolytic cell.

4. The method according to claim 1, characterized in that, The autonomous active frequency modulation control is a cascaded frequency-torque double closed-loop structure, composed of a frequency inner loop and a torque outer loop.

5. The method according to claim 1, wherein The autonomous reactive voltage regulation control adopts a double closed-loop control structure, composed of a power outer loop and a current inner loop.

6. A control device for a virtual synchronous PEM electrolytic water hydrogen production module, characterized in that, It includes: A virtual synchronous module that can combine a PWM three-phase converter with load virtual synchronous control function with a PEM hydrogen production device; A power adjustment module that can make the PEM hydrogen production device sense the state of the power grid and automatically adjust the speed of the absorbed power; A wiring module that can be connected to the power supply system based on a high-frequency PWM rectifier circuit; A frequency regulation module that can adjust the grid connection frequency based on autonomous active frequency modulation control; A torque control module that can perform torque control based on the simulated synchronous generator rotor motion equation; A voltage regulation module that can adjust the amplitude of the output voltage based on autonomous reactive voltage regulation control.

7. The device according to claim 6, characterized in that, The virtual synchronous module can make the electrolytic water hydrogen production module simulate the internal electromagnetic conversion mechanism and external operating characteristics of a synchronous generator, so that the PEM hydrogen production device has an inertia mechanism and damping resources.

8. The device according to claim 6, characterized in that The high-frequency PWM rectifier circuit includes an AC interface and a DC interface, where: The AC interface uses an H-bridge AC / DC rectifier circuit to rectify the grid voltage into a DC voltage of 600V; The DC interface uses an isolated DC / DC converter to convert the 600V DC voltage into the DC voltage required by the PEM electrolytic cell.

9. The device according to claim 6, characterized in that, The autonomous active frequency modulation control is a cascaded frequency-torque double closed-loop structure, composed of a frequency inner loop and a torque outer loop.

10. The device according to claim 6, characterized in that, The autonomous reactive voltage regulation control adopts a double closed-loop control structure, composed of a power outer loop and a current inner loop.

Images