Two-stage high-frequency isolation inverter power supply adopting fixed modulation ratio control method

Abstract

The invention provides a two-stage high-frequency isolation inverter power supply adopting a fixed modulation ratio control method. The two-stage high-frequency isolation inverter power supply comprises a DC / DC conversion unit, a DC / AC inversion unit and a control unit, the DC / DC conversion unit receives the modulation signal, and modulates the input direct-current voltage of the input side into the output direct-current voltage of the output side according to the modulation signal; the DC / AC inverter unit is provided with an SVPWM with a fixed modulation ratio; the control unit samples the DC output voltage and the output AC voltage, and updates the modulation signal according to the output DC voltage and the output AC voltage. According to the invention, the DC / DC conversion unit is firstly subjected to voltage regulation, and then the DC / AC inversion unit adopts an SVPWM modulation strategy with a fixed modulation ratio, so that modulation waves of an SVPWM switch can be calculated only through judgment of a reference voltage angle, and then a switch action signal is generated, links of sector judgment, vector distribution and time distribution in traditional SVPWM modulation are omitted, the calculation amount is reduced, and the efficiency is improved. Switching frequency can be increased, and switching loss can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of energy storage and current conversion, and in particular to a two-stage high-frequency isolation inverter power supply adopting a fixed modulation ratio control method. Background Art

[0002] With the rapid development of economy and society, power energy storage technology has developed rapidly. Energy storage technology provides an effective solution to solve the problems of frequency and peak regulation of power grid, friendly access of renewable energy on the power generation side, peak shaving and valley filling on the user side, and maintaining stable operation of isolated grids. It is considered to be one of the most critical technologies for realizing a power system dominated by renewable energy.

[0003] The most popular energy storage method is electrochemical energy storage. The electrochemical energy storage system is mainly composed of battery packs, battery management system (BMS), energy management system (EMS), power storage converter (PCS) and other electrical equipment. The power storage converter (PCS) of battery energy storage is the unit that realizes the power exchange between energy storage batteries and the power grid, and is the key component that determines the electrochemical energy storage system.

[0004] At present, energy storage converters can be divided into two structures: single-stage and double-stage:

[0005] The topology of a single-stage energy storage converter consists of only one level of power electronic conversion device, i.e., an inverter. Its advantages are simple structure, simple control method, low loss, and high energy conversion efficiency. However, in practical applications, the capacity selection of single-stage isolated PCS energy storage units lacks flexibility and is easily limited by the number of parallel connections. Due to the battery voltage on the DC side of the energy storage unit, a transformer is required for step-up isolation to reach the voltage level on the AC side. When a short circuit occurs on the load side, a large current shock will occur on the PCS DC side, thus affecting the life of the battery pack. An industrial frequency transformer is required to achieve electrical isolation between the load side and the grid side, which is large in size, heavy in weight, and high in loss.

[0006] The topology of the two-stage energy storage converter generally sets a DC-DC converter before the inverter circuit to play a buck-boost conversion role. The advantage of this topology is that the voltage level of the AC side power grid can be achieved at the later stage. At the same time, the use of the later stage step-up transformer is reduced, and the capacity limit range on the battery side is increased. Compared with the single-stage inverter, the addition of a DC-DC converter makes the capacity configuration of the battery side more flexible, increases energy utilization, and reduces the cost of use. The use of a two-stage energy storage converter structure can greatly reduce the volume and weight of the required transformer and improve the power density of the device.

[0007] Therefore, from the perspective of power density, the isolated two-stage energy storage converter is a better solution, and how to improve its efficiency is of great significance.

[0008] The inverter circuit of the existing two-stage energy storage converter generally adopts SVPWM modulation to achieve the voltage regulation function. Traditional SVPWM modulation needs to complete the operations such as sector judgment, action time calculation, switch sequence generation, and PWM signal output within the calculation cycle, which will cause the application of traditional SVPWM modulation in two-stage energy storage converters to have problems such as long cycle and complex control.

[0009] Therefore, the technical problems existing in the prior art include complex inverter SVPWM modulation, long control cycle algorithm time, limited switching frequency increase, complex and long multi-level control cycle, and large size of the power frequency isolation transformer. Summary of the invention

[0010] In view of this, the first aspect of the present invention discloses a two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method, which includes a DC / DC conversion unit, a DC / AC inverter unit and a control unit;

[0011] The DC / DC conversion unit receives a modulation signal, and the DC / DC conversion unit modulates an input DC voltage at an input side into an output DC voltage at an output side according to the modulation signal;

[0012] The DC / AC inverter unit is configured with a SVPWM with a fixed modulation ratio, and the DC / AC inverter unit uses the SVPWM to modulate the output DC voltage on the input side to the output AC voltage on the output side;

[0013] The control unit samples the DC output voltage and the output AC voltage, and the control unit updates the modulation signal according to the output DC voltage and the output AC voltage.

[0014] In some embodiments of the present invention,

[0015] The DC / DC conversion unit includes a dual active bridge converter;

[0016] The input side of the dual active bridge converter receives the input DC voltage, the output side sends the output DC voltage, the control side receives the modulation signal, and the dual active bridge converter modulates the input DC voltage into the output DC voltage according to the modulation signal.

[0017] In some embodiments of the present invention,

[0018] The dual active bridge converter comprises an H-bridge circuit, an inductor L, a transformer T and an ANPC circuit;

[0019] The primary side of the transformer T is connected to the H-bridge circuit and the inductor L, and the secondary side is connected to the ANPC circuit.

[0020] In some embodiments of the present invention,

[0021] The H-bridge circuit includes switching devices Q11, Q12, Q13, and Q14;

[0022] The switch device Q11 and the switch device Q12 form a first bridge arm topology;

[0023] The switch device Q13 and the switch device Q14 form a second bridge arm topology;

[0024] The first bridge arm topology and the second bridge arm topology are respectively connected in parallel with a power supply;

[0025] Two ends of the primary side of the transformer T are respectively connected to the midpoint of the first bridge arm topology and the midpoint of the second bridge arm topology;

[0026] The inductor L is connected between a midpoint of the first bridge arm topology or the second bridge arm topology and a primary side coil of the transformer T.

[0027] In some embodiments of the present invention,

[0028] The ANPC circuit includes switch devices Q21, Q22, Q23, Q24, Q25, and Q26;

[0029] The switch device Q22 and the switch device Q23 form a third bridge arm topology;

[0030] The switch device Q25 and the switch device Q26 form a fourth bridge arm topology;

[0031] The third bridge arm topology is connected in parallel with the fourth bridge arm topology;

[0032] The first end of the third bridge arm topology is connected to one end of the DC bus through the switch device Q21, and the second end is connected to the other end of the DC bus through the switch device Q24;

[0033] Two ends of the secondary side of the transformer T are connected to the midpoint of the third bridge arm topology and the midpoint of the fourth bridge arm topology respectively.

[0034] In some embodiments of the present invention,

[0035] The DC / AC inverter unit includes an inverter with a two-level topology;

[0036] The inverter is configured with a SVPWM with a fixed modulation ratio, and the inverter uses SVPWM to modulate the output DC voltage into the output AC voltage.

[0037] In some embodiments of the present invention,

[0038] The inverter includes switching devices Q31, Q32, Q33, Q34, Q35, Q36;

[0039] The switch device Q31 and the switch device Q32 form a fifth bridge arm topology;

[0040] The switch device Q33 and the switch device Q34 form a sixth bridge arm topology;

[0041] The switch device Q35 and the switch device Q36 form a seventh bridge arm topology;

[0042] The fifth bridge arm topology, the sixth bridge arm topology, and the seventh bridge arm topology are connected in parallel to a DC bus;

[0043] Midpoints of the fifth bridge arm topology, the sixth bridge arm topology, and the seventh bridge arm topology are respectively connected to loads.

[0044] In some embodiments of the present invention,

[0045] The control unit transforms the output AC voltage into a measurement signal;

[0046] The control unit generates the modulation signal according to the output DC voltage and the measurement signal.

[0047] In some embodiments of the present invention,

[0048] The control unit includes a transformation module, a first error calculation module, a first modulation module, a second error calculation module and a second modulation module;

[0049] The conversion module samples the output DC voltage, and the conversion module converts the output DC voltage into the measurement signal;

[0050] The first error calculation module is configured with a reference signal, and the first error calculation module calculates a first error value between the measurement signal and the reference signal;

[0051] The first modulation module generates the measured DC voltage according to the first error value;

[0052] The second error calculation module calculates a second error value between the measured DC voltage and the output DC voltage;

[0053] The second modulation module generates the modulation signal according to the second error value.

[0054] In some embodiments of the present invention,

[0055] The conversion module is configured to dq transform the output DC voltage of the three phases into a measurement signal.

[0056] In some embodiments of the present invention,

[0057] The first modulation module generates the measured DC voltage by adopting a double closed-loop modulation of the inverter DC bus;

[0058] In some embodiments of the present invention,

[0059] The second modulation module generates the modulation signal by adopting DAB voltage regulation dual closed-loop modulation.

[0060] A second aspect of this embodiment discloses a power control method.

[0061] The power supply control method uses the power supply device, including:

[0062] The DC / DC conversion unit is driven by a modulation signal to modulate the input DC voltage at the input side to the output DC voltage at the output side;

[0063] The DC / AC inverter unit is driven by SVPWM with a fixed modulation ratio to modulate the output DC voltage on the input side to the output AC voltage on the output side;

[0064] The control unit is driven by the output DC voltage and the output AC voltage to update the modulation signal.

[0065] Compared with the prior art, the power supply device of the present invention adopts an SVPWM modulation strategy with a fixed modulation ratio, which can calculate the modulation wave of the SVPWM switch by judging the reference voltage angle, and then generate a switching action signal, thereby reducing the calculation time required for sector judgment, vector allocation and time allocation in traditional SVPWM modulation and increasing the switching frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0067] Figure 1 A topological schematic diagram showing a two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method of the present invention;

[0068] Figure 2 A circuit diagram of a dual active bridge converter according to the present invention is shown;

[0069] Figure 3 A circuit schematic diagram of the inverter of the present invention is shown;

[0070] Figure 4 A topological schematic diagram showing a control unit of the present invention;

[0071] Figure 5 A control principle diagram of a power supply device of the present invention is shown;

[0072] Figure 6 It shows that the reference vector of the power supply device of the present invention is in the trajectory of the first largest sector when M=0.8. DETAILED DESCRIPTION

[0073] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0074] Figure 1 The topological diagram of the double-stage high-frequency isolated inverter power supply adopting the fixed modulation ratio control method of the present invention is shown.

[0075] The two-stage high-frequency isolated inverter power supply adopting the fixed modulation ratio control method includes a DC / DC conversion unit, a DC / AC inverter unit and a control unit. The DC / DC conversion unit, as the front-stage topology of the power supply device, receives the input DC voltage Udc1 from the external DC bus and the modulation signal of the internal feedback, and modulates the input DC voltage Udc1 on the input side into the output DC voltage Udc2 on the output side according to the modulation signal.

[0076] Among them, the DC / AC inverter unit serves as the back-stage topology of the power supply device, receives the output DC voltage Udc1 from the DC / DC conversion unit, and uses a SVPWM with a fixed modulation ratio M to modulate the output DC voltage Udc2 on the input side into the output AC voltage (Ua, Ub, Uc) on the output side.

[0077] The control unit samples the DC output voltage and the output AC voltage, and updates the modulation signal according to feedback of the output DC voltage and the output AC voltage.

[0078] Furthermore, the DC / DC conversion unit of this embodiment has a dual active bridge converter.

[0079] The input side of the dual active bridge converter receives the input DC voltage, the output side sends the output DC voltage, the control side receives the modulation signal, and the dual active bridge converter modulates the input DC voltage into the output DC voltage according to the modulation signal.

[0080] Figure 2The circuit schematic diagram of the dual active bridge converter of this embodiment is shown.

[0081] Figure 2 The dual active bridge converter shown includes an H-bridge circuit B1, an inductor L, a transformer T and an ANPC circuit B2. The primary side of the transformer T is connected to the H-bridge circuit B1 and the inductor L, and the secondary side is connected to the ANPC circuit B2.

[0082] The H-bridge circuit includes switching devices (Q11, Q12, Q13, Q14).

[0083] The switch device Q11 and the switch device Q12 form a first bridge arm topology. The switch device Q13 and the switch device Q14 form a second bridge arm topology. The first bridge arm topology and the second bridge arm topology are respectively connected in parallel to the positive and negative poles of the DC input bus. The two ends of the primary side of the transformer T are respectively connected to the midpoint of the first bridge arm topology and the midpoint of the second bridge arm topology. The inductor L is connected between the midpoint a of the first bridge arm topology and the primary side coil of the transformer T. The midpoint b of the second bridge arm topology is respectively connected to the positive pole of the DC input bus through the capacitor C11 and connected to the negative pole of the DC input bus through the capacitor C12.

[0084] Preferably, the switch devices (Q11, Q12, Q13, Q14) are all SiIGBT switch devices.

[0085] Wherein, the ANPC circuit includes switch devices (Q21, Q22, Q23, Q24, Q25, Q26). The switch device Q22 and the switch device Q23 form a third bridge arm topology. The switch device Q25 and the switch device Q26 form a fourth bridge arm topology. The third bridge arm topology is connected in parallel with the fourth bridge arm topology. The first end of the third bridge arm topology is connected to the midpoint d of the fourth bridge arm topology through the switch device Q21, and the second end is connected to the midpoint d of the fourth bridge arm topology through the switch device Q24. The two ends of the secondary side of the transformer T are respectively connected to the midpoint c of the third bridge arm topology and the midpoint d of the fourth bridge arm topology.

[0086] Preferably, the switch devices (Q21, Q24, Q25, Q26) are all Si IGBT switch devices, and the switch devices (Q22, Q23) are all SiC MOSFET switch devices.

[0087] Furthermore, the DC / AC inverter unit in this embodiment includes a two-level topology inverter.

[0088] The inverter is configured with a SVPWM with a fixed modulation ratio, and the inverter uses SVPWM to modulate the output DC voltage into the output AC voltage.

[0089] Among them, the fixed modulation ratio of SVPWM usually means that during the SVPWM modulation process, the ratio of the effective value of the inverter's output voltage to the DC voltage remains unchanged, that is, the duty cycle, phase offset and modulation ratio remain fixed under certain conditions.

[0090] Figure 3 The circuit diagram of the inverter of this embodiment is shown.

[0091] Figure 3 The inverter is shown to include switch devices (Q31, Q32, Q33, Q34, Q35, Q36). The switch device Q31 and the switch device Q32 form a fifth bridge arm topology. The switch device Q33 and the switch device Q34 form a sixth bridge arm topology. The switch device Q35 and the switch device Q36 form a seventh bridge arm topology. The fifth bridge arm topology, the sixth bridge arm topology, and the seventh bridge arm topology are connected in parallel to a DC bus. The midpoints (a, b, c) of the fifth bridge arm topology, the sixth bridge arm topology, and the seventh bridge arm topology are respectively connected to a load.

[0092] Preferably, the midpoints (a, b, c) of the fifth bridge arm topology, the sixth bridge arm topology, and the seventh bridge arm topology are respectively connected to the load through LC filters.

[0093] Furthermore, the control unit of this embodiment modulates the dual active bridge converter and the inverter according to the output DC voltage and the output AC voltage.

[0094] Figure 4 A topological diagram of the control unit of this embodiment is shown.

[0095] Figure 4 The control unit is shown to include a transformation module, a first error calculation module, a first modulation module, a second error calculation module and a second modulation module.

[0096] The conversion module samples the output AC voltage (Ua, Ub, Uc), and the conversion module converts the output AC voltage (Ua, Ub, Uc) into the measurement signal (Ud, Uq).

[0097] Wherein, the first error calculation module is configured with a reference signal (Ud * , Uq * ), the first error calculation module calculates the error according to the measurement signal (Ud, Uq) and the reference signal (Ud * , Uq * ) generates a first error value.

[0098] The first modulation module implements a voltage regulation double closed-loop control of the inverter according to the first error value and represents the measured DC voltage Udc2 of the output control quantity.* .

[0099] The second error calculation module calculates the measured DC voltage Udc2 * And the output DC voltage Udc2 generates a second error value.

[0100] Among them, the second modulation module implements dual closed-loop voltage regulation control of the dual active bridge converter according to the second error value and outputs a modulation signal, and the modulation signal is used to phase-shift control the transformer ratio of the dual active bridge converter, thereby realizing the regulation of the output DC voltage Udc2.

[0101] Figure 5 A control principle diagram of the power supply device of this embodiment is shown.

[0102] Figure 5 The conversion module is shown as an abc / qd module, which is used for dq conversion of three-phase output DC voltage into a measurement signal. The first error calculation module and the second error calculation module are difference operation modules. The first modulation module is an inverter DC bus control module. The second modulation module is a DAB voltage regulation control module. The modulation signal is used to adjust the transformer ratio through the phase shift control module.

[0103] When the abc / qd module transforms the output AC voltage, the reference electrical angle w converts the output AC voltage into dq axis components.

[0104] The phase shift control module drives the tap switch to change the turns ratio of the transformer according to the modulation signal.

[0105] Based on this, compared with the prior art, the power supply device of this embodiment adopts a SVPWM modulation strategy with a fixed modulation ratio in the control of the inverter. The modulation wave of the SVPWM switch can be calculated by simply judging the reference voltage angle θ, and then the modulation wave can be compared with the carrier to generate a switch action signal, which reduces the calculation time required for sector judgment, vector allocation and time allocation in the existing SVPWM modulation, and increases the switching frequency. At the same time, the SVPWM modulation strategy with a fixed modulation ratio is adopted to achieve the voltage regulation control of the output voltage through the control of UDC2 by the DC / DC unit, and minimizes the voltage borne by the switching device of the inverter during the switching process, further reducing the switching loss and improving the efficiency of the converter.

[0106] Furthermore, each vector time is calculated according to the fixed modulation ratio of SVPWM, which can be obtained through the following table.

[0107]

[0108] Table 1 Action time of each vector

[0109]

[0110] Table 2SVPWM modulation wave

[0111] Wherein, when M>0.5, in the first large sector, θ is the angle of the reference voltage, and Ts is the switching period of the subsequent three-phase three-level inverter circuit.

[0112] For example, when 0<θ≤27.23, the reference vector is located in the 5th small sector. When 27.23<θ≤30., the reference vector is located in the 3rd small sector. When 30<θ≤32.77., the reference vector is located in the 4th small sector. When 32.77<θ≤60., the reference vector is located in the 6th small sector.

[0113] Then, for any given M, the data table of each vector action time of the synthetic reference vector can be directly generated from Table 1, so that the controller only needs to look up the table, and the real-time calculation complexity is greatly reduced. According to the vector action time, only the table can be looked up to obtain the duty cycle of each switch.

[0114] Therefore, compared with the prior art, the present invention reduces the device loss of the two-stage high-frequency isolated PCS, increases the conversion efficiency, improves the conversion efficiency (the conversion efficiency is increased by 1.8% to 2.4% through simulation analysis), reduces the control algorithm time, increases the switching frequency, eliminates the bulky power frequency transformer, and realizes the high efficiency and miniaturization of the battery energy storage system.

[0115] This embodiment discloses a power supply control method. The power supply control method applies the power supply control method device. The power supply control method includes: driving a DC / DC conversion unit to modulate an input DC voltage on an input side to an output DC voltage on an output side through a modulation signal; driving the DC / AC inverter unit to modulate the output DC voltage on an input side to an output AC voltage on an output side through SVPWM with a fixed modulation ratio; and driving the control unit to update the modulation signal through the output DC voltage and the output AC voltage.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A two-stage high-frequency isolated inverter power supply adopting a fixed modulation ratio control method, characterized in that: include: It includes a DC / DC conversion unit, a DC / AC inverter unit and a control unit; The DC / DC conversion unit receives a modulation signal, and the DC / DC conversion unit modulates an input DC voltage at an input side into an output DC voltage at an output side according to the modulation signal; The DC / AC inverter unit is configured with a SVPWM with a fixed modulation ratio, and the DC / AC inverter unit uses the SVPWM to modulate the output DC voltage on the input side to the output AC voltage on the output side; The control unit samples the DC output voltage and the output AC voltage, and the control unit updates the modulation signal according to the output DC voltage and the output AC voltage.

2. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 1 is characterized in that: The DC / DC conversion unit includes a dual active bridge converter; The input side of the dual active bridge converter receives the input DC voltage, the output side sends the output DC voltage, the control side receives the modulation signal, and the dual active bridge converter modulates the input DC voltage into the output DC voltage according to the modulation signal.

3. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 2, characterized in that: The dual active bridge converter comprises an H-bridge circuit, an inductor (L), a transformer (T) and an ANPC circuit; The transformer (T) has a primary side connected to the H-bridge circuit and the inductor (L), and a secondary side connected to the ANPC circuit.

4. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 3 is characterized in that: The H-bridge circuit includes switching devices (Q11, Q12, Q13, Q14); The switch device (Q11) and the switch device (Q12) form a first bridge arm topology; The switch device (Q13) and the switch device (Q14) form a second bridge arm topology; The first bridge arm topology and the second bridge arm topology are respectively connected in parallel with a power supply; Two ends of the primary side of the transformer (T) are respectively connected to the midpoint of the first bridge arm topology and the midpoint of the second bridge arm topology; The inductor (L) is connected between a midpoint of the first bridge arm topology or the second bridge arm topology and a primary side coil of the transformer (T).

5. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 3, characterized in that: The ANPC circuit includes switch devices (Q21, Q22, Q23, Q24, Q25, Q26); The switch device (Q22) and the switch device (Q23) form a third bridge arm topology; The switch device (Q25) and the switch device (Q26) form a fourth bridge arm topology; The third bridge arm topology is connected in parallel with the fourth bridge arm topology; The first end of the third bridge arm topology is connected to one end of the DC bus through the switch device (Q21), and the second end is connected to the other end of the DC bus through the switch device (Q24); Two ends of the secondary side of the transformer (T) are respectively connected to the midpoint of the third bridge arm topology and the midpoint of the fourth bridge arm topology.

6. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 3, characterized in that: The DC / AC inverter unit includes an inverter with a two-level topology; The inverter is configured with a SVPWM with a fixed modulation ratio, and the inverter uses SVPWM to modulate the output DC voltage into the output AC voltage.

7. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 6, characterized in that: The inverter includes switching devices (Q31, Q32, Q33, Q34, Q35, Q36); The switch device (Q31) and the switch device (Q32) form a fifth bridge arm topology; The switch device (Q33) and the switch device (Q34) form a sixth bridge arm topology; The switch device (Q35) and the switch device (Q36) form a seventh bridge arm topology; The fifth bridge arm topology, the sixth bridge arm topology, and the seventh bridge arm topology are connected in parallel to a DC bus; Midpoints of the fifth bridge arm topology, the sixth bridge arm topology, and the seventh bridge arm topology are respectively connected to three-phase loads.

8. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 1, characterized in that: The control unit includes a transformation module, a first error calculation module, a first modulation module, a second error calculation module and a second modulation module; The conversion module samples the output DC voltage, and the conversion module converts the output DC voltage into the measurement signal; The first error calculation module is configured with a reference signal, and the first error calculation module calculates a first error value between the measurement signal and the reference signal; The first modulation module generates the measured DC voltage according to the first error value; The second error calculation module calculates a second error value between the measured DC voltage and the output DC voltage; The second modulation module generates the modulation signal according to the second error value.

9. The two-stage high-frequency isolated inverter power supply using a fixed modulation ratio control method according to claim 8, characterized in that: The conversion module is configured to dq transform the output DC voltage of the three phases into a measurement signal.

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