A control method for hybrid parallel integrated power supply

Abstract

The present invention discloses a control method for a hybrid parallel integrated power supply. Taking a current distribution ratio of 2:1 between a Si-based inverter and a SiC-based inverter as an example, the optimal power distribution ratio of the two inverters is obtained by reducing the power loss of the fundamental component on the Si-based inverter. Based on the fitting of the effective value of the harmonic current on the Si-based inverter, its optimal switching frequency and the relationship between the minimum harmonic current conduction loss and switching loss at this frequency are obtained. The zero-sequence component of the current is eliminated through the fast switching of the SiC inverter to suppress harmonics. The present invention provides a power distribution optimization method for the hybrid parallel integrated power supply topology that minimizes total power loss while ensuring a reasonable THD of the hybrid parallel integrated power supply topology.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply control, and in particular to a control method for a hybrid parallel integrated power supply. Background Art

[0002] As a core component of shore power system power conversion and system control, the inverter determines the stable, reliable, and efficient operation of the shore power system. Therefore, research on high-power, high-performance, and cost-effective integrated power supplies is urgent. Existing technologies have the limitations of single-device inverters, lack redundancy, and have weak scalability, making them unsuitable for existing diverse power systems. Secondly, existing technologies also use inverter power topologies composed of large-capacity Si-based inverters connected in parallel with small-capacity SiC-based inverters. Their scalability and redundancy have attracted widespread attention, but their power control calculation methods are insufficient to eliminate harmonic compensation control and optimize conduction losses.

[0003] After searching, publication number CN107834561A - A harmonic improvement method for an inverter of a power generation system discloses converting wind speed / light energy into the output power of the inverter, and then dividing the output power into several power level intervals according to the curve of total harmonic distortion (THD) changing with output power. Each power level interval corresponds to a switching frequency to make the THD lower than 5%. When the wind / photovoltaic power generation system is operating throughout the year, a corresponding switching frequency is used according to the power level interval where the output power is located to adapt to the changing output power and achieve the purpose of improving harmonics; however, it does not have the redundancy advantage, has poor scalability, and has limited high harmonic suppression capability. The power quality provided is still not enough to meet high standards, and is not suitable for complex and diverse power supply systems. Summary of the Invention

[0004] To address the scientific challenge of the immature power distribution scheme for topological hybrid parallel integrated power supplies, the present invention designs a control method for topological hybrid parallel integrated power supplies. When the current ratio of the Si-based inverter to the SiC-based inverter in the hybrid parallel integrated power supply is 2:1, the load current distribution is optimized with the goal of minimizing power loss, thereby achieving a compromise between the impact of the Si-based inverter switching frequency on device losses and the total THD of the load current, and optimizing its PWM frequency selection. To achieve the above objectives, the present invention provides the following technical solution: a control method for a hybrid parallel integrated power supply, comprising the following steps:

[0005] Step S1, connecting a Si-based inverter and a SiC-based inverter in parallel on a DC bus;

[0006] Step S2, setting two proportional-integral controllers in the dq coordinate system, respectively used to control the Si-based inverter and the SiC-based inverter;

[0007] Step S3, setting a proportional harmonic compensation controller for the SiC-based inverter in the abc coordinate system, for calculating the minimum value of harmonic distortion in the output load current of the Si-based inverter;

[0008] Step S4, minimizing the conduction loss of the fundamental current in the Si-based inverter and the SiC-based inverter by using a novel current distribution method;

[0009] Step S5 , calculating the optimal frequency value of the PWM wave according to the conduction loss caused by the harmonics of the PWM wave at different frequencies and the switching loss of the Si-based inverter.

[0010] Preferably, the proportional-integral controller for controlling the Si-based inverter processes the base power in the range of 1-10 kHz.

[0011] Preferably, the proportional-integral controller controlling the SiC-based inverter processes part of the power in a range above 10 kHz.

[0012] Preferably, the proportional harmonic compensation controller is used to calculate the values ​​of the fundamental current and fundamental operating frequency of the SiC-based inverter.

[0013] Preferably, the proportional-integral controller suppresses harmonics by controlling the fast switching of the SiC inverter, thereby eliminating the zero-sequence component caused by the circulating current.

[0014] Preferably, in step S4, the method for calculating the minimum value of the conduction loss P1 is:

[0015]

[0016] By calculating the global minimum of P1:

[0017]

[0018]

[0019] Get the current value of the Si-based inverter when P1 is the minimum value; where V CE0 is the on-state zero-current collector-emitter voltage of the Si-based inverter, r Si is the collector-emitter on-resistance of the Si-based inverter, R DS(ON) is the drain-source on-resistance of the SiC-based inverter, is the average current of the Si-based inverter, |I o | RMS is the total load current value delivered by the topology hybrid parallel integrated power supply, |I Si | RMS is the current value of the Si-based inverter in the topology hybrid parallel integration, |ISiC | RMS is the current value of the SiC-based inverter in the topology hybrid parallel integration.

[0020] Preferably, in step S4, the optimal current loads of the two inverters obtained by the new current distribution method are:

[0021]

[0022]

[0023] Where k1 and k2 are:

[0024]

[0025]

[0026] Among them, m si is the modulation index, is the power factor of the Si-based inverter.

[0027] Preferably, in step S5, the expression equation for the conduction loss caused by harmonics and the switching loss P2 of the Si-based inverter is:

[0028]

[0029] |I si_harm | RMS =THD x I si_fund_rms

[0030] Where THD is the total harmonic distortion of the inverter under a given filter inductance value, and its expression is:

[0031] THD=0.00005f 2 sw_si -0.0977f sw_si +63.118

[0032] The calculation can obtain the minimum value of loss P2; where |I si_harm |RMS and f sw_si are the harmonic current and switching frequency generated by the Si-based inverter, E max_si is the maximum switching energy loss of the Si-based inverter, I si_fund_rms is the fundamental current of the Si-based inverter.

[0033] Preferably, the optimal frequency of the PWM wave satisfies

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The beneficial effects of the present invention are as follows: In order to overcome the limitations of inverter power supplies based on a single device, the present invention combines the advantages of large capacity and low cost of SiIGBT inverter power supply devices with the advantages of low loss, high switching frequency, and high harmonic suppression capability of SiC MOSFET inverter power supplies, which can not only improve system redundancy and power quality, but also has the advantages of easy expansion and low cost; secondly, the present invention designs a control method for a topology hybrid parallel integrated power supply, conducts a comprehensive power loss analysis and calculation of the fundamental and harmonic currents, and optimizes the load current distribution between the Si-based inverter and the SiC-based inverter and the switching frequency of the Si-based inverter while ensuring a reasonable THD of the topology hybrid parallel integrated power supply, so as to minimize the total power loss and the power loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the specific control method of the present invention.

[0037] Figure 2 This is a block diagram of the proportional-integral controller for controlling the Si-based inverter according to the present invention.

[0038] Figure 3 This is a block diagram of the proportional-integral controller for controlling the SiC-based inverter according to the present invention.

[0039] Figure 4 This is a topological diagram of the integrated power supply of the present invention, which includes a Si-based inverter and a SiC-based inverter connected in parallel.

[0040] Figure 5 This is a block diagram of the harmonic compensation controller of the present invention.

[0041] Figure 6 Graph showing the functional relationship between the THD of the output current of the Si-based inverter of the present invention and the PWM switching frequency. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0043] In order to better illustrate the technical solution of the present invention, Figures 1-6 As shown, the present invention provides a specific embodiment of a hybrid parallel integrated power supply power control method, including the following parts:

[0044] Figure 1 and Figure 2As shown, a schematic diagram of a specific control method of a hybrid parallel integrated power supply power control method of the present invention is shown. Since the Si-based inverter and the SiC-based inverter share the same common DC bus when operating in parallel, the circulating current generated will cause a zero-sequence component to appear in the phase current of the two inverters. Therefore, it is necessary to measure the three-phase currents of the Si-based inverter and the SiC-based inverter separately.

[0045] Figure 3 A proportional-integral controller is designed in the dq coordinate system to process the basic power of Si-based inverter at 1~10kHz.

[0046] Figure 4 A proportional-integral controller is designed for the SiC-based inverter in the dq coordinate system to process the partial power of the SiC-based inverter at frequencies greater than 10 kHz.

[0047] like Figure 5 The block diagram of the harmonic compensation controller shown in Figure 1 minimizes harmonic distortion in the output load current of a low-frequency Si-based inverter. A proportional harmonic compensation controller is designed for a high-frequency SiC-based inverter in the abc coordinate system. This controller conveniently calculates the fundamental current and fundamental operating frequency. The fast switching action of the SiC-based inverter can be used to suppress harmonics, and the designed harmonic compensation control eliminates the zero-sequence component caused by circulating current.

[0048] Furthermore, a novel current distribution method is used to change the conduction loss of the fundamental current in the Si-based inverter and the SiC-based inverter according to the current distributed between the Si-based inverter and the SiC-based inverter.

[0049] As a preferred method, the expression of conduction loss P1 can be expressed as:

[0050]

[0051]

[0052]

[0053] The global minimum value of P1 is obtained through the expression equation of conduction loss P1:

[0054]

[0055]

[0056] The optimal current load of the two inverters obtained by the new current distribution method is:

[0057]

[0058]

[0059] Where k1 and k2 are:

[0060]

[0061]

[0062] The current value on the Si-based inverter is obtained to select the optimal current distribution ratio range, where V CEO is the zero-current collector-emitter voltage value of the on-state of the Si-based inverter, r Si is the collector-emitter on-resistance of the Si-based inverter, R DS() is the drain-source on-resistance of the SiC-based inverter, is the average current value of the Si-based inverter, |I o | RMS is the total load current value delivered by the topology hybrid parallel integrated power supply, |I Si | RMS is the current value of the Si-based inverter in the topology hybrid parallel integration, |I SiC | RMS is the current value of the SiC-based inverter in the topology hybrid parallel integration; where m Si is the modulation index, is the power factor of the Si-based inverter.

[0063] For a total load current of 30A, the above equation shows that the Si-based inverter should provide a load current of 22A, while the SiC inverter should provide a load current of 8A. For the selected devices, the hybrid parallel integrated power supply has the lowest combined conduction losses when the power distribution of the Si-based inverter and the SiC-based inverter is 73.33% and 26.67%, respectively.

[0064] The conduction loss caused by harmonic current in Si-based inverters and SiC-based inverters and the switching loss of Si-based inverters vary according to the switching frequency of the Si-based inverter.

[0065] The expression equation of the conduction loss caused by harmonics and the switching loss P2 of the Si-based inverter is:

[0066]

[0067] |I si_harm | RMS =THD x I si_fund_rms

[0068] Among them, the expression of total harmonic distortion (THD) is:

[0069] THD=0.00005f 2 sw_si -0.0977f sw_si +63.118

[0070] By calculating the minimum value of the loss P2, the optimal PWM frequency is further optimized as follows:

[0071]

[0072] where |I si_harm | RMS and f sw_Si are the harmonic current and switching frequency generated by the Si-based inverter, E max_Si is the maximum switching energy loss of the Si-based inverter; I Si_fund_RMS is the fundamental current of the Si-based inverter, and THD is the total harmonic distortion of the inverter under a given filter inductance value; the THD expression is obtained according to the function P2 formula, and is obtained by f sw_Si The third-order equation shows that when the base load current is 22A, the optimal switching frequency of the Si-based inverter is 2kHz.

[0073] like Figure 6 The functional relationship between the THD of the Si-based inverter output current and the PWM switching frequency shown in the figure provides a more direct way to observe the inverse relationship between the total harmonic distortion (THD) and the switching frequency (PWM). Through the above steps, harmonic compensation control is achieved to eliminate the zero-sequence component caused by the circulating current, optimize the conduction losses caused by the fundamental and harmonic currents, and the losses caused by the Si-based inverter switches, and ultimately minimize the losses of the hybrid parallel integrated power supply.

[0074] It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure marks in the claims should not be regarded as limiting the claims involved.

Claims

1. A control method for a hybrid parallel integrated power supply, characterized in that: The steps include: Step S1, connecting a Si-based inverter and a SiC-based inverter in parallel on a DC bus; Step S2, setting two proportional-integral controllers in the dq coordinate system, respectively used to control the Si-based inverter and the SiC-based inverter; Step S3, setting a proportional harmonic compensation controller for the SiC-based inverter in the abc coordinate system, for calculating the minimum value of harmonic distortion in the output load current of the Si-based inverter; Step S4, minimizing the conduction loss P1 of the fundamental current on the Si-based inverter and the SiC-based inverter by using a current distribution method; The optimal current load of the two inverters obtained by the current distribution method is: Where k1 and k2 are: The calculation method of the minimum value of the conduction loss P1 is: By calculating the global minimum of P1: Get the current value of the Si-based inverter when P1 is minimum; Among them, I RMS is the effective value of the total load current output by the hybrid parallel power supply; R DS(ON) is the drain-source on-resistance of the SiC-based inverter; k1 is the coefficient related to the average current of the Si-based inverter; k2 is the coefficient related to the effective value of the current of the Si-based inverter; V CE0 is the on-state zero-current collector-emitter voltage of the Si-based inverter; r Si is the collector-emitter on-resistance of the Si-based inverter; The effective value of the load current allocated to the SiC-based inverter; is the effective value of the total load current; The effective value of the load current allocated to the Si-based inverter; is the average current of the Si-based inverter; |I Si | RMS is the current value of the Si-based inverter in the topology hybrid parallel integration; |I o | RMS The total load current value delivered by the topology hybrid parallel integrated power supply; |I SiC | RMS is the current value of the SiC-based inverter in the topology hybrid parallel integration; is the power factor of the Si-based inverter; m si is the modulation index; Step S5 , calculating the optimal frequency value of the PWM wave according to the conduction loss caused by the harmonics of the PWM wave at different frequencies and the switching loss of the Si-based inverter.

2. The control method of a hybrid parallel integrated power supply according to claim 1, characterized in that: The proportional-integral controller controlling the Si-based inverter processes the base power in the range of 1-10 kHz.

3. The control method of a hybrid parallel integrated power supply according to claim 1, characterized in that: The proportional-integral controller controlling the SiC-based inverter processes part of the power in a range above 10 kHz.

4. The control method of a hybrid parallel integrated power supply according to claim 1, characterized in that: The proportional harmonic compensation controller is used to calculate the fundamental current and fundamental operating frequency values ​​of the SiC-based inverter.

5. The control method of a hybrid parallel integrated power supply according to claim 1, characterized in that: The proportional-integral controller suppresses harmonics by controlling the switches of the SiC inverter, thereby eliminating the zero-sequence component caused by the circulating current.

6. The control method of a hybrid parallel integrated power supply according to claim 1, characterized in that: In step S5, the expression equation for the conduction loss caused by harmonics and the switching loss P2 of the Si-based inverter is: |I si_harm | RMS =THD x I si_fund_rms Where THD is the total harmonic distortion of the inverter under a given filter inductance value, and its expression is: THD=0.00005f 2 sw_si -0.0977f sw_si +63.118 The calculation can obtain the minimum value of loss P2; where |I si_harm | RMS and f sw_si are the harmonic current and switching frequency generated by the Si-based inverter; E max_si is the maximum switching energy loss of the Si-based inverter; I si_fund_rms is the fundamental current of the Si-based inverter.

7. The control method of a hybrid parallel integrated power supply according to claim 6, characterized in that: The optimal frequency of the PWM wave satisfies

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