Modular parallel solid state circuit breaker current sharing control device and method

Abstract

The application discloses a kind of modular parallel solid-state circuit breaker current sharing control device and method, multiple solid-state circuit breakers are parallel, and current balance between solid-state circuit breaker is realized based on current sharing control technology.The current of n solid-state circuit breakers is detected in real time, the actual current of the first n-1 solid-state circuit breakers is closed-loop regulated using closed-loop control technology, corresponding drive control signal correction is generated, and then the equivalent on-resistance of solid-state circuit breaker is adjusted by drive control signal, so that the actual current of n-1 solid-state circuit breakers is equal to average current.The drive control signal correction of the first n-1 solid-state circuit breakers is summed and inverted, and used as the drive control signal correction of the nth solid-state circuit breaker, so that the overall average equivalent resistance remains unchanged.The application realizes the modular combination of solid-state circuit breaker, and only one specification of solid-state circuit breaker can meet the needs of circuit breaker of different current levels, with great application prospect.

Description

Technical Field

[0001] This invention relates to the field of power distribution and consumption, and in particular to a current sharing control device and method for modular parallel solid-state circuit breakers. Background Technology

[0002] Solid-state circuit breakers (SSDs) are primarily based on modern electronic technology, using semiconductor devices to control circuit opening and closing. Compared to traditional mechanical circuit breakers, SSDs offer advantages such as no need for arc extinguishing and rapid breaking, making them a major direction for the intelligent and modern development of circuit breakers. In recent years, with the large-scale integration of new energy sources such as wind power and photovoltaics, and the rapid development of microgrids, the application demand for SSDs has been increasing. Both domestic and international academic and industrial communities have invested significant research efforts in SSDs of different voltage and current ratings. For example, a high-power power electronics manufacturer in Malvern, USA, manufactured a 15kV / 600A SSD prototype as early as the 1990s; renowned electrical manufacturer ABB also developed a megawatt-level SSD prototype; Tohoku Electric Power Company in Japan conducted in-depth research on a 6.6kV / 400A SSD through extensive experiments; and RWTH Aachen University in Germany has also carried out research on the topology, simulation, and experimental techniques of SSDs.

[0003] For different current applications, current circuit breaker manufacturers must produce mechanical circuit breakers with corresponding current ratings. They cannot achieve different current short-circuit requirements through modular parallel connection of circuit breakers. This is because, during the production of mechanical circuit breakers, due to factors such as manufacturing processes and materials, even circuit breakers from the same production batch have varying contact resistances. Since the resistance in a circuit is generally small, even slight differences in contact resistance can lead to significant differences in the current flowing through parallel circuit breakers. This results in some circuit breakers carrying a larger current while others carry a smaller current. In the event of a fault, the circuit breaker carrying the larger current will trip first, causing the remaining circuit breakers to carry the entire fault current and also trip immediately, thus failing to achieve the desired effect of parallel connection.

[0004] Unlike traditional mechanical circuit breakers, solid-state circuit breakers offer high controllability. By adjusting the drive voltage, their on-resistance can be altered, thereby changing the current flowing through each circuit breaker in parallel and achieving current balancing. If this effect can be realized, it is possible to use a single solid-state circuit breaker with a specific current rating. Modular parallel technology could then meet the application requirements of different current ratings, significantly reducing the R&D and production costs of circuit breakers, improving their economic efficiency, and enabling standardized production and maintenance. This would have significant market application value, although related research and production work has not yet been publicly reported. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a modular parallel solid-state circuit breaker current sharing control device and method. Using a single solid-state circuit breaker specification, different numbers of circuit breakers are connected in a modular parallel configuration and their current is controlled to achieve balanced distribution, meeting the application requirements of different current scenarios. This significantly reduces the R&D and production costs of circuit breakers, improves the economic efficiency of circuit breakers, and enables standardized production and maintenance.

[0006] Technical solution: To achieve this objective, the present invention adopts the following technical solution:

[0007] A modular parallel solid-state circuit breaker current sharing control device, characterized in that it comprises:

[0008] n solid-state circuit breakers, with their power terminals connected in parallel, and each solid-state circuit breaker having its own individually controlled drive controller;

[0009] n current detection modules are used to detect the current of each solid-state circuit breaker.

[0010] The average current calculation module calculates the average value of the current detected by each current detection module for all solid-state circuit breakers.

[0011] n-1 closed-loop control modules generate drive control signal correction values ​​for the first n-1 solid-state circuit breakers based on the average current of all solid-state circuit breakers and the current of the first n-1 solid-state circuit breakers, and perform closed-loop control on the current of the first n-1 solid-state circuit breakers respectively.

[0012] The summation module sums the drive control signal corrections of the first n-1 solid-state circuit breakers and then inverts the sum to obtain the drive control signal correction for the nth solid-state circuit breaker.

[0013] The correction amount of the drive control signal for each solid-state circuit breaker is superimposed on the output voltage of the corresponding drive controller to generate a corrected drive control signal, which is then applied to the corresponding solid-state circuit breaker.

[0014] Preferably, the closed-loop control module includes a subtractor, a proportional-integral-derivative controller, and a limiter connected in sequence.

[0015] A method for current sharing control of modular parallel solid-state circuit breakers, comprising the following steps:

[0016] S1, n solid-state circuit breakers are directly connected in parallel at their power terminals, and each solid-state circuit breaker has an independent drive controller;

[0017] S2. Each solid-state circuit breaker has a current detection module to detect the current I of the i-th solid-state circuit breaker. i , where i = 1, 2, ..., n-1, n;

[0018] S3. Calculate the average current I of all solid-state circuit breakers. AVE :

[0019]

[0020] S4. Perform closed-loop control on the current of the first n-1 solid-state circuit breakers respectively, and generate the drive control signal correction amount ΔU for the j-th solid-state circuit breaker. Gj , where j = 1, 2, ..., n-1;

[0021] S5. Sum the correction values ​​of the drive control signals of the first n-1 solid-state circuit breakers and invert the sum to obtain the correction value ΔU of the drive control signal of the nth solid-state circuit breaker. Gj :

[0022]

[0023] S6. Adjust the drive control signal correction amount ΔU for each solid-state circuit breaker. Gi Each voltage U is superimposed on the corresponding drive controller output voltage. Gi The above generates the corrected drive control signal U. Gi * ;

[0024] S7. Transfer the corrected drive control signal U to... Gi * It applies to the i-th solid-state circuit breaker.

[0025] Preferably, the closed-loop control method in step S4 is as follows:

[0026] S4.1, Average current I AVE The current I of the j-th solid-state circuit breaker j The difference is calculated to generate the current deviation signal ΔI of the j-th solid-state circuit breaker. j ;

[0027] S4.2. A proportional-integral-derivative controller is used to control the current deviation signal ΔI. j After adjustment, the output signal is ΔU. Gj0 ;

[0028] S4.3, Adjusted signal ΔU Gj0 Amplitude limiting is applied to generate a drive control signal correction amount ΔU. Gj The limiting relationship is as follows:

[0029]

[0030] Where ΔU GMAX and ΔU GMIN These are the maximum and minimum values ​​of the set drive control signal correction amount, respectively.

[0031] Beneficial effects:

[0032] The modular parallel solid-state circuit breaker current sharing control device and method of the present invention can produce the following beneficial effects:

[0033] (1) Modular parallel operation of solid-state circuit breakers and current balancing operation among circuit breakers have been realized;

[0034] (2) Only one type of solid-state circuit breaker with a current rating is required. By connecting different numbers of modular circuit breakers in parallel, the circuit breaker requirements of different applications can be met.

[0035] (3) It helps reduce the research and development and production costs of circuit breakers, and has significant economic benefits. Attached Figure Description

[0036] Figure 1 The circuit symbol and control characteristics of IGBT;

[0037] Figure 2 The circuit symbol for MOSFETs and their control characteristics;

[0038] Figure 3 Structural schematic diagram of a current sharing control device for modular parallel solid-state circuit breakers;

[0039] Figure 4 This is a schematic diagram of the closed-loop control module.

[0040] Figure 5 Schematic diagram of the control method for Simulink simulation;

[0041] Figure 6 The current waveforms of solid-state circuit breakers 1, 2, and 3 under ideal conditions are shown.

[0042] Figure 7 The current waveforms of solid-state circuit breakers 1, 2, and 3 under the condition of added disturbance but no control.

[0043] Figure 8 Current waveforms of solid-state circuit breakers 1, 2, and 3 under the condition of adding disturbance and control;

[0044] Figure 9 The tracking effect diagram of the PI regulator of solid-state circuit breaker 1;

[0045] Figure 10 The image shows the tracking effect of the PI regulator of solid-state circuit breaker 2. Detailed Implementation

[0046] The technical solution of the present invention will be further described below with reference to specific embodiments. Currently, solid-state circuit breakers commonly employ fully controllable power devices such as insulated-gate bipolar transistors (IGBTs) and metal-oxide-semiconductor field-effect transistors (MOSFETs). (Appendix) Figure 1 (a) is the circuit symbol for an IGBT, which has a gate (G), collector (C), and emitter (E). The principle of IGBT control is that applying different voltages between G and E changes the current flowing through the collector (CE) and the voltage relationship between them. (See appendix) Figure 1 (b) shows the control characteristics of a certain type of IGBT. As can be seen from the figure, under different gate drive voltages U... GE Below, current I C and pressure drop U CE The relationship is different, meaning the equivalent on-resistance of IGBTs is different. Similar to IGBTs, MOSFETs also have similar characteristics; their circuit symbols and control characteristics are as follows... Figure 2 As shown in the figure, it can also be seen that the gate drive voltage U of the MOSFET can be changed. GS This is used to adjust the equivalent on-resistance of the MOSFET.

[0047] Based on this principle, the present invention proposes... Figure 3 The diagram illustrates a modular parallel connection scheme for solid-state circuit breakers. This scheme consists of n solid-state circuit breakers connected in parallel, where the solid-state switches are semiconductor devices. The power terminals of these solid-state circuit breakers are directly connected in parallel: for solid-state circuit breakers using IGBTs, the collectors (C) and emitters (E) are connected together; for solid-state circuit breakers using MOSFETs, the drains (D) and source (S) are connected together. Each solid-state circuit breaker has a drive controller to generate a suitable drive control voltage.

[0048] Due to limitations in manufacturing processes, even semiconductor devices from the same batch can exhibit variations in their control characteristics. In circuit breaker applications, where line impedance is typically very low, even subtle differences in control characteristics (i.e., slight differences in equivalent resistance) can lead to current imbalances when solid-state circuit breakers are connected in parallel. This can result in some circuit breakers carrying the majority of the current, while the remaining circuit breakers carry almost no current. Under normal circumstances, these circuit breakers are likely to trip sequentially, failing to achieve the intended parallel capacity expansion effect.

[0049] Therefore, it is necessary to employ current sharing control technology to achieve current balancing in solid-state circuit breakers. For example... Figure 3 As shown, this invention detects the current flowing through n solid-state circuit breakers, denoted as I1, I2, ..., I... nSpecific current detection methods can be based on sensing resistors or Hall effect sensors. Sensing resistors are low-cost but incur some losses; Hall effect sensors have relatively low losses but are more expensive. In practice, a suitable solution can be selected based on performance requirements. Due to the differences in the equivalent on-resistance of each solid-state circuit breaker, these currents are not equal, with some being larger and others smaller. To achieve current balance among the solid-state circuit breakers, this invention uses a closed-loop control method to adjust the current of each solid-state circuit breaker to near its average value. The specific method is as follows:

[0050] S1. Calculate the average current I of the n solid-state circuit breakers. AVE :

[0051]

[0052] S2. Perform closed-loop regulation of the current of the first n-1 solid-state circuit breakers. The control block diagram is as follows: Figure 4 As shown. That is, for the j-th (j = 1, 2, ..., n) solid-state circuit breaker, I... AVE with I j The deviation is fed into a proportional-integral-derivative (PID) controller, which generates a signal ΔU under the action of the PID controller. Gj0 Theoretically, ΔU Gj0 This can be used to correct the drive control signal of the j-th solid-state circuit breaker, but in practice, ΔU needs to be adjusted. Gj0 Amplification is performed. The reason is that for semiconductor devices, the drive control signal cannot be too low, otherwise the semiconductor device will enter the linear amplification region and lose its switching characteristics; conversely, the drive control signal cannot be too high, otherwise it will exceed the withstand voltage of the semiconductor device, thus causing it to become a lossy component. The specific limiting method is as follows:

[0053]

[0054] Where ΔU GMAX and ΔU GMIN These are the maximum and minimum values ​​of the set drive control signal correction amount, respectively.

[0055] S3, Limit the signal ΔU Gj Used to correct the drive control signal of the j-th solid-state circuit breaker, generating the corrected drive control signal U. Gj * This is applied to the gate circuit of the solid-state circuit breaker. PID-based closed-loop control can achieve zero steady-state error regulation of the DC signal; therefore, in steady state, the current of the j-th solid-state circuit breaker is equal to the average current I. AVE equal.

[0056] S4. For the nth solid-state circuit breaker, PID-based closed-loop control should no longer be used. The reason is that if all n solid-state circuit breakers use PID-based closed-loop control, although the current of all solid-state circuit breakers will be equal to the average current in steady state, it will easily lead to an increase or decrease in the equivalent resistance of all solid-state circuit breakers, thus changing the overall characteristics of the solid-state circuit breakers, which is undesirable in practice. In practice, current balancing of solid-state circuit breakers requires increasing the equivalent resistance of circuit breakers with larger currents and decreasing the equivalent resistance of circuit breakers with smaller currents. To achieve this effect, this invention directly uses the negative of the sum of the drive control signal corrections of the first n-1 solid-state circuit breakers as the drive control signal correction for the nth solid-state circuit breaker, that is:

[0057]

[0058] ΔU Gn It is also used to correct the drive control signal of the nth solid-state circuit breaker, thereby adjusting its equivalent on-resistance. Under this method proposed in this invention, it can be guaranteed that the sum of the correction amounts of the drive control signals of all solid-state circuit breakers is always 0 in steady state, thus maintaining the overall characteristics of the solid-state circuit breaker while achieving current balancing.

[0059] The principle of the method of this invention will be further illustrated below with specific simulation examples. The simulation model is as follows: Figure 5 As shown. The simulation scheme uses three solid-state circuit breakers connected in parallel to a current source to supply a constant current of 1000A. Current control is the primary function of modular solid-state circuit breaker parallel technology. Firstly, the magnitude of the current passing through all solid-state circuit breakers should be sampled, such as... Figure 6 As shown, since all three solid-state circuit breakers are given a reference voltage of 15V, under ideal simulation conditions, the equivalent resistance of all three solid-state circuit breakers is 100 ohms, and therefore their output current is 333 amps.

[0060] In real-world environments, factors such as temperature, climate, and environmental conditions can cause a shift in the equivalent on-resistance of a solid-state circuit breaker under a reference voltage. To simulate this characteristic, the simulation scheme employs a perturbation-based approach to achieve this effect. The equivalent resistance of solid-state circuit breaker 1 remains constant, the equivalent resistance of solid-state circuit breaker 2 decreases by 10 ohms at 0.2s, and the equivalent resistance of solid-state circuit breaker 3 increases by 20 ohms at 0.3s. The waveform of the current sampling after adding the perturbation is shown below. Figure 7 As shown, due to the slight difference in equivalent on-resistance, the resistance values ​​of the three solid-state circuit breakers are inconsistent, and therefore their current distribution is also inconsistent. This is a problem that exists when solid-state circuit breakers are directly connected in parallel in practice.

[0061] The control technology employed in this invention involves sampling the current magnitudes of solid-state circuit breakers 1, 2, and 3, calculating their average values, and using these averages as the setpoints for the PID control of solid-state circuit breakers 1 and 2. The sampled current values ​​of solid-state circuit breakers 1 and 2 are then used as feedback values ​​for the PID controllers. The PID control outputs of solid-state circuit breakers 1 and 2 are superimposed on their reference voltages to serve as the control voltages for solid-state circuit breakers 1 and 2, respectively. The superimposed voltage for solid-state circuit breaker 3 is the negative of the sum of the PID control outputs of solid-state circuit breakers 1 and 2.

[0062] The dynamic waveforms of the currents passing through solid-state circuit breakers 1, 2, and 3 after PID regulation are shown in the figure below. Figure 8 As shown. The current eventually returned to 333 amps. The PI regulation tracking effect of solid-state circuit breaker 1 is as follows: Figure 9 As shown, the PID control tracking effect of solid-state circuit breaker 2 is as follows: Figure 10 As shown, this invention achieves parallel control of solid-state circuit breakers and realizes a balanced distribution of the total current among the parallel solid-state circuit breakers.

Claims

1. A modular parallel solid-state circuit breaker current sharing control device, characterized in that, include: n solid-state circuit breakers, with their power terminals connected in parallel, and each solid-state circuit breaker having its own individually controlled drive controller; n current detection modules are used to detect the current of each solid-state circuit breaker. The average current calculation module calculates the average value of the current detected by each current detection module for all solid-state circuit breakers. n-1 closed-loop control modules generate drive control signal correction values ​​for the first n-1 solid-state circuit breakers based on the average current of all solid-state circuit breakers and the current of the first n-1 solid-state circuit breakers, and perform closed-loop control on the current of the first n-1 solid-state circuit breakers respectively. The summation module sums the drive control signal corrections of the first n-1 solid-state circuit breakers and then inverts the sum to obtain the drive control signal correction for the nth solid-state circuit breaker. The correction amount of the drive control signal for each solid-state circuit breaker is superimposed on the output voltage of the corresponding drive controller to generate a corrected drive control signal, which is then applied to the corresponding solid-state circuit breaker.

2. The modular parallel solid-state circuit breaker current sharing control device according to claim 1, characterized in that, The closed-loop control module includes a subtractor, a proportional-integral-derivative controller, and a limiter connected in sequence.

3. A current sharing control method for modular parallel solid-state circuit breakers, characterized in that, Including the following steps: S1, n solid-state circuit breakers are directly connected in parallel at their power terminals, and each solid-state circuit breaker has an independent drive controller; S2. Each solid-state circuit breaker has a current detection module to detect the current I of the i-th solid-state circuit breaker. i , where i = 1, 2, ..., n-1, n; S3. Calculate the average current I of all solid-state circuit breakers. AVE : S4. Perform closed-loop control on the current of the first n-1 solid-state circuit breakers respectively, and generate the drive control signal correction amount ΔU for the j-th solid-state circuit breaker. Gj , where j = 1, 2, ..., n-1; S5. Sum the correction values ​​of the drive control signals of the first n-1 solid-state circuit breakers and invert the sum to obtain the correction value ΔU of the drive control signal of the nth solid-state circuit breaker. Gj : S6. Adjust the drive control signal correction amount ΔU for each solid-state circuit breaker. Gi Each voltage U is superimposed on the corresponding drive controller output voltage. Gi The above generates the corrected drive control signal U. Gi * ; S7. Transfer the corrected drive control signal U to... Gi * It applies to the i-th solid-state circuit breaker.

4. The current sharing control method for modular parallel solid-state circuit breakers according to claim 3, characterized in that, The closed-loop control method in step S4 is as follows: S4.1, Average current I AVE The current I of the j-th solid-state circuit breaker j The difference is calculated to generate the current deviation signal ΔI of the j-th solid-state circuit breaker. j ; S4.

2. A proportional-integral-derivative controller is used to control the current deviation signal ΔI. j After adjustment, the output signal is ΔU. Gj0 ; S4.3, Adjusted signal ΔU Gj0 Amplitude limiting is applied to generate a drive control signal correction amount ΔU. Gj The limiting relationship is as follows: Where ΔU GMAX and ΔU GMIN These are the maximum and minimum values ​​of the set drive control signal correction amount, respectively.

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