Efficient converter for adjusting power grid voltage

Abstract

The invention discloses a high-efficiency converter for adjusting the voltage of a power grid, and belongs to the technical field of power electronics. The converter comprises a first voltage regulation circuit, a second voltage regulation circuit, a filter circuit, a detection circuit and a control circuit. By detecting the amplitude difference between the power grid voltage and the load voltage, the control circuit automatically switches the Buck working mode or the Boost working mode, and stable alternating current output in a wide input voltage range is achieved. The invention has the advantages of compact structure, high efficiency, fast response, small harmonic wave and the like, and is suitable for industrial and civil occasions with large-range fluctuation and frequent power grid voltage.

Description

A high-efficiency converter for regulating grid voltage Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a high-efficiency converter for regulating grid voltage, suitable for stable AC power supply under grid voltage fluctuation scenarios. Background Technology

[0002] In power systems and industrial applications, stable regulation of AC voltage is crucial for the normal operation of electrical equipment. Traditional AC-AC voltage regulators, such as transformer voltage regulators, can only achieve fixed-level or small-range voltage regulation, and are large in size and slow in response; thyristor phase-controlled voltage regulators have drawbacks such as severe harmonic pollution and low power factor.

[0003] With the development of power electronics technology, AC-AC voltage regulation solutions for grid fluctuations have gradually emerged. However, existing solutions mostly use a single Buck or Boost topology, which cannot simultaneously achieve boost and buck functions in the same circuit, resulting in insufficient adaptability when the grid voltage fluctuates over a wide range. For example, when the grid voltage is higher than the load's rated voltage, a buck function is required; when the grid voltage is lower than the load's rated voltage, a boost function is required. A single topology is insufficient to meet these buck-boost regulation needs, and cascading two-stage circuits would increase system complexity, cost, and losses.

[0004] Therefore, it is of great significance to develop an AC-AC converter that can adapt to changes in input voltage and achieve efficient step-up and step-down in a single topology. Summary of the Invention

[0005] 1. Technical problem to be solved: The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-efficiency converter for regulating grid voltage. Through innovative circuit topology and control methods, it solves the problems of existing voltage regulators, such as inability to adapt to wide-range voltage fluctuations, low efficiency, and large size.

[0006] 2. Technical Solution: To solve the above problems, the present invention adopts the following technical solution.

[0007] A high-efficiency converter for regulating grid voltage includes a first voltage regulating circuit, a second voltage regulating circuit, a filter circuit, a detection circuit, and a control circuit.

[0008] The first voltage regulating circuit includes a first inductor, a first power switch, a second power switch, a third power switch, a fourth power switch, a first control switch, a second control switch, a fifth control switch, and a sixth control switch. Their connections are as follows: the first terminal of the first control switch is connected to the AC input terminal, and its second terminal is connected to the first terminal of the fourth power switch; the second terminal of the fourth power switch is connected to the second terminal of the third power switch; the first terminal of the third power switch is connected to the first terminal of the first power switch and the second terminal of the first inductor; the first terminal of the first inductor is connected to the first terminal of the fifth control switch; the second terminal of the first power switch is connected to the second terminal of the second power switch; and the first terminal of the second power switch is connected to the first terminal of the sixth control switch and the second terminal of the second control switch, and grounded.

[0009] The second voltage regulating circuit shares the first inductor and the first to fourth power switches with the first voltage regulating circuit, and additionally includes a third control switch, a fourth control switch, a seventh control switch, and an eighth control switch. Their connections are as follows: the first terminal of the third control switch is connected to the AC input terminal, and the second terminal is connected to the first terminal of the first inductor; the second terminal of the first inductor is connected to the first terminals of the first and third power switches; the second terminal of the first power switch is connected to the second terminal of the second power switch; the first terminal of the second power switch is connected to the second terminal of the fourth and eighth control switches and grounded; the second terminal of the third power switch is connected to the second terminal of the fourth power switch; and the first terminal of the fourth power switch is connected to the first terminal of the seventh control switch.

[0010] The filter circuit is connected to the AC input and / or output terminals to suppress harmonic interference.

[0011] The detection circuit is used to detect the grid-side voltage and the branch current of the first inductor in real time.

[0012] The control circuit receives signals from the detection circuit and generates drive signals to control the switching states of the first to eighth control switches and the first to fourth power switches based on the amplitude comparison results of the grid voltage and the load-side demand voltage, thereby realizing automatic switching of the buck-boost mode.

[0013] 3. Beneficial effects: Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: (1) Adaptive buck-boost: Through intelligent judgment by the control circuit, it automatically switches between Buck and Boost modes, and can stably output the target AC voltage under a wide range of input voltage fluctuations.

[0014] (2) High efficiency and energy saving: It adopts a single-stage conversion structure, optimizes the number of components, has low circuit conduction loss, and its overall efficiency far exceeds that of traditional voltage regulators.

[0015] (3) Fast response: Based on digital control logic and PWM modulation, the dynamic response speed is fast and can effectively suppress instantaneous fluctuations in grid voltage.

[0016] (4) Compact structure: The dual voltage regulation circuits share the inductor and power switch, have no traditional transformer core, have high power density and small size.

[0017] (5) High power quality: Built-in filter circuit, low output harmonics, good electromagnetic compatibility, and minimal impact on load.

[0018] It should be noted that the structures not described in this invention are not related to the design points and improvement directions of this invention, and are the same as or can be implemented using existing technologies, so they will not be elaborated here. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the circuit structure of the present invention; Figure 2 is a schematic diagram of the working mode and control flow of the present invention; Figure 3 is a schematic diagram of the system structure of the present invention.

[0020] Explanation of the labels in the diagram: S 1a First power switch; S 1b Second power switch; S 2a Third power switch; S 2b Fourth power switch; L 1a First inductor (shared energy storage inductor for step-up and step-down converters); L ga , grid-side equivalent inductance; L oa Output filter inductor; C fa Input filter capacitor; C oa Output filter capacitor; Q1, first control switch; Q2, second control switch; Q3, third control switch; Q4, fourth control switch; Q5, fifth control switch; Q6, sixth control switch; Q7, seventh control switch; Q8, eighth control switch; V g : Grid test voltage V high The voltage when the grid voltage is higher than the load demand voltage; V load : Load required voltage; V low The voltage when the grid voltage is lower than the load demand voltage; V in : Grid voltage; V out Load voltage. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more complete description of the invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be more thorough and complete.

[0022] Example 1: Basic Implementation Scheme Referring to Figure 1, the high-efficiency converter system of the present invention is constructed.

[0023] Hardware selection and key parameter design: Power switching transistor (S) 1a ,S 1b ,S 2a ,S 2b ): Select power MOSFETs or IGBTs with a withstand voltage rating of not less than 600V and fast reverse recovery characteristics to ensure efficiency and reliability under high-frequency switching. Their on-resistance should be as low as possible to reduce conduction losses.

[0024] Control switches (Q1-Q8): Relays or bidirectional controllable semiconductor switches (such as back-to-back connected MOSFETs) can be used. Their current capacity needs to be determined according to the system rated current. They are used to safely and reliably switch the main circuit topology within the power frequency cycle.

[0025] First inductor (L) 1a ): The design sensitivity is between 200μH and 300μH. It is wound with high-frequency magnetic core materials (such as iron-silicon-aluminum or manganese-zinc ferrite). Its saturation current must be greater than the maximum peak current of the system to avoid magnetic saturation when the load changes suddenly.

[0026] Since this converter has a bidirectional power flow structure, its filtering circuit includes input-side filtering and output-side filtering. The input side uses a common-mode inductor and an X-type safety capacitor to form an EMI filter, which is used to suppress high-frequency interference from the power grid and prevent noise generated by the converter from being fed into the power grid. The output side uses an LC filter (Loa, Coa in the figure), with an inductance of approximately 1mH and a capacitance of approximately 4.7μF, to filter out switching frequency harmonics and smooth the output voltage waveform.

[0027] Detection circuit: High-precision voltage and current sensors (such as Hall sensors or sampling resistors with isolation operational amplifiers) are used to collect grid voltage and inductor current in real time, and to ensure that the signals are isolated from the controller by a common ground.

[0028] Control circuit: It is implemented with a microprocessor or digital signal processor (DSP) as the core, which has a high-speed ADC module and a multi-functional PWM timer.

[0029] Control Logic and Workflow (refer to Figure 2): Signal Sampling and Judgment: The control circuit samples the mains voltage V at a fixed high frequency (e.g., 20kHz). in and load voltage V out Calculate V in The instantaneous value or amplitude, and compared with V out Compare with a reference value (such as 220V).

[0030] Pattern Decision: If Vin If the amplitude of the voltage continuously exceeds the set upper limit of the load-side required voltage (e.g., 230V), it is determined to be in buck mode; if V in If the amplitude is consistently lower than the set load-side required voltage lower limit (e.g., 210V), it is determined to be in boost mode.

[0031] To avoid frequent mode switching near the voltage critical point, the control circuit incorporates a hysteresis range. For example, if the upper limit is set to 230V and the lower limit to 210V, then when the voltage drops from above 230V to 228V, it will remain in buck mode until the voltage drops below 210V before switching to boost mode. Similarly, when the voltage rises from below 210V to 212V, it will remain in boost mode until the voltage rises above 230V before switching to buck mode. This hysteresis range can be defined as the critical voltage ±2V.

[0032] Switching state control: Entering buck mode: The control circuit outputs a signal to close Q1, Q2, Q5, and Q6; and to open Q3, Q4, Q7, and Q8, reconfiguring the main circuit into a Buck topology.

[0033] Positive half-cycle control: Control S 1a Disconnect, S 2a and S 1b Closed, S 2b High-frequency operation. Energy is drawn from the grid via Q1 and S... 2b (PWM), L 1a S 1b (Conduction), Q2 flows to the load. By adjusting S... 2b The duty cycle D_buck is used to stabilize the output voltage, ideally satisfying V. out ≈D buck *V in .

[0034] Negative half-cycle control: Control S 1b Disconnect, S 2b and S 1a Closed, S 2a It operates at high frequency. Its working principle is mirror-symmetrical to that of the positive half-cycle.

[0035] Entering boost mode: The control circuit outputs a signal to disconnect Q1, Q2, Q5, and Q6; and close Q3, Q4, Q7, and Q8, reconstructing the main circuit into a boost topology.

[0036] Positive half-cycle control: Control S 2b Disconnect, S 2a and S 1b Closed, S 1a High-frequency operation. When S... 1a When the circuit is turned on, the grid energy is stored in the inductor L. 1a In the middle; when S1a When turned off, the inductor energy is superimposed on the input voltage, and then flows through S... 2a (Conducting), Q4 releases power to the load. Output voltage V out ≈V in / (1-D_boost), where D_boost is S 1a Duty cycle.

[0037] Negative half-cycle control: Control S 2a Disconnect, S 2b and S 1a Closed, S 1b It operates at high frequency. Its working principle is mirror-symmetrical to that of the positive half-cycle.

[0038] Example 2: Optimized Implementation Scheme Based on Example 1, the following optimizations are made to improve the dynamic performance and efficiency of the system: Optimization of control algorithm: A dual closed-loop control strategy of voltage and current is adopted.

[0039] Outer loop (voltage loop): Samples the output voltage, compares it with a reference value, and then generates a current command signal through a PI regulator. This loop is responsible for ensuring the stability and accuracy of the output voltage.

[0040] Inner loop (current loop): Samples the inductor current and compares it with the current command output from the voltage loop. This data is then used to directly generate a PWM modulation wave via another PI regulator or proportional-resonant (PR) regulator. Inner loop control can significantly improve the system's response speed and effectively suppress voltage fluctuations caused by sudden load changes.

[0041] Protection Mechanism: The control program integrates comprehensive protection logic, including: Overcurrent Protection: Real-time monitoring of the power switch current; if it exceeds the safety threshold, the PWM output is immediately blocked.

[0042] Over / under voltage protection: Detects input and output voltages and enters protection mode when abnormal.

[0043] Soft start: When the system starts, the PWM duty cycle is gradually increased from zero to avoid large inrush current.

[0044] Performance: The prototype built based on the above implementation scheme was tested for rated 220V / 50Hz output within the input voltage range of 160V-250V, and showed the following performance: Voltage regulation accuracy: The output voltage can be stabilized within 220V±2%.

[0045] Conversion efficiency: Under rated load, the overall system efficiency can exceed 95%.

[0046] Dynamic response: When the load undergoes a step change from 50% to 100%, the output voltage recovery time is less than 5 milliseconds, and the overshoot is low.

[0047] Waveform quality: The total harmonic distortion (THD) of the output voltage is less than 5%, meeting the requirements of relevant power quality standards.

[0048] Example 3: Topology Variation The core concept of this invention lies in reconstructing the circuit through control switches to achieve buck-boost functionality. Those skilled in the art will understand that, without departing from the core idea of ​​this invention, some equivalent changes can be made to the topology. For example, the first inductor (L... 1a It can be a coupled inductor consisting of two windings. Under certain connection methods, the number of magnetic core components can be further reduced or electrical isolation can be achieved.

[0049] The above-described embodiments are merely illustrative of certain implementations of the present invention, and are described in a relatively specific and detailed manner. However, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A high-efficiency converter for regulating grid voltage, suitable for stable AC power supply under grid voltage fluctuation scenarios, characterized in that, include: The circuit comprises a first voltage regulating circuit, a second voltage regulating circuit, a filter circuit, a detection circuit, and a control circuit; the first voltage regulating circuit includes a first inductor (L... 1a ), first power switch (S) 1a ), second power switch (S) 1b ), third power switch (S) 2a ), fourth power switch (S) 2b The system comprises a first control switch (Q1), a second control switch (Q2), a fifth control switch (Q5), and a sixth control switch (Q6), wherein: the first terminal of the first control switch (Q1) is connected to the AC input terminal of the converter, and the second terminal of the first control switch (Q1) is connected to the fourth power switch (S). 2b The first terminal of the fourth power switch (S) is connected; 2b The second terminal of ) and the third power switch (S) 2a The second terminal of the third power switch (S) is connected; 2a The first terminal of ) and the first power switch (S) 1a The first terminal of ) and the first inductor (L 1a The second end of the first inductor (L) is connected to the second end of the first inductor (L). 1a The first terminal of the first power switch (S) is connected to the first terminal of the fifth control switch (Q5); the first power switch (S) 1a The second terminal of ) and the second power switch (S) 1b The second terminal of the second power switch (S) is connected to the second terminal of the second power switch (S). 1b The first terminal of the first inductor (L) is connected to the first terminal of the sixth control switch (Q6) and the second terminal of the second control switch (Q2) and grounded; the second voltage regulating circuit includes the first inductor (L) 1a ), the first power switch (S) 1a ), the second power switch (S) 1b The third power switch (S) 2a The fourth power switch (S) 2b The system includes a third control switch (Q3), a fourth control switch (Q4), a seventh control switch (Q7), and an eighth control switch (Q8), wherein: the first terminal of the third control switch (Q3) is connected to the AC input terminal of the converter, and the second terminal of the third control switch (Q3) is connected to the first inductor (L). 1a The first terminal of the first inductor (L) is connected; 1a The second terminal of ) and the first power switch (S) 1a The first terminal of the third power switch (S) 2a The first terminal of the first power switch (S) is connected; 1a The second terminal of ) and the second power switch (S) 1b The second terminal of the second power switch (S) is connected to the second terminal of the second power switch (S). 1b The first terminal of the third power switch (S) is connected to the second terminal of the fourth control switch (Q4) and the first terminal of the eighth control switch (Q8) and grounded; 2a The second terminal of ) and the fourth power switch (S) 2b The second terminal of the fourth power switch (S) is connected; 2b The first terminal of the first power switch (S) is connected to the first terminal of the seventh control switch (Q7); the first power switch (S) 1a ), second power switch (S) 1b ), third power switch (S) 2a ), fourth power switch (S) 2b ) and the first inductor (L 1a The first voltage regulating circuit and the second voltage regulating circuit share a common component; the filtering circuit includes an input filter on the AC input side and an output filter on the AC output side, used to filter the input voltage and the output voltage; the detection circuit is used to detect voltage fluctuations on the mains side and the first inductor (L) 1a The current of the branch containing the mains switch is measured and fed back to the control circuit. Based on the grid voltage and the branch current, the control circuit sends switch control signals to the first control switch (Q1) through the eighth control switch (Q8), and the first power switch (S). 1a ) to the fourth power switch (S 2b The controlled terminal of the converter; the control circuit is configured to: control the converter to operate in buck mode when the grid voltage amplitude is determined to be greater than the load side demand voltage; and control the converter to operate in boost mode when the grid voltage amplitude is determined to be less than the load side demand voltage.

2. The high-efficiency converter for regulating grid voltage according to claim 1, characterized in that, When the control circuit determines that the grid voltage amplitude is greater than the load-side required voltage, it controls the first control switch (Q1), the second control switch (Q2), the fifth control switch (Q5), and the sixth control switch (Q6) to close, and controls the third control switch (Q3), the fourth control switch (Q4), the seventh control switch (Q7), and the eighth control switch (Q8) to open.

3. A high-efficiency converter for regulating grid voltage according to claim 2, characterized in that, When the control circuit determines that the grid voltage amplitude is greater than the load-side demand voltage, it controls the first power switch (S) during the positive half-cycle of the power frequency. 1a Disconnect, controlling the third power switch (S) 2a ) and second power switch (S 1b ) closes, controlling the fourth power switch (S) 2b High-frequency operation.

4. A high-efficiency converter for regulating grid voltage according to claim 2, characterized in that, When the control circuit determines that the grid voltage amplitude is greater than the load-side demand voltage, it controls the second power switch (S) during the negative half-cycle of the power frequency. 1b ) is disconnected, controlling the fourth power switch (S) 2b ) and the first power switch (S) 1a ) closes, controlling the third power switch (S) 2a High-frequency operation.

5. A high-efficiency converter for regulating grid voltage according to claim 1, characterized in that, When the control circuit determines that the grid voltage amplitude is less than the load-side required voltage, it controls the first control switch (Q1), the second control switch (Q2), the fifth control switch (Q5), and the sixth control switch (Q6) to open, and controls the third control switch (Q3), the fourth control switch (Q4), the seventh control switch (Q7), and the eighth control switch (Q8) to close.

6. A high-efficiency converter for regulating grid voltage according to claim 5, characterized in that, When the control circuit determines that the grid voltage amplitude is less than the load-side required voltage, it controls the fourth power switch (S) during the positive half-cycle of the power frequency. 2b Disconnect, controlling the third power switch (S) 2a ) and second power switch (S 1b ) closes, controlling the first power switch (S) 1a High-frequency operation.

7. A high-efficiency converter for regulating grid voltage according to claim 5, characterized in that, When the control circuit determines that the grid voltage amplitude is less than the load-side demand voltage, it controls the third power switch (S) during the negative half-cycle of the power frequency. 2a ) is disconnected, controlling the fourth power switch (S) 2b ) and the first power switch (S) 1a ) closes, controlling the second power switch (S) 1b High-frequency operation.

8. The high-efficiency converter according to any one of claims 1-7, characterized in that, The control circuit is further configured to: during the positive half-cycle of the power frequency, when the grid voltage amplitude is greater than the load-side required voltage, control the first voltage regulating circuit to operate in buck mode; when the grid voltage amplitude is less than the load-side required voltage, control the second voltage regulating circuit to operate in boost mode; during the negative half-cycle of the power frequency, when the grid voltage amplitude is greater than the load-side required voltage, control the first voltage regulating circuit to operate in buck mode; when the grid voltage amplitude is less than the load-side required voltage, control the second voltage regulating circuit to operate in boost mode.

9. The high-efficiency converter according to any one of claims 1-7, characterized in that, The first power switch (S) 1a ), second power switch (S) 1b ), third power switch (S) 2a ) and the fourth power switch (S 2b () can be a MOS type field-effect transistor, an insulated gate bipolar transistor, or an integrated gate commutated thyristor.

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