Novel power spring device based on matrix converter

Abstract

The utility model relates to a novel power spring device based on a matrix converter, and belongs to the technical field of power electronic converters and power springs. The structure mainly comprises an AC power grid, a line impedance, a voltage decomposition control module, an input LC filter, a matrix converter, an output LC filter, a non-critical load, an isolation transformer and a critical load. The matrix converter is a three-phase direct AC-AC matrix converter without a direct-current link, the matrix converter and an alternating-current power grid form a main circuit of the power spring, and a rectifying circuit and an electrolytic capacitor of the direct-current link are not needed. The novel power spring based on the matrix converter is connected in series with a non-critical load through an isolation transformer to form an intelligent load. And a voltage decomposition control strategy is adopted to realize the functions of stabilizing key load voltage, adjusting intelligent load power factors, reducing three-phase voltage unbalance degree, suppressing harmonic waves and the like.

Description

Technical Field

[0001] The utility model relates to a novel electric spring device based on a matrix converter, belonging to the technical field of power electronic converters and electric springs. Background Art

[0002] Renewable energy has the advantages of being clean and sustainable, and is one of the effective ways to solve energy problems. Affected by factors such as light, climate, and temperature, renewable energy has the problem of output power fluctuations, which seriously affects the quality of power and the reliability of system operation. To solve this problem, experts and scholars have proposed the concept of power springs. Power springs are installed in the distribution network and connected in series with non-critical loads to form smart loads. When the output of renewable energy fluctuates, the voltage fluctuations are transferred to non-critical loads, thereby ensuring that the voltage of critical loads meets the requirements.

[0003] Traditional power springs are powered by a DC power supply, which is usually obtained by rectifying the AC power of the power grid. Therefore, the traditional power spring structure has a DC link and an electrolytic capacitor, which makes the structure complex, large in size, and requires frequent maintenance. If the DC power supply is a diode rectifier, it will bring harmonic pollution to the system. The new power spring based on the matrix converter not only does not have the above problems, but also can achieve the functions of stabilizing the voltage of key loads, adjusting the power factor of intelligent loads, suppressing harmonics, and reducing the imbalance of three-phase voltage. Therefore, it is of great significance to study the new power spring based on the matrix converter.

[0004] The main technical problems solved by this utility model are:

[0005] 1. Aiming at the problems of high cost of DC side power supply, excessive electrolytic capacitor in the intermediate DC link, single function and so on in traditional power springs, the utility model studies a new power spring based on matrix converter, which does not need additional DC side power supply and intermediate DC link, can realize bidirectional energy flow and unit power factor operation, and has the advantages of small size, compact structure and high efficiency.

[0006] 2. In order to solve the problems of load voltage fluctuation and three-phase voltage imbalance caused by the fluctuation of renewable energy output, a voltage decomposition control strategy is adopted to control the power spring to output the corresponding voltage to achieve the control goals of stabilizing the key load voltage, controlling the power factor of the intelligent load, reducing the three-phase voltage imbalance and harmonic suppression.

[0007] A novel electric spring device based on a matrix converter mainly comprises an AC power grid, a line impedance, a voltage decomposition control module, an input LC filter, a matrix converter, an output LC filter, a non-critical load, an isolation transformer and a critical load. Utility Model Content

[0008] The utility model mainly aims at the problems of traditional power springs, such as high cost of DC side power supply, excessive electrolytic capacitor in the intermediate DC link, single function, etc., and proposes a new power spring based on a matrix converter. The new power spring effectively integrates the advantages of the matrix converter, does not have the problems of the above-mentioned traditional power springs, and has the functions of stabilizing key load voltage, adjusting intelligent load power factor, reducing three-phase voltage imbalance, and suppressing harmonics.

[0009] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a new type of electric spring device based on a matrix converter, including an AC power grid, a line impedance, a voltage decomposition control module, an input LC filter, a matrix converter, an output LC filter, a non-critical load, an isolation transformer, and a critical load. The matrix converter is a three-phase direct AC / AC matrix converter, which is composed of 9 groups of bidirectional power electronic switch devices, has a total of 27 effective switch states, does not have a DC link, and can achieve direct AC / AC conversion. In addition, the matrix converter also has the advantages of sinusoidal input and output waveforms, bidirectional energy flow, unity power factor operation, simple circuit structure, small size, and high efficiency. The input side of the matrix converter is connected to the AC power grid through an LC filter and a transformer.

[0010] Compared with the prior art, the utility model has the following beneficial effects: the new power spring in the utility model adopts a three-phase direct matrix converter, which does not require a DC side power supply and an intermediate DC link, and has the advantages of bidirectional energy flow and unit power factor operation. It can effectively avoid the problems of excessively large DC electrolytic capacitors and excessively high cost of DC side power supplies in traditional power springs. The new power spring has the characteristics of high controllability, multiple functions, high integration and small size. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The utility model is further described below in conjunction with the accompanying drawings.

[0012] Figure 1 This is a new type of power spring structure diagram based on a matrix converter of the utility model, which specifically includes ① AC power grid ② line impedance ③ voltage decomposition control module ④ input LC filter ⑤ matrix converter ⑥ output LC filter ⑦ non-critical load ⑧ isolation transformer ⑨ critical load;

[0013] Figure 2 The working principle diagram of the power spring in the utility model when the critical load voltage is high, in which U s ref is the rated voltage of the critical load, U esr is the radial voltage after the power spring is decomposed, U esc is the chord voltage after decomposition of the electric spring, U o is the non-critical load voltage, U sis the critical load voltage, U es is the power spring voltage, I2 is the current of the key load branch, θ o For U o and U s The angle, θ esr is the radial voltage angle, θ esc is the chord voltage angle, φ1 is the non-critical load impedance angle, φ sl is the intelligent load impedance angle;

[0014] Figure 3 This is a working principle diagram of the power spring in the utility model when the critical load voltage is low. s_ref is the rated voltage of the critical load, U esr is the radial voltage after the power spring is decomposed, U esc is the chord voltage after decomposition of the electric spring, U o is the non-critical load voltage, U s is the critical load voltage, U es is the power spring voltage, I2 is the current of the key load branch, θ o For U o and U s The angle, θ esr is the radial voltage angle, θ esc is the chord voltage angle, φ1 is the non-critical load impedance angle, φ sl is the intelligent load impedance angle. DETAILED DESCRIPTION

[0015] The utility model is further described in detail below in conjunction with the accompanying drawings.

[0016] like Figure 1 As shown, a novel power spring device based on a matrix converter includes an AC power grid, a line impedance, a voltage decomposition control module, an input LC filter, a matrix converter, an output LC filter, a non-critical load, an isolation transformer, and a critical load. The AC power grid provides power to the critical load, the non-critical load, and the power spring. The input side of the matrix converter is connected to the AC power grid through the input LC filter to obtain power. The function of the isolation transformer is to achieve voltage matching and electrical isolation between the matrix converter and the AC power grid. The power spring is connected in series with the non-critical load through the isolation transformer to form an intelligent load, and then connected in parallel with the critical load to form a main circuit.

[0017] Figure 1The matrix converter is composed of 9 groups of bidirectional switch devices, with a total of 27 effective switch states, which can realize direct three-phase AC-AC conversion. Each group of bidirectional switch devices is composed of two fully controlled power electronic devices and corresponding anti-parallel diodes. The bidirectional switches of the matrix converter in this embodiment are composed of insulated gate bipolar transistors (IGBTs) and anti-parallel diodes. In actual applications, bidirectional switches composed of other types of power electronic switch devices can be used.

[0018] The voltage decomposition control module decomposes the power spring voltage into radial voltage and chordal voltage. The radial voltage component is in the same or opposite direction as the non-critical load voltage, which can control the magnitude of the power spring output voltage. The chordal voltage can adjust the angle between the current and voltage of the intelligent load branch to achieve the purpose of adjusting the power factor of the intelligent load. Each phase of the power spring of the utility model adopts the same control strategy, and independently generates the reference voltage of the phase according to the actual situation, so as to reduce the impact caused by the imbalance of the three-phase voltage.

[0019] The schematic diagram of the voltage decomposition control module is as follows: Figure 2 and Figure 3 As shown, by real-time monitoring of the grid voltage, when the critical load voltage U s Higher than rated voltage U s ref When the voltage of the power spring is along the non-critical load U o The direction is decomposed into radial voltage U esr Chordal voltage U esc , according to the radial voltage U esr Chordal voltage U esc Given the reference voltage U of the electric spring es_ref , the matrix converter outputs the corresponding voltage through space vector modulation to achieve a stable critical load voltage U s When the critical load voltage U s Lower than rated voltage U s_ref The working principle is similar to the above. In this implementation example, the matrix converter is implemented by space vector modulation. In the specific implementation process, other modulation or control methods can be used to control the matrix converter.

Claims

1. A novel power spring device based on a matrix converter, comprising an AC power grid, a line impedance, a voltage decomposition control module, an input LC filter, a matrix converter, an output LC filter, a non-critical load, an isolation transformer, and a critical load, characterized in that A three-phase direct matrix converter is used to realize the function of the power spring, which is directly powered by the AC power grid without the need for an additional DC power supply or rectifier.

2. A novel power spring device based on a matrix converter according to claim 1, characterized in that The matrix converter used is a three-phase direct matrix converter, which consists of 9 groups of bidirectional power electronic switching devices. There are 27 effective switch state combinations, no DC link, and direct AC / AC conversion can be achieved. The matrix converter also has the characteristics of sinusoidal input and output waveforms, bidirectional energy flow, unity power factor operation, simple circuit structure, small size, and high efficiency.

3. A novel electric spring device based on a matrix converter according to claim 1, characterized in that The input power source is an AC power grid, rather than a DC power supply or a rectifier device in a traditional power spring. A transformer can be used to achieve matching between the AC power grid and the input voltage of the matrix converter.

4. A novel electric spring device based on a matrix converter according to claim 1, characterized in that The input side of the matrix converter is connected to the AC power grid through a transformer and an LC filter, and the output side is connected in series with a non-critical load through an LC filter and an isolation transformer to form an intelligent load, which is then connected in parallel with the critical load.

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